NOAA Technical Memorandum NMFS-NE-169

U.S. Atlantic and Gulf of Mexico

Marine Mammal

Stock Assessments -- 2002

U. S. DEPARTMENT OF COMMERCE

National Oceanic and Atmospheric Administration

National Marine Fisheries Service

Northeast Region

Northeast Fisheries Science Center

Woods Hole, Massachusetts

September 2002
154. Report of the Joint Scientific Review Group Workshop, April 13-14, 1999, Seattle, Washington. By Richard

L. Merrick, compiler. November 1999. v + 22 p., 3 figs., 6 tables, 5 app. NTIS Access. No. PB2000-105393.

155. Food of Northwest Atlantic Fishes and Two Common Species of Squid. By Ray E. Bowman, Charles E.

Stillwell, William L. Michaels, and Marvin D. Grosslein. January 2000. xiv + 138 p., 1 fig., 7 tables, 2 app. NTIS Access.

No. PB2000-106735.

156. Proceedings of the Summer Flounder Aging Workshop, 1-2 February 1999, Woods Hole, Massachusetts. By

George R. Bolz, James Patrick Monaghan, Jr., Kathy L. Lang, Randall W. Gregory, and Jay M. Burnett. May 2000. v

+ 15 p., 5 figs., 5 tables. NTIS Access. No. PB2000-107403.

157. Contaminant Levels in Muscle of Four Species of Recreational Fish from the New York Bight Apex. By Ashok

D. Deshpande, Andrew F.J. Draxler, Vincent S. Zdanowicz, Mary E. Schrock, Anthony J. Paulson, Thomas W. Finneran,

Beth L. Sharack, Kathy Corbo, Linda Arlen, Elizabeth A. Leimburg, Bruce W. Dockum, Robert A. Pikanowski, Brian

May, and Lisa B. Rosman. June 2000. xxii + 99 p., 6 figs., 80 tables, 3 app., glossary. NTIS Access. No. PB2001-107346.

158. A Framework for Monitoring and Assessing Socioeconomics and Governance of Large Marine Ecosystems.

By Jon G. Sutinen, editor, with contributors (listed alphabetically) Patricia Clay, Christopher L. Dyer, Steven F.

Edwards, John Gates, Tom A. Grigalunas, Timothy Hennessey, Lawrence Juda, Andrew W. Kitts, Philip N. Logan, John

J. Poggie, Jr., Barbara Pollard Rountree, Scott R. Steinback, Eric M. Thunberg, Harold F. Upton, and John B. Walden.

August 2000. v + 32 p., 4 figs., 1 table, glossary. NTIS Access. No. PB2001-106847.

159. An Overview and History of the Food Web Dynamics Program of the Northeast Fisheries Science Center,

Woods Hole, Massachusetts. By Jason S. Link and Frank P. Almeida. October 2000. iv + 60 p., 20 figs., 18 tables,

1 app. NTIS Access. No. PB2001-103996.

160. Measuring Technical Efficiency and Capacity in Fisheries by Data Envelopment Analysis Using the General

Algebraic Modeling System (GAMS): A Workbook. By John B. Walden and James E. Kirkley. October 2000. iii

+ 15 p., 9 figs., 5 tables. NTIS Access. No. PB2001-106502.

161. Demersal Fish and American Lobster Diets in the Lower Hudson - Raritan Estuary. By Frank W. Steimle,

Robert A. Pikanowski, Donald G. McMillan, Christine A. Zetlin, and Stuart J. Wilk. November 2000. vii + 106 p., 24

figs., 51 tables. NTIS Access. No. PB2002-105456.

162. U.S. Atlantic and Gulf of Mexico Marine Mammal Stock Assessments – 2000. Edited by Gordon T. Waring,

Janeen M. Quintal, and Steven L. Swartz, with contributions from (listed alphabetically) Neilo B. Barros, Phillip J.

Clapham, Timothy V.N. Cole, Carol P. Fairfield, Larry J. Hansen, Keith D. Mullin, Daniel K. Odell, Debra L. Palka,

Marjorie C. Rossman, U.S. Fish and Wildlife Service, Randall S. Wells, and Cynthia Yeung. November 2000. ix + 303

p., 43 figs., 55 tables, 3 app. NTIS Access. No. PB2001-104091.

163. Essential Fish Habitat Source Document: Red Deepsea Crab, Chaceon (Geryon) quinquedens, Life History

and Habitat Characteristics. By Frank W. Steimle, Christine A. Zetlin, and Sukwoo Chang. January 2001. v + 27

p., 8 figs., 1 table. NTIS Access. No. PB2001-103542.

164. An Overview of the Social and Economic Survey Administered during Round II of the Northeast

Multispecies Fishery Disaster Assistance Program. By Julia Olson and Patricia M. Clay. December 2001. v + 69

p., 3 figs., 18 tables, 2 app. NTIS Access. No. PB2002-105406.

165. A Baseline Socioeconomic Study of Massachusetts’ Marine Recreational Fisheries. By Ronald J. Salz, David

K. Loomis, Michael R. Ross, and Scott R. Steinback. December 2001. viii + 129 p., 1 fig., 81 tables, 4 app.

Recent Issues in This Series:
U. S. DEPARTMENT OF COMMERCE

Donald L. Evans, Secretary

National Oceanic and Atmospheric Administration

Conrad C. Lautenbacher, Jr., Administrator

National Marine Fisheries Service

William T. Hogarth, Assistant Administrator for Fisheries

Northeast Region

Northeast Fisheries Science Center

Woods Hole, Massachusetts

September 2002

NOAA Technical Memorandum NMFS-NE-169

U.S. Atlantic and Gulf of Mexico

Marine Mammal Stock Assessments -- 2002

This series represents a secondary level of scientifiic publishing. All issues employ thorough internal

scientific review; some issues employ external scientific review. Reviews are -- by design -- transparent

collegial reviews, not anonymous peer reviews. All issues may be cited in formal scientific communications.

Gordon T. Waring1, Janeen M. Quintal1, and Carol P. Fairfield2, Editors

with contributions from (listed alphabetically)

Phillip J. Clapham1, Timothy V.N. Cole1, Lance P. Garrison2,

Georgia Department of Natural Resources3, Aleta A. Hohn4, Blair G. Maise2,

Wayne E. McFee5

, Debra L. Palka1, Patricia E. Rosel5, Marjorie C. Rossman1,

U.S. Fish & Wildlife Service6, and Cynthia Yeung2

1

National Marine Fisheries Serv., 166 Water St., Woods Hole, MA 02543-1026

2

National Marine Fisheries Serv., 75 Virginia Beach Dr., Miami, FL 33149-1003

3

Georgia Dept. of Natural Resources, 2070 U.S. Hwy. 278 S.E., Social Circle, GA 30025

4

National Marine Fisheries Serv., 101 Pivers Island Rd., Beaufort, NC 28516-9722

5

National Marine Fisheries Serv., 219 Fort Johnson Rd., Charleston, SC 29412

6

U.S. Fish & Wildlife Serv., 300 Westgate Center Dr., Hadley, MA 01035-9589
About This Report:

Report History: This report is the seventh in a series – which began in 1995 – compiling marine mammal stock

assessments for U.S. Atlantic and Gulf of Mexico waters. The first report was issued in the NOAA Technical

Memorandum NMFS-SEFSC series. The six subsequent reports were issued in the NOAA Technical Memorandum

NMFS-NE series.

Editorial Treatment: To distribute this report quickly, it has not undergone the normal technical and copy editing

by the Northeast Fisheries Science Center's (NEFSC's) Editorial Office as have most other issues in the NOAA Technical

Memorandum NMFS-NE series. Other than the four covers and first two preliminary pages, all writing and editing have

been performed by – and all credit for such writing and editing rightfully belongs to – those so listed on the title page.

Species Names: The NMFS Northeast Region's policy on the use of species names in all technical communications

is generally to follow the American Fisheries Society's lists of scientific and common names for fishes (i.e., Robins et

al. 1991)a, mollusks (i.e., Turgeon et al. 1998)b, and decapod crustaceans (i.e., Williams et al. 1989)c, and to follow

the Society for Marine Mammalogy's list of scientific and common names for marine mammals (i.e., Rice 1998)d.

Exceptions to this policy occur when there are subsequent compelling revisions in the classifications of species,

resulting in changes in the names of species (e.g., Cooper and Chapleau 1998)e.

Obtaining/Viewing Copies: Copies of the first report can be obtained from the NMFS Southeast Fisheries Science

Center's headquarters (75 Virginia Beach Dr., Miami, FL 33149-1003; 305-361-4284). Copies of the second-throughsixth reports, as well as copies of this report, can be obtained from the NEFSC's headquarters (166 Water St., Woods

Hole, MA 02543-1026; 508-495-2260).

 Additionally, all seven reports are available (as of the publication date of this issue) online in PDF format at:

http://www.nefsc.noaa.gov/psb/assesspdfs.htm.

a

Robins, C.R. (chair); Bailey, R.M.; Bond, C.E.; Brooker, J.R.; Lachner, E.A.; Lea, R.N.; Scott, W.B. 1991. Common and scientific names of fishes from

the United States and Canada. 5th ed. Amer. Fish. Soc. Spec. Publ. 20; 183 p.

b

Turgeon, D.D. (chair); Quinn, J.F., Jr.; Bogan, A.E.; Coan, E.V.; Hochberg, F.G.; Lyons, W.G.; Mikkelsen, P.M.; Neves, R.J.; Roper, C.F.E.; Rosenberg,

G.; Roth, B.; Scheltema, A.; Thompson, F.G.; Vecchione, M.; Williams, J.D. 1998. Common and scientific names of aquatic invertebrates from the United

States and Canada: mollusks. 2nd ed. Amer. Fish. Soc. Spec. Publ. 26; 526 p.

c

Williams, A.B. (chair); Abele, L.G.; Felder, D.L.; Hobbs, H.H., Jr.; Manning, R.B.; McLaughlin, P.A.; Pérez Farfante, I. 1989. Common and scientific

names of aquatic invertebrates from the United States and Canada: decapod crustaceans. Amer. Fish. Soc. Spec. Publ. 17; 77 p.

d

Rice, D.W. 1998. Marine mammals of the world: systematics and distribution. Soc. Mar. Mammal. Spec. Publ. 4; 231 p.

e

Cooper, J.A.; Chapleau, F. 1998. Monophyly and interrelationships of the family Pleuronectidae (Pleuronectiformes), with a revised classification. Fish.

Bull. (U.S.) 96:686-726.
ii

TABLE OF CONTENTS

ACKNOWLEDGMENTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . v

EXECUTIVE SUMMARY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . vii

INTRODUCTION ................................................................................ 1

TABLE 1. A SUMMARY(including footnotes) OF ATLANTIC MARINE MAMMAL STOCK ASSESSMENT

REPORTS FOR STOCKS OF MARINE MAMMALS UNDER NMFS AUTHORITY THAT OCCUPY

WATERS UNDER USA JURISDICTION. .................................................... 2

NORTH ATLANTIC RIGHT WHALE (Eubalaena glacialis):

Western Stock . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

HUMPBACK WHALE (Megaptera novaeangliae):

Gulf of Maine Stock . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

FIN WHALE (Balaenoptera physalus):

Western North Atlantic Stock . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27

SEI WHALE (Balaenoptera borealis):

Nova Scotia Stock . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33

BLUE WHALE (Balaenoptera musculus):

Western North Atlantic Stock . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36

SPERM WHALE (Physeter macrocephalus):

 North Atlantic Stock . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39

CUVIER'S BEAKED WHALE (Ziphius cavirostris):

Western North Atlantic Stock . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46

MESOPLODON BEAKED WHALES (Mesoplodon spp.):

Western North Atlantic Stock . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52

RISSO'S DOLPHIN (Grampus griseus):

Western North Atlantic Stock . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59

COMMON DOLPHIN (Delphinus delphis):

Western North Atlantic Stock . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66

HARBOR SEAL (Phoca vitulina):

Western North Atlantic Stock . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75

GRAY SEAL (Halichoerus grypus):

Western North Atlantic Stock . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81

HARP SEAL (Phoca groenlandica):

Western North Atlantic Stock . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 87
iii

MINKE WHALE (Balaenoptera acutorostrata):

Canadian East Coast Stock . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 93

WHITE-SIDED DOLPHIN (Lagenorhynchus acutus):

Western North Atlantic Stock . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 104

HARBOR PORPOISE (Phocoena phocoena):

Gulf of Maine/Bay of Fundy Stock . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 113

LONG-FINNED PILOT WHALE (Globicephala melas):

Western North Atlantic Stock . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 128

SHORT-FINNED PILOT WHALE (Globicephala macrorhynchus): 

Western North Atlantic Stock . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 139

DWARF SPERM WHALE (Kogia simus): 

Western North Atlantic Stock . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 149

PYGMY SPERM WHALE (Kogia breviceps):

Western North Atlantic Stock . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 153

PANTROPICAL SPOTTED DOLPHIN (Stenella attenuata):

Western North Atlantic Stock . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 157

BOTTLENOSE DOLPHIN (Tursiops truncatus):

Western North Atlantic Offshore Stock . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 162

BOTTLENOSE DOLPHIN (Tursiops truncatus):

Western North Atlantic Coastal Stock . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 169

APPENDIX I. Estimated serious injury and mortality (SI&M) of Western North Atlantic marine mammals listed by

U.S. observed fisheries - 1996-2000. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 181

APPENDIX II. Numbers of NMFS (Northeast and Southeast Region) large whale/human interaction records (1996-

2000) that were examined for substantiation of mortalities and serious injuries (SI’s) for the 2002 Stock

Assessment Report. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 186

APPENDIX III. Marine mammal stock assessment reports not updated in the year 2002. . . . . . . . . . . . . . . . . . . . . . 187

APPENDIX IV. West Indian manatees stock assessments - Florida and Antilles stocks. . . . . . . . . . . . . . . . . . . . . . . 308

INDEX . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 315
v

ACKNOWLEDGMENTS

The authors wish to acknowledge contributions by the Northeast Fisheries Science Center (NEFSC) Sea

Sampling Investigation, and Dana Hartley, NMFS Northeast Stranding and Disentanglement Program. Also, we

acknowledge advice and comments provided by: Jon Gibson, Richard Merrick, and Fred Serchuk (NEFSC); Kim

Thounhurst and Diane Borggaard, Northeast Regional Office (NERO); Steven Swartz, Southeast Fisheries Science

Center (SEFSC); Katie Moore and Kathy Wang, Southeast Regional Office (SERO); Tom Eagle and Emily

Menashes, NMFS Office of Protected Resources; Solange Brault, Don Baltz, Joseph DeAlteris, James Gilbert,

Robert Kenney, Bill Lang, James Mead, Daniel Odell, Andrew Read, Richard Seagraves, Randall Wells, and Sharon

Young of the Atlantic Scientific Review Group; Robin Baird and Jim Valade, U.S. Fish and Wildlife Service; and

Barbara Zoodsma of the Georgia Department of Natural Resources. We also thank the Marine Mammal

Commission, the Ocean Conservancy, and the Humane Society of the United States for their constructive comments

and advice.
vii

EXECUTIVE SUMMARY

Under the 1994 amendments of the Marine Mammal Protection Act (MMPA), the National Marine

Fisheries Service (NMFS) and the United States Fish and Wildlife Service (USFWS) were required to generate stock

assessment reports (SAR) for all marine mammal stocks in waters within the U.S. Exclusive Economic Zone (EEZ). 

The first reports for the Atlantic (includes the Gulf of Mexico) were published in July 1995 (Blaylock et al. 1995). 

The MMPA requires NMFS and USFWS to review these reports annually for strategic stocks of marine mammals

and at least every 3 years for stocks determined to be non-strategic. The second edition of the SARs (1996

assessments) was published in October 1997 and contained all the previous reports, but major revisions and updating

were only completed for strategic stocks (Waring et al. 1997). Updated reports were identified by a 1997 date-stamp

at the top right corner at the beginning of each report. The 3rd edition of the SARs (1998 assessments) only

contained reports for Atlantic stocks, and updated reports were identified by a 1998 date-stamp (Waring et al. 1999). 

The 4th edition of the SARs (1999 assessments) only contained reports for Atlantic stocks, and updated reports were

identified by a 1999 date-stamp (Waring et al. 1999). The 5th and 6th editions of the SAR contained all NMFS

reports for the Atlantic (includes the Gulf of Mexico) and the USFWS West Indian manatee assessments. Updated

reports were identified, respectively, by 2000 and 2001date-stamps (Waring et al. 2000, 2001). The current (2002)

report contains updated assessments for Atlantic strategic stocks and for any additional stocks which had significant

new information available. These reports are identified by a January 2002 date-stamp at the beginning of each

report. Appendix I contains a summary of serious injury/mortality estimates of marine mammals in observed U.S.

fisheries. Appendix II summarizes NMFS records of large whale/human interactions examined for this assessment. 

Appendices III and IV contain stock assessments not updated in the year 2001and the West Indian Manatees stock

assessments, respectively. 

This report was prepared by staff of the Northeast Fisheries Science Center (NEFSC), Southeast Fisheries

Science Center (SEFSC), and USFWS. NMFS and USFWS staff presented the reports at the November 2001

meeting of the Atlantic Scientific Review Group (ASRG), and subsequent revisions were based on their

contributions and constructive criticism. 

Table 1 contains a summary, by species, of the information included in the stock assessments, and also

indicates those that have been revised since the 2001 publication. A total of 23 of the 60 Atlantic and Gulf of

Mexico stock assessment reports were revised for 2002. Most of the proposed changes incorporate new information

into sections on population size and/or mortality estimates. The revised SARs include 14 strategic and 9 nonstrategic stocks. Information on human interactions (fishery and ship strikes) between the right whale, humpback

whale, fin whale, and minke whale stocks were re-reviewed and updated. This is a working document and

individual stock assessment reports will be updated as new information becomes available and as changes to marine

mammal stocks and fisheries occur. The authors solicit any new information or comments which would improve

future stock assessment reports.
1

INTRODUCTION

Section 117 of the 1994 amendments to the Marine Mammal Protection Act (MMPA) requires that an

annual stock assessment report (SAR) for each stock of marine mammals that occurs in waters under USA

jurisdiction, be prepared by the National Marine Fisheries Service (NMFS) and the U.S. Fish and Wildlife Service

(USFWS), in consultation with regional Scientific Review Groups (SRGs). The SRGs are a broad representation of

marine mammal and fishery scientists and members of the commercial fishing industry mandated to review the

marine mammal stock assessments and provide advice to the NOAA Assistant Administrator for Fisheries. The

reports are then made available on the Federal Register for public review and comment before final publication.

The MMPA requires that each SAR contain several items, including: (1) a description of the stock,

including its geographic range; (2) a minimum population estimate, a maximum net productivity rate, and a

description of current population trend, including a description of the information upon which these are based; (3) an

estimate of the annual human-caused mortality and serious injury of the stock, and, for a strategic stock, other factors

that may be causing a decline or impeding recovery of the stock, including effects on marine mammal habitat and

prey; (4) a description of the commercial fisheries that interact with the stock, including the estimated number of

vessels actively participating in the fishery and the level of incidental mortality and serious injury of the stock by

each fishery on an annual basis; (5) a statement categorizing the stock as strategic or not, and why; and (6) an

estimate of the potential biological removal (PBR) level for the stock, describing the information used to calculate it. 

The MMPA also requires that SARs be updated annually for stocks which are specified as strategic stocks, or for

which significant new information is available, and once every three years for non-strategic stocks.

Following enactment of the 1994 amendments, the NMFS and USFWS held a series of workshops to

develop guidelines for preparing the SARs. The first set of stock assessments for the Atlantic Coast (including the

Gulf of Mexico) were published in July 1995 in the NOAA Technical Memorandum series (Blaylock et al. 1995). In

April 1996, the NMFS held a workshop to review proposed additions and revisions to the guidelines for preparing

SARs (Wade and Angliss 1997). Guidelines developed at the workshop were followed in preparing the 1996

(Waring et al. 1997), 1998 (Waring et al. 1999), 1999 (Waring et al. 1999), 2000 (Waring et al. 2000), and 2001

(Waring et al. 2001) SARs. A 1997 SAR was not produced.

In this document, major revisions and updating of the SARs were only completed for Atlantic Coast

strategic stocks and Atlantic Coast stocks for which significant new information were available. These are identified

by the January 2002 date-stamp at the top right corner at the beginning of each report. 

REFERENCES

Blaylock, R. A., J. W. Hain, L. J. Hansen, D. L. Palka and G. T. Waring. 1995. U.S. Atlantic and Gulf of Mexico

marine mammal stock assessments. NOAA Tech. Memo. NMFS-SEFSC-363, 211 pp.

Wade, P. R. and R. P. Angliss. 1997. Guidelines for assessing marine mammal stocks: Report of the GAMMS

workshop April 3-5, 1996, Seattle, Washington. NOAA Tech. Memo. NMFS-OPR-12, 93 pp.

Waring, G. T., D. L. Palka, K. D. Mullin, J. H. W. Hain, L. J. Hansen and K. D. Bisack. 1997. U.S. Atlantic and

Gulf of Mexico marine mammal stock assessments. NOAA Tech. Memo. NMFS-NE-114, 250 pp.

Waring, G. T., D. L. Palka, P, J. Clapham, S. Swartz, M. Rossman, T.V.N. Cole, K. D. Bisack and L. J. Hansen. 

1999. U.S. Atlantic marine mammal stock assessments-1998. NOAA Tech. Memo. NMFS-NE-116, 182

pp.

Waring, G. T., D. L. Palka, P. J. Clapham, S. Swartz, M. C. Rossman, T. V. N. Cole, L .J. Hansen, K. D. Bisack, K.

D. Mullin, R. S. Wells, D. K. Odell and N. B. Barros. 1999. U. S. Atlantic and Gulf of Mexico marine

mammal stock assessments - 1999. NOAA Tech. Memo. NMFS-NE-153, 196 pp.

Waring, G. T., J. M. Quintal and S. Swartz. 2000. U. S. Atlantic and Gulf of Mexico marine mammal stock

assessments - 2000. NOAA Tech. Memo. NMFS-NE-162, 303 pp.

Waring, G. T., J. M. Quintal and S. Swartz. 2001. U. S. Atlantic and Gulf of Mexico marine mammal stock

assessments - 2001. NOAA Tech. Memo. NMFS-NE-168, 310 pp.
2

TABLE 1. A SUMMARY(including footnotes) OF ATLANTIC MARINE MAMMAL STOCK ASSESSMENT

REPORTS FOR STOCKS OF MARINE MAMMALS UNDER NMFS AUTHORITY THAT OCCUPY

WATERS UNDER USA JURISDICTION. The “SAR revised” column indicates 2002 stock assessment

reports that have been revised relative to the 2001 reports (Y=yes N=no). If abundance, mortality or PBR 

estimates have been revised, they are indicated with the letters “a”, “m” and “p” respectively. For those

species not updated in this edition, the year of last revision is indicated.

Species Stock Area SRG

Region

NMFS

Center

Nmin Rmax Fr PBR

Total

Annual

Mort.

Annual

Fish.

Mort.

Strategic

Status

SAR

Revised

North Atlantic

right whale

Western North

Atlantic

ATL NEC 291 0 0.1 0.0 1.8 1 1.0 1 Y Y

m

Humpback

whale

Gulf of Maine ATL NEC 647 0.04 0.1 1.3 3.0 2 2.82

 YY

a,m,p

Fin whale Western North

Atlantic

ATL NEC 2,362 0.04 0.1 4.7 1.6 3 0.43 Y Y

m

Sei whale Nova Scotia ATL NEC N/A 0.04 0.1 N/A 0.00 0.00 Y Y

Minke whale Canadian east

coast

ATL NEC 3,515 0.04 0.5 35 2.6 4 2.4 4 N Y

m

Blue whale Western North

Atlantic

ATL NEC 308 0.04 0.1 N/A 0.2 0.00 Y Y

p

Sperm whale North Atlantic ATL NEC 3,505 0.04 0.1 7.0 0.00 0.2 Y Y

m

Dwarf sperm

whale

Western North

Atlantic

ATL SEC 373 5 0.04 0.5 3.7 0 0 N Y

m

Pygmy sperm

whale

Western North

Atlantic

ATL SEC 373 5 0.04 0.5 3.7 6 6 Y Y

m

Killer whale Western North

Atlantic

ATL NEC N/A 0.04 N/A N/A 0.00 0.00 N N

(1995)

Pygmy killer

whale

Western North

Atlantic

ATL SEC 6 0.04 0.5 0.1 0.00 0.00 N N

(1995)

Northern

bottlenose whale

Western North

Atlantic 

ATL NEC N/A 0.04 N/A N/A 0.00 0.00 N N

(1998)

Cuvier's beaked

whale

Western North

Atlantic

ATL NEC 2,419 6 0.04 0.5 24 0 0 7 Y Y

 m

Mesoplodon 

beaked whales

Western North

Atlantic

ATL NEC 2,419 6

 0.04 0.5 24 0 0 7 Y Y

 m

Risso's dolphin Western North

Atlantic

ATL NEC 22,916 0.04 0.48 220 51 51 N Y

 m, p

Pilot whale,

long-finned 

Western North

Atlantic

ATL NEC 11,343 8

 0.04 0.48 108 199 9 199 9 Y Y

 m

Pilot whale,

short-finned

Western North

Atlantic

ATL SEC 11,343 8 0.04 0.48 108 1999 1999 Y Y

m

Atlantic whitesided dolphinWestern North

Atlantic

ATL NEC 37,904 0.04 0.48 364 118 118 N Y

m

White-beaked

dolphin

Western North

Atlantic

ATL NEC N/A 0.04 N/A N/A 0.00 0.00 N N

(1997)
Species Stock Area SRG

Region

NMFS

Center

Nmin Rmax Fr PBR

Total

Annual

Mort.

Annual

Fish.

Mort.

Strategic

Status

SAR

Revised

3

Common

dolphin

Western North

Atlantic

ATL NEC 23,655 0.04 0.48 227 375 375 Y Y

 m

Atlantic spotted

dolphin

Western North

Atlantic

ATL NEC 27,785 10 0.04 0.5 278 7.8 11 7.8 11 N N

(2000)

Pantropical

spotted dolphin

Western North

Atlantic

ATL SEC 8,450 0.04 0.5 84 111 111 N Y 

m

Striped dolphin Western North

Atlantic

ATL NEC 44,500 0.04 0.5 445 7.3 7.3 N N

(2000)

Spinner dolphin Western North

Atlantic

ATL NEC N/A N/A N/A N/A 0.31 0.31 N N

(1998)

Bottlenose

dolphin

Western North

Atlantic,

offshore

ATL SEC 24,897 10 0.04 0.5 249 27 27 N Y 

m

Bottlenose

dolphin

Western North

Atlantic, coastal

ATL SEC N/A14 0.04 0.5 N/A14 N/A14 N/A14 Y Y

a, m, p 

Harbor porpoise Gulf of Maine/

Bay of Fundy

ATL NEC 74,695 0.04 0.5 747 459 12 435 12 Y Y

m

Harbor seal Western North

Atlantic

ATL NEC 30,990 0.12 1.0 1,859 857 843 N Y

m

Gray seal Western North

Atlantic

ATL NEC NA NA NA NA 307 118 N Y

m

Harp seal Western North

Atlantic

ATL NEC N/A N/A N/A N/A 321,222 13 111 N Y

m

Hooded seal Western North

Atlantic

ATL NEC N/A N/A N/A N/A 5.6 5.6 N N

(1998)

Sperm whale Northern Gulf of

Mexico

ATL SEC 411 0.04 0.1 0.8 0.00 0.00 Y N

(1995)

Bryde’s whale Northern Gulf of

Mexico

ATL SEC 17 0.04 0.5 0.2 0.00 0.00 N N

(1995)

Cuvier’s beaked

whale

Northern Gulf of

Mexico

ATL SEC 20 0.04 0.5 0.2 0.00 0.00 N N

(1995)

Blainville’s

beaked whale

Northern Gulf of

Mexico

ATL SEC N/A N/A N/A N/A 0.00 0.00 N N

(1995)

Gervais’ beaked

whale

Northern Gulf of

Mexico

ATL SEC N/A N/A N/A N/A 0.00 0.00 N N

(1995)

Bottlenose

dolphin

Gulf of Mexico

Outer

continental shelf

ATL SEC 43,233 0.04 0.5 432 2.8 2.8 N N

(1995)

Bottlenose

dolphin

Gulf of Mexico

Continental shelf

edge and slope

ATL SEC 4,530 0.04 0.5 45 2.8 2.8 N N

(1995)

Bottlenose

dolphin

Western Gulf of

Mexico

ATL SEC 2,938 0.04 0.5 29 13 13 N N

(1996)
Species Stock Area SRG

Region

NMFS

Center

Nmin Rmax Fr PBR

Total

Annual

Mort.

Annual

Fish.

Mort.

Strategic

Status

SAR

Revised

4

Bottlenose

dolphin

Northern Gulf of

Mexico

ATL SEC 3,518 0.04 0.5 35 10 10 N N

(1996)

Bottlenose

dolphin

Eastern Gulf of

Mexico

ATL SEC 8,963 0.04 0.5 90 8 8 N N

(1996)

Bottlenose

dolphin

Gulf of Mexico

bay, sound, and

estuarine

ATL SEC 3,933 0.04 0.5 39 N/A N/A Y N

(2000)

Atlantic spotted

dolphin

Northern Gulf of

Mexico

ATL SEC 2,255 0.04 0.5 23 1.5 1.5 N N

(1995)

Pantropical

spotted dolphin

Northern Gulf of

Mexico

ATL SEC 26,510 0.04 0.5 265 1.5 1.5 N N

(1995)

Striped dolphin Northern Gulf of

Mexico

ATL SEC 3,409 0.04 0.5 34 0.00 0.00 N N

(1995)

Spinner dolphin Northern Gulf of

Mexico

ATL SEC 4,465 0.04 0.5 45 0.00 0.00 N N

(1995)

Rough-toothed

dolphin

Northern Gulf of

Mexico

ATL SEC 660 0.04 0.5 6.6 0.00 0.00 N N

(1995)

Clymene dolphin Northern Gulf of

Mexico

ATL SEC 4,120 0.04 0.5 41 0.00 0.00 N N

(1995)

Fraser’s dolphin Northern Gulf of

Mexico

ATL SEC 66 0.04 0.5 0.7 0.00 0.00 N N

(1995)

Killer whale Northern Gulf of

Mexico

ATL SEC 197 0.04 0.5 2.0 0.00 0.00 N N

(1995)

False killer

whale

Northern Gulf of

Mexico

ATL SEC 236 0.04 0.5 2.4 0.00 0.00 N N

(1995)

Pygmy killer

whale

Northern Gulf of

Mexico

ATL SEC 285 0.04 0.05 2.8 0.00 0.00 N N

(1995)

Dwarf sperm

whale

Northern Gulf of

Mexico

ATL SEC N/A 0.04 N/A N/A 0.00 0.00 N N

(2000)

Pygmy sperm

whale

Northern Gulf of

Mexico

ATL SEC N/A 0.04 N/A N/A 0.00 0.00 N N

(2000)

Melon-headed

whale

Northern Gulf of

Mexico

ATL SEC 2,888 0.04 0.5 29 0.00 0.00 N N

(1995)

Risso’s dolphin Northern Gulf of

Mexico

ATL SEC 2,199 0.04 0.5 22 19 19 N N

(1995)

Pilot whale,

short-finned

Northern Gulf of

Mexico

ATL SEC 186 0.04 0.5 1.9 0.3 0.3 Y N

(1995)

1. The total estimated human-caused mortality and serious injury to right whales is estimated at 1.8 per year (USA waters, 1.2; Canadian waters, 0.6). This

is derived from two components: 1) non-observed fishery entanglement records at 1.0 per year (USA waters, 0.6 ; Canadian waters, 0.4 ), and 2) ship

strike records at 0.8 per year (USA waters, 0.6 ; Canadian waters, 0.2).

2. The total estimated human-caused mortality and serious injury to the Gulf of Maine humpback whale stock is estimated as 3.0 per year (USA waters,

2.4; Canadian waters, 0.6). This average is derived from two components: 1) incidental fishery interaction records 2.8 (USA waters, 2.2; Canadian

waters, 0.6); and 2) records of vessel collisions, 0.2 (USA waters, 0.2; Canadian waters, 0).
5

3. This is based on a review of NMFS anecdotal records from 1996-2000, that yielded an average of 1.6 human caused mortality -1.2 ship strikes (all US

waters), 0.4 fishery interactions (0.2 US waters, 0.2 Canadian waters).

4. During 1996 to 2000, the USA total annual estimated average human-caused mortality is 2.6 minke whales per year. This is derived from three

components: 0 minke whales per year (CV=0.0) from USA fisheries using observer data, 2.4 minke whales per year from USA fisheries using strandings

and entanglement data, and 0.2 minke whales per year from ship strikes.

5. This estimate may include both the dwarf and pygmy sperm whales.

6. This estimate includes Cuvier’s beaked whales and undifferentiated Mesoplodon spp. beaked whales.

7. This is the average mortality of undifferentiated beaked whales (Mesoplodon spp.)

8. This estimate may include both long-finned and short-finned pilot whales.

9. Mortality data are not separated by species; therefore, species-specific estimates are not available. This mortality estimate represents both long-finned

and short-finned pilot whales. Total annual mortality includes Nova Scotia 1996 average of 6 long-finned pilot whales.

10. Estimates may include sightings of the coastal form.

11. Mortality data are not separated by species; therefore, species-specific estimates are not available. The mortality estimate represents both Atlantic and

Pantropical spotted dolphins

12. The total annual estimated average human-caused mortality is 459 harbor porpoises per year. This is derived from four components: 425 harbor

porpoise per year (CV=0.24) from USA fisheries using observer data, 23 per year (unknown CV) from Canadian fisheries using observer data, 10 per

year from USA unknown fisheries using strandings data, and 1 per year from unknown human-caused mortality (a mutilated stranded harbor porpoise).

13. The total estimated human caused annual mortality and serious injury to harp seals was 321,222. This is derived from three components: 1) 1996-2000

average catches of Northwest Atlantic harp seals by Canada and Greenland 301,611; 2) 1996-2000 average bycatches in the Newfoundland lumpfish

fishery (16,000 - 23,000 annually); and 3) the 1996-2000 observed USA fisheries, 111 harp seals (CV= 0.29)

14. Several seasonal management units have been defined for the coastal bottlenose dolphin. Each has a unique abundance estimate, PBR and mortality

estimate provided in the Western North Atlantic coastal bottlenose dolphin species section of the text. 
6

January 2002

NORTH ATLANTIC RIGHT WHALE (Eubalaena glacialis):

Western Stock

STOCK DEFINITION AND GEOGRAPHIC RANGE

Individuals of the western North Atlantic right whale population range from wintering and calving grounds

in coastal waters of the southeastern United States to summer feeding and nursery grounds in New England waters

and northward to the Bay of Fundy and the Scotian Shelf. Knowlton et al. (1992) reported several long-distance

movements as far north as Newfoundland, the Labrador Basin, and southeast of Greenland; in addition, recent

resightings of photographically identified individuals have been made off Iceland and arctic Norway. The latter (in

September 1999) represents one of only two sightings this century of a right whale in Norwegian waters, and the

first since 1926. Together, these long-range matches indicate an extended range for at least some individuals and

perhaps the existence of important habitat areas not presently well described. Similarly, records from the Gulf of

Mexico (Moore and Clark 1963; Schmidly et al. 1972) represent either geographic anomalies or a more extensive

historic range beyond the sole known calving and wintering ground in the waters of the southeastern United States. 

Whatever the case, the location of a large segment of the population is unknown during the winter. Offshore surveys

flown off the coast of northeastern Florida and southeastern Georgia from 1996 to 2001 had three sightings in 1996,

one in 1997, thirteen in 1998, six in 1999, eleven in 2000, and six in 2001 (within each year, some were repeat

sightings of previously recorded individuals). The frequency with which right whales occur in offshore waters in the

southeastern U.S. remains unclear.

Research results to date suggest the existence of six major habitats or congregation areas for western North

Atlantic right whales; these are the coastal waters of the southeastern United States, the Great South Channel,

Georges Bank/Gulf of Maine, Cape Cod and Massachusetts Bays, the Bay of Fundy, and the Scotian Shelf. 

However, movements within and between habitats may be more extensive than is sometimes thought. Results from

satellite tags clearly indicate that sightings separated by perhaps two weeks should not necessarily be assumed to

indicate a stationary or resident animal. Instead, telemetry data have shown rather lengthy and somewhat distant

excursions, including into deep water off the continental shelf (Mate et al. 1997). These findings indicate that

movements and habitat use are more complex than previously thought.

New England waters are a primary feeding habitat for the right whale, which appears to feed primarily on 

copepods (largely of the genera Calanus and Pseudocalanus) in this area. Research suggests that right whales must

locate and exploit extremely dense patches of zooplankton to feed efficiently (Mayo and Marx 1990). These dense

zooplankton patches are likely a primary characteristic of the spring, summer, and fall right whale habitats (Kenney

et al. 1986, 1995). Acceptable surface copepod resources are limited to perhaps 3% of the region during the peak

feeding season in Cape Cod and Massachusetts Bays (C. Mayo pers. comm.). While feeding in the coastal waters

off Massachusetts has been better studied than in most areas, feeding by right whales has also been observed on the

margins of Georges Bank, in the Gulf of Maine, in the Bay of Fundy, and over the Scotian Shelf. The characteristics

of acceptable prey distribution in these areas are not well known. In addition, New England waters serve as a

nursery for calves and perhaps also as a mating ground. NMFS and Center for Coastal Studies aerial surveys in the

spring of 1999, 2000 and 2001 found substantial numbers of right whales along the Northern Edge of Georges Bank,

in Georges Basin, and in various locations in the Gulf of Maine including Cashes Ledge, Platts Bank and Wilkinson

Basin. The predictability with which right whales occur in such locations remains unclear, and these new data

highlight the need for more extensive surveys of habitats which have previously received minimal coverage.

Genetic analyses based upon direct sequencing of mitochondrial DNA (mtDNA) have identified five

mtDNA haplotypes in the western North Atlantic population (Malik et al. 1999). Schaeff et al. (1997) compared the

genetic variability of North Atlantic and southern right whales (E. australis), and found the former to be significantly

less diverse, a finding broadly replicated from sequence data by Malik et al. (2000). These findings might be

indicative of inbreeding in the population, but no definitive conclusion can be reached using current data. Additional

work comparing modern and historic genetic population structure in right whales, using DNA extracted from

museum and archaeological specimens of baleen and bone, is also underway (Rosenbaum et al. 1997, 2000). 

Preliminary results suggest that the eastern and western North Atlantic populations were not genetically distinct

(Rosenbaum et al. 2000). However, the virtual extirpation of the eastern stock and its lack of recovery in the last
7

 hundred years strongly suggests population subdivision over a protracted (but not evolutionary) timescale. Results

also suggest that, as expected, the principal loss of genetic diversity occurred during major exploitation events prior

to the 20th century.

To date, skin biopsy sampling has resulted in the compilation of a DNA library of more than 280 North

Atlantic right whales. When work is completed, a genetic profile will be established for each individual, and an

assessment provided on the level of genetic variation in the population, the number of reproductively active

individuals, reproductive fitness, the basis for associations and social units in each habitat area, and the mating

system. Tissue analysis has also aided in sex identification: the sex ratio of the photo-identified and catalogued

population does not differ significantly from parity (M.W. Brown, pers. comm.). Analyses based on both genetics 

and sighting histories of photographically identified individuals also suggest that approximately one-third of the

population utilizes summer nursery grounds other than the Bay of Fundy. As described above, a related question is

where individuals other than calving females and a few juveniles overwinter. One or more additional wintering and

summering grounds may exist in unsurveyed locations, although it is also possible that “missing” animals simply

disperse over a wide area at these times. Identification of such areas, and the possible threats to right whales there, is

recognized as a priority for research efforts.

POPULATION SIZE

Based on a census of individual whales identified using photo-identification techniques, the western North

Atlantic population size was estimated to be 295 individuals in 1992 (Knowlton et al. 1994); an updated analysis

using the same method gave an estimate of 291 animals in 1998 (Kraus et al. 2001) Because this was a nearly

complete census, it is assumed that this represents a minimum population size estimate. However, no estimate of

abundance with an associated coefficient of variation has been calculated for this population. Calculation of a

reliable point estimate is likely to be difficult given the known problem of heterogeneity of distribution in this

population. An IWC workshop on status and trends of western North Atlantic right whales gave a minimum directcount estimate of 263 right whales alive in 1996 and noted that the true population was unlikely to be substantially

greater than this (Best et al. 2001).

Historical Abundance

An estimate of pre-exploitation population size is not available. Basque whalers may have taken substantial

numbers of right whales at times during the 1500s in the Strait of Belle Isle region (Aguilar 1986), and the stock of

right whales may have already been substantially reduced by the time whaling was begun by colonists in the

Plymouth area in the 1600s (Reeves and Mitchell 1987). A modest but persistent whaling effort along the coast of

the eastern USA lasted three centuries, and the records include one report of 29 whales killed in Cape Cod Bay in a

single day during January 1700. Based on incomplete historical whaling data, Reeves and Mitchell (1987) could

conclude only that there were at least some hundreds of right whales present in the western North Atlantic during the

late 1600s. In a later study (Reeves et al. 1992), a series of population trajectories using historical data and an

estimated present population size of 350 were plotted. The results suggest that there may have been at least 1,000

right whales in this population during the early to mid-1600s, with the greatest population decline occurring in the

early 1700s. The authors cautioned, however, that the record of removals is incomplete, the results were

preliminary, and refinements are required. Based on back calculations using the present population size and growth

rate, the population may have numbered fewer than 100 individuals by the time international protection for right

whales came into effect in 1935 (Hain 1975; Reeves et al. 1992; Kenney et al. 1995). However, too little is known

about the population dynamics of right whales in the intervening years to state anything with confidence.

Minimum Population Estimate

The western North Atlantic population size was estimated to be 291 individuals in 1998 (Kraus et al. 2001),

based on a census of individual whales identified using photo-identification techniques. A bias that might result

from including catalogued whales that had not been seen for an extended period of time and therefore might be dead,

was addressed by assuming that an individual whale not sighted for five or more years was dead (Knowlton et al.

1994). It is assumed that the census of identified and presumed living whales represents a minimum population size

estimate. The true population size in 1998 may have been higher if: 1) there were animals not photographed and

identified, and/or 2) some animals presumed dead were not.
8

Current Population Trend

The population growth rate reported for the period 1986-92 by Knowlton et al. (1994) was 2.5%

(CV=0.12), suggesting that the stock was showing signs of slow recovery. However, work by Caswell et al. (1999)

has suggested that crude survival probability declined from about 0.99 in the early 1980's to about 0.94 in the late

1990's. The decline was statistically significant. Additional work conducted in 1999 was reviewed by the IWC

workshop on status and trends in this population (Best et al. 2001); the workshop concluded based on several

analytical approaches that survival had indeed declined in the 1990's. Although heterogeneity of capture could

negatively bias survival estimates, the workshop concluded that this factor could not account for all of the observed

decline, which appeared to be particularly marked in adult females.

CURRENT AND MAXIMUM NET PRODUCTIVITY RATES

During 1980-1992, 145 calves were born to 65 identified cows. The number of calves born annually ranged

from 5 to 17, with a mean of 11.2 (SE = 0.90). The reproductively active female pool was static at approximately 51

individuals during 1987-1992. Mean calving interval, based on 86 records, was 3.67 years. There was an indication

that calving intervals may be increasing over time, although the trend was not statistically significant (P = 0.083)

(Knowlton et al. 1994).

Since that report, total reported calf production in 92/93 was 6; 93/94, 9; 94/95, 7; 95/96, 21; 96/97, 20;

97/98, 6; 98/99, 4; and 99/2000, 1. The total calf production was reduced by reported calf mortalities: 2 mortalities

in 1993, 3 in 1996, 1 in 1997, and 1 in 1998. Of the three calf mortalities in 1996, available data suggested one was

not included in the reported 20 mother/calf pairs, resulting in a total of 21 calves born. Eleven of the 21 mothers in

1996 were observed with calves for the first time (i.e., were “new” mothers) that year. Three of these were at least

10 years old, two were 9 years old, and six were of unknown age. An updated analysis of calving interval through

the 1997/98 season suggests that mean calving interval increased since 1992 from 3.67 years to more than 5 years, a

significant trend (Kraus et al. 2001). This conclusion is supported by modeling work reviewed by the IWC

workshop on status and trends in this population (Best et al. 2001); the workshop agreed that calving intervals had

indeed increased and further that the reproductive rate was approximately half that reported from studied populations

of E. australis. The low calf production in subsequent years (4 in 1999 and only 1 in 2000) gives added cause for

concern, although a record 31 calves were born in 2001. A workshop on possible causes of reproductive failure was

held in April 2000 (Reeves et al. 2001). Factors considered included contaminants, biotoxins, nutrition/food

limitation, disease and inbreeding problems. While no conclusions were reached, a research plan to further

investigate this topic was developed.

The annual population growth rate during 1986-1992 was estimated to be 2.5% (CV=0.12) using photoidentification techniques (Knowlton et al. 1994). A population increase rate of 3.8% was estimated from the annual

increase in aerial sighting rates in the Great South Channel, 1979-1989 (Kenney et al. 1995). However, as noted

above, more recent work indicated that the population was in decline in the 1990's (Caswell et al. 1999, Best et al.

2001).

An analysis of the age structure of this population suggests that it contains a smaller proportion of juvenile

whales than expected (Hamilton et al. 1998a; Best et al. 2001), which may reflect lowered recruitment and/or high

juvenile mortality. In addition, it is possible that the apparently low reproductive rate is due in part to unstable age

structure or to reproductive senescence on the part of some females. However, data on either factor are poor;

senescence has been demonstrated in relatively few mammals (including humans, pilot whales and killer whales) and

is currently undocumented for any baleen whale.

The relatively low population size indicates that this stock is well below its optimum sustainable population

size (OSP); therefore, the current population growth rate should reflect the maximum net productivity rate for this

stock. The population growth rate reported by Knowlton et al. (1994) of 2.5% (CV=0.12) was assumed to reflect the

maximum net productivity rate for this stock for purposes of previous assessments. However, review by the IWC

workshop of modeling and other work indicates that the population was in decline in the 1990's (Best et al. 2001);

consequently, no growth rate can be used for western North Atlantic right whales.

POTENTIAL BIOLOGICAL REMOVAL

Potential biological removal (PBR) is specified as the product of minimum population size, one-half the

maximum net productivity rate and a "recovery" factor for endangered, depleted, threatened stocks, or stocks of

unknown status relative to OSP (MMPA Sec. 3. 16 U.S.C. 1362; Wade and Angliss 1997). The recovery factor for
9

right whales is 0.10 because this species is listed as endangered under the Endangered Species Act (ESA). However,

in view of the decline indicated by recent demographic analyses (Caswell et al. 1999, Best et al. 2001), the PBR for

this population is set to zero.

ANNUAL HUMAN-CAUSED SERIOUS INJURY AND MORTALITY

For the period 1996 through 2000, the total estimated human-caused mortality and serious injury to right

whales is estimated at 1.8 per year (USA waters, 1.2; Canadian waters, 0.6 ). This is derived from two components:

1) non-observed fishery entanglement records at 1.0 per year (USA waters, 0.6 ; Canadian waters, 0.4 ), and 2) ship

strike records at 0.8 per year (USA waters, 0.6; Canadian waters, 0.2). Note that in the 1996 and 1998 stock

assessment reports, a six-year time frame was used to calculate these averages. A five-year period has been used

since to be consistent with the time frames used for calculating the averages for other species. Beginning with the

2001 Stock Assessment Report, Canadian records were incorporated into the mortality and serious injury rates of

this report to reflect the effective range of this stock. It is also important to stress that serious injury determinations

are made based upon the best available information; these determinations may change with the availability of new

information. For the purposes of this report, discussion is primarily limited to those records considered confirmed

human-caused mortalities or serious injuries.

Background

The details of a particular mortality or serious injury record often require a degree of interpretation. The

assigned cause is based on the best judgement of the available data; additional information may result in revisions. 

When reviewing Table 1 below, several factors should be considered: 1) a ship strike or entanglement may occur at

some distance from the reported location; 2) the mortality or injury may involve multiple factors; for example,

whales that have been both ship struck and entangled are not uncommon; 3) the actual vessel or gear type/source is

often uncertain; and 4) in entanglements, several types of gear may be involved.

The serious injury determinations are most susceptible to revision. There are several records where a struck

and injured whale was re-sighted later, apparently healthy, or an entangled or partially disentangled whale was resighted later free of gear. The reverse may also be true: a whale initially appearing in good condition after being

struck or entangled is later re-sighted and found to have been seriously injured by the event. Entanglements of

juvenile whales are typically considered serious injuries because the constriction on the animal is likely to become

increasingly harmful as the whale grows.

We have limited the serious injury designation to only those reports that had substantiated evidence that the

injury, whether from entanglement or vessel collision, was likely to lead to the whale’s death. Injuries that impeded

the whale’s locomotion or feeding were not considered serious injuries unless they were likely to be fatal in the

foreseeable future. There was no forecasting of how the entanglement or injury may increase the whale’s 

susceptibility to further injury, namely from additional entanglements or vessel collisions. This conservative

approach likely underestimates serious injury rates.

With these caveats, the total estimated annual average human-induced mortality and serious injury incurred

by this stock (including fishery and non-fishery related causes) was 1.8 right whales per year (USA waters 1.2;

Canadian waters, 0.6). As with entanglements, some injury or mortality due to ship strikes almost certainly passes

undetected, particularly in offshore waters. Decomposed and/or unexamined animals (e.g., carcasses reported but

not retrieved or necropsied) represent ‘lost data’, some of which may relate to human impacts. For these reasons, the

figure of 1.8 right whales per year must be regarded as a minimum estimate. 

Further, the small population size and low annual reproductive rate suggest that human sources of mortality

may have a greater effect relative to population growth rates than for other whales. The principal factors believed to

be retarding growth and recovery of the population are ship strikes and entanglement with fishing gear. Between

1970 and 1999, a total of 45 right whale mortalities were recorded (IWC 1999, Knowlton and Kraus 2001). Of

these, 13 (28.9%) were neonates which are believed to have died from perinatal complications or other natural

causes. Of the remainder, 16 (35.6%) were determined to be the result of ship strikes, three (6.7%) were related to

entanglement in fishing gear (in two cases lobster gear, and one gillnet gear), and 13 (28.9%) were of unknown

cause. At a minimum, therefore, 41.3% of the observed total for the period, and 59.4% of the 32 non-calf deaths,

were attributable to human impacts.

Young animals, ages 0-4 years, are apparently the most impacted portion of the population (Kraus 1990). 

Finally, entanglement or minor vessel collisions may not kill an animal directly, but may weaken or otherwise affect
10

it so that it is more likely to become vulnerable to further injury. Such was apparently the case with the two-year old

right whale killed by a ship off Amelia Island, Florida, in March 1991 after having carried gillnet gear wrapped

around its tail region since the previous summer (Kenney and Kraus 1993). A similar fate befell right whale #2220,

found dead on Cape Cod in 1996.

For waters of the northeastern USA, a present concern not yet completely defined, is the possibility of

habitat degradation in Massachusetts and Cape Cod Bays due to a Boston sewage outfall which came on-line in

September 2000.

Awareness and mitigation programs for reducing anthropogenic injury and mortality to right whales have

been set up in two areas of concern. The first was initiated in 1992 off the coastal waters of the southeastern USA,

and it has been upgraded and expanded annually. It involves both government and non-government organizations,

including the Navy, Army Corps of Engineers, U.S. Coast Guard, and Florida and Georgia state agencies. In 1996,

a program was established in the northeastern USA, largely in cooperation with the U.S. Coast Guard and the State

of Massachusetts. In July 1999, a Mandatory Ship Reporting System was implemented in both the southeastern

United States and in the Great South Channel/Cape Cod Bay/Massachusetts Bay critical habitats. This system

requires vessels over 300 tons to report information about their identity, location, course and speed; in return, they

receive information on right whale occurrence and recommendations on measures to avoid collisions with whales. 

This system is providing much-needed information on patterns of vessel traffic in critical habitat areas. 

Fishery-Related Serious Injury and Mortality

Reports of mortality and serious injury relative to PBR as well as total human impacts are contained in

records maintained by the New England Aquarium and the NMFS Northeast and Southeast Regional Offices (Table

1). From 1996 through 2000, 5 of 9 records of mortality or serious injury (including records from both USA and

Canadian waters) involved entanglement or fishery interactions. The reports often do not contain the detail

necessary to assign the entanglements to a particular fishery or location. However, based on re-examination of the

records for the right whale observed entangled in pelagic drift gillnet in July 1993, which included the observer’s

documentation of lobster gear on the whale’s tail stock, and subsequent entanglement reports of this whale, the

suspected mortality of this whale was reassigned to the Gulf of Maine and USA mid-Atlantic lobster pot fisheries. 

In this case, the pre-existing entanglement of lobster gear was judged to have been sufficient cause of eventual

mortality independent of the drift net entanglement. In another instance, a 2 year-old dead male right whale with

lobster line through the mouth and deeply embedded at the base of the right flipper beached in Rhode Island in July

1995. This individual had been sighted previously, entangled, east of Georgia in December 1993, and again in

August 1994 in Cape Cod Bay. In this case, the entanglement became a serious injury and (directly or indirectly) the

cause of the mortality. 

During the period 1996 through 2000, there were at least four documented cases of entanglements for

which the intervention of disentanglement teams averted a likely serious injury determination. On 6/5/1999, a two

year old female, #2753, was found with a line through the mouth and trailing a norwegian ball and highflyer. The

nature of the entanglement would likely not have allowed the whale to shed the gear, and over a prolonged period,

the rope’s chaffing would have likely caused systemic infection. Another two year old female, #2710, was sighted

on 7/21/1999 wrapped in Canadian pot gear. A line passed through the mouth and around at least the right flipper. 

This entanglement would have become more constrictive as the whale grew. On 7/9/00, #2746, a three year old of

unknown gender, was seen with a line running through either side of the mouth and bridled behind the blowholes,

while another portion of the line pinned the left flipper to the whale’s flank. A nine year old female, #2223, was

sighted on 8/18/00 with line tightly wrapped across her back, running through the mouth, and possibly wrapped on

the left flipper. Subsequent sightings prior to the disentanglement revealed that the line across the back was

beginning to tighten. 

In January 1997, NMFS changed the classification of the Gulf of Maine and USA mid-Atlantic lobster pot

fisheries from Category III to Category I based on examination of stranding and entanglement records of large

whales from 1990 to 1994 (62 FR 33, Jan. 2, 1997). 

Fishery Information

Data on current incidental takes in USA fisheries are available from several sources. In 1986, NMFS

established a mandatory self-reported fisheries information system for large pelagic fisheries. Data files are

maintained at the Southeast Fisheries Science Center (SEFSC). The Northeast Fisheries Science Center (NEFSC)
11

Sea Sampling Observer Program was initiated in 1989, and since that year, several fisheries have been covered by

the program. In late 1992 and in 1993, the SEFSC provided observer coverage of pelagic longline vessels fishing off

the Grand Banks (Tail of the Banks), and currently provides observer coverage of vessels fishing south of Cape 

Hatteras. Bycatch has been observed by NMFS Sea Samplers in the pelagic drift gillnet fishery, but no mortalities or

serious injuries have been documented in either the pelagic longline, pelagic pair trawl, or other fisheries monitored

by NMFS. The only bycatch of a right whale documented by NMFS Sea Samplers was a female released from a

pelagic drift gillnet in 1993, as noted above.

In a recent analysis of the scarification of right whales, a total of 61.6% of the whales bore evidence of

entanglements with fishing gear (Hamilton et al. 1998b). Further research using the North Atlantic Right Whale

Catalogue has indicated that, each year, between 10% and 28% of right whales are involved in entanglements

(Knowlton et al. 2001). Entanglement records maintained by NMFS Northeast Regional Office (NMFS,

unpublished data) from 1970 through 2000, included at least 72 right whale entanglements or possible

entanglements, including right whales in weirs, entangled in gillnets, and trailing line and buoys. An additional

record (M. J. Harris, pers. comm.) reported a 9.1-10.6 m right whale entangled and released south of Ft. Pierce,

Florida, in March 1982 (this event occurred during a sampling program and was not related to a commercial fishery). 

Incidents of entanglements in groundfish gillnet gear, cod traps, and herring weirs in waters of Atlantic Canada and

the USA east coast were summarized by Read (1994). In six records of right whales becoming entangled in

groundfish gillnet gear in the Bay of Fundy and Gulf of Maine between 1975 and 1990, the right whales were either

released or escaped on their own, although several whales have been observed carrying net or line fragments. A

right whale mother and calf were released alive from a herring weir in the Bay of Fundy in 1976. For all areas,

specific details of right whale entanglement in fishing gear are often lacking. When direct or indirect mortality

occurs, some carcasses come ashore and are subsequently examined, or are reported as "floaters" at sea; however,

the number of unreported and unexamined carcasses is unknown, but may be significant in the case of floaters. 

More information is needed about fisheries interactions and where they occur. 

Other Mortality

Ship strikes are a major cause of mortality and injury to right whales (Kraus 1990; Knowlton and Kraus

2001). Records from 1996 through 2000 have been summarized in Table 1. For this time frame, the average

reported mortality and serious injury to right whales due to ship strikes was 0.8 whales per year (USA waters, 0.6;

Canadian waters, 0.2).

In the period January to March 1996, an ‘unusual mortality event’ was declared for right whales in

southeastern USA waters. Five mortalities were reported, at least one of which (on 1/30/96) was attributable to ship

strike. A second mortality (on 2/22/96) showed evidence of barotrauma but no proximate cause of death could be

determined. Of the remaining three mortalities, two were calves (1⁄2/96 and 2/19/96), one of which may have died

from birthing trauma (inconclusive). The third (2/7/96) was decomposed and could not be towed in for examination. 

In 2000, two right whales were sighted in the Bay of Fundy with large open wounds that were likely the

result of collisions with vessels. Right whale #2820, a male of unknown age, was first seen injured on 7/9/00. He

was sighted intermittently throughout the remainder of that summer, and was seen again in the Bay of Fundy in

2001. The second whale, #2660, is a five year old female who was sighted with a wound on the left side of her head,

just forward of the blowholes. She has not been resighted since. Although both of these injuries have a gruesome

appearance, in the absence of a chronic stressor (i.e., line), they are not likely to fatal.

In 2001, a total of five right whale mortalities were reported. One of these carcasses had indications of a

collision with a vessel. In addition, four entanglements were reported in 2001. In 2002, two mortalities and four

entanglements had been reported at the time of this writing. A comprehensive review of all available information

pertaining to these reports has not been completed, and therefore determinations of the total levels of anthropogenic

mortality and serious injury for these years have yet to be done.
12

Table 1. Summarized records of mortality and serious injury likely to result in mortality, North Atlantic right whales, 

January 1996 through December 2000. Causes of mortality or injury, assigned as primary or secondary, are

based on records maintained by NMFS/NER and NMFS/SER.

Date Report 

Type

Sex, age,

ID

Location Assigned Cause:

P=primary,

S=secondary

Notes

Ship

strike

 Entang./

Fsh inter

1/30/96 mortality,

offshore

adult

male,

#1623

offshore

GA

P shattered skull, broken vertebrae

and ribs

3/9/96 mortality,

beached

 male, age

unknown

#2220

Cape Cod

MA

P S 3.3 meter gash on back, broken

skull, Canadian lobster gear

wrapped through mouth and

around tail

8/5/96 serious

injury

unknown SE of

Gloucester, 

MA

P unknown type of gear entangled

around head

8/19/97 mortality female,

age

unknown

#2450

Bay of Fundy P necropsy found evidence of

traumatic impact on left side and

lower jaw 

8/23/97 serious

injury

5 y.o.

male

#2212

Bay of Fundy P reports from subsequent

observations indicate the whale

ingested some gear of an unknown

type 

8/29/97 serious

injury

2 yr old

female

#2557

Bay of Fundy

Canada

P Line of unknown origin tightly

wrapped on body and one flipper,

whale emaciated

4/20/99 mortality 27+ y.o.

female,

#1014

Cape Cod,

MA

P Fractures to mandible and

vertebral column, abrasion and

edema around right flipper

5/10/99 mortality,

offshore

adult

female,

#2030

80mi east of

Cape Cod,

MA

P Constricting sink gillnet gear

created deep, extensive lacerations

3/01/00 serious

injury

adult

male,

#1130

6mi east of

Manomet,

MA

P Line apparently constricting left

flipper; flipper discolored;

abnormal cyamid distribution;

bullet buoy trailing, line weighted

down between whale and buoy 
13

STATUS OF STOCK

The size of this stock is considered to be extremely low relative to OSP in the US Atlantic EEZ, and this

species is listed as endangered under the ESA. The North Atlantic right whale is considered one of the most

critically endangered populations of large whales in the world (Clapham et al. 1999). A Recovery Plan has been

published and is in effect (NMFS 1991), and a revised plan is under review. Three critical habitats, Cape Cod

Bay/Massachusetts Bay, Great South Channel, and the Southeastern USA, were designated by NMFS (59 FR 28793,

June 3, 1994). The NMFS ESA 1996 Northern Right Whale Status Review concluded that the status of the western

North Atlantic population of the northern right whale remains endangered; this conclusion was reinforced by the

International Whaling Commission (Best et al. 2001), which expressed grave concern regarding the status of this

stock. The total level of human-caused mortality and serious injury is unknown, but reported human-caused

mortality and serious injury has been a minimum of 1.8 right whales per year from 1996 through 2000. Given that

PBR has been set to zero, no mortality or serious injury for this stock can be considered insignificant. This is a

strategic stock because the average annual fishery-related mortality and serious injury exceeds PBR, and because the

North Atlantic right whale is an endangered species. Relative to populations of southern right whales, there are also

concerns about growth rate, percentage of reproductive females, and calving intervals in this population.

REFERENCES

Aguilar, A. 1986. A review of old Basque whaling and its effect on the right whales of the North Atlantic. Rep. int.

Whal. Commn, Special Issue 10: 191-199.

Best, P.B., Bannister, J.L., Brownell Jr., R.L., Donovan, G.P. (eds.) 2001. Right whales: worldwide status. J.

Cetacean Res. Manage. (Special Issue) 2. 309pp.

Caswell, H., Brault, S. and Fujiwara, M. 1999. Declining survival probability threatens the North Atlantic right

whale. Proc. Natl. Acad. Sci. USA 96: 3308-3313.

Clapham, P. J., S. B. Young and R. L. Brownell, Jr. 1999. Baleen whales: conservation issues and the status of the

most endangered populations. Mammal Review 29: 35-60.

Hain, J. H. W. 1975. The international regulation of whaling. Marine Affairs J. 3: 28-48.

Hamilton, P. K., A. R. Knowlton, M. K. Marx and S. D. Kraus. 1998. Age structure and longevity in North Atlantic

right whales Eubalaena glacialis and their relation to reproduction. Marine Ecology Progress Series 171:

285-292.

Hamilton, P. K., M. K. Marx, and S. D. Kraus. 1998. Scarification analysis of North Atlantic right whales

(Eubalaena glacialis) as a method of assessing human impacts. Final report to the Northeast Fisheries

Science Center, Contract No. 4EANF-6-0004.

IWC. 1999. Report of the workshop on the comprehensive assessment of right whales worldwide. J. Cetacean Res.

Manage. 1 (supplement): 119-120.

Kenney, R. D., M. A. M. Hyman, R. E. Owen, G. P. Scott, and H. E. Won. 1986. Estimation of prey densities

required by western North Atlantic right whales. Mar. Mammal Sci. 2(1): 1-13. 

Kenney, R. D. and S. D. Kraus. 1993. Right whale mortality — a correction and an update. Mar. Mammal Sci.

9:445-446. 

Kenney, R. D., H. E. Won, and M. C. Macaulay. 1995. Cetaceans in the Great South Channel, 1979-1989: right

whale (Eubalaena glacialis). Cont. Shelf Res. 15: 385-414.

Knowlton, A. R., J. Sigurjonsson, J. N. Ciano, and S. D. Kraus. 1992. Long-distance movements of North Atlantic

Right whales (Eubalaena glacialis). Mar. Mammal Sci. 8(4): 397-405.

Knowlton, A. R. and S. D. Kraus. 2001. Mortality and serious injury of North Atlantic right whales (Eubalaena

glacialis) in the North Atlantic Ocean. J. Cetacean Res. Manage. (Special Issue) 2: 193-208.

Knowlton, A. R., S. D. Kraus, and R. D. Kenney. 1994. Reproduction in North Atlantic right whales (Eubalaena

glacialis). Can. J. Zool. 72: 1297-1305.

Knowlton, A.R., M.K. Marx, H.M. Pettis, P.K. Hamilton and S.D. Kraus. 2001. Scarification analysis of North

Atlantic right whales (Eubalaena glacialis): monitoring rates of entanglement interaction. Report to the

National Marine Fisheries Service. Available from: New England Aquarium, Central Wharf, Boston, MA

02110. 

Kraus, S. D. 1990. Rates and potential causes of mortality in North Atlantic right whales (Eubalaena glacialis). 

Mar. Mammal Sci. 6(4): 278-291.
14

Kraus, S. D., P. K. Hamilton, R. D. Kenney, A. Knowlton and C. K. Slay. 2001. Reproductive parameters of the

North Atlantic right whale. J. Cetacean Res. Manage. (Special Issue) 2: 231-236.

Malik, S., M. W. Brown, S. D. Kraus, A. Knowlton, P. Hamilton and B. N. White. 1999. Assessment of genetic

structuring and habitat philopatry in the North Atlantic right whale (Eubalaena glacialis). Can. J. Zool. 77:

1217-1222.

Malik, S., M. W. Brown, S. D. Kraus and B. N. White. 2000. Analysis of mitochondrial DNA diversity within and

between North and South Atlantic right whales. Mar. Mammal Sci. 16: 545-558.

Mate, B. M., S. L. Nieukirk and S. D. Kraus. 1997. Satellite-monitored movements of the northern right whale. J.

Wildl. Manage. 61: 1393-1405. 

Mayo, C. A. and M .K. Marx. 1990. Surface foraging behaviour of the North Atlantic right whale, Eubalaena

glacialis, and associated zooplankton characteristics. Can. J. Zool. 68: 2214-2220.

Moore, J. C. and E. Clark. 1963. Discovery of right whales in the Gulf of Mexico. Science 141(3577): 269. 

NMFS. 1991. Recovery plan for the northern right whale (Eubalaena glacialis). Prepared by the Right Whale

Recovery Team for the National Marine Fisheries Service, Silver Spring, Maryland, 86 pp. 

Read, A. J. 1994. Interactions between cetaceans and gillnet and trap fisheries in the northwest Atlantic. Rep. int.

Whal. Commn., Special Issue 15: 133-147.

Reeves, R.R., R. Rolland, and P. Clapham (eds.) 2001. Report of the workshop on the causes of reproductive

failure in North Atlantic right whales: new avenues of research. NOAA-NMFS-NEFSC Ref. Doc. 01-16. 

46p. Northeast Fisheries Science Center, Woods Hole, MA 02543.

Reeves, R. R. and E. Mitchell. 1987. Shore whaling for right whales in the northeastern United States. Contract

Report No. NA85-WCC-06194, Southeast Fisheries Science Center, Miami, FL, 108 pp. 

Reeves, R. R., J. M. Breiwick and E. Mitchell. 1992. Pre-exploitation abundance of right whales off the eastern

United States. Pages 5-7. In: J. Hain (ed.), The right whale in the western North Atlantic: A science and

management workshop, 14-15 April 1992, Silver Spring, Maryland. NOAA-NMFS-NEFSC Ref. Doc. No.

92-05. Northeast Fisheries Science Center, Woods Hole, Massachusetts, 88 pp. 

Rosenbaum, H. C., M. Egan, P. J. Clapham, R. L. Brownell Jr. and R. DeSalle. 1997. An effective method for

isolating DNA from non-conventional museum specimens. Mol. Ecol. 6: 677-681.

Rosenbaum, H.C., Egan, M.S., Clapham, P.J., Brownell, R.L. Jr., Malik, S., Brown, M.W., White, B.N., Walsh, P.

and DeSalle, R. 2000. Utility of North Atlantic right whale museum specimens for assessing changes in

genetic diversity. Conservation Biology 14: 1837-1842.

Schaeff, C. M., S. D. Kraus, M. W. Brown, J. Perkins, R. Payne and B. N. White. 1997. Comparison of genetic

variability of North and South Atlantic right whales (Eubalaena) using DNA fingerprinting. Can. J. Zool.

75: 1073-1080.

Schmidly, D. J., C. O. Martin and G. F. Collins. 1972. First occurrence of a black right whale (Balaena glacialis)

along the Texas coast. Southw. Nat. 17(2): 214-215.

Wade, P. R., and R. P. Angliss. 1997. Guidelines for assessing marine mammal stocks: Report of the GAMMS

Workshop, April 3-5, 1996, Seattle, Washington. NOAA Technical Memorandum NMFS-OPR-12. U.S.

Dept. of Commerce, Washington, D.C. 93 pp. 
15

January 2002

HUMPBACK WHALE (Megaptera novaeangliae):

Gulf of Maine Stock

STOCK DEFINITION AND GEOGRAPHIC RANGE

In the western North Atlantic, humpback whales feed during spring, summer and fall over a range which

encompasses the eastern coast of the United States (including the Gulf of Maine), the Gulf of St. Lawrence,

Newfoundland/Labrador, and western Greenland (Katona and Beard 1990). Other North Atlantic feeding grounds

occur off Iceland and northern Norway, including off Bear Island and Jan Mayen (Christensen et al. 1992; Palsbøll

et al. 1997). These six regions represent relatively discrete subpopulations, fidelity to which is determined

matrilineally (Clapham and Mayo 1987). Genetic analysis of mitochondrial DNA (mtDNA) has indicated that this

fidelity has persisted over an evolutionary timescale in at least the Icelandic and Norwegian feeding grounds

(Palsbøll et al. 1995; Larsen et al. 1996).

Previously, the North Atlantic humpback whale population was treated as a single stock for management

purposes (Waring et al. 1999). Indeed, earlier genetic analyses (Palsbøll et al. 1995), based upon relatively small

sample sizes, had failed to discriminate among the four western North Atlantic feeding areas. However, genetic

analyses often reflect a timescale of thousands of years, well beyond those commonly used by managers. 

Accordingly, the decision was recently made to reclassify the Gulf of Maine as a separate feeding stock; this was

based upon the strong fidelity by individual whales to this region, and the attendant assumption that, were this

subpopulation wiped out, repopulation by immigration from adjacent areas would not occur on any reasonable

management timescale. This reclassification has subsequently been supported by new genetic analysis based upon a

much larger collection of samples than those utilized by Palsbøll et al. (1995). These analyses have found

significant differences in mtDNA haplotype frequencies of the four western feeding areas, including the Gulf of

Maine (Palsbøll et al. 2001). During the recent Comprehensive Assessment of North Atlantic humpback whales, the

International Whaling Commission acknowledged the evidence for treating the Gulf of Maine as a separate stock for

the purpose of management (IWC 2002).

 During the summers of 1998 and 1999, the Northeast Fisheries Science Center conducted surveys for

humpback whales on the Scotian Shelf. The objective of these surveys was to establish the occurrence and

population identity of the animals found in this region, which lies between the well-studied populations of the Gulf

of Maine and Newfoundland. Photographs from both surveys have now been compared to both the overall North

Atlantic Humpback Whale Catalogue and a large regional catalogue from the Gulf of Maine (maintained by the

College of the Atlantic and the Center for Coastal Studies, respectively); this work is summarized in Clapham et al.

(2001a). The match rate between the Scotian Shelf and the Gulf of Maine was 25% (13 of 53 Scotian Shelf

individuals from both years). Comparable rates of exchange were obtained from the southern (24%, n=9) and

northern (27%, n=4) ends of the Scotian Shelf, despite the additional distance of nearly 100 nautical miles. In

contrast, almost all humpback whales identified by the same NMFS surveys elsewhere in the Gulf of Maine

(including from the southwestern shore of Nova Scotia and Bay of Fundy area) had been previously observed in the

Gulf of Maine region. The sighting histories of the 13 Scotian Shelf whales matched to the Gulf of Maine suggested

that most of them were transient through the latter area. Only one Scotian Shelf animal was matched to any other

North Atlantic feeding ground, Newfoundland; however, instructive comparisons are compromised by the lack of

effort in that region in recent years. Overall, while it is not possible to define the Gulf of Maine population by

drawing a strict geographical boundary, it appears that the effective range of many members of this stock does not

extend onto the Scotian Shelf. Further work on the Scotian Shelf is planned for 2002. The very low match rate

between the two sampled years (only one animal was resighted in the region in both 1998 and 1999) suggests that

the Scotian Shelf is host to a larger population of humpback whales than was previously thought.

In winter, whales from all six feeding areas (including the Gulf of Maine) mate and calve primarily in the

West Indies, where spatial and genetic mixing among subpopulations occurs (Clapham et al. 1993; Katona and

Beard 1990; Palsbøll et al. 1997; Stevick et al. 1998). A few whales of unknown northern origin migrate to the

Cape Verde Islands (Reiner et al., 1996). In the West Indies, the majority of whales are found in the waters of the

Dominican Republic, notably on Silver Bank, on Navidad Bank, and in Samana Bay (Balcomb and Nichols 1982;

Whitehead and Moore 1982; Mattila et al. 1989, 1994). Humpback whales are also found at much lower densities
16

throughout the remainder of the Antillean arc, from Puerto Rico to the coast of Venezuela (Winn et al. 1975;

Levenson and Leapley 1978; Price 1985; Mattila and Clapham 1989).

It is apparent that not all whales migrate to the West Indies every winter, and that significant numbers of

animals are found in mid- and high-latitude regions at this time (Clapham et al. 1993; Swingle et al. 1993). An

increased number of sightings of humpback whales in the vicinity of the Chesapeake and Delaware Bays occurred in

1992 (Swingle et al. 1993). Wiley et al. (1995) reported 38 humpback whale strandings which occurred during

1985-1992 in the US mid-Atlantic and southeastern states. Humpback whale strandings increased, particularly along

the Virginia and North Carolina coasts, and most stranded animals were sexually immature; in addition, the small

size of many of these whales strongly suggested that they had only recently separated from their mothers. Wiley et

al. (1995) concluded that these areas are becoming an increasingly important habitat for juvenile humpback whales

and that anthropogenic factors may negatively impact whales in this area. There have also been a number of

wintertime humpback sightings in coastal waters of the southeastern USA (NMFS unpublished data; New England

Aquarium unpublished data; Florida DEP unpublished data). Whether the increased sightings represent a

distributional change, or are simply due to an increase in sighting effort and/or whale abundance, is presently

unknown. 

A key question with regard to humpback whales off the southeastern and mid-Atlantic states is their

population identity. This topic was recently investigated using fluke photographs of living and dead whales

observed in the region (Barco et al. 2001). In this study, photographs of 40 whales (live or dead) were of sufficient

quality to be compared to catalogues from the Gulf of Maine (the closest feeding ground) and other areas in the

North Atlantic. Of 21 live whales, 9 (42.9%) matched to the Gulf of Maine, 4 (19.0%) to Newfoundland and 1

(4.8%) to the Gulf of St Lawrence. Of 19 dead humpbacks, 6 (31.6%) were known Gulf of Maine whales. Although

the population composition of the mid-Atlantic is dominated by Gulf of Maine whales, lack of recent photographic

effort in Newfoundland makes it likely that the observed match rates underrepresent the true presence of Canadian

whales in the region. Barco et al. (2001) suggested that the mid-Atlantic region primarily represents a supplemental

winter feeding ground that is used by humpbacks for more than one purpose. 

Feeding is the principal activity of humpback whales in New England waters, and their distribution in New

England waters has been largely correlated to prey species and abundance, although behavior and bottom

topography are factors in foraging strategy (Payne et al. 1986, 1990). Humpback whales are frequently piscivorus

when in these waters, feeding on herring (Clupea harengus), sand lance (Ammodytes spp.), and other small fishes. 

In the northern Gulf of Maine, euphausiids are also frequently taken (Paquet et al. 1997). Commercial depletion of

herring and mackerel led to an increase in sand lance in the southwestern Gulf of Maine in the mid 1970s with a

concurrent decrease in humpback whale abundance in the northern Gulf of Maine. Humpback whales were densest

over the sandy shoals in the southwestern Gulf of Maine favored by the sand lance during much of the late 1970s

and early 1980s, and humpback distribution appeared to have shifted to this area (Payne et al. 1986). An apparent

reversal began in the mid 1980s, and herring and mackerel increased as sand lance again decreased (Fogarty et al.

1991). Humpback whale abundance in the northern Gulf of Maine increased dramatically during 1992-93 , along

with a major influx of herring (P. Stevick, pers. comm.). Humpback whales were few in nearshore Massachusetts

waters in the 1992-93 summer seasons. They were more abundant in the offshore waters of Cultivator Shoal and the

Northeast Peak on Georges Bank, and on Jeffreys Ledge; these latter areas are more traditional locations of herring

occurrence. In 1996 and 1997, sand lance, and thus humpback whales, were once again abundant in the Stellwagen

Bank area. However, unlike previous cycles, where an increase in sand lance corresponded to a decrease in herring,

herring remained relatively abundant in the northern Gulf of Maine, and humpbacks correspondingly continued to

occupy this portion of the habitat, where they also fed on euphausiids (unpublished data, Center for Coastal Studies

and College of the Atlantic).

In early 1992, a major research initiative known as the Years of the North Atlantic Humpback (YONAH)

(Smith et al. 1999) was initiated. This project was a large-scale, intensive study of humpback whales throughout

almost their entire North Atlantic range, from the West Indies to the Arctic. During two primary years of field work,

photographs for individual identification and biopsy samples for genetic analysis were collected from summer

feeding areas and from the breeding grounds in the West Indies. Additional samples were collected from certain

areas in other years. Results pertaining to the estimation of abundance and to genetic population structure are

summarized below.
17

POPULATION SIZE

The overall North Atlantic population (including the Gulf of Maine) was estimated from genetic tagging

data collected by the YONAH project in the breeding range at 4,894 males (95% c.i. 3,374-7,123) and 2,804 females

(95% c.i. 1,776-4,463) (Palsbøll et al. 1997). Since the sex ratio in this population is known to be even (Palsbøll et

al. 1997), the excess of males is presumed to be a result of sampling bias, lower rates of migration among females or

sex-specific habitat partitioning in the West Indies; whatever the reason, the combined total is an underestimate of

overall population size in this ocean. Photographic mark-recapture analyses from the YONAH project gave an

ocean-basin-wide estimate of 11,570 for 1992/93 (CV = 0.069, Stevick et al. 2001), and an additional genotypebased analysis yielded a similar but less precise estimate of 10,400 (95% c.i. 8,000 to 13,600) (Smith et al. 1999). 

The estimate of 11,570(CV=0.069) is regarded as the best available estimate for the North Atlantic, although

because YONAH sampling was not spatially representative in the feeding grounds, this figure is negatively biased. 

In the northeastern North Atlantic, Øien (2001) estimated from sighting survey data that there were 889

(CV=0.32)humpback whales in the Barents and Norwegian Seas region.

Estimating abundance for the Gulf of Maine stock has proved problematic. Three approaches have been

investigated: mark-recapture estimates, minimum population size, and line-transect estimates. Most of the markrecapture estimates were affected by heterogeneity of sampling, which was heavily focused on the southwestern

Gulf of Maine. However, an estimate of 652 (CV=0.29) derived from the more extensive and representative

YONAH sampling in 1992 and 1993 was probably less subject to this bias.

The second approach uses photo-identification data to establish the minimum number of humpback whales

known to be alive in a particular year, 1997. By determining the number of identified individuals seen either in that

year, or in both a previous and subsequent year, it is possible to determine that at least 497 humpbacks were alive in

1997. This figure is also likely to be negatively biased, again because of heterogeneity of sampling. A similar

calculation for 1992 (which would correspond to the YONAH estimate for the Gulf of Maine) yields a figure of 501

whales.

In the third approach, data were used from a 28 July to 31 August 1999 line-transect sighting survey

conducted by a ship and airplane covering waters from Georges Bank to the mouth of the Gulf of St. Lawrence. 

Total track line length was 8,212 km. However, in light of the information on stock identity of Scotian Shelf

humpback whales noted above, only the portions of the survey covering the Gulf of Maine were used; surveys

blocks along the eastern coast of Nova Scotia were excluded. Shipboard data were analyzed using the modified

direct duplicate method (Palka 1995) that accounts for school size bias and g(0), the probability of detecting a group

on the track line. Aerial data were not corrected for g(0) (Palka 2000). These surveys yielded an estimate of 816

humpbacks (CV = 0.45). However, given that the rate of exchange between the Gulf of Maine and both the Scotian

Shelf and mid-Atlantic region is not zero, this estimate is likely to be somewhat conservative. Accordingly,

inclusion of data from 25% of the Scotian Shelf survey area (to reflect the match rate of 25% between the Scotian

Shelf and the Gulf of Maine) gives an estimate of 902 whales (CV=0.41). Since the mark-recapture figures for

abundance and minimum population size given above falls above the lower bound of the CV of the line transect

estimate, and given the known exchange between the Gulf of Maine and the Scotian Shelf, we have chosen to use

the latter as the best estimate of abundance for Gulf of Maine humpback whales. 

Minimum Population Estimate

The minimum population estimate is the lower limit of the two-tailed 60% confidence interval of the lognormally distributed best abundance estimate. This is equivalent to the 20th percentile of the log-normal distribution

as specified by Wade and Angliss (1997). The best estimate of abundance for Gulf of Maine humpback whales is

902(CV=0.41). The minimum population estimate for this stock is 647.

Table 1. Summary of abundance estimates for Gulf of Maine humpback whales. CCS = Center for Coastal Studies. 

COA = College of the Atlantic.

Month/Year Type N CV Source

1992/93 Mark-recapture estimate 652 0.29 Clapham et al. (2001a)

1997 Minimum known to be alive 497 - CCS+COA data

July/August 1999 Line transect, including a portion of

the Scotian Shelf stratum 902 0.41 Palka 2000, Clapham

et al. 2001a
18

Current Population Trend

As detailed below, current data suggest that the Gulf of Maine humpback whale stock is steadily increasing

in size. This is consistent with an estimated average trend of 3.2% (SE=0.005) in the North Atlantic population

overall for the period 1979–1993 (Stevick et al. 2001), although there are no other feeding-area-specific estimates.

CURRENT AND MAXIMUM NET PRODUCTIVITY RATES

Barlow and Clapham (1997) applied an interbirth interval model to photographic mark-recapture data and

estimated the population growth rate of the Gulf of Maine humpback whale stock at 6.5% (CV=0.012). Maximum

net productivity is unknown for this population, although a theoretical maximum for any humpback population can

be calculated using known values for biological parameters (Brandão et al. 2000, Clapham et al. 2001b). For the

Gulf of Maine, data supplied by Barlow and Clapham (1997) and Clapham et al. (1995) gives values of 0.96 for

survival rate, 6y as mean age at first parturition, 0.5 as the proportion of females, and 0.42 for annual pregnancy rate. 

From this, a maximum population growth rate of 0.072 is obtained according to the method described by Brandão et

al. (2000). This suggests that the observed rate of 6.5% (Barlow and Clapham 1997) was close to the maximum for

this stock.

Clapham et al. (2001a) updated the Barlow and Clapham (1997) analysis using data from the period 1992 to

2000. The estimate was either 0% (for a calf survival rate of 0.51) or 4.0% (for a calf survival rate of 0.875). 

Although confidence limits are not available (because maturation parameters could not be estimated), both estimates

of population growth rate are outside the 95% confidence intervals of the previous estimate of 6.5% for the period

1979 to 1991 (Barlow and Clapham 1997). It is unclear whether this apparent decline is an artifact resulting from a

shift in distribution; indeed, such a shift occurred during exactly the period (1992-95) in which survival rates

declined. It is possible that this shift resulted in calves born in those years imprinting on (and thus subsequently

returning to) areas other than those in which intensive sampling occurs. If the decline is a real phenomenon it may

be related to known high mortality among young-of-the-year whales in the waters of the U.S. mid-Atlantic states. 

However, calf survival appears to have increased since 1996, presumably accompanied by an increase in population

growth.

In light of the uncertainty accompanying the more recent estimate of population growth rate for the Gulf of

Maine, for purposes of this assessment the maximum net productivity rate was assumed to be the default value for

cetaceans of 0.04 (Barlow et al. 1995). 

Current and maximum net productivity rates are unknown for the North Atlantic population overall. As

noted above, Stevick et al. (2001) calculated an average population growth rate of 3.2% (SE=0.005) for the period

1979–1993. 

POTENTIAL BIOLOGICAL REMOVAL

Potential Biological Removal (PBR) is the product of minimum population size, one-half the maximum

productivity rate, and a “recovery” factor (MMPA Sec. 3. 16 U.S.C. 1362; Wade and Angliss 1997). The minimum

population size is 647 . The maximum productivity rate is the default value of 0.04. The “recovery” factor, which

accounts for endangered, depleted, threatened stocks, or stocks of unknown status relative to optimum sustainable

population (OSP) is assumed to be 0.10 because this stock is listed as an endangered species under the Endangered

Species Act (ESA). PBR for the Gulf of Maine humpback whale stock is 1.3 whales. 

ANNUAL HUMAN-CAUSED SERIOUS INJURY AND MORTALITY

For the period 1996 through 2000, the total estimated human-caused mortality and serious injury to the Gulf

of Maine humpback whale stock is estimated as 3.0 per year (USA waters, 2.4; Canadian waters, 0.6). This

average is derived from two components: 1) incidental fishery interaction records, 2.8 (USA waters, 2.2; Canadian

waters, 0.6); and 2) records of vessel collisions, 0.2 (USA waters, 0.2; Canadian waters, 0). There were additional

humpback mortalities and serious injuries that occurred in the southeastern and mid-Atlantic states that could not be

confirmed as involving members of the Gulf of Maine stock. These records represent an additional minimum annual

average of 1.6 human-caused mortalities and serious injuries to humpbacks over the time period, of which 1.0 per

year are attributable to incidental fishery interactions and 0.6 per year are attributable to vessel collisions. 

Note that in the 1996 and 1998 stock assessment reports, a six-year time frame was used to calculate the

averages for fishery interactions and vessel collisions. A five-year period has been used since to be consistent with

the time frames used for calculating the averages for the observed fishery and for other species. Beginning with the
19

2001 Stock Assessment Report, Canadian records were incorporated into the mortality and serious injury rates of

this report to reflect the effective range of this stock as described above. Beginning with this report, records from

the southeastern and mid-Atlantic states involving individuals that could not be identified as members of the Gulf of

Maine stock were tallied separately. Conversely, records involving unidentified individuals reported between New

York and the Bay of Fundy were assumed to be whales from the Gulf of Maine stock. It is also important to stress

that serious injury determinations are made based upon the best available information at the time of writing; these

determinations may change with the availability of new information. For the purposes of this report, discussion is

primarily limited to those records considered confirmed human-caused mortalities or serious injuries.

To better assess human impacts (both vessel collision and net entanglement), and considering the number of

decomposed and incompletely or unexamined animals in the records, there needs to be greater emphasis on the

timely recovery of carcasses and complete necropsies. The literature and review of records described here suggest

that there are significant human impacts beyond those recorded in the fishery observer data. For example, a study of

entanglement-related scarring on the caudal peduncle of 134 individual humpback whales in the Gulf of Maine

suggested that between 48% and 65% had experienced entanglements (Robbins and Mattila 2001). Decomposed

and/or unexamined animals (e.g., carcasses reported but not retrieved or necropsied) represent ‘lost data’, some of

which may relate to human impacts. 

In addition, we have limited the serious injury designation to only those reports that had substantiated

evidence that the injury, whether from entanglement or vessel collision, was likely to lead to the whale’s death. 

Injuries that impeded the whale’s locomotion or feeding were not considered serious injuries unless they were likely

to be fatal in the foreseeable future. There was no forecasting of how the entanglement or injury may increase the

whale’s susceptibility to further injury, namely from additional entanglements or vessel collisions. For these

reasons, the human impacts listed in this report must be considered a minimum estimate.

Background

As with right whales, human impacts (vessel collisions and entanglements) are factors which may be

slowing recovery of the humpback whale population. There is an average of four to six entanglements of humpback

whales a year in waters of the southern Gulf of Maine and additional reports of vessel-collision scars (unpublished

data, Center for Coastal Studies). Of 20 dead humpback whales (principally in the mid-Atlantic, where

decomposition did not preclude examination for human impacts), Wiley et al. (1995) reported that 6 (30%) had

major injuries possibly attributable to ship strikes, and 5 (25%) had injuries consistent with possible entanglement in

fishing gear. One whale displayed scars that may have been caused by both ship strike and entanglement. Thus,

60% of the whale carcasses which were suitable for examination showed signs that anthropogenic factors may have

contributed to, or been responsible for, their death. Wiley et al. (1995) further reported that all stranded animals

were sexually immature, suggesting a winter or migratory segregation and/or that juvenile animals are more

susceptible to human impacts. 

An updated analysis of humpback whale mortalities from the mid-Atlantic states region has recently been

produced by Barco et al. (2001). Between 1990 and 2000, there were 52 known humpback whale mortalities in the

waters of the U.S. mid-Atlantic states (summarized by Barco et al. 2001). Length data from 48 of these whales (18

females, 22 males and 8 of unknown sex) suggested that 39 (81.2%) were first-year animals, 7 (14.6%) were

immature and 2 (4.2%) were adults. However, sighting histories of 5 of the dead whales indicate that some were

small for their age, and histories of live whales further indicate that the population contains a greater percentage of

mature animals than is suggested by the stranded sample.

In their study of entanglement rates estimated from caudal peduncle scars, Robbins and Mattila (2001)

found that males were more likely to be entangled than females. The scarring data also suggested that yearlings

were more likely than other age classes to be involved in entanglements. Finally, female humpbacks showing

evidence of prior entanglements produced significantly fewer calves, suggesting that entanglement may significantly

impact reproductive success.

Humpback whale entanglements also occur in relatively high numbers in Canadian waters. Reports of

collisions with fixed fishing gear set for groundfish around Newfoundland averaged 365 annually from 1979 to 1987

(range 174-813). An average of 50 humpback whale entanglements (range 26-66) were reported annually between

1979 and 1988, and 12 of 66 humpback whales that were entangled in 1988 died (Lien et al. 1988). Volgenau et al.

(1995) also summarized existing data and concluded that in Newfoundland and Labrador, cod traps caused the most

entanglements and entanglement mortalities (21%) of humpbacks between 1979 and 1992. They also reported that
20

gillnets are the gear that has been the primary cause of entanglements and entanglement mortalities (20%) of

humpbacks in the Gulf of Maine between 1975 and 1990.

Fishery-Related Serious Injuries and Mortalities

 Two mortalities were observed in the pelagic drift gillnet fishery since 1989. In winter 1993, a juvenile

humpback was observed entangled dead in a pelagic drift gillnet along the 200 m isobath northeast of Cape Hatteras;

in early summer 1995, a humpback was entangled and dead in a pelagic drift gillnet on southwestern Georges Bank

(see below).

Additional reports of mortality and serious injury relevant to comparison to PBR, as well as description of

total human impacts, are contained in records maintained by the Northeast Regional Office/NMFS. A number of

these records (11 entanglements involving lobster gear) from the 1990-94 period were used in the 1997 List of

Fisheries classification (62 FR 33, Jan. 2, 1997). For this report, the records of dead, injured, and/or entangled

humpbacks (either found stranded or at sea) for the period 1996 through 2000 were reviewed. Out of 99 records,

over 80 were eliminated from further consideration due to an absence of any evidence of human impact or, in the

case of an entangled whale, it was documented that the animal had become disentangled. Of the remaining records,

the Gulf of Maine stock sustained 2 mortalities attributable to fishery interactions and 12 cases of serious injuries —

14 records in the five-year period (Table 2). In addition, 2 mortalities and 3 serious injuries were documented in the

southeastern and mid-Atlantic states that involved interactions with fisheries. At the time of this writing, no genetic

results were available to identify which of these cases may have involved whales from the Gulf of Maine stock.

While these records are not statistically quantifiable in the same way as the observed fishery records, they provide

some indication of the frequency of entanglements. 

Fishery Information

Data on current incidental takes in USA fisheries are available from several sources. In 1986, NMFS

established a mandatory self-reported fisheries information system for large pelagic fisheries. Data files are

maintained at the Southeast Fisheries Science Center (SEFSC). The Northeast Fisheries Science Center (NEFSC)

Sea Sampling Observer Program was initiated in 1989, and several fisheries have been covered by the program. In

late 1992 and in 1993, the SEFSC provided coverage of pelagic longline vessels fishing off the Grand Banks (Tail of

the Banks) and provides observer coverage of vessels fishing south of Cape Hatteras. Bycatch has been observed by

NMFS Sea Samplers in the pelagic drift gillnet fishery, but no mortalities or serious injuries have been documented

in the pelagic longline, pelagic pair trawl, or other fisheries monitored by NMFS. 

In January 1997 (62 FR 33, Jan. 2, 1997), NMFS changed the classification of the Gulf of Maine and USA

mid-Atlantic lobster pot fisheries from Category III to Category I based on examination of stranding and

entanglement records of large whales from 1990 to 1994 (including 11 serious injuries or mortalities of humpback

whales).

Pelagic Drift Gillnet

In 1996 and 1997, the NMFS issued management regulations which prohibited the operation of this fishery

in 1997. The fishery was active during 1998. Then, in January 1999 NMFS issued a Final Rule to prohibit the use of

drift net gear in the North Atlantic swordfish fishery (50 CFR Part 630). The estimated total number of hauls in the

Atlantic pelagic drift gillnet fishery increased from 714 in 1989 to 1,144 in 1990; thereafter, with the introduction of

quotas, effort was severely reduced. The estimated number of hauls in 1991, 1992, 1993, 1994, 1995 and 1996 were

233, 243, 232, 197, 164, and 149 respectively. Fifty-nine different vessels participated in this fishery at one time or

another between 1989 and 1993. In 1994 to 1998, there were 12, 11, 10, 0, and 11 vessels, respectively, in the

fishery . Observer coverage, expressed as percent of sets, was 8% in 1989, 6% in 1990, 20% in 1991, 40% in 1992,

42% in 1993, 87% in 1994, 99% in 1995, 64% in 1996, no fishery in 1997, and 99% coverage during 1998. 

Observer coverage dropped during 1996 because some vessels were deemed too small or unsafe by the contractor

that provided observer coverage to NMFS. Fishing effort was concentrated along the southern edge of Georges

Bank and off Cape Hatteras. Examination of the species composition of the catch and locations of the fishery

throughout the year, suggested that the drift gillnet fishery be stratified into two strata, a southern or winter stratum,

and a northern or summer stratum. Estimates of the total bycatch, for each year from 1989 to 1993, were obtained

using the aggregated (pooled 1989-1993) catch rates, by strata (Northridge 1996). Total annual bycatches after 1993

were estimated separately for each year by summing the observed caught with the product of the average bycatch per

haul and number of unobserved hauls as recorded in SEFSC logbooks. Variances were estimated using bootstrap 
21

re-sampling techniques. Estimated annual fishery-related mortality and serious injury (CV in parentheses) was 0 in

1994 (0), 1.0 in 1995 (0), 0 in 1996 (0), and 0 in 1998 (0). Since this fishery no longer exists, records of its

incidental takes have been excluded from Table 2. 

Table 2. Summarized records of mortality and serious injury likely to result in mortality, for North Atlantic 

humpback whales, January 1996 - December 2000. Causes of mortality or injury, assigned as primary or

secondary, are based on records maintained by NMFS/NER and NMFS/SER. Records counted as from the

Gulf of Maine humpback whale stock are indicated by an asterisk (*) following the date.

Date Report 

Type

Sex, age, ID

length

Location Assigned Cause:

P=primary,

S=secondary

Notes

Ship

strike

Entang./

Fsh.inter

1/30/96* serious

injury

juvenile Northern Edge

of Georges

Bank 

(42° 26'

 67° 30')

P gear wrapped on body, some

gear removed

2/22/96 serious

injury

length (est.)

= 8 m

Florida Keys P heavy line extending around

maximum girth, pinning both

pectorals; grooves/healed scars

on dorsal ridge and on leading

edge of both pectorals; fairly

emaciated; disentangled

4/2/96* mortality 7.2 m

female

Cape Story,

Virginia

Beach,

Virginia

P fresh dead; fractured left

mandible; emaciated

5/9/96 mortality 6.7 m

female

mouth of

Delaware Bay

P propeller cuts behind

blowhole, moderate

decomposition; ship strike

7/18/96* serious

injury

length (est.)

= 10 m

25 mi S of Bar

Harbor Maine

(44° 01'

 68° 00')

P disentanglement unsuccessful;

weighted gear wrapped around

tail stock; whale swimming

abnormally

10/7/96* serious

Injury

unknown Great South

Channel

(41° 04'

 69° 10')

P gear wrapped around tail and

trailing 30 m behind whale

10/18/96* serious

injury

unknown Great South

Channel

(41° 00'

69° 10')

P Whale entangled in steel cable

11/3/96 mortality 8.4 m male Carrituck,

North Carolina

P acute trauma to skull found by

necropsy
Date Report 

Type

Sex, age, ID

length

Location Assigned Cause:

P=primary,

S=secondary

Notes

Ship

strike

Entang./

Fsh.inter

22

12/10/97 mortality 9.0 m male Beaufort Inlet,

NC

P massive hemorrhage consistent

with forceful blunt trauma

3/4/98 mortality 8.6 m

female

Ocracoke

Island, NC 

(35° 12'

75° 40')

P Coast Guard present when

whale drowned entangled in

croaker gillnet gear

5/3/98* mortality 10.2 m male Cape Cod, MA P fresh entanglement lesions

around head and flippers

7/19/98* serious

injury

age and sex

unknown

Bay of Fundy,

Canada

P whale partially disentangled

from gillnet gear, but swam

away still badly wrapped

8/4/98* serious

injury

age and sex

unknown

Mount Desert

Rock (44° 06'

67° 44')

P line through mouth and several

wraps around tail with fresh

chaffing

8/23/98* serious

injury

adult, sex

unknown

Montauk Pt.,

NY

(40° 36'

70° 43')

P whale anchored by offshore

lobster gear, struggling to

breathe; not relocated by Coast

Guard search

11/5/98 mortality 8.9 m male Nags Head,

NC (35° 59'

75° 38')

P Deep abrasions around tail

stock with subdermal

hemorrhaging

1/12/99* mortality 9.7m male Martha’s

Vineyard, MA

P Fresh and extensive rope

marks on carcass with

associated hemorrhaging

8/2/99* serious

injury

9.4m

estimated

Bay of Fundy,

Canada

P Single wrap of 1⁄2 inch poly

line pinning flippers

9/23/99* serious

injury

unknown off Chatham,

MA

P Line out of mouth and several

wraps around body; possibly

anchored

1/8/00 serious

injury

9.9

estimated

30mi east

Cape Lookout,

NC

P whale swam off with 600' of

sea trout sink gillnet, a chain

anchor and a high flyer in tow

8/4/00* serious

injury

10.7

estimated

Bay of Fundy,

Canada

P gillnet wrapped on head with 

weighted trailing line giving

tension
Date Report 

Type

Sex, age, ID

length

Location Assigned Cause:

P=primary,

S=secondary

Notes

Ship

strike

Entang./

Fsh.inter

23

9/6/00* serious

injury

<1 y.o., calf

of “Giraffe”

Stellwagen

Bank, MA

P single line wrapped across

back; constriction will increase

as whale grows

10/14/00 serious

injury

9.9m

estimated

off Ocean City

Inlet, MD

P Heavily entangled in line and

netting; constrictive--fresh

wounds noted

10/20/00* serious

injury

10 y.o. male

“Tribble”

Stellwagen

Bank, MA

P Entangled in green poly line on

multiple body parts; appears

constrictive

Table notes:

1. The date sighted and location provided in the table are not necessarily when or where the serious injury or

mortality occurred; rather, this information indicates when and where the whale was first reported beached,

entangled, or injured. 

2. National guidelines for determining what constitutes a serious injury have not been finalized. Interim

criteria as established by NERO/NMFS (62 FR 33, Jan. 2, 1997) have been used here. Some assignments

may change as new information becomes available and/or when national standards are established.

3. Assigned cause based on best judgement of available data. Additional information may result in revisions.

4. Entanglements of juvenile whales may become more serious as the whale grows.

Other Mortality

Between November 1987 and January 1988, 14 humpback whales died after consuming Atlantic mackerel

containing a dinoflagellate saxitoxin (Geraci et al. 1989). The whales subsequently stranded or were recovered in

the vicinity of Cape Cod Bay and Nantucket Sound, and it is highly likely that other mortalities occurred during this

event which went unrecorded. During the first six months of 1990, seven dead juvenile (7.6 to 9.1 m long)

humpback whales stranded between North Carolina and New Jersey. The significance of these strandings is

unknown, but is a cause for some concern.

As reported by Wiley et al. (1995), injuries possibly attributable to ship strikes are more common and

probably more serious than those from entanglements. In the NER/NMFS records for 1996 through 2000, 8 records

had some evidence of a collision with a vessel. Of these, 4 were mortalities as a result of the collision, 3 did not

have sufficient information to confirm the collision as the cause of death, and for 1, the seriousness of the injury

could not be assessed. This last record involved a whale watch vessel that collided with a humpback on 8/2/98. The

whale was sighted after the collision with a large gash in its back, but was reported as “not struggling to breathe”. It

was seen in the company of other humpbacks several times over three weeks following the incident, but has not been

seen since. It is the only member of its cohort to not be resighted. Only one case of a mortality from a vessel

collision involved a whale identified as a member of the Gulf of Maine stock (on 4/2/96; see Table 2).

In 2001, a total of 20 humpback whale mortalities were reported. Three of the carcasses had indications of

a collision with a vessel, and 3 others showed signs of entanglement. Also in 2001, 7 entanglements and 2 vessel

collisions were reported. In 2002, 7 mortalities and 7 entanglements involving humpbacks had been reported at the

time of this writing. A comprehensive review of all available information pertaining to these reports has not been

completed, and therefore determinations of the total levels of anthropogenic mortality and serious injury for these

years have yet to be done.
24

STATUS OF STOCK

The status of the North Atlantic humpback whale population was the topic of an International Whaling

Commission Comprehensive Assessment in June 2001; this meeting conducted a detailed review of all aspects of this 

population (IWC 2002). Although the most recent estimates of abundance indicate continued population growth, the 

size of the humpback whale stock may be below OSP in the US Atlantic EEZ. This is a strategic stock because the 

humpback whale is listed as an endangered species under the ESA. A Recovery Plan has been published and is in 

effect (NMFS 1991). There are insufficient data to reliably determine population trends for humpback whales in the 

North Atlantic overall. The average annual rate of population increase was estimated at 3.2% (SE=0.005, Stevick et 

al. 2001). As noted above, a recent analysis of demographic parameters for the Gulf of Maine (Clapham et al. 2001a) 

suggested a lower rate of increase than the 6.5% reported by Barlow and Clapham (1997), but results may have been 

confounded by distribution shifts. The total level of human-caused mortality and serious injury is not less than 10% of 

the calculated PBR and, therefore, cannot be considered to be insignificant and approaching zero mortality and 

serious injury rate. In particular, the continued high level of mortality among humpback whales off the U.S. midAtlantic states (Barco et al.. 2001), is cause for considerable concern given that at least some of these animals are 

known to be from the Gulf of Maine. This is a strategic stock because the average annual fishery- related mortality and 

serious injury exceeds PBR, and because the North Atlantic humpback whale is an endangered species. 

Disturbance by whalewatching may prove to be an important habitat issue in some areas of this

population’s range, notably the coastal waters of New England where the density of whalewatching traffic is

seasonally high. No studies have been conducted to address this question, and its impact (if any) on habitat

occupancy and reproductive success is unknown.

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27

Figure 1. Distribution of fin whale sightings from

NEFSC and SEFSC shipboard and aerial surveys during

the summer in 1990-1998. Isobaths are at 100 m and

1,000 m. 

January 2002

FIN WHALE (Balaenoptera physalus):

Western North Atlantic Stock

STOCK DEFINITION AND GEOGRAPHIC RANGE

The Scientific Committee of the International Whaling Commission (IWC) has proposed stock boundaries

for North Atlantic fin whales. Fin whales off the eastern USA, north to Nova Scotia and on to the southeastern coast

of Newfoundland are believed to constitute a single

stock under the present IWC scheme (Donovan

1991). However, the stock identity of North Atlantic

fin whales has received relatively little attention, and

whether the current stock boundaries define

biologically isolated units has long been uncertain. 

The existence of a subpopulation structure was

suggested by local depletions that resulted from

commercial overharvesting (Mizroch et al. 1984).

A genetic study conducted by Bérubé et al.

(1998) using both mitochondrial and nuclear DNA

provided strong support for an earlier population

model proposed by Kellogg (1929) and others. This

postulates the existence of several subpopulations of

fin whales in the North Atlantic and Mediterranean,

with limited gene flow among them. Bérubé et al.

(1998) also proposed that the North Atlantic

population showed recent divergence due to climatic

changes (i.e. postglacial expansion), as well as

substructuring over even relatively short distances. 

The genetic data are consistent with the idea that

different subpopulations use the same feeding

ground, a hypothesis that was also originally

proposed by Kellogg (1929).

Fin whales are common in waters of the US

Atlantic Exclusive Economic Zone (EEZ), principally

from Cape Hatteras northward (Figure 1). Fin whales

accounted for 46% of the large whales and 24% of all

cetaceans sighted over the continental shelf during

aerial surveys (CETAP 1982) between Cape Hatteras

and Nova Scotia during 1978-82. While a great deal

remains unknown, the magnitude of the ecological

role of the fin whale is impressive. In this region fin

whales are probably the dominant large cetacean species in all seasons, with the largest standing stock, the largest

food requirements, and therefore the largest impact on the ecosystem of any cetacean species (Kenney et al. 1997;

Hain et al. 1993).

 There is little doubt that New England waters represent a major feeding ground for the fin whale. There is

evidence of site fidelity by females, and perhaps some segregation by sexual, maturational or reproductive class on

the feeding range (Agler et al. 1993). Seipt et al. (1990) reported that 49% of identified fin whales on Massachusetts

Bay area feeding grounds were resighted within the same year, and 45% were resighted in multiple years. While

recognizing localized as well as more extensive movements, these authors suggested that fin whales on these

grounds exhibited patterns of seasonal occurrence and annual return that are in some respects similar to those shown

for humpback whales. This was reinforced by Clapham and Seipt (1991), who showed maternally directed site

fidelity by fin whales in the Gulf of Maine. Information on life history and vital rates is also available in data from

the
28

Canadian fishery, 1965-1971 (Mitchell 1974). In seven years, 3,528 fin whales were taken at three whaling stations. 

The station at Blandford, Nova Scotia, took 1,402 fin whales. 

Hain et al. (1993), based on an analysis of neonate stranding data, suggested that calving takes place during

approximately four months from October to January in latitudes of the US mid-Atlantic region; however, it is

unknown where calving, mating, and wintering for most of the population occurs. Results from the Navy's SOSUS

program (Clark 1995) indicate a substantial deep-ocean component to fin whale distribution. It is likely that fin

whales occurring in the US Atlantic EEZ undergo migrations into Canadian waters, open-ocean areas, and perhaps

even subtropical or tropical regions. However, the popular notion that entire fin whale populations make distinct

annual migrations like some other mysticetes has questionable support in the data; in the North Pacific, year-round

monitoring of fin whale calls found no evidence for large-scale migratory movements (Watkins et al. 2000).

POPULATION SIZE

Two estimates of abundance from line transect surveys are available. An abundance of 2,200 (CV=0.24)

fin whales was estimated from a July to September 1995 sighting survey conducted by two ships and an airplane that

covered waters from Virginia to the mouth of the Gulf of St. Lawrence. Total track line length was 32,600 km. The

ships covered waters between the 50- and 1000-fathom isobaths, the northern edge of the Gulf Stream, and the

northern Gulf of Maine/Bay of Fundy region. The airplane covered waters in the mid-Atlantic from the coastline to

the 50-fathom isobath, the southern Gulf of Maine, and shelf waters off Nova Scotia from the coastline to the 1000-

fathom isobath. Data collection and analysis methods used were described in Palka (1995).

A more recent estimate of 2,814 (CV=0.21) fin whales was derived from a 28 July to 31 August 1999 linetransect sighting survey conducted by a ship and airplane covering waters from Georges Bank to the mouth of the

Gulf of St. Lawrence. Total track line length was 8,212 km. Similar to that used in the above 1995 Virginia to Gulf

of St. Lawrence survey, shipboard data were analyzed using the modified direct duplicate method (Palka 1995) that

accounts for school size bias and g(0), the probability of detecting a group on the track line. Aerial data were not

corrected for g(0) (Palka 2000).

The latter abundance estimate is considered the best available for the western North Atlantic fin whale

because it is relatively recent . However, this estimate must be considered extremely conservative in view of the

known range of the fin whale in the entire western North Atlantic, and uncertainties regarding population structure

and exchange between surveyed and unsurveyed areas.

Minimum Population Estimate

The minimum population estimate is the lower limit of the two-tailed 60% confidence interval of the lognormally distributed best abundance estimate. This is equivalent to the 20th percentile of the log-normal distribution

as specified by Wade and Angliss (1997). The best estimate of abundance for fin whales is 2,814 (CV=0.21). The

minimum population estimate for the western North Atlantic fin whale is 2,362.

Current Population Trend

There are insufficient data to determine population trends for this species. Even at a conservatively

estimated rate of increase, however, the numbers of fin whales may have increased substantially in recent years

(Hain et al. 1993).

CURRENT AND MAXIMUM NET PRODUCTIVITY RATES

Current and maximum net productivity rates are unknown for this stock. Based on photographically

identified fin whales, Agler et al. (1993) estimated that the gross annual reproduction rate was at 8%, with a mean

calving interval of 2.7 years.

For purposes of this assessment, the maximum net productivity rate was assumed to be 0.04. This value is

based on theoretical modeling showing that cetacean populations may not grow at rates much greater than 4% given

the constraints of their reproductive life history (Barlow et al. 1995). 

POTENTIAL BIOLOGICAL REMOVAL

Potential Biological Removal (PBR) is the product of minimum population size, one-half the maximum

productivity rate, and a “recovery” factor (MMPA Sec. 3. 16 U.S.C. 1362; Wade and Angliss 1997). The minimum

population size is 2,362. The maximum productivity rate is 0.04, the default value for cetaceans. The “recovery”
29

factor, which accounts for endangered, depleted, threatened stocks, or stocks of unknown status relative to optimum

sustainable population (OSP) is assumed to be 0.10 because the fin whale is listed as endangered under the

Endangered Species Act (ESA). PBR for the western North Atlantic fin whale is 4.7.

ANNUAL HUMAN-CAUSED MORTALITY AND SERIOUS INJURY

The number of fin whales taken at three whaling stations in Canada from 1965 to 1971 totaled 3,528 whales

(Mitchell 1974). Reports of non-directed takes of fin whales are fewer over the last two decades than for other

endangered large whales such as right and humpback whales. There was no reported fishery-related mortality or

serious injury to fin whales in fisheries observed by NMFS during 1995 through 1999. A review of NER/NMFS

anecdotal records from 1996 through 2000 yielded an average of 1.6 human caused mortalities per year– 0.4 per year

resulting from fishery interactions/entanglements (USA waters, 0.2; Canadian waters, 0.2), and 1.2 due to vessel

collisions--all in USA waters (Table 1.). 

Fishery-Related Serious Injury and Mortality 

No confirmed fishery-related mortality or serious injury of fin whales was reported in the Sea Sampling

bycatch database; therefore, no detailed fishery information is presented here. A review of the records of stranded, 

floating or injured fin whales for the period 1996 through 2000 on file at NER/NMFS found two records with

substantial evidence of fishery interactions causing mortality or serious injury (Table 1.). There was a live fin whale

sighted entangled on 6/24/97 with line wrapped over its back. The animal appeared emaciated, and scarring visible

on the leading edge of the dorsal fin and the whale’s left flank suggests this was a prolonged entanglement. Whether

the entanglement initiated the whale’s decline in health is unclear, but the chronic stress of the entanglement is likely

lethal given the whale’s depressed condition. 

 The two substantiated records provide a minimum annual rate of serious injury and mortality of 0.4 fin

whales from fishery interactions. While these records are not statistically quantifiable in the same way as the

observed fishery records, they give a minimum estimate of the frequency of entanglements for this species. In

addition to the records above, there are five records within the period that lacked substantial evidence of the severity

of the entanglement for a serious injury determination, or that did not provide the detail necessary to determine if an

entanglement had been a contributing factor in the mortality.
30

Table 1. Summarized records of mortality and serious injury likely to result in mortality, Western North Atlantic fin

whale stock, January 1996 - December 2000. Causes of mortality or injury, assigned as primary or

secondary, are based on records maintained by NMFS/NER and NMFS/SER

Date Report 

Type

Sex, age, ID

length

Location Assigned Cause:

P=primary,

S=secondary

Notes

Ship

strike

Entang./

Fsh.inter

12/20/96 mortality 14.0 m male Savannah,

GA

P hematoma and broken ribs on

right side

6/24/97 serious

injury

unknown 20 mi east

Nantucket

Island, MA

P line wrapped over back; whale

emaciated; scarring indicative

of prolonged entanglement

8/4/97 mortality 16.8 m female Eastham,

MA

P exhumed skeleton with broken

jaw, cracked scapula partially

healed

3/21/98 mortality 16.9 m female Salvo

County, NC

P large hematoma, disarticulated

spine and numerous broken

vertebrae

9/28/98 mortality unknown Digby Neck,

Nova Scotia

P gear wrapped through mouth

and ten wraps on tail stock

2/10/99 mortality 15.5 m male Virginia

Beach, VA

P large external wound,

extensive fractures to vertebral

column, hemorrhaging

11/5/99 mortality 16.2 m male Elizabeth,

NJ

P large wound anterior of the

blowhole, severed left flipper,

shattered bones

12/11/00 mortality 10.9 m female New York

harbor

P hemorrhage and fractured

bones on right side

Table notes:

1. The date sighted and location provided in the table are not necessarily when or where the serious injury or

mortality occurred; rather, this information indicates when and where the whale was first reported beached,

entangled, or injured. 

2. National guidelines for determining what constitutes a serious injury have not been finalized. Interim

criteria as established by NERO/NMFS (62 FR 33, Jan. 2, 1997) have been used here. Some assignments

may change as new information becomes available and/or when national standards are established.

3. Assigned cause based on best judgement of available data. Additional information may result in revisions.

Other Mortality

After reviewing NER/NMFS records for 1996 through 2000, six were found that had sufficient information

to confirm the cause of death as collisions with vessels (Table 1). One record (8/4/97) had been omitted from

previous reports, but is inserted here following an examination of the exhumed skeletal remains which found a

broken jaw and cracked scapula which had partially healed. The partial healing indicates the whale was alive at the

time of the incident. 
31

The above records constitute an annual rate of serious injury or mortality of 1.2 fin whales from collisions

with vessels. NMFS/NER data holdings include five additional records of fin whale collisions with vessels, but the

available supporting documentation was not conclusive as to whether these constituted serious injury or were the

proximal cause of the mortality. Continuing follow-up efforts may yield additional confirmed events from these

records.

STATUS OF STOCK

 The status of this stock relative to OSP in the US Atlantic EEZ is unknown, but the species is listed as

endangered under the ESA. There are insufficient data to determine the population trend for fin whales. The total

level of human-caused mortality and serious injury is unknown. The records on hand at NER/NMFS represent

coverage of only a portion of the area surveyed for the population estimate for the stock. Despite this, the total

fishery-related mortality and serious injury for this stock is not less than 10% of the calculated PBR and, therefore,

cannot be considered to be insignificant and approaching a zero mortality and serious injury rate. This is a strategic

stock because the fin whale is listed as an endangered species under the ESA. A Recovery Plan for fin whales has 

been prepared and is currently awaiting legal clearance.

REFERENCES

Agler, B. A., R. L. Schooley, S. E. Frohock, S. K. Katona, and I. E. Seipt. 1993. Reproduction of photographically

identified fin whales, Balaenoptera physalus, from the Gulf of Maine. J. Mamm. 74(3): 577-587.

Barlow, J., S. L. Swartz, T. C. Eagle, and P. R. Wade. 1995. U.S. Marine Mammal Stock Assessments: Guidelines

for preparation, background, and a summary of the 1995 assessments. NOAA Technical Memorandum

NMFS-OPR-6. U.S. Department of Commerce, Washington, DC. 73 pp.

Bérubé, M., A. Aguilar, D. Dendanto, F. Larsen, G. Notarbartolo di Sciara, R. Sears, J. Sigurjónsson, J. Urban-R.

and P. J. Palsbøll. 1998. Population genetic structure of North Atlantic, Mediterranean and Sea of Cortez

fin whales, Balaenoptera physalus (Linnaeus 1758): analysis of mitochondrial and nuclear loci. Mol. Ecol.

15: 585-599.

CETAP. 1982. A characterization of marine mammals and turtles in the Mid- and north Atlantic areas of the U.S.

outer continental shelf. Cetacean and Turtle Assessment Program, University of Rhode Island. Final

Report #AA551-CT8-48 to the Bureau of Land Management, Washington, DC, 538 pp.

Clapham, P. J. and I. E. Seipt. 1991. Resightings of independent fin whales, Balaenoptera physalus, on maternal

summer ranges. J. Mamm. 72: 788-790.

Clark, C. W. 1995. Application of U.S. Navy underwater hydrophone arrays for scientific research on whales. Rep.

int. Whal. Commn. 45: 210-212.

Donovan, G. P. 1991. A review of IWC stock boundaries. Rep. int. Whal. Commn. Special Issue 13: 39-68. 

Hain, J. H. W., M. J. Ratnaswamy, R. D. Kenney, and H. E. Winn. 1993. The fin whale, Balaenoptera physalus, in

waters of the northeastern United States continental shelf. Rep. int. Whal. Commn. 42: 653-669. 

Kellogg, R. 1929. What is known of the migration of some of the whalebone whales. Ann. Rep. Smithsonian Inst.

1928: 467-494.

Kenney, R. D., G. P. Scott, T. J. Thompson, and H. E. Winn. 1997. Estimates of prey consumption and trophic

impacts of cetaceans in the USA northeast continental shelf ecosystem. J. Northw. Atl. Fish. Sci. 22: 155-

171.

Mizroch, A. A., D. W. Rice and J. M. Breiwick. 1984. The fin whale, Balaenoptera physalus. Mar. Fisheries Rev.

46: 20-24.

Mitchell, E. 1974. Present status of Northwest Atlantic fin and other whale stocks. Pages 109-169. In: W. E.

Schevill (ed), The whale problem: A status report. Harvard University Press, Cambridge, Massachusetts,

419 pp.

Palka, D. 1995. Abundance estimate of the Gulf of Maine harbor porpoise. Rep. int. Whal. Commn. Special Issue

16: 27-50. 

Palka, D. 2000. Abundance of the Gulf of Maine/Bay of Fundy harbor porpoise based on shipboard and aerial

surveys during 1999. NOAA/NMFS/NEFSC Ref. Doc. 00-07; 29 pp. Available from: National Marine

Fisheries Service, 166 Water Street, Woods Hole, MA 02543-1026.
32

Seipt, I. E., P. J. Clapham, C. A. Mayo and M. P. Hawvermale. 1990. Population characteristics of individually

identified fin whales, Balaenoptera physalus, in Massachusetts Bay. Fish. Bull., U.S. 88(2): 271-278

Wade, P. R. and R. P. Angliss. 1997. Guidelines for assessing marine mammal stocks: Report of the GAMMS

Workshop, April 3-5, 1996, Seattle, Washington. NOAA Technical Memorandum NMFS-OPR-12. U.S.

Dept. of Commerce, Washington, DC. 93 pp. 

Watkins, W.A., M.A. Daher, G.M. Reppucci, J.E. George, D.L. Martin, N.A. DiMarzio and D.P. Gannon. 2000. 

Seasonality and distribution of whale calls in the North Pacific. Oceanography 13: 62-67.
33

January 2002

SEI WHALE (Balaenoptera borealis):

Nova Scotia Stock

STOCK DEFINITION AND GEOGRAPHIC RANGE

Indications are that, at least during the feeding season, a major portion of the sei whale population is

centered in northerly waters, perhaps on the Scotian Shelf (Mitchell and Chapman 1977). The southern portion of

the species' range during spring and summer includes the northern portions of the US Atlantic Exclusive Economic

Zone (EEZ) — the Gulf of Maine and Georges Bank. The period of greatest abundance there is in spring, with

sightings concentrated along the eastern margin of Georges Bank and into the Northeast Channel area, and along the

southwestern edge of Georges Bank in the area of Hydrographer Canyon (CETAP 1982). NMFS aerial surveys in

1999, 2000 and 2001 found concentrations of sei and right whales along the Northern Edge of Georges Bank in the

spring. The sei whale is often found in the deeper waters characteristic of the continental shelf edge region (Hain et

al. 1985), and NMFS aerial surveys found substantial numbers of sei whales in this region, south of Nantucket, in

the spring of 2001. Similarly, Mitchell (1975) reported that sei whales off Nova Scotia were often distributed closer

to the 2,000 m depth contour than were fin whales. 

This general offshore pattern of sei whale distribution is disrupted during episodic incursions into more

shallow and inshore waters. Although known to take piscine prey, sei whales (like right whales) are largely

planktivorous, feeding primarily on euphausiids and copepods. In years of reduced predation on copepods by other

predators, and thus greater abundance of this prey source, sei whales are reported in more inshore locations, such as

the Great South Channel (in 1987 and 1989) and Stellwagen Bank (in 1986) areas (R.D. Kenney, pers. comm.;

Payne et al. 1990). An influx of sei whales into the southern Gulf of Maine occurred in the summer of 1986

(Schilling et al. 1993). Such episodes, often punctuated by years or even decades of absence from an area, have

been reported for sei whales from various places worldwide.

Based on analysis of records from the Blandford, Nova Scotia, whaling station, where 825 sei whales were

taken between 1965 and 1972, Mitchell (1975) described two "runs" of sei whales, in June-July and in SeptemberOctober. He speculated that the sei whale population migrates from south of Cape Cod and along the coast of

eastern Canada in June and July, and returns on a southward migration again in September and October; however,

such a migration remains unverified.

Mitchell and Chapman (1977) reviewed the sparse evidence on stock identity of northwest Atlantic sei

whales, and suggested two stocks — a Nova Scotia stock and a Labrador Sea stock. The Nova Scotia stock includes

the continental shelf waters of the northeastern USA, and extends northeastward to south of Newfoundland. The

Scientific Committee of the IWC, while adopting these general boundaries, noted that the stock identity of sei

whales (and indeed all North Atlantic whales) was a major research problem (Donovan 1991). In the absence of

evidence to the contrary, the proposed IWC stock definition is provisionally adopted, and the “Nova Scotia stock” is

used here as the management unit for this stock assessment. The IWC boundaries for this stock are from the USA

east coast to Cape Breton, Nova Scotia, thence east to longitude 42o

 W.

POPULATION SIZE

The total number of sei whales in the US Atlantic EEZ is unknown. However, two abundance estimates are

available for portions of the sei whale habitat (Table 1): from Nova Scotia during the 1970's, and in the US Atlantic

EEZ during the springs of 1979-81.

Mitchell and Chapman (1977), based on tag-recapture data, estimated the Nova Scotia, Canada, stock to

contain between 1,393 and 2,248 sei whales (Table 1). Based on census data, they estimated a minimum Nova

Scotian population of 870 sei whales. 

An abundance of 253 sei whales (CV=0.63) was estimated from an aerial survey program conducted from

1978 to 1982 on the continental shelf and shelf edge waters between Cape Hatteras, North Carolina and Nova Scotia

(Table 1; CETAP 1982). The estimate is based on data collected during the spring when the greatest proportion of

the population off the northeast USA coast appeared in the study area. This estimate does not include a correction for

dive-time or g(0), the probability of detecting an animal group on the track line. The CETAP report suggested,

however, that correcting the estimated abundance for dive time would increase the estimate to approximately the

same as Mitchell and Chapman’s (1977) tag-recapture estimate. This estimate is almost 20 years out of date and

thus
34

almost certainly does not reflect the current true population size; in addition, the estimate has a high degree of

uncertainty (i.e., it has a large CV), and it was estimated just after cessation of extensive foreign fishing operations

in the region. There are no recent abundance estimates for the sei whale.

Table 1. Summary of abundance estimates for the Nova Scotia stock of the sei whale. Month, year, and area

covered during each abundance survey, and resulting abundance estimate (Nbest) and coefficient of variation

(CV). 

Month/Year Area Nbest CV

1966 - 1972 Nova Scotia,

Canada 1,393 to 2,248 None reported

spring 1978-82 Cape Hatteras, NC

to Nova Scotia 253 0.63

Minimum Population Estimate

The minimum population estimate is the lower limit of the two-tailed 60% confidence interval of the lognormally distributed best abundance estimate. This is equivalent to the 20th percentile of the log-normal distribution

as specified by Wade and Angliss (1997). A current minimum population size cannot be estimated because there are

no current abundance estimates (within the last 10 years). 

Current Population Trend

There are insufficient data to determine the population trends for this species. 

CURRENT AND MAXIMUM NET PRODUCTIVITY RATES

Current and maximum net productivity rates are unknown for this stock. For purposes of this assessment,

the maximum net productivity rate was assumed to be 0.04. This value is based on theoretical modeling showing

that cetacean populations may not grow at rates much greater than 4% given the constraints of their reproductive life

history (Barlow et al. 1995).

POTENTIAL BIOLOGICAL REMOVAL

Potential Biological Removal (PBR) is the product of minimum population size, one-half the maximum

productivity rate, and a “recovery” factor (MMPA Sec. 3. 16 U.S.C. 1362; Wade and Angliss 1997). The minimum

population size is unknown. The maximum productivity rate is 0.04, the default value for cetaceans. The

“recovery” factor, which accounts for endangered, depleted, threatened stocks, or stocks of unknown status relative

to optimum sustainable population (OSP) is assumed to be 0.10 because the sei whale is listed as endangered under

the Endangered Species Act (ESA). PBR for the Nova Scotia stock of the sei whale is unknown because the

minimum population size is unknown.

ANNUAL HUMAN-CAUSED MORTALITY AND SERIOUS INJURY

There are few if any data on fishery interactions or human impacts. There was no reported fishery-related

mortality or serious injury to sei whales in fisheries observed by NMFS during 1994-1998. There are no reports of

mortality, entanglement, or injury in the NEFSC or NE Regional Office databases; however, there is a report of a

ship strike. The New England Aquarium documented a sei whale carcass hung on the bow of a container ship as it

docked in Boston on November 17, 1994.

Fishery Information

There have been no reported entanglements or other interactions between sei whales and commercial

fishing activities; therefore there are no descriptions of fisheries.

STATUS OF STOCK

The status of this stock relative to OSP in the US Atlantic EEZ is unknown, but the species is listed as

endangered under the ESA. There are insufficient data to determine the population trends for sei whales. The total
35

level of human-caused mortality and serious injury is unknown, but the rarity of mortality reports for this species

suggests that this level is insignificant and approaching a zero mortality and serious injury rate. This is a strategic

stock because the sei whale is listed as an endangered species under the ESA. A Recovery Plan for sei whales has

been written and is awaiting legal clearance.

REFERENCES

Barlow, J., S. L. Swartz, T. C. Eagle and P. R. Wade. 1995. U.S. Marine Mammal Stock Assessments: Guidelines

for preparation, background, and a summary of the 1995 assessments. NOAA Technical Memorandum

NMFS-OPR-6. U.S. Department of Commerce, Washington, DC. 73 pp.

CETAP. 1982. A characterization of marine mammals and turtles in the mid- and north Atlantic areas of the U.S.

outer continental shelf. Cetacean and Turtle Assessment Program, University of Rhode Island. Final

Report #AA551-CT8-48 to the Bureau of Land Management, Washington, DC, 538 pp. 

Donovan, G. P. 1991. A review of IWC stock boundaries. Rep. int. Whal. Commn. Special Issue 13: 39-68. 

Hain, J. H. W., M. A. M. Hyman, R. D. Kenney and H. E. Winn. 1985. The role of cetaceans in the shelf-edge

region of the northeastern United States. Mar. Fish. Rev. 47(1): 13-17. 

Mitchell, E. 1975. Preliminary report on Nova Scotia fishery for sei whales (Balaenoptera borealis). Rep. int.

Whal. Commn. 25: 218-225. 

Mitchell, E. and D. G. Chapman. 1977. Preliminary assessment of stocks of northwest Atlantic sei whales

(Balaenoptera borealis). Rep. int. Whal. Commn. Special Issue 1: 117-120.

Payne, P. M., D. N. Wiley, S. B. Young, S. Pittman, P. J. Clapham and J. W. Jossi. 1990. Recent fluctuations in the

abundance of baleen whales in the southern Gulf of Maine in relation to changes in selected prey. Fish.

Bull., U.S. 88: 687-696. 

Schilling, M. R., I. Seipt, M. T. Weinrich, S. E. Frohock, A. E. Kuhlberg and P. J. Clapham. 1993. Behavior of

individually identified sei whales, Balaenoptera borealis, during an episodic influx into the southern Gulf

of Maine in 1986. Fish. Bull., U.S. 90(4): 749-755. 

Wade, P. R. and R. P. Angliss. 1997. Guidelines for assessing marine mammal stocks: Report of the GAMMS

Workshop, April 3-5, 1996, Seattle, Washington. NOAA Technical Memorandum NMFS-OPR-12. U.S.

Dept. of Commerce, Washington, DC. 93 pp.
36

January 2002

BLUE WHALE (Balaenoptera musculus):

Western North Atlantic Stock

STOCK DEFINITION AND GEOGRAPHIC RANGE

The distribution of the blue whale, Balaenoptera musculus, in the western North Atlantic generally extends

from the Arctic to at least mid-latitude waters. Blue whales are most frequently sighted in the waters off eastern

Canada, with the majority of recent records from the Gulf of St. Lawrence (Sears et al. 1987). The species was

hunted around Newfoundland in the first half of the 20th century (Sergeant 1966). The present Canadian

distribution, broadly described, is spring, summer, and fall in the Gulf of St. Lawrence, especially along the north

shore from the St. Lawrence River estuary to the Strait of Belle Isle and off eastern Nova Scotia. The species occurs

in winter off southern Newfoundland and also in summer in Davis Strait (Mansfield 1985). Individual identification

has confirmed the movement of a blue whale between the Gulf of St. Lawrence and western Greenland (R. Sears and

F. Larsen, unpublished data), although the extent of exchange between these two areas remains unknown. Similarly,

a blue whale photographed by a NMFS large whale survey in August 1999 had previously been observed in the Gulf

of St. Lawrence in 1985 (R. Sears and P. Clapham, unpublished data).

The blue whale is best considered as an occasional visitor in US Atlantic Exclusive Economic Zone (EEZ)

waters, which may represent the current southern limit of its feeding range (CETAP 1982; Wenzel et al. 1988). All

of the five sightings described in the foregoing two references were in August. Yochem and Leatherwood (1985)

summarized records that suggested an occurrence of this species south to Florida and the Gulf of Mexico, although

the actual southern limit of the species’ range is unknown. 

Using the U.S. Navy’s SOSUS program, blue whales have been detected and tracked acoustically in much

of the North Atlantic, including in subtropical waters north of the West Indies and in deep water east of the US

Atlantic EEZ (Clark 1995). Most of the acoustic detections were around the Grand Banks area of Newfoundland

and west of the British Isles. Sigurjónsson and Gunnlaugsson (1990) note that North Atlantic blue whales appear to

have been depleted by commercial whaling to such an extent that they remain rare in some formerly important

habitats, notably in the northern and northeastern North Atlantic.

POPULATION SIZE

Little is known about the population size of blue whales except for in the Gulf of St. Lawrence area. Here,

308 individuals have been catalogued (Sears et al. 1987), but the data were deemed to be unusable for abundance

estimation (Hammond et al. 1990). Mitchell (1974) estimated that the blue whale population in the western North

Atlantic may number only in the low hundreds. R. Sears (pers. comm.) suggests that no present evidence exists to

refute this estimate. 

Minimum Population Estimate

The 308 recognizable individuals from the Gulf of St. Lawrence area which were catalogued by Sears et al.

(1987) is considered to be a minimum population estimate for the western North Atlantic stock. 

Current Population Trend

There are insufficient data to determine population trends for this species. Off western and southwestern

Iceland, an increasing trend of 4.9% a year was reported for the period 1969-1988 (Sigurjónsson and Gunnlaugsson

1990), although this estimate should be treated with caution given the effort biases underlying the sightings data on

which it was based.

CURRENT AND MAXIMUM NET PRODUCTIVITY RATES

Current and maximum net productivity rates are unknown for this stock. For purposes of this assessment,

the maximum net productivity rate was assumed to be 0.04. This value is based on theoretical modeling showing

that cetacean populations may not grow at rates much greater than 4% given the constraints of their reproductive life

history (Barlow et al. 1995). 
37

POTENTIAL BIOLOGICAL REMOVAL

Potential Biological Removal (PBR) is the product of minimum population size, one-half the maximum

productivity rate, and a “recovery” factor (MMPA Sec. 3. 16 U.S.C. 1362; Wade and Angliss 1997). The minimum

population size is 308. The maximum productivity rate is 0.04, the default value for cetaceans. The “recovery”

factor, which accounts for endangered, depleted, threatened stocks, or stocks of unknown status relative to optimum

sustainable population (OSP) is assumed to be 0.10 because the blue whale is listed as endangered under the

Endangered Species Act (ESA). However, the minimum population size figure given above is now 14 years old and

thus is not usable for the calculation of PBR (see Wade and Angliss 1997). Consequently, no PBR can be calculated

for this stock because of lack of any data on current minimum population size.

ANNUAL HUMAN-CAUSED MORTALITY AND SERIOUS INJURY

There are no confirmed records of mortality or serious injury to blue whales in the US Atlantic EEZ. 

However, in March 1998 a dead 20 m (66ft) male blue whale was brought into Rhode Island waters on the bow of a

tanker. The cause of death was determined to be ship strike. Although it appears likely that the vessel concerned

was responsible, the necropsy revealed some injuries that were difficult to explain in this context. The location of

the strike was not determined; given the known rarity of blue whales in US Atlantic waters, and the vessel’s port of

origin (Antwerp), it seems reasonable to suppose that the whale died somewhere to the north of the US Atlantic

EEZ. However, this incident was used in calculating the total annual mortality rate of 0.2 (Table 1 on page 2).

Fishery Information

No fishery information is presented because there are no observed fishery-related mortalities or serious

injury.

STATUS OF STOCK

The status of this stock relative to OSP in the US Atlantic EEZ is unknown, but the species is listed as

endangered under the ESA. There are insufficient data to determine population trends for blue whales. The total

level of human-caused mortality and serious injury is unknown, but it is believed to be insignificant and approaching

a zero mortality and serious injury rate. This is a strategic stock because the blue whale is listed as an endangered

species under the ESA. A Recovery Plan has been published (Reeves et al. 1998) and is in effect.

REFERENCES

Barlow, J., S. L. Swartz, T. C. Eagle and P. R. Wade. 1995. U.S. Marine Mammal Stock Assessments: Guidelines

for preparation, background, and a summary of the 1995 assessments. NOAA Technical Memorandum

NMFS-OPR-6. U.S. Department of Commerce, Washington, DC. 73 pp.

CETAP. 1982. A characterization of marine mammals and turtles in the mid- and north Atlantic areas of the U.S.

outer continental shelf. Cetacean and Turtle Assessment Program, University of Rhode Island. Final

Report #AA551-CT8-48 to the Bureau of Land Management, Washington, DC, 538 pp. 

Clark, C. W. 1995. Application of U.S. Navy underwater hydrophone arrays for scientific research on whales. Rep.

int. Whal. Commn. 45: 210-212.

Hammond, P. S., R. Sears and M. Bérubé. 1990. A note on problems in estimating the number of blue whales in the

Gulf of St Lawrence from photo-identification data. Rep. int. Whal. Commn., Special Issue 12: 141-142.

Mansfield, A. W. 1985. Status of the blue whale, Balaenoptera musculus, in Canada. Canadian Field Naturalist

99(3): 417-420.

Mitchell, E. 1974. Present status of northwest Atlantic fin and other whale stocks. Pages 108-169 in W. E. Schevill

(ed), The whale problem: A status report. Harvard University Press, Cambridge, MA, 419 pp.

Reeves, R. R., P. J. Clapham, R. L. Brownell, Jr. and G. K. Silber. 1998. Recovery Plan for the blue whale

(Balaenoptera musculus). Office of Protected Resources, National Marine Fisheries Service, Silver Spring,

MD 20910. 39 pp.

Sears, R., F. Wenzel and J. M. Williamson. 1987. The blue whale: a catalog of individuals from the western North

Atlantic (Gulf of St. Lawrence). Mingan Island Cetacean Study, St. Lambert, Quebec, Canada, 27 pp. 

Sergeant, D. E. 1966. Populations of large whale species in the western North Atlantic with special reference to the

fin whale. Fish. Res. Board. Canada Circular No. 9, 30 pp. 
38

Sigurjonsson, J. and T. Gunnlaugsson. 1990. Recent trends in abundance of blue (Balaenoptera musculus) and

humpback whales (Megaptera novaeangliae) off west and southwest Iceland, with a note on occurrence of

other cetacean species. Rep. int. Whal. Commn. 40: 537-551.

Wade, P. R. and R. P. Angliss. 1997. Guidelines for assessing marine mammal stocks: Report of the GAMMS

Workshop, April 3-5, 1996, Seattle, Washington. NOAA Technical Memorandum NMFS-OPR-12. U.S.

Dept. of Commerce, Washington, DC. 93 pp.

Wenzel, F., D. K. Mattila and P. J. Clapham. 1988. Balaenoptera musculus in the Gulf of Maine. Mar. Mammal

Sci. 4(2): 172-175. 

Yochem, P. K. and S. Leatherwood. 1985. Blue whale. Pages 193-240 in: S. H. Ridgeway and R. Harrison (eds),

Handbook of Marine Mammals, Vol. 3: The Sirenians and Baleen Whales. Academic Press, New York. 
39

Figure 1. Distribution of sperm whale sightings from

NEFSC and SEFSC shipboard and aerial surveys during

the summer in 1990-1998. Isobaths are at 100 m and

1,000 m. 

January 2002

SPERM WHALE (Physeter macrocephalus):

 North Atlantic Stock

STOCK DEFINITION AND GEOGRAPHIC RANGE

The distribution of the sperm whale in the USA Exclusive Economic Zone (EEZ) occurs on the continental

shelf edge, over the continental slope, and into mid-ocean regions (Figure 1). Waring et al. (1993) suggest that this

offshore distribution is more commonly associated

with the Gulf Stream edge and other features. 

However, the sperm whales that occur in the eastern

US Atlantic EEZ likely represent only a fraction of

the total stock. The nature of linkages of the USA

habitat with those to the south, north, and offshore is

unknown. Historical whaling records compiled by

Schmidly (1981) suggested an offshore distribution

off the southeast USA, over the Blake Plateau, and

into deep ocean. In the southeast Caribbean, both

large and small adults, as well as calves and juveniles

of different sizes are reported (Watkins et al. 1985). 

Whether the northwestern Atlantic population is

discrete from northeastern Atlantic is currently

unresolved. The International Whaling Commission

recognizes one stock for the North Atlantic. Based on

reviews of many types of stock studies, (i.e., tagging,

genetics, catch data, mark-recapture, biochemical

markers, etc.) Reeves and Whitehead (1997) and

Dufault et al. (1999) suggest that sperm whale

populations have no clear geographic structure. 

Recent ocean wide genetic studies (Lyrholm and

Gyllensten 1998; Lyrholm et al. 1999) indicate low

genetic diversity, but strong differentiation between

potential social (matrilineally related) groups. 

Further, the ocean-wide findings, combined with

observations from other studies, indicate stable social

groups, site fidelity, and latitudinal range limitations

in groups of females and juveniles. Whereas, males

migrate to polar regions to feed and return to more

tropical waters to breed. There exists one tag return

of a male tagged off Browns Bank (Nova Scotia) in

1966 and returned from Spain in 1973 (Mitchell 1975). Another male taken off northern Denmark in August 1981

had been wounded the previous summer by whalers off the Azores (Reeves and Whitehead 1997).

In the US Atlantic EEZ waters, there appears to be a distinct seasonal cycle (CETAP 1982; Scott and

Sadove 1997). In winter, sperm whales are concentrated east and northeast of Cape Hatteras. In spring, the center

of distribution shifts northward to east of Delaware and Virginia, and is widespread throughout the central portion of

the mid-Atlantic bight and the southern portion of Georges Bank. In summer, the distribution is similar but now also

includes the area east and north of Georges Bank and into the Northeast Channel region, as well as the continental

shelf (inshore of the 100m isobath) south of New England. In the fall, sperm whale occurrence south of New

England on the continental shelf is at its highest level, and there remains a continental shelf edge occurrence in the

mid-Atlantic bight. Similar inshore (<200m) observations have been made on the southwestern (Kenney, pers.

comm) and eastern Scotian Shelf, particularly in the region of “the Gully” (Whitehead et al. 1991).

Geographic distribution of sperm whales may be linked to their social structure and their low reproductive

rate and both of these factors have management implications. Several basic groupings or social units are generally
40

recognized — nursery schools, harem or mixed schools, juvenile or immature schools, bachelor schools, bull schools

or pairs, and solitary bulls (Best 1979; Whitehead et al. 1991). These groupings have a distinct geographical

distribution, with females and juveniles generally based in tropical and subtropical waters, and males more wideranging and occurring in higher latitudes. Male sperm whales are present off and sometimes on the continental shelf

along the entire east coast of Canada south of Hudson Strait, whereas, females rarely migrate north of the southern

limit of the Canadian EEZ (Reeves and Whitehead 1997). Whereas, off the northeast USA, CETAP and

NMFS/NEFSC sightings in shelf-edge and off-shelf waters included many social groups with calves/juveniles

(CETAP 1981; Waring et al. 1992, 1993). The basic social unit of the sperm whale appears to be the mixed school

of adult females plus their calves and some juveniles of both sexes, normally numbering 20-40 animals in all. There

is evidence that some social bonds persist for many years.

POPULATION SIZE

Total numbers of sperm whales off the USA or Canadian Atlantic coast are unknown, although eight

estimates from selected regions of the habitat do exist for select time periods. Sightings were almost exclusively in

the continental shelf edge and continental slope areas (Figure 1). An abundance of 219 (CV=0.36) sperm whales

was estimated from an aerial survey program conducted from 1978 to 1982 on the continental shelf and shelf edge

waters between Cape Hatteras, North Carolina and Nova Scotia (CETAP 1982). An abundance of 338 (CV=0.31)

sperm whales was estimated from an August 1990 shipboard line transect sighting survey, conducted principally

along the Gulf Stream north wall between Cape Hatteras and Georges Bank (Anon. 1990; Waring et al. 1992). An

abundance of 736 (CV=0.33) sperm whales was estimated from a June and July 1991 shipboard line transect

sighting survey conducted primarily between the 200 and 2,000m isobaths from Cape Hatteras to Georges Bank

(Waring et al. 1992; Waring 1998). An abundance of 705 (CV=0.66) and 337 (CV=0.50) sperm whales was

estimated from line transect aerial surveys conducted from August to September 1991 using the Twin Otter and AT11, respectively (Anon. 1991). As recommended in the GAMMS Workshop Report (Wade and Angliss 1997),

estimates older than eight years are deemed unreliable, therefore should not be used for PBR determinations. 

Further, due to changes in survey methodology these data should not be used to make comparisons to more current

estimates. 

An abundance of 116 (CV=0.40) sperm whales was estimated from a June and July 1993 shipboard line

transect sighting survey conducted principally between the 200 and 2,000m isobaths from the southern edge of

Georges Bank, across the Northeast Channel to the southeastern edge of the Scotian Shelf (Anon. 1993). Data were

collected by two alternating teams that searched with 25x150 binoculars and were analyzed using DISTANCE

(Buckland et al. 1993; Laake et al. 1993). Estimates include school-size bias, if applicable, but do not include

corrections for g(0) or dive-time. Variability was estimated using bootstrap resampling techniques.

An abundance of 623 (CV=0.52) sperm whales was estimated from an August 1994 shipboard line transect

survey conducted within a Gulf Stream warm-core ring located in continental slope waters southeast of Georges

Bank (Table 1; Anon. 1994). Data were collected by two alternating teams that searched with 25x150 binoculars

and an independent observer who searched by naked eye from a separate platform on the bow. Data were analyzed

using DISTANCE (Buckland et al. 1993; Laake et al. 1993). Estimates include school-size bias, if applicable, but

do not include corrections for g(0) or dive-time. Variability was estimated using bootstrap resampling techniques.

An abundance of 2,698 (CV=0.67) sperm whales was estimated from a July to September 1995 sighting

survey conducted by two ships and an airplane that covered waters from Virginia to the mouth of the Gulf of St.

Lawrence (Table 1; Palka et al. in review). Total track line length was 32,600 km. The ships covered waters

between the 50 and 1000 fathom depth contour lines, the northern edge of the Gulf Stream, and the northern Gulf of

Maine/Bay of Fundy region. The airplane covered waters in the mid-Atlantic from the coastline to the 50 fathom

depth contour line, the southern Gulf of Maine, and shelf waters off Nova Scotia from the coastline to the 1000

fathom depth contour line. Data collection and analysis methods used were described in Palka (1996). 

An abundance of 2,848 (CV=0.49) sperm whales was estimated from a line transect sighting survey

conducted during July 6 to September 6, 1998 by a ship and plane that surveyed 15,900 km of track line in waters

north of Maryland (38° N) (Figure 1; Palka et al. in review). Shipboard data were analyzed using the modified

direct duplicate method (Palka 1995) that accounts for school size bias and g(0), the probability of detecting a group

on the track line. Aerial data were not corrected for g(0).

An abundance of 1,854 (CV=0.53) sperm whales was estimated from a shipboard line transect sighting

survey conducted between 8 July and 17 August 1998 that surveyed 5,570 km of track line in waters south of
41

Maryland (38°N) (Figure 1; Mullin in review). Abundance estimates were made using the program DISTANCE

(Buckland et al. 1993; Laake et al. 1993) where school size bias and ship attraction were accounted for.

The best available abundance estimate for sperm whales is the sum of the estimates from the two 1998 USA

Atlantic surveys, 4,702 (CV=0.36), where the estimate from the northern USA Atlantic is 2,848 (CV=0.49) and from

the southern USA Atlantic is 1,854 (CV=0.53). This joint estimate is considered best because together these two

surveys have the most complete coverage of the species’ habitat.

Because all the sperm whale estimates presented here were not corrected for dive-time, they are likely

downwardly biased and an underestimate of actual abundance. The average dive-time of sperm whales is

approximately 45 min (Whitehead et al. 1991; Watkins et al. 1993), therefore, the proportion of time that they are at

the surface and available to visual observers is assumed to be low. 

Although the stratification schemes used in the 1990-1998 surveys did not always sample the same areas or

encompass the entire sperm whale habitat, they did focus on segments of known or suspected high-use habitats off

the northeastern USA coast. The collective 1990-1998 data suggest that, seasonally, at least several thousand sperm

whales are occupying these waters. The 1998 estimate is 1.7 times greater than the 1995 estimate, reflecting the

contribution from the southern USA Atlantic. Sperm whale abundance may increase offshore, particularly in

association with Gulf Stream and warm-core ring features; however, at present there is no reliable estimate of total

sperm whale abundance in the western North Atlantic. 

Table 1. Summary of abundance estimates1

 for the western North Atlantic sperm whale. Month, year, and area

covered during each abundance survey, and resulting abundance estimate (Nbest) and coefficient of variation

(CV).

Month/Year Area Nbest CV

Aug 1994 warm-core ring SE of

Georges Bank 623 0.52

Jul-Sep 1995 Virginia to Gulf of St.

Lawrence 2,698 0.67

Jul-Sep 1998 Maryland to Gulf of St.

Lawrence 2,848 0.49

Jul-Aug 1998 Florida to Maryland 1,854 0.53

Jul-Sep 1998 Gulf of St. Lawrence to

Florida (COMBINED) 4,702 0.36

1

 As recommended in the GAMMS Workshop Report (Wade and Angliss 1997), estimates older than eight

years are deemed unreliable, therefore are not reported in this table.

Minimum Population Estimate

The minimum population estimate is the lower limit of the two-tailed 60% confidence interval of the lognormally distributed best abundance estimate. This is equivalent to the 20th percentile of the log-normal distribution

as specified by Wade and Angliss (1997). The best estimate of abundance for sperm whales is 4,702 (CV=0.36). 

The minimum population estimate for the western North Atlantic sperm whale is 3,505 (CV=0.36).

Current Population Trend

There are insufficient data to determine the population trends for this species. 

CURRENT AND MAXIMUM NET PRODUCTIVITY RATES

Current and maximum net productivity rates are unknown for this stock. While more is probably known

about sperm whale life history in other areas, some life history and vital rates information is available for the

northwest Atlantic. These include: calving interval is 4-6 years; lactation period is 24 months; gestation period is

14.5-16.5 months; births occur mainly in July to November; length at birth is 4.0 m; length at sexual maturity is 
42

11.0 -12.5 m for males and 8.3-9.2 m for females; mean age at sexual maturity is 19 years for males and 9 years for

females; and mean age at physical maturity is 45 years for males and 30 years for females (Best 1974; Best et al.

1984; Lockyer 1981; Rice 1989). 

For purposes of this assessment, the maximum net productivity rate was assumed to be 0.04. This value is

based on theoretical modeling showing that cetacean populations may not grow at rates much greater than 4% given

the constraints of their reproductive life history (Barlow et al. 1995). 

POTENTIAL BIOLOGICAL REMOVAL

Potential Biological Removal (PBR) is the product of minimum population size, one-half the maximum

productivity rate, and a “recovery” factor (MMPA Sec. 3. 16 U.S.C. 1362; Wade and Angliss 1997). The minimum

population size is 3,505 (CV=0.36). The maximum productivity rate is 0.04, the default value for cetaceans. The

“recovery” factor, which accounts for endangered, depleted, threatened stocks, or stocks of unknown status relative

to optimum sustainable population (OSP) is assumed to be 0.10 because the sperm whale is listed as endangered

under the Endangered Species Act (ESA). PBR for the western North Atlantic sperm whale is 7.0.

ANNUAL HUMAN-CAUSED MORTALITY

Four hundred twenty-four sperm whales were harvested in the Newfoundland-Labrador area between 1904-

1972 and 109 male and no female sperm whales were taken near Nova Scotia in 1964-1972 (Mitchell and Kozicki

1984) in a Canadian whaling fishery. There was also a well-documented sperm whale fishery based on the west

coast of Iceland. Other sperm whale catches occurred near West Greenland, the Azores, Madeira, Spain, Spanish

Morocco, Norway (coastal and pelagic), Faroes, and British coastal. At present, because of their general offshore

distribution, sperm whales are less likely to be impacted by humans and those impacts that do occur are less likely to

be recorded. There has been no complete analysis and reporting of existing data on this topic for the western North

Atlantic.

Total annual estimated average fishery-related mortality or serious injury to this stock during 1996-

2000 was 0.2 sperm whales based on the 2000 stranding of a sperm whale off Florida which had fishing gear in its 

blow hole. Although, in 1995 one sperm whale was entangled in a pelagic drift gillnet and was released alive 

with gear around several body parts. Presently, this injury has not been used to estimate mortality.

Fishery Information

Three sperm whale entanglements have been documented from August 1993 to May 1998. In August 1993,

a dead sperm whale, with longline gear wound tightly around the jaw, was found floating about 20 miles off Mt

Desert Rock. In October 1994, a sperm whale was successfully disentangled from a fine mesh gillnet in Birch

Harbor, Maine. In May 1997, a sperm whale entangled in net with three buoys trailing was sighted 130 nmi

northwest of Bermuda. No information on the status of the animal was provided. 

Data on current incidental takes in USA fisheries are available from several sources. In 1986, NMFS

established a mandatory self-reported fisheries information system for large pelagic fisheries. Data files are

maintained at the Southeast Fisheries Science Center (SEFSC). The Northeast Fisheries Science Center (NEFSC)

Sea Sampling Observer Program was initiated in 1989, and since that year several fisheries have been covered by the

program. In late 1992 and in 1993, the SEFSC provided observer coverage of pelagic longline vessels fishing off the

Grand Banks (Tail of the Banks) and currently provides observer coverage of vessels fishing south of Cape Hatteras.

Bycatch has been observed by NMFS Sea Samplers in the pelagic drift gillnet fishery, but no mortalities or

serious injuries have been documented in the pelagic longline, pelagic pair trawl, Northeast multispecies sink gillnet,

mid-Atlantic coastal gillnet, or North Atlantic bottom trawl fisheries by NMFS Sea Samplers.

Pelagic Drift Gillnet

Only two records exist in the present NEFSC bycatch database. In July 1990, a sperm whale was entangled

and subsequently released (injured) from a pelagic drift gillnet near the continental shelf edge on southern Georges

Bank. During June 1995, one sperm whale was entangled with “gear in/around several body parts” then released

injured from a pelagic drift gillnet haul located on the shelf edge between Oceanographer and Hydrographer

Canyons on Georges Bank.

The estimated total number of hauls in the pelagic drift net fishery increased from 714 in 1989 to 1144 in

1990; thereafter, with the introduction of quotas, effort was severely reduced. The estimated number of hauls in

1991, 1992, 1993, 1994, 1995, 1996, and 1998 were 233, 243, 232, 197, 164, 149, and 113 respectively. In 1996

and 1997, NMFS issued management regulations which prohibited the operation of this fishery in 1997. Further, in
43

January 1999 NMFS issued a Final Rule to prohibit the use of driftnets (i.e., permanent closure) in the North

Atlantic swordfish fishery (50 CFR Part 630). Fifty-nine vessels participated in this fishery between 1989 and 1993. 

Since 1994, between 10 and 13 vessels have participated in the fishery. Observer coverage, percent of sets observed,

was 8% in 1989, 6% in 1990, 20% in 1991, 40% in 1992, 42% in 1993, 87% in 1994, 99% in 1995, 64% in 1996,

and 99% in 1998. The greatest concentrations of effort were located along the southern edge of Georges Bank and

off Cape Hatteras. Examination of the species composition of the catch and locations of the fishery throughout the

year, suggested that the pelagic drift gillnet fishery be stratified into two strata, a southern or winter stratum, and a

northern or summer stratum. Estimates of total bycatch, for each year from 1989 to 1993, were obtained using the

aggregated (pooled 1989-1993) catch rates, by strata, assuming the 1990 injury was a mortality (Northridge 1996). 

Estimated annual fishery-related mortality and serious injury (CV in parentheses) was 2.2 sperm whales in 1989

(2.43), 4.4 in 1990 (1.77), 0 in 1991, 0 in 1992, 0 in 1993, 0 in 1994, 0 in 1995, 0 in 1996, no fishery in 1997, and 0

in 1998. 

Other Mortality

 Eighteen sperm whale strandings have been documented along the USA Atlantic coast between Maine and

Miami, Florida, during 1994-2000 (NMFS unpublished data). One 1998 and one 2000 stranding off Florida showed

signs of human interactions. The 1998 animal’s head was severed, but it is unknown if it occurred pre or postmortem. The 2000 animal had fishing gear in the blowhole. In October 1999, a live sperm whale calf stranded on

eastern Long Island, and was subsequently euthanized. Also, a dead calf was found in the surf off Florida in 2000.

In eastern Canada, five dead strandings were reported in Newfoundland/Labrador from 1987-1995; thirteen

dead strandings along Nova Scotia from 1988-1996; seven dead strandings on Prince Edward Island from 1988-

1991; two dead strandings in Quebec in 1992; and thirteen animals in eight stranding events on Sable Island, Nova

Scotia from 1970-1998 (Reeves and Whitehead 1997; Hooker et al. 1997; Lucas and Hooker 1997; Lucas and

Hooker 2000). Sex was recorded for eleven of the thirteen animals, and all were male, which is consistent with

sperm whale distribution patterns (Lucas and Hooker 2000).

Recent mass strandings have also been reported in the North Sea, including; winter 1994/95 (21); winter

1995/96 (16); and winter 1997/98 (20). Reasons for the stranding are unknown, although multiple causes (e.g.,

unfavorable North Sea topography, ship strikes, global changes in water temperature and prey distribution, and

pollution) have been suggested (Holsbee et al. 1999). 

Ship strikes are another source of human induced mortality. In May 1994 a ship-struck sperm whale was 

observed south of Nova Scotia (Reeves and Whitehead 1997), and in May 2000 a merchant ship reported a strike in

Block Canyon (NMFS, unpublished data). In spring, Block Canyon is a major pathway for sperm whales entering 

southern New England continental shelf waters in pursuit of migrating squid (CETAP 1982; Scott and Sadove 1997).

A potential human-caused source of mortality is from accumulation of stable pollutants (e.g.,

polychlorobiphenyls (PCBs), chlorinated pesticides (DDT, DDE, dieldrin, etc.), polycyclic aromatic hydrocarbons

(PAHs), and heavy metals) in long lived high trophic level animals. Analysis of tissue samples obtained from 21

sperm whales that mass stranded in the North Sea in 1994/95 indicated that mercury, PCB, DDE, and PAH levels

were low and similar to levels reported for other marine mammals (Holsbeek et al. 1999). Whereas, cadmium levels

were high and double reported levels in North Pacific sperm whales. Although the 1994/95 strandings were not

attributable to contaminant burdens, Holsbeek et al. (1999) suggest that the stable pollutants might affect the health

or behavior of North Atlantic sperm whales.

STATUS OF STOCK

The status of this stock relative to OSP in USA Atlantic EEZ is unknown, but the species is listed as

endangered under the ESA. There are insufficient data to determine population trends. The current stock abundance

estimate was based upon a small portion of the known stock range. Total fishery-related mortality and serious injury

for this stock is less than 10% of the calculated PBR, and therefore can be considered to be insignificant and

approaching a zero mortality and serious injury rate. This is a strategic stock because the species is listed as

endangered under the ESA.
44

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Available from: National Marine Fisheries Service, 166 Water Street, Woods Hole, MA 02543-1026.

Anon. 1991. Northeast cetacean aerial survey and interplatform study. NOAA-NMFS-SEFSC and NEFSC. 4 pp.

Available from: National Marine Fisheries Service, 166 Water Street, Woods Hole, MA 02543-1026.

Anon. 1993. Cruise results, NOAA Ship DELAWARE II, Cruise No. DEL 93-06, Marine Mammal Survey. 5 pp.

Available from: National Marine Fisheries Service, 166 Water Street, Woods Hole, MA 02543-1026.

Anon. 1994. Cruise results, NOAA Ship RELENTLESS, Cruise No. RS 94-02, Marine Mammal Survey/Warm

Core Ring Study. 8 pp. Available from: National Marine Fisheries Service, 166 Water Street, Woods

Hole, MA 02543-1026.

Barlow, J., S. L. Swartz, T. C. Eagle and P. R. Wade. 1995. U.S. Marine Mammal Stock Assessments: Guidelines

for Preparation, Background, and a Summary of the 1995 Assessments. U.S. Dep. Commer., NOAA Tech.

Memo. NMFS-OPR-6, 73 pp.

Best, P. B. 1974. Biology of the sperm whale. Pages 53-81. In: W. E. Schevill (ed), The whale problem: A status

report. Harvard University Press, Cambridge, Massachusetts, 419 pp. 

Best, P. B. 1979. Social organization in sperm whales, Physeter macrocephalus. Pages 227-289. In: H. E. Winn

and B. L. Olla (eds), Behavior of marine animals, Vol. 3: Cetaceans. Plenum Press, New York. 

Best, P. B., P. A. S. Canham and N. Macleod. 1984. Patterns of reproduction in sperm whales, Physeter

macrocephlus. Rep. int Whal. Commn. (Special Issue 8):51-79.

Buckland, S. T., D. R. Andersen, K. P. Burnham and J. L. Laake. 1993. Distance sampling: Estimating abundance

of biological populations. Chapman and Hall, New York, 442 pp. 

CETAP. 1982. A characterization of marine mammals and turtles in the mid- and north Atlantic areas of the U.S.

outer continental shelf. Cetacean and Turtle Assessment Program, University of Rhode Island. Final

Report #AA551-CT8-48 to the Bureau of Land Management, Washington, DC, 538 pp. 

Dufault, S., H. Whitehead, and M. Dillon. 1999. An examination of the current knowledge on the stock structure of

sperm whales (Physeter macrocephalus) Worldwide. J. Cetacean Res. Manage. 1(1):1-10.

Holsbeek, L., C. R. Joiris, V. Debacker, I. B. Ali, P. Roose, J-P. Nellissen, S. Gobert, J-M. Bouquegneau, and M.

Bossicart. 1999. Heavy metals, organochlorines and polycyclic aromatic hydrocarbons in sperm whales

stranded in the southern North Sea during the 1994/1995 winter. Mar. Pollu. Bull. 38: 4 304-313.

Hooker, S. K., R. W. Baird, and M. A. Showell. 1997. Cetacean Strandings and bycatches in Nova Scotia, Eastern

Canada, 1991-1996. Paper SC/49/05 presented to the IWC Scientific Committee, September 1997. 11 pp.

Laake, J. L., S. T. Buckland, D. R. Anderson and K. P. Burnham. 1993. DISTANCE user’s guide, V2.0. Colorado

Cooperative Fish & Wildlife Research Unit, Colorado State University, Ft. Collins, Colorado, 72 pp. 

Lockyer, C. 1981. Estimates of growth and energy budget for the sperm whale. Pages 491-504 in: Mammals in the

seas, III. FAO Fish. Ser. No. 5. FAO, Rome, 504 pp.

Lucas, Z. N. and S. K. Hooker. 1997. Cetacean strandings on Sable Island, Nova Scotia, 1990-1996. Paper

SC/49/06 presented to the IWC Scientific Committee, September 1997. 10 pp.

Lucas, Z. N. and S. K. Hooker. 2000. Cetacean strandings on Sable Island, Nova Scotia, 1970-1998. Can. Field

Nat.:114 (45-61).

Lyrholm, T. and U. Gyllensten. 1998. Global matrilineal population structure in sperm whales as indicated by

mitochondrial DNA sequences. Proc. R. Soc. Lond. B 265:1679-1684.

Lyrholm, T., O. Leimar, B. Johanneson, and U. Gyllensten. 1999. Sex-biased dispersal in sperm whales:

contrasting mitochondrial and nuclear genetic structure of global populations. Proc. R. Soc. Lond. B 266:

347-354.

Mitchell, E. 1975. Progress report on whale research, Canada. Rep. int Whal. Commn. 25:270-272.

Mitchell, E. and V. M. Kozicki. 1984. Reproductive condition of male sperm whales, Physeter macrocephalus,

taken off Nova Scotia. Rep. int Whal. Commn. (Special Issue 6):243-252.

Mullin, K. D. (in review). Abundance and distribution of cetaceans in the southern U.S. Atlantic Ocean during

summer 1998. Fish. Bull., U.S. 

Northridge, S. 1996. Estimation of cetacean mortality in the U.S. Atlantic swordfish and tuna drift gillnet and pair

trawl fisheries. Final report to the NMFS, Northeast Fisheries Science Center, Contract No.

40ENNF500160. 21p.
45

Palka, D. 1995. Abundance estimate of the Gulf of Maine harbor porpoise. Rep. int Whal. Commn. (Special Issue

16):27-50.

Palka, D. 1996. Update on abundance of Gulf of Maine/Bay of Fundy harbor porpoises. NOAA/NMFS/NEFSC.

Ref. Doc. 96-04; 37 pp. Available from: National Marine Fisheries Service, 166 Water Street, Woods

Hole, MA 02543-1026.

Palka, D., G. Waring and D. Potter. (in review). Abundances of cetaceans and sea turtles in the northwest Atlantic 

during summer 1995 and 1998. Fish. Bull., U.S.

Reeves, R. R. and H. Whitehead. 1997. Status of sperm whale, Physeter macrocephalus, in Canada. Can. Field

Nat. 111:293-307.

Rice, D. W. 1989. Sperm whale. Physeter macrocephalus Linnaeus, 1758. Pp. 177-233 in: Handbook of marine

animals. Vol. 4. Ed. S. H. Ridgway and R Harrison. Academic Press, London.

Scott, T. M. and S. S. Sadove. 1997. Sperm whale, Physeter macrocephalus, sightings in the shallow shelf waters

off Long Island, New York. Mar. Mammal Sci. 13:317-321.

Schmidly, D. J. 1981. Marine mammals of the southeastern United States and the Gulf of Mexico. Department of

the Interior, U.S. Fish and Wildlife Service Publication FWS/OBS-80/41, Washington, DC, 166 pp. 

Wade P. R., and R. P. Angliss. 1997. Guidelines for assessing marine mammal stocks: Report of the GAMMS

Workshop April 3-5, 1996, Seattle, Washington. U.S. Dep. Commer., NOAA Tech. Memo. NMFS-OPR12, 93 pp.

Waring, G. T., C. P. Fairfield, C. M. Ruhsam and M. Sano. 1992. Cetaceans associated with Gulf Stream features

off the northeastern USA shelf. ICES. C.M. 1992/N:12. 29 pp.

Waring, G. T., C. P. Fairfield, C. M. Ruhsam and M. Sano. 1993. Sperm whales associated with Gulf Stream

features off the northeastern USA shelf. Fish. Oceanogr. 2:101-105

Waring, G. T. 1998. Results of the summer 1991 R/V Chapman marine mammal sighting survey. NOAA-NMFSNEFSC, Lab. Ref. Doc. No. 98-09, 21 pp. Available from: National Marine Fisheries Service, 166 Water

Street, Woods Hole, MA 02543-1026.

Waring, G. T., D. L. Palka, P. J. Clapham, S. Swartz, M. C. Rossman, T. V. N. Cole, L. J. Hansen, K. D. Bisack, K.

D. Mullin, R. S. Wells, D. K. Odell, and N. B. Barros. 1999. U.S. Atlantic and Gulf of Mexico marine

mammal stock assessments — 1999. U.S. Dep. Commer., NOAA Tech. Memo NMFS-NE-153, 196 pp. 

Watkins, W. A., K. E. Moore and P. Tyack. 1985. Sperm whale acoustic behavior in the southeast Caribbean. 

Cetology 49:1-15. 

Watkins, W. A., M. A. Daher, K. M. Fristrup and T. J. Howald. 1993. Sperm whales tagged with transponders and

tracked underwater by sonar. Mar. Mammal Sci. 9:55-67.

Whitehead, H., S. Brennan and D. Grover. 1991. Distribution and behavior of male sperm whales on the Scotian

Shelf, Canada. Can. J. Zool. 70:912-918.
46

Figure 1. Distribution of beaked whale sightings from

NEFSC and SEFSC shipboard and aerial surveys during

the summer in 1990-1998. Isobaths are at 100 m and

1,000 m. 

January 2002

CUVIER'S BEAKED WHALE (Ziphius cavirostris):

Western North Atlantic Stock

STOCK DEFINITION AND GEOGRAPHIC RANGE

The distribution of Cuvier's beaked whales is poorly known, and is based mainly on stranding records

(Leatherwood et al. 1976). Strandings have been reported from Nova Scotia along the eastern USA coast south to

Florida, around the Gulf of Mexico, and within the

Caribbean (Leatherwood et al. 1976; CETAP 1982;

Heyning 1989; Houston 1990; Mignucci-Giannoni et

al. 1999). Stock structure in the North Atlantic is

unknown. 

Cuvier's beaked whale sightings have

occurred principally along the continental shelf edge

in the mid-Atlantic region off the northeast USA

coast (CETAP 1982; Waring et al. 1992; NMFS

unpublished data). Most sightings were in late

spring or summer. Based on sighting data, this

species is a rare inhabitant of waters off the northeast

USA coast (CETAP 1982).

POPULATION SIZE

The total number of Cuvier's beaked whales

off the eastern USA Canadian Atlantic coast is

unknown. 

However, eight estimates of the

undifferentiated complex of beaked whales (Ziphius

and Mesoplodon spp.) from selected regions of the

habitat do exist for select time periods. Sightings

were almost exclusively in the continental shelf edge

and continental slope areas (Figure 1). An

abundance of 120 undifferentiated beaked whales

(CV=0.71) was estimated from an aerial survey

program conducted from 1978 to 1982 on the

continental shelf and shelf edge waters between Cape

Hatteras, North Carolina and Nova Scotia (CETAP

1982). An abundance of 442 (CV=0.51)

undifferentiated beaked whales was estimated from

an August 1990 shipboard line transect sighting

survey, conducted principally along the Gulf Stream north wall between Cape Hatteras and Georges Bank (Anon.

1990; Waring et al. 1992). An abundance of 262 (CV=0.99) undifferentiated beaked whales was estimated from a

June and July 1991 shipboard line transect sighting survey conducted primarily between the 200 and 2,000m

isobaths from Cape Hatteras to Georges Bank (Waring et al. 1992; Waring 1998). An abundance of 370 (CV=0.65)

and 612 (CV=0.73) undifferentiated beaked whales was estimated from line transect aerial surveys conducted from

August to September 1991 using the Twin Otter and AT-11, respectively (Anon. 1991). As recommended in the

GAMMS Workshop Report (Wade and Angliss 1997), estimates older than eight years are deemed unreliable,

therefore should not be used for PBR determinations. Further, due to changes in survey methodology these data

should not be used to make comparisons to more current estimates. 

An abundance of 330 (CV=0.66) undifferentiated beaked whales was estimated from a June and July 1993

shipboard line transect sighting survey conducted principally between the 200 and 2,000 m isobaths from the

southern edge of Georges Bank, across the Northeast Channel to the southeastern edge of the Scotian Shelf (Anon.
47

 1993). Data were collected by two alternating teams that searched with 25x150 binoculars and were analyzed using

DISTANCE (Buckland et al. 1993; Laake et al. 1993). Estimates include school-size bias, if applicable, but do not

include corrections for g(0) or dive-time. Variability was estimated using bootstrap resampling techniques.

An abundance of 99 (CV=0.64) undifferentiated beaked whales was estimated from an August 1994

shipboard line transect survey conducted within a Gulf Stream warm-core ring located in continental slope waters

southeast of Georges Bank (Table 1; Anon. 1994). Data were collected by two alternating teams that searched with

25x150 binoculars and an independent observer who searched by naked eye from a separate platform on the bow. 

Data were analyzed using DISTANCE (Buckland et al. 1993; Laake et al. 1993). Estimates include school-size bias,

if applicable, but do not include corrections for g(0) or dive-time. Variability was estimated using bootstrap

resampling techniques.

An abundance of 1,519 (CV=0.69) undifferentiated beaked whales was estimated from a July to September

1995 sighting survey conducted by two ships and an airplane that covered waters from Virginia to the mouth of the

Gulf of St. Lawrence (Table 1; Palka et al. in review). Total track line length was 32,600 km. The ships covered

waters between the 50 and 1000 fathom depth contour lines, the northern edge of the Gulf Stream, and the northern

Gulf of Maine/Bay of Fundy region. The airplane covered waters in the mid-Atlantic from the coastline to the 50

fathom depth contour line, the southern Gulf of Maine, and shelf waters off Nova Scotia from the coastline to the

1000 fathom depth contour line. Data collection and analysis methods used were described in Palka (1996). 

An abundance of 2,600 (CV=0.40) undifferentiated beaked whales was estimated from a line transect

sighting survey conducted during July 6 to September 6, 1998 by a ship and plane that surveyed 15,900 km of track

line in waters north of Maryland (38° N) (Figure 1; Palka et al. in review). Shipboard data were analyzed using the

modified direct duplicate method (Palka 1995) that accounts for school size bias and g(0), the probability of

detecting a group on the track line. Aerial data were not corrected for g(0).

An abundance of 596 (CV=0.50) undifferentiated beaked whales was estimated from a shipboard line

transect sighting survey conducted between 8 July and 17 August 1998 that surveyed 5,570 km of track line in

waters south of Maryland (38°N) (Figure 1; Mullin in review). Abundance estimates were made using the program

DISTANCE (Buckland et al. 1993; Laake et al. 1993) where school size bias and ship attraction were accounted for.

The best available abundance estimate for undifferentiated beaked whales is the sum of the estimates from

the two 1998 USA Atlantic surveys, 3,196 (CV=0.34), where the estimate from the northern USA Atlantic is 2,600

(CV=0.40) and from the southern USA Atlantic is 596 (CV=0.50). This joint estimate is considered best because

together these two surveys have the most complete coverage of the species’ habitat.

Because the estimates presented here were not dive-time corrected, they are likely negatively biased and

probably underestimate actual abundance. Given that Mesoplodon spp. prefers deep-water habitats (Mead 1989) the

bias may be substantial.

Table 1. Summary of abundance estimates for the undifferentiated complex of beaked whales which include Ziphius

and Mesoplodon spp. Month, year, and area covered during each abundance survey, and resulting

abundance estimate (Nbest) and coefficient of variation (CV).

Month/Year Area Nbest CV

Aug 1994 warm-core ring SE of Georges Bank 99 0.64

Jul-Sep 1995 Virginia to Gulf of St. Lawrence 1,519 0.69

Jul-Sep 1998 Maryland to Gulf of St. Lawrence 2,600 0.40

Jul-Aug 1998 Florida to Maryland 596 0.50

Jul-Sep 1998 Gulf of St. Lawrence to Florida (COMBINED) 3,196 0.34

Minimum Population Estimate

The minimum population estimate is the lower limit of the two-tailed 60% confidence interval of the lognormally distributed best abundance estimate. This is equivalent to the 20th percentile of the log-normal distribution

as specified by Wade and Angliss (1997). The best estimate of abundance for undifferentiated beaked whales is
48

3,196 (CV=0.34). The minimum population estimate for the undifferentiated complex of beaked whales (Ziphius

and Mesoplodon spp.) is 2,419 (CV=0.34). It is not possible to determine the minimum population estimate of only

Cuvier’s beaked whales.

Current Population Trend

There are insufficient data to determine the population trends for this species. 

CURRENT AND MAXIMUM NET PRODUCTIVITY RATES

Current and maximum net productivity rates are unknown for this stock. Life history parameters that could

be used to estimate net productivity include: length at birth is 2 to 3 m, length at sexual maturity is 6.1 m for females,

and 5.5 m for males, maximum age for females were 30 growth layer groups (GLG's) and for males was 36 GLG's,

which may be annual layers (Mitchell 1975; Mead 1984; Houston 1990). 

For purposes of this assessment, the maximum net productivity rate was assumed to be 0.04. This value is

based on theoretical modeling showing that cetacean populations may not grow at rates much greater than 4% given

the constraints of their reproductive life history (Barlow et al. 1995). 

POTENTIAL BIOLOGICAL REMOVAL

Potential Biological Removal (PBR) is the product of minimum population size, one-half the maximum

productivity rate, and a “recovery” factor (MMPA Sec. 3. 16 U.S.C. 1362; Wade and Angliss 1997). The minimum

population size for the undifferentiated complex of beaked whales is 2,419 (CV=0.34). The maximum productivity

rate is 0.04, the default value for cetaceans. The “recovery” factor, which accounts for endangered, depleted,

threatened stocks, or stocks of unknown status relative to optimum sustainable population (OSP) is assumed to be

0.5 because this stock is of unknown status. PBR for all species in the undifferentiated complex of beaked whales

(Ziphius and Mesoplodon spp.) is 24. It is not possible to determine the PBR for only Cuvier’s beaked whales.

ANNUAL HUMAN-CAUSED MORTALITY AND SERIOUS INJURY

 The 1996-2000 total average estimated annual fishery-related mortality of beaked whales in open fisheries

in the US Atlantic EEZ was zero. 

Fishery Information

There is no historical information available that documents incidental mortality in either USA or Canadian

Atlantic coast fisheries (Read 1994). 

Current data on incidental takes in USA fisheries are available from several sources. In 1986, NMFS

established a mandatory self-reported fisheries information system for large pelagic fisheries. Data files are

maintained at Southeast Fisheries Science Center (SEFSC). The Northeast Fisheries Science Center (NEFSC) Sea

Sampling Observer Program was initiated in 1989, and since that year several fisheries have been covered by the

program. In late 1992 and in 1993 the SEFSC provided observer coverage of pelagic longline vessels fishing off the

Grand Banks (Tail of the Banks) and currently provides observer coverage of vessels fishing south of Cape Hatteras. 

Total fishery-related mortality and serious injury cannot be estimated separately for each beaked whale

species because of the uncertainty in species identification by fishery observers. The Atlantic Scientific Review

Group advised adopting the risk-averse strategy of assuming that any beaked whale stock which occurred in the US

Atlantic EEZ might have been subject to the observed fishery-related mortality and serious injury.

Bycatch has been observed by NMFS Sea Samplers in the pelagic drift gillnet fishery, but no mortalities or

serious injuries have been documented in the pelagic longline, pelagic pair trawl, Northeast multispecies sink gillnet,

mid-Atlantic coastal gillnet, or North Atlantic bottom trawl fisheries by NMFS Sea Samplers.

Pelagic Drift Gillnet

The estimated total number of hauls in the pelagic drift gillnet fishery increased from 714 in 1989 to 1,144

in 1990; thereafter, with the introduction of quotas, effort was severely reduced. The estimated number of hauls in

1991, 1992, 1993, 1994, 1995,1996, and 1998 were 233, 243, 232, 197, 164, 143, and 113 respectively. In 1996 and

1997, NMFS issued management regulations which prohibited the operation of this fishery in 1997. Further, in

January 1999 NMFS issued a Final Rule to prohibit the use of driftnets (i.e., permanent closure) in the North

Atlantic swordfish fishery (50 CFR Part 630). Fifty-nine different vessels participated in this fishery at one time or

another between 1989 and 1993. From 1994 - 1998, between 10 and 13 vessels have participated in the fishery. 
49

Observer coverage, expressed as percent of sets observed, was 8% in 1989, 6% in 1990, 20% in 1991, 40% in 1992,

42% in 1993, 87% in 1994, 99% in 1995, 64% in 1996, and 99% in 1998. Effort was concentrated along the

southern edge of Georges Bank and off Cape Hatteras. Examination of the species composition of the catch and

locations of the fishery throughout the year, suggested that the pelagic drift gillnet fishery be stratified into two

strata, a southern or winter stratum, and a northern or summer stratum. Estimates of the total bycatch, for each year

from 1989 to 1993, were obtained using the aggregated (pooled 1989-1993) catch rates, by strata (Northridge 1996). 

Estimates of total annual bycatch for 1994 - 1998 were estimated from the sum of the observed caught and the

product of the average bycatch per haul and the number of unobserved hauls as recorded in self-reported fisheries

information. Variances were estimated using bootstrap re-sampling techniques. Bycatch of beaked whales has only

occurred from Georges Canyon to Hydrographer Canyon along the continental shelf break and continental slope

during July to October. Forty-six fishery-related beaked whale mortalities were observed between 1989 and 1998. 

These included: 24 Sowerby’s; 4 True’s; 1 Cuvier’s; and 17 undifferentiated beaked whales. Recent analysis of

biological samples (genetics and morphological analysis) have been used to determine species identifications for

some of the by-caught animals. Estimation of by-catch mortalities by species are available for the 1994-1998

period. Prior estimates are for undifferentiated beaked whales. The estimated annual fishery-related mortality (CV in

parentheses) was 60 in 1989 (0.21), 76 in 1990 (0.26), 13 in 1991 (0.21), 9.7 in 1992 (0.24), and 12 in 1993 (0.16). 

The 1994-1998 estimates by ‘species’ are:

Year Cuvier’s Sowerby’s True’s Mesoplodon spp.

1994 1 (0.14) 3 (0.09) 0 0

 1995 0 6 (0) 1 (0) 3 (0)

1996 0 9 (0.12) 2 (0.26) 2 (0.25)

1997 NA NA NA NA

1998 0 2 (0) 2 (0) 7 (0)

During July 1996, one beaked whale was entangled and released alive with “gear in/around a single body part”. 

Annual mortality estimates do not include any animals injured and released alive. 

Other Mortality

From 1992- to 2000, a total of 53 beaked whales stranded along the USA Atlantic coast between Florida

and Massachusetts (NMFS unpublished data). This includes: 28 (includes one tentative identification) Gervais'

beaked whales (one 1997 animal had plastics in esophagus and stomach, and Sargassum in esophagus; 2 animals that

stranded in September 1998 in South Carolina showed signs of fishery interactions); 2 True's beaked whales; 5

Blainville’s beaked whales; 1 Sowerby’s beaked whales; 13 Cuvier's beaked whales (one 1996 animal had propeller

marks, and one 2000 animal had a longline hook in the lower jaw) and 4 unidentified animals. 

Also, several unusual mass strandings of beaked whales in North Atlantic marine environments have been

associated with naval activities. During the mid- to late 1980's multiple mass strandings of Cuvier’s beaked whales

(4 to about 20 per event) and small numbers of Gervais’ beaked whale and Blainville’s beaked whale occurred in the

Canary Islands (Simmonds and Lopez-Jurado (1991). Twelve Cuvier’s beaked whales that live stranded and

subsequently died in the Mediterranean Sea on 12-13 May 1996 were associated with low frequency acoustic sonar

tests conducted by the North Atlantic Treaty Organization (Frantzis 1998). In March 2000, 14 beaked whales live

stranded in the Bahamas; 6 beaked whales ( 5 Cuvier’s and 1 Blainville’s) died (Balcomb and Claridge 2001; Anon.

2002). Four Cuvier’s, 2 Blainville’s , and 2 unidentified beaked whales were returned to sea. The fate of the

animals returned to sea is unknown. Necropsies of 6 dead beaked whales revealed evidence of tissue trauma

associated with an acoustic or impulse injury that caused the animals to strand. Subsequently, the animals died due

to extreme physiologic stress associated with the physical stranding (i.e., hyperthermia, high endogenous

catecholamine release) (Anon. 2002). 
50

STATUS OF STOCK

The status of Cuvier's beaked whale relative to OSP in US Atlantic EEZ is unknown. This species is not

listed as threatened or endangered under the Endangered Species Act. Although a species specific PBR cannot be

determined, the permanent closure of the pelagic drift gillnet fishery has eliminated the principal known source of

incidental fishery mortality. The total fishery mortality and serious injury for this group is less than 10% of the

calculated PBR and, therefore, can be considered to be insignificant and approaching zero mortality and serious

injury rate. This is a strategic stock because of uncertainty regarding stock size and evidence of human induced

mortality and serious injury associated with acoustic activities. 

REFERENCES

Anon. 1990. Cruise results, NOAA Ship CHAPMAN, Cruise No. 90-05. Marine Mammal Sighting Survey. 5pp.

Available from: National Marine Fisheries Service, 166 Water Street, Woods Hole, MA 02543-1026.

Anon. 1991. Northeast cetacean aerial survey and interplatform study. NOAA-NMFS-SEFSC and NEFSC. 4 pp. 

Available from: National Marine Fisheries Service, 166 Water Street, Woods Hole, MA 02543-1026.

Anon. 1993. Cruise results, NOAA ship DELAWARE II, Cruise No. DEL 93-06, Marine mammal Survey. 5 pp. 

Available from: National Marine Fisheries Service, 166 Water Street, Woods Hole, MA 02543-1026.

Anon. 1994. Cruise results, NOAA Ship RELENTLESS, Cruise No. RS 94-02, Marine Mammal Survey/Warm

Core Ring Study. 8p. Available from: National Marine Fisheries Service, 166 Water Street, Woods Hole,

MA 02543-1026.

Anon. 2001. Joint interim report Bahamas marine mammal stranding event of 15-16 March 2000. (available from

National Marine Fisheries Service Office of Protected Resources, Silver Spring, MD). 66 pp.

Balcomb, K. C. III and D. E. Claridge. 2001. A mass stranding of cetaceans caused by naval sonar in the Bahamas. 

Bahamas J. Sci. 2:2-12.

Barlow, J., S. L. Swartz, T. C. Eagle and P. R. Wade. 1995. U.S. Marine Mammal Stock Assessments: Guidelines

for Preparation, Background, and a Summary of the 1995 Assessments. U.S. Dep. Commer., NOAA Tech.

Memo. NMFS-OPR-6, 73 pp. 

Buckland, S. T., D. R. Anderson, K. P. Burnham and J. L. Laake. 1993. Distance sampling: estimating abundance

of biological populations. Chapman and Hall, New York, NY, 442 pp.

CETAP. 1982. A characterization of marine mammals and turtles in the mid- and north Atlantic areas of the U.S.

outer continental shelf. Cetacean and Turtle Assessment Program, University of Rhode Island. Final

Report #AA551-CT8-48 to the Bureau of Land Management, Washington, DC, 538 pp.

Frantzis, A. 1998. Does acoustic testing strand whales? Nature 392:29. 

Heyning, J. E. 1989. Cuvier's beaked whale, Ziphius cavirostris G. Cuvier, 1823. Pages 289-308 In: S. H. Ridgway

and R. Harrison (eds), Handbook of Marine Mammals, Vol. 4: River dolphins and larger toothed whales. 

Academic Press, London, 442 pp. 

Houston, J. 1990. Status of Cuvier's Beaked Whale, Ziphius cavirostris, in Canada. Can. Fld. Nat. 105(2): 215-

218.

Laake, J. L., S. T. Buckland, D. R. Anderson and K. P. Burnham. 1993. DISTANCE user’s guide, V2.0. Colorado

Cooperative Fish and Wildlife Research Unit, Colorado State University, Ft. Collins, Colorado. 72 pp.

Leatherwood, S., D. K. Caldwell and H. E. Winn. 1976. Whales, dolphins, and porpoises of the western North

Atlantic. A guide to their identification. U.S. Dept. of Commerce, NOAA Tech. Rep. NMFS Circ. 396,

176 pp. 

Mead, J. G. 1984. Survey of reproductive data for the beaked whales (Ziphiidae). Rep. int Whal. Commn. (Special

Issue 6): 91-96. 

Mead, J.G. 1989. Beaked whales of the genus Mesoplodon. Pages 349-430. In: S.H. Ridgeway and R. Harrison

(eds.), Handbook of Marine Mammals, Vol. 4: River Dolphins and Toothed Whales. Academic Press, San

Diego, CA, 442 pp.

Mignucci-Giannoni, A. A., B. Pinto-Rodríguez, M. Velasco-Escudero, R. A. Montoya-Ospina, N. M. Jiménez, M.A.

Rodríguez-López, E. H. Williams, Jr., and D. K. Odell. 1999. Cetacean strandings in Puerto Rico and the

Virgin Islands. J. Cetacean Res. Manage. 1:191-198.

Mitchell, E. D. (ed). 1975. Review of the biology and fisheries for smaller cetaceans. Report of the meeting on

smaller cetaceans. Int Whal. Commn. J. Fish. Res. Bd. Can. 32(7): 875-1240.
51

Mullin, K. D. (in review). Abundance and distribution of cetaceans in the southern U.S. Atlantic Ocean during

summer 1998. Fish. Bull., U.S. 

Northridge, S. 1996. Estimation of cetacean mortality in the U.S. Atlantic swordfish and tuna drift gillnet and pair

trawl fisheries. Final report to the Northeast Fisheries Science Center, Contract No. 40ENNF500160.

Palka, D. 1995. Abundance estimate of the Gulf of Maine harbor porpoise. Rep. int Whal. Commn. (Special Issue

16):27-50.

Palka, D. 1996. Update on abundance of Gulf of Maine/Bay of Fundy harbor porpoises. NOAA/NMFS/NEFSC.

Ref. Doc. 96-04; 37 pp. Available from: National Marine Fisheries Service, 166 Water Street, Woods

Hole, MA 02543-1026.

Palka, D., G. Waring and D. Potter. (in review). Abundances of cetaceans and sea turtles in the northwest Atlantic

during summer 1995 and 1998. Fish Bull.

Read, A. J. 1994. Interactions between cetaceans and gillnet and trap fisheries in the Northwest Atlantic. Rep. int

Whal. Commn. (Special Issue 15): 133-147.

Simmonds, M. P. and L. F. Lopez-Jurado. 1991. Whales and the military. Nature 351:448.

Wade, P. R., and R. P. Angliss. 1997. Guidelines for assessing marine mammal stocks: Report of the GAMMS

Workshop April 3-5, 1996, Seattle, Washington. U.S. Dep. Commer., NOAA Tech. Memo. NMFS-OPR12, 93 pp.

Waring, G. T., C. P. Fairfield, C. M. Ruhsam, and M. Sano. 1992. Cetaceans associated with Gulf Stream features

off the northeastern USA shelf. ICES C.M. 1992/N:12 29 pp.

Waring, G. T. 1998. Results of the summer 1991 R/V Chapman marine mammal sighting survey. NOAA-NMFSNEFSC Lab. Ref. Doc. No. 98-09, 21 pp. Available from: National Marine Fisheries Service, 166 Water

St., Woods Hole, Massachusetts 02543-1026.

Waring, G. T., D. L. Palka, P. J. Clapham, S. Swartz, M. C. Rossman, T. V. N. Cole, L. J. Hansen, K. D. Bisack, K.

D. Mullin, R. S. Wells, D. K. Odell, and N. B. Barros. 1999. U.S. Atlantic and Gulf of Mexico marine

mammal stock assessments — 1999. U.S. Dep. Commer., NOAA Tech. Memo NMFS-NE-153, 196 pp. 
52

Figure 1. Distribution of beaked whale sightings from

NEFSC and SEFSC shipboard and aerial surveys during

the summer in 1990-1998. Isobaths are at 100 m and

1,000 m. 

January 2002

MESOPLODON BEAKED WHALES (Mesoplodon spp.):

Western North Atlantic Stock

STOCK DEFINITION AND GEOGRAPHIC RANGE

Within the genus Mesoplodon, there are four species of beaked whales that reside in the northwest Atlantic.

These include True's beaked whale, Mesoplodon mirus; Gervais' beaked whale, M. europaeus; Blainville's beaked

whale, M. densirostris; and Sowerby's beaked whale,

M. bidens (Mead 1989). These species are difficult

to identify to the species level at sea; therefore, much

of the available characterization for beaked whales is

to genus level only. Stock structure for each species

is unknown.

The distribution of Mesoplodon spp. in the

northwest Atlantic is known principally from

stranding records (Mead 1989; Nawojchik 1994;

Mignucci-Giannoni et al. 1999). Off the northeast

USA coast, beaked whale (Mesoplodon spp.)

sightings have occurred principally along the

southern edge of Georges Bank (CETAP, 1982;

Waring et al. 1992; NMFS unpublished data). Most

sightings were in late spring and summer. In

addition, beaked whales were also sighted in Gulf

Stream features during NEFSC 1990-1995 surveys

(Waring et al. 1992; Anon 1994; Tove 1995; NMFS

unpublished data). 

True's beaked whale is a temperate-water

species that has been reported from Cape Breton

Island, Nova Scotia, to the Bahamas (Leatherwood et

al. 1976; Mead 1989). It is considered rare in

Canadian waters (Houston 1990). 

Gervais' beaked whales are believed to be

principally oceanic, and strandings have been

reported from Cape Cod Bay to Florida, into the

Caribbean and the Gulf of Mexico (Leatherwood et

al. 1976; Mead 1989; NMFS unpublished data). 

This is the most common species of Mesoplodon to

strand along the USA Atlantic coast. The

northernmost stranding was on Cape Cod. 

Blainville's beaked whales have been reported from southwestern Nova Scotia to Florida, and are believed

to be widely but sparsely distributed in tropical to warm-temperate waters (Leatherwood et al. 1976; Mead 1989,

Nicolas et al. 1993). There are two records of strandings in Nova Scotia which probably represent strays from the

Gulf Stream (Mead 1989). They are considered rare in Canadian waters (Houston 1990). 

Sowerby's beaked whales have been reported from New England waters north to the ice pack, and

individuals are seen along the Newfoundland coast in summer (Leatherwood et al. 1976; Mead 1989). Furthermore,

a single stranding occurred off the Florida west coast (Mead 1989). This species is considered rare in Canadian

waters (Lien et al. 1990). 

POPULATION SIZE

The total number of Mesoplodon spp. beaked whales off the eastern USA and Canadian Atlantic coast is

unknown.
53

However, eight estimates of the undifferentiated complex of beaked whales (Ziphius and Mesoplodon spp.)

from selected regions of the habitat do exist for select time periods. Sightings were almost exclusively in the

continental shelf edge and continental slope areas (Figure 1). An abundance of 120 (CV=0.71) undifferentiated

beaked whales was estimated from an aerial survey program conducted from 1978 to 1982 on the continental shelf

and shelf edge waters between Cape Hatteras, North Carolina and Nova Scotia (CETAP 1982). An abundance of

442 (CV=0.51) undifferentiated beaked whales was estimated from an August 1990 shipboard line transect sighting

survey, conducted principally along the Gulf Stream north wall between Cape Hatteras and Georges Bank (Anon.

1990; Waring et al. 1992). An abundance of 262 (CV=0.99) undifferentiated beaked whales was estimated from a

June and July 1991 shipboard line transect sighting survey conducted primarily between the 200 and 2,000m

isobaths from Cape Hatteras to Georges Bank (Waring et al. 1992; Waring 1998). An abundance of 370

(CV=0.65) and 612 (CV=0.73) undifferentiated beaked whales was estimated from line transect aerial surveys

conducted from August to September 1991 using the Twin Otter and AT-11, respectively (Anon. 1991). As

recommended in the GAMMS Workshop Report (Wade and Angliss 1997), estimates older than eight years are

deemed unreliable, therefore should not be used for PBR determinations. Further, due to changes in survey

methodology these data should not be used to make comparisons to more current estimates. 

An abundance of 330 (CV=0.66) undifferentiated beaked whales was estimated from a June and July 1993

shipboard line transect sighting survey conducted principally between the 200 and 2,000m isobaths from the

southern edge of Georges Bank, across the Northeast Channel to the southeastern edge of the Scotian Shelf (Anon.

1993). Data were collected by two alternating teams that searched with 25x150 binoculars and were analyzed using

DISTANCE (Buckland et al. 1993; Laake et al. 1993). Estimates include school-size bias, if applicable, but do not

include corrections for g(0) or dive-time. Variability was estimated using bootstrap resampling techniques.

An abundance of 99 (CV=0.64) undifferentiated beaked whales was estimated from an August 1994

shipboard line transect survey conducted within a Gulf Stream warm-core ring located in continental slope waters

southeast of Georges Bank (Table 1; Anon. 1994). Data were collected by two alternating teams that searched with

25x150 binoculars and an independent observer who searched by naked eye from a separate platform on the bow. 

Data were analyzed using DISTANCE (Buckland et al. 1993; Laake et al. 1993). Estimates include school-size bias,

if applicable, but do not include corrections for g(0) or dive-time. Variability was estimated using bootstrap

resampling techniques.

An abundance of 1,519 (CV=0.69) undifferentiated beaked whales was estimated from a July to September

1995 sighting survey conducted by two ships and an airplane that covered waters from Virginia to the mouth of the

Gulf of St. Lawrence (Table 1; Palka et al. in review). Total track line length was 32,600 km. The ships covered

waters between the 50 and 1000 fathom depth contour lines, the northern edge of the Gulf Stream, and the northern

Gulf of Maine/Bay of Fundy region. The airplane covered waters in the mid-Atlantic from the coastline to the 50

fathom depth contour line, the southern Gulf of Maine, and shelf waters off Nova Scotia from the coastline to the

1000 fathom depth contour line. Data collection and analysis methods used were described in Palka (1996). 

An abundance of 2,600 (CV=0.40) undifferentiated beaked whales was estimated from a line transect

sighting survey conducted during July 6 to September 6, 1998 by a ship and plane that surveyed 15,900 km of track

line in waters north of Maryland (38° N) (Figure 1; Palka et al. in review). Shipboard data were analyzed using the

modified direct duplicate method (Palka 1995) that accounts for school size bias and g(0), the probability of

detecting a group on the track line. Aerial data were not corrected for g(0).

An abundance of 596 (CV=0.50) for undifferentiated beaked whales was estimated from a shipboard line

transect sighting survey conducted between 8 July and 17 August 1998 that surveyed 5,570 km of track line in

waters south of Maryland (38°N) (Figure 1; Mullin in review). Abundance estimates were made using the program

DISTANCE (Buckland et al. 1993; Laake et al. 1993) where school size bias and ship attraction were accounted for.

The best available abundance estimate for undifferentiated beaked whales is the sum of the estimates from

the two 1998 USA Atlantic surveys, 3,196 (CV=0.34), where the estimate from the northern USA Atlantic is 2,600

(CV=0.40) and from the southern USA Atlantic is 596 (CV=0.50). This joint estimate is considered best because

together these two surveys have the most complete coverage of the species’ habitat.

Although the 1990-1998 surveys did not sample exactly the same areas or encompass the entire beaked

whale habitat, they did focus on segments of known or suspected high-use habitats off the northeastern USA coast. 

The collective 1990-98 data suggest that, seasonally, at least several thousand beaked whales are occupying these

waters, with highest levels of abundance in the Georges Bank region. Recent results suggest that beaked whale

abundance may be highest in association with Gulf Stream and warm-core ring features. 
54

Because the estimates presented here were not dive-time corrected, they are likely negatively biased and

probably underestimate actual abundance. Given that Mesoplodon spp. prefers deep-water habitats (Mead 1989) the

bias may be substantial. 

Table 1. Summary of abundance estimates for the undifferentiated complex of beaked whales which include Ziphius

and Mesoplodon spp. Month, year, and area covered during each abundance survey, and resulting

abundance estimate (Nbest) and coefficient of variation (CV).

Month/Year Area Nbest CV

Aug 1994 warm-core ring SE of Georges Bank 99 0.64

Jul-Sep 1995 Virginia to Gulf of St. Lawrence 1,519 0.69

Jul-Sep 1998 Maryland to Gulf of St. Lawrence 2,600 0.40

Jul-Aug 1998 Florida to Maryland 596 0.50

Jul-Sep 1998 Gulf of St. Lawrence to Florida (COMBINED) 3,196 0.34

Minimum Population Estimate

The minimum population estimate is the lower limit of the two-tailed 60% confidence interval of the lognormally distributed best abundance estimate. This is equivalent to the 20th percentile of the log-normal distribution

as specified by Wade and Angliss (1997). The best estimate of abundance for undifferentiated beaked whales is 

3,196 (CV=0.34). The minimum population estimate for the undifferentiated complex of beaked whales (Ziphius

and Mesoplodon spp.) is 2,419 (CV=0.34). It is not possible to determine the minimum population estimate of only

Mesoplodon beaked whales.

Current Population Trend

There are insufficient data to determine the population trends for these species. 

CURRENT AND MAXIMUM NET PRODUCTIVITY RATES

Current and maximum net productivity rates are unknown for this stock. Life history parameters that could

be used to estimate net productivity include: length at birth is 2 to 3 m, length at sexual maturity 6.1 m for females,

and 5.5 m for males, maximum age for females were 30 growth layer groups (GLG's) and for males was 36 GLG's,

which may be annual layers (Mead 1984). 

For purposes of this assessment, the maximum net productivity rate was assumed to be 0.04. This value is

based on theoretical modeling showing that cetacean populations may not grow at rates much greater than 4% given

the constraints of their reproductive life history (Barlow et al. 1995). 

POTENTIAL BIOLOGICAL REMOVAL

Potential Biological Removal (PBR) is the product of minimum population size, one-half the maximum

productivity rate, and a “recovery” factor (MMPA Sec. 3. 16 U.S.C. 1362; Wade and Angliss 1997). The minimum

population size for the undifferentiated complex of beaked whales is 2,419 (CV=0.34). The maximum productivity

rate is 0.04, the default value for cetaceans. The “recovery” factor, which accounts for endangered, depleted,

threatened stocks, or stocks of unknown status relative to optimum sustainable population (OSP) is assumed to be

0.5 because this stock is of unknown status. PBR for all species in the undifferentiated complex of beaked whales

(Ziphius and Mesoplodon spp.) is 24. It is not possible to determine the PBR for only Mesoplodon beaked whales.

ANNUAL HUMAN-CAUSED MORTALITY AND SERIOUS INJURY

The 1996-2000 total average estimated annual fishery-related mortality of beaked whales in open fisheries

in the US Atlantic EEZ was zero.
55

Fishery Information

There is no historical information available that documents incidental mortality in either USA or Canadian

Atlantic coast fisheries (Read 1994). 

Current data on incidental takes in USA fisheries are available from several sources. In 1986, NMFS

established a mandatory self-reported fisheries information system for large pelagic fisheries. Data files are

maintained at Southeast Fisheries Science Center (SEFSC). The Northeast Fisheries Science Center (NEFSC) Sea

Sampling Observer Program was initiated in 1989, and since that year several fisheries have been covered by the

program. In late 1992 and in 1993 the SEFSC provided observer coverage of pelagic longline vessels fishing off the

Grand Banks (Tail of the Banks) and currently provides observer coverage of vessels fishing south of Cape Hatteras.

 Total fishery-related mortality and serious injury cannot be estimated separately for each beaked whale

species because of the uncertainty in species identification by fishery observers. The Atlantic Scientific Review

Group advised adopting the risk-averse strategy of assuming that any beaked whale stock which occurred in the US

Atlantic EEZ might have been subject to the observed fishery-related mortality and serious injury.

Bycatch has been observed by NMFS sea samplers in the pelagic drift gillnet fishery, but no mortalities or

serious injuries have been documented in the pelagic longline, pelagic trawl, Northeast multispecies sink gillnet,

mid-Atlantic coastal gillnet, or North Atlantic bottom trawl fisheries by NMFS sea samplers. 

Pelagic Drift Gillnet

The estimated total number of hauls in the pelagic drift gillnet fishery increased from 714 in 1989 to 1,144

in 1990; thereafter, with the introduction of quotas, effort was severely reduced. The estimated number of hauls in

1991, 1992, 1993, 1994, 1995, 1996, and 1998 were 233, 243, 232, 197, 164, 143, and 113 respectively. In 1996

and 1997, NMFS issued management regulations which prohibited the operation of this fishery in 1997. Further, in

January 1999, NMFS issued a Final Rule to prohibit the use of driftnets (i.e., permanent closure) in the North

Atlantic swordfish fishery (50 CFR Part 630). Fifty-nine different vessels participated in this fishery at one time or

another between 1989 and 1993. From 1994 to 1998, between 10 and 13 vessels have participated in the fishery. 

Observer coverage, expressed as percent of sets observed, was 8% in 1989, 6% in 1990, 20% in 1991, 40% in 1992,

42% in 1993, 87% in 1994, 99% in 1995, 64% in 1996, and 99% in 1998. Effort was concentrated along the

southern edge of Georges Bank and off Cape Hatteras. Examination of the species composition of the catch and

locations of the fishery throughout the year, suggested that the pelagic drift gillnet fishery be stratified into two

strata, a southern or winter stratum, and a northern or summer stratum. Estimates of the total bycatch, for each year

from 1989 to 1993, were obtained using the aggregated (pooled 1989-1993) catch rates, by strata (Northridge 1996). 

Estimates of total annual bycatch for 1994-1998 were estimated from the sum of the observed caught and the product

of the average bycatch per haul and the number of unobserved hauls as recorded in self-reported fisheries

information. Variances were estimated using bootstrap re-sampling techniques. Bycatch of beaked whales has only

occurred from Georges Canyon to Hydrographer Canyon along the continental shelf break and continental slope

during July to October. Forty-six fishery-related beaked whale mortalities were observed between 1989 and 1998. 

These included: 24 Sowerby’s; 4 True’s; 1 Cuvier’s; and 17 undifferentiated beaked whales. Recent analysis of

biological samples (genetics and morphological analysis) have been used to determine species identifications for

some of the by-caught animals. Estimation of bycatch mortality by species are available for the 1994-1998 period.

Prior estimates are for undifferentiated beaked whales. The estimated annual fishery-related mortality (CV in

parentheses) was 60 in 1989 (0.21), 76 in 1990 (0.26), 13 in 1991 (0.21), 9.7 in 1992 (0.24), and 12 in 1993 (0.16). 

The 1994-1998 estimates by ‘species’ are:

Year Cuvier’s Sowerby’s True’s Mesoplodon spp.

1994 1 (0.14) 3 (0.09) 0 0

 1995 0 6 (0) 1 (0) 3 (0)

1996 0 9 (0.12) 2 (0.26) 2 (0.25)

1997 NA NA NA NA

1998 0 2 (0) 2 (0) 7 (0)
56

During July 1996, one beaked whale was entangled and released alive with “gear in/around a single body part”. 

Annual mortality estimates do not include any animals injured and released alive. 

Other Mortality

From 1992-2000, a total of 53 beaked whales stranded along the USA Atlantic coast between Florida and

Massachusetts (NMFS unpublished data). This includes: 28 (includes one tentative identification) Gervais' beaked

whales (one 1997 animal had plastics in esophagus and stomach, and Sargassum in esophagus; 2 animals that

stranded in September 1998 in South Carolina showed signs of fishery interactions); 2 True's beaked whales; 5

Blainville’s beaked whales; 1 Sowerby’s beaked whale; 13 Cuvier's beaked whales (one 1996 animal had propeller

marks, and one 2000 animal had a longline hook in the lower jaw ) and 4 unidentified animals. The 1999 strandings

data are still under review.

One stranding of Sowerby’s beaked whale was recorded on Sable Island between 1970-1998 (Lucas and

Hooker 2000). The whale’s body was marked by wounds made by the cookiecutter shark (Isistius brasiliensis),

which has previously been observed on beaked whales (Lucas and Hooker 2000).

Also, several unusual mass strandings of beaked whales in North Atlantic marine environments have been

associated with naval activities. During the mid- to late 1980's multiple mass strandings of Cuvier’s beaked whales

(4 to about 20 per event) and small numbers of Gervais’ beaked whale and Blainville’s beaked whale occurred in

the Canary Islands (Simmonds and Lopez-Jurado (1991). Twelve Cuvier’s beaked whales that live stranded and 

subsequently died in the Mediterranean Sea on 12-13 May 1996 was associated with low frequency acoustic sonar

tests conducted by the North Atlantic Treaty Organization (Frantzis 1998). In March 2000, fourteen beaked whales

live stranded in the Bahamas; six beaked whales ( 5 Cuvier’s and 1 Blainville’s) died (Balcomb and Claridge 2001;

Anon. 2002). Four Cuvier’s, 2 Blainville’s , and 2 unidentified beaked whales were returned to sea. The fate of the

animals returned to sea is unknown. Necropsy of six dead beaked whales revealed evidence of tissue trauma

associated with an acoustic or impulse injury that caused the animals to strand. Subsequently, the animals died due

to extreme physiologic stress associated with the physical stranding (i.e., hyperthermia, high endogenous

catecholamine release) (Anon. 2002). 

STATUS OF STOCK

The status of Mesoplodon beaked whales relative to OSP in US Atlantic EEZ is unknown. These species

are not listed as threatened or endangered under the Endangered Species Act. Although a species specific PBR

cannot be determined, the permanent closure of the pelagic drift gillnet fishery has eliminated the principal known

source of incidental fishery mortality. The total fishery mortality and serious injury for this group is less than 10%

of the calculated PBR and, therefore, can be considered to be insignificant and approaching zero mortality and

serious injury rate. This is a strategic stock because of uncertainty regarding stock size and evidence of human

induced mortality and serious injury associated with acoustic activities. 

REFERENCES

Anon. 1990. Cruise results, NOAA Ship CHAPMAN, Cruise No. 90-05. Marine Mammal Sighting Survey. 5 pp.

Available from: National Marine Fisheries Service, 166 Water Street, Woods Hole, MA 02543-1026.

Anon. 1991. Northeast cetacean aerial survey and interplatform study. NOAA-NMFS- SEFSC and NEFSC. 4 pp. 

Available from: National Marine Fisheries Service, 166 Water Street, Woods Hole, MA 02543-1026.

Anon. 1993. Cruise results, NOAA ship DELAWARE II, Cruise No. DEL 93-06, Marine mammal Survey. 5 pp. 

Available from: National Marine Fisheries Service, 166 Water Street, Woods Hole, MA 02543-1026.

Anon. 1994. Cruise results, NOAA ship RELENTLESS, Cruise No. RS 9402, Marine Mammal Survey/Warm Core

Ring Study. 8 pp. Available from: National Marine Fisheries Service, 166 Water Street, Woods Hole, MA

02543-1026.

Anon. 2001. Joint interim report Bahamas marine mammal stranding event of 15-16 March 2000. (available from

National Marine Fisheries Service Office of Protected Resources, Silver Spring, MD). 66 pp.

Balcomb, K. C. III and D. E. Claridge. 2001. A mass stranding of cetaceans caused by naval sonar in the Bahamas. 

Bahamas J. Sci. 2:2-12.

Barlow, J., S. L. Swartz, T. C. Eagle and P. R. Wade. 1995. U.S. Marine Mammal Stock Assessments: Guidelines

for Preparation, Background, and a Summary of the 1995 Assessments. U.S. Dep. Commer., NOAA Tech.

Memo. NMFS-OPR-6, 73 pp.
57

Buckland, S. T., D. R. Andersen, K. P. Burnham and J. L. Laake. 1993. Distance sampling: Estimating abundance

of biological populations. Chapman and Hall, New York, 446 pp. 

CETAP. 1982. A characterization of marine mammals and turtles in the mid- and north Atlantic areas of the U.S.

outer continental shelf. Cetacean and Turtle Assessment Program, University of Rhode Island. Final

Report #AA551-CT8-48 to the Bureau of Land Management, Washington, DC, 538 pp. 

Frantzis, A. 1998. Does acoustic testing strand whales? Nature 392:29. 

Houston, J. 1990. Status of Blainville’s beaked whale, Mesoplodon densirostris, in Canada. Can. Field Nat.

104(1): 117-120. 

Laake, J. L., S. T. Buckland, D. R. Anderson and K. P. Burnham. 1993. DISTANCE user’s guide, V2.0. Colorado

Cooperative Fish & Wildlife Research Unit, Colorado State University, Ft. Collins, Colorado, 72 pp. 

Leatherwood, S., D. K. Caldwell and H. E. Winn. 1976. Whales, dolphins, and porpoises of the western North

Atlantic. A guide to their identification. U.S. Dept. of Commerce, NOAA Tech. Rep. NMFS Circ. 396, 176

pp. 

Lien J., F. Barry, K. Breeck, and U. Zuschlag. 1990. Status of Sowerby's Beaked Whale, Mesoplodon bidens, in

Canada. Can. Field Nat. 104(1): 125-130.

Lucas, Z. N. and S. K. Hooker. 2000. Cetacean strandings on Sable Island, Nova Scotia, 1970-1998. Can. Field

Nat.:114 (45-61).

Mead, J. G. 1984. Survey of reproductive data for the beaked whales (Ziphiidae). Rep. int Whal. Commn. Special

Issue 6:91-96.

Mead, J. G. 1989. Beaked whales of the genus Mesoplodon. Pages 349-430 in: S. H., Ridgway and R. Harrison

(eds), Handbook of marine mammals, Vol. 4: River Dolphins and toothed whales. Academic press, San

Diego, 442 pp. 

Mignucci-Giannoni, A. A., B. Pinto-Rodríguez, M. Velasco-Escudero, R. A. Montoya-Ospina, N. M. Jiménez, M.A.

Rodríguez-López, E. H. Williams, Jr., and D. K. Odell. 1999. Cetacean strandings in Puerto Rico and the

Virgin Islands. J. Cetacean Res. Manage. 1:191-198.

Mullin, K. D. (in review). Abundance and distribution of cetaceans in the southern U.S. Atlantic Ocean during

summer 1998. Fish. Bull., U.S.

Nawojchik, R. 1994. First record of Mesoplodon densirostris (Cetacea: Ziphiidae) from Rhode Island. Mar.

Mammal. Sci. 10: 477-480.

Nicolas, J., A. Williams and G. Repucci. 1993. Observations of beaked whales (Mesoplodon spp.) in the western

North Atlantic Ocean. Proceedings of the Tenth Biennial Conference on the Biology of Marine Mammals,

Nov. 11-15, 1993, Galveston, TX (Abstract). 

Palka, D. 1995. Abundance estimate of the Gulf of Maine harbor porpoise. Rep. int Whal. Commn. (Special Issue

16):27-50.

Palka, D., G. Waring and D. Potter. (in review). Abundances of cetaceans and sea turtles in the northwest Atlantic 

during summer 1995 and 1998. Fish. Bull., U.S.

Northridge, S. 1996. Estimation of cetacean mortality in the U.S. Atlantic swordfish and tuna drift gillnet and pair

trawl fisheries. Final report to the Northeast Fisheries Science Center, Contract No. 40ENNF500160. 

Read, A. J. 1994. Interactions between cetaceans and gillnet and trap fisheries in the Northwest Atlantic. Rep. int

Whal. Commn. (Special Issue 1): 133-147.

Simmonds, M. P. and L. F. Lopez-Jurado. 1991. Whales and the military. Nature 351:448.

Trove, M. 1995. Live sighting of Mesoplodon CF. M. Mirus, True’s Beaked Whale. Mar. Mammal Sci. 11(1): 80-

85.

Wade, P. R., and R. P. Angliss. 1997. Guidelines for assessing marine mammal stocks: Report of the GAMMS

Workshop April 3-5, 1996, Seattle, Washington. U.S. Dep. Commer., NOAA Tech. Memo. NMFS-OPR12, 93 pp.

Waring, G. T., C. P. Fairfield, C. M. Ruhsam and M. Sano. 1992. Cetaceans associated with Gulf Stream features

off the northeastern USA shelf. ICES C.M. 1992/N:12. 29 pp.

Waring, G. T. 1998. Results of the summer 1991 R/V Chapman marine mammal sighting survey. NOAA NMFS

NEFSC, Lab. Ref. Doc. No. 98-09, 21 pp. Available from: National Marine Fisheries Service, 166 Water

Street, Woods Hole, MA 02543-1026.
58

Waring, G. T., D. L. Palka, P. J. Clapham, S. Swartz, M. C. Rossman, T. V. N. Cole, L. J. Hansen, K. D. Bisack, K.

D. Mullin, R. S. Wells, D. K. Odell, and N. B. Barros. 1999. U.S. Atlantic and Gulf of Mexico marine

mammal stock assessments — 1999. U.S. Dep. Commer., NOAA Tech. Memo NMFS-NE-153, 196 pp.
59

Figure 1. Distribution of Risso’s dolphin sightings from

NEFSC and SEFSC shipboard and aerial surveys during

the summer in 1990-1998. Isobaths are at 100 m and

1,000 m.

January 2002

RISSO'S DOLPHIN (Grampus griseus):

Western North Atlantic Stock

STOCK DEFINITION AND GEOGRAPHIC RANGE

Risso's dolphins are distributed worldwide in tropical and temperate seas. They generally have an oceanic

range, and occur along the Atlantic coast of North America from Florida to eastern Newfoundland (Leatherwood et

al. 1976; Baird and Stacey 1990). Off the northeast USA coast, Risso's dolphins are distributed along the

continental shelf edge from Cape Hatteras northward to Georges Bank during the spring, summer, and autumn

(CETAP 1982; Payne et al. 1984). In winter, the range begins at the mid-Atlantic bight and extends further into

oceanic waters (Payne et al. 1984). In general, the population occupies the mid-Atlantic continental shelf edge year

round, and is rarely seen in the Gulf of Maine (Payne et al. 1984). During 1990, 1991 and 1993, spring/summer

surveys conducted in continental shelf edge and deeper oceanic waters had sightings of Risso's dolphins associated

with strong bathymetric features, Gulf Stream warm-core rings, and the Gulf Stream north wall (Waring et al. 1992;

Waring 1993). There is no information on stock differentiation of Risso's dolphin in the western North Atlantic. 

POPULATION SIZE

Total numbers of Risso’s dolphins off the USA or Canadian Atlantic coast are unknown, although eight

estimates from selected regions of the habitat do exist for select time periods. Sightings were almost exclusively in

the continental shelf edge and continental slope areas

(Figure 1). An abundance of 4,980 Risso’s dolphins

(CV=0.34) was estimated from an aerial survey

program conducted from 1978 to 1982 on the

continental shelf and shelf edge waters between Cape

Hatteras, North Carolina and Nova Scotia (CETAP

1982). An abundance of 11,017 (CV=0.58) Risso’s

dolphins was estimated from a June and July 1991

shipboard line transect sighting survey conducted

primarily between the 200 and 2,000m isobaths from

Cape Hatteras to Georges Bank (Waring et al. 1992;

Waring 1998). An abundance of 6,496 (CV=0.74)

and 16,818 (CV=0.52) Risso’s dolphins was

estimated from line transect aerial surveys conducted

from August to September 1991 using the Twin Otter

and AT-11, respectively (Anon. 1991). As

recommended in the GAMS Workshop Report

(Wade and Angliss 1997), estimates older than eight

years are deemed unreliable, therefore should not be

used for PBR determinations. Further, due to

changes in survey methodology these data should not

be used to make comparisons to more current

estimates. 

An abundance of 212 (CV=0.62) Risso’s

dolphins was estimated from a June and July 1993

shipboard line transect sighting survey conducted

principally between the 200 and 2,000m isobaths

from the southern edge of Georges Bank, across the

Northeast Channel to the southeastern edge of the

Scotian Shelf (Anon. 1993). Data were collected by

two alternating teams that searched with 25x150

binoculars and were analyzed using DISTANCE 
60

(Buckland et al. 1993; Laake et al. 1993). Estimates include school-size bias, if applicable, but do not include

corrections for g(0) or dive-time. Variability was estimated using bootstrap resampling techniques.

An abundance of 5,587 (CV=1.16) Risso’s dolphins was estimated from a July to September 1995 sighting

survey conducted by two ships and an airplane that covered waters from Virginia to the mouth of the Gulf of St.

Lawrence (Table 1; Palka et al. in review). Total track line length was 32,600 km. The ships covered waters

between the 50 and 1000 fathom depth contour lines, the northern edge of the Gulf Stream, and the northern Gulf of

Maine/Bay of Fundy region. The airplane covered waters in the mid-Atlantic from the coastline to the 50 fathom

depth contour line, the southern Gulf of Maine, and shelf waters off Nova Scotia from the coastline to the 1000

fathom depth contour line. Data collection and analysis methods used were described in Palka (1996). 

An abundance of 18,631 (CV=0.35) Risso’s dolphins was estimated from a line transect sighting survey

conducted during July 6 to September 6, 1998 by a ship and plane that surveyed 15,900 km of track line in waters

north of Maryland (38° N) (Figure 1; Palka et al. in review). Shipboard data were analyzed using the modified

direct duplicate method (Palka 1995) that accounts for school size bias and g(0), the probability of detecting a group

on the track line. Aerial data were not corrected for g(0).

An abundance of 10,479 (CV=0.51) Risso’s dolphins was estimated from a shipboard line transect sighting

survey conducted between 8 July and 17 August 1998 that surveyed 5,570 km of track line in waters south of

Maryland (38°N) (Figure 1; Mullin in review). Abundance estimates were made using the program DISTANCE

(Buckland et al. 1993; Laake et al. 1993) where school size bias and ship attraction were accounted for.

The best available abundance estimate for Risso’s dolphins, 29,110 (CV=0.29), is the sum of the estimates

from the two 1998 USA Atlantic surveys where the estimate from the northern USA Atlantic is 18,631 (CV=0.35)

and from the southern USA Atlantic is 10,479 (CV=0.51). This joint estimate is considered best because together

these two surveys have the most complete coverage of the species’ habitat.

Table 1. Summary of abundance estimates for the western North Atlantic Risso’s dolphin. Month, year, and area

covered during each abundance survey, resulting abundance estimate (Nbest) and coefficient of variation

(CV).

Month/Year Area Nbest CV

Jul-Sep 1995 Virginia to Gulf of St. Lawrence 5587 1.16

Jul-Sep 1998 Maryland to Gulf of St. Lawrence 18,631 0.35

Jul-Aug 1998 Florida to Maryland 10,479 0.51

Jul-Sep 1998 Gulf of St. Lawrence to Florida (COMBINED) 29,110 0.29

Minimum Population Estimate

The minimum population estimate is the lower limit of the two-tailed 60% confidence interval of the lognormally distributed best abundance estimate. This is equivalent to the 20th percentile of the log-normal distribution

as specified by Wade and Angliss (1997). The best estimate of abundance for Risso’s dolphins is 29,110

(CV=0.29). The minimum population estimate for the western North Atlantic Risso’s dolphin is 22,916 (CV=0.29).

Current Population Trend

There are insufficient data to determine the population trends for this species. 

CURRENT AND MAXIMUM NET PRODUCTIVITY RATES

Current and maximum net productivity rates are unknown for this stock. For purposes of this assessment,

the maximum net productivity rate was assumed to be 0.04. This value is based on theoretical modeling showing

that cetacean populations may not grow at rates much greater than 4% given the constraints of their reproductive life

history (Barlow et al. 1995).
61

POTENTIAL BIOLOGICAL REMOVAL

Potential Biological Removal (PBR) is the product of minimum population size, one-half the maximum

productivity rate, and a “recovery” factor (MMPA Sec. 3. 16 U.S.C. 1362; Wade and Angliss 1997). The minimum

population size is 22,916 (CV=0.29). The maximum productivity rate is 0.04 , the default value for cetaceans

(Barlow et al. 1995). The “recovery” factor, which accounts for endangered, depleted, threatened stocks, or stocks

of unknown status relative to optimum sustainable population (OSP) is assumed to be 0.48 because the CV of the

average mortality estimate is between 0.3 and 0.6 (Wade and Angliss 1997). PBR for the western North Atlantic

Risso’s dolphin is 220.

ANNUAL HUMAN-CAUSED MORTALITY

 Total annual estimated average fishery-related mortality or serious injury to this stock during 1996-2000

was 51 Risso's dolphins (CV=0.52; Table 2). 

Fishery Information

Prior to 1977, there was no documentation of marine mammal bycatch in distant-water fleet (DWF)

activities off the northeast coast of the USA. With implementation of the Magnuson Fisheries Conservation and

Management Act (MFCMA) in that year, an observer program was established which has recorded fishery data and

information of incidental bycatch of marine mammals. DWF effort in the USA Atlantic Exclusive Economic Zone

(EEZ) under MFCMA has been directed primarily towards Atlantic mackerel and squid. From 1977 through 1982,

an average of 120 different foreign vessels per year (range 102-161) operated within the US Atlantic EEZ. In 1982,

there were 112 different foreign vessels; 16%, or 18, were Japanese tuna longline vessels operating along the USA

east coast. This was the first year that the Northeast Regional Observer Program assumed responsibility for observer

coverage of the longline vessels. Between 1983 and 1991, the numbers of foreign vessels operating within US

Atlantic EEZ each year were 67, 52, 62, 33, 27, 26, 14, 13, and 9, respectively. Between 1983 and 1988, the

numbers of DWF vessels included 3, 5, 7, 6, 8, and 8, respectively, Japanese longline vessels. Observer coverage on

DWF vessels was 25-35% during 1977-82, and increased to 58%, 86%, 95%, and 98%, respectively, in 1983-86. 

From 1987-91, 100% observer coverage was maintained. Foreign fishing operations for squid and mackerel ceased

at the end of the 1986 and 1991 fishing seasons, respectively. NMFS foreign-fishery observers have reported four

deaths of Risso's dolphins incidental to squid and mackerel fishing activities in the continental shelf and continental

slope waters between March 1977 and December 1991 (Waring et al. 1990; NMFS unpublished data). Three

animals were taken by squid trawlers and a single animal was killed in longline fishing operations. 

 Data on current incidental takes in USA fisheries are available from several sources. In 1986, NMFS

established a mandatory self-reported fisheries information system for large pelagic fisheries. Data files are

maintained at the Southeast Fisheries Science Center (SEFSC). The Northeast Fisheries Science Center (NEFSC)

Sea Sampling Observer Program was initiated in 1989, and since that year several fisheries have been covered by the

program. In late 1992 and in 1993, the SEFSC provided observer coverage of pelagic longline vessels fishing off the

Grand Banks (Tail of the Banks) and provides observer coverage of vessels fishing south of Cape Hatteras. 

Bycatch has been observed by NMFS Sea Samplers in the pelagic drift gillnet fishery, pelagic pair trawl

fishery, and pelagic longline fishery, but no mortalities or serious injuries have been documented in the Northeast

multispecies sink gillnet, mid-Atlantic coastal gillnet, or North Atlantic bottom trawl observed fisheries.

Pelagic Drift Gillnet

The estimated total number of hauls in the pelagic drift gillnet fishery increased from 714 in 1989 to 1,144

in 1990; thereafter, with the introduction of quotas, effort was severely reduced. The estimated number of hauls in

1991, 1992, 1993, 1994, 1995,1996, and 1998 were 233, 243, 232, 197, 164,149, and 113 respectively. In 1996 and

1997, NMFS issued management regulations which prohibited the operation of this fishery in 1997. Further, in

January 1999 NMFS issued a Final Rule to prohibit the use of driftnets (i.e., permanent closure) in the North

Atlantic swordfish fishery (50 CFR Part 630). Fifty-nine different vessels participated in this fishery at one time or

another between 1989 and 1993. From 1994-1998, between 10 and 13 vessels have participated in the fishery. 

Observer coverage, expressed as percent of sets observed, was 8% in 1989, 6% in 1990, 20% in 1991, 40% in 1992,

42% in 1993, 87% in 1994, 99% in 1995, 64% in 1996, and 99% in 1998. Effort was concentrated along the

southern edge of Georges Bank and off Cape Hatteras. Examination of the species composition of the catch and

locations of the fishery throughout the year, suggested that the pelagic drift gillnet fishery be stratified into two

strata, a southern or winter stratum, and a northern or summer stratum. Estimates of the total bycatch, for each year
62

from 1989 to 1993, were obtained using the aggregated (pooled 1989-1993) catch rates, by strata (Northridge 1996). 

Estimates of total annual bycatch for 1994 and 1995 were estimated from the sum of the observed caught and the

product of the average bycatch per haul and the number of unobserved hauls as recorded in self-reported fisheries

information. Variances were estimated using bootstrap re-sampling techniques. Fifty-one Risso's dolphin

mortalities were observed between 1989 and 1998. One animal was entangled and released alive. Bycatch occurred

during July, September and October along continental shelf edge canyons off the southern New England coast. 

Estimated annual mortality and serious injury (CV in parentheses) attributable to the drift gillnet fishery was 87 in

1989 (0.52), 144 in 1990 (0.46), 21 in 1991 (0.55), 31 in 1992 (0.27), 14 in 1993 (0.42), 1.5 in 1994 (0.16), 6 in

1995 (0), 0 in 1996, no fishery in 1997, 9 in 1998 (0). Since this fishery no longer exists, it has been excluded from

Table 2.

Pelagic Pair Trawl

 Effort in the pelagic pair trawl fishery increased during the period 1989 to 1993, from zero hauls in 1989

and 1990, to an estimated 171 hauls in 1991, and then to an estimated 536 hauls in 1992, 586 in 1993, 407 in 1994,

and 440 in 1995, respectively. This fishery ceased operations in 1996, when NMFS rejected a petition to consider

pair trawl gear as an authorized gear type in the Atlantic tuna fishery. The fishery operated from August-November

in 1991, from June-November in 1992, from June-October in 1993 (Northridge 1996), and from mid-summer to

November in 1994 and 1995. Sea sampling began in October 1992 (Gerrior et al. 1994), and 48 sets (9% of the

total) were sampled in that season, 102 hauls (17% of the total) were sampled in 1993. In 1994 and 1995, 52% and

55%, respectively, of the sets were observed. Nineteen vessels have operated in this fishery. The fishery extends

from 35o

N to 41oN, and from 69°W to 72°W. Approximately 50% of the total effort was within a one degree square

at 39o

N, 72oW, around Hudson Canyon. Examination of the 1991-1993 locations and species composition of the

bycatch, showed little seasonal change for the six months of operation and did not warrant any seasonal or areal

stratification of this fishery (Northridge 1996). One mortality was observed in 1992. Estimated annual fisheryrelated mortality (CV in parentheses) was 0.6 dolphins in 1991 (1.0), 4.3 in 1992 (0.76), 3.2 in 1993 (1.0), 0 in 1994

and 3.7 in 1995 (0.45). Since this fishery no longer exists, it has been excluded from Table 2.

During the 1994 and 1995 experimental fishing seasons, fishing gear experiments were conducted to collect

data on environmental parameters, gear behavior, and gear handling practices to evaluate factors affecting catch and

bycatch (Goudey 1995, 1996). Results of these studies were inconclusive in identifying factors responsible for

marine mammal bycatch.

Pelagic Longline

Total effort, excluding the Gulf of Mexico, for the pelagic longline fishery, based on mandatory selfreported fisheries information, was 11,279 sets in 1991, 10,311 sets in 1992, 10,444 sets in 1993, 11,082 sets in

1994, 11,493 sets in 1995, 9,864 sets in 1996, 9,499 sets in 1997, 7,589 sets in 1998, 6,786 sets in 1999, and 6,582

sets in 2000 (Cramer 1994; Scott and Brown 1997; Johnson et al. 1999; Yeung 1999a; Yeung et al. 2000; Yeung

2001). This annual effort has been recalculated to include those sets targeting other species in conjunction with

tuna/swordfish, instead of just effort that exclusively targeted tuna/swordfish as in previous reports (Johnson et al.

1999; Yeung 1999a). The result is an average increase in self-reported effort of roughly 10% on the average (Yeung

et al. 2000). The fishery has been observed from January to March off Cape Hatteras, in May and June in the entire

mid-Atlantic, and in July through December in the mid-Atlantic Bight and off Nova Scotia. This fishery has been

monitored with 3-6% observer coverage, in terms of sets observed, since 1992. The 1993-1997 estimated take was

based on a revised analysis of the observed incidental take and self-reported incidental take and effort data, and

replaces previous estimates for the 1990-1993 and 1994-1995 periods (Cramer 1994; Scott and Brown 1997;

Johnson et al. 1999). Further, Yeung (1999b), revised the 1992-1997 fishery mortality estimates in Johnson et al.

(1999) to include seriously injured animals. The 1998, 1999, and 2000 bycatch estimates were from Yeung (1999a),

Yeung et al. (2000), and Yeung (2001), respectively. Most of the estimated marine mammal bycatch was from US

Atlantic EEZ waters between South Carolina and Cape Cod. Excluding the Gulf of Mexico, from 1992-2000 one

mortality was observed in both 1994 and 2000, and 0 in other years. The observed number of seriously-injured but

released alive individuals from 1992- 2000 was respectively 2, 0, 6, 4, 1, 0, 1, 1, and 1 (Cramer 1994; Scott and

Brown 1997; Johnson et al. 1999; Yeung 1999a; Yeung et al. 2000; Yeung 2001) ) (Table 2). Estimated annual

fishery-related mortality (CV in parentheses) was 17 in 1994 (1.0), 41 in 2000 (1.0), and 0 in other years (Table 2). 

Seriously injured and released alive animals were estimated to be 54 (0.7) in 1992, 0 in 1993, 120 (0.57) in 1994,

103 (0.68) in 1995, 99 (1.0) in 1996, 0 in 1997, 57 (1.0) in 1998, 22 (1.0) in 1999, and 23 (1.0) in 2000 (Table 2). 
63

Table 2. Summary of the incidental mortality of Risso’s dolphin (Grampus griseus) by commercial fishery including

the years sampled (Years), the number of vessels active within the fishery (Vessels), the type of data used

(Data Type), the annual observer coverage (Observer Coverage), the observed mortalities and serious

injuries recorded by on-board observers , the estimated annual mortality and serious injury , the combined

annual estimates of mortality and serious injury (Estimated Combined Mortality), the estimated CV of the

combined estimates (Estimated CVs) and the mean of the combined estimates (CV in parentheses).

Fishery Years Vessels3 Data

Type 1

Observer

Coverage

Observed

Serious

Injury

Observed

Mortality

Estimated

Serious

Injury

Estimated

Mortality 

Estimated

Combined

Mortality

Estimated

CVs 

Mean

Annual

Mortality

Pelagic

Longline2 96-00

253, 245,

205,

193,186

Obs.

Data

Logbook

 .03, .03,

.03, .04,

.04

1, 0, 1, 1, 1 0, 0, 0,

0, 1

99, 0, 57,

22, 23

 0, 0, 0, 

0, 41

 99, 0, 57,

22, 64

 1.0, 0, 1.0,

1.0, 1.0

48

 (.55)

Northeast

Multispecie

s Sink

Gillnet

96-00

1993=349

1998=301

Obs.

Data

Weighout

Trip

Logbook

.04, .06,

.05, .06,

.06

0, 0, 0, 

0, 1

0, 0, 0, 

0, 15

0, 0, 0, 0,

1.06

3

(1.06)

TOTAL 51 (.52)

1 Observer data (Obs. Data) are used to measure bycatch rates and the data are collected within the Northeast

Fisheries Science Center (NEFSC) Sea Sampling Program. NEFSC collects landings data (Weighout), and

total landings are used as a measure of total effort for the coastal gillnet fishery. 2 1996-1999 mortality estimates were taken from Table 9 in Yeung et al. (NMFS Miami Laboratory PRD

99/00-13), and exclude the Gulf of Mexico. 2000 mortality estimates were taken from Table 10 in Yeung

(2001). 3 Number of vessels in the fishery are based on vessels reporting effort to the pelagic longline logbook.

Other mortality

From 1995-2000, thirteen Risso’s dolphin strandings were recorded along the USA Atlantic coast (NMFS

unpublished data). In eastern Canada, one Risso’s dolphin stranding was reported on Sable Island, Nova Scotia

from 1970-1998 (Lucas and Hooker 2000).

STATUS OF STOCK

The status of Risso's dolphins relative to OSP in the US Atlantic EEZ is unknown. The species is not listed

as threatened or endangered under the Endangered Species Act. There are insufficient data to determine the

population trends for this species. The total fishery mortality and serious injury for this stock is not less than 10% of

the calculated PBR and, therefore, can not be considered to be insignificant and approaching a zero mortality and

serious injury rate. The 1996-2000 average annual fishery-related mortality does not exceed PBR; therefore, this is

not a strategic stock. 

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Waring, G.T. 1998. Results of the summer 1991 R/V Chapman marine mammal sighting survey. NOAA-NMFSNEFSC, Lab. Ref. Doc. No. 98-09, 21 pp. Available from: National Marine Fisheries Service, 166 Water

Street, Woods Hole, MA 02543-1026. 

Waring, G. T., D. L. Palka, P. J. Clapham, S. Swartz, M. C. Rossman, T. V. N. Cole, L. J. Hansen, K. D. Bisack, K.

D. Mullin, R. S. Wells, D. K. Odell, and N. B. Barros. 1999. U.S. Atlantic and Gulf of Mexico marine

mammal stock assessments — 1999. U.S. Dep. Commer., NOAA Tech. Memo NMFS-NE-153, 196pp.
65

Yeung, C. 1999a. Estimates of marine mammal and marine turtle bycatch by the U.S. Atlantic pelagic longline fleet

in 1998. NOAA Tech. Memo. NMFS-SEFSC-430, 26 pp. NMFS, Southeast Fisheries Science Center,

Miami, FL.

Yeung, C. 1999b. Revised Mortality Estimates of Marine Mammal Bycatch in 1992-1997 based on Serious Injury

Guidelines. NOAA Tech. Memo. NMFS-SEFSC-429, 23 pp. NMFS, Southeast Fisheries Science Center,

Miami, FL.

Yeung, C., S. Epperly, and C. A. Brown. 2000. Preliminary revised estimates of marine mammal and marine turtle

bycatch by the U.S. Atlantic pelagic longline fleet, 1992-1999. NMFS, Miami Lab. PRD Contribution

Number 99/00-13. 58 pp.

Yeung, C. 2001. Estimates of marine mammal and marine turtle bycatch by the U.S. Atlantic pelagic longline fleet

in 1999-2000. NOAA Tech. Memo. NMFS-SEFSC-467, 43 p. NMFS, Southeast Fisheries Science Center,

Miami, FL.
66

Figure 1. Distribution of common dolphin sightings from

NEFSC and SEFSC shipboard and aerial surveys during

the summer in 1990-1998. Isobaths are at 100 m and

1,000 m. 

January 2002

COMMON DOLPHIN (Delphinus delphis):

Western North Atlantic Stock

STOCK DEFINITION AND GEOGRAPHIC RANGE

The common dolphin may be one of the most widely distributed species of cetaceans, as it is found worldwide in temperate, tropical, and subtropical seas. In the North Atlantic, common dolphin appear to be present along

the coast over the continental shelf along the 200-

300m isobaths or over prominent underwater

topography from 50° N to 40°S latitude (Evans

1994). The species is less common south of Cape

Hatteras, although schools have been reported as far

south as eastern Florida (Gaskin 1992). At least some

of the reported sightings of common dolphins in the

Gulf of Mexico may have been Stenella clymene,

which has a color pattern similar to that of common

dolphins (Evans 1994). NMFS is currently funding

genetic and skull morphometric studies, which will

provide information on common dolphin stock

structure in the western North Atlantic. Preliminary

work had documented a high variance in skull

morphometric measurements suggesting the

existence of more than a single stock (J. G. Mead,

pers. comm.). Common dolphins are distributed 

along the continental slope (100 to 2,000 meters),

and are associated with Gulf Stream features in

waters off the northeastern USA coast (CETAP 1982;

Selzer and Payne 1988; Waring et al. 1992). They

are widespread from Cape Hatteras northeast to

Georges Bank (35o

 to 42o North latitude) in outer

continental shelf waters from mid-January to May

(Hain et al. 1981; CETAP 1982; Payne et al. 1984). 

Common dolphins move northward onto Georges

Bank and the Scotian Shelf from mid-summer to

autumn (Palka et al. in review). Selzer and Payne

(1988) reported very large aggregations (greater than

3,000 animals) on Georges Bank in autumn.

Common dolphins are rarely found in the Gulf of

Maine, where temperature and salinity regimes are

lower than on the continental slope of the Georges Bank/mid-Atlantic region (Selzer and Payne 1988). Migration

onto the Scotian Shelf and continental shelf off Newfoundland occurs during summer and autumn when water

temperatures exceed 11°C (Sergeant et al. 1970; Gowans and Whitehead 1995).

POPULATION SIZE

Total numbers of common dolphins off the USA or Canadian Atlantic coast are unknown, although five

estimates from selected regions of the habitat do exist for select time periods. Sightings were almost exclusively in

the continental shelf edge and continental slope areas (Figure 1). An abundance of 29,610 common dolphins

(CV=0.39) was estimated from an aerial survey program conducted from 1978 to 1982 on the continental shelf and

shelf edge waters between Cape Hatteras, North Carolina and Nova Scotia (CETAP 1982). An abundance of

22,215 (CV=0.40) common dolphins was estimated from a June and July 1991 shipboard line transect sighting

survey conducted primarily between the 200 and 2,000m isobaths from Cape Hatteras to Georges Bank (Waring et

al. 1992; Waring 1998). As recommended in the GAMS Workshop Report (Wade and Angliss 1997), estimates
67

older than eight years are deemed unreliable, therefore should not be used for PBR determinations. Further, due to

changes in survey methodology these data should not be used to make comparisons to more current estimates. 

 An abundance of 1,645 (CV=0.47) common dolphins was estimated from a June and July 1993 shipboard

line transect sighting survey conducted principally between the 200 and 2,000 m isobaths from the southern edge of

Georges Bank, across the Northeast Channel to the southeastern edge of the Scotian Shelf (Anon. 1993). Data were

collected by two alternating teams that searched with 25x150 binoculars and were analyzed using DISTANCE

(Buckland et al. 1993; Laake et al. 1993). Estimates include school size-bias, if applicable, but do not include

corrections for g(0) or dive-time. Variability was estimated using bootstrap resampling techniques.

An abundance of 6,741 (CV=0.69) common dolphins was estimated from a July to September 1995 sighting

survey conducted by two ships and an airplane that covered waters from Virginia to the mouth of the Gulf of St.

Lawrence (Table 1; Palka et al. in review). Total track line length was 32,600 km. The ships covered waters

between the 50 and 1000 fathom depth contour lines, the northern edge of the Gulf Stream, and the northern Gulf of

Maine/Bay of Fundy region. The airplane covered waters in the mid-Atlantic from the coastline to the 50 fathom

depth contour line, the southern Gulf of Maine, and shelf waters off Nova Scotia from the coastline to the 1000

fathom depth contour line. Data collection and analysis methods used were described in Palka (1996). 

An abundance of 30,768 (CV=0.32) common dolphins was estimated from a line transect sighting survey

conducted during July 6 to September 6, 1998 by a ship and plane that surveyed 15,900 km of track line in waters

north of Maryland (38° N) (Figure 1; Palka et al. in review). Shipboard data were analyzed using the modified

direct duplicate method (Palka 1995) that accounts for school size bias and g(0), the probability of detecting a group

on the track line. Aerial data were not corrected for g(0).

No common dolphins were encountered during the SEFSC component of the joint surveys. That shipboard

line transect sighting survey was conducted between 8 July and 17 August 1998 and surveyed 5,570 km of track line

in waters south of Maryland (38°N) (Mullin in review). 

Although the 1991, 1993, 1995, and 1998 surveys did not sample the same areas or encompass the entire

common dolphin habitat (e.g., little effort in Scotian shelf edge waters), they did focus on segments of known or

suspected high-use habitats off the northeastern USA coast. The 1993, 1995, and 1998 data suggest that, seasonally,

at least several thousand common dolphins are occupying continental shelf edge waters, with perhaps highest

abundance in the Georges Bank region. 

The best available abundance estimate for common dolphins is 30,768 (CV=0.32) as estimated from the 

July 6 to September 6, 1998 USA Atlantic surveys. This estimate is considered best because these surveys have the

most complete coverage of the species’ habitat. The previous best estimate of 22,215 (CV=0.40) is nearly eight

years old. 

Table 1. Summary of abundance estimates for western North Atlantic common dolphin. Month, year, and area

covered during each abundance survey, and resulting abundance estimate (Nbest) and coefficient of variation

(CV).

Month/Year Area Nbest CV

Jul-Sep 1995 Virginia to Gulf of St. Lawrence 6,741 0.69

Jul-Sep 1998 Maryland to Gulf of St. Lawrence 30,768 0.32

Minimum Population Estimate

The minimum population estimate is the lower limit of the two-tailed 60% confidence interval of the lognormally distributed best abundance estimate. This is equivalent to the 20th percentile of the log-normal distribution

as specified by Wade and Angliss (1997). The best estimate of abundance for common dolphins is 30,768

(CV=0.32). The minimum population estimate for the western North Atlantic common dolphin is 23,655

(CV=0.32).

Current Population Trend

There are insufficient data to determine the population trends for this species. 
68

CURRENT AND MAXIMUM NET PRODUCTIVITY RATES

Current and maximum net productivity rates are unknown for this stock. For purposes of this assessment,

the maximum net productivity rate was assumed to be 0.04. This value is based on theoretical modeling showing

that cetacean populations may not grow at rates much greater than 4% given the constraints of their reproductive life

history (Barlow et al. 1995). 

POTENTIAL BIOLOGICAL REMOVAL

Potential Biological Removal (PBR) is the product of minimum population size, one-half the maximum

productivity rate, and a “recovery” factor (MMPA Sec. 3. 16 U.S.C. 1362; Wade and Angliss 1997). The minimum

population size is 23,655 (CV=0.32). The maximum productivity rate is 0.04, the default value for cetaceans. The

“recovery” factor, which accounts for endangered, depleted, threatened stocks, or stocks of unknown status relative

to optimum sustainable population (OSP) is assumed to be 0.48 because the CV of the average mortality estimate is

between 0.3-0.6 (Wade and Angliss 1997), and because this stock is of unknown status. PBR for the western North

Atlantic common dolphin is 227.

ANNUAL HUMAN-CAUSED MORTALITY AND SERIOUS INJURY

 Total annual estimated average fishery-related mortality or serious injury to this stock during 1996-2000

was 375 common dolphins (CV=0.40; Table 2).

Fishery Information

USA

Prior to 1977, there was no documentation of marine mammal bycatch in distant-water fleet (DWF)

activities off the northeast coast of the USA. With implementation of the Magnuson Fisheries Conservation and

Management Act (MFCMA), an observer program was established which has recorded fishery data and information

of incidental bycatch of marine mammals. DWF effort in the Atlantic coast Exclusive Economic Zone (EEZ) under

MFCMA has been directed primarily towards Atlantic mackerel and squid. From 1977 through 1982, an average of

120 different foreign vessels per year (range 102-161) operated within the US Atlantic EEZ. In 1982, there were

112 different foreign vessels; 16%, or 18, were Japanese tuna longline vessels operating along the USA east coast. 

This was the first year that the Northeast Regional Observer Program assumed responsibility for observer coverage

of the longline vessels. Between 1983 and 1991, the numbers of foreign vessels operating within the US Atlantic

EEZ each year were 67, 52, 62, 33, 27, 26, 14, 13, and 9, respectively. Between 1983 and 1988, the numbers of

DWF vessels included 3, 5, 7, 6, 8, and 8, respectively, Japanese longline vessels. Observer coverage on DWF

vessels was 25-35% during 1977-1982, and increased to 58%, 86%, 95%, and 98%, respectively, in 1983-1986. 

From 1987-91, 100% observer coverage was maintained. Foreign fishing operations for squid and mackerel ceased

at the end of the 1986 and 1991 fishing seasons, respectively. 

During the period 1977-1986, observers recorded 123 mortalities in foreign Loligo squid-fishing activities

(Waring et al. 1990). In 1985 and 1986, Italian vessels took 56 and 54 animals, respectively, which accounts for

89% (n = 110) of the total takes in foreign Loligo squid-fishing operations. No mortalities were reported in foreign

Illex squid fishing operations. Because of spatial/temporal fishing restrictions, most of the bycatch occurred along

the continental shelf edge (100 m) isobath during winter (December to February). 

From 1977-1991, observers recorded 110 mortalities in foreign mackerel-fishing operations (Waring et al.

1990; NMFS unpublished data). This total includes one documented take by a USA vessel involved in joint-venture

fishing operations in which USA captains transfer their catches to foreign processing vessels. The bycatch occurred

during winter/spring (December to May). 

Data on current incidental takes in USA fisheries are available from several sources. In 1986, NMFS

established a mandatory self-reported fisheries information system for large pelagic fisheries. Data files are

maintained at the Southeast Fisheries Science Center (SEFSC). The Northeast Fisheries Science Center (NEFSC)

Sea Sampling Observer Program was initiated in 1989, and since that year several fisheries have been covered by the

program. In late 1992 and in 1993, the SEFSC provided observer coverage of pelagic longline vessels fishing off the

Grand Banks (Tail of the Banks) and provides observer coverage of vessels fishing south of Cape Hatteras. 

Bycatch has been observed by NMFS Sea Samplers in the pelagic drift gillnet, pelagic pair trawl, pelagic

longline fishery, mid-Atlantic coastal gillnet, North Atlantic bottom trawl, Northeast multispecies sink gillnet, and

Atlantic squid, mackerel, butterfish trawl fisheries. 
69

Pelagic Drift Gillnet

The estimated total number of hauls in the pelagic drift gillnet fishery increased from 714 in 1989 to 1,144

in 1990; thereafter, with the introduction of quotas, effort was severely reduced. The estimated number of hauls in

1991, 1992, 1993, 1994, 1995, 1996, and 1998 were 233, 243, 232, 197, 164, 149, and 113 respectively. In 1996

and 1997, NMFS issued management regulations which prohibited the operation of this fishery in 1997. Further, in

January 1999 NMFS issued a Final Rule to prohibit the use of driftnets (i.e., permanent closure) in the North

Atlantic swordfish fishery (50 CFR Part 630). Fifty-nine different vessels participated in this fishery at one time or

another between 1989 and 1993. From 1994-1998, between 10 and 13 vessels have participated in the fishery. 

Observer coverage, expressed as percent of sets observed, was 8% in 1989, 6% in 1990, 20% in 1991, 40% in 1992,

42% in 1993, 87% in 1994, 99% in 1995, 64% in 1996, and 99% in 1998. Effort was concentrated along the

southern edge of Georges Bank and off Cape Hatteras. Examination of the species composition of the catch and

locations of the fishery throughout the year, suggested that the pelagic drift gillnet fishery be stratified into two

strata, a southern or winter stratum, and a northern or summer stratum. Estimates of the total bycatch, from 1989 to

1993, were obtained using the aggregated (pooled 1989-1993) catch rates, by strata (Northridge 1996). Estimates of

total annual bycatch for 1994 and 1995 were estimated from the sum of the observed caught and the product of the

average bycatch per haul and the number of unobserved hauls as recorded in self-reported fisheries information. 

Variances were estimated using bootstrap re-sampling techniques. Eight hundred and sixty-one common dolphin

mortalities were observed between 1989 and 1998 in this fishery. Mortalities were observed in all seasons and areas. 

Seven animals were released alive, but six were injured. Estimated annual mortality and serious injury attributable

to this fishery (CV in parentheses) was 540 in 1989 (0.19), 893 in 1990 (0.18), 223 in 1991 (0.12), 227 in 1992

(0.09), 238 in 1993 (0.08), 163 in 1994 (0.02), 83 in 1995 (0), 106 in 1996 (0.07), and 255 in 1998 (0). Since this

fishery no longer exists, it has been excluded from Table 2 (see Waring et al. 1999).

Pelagic Pair Trawl

During the period 1989 to 1993, effort in the pelagic pair trawl fishery increased from zero hauls in 1989

and 1990, to an estimated 171 hauls in 1991 and then to an estimated 536 hauls in 1992 and 586 in 1993, 407 in

1994 and 440 in 1995. This fishery ceased operations in 1996, when NMFS rejected a petition to consider pair trawl

gear as an authorized gear type in the Atlantic tuna fishery. The fishery operated from August to November in 1991,

from June to November in 1992, from June to October in 1993 (Northridge 1996), and from mid-summer to

December in 1994 and 1995. Sea sampling began in October of 1992 (Gerrior et al. 1994) where 48 sets (9% of the

total) were sampled. In 1993, 102 hauls (17% of the total) were sampled. In 1994 and 1995, 52% (212) and 55%

(238), respectively, of the sets were observed. Nineteen vessels have operated in this fishery. The fishery operates

in the area between 35°N to 41°N and 69°W to 72°W. Approximately 50% of the total effort was within a one

degree square at 39°N, 72°W, around Hudson Canyon from 1991 to 1993. Examination of the 1991-1993 locations

and species composition of the bycatch, showed little seasonal change for the six months of operation and did not

warrant any seasonal or areal stratification of this fishery (Northridge 1996). Twelve mortalities were observed

between 1991 and 1995. The estimated annual fishery-related mortality and serious injury attributable to this fishery

(CV in parentheses) was 5.6 in 1991 (0.53), 32 in 1992 (0.48), 35 in 1993 (0.43), 0 in 1994, and 5.6 in 1995 (0.35). 

Since this fishery is no longer in operation it has been deleted from Table 2. During the 1994 and 1995 experimental

pelagic pair trawl fishing seasons, fishing gear experiments were conducted to collect data on environmental

parameters, gear behavior, and gear handling practices to evaluate factors affecting catch and bycatch (Goudey 1995,

1996). Results of these studies have been presented at Offshore Cetacean Take Reduction Team Meetings. 

Pelagic Longline

 Total effort, excluding the Gulf of Mexico and fishing regions east of 60°W longitude, for the pelagic

longline fishery, based on mandatory self-reported fisheries information, was 11,279 sets in 1991, 8,579 sets in

1992, 8,644 sets in 1993, 9,191 sets in 1994, 9,124 sets in 1995, 7,818 sets in 1996, 7,707 sets in 1997, 6,305 sets in

1998, 5,832 sets in 1999, and 6,582 in 2000 (Cramer 1994; Scott and Brown 1997; Johnson et al. 1999; Yeung

1999a; Yeung et al. 2000; Yeung 2001). Since 1992, this fishery has been monitored with about 5% observer

coverage, in terms of trips observed, within every statistical reporting area within the US Atlantic EEZ and beyond. 

Off the USA Atlantic coast, the fishery has been observed from January to March off Cape Hatteras, in May and

June in the entire mid-Atlantic, and in July through December in the mid-Atlantic Bight and off Nova Scotia. The

1994-1998 estimated take was based on a revised analysis of the observed incidental take and self-reported

incidental take and effort data, and replace previous estimates for the 1992-1993 and 1994-1995 periods (Cramer

1994; Scott and Brown 1997; Johnson et al. 1999). Further, Yeung (1999b) revised the 1992-1997 fishery mortality
70

estimates in Johnson et al. (1999) to include seriously injured animals. The 1998 bycatch estimates were from

Yeung (1999a). Most of the estimated marine mammal bycatch was from US Atlantic EEZ waters between South

Carolina and Cape Cod (Johnson et al. 1999). Between 1990- 2000 sixteen common dolphins were hooked and

released alive (Yeung et al. 2000;Yeung 2001).

Northeast Multispecies Sink Gillnet

 In 1993, there were approximately 349 full and part-time vessels in the Northeast multispecies sink gillnet

fishery, which covered the Gulf of Maine and southern New England (Table 2). An additional 187 vessels were

reported to occasionally fish in the Gulf of Maine with gillnets for bait or personal use; however, these vessels were

not covered by the observer program (Walden 1996) and their fishing effort was not used in estimating mortality.

Observer coverage in terms of trips has been 1%, 6%, 7%, 5%, 7%, 5%, 4%, 6%, 5%, 6%, and 6% for 1990 to,2000

respectively. The fishery has been observed in the Gulf of Maine and in Southern New England. In 1996, the first

observed mortality of common dolphins in this fishery was recorded. The estimated annual fishery-related mortality

and serious injury attributable to this fishery (CV in parentheses) was 0 in 1995, 63 in 1996 (CV=1.39), 0 in 1997, 0

in 1998, 146 in 1999 (0.97), and zero in 2000; estimated annual mortality (1996-2000) was 42 common dolphins

(CV= 0.78) (Table 2). Annual estimates of common dolphin bycatch in the Northeast multispecies sink gillnet

fishery reflect seasonal distribution of the species and of fishing effort.

Mid-Atlantic Coastal Gillnet

Observer coverage of the USA Atlantic coastal gillnet fishery was initiated by the NEFSC Sea Sampling

program in July, 1993; and from July to December 1993, 20 trips were observed. During 1994 and 1995 221 and

382 trips were observed, respectively. This fishery, which extends from North Carolina to New York, is actually a

combination of small vessel fisheries that target a variety of fish species, some of which operate right off the beach. 

The number of vessels in this fishery is unknown, because records which are held by both state and federal agencies

have not been centralized and standardized. Observer coverage, expressed as percent of tons of fish landed, was 5%,

4%, 3%, 5%, 2%, and 2% for 1995, 1996, 1997, 1998, 1999, and 2000, respectively (Table 2).

No common dolphins were taken in observed trips during 1993 and 1994. Two common dolphin were

observed taken in 1995, 1996, and 1997, and no takes were observed from 1998 - 2000 (Table 2). Observed effort

was concentrated off NJ and scattered between DE and NC from 1 to 50 miles off the beach. All bycatches were

documented during January to April. Using the observed takes, the estimated annual mortality (CV in parentheses)

attributed to this fishery was 7.4 in 1995 (CV=0.69), 43 in 1996 (0.79), 16 in 1997 (0.53), and 0 in 1998-2000. 

Average annual estimated fishery-related mortality attributable to this fishery during 1996-2000 was 12 common

dolphins (CV=0.59)

North Atlantic Bottom Trawl

Vessels in the North Atlantic bottom trawl fishery, a Category III fishery under MMPA, were observed in

order to meet fishery management needs, rather than marine mammal management needs. An average of 970 vessels

(full and part time) participated annually in the fishery during 1991-1995. The fishery is active in all seasons in New

England waters. Four mortalities were observed between 1991-2000. Observer coverage, expressed as number of

trips, was < 1% from 1996-2000 (Table 2). The estimated annual fishery-related mortality and serious injury

attributable to this fishery (CV in parentheses) was 0 in 1991, 0 in 1992, 0 in 1993, 0 in 1994, 142 in 1995 (0.77), 0

in 1996, 93 in 1997 (1.06), and 0 in 1998, 1999 and 2000. Average annual estimated fishery-related mortality

attributable to this fishery during 1996-2000 was 19 common dolphins (CV=1.06) (Table 2). However, these

estimates should be viewed with caution due to the extremely low (<1%) observer coverage.

Squid, Mackerel, Butterfish Trawl

The mid-Atlantic mackerel and squid trawl fisheries were combined into the Atlantic mid-water trawl

fishery in the revised proposed list of fisheries in 1995. The fishery occurs along the USA mid-Atlantic continental

shelf region between New Brunswick, Canada, and Cape Hatteras year around. The mackerel trawl fishery was

classified as a Category II fishery since 1990 and the squid fishery was originally classified as a Category II fishery

in 1990, but was reclassified as a Category III fishery in 1992. The combined fishery was reclassified as a Category

II fishery in 1995. In 1996, mackerel, squid, and butterfish trawl fisheries were combined into the Atlantic squid,

mackerel, and butterfish trawl fishery, and maintained a Category II classification. Observer coverage, expressed as

number of trips, was < 1% from 1996-2000 (Table 2). Three common dolphin mortalities were observed in 1996, 1

in 1997, 0 in 1998, 1 in 1999, and 6 in 2000 (Table 2). The 1996 and 2000 mortalities were in the Loligo squid

fishery and the 1997 mortality occurred in the Atlantic mackerel fishery. The estimated annual fishery-related

mortality and serious injury attributable to this fishery (CV in parentheses) was 940 in 1996 (0.75), 161 in 1997
71

(0.49), 0 in 1998, 49 in 1999 (0.78), and 235 in 2000 (0.57). Average annual estimated fishery-related mortality

attributable to this fishery during 1996-2000 was 285 common dolphins (CV= 0.51) (Table 2). However, these

estimates should be viewed with caution due to the extremely low (<1%) observer coverage and uncertainties

regarding number of vessels participating in this "fishery". 

Mackerel Joint Venture

A USA joint venture fishery was conducted in the mid-Atlantic region from February-May 1998. NMFS,

maintained 100% observer coverage on the foreign joint venture vessels. One hundred and fifty-two transfers from

the USA vessels were observed. Seventeen common dolphin mortalities were observed in March. The principal fish

species in the transferred trawl nets and number of bycaught animals (in parentheses) were: squid (11), butterfish (4),

and mackerel (2). Average annual estimated fishery-related mortality attributable to this fishery in 1998 was 17

common dolphins (CV=0) (Table 2).

CANADA

Between January 1993 and December 1994, 36 Spanish deep water trawlers, covering 74 fishing trips

(4,726 fishing days and 14,211 sets), were observed in NAFO Fishing Area 3 (off the Grand Bank) (Lens 1997). A

total of 47 incidental catches were recorded, which included 1 common dolphin. The incidental mortality rate for

common dolphins was 0.007/set.

Table 2. Summary of the incidental mortality of common dolphins (Delphinus delphis) by commercial fishery

including the years sampled (Years), the number of vessels active within the fishery (Vessels), the type of

data used (Data Type), the annual observer coverage (Observer Coverage), the mortalities recorded by onboard observers (Observed Mortality), the estimated annual mortality (Estimated Mortality), the estimated

CV of the annual mortality (Estimated CVs) and the mean annual mortality (CV in parentheses).

Fishery Years Vessels Data Type 1 Observed

 Serious

 Injury

Observer

 Coverage 2 

Observed

Mortality

Estimated

 Mortality 

Estimated

 CVs 

Mean

 Annual

Mortality

Northeast

Multispecies

 Sink Gillnet

96-00 349

Obs. Data

 Weighout,

 Logbooks

0, 0, 0,

 0, 0

 .04, .06,

 .05, .06, .06

1, 0, 0, 

2, 0

63, 0, 0,

146, 0

 1.39, 0, 0

.97, 0

42 

(.78)

mid-Atlantic

Coastal Gillnet 96-00

NA Obs. Data

Weighout

 0, 0, 0,

 0, 0

.04, .03, .05,

.02, .02

2, 2, 

0, 0, 0

43, 

16, 0, 0, 0

.79, .53, 0,

0, 0

12 

(.59)

Atlantic squid,

mackerel,

butterfish trawl

96-00

NA Obs. Data

 Weighout

0, 0, 0, 0,

0 

 .007, .008,

 .003, .004,

.007

3 3 , 1 3 , 

0, 1 3,, 63

 940, 161,

 0, 49, 273

 .75, .49,

 0, .78, .57

 285

(.51)

North Atlantic

 Bottom Trawl 96-00

970 Obs. Data

Weighout

 0, 0, 0,

 0, 0

 .002, .002,

.001, .003,

.003

0,

 1, 0, 0, 0

0, 93, 0,

0, 0

0, 1.06, 0,

0, 0

 19

(1.06)

Mackerel

 joint venture

98 4 Obs. Data 0 1.00 17 17 0 17

 (0)

TOTAL 375 

(.40)

 1 Observer data (Obs. Data) are used to measure bycatch rates, and the data are collected within the Northeast

Fisheries Science Center (NEFSC) Sea Sampling Program. NEFSC collects dealer reported landings data. 

Total landings are used as a measure of total effort for the coastal gillnet, Northeast sink gillnet and the

North Atlantic bottom trawl fisheries. 2 The observer coverage for the North Atlantic bottom trawl fishery are measured in trips. 3 During 1996, 1999, and 2000 the observed common dolphins were taken in the Loligo squid otter trawl

sub-fisheries, and during 1997 the observed common dolphin was taken in the Atlantic mackerel otter trawl

sub-fishery. 
72

Other Mortality

From 1992-2000, 156 common dolphins were stranded between North Carolina and Massachusetts,

predominantly along beaches in the latter state (NMFS unpublished data). The total includes 10 and 9 common

dolphins, respectively, that mass stranded in November 1997 and January 1998 on Cape Cod. Three of 4 live

strandings in Massachusetts in 2000 were released alive. In 1999, 1 stranding mortality in New Jersey was

designated as a human interaction (fishing gear). 

Four common dolphin strandings (6 individuals) were reported on Sable Island, Nova Scotia from 1970-

1998, and all strandings have occurred since 1996 (Lucas and Hooker 1997; Lucas and Hooker 2000.) ). 

STATUS OF STOCK

The status of common dolphins, relative to OSP, in the US Atlantic EEZ is unknown. The species is not

listed as threatened or endangered under the Endangered Species Act. There are insufficient data to determine the

population trends for this species. The total fishery-related mortality and serious injury for this stock is not less than

10% of the calculated PBR and, therefore, cannot be considered to be insignificant and approaching zero mortality

and serious injury rate. This is a strategic stock because the1996-2000 average annual fishery-related mortality and

serious injury exceeds PBR. 

REFERENCES

Anon. 1993. Cruise results, NOAA ship DELAWARE II, Cruise No. DEL 93-06, Marine mammal Survey. 5 pp. 

Available from: National Marine Fisheries Service, 166 Water Street, Woods Hole, MA 02543-1026.

Barlow, J., S. L. Swartz, T. C. Eagle and P. R. Wade. 1995. U.S. Marine Mammal Stock Assessments: Guidelines

for Preparation, Background, and a Summary of the 1995 Assessments. U.S. Dep. Commer., NOAA Tech.

Memo. NMFS-OPR-6, 73 pp. 

Buckland, S. T., D. R. Andersen, K. P. Burnham and J. L. Laake. 1993. Distance Sampling: Estimating abundance

of biological populations. Chapman and Hall, New York, 446 pp. 

CETAP. 1982. A characterization of marine mammals and turtles in the mid- and north Atlantic areas of the U.S.

outer continental shelf. Cetacean and Turtle Assessment Program, University of Rhode Island. Final

Report, Contract AA51-C78-48, Bureau of Land Management, Washington, DC, 538 pp. 

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74

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Center, Miami, FL.
75

January 2002

HARBOR SEAL (Phoca vitulina):

Western North Atlantic Stock

STOCK DEFINITION AND GEOGRAPHIC RANGE

The harbor seal is found in all nearshore waters of the Atlantic Ocean and adjoining seas above about 30

degrees latitude (Katona et al. 1993). In the western North Atlantic, they are distributed from the eastern Canadian

Arctic and Greenland south to southern New England and New York, and occasionally to the Carolinas (Boulva and

McLaren 1979; Katona et al. 1993; Gilbert and Guldager 1998). Stanley et al. (1996) examined worldwide patterns

in harbor seal mitochondrial DNA, which indicate that western and eastern North Atlantic harbor seals populations

are highly differentiated. Further, they suggest that harbor seal females are only regionally philopatric, thus

population or management units are on the scale of a few hundred kilometers. Although the stock structure of the

western North Atlantic population is unknown, it is thought that harbor seals found along the eastern USA and

Canadian coasts represent one population (Temte et al. 1991). In U.S. waters, breeding and pupping normally occur

in waters north of the New Hampshire/Maine border, although breeding occurred as far south as Cape Cod in the

early part of the twentieth century (Temte et al. 1991; Katona et al. 1993). 

Harbor seals are year-round inhabitants of the coastal waters of eastern Canada and Maine (Katona et al.

1993), and occur seasonally along the southern New England and New York coasts from September through late

May (Schneider and Payne 1983). In recent years, their seasonal interval along the southern New England to New

Jersey coasts has increased (Barlas 1999; Hoover et al. 1999; Slocum et al. 1999). Scattered sightings and

strandings have been recorded as far south as Florida (NMFS unpublished data). A general southward movement

from the Bay of Fundy to southern New England waters occurs in autumn and early winter (Rosenfeld et al. 1988;

Whitman and Payne 1990; Barlas 1999). A northward movement from southern New England to Maine and eastern

Canada occurs prior to the pupping season, which takes place from mid-May through June along the Maine Coast

(Richardson 1976; Wilson 1978; Whitman and Payne 1990; Kenney 1994). No pupping areas have been identified

in southern New England (Payne and Schneider 1984; Barlas 1999). The overall geographic range throughout

coastal New England has not changed significantly during the last century (Payne and Selzer 1989). 

The majority of seals moving into southern New England and mid-Atlantic waters are subadults and

juveniles (Whitman and Payne 1990; Katona et al. 1993; Slocum et al. 1999). Whitman and Payne (1990) suggest

that the age-related dispersal may reflect the higher energy requirements of younger animals. 

POPULATION SIZE

 Since passage of the MMPA in 1972, the number of seals along the New England coast has increased

nearly five-fold. Coast-wide aerial surveys along the Maine coast have been conducted in May/June during pupping

in 1981, 1982, 1986, 1993, and 1997 (Table 1; Gilbert and Stein 1981; Gilbert and Wynne 1983, 1984; Kenney

1994; and Gilbert and Guldager 1998). The following numbers are considered to be a minimum abundance estimate

because they are uncorrected for animals in the water or outside the survey area. A coast-wide survey, which

included replicate surveys and radio tagged seals to obtain a correction factor, was conducted in May/June 2001. 

Data are presently under analysis. Increased abundance of seals in the northeast region has also been documented

during aerial and boat surveys of overwintering haul-out sites in between the Maine/New Hampshire border to

eastern Long Island and New Jersey (Payne and Selzer 1989; Rough 1995; Barlas 1999; Hoover et al. 1999; Slocum

et al. 1999). Canadian scientists counted 3,500 harbor seals during an August 1992 aerial survey in the Bay of

Fundy (Stobo and Fowler 1994), but noted that the survey was not designed to obtain a population estimate. 

Table 1. Summary of abundance estimates for the western Atlantic harbor seal. Month, year, and area covered

during each abundance survey, resulting abundance estimate (Nmin) and coefficient of variation (CV). 

Month/Year Area Nmin CV

May/June 1997 Maine coast 30,990 (5,359) None reported

 1

Pup counts are in brackets 
76

Minimum Population Estimate

A minimum population estimate is 30,990 seals, based on uncorrected total counts along the Maine coast in 

1997. 

Current Population Trend

 The average increase in counts over the 1981-1997 survey period (e.g., 1981, 1982, 1986, 1993 and

1997) has been 4.2 % (Gilbert and Guldager 1998), about 50% of the 8.9 percent annual increase estimated by

Kenney (1994) from counts through 1993. This suggests that population increase may have slowed. Similarly, the

number of pups along the Maine coast has increased at an annual rate of 12.9% over the 1981-1997 period (Gilbert

and Guldager 1998). Possible factors contributing to harbor seal population increase include MMPA protection, 

increased prey, and fishery management regulations (e.g., closed areas, fishing effort reduction) designed to rebuild

groundfish stocks.

CURRENT AND MAXIMUM NET PRODUCTIVITY RATES

Current and maximum net productivity rates are unknown for this stock. For purposes of this assessment,

the maximum net productivity rate was assumed to be 0.12. This value is based on theoretical modeling showing

that pinniped populations may not grow at rates much greater than 12% given the constraints of their reproductive

life history (Barlow et al. 1995). 

POTENTIAL BIOLOGICAL REMOVAL

Potential Biological Removal (PBR) is the product of minimum population size, one-half the maximum

productivity rate, and a “recovery” factor (MMPA Sec. 3. 16 U.S.C. 1362; Wade and Angliss 1997). The minimum

population size is 30,990. The maximum productivity rate is 0.12, the default value for pinnipeds. The recovery

factor (FR) for this stock is 1.0, the value for stocks of unknown status, but known to be increasing. PBR for USA

waters is 1,859.

ANNUAL HUMAN-CAUSED MORTALITY

For the period 1996-2000, the total estimated human caused mortality and serious injury to harbor seals is

estimated to be 857 per year. The average is derived from two components: 1) 843 (CV=0.17; Table 2) from the

1995-1999 observed fishery; and 2) 14 from average 1997-2000 stranding mortalities resulting from boat strikes,

power plant entrainments, shooting, and other sources. 

Researchers and fishery observers have documented incidental mortality in several fisheries, particularly

within the Gulf of Maine (see below). An unknown level of mortality also occurred in the mariculture industry (i.e.,

salmon farming), and by deliberate shooting (NMFS unpublished data). However, no data are available to 

determine whether shooting still takes place. 

Fishery Information

USA

Data on current incidental takes in USA fisheries are available from several sources. In 1986, NMFS

established a mandatory self-reported fisheries information system for large pelagic fisheries. Data files are

maintained at the Southeast Fisheries Science Center (SEFSC). The Northeast Fisheries Science Center (NEFSC)

Sea Sampling Observer Program was initiated in 1989, and since that year several fisheries have been covered by the

program. In late 1992 and in 1993, the SEFSC provided observer coverage of pelagic longline vessels fishing off the

Grand Banks (Tail of the Banks) and provides observer coverage of vessels fishing south of Cape Hatteras. 

Incidental takes of harbor seals have been recorded in groundfish gillnet, herring purse seine, halibut tub

trawl, and lobster fisheries (Gilbert and Wynne, 1985 and 1987). A study conducted by the University of Maine

reported a combined average of 22 seals entangled annually by 17 groundfish gillnetters off the coast of Maine

(Gilbert and Wynne 1987). All seals were young of the year and were caught from late June through August and in

early October. Interviews with a limited number of mackerel gillnetters indicated only one harbor seal entanglement

and a negligible loss of fish to seals. Net damage and fish robbing were not reported to be a major economic

concern to gillnetters interviewed (Gilbert and Wynne 1987). 

Herring purse seiners have reported accidentally entrapping seals off the mid-coast of Maine, but indicated

that the seals were rarely drowned before the seine was emptied (Gilbert and Wynne 1985). Capture of seals by
77

halibut tub trawls are rare. One vessel captain indicated that he took one or two seals a year. These seals were all

hooked through the skin and released alive, indicating they were snagged as they followed baited hooks. Infrequent

reports suggest seals may rob bait off longlines, although this loss is considered negligible (Gilbert and Wynne

1985). 

Incidental takes in lobster traps in inshore waters off Maine are reportedly rare. Captures of approximately

two seal pups per port per year were recorded by mid-coastal lobstermen off Maine (Gilbert and Wynne 1985). 

Seals have been reported to rob bait from inshore lobster traps, especially in the spring, when fresh bait is used. 

These incidents may involve only a few individual animals. Lobstermen claim that seals consume shedding lobsters. 

Northeast Multispecies Sink Gillnet:

In 1993, there were approximately 349 full and part-time vessels in the Northeast multispecies sink gillnet

fishery, which covered the Gulf of Maine and southern New England (Table 2). An additional 187 vessels were

reported to occasionally fish in the Gulf of Maine with gillnets for bait or personal use; however, these vessels were

not covered by the observer program (Walden 1996) and their fishing effort was not used in estimating mortality. In

1998, there were approximately 301 vessels in this fishery (NMFS unpublished data). Observer coverage in terms of

trips has been 1%, 6%, 7%, 5%, 7%, 5%, 4%, 6%, 5%, 6%, and 6% for 1990 to 2000, respectively. The fishery has

been observed in the Gulf of Maine and in Southern New England. There were 362 harbor seal mortalities,

excluding three animals taken in the 1994 pinger experiment (NMFS unpublished data), observed in the Northeast

multispecies sink gillnet fishery between 1990 and 2000. Annual estimates of harbor seal bycatch in the Northeast

multispecies sink gillnet fishery reflect seasonal distribution of the species and of fishing effort. Estimated annual

mortalities (CV in parentheses) from this fishery during 1990- 2000 were 602 in 1990 (0.68), 231 in 1991 (0.22),

373 in 1992 (0.23), 698 in 1993 (0.19), 1,330 in 1994 (0.25), 1,179 in 1995 (0.21), 911 in 1996 (0.27), 598 in 1997

(0.26), 332 in 1998 (0.33), 1446 in 1999 (0.34), and 917 (0.43) in 2000. The 1994 and 1995 bycatches, respectively,

include 14 and 179 animals from the estimated number of unknown seals (based on observed mortalities of seals that

could not be identified to species). The unknown seals were prorated, based on spatial/temporal patterns of bycatch

of harbor seals, gray seals, harp seals, and hooded seals. Average annual estimated fishery-related mortality and

serious injury to this stock attributable to this fishery during 1996-2000 was 843 harbor seals (CV= 0.17). The

stratification design used is the same as that for harbor porpoise (Bravington and Bisack 1996). The bycatch

occurred in Massachusetts Bay, south of Cape Ann and west of Stellwagen Bank during January-March. Bycatch

locations became more dispersed during April-June from Casco Bay to Cape Ann, along the 30 fathom contour out

to Jeffreys Ledge, with one take location near Cultivator Shoal and one off southern New England near Block Island. 

Incidental takes occurred from Frenchman's Bay to Massachusetts Bay during July-September. In inshore waters,

the takes were aggregated while offshore takes were more dispersed. Incidental takes were confined from Cape

Elizabeth out to Jeffreys Ledge and south to Nantucket Sound during October-December. 

Mid-Atlantic Coastal Gillnet

Observer coverage of the USA Atlantic coastal gillnet fishery was initiated by the NEFSC Sea Sampling

program in July, 1993; and from July to December 1993, 20 trips were observed. During 1994 and 1995, 221 and

382 trips were observed, respectively. This fishery, which extends from North Carolina to New York, is actually a

combination of small vessel fisheries that target a variety of fish species, some of which operate right off the beach. 

The number of vessels in this fishery is unknown, because records which are held by both state and federal agencies

have not been centralized and standardized. Observer coverage, expressed as percent of tons of fish landed, was 5%,

4%, 3%, 5%, 2%, and 2% for 1995, 1996, 1997, 1998, 1999, and 2000, respectively (Table 2).

No harbor seals were taken in observed trips during 1993-1997, and 1999-2000. Two harbor seals were

observed taken in 1998 (Table 2). Observed effort was concentrated off NJ and scattered between DE and NC from

1 to 50 miles off the beach. All bycatches were documented during January to April. Using the observed takes, the

estimated annual mortality (CV in parentheses) attributed to this fishery was 0 in 1995-1997 and 1999-2000 and 11

in 1998 (0.77). Average annual estimated fishery-related mortality attributable to this fishery during 1996-2000 was

2 harbor seals (CV=0.77).

CANADA

An unknown number of harbor seals have been taken in Newfoundland, Labrador, Gulf of St. Lawrence

and Bay of Fundy groundfish gillnets, Atlantic Canada and Greenland salmon gillnets, Atlantic Canada cod traps,

and in Bay of Fundy herring weirs (Read 1994). Furthermore, some of these mortalities (e.g., seals trapped in

herring weirs) are the result of direct shooting.
78

There were 3,121 cod traps operating in Newfoundland and Labrador during 1979, and about 7,500 in 1980

(Read 1994). This fishery was closed at the end of 1993 due to collapse of Canadian groundfish resources. 

Herring weirs are also distributed throughout the Bay of Fundy; it has been reported that 180 weirs were

operating in the Bay of Fundy in 1990 (Read 1994). 

In 1996, observers recorded seven harbor seals (one released alive) in Spanish deep water trawl fishing on

the southern edge of the Grand Bank (NAFO Areas 3) (Lens, 1997). Seal bycatches occurred year-round, but

interactions were highest during April-June. Many of the seals that died during fishing activities were unidentified. 

The proportion of sets with mortality (all seals) was 2.7 per 1,000 hauls (0.003).

Table 2. Summary of the incidental mortality of harbor seals (Phoca vitulina) by commercial fishery including the

years sampled (Years), the number of vessels active within the fishery (Vessels), the type of data used (Data

Type), the annual observer coverage (Observer Coverage), the mortalities recorded by on-board observers

(Observed Mortality), the estimated annual mortality (Estimated Mortality), the estimated CV of the annual

mortality (Estimated CVs) and the mean annual mortality (CV in parentheses).

Fishery Years Vessels Data Type 1 Observer

 Coverage 2 

Observed

 Mortality

Estimated

 Mortality 

Estimated

 CVs 

Mean

 Annual

 Mortality

Northeast 3

Multispecies

 Sink Gillnet

96-00 301

Obs. Data

 Weighout,

 Logbooks

.04, .06, .05,

.06, .06

36,

 48, 15,

49, 26

911,

 598, 332,

1446, 917

.27, .26, .33,

.34, .43

 841

( 0.17)

mid-Atlantic

 Coastal Sink

 Gillnet 

96-00 Unk4

Obs. Data

Weighout

.04,

 .03, .05,

.02, .02

0, 0, 2,

0, 0

 0, 0, 11,

0, 0

0, 0, .77,

0, 0

2

 (.77) 

TOTAL 843

( 0.17)

1 Observer data (Obs. Data) are used to measure bycatch rates, and the data are collected within the Northeast

Fisheries Science Center (NEFSC) Sea Sampling Program. NEFSC collects landings data (Weighout), and

total landings are used as a measure of total effort for the sink gillnet fishery. Mandatory logbook

(Logbook) data are used to determine the spatial distribution of fishing effort in the Northeast multispecies

sink gillnet fishery. 2 The effort for the Northeast multispecies sink gillnet fishery is measured in trips. Observer coverage of the

mid-Atlantic coastal gillnet fishery is measured in tons of fish landed. 3

 In 1996, 1997, 1998, 1999, and 2000 respectively, observed mortality on “marine mammal trips” was 37,

14, 13, 45, and 26 animals. Only these mortalities were used to estimate total harbor seal bycatch. See

Bisack (1997) for “trip” type definitions. In 1996 to 2000, 3, 1, 2, 4, and 3 harbor seals were observed on

dedicated fish sampling trips. In 1996 to 2000, 2, 14, 1, 5, and 8 harbor seals were observed taken in nets

equipped with pingers. 4 Number of vessels is not known.

Other Mortality

Harbor seals were bounty hunted in New England waters until the mid- 1960's. This hunt may have caused

the demise of this stock in USA waters (Katona et al. 1993). 

Annually, small numbers of harbor seals regularly strand throughout their migratory range. Most reported

strandings, however, occur during the winter period in southern New England and mid-Atlantic regions (NMFS

unpublished data). Sources of mortality include human interactions (boat strikes and fishing gear, power plant intake

(12-20 per year; NMFS unpublished data), oil, shooting (around salmon aquaculture sites and fixed fishing gear),

storms, abandonment by the mother, and disease (Katona et al. 1993; NMFS unpublished data). Interactions with

Maine salmon aquaculture operations appears to be increasing, although the magnitude of interactions and seal

mortalities has not been quantified (Anon 1996). In 1980, more than 350 seals were found dead in the Cape Cod

area from an influenza outbreak (Geraci et al. 1981). 
79

The 1992-1996 harbor seal strandings data are currently under review. In 1995 one stranding was in South

Carolina. Reported harbor seal strandings during 1997-2000 were: 1997 (153),1998 (256), 1999 (150), and 2000

(219). Strandings were reported in all states between Maine and North Carolina, and in 1997 one each was reported

in Georgia and Florida. Maine (350/778), Massachusetts (190/778), New York (78/778) and New Jersey (46/778)

accounted for most of the strandings, reflecting both long coastlines and habitat use. Fifty five (7%) of the stranded

animals during this four year period showed signs of human interactions: fishery (14), vessel strike (4), power plant

(22), and other (15). Further, many live strandings are euthanized due to condition of the animals. Some sick and

injured seals are transported to rehabilitation facilities. 

Stranding data probably underestimate the extent of fishery-related mortality and serious injury because not

all of the marine mammals which die or are seriously injured may wash ashore, nor will all of those that do wash

ashore necessarily show signs of entanglement or other fishery-interaction. 

Stobo and Lucas (2000) have documented shark predation as an important source of natural mortality at

Sable Island, Nova Scotia. They suggest that shark-inflicted mortality in pups, as a proportion of total production,

was less than 10% (1980-1993), approximately 25% (1994-1995), and increasing to 45% in 1996. Also, shark

predation on adults was selective towards mature females. They suggest that the combined predation mortality is

likely impacting the Sable Island population growth, and may be contributing to the observed population decline.

STATUS OF STOCK

The status of harbor seals, relative to OSP, in the US Atlantic EEZ is unknown, but the population is

increasing. The species is not listed as threatened or endangered under the Endangered Species Act. Gilbert and

Guldager (1998) estimated a 4.4% annual rate of increase of this stock in Maine coastal waters based on 1981, 1982,

1986, 1993, 1997 surveys conducted along the Maine coast. The population is increasing despite the known fisheryrelated and other human sources of mortality. Total fishery-related mortality and serious injury for this stock is not

less than 10% of the calculated PBR and, therefore, cannot be considered to be approaching zero mortality and

serious injury rate. This is not a strategic stock because fishery-related mortality and serious injury does not exceed

PBR.

REFERENCES

Anon. 1996. Report of the Gulf of Maine Aquaculture-Pinniped Interaction task Force. Available from NMFS,

Office of Protected Resources. Silver Spring, MD. 70 pp.

Barlas, M. E. 1999. The distribution and abundance of harbor seals (Phoca vitulina concolor) and gray seals

(Halichoerus grypus) in southern New England, winter 1998- summer 1999. MA Thesis, Boston

University, Graduate School of Arts and Sciences., Boston, MA. 52 pp. 

Barlow, J., S. L. Swartz, T. C. Eagle and P. R. Wade. 1995. U.S. Marine Mammal Stock Assessments: Guidelines

for Preparation, Background, and a Summary of the 1995 Assessments. U.S. Dep. Commer., NOAA Tech.

Memo. NMFS-OPR-6, 73 pp. 

Bisack, K. D. 1997. Harbor porpoise bycatch estimates in the New England multispecies sink gillnet fishery: 1994

and 1995. Rep. int Whal. Commn. 47:705-14.

Boulva, J. and I. A. McLaren. 1979. Biology of the harbor seal, Phoca vitulina, in eastern Canada. Bull. Fish. Res.

Bd. Can. 200:1-24. 

Bravington, M. V. and K. D. Bisack. 1996. Estimates of harbor porpoise bycatch in the Gulf of Maine sink gillnet

fishery, 1990-93. Rep. int Whal. Commn. 46:567-574. 

Geraci, R., D. J. St. Aubin and I. K. Barker. 1981. Mass mortality of harbor seals: pneumonia associated with

influenza A virus. Science 215: 1129-1131.

Gilbert, J. R. and J. L. Stein. 1981. Harbor seal populations and marine mammal fisheries interactions, 1981.

Annual report to Northeast Fisheries Science Center. Contract NA-80-FA-C-00029. 35p.

Gilbert, J. R. and K. M. Wynne. 1983. Harbor seal populations and marine mammal fisheries interactions, 1982.

Second annual report. Northeast Fisheries Science Center. Contract NA-80-FA-C-00029. 43p.

Gilbert, J. R. and K. M. Wynne. 1984. Harbor seal populations and marine mammal fisheries interactions, 1983.

Third annual report. Northeast Fisheries Science Center. Contract NA-80-FA-C-00029. 52p.

Gilbert, J. R. and K. M. Wynne. 1985. Harbor seal populations and fisheries interactions with marine mammals in

New England, 1984. Interim Rep., NOAA NA-84-EAC-00070, NMFS, NEFSC, Woods Hole, MA, 15 pp.
80

Gilbert, J. R. and K. M. Wynne. 1987. Marine mammal interactions with New England gillnet fisheries. Final

Report Contract No. NA-84-EAC-00070, NOAA, NMFS, NEFSC, Woods Hole, MA. 21 pp. 

Gilbert, J. R. and N. Guldager. 1998. Status of harbor and gray seal populations in northern New England. Final

Report to: National Marine Fisheries Service, Northeast Fisheries Science Center, Woods Hole, MA. 

Under NMFS/NER Cooperative Agreement 14-16-009-1557. 13 pp. 

Hoover, K., S. Sadove and P. Forestell. 1999. Trends of harbor seal, Phoca vitulina, abundance from aerial surveys

in New York waters: 1985-1999. Proceedings of the 13th Biennial Conference on the Biology of Marine

Mammals, Wailea, Hawaii, Nov. 28 - Dec. 3, 1999. (Abstract). 

Katona, S. K., V. Rough and D. T. Richardson. 1993. A field guide to whales, porpoises, and seals from Cape Cod

to Newfoundland. Smithsonian Institution Press: Washington, DC, 316 pp. 

Kenney, M. K. 1994. Harbor seal population trends and habitat use in Maine. M.S. Thesis. University of Maine,

Orono, ME. 55 pp.

Kenney, M. K. and J. R. Gilbert. 1994. Increase in harbor and gray seal populations in Maine. Final Report

Contract No. 50-EANF-2-00064. NOAA, NMFS, NEFSC, Woods Hole, MA. 19 pp. 

Lens, S. 1997. Interactions between marine mammals and deep water trawlers in the NAFO regulatory area. ICES

C.M. 8/Q. 10 pp.

Payne. P. M. and D. C. Schneider. 1984. Yearly changes in abundance of harbor seals, Phoca vitulina, at a winter

haul-out site in Massachusetts. Fish. Bull., U.S. 82: 440-442. 

Payne, P. M. and L. A. Selzer. 1989. The distribution, abundance and selected prey of the harbor seal, Phoca

vitulina concolor, in southern New England. Mar. Mammal Sci. 5(2): 173-192. 

Read, A. J. 1994. Interactions between cetaceans and gillnet and trap fisheries in the northwest Atlantic. Rep. int

Whal. Commn. Special Issue 15: 133-147. 

Richardson, D. T. 1976. Assessment of harbor and gray seal populations in Maine 1974-1975. Final report to

Marine Mammal Commission. Contract No. MM4AC009.

Rosenfeld M., M. George and J. M. Terhune. 1988. Evidence of autumnal harbour seal, Phoca vitulina, movement

from Canada to the United States. Can. Field-Nat. 102(3): 527-529. 

Rough, V. 1995. Gray seals in Nantucket Sound, Massachusetts, winter and spring, 1994. Final report to Marine

Mammal Commission, Contract T10155615, 28 pp. NTIS Pub. PB95-191391.

Schneider, D. C. and P. M. Payne. 1983. Factors affecting haul-out of harbor seals at a site in southeastern

Massachusetts. J. Mamm. 64(3): 518-520.

Slocum, C.J., R. Schoelkopf, S. Tulevech, M. Stevens, S. Evert and M. Moyer. 1999. Seal populations wintering in

New Jersey (USA) have increased in abundance and diversity. Proceedings of the 13th Biennial Conference

on the Biology of Marine Mammals, Wailea, Hawaii, Nov. 28 - Dec. 3, 1999. (Abstract).

Stanley, H. F., S. Casey, J. M. Carnahan, S. Goodman, J. Harwood, and R. K. Wayne. 1996. Worldwide patterns of

mitochondrial DNA differentiation in the harbor seal (Phoca vitulina). Mol. Biol. Evol. 13: 368-382.

Stobo, W. T. and G. M. Fowler. 1994. Aerial surveys of seals in the Bay of Fundy and off southwest Nova Scotia.

Can. Tech. Rep. Fish. Aquat. Sci. 1943:57 pp.

Stobo, W. T. and Z. Lucas. 2000. Shark-inflicted mortality on a population of harbour seals (Phoca vitulina) at

Sable Island, Nova Scotia. J. Zool. Lond. 252: 405-414.

Temte, J. L., M. A. Bigg and O. Wiig. 1991. Clines revisited: the timing of pupping in the harbour seal (Phoca

vitulina). J. Zool. Lond. 224: 617-632.

Wade, P. R. and R. P. Angliss. 1997. Guidelines for assessing marine mammal stocks: Report of the GAMMS

Workshop April 3-5, 1996, Seattle, Washington. U.S. Dep. Commer., NOAA Tech. Memo. NMFS-OPR12, 93 pp.

Walden, J. 1996. The New England gillnet effort survey. NOAA-NMFS-NEFSC Ref. Doc. 99-10. 38 pp. 

Available from: National Marine Fisheries Service, 166 Water Street, Woods Hole, MA 02543-1026.

Whitman, A. A. and P. M. Payne. 1990. Age of harbour seals, Phoca vitulina concolor, wintering in southern New

England. Can. Field-Nat. 104(4): 579-582. 

Wilson, S. C. 1978. Social organization and behavior of harbor seals, Phoca concolor, in Maine. Final Report to

Marine Mammal Commission, Contract MM6ACO13, GPO-PB-280-188. 
81

January 2002

GRAY SEAL (Halichoerus grypus):

Western North Atlantic Stock

STOCK DEFINITION AND GEOGRAPHIC RANGE

The gray seal is found on both sides of the North Atlantic, with three major populations: eastern Canada,

northwestern Europe and the Baltic Sea (Katona et al. 1993). The western North Atlantic population occurs from

New England to Labrador and is centered in the Sable Island region of Nova Scotia (Katona et al. 1993; Davies

1957). This stock is separated by both geography and differences in the breeding season from the eastern Atlantic

stock (Bonner 1981). The western North Atlantic stock is distributed and breeds principally in eastern Canadian

waters (Mansfield 1966). There are two breeding concentrations in eastern Canada; one at Sable Island, and a

second that breeds on the pack ice in the Gulf of St. Lawrence (Laviguer and Hammill 1993). Tagging studies

indicate that there is little intermixing between the two breeding groups (Zwanenberg and Bowen 1990) and, for

management purposes, they are treated as separate populations (Mohn and Bowen 1996). However, small numbers

of animals and pupping have been observed on several isolated islands along the Maine coast and in NantucketVineyard Sound, Massachusetts (Katona et al. 1993; Rough 1995; J. R. Gilbert, pers. comm., University of Maine,

Orono, ME). In the late 1990's, a year-round breeding population of approximately 400+ animals was documented

on outer Cape Cod and Muskeget Island (Dennis Murley, pers. comm., Mass. Audubon Society, Wellfleet, MA). In

December 2001, NMFS initiated aerial surveys to monitor gray seal pup production on Muskeget Island and at the

Monomoy National Wildlife Refuge (NWR). Gilbert (pers. comm.) has also documented resident colonies and

pupping in Maine. 

POPULATION SIZE

Current estimates of the total western Atlantic gray seal population are not available; although four

estimates of portions of the stock are available for select time periods. In 1993 an estimate of the Sable Island and

Gulf of St. Lawrence stocks was 143,000 animals (Mohn and Bowen 1994). The population in waters off Maine has

increased from about 30 in the early 1980's to between 500-1,000 animals in 1993 (J.R. Gilbert, pers. Comm). 

Recently 29-49 pups/year have been recorded at one pupping site in Penobscot Bay, and in winter 2000

approximately 150 gray seals (adults and pups) were recorded at a second pupping site (J. R. Gilbert, pers. comm.). 

Maximum counts of individuals obtained during the spring molt at a winter breeding colony on Muskeget Island,

west of Nantucket Island did not exceed 13 in any year during the 1970s, but rose to 61 in 1984, 192 in 1988, 503 in

1992, and 1,549 in 1993. Aerial surveys in April and May of 1994 recorded a peak count of 2,010 gray seals for

Muskeget Island and Monomoy combined (Rough 1995; Table 1). From December 1998 to July 1999 the Northeast

Fisheries Science Center conducted aerial surveys in the same region surveyed by Payne and Selzer (1989) and

Rough (1995). The peak gray seal count in the region between Isle of Shoals, New Hampshire and Woods Hole,

Massachusetts was 5,611 (5/21/99; Table 1). No gray seals were recorded at haulout sites between Newport, Rhode

Island and Montauk Pt., New York (Barlas 1999). The 1999 count is 2.8 times greater than the 1994 count. Ninety

three percent of the gray seals were located at two sites in the eastern end of Nantucket Sound. Fifty-four percent of

the seasonal count was on Muskeget Island and adjacent sand bars in Nantucket sound, and 39% was on Monomoy

Island.

Table 1. Summary of abundance estimates for the western North Atlantic gray seal. Month, year, and area covered

during each abundance survey, resulting abundance estimate (Nmin) and coefficient of variation (CV). 

Month/Year Area Nmin CV

Apr-May 1994 Muskeget Island and Monomoy, MA1 2,010 none reported

Spring 1999 Muskeget Island and Monomoy, MA1

 5,611 none reported 

 1

 These counts pertain to animals seen in USA waters, and the stock relationship to animals in Canadian waters is

unknown.
82

Minimum Population Estimate

At the November 1998 meeting of the Atlantic Scientific Review Group (SRG), the SRG recommended that

the minimum estimate (2,010) used in previous assessments be discontinued, because it can not be determined what

part of the mortality comes from the Massachusetts, Maine, and Sable Island portions of the population. Therefore,

present data are insufficient to calculate the minimum population estimate for USA waters. It is estimated that there

are at least 143,000 gray seals in Canada (Mohn and Bowen 1996). 

Current Population Trend

Gray seal abundance is likely increasing in the USA Atlantic Exclusive Economic Zone (EEZ), but the rate

of increase is unknown. The population has been increasing for several decades in Canadian waters. Pup production

on Sable Island, Nova Scotia, has been about 13% per year since 1962 (Stobo and Zwanenberg 1990; Mohn and

Bowen 1996); whereas, in the Gulf of St. Lawrence it is increasing at a slower rate of 7.4% (Hammill et al. 1998). 

Approximately 57% of the western North Atlantic population is from the Sable Island stock. 

 Winter breeding colonies in Maine and on Muskeget Island may provide some measure of gray seal

population trends and expansion in distribution. Sightings in New England increased during the 1980s as the gray

seal population and range expanded in eastern Canada. Five pups were born at Muskeget in 1988. The number of

pups increased to 12 in 1992, 30 in 1993, and 59 in 1994 (Rough 1995). Gray seal pups were recorded on three

flight days during the 1998/1999 winter surveys (26 January, 9 February, and 10 March). On 9 February, 77 gray

seal pups (59 on Muskeget Island and 18 on South Monomoy) were recorded (Barlas 1999). The 1999 NMFS

flights only surveyed the Muskeget shoreline and are believed to be negatively biased, since recent anecdotal

information suggests that peak pupping occurs by mid-January. Further, naturalists conducting seal watch trips to

Muskeget, and aerial surveys conducted by V. Rough (deceased) suggests hundreds of gray seal pups were born. in

2000. These observations continue the increasing trend in pup production reported by Rough (1995). The change in

gray seal counts at Muskeget and Monomoy from 2,010 in 1994 to 5,611 in 1999 represents an annual increase rate

of 20.5%, however, it can not be determined what proportion of the increase represents growth or immigration. 

CURRENT AND MAXIMUM NET PRODUCTIVITY RATES

Current and maximum net productivity rates are unknown for this stock. One study that estimated pup

production on Sable Island estimated the annual production rate was 13% (Mohn and Bowen 1994).

For purposes of this assessment, the maximum net productivity rate was assumed to be 0.12. This value is

based on theoretical modeling showing that pinniped populations may not grow at rates much greater than 12%

given the constraints of their reproductive life history (Barlow et al. 1995). 

POTENTIAL BIOLOGICAL REMOVAL

Potential Biological Removal (PBR) is the product of minimum population size, one-half the maximum

productivity rate, and a “recovery” factor (MMPA Sec. 3. 16 U.S.C. 1362; Wade and Angliss 1997). The minimum

population size is unknown. The maximum productivity rate is 0.12, the default value for pinnipeds. The recovery

factor (FR) for this stock is 1.0, the value for stocks of unknown status, but is known to be increasing. PBR for the

western North Atlantic gray seals in USA waters is unknown. 

ANNUAL HUMAN-CAUSED MORTALITY AND SERIOUS INJURY

For the period 1996-2000, the total estimated human caused mortality and serious injury to gray seals is

estimated to be 307 per year. The average is derived from three components: 1) 118 (CV=0.35; Table 2) from the

1996-2000 USA observed fishery; 2) 4.5 from average1997-2000 stranding mortalities in USA waters resulting from

power plant entrainments, oil spill, shooting, and other sources, and 3) 184 from average 1996-2000 kill in the

Canadian hunt (Anon. 2001). 

Fishery Information

USA

Data on current incidental takes in USA fisheries are available from several sources. In 1986, NMFS

established a mandatory self-reported fisheries information system for large pelagic fisheries. Data files are

maintained at the Southeast Fisheries Science Center (SEFSC). The Northeast Fisheries Science Center (NEFSC)

Sea Sampling Observer Program was initiated in 1989, and since that year several fisheries have been covered by the
83

program. In late 1992 and in 1993, the SEFSC provided observer coverage of pelagic longline vessels fishing off the

Grand Banks (Tail of the Banks) and provides observer coverage of vessels fishing south of Cape Hatteras. 

Northeast Multispecies Sink Gillnet

In 1993, there were approximately 349 full and part-time vessels in the Northeast multispecies sink gillnet

fishery, which covered the Gulf of Maine and southern New England (Table 2). An additional 187 vessels were

reported to occasionally fish in the Gulf of Maine with gillnets for bait or personal use; however, these vessels were

not covered by the observer program (Walden 1996) and their fishing effort was not used in estimating mortality. In

1998, there were approximately 301 vessels in this fishery (NMFS unpublished data). Observer coverage in terms of

trips has been 1%, 6%, 7%, 5%, 7%, 5%, 4%, 6%, and 6% for 1990- 2000, respectively. The fishery has been

observed in the Gulf of Maine and in Southern New England. There were 45 gray seal mortalities observed in the

Northeast multispecies sink gillnet fishery between 1993-2000. Twenty-one of the observed mortalities occurred in

winter (January - May), 9 in the southern Gulf of Maine, 2 in the "mid-coast closed area”, and 2 in the South Cape

closure. Only 1 mortality was observed in northern Maine waters, which occurred in autumn (September-December)

1995. One of the 1993 observed mortalities was in May and was from SE of Block Island. Seasonality of takes

needs to be updated.

Annual estimates of gray seal bycatch in the Northeast multispecies sink gillnet fishery reflect seasonal

distribution of the species and of fishing effort. Estimated annual mortalities (CV in parentheses) from this fishery

during 1990-1996 was 0 in 1990-1992, 18 in 1993 (1.00), 19 in 1994 (0.95), 117 in 1995 (0.42), 49 in 1996 (0.49),

131 in 1997 (0.50), 61 in 1998 (0.98), 155 in 1999 (0.51), and 193 in 2000. The 1995 bycatch includes 28 animals

from the estimated number of unknown seals (based on observed mortalities of seals that could not be identified to

species). The unknown seals were prorated, based on spatial/temporal patterns of bycatch of harbor seals, gray

seals, harp seals, and hooded seals. Further, they will likely have little impact on the estimates presented. Average

annual estimated fishery-related mortality and serious injury to this stock attributable to this fishery during 1996-

2000 was 118 gray seals (CV=0.35). The stratification design used is the same as that for harbor porpoise

(Bravington and Bisack 1996).

CANADA

An unknown number of gray seals have been taken in Newfoundland and Labrador, Gulf of St. Lawrence,

and Bay of Fundy groundfish gillnets, Atlantic Canada and Greenland salmon gillnets, Atlantic Canada cod traps,

and in Bay of Fundy herring weirs (Read 1994). In addition to incidental catches, some mortalities (e.g., seals

trapped in herring weirs) were the result of direct shooting, and there were culls of about 1,700 animals annually

during the 1970's and early 1980's on Sable Island (Anon. 1986). 

There were 3,121 cod traps operating in Newfoundland and Labrador during 1979, and about 7,500 in 1980

(Read 1994). This fishery was closed at the end of 1993 due to collapse of Canadian groundfish resources. 

Herring weirs are also distributed throughout the Bay of Fundy; it has been reported that 180 weirs were

operating in the Bay of Fundy in 1990 (Read 1994). 

In 1996, observers recorded 3 gray seals (1 released alive) in Spanish deep water trawl fishing on the

southern edge of the Grand Bank (NAFO Areas 3) (Lens, 1997). Seal bycatches occurred year-round, but

interactions were highest during April-June. Many of the seals that died during fishing activities were unidentified. 

The proportion of sets with mortality (all seals) was 2.7 per 1,000 hauls (0.003).
84

Table 2. Summary of the incidental mortality of gray seal (Halichoerus grypus) by commercial fishery including the

years sampled (Years), the number of vessels active within the fishery (Vessels), the type of data used (Data

Type), the annual observer coverage (Observer Coverage), the mortalities recorded by on-board observers

(Observed Mortality), the estimated annual mortality (Estimated Mortality), the estimated CV of the annual

mortality (Estimated CVs) and the mean annual mortality (CV in parentheses).

Fishery Years Vessels Data Type 1 Observer

 Coverage 2

Observed

 Mortality3

Estimated

 Mortality3

Estimated

 CVs 

Mean

 Annual

 Mortality

 Northeast

Multispecies

 Sink Gillnet

96-00 301 Obs. Data

 Weighout,

 Logbooks

.04, .06, 

.05, .06,

.06

3, 16,

4, 5, 5

 49, 131, 

61, 155, 193

.49,

 .50, .98,

.51, .55

118

(.35)

 TOTAL 118

(.35)

1

 Observer data (Obs. Data) are used to measure bycatch rates, and the data are collected within the Northeast

Fisheries Science Center (NEFSC) Sea Sampling Program. NEFSC collects landings data (Weighout), and

total landings are used as a measure of total effort for the sink gillnet fishery. Mandatory logbook

(Logbook) data are used to determine the spatial distribution of fishing effort in the Northeast multispecies

sink gillnet fishery. 2

 The observer coverage for the Northeast multispecies sink gillnet fishery is measured in trips. 3

 In 1995, 1998 and 2000, respectively, observed mortality on “marine mammal trips” was 6, 3 and 3

animals. Only these mortalities were used to estimate total gray seal bycatch. See Bisack (1997) for “trip”

type definitions. 1995 and 1998 had 1 mortality in each year and in 2000, 2 mortalities were recorded on

“fish trips”. In 1997 all observed takes were on marine mammal trips, including 12 taken on pingered trips. 

Since 1998, takes from nonpingered nets within a marine mammal time/area closure that required pingers

and takes from pingered nets not within a marine mammal time/area closure that required pingers were

pooled with the takes from nets with and without pingers from the same stratum. The pooled bycatch rate

was weighted by the total number of samples taken from the stratum and used to estimate the mortality. In

1998, 1 take was observed in a net without a pinger that was within a marine mammal closure that required

pingers. In 1999 and 2000, 2 takes were observed each year in nets with pingers.

Other Mortality

 Gray seals, like harbor seals, were hunted for bounty in New England waters until the late 1960's. This

hunt may have severely depleted this stock in USA waters (Rough 1995). In addition, the Cape Cod stranding

network has documented several animals with netting or plastic debris around their necks in the Cape Cod/Nantucket

area. An unknown level of mortality also occurs in the mariculture industry (i.e., salmon farming) and by deliberate

shooting (NMFS unpublished data). 

In Canada, gray seals were hunted for several centuries by indigenous people and European settlers in the

Gulf of St. Lawrence and along the Nova Scotia eastern shore, and were locally extirpated ( Lavigueru and Hammill

1993). By the mid-1900s gray seals were considered to be rare, and in the mid-1960s the population in eastern

Canada was estimated to be 5,600 (Mansfield 1966). Since the mid-1960s the population has been increasing. 

During a bounty program (1976-1983) and a culling program (1967-1983), the average annual removals were 720

and 1,000 seals, respectively (Anon 2001). Between 1993-2000, the annual kill of gray seals by hunters was: 1993

(0), 1994 (40), 1995 (364), 1996 (132), 1997 (72), 1998 (275), 1999 (98), and 2000 (342) (Anon 2001). The

traditional hunt of a few hundred animals is expected to continue in 2001 (Anon 2001) off the Magdalen Islands and

in other areas, except Sable Island, where commercial hunting is not permitted.

The 1992-1996 gray seal strandings data are currently under review. In 1997-2000, 133 gray seal

strandings were recorded, extending from Maine (19) to No. Carolina (1). Most of the strandings were in

Massachusetts (48), New York (31), and Maine (19). Eighteen animals showed signs of human interactions: fishery

(6), power plant (3), oil spill (4), shot (1), mutilated (1), other (3). Further, many live strandings are euthanized due

to the animal’s condition. Some sick and injured seals are transported to rehabilitation facilities. Stranding data
85

probably underestimate the extent of fishery-related mortality and serious injury because not all of the marine

mammals which die or are seriously injured wash ashore, nor will all of those that do wash ashore necessarily show

signs of entanglement or other fishery interaction. 

 STATUS OF STOCK

The status of the gray seal population, relative to OSP, in US Atlantic EEZ waters is unknown, but the

populations appear to be increasing in Canadian and USA waters. The species is not listed as threatened or

endangered under the Endangered Species Act. Recent data indicate that this population is increasing. The total

fishery-related mortality and serious injury for this stock is believed to be very low relative to the population size in

Canadian waters and can be considered insignificant and approaching zero mortality and serious injury rate. The

level of human-caused mortality and serious injury in the US Atlantic EEZ is unknown, but believed to be very low

relative to the total stock size; therefore, this is not a strategic stock. 

REFERENCES

Anon. 1986. Seals and sealing in Canada. Rep. of the Royal Commission on Seals and Sealing, Vol. 1, 65 pp.

Available from Canadian Government Publishing Centre, Ottawa, Canada.

Anon. 2001. Atlantic seal hunt: 2001 management plan. Available from Canadian Department of Fisheries and

Oceans, Ottawa, Ontario Canada, K1A OE6, Resource Management - Atlantic. 34 pp.

Bonner, W. N. 1981. Grey seal, Halichoerus grypus. In: S. H. Ridgway and R. J. Harrison (eds.), Handbook of

Marine Mammals, Vol. 2. Pp. 111-144. London: Academic Press.

Barlas, M. E. 1999. The distribution and abundance of harbor seals (Phoca vitulina concolor) and gray seals

(Halichoerus grypus) in southern New England, winter 1998- summer 1999. MA Thesis, Boston

University, Graduate School of Arts and Sciences., Boston, MA. 52 pp. 

Barlow, J., S. L. Swartz, T. C. Eagle and P. R. Wade. 1995. U.S. Marine Mammal Stock Assessments: Guidelines

for Preparation, Background, and a Summary of the 1995 Assessments. U.S. Dep. Commer., NOAA Tech.

Memo. NMFS-OPR-6, 73 pp.

Bisack, K. D. 1997. Harbor porpoise bycatch estimates in the New England multispecies sink gillnet fishery: 1994

and 1995. Rep. int Whal. Commn. 47:705-14. 

Bravington, M. V. and K. D. Bisack. 1996. Estimates of harbor porpoise bycatch in the Gulf of Maine sink gillnet

fishery, 1990-93. Rep. int Whal. Commn. 46:567-574. 

Bonner, W. N. 1981. Grey seal Halichoerus grypus Fabricus, 1791. Pages 111-144 in: S. H. Ridgway and R. J.

Harrison (eds), Handbook of Marine Mammals, Vol. 2: Seals. Academic Press, London, 359 pp. 

Davies, J. L. 1957. The geography of the gray seal. J. Mamm. 38: 297-310.

Hammill, M.O., G.B. Stenson, R.A. Myers and W.T. Stobo. 1998. Pup production and population trends of the grey

seal (Halichoerus grypus) in the Gulf of St. Lawrence. Can. J. Fish. Aquat. Sci. 55:423-430.

Katona, S. K., V. Rough and D. T. Richardson. 1993. A field guide to whales, porpoises, and seals from Cape Cod

to Newfoundland. Smithsonian Institution Press, Washington, DC. 316 pp. 

Laviguer, L. and M. O. Hammill. 1993. Distribution and seasonal movements of grey seals, Halichoerus grypus,

born in the Gulf of St. Lawrence and eastern Nova Scotia shore. Can. Field-Nat. 107: 329-340.

Lens, S. 1997. Interactions between marine mammals and deep water trawlers in the NAFO regulatory area. ICES

C.M. 8/Q. 10 pp.

Mansfield, A.W. 1966. The grey seal in eastern Canadian waters. Can. Audubon Mag. 28:161-166.

Mohn, R. and W. D. Bowen. 1996. Grey seal predation on the eastern Scotian Shelf: Modeling the impact on

Atlantic cod. Can. J. Aquat. Sci. 53:2722-2738.

Payne, P. M. and L. A. Selzer. 1989. The distribution, abundance and selected prey of the harbor seal, Phoca

vitulina concolor, in southern New England. Mar. Mammal Sci. 5(2): 173-192. 

Read, A. J. 1994. Interactions between cetaceans and gillnet and trap fisheries in the northwest Atlantic. Rep. int

Whal. Commn. Special Issue 15: 133-147. 

Rough, V. 1995. Gray seals in Nantucket Sound, Massachusetts, winter and spring, 1994. Final report to Marine

Mammal Commission, Contract T10155615, 28 pp. NTIS Pub. PB95-191391.

Stobo, W. T. and K. C. T. Zwanenburg. 1990. Grey seal (Halichoerus grypus) pup production on Sable Island and

estimates of recent production in the northwest Atlantic. Pages 171-184 in: W. D. Bowen (ed), Population
86

 biology of sealworm (Pseudoterranova decipiens) in relation to its intermediate and seal hosts. Can. Bull. Fish.

 and Aq. Sci. 222. 

Wade, P. R. and R. P. Angliss. 1997. Guidelines for assessing marine mammal stocks: Report of the GAMMS

Workshop April 3-5, 1996, Seattle, Washington. U.S. Dep. Commer., NOAA Tech. Memo. NMFS-OPR12, 93 pp.

Walden, J. 1996. The New England gillnet effort survey. NOAA-NMFS-NEFSC Ref. Doc. 99-10. 38 pp. 

Available from: National Marine Fisheries Service, 166 Water Street, Woods Hole, MA 02543-1026.

Zwanenberg, K.C.T. and W.D. Bowen. 1990. Population trends of the grey seal (Halichoerus grypus) in eastern

Canada. Pgs. 185-197 in: W.D. Bowen (ed.), Population Biology of Sealworm (Pseudoterranova

decipiens) in Relation to its Intermediate and Seal Hosts. Can. Bull. Fish. and Aq. Sci. 222.
87

January 2002

HARP SEAL (Phoca groenlandica):

Western North Atlantic Stock

STOCK DEFINITION AND GEOGRAPHIC RANGE

The harp seal occurs throughout much of the North Atlantic and Arctic Oceans (Ronald and Healey 1981;

Lavigne and Kovacs 1988); however, in recent years, numbers of sightings and strandings have been increasing off

the east coast of the United States from Maine to New Jersey (Katona et al. 1993; Stevick and Fernald 1998; B.

Rubinstein, pers. comm., New England Aquarium; Lacoste and Stenson 2000). These extralimital appearances

usually occur in January-May, when the western North Atlantic stock of harp seals is at its most southern point of

migration. Concomitantly, a southward shift in winter distribution off Newfoundland was observed during the mid1990s, which was attributed to abnormal environmental conditions (Lacoste and Stenson 2000). The world’s harp

seal population is divided into three separate stocks, each identified with a specific breeding site (Bonner 1990;

Lavigne and Kovacs 1988). The largest stock is located in the western North Atlantic off eastern Canada and is

divided into two breeding herds which breed on the pack ice. The Front herd breeds off the coast of Newfoundland

and Labrador, and the Gulf herd breeds near the Magdalen Islands in the middle of the Gulf of St. Lawrence

(Sergeant 1965; Lavigne and Kovacs 1988). The second stock breeds in the White Sea off the coast of the Soviet

Union, and the third stock breeds on the West Ice off of eastern Greenland (Lavigne and Kovacs 1988; Anon 1998). 

Harp seals are highly migratory (Sergeant 1965; Stenson and Sjare 1997). Breeding occurs at different times

between mid-February and April for each stock. Adults then assemble north of their whelping patches to undergo

the annual molt. The migration then continues north to Arctic summer feeding grounds. In late September, after a

summer of feeding, nearly all adults and some of the immature animals migrate southward along the Labrador coast,

usually reaching the entrance to the Gulf of St. Lawrence by early winter. There they split into two groups, one

moving into the Gulf and the other remaining off the coast of Newfoundland. Following mating, the seals disperse

to feed, and in late April they again concentrate in large numbers on the ice to molt.

The extreme southern limit of the harp seal's habitat extends into the USA Atlantic Exclusive Economic

Zone (EEZ) during winter and spring. The increase in numbers and geographic distribution of harp seals in New

England to mid-Atlantic waters is based primarily on strandings, and secondarily on fishery bycatch (McAlpine and

Walker 1990; Rubinstein 1994).

POPULATION SIZE

The total population size of harp seals is unknown; however, three seasonal abundance estimates are

available which use a variety of methods including aerial surveys and mark-recapture (Table 1). Generally, these

methods include surveying the whelping concentrations and modeling pup production. Harp seal pup production in

the 1950s was estimated at 645,000 (Sergeant 1975), decreasing to 225,000 by 1970 (Sergeant 1975). Estimates

began to increase at that time and have continued to rise, reaching 478,000 in 1979 (Bowen and Sergeant 1983;

Bowen and Sergeant 1985) 577,900 in 1990 (Stenson et al. 1993) and 998,000 in 1999 (Stenson et al. 2000).

Roff and Bowen (1983) developed an estimation model to provide a more precise estimate of total

population. This technique incorporates recent pregnancy rates and estimates of age-specific hunting mortality

(CAFSAC 1992). Shelton et al. (1992) applied a harp seal estimation model to the 1990 pup production and

obtained an estimate of 3.1 million (range 2.7-3.5 million; Stenson 1993). Using a revised population model, 1994

pup count data, and two assumptions regarding pup mortality rates, Shelton et al. (1996) estimated pup production

and total population size for the period 1955-1994. The 1994 total population estimate was 4.8 million (95% CI =

4.1-5.5) harp seals (Warren et al. 1997; Table1). The 1999 population estimate was 5.2 million (95% CI = 4.0 - 6.4

million) harp seals (Healey and Stenson 2000) (Table 1).
88

Table 1. Summary of abundance estimates (pups and total) for western North Atlantic harp seals. Year and area

covered during each abundance survey, resulting abundance estimate (Nmin) and coefficient of variation

(CV). 

Month/Year Area Nmin CV

1994 Eastern Atlantic Canada-Labrador 702,900 pups 0.09

1994 Eastern Atlantic Canada-Labrador 4.8 million ±772,0001

1999 Eastern Atlantic Canada - Labrador 998,000 pups ±200,000 (95% CI)

1999 Eastern Atlantic Canada - Labrador 5.2 million ±1,200,000 (95% CI)

1

 Original confidence intervals provided by Shelton et al. (1996) were skewed and recalculated by Warren et al.

(1997).

Minimum population estimate

Present data are insufficient to calculate the minimum population estimate for USA waters. It is estimated

there are at least 5.2 million (±1.2 million) harp seals in Canada (Healey and Stenson 2000). 

Current population trend

The population appears to be increasing in USA waters, judging from the increased number of stranded

harp seals, but the magnitude of the suspected increase is unknown. In Canada, since 1996 the population has been

stable (5.2 million; ±1.2 million) due to large harvests of young animals in recent years (Healey and Stenson 2000). 

CURRENT AND MAXIMUM NET PRODUCTIVITY RATES

Current and maximum net productivity rates are unknown for this stock. The best data are based on

Canadian studies. Recent studies indicate that pup production has increased, but the rate of population increase

cannot be quantified at this time (Stenson et al. 1996). The mean age of sexual maturity was 5.8 yrs in the mid1950's, declining to 4.6 yrs in the early 1980's and then increasing to 5.6 yrs in the mid-1990s (Sjare et al. 1996;

Sjare and Stenson 2000).

For purposes of this assessment, the maximum net productivity rate was assumed to be 0.12. This value is

based on theoretical modeling showing that pinniped populations may not grow at rates much greater than 12%

given the constraints of their reproductive life history (Barlow et al. 1995). 

POTENTIAL BIOLOGICAL REMOVAL

Potential Biological Removal (PBR) is the product of minimum population size, one-half the maximum

productivity rate, and a “recovery” factor (MMPA Sec. 3. 16 U.S.C. 1362; Wade and Angliss 1997). The minimum

population size in USA waters is unknown. The maximum productivity rate is 0.12, the default value for pinnipeds. 

The “recovery” factor, which accounts for endangered, depleted, threatened stocks, or stocks of unknown status

relative to optimum sustainable population (OSP) was set at 1.0 because it was believed that harp seals are within

OSP. PBR for the western North Atlantic harp seal in USA waters is unknown. Applying the formula to the

minimum population estimate for Canadian waters results in a "PBR" of 312,000 harp seals. However, Johnston et

al. (2000) suggests that catch statistics from the Canadian hunt are negatively biased due to under reporting;

therefore, an FR of 0.5 would be appropriate. Using the lower FR results in a “PBR” of 156,000 harp seals. 

ANNUAL HUMAN-CAUSED MORTALITY AND SERIOUS INJURY

For the period 1996-2000, the total estimated human caused mortality and serious injury to harp seals was

321,222. This is derived from three components: 1) 301,611 from 1996-2000 average catches of Northwest Atlantic

harp seals by Canada and Greenland; 2) 16,000 - 23,000 (annually) from average bycatches in the Newfoundland

lumpfish fishery; and 3) 111 harp seals CV=0.29 from the observed USA fisheries (Table 2). 
89

Fishery Information

USA

Data on current incidental takes in USA fisheries are available from several sources. In 1986, NMFS

established a mandatory self-reported fisheries information system for large pelagic fisheries. Data files are

maintained at the Southeast Fisheries Science Center (SEFSC). The Northeast Fisheries Science Center (NEFSC)

Sea Sampling Observer Program was initiated in 1989, and since that year several fisheries have been covered by the

program. In late 1992 and in 1993, the SEFSC provided observer coverage of pelagic longline vessels fishing off the

Grand Banks (Tail of the Banks) and provides observer coverage of vessels fishing south of Cape Hatteras. 

Recent bycatch has been observed by NMFS Sea Samplers in the Northeast multispecies sink gillnet

fisheries, but no mortalities have been documented in the mid-Atlantic coastal gillnet, Atlantic drift gillnet, pelagic

pair trawl or pelagic longline fisheries. 

Northeast Multispecies Sink Gillnet:

In 1993, there were approximately 349 full and part-time vessels in the Northeast multispecies sink gillnet

fishery which covered the Gulf of Maine and southern New England (Table 2). An additional 187 vessels were

reported to occasionally fish in the Gulf of Maine with gillnets for bait or personal use; however, these vessels were

not covered by the observer program (Walden 1996) and their fishing effort was not used in estimating mortality. In

1998, there were approximately 310 vessels in this fishery (NMFS unpublished data). Observer coverage in terms of

trips has been 1%, 6%, 7%, 5%, 7%, 5%, 4%, 6%, 5%, 6%, and 6% for 1990 to 2000, respectively. The fishery has

been observed in the Gulf of Maine and in Southern New England. There were 121 harp seal mortalities observed in

the Northeast multispecies sink gillnet fishery between 1990 and2000. Annual estimates of harp seal bycatch in the

Northeast multispecies sink gillnet fishery reflect seasonal distribution of the species and of fishing effort. Estimated

annual mortalities (CV in parentheses) from this fishery during 1990-1999 were 0 during 1990-1993, 861 in 1994

(0.58), 694 in 1995 (0.27), 89 in 1996 (0.55), 269 in 1997 (0.50), 78 in 1998 (0.48), 81 in 1999 (0.78), and 24 in

2000 (0.30). The 1994 and 1995 bycatches include 16 and 153 animals, respectively, from the estimated number of

unknown seals (based on observed mortalities of seals that could not be identified to species). The unknown seals

were prorated, based on spatial/temporal patterns of bycatch of harbor seals, gray seals, harp seals, and hooded seals.

Average annual estimated fishery-related mortality and serious injury to this stock attributable to this fishery during

1996-2000 was 108 harp seals (CV=0.30). The stratification design used is the same as that for harbor porpoise

(Bravington and Bisack 1996). The bycatch occurred principally in winter (January-May) and was mainly in waters

between Cape Ann and New Hampshire. One observed winter mortality was in waters south of Cape Cod.

Mid-Atlantic Coastal Gillnet:

Observer coverage of the USA Atlantic coastal gillnet fishery was initiated by the NEFSC Sea Sampling

program in July 1993 and, from July to December 1993, 20 trips were observed. During 1994 and 1995, 221 and

382 trips were observed, respectively. This fishery, which extends from North Carolina to New York, is actually a

combination of small vessel fisheries that target a variety of fish species, some of which operate right off the beach. 

The number of vessels in this fishery is unknown because records which are held by both state and federal agencies

have not been centralized and standardized. Observer coverage, expressed as percent of tons of fish landed, was 5%,

4%, 3%, 5%, 2%, and 2% for 1995, 1996, 1997, 1998, 1999, and 2000, respectively (Table 2).

No harp seals were taken in observed trips during 1993-1997, and 1999. One harp seal was observed taken

in 1998 (Table 2). Observed effort was concentrated off NJ and scattered between DE and NC from 1 to 50 miles

off the beach. All bycatches were documented during January to April. Using the observed takes, the estimated

annual mortality (CV in parentheses) attributed to this fishery was 0 in 1995-1997, 17 in 1998 (1.02), and 0 in both

1999 and 2000. Average annual estimated fishery-related mortality attributable to this fishery during 1996-2000 was

3.0 harp seals (CV=1.02).

CANADA

An unknown number of harp seals have been taken in Newfoundland and Labrador groundfish gillnets

(Read 1994). Harp seals are being taken in Canadian lumpfish and groundfish gillnets and trawls, but estimates of

total removals have not been calculated to date (Anon. 1994). A recent analysis of bycatch in the Newfoundland

lumpfish fishery indicates that fewer than 10,000 seals were taken annually from the start of the fishery in 1968 until

1984 (Walsh et al. 2000). Between 1984-1995, annual bycatches have been more variable, ranging between 3,000

and 36,000 animals. Since 1996, bycatches have varied between 16,000 and 23,000 seals annually (DFO 2000).
90

There were 3,121 cod traps operating in Newfoundland and Labrador during 1979, and about 7,500 in 1980

(Read 1994). This fishery was closed at the end of 1993 due to collapse of Canadian groundfish resources.

In 1996, observers recorded 4 harp seals (1 released alive) in Spanish deep water trawl fishing on the

southern edge of the Grand Bank (NAFO Areas 3) (Lens 1997). Seal bycatches occurred year-round, but

interactions were highest during April-June. Many of the seals that died during fishing activities were unidentified. 

The proportion of sets with mortality (all seals) was 2.7 per 1,000 hauls (0.003).

Table 2. Summary of the incidental mortality of harp seal (Phoca groenlandica) by commercial fishery including the

years sampled (Years), the number of vessels active within the fishery (Vessels), the type of data used (Data

Type), the annual observer coverage (Observer Coverage), the mortalities recorded by on-board observers

(Observed Mortality), the estimated annual mortality (Estimated Mortality), the estimated CV of the annual

mortality (Estimated CVs) and the mean annual mortality (CV in parentheses).

Fishery Years Vessels Data Type 1 Observer

 Coverage 2 

Observed

 Mortality3

Estimated

 Mortality 

Estimated

 CVs 

Mean

 Annual

 Mortality

 Northeast

Multispecies

 Sink Gillnet

96-00 301

Obs. Data

 Weighout,

 Logbooks

.04, .06, .05,

.06, .06

9, 40, 4,

4, 3

89, 269,

78, 81, 24

.55, .50,

.48, .78,

1.57

108

(.30)

Mid Atlantic

Coastal Sink

Gillnet

96-00 Unk4

Obs. Data

Weighout

.04, .03, .05,

.02, .02

0, 0, 1,

0, 0

0, 0,17,

0, 0

0, 0, 1.02,

0, 0

3

(1.02)

TOTAL 111

(.29)

1

 Observer data (Obs. Data) are used to measure bycatch rates, and the data are collected within the Northeast

Fisheries Science Center (NEFSC) Sea Sampling Program. NEFSC collects landings data (Weighout) and

total landings are used as a measure of total effort for the sink gillnet fishery. Mandatory logbook

(Logbook) data are used to determine the spatial distribution of fishing effort in the Northeast multispecies

sink gillnet fishery. 2

 The observer coverage for the Northeast multispecies sink gillnet fishery is measured in trips. Observer

coverage for the Mid Atlantic coastal sink gillnet fishery is measured in tons of fish landed. 3 In the New England sink gillnet fishery, 31 and 0 harp seals were taken on pingered trips during 1997 and

1998, respectively. During 1997, 1998, 1999 and 2000, there were 31, 4, 2, and 2 harp seals observed on

"mammal trips", respectively. See Bisack (1997) for “trip” type definitions. During 1999 and 2000, 2 and

1 harp seals, respectively, were observed on “fish trips” and 3 and 2 were observed taken from pingered

nets. 4 Number of vessels is not known.

Other Mortality

 Harp seals have been commercially hunted since the mid-1800's in the Canadian Atlantic (Stenson 1993). 

A total allowable catch (TAC) of 200,000 harp seals was set for the large vessel hunt in 1971. The TAC varied until

1982 when it was set at 186,000 seals and remained at this level through 1995 (Stenson 1993; Anon 1998). The

TAC was increased to 250,000 and 275,000, respectively in 1996 and 1997 (Anon 1998). The 1997 TAC has

remained in effect through 2001 (Anon 2001). In 2001, the Canadian Minister of Fisheries and Oceans established a

panel of eminent persons to provide advice on a long-term strategy for the management of seal populations (Anon

2001). Catches ranged from 124,000 to 231,000 from 1971-1982, declined to a range of 19,000 to 94,000 between

1983-1995, and increased dramatically to 243,000 (1996) and 282,000 (1998) (Stenson 1993; Anon 1998; Anon

2001). Catches declined to 92,000 in 2000 (Anon 2000). Harp seals are also hunted in the Canadian Arctic and in

Greenland (DFO 2000). There are no recent statistics for the Canadian Arctic, but during the late 1970's annual

catches ranged between 1,200 and 6,500 animals. Prior to 1980, Greenland catches were less than 20,000 annually,

but in recent years have dramatically increased to around 100,000 (DFO 2000). The commercial catches do not
91

account for subsistence takes and animals that are killed but not landed (struck and lost) (Lavine 1999). A recent

analysis of the struck and loss rates suggests that the rate for young seals (majority of Canadian take) is less than 5%,

while losses of older seals is higher (approximately 50%) (DFO 2000). 

From 1988-1993 strandings each year were under 50, approaching 100 animals in 1994, and exceeding 100

animals in 1995-1996 (Rubinstein 1994; B. Rubinstein, New England Aquarium, pers. comm.). In addition, in 1996

there was a stranding in North Carolina. From 1997-2000, 485 strandings were recorded, including one in North

Carolina. Most of the strandings occurred in Maine (73), Massachusetts (158), New York (166) and New Jersey

(32). Further, many are live strandings and some are euthanized due to the animal’s condition. Some sick and

injured seals are transported to rehabilitation facilities. Few animals showed signs of human interactions and, except

for 4 shot animals, 1 fishery interaction, and 1 mutilated animal, the interactions were classified as other. The

increased number of strandings may indicate a possible shift in distribution or expansion southward into USA

waters.

STATUS OF STOCK

The status of the harp seal stock, relative to OSP, in the US Atlantic EEZ is unknown, but the population

appears to be stable in Canadian waters, due to harvest of young animals. The species is not listed as threatened or

endangered under the Endangered Species Act. The total fishery-related mortality and serious injury for this stock is

believed to be very low relative to the population size in Canadian waters and can be considered insignificant and

approaching zero mortality and serious injury rate. The level of human-caused mortality and serious injury in the

US Atlantic EEZ is unknown, but believed to be very low relative to the total stock size; therefore, this is not a

strategic stock. 

REFERENCES

Anon. 1998. Report of the Joint ICES/NAFO Working Group on Harp and Hooded Seals. 28 August-3 September

1997, Copenhagen, Denmark. ICES CM 1998/Assess:3. 35 pp.

Anon. 2000. Report of the Joint ICES/NAFO Working Group on Harp and Hooded Seals. 2-6 October 2000,

Copenhagen, Denmark. ICES CM 2001/ACFM:08. 40 pp.

Anon. 2001. Atlantic Seal Hunt: 2001 management plan. Available from Canadian Department of Fisheries and

Oceans, Ottawa, Ontario Canada, K1A OE6, Resource Management - Atlantic. 34 pp.

Barlow, J., S. L. Swartz, T. C. Eagle and P. R. Wade. 1995. U.S. Marine Mammal Stock Assessments: Guidelines

for Preparation, Background, and a Summary of the 1995 Assessments. U.S. Dep. Commer., NOAA Tech.

Memo. NMFS-OPR-6, 73 pp. 

Bravington, M. V. and K. D. Bisack. 1996. Estimates of harbor porpoise bycatch in the Gulf of Maine sink gillnet

fishery, 1990-93. Rep. int Whal. Commn. 46:567-574. 

Bisack, K. D. 1997. Harbor porpoise bycatch estimates in the New England multispecies sink gillnet fishery: 1994

and 1995. Rep. int Whal. Commn. 47:705-14. 

Bonner, W. N. 1990. The natural history of seals. Fact on File, New York, 196 pp. 

Bowen, W. D. and D. E. Sergeant. 1983. Mark-recapture estimates of harp seal pup (Phoca groenlandica)

production in the northwest Atlantic. Can. J. Fish. Aquat. Sci. 40: 728-742.

Bowen, W. D. and D. E. Sergeant. 1985. A mark-recapture estimate of 1983 harp seal pup production in the

Northwest Atlantic. NAFO SCR. Doc. 85/I/1. 

CAFSAC. 1992. Update on population estimates of Harp seal in the Northwest Atlantic. Canadian Atlantic

Fisheries Scientific Advisory Committee, CAFSAC Adv. Doc. 92/8.

DFO [Dept. Of Fisheries and Oceans]. 2000. Northwest Atlantic harp seals. DFO Science Stock Status Report E1-

01. Available from the Canadian Stock Assessment Secretariat, Ottawa, Ontario.

Healey, B. P., and G. B. Stenson. 2000. Estimating pup production and population size of the northwest Atlantic

harp seal (Phoca groenlandica). Can. Stock Assess. Sec. Res. Doc. 2000/081.

Johnston, D. W., P., Meisenheimer, and D. M. Lavigne. 2000. An evaluation of management objectives for

Canada’s commercial harp seal hunt, 1996-1998. Cons. Biol. 14: 729-737.

Katona, S. K., V. Rough and D. T. Richardson. 1993. A field guide to whales, porpoises, and seals from Cape Cod

to Newfoundland. Smithsonian Institution Press, Washington, DC. 316 pp. 

Lavigne, D. M. and K. M. Kovacs. 1988. Harps and Hoods Ice Breeding Seals of the Northwest Atlantic. 

University of Waterloo Press, Waterloo, Ontario, Canada, 174 pp.
92

Lavigne, D. M. 1999. Estimating total kill of Northwest Atlantic harp seals, 1994-1998. Mar. Mammal Sci.,

15(3):871-878. 

Lens, S. 1997. Interactions between marine mammals and deep water trawlers in the NAFO regulatory area. ICES

C.M. 8/Q. 10 pp.

McAlpine , D. F. and R. H. Walker. 1990. Extralimital records of the harp seal, Phoca groenlandica, from the

western North Atlantic: a review. Mar. Mammal Sci. 6:243-247.

Read, A. J. 1994. Interactions between cetaceans and gillnet and trap fisheries in the Northwest Atlantic. Rep. int

Whal. Commn. Special Issue 15: 133-147. 

Roff, D. A. and W. D. Bowen. 1983. Population dynamics and management of the Northwest Atlantic harp seal.

Can. J. Fish. Aquat. Sci. 40: 919-932. 

Ronald, K. and P. J. Healey. 1981. Harp Seal. Pages 55-87 in: S. H. Ridgway and R. J. Harrison (eds), Handbook

of marine mammals, Vol. 2: Seals. Academic Press, New York, 359 pp. 

Rubinstein, B. 1994. An apparent shift in distribution of ice seals, Phoca groenlandica, Cystophora cristata, and

Phoca hispida, toward the east coast of the United States. M.A. Thesis, Boston University, Boston, MA, 45

pp. 

Sergeant, D. E. 1965. Migrations of harp seal Pagophilus groenlandicus (Erxleben) in the Northwest Atlantic. J.

Fish. Res. Bd. Can. 22:433-464.

Sergeant, D. E. 1975. Estimating numbers of harp seals. Rapp. P. -v. Reun. Cons. int Explor. Mer. 169: 274-280.

Shelton, P. A., N. G. Caddigan and G. B. Stenson. 1992. Model estimates of harp seal population trajectories in the

Northwest Atlantic. CAFSAC Res. Doc. 92/89, 23 pp. 

Shelton, P. A., G. B. Stenson, B. Sjare and W. G. Warren. 1996. Model estimates of harp seal numbers-at-age for

the Northwest Atlantic. NAFO Sci. Coun. Studies 26:1-14.

Sjare, B., G. B. Stenson and W. G. Warren. 1996. Summary of female harp seal reproductive parameters in the

Northwest Atlantic. NAFO Sci. Coun. Studies 26:41-46.

Sjare, B. and G. B. Stenson. 2000. Estimating struck and loss rates for harp seals in the Northwest Atlantic. Can.

Stock Assess. Sec. Res. Doc. 2000/076.

Sjare, B. and G. B. Stenson. 2000. Recent estimates of reproductive rates for harp seals in the Northwest Atlantic. 

Can. Stock Assess. Sec. Res. Doc. 2000/077.

Stenson, G. B. 1993. The status of pinnipeds in the Newfoundland region. NAFO SCR Doc. 93/34. 

Stenson, G. B., R. A. Myers, M. O. Hammill, I-H Ni, W. G. Warren and M. S. Kingsley. 1993. Pup production of

harp seals, Phoca groenlandica, in the Northwest Atlantic. Can. J. Fish. Aquat. Sci. 50: 2429-2439.

Stenson, G. B., M. O. Hammill, M. C. S. Kingsley, B. Sjare, W. G. Warren and R. A. Myers. 1996. 1994 pup

production of Northwest Atlantic harp seals, Phoca groenlandica. NAFO Sci. Coun. Studies 26: 47-62.

Stenson, G. B. and B. Sjare. 1997. Seasonal distribution of harp seals, Phoca groenlandica, in the Northwest

Atlantic. ICES C.M. 1997/CC:10 (Biology and Behavior II). 23 pp.

Stenson, G. B., M. O. Hammill, J. F. Gosselin and B. Sjare. 2000. 1999 pup production of harp seals, Phoca

groenlandica, in the Northwest Atlantic. Can. Stock Assess. Sec. Res. Doc. 2000/080.

Stevick, P. T. and T. W. Fernald. 1998. Increase in extralimital records of harp seals in Maine. Northeastern

Naturalist 5(1)75-82.

Wade, P. R. and R. P. Angliss. 1997. Guidelines for assessing marine mammal stocks: Report of the GAMMS

Workshop April 3-5, 1996, Seattle, Washington. U.S. Dep. Commer., NOAA Tech. Memo. NMFS-OPR12, 93 pp.

Walden, J. 1996. The New England gillnet effort survey. NOAA-NMFS-NEFSC Ref. Doc. 99-10. 38 pp. 

Available from: National Marine Fisheries Service, 166 Water Street, Woods Hole, MA 02543-1026.

Walsh, D., B. Sjare and G. B. Stenson. 2000. Preliminary estimates of harp seal by-catch in the Newfoundland

lumpfish fishery. Can. Stock Assess. Sec. Res. Doc. 2000/078.

Warren, W. G., P. A. Shelton and G. B. Stenson. 1997. Quantifying some of the major sources of uncertainty

associated with estimates of harp seal prey consumption. Part 1: Uncertainty in the estimates of harp seal

population size. J. Northwest Atl. Fish. Sci., 22: 289-302.
93

Figure 1. Distribution of minke whale sightings from

NEFSC and SEFSC shipboard and aerial surveys during

the summer in 1990-1998. Isobaths are at 100 m and

1,000 m. 

January 2002

MINKE WHALE (Balaenoptera acutorostrata):

Canadian East Coast Stock

STOCK DEFINITION AND GEOGRAPHIC RANGE

Minke whales have a cosmopolitan distribution in polar, temperate and tropical waters. In the North

Atlantic there are four recognized populations — Canadian east coast, west Greenland, central North Atlantic, and

northeastern North Atlantic (Donovan 1991). These

four population divisions were defined by examining

segregation by sex and length, catch distributions,

sightings, marking data and pre-existing ICES

boundaries; however, there are very few data from

the Canadian east coast population. 

Minke whales off the eastern coast of the

United States are considered to be part of the

Canadian east coast stock, which inhabits the area

from the eastern half of the Davis Strait out to 45°W

and south to the Gulf of Mexico. The relationship

between this and the other three stocks is uncertain. It

is also uncertain if there are separate stocks within

the Canadian east coast stock.

The minke whale is common and widely

distributed within the USA Atlantic Exclusive

Economic Zone (EEZ) (CETAP 1982). There

appears to be a strong seasonal component to minke

whale distribution. Spring and summer are times of

relatively widespread and common occurrence, and

during this time they are most abundant in New

England waters. During fall in New England waters,

there are fewer minke whales, while during winter,

the species appears to be largely absent. Like most

other baleen whales, the minke whale generally

occupies the continental shelf proper, rather than the

continental shelf edge region. Records summarized

by Mitchell (1991) hint at a possible winter

distribution in the West Indies and in mid-ocean

south and east of Bermuda. As with several other

cetacean species, the possibility of a deep-ocean

component to distribution exists but remains

unconfirmed. 

POPULATION SIZE

The total number of minke whales in the Canadian East Coast population is unknown. However, seven

estimates are available for portions of the habitat — a 1978-1982 estimate, a shipboard survey estimate from the

summers of 1991 and 1992, a shipboard estimate from June-July 1993, an estimate made from a combination of 

shipboard and aerial surveys conducted during July to September 1995, an aerial survey estimate of the entire Gulf

of St. Lawrence conducted in August to September 1995, an aerial survey estimate from the northern Gulf of St.

Lawrence conducted during July and August 1996, and an aerial/shipboard survey conducted from Georges Bank to

the mouth of the Gulf of St. Lawrence during July and August 1999 (Table 1; Figure 1). 

An abundance of 320 minke whales (CV=0.23) was estimated from an aerial survey program conducted

from 1978 to 1982 on the continental shelf and shelf edge waters between Cape Hatteras, North Carolina and Nova

Scotia (CETAP 1982).
94

An abundance of 2,650 (CV=0.31) minke whales was estimated from two shipboard line transect surveys

conducted during July to September 1991 and 1992 in the northern Gulf of Maine-lower Bay of Fundy region (Table

1). This population size is a weighted-average of the 1991 and 1992 estimates, where each annual estimate was

weighted by the inverse of its variance, using methods as described in Palka (1995). 

An abundance of 330 minke whales (CV=0.66) was estimated from a June and July 1993 shipboard line

transect sighting survey conducted principally between the 200 and 2,000 m isobaths from the southern edge of

Georges Bank, across the Northeast Channel to the southeastern edge of the Scotian Shelf (Table 1; Anon. 1993).

An abundance of 2,790 (CV=0.32) minke whales was estimated from a July to September 1995 sighting

survey conducted by two ships and an airplane that covered waters from Virginia to the mouth of the Gulf of St.

Lawrence (Table 1; Palka et al. in review). Total track line length was 32,600 km. The ships covered waters

between the 50 and 1000 fathom depth contour isobaths, the northern edge of the Gulf Stream, and the northern Gulf

of Maine/Bay of Fundy region. The airplane covered waters in the mid-Atlantic from the coastline to the 50 fathom

depth contour line, the southern Gulf of Maine, and shelf waters off Nova Scotia from the coastline to the 1000

fathom depth contour line. Data collection and analysis methods were described in Palka (1996). 

Kingsley and Reeves (1998) estimated there were 1,020 (CV=0.27) minke whales in the entire Gulf of St.

Lawrence in 1995 and 620 (CV=0.52) in the northern Gulf of St. Lawrence in 1996. During the 1995 survey, 8,427

km of track lines were flown in an area of 221,949 km2

 during August and September. During the 1996 survey,

3,993 km of track lines were flown in an area of 94,665 km2

 during July and August. Data were analyzed using

Quenouille’s jackknife bias reduction procedure on line transect methods that model the left truncated sighting

curve. These estimates were uncorrected for visibility biases such as g(0).

An abundance of 2,998 (CV=0.19) minke whales was estimated from a July to August 1999 sighting survey

conducted by a ship and airplane covering waters from Georges Bank to the mouth of the Gulf of St. Lawrence

(Table 1; D. Palka, pers. comm.). Total track line length was 8,212 km. Similar to that used in the above 1995

Virginia to Gulf of St. Lawrence survey, shipboard data were analyzed using the modified direct duplicate method

that accounts for school size bias and g(0), the probability of detecting a group on the track line. Aerial data were

not corrected for g(0) (Palka 2000).

The best available current abundance estimate for minke whales is the sum of the 1999 Georges Bank to

Gulf of St. Lawrence survey (2,998 (CV=0.19)) and the 1995 Gulf of St. Lawrence survey (1,020 (CV=0.27)), 4,018

(CV=0.16), because these surveys are recent and provided the most complete coverage of the known habitat.

Table 1. Summary of abundance estimates for Canadian East Coast minke whales. Month, year, and area covered

during each abundance survey, and resulting abundance estimate (Nbest) and coefficient of variation (CV).

Row

Number Month/Year Area Nbest CV

1 Jul -Sep 1991-92 No. Gulf of Maine and Bay of Fundy 2,650 0.31

2 Jun-Jul 1993 Georges Bank to Scotian shelf, shelf edge only 330 0.66

3 Jul-Sep 1995 Virginia to mouth of Gulf of St. Lawrence 2,790 0.32

4 Aug-Sep 1995 Gulf of St. Lawrence 1,020 0.27

5 Jul-Sep 1995 Virginia to Gulf of St. Lawrence

(SUM OF ROWS 3 and 4) 3,810 0.25

6 Jul-Aug 1996 northern Gulf of St. Lawrence 620 0.52

7 July-Aug 1999 Georges Bank to mouth of Gulf of St. Lawrence 2,998 0.19

8 Aug-Sep 1995 +

July-Aug 1999

Georges Bank to Gulf of St. Lawrence

(SUM OF ROWS 4 AND 7) 4,018 0.16
95

Minimum Population Estimate

The minimum population estimate is the lower limit of the two-tailed 60% confidence interval of the lognormally distributed best abundance estimate. This is equivalent to the 20th percentile of the log-normal distribution

as specified by Wade and Angliss (1997). The best estimate of abundance for minke whales is 4,018 (CV=0.16). 

The minimum population estimate for the Canadian East Coast minke whale is 3,515 (CV=0.16).

Current Population Trend

There are insufficient data to determine population trends for this species. 

CURRENT AND MAXIMUM NET PRODUCTIVITY RATES

Current and maximum net productivity rates are unknown for this stock. Life history parameters that could

be used to estimate net productivity include: females mature when 6-8 years old; pregnancy rates are approximately

0.86 to 0.93; thus, the calving interval is between 1 and 2 years; calves are probably born during October to March,

after 10 to 11 months gestation; nursing lasts for less than 6 months; maximum ages are not known, but for Southern

Hemisphere minke whales the maximum age appears to be about 50 years (Katona et al. 1993; IWC 1991). 

For purposes of this assessment, the maximum net productivity rate was assumed to be 0.04. This value is

based on theoretical modeling showing that cetacean populations may not grow at rates much greater than 4% given

the constraints of their reproductive life history (Barlow et al. 1995). 

POTENTIAL BIOLOGICAL REMOVAL

Potential Biological Removal (PBR) is the product of minimum population size, one-half the maximum

productivity rate, and a “recovery” factor (MMPA Sec. 3. 16 U.S.C. 1362; Wade and Angliss 1997). The minimum

population size is 3,515 (CV=0.16). The maximum productivity rate is 0.04, the default value for cetaceans. The

“recovery” factor, which accounts for endangered, depleted, threatened, or stocks of unknown status relative to

optimum sustainable population (OSP) is assumed to be 0.5 because this stock is of unknown status. PBR for the

Canadian east coast minke whale is 35.

ANNUAL HUMAN-CAUSED MORTALITY AND INJURY

Recent minke whale takes have been observed or attributed to the Atlantic tuna purse seine, Gulf of Maine

and mid-Atlantic lobster trap/pot, mid-Atlantic coastal gillnet, and unknown fisheries; though all takes have not

resulted in mortalities (Tables 2-5).

Data to estimate the mortality and serious injury of minke whales come from the USA Sea Sampling

Program and from records of strandings and entanglements in USA waters. Estimates using the Sea Sampling

Program data are discussed by fishery under the Fishery Information section below (Table 2). Strandings and

entanglement records are discussed under the lobster trap fishery, mid-Atlantic coastal gillnet fishery, and

“Unknown Fisheries” within the Fishery Information section and under the Other Mortality section (Tables 3 and 4). 

Ship strike mortalities and serious injuries are discussed under the Other Mortality section. For the purposes of this

report, only those strandings and entanglement records considered confirmed human-caused mortalities or serious

injuries are discussed.

 During 1996 to 2000, the USA total annual estimated average human-caused mortality was 2.6 minke

whales per year. This is derived from three components: 0 minke whales per year (CV=0.0) from USA fisheries

using observer data, 2.4 minke whales per year from USA fisheries using strandings and entanglement data, and 

0.2 minke whales per year from ship strikes. During 1996 to 2000, there were no confirmed mortalities or serious

injuries in Canadian waters as reported by the various small scale stranding and observer data collection programs 

in Atlantic Canada.

Fishery Information

EARLIER INTERACTIONS

 Little information is available about fishery interactions that took place before the 1990's. Read (1994)

reported that a minke whale was found dead in a Rhode Island fish trap in 1976.

Distant-water Fleet

Prior to 1977, there was no documentation of marine mammal bycatch in the distant-water fleet (DWF)

activities off the northeast coast of the USA. With implementation of the Magnuson Fisheries Conservation and

Management Act in that year, an observer program was established which recorded fishery data and information on
96

incidental bycatch of marine mammals. A minke whale was caught and released alive in the Japanese tuna longline

fishery in 3,000 m of water, south of Lydonia Canyon on Georges Bank, in September 1986 (Waring et al. 1990). In

1982, there were 112 different foreign vessels; 16%, or 18, were Japanese tuna longline vessels operating along the

USA east coast. This was the first year that the Northeast Regional Observer Program assumed responsibility for

observer coverage of the longline vessels. Between 1983 and 1988, the numbers of Japanese longline vessels

operating within the US Atlantic EEZ each year were 3, 5, 7, 6, 8, and 8, respectively. Observer coverage was

100%.

Northeast Sink Gillnet

Two minke whales were observed taken in the Northeast sink gillnet fishery between 1989 and the present. 

The take in July 1991, south of Penobscot Bay, Maine resulted in a mortality, and the take in October 1992, off the

coast of New Hampshire near Jeffreys Ledge was released alive. There were approximately 349 vessels (full and

part time) in the Northeast sink gillnet fishery in 1993 (Walden 1996) and 301 full and part time vessels in 1998. 

Observer coverage as a percentage of trips has been 1%, 6%, 7%, 5%, 7%, 5%, 4%, 6%, 5%, 6%, and 6% for years

1990 to 2000, respectively. Because no mortalities have been observed since 1991, the annual estimated average

Northeast sink gillnet fishery-related mortality for minke whales is zero.

Herring Weir

A minke whale got trapped and was released alive from a herring weir off northern Maine in 1990. In USA

and Canadian waters the herring weir fishery occurred from May to September each year along the southwestern

shore of the Bay of Fundy, and was scattered along the coasts of western Nova Scotia and northern Maine. In 1990

there were 56 active weirs in Maine (Read 1994). According to state officials, in 1998, the number of weirs in

Maine waters dropped to nearly nothing due to the limited herring market (Jean Chenoweth, pers. comm.) and in

2000 only 11 weirs were built (Molyneaux 2000). The number of active weirs in the USA is unknown. It is also

unknown if the active weirs incidentally take any marine mammals.

Pelagic Drift Gillnet

In 1996 and 1997, NMFS issued management regulations which prohibited the operation of this fishery in

1997. The fishery was active during 1998. Then, in January 1999, NMFS issued a Final Rule to prohibit the use of

drift net gear in the North Atlantic swordfish fishery (50 CFR Part 630). Four minke whale mortalities were

observed in the Atlantic pelagic drift gillnet fishery during 1995. The estimated total number of hauls in the Atlantic

pelagic drift gillnet fishery increased from 714 in 1989 to 1,144 in 1990; thereafter, with the introduction of quotas,

effort was severely reduced. The estimated number of hauls in 1991 to 1996 were 233, 243, 232, 197, 164, and 149

respectively. Fifty-nine different vessels participated in this fishery at one time or another between 1989 and 1993. 

In 1994 to 1998, there were 12, 11, 10, 0, and 11 vessels, respectively, in the fishery. Observer coverage, expressed

as percent of sets, was 8% in 1989, 6% in 1990, 20% in 1991, 40% in 1992, 42% in 1993, 87% in 1994, 99% in

1995, 64% in 1996, no fishery in 1997 and 99% coverage during 1998. Observer coverage dropped during 1996

because some vessels were deemed too small or unsafe by the contractor that provided observer coverage to NMFS. 

Fishing effort was concentrated along the southern edge of Georges Bank and off Cape Hatteras. Examination of the

species composition of the catch and locations of the fishery throughout the year, suggested that the drift gillnet

fishery be stratified into two strata, a southern or winter stratum, and a northern or summer stratum. Estimates of the

total bycatch, for each year from 1989 to 1993, were obtained using the aggregated (pooled 1989-1993) catch rates,

by strata (Northridge 1996). Total annual bycatch after 1993 was estimated separately for each year by summing the

observed caught with the product of the average bycatch per haul and number of unobserved hauls as recorded in

SEFSC logbooks. Variances were estimated using bootstrap re-sampling techniques. Estimated annual fisheryrelated mortality and serious injury (CV in parentheses) was 0 for 1989 to 1994, 4.5 (0) for 1995, 0 for 1996 (Bisack

1997), and 0 for 1998. The fishery was closed during 1997. Estimated average annual mortality and serious injury 

related to this fishery during 1994 to 1996, and 1998 was 1.1 minke whales (CV=0.00). There is no current

mortality related to this fishery because the fishery closed in 1999.

USA

Atlantic Tuna Purse Seine

In an Atlantic tuna purse seine off Stellwagen Bank, one minke whale was reported caught and released

uninjured in 1991(D. Beach, NMFS NE Regional Office, pers. comm.) and in 1996. The minke caught during 1991

escaped after a crew member cut the rope that was wrapped around the tail. The minke whale caught during 1996
97

escaped by diving beneath the net (Table 2). The tuna purse seine fishery occurring between Cape Hatteras and

Cape Cod is directed at small and medium bluefin and skipjack for the canning industry, while the fishery north of

Cape Cod is directed at large medium and giant bluefin tuna (NMFS 1995). These two fisheries are entirely separate

from other Atlantic tuna purse seine fisheries. Spotter aircraft were used to locate fish schools. The official start

date, set by regulation, was August 15. Individual vessel quotas (IVQs) and a limited access system prevent a derby

fishery situation. Catch rates for large mediums and giant tuna are high and consequently, the season usually only

lasts a few weeks. The 1996 regulations allocated 250 MT (5 IVQs) with a minimum of 90% giants and 10% large

mediums.

Limited observer data are available for the Atlantic tuna purse seine fishery. Out of 45 total trips made in

1996, 43 trips (95.6%) were observed. Forty-four sets were made on the 43 observed trips and all sets were

observed. A total of 136 days were covered. No trips were observed during 1997 through 1999. Two trips (seven

hauls) were observed in October 2000 in the Great South Channel region. No marine mammals were observed taken

during these trips.

Gulf of Maine and mid-Atlantic Lobster Trap/Pot Fishery

The strandings and entanglement database, maintained by the New England Aquarium and the Northeast

Regional Office/NMFS, reported seven minke whale mortalities and serious injuries that were attributed to the

lobster fishery during 1990 to 1994, 1 in 1990 (may be serious injury), 2 in 1991 (one mortality and one serious

injury), 2 in 1992 (both mortalities), 1 in 1993 (serious injury) and 1 in 1994 (mortality) (1997 List of Fisheries

62FR33, January 2, 1997). The one confirmed minke whale mortality during 1995 was attributed to the lobster

fishery (Tables 3 and 4). No confirmed mortalities or serious injuries of minke whales occurred in 1996. From the

four confirmed 1997 records, one minke whale mortality was attributed to the lobster trap fishery. No fishery could

be attributed to the other three 1997 minke mortalities (see unknown fisheries). No minke whale mortalities were

attributed to a fishery for 1998. None of the five confirmed minke whale mortalities in 1999, and neither of the two

confirmed mortalities or serious injuries from 2000 were attributed to this fishery.

There are three distinctly identified stock areas for the American lobster: 1) Gulf of Maine, 2) south of Cape

Cod to Long Island Sound, and 3) Georges Bank and south to Cape Hatteras. In 1997, there were 3,431 vessels

holding licenses to harvest lobsters in federal waters, 2,674 vessels licensed to use lobster pot gear in state waters,

675 vessels licensed to use bottom trawls and approximately 100 licenses to use dredge gear to harvest lobsters. In

2000, there were 7,539 vessels from Maine to North Carolina holding licenses. Lobsters are taken primarily by

traps, with about 2-3% of the harvest being taken by mobile gear (trawlers and dredges). About 80% of lobsters

were harvested from state waters. The offshore fishery in federal waters has developed in the past 10 to 15 years,

largely due to technological improvements in equipment and lower competition in the offshore areas. In January

1997, NMFS changed the classification of the Gulf of Maine and USA mid-Atlantic lobster pot fisheries from

Category III to Category I (1997 List of Fisheries 62FR33, January 2, 1997) based on examination of 1990 to 1994

stranding and entanglement records of large whales (including right, humpback and minke whales). This fishery is

operating under regulations from the Large Whale Take Reduction Plan (July 22, 1997; 62 FR 39157) and the

federal American Lobster fishery plan (December 6, 1999; 64 FR 68228). Annual mortalities due to this fishery, as

determined from strandings and entanglement records that have been audited, were 1 in 1991, 2 in 1992, 1 in 1994, 1

in 1995, 0 in 1996, 1 in 1997, and 0 in 1998 to 2000. Estimated average annual mortality related to this fishery

during 1996 to 2000 was 0.2 minke whales per year (Table 3).

Mid-Atlantic Coastal Gillnet

One minke whale, reported in the strandings and entanglement database, maintained by the New England

Aquarium and the Northeast Regional Office/NMFS, was taken in a 6-inch gill net on 06 July 1998 off Long Island,

New York (Tables 3 and 4). This take is being assigned to the mid-Atlantic coastal gillnet fishery. No minke whales

have been taken from this fishery during observed trips in 1993 to 2000. In July 1993, an observer program was

initiated in the USA Atlantic coastal gillnet fishery by the NEFSC Sea Sampling program. Twenty trips were

observed during 1993. During 1994 and 1995, 221 and 382 trips were observed, respectively. This fishery, which

extends from North Carolina to New York, is actually a combination of small vessel fisheries that target a variety of

fish species, some of these vessels operate right off the beach, some using drift nets and others using sink nets. 

During 1998, it was estimated that 302 full and part-time sink gillnet vessels and an undetermined number of drift

gillnet vessels participated in this fishery. This is the number of unique vessels in the commercial landings database

(Weighout) that reported catch from fisheries during 1998 from the states of Connecticut to North Carolina. This

does not include a small percentage of records where the vessel number was missing. Observer coverage, expressed
98

 as percent of tons of fish landed, was 5%, 4%, 3%, 5%, 2%, and 2% for 1995 to 2000, respectively . Observed

fishing effort was concentrated off New Jersey and scattered between Delaware and North Carolina from the beach

to 50 miles off the beach.

Annual mortalities due to this fishery, as determined from strandings and entanglement records were 0 in

1991, 1992, 1994 to 1997 and 1999 to 2000, and 1 in 1998. Estimated average annual mortality related to this

fishery during 1996 to 2000 was 0.2 minke whales per year (Tables 3 and 4).

Unknown Fisheries

 The strandings and entanglement database, maintained by the New England Aquarium and the Northeast

Regional Office/NMFS, included 36 records of minke whales within USA waters for 1975-1992. The gear included

unspecified fishing net, unspecified cable or line, fish trap, weirs, seines, gillnets, and lobster gear. A review of

these records is not complete. One confirmed entanglement was an immature female minke whale, entangled with

line around the tail stock, that came ashore on the Jacksonville, Florida jetty on 31 January 1990 (R. Bonde,

USFWS, Gainesville, FL, pers. comm.). The audited NE Regional Office entanglement/stranding database for 1995

to 1999 contains 33 records of minke whales, the confirmed mortalities are reported in Table 4. Mortalities that

were likely a result of a fishery interaction with an unknown fishery include 3 in 1997, 5 in 1999, 2 in 2000 and 0 in

other years. The examination of the minke entanglement records from 1997 indicate that 4 out of 4 confirmed

records of mortality are likely a result of fishery interactions, one attributed to the lobster pot fishery (see above),

and three not attributed to any particular fishery because the reports do not contain the necessary details. Of the 5

mortalities in 1999, 2 were attributed to an unknown trawl fishery and 3 to some other fishery. One of the

interactions with an unknown fishery in 2000 was a mortality and one was a serious injury (Tables 3 and 4).

In general, an entangled or stranded cetacean could be an animal that is part of an expanded bycatch

estimate from an observed fishery and thus it is not possible to know if an entangled or stranded animal is an

additional mortality. During 1997 to 1999, there were no minke whales observed taken in any fishery that

participated in the Sea Sampling Program, therefore, the strandings where mortality was due to a fishery interaction

can be added into the human-caused mortality estimate. During 1996 to 2000, as determined from strandings and

entanglement records, the estimated average annual mortality is 0.4 minke whales per year in unknown trawl

fisheries, and 1.6 minke whales per year in unknown fisheries (Table 3).

CANADA

In Canadian waters, information about minke whale interactions with fishing gear is not well quantified or

recorded, though some records are available. Read (1994) reported interactions between minke whales and gillnets

in Newfoundland and Labrador, cod traps in Newfoundland, and herring weirs in the Bay of Fundy. Hooker et al.

(1997) summarized bycatch data from a Canadian fisheries observer program that placed observers on all foreign

fishing vessels operating in Canadian waters, on between 25% and 40% of large Canadian fishing vessels (greater

than 100 feet long), and on approximately 5% of smaller Canadian fishing vessels. During 1991 through 1996, no

minke whales were observed taken.

Herring Weirs

During 1980 and 1990, 15 of 17 minke whales were released alive from herring weirs in the Bay of Fundy. 

Due to the formation of a cooperative program between Canadian fishermen and biologists it is expected that now

most minke whales will be able to be released alive. During 1999 to 2000, several minke whales were released alive

and unharmed, none died. (A. Westgate, pers. comm.).

In USA and Canadian waters, the herring weir fishery occurred from May to September each year along the

southwestern shore of the Bay of Fundy, and was scattered along the coasts of western Nova Scotia and northern

Maine. In 1990 there were 180 active weirs in western Bay of Fundy (Read 1994). According to Canadian DFO

officials, for 1998, there were 225 licenses for herring weirs on the New Brunswick and Nova Scotia sides of the

Bay of Fundy (60 from Grand Manan Island, 95 from Deer and Campobello Islands, 30 from Passamaquoddy Bay,

35 from East Charlotte area, and 5 from the Saint John area). The number of licenses has been fairly consistent since

1985 (Ed Trippel, pers. comm.), but the number of active weirs is less than the number of licenses, and the number

has been decreasing every year, primarily due to competition with salmon mariculture sites (A. Read, pers. comm.).
99

Other Fisheries

Six minke whales were reported entangled during 1989 in the now non-operational groundfish gillnet

fishery in Newfoundland and Labrador (Read 1994). One of these animals escaped and was still towing gear, the

remaining 5 animals died. 

Salmon gillnets in Canada, now no longer being used, had taken a few minke whales. In Newfoundland in

1979, one minke whale died in a salmon net. In Newfoundland and Labrador, between 1979 and 1990, it was

estimated that 15% of the Canadian minke whale takes were in salmon gillnets. A total of 124 minke whale

interactions were documented in cod traps, groundfish gillnets, salmon gillnets, other gillnets and other traps. This

fishery ended in 1993 as a result of an agreement between the fishermen and North Atlantic Salmon Fund (Read

1994).

Five minke whales were entrapped and died in Newfoundland cod traps during 1989. The cod trap fishery

in Newfoundland closed in 1993 due to the depleted groundfish resources (Read 1994).

Table 2. Summary of minke whales (Balaenoptera acutorostrata) released alive, by commercial fishery, years

sampled (Years), ratio of observed mortalities recorded by on-board observers to the estimated mortality

(Ratio), the number of observed animals released alive and injured (Injured), and the number of observed

animals released alive and uninjured (Uninjured).

Fishery Years Ratio Injured Uninjured

Tuna purse seine 96-00 0/0, NA2

, NA2,

 NA2

, 0/0 

0, NA2

, NA2,

NA2

, 03

11, NA2, NA2,

NA2

, 03

NA=Not Available.

1

 The minke whale escaped by diving beneath the net.

2

 No observer coverage during 1997 through 1999. 3 Two trips observed during September 2000.

Table 3. From strandings and entanglement data, summary of confirmed incidental mortality of minke whales

(Balaenoptera acutorostrata) by commercial fishery: includes years sampled (Years), number of vessels

active within the fishery (Vessels), type of data used (Data Type), mortalities assigned to this fishery

(Assigned Mortality), and mean annual mortality. See Table 4 for details.

Fishery Years Vessels Data Type 1 Assigned

Mortality

Mean Annual

Mortality

GOM and mid-Atlantic

Lobster Trap/Pot 96-00

1997=6880

2000=7539

licenses2

Entanglement 

& Strandings 0, 1, 0, 0, 0 0.2

(0)

mid-Atlantic Coastal

Gillnet

96-00 1998=3023 Entanglement

& Strandings

0, 0, 1, 0, 0 0.2

Unknown Trawl 96-00 NA Entanglement

& Strandings

0, 0, 0, 2, 0 0.4

Unknown Fisheries 96-00 NA Entanglement

& Strandings 

0, 3, 0, 3, 2 1.6

(0)

TOTAL 2.4

(0)

NA=Not Available.

1

 Data from records in the entanglement and strandings data base maintained by the New England Aquarium

and the Northeast Regional Office/NMFS (Entanglement and Strandings). 2

 Number of vessels licensed to harvest lobsters in federal and state waters, with lobster traps/pots, bottom

trawls, and dredge gear. 3 Number of sink gillnet vessels.
100

Table 4. Summarized records of mortality and serious injury likely to result in mortality. Canadian East Coast stock

of minke whales, January 1994 - December 1999. This listing includes only confirmed records related to

USA commercial fisheries and/or ship strikes in USA waters. Causes of mortality or injury, assigned as

primary or secondary, are based on records maintained by NMFS/NER and NMFS/SER.

Date Report 

Type

Sex,

age, ID

Location Assigned Cause: P=primary, 

 S=secondary

Notes

Ship

strike

 Entang./

Fsh.inter

Unk/

uncertain

7/2/94 mortality unk sex

and size

off NH P Lobster fishery. Lobster

lines (3 pair traps

involved; line through

mouth; one line around

lower jaw; chafing on

tail; whale brought up

dead with traps.

8/23/95 mortality unk sex

and size

near Swan

Island, ME

P Lobster fishery. 

Entangled in inshore

lobster gear.

5/15/97 mortality female

5.5 m

(est)

Gloucester,

MA

(42°36' N

70°38' W)

P Unknown fishery. Deep

lacerations around tail

stock, abrasions around

flukes and mouth

5/16/97 mortality female

5.5 m

(est)

Rockport, MA

(42°40' N

70°35' W)

P Unknown fishery. 

Abrasions around flukes;

feeding prior to

entanglement

8/14/97 mortality female

2.8 m

Jewell Island,

ME

(43°39' N

70°02' W)

P Unknown fishery. Fresh

lacerations on flukes and

pectoral fins

8/30/97 mortality female

8 m

(est)

Cape Small,

ME

(43°40' N

69°57' W)

P Lobster fishery. 

Observed entangled in

lobster gear by ME

Marine Patrol

6/24/98 mortality male

3.4 m

Long Beach,

NY

(40° 34' N

73° 42' W)

P mid-Atlantic coastal

gillnet fishery. Alive

initially, then died in a

6-inch mesh gillnet.

12/12/98 mortality unk sex

and size

Cape Cod Bay,

MA

P Body of whale seen in

wake of a whale

watching vessel.

5/9/99 mortality female

5.6 m

Cape Lookout

Bight

(34° 61'N 

76° 54'W)

P Unknown fishery. Fresh

open wounds around

fluke and line marks

from pectoral fins

through mouth.
Date Report 

Type

Sex,

age, ID

Location Assigned Cause: P=primary, 

 S=secondary

Notes

Ship

strike

 Entang./

Fsh.inter

Unk/

uncertain

101

6/16/99 mortality female

6.9 m

Orleans, MA

(41° 48'N

65° 56'W)

P Unknown fishery.

Extensive rope markings

with hemorrhaging. 

7/3/99 mortality unk sex

and size

Sakonnet

River, RI

(41°48'N

71°12'W)

P Trawl fishery. 4.5 inch

stretched mesh driven

into rostrum.

8/2/99 mortality unk sex

and size

Point Judith

Light, RI

(41°23'N

71°28'W)

P Trawl fishery. 6 inch

stretched mesh tightly

wrapped around rostrum.

10/2/99 mortality female

7.2 m

Provincetown,

MA

(42°03'N

70°21'W)

P Unknown fishery. Rope

marks on left gape of

mouth, left pectoral fin,

caudal peduncle, and

dorsal and ventral

surfaces of fluke blades.

8/11/00 serious

injury

unk sex

and size

Port Clyde,

ME

(43°55'N

69°11'W)

P Unknown fishery. Dark

line with several bullet

buoys. Unusual minke

behavior - whale

probably anchored.

8/26/00 mortality unk sex

and size

Rockland ME

(44°05'N

69°01'W)

P Unknown fishery. Very

fresh carcass with fresh

entanglement wounds on

tail stock.

Other Mortality

Minke whales have been and are still being hunted in the North Atlantic. From the Canadian East Coast

population, documented whaling occurred from 1948 to 1972 with a total kill of 1,103 animals (IWC 1992). 

Animals from other North Atlantic populations are presently still being harvested at low levels.

USA

 Minke whales inhabit coastal waters during much of the year and are subject to collision with vessels. 

According to the NMFS/NER marine mammal entanglement and stranding database, on 7 July 1974, a necropsy on a

minke whale suggested a vessel collision occurred; on 15 March 1992, a juvenile female minke whale with propeller

scars was found floating east of the St. Johns Channel entrance (R. Bonde, USFWS, Gainesville, FL, pers. comm.);

and on 15 July 1996 the captain of a vessel reported they hit a minke whale offshore of Massachusetts. After

reviewing this record, it was concluded the animal struck was not a serious injury or mortality. On 12 December

1998, a minke whale was struck and presumed killed by a whale watching vessel in Cape Cod Bay off

Massachusetts.

During 1996 to 2000, 1 minke whale was confirmed struck by a ship, thus, there is an annual average of 0.2

minke whales per year struck by ships (Table 4).
102

CANADA

Whales and dolphins stranded between 1991 and 1996 on the coast of Nova Scotia were documented by the

Nova Scotia Stranding Network (Hooker et al. 1997). Strandings on the beaches of Sable Island were documented

by researchers with Dept. of Fisheries and Oceans, Canada (Lucas and Hooker 2000). Sable Island is approximately

170 km southeast of mainland Nova Scotia. Lucas and Hooker (2000) report 4 minke whales stranded on Sable

Island between 1970 and 1998, 1 in spring 1982, 1 in January 1992, and a mother/calf in December 1998 (Table 5). 

On the mainland of Nova Scotia, a total of 7 reported minke whales stranded during 1991 to 1996 (Table 5). The

1996 stranded minke whale was released alive off Cape Breton on the Atlantic Ocean side, the rest were found dead. 

All the minke whales stranded between July and October. One was from the Atlantic Ocean side of Cape Breton, 1

from Minas Basin, 1 was at an unknown location, and the rest stranded in the vicinity of Halifax, Nova Scotia. It is

unknown how many of the strandings can be attributed to fishery interactions. 

Table 5. Documented number of stranded minke whales along the coast of Nova Scotia and on Sable Island by

month and year, according to Hooker et al. (1997) and Lucas and Hooker (2000).

Year Month

Number of strandings

Sable Isl. Nova Scotia

1991 Sept 1

1992 Jan 1

July 1

1993 July 1

Oct 2

1994 Aug 1

1996 July 1

1998 Dec 1

TOTAL 2 7

STATUS OF STOCK

The status of minke whales, relative to OSP, in the US Atlantic EEZ is unknown. The minke whale is not

listed as endangered under the Endangered Species Act (ESA). The total fishery-related mortality and serious injury

for this stock is less than 10% of the calculated PBR and, therefore, can be considered to be insignificant and

approaching zero mortality and serious injury rate. This is not a strategic stock because estimated fishery-related

mortality and serious injury does not exceed PBR and the minke whale is not listed as a threatened or endangered

species under the ESA. 

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Bisack, K. D. 1997. Marine mammal bycatch estimates and their sampling distributions in the U.S. New England

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103

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Canada, 1991-1996. Meeting document SC/49/O5 submitted to the 1997 International Whaling

Commission meeting in Bournemouth, UK.

IWC [International Whaling Commission]. 1991. Appendix 11. Biological parameters of North Atlantic minke

whales in Annex F Report of the sub-committee on North Atlantic Minke whales. Rep. int Whal. Commn

41: 160.

IWC [International Whaling Commission]. 1992. Annex K. Report of the working group on North Atlantic Minke

trials. Rep. int Whal. Commn 42: 246-251.

Katona, S. K., V. Rough and D. T. Richardson. 1993. A field guide to whales, porpoises, and seals from Cape Cod

to Newfoundland. Smithsonian Institution Press. Washington DC. 316 pp. 

Kingsley, M.C.S. and R.R. Reeves. 1998. Aerial surveys of cetaceans in the Gulf of St. Lawrence in 1995 and

1996. Can. J. Zool. 76:1529-1550.

Lucas, Z. N. and S. K. Hooker. 2000. Cetacean strandings on Sable Island, Nova Scotia, 1970-1998. Canadian

Field-Naturalist 114(1): 46-61.

Mitchell, E. D. 1991. Winter records of the minke whale (Balaenoptera acutorostrata Lacepede 1804) in the

southern North Atlantic. Rep. int Whal. Commn 41: 455-457.

Molyneaux, P. 2000. Tradition at stake. National Fisherman 80(11): 26-29.

National Marine Fisheries Service (NMFS). 1995. Final environmental impact statement for a regulatory

amendment for the western Atlantic bluefin tuna fishery. July 20, 1995.

Northridge, S. 1996. Estimation of cetacean mortality in the U.S. Atlantic swordfish and tuna driftnet and pair trawl

fisheries. Final report to the Northeast Fisheries Science Center, Contract No. 40ENNF500160.

Palka, D. 2000. Abundance of the Gulf of Maine/Bay of Fundy harbor porpoise based on shipboard and aerial

surveys during 1999. NOAA/NMFS/NEFSC Ref. Doc. 00-07; 29 pp. Available from: National Marine

Fisheries Service, 166 Water Street, Woods Hole, MA 02543-1026.

Palka, D. 1995. Abundance estimate of the Gulf of Maine harbor porpoise. pp. 27-50. In: A. Bjørge and G.P.

Donovan (eds.) Biology of the Phocoenids. Rep. int Whal. Commn Special Issue 16. 

Palka, D. 1996. Update on abundance of Gulf of Maine/Bay of Fundy harbor porpoises. NOAA-NMFS-NEFSC

Ref. Doc. 96-04; 37p. Available from: National Marine Fisheries Service, 166 Water Street, Woods Hole,

MA 02543-1026.

Palka, D., G. Waring and D. Potter. (in review). Abundances of cetaceans and sea turtles in the northwest Atlantic

during summer 1995 and 1998. Fish. Bull., U.S.

Read, A. J. 1994. Interactions between cetaceans and gillnet and trap fisheries in the northwest Atlantic. Rep. int

Whal. Commn Special Issue 15: 133-147. 

Wade, P. R. and R. P. Angliss. 1997. Guidelines for assessing marine mammal stocks: Report of the GAMMS

workshop April 3-5, 1996, Seattle, Washington. U.S. Dep. Commer., NOAA Tech. Memo. NMFS-OPR12, 93 pp.

Walden, J. 1996. The New England gillnet effort study. NOAA-NMFS-NEFSC Ref. Doc. No. 96-10, 38pp. 

Available from: National Marine Fisheries Service, 166 Water Street, Woods Hole, MA 02543-1026.

Waring, G. T., P. Gerrior, P. M. Payne, B. L. Parry and J. R. Nicolas. 1990. Incidental take of marine mammals in

foreign fishery activities off the northeast United States, 1977-1988. Fish. Bull., U.S. 88(2): 347-360.
104

Figure 1. Distribution of white-sided dolphin sightings

from NEFSC and SEFSC shipboard and aerial surveys

during the summer in 1990-1998. Isobaths are at 100 m

and 1,000 m. 

January 2002

WHITE-SIDED DOLPHIN (Lagenorhynchus acutus):

Western North Atlantic Stock

STOCK DEFINITION AND GEOGRAPHIC RANGE

White-sided dolphins are found in temperate and sub-polar waters of the North Atlantic, primarily on

continental shelf waters to the 100 m depth contour. The species inhabits waters from central west Greenland to

North Carolina (about 35o

 N) and perhaps as far east as 43o W (Evans 1987). Distribution of sightings, strandings

and incidental takes suggest the possible existence of three stocks units: a Gulf of Maine, a Gulf of St. Lawrence and

a Labrador Sea stock (Palka et al. 1997). A genetic study is currently being conducted to test this proposed

population structure and should be available during 2002. Evidence for a separation between the well documented

unit in the southern Gulf of Maine and a Gulf of St. Lawrence population comes from a hiatus of summer sightings

along the Atlantic side of Nova Scotia. This has been reported in Gaskin (1992), is evident in Smithsonian stranding

records, and was seen during abundance surveys conducted in summers 1995 and 1999 that covered waters from

Virginia to the entrance of the Gulf of St. Lawrence. White-sided dolphins were seen frequently in eastern Gulf of

Maine waters and in waters at the mouth of the Gulf of St. Lawrence, but only a few sightings were recorded in the

waters between these two regions.

The Gulf of Maine stock of white-sided dolphins is most common in continental shelf waters from Hudson

Canyon (approximately 39°N) north through Georges Bank, and in the Gulf of Maine to the lower Bay of Fundy. 

Sightings data indicate seasonal shifts in distribution (Northridge et al. 1997). During January to April, low

numbers of white-sided dolphins are found from Georges Bank to Jeffreys Ledge (off New Hampshire), and even

lower numbers are south of Georges Bank, as documented by a few strandings collected on beaches of Virginia and

North Carolina. From June through September, large numbers of white-sided dolphins are found from Georges

Bank to lower Bay of Fundy. From October to December, white-sided dolphins occur at intermediate densities from

southern Georges Bank to southern Gulf of Maine (Payne and Heinemann 1990). Sightings south of Georges Bank,

in particular, around Hudson Canyon have been seen

at all times of the year but at low densities. The

Virginia and North Carolina observations appear to

represent the southern extent of the species range.

Prior to the 1970's, white-sided dolphins in

USA waters were found primarily offshore on the

continental slope, while white-beaked dolphins (L.

albirostris) were found on the continental shelf. 

During the 1970's, there was an apparent switch in

habitat use between these two species. This shift

may have been a result of the increase in sand lance

in the continental shelf waters (Katona et al. 1993;

Kenney et al. 1996). 

POPULATION SIZE

The total number of white-sided dolphins

along the eastern USA and Canadian Atlantic coast is

unknown, although five estimates from select regions

are available: 1) from spring, summer and autumn

1978-82; 2) July-September 1991-92; 3) June-July

1993; 4) July-September 1995 (Figure 1); and 5)

July-August 1999 (Table 1). An abundance of

28,600 white-sided dolphins (CV=0.21) was

estimated from an aerial survey program conducted

from 1978 to 1982 on the continental shelf and shelf

edge waters between Cape Hatteras, North Carolina

and Nova Scotia ( CETAP 1982).
105

An abundance of 20,400 (CV=0.63) white-sided dolphins was estimated from two shipboard line transect

surveys conducted during July to September 1991 and 1992 in the northern Gulf of Maine-lower Bay of Fundy

region (Table 1; Palka et al. 1997). This population size is a weighted-average of the 1991 and 1992 estimates,

where each annual estimate was weighted by the inverse of its variance.

An abundance of 729 (CV= 0.47) white-sided dolphins was estimated from a June and July 1993 shipboard

line transect sighting survey conducted principally between the 200 and 2,000 m isobaths from the southern edge of

Georges Bank, across the Northeast Channel to the southeastern edge of the Scotian Shelf (Table 1; Anon. 1993).

An abundance of 27,200 (CV=0.43) white-sided dolphins was estimated from a July to September 1995

sighting survey conducted by two ships and an airplane that covered waters from Virginia to the mouth of the Gulf

of St. Lawrence (Table 1; Palka et al. in review). Total track line length was 32,600 km. The ships covered waters

between the 50 and 1000 fathom contour lines, the northern edge of the Gulf Stream, and the northern Gulf of

Maine/Bay of Fundy region. The airplane covered waters in the mid-Atlantic from the coastline to the 50 fathom

contour line, the southern Gulf of Maine, and shelf waters off Nova Scotia from the coastline to the 1000 fathom

contour line. Data collection and analysis methods used were described in Palka (1996). 

An abundance of 51,640 (CV=0.38) white-sided dolphins was estimated from a 28 July to 31 August 1999

line-transect sighting survey conducted from a ship and an airplane covering waters from Georges Bank to the mouth

of the Gulf of St. Lawrence (Table 1; Figure 1; D. Palka, pers. comm.). Total track line length was 8,212 km. 

Similar to that used in the above 1995 survey, shipboard data were analyzed using the modified direct duplicate

method (Palka 1995) that accounts for school size bias and g(0), the probability of detecting a group on the track

line. Aerial data were not corrected for g(0) (Palka 2000). The 1999 estimate is larger than the 1995 estimate due

to, at least in part, the fact that the 1999 survey covered the upper Bay of Fundy and the northern edge of Georges

Bank for the first time and white-sided dolphins were seen. 

Kingsley and Reeves (1998) estimated there were 11,740 (CV=0.47) white-sided dolphins in the Gulf of St.

Lawrence during 1995, and 560 (CV=0.89) white-sided dolphins in the northern Gulf of St. Lawrence during 1996

(Table 1). It is assumed these estimates apply to the Gulf of St. Lawrence stock. During the 1995 survey, 8,427 km

of track lines were flown in an area of 221,949 km2

 during August and September. During the 1996 survey, 3,993

km of track lines were flown in an area of 94,665 km2

 during July and August. Data were analyzed using

Quenouille’s jackknife bias reduction procedure on line transect methods that model the left truncated sighting

curve. These estimates were uncorrected for visibility biases, such as g(0).

The best available current abundance estimate for white-sided dolphins in the Gulf of Maine stock is 51,640

(CV=0.38) as estimated from the July to August 1999 line transect survey because this survey is recent and provided

the most complete coverage of the known habitat.

Table 1. Summary of abundance estimates for western North Atlantic white-sided dolphins. Month, year, and area

covered during each abundance survey, and resulting abundance estimate (Nbest) and coefficient of variation

(CV).

Month/Year Area Nbest CV

Gulf of Maine stock

Jul-Sep 1991-92 No. Gulf of Maine and lower Bay of Fundy 20,400 0.63

Jun-Jul 1993 Georges Bank to Scotian shelf, shelf edge only 729 0.47

Jul-Sep 1995 Virginia to mouth of Gulf of St. Lawrence 27,200 0.43

Jul-Aug 1999 Georges Bank to mouth of Gulf of St. Lawrence 51,640 0.38

Gulf of St. Lawrence stock

Aug-Sep 1995 entire Gulf of St. Lawrence 11,740 0.47

July-Aug 1996 northern Gulf of St. Lawrence 560 0.89
106

Minimum Population Estimate

The minimum population estimate is the lower limit of the two-tailed 60% confidence interval of the lognormally distributed best abundance estimate. This is equivalent to the 20th percentile of the log-normal distribution

as specified by Wade and Angliss (1997). The best estimate of abundance for the Gulf of Maine stock of whitesided dolphins is 51,640 (CV=0.38). The minimum population estimate for these white-sided dolphins is 37,904

(CV=0.38).

Current Population Trend

There are insufficient data to determine population trends for this species. 

CURRENT AND MAXIMUM NET PRODUCTIVITY RATES

Current and maximum net productivity rates are unknown for this stock. Life history parameters that could

be used to estimate net productivity include: calving interval is 2-3 years; lactation period is 18 months; gestation

period is 10-12 months and births occur from May to early August, mainly in June and July; length at birth is 110

cm; length at sexual maturity is 230-240 cm for males, and 201-222 cm for females; age at sexual maturity is 8-9

years for males and 6-8 years for females; mean adult length is 250 cm for males and 224 cm for females (Evans

1987); and maximum reported age for males is 22 years and for females, 27 years (Sergeant et al. 1980). 

For purposes of this assessment, the maximum net productivity rate was assumed to be 0.04. This value is

based on theoretical modeling showing that cetacean populations may not grow at rates much greater than 4% given

the constraints of their reproductive life history (Barlow et al. 1995).

POTENTIAL BIOLOGICAL REMOVAL

Potential Biological Removal (PBR) is the product of minimum population size, one-half the maximum

productivity rate, and a “recovery” factor (MMPA Sec. 3. 16 U.S.C. 1362; Wade and Angliss 1997). The minimum

population size is 37,904 (CV=0.38). The maximum productivity rate is 0.04, the default value for cetaceans. The

“recovery” factor, which accounts for endangered, depleted, threatened, or stocks of unknown status relative to

optimum sustainable population (OSP) is assumed to be 0.48 because this stock is of unknown status and the CV of

the mortality estimate is between 0.3 and 0.6. PBR for the Gulf of Maine stock of the western North Atlantic whitesided dolphin is 364.

ANNUAL HUMAN-CAUSED MORTALITY AND SERIOUS INJURY

Fishery Information

Recently, within USA waters, white-sided dolphins have been observed caught in the Northeast sink gillnet,

mid-Atlantic coastal gillnet, pelagic drift gillnet, North Atlantic bottom trawl, and Atlantic squid, mackerel,

butterfish trawl fisheries (Table 2). Estimated average annual fishery-related mortality and serious injury to the Gulf

of Maine stock of the western North Atlantic white-sided dolphin from these USA fisheries during 1996-2000 was

118 (CV=0.48) dolphins per year.

EARLIER INTERACTIONS

In the past, incidental takes of white-sided dolphins have been recorded in the Atlantic foreign mackerel

fishery and pelagic drift gillnet fishery. In the mid 1980's, during a University of Maine study, gillnet fishermen

reported 6 takes of white-sided dolphins of which 2 carcasses were necropsied for biological studies (Gilbert and

Wynne 1987; Gaskin 1992). 

Atlantic foreign mackerel

NMFS foreign fishery observers have reported 44 takes of Atlantic white-sided dolphins incidental to

fishing activities in the continental shelf and continental slope waters between March 1977 and December 1991

(Waring et al. 1990; NMFS unpublished data). Of these animals, 96% were taken in the Atlantic mackerel fishery. 

This total includes 9 documented takes by USA vessels involved in joint-venture fishing operations in which USA

captains transfer their catches to foreign processing vessels. Prior to 1977, there was no documentation of marine

mammal bycatch in distant-water fleet (DWF) activities off the northeast coast of the USA. With implementation of

the Magnuson Fisheries Conservation and Management Act (MFCMA) in that year, an observer program was

established which recorded fishery data and information of incidental bycatch of marine mammals. DWF effort in

the USA Atlantic Exclusive Economic Zone (EEZ) under MFCMA had been directed primarily towards Atlantic

mackerel and squid. From 1977 through 1982, an average of 120 different foreign vessels per year (range 102-161)
107

operated within the US Atlantic EEZ. In 1982, there were 112 different foreign vessels; 16%, or 18, were Japanese

tuna longline vessels operating along the USA east coast. This was the first year that the Northeast Regional

Observer Program assumed responsibility for observer coverage of the longline vessels. Between 1983 and 1991,

the numbers of foreign vessels operating within the US Atlantic EEZ each year were 67, 52, 62, 33, 27, 26, 14, 13,

and 9, respectively. Between 1983 and 1988, the numbers of DWF vessels included 3, 5, 7, 6, 8, and 8, respectively,

Japanese longline vessels. Observer coverage on DWF vessels was 25-35% during 1977-82, and increased to 58%,

86%, 95%, 98%, respectively, in 1983-86 and 100% observer coverage was maintained during 1987-91. Foreign

fishing operations for squid ceased at the end of the 1986 fishing season and for mackerel at the end of the 1991

season.

Pelagic Drift Gillnet 

In 1996 and 1997, NMFS issued management regulations which prohibited the operation of this fishery in

1997. The fishery operated during 1998. Then, in January 1999 NMFS issued a Final Rule to prohibit the use of

drift net gear in the North Atlantic swordfish fishery (50 CFR Part 630). During 1991 to 2001, 2 white-sided

dolphins were observed taken in the Atlantic pelagic drift gillnet fishery, both in 1993. In 1986, NMFS established a

mandatory self-reported fisheries information system for large pelagic fisheries. Data files are maintained at the

Southeast Fisheries Science Center (SEFSC). The estimated total number of hauls in the Atlantic pelagic drift gillnet

fishery increased from 714 in 1989 to 1,144 in 1990; thereafter, with the introduction of quotas, effort was severely

reduced. The estimated number of hauls in 1991 to 1996 were 233, 243, 232, 197, 164, and 149, respectively. Fiftynine different vessels participated in this fishery at one time or another between 1989 and 1993. In 1994 to 1998,

there were 11, 12, 10, 0, and 11 vessels, respectively, in the fishery. Observer coverage, expressed as percent of sets

observed was 8% in 1989, 6% in 1990, 20% in 1991, 40% in 1992, 42% in 1993, 87% in 1994, 99% in 1995, 64% in

1996, no fishery in 1997, and 99% coverage during 1998. Observer coverage dropped during 1996 because some

vessels were deemed too small or unsafe by the contractor that provided observer coverage to NMFS. Fishing effort

was concentrated along the southern edge of Georges Bank and off Cape Hatteras. Examination of the species

composition of the catch and locations of the fishery throughout the year, suggest that the drift gillnet fishery is

stratified into two strata, a southern or winter stratum, and a northern or summer stratum. Estimates of the total

bycatch, for each year from 1989 to 1993, were obtained using the aggregated (pooled 1989-1993) catch rates, by

strata (Northridge 1996). Total annual bycatch after 1993 were estimated for each year separately by summing the

observed caught with the product of the average bycatch per haul and the number of unobserved hauls as recorded in

logbooks. Variances were estimated using bootstrap re-sampling techniques (Bisack 1997b). Estimated annual

fishery-related mortality and serious injury (CV in parentheses) was 4.4 (.71) in 1989, 6.8 (.71) in 1990, 0.9 (.71) in

1991, 0.8 (.71) in 1992, 2.7 (0.17) in 1993, and 0 in 1994 to 1998. There was no fishery during 1997.

North Atlantic Bottom Trawl

Because there have been no observed takes of white-sided dolphins in this fishery since 1995, this section

was moved to the “Earlier Interactions” section. Three mortalities were documented between 1991 and 2000 in the

North Atlantic bottom trawl fishery; one during 1992 and two during 1994. The Northeast Fisheries Science Center

(NEFSC) Sea Sampling Observer Program was initiated in 1989, and since that year this fishery has been covered by

the program, though at a low level. The observer coverage was 0.4% in 1994, 1.1% in 1995, 0.2% in 1996, 0.2% in

1997, 0.1% in 1998, 0.3% in 1999, and 0.4% in 2000. Vessels in the North Atlantic bottom trawl fishery, a

Category III fishery under the MMPA, were observed in order to meet fishery management needs rather than marine

mammal management needs. An average of 970 (CV= 0.04) vessels (full and part time) participated annually in the

fishery during 1989-1993. The fishery is active in New England waters in all seasons. The 1 white-sided dolphin

taken in 1992 was taken in a haul that was composed of 43% cod, 20% silver hake, and 17% pollock. One of the

1994 takes was in a haul that was composed of 42% white hake, 19% pollock, and 16% monkfish. The other 1994

take was in a haul that kept seven species of which none were dominant. The estimated fishery-related mortality in

1992 was 110 (CV=0.97), in 1994 it was 182 (CV=0.71), and it was 0 in other years (Bisack 1997b). The average

annual estimate fishery-related mortality during 1996-2000 was 0 white-sided dolphins.

USA

Northeast Sink Gillnet 

Between 1990 and 2000 there were 45 mortalities observed in the Northeast sink gillnet fishery (Table 2). 

The Northeast Fisheries Science Center (NEFSC) Sea Sampling Observer Program was initiated in 1989, and since

that year this fishery has been covered by the program. In 1993 there were approximately 349 vessels (full and part
108

time) in the Northeast sink gillnet fishery (Walden 1996). During 1998, it was estimated there were 301 full and

part-time vessels participating in this fishery. This is the number of unique vessels in the commercial landings

database (Weighout) that reported catch from this fishery during 1998 from the states of Rhode Island and north. 

This does not include a small percentage of records where the vessel number was missing. Observer coverage,

expressed as a percentage of the number of trips, has been 1%, 6%, 7%, 5%, 7%, 5%, 4%, 6%, 5%, 6%, and 6% for

years 1990 to 2000, respectively. Most white-sided dolphins have been taken in waters south of Cape Ann during

April to December. In recent years, the majority of the takes have been east and south of Cape Cod. Estimated

annual fishery-related mortalities (CV in parentheses) were 49 (0.46) in 1991, 154 (0.35) in 1992, 205 (0.31) in

1993, 240 (0.51) in 1994, 80 (1.16) in 1995, 114 (0.61) in 1996 (Bisack 1997a), 140 (0.61) in 1997, 34 (0.92) in

1998, 69 (0.70) in 1999, and 26 (1.00) in 2000. Average annual estimated fishery-related mortality during 1996-

2000 was 77 white-sided dolphins per year (0.33) (Table 2).

Mid-Atlantic Coastal Gillnet

One white-sided dolphin was observed taken in this fishery during 1997 (Table 2). None were taken in

observed trips during 1993 to 1996, and none during 1998 to 2000. In July 1993, an observer program was initiated 

in the USA mid-Atlantic coastal gillnet fishery by the NEFSC Sea Sampling program. Twenty trips were observed

during 1993. During 1994 and 1995, 221 and 382 trips were observed, respectively. This fishery, which extends

from North Carolina to New York, is actually a combination of small vessel fisheries that target a variety of fish

species. Some of the vessels operate right off the beach with some using drift nets, and others using sink nets

attached to the bottom. During 1998, it was estimated that 302 full and part-time sink gillnet vessels and an

undetermined number of drift gillnet vessels participated in this fishery. This is the number of unique vessels in the

commercial landings database (Weighout) that reported catch from this fishery during 1998 from the states of

Connecticut to North Carolina. This does not include a small percentage of records where the vessel number was

missing. Observer coverage, expressed as percent of tons of fish landed, was 5%, 4%, 3%, 5%, 2%, and 2% for

1995 to 2000, respectively (Table 2). Observed fishing effort was from New York to North Carolina, from the beach

to 50 miles off the beach. Bycatch estimates were determined using methods similar to that used for bycatch

estimates in the Northeast gillnet fishery (Bravington and Bisack 1996; Bisack 1997a). Using the observed takes of

white-sided dolphins, the estimated annual mortality (CV in parentheses) attributed to this fishery was 0 for 1993 to

1996, and 1998 to 2000, and 45 (0.82) for 1997. However, because the spatial-temporal distribution of observer

coverage did not cover all types of gillnet fisheries in the mid-Atlantic region during all times of the year, it is likely

that these figures are under-estimates. Average estimated white-sided dolphin mortality and serious injury from the

mid-Atlantic coastal gillnet fishery during 1996 to 2000 was 9 (CV=0.82) (Table 2).

Squid, Mackerel, Butterfish Trawl

One white-sided dolphin was observed taken in the mackerel sub-fishery during 1997 (Table 2). The squid,

mackerel, butterfish trawl fishery, though managed under one fishery management plan by the mid-Atlantic

Fisheries Management Council, is actually three independent fisheries operating in different areas during different

times of the year (NMFS 1998). The Loligo squid sub-fishery is mostly in southern New England, New York and

mid-Atlantic waters, where fishing patterns reflect the seasonal migration of the Loligo (offshore during October to

March and inshore during April to September). The Illex squid sub-fishery is primarily on the continental slope

during June to September. The mackerel sub-fishery during January to May is primarily in the southern New

England and mid-Atlantic waters, while during May to December, it is primarily in the Gulf of Maine. Butterfish is

primarily a bycatch of the squid and mackerel sub-fisheries. Butterfish migrate north and inshore during the

summer, and south and offshore during the winter. In 1995, the squid, mackerel, butterfish trawl fishery was

classified as a Category II fishery. Observer coverage was very low. Expressed as percentage of trips observed, it

was 0.7% in 1996, 0.8% in 1997, 0.3% in 1998, 0.4% in 1999, and 0.7% in 2000. The bycatch, stratified by subfishery, season and geographical area, was estimated using the ratio estimator method, as was documented in Bisack

(1997b). The estimated fishery-related mortality was 0 in 1996, 161 (CV=1.58) in 1997, and 0 in 1998 to 2000. 

The average annual estimated fishery-related mortality during 1996 to 2000 was 32 (CV=1.58) (Table 2).
109

Table 2. Summary of the incidental mortality of white-sided dolphins (Lagenorhynchus acutus) by commercial

fishery including the years sampled (Years), the number of vessels active within the fishery (Vessels), the

type of data used (Data Type), the annual observer coverage (Observer Coverage), the mortalities recorded

by on-board observers (Observed Mortality), the estimated annual mortality (Estimated Mortality), the

estimated CV of the annual mortality (Estimated CVs) and the mean annual mortality (CV in parentheses).

Fishery Years Vessels Data Type 1 Observer

 Coverage 2 

Observed

 Mortality

Estimated

 Mortality 

Estimated

 CVs 

Mean

 Annual

 Mortality

Northeast

Sink Gillnet 96-00

1993=349

1998=301

Obs. Data

 Weighout

Trip Logbook

 .04, .06,

.05, .06, .06

23,, 43

, 13,

43

,13

1143

,

1403

,343,

693

,263

.61,

.61,.92,

.70,1.00

77

(0.33)

mid-Atlantic

Coastal Gillnet 96-00 1998=3026

Obs. Data

 Weighout

 .04, .03,

.05, .02,.02

0, 1 ,0, 0,

0

0, 

45, 0, 0, 0

0 ,

.82, 0, 0, 0

9

(0.82)

Squid, Mackerel,

 Butterfish

 Trawl

96-00 Unk5

Obs. Data

 Weighout

.007, .008,

.003, .004,

.007

0, 14, 0, 0,

0

0, 1614,

0, 0, 0

0, 1.584,

0, 0, 0

32

(1.58)

Total 118

(.48)

1 Observer data (Obs. Data), used to measure bycatch rates, are collected within the Northeast Fisheries

Science Center (NEFSC) Sea Sampling Program. NEFSC collects landings data (Weighout) which is used

as a measure of total effort. Mandatory trip logbook (VTR) (Trip Logbook) data are used to determine the

spatial distribution of fishing effort in the sink gillnet fishery. 2

 Observer coverage for the Northeast sink gillnet and both trawl fisheries are measured in trips and the midAtlantic coastal gillnet fishery is measured in tons of fish landed. 3 White-sided dolphins taken before 1997 in observed pinger trips were added directly to the estimated total

bycatch for that year. After 1998, a weighted bycatch rate was applied to effort from both pingered and

non-pingered hauls within the stratum where white-sided dolphins were observed taken. During the years

1997 and 1999, respectively, there were 2 and 1 observed white-sided dolphins taken on pingered trips. 

No takes were observed on pinger trips during 1995, 1996, 1998, and 2000. 4

 The observed take was in the mackerel sub-fishery.

5 Number of vessels is unknown. 6 Number of sink gillnet vessels, undetermined number of drift gillnet vessels.

CANADA

There is little information available which quantifies fishery interactions involving white-sided dolphins in

Canadian waters. Two white-sided dolphins were reported caught in groundfish gillnet sets in the Bay of Fundy

during 1985 to 1989, and 9 were reported taken in West Greenland between 1964 and 1966 in the now nonoperational salmon drift nets (Gaskin 1992). Several (number not specified) were also taken during the 1960's in the

now non-operational Newfoundland and Labrador groundfish gillnets. A few were taken in an experimental drift

gillnet fishery for salmon off West Greenland which took place from 1965 to 1982 (Read 1994). 

Hooker et al. (1997) summarized bycatch data from a Canadian fisheries observer program that placed

observers on all foreign fishing vessels operating in Canadian waters, on between 25-40% of large Canadian fishing

vessels (greater than 100 feet long), and on approximately 5% of smaller Canadian fishing vessels. By-caught

marine mammals were noted as weight in kilos rather than by the numbers of animals caught. Thus the number of

individuals was estimated by dividing the total weight per species per trip by the maximum recorded weight of each

species. During 1991 through 1996, an estimated 6 white-sided dolphins were observed taken. One animal was

from a long line trip south of the Grand Banks (43° 10'N 53° 08'W) in November 1996 and the other 5 were taken in
110

the bottom trawl fishery off Nova Scotia in the Atlantic Ocean; 1 in July 1991, 1 in April 1992, 1 in May 1992, 1 in

April 1993, 1 in June 1993 and 0 in 1994 to 1996.

Herring Weirs

During the last several years, one white sided dolphin was released alive and unharmed from a herring weir

in the Bay of Fundy (A. Westgate, pers. comm.). Due to the formation of a cooperative program between Canadian

fishermen and biologists, it is expected that most dolphins and whales will be able to be released alive.

In USA and Canadian waters, the herring weir fishery occurred from May to September each year along the

southwestern shore of the Bay of Fundy, and was scattered along the coasts of western Nova Scotia and northern

Maine. In 1990 there were 180 active weirs in western Bay of Fundy (Read 1994). According to Canadian DFO

officials, for 1998, there were 225 weir licenses for herring weirs on the New Brunswick and Nova Scotia sides of

the Bay of Fundy (60 from Grand Manan Island, 95 from Deer and Campobello Islands, 30 from Passamaquoddy

Bay, 35 from East Charlotte area, and 5 from the Saint John area). The number of licenses has been fairly consistent

since 1985 (Ed Trippel, pers. comm.), but the number of active weirs is less than the number of licenses, and the

number has been decreasing every year, primarily due to competition with salmon mariculture sites (A. Read, pers.

comm.).

Other Mortality

USA

Mass strandings involving up to a hundred or more animals at one time are common for this species. From

1968 to 1995, 349 Atlantic white-sided dolphins were known to have stranded on the New England coast (Hain and

Waring 1994; Smithsonian stranding records 1996). The causes of these strandings are not known. Because such

strandings have been known since antiquity, it could be presumed that recent strandings are a normal condition

(Gaskin 1992). It is unknown whether human causes, such as fishery interactions and pollution, have increased the

number of strandings. Stranding data probably underestimate the extent of fishery-related mortality and serious

injury because all of the marine mammals which die or are seriously injured may not wash ashore, nor will all of

those that do wash ashore necessarily show signs of entanglement or other fishery-interaction. Finally, the level of

technical expertise among stranding network personnel varies widely as does the ability to recognize signs of fishery

interaction.

During 1997, there were 17 recorded stranded white-sided dolphins, of which 16 died and 1 was released

alive (from Rhode Island during February), according to the NE Regional Office/NMFS strandings and

entanglement database. One stranding was in Virginia during March, the rest were from Maryland to Maine during

January to August, where 10 were from Massachusetts. The cause of death of these strandings were not determined.

During 1998, there were 88 stranded white-sided dolphins documented in the NE Regional Office/NMFS

strandings and entanglement database. One stranding, from Delaware during May, was probably a fishery

interaction. The rest of the recorded strandings were from Massachusetts, where 65, 16, 2 and 4 were recorded

during January, February, April, May, and November, respectively. There were 70 animals found in a mass

stranding, near Wellfleet, Massachusetts, during the week of January 29 to February 3. Of these, 2 were released

alive. Of the 4 found during the November mass stranding, 1 was released alive.

During 1999, there were 72 stranded white-sided dolphins documented in the NE Regional Office/NMFS

stranding and entanglement database. Most were from Massachusetts (66), of which 53 stranded in Wellfleet, MA

during 19-24 March 1999. Thirteen white-sided dolphins stranded in New Jersey (May and June), while 1 stranded

in each of the following states: Delaware (May), Virginia (April), and Maine (November). Of all 72 strandings, 38

were found alive, and 3 of these animals were released alive. It is not known how many strandings, if any, were

fishery interactions.

During 2000, there were 24 stranded white-sided dolphins documented in the NE Regional Office/NMFS

stranding and entanglement database. All were from Massachusetts, they were found in March (1), April (7), May

(1), August (14), and October (1). Five were found alive (3 in April and 2 in August), and 2 of these were released

alive (from August). It is not known how many, if any, were fishery interactions. 

CANADA

Whales and dolphins stranded during 1991 and 1996 on the coast of Nova Scotia were documented by the

Nova Scotia Stranding Network (Hooker et al. 1997). Strandings on the beaches of Sable Island during 1970 to

1998 were documented by researchers with Dept. of Fisheries and Oceans, Canada (Lucas and Hooker 2000). Sable
111

Island is approximately 170 km southeast of mainland Nova Scotia. The white-sided dolphins stranded at nearly all

times of the year on the mainland and on Sable Island. On the mainland of Nova Scotia, a total of 34 stranded whitesided dolphins was recorded between 1991 and 1996: 2 in 1991 (August and October), 26 in July 1992, 1 in Nov

1993, 2 in 1994 (February and November), 2 in 1995 (April and August), and 1 in October 1996. During July 1992,

26 white-sided dolphins stranded on the Atlantic side of Cape Breton. Of these 26, 11 were released alive and the

rest were found dead. Among the rest of the Nova Scotia strandings, 1 was found in Minas Basin, 2 near Yarmouth

and the rest near Halifax. On Sable Island, 10 stranded white-sided dolphins were documented between 1991and

1998, all were males, 7 were young males (< 200 cm), 1 in January 1993, 5 in March 1993, 1 in August 1995, 1 in

December 1996, 1 in April 1997, and 1 in February 1998.

STATUS OF STOCK

The status of white-sided dolphins, relative to OSP, in the US Atlantic EEZ is unknown. The species is not

listed as threatened or endangered under the Endangered Species Act. There are insufficient data to determine

population trends for this species. The total fishery-related mortality and serious injury for this stock is not less than

10% of the calculated PBR and, therefore, cannot be considered to be insignificant and approaching zero mortality

and serious injury rate. This is a non-strategic stock because estimated average annual fishery-related mortality and

serious injury does not exceed PBR. 

REFERENCES

Anon. 1993. Cruise results, NOAA ship DELAWARE II, Cruise No. DEL 93-06, Marine Mammal Survey. 5 pp. 

Available from: National Marine Fisheries Service, 166 Water Street, Woods Hole, MA 02543-1026.

Barlow, J., S. L. Swartz, T. C. Eagle and P. R. Wade. 1995. U.S. Marine mammal stock assessments: Guidelines

for preparation, background, and a summary of the 1995 assessments. U.S.Dep. Commer., NOAA Tech.

Memo. NMFS-OPR-6, 73 pp.

Bisack, K. D. 1997a. Harbor porpoise bycatch estimates in the New England multispecies sink gillnet fishery: 1994

and 1995. Rep. int Whal. Comm 47: 705-14.

Bisack, K. D. 1997b. Marine mammal bycatch estimates and their sampling distributions in the U.S. New England

sink gillnet, pair trawl, Atlantic pelagic drift gillnet and North Atlantic bottom trawl fisheries - 1994 to

1996. NOAA, NMFS, NEFSC. Woods Hole, MA. Working paper SC/49/SM35 submitted to the IWC

Scientific Committee meeting in Bournemouth, UK, Aug/Sept 1997.

Bravington, M. V. and K. D. Bisack. 1996. Estimates of harbor porpoise bycatch in the Gulf of Maine sink gillnet

fishery, 1990-1993. Rep. int Whal. Comm 46: 567-74.

CETAP. 1982. A characterization of marine mammals and turtles in the mid- and north Atlantic areas of the U.S.

outer continental shelf. Cetacean and Turtle Assessment Program, University of Rhode Island. Final

Report, Contract AA51-C78-48, Bureau of Land Management, Washington, DC, 538 pp. 

Evans, P. G. H. 1987. The natural history of whales and dolphins. Facts on File Publications, New York, 343 pp. 

Gaskin, D. E. 1992. Status of Atlantic white-sided dolphin, Lagenorhynchus acutus, in Canada. Can. Fld. Nat.

106: 64-72.

Gilbert, J. R. and K. M. Wynne. 1987. Marine mammal interactions with New England gillnet fisheries. Final

Report, Contract No. NA-84-EAC-00070, to National Marine Fisheries Service, Northeast Fisheries

Science Center, Woods Hole, Massachusetts, 12 pp. 

Hain, J. H. W. and G. T. Waring. 1994. Status of and human effects upon marine mammals. Pp. 9-20 in: R. W.

Langton , J. B. Pearce, and J.A. Gibson (eds), Selected living resources, habitat conditions, and human

perturbations of the Gulf of Maine: Environmental and ecological considerations for fishery managements. 

NOAA Tech. Mem. NMFS-NE-106, Northeast Fisheries Science Center, Woods Hole, Massachusetts. 

Hooker, S. K., R. W. Baird and M. A. Showell. 1997. Cetacean strandings and bycatches in Nova Scotia, Eastern

Canada, 1991-1996. Meeting document SC/49/O5 submitted to the 1997 International Whaling

Commission meeting in Bournemouth, UK.

Katona, S. K., V. Rough, and D. T. Richardson. 1993. A field guide to whales, porpoises, and seals from Cape Cod

to Newfoundland. Smithsonian Institution Press, Washington, DC, 316 pp. 

Kenney, R. D., P. M. Payne, D. W. Heinemann and H. E. Winn. 1996. Shifts in Northeast shelf cetacean

distributions relative to trends in Gulf of Maine/Georges Bank finfish abundance. Pp. 169-196 in: K.
112

Sherman, N.A. Jaworski and T. Smada (eds.). The northeast shelf ecosystem: assessment, sustainability,

and management. Blackwell Science, Cambridge, MA 02142, USA.

Kingsley, M. C. S. and R. R. Reeves. 1998. Aerial surveys of cetaceans in the Gulf of St. Lawrence in 1995 and

1996. Can. J. Zool. 76:1529-1550.

Lucas, Z. N. and S. K. Hooker. 2000. Cetacean strandings on Sable Island, Nova Scotia, 1970-1998. Canadian

Field-Naturalist 114(1): 46-61.

NMFS (National Marine Fisheries Service). 1998. Status of the fishery resources off northeastern United States for

1998. NOAA Technical Memorandum NMFS-NE-115.

Northridge, S. 1996. Estimation of cetacean mortality in the U.S. Atlantic swordfish and tuna driftnet and pair trawl

fisheries. Final report to the NMFS Contract No. 40ENNF500160.

Northridge, S., M. Tasker, A. Webb, K. Camphuysen and M. Leopold. 1997. White-beaked Lagenorhynchus

albirostris and Atlantic white-sided dolphin L. acutus distributions in northwest European and U.S. North

Atlantic waters. Rep. int. Whal. Commn 47:797-805.

Palka, D. 2000. Abundance of the Gulf of Maine/Bay of Fundy harbor porpoise based on shipboard and aerial

surveys during 1999. NOAA/NMFS/NEFSC Ref. Doc. 00-07. 29 pp. Available from: National Marine

Fisheries Service, 166 Water Street, Woods Hole, MA 02543-1026.

Palka, D. 1996. Update on abundance of Gulf of Maine/Bay of Fundy harbor porpoises. NOAA/NMFS/NEFSC

Ref. Doc. 96-04. 37 pp. Available from: National Marine Fisheries Service, 166 Water Street, Woods

Hole, MA 02543-1026.

Palka, D. 1995. Abundance estimate of the Gulf of Maine harbor porpoise. pp. 27-50 In: A. Bjørge and G.P.

Donovan (eds.) Biology of the Phocoenids. Rep. int Whal. Commn Special Issue 16. 

Palka, D., A. Read and C. Potter. 1997. Summary of knowledge of white-sided dolphins (Lagenorhynchus acutus)

from the U.S. and Canadian North Atlantic waters. Rep. int Whal. Commn 47: 729-34.

Palka, D., G. Waring and D. Potter. (in review). Abundances of cetaceans and sea turtles in the northwest Atlantic

during summer 1995 and 1998. Fish. Bull., U.S.

Payne, M. and D. W. Heinemann. 1990. A distributional assessment of cetaceans in the shelf and shelf edge waters

of the northeastern United States based on aerial and shipboard surveys, 1978-1988. Report to National

Marine Fisheries Science Center, Woods Hole, Massachusetts. 108p.

Read, A. J. 1994. Interactions between cetaceans and gillnet and trap fisheries in the northwest Atlantic. Rep. int

Whal. Commn Special Issue 15: 133-147. 

Sergeant, D. E., D. J. St. Aubin and J. R. Geraci. 1980. Life history and northwest Atlantic status of the Atlantic

white-sided dolphin, Lagenorhynchus acutus. Cetology No. 37: 1-12.

Wade, P. R. and R. P. Angliss. 1997. Guidelines for assessing marine mammal stocks: Report of the GAMMS

workshop April 3-5, 1996, Seattle, Washington. U.S. Dep. Commer., NOAA Tech. Memo. NMFS-OPR-12,

93 pp.

Walden, J. 1996. The New England gillnet effort study. NOAA-NMFS-NEFSC Ref. Doc. No. 96-10. 38 pp. 

Available from: National Marine Fisheries Service, 166 Water Street, Woods Hole, MA 02543-1026.

Waring, G. T., P. Gerrior, P. M. Payne, B. L. Parry, and J. R. Nicolas. 1990. Incidental take of marine mammals in

foreign fishery activities off the northeast United States, 1977-1988. Fish. Bull., U.S. 88(2): 347-360.
113

Figure 1. Distribution of harbor porpoise sightings from

NEFSC and SEFSC shipboard and aerial surveys during

the summer in 1990-1998. Isobaths are at 100 m and

1,000 m. 

January 2002

HARBOR PORPOISE (Phocoena phocoena):

Gulf of Maine/Bay of Fundy Stock

STOCK DEFINITION AND GEOGRAPHIC RANGE

This stock is found in USA and Canadian Atlantic waters. The distribution of harbor porpoises has been

documented by sighting surveys, strandings, and takes reported by NMFS observers in the Sea Sampling Program. 

During summer (July to September), harbor porpoises are concentrated in the northern Gulf of Maine and southern

Bay of Fundy region, generally in waters less than 150 m deep (Gaskin 1977; Kraus et al. 1983; Palka 1995a, b),

with a few sightings in the upper Bay of Fundy and on the northern edge of Georges Bank (Palka 2000). During fall

(October-December) and spring (April-June), harbor porpoises are widely dispersed from New Jersey to Maine, with

lower densities farther north and south. They are seen from the coastline to deep waters (> 1800 m; Westgate et al.

1998), although the majority of the population is found over the continental shelf. During winter (January to

March), intermediate densities of harbor porpoises can be found in waters off New Jersey to North Carolina, and

lower densities are found in waters off New York to

New Brunswick, Canada. There does not appear to be

a temporally coordinated migration or a specific

migratory route to and from the Bay of Fundy region. 

Though, during the fall, several satellite tagged harbor

porpoises did favor the waters around the 92m isobath,

which is consistent with observations of high rates of

incidental catches in this depth range (Read and

Westgate 1997). There were two stranding records

from Florida (Smithsonian strandings data base). 

Gaskin (1984, 1992) proposed that there were

four separate populations in the western North Atlantic:

the Gulf of Maine/Bay of Fundy, Gulf of St. Lawrence,

Newfoundland and Greenland populations. Recent

analyses involving mtDNA (Wang et al. 1996; Rosel et

al. 1999a; Rosel et al. 1999b), organochlorine

contaminants (Westgate et al.1997; Westgate and

Tolley 1999), heavy metals (Johnston 1995), and life

history parameters (Read and Hohn 1995) support

Gaskin’s proposal. Genetic studies using mitochondrial

DNA (Rosel et al. 1999a) and contaminant studies

using total PCBs (Westgate and Tolley 1999) indicate 

that the Gulf of Maine/Bay of Fundy females were

distinct from females from the other populations in the

NW Atlantic. Gulf of Maine/Bay of Fundy males were

distinct from Newfoundland and Greenland males, but

not from Gulf of St. Lawrence males according to

studies comparing mtDNA (Rosel et al. 1999a; Palka et

al. 1996) and CHLORs, DDTs, PCBs and CHBs

(Westgate and Tolley 1999). Analyses of stranded

animals from the mid-Atlantic states suggest that this

aggregation of harbor porpoises consists of animals

from more than just the Gulf of Maine/Bay of Fundy stock (Rosel et al. 1999a). However, the majority of the

samples used in the Rosel et al. (1999a) study were from stranded juvenile animals. Further work is underway to

examine adult animals from this region. Nuclear microsatellite markers have also been applied to samples from

these four populations, but this analysis failed to detect significant population sub-division in either sex (Rosel et al.

1999a). This pattern may be indicative of female philopatry coupled with dispersal of male harbor porpoises. This

report follows Gaskin's hypothesis on harbor porpoise stock structure in the western North Atlantic; Gulf of Maine
114

and Bay of Fundy harbor porpoises are recognized as a single management stock separate from harbor porpoise

populations in the Gulf of St. Lawrence, Newfoundland, and Greenland. 

POPULATION SIZE

To estimate the population size of harbor porpoises in the Gulf of Maine/Bay of Fundy region, four linetransect sighting surveys were conducted during the summers of 1991, 1992, 1995, and 1999 (Table 1; Figure 1). 

The population sizes were 37,500 harbor porpoises in 1991 (CV=0.29, 95% confidence interval (CI)=26,700-86,400)

(Palka 1995a), 67,500 harbor porpoises in 1992 (CV=0.23, 95% CI=32,900-104,600), 74,000 harbor porpoises in

1995 (CV=0.20, 95% CI = 40,900-109,100) (Palka 1996), and 89,700 in 1999 (CV=0.22, 95% CI=53,400 - 150,900)

(Palka 2000). The inverse variance weighted-average abundance estimate (Smith et al. 1993) of the 1991 to 1995

estimates was 54,300 harbor porpoises (CV=0.14, 95% CI=41,300-71,400). Possible reasons for inter-annual

differences in abundance and distribution include experimental error, inter-annual changes in water temperature and

availability of primary prey species (Palka 1995b), and movement among population units (e.g., between the Gulf of

Maine and Gulf of St. Lawrence). One of the reasons the 1999 estimate is larger than previous estimates is that, for

the first time, the upper Bay of Fundy and northern Georges Bank were surveyed and harbor porpoises were seen

during 1999. This indicates the harbor porpoise summer habitat is larger than previously thought (Palka 2000).

The shipboard sighting survey procedure used in all four surveys involved two independent teams on one

ship that searched using the naked eye in non-closing mode. Abundance, corrected for g(0), the probability of

detecting an animal group on the track line, was estimated using the direct-duplicate method (Palka 1995a) and

variability was estimated using bootstrap re-sampling methods. Potential biases not explicitly accounted for include

ship avoidance and submergence time. The effects of these two potential biases are unknown. During 1995 and

1999 a section of the region was surveyed by airplane while the rest of the region was surveyed by ship, as in

previous years (Palka 1996; 2000). During 1995, in addition to the Gulf of Maine/Bay of Fundy area, waters from

Virginia to the mouth of the Gulf of St. Lawrence were surveyed and harbor porpoises were seen only in the vicinity

of the Gulf of Maine/Bay of Fundy. During 1999, waters from south of Cape Cod to the mouth of the Gulf of St.

Lawrence were surveyed (Palka 2000).

The best current abundance estimate of the Gulf of Maine/Bay of Fundy harbor porpoise stock is 89,700

(CV=0.22), this is the 1999 survey results not averaged with other years. This is because the 1999 estimate is the

most current, and this survey discovered portions of the harbor porpoise range not covered previously. 

 Kingsley and Reeves (1998) estimated there were 12,100 (CV=0.26) harbor porpoises in the entire Gulf of

St. Lawrence during 1995, and 21,700 (CV=0.38) in the northern Gulf of St. Lawrence during 1996. These

estimates are presumed to be of the Gulf of St. Lawrence stock of harbor porpoises. The highest densities were

north of Anticosti Island, with lower densities in the central and southern Gulf. During the 1995 survey, 8,427 km of

track lines were flown in an area of 221,949 km2

 during August and September. During the 1996 survey, 3,993 km

of track lines were flown in an area of 94,665 km2

 during July and August. Data were analyzed using Quenouille’s

jackknife bias reduction procedure on line transect methods that modeled the left truncated sighting curve. These

estimates were not corrected for visibility biases such as g(0).

Table 1. Summary of abundance estimates for the Gulf of Maine/Bay of Fundy harbor porpoise for the entire area

that was surveyed and a common area that was surveyed in all years. Month, year, and area covered during

each abundance survey, and resulting abundance estimate (Nbest) and coefficient of variation (CV).

Month/Year Area

Entire survey area Common

survey area 

Nbest CV N

Jul-Aug 1991 N. Gulf of Maine & lower Bay of Fundy 37,500 0.29 29,000

Jul-Sep 1992 N. Gulf of Maine & lower Bay of Fundy 67,500 0.23 57,600

Jul-Sep 1995 N. Gulf of Maine & lower Bay of Fundy 74,000 0.20 71,900

Inverse variance-weighted average of above 1991, 1992 and 1995 estimates 54,300 0.14 -

Jul-Aug 1999 S. Gulf of Maine to upper Bay of Fundy 89,700 0.22 67,600
115

Minimum Population Estimate 

The minimum population estimate is the lower limit of the two-tailed 60% confidence interval of the lognormally distributed best abundance estimate. This is equivalent to the 20th percentile of the log-normal distribution

as specified by Wade and Angliss (1997). The best estimate of abundance for harbor porpoises is 89,700

(CV=0.22). The minimum population estimate for the Gulf of Maine/Bay of Fundy harbor porpoise is 74,695

(CV=0.22).

Current Population Trend

 Analyses are underway to determine if trend information can be obtained from the four NEFSC surveys.

Previous abundance estimates for harbor porpoises in the Gulf of Maine/Bay of Fundy are available from earlier

studies, (e.g., 4,000 animals (Gaskin 1977), and 15,800 animals (Kraus et al. 1983)). These estimates cannot be used

in a trends analysis because they were for selected small regions within the entire known summer range and, in some

cases, did not incorporate an estimate of g(0) (NEFSC 1992).

CURRENT AND MAXIMUM NET PRODUCTIVITY RATES

Although current population growth rates of Gulf of Maine/Bay of Fundy harbor porpoises have not been

estimated due to lack of data, several attempts have been made to estimate potential population growth rates. Barlow

and Boveng (1991), who used a re-scaled human life table, estimated the upper bound of the annual potential growth

rate to be 9.4%. Woodley and Read (1991) used a re-scaled Himalayan tahr life table to estimate a likely annual

growth rate of 4%. In an attempt to estimate a potential population growth rate that incorporates many of the

uncertainties in survivorship and reproduction, Caswell et al. (1998) used a Monte Carlo method to calculate a

probability distribution of growth rates. The median potential annual rate of increase was approximately 10%, with

a 90% confidence interval of 3-15%. This analysis underscored the considerable uncertainty that exists regarding

the potential rate of increase in this population. Consequently, for the purposes of this assessment, the maximum net

productivity rate was assumed to be 4%, consistent with values used for other cetaceans for which direct

observations of maximum rate of increase are not available, and following a recommendation from the Atlantic

Scientific Review Group. The 4% value is based on theoretical modeling showing that cetacean populations may

not grow at rates much greater than 4% given the constraints of their reproductive life history (Barlow et al. 1995). 

POTENTIAL BIOLOGICAL REMOVAL

Potential Biological Removal (PBR) is the product of minimum population size, one-half the maximum

productivity rate, and a “recovery” factor (MMPA Sec. 3. 16 U.S.C. 1362; Wade and Angliss 1997). The minimum

population size is 74,695 (CV=0.22). The maximum productivity rate is 0.04, the default value for cetaceans. The

“recovery” factor, which accounts for endangered, depleted, threatened stocks, or stocks of unknown status relative

to optimum sustainable population (OSP) is assumed to be 0.5 because this stock is of unknown status. PBR for the

Gulf of Maine/Bay of Fundy harbor porpoise is 747.

ANNUAL HUMAN-CAUSED MORTALITY

Data to estimate the mortality and serious injury of harbor porpoise come from USA and Canadian Sea

Sampling Programs and from records of strandings in USA waters. Estimates using Sea Sampling Program data are

discussed by fishery under the Fishery Information section (Table 2). Strandings records are discussed under the

unknown gill net fishery in the Fishery Information section (Table 3) and under the Other Mortality section (Tables 4

to 5).

A take reduction plan was implemented 01 January 1999 to reduce takes of harbor porpoises in USA

Atlantic gillnet fisheries. In addition, several New England and mid-Atlantic fishery management council plans that

apply to parts of the gillnet fisheries were also implemented during 1999. Because these plans changed the USA

gillnet fisheries, only 1999 and 2000 USA mortality estimates are representative of the current USA mortality. The

total annual estimated average human-caused mortality is 459 (CV=0.24) harbor porpoises per year. This is derived

from four components: 425 harbor porpoise per year (CV=0.24) from USA fisheries using observer data, 23 per year

(unknown CV) from Canadian fisheries using observer data, 10 per year from USA unknown fisheries using

strandings data, and 1 per year from unknown human-caused mortality (a mutilated stranded harbor porpoise).
116

Fishery Information

Recently, Gulf of Maine/Bay of Fundy harbor porpoise takes have been documented in the USA Northeast 

sink gillnet, mid-Atlantic coastal gillnet, and in the Canadian Bay of Fundy groundfish sink gillnet and herring weir

fisheries (Table 2).

EARLIER INTERACTIONS

Pelagic Drift Gillnet 

In 1996 and 1997, NMFS issued management regulations which prohibited the operation of this fishery in

1997. The fishery operated during 1998. Then, in January 1999 NMFS issued a Final Rule to prohibit the use of

drift net gear in the North Atlantic swordfish fishery (50 CFR Part 630). One harbor porpoise was observed taken

from the Atlantic pelagic drift gillnet fishery during 1991-1998. The estimated total number of hauls in the Atlantic

pelagic drift gillnet fishery increased from 714 in 1989 to 1,144 in 1990; thereafter, with the introduction of quotas,

effort was severely reduced. Fifty-nine different vessels participated in this fishery at one time or another between

1989 and 1993. In 1994 to 1998 there were 11, 12, 10, 0, and 11 vessels, respectively, in the fishery. The estimated

number of hauls in 1991, 1992, 1993, 1994, 1995 and 1996 were 233, 243, 232, 197, 164, and 149 respectively. 

Observer coverage, expressed as percent of sets observed was 8% in 1989, 6% in 1990, 20% in 1991, 40% in 1992,

42% in 1993, 87% in 1994, 99% in 1995, 64% in 1996, and 99% in 1998. The decline in observer coverage in 1996

is attributable to trips made by vessels that were deemed unsafe for observers due to the size or condition of the

fishing vessel. Fishing effort was concentrated along the southern edge of Georges Bank and off Cape Hatteras. 

Examination of the species composition of the catch and locations of the fishery throughout the year suggested that

the drift gillnet fishery be stratified into two strata, a southern or winter stratum, and a northern or summer stratum. 

Estimates of the total bycatch, for each year from 1989 to 1993, were obtained using the aggregated (pooled 1989-

1993) catch rates, by strata (Northridge 1996). Estimates of total annual bycatch after 1993 were estimated from the

sum of the observed caught and the product of the average bycatch per haul and the number of unobserved hauls as

recorded in logbooks. Variances were estimated using bootstrap re-sampling techniques (Bisack 1997b). The one

observed bycatch was notable because it occurred in continental shelf edge waters adjacent to Cape Hatteras (Read

et al. 1996). Estimated annual fishery-related mortality (CV in parentheses) attributable to this fishery was 0.7 in

1989 (7. 00), 1.7 in 1990 (2.65), 0.7 in 1991 (1.00), 0.4 in 1992 (1.00), 1.5 in 1993 (0.34), 0 in 1994 to 1996, and 0

in 1998. The fishery was closed during 1997. Average estimated harbor porpoise mortality and serious injury in the

Atlantic pelagic drift gillnet fishery during 1994-1998 was 0.0. 

USA

Recent data on incidental takes in USA fisheries are available from several sources. The only source that

documented harbor porpoise bycatch is the Northeast Fisheries Science Center (NEFSC) Sea Sampling Observer

Program that was initiated in 1990, and since that year, several fisheries have been covered by the program.

Northeast Sink Gillnet 

Before 1998 most of the harbor porpoise takes from USA fisheries were from the Northeast sink gillnet

fishery. In 1984 the Northeast sink gillnet fishery was investigated by a sampling program that collected information

concerning marine mammal bycatch. Approximately 10% of the vessels fishing in Maine, New Hampshire, and

Massachusetts were sampled. Among the eleven gillnetters who received permits and logbooks, 30 harbor porpoises

were reported caught. It was estimated, using rough estimates of fishing effort, that a maximum of 600 harbor

porpoises were killed annually in this fishery (Gilbert and Wynne 1985, 1987). 

In 1990, an observer program was started by NMFS to investigate marine mammal takes in the Northeast 

sink gillnet fishery. There have been 452 harbor porpoise mortalities related to this fishery observed between 1990

and 2000 and one was released alive and uninjured. In 1993, there were approximately 349 full and part-time

vessels in the Northeast sink gillnet fishery (Table 2). An additional 187 vessels were reported to occasionally fish

in the Gulf of Maine with gillnets for bait or personal use; however, these vessels were not covered by the observer

program (Walden 1996) and their fishing effort was not used in estimating mortality. During 1998, an estimated 301

full and part-time vessels participated in this fishery. This is the number of unique vessels in the commercial

landings database (Weighout) that reported catch from this fishery during 1998 from the states of Rhode Island to

Maine. This does not include a small percentage of records where the vessel number was missing. Observer

coverage in terms of trips was 1%, 6%, 7%, 5%, 7%, 5%, 4%, 6%, 5%, 6%, and 6% for 1990 to 2000, respectively. 

Bycatch in the northern Gulf of Maine occurs primarily from June to September, while in the southern Gulf of
117

Maine, bycatch occurs from January to May and September to December. Annual estimates of harbor porpoise

bycatch in the Northeast sink gillnet fishery reflect seasonal distribution of the species and of fishing effort. 

Bycatch estimates included a correction factor for the under-recorded number of by-caught animals that occurred

during unobserved hauls on trips with observers on the boat, when applicable. Need for such a correction became

evident following re-analysis of data from the sea sampling program indicating that for some years bycatch rates

from unobserved hauls were lower than that for observed hauls. Further analytical details are given in Palka (1994), 

CUD (1994), and Bravington and Bisack (1996). These revised bycatch estimates replace those published earlier

(Smith et al. 1993). Estimates presented here are still negatively biased because they do not include harbor

porpoises that fell out of the net while still underwater. This bias cannot be quantified at this time. Estimated annual

bycatch (CV in parentheses) from this fishery during 1990-2000 was 2,900 in 1990 (0.32), 2,000 in 1991 (0.35),

1,200 in 1992 (0.21), 1,400 in 1993 (0.18) (Bravington and Bisack 1996; CUD 1994), 2100 in 1994 (0.18), 1400 in

1995 (0.27) (Bisack 1997a), 1200 in 1996 (0.25), 782 in 1997 (0.22), 332 in 1998 (0.46), 270 in 1999 (0.28)

(Rossman and Merrick 1999), and 507 in 2000 (0.37). The increase in the 1998 CV is mainly due to the small

number of observed takes. 

There appeared to be no evidence of differential mortality in USA or Canadian gillnet fisheries by age or

sex in animals collected before 1994, although there was substantial inter-annual variation in the age and sex

composition of the bycatch (Read and Hohn 1995). Using observer data collected during 1990 to 1998 and a logit

regression model, females were 11 times more likely to be caught in the offshore southern Gulf of Maine region,

males were more likely to be caught in the south Cape Cod region, and the overall proportion of males and females

caught in a gillnet and brought back to land were not significantly different (Lamb 2000). 

Two preliminary experiments, using acoustic alarms (pingers) attached to gillnets, were conducted in the

Gulf of Maine during 1992 and 1993 and took 10 and 33 harbor porpoises, respectively. During fall 1994, a

controlled scientific experiment was conducted in the southern Gulf of Maine, where all nets with and without active

pingers were observed (Kraus et al. 1997). In this experiment 25 harbor porpoises were taken in 423 strings with

non-active pingers (controls) and 2 harbor porpoises were taken in 421 strings with active pingers. In addition, 17

other harbor porpoises were taken in nets that did not follow the experimental protocol (Table 2). From 1995 to

1997, experimental fisheries were conducted where all nets in a designated area were required to use pingers and

only a sample of the nets were observed. During November-December 1995, an experimental fishery was conducted

in the southern Gulf of Maine (Jeffreys Ledge) region, where no harbor porpoises were observed taken in 225

pingered nets. During 1995, all takes from pingered nets were added directly to the estimated total bycatch for that

year. During April 1996, 3 other experimental fisheries occurred. In the Jeffreys Ledge area, in 88 observed hauls

using pingered nets 9 harbor porpoises were taken. In the Massachusetts Bay region, in 171 observed hauls using

pingered nets, 2 harbor porpoises were taken. And, in a region just south of Cape Cod, in 53 observed hauls using

pingered nets, no harbor porpoises were taken. During 1997, experimental fisheries were allowed in the mid-coast

region during March 25 to April 25 and November 1 to December 31. During the 1997 spring experimental fishery,

180 hauls were observed with active pingers and 220 hauls were controls (silent). All observed harbor porpoise

takes were in silent nets: 8 in nets with control (silent) pingers, and 3 in nets without pingers. Thus, there was a

statistical difference between the catch rate in nets with pingers and silent nets (Kraus and Brault in press). During

the 1997 fall experimental fishery, out of 125 observed hauls using pingered nets no harbor porpoises were taken.

From 95 stomachs of harbor porpoises collected in groundfish gillnets in the Gulf of Maine between

September and December 1989-94, Atlantic herring (Clupea harengus) was the most important prey. Pearlsides

(Maurolicus weitzmani), silver hake (Merluccius bilinearis) and red and white hake (Urophycis spp.) were the next

most common prey species (Gannon et al. 1998).

Average estimated harbor porpoise mortality and serious injury in the Northeast sink gillnet fishery during

1994-1998 before the Take Reduction Plan was 1,163 (0.11). Because of the Take Reduction Plan to reduce takes in

USA Atlantic gillnets, and the NEFMC fishery management plans to manage groundfish, fishing practices changed

during 1999. Subsequently, the average annual harbor porpoise mortality and serious injury in the Northeast sink

gillnet fishery from 1999 to 2000 is only 388 (0.26).

Mid-Atlantic Coastal Gillnet 

Before an observer program was in place, Polacheck et al. (1995) reported one harbor porpoise incidentally

taken in shad nets in the York River, Virginia. In July 1993 an observer program was initiated in the mid-Atlantic

coastal gillnet fishery by the NEFSC Sea Sampling program. This fishery, which extends from North Carolina to

New York, is actually a combination of small vessel fisheries that target a variety of fish species, some of the vessels
118

operate right off the beach, some using drift nets and others using sink nets. During 1998, it was estimated that there

were 302 full and part-time sink gillnet vessels and an undetermined number of drift gillnet vessels participating in

this fishery. This is the number of unique vessels in the commercial landings database (Weighout) that reported

catch from this fishery during 1998 from the states of Connecticut to North Carolina. This does not include a small

percentage of records where the vessel number was missing. Twenty trips were observed during 1993. During 1994

and 1995, 221 and 382 trips were observed, respectively. Observer coverage, expressed as percent of tons of fish

landed, was 5% for 1995, 4% for 1996, 3% for 1997, 5% for 1998, 2% for 1999, and 2% for 2000 (Table 2). No

harbor porpoises were taken in observed trips during 1993 and 1994. During 1995 to 2000, respectively, 6, 19, 32,

53, 3, and 1 harbor porpoises were observed taken (Table 2). Observed fishing effort has been scattered between

New York and North Carolina from the beach to 50 miles off the beach. Documented bycatches after 1995 were

from December to May. Bycatch estimates were calculated using methods similar to that used for bycatch estimates

in the Northeast gillnet fishery (Bravington and Bisack 1996; Bisack 1997a). After 1998, a separate bycatch

estimate was made for the drift gillnet and set gillnet sub-fisheries. The number presented here is the sum of these

two sub-fisheries. The estimated annual mortality (CV in parentheses) attributed to this fishery was 103 (0.57) for

1995, 311 (0.31) for 1996, 572 (0.35) for 1997, 446 (0.36) for 1998, 53 (0.49) for 1999, and 21 (0.76) for 2000. 

Annual average estimated harbor porpoise mortality and serious injury from the mid-Atlantic coastal gillnet fishery

before the Take Reduction Plan (during 1995 to 1998) was 358 (CV=0.20) (Table 2). Because of the Take

Reduction Plan to reduce takes in USA Atlantic gillnets, and the fishery management plans to manage groundfish, 

fishing practices changed during 1999. Subsequently, the average annual harbor porpoise mortality and serious

injury in the mid-Atlantic coastal gillnet fishery from 1999 and 2000 is only 37 (0.41). 

Unknown Fishery

The strandings and entanglement database, maintained by the New England Aquarium and the Northeast

Regional Office/NMFS, reported 228 and 26 stranded harbor porpoises during 1999 and 2000, respectively (see

Other Mortality section for more details). Of these, it was determined that the cause of death of 19, and 1 stranded

harbor porpoises was due to gillnets in 1999 and 2000, respectively, and these animals were in areas and times that

were not included in the above mortality estimate derived from observer program data (Table 3). The current

average harbor porpoise mortality and serious injury in this unknown fishery category from 1999 and 2000 is 10 (CV

is unknown).

North Atlantic Bottom Trawl 

One harbor porpoise mortality was observed in the North Atlantic bottom trawl fishery between 1989 and

2000. Vessels in this fishery, a Category III fishery under the MMPA, were observed in order to meet fishery

management needs

 rather than marine mammal management needs. An average of 970 (CV=0.04) vessels (full and part time)

participated annually in the fishery during 1989-1993. This fishery is active in New England waters in all seasons. 

The one take occurred in February 1992 east of Barnegatt Inlet, New York at the continental shelf break. The

animal was clearly dead prior to being taken by the trawl, because it was severely decomposed and the tow duration

of 3.3 hours was insufficient to allow extensive decomposition; therefore, the estimated bycatch for this fishery is 0.

CANADA

Hooker et al. (1997) summarized bycatch data from a Canadian fisheries observer program that placed

observers on all foreign fishing vessels operating in Canadian waters, on between 25-40% of large Canadian fishing

vessels (greater than 100 feet long), and on approximately 5% of smaller Canadian fishing vessels. No harbor

porpoises were observed taken.

Bay of Fundy Sink Gillnet 

During the early 1980's, Canadian harbor porpoise bycatch in the Bay of Fundy sink gillnet fishery, based

on casual observations and discussions with fishermen, was thought to be low. The estimated harbor porpoise

bycatch in 1986 was 94-116 and in 1989 it was 130 (Trippel et al. 1996). The Canadian gillnet fishery occurs

mostly in the western portion of the Bay of Fundy during the summer and early autumn months, when the density of

harbor porpoises is highest. Polacheck (1989) reported there were 19 gillnetters active in 1986, 28 active in 1987,

and 21 in 1988. 

More recently, an observer program implemented in the summer of 1993 provided a total bycatch estimate

of 424 harbor porpoises (± 1 SE: 200-648) from 62 observed trips, (approximately 11.3% coverage of the Bay of

Fundy trips) (Trippel et al. 1996).
119

During 1994, the observer program was expanded to cover 49% of the gillnet trips (171 observed trips). 

The bycatch was estimated to be 101 harbor porpoises (95% confidence limit: 80-122), and the fishing fleet

consisted of 28 vessels (Trippel et al. 1996). 

During 1995, due to groundfish quotas being exceeded, the gillnet fishery was closed from July 21 to

August 31, 1995. During the open fishing period of 1995, 89% of the trips were observed, all in the Swallowtail

region. Approximately 30% of these observed trips used pingered nets. The estimated bycatch was 87 harbor

porpoises (Trippel et al. 1996). No confidence interval was computed due to lack of coverage in the Wolves fishing

grounds.

During 1996, the Canadian gillnet fishery was closed during July 20-31 and August 16-31 due to

groundfish quotas. From the 107 monitored trips, the bycatch in 1996 was estimated to be 20 harbor porpoises

(Trippel et al. 1999; DFO 1998). Trippel et al. (1999) estimated that during 1996, gillnets equipped with acoustic

alarms reduced harbor porpoise bycatch rates by 68% over nets without alarms in the Swallowtail area of the lower

Bay of Fundy.

During 1997, the fishery was closed to the majority of the gillnet fleet during July 18-31 and August 16-31,

due to groundfish quotas. In addition a time-area closure to reduce porpoise bycatch in the Swallowtail area

occurred during September 1-7, 1997. From the 75 monitored trips during 1997, 19 harbor porpoises were observed

taken. After accounting for total fishing effort, the estimated bycatch in 1997 was 43 animals (DFO 1998). Trippel

et al. (1999) estimated that during 1997, gillnets equipped with acoustic alarms reduced harbor porpoise bycatch

rates by 85% over nets without alarms in the Swallowtail area of the lower Bay of Fundy.

During 1998, the number of fishing vessels was appreciably lower than in previous years due to very poor

groundfish catch rates, even though the fishery was open July to September. Seventeen trips were monitored and 1

harbor porpoise mortality was observed. Fishers independently reported an additional 4 porpoises. The Wolves and

Head Harbour area had 7 fishing trips in July and did not receive observer coverage. A preliminary total bycatch for

Bay of Fundy in 1998 was estimated at 10 porpoises. Estimates of variance are not available (DFO 1998).

During 1999, observer coverage was from July to early September. Three fishing vessels were observed,

one each near the Wolves, Digby Neck, and McDormand Patch, for a total of 179 observed hauls. Three harbor

porpoise takes were observed. Preliminary analyses indicate the total mortality estimate is not likely to exceed 20

harbor porpoises (Trippel, pers. comm.). Acoustic reflective nets were also tested during this fishing season.

During 2000 there was an observer program. Preliminary analyses indicate that the total mortality estimate

is approximately 10 (Trippel, pers. comm.). More detailed information will be available later.

 Average estimated harbor porpoise mortality in the Canadian groundfish sink gillnet fishery during 1996-

2000 was 23 (Table 2). An estimate of variance is not possible.

Herring Weirs

Harbor porpoises are taken frequently in Canadian herring weirs, but there have been no recent efforts to

observe takes in the USA component of this fishery. Weirs operate from May to September each year along the

southwestern shore of the Bay of Fundy, and the coasts of western Nova Scotia and northern Maine. In 1990, there

were 180 active weirs in the western Bay of Fundy and 56 active weirs in Maine (Read 1994). According to state

officials, in 1998, the number of weirs in Maine waters dropped to nearly zero due to the limited herring market

(Jean Chenoweth, pers. comm.), and in 2000, only 11 weirs were built (Molyneaux 2000). According to Canadian

officials, for 1998, there were 225 licenses for herring weirs on the New Brunswick side and 30 from the Nova

Scotia side of the Bay of Fundy (in New Brunswick: 60 from Grand Manan Island, 95 from Deer and Campobello

Islands, 30 from Passamaquoddy Bay, 35 from East Charlotte area, and 5 from the Saint John area). The number of

licenses has been fairly consistent since 1985 (Ed Trippel, pers. comm.), but the number of active weirs is less than

the number of licenses, and has been decreasing every year, primarily due to competition with salmon mariculture

sites (A. Read, pers. comm.).

Smith et al. (1983) estimated that, in 1980, approximately 70 harbor porpoises become trapped annually

and, on average, 27 died annually. In 1990, at least 43 harbor porpoises were trapped in Bay of Fundy weirs (Read

1994). In 1993, after a cooperative program between fishermen and Canadian biologists was initiated over 100

harbor porpoises were released alive (Read 1994). Between 1992 and 1994, this cooperative program resulted in the

live release of 206 of 263 harbor porpoises caught in herring weirs. Mortalities (and releases) were 11 (and 50) in

1992, 33 (and 113) in 1993, and 13 (and 43) in 1994 (Neimanis et al. 1995). Since that time, an additional 488

harbor porpoises have been documented in Canadian herring weirs, of which 460 were released or escaped and 28
120

died. Mortalities (and releases) were 5 (and 60) in 1995; 2 (and 4) in 1996; 2 (and 24) in 1997; 2 (and 26) in 1998; 3

(and 89) in 1999; 0 (and 13) in 2000, and 14 (and 244) in 2001 (A. Read, pers. comm.).

Clinical hematology values were obtained from 29 harbor porpoises released from Bay of Fundy herring

weirs (Koopman et al. 1999). These data represent a baseline for free-ranging harbor porpoises that can be used as a

reference for long-term monitoring of the health of this population, a mandate by the MMPA.

 Average estimated harbor porpoise mortality in the Canadian herring weir fishery during 1996-2000 was

1.8 (Table 2). An estimate of variance is not possible.

Table 2. From observer program data, summary of the incidental mortality of harbor porpoise (Phocoena phocoena)

by commercial fishery including the years sampled (Years), the number of vessels active within the fishery

(Vessels), the type of data used (Data Type), the annual observer coverage (Observer Coverage), the

mortalities recorded by on-board observers (Observed Mortality), the estimated annual mortality (Estimated

Mortality), the estimated CV of the annual mortality (Estimated CVs) and the mean annual mortality (CV in

parentheses).

Fishery Years Vessels Data Type 1 Observer

Coverage 2 

Observed

Mortality

Estimated

Mortality 

Estimated

CVs 

Mean Annual

Mortality

USA

Northeast Sink

Gillnet

Before

TRP6

94-98

1993=349

1998=301

Obs. Data

Weighout, Trip

Logbook

.07, .05, .04,

.06, .05

 993

, 433, 523,

473

, 123

21003, 14003,

12003

, 7823,

3323

.18, .27, .25,

.22,

.46

1163

(0.11)

After

TRP6

99-00

NA Obs. Data,

Weighout,

Trip Logbook

.06, .06 143

,153 2703, 5073 .28, .37 388

(0.26)

mid-Atlantic

Coastal Gillnet

Before

TRP6

95-984

1998=3028

Obs. Data

Weighout

.05, .04, .03,

.05

6, 19, 

32, 53

103, 311,

572, 446

.57, .31,

.35, .36

358

(0.20)

After

TRP6

99-00

NA Obs. Data

Weighout

.02, .02 3, 1 53, 21 .49, .76 37

(0.41)

USA TOTAL 1999-2000 only 425

(0.24)

CANADA

Groundfish Sink

Gillnet 96-00

NA

(1994=28)

Obs. Data

Can. Trips

 .8, .8, .8,

NA7

, NA9

13, 19, 1, 3,

NA9

 20, 43, 10, 207,

109

NA 21

(NA)

Herring Weir

96-00

1998=255

licenses5

Coop. Data NA 2, 2, 2, 3, 0 2, 2, 2, 3, 0 NA 1.8

(NA)

CANADIAN

TOTAL

1996 - 2000 23

(NA)

GRAND TOTAL 448

(NA)

NA = Not available.

1 Observer data (Obs. Data) are used to measure bycatch rates; the USA data are collected by the Northeast

Fisheries Science Center (NEFSC) Sea Sampling Program, the Canadian data are collected by DFO.

NEFSC collects Weighout (Weighout) landings data, that are used as a measure of total effort for the USA

gillnet fisheries. The Canadian DFO catch and effort statistical system collected the total number of trips

fished by the Canadians (Can. trips), which was the measure of total effort for the Canadian groundfish

gillnet fishery. Mandatory trip logbook (VTR) (Trip Logbook) data are used to determine the spatial
121

distribution of fishing effort in the Northeast sink gillnet fishery. Observed mortalities from herring weirs

are collected by a cooperative program between fishermen and Canadian biologists (Coop. Data). 2 The observer coverage for the USA and Canadian sink gillnet fishery is measured in trips, and for the midAtlantic coastal gillnet fishery, the unit of effort is tons of fish landed. 3 Harbor porpoise taken before 1997 in observed pinger trips were added directly to the estimated total

bycatch for that year. During 1997, harbor porpoises were taken on non-pingered scientific experimental

strings within a time/area stratum that required pingers; during 1998, harbor porpoises were taken on a

pingered string within a stratum that did not require pingers; during 2000, a harbor porpoise was taken on a

non-pingered string within a stratum that did not require pingers but that stratum also had strings with

pingers; and during 1999-2000, harbor porpoises were taken on pingered strings within strata that required

pingers but that stratum also had observed strings without pingers. For estimates made during 1998 and

after, a weighted bycatch rate was applied to effort from both pingered and non-pingered hauls within the

above stratum. The weighted bycatch rate was:

# #

#

, porpoise

sslandings

hauls

total hauls

i

i

i

i

ping non ping

⋅

−

∑

There were 10, 33, 44, 0, 11, 0, 2, 8, and 6 observed harbor porpoise takes on pinger trips from 1992 to

2000, respectively, that are included in the observed mortality column. In addition, there were 9, 0, 2, 1,1,

and 4 observed harbor porpoise takes in 1995 to 2000, respectively, on trips dedicated to fish sampling

versus dedicated to watching for marine mammals; these are included in the observed mortality column

(Bisack 1997a). 4 Only data after 1994 are reported because the observed coverages during 1993 and 1994 were negligible

during the times of the year when harbor porpoise takes were possible. 5 There were 255 licenses for herring weirs in the Canadian Bay of Fundy region. 6

 Effective 01 January 1999, a take reduction plan (TRP) was put into place to reduce bycatch of harbor

porpoises in gillnets. See the section “USA Management Measures Taken to Reduce Bycatch” for more

details. 7 1999 Canadian gillnet bycatch estimates are not completed. In total, 179 strings (60 trips) were observed. 

Preliminary analyses indicate bycatch is likely not to exceed 20 animals. (Trippel, pers. comm.) 8 Sink gillnet vessels only. Number of drift gillnet vessels presently undetermined. 9 2000 Canadian gillnet bycatch estimate are not complete. Preliminary analyses indicate bycatch will not

exceed 10 animals (Trippel, pers. comm).

Table 3. From strandings and entanglement data, summary of confirmed incidental mortality of harbor porpoises

(Phocoena phocoena) by fishery: includes years sampled (Years), number of vessels active within the

fishery (Vessels), type of data used (Data Type), mortalities assigned to this fishery (Assigned Mortality),

and mean annual mortality.

Fishery Years Vessels Data Type 1 Assigned

Mortality

Mean Annual

Mortality

Unknown gillnet fishery 99-00 NA Entanglement

& Strandings

19, 1 10

TOTAL 10

NA=Not Available.

1

 Data from records in the entanglement and strandings data base maintained by the New England Aquarium

and the Northeast Regional Office/NMFS (Entanglement and Strandings).

Other Mortality

USA

There is evidence that harbor porpoises were harvested by natives in Maine and Canada before the 1960's,

and the meat was used for human consumption, oil, and fish bait (NEFSC 1992). The extent of these past harvests is
122

unknown, though it is believed to have been small. Up until the early 1980's, small kills by native hunters

(Passamaquoddy Indians) were reported. In recent years it was believed to have nearly stopped (Polacheck 1989)

until recent public media reports in September 1997 depicted a Passamaquoddy tribe member dressing out a harbor

porpoise. Further articles describing use of porpoise products for food and other purposes were timed to coincide

with ongoing legal action in state court.

During 1993, 73 harbor porpoises were reported stranded on beaches from Maine to North Carolina (Table

4; Smithsonian Marine Mammal Database ). Sixty-three of those harbor porpoises were reported stranded in the

USA mid-Atlantic region from New York to North Carolina between February and May. Many of the mid-Atlantic

carcasses recovered in this area during this time period had cuts and body damage suggestive of net marking (Haley

and Read 1993). Five out of 8 carcasses and 15 heads from the strandings that were examined showed signs of

human interactions (net markings on skin and missing flippers or flukes). Decomposition of the remaining animals

prevented determination of the cause of death. Earlier reports of harbor porpoise entangled in gillnets in Chesapeake

Bay and along the New Jersey coast and reports of apparent mutilation of harbor porpoise carcasses, raised concern

that the 1993 strandings were related to a coastal net fishery, such as the American shad coastal gillnet fishery

(Haley and Read 1993). Between 1994 and 1996, 107 harbor porpoise carcasses were recovered from beaches in

Maryland, Virginia, and North Carolina and investigated by scientists. Only juvenile harbor porpoises were present

in this sample. Of the 40 harbor porpoises for which cause of death could be established, 25 displayed definitive

evidence of entanglement in fishing gear. In 4 cases it was possible to determine that the animal was entangled in

monofilament nets (Cox et al. 1998).

Records of harbor porpoise strandings prior to 1997 are stored in the Smithsonian’s Marine Mammal

Database and records from 1997 to present are stored in the NE Regional Office/NMFS strandings and

entanglement database. According to these records, the number of harbor porpoises that stranded on beaches from

North Carolina to Maine during 1994 to 2000 were 106, 86, 94, 118, 59, 228, and 26, respectively (Table 4). Of

these, 3 stranded alive on a Massachusetts beach in 1996, were tagged, and subsequently released. In 1998, 2

porpoises that stranded on a New Jersey beach had tags on them indicating they were originally taken on an

observed mid-Atlantic coastal gill net vessel. During 1999, 6 animals stranded alive and were either tagged and

released or brought to Mystic Aquarium for rehabilitation (Table 4). 

During 1999, over half of the strandings occurred on beaches of Massachusetts and North Carolina. The

states with the next largest numbers were Virginia, New Jersey, and Maryland, in that order. The cause of death was

investigated for all the 1999 strandings (Table 5). Of these, it was possible to determine that the cause of death of 36

animals was fishery interactions. Of these 36, 19 animals were in an area and time that were not part of a bycatch

estimate derived using observer data. Thus, these 19 mortalities are attributed to an unknown gillnet fishery (Table

3). One additional animal was mutilated (right flipper and fluke was cut off). This animal was attributed to an

unknown human-caused mortality.

During 2000, only 26 harbor porpoises stranded on beaches from Maine to North Carolina (Table 4). Of

these most came from Massachusetts (8) or North Carolina (6). The cause of death for 1 animal was in an area and

time that was not part of a bycatch estimate derived from observer data, and thus was attributed to an unknown

gillnet fishery (Tables 3 and 5). This animal was found on a beach in Virginia during May with mono-filament line

wrapped around it. In addition, 1 animal was found mutilated and so was attributed to an unknown human-caused

mortality (Table 5).

Averaging 1999 to 2000, there was 1 animal per year that was stranded and mutilated and so attributed to

an unknown human-caused mortality (Table 5).

Stranding data probably underestimate the extent of fishery-related mortality and serious injury because all

of the marine mammals which die or are seriously injured may not wash ashore, nor will all of those that do wash

ashore necessarily show signs of entanglement or other fishery-interaction. Finally, the level of technical expertise

among stranding network personnel varies widely as does the ability to recognize signs of fishery interaction.
123

Table 4. Summary of number of stranded harbor porpoises during January 1, 1994 to December 31, 1999, by state

and year.

State Year Total

1994 1995 1996 1997 1998 1999 2000

Maine 0 0 5 6 5 3 1 20

New Hampshire 0 0 2 0 0 0 0 2

Massachusetts1,3 9 26 31 28 18 60 8 180

Rhode Island 3 0 1 1 0 3 0 8

Connecticut 0 0 1 0 0 0 0 1

New York4 7 6 3 10 5 10 2 43

New Jersey2 17 18 12 21 16 23 2 109

Delaware 3 5 4 4 7 9 1 33

Maryland 10 4 3 10 1 21 3 52

Virginia 42 18 20 12 3 40 3 138

North Carolina 15 9 12 26 4 59 6 131

TOTAL 106 86 94 118 59 228 26 717

1 During 1996 three animals stranded alive on a Massachusetts beach. They were tagged and released. 2 Two of the porpoises that stranded on a New Jersey beach in 1998 had been previously tagged and released

from an observed mid-Atlantic coastal gill net fishing vessel. 3 Five animals stranded alive in 1999 and were tagged and released. 4 One animal stranded alive in 1999, rehabilitated at Mystic Aquarium and died at the aquarium in April

2000.

Table 5. Cause of mortality of USA stranded harbor porpoises during January 1, 1999 to December 31, 1999.

“Unique FI” is a fishery interaction that is in a time and area that could not be part of the mortality estimate

derived from the observer program. “Not unique FI” is a fishery interaction that was in a time and area that

may be part of the observer program derived mortality estimate. “No FI” is the cause of death was

determined not to be related to a fishery interaction. “Alive” is stranded animal not dead. “CBD/Unk” is

could not be determined or unknown cause of death.

Year Unique FI1 Mutilation2 Not unique FI No FI Emaciated CBD/Unk Alive Total

1999 19 1 19 41 30 112 6 228

2000 1 1 0 2 0 22 0 26

Avg

99-00

10 1 9.5 21 15 67 3 127

1 Attributed to an unknown gillnet fishery. 2 Attributed to an unknown human-caused mortality.
124

CANADA

Whales and dolphins stranded between 1991 and 1996 on the coast of Nova Scotia were documented by the

Nova Scotia Stranding Network (Hooker et al. 1997). Strandings on the beaches of Sable Island during 1970 to

1998 were documented by researchers with Dept. of Fisheries and Oceans, Canada (Lucas and Hooker 2000). Sable

Island is approximately 170 km southeast of mainland Nova Scotia. On the mainland of Nova Scotia, a total of 8

stranded harbor porpoises were recorded between 1991 and 1996, 1 in May 1991, 2 in 1993 (July and September), 1

in August 1994 was released alive, 1 in August 1994, and 3 in 1996 (March, April, and July (released alive)). On

Sable Island, 8 stranded dead harbor porpoises were documented, most in January and February; 1 in May 1991, 1 in

January 1992, 1 in January 1993, 3 in February 1997, 1 in May 1997, and 1 in June 1997. Two strandings during

May-June 1997 were neonates (> 80 cm). The harbor porpoises that stranded in the winter (January-February) were

on Sable Island, those in the spring (March to June) were in the Bay of Fundy (2 in Minas Basin and 1 near

Yarmouth) and on Sable Island (2), and those in the summer (July to September) were scattered along the coast from

the Bay of Fundy to Halifax.

USA Management Measures Taken to Reduce Bycatch

A ruling to reduce harbor porpoise bycatch in USA Atlantic gill nets was published in the Federal Register

(63 FR 66464) on 01 December 1998 and became effective 01 January 1999. The Gulf of Maine portion of the plan

pertains to all fishing with sink gillnets and other gillnets capable of catching multispecies in New England waters,

from Maine through Rhode Island. This portion of the rule includes time and area closures, some of which are

complete closures; others are closed to multispecies gillnet fishing unless pingers are used in the prescribed manner. 

Also the rule requires those who intend to fish using pingers must attend training and certification sessions on the

use of the technology. The mid-Atlantic portion of the plan pertains to waters west of 72° 30' W longitude to the

mid-Atlantic shore line from New York to North Carolina. This portion of the rule includes time and area closures,

some of which are complete closures; others are closed to gillnet fishing unless the gear meets certain specifications.

STATUS OF STOCK

The status of harbor porpoises, relative to OSP, in the US Atlantic EEZ is unknown. On January 7, 1993,

the National Marine Fisheries Service (NMFS) proposed listing the Gulf of Maine harbor porpoise as threatened

under the Endangered Species Act (NMFS 1993). On January 5, 1999, NMFS determined the proposed listing was

not warranted (NMFS 1999). On August 2, 2001, NMFS made available a review of the biological status of the Gulf

of Maine/Bay of Fundy harbor porpoise population. The determination was made that listing to the Endangered

Species Act (ESA) was not warranted and this stock was removed from the ESA candidate species list (50 CFR Part

233). There are insufficient data to determine population trends for this species. The total fishery-related mortality

and serious injury for this stock is not less than 10% of the calculated PBR and, therefore, cannot be considered to be

insignificant and approaching zero mortality and serious injury rate. This is not a strategic stock because average

annual fishery-related mortality and serious injury has not exceeded PBR for the last two years.

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128

Figure 1. Distribution of pilot whale sightings from

NEFSC and SEFSC shipboard and aerial surveys during

the summer in 1990-1998. Isobaths are at 100 m and

1,000 m.

 January 2002

LONG-FINNED PILOT WHALE (Globicephala melas):

Western North Atlantic Stock

STOCK DEFINITION AND GEOGRAPHIC RANGE

There are two species of pilot whales in the Western Atlantic — the Atlantic or long-finned pilot whale,

Globicephala melas, and the short-finned pilot whale, G. macrorhynchus. These species are difficult to identify to

the species level at sea; therefore, some of the descriptive material below refers to Globicephala sp., and is identified

as such. The species boundary is considered to be in the New Jersey to Cape Hatteras area. Sightings north of this

area are likely G. melas. 

Pilot whales (Globicephala sp.) are distributed principally along the continental shelf edge in the winter and

early spring off the northeast USA coast, (CETAP 1982; Payne and Heinemann 1993). In late spring, pilot whales

move onto Georges Bank and into the Gulf of Maine and more northern waters, and remain in these areas through

late autumn (CETAP 1982; Payne and Heinemann 1993). In general, pilot whales occupy areas of high relief or

submerged banks. They are also associated with the Gulf Stream north wall and thermal fronts along the continental

shelf edge (Waring et al. 1992; NMFS unpublished data). 

The long-finned pilot whale is distributed from North Carolina to North Africa (and the Mediterranean) and

north to Iceland, Greenland and the Barents Sea (Sergeant 1962; Leatherwood et al. 1976; Abend 1993; Buckland et

al. 1993). The stock structure of the North Atlantic population is uncertain (Anon. 1993a; Fullard et al. 2000). 

Recent morphometrics (Bloch and Lastein 1993) and

genetics (Siemann 1994; Fullard et al. 2000) studies

have provided little support for stock structure across

the Atlantic (Fullard et al. 2000). However, Fullard et

al. (2000) have proposed a stock structure that is

correlated to sea surface temperature: 1) a cold-water

population west of the Labrador/North Atlantic

current and 2) a warm-water population that extends

across the Atlantic in the Gulf Stream. 

POPULATION SIZE

The total number of long-finned pilot whales

off the eastern USA and Canadian Atlantic coast is

unknown, although ten estimates from selected

regions of the habitat do exist for select time periods. 

Sightings were almost exclusively in the continental

shelf edge and continental slope areas (Figure 1). Two

estimates were derived from catch data and

population models that estimated the abundance of the

entire stock. Seven seasonal estimates are available

from selected regions in USA waters during spring,

summer and autumn 1978-82, August 1990, June-July

1991, August-September 1991, June-July 1993, JulySeptember 1995, and July-August 1998. Because

long-finned and short-finned pilot whales are difficult

to identify at sea, seasonal abundance estimates were

reported for Globicephala sp., both long-finned and

short-finned pilot whales. One estimate is available

from the Gulf of St. Lawrence.

Mitchell (1974) used cumulative catch data

from the 1951-61 drive fishery off Newfoundland to

estimate the initial population size (ca. 50,000

animals).
129

Mercer (1975), used population models to estimate a population in the same region of between 43,000-

96,000 long-finned pilot whales, with a range of 50,000-60,000 being considered the best estimate. 

An abundance of 11,120 (CV=0.29) Globicephala sp. was estimated from an aerial survey program

conducted from 1978 to 1982 on the continental shelf and shelf edge waters between Cape Hatteras, North Carolina

and Nova Scotia (CETAP 1982). An abundance of 3,636 (CV=0.36) Globicephala sp. was estimated from a June

and July 1991 shipboard line transect sighting survey conducted primarily between the 200 and 2,000 m isobaths

from Cape Hatteras to Georges Bank (Waring et al. 1992; Waring 1998). An abundance of 3,368 (CV=0.28) and

5,377 (CV=0.53) Globicephala sp. was estimated from line transect aerial surveys conducted from August to

September 1991 using the Twin Otter and AT-11, respectively (Anon. 1991). As recommended in the GAMS

Workshop Report (Wade and Angliss 1997), estimates older than eight years are deemed unreliable, and therefore

should not be used for PBR determinations. Further, due to changes in survey methodology, these data should not

be used to make comparisons to more current estimates. 

 An abundance of 668 (CV=0.55) Globicephala sp. was estimated from a June and July 1993 shipboard line

transect sighting survey conducted principally between the 200 and 2,000 m isobaths from the southern edge of

Georges Bank, across the Northeast Channel to the southeastern edge of the Scotian Shelf (Anon. 1993b). Data

were collected by two alternating teams that searched with 25x150 binoculars and were analyzed using DISTANCE

(Buckland et al. 1993; Laake et al. 1993). Estimates include school-size bias, if applicable, but do not include

corrections for g(0) or dive-time. Variability was estimated using bootstrap resampling techniques.

An abundance of 8,176 (CV=0.65) Globicephala sp. was estimated from a July to September 1995 sighting

survey conducted by two ships and an airplane that covered waters from Virginia to the mouth of the Gulf of St.

Lawrence (Table 1; Palka et al. in review). Total track line length was 32,600 km. The ships covered waters

between the 50 and 1000 fathom depth contour lines, the northern edge of the Gulf Stream, and the northern Gulf of

Maine/Bay of Fundy region. The airplane covered waters in the mid-Atlantic from the coastline to the 50 fathom

depth contour line, the southern Gulf of Maine, and shelf waters off Nova Scotia from the coastline to the 1000

fathom depth contour line. Data collection and analysis methods used were described in Palka (1996). 

Kingsley and Reeves (1998) obtained an abundance estimate of 1,600 long-finned pilot whales (CV=0.65)

from a late August and early September aerial survey of cetaceans in the Gulf of St. Lawrence in 1995 and 1998

(Table 1). Based on an examination of long-finned pilot whale summer distribution patterns and information on

stock structure, it was deemed appropriate to combine these estimates with NMFS 1995 summer survey data. The

best 1995 abundance estimate for Globicephala sp. is 9,776 (CV=0.55), the sum of the estimates from the USA and

Canadian surveys, where the estimate from the USA survey is 8,176 (CV=0.65) and from the Canadian 1,600

(CV=0.65). 

An abundance of 9,800 (CV=0.34) Globicephala sp. was estimated from a line transect sighting survey

conducted during July 6 to September 6, 1998 by a ship and plane that surveyed 15,900 km of track line in waters

north of Maryland (38° N) (Figure 1; Palka et al. in review). Shipboard data were analyzed using the modified

direct duplicate method (Palka 1995) that accounts for school size bias and g(0), the probability of detecting a group

on the track line. Aerial data were not corrected for g(0).

An abundance of 4,724 (CV=0.61) Globicephala sp. was estimated from a shipboard line transect sighting

survey conducted between 8 July and 17 August 1998 that surveyed 5,570 km of track line in waters south of

Maryland (38°N) (Figure 1; Mullin in review). Abundance estimates were made using the program DISTANCE

(Buckland et al. 1993; Laake et al. 1993) where school size bias and ship attraction were accounted for.

The best available abundance estimate for Globicephala sp. is 14,524 (CV=0.30), the sum of the estimates

from the two 1998 USA Atlantic surveys, where the estimate from the northern USA Atlantic is 9,800 (CV=0.34)

and from the southern USA Atlantic is 4,724 (CV=0.61). This joint estimate is considered best because together

these two surveys have the most complete coverage of the species’ habitat.
130

Table 1. Summary of abundance estimates for the western North Atlantic Globicephala sp. Month, year, and area

covered during each abundance survey, and resulting abundance estimate (Nbest) and coefficient of variation

(CV).

Month/Year Area Nbest CV

Jul-Sep 1995 Virginia to Gulf of St. Lawrence 8,176 0.65

Aug-Sep 1995 Gulf of St. Lawrence 1,600 0.65

Jul-Sep 1995 Virginia to Gulf of St. Lawrence 9,776 0.55

Jul-Sep 1998 Maryland to Gulf of St. Lawrence 9,800 0.34

Jul-Aug 1998 Florida to Maryland 4,724 0.61

Jul-Sep 1998 Gulf of St. Lawrence to Florida (COMBINED) 14,524 0.30

Minimum Population Estimate

The minimum population estimate is the lower limit of the two-tailed 60% confidence interval of the lognormally distributed best abundance estimate. This is equivalent to the 20th percentile of the log-normal distribution

as specified by Wade and Angliss (1997). The best estimate of abundance for Globicephala sp. is 14,524

(CV=0.30). The minimum population estimate for Globicephala sp. is 11,343 (CV=0.30).

Current Population Trend

There are insufficient data to determine the population trends for this species. 

CURRENT AND MAXIMUM NET PRODUCTIVITY RATES

Current and maximum net productivity rates are unknown for this stock. Life history parameters that could

be used to estimate net productivity include those from animals taken in the Newfoundland drive fishery: calving

interval 3.3 years; lactation period about 21-22 months; gestation period 12 months; births mainly from June to

November; length at birth is 177 cm; mean length at sexual maturity is 490 cm for males and 356 cm for females;

age at sexual maturity is 12 years for males and 6 years for females; mean adult length is 557 cm for males and 448

cm for females; and maximum age was 40 for males and 50 for females (Sergeant 1962; Kasuya et al. 1988). 

Analysis of data recently collected from animals taken in the Faroe Islands drive fishery produced higher values for

all parameters (Bloch et al. 1993; Desportes et al. 1993; Martin and Rothery 1993). These differences are likely

related, at least in part, to larger sample sizes and newer analytical techniques. 

For purposes of this assessment, the maximum net productivity rate was assumed to be 0.04. This value is

based on theoretical modeling showing that cetacean populations may not grow at rates much greater than 4% given

the constraints of their reproductive life history (Barlow et al. 1995). 

POTENTIAL BIOLOGICAL REMOVAL

Potential Biological Removal (PBR) is the product of minimum population size, one-half the maximum

productivity rate, and a “recovery” factor (MMPA Sec. 3. 16 U.S.C. 1362; Wade and Angliss 1997). The minimum

population size for Globicephala sp. is 11,343 (CV=0.30). The maximum productivity rate is 0.04, the default value

for cetaceans. The “recovery” factor, which accounts for endangered, depleted, threatened stocks, or stocks of

unknown status relative to optimum sustainable population (OSP) is assumed to be 0.48 because the CV of the

average mortality estimate is between 0.3-0.6 (Wade and Angliss 1997) and because this stock is of unknown status. 

PBR for the western North Atlantic Globicephala sp. is 108.

ANNUAL HUMAN-CAUSED MORTALITY

Total fishery-related mortality and serious injury cannot be estimated separately for the two species of pilot

whales in the US Atlantic EEZ because of the uncertainty in species identification by fishery observers. The

Atlantic Scientific Review Group advised adopting the risk-averse strategy of assuming that either species might

have been
131

subject to the observed fishery-related mortality and serious injury. Total annual estimated average fishery-related

mortality or serious injury to this stock during 1996-2000 in the USA fisheries listed below was 193 pilot whales

(CV=0.43) (Table 2). The Canadian mortality estimate for 1996 from the Nova Scotia trawl fisheries is 6 longfinned pilot whales. It is not possible to estimate variance of the Canadian estimate. The total average annual

mortality estimate for 1996-2000 from the USA and Nova Scotia trawl fisheries is 199 (CV=0.43) (Table 2).

Fishery Information

USA

Prior to 1977, there was no documentation of marine mammal bycatch in distant-water fleet (DWF)

activities off the northeast coast of the USA. A fishery observer program, which has collected fishery data and

information on incidental bycatch of marine mammals, was established in 1977 with the implementation of the

Magnuson Fisheries Conservation and Management Act (MFCMA). DWF effort in the US Atlantic EEZ under

MFCMA has been directed primarily towards Atlantic mackerel and squid. An average of 120 different foreign

vessels per year (range 102-161) operated within the US Atlantic EEZ during 1977 through 1982. In 1982, there

were 112 different foreign vessels; 18 (16%) were Japanese tuna longline vessels operating along the USA Atlantic

coast. This was the first year that the Northeast Regional Observer Program assumed responsibility for observer

coverage of the longline vessels. The number of foreign vessels operating within the US Atlantic EEZ each year

between 1983 and 1991 averaged 33 and ranged from 9 to 67. The number of Japanese longline vessels included

among the DWF vessels averaged 6 and ranged from 3 to 8 between 1983 and 1988. MFCMA observer coverage on

DWF vessels was 25-35% during 1977-1982, increased to 58%, 86%, 95%, and 98%, respectively, during 1983-

1986, and 100% observer coverage was maintained from 1987-1991. Foreign fishing operations for squid ceased at

the end of the 1986 fishing season and, for mackerel, at the end of the 1991 fishing season. 

During 1977-1991, observers in this program recorded 436 pilot whale mortalities in foreign-fishing

activities (Waring et al. 1990; Waring 1995). A total of 391 (90%) were taken in the mackerel fishery, and 41 (9%)

occurred during Loligo and Illex squid-fishing operations. This total includes 48 documented takes by USA vessels

involved in joint venture fishing operations in which USA captains transfer their catches to foreign processing

vessels. Due to temporal fishing restrictions, the bycatch occurred during winter/spring (December to May) in

continental shelf and continental shelf edge waters (Fairfield et al. 1993; Waring 1995); however, the majority of the

takes occurred in late spring along the 100 m isobath. Two animals were also caught in both the hake fishery and

tuna longline fisheries (Waring et al. 1990). 

The distribution of long-finned pilot whales, a northern species, overlaps with that of the short-finned pilot

whales, a predominantly southern species, between 35°30'N to 38°00'N (Leatherwood et al. 1976). Although longfinned pilot whales are most likely taken in the waters north of Delaware Bay, many of the pilot whale takes are not

identified to species and bycatch does occur in the overlap area. In this summary, therefore, long-finned pilot whales

(Globicephala melas) and unidentified pilot whales (Globicephala sp.) are considered together. 

Data on current incidental takes in USA fisheries are available from several sources. In 1986, NMFS

established a mandatory self-reported fisheries information system for large pelagic fisheries. Data files are

maintained at the Southeast Fisheries Science Center (SEFSC). The Northeast Fisheries Science Center (NEFSC)

Sea Sampling Observer Program was initiated in 1989, and since that year several fisheries have been covered by the

program. In late 1992 and in 1993, the SEFSC provided observer coverage of pelagic longline vessels fishing off the

Grand Banks (Tail of the Banks) and provides observer coverage of vessels fishing south of Cape Hatteras.

Bycatch has been observed by NMFS Sea Samplers in the pelagic drift gillnet, pelagic longline, pelagic pair

trawl, bluefin tuna purse seine, North Atlantic bottom trawl, Atlantic squid, mackerel, butterfish trawl, and MidAtlantic coastal gillnet fisheries, but no mortalities or serious injuries have been documented in the Northeast

multispecies sink gillnet fisheries.

Pelagic Drift Gillnet

The estimated total number of hauls in the pelagic drift gillnet fishery increased from 714 in 1989 to 1,144

in 1990; thereafter, with the introduction of quotas, effort was severely reduced. The estimated number of hauls in

1991, 1992, 1993, 1994, 1995, 1996, and 1998 were 233, 243, 232, 197, 164, 149, and 113 respectively. In 1996

and 1997, NMFS issued management regulations which prohibited the operation of this fishery in 1997. Further, in

January 1999 NMFS issued a Final Rule to prohibit the use of driftnets (i.e., permanent closure) in the North 

Atlantic swordfish fishery (50 CFR Part 630). Fifty-nine different vessels participated in this fishery at one time or

another between 1989 and 1993. From 1994 to 1998, between 10 and 13 vessels participated in the fishery. 
132

Observer coverage, expressed as percent of sets observed, was 8% in 1989, 6% in 1990, 20% in 1991, 40% in 1992,

42% in 1993, 87% in 1994, 99% in 1995, 64% in 1996, no fishery in 1997, and 99% in 1998. Effort was

concentrated along the southern edge of Georges Bank and off Cape Hatteras. Examination of the species

composition of the catch and locations of the fishery throughout the year, suggested that the pelagic drift gillnet

fishery be stratified into two strata, a southern or winter stratum, and a northern or summer stratum. Estimates of the

total bycatch from 1989 to 1993, were obtained using the aggregated (pooled 1989-1993) catch rates, by strata

(Northridge 1996). Estimates of total annual bycatch for 1994 and 1995 were estimated from the sum of the

observed caught and the product of the average bycatch per haul and the number of unobserved hauls as recorded in

self-reported fisheries information. Variances were estimated using bootstrap re-sampling techniques. Between

1989 and 1998, 87 mortalities were observed in the large pelagic drift gillnet fishery. The annual fishery-related

mortality (CV in parentheses) was 77 in 1989 (0.24), 132 in 1990 (0.24), 30 in 1991 (0.26), 33 in 1992 (0.16), 31 in

1993 (0.19), 20 in 1994 (0.06), 9.1 in 1995 (0), 11 in 1996 (.17), no fishery in 1997, and 12 in 1998 (0). Since this

fishery no longer exists it has been excluded from Table 2. Pilot whales were taken along the continental shelf edge,

northeast of Cape Hatteras in January and February. Takes were recorded at the continental shelf edge east of Cape

Charles, Virginia, in June. Pilot whales were taken from Hydrographer Canyon along the Great South Channel to

Georges Bank from July-November. Takes occurred at the Oceanographer Canyon continental shelf break and along

the continental shelf northeast of Cape Hatteras in October-November.

Pelagic Pair Trawl

Effort in the pelagic pair trawl fishery increased during the period 1989 to 1993, from zero hauls in 1989

and 1990, to an estimated 171 hauls in 1991, and then to an estimated 536 hauls in 1992, 586 in 1993, 407 in 1994,

and 440 in 1995. This fishery ceased operations in 1996 when NMFS rejected a petition to consider pair trawl gear

as an authorized gear type in Atlantic tunas fishery. The fishery operated from August-November in 1991, from

June-November in 1992, from June-October in 1993, and from mid-summer to November in 1994 and 1995. Sea

sampling began in October 1992 (Gerrior et al. 1994), and 48 sets (9% of the total) were sampled in that season, 102

hauls (17% of the total) were sampled in 1993. In 1994 and 1995, 212 (52%) and 238 (54%), respectively, of the

sets were observed. Twelve vessels have operated in this fishery. The fishery extends from 35o

N to 41oN, and from

69°W to 72°W. Approximately 50% of the total effort was within a one degree square at 39o

N, 72oW, around

Hudson Canyon. Examination of the 1991-1993 locations and species composition of the bycatch, showed little

seasonal change for the six months of operation and did not warrant any seasonal or areal stratification of this fishery

(Northridge 1996). Five pilot whale (Globicephala sp.) mortalities were reported in the self-reported fisheries

information in 1993. In 1994 and 1995 observers reported 1 and 12 mortalities, respectively. The estimated fisheryrelated mortality to pilot whales in the USA Atlantic attributable to this fishery in 1994 was 2.0 (CV=0.49) and 22

(CV=0.33) in 1995. Since this fishery no longer exists, it has been excluded from Table 2.

During the 1994 and 1995 experimental fishing seasons, fishing gear experiments were conducted to collect

data on environmental parameters, gear behavior, and gear handling practices to evaluate factors affecting catch and

bycatch (Goudey 1995, 1996). Results of these studies were inconclusive in identifying factors responsible for

marine mammal bycatch.

Pelagic Longline

Total effort, excluding the Gulf of Mexico, for the pelagic longline fishery, based on mandatory selfreported fisheries information, was 11,279 sets in 1991, 10,311 sets in 1992, 10,444 sets in 1993, 11,082 sets in

1994, 11,493 sets in 1995, 9,864 sets in 1996, 9,499 sets in 1997, 7,589 sets in 1998, 6,786 sets in 1999, and 6,582

sets in 2000 (Cramer 1994; Scott and Brown 1997; Johnson et al. 1999; Yeung 1999a; Yeung et al. 2000). This

annual effort has been recalculated to include those sets targeting other species in conjunction with tuna/swordfish,

instead of just effort that exclusively targeted tuna/swordfish as in previous reports (Johnson et al. 1999; Yeung

1999a). The result is an average increase in self-reported effort of roughly 10% on the average (Yeung et al. 2000). 

The fishery has been observed from January to March off Cape Hatteras, in May and June in the entire mid-Atlantic,

and in July through December in the mid-Atlantic Bight and off Nova Scotia. This fishery has been monitored with

3-6% observer coverage, in terms of sets observed, since 1992. The 1993-1997 estimated take was based on a

revised analysis of the observed incidental take and self-reported incidental take and effort data, and replace

previous estimates for the 1990-1993 and 1994-1995 periods (Cramer 1994; Scott and Brown 1997; Johnson et al.

1999). Further, Yeung (1999b), revised the 1992-1997 fishery mortality estimates in Johnson et al. (1999) to include

seriously injured animals. The 1998 and 1999 bycatch estimates were from Yeung (1999a) and Yeung et al. (2000),

respectively. Most of the estimated marine mammal bycatch was from US Atlantic EEZ waters between
133

South Carolina and Cape Cod (Johnson et al. 1999). Pilot whales are frequently observed to feed on hooked fish,

particularly big-eye tuna (NMFS unpublished data). Between 1992-2000, 62 pilot whales (including 2 identified as

a short-finned pilot whales) were released alive, including 32 that were considered seriously injured (of which 1 was

identified as a short-finned pilot whale), and 2 mortalities were observed. January-March bycatch was concentrated

on the continental shelf edge northeast of Cape Hatteras. Bycatch was recorded in this area during April-June, and

takes also occurred north of Hydrographer Canyon off the continental shelf in water over 1,000 fathoms during

April-June. During the July-September period, takes occurred on the continental shelf edge east of Cape Charles,

Virginia, and on Block Canyon slope in over 1,000 fathoms of water. October-December bycatch occurred along

the 20 to 50 fathom contour lines between Barnegatt Bay and Cape Hatteras. The estimated fishery-related mortality

to pilot whales in the USA Atlantic (excluding the Gulf of Mexico) attributable to this fishery was: 127 in 1992

(CV=1.00), 93 in 1999 (CV=1.00), and 24 in 2000 (CV=1.0). The estimated serious injuries were 40 (CV=0.71) in

1992, 19 (CV=1.00) in 1993, 232 (CV=0.53) in 1994, 345 (CV= 0.51) in 1995, 0 from 1996 to 1998, 288 (CV=0.74)

in 1999, and 109 (CV=1.0) in 2000 (includes 37 estimated short-finned pilot whales in 1995 (CV=1.00)); average

annual mortality between 1996-2000 was 103 pilot whales (CV=0.63) (Table 2). Seriously injured and released

alive animals are combined with mortalities in the category ‘combined mortality’. 

Bluefin Tuna Purse Seine

The tuna purse seine fishery between Cape Hatteras and Cape Cod is directed at small and medium bluefin

and skip jack for the canning industry, while north of Cape Cod, purse seine vessels are directed at large medium

and giant bluefin tuna (NMFS 1995). The latter fishery is entirely separate from any other Atlantic tuna purse seine

fishery. Spotter aircraft are used to locate fish schools. The official start date is August 15, set by regulation. 

Individual vessel quotas (IVQs) and a limited access system prevent a derby fishery situation. Catch rates are high

with this gear and consequently the season usually only lasts a few weeks for large mediums and giants. The 1996

regulations allocated 250 MT (5 IVQs) with a minimum of 90% giants and 10% large mediums. Limited observer

data are available for the bluefin tuna purse seine fishery. Out of 45 total trips made in 1996, 43 trips (95.6%) were

observed. Forty-four sets were made on the 43 observed trips and all sets were observed. A total of 136 days were

covered. Two interactions with pilot whales were observed in 1996. In one interaction, the net was actually pursed

around one pilot whale, the rings were released and the animal escaped alive, condition unknown. This set occurred

east of the Great South Channel and just north of the Cultivator Shoals region on Georges Bank. In a second

interaction, 5 pilot whales were encircled in a set. The net was opened prior to pursing to let the whales swim free,

apparently uninjured. This set occurred on the Cultivator Shoals region on Georges Bank. Since 1996, this fishery

has not been observed. 

North Atlantic Bottom Trawl 

Vessels in the North Atlantic bottom trawl fishery, a Category III fishery under the MMPA, were observed

in order to meet fishery management needs, rather than marine mammal management needs. An average of 970

(CV=0.04) vessels (full and part time) participated annually in the fishery during 1989-1993. The fishery is active in

New England in all seasons. One mortality was documented in 1990, and 1 animal was released alive and uninjured

in 1993. The estimated fishery-related mortality to pilot whales in the USA Atlantic attributable to this fishery was: 

0 in 1994-1998, 228 in 1999, and 0 in 2000. The average annual mortality between 1996-2000 was 46 pilot whales

(CV=1.03) (Table 2). However, these estimates should be viewed with caution due to the extremely low (<1%)

observer coverage. 

Atlantic Squid, Mackerel, Butterfish Trawl

The mid-Atlantic mackerel and squid trawl fisheries were combined into the Atlantic mid-water trawl

fishery in the revised proposed list of fisheries in 1995. The fishery occurs along the USA mid-Atlantic continental

shelf region between New Brunswick, Canada, and Cape Hatteras year around. The mackerel trawl fishery was

classified as a Category II fishery since 1990 and the squid fishery was originally classified as a Category II fishery

in 1990, but was reclassified as a Category III fishery in 1992. The combined fishery was then reclassified as a

Category II fishery in 1995. In 1996, mackerel, squid, and butterfish trawl fisheries were combined into the Atlantic

squid, mackerel, butterfish trawl fishery, and maintained a Category II classification. Three fishery-related

mortalities of pilot whales were reported in self-reported fisheries information from the mackerel trawl fishery

between 1990-1992. Six mortalities were observed in 1996, 1 in years 1998, 1999, and 2 in 2000. The 1996, 1998

and 2000 bycatch occurred in the Illex squid fishery, and the 1999 in the Loligo fishery. The estimated fisheryrelated mortality of pilot whales in the USA Atlantic attributable to this fishery was: 45 in 1996 (CV=1.27), 0 in

1997, 85 in 1998 (CV=0.65), 49 in 1999 (CV=0.97), and 34 in 2000 (CV=0.65); average annual mortality between
134

1996 and 2000 was 43 pilot whales (CV=0.45) (Table 2). However, these estimates should be viewed with caution

due to the extremely low (<1%) observer coverage.

Mid-Atlantic Coastal Gillnet

Observer coverage of the USA Atlantic coastal gillnet fishery was initiated by the NEFSC Sea Sampling

program in July 1993 and from July to December 1993, 20 trips were observed. During 1994 and 1995, 221 and 382

trips were observed, respectively. This fishery, which extends from North Carolina to New York, is actually a

combination of small vessel fisheries that target a variety of fish species, some of which operate right off the beach. 

The number of vessels in this fishery is unknown, because records which are held by both state and federal agencies

have not been centralized and standardized. Observer coverage, expressed as percent of tons of fish landed, was 5%, 

4%, 3%, 5%, 2%, and 2% for 1995, 1996, 1997, 1998, 1999, and 2000, respectively (Table 2).

No pilot whales were taken in observed trips during 1993-1997. One pilot whale was observed taken in

1998, 0 in 1999 and 2000 (Table 2). Observed effort was concentrated off NJ and scattered between DE and NC

from 1 to 50 miles off the beach. All bycatches were documented during January to April. Using the observed

takes, the estimated annual mortality (CV in parentheses) attributed to this fishery was 7 in 1998 (1.1). Average

annual estimated fishery-related mortality attributable to this fishery during1996-2000 was 1 pilot whale (CV=1.1)

CANADA

An unknown number of pilot whales have also been taken in Newfoundland and Labrador, and Bay of

Fundy, groundfish gillnets, Atlantic Canada and Greenland salmon gillnets, and Atlantic Canada cod traps (Read

1994). The Atlantic Canadian and Greenland salmon gillnet fishery is seasonal, with the peak from June to

September, depending on location. During 1989, in southern and eastern Newfoundland and in Labrador, 2,196 nets

91 m long were used. There are no effort data available for the Greenland fishery; however, the fishery was

terminated in 1993 under an agreement between Canada and North Atlantic Salmon Fund (Read 1994). 

There were 3,121 cod traps operating in Newfoundland and Labrador during 1979, and about 7,500 in 1980

(Read 1994). This fishery was closed at the end of 1993 due to collapse of Canadian groundfish resources. 

Between January 1993 and December 1994, 36 Spanish deep-water trawlers, covering 74 fishing trips

(4,726 fishing days and 14,211 sets), were observed in NAFO Fishing Area 3 (off the Grand Bank) (Lens 1997). A

total of 47 incidental catches were recorded, which included 1 long-finned pilot whale. The incidental mortality rate

for pilot whales was 0.007/set.

In Canada, the fisheries observer program places observers on all foreign fishing vessels, on between 25%-

40% of large Canadian vessels (greater than 100 ft), and on approximately 5% of small vessels (Hooker et al. 1997). 

Fishery observer effort off the coast of Nova Scotia during 1991-1996 varied on a seasonal and annual basis,

reflecting changes in fishing effort (see Figure 3, Hooker et al. 1997). During the 1991-96 period, long-finned pilot

whales were bycaught (number of animals in parentheses) in bottom trawl (65); midwater trawl (6); and longline (1)

gear. Recorded bycatches by year were: 16 in 1991, 21 in 1992, 14 in 1993, 3 in 1994, 9 in 1995, and 6 in 1996. 

Pilot whale bycatches occurred in all months except January-March and September (Hooker et al. 1997).
135

Table 2. Summary of the incidental mortality of pilot whales (Globicephala sp.) by commercial fishery including the

years sampled (Years), the number of vessels active within the fishery (Vessels), the type of data used (Data

Type), the annual observer coverage (Observer Coverage), the observed mortalities and serious injuries

recorded by on-board observers, the estimated annual mortality and serious injury, the combined annual

estimates of mortality and serious injury (Estimated Combined Mortality), the estimated CV of the

combined estimates (Estimated CVs) and the mean of the combined estimates (CV in parentheses).

Fishery Years Vessels5 Data 

Type 1

Observer

 Coverage 2 

Observed

 Serious

 Injury

Observed

 Mortality

Estimated

Serious 

Injury

Estimated

 Mortality 

Estimated

Combined

Mortality

Estimated

 CVs 

Mean

 Annual

Mortality

Atlantic 5

squid, mackerel, 

butterfish trawl

96-00 NA

Obs. Data

Weighouts

.007, .008,

 .003, .004,

.007 

 0, 0, 0, 0, 0 6, 0, 1,

1, 2

0, 0, 0, 0, 0 45, 0, 

85, 49, 34

45, 0, 85,

49, 17

 1.27, 0,

 .65, .97, .65

43

(.45)

N. Atl. 3

Bottom Trawl 96-00 NA

Obs. Data

Weighouts

 .002, .002,

.001, .003,

.003

 0, 0, 0, 0, 0 0, 0, 0, 1, 0 0, 0, 0, 0, 0 0, 0, 0,

228, 0

0, 0, 0,

 228, 0

 0, 0, 0,

1.03, 0

46

(1.03)

Pelagic 4

Longline 96-00

253, 245,

205, 193,

186

Obs. Data

Logbook

.03, .03, .03,

.04, .04

 0, 0, 0, 4, 4 0, 0, 0, 1, 1 0, 0, 0, 

288, 109

 0, 0, 0, 93,

24

 0, 0, 0, 381,

133

 0, 0, 0,

0.79, .88

 103

 (.63)

Mid-Atlantic

Coastal Gillnet 96-00 NA

Obs. Data

Weighouts

.04,

 .03, .05,

.02, .02

 0, 0, 0, 0, 0 0, 0, 1,

0, 0

0, 0, 0, 0, 0 0, 0, 7,

0, 0

0, 0, 7, 0, 0 0, 0,

 1.1,

0, 0

1

 (1.1)

Nova Scotia

trawl fisheries

1996 NA Obs. Data NA 0 6 6 NA 6

(NA)

TOTAL 199

(.43)

1 Observer data (Obs. Data) are used to measure bycatch rates, and the data are collected within the Northeast

Fisheries Science Center (NEFSC) Sea Sampling Program. Mandatory logbook data were used to measure

total effort for the longline fishery . These data are collected at the Southeast Fisheries Science Center

(SEFSC). 2 Observer coverage of the mid-Atlantic coastal gillnet fishery is measured in tons of fish landed. Observer

coverage for the longline fishery are in terms of sets. The trawl fisheries are measured in trips. 3 In 1997, 1998, and 2000, the observed pilot whales were taken from the Illex squid otter trawl sub-fishery.

The 1999 observed pilot whales were taken from the Loligo squid and N. Atlantic otter trawl subfisheries. 4 1996-1998 mortality estimates were taken from Table 9a in Yeung et al. (NMFS Miami Laboratory PRD

99/00-13), and excludes the Gulf of Mexico. 1999-2000 mortality estimates were taken from Table 10 in

Yeung 2000 (NOAA Technical Memorandum NMFS-SEFSC-467). 5 Number of vessels in the fishery are based on vessels reporting effort to the pelagic longline logbook.

Other Mortality

Pilot whales have a propensity to mass strand throughout their range, but the role of human activity in these

events is unknown. Between 2 and 120 pilot whales have stranded annually, either individually or in groups, in

NMFS Northeast Region (Anon. 1993b) since 1980. From 1992-2000, 98 long-finned pilot whale stranded between

South Carolina and Maine, including 22 and 11 animals that mass stranded in 1992 and 2000, respectively, along the

Massachusetts coast (NMFS unpublished data). Four of 6 animals from one live stranding event in Massachusetts in

2000 were rehabilitated and released. In addition, 11 pilot whales that live stranded on Nantucket were returned to

the water.

In eastern Canada, 37 strandings of long-finned pilot whales (173 individuals) were reported on Sable

Island, Nova Scotia from 1970-1998 (Lucas and Hooker 1997; Lucas and Hooker 2000). This included 130 animals

that mass stranded in December 1976, and 2 smaller groups (<10 each) in autumn 1979 and summer 1992. Fourteen

strandings were also recorded along Nova Scotia from 1991-1996 (Hooker et al. 1997).
136

A potential human-caused source of mortality is from polychlorinated biphenyls (PCBs) and chlorinated

pesticides (DDT, DDE, dieldrin, etc.) moderate levels of which have been found in pilot whale blubber (Taruski

1975; Muir et al. 1988; Weisbrod et al. 2000). Weisbrod et al. (2000), reported that bioaccumulation levels were

more similar in whales from the same standing group than animals of the same sex or age. Also, high levels of toxic

metals (mercury, lead, cadmium) and selenium were measured in pilot whales harvested in the Faroe Island drive

fishery (Nielsen et al. 2000). Similarly, Dam and Bloch (2000) found very high PCB levels in pilot whales in the

Faroes. The population effect of the observed levels of such contaminants is unknown. 

STATUS OF STOCK

The status of long-finned pilot whales relative to OSP in US Atlantic EEZ is unknown, but stock abundance

may have been affected by reduction in foreign fishing, curtailment of the Newfoundland drive fishery for pilot

whales in 1971, and increased abundance of herring, mackerel, and squid stocks. There are insufficient data to

determine the population trends for this species. The species is not listed under the Endangered Species Act. The

total fishery-related mortality and serious injury for this stock is not less than 10% of the calculated PBR and,

therefore, cannot be considered to be insignificant and approaching zero mortality and serious injury rate. This is a

strategic stock because the1996-2000 estimated average annual fishery-related mortality, excluding Nova Scotia

bycatches to pilot whales, Globicephala sp., exceeds PBR.

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139

Figure 1. Distribution of pilot whale sightings from

NEFSC and SEFSC shipboard and aerial surveys

during the summer in 1990-1998. Isobaths are at 

100 m and 1,000 m.

January 2002

SHORT-FINNED PILOT WHALE (Globicephala macrorhynchus): 

Western North Atlantic Stock

STOCK DEFINITION AND GEOGRAPHIC RANGE

There are two species of pilot whales in the Western Atlantic: the Atlantic or long-finned pilot whale,

Globicephala melas, and the short-finned pilot whale, G. macrorhynchus. These species are difficult to identify to

the species level at sea; therefore, some of the descriptive material below refers to Globicephala sp. and is identified

as such. The species boundary is considered to be in the

New Jersey to Cape Hatteras area. Sightings north of this

area are likely G. melas. The short-finned pilot whale is

distributed worldwide in tropical to warm temperate

waters (Leatherwood and Reeves 1983). The northern

extent of the range of this species within the USA

Atlantic Exclusive Economic Zone (EEZ) is generally

thought to be Cape Hatteras, North Carolina

(Leatherwood and Reeves 1983). Sightings of these

animals in US Atlantic EEZ occur primarily within the

Gulf Stream [Southeast Fisheries Science Center

(SEFSC) unpublished data], and along the continental

shelf and continental slope in the northern Gulf of

Mexico (Mullin et al. 1991; SEFSC unpublished data).

There is no information on stock differentiation for the

Atlantic population. 

POPULATION SIZE

The total number of short-finned pilot whales

off the eastern USA and Canadian Atlantic coast is

unknown, although ten estimates from selected regions

of the habitat do exist for select time periods. Sightings

were almost exclusively in the continental shelf edge and

continental slope areas (Figure 1). Two estimates were

derived from catch data and population models that

estimated the abundance of the entire stock. Seven

seasonal estimates are available from selected regions in

USA waters during spring, summer and autumn 1978-82,

August 1990, June-July 1991, August-September 1991,

June-July 1993, July-September 1995, and July-August

1998. Because long-finned and short-finned pilot whales

are difficult to identify at sea, seasonal abundance

estimates were reported for Globicephala sp., both long-finned and short-finned pilot whales. One estimate is

available from the Gulf of St. Lawrence.

Mitchell (1974) used cumulative catch data from the 1951-61 drive fishery off Newfoundland to estimate

the initial population size (ca. 50,000 animals).

Mercer (1975), used population models to estimate a population in the same region of between 43,000-

96,000 long-finned pilot whales, with a range of 50,000-60,000 being considered the best estimate. 

An abundance of 11,120 (CV=0.29) Globicephala sp. was estimated from an aerial survey program

conducted from 1978 to 1982 on the continental shelf and shelf edge waters between Cape Hatteras, North Carolina

and Nova Scotia (CETAP 1982). An abundance of 3,636 (CV=0.36) Globicephala sp. was estimated from a June

and July 1991 shipboard line transect sighting survey conducted primarily between the 200 and 2,000 m isobaths

from Cape Hatteras to Georges Bank (Waring et al. 1992; Waring 1998). An abundance of 3,368 (CV=0.28) and
140

5,377 (CV=0.53) Globicephala sp. was estimated from line transect aerial surveys conducted from August to

September 1991 using the Twin Otter and AT-11, respectively (Anon. 1991). As recommended in the GAMS

Workshop Report (Wade and Angliss 1997), estimates older than eight years are deemed unreliable, and therefore

should not be used for PBR determinations. Further, due to changes in survey methodology, these data should not

be used to make comparisons to more current estimates. 

 An abundance of 668 (CV=0.55) Globicephala sp. was estimated from a June and July 1993 shipboard line

transect sighting survey conducted principally between the 200 and 2,000 m isobaths from the southern edge of

Georges Bank, across the Northeast Channel to the southeastern edge of the Scotian Shelf (Table 1; Anon. 1993b). 

Data were collected by two alternating teams that searched with 25x150 binoculars and were analyzed using

DISTANCE (Buckland et al. 1993; Laake et al. 1993). Estimates include school-size bias, if applicable, but do not

include corrections for g(0) or dive-time. Variability was estimated using bootstrap resampling techniques.

An abundance of 8,176 (CV=0.65) Globicephala sp. was estimated from a July to September 1995 sighting

survey conducted by two ships and an airplane that covered waters from Virginia to the mouth of the Gulf of St.

Lawrence (Table 1; Palka et al. in review). Total track line length was 32,600 km. The ships covered waters

between the 50 and 1000 fathom depth contour lines, the northern edge of the Gulf Stream, and the northern Gulf of

Maine/Bay of Fundy region. The airplane covered waters in the mid-Atlantic from the coastline to the 50 fathom

depth contour line, the southern Gulf of Maine, and shelf waters off Nova Scotia from the coastline to the 1000

fathom depth contour line. Data collection and analysis methods used were described in Palka (1996). 

Kingsley and Reeves (1998) obtained an abundance estimate of 1,600 long-finned pilot whales (CV=0.65)

from a late August and early September aerial survey of cetaceans in the Gulf of St. Lawrence in 1995 and 1998

(Table 1). Based on an examination of long-finned pilot whale summer distribution patterns and information on

stock structure, it was deemed appropriate to combine these estimates with NMFS 1995 summer survey data. The

best 1995 abundance estimate for Globicephala sp., 9,776 (CV=0.55), is the sum of the estimates from the USA and

Canadian surveys, where the estimate from the USA survey is 8,176 (CV=0.65) and from the Canadian, 1,600

(CV=0.65). 

An abundance of 9,800 (CV=0.34) Globicephala sp. was estimated from a line transect sighting survey

conducted during July 6 to September 6, 1998 by a ship and plane that surveyed 15,900 km of track line in waters

north of Maryland (38° N) (Figure 1; Palka et al. in review). Shipboard data were analyzed using the modified

direct duplicate method (Palka 1995) that accounts for school size bias and g(0), the probability of detecting a group

on the track line. Aerial data were not corrected for g(0).

An abundance of 4,724 (CV=0.61) Globicephala sp. was estimated from a shipboard line transect sighting

survey conducted between 8 July and 17 August 1998 that surveyed 5,570 km of track line in waters south of

Maryland (38°N) (Figure 1; Mullin in review). Abundance estimates were made using the program DISTANCE

(Buckland et al. 1993; Laake et al. 1993) where school size bias and ship attraction were accounted for.

The best available abundance estimate for Globicephala sp., 14,524 (CV=0.30), is the sum of the estimates

from the two 1998 USA Atlantic surveys, where the estimate from the northern USA Atlantic is 9,800 (CV=0.34)

and from the southern USA Atlantic is 4,724 (CV=0.61). This joint estimate is considered best because together

these two surveys have the most complete coverage of the species’ habitat.

Table 1. Summary of abundance estimates for the western North Atlantic Globicephala sp. Month, year, and area

covered during each abundance survey, and resulting abundance estimate (Nbest) and coefficient of variation

(CV).

Month/Year Area Nbest CV

Jun-Jul 1993 Georges Bank to Scotian shelf, shelf edge only 668 0.55

Jul-Sep 1995 Virginia to Gulf of St. Lawrence 8,176 0.65

Aug-Sep 1995 Gulf of St. Lawrence 1,600 0.65

Jul-Sep 1995 Virginia to Gulf of St. Lawrence 9,776 0.55

Jul-Sep 1998 Maryland to Gulf of St. Lawrence 9,800 0.34

Jul-Aug 1998 Florida to Maryland 4,724 0.61

Jul-Sep 1998 Gulf of St. Lawrence to Florida (COMBINED) 14,524 0.30
141

Minimum Population Estimate

The minimum population estimate is the lower limit of the two-tailed 60% confidence interval of the lognormally distributed best abundance estimate. This is equivalent to the 20th percentile of the log-normal distribution

as specified by Wade and Angliss (1997). The best estimate of abundance for Globicephala sp. is 14,524

(CV=0.30). The minimum population estimate for Globicephala sp. is 11,343 (CV=0.30).

Current Population Trend

There are insufficient data to determine the population trends for this species. 

CURRENT AND MAXIMUM NET PRODUCTIVITY RATES

Current and maximum net productivity rates are unknown for this stock. For purposes of this assessment,

the maximum net productivity rate was assumed to be 0.04. This value is based on theoretical modeling showing

that cetacean populations may not grow at rates much greater than 4% given the constraints of their reproductive life

history (Barlow et al. 1995). 

POTENTIAL BIOLOGICAL REMOVAL

Potential Biological Removal (PBR) is the product of minimum population size, one-half the maximum

productivity rate, and a “recovery” factor (MMPA Sec. 3. 16 U.S.C. 1362; Wade and Angliss 1997). The minimum

population size for Globicephala sp. is 11,343 (CV=0.30). The maximum productivity rate is 0.04, the default value

for cetaceans. The “recovery” factor, which accounts for endangered, depleted, threatened stocks, or stocks of

unknown status relative to optimum sustainable population (OSP) is assumed to be .48 because the CV of the

average mortality estimate is between 0.3-0.6 (Wade and Angliss 1997), and because this stock is of unknown status. 

PBR for the western North Atlantic Globicephala sp. is 108.

ANNUAL HUMAN-CAUSED MORTALITY

Total fishery-related mortality and serious injury cannot be estimated separately for the two species of pilot

whales in the US Atlantic EEZ because of the uncertainty in species identification by fishery observers. The

Atlantic Scientific Review Group advised adopting the risk-averse strategy of assuming that either species might

have been subject to the observed fishery-related mortality and serious injury. Total annual estimated average

fishery-related mortality or serious injury of this stock during 1996-2000 in the USA fisheries listed below was 193

pilot whales (CV=0.43) (Table 2). The Canadian average annual mortality estimate for 1996 from the Nova Scotia

trawl fisheries is 6 long-finned pilot whales. It is not possible to estimate variance of the Canadian estimate. The

total average annual mortality estimate for 1996-2000 from the USA and Nova Scotia trawl fisheries is 199 (CV =

0.43) (Table 2).

Fishery Information

USA

The level of past or current, direct, human-caused mortality of short-finned pilot whales in the US Atlantic

EEZ is unknown. The short-finned pilot whale has been taken in the pelagic longline fishery in Atlantic waters off

the southeastern USA (Lee et al. 1994; SEFSC unpublished data). 

Prior to 1977, there was no documentation of marine mammal bycatch in distant-water fleet (DWF)

activities off the northeast coast of the USA. A fishery observer program, which has collected fishery data and

information on incidental bycatch of marine mammals, was established in 1977 with the implementation of the

Magnuson Fisheries Conservation and Management Act (MFCMA). DWF effort in the US Atlantic EEZ under

MFCMA has been directed primarily towards Atlantic mackerel and squid. An average of 120 different foreign

vessels per year (range 102-161) operated within the US Atlantic EEZ during 1977 through 1982. In 1982, there

were 112 different foreign vessels; 18 (16%) were Japanese tuna longline vessels operating along the USA Atlantic

coast. This was the first year that the Northeast Regional Observer Program assumed responsibility for observer

coverage of the longline vessels. The number of foreign vessels operating within the US Atlantic EEZ each year

between 1983 and 1991 averaged 33 and ranged from 9 to 67. The number of Japanese longline vessels included

among the DWF vessels averaged 6 and ranged from 3 to 8 between 1983 and 1988. MFCMA observer coverage on

DWF vessels was 25-35% during 1977-82, increased to 58%, 86%, 95%, and 98%, respectively, during 1983-86,
142

and 100% observer coverage was maintained from 1987-91. Foreign fishing operations for squid ceased at the end

of the 1986 fishing season and, for mackerel, at the end of the 1991 fishing season. 

During 1977-1991, observers in this program recorded 436 pilot whale mortalities in foreign-fishing

activities (Waring et al. 1990; Waring 1995). A total of 391 (90%) were taken in the mackerel fishery, and 41 (9%)

occurred during Loligo and Illex squid-fishing operations. This total includes 48 documented takes by USA vessels

involved in joint venture fishing operations in which USA captains transfer their catches to foreign processing

vessels. Due to temporal fishing restrictions, the bycatch occurred during winter/spring (December to May) in

continental shelf and continental shelf edge waters (Fairfield et al. 1993; Waring 1995); however, the majority of the

takes occurred in late spring along the 100 m isobath. Two animals were also caught in both the hake fishery and

tuna longline fisheries (Waring et al. 1990). 

The distribution of long-finned pilot whale, a northern species, overlaps with that of the short-finned pilot

whale, a predominantly southern species, between 35°30'N to 38°00'N (Leatherwood et al. 1976). Although longfinned pilot whales are most likely taken in the waters north of Delaware Bay, many of the pilot whale takes are not

identified to species and bycatch does occur in the overlap area. In this summary, therefore, long-finned pilot whales

(Globicephala melas) and unidentified pilot whales (Globicephala sp.) are considered together. 

Data on current incidental takes in USA fisheries are available from several sources. In 1986, NMFS

established a mandatory self-reported fisheries information system for large pelagic fisheries. Data files are

maintained at the Southeast Fisheries Science Center (SEFSC). The Northeast Fisheries Science Center (NEFSC)

Sea Sampling Observer Program was initiated in 1989, and since that year several fisheries have been covered by the

program. In late 1992 and in 1993, the SEFSC provided observer coverage of pelagic longline vessels fishing off the

Grand Banks (Tail of the Banks) and provides observer coverage of vessels fishing south of Cape Hatteras.

Bycatch has been observed by NMFS Sea Samplers in the pelagic drift gillnet, pelagic longline, and pelagic

pair trawl, bluefin tuna purse seine, North Atlantic bottom trawl, Atlantic squid, mackerel, butterfish trawl, and MidAtlantic coastal gillnet fisheries, but no mortalities or serious injuries have documented in the Northeast multispecies

sink gillnet fishery .

Pelagic Drift Gillnet

The estimated total number of hauls in the pelagic drift gillnet fishery increased from 714 in 1989 to 1,144

in 1990; thereafter, with the introduction of quotas, effort was severely reduced. The estimated number of hauls in

1991, 1992, 1993, 1994, 1995, 1996, and 1998 were 233, 243, 232, 197, 164, 149, and 113 respectively. In 1996

and 1997, NMFS issued management regulations which prohibited the operation of this fishery in 1997. Further, in

January 1999 NMFS issued a Final Rule to prohibit the use of driftnets (i.e., permanent closure) in the North 

Atlantic swordfish fishery (50 CFR Part 630). Fifty-nine different vessels participated in this fishery at one time or

another between 1989 and 1993. From 1994 to 1998, between 10 and 13 vessels participated in the fishery. 

Observer coverage, expressed as percent of sets observed, was 8% in 1989, 6% in 1990, 20% in 1991, 40% in 1992,

42% in 1993, 87% in 1994, 99% in 1995, 64% in 1996, no fishery in 1997, and 99% in 1998. Effort was

concentrated along the southern edge of Georges Bank and off Cape Hatteras. Examination of the species

composition of the catch and locations of the fishery throughout the year, suggested that the pelagic drift gillnet

fishery be stratified into two strata, a southern or winter stratum, and a northern or summer stratum. Estimates of the

total bycatch, from 1989 to 1993, were obtained using the aggregated (pooled 1989-1993) catch rates, by strata

(Northridge 1996). Estimates of total annual bycatch for 1994 and 1995 were estimated from the sum of the

observed caught and the product of the average bycatch per haul and the number of unobserved hauls as recorded in

self-reported fisheries information. Variances were estimated using bootstrap re-sampling techniques. Between

1989 and 1998, 87 mortalities were observed in the large pelagic drift gillnet fishery. The annual fishery-related

mortality (CV in parentheses) was 77 in 1989 (0.24), 132 in 1990 (0.24), 30 in 1991 (0.26), 33 in 1992 (0.16), 31 in

1993 (0.19), 20 in 1994 (0.06), 9.1 in 1995 (0), 11 in 1996 (.17), no fishery in 1997, and 12 in 1998 (0). Since this

fishery no longer exists it has been excluded from Table 2. Pilot whales were taken along the continental shelf edge,

northeast of Cape Hatteras in January and February. Takes were recorded at the continental shelf edge east of Cape

Charles, Virginia, in June. Pilot whales were taken from Hydrographer Canyon along the Great South Channel to

Georges Bank from July-November. Takes occurred at the Oceanographer Canyon continental shelf break and along

the continental shelf northeast of Cape Hatteras in October-November.

Pelagic Pair Trawl

Effort in the pelagic pair trawl fishery has increased during the period 1989 to 1993, from zero hauls in

1989 and 1990, to an estimated 171 hauls in 1991, and then to an estimated 536 hauls in 1992, 586 in 1993, 407 in
143

1994, and 440 in 1995. This fishery ceased operations in 1996, when NMFS rejected a petition to consider pair

trawl gear as an authorized gear type in the Atlantic tunas fishery. The fishery operated from August-November in

1991, from June-November in 1992, from June-October in 1993, and from mid-summer to November in 1994 and

1995. Sea sampling began in October 1992 (Gerrior et al. 1994), and 48 sets (9% of the total) were sampled in that

season, 102 hauls (17% of the total) were sampled in 1993. In 1994 and 1995, 52% and 54%, respectively, of the

sets were observed. Twelve vessels have operated in this fishery. The fishery extends from 35o

N to 41oN, and from

69°W to 72°W. Approximately 50% of the total effort was within a one degree square at 39o

N, 72oW, around

Hudson Canyon. Examination of the 1991-1993 locations and species composition of the bycatch, showed little

seasonal change for the six months of operation and did not warrant any seasonal or areal stratification of this fishery

(Northridge 1996). Five pilot whale (Globicephala sp.) mortalities were reported in the self-reported fisheries

information in 1993. In 1994 and 1995 observers reported 1 and 12 mortalities, respectively. Since this fishery no

longer exists, it has been excluded from Table 2. 

During the 1994 and 1995 experimental fishing seasons, fishing gear experiments were conducted to collect

data on environmental parameters, gear behavior, and gear handling practices to evaluate factors affecting catch and

bycatch (Goudey 1995, 1996). Results of these studies were inconclusive in identifying factors responsible for

marine mammal bycatch.

Pelagic Longline

Total effort, excluding the Gulf of Mexico, for the pelagic longline fishery, based on mandatory selfreported fisheries information, was 11,279 sets in 1991, 10,311 sets in 1992, 10,444 sets in 1993, 11,082 sets in

1994, 11,493 sets in 1995, 9,864 sets in 1996, 9,499 sets in 1997, 7,589 sets in 1998, 6,770 sets in 1999, and 6,582

sets in 2000 (Cramer 1994; Scott and Brown 1997; Johnson et al. 1999; Yeung 1999a; Yeung et al. 2000; Yeung,

2001). This annual effort has been recalculated to include those sets targeting other species in conjunction with

tuna/swordfish, instead of just effort that exclusively targeted tuna/swordfish as in previous reports (Johnson et al.

1999; Yeung 1999a). The result is an average increase in self-reported effort of roughly 10% (Yeung et al. 2000). 

The fishery has been observed from January to March off Cape Hatteras, in May and June in the entire mid-Atlantic,

and in July through December in the mid-Atlantic Bight and off Nova Scotia. This fishery has been monitored with 

3-6% observer coverage, in terms of sets observed, since 1992. The 1993-1997 estimated take was based on a

revised analysis of the observed incidental take and self-reported incidental take and effort data, and replaces

previous estimates for the 1990-1993 and 1994-1995 periods (Cramer 1994; Scott and Brown 1997; Johnson et al.

1999). Further, Yeung (1999b) revised the 1992-1997 fishery mortality estimates in Johnson et al. (1999) to include

seriously injured animals. The 1998, 1999 and 2000 bycatch estimates were from Yeung (1999a), Yeung et al.

(2000), and Yeung (2001), respectively. Most of the estimated marine mammal bycatch was from US Atlantic EEZ

waters between South Carolina and Cape Cod (Johnson et al. 1999). Pilot whales are frequently observed feeding

on hooked fish, particularly big-eye tuna (NMFS unpublished data). Between 1992-2000, 70 pilot whales (including

2 identified as a short-finned pilot whales) were released alive, including 36 that were considered seriously injured

(of which 1 was identified as a short-finned pilot whale), and 4 mortalities were observed. January-March bycatch

was concentrated on the continental shelf edge northeast of Cape Hatteras. Bycatch was recorded in this area during

April-June, and takes also occurred north of Hydrographer Canyon off the continental shelf in water over 1,000

fathoms during April-June. During the July-September period, takes occurred on the continental shelf edge east of

Cape Charles, Virginia, and on Block Canyon slope in over 1,000 fathoms of water. October-December bycatch

occurred along the 20 to 50 fathom contour lines between Barnegatt Bay and Cape Hatteras. The estimated fisheryrelated mortality to pilot whales in the US Atlantic (excluding the Gulf of Mexico) attributable to this fishery was:

127 in 1992 (CV=1.00) and 93 in 1999 (CV=1.00). The estimated serious injuries were 40 (CV=0.71) in 1992, 19

(CV=1.00) in 1993, 232 (CV=0.53) in 1994, 345 (CV=0.51) in 1995, 0 from 1996 to 1998, 288 (CV=0.79) in 1999,

and 109 (CV=0.88) in 2000. This includes 37 estimated short-finned pilot whales in 1995 (CV=1.00). The average

annual mortality between 1996 and 2000 was 103 pilot whales (CV=0.63) (Table 2). Seriously injured and released

alive animals are combined with mortalities in the category ‘combined mortality’. 

Bluefin Tuna Purse Seine

The tuna purse seine fishery between Cape Hatteras and Cape Cod is directed at small and medium bluefin

and skip jack for the canning industry, while north of Cape Cod purse seine vessels are directed at large medium and

giant bluefin tuna (NMFS 1995). The latter fishery is entirely separate from any other Atlantic tuna purse seine

fishery. Spotter aircraft are used to locate fish schools. The official start date is August 15, set by regulation. 

Individual vessel quotas (IVQs) and a limited access system prevent a derby fishery situation. Catch rates are high
144

with this gear and consequently, the season usually only lasts a few weeks for large mediums and giants. The 1996

regulations allocated 250 MT (5 IVQs) with a minimum of 90% giants and 10% large mediums. Limited observer

data are available for the bluefin tuna purse seine fishery. Out of 45 total trips made in 1996, 43 trips (95.6%) were

observed. Forty-four sets were made on the 43 observed trips and all sets were observed. A total of 136 days were

covered. Two interactions with pilot whales were observed in 1996. In one interaction, the net was actually pursed

around 1 pilot whale, the rings were released and the animal escaped alive, condition unknown. This set occurred

east of the Great South Channel and just north of the Cultivator Shoals region on Georges Bank. In a second

interaction, 5 pilot whales were encircled in a set. The net was opened prior to pursing to let the whales swim free,

apparently uninjured. This set occurred on the Cultivator Shoals region on Georges Bank. Since 1996, this fishery

has not been observed. 

North Atlantic Bottom Trawl 

Vessels in the North Atlantic bottom trawl fishery, a Category III fishery under the MMPA, were observed

in order to meet fishery management needs, rather than marine mammal management needs. An average of 970

(CV=0.04) vessels (full and part time) participated annually in the fishery during 1989-1993. The fishery is active in

New England in all seasons. One mortality was documented in 1990, and one animal was released alive and

uninjured in 1993. The estimated fishery-related mortality to pilot whales in the USA Atlantic attributable to this

fishery was: 0 in 1994-1998, 228 in 1999, and 0 in 2000. The average annual mortality between 1996-2000 was 46

pilot whales (CV=1.03) (Table 2). However, these estimates should be viewed with caution due to the extremely

low (<1%) observer coverage. 

Atlantic Squid, Mackerel, Butterfish Trawl

The mid-Atlantic mackerel and squid trawl fisheries were combined into the Atlantic mid-water trawl

fishery in the revised proposed list of fisheries in 1995. The fishery occurs along the USA mid-Atlantic continental

shelf region between New Brunswick, Canada, and Cape Hatteras year around. The mackerel trawl fishery was

classified as a Category II fishery since 1990 and the squid fishery was originally classified as a Category II fishery

in 1990, but was reclassified as a Category III fishery in 1992. The combined fishery was then reclassified as a

Category II fishery in 1995. In 1996, mackerel, squid, and butterfish trawl fisheries were combined into the Atlantic

squid, mackerel, butterfish trawl fishery, and maintained a Category II classification. Three fishery-related

mortalities of pilot whales were reported in self-reported fisheries information from the mackerel trawl fishery

between 1990-1992. Six mortalities were observed in 1996, 1 in years 1998 and 1999 and 2 in 2000. The 1996 and 1998

bycatch occurred in the Illex squid fishery, and the 1999 in the Loligo fishery. The estimated fishery-related

mortality to pilot whales in the USA Atlantic attributable to this fishery was: 45 in 1996 (CV=1.27), 0 in 1997, 85 in

1998 (CV=0.65), 49 in 1999 (CV=0.97) and 34 in 2000 (CV=0.65); average annual mortality between 1996 and

2000 was 43 pilot whales (CV=0.45) (Table 2). However, these estimates should be viewed with caution due to the

extremely low (<1%) observer coverage.

Mid-Atlantic Coastal Gillnet

Observer coverage of the USA Atlantic coastal gillnet fishery was initiated by the NEFSC Sea Sampling

program in July 1993; and from July to December 1993, 20 trips were observed. During 1994 and 1995, 221 and

382 trips were observed, respectively. This fishery, which extends from North Carolina to New York, is actually a

combination of small vessel fisheries that target a variety of fish species, some of which operate right off the beach. 

The number of vessels in this fishery is unknown, because records which are held by both state and federal agencies

have not been centralized and standardized. Observer coverage, expressed as percent of tons of fish landed, was 5% 

4%, 3%, 5%, 2%, and 2% for 1995, 1996, 1997, 1998, 1999, and 2000, respectively (Table 2).

No pilot whales were taken in observed trips during 1993-1997. One pilot whale was observed taken in

1998, 0 in 1999 and 2000 (Table 2). Observed effort was concentrated off NJ and scattered between DE and NC

from 1 to 50 miles off the beach. All bycatches were documented during January to April. Using the observed

takes, the estimated annual mortality (CV in parentheses) attributed to this fishery was 7 in 1998 (1.1). Average

annual estimated fishery-related mortality attributable to this fishery during 1996-2000 was 1 pilot whale (CV=1.1).

CANADA

An unknown number of pilot whales have also been taken in Newfoundland, Labrador, and in Bay of

Fundy groundfish gillnets, Atlantic Canada and Greenland salmon gillnets, and Atlantic Canada cod traps (Read

1994). The Atlantic Canadian and Greenland salmon gillnet fishery is seasonal, with the peak from June to

September,
145

depending on location. During 1989 in southern and eastern Newfoundland and in Labrador, 2,196 nets 91 m long

were used. There are no effort data available for the Greenland fishery; however, the fishery was terminated in 1993

under an agreement between Canada and North Atlantic Salmon Fund (Read 1994). 

There were 3,121 cod traps operating in Newfoundland and Labrador during 1979, and about 7,500 in 1980

(Read 1994). This fishery was closed at the end of 1993 due to collapse of Canadian groundfish resources. 

Between January 1993 and December 1994, 36 Spanish deep-water trawlers, covering 74 fishing trips, were

observed in NAFO Fishing Area 3 (off the Grand Bank) (Lens 1997). A total of 47 incidental catches were

recorded, which included 1 long-finned pilot whale. The incidental mortality rate for pilot whales was 0.007/set.

In Canada, the fisheries observer program places observers on all foreign fishing vessels, on between 25-

40% of large Canadian vessels (greater than 100 ft), and on approximately 5% of small vessels (Hooker et al. 1997). 

Fishery observer effort off the coast of Nova Scotia during 1991-1996 varied on a seasonal and annual basis,

reflecting changes in fishing effort (see Figure 3, Hooker et al. 1997). During the 1991-96 period, long-finned pilot

whales were bycaught (number of animals in parentheses) in bottom trawl (65); midwater trawl (6); and longline (1)

gear. Recorded bycatches by year were: 16 in 1991, 21 in 1992, 14 in 1993, 3 in 1994, 9 in 1995, and 6 in 1996. 

Pilot whale bycatches occurred in all months except January-March and September (Hooker et al. 1997).

Table 2. Summary of the incidental mortality of pilot whales (Globicephala sp.) by commercial fishery including

the years sampled (Years), the number of vessels active within the fishery (Vessels), the type of data used

(Data Type), the annual observer coverage (Observer Coverage), the observed mortalities and serious

injuries recorded by on-board observers, the estimated annual mortality and serious injury, the combined

annual estimates of mortality and serious injury (Estimated Combined Mortality), the estimated CV of the

combined estimates (Estimated CVs) and the mean of the combined estimates (CV in parentheses).

Fishery Years Vessels Data 

Type 1

Observer

 Coverage 2 

Observed

 Serious

 Injury

Observed

Mortality

Estimated

Serious 

Injury

Estimated

 Mortality 

Estimated

Combined

Mortality

Estimated

 CVs 

Mean

 Annual

Mortality

Atlantic 5

squid, mackerel, 

butterfish trawl

1996-

2000

NA Obs.

 Data

Weighouts

.007, .008,

 .003, .004,

.007 

 0, 0, 0, 0,

0

6, 0, 1, 1,

1

0, 0, 0, 0,

0

 45, 0, 

85, 49, 34

45 ,0, 85,

49, 34

 1.27, 0,

 .65, .97,

.65

43

(.45)

No. Atlantic

Bottom Trawl 3

1996-

2000

NA Obs.

 Data

Weighouts

 .002, .002,

.001, .003,

.003

0, 0, 0, 0,

0

 0, 0, 0,

1, 0

0, 0, 0, 0,

0

 0, 0, 0,

228, 0

 0, 0, 0,

228, 0

 0, 0, 0,

1.03, 0

46

(1.03)

Pelagic 4

Longline 

1996-

2000

253, 245,

205, 1935,

186

Obs. Data

Logbook

.03, .03, 

.03, .04, .04

0, 0, 0, 4,

4

0, 0, 0, 1,

1

0, 0, 0, 

288, 109

0, 0, 0,

 93, 24

0, 0, 0,

381, 133

0, 0, 0,

0.79, 0.88

103

(0.63)

Mid-Atlantic

Coastal Gillnet 

1996-

2000

NA Obs. Data

Weighouts

.04, .03, .05,

.02, .02

0, 0, 0, 0,

0

0, 0, 1, 0,

0

0, 0, 0, 0,

0

0, 0, 7,

0, 0

0, 0, 7,

0, 0

0, 0, 1.1,

0, 0

1

(1.1)

Nova Scotia

trawl fisheries

1996 NA Obs. Data NA 0 6 6 NA 6

(NA)

TOTAL 199

(0.43)

1 Observer data (Obs. Data) are used to measure bycatch rates, and the data are collected within the Northeast

Fisheries Science Center (NEFSC) Sea Sampling Program. Mandatory logbook data were used to measure

total effort for the longline fishery . These data are collected at the Southeast Fisheries Science Center

(SEFSC). 2 Observer coverage of the mid-Atlantic coastal gillnet fishery is measured in tons of fish landed. Observer

coverage for the longline fishery are in terms of sets. The trawl fisheries are measured in trips. 3 In 1997, 1998, and 2000, the observed pilot whales were taken from the Illex squid otter trawl subfishery.

The 1999 observed pilot whales were taken from the Loligo squid and N. Atlantic otter trawl subfisheries. 4 1996-2000 mortality estimates were taken from Table 9a in Yeung et al. (NMFS Miami Laboratory PRD

99/00-13), and exclude the Gulf of Mexico. 2000 mortality estimates were taken from Table 10 in Yeung

2000 (NMFS, Miami Lab. Ref. Doc. 00/01-17) and excludes the Gulf of Mexico. 5 Number of vessels in the fishery are based on vessels reporting effort to the pelagic longline logbook.
146

Other Mortality

Pilot whales have a propensity to mass strand throughout their range, but the role of human activity in these

events is unknown. Between 2 and 120 pilot whales have stranded annually either individually or in groups in

NMFS Northeast Region (Anon. 1993b) since 1980. From 1992-2000, 98 long-finned pilot whale stranded between

South Carolina and Maine, including 22 and 11 animals that mass stranded in 1992 and 2000, respectively, along the

Massachusetts coast (NMFS unpublished data). Four of 6 animals from 1 live stranding event in Massachusetts in

2000 were rehabilitated and released. In addition 11 pilot whales that live stranded on Nantucket were returned to

the water. 

In eastern Canada, 37 strandings of long-finned pilot whales (173 individuals) were reported on Sable

Island, Nova Scotia from 1970-1998 (Lucas and Hooker 1997; Lucas and Hooker 2000). This included 130 animals

that mass stranded in December 1976, and 2 smaller groups (<10 each) in autumn 1979 and summer 1992. Fourteen

strandings were also recorded along Nova Scotia from 1991-1996 (Hooker et al. 1997).

A potential human-caused source of mortality is from polychlorinated biphenyls (PCBs) and chlorinated

pesticides (DDT, DDE, dieldrin, etc.) moderate levels of which have been found in pilot whale blubber (Taruski

1975; Muir et al. 1988; Weisbrod et al. 2000). Weisbrod et al. (2000) reported that bioaccumulation levels were

more similar in whales from the same standing group than animals of the same sex or age. Also, high levels of toxic

metals (mercury, lead, cadmium) and selenium were measured in pilot whales harvested in the Faroe Island drive

fishery (Nielsen et al. 2000). Similarly, Dam and Bloch (2000) found very high PCB levels in pilot whales in the

Faroes. The population effect of the observed levels of such contaminants is unknown. 

STATUS OF STOCK

The status of long-finned pilot whales relative to OSP in US Atlantic EEZ is unknown, but stock abundance

may have been affected by reduction in foreign fishing, curtailment of the Newfoundland drive fishery for pilot

whales in 1971, and increased abundance of herring, mackerel, and squid stocks. There are insufficient data to

determine the population trends for this species. The species is not listed under the Endangered Species Act. The

total fishery-related mortality and serious injury for this stock is not less than 10% of the calculated PBR and,

therefore, cannot be considered to be insignificant and approaching zero mortality and serious injury rate. This is a

strategic stock because the 1996-2000 estimated average annual fishery-related mortality, excluding Nova Scotia

bycatches to pilot whales, Globicephala sp., exceeds PBR.

REFERENCES

Barlow, J., S. L. Swartz, T. C. Eagle and P. R. Wade. 1995. U.S. Marine Mammal Stock Assessments: Guidelines

for Preparation, Background, and a Summary of the 1995 Assessments. U.S. Dep. Commer., NOAA Tech.

Memo. NMFS-OPR-6, 73 pp. 

Buckland, S. T., D. R. Anderson, K. P. Burnham and J. L. Laake. 1993. Distance Sampling: estimating abundance

of biological populations. Chapman & Hall, London, 446 pp. 

Cramer J. 1994. Large pelagic logbook newsletter - 1993. NOAA Tech. Mem. NMFS-SEFSC-352, 19 pp. NMFS,

Southeast Fisheries Science Center, Miami, FL.

Dam, M. and D. Bloch. 2000. Screening of mercury and persistent organochlorine pollutants in long-finned pilot

whale (Globicephala melas) in the Faroe Islands. Marine Pollution Bulletin 40:1090-1099.

Fairfield, C. P., G. T. Waring and M. H. Sano. 1993. Pilot whales incidentally taken during the distant water fleet

Atlantic mackerel fishery in the mid-Atlantic Bight, 1984-88. Rep. int Whal. Commn. (Special Issue 14):

107-116. 

Gerrior, P., A. S. Williams and D. J. Christensen. 1994. Observations of the 1992 U.S. pelagic pair trawl fishery in

the Northwest Atlantic. Mar. Fish. Rev. 56(3): 24-27.

Goudey, C.A. 1995. The 1994 experimental pair trawl fishery for tuna in the northwest Atlantic, Massachusetts

Institute of Technology, Sea Grant, MITSG 95-6, Cambridge, MA. 10 pp.

Goudey, C.A. 1996. The 1995 experimental pair trawl fishery for tuna in the northwest Atlantic, Massachusetts

Institute of Technology, Sea Grant, MITSG 95-6, Cambridge, MA. 13 pp.

Hooker, S. K., R. W. Baird and M. A. Showell. 1997. Cetacean strandings and bycatches in Nova Scotia, Eastern

Canada, 1991-1996. Paper SC/49/05 presented to the IWC Scientific Committee, September 1997. 11 pp.
147

Johnson, D. R., C. Yeung and C. A. Brown. 1999. Estimates of marine mammal and marine turtle catch by the U.S.

Atlantic pelagic longline fleet in 1992-1997. NOAA Tech. Mem. NMFS-SEFSC-418. 70 pp. NMFS,

Southeast Fisheries Science Center, Miami, FL.

Laake, J. L., S. T. Buckland, D. R. Anderson and K. P. Burnham. 1993. DISTANCE user’s guide, V2.0. Colorado

Cooperative Fish & Wildlife Research Unit, Colorado State University, Ft. Collins, Colorado, 

72 pp.

Lucas, Z. N. and S. K. Hooker. 1997. Cetacean strandings on Sable Island, Nova Scotia, 1990-1996. Paper

SC/49/06 presented to the IWC Scientific Committee, September 1997. 10 pp.

Lucas, Z. N. and S. K. Hooker. 2000. Cetacean strandings on Sable Island, Nova Scotia, 1970-1998. Can. Field

Nat.:114 (45-61).

Leatherwood, S. and R. R. Reeves. 1983. The Sierra Club handbook of whales and dolphins. Sierra Club Books,

San Francisco, 302 pp.

Lee, D. W., C. J. Brown, A. J. Catalano, J. R. Grubich, T. W. Greig, R. J. Miller and M. T. Judge. 1994. SEFSC

pelagic longline observer program data summary for 1992-1993. NOAA Tech. Mem. NMFS-SEFSC-347.

19 pp. NMFS, Southeast Fisheries Science Center, Miami, FL.

Lens, S. 1997. Interactions between marine mammals and deep water trawlers in the NAFO regulatory area. ICES

CM 1997/Q:8. 10 pp.

Mullin, K. D. (in review). Abundance and distribution of cetaceans in the southern U.S. Atlantic Ocean during

summer 1998. Fish. Bull.

Mullin, K., W. Hoggard, C. Roden, R. Lohoefener, C. Rogers and B. Taggart. 1991. Cetaceans on the upper

continental slope in the north-central Gulf of Mexico. OCS Study/MMS 91-0027. U.S. Dept. of the

Interior, Minerals Management Service, Gulf of Mexico OCS Regional Office, New Orleans, Louisiana,

108 pp. 

Nielsen, J. B., F. Nielsen, P-J. Jørgensen, and P. Grandjean. 2000. Toxic metals and selenium in blood from pilot

whales (Globicephala melas) and sperm whales (Physeter catodon). Mar. Pollut. Bull. 40:348-351. 

Northridge, S. 1996. Estimation of cetacean mortality in the U.S. Atlantic swordfish and tuna drift gillnet and pair

trawl fisheries. Final report to the Northeast Fisheries Science Center, Contract No. 40ENNF500160. 

Palka, D. 1995. Abundance estimate of the Gulf of Maine harbor porpoise. Rep. int Whal. Commn. (Special Issue

16):27-50.

Palka, D., G. Waring and D. Potter. (in review). Abundances of cetaceans and sea turtles in the northwest Atlantic

during summer 1995 and 1998. Fish. Bull., U.S.

Read, A. J. 1994. Interactions between cetaceans and gillnet and trap fisheries in the northwest Atlantic. Rep. int

Whal. Commn. Special Issue 15: 133-147.

Scott, G. P. and C. A. Brown. 1997. Estimates of marine mammal and marine turtle catch by the U.S. Atlantic

pelagic longline fleet in 1994-1995. Miami Laboratory Contribution MIA-96/97-28.

Wade, P. R. and R. P. Angliss. 1997. Guidelines for assessing marine mammal stocks: Report of the GAMMS

Workshop April 3-5, 1996, Seattle, Washington. U.S. Dep. Commer., NOAA Tech. Memo. NMFS-OPR12, 93 pp.

Waring, G. T., P. Gerrior, P. M. Payne, B. L. Parry and J. R. Nicolas. 1990. Incidental take of marine mammals in

foreign fishery activities off the northeast United States, 1977-1988. Fish. Bull., U.S. 88(2): 347-360.

Waring, G. T., C. P. Fairfield, C. M. Ruhsam and M. Sano. 1992. Cetaceans associated with Gulf Stream features

off the northeastern USA shelf. ICES Marine Mammals Comm. CM 1992/N:12, 29 pp. 

Waring, G. T. 1998. Results of the summer 1991 R/V Chapman marine mammal sighting survey. NOAA NMFS

NEFSC, Lab. Ref. Doc. No. 98-09, 21pp. Available from: National Marine Fisheries Service, 166 Water

Street, Woods Hole, MA 02543-1026.

Waring, G. T. 1995. Fishery and ecological interactions for selected cetaceans off the northeast USA. Ph.D.

dissertation, University of Massachusetts, Amherst, 260 pp.

Waring, G. T., D. L. Palka, P. J. Clapham, S. Swartz, M. C. Rossman, T. V. N. Cole, L. J. Hansen, K. D. Bisack, K.

D. Mullin, R. S. Wells, D. K. Odell, and N. B. Barros. 1999. U.S. Atlantic and Gulf of Mexico marine

mammal stock assessments — 1999. U.S. Dep. Commer., NOAA Tech. Memo NMFS-NE-153, 196pp. 

Weisbrod, A. V., D. Shea, M. J. Moore, and J. J. Stegeman. 2000. Bioaccumulation patterns of polychlorinated

biphenyls and chlorinated pesticides in northwest Atlantic pilot whales. Environ. Toxicol. Chem. 19:667-

677.
148

Yeung, C. 2001. Estimates of marine mammal and marine turtle bycatch by the U.S. Atlantic pelagic longline fleet

in 1999-2000. NOAA Tech. Memo. NMFS-SEFSC-467, 43 pp. NMFS, Southeast Fisheries Science

Center, Miami, FL.

Yeung, C. 1999a. Estimates of marine mammal and marine turtle bycatch by the U.S. Atlantic pelagic longline fleet

in 1998. NOAA Tech. Memo. NMFS-SEFSC-430, 26 pp. NMFS, Southeast Fisheries Science Center,

Miami, FL.

Yeung, C. 1999b. Revised Mortality Estimates of Marine Mammal Bycatch in 1992-1997 based on Serious Injury

Guidelines. NOAA Tech. Memo. NMFS-SEFSC-429, 23 pp. NMFS, Southeast Fisheries Science Center,

Miami, FL.

Yeung, C., S. Epperly, and C. A. Brown. 2000. Preliminary revised estimates of marine mammal and marine turtle

bycatch by the U.S. Atlantic pelagic longline fleet, 1992-1999. NMFS, Miami Lab. PRD Contribution

Number 99/00-13. 58 pp.
149

Figure 1. Distribution of Kogia sp. whale sightings from

NEFSC and SEFSC shipboard and aerial surveys during the

summer 1990-1998. Isobaths are at 100 m and 1,000 m.

January 2002

DWARF SPERM WHALE (Kogia simus): 

Western North Atlantic Stock

STOCK DEFINITION AND GEOGRAPHIC RANGE

The dwarf sperm whale (Kogia simus) appears to be distributed worldwide in temperate to tropical waters

(Caldwell and Caldwell 1989). There are no stranding records for the east Canadian coast (Willis and Baird 1998).

Sightings of these animals in the western North Atlantic occur primarily along the continental shelf edge and over

the deeper waters off the continental shelf (Hansen et al. 1994; NMFS unpublished data). Dwarf sperm whales and

pygmy sperm whales are difficult to distinguish and sightings of either species are often categorized as Kogia sp. 

There is no information on stock differentiation for the Atlantic population. In a recent study using hematological

and stable-isotope data, Barros et al. (1998) speculated that dwarf sperm whales may have a more pelagic

distribution than pygmy sperm whales, and/or dive deeper during feeding bouts. 

POPULATION SIZE

An abundance of 115 (CV=0.61) for Kogia sp. was estimated from a line transect sighting survey

conducted during July 6 to September 6, 1998 by a ship and plane that surveyed 15,900 km of track line in waters

north of Maryland (38° N) (Figure 1; Palka et al. in review). Shipboard data were analyzed using the modified

direct duplicate method (Palka 1995) that accounts for school size bias and g(0), the probability of detecting a group

on the track line. Aerial data were not corrected for g(0).

An abundance of 421 (CV=0.55) for Kogia sp. was estimated from a shipboard line transect sighting survey

conducted between 8 July and 17 August 1998

that surveyed 5,570 km of track line in waters

south of Maryland (38°N) (Figure 1; Mullin in

review). Abundance estimates were made using

the program DISTANCE (Buckland et al. 1993;

Laake et al. 1993) where school size bias and ship

attraction were accounted for.

The best available abundance estimate

for Kogia sp. is the sum of the estimates from the

two 1998 USA Atlantic surveys, 536 (CV=0.45),

where the estimate from the northern USA

Atlantic is 115 (CV=0.61) and from the southern

USA Atlantic is 421 (CV=0.55). This joint

estimate is considered best because together these

two surveys have the most complete coverage of

the species’ habitat.

Minimum Population Estimate

The minimum population estimate is the

lower limit of the two-tailed 60% confidence

interval of the log-normally distributed best

abundance estimate. This is equivalent to the

20th percentile of the log-normal distribution as

specified by Wade and Angliss (1997). The best

estimate of abundance for Kogia sp. is 536

(CV=0.45). The minimum population estimate

for Kogia sp. is 373.
150

Current Population Trend

The available information is insufficient to evaluate trends in population size for this species in the western

North Atlantic. 

CURRENT AND MAXIMUM NET PRODUCTIVITY RATES

Current and maximum net productivity rates are unknown for this stock. For purposes of this assessment,

the maximum net productivity rate was assumed to be 0.04. This value is based on theoretical modeling showing

that cetacean populations may not grow at rates much greater than 4% given the constraints of their reproductive life

history (Barlow et al. 1995). 

POTENTIAL BIOLOGICAL REMOVAL

Potential Biological Removal (PBR) is the product of minimum population size, one-half the maximum

productivity rate, and a “recovery” factor (Wade and Angliss 1997). The minimum population size is 373. The

maximum productivity rate is 0.04, the default value for cetaceans. The “recovery” factor, which accounts for

endangered, depleted, threatened stocks, or stocks of unknown status relative to optimum sustainable population

(OSP) is assumed to be 0.5 because this stock is of unknown status. PBR for the western North Atlantic Kogia sp. is

3.7. 

ANNUAL HUMAN-CAUSED MORTALITY AND SERIOUS INJURY

The level of past or current, direct, human-caused mortality of dwarf sperm whales in the US Atlantic EEZ

is unknown. Available information indicates there is likely little fisheries interaction with dwarf sperm whales in the

US Atlantic EEZ. Total annual estimated average fishery-related mortality or serious injury to this stock during

1996-2000 was 0 dwarf sperm whales (Table 1).

Fishery Information

Data on current incidental takes in USA fisheries are available from several sources. In 1986, NMFS

established a mandatory logbook system for large pelagic fisheries. The Northeast Fisheries Science Center

(NEFSC) Sea Sampling Observer Program was initiated in 1989, and since that year several fisheries have been

covered by the program. In late 1992 and in 1993 the SEFSC provided observer coverage of pelagic longline vessels

fishing off the Grand Banks (Tail of the Banks) and provides observer coverage of vessels fishing south of Cape

Hatteras.

Bycatch has been observed by NMFS Sea Samplers in the pelagic drift gillnet fishery, but no mortalities or

serious injuries have been documented in other fisheries. 

Pelagic Drift Gillnet

The estimated total number of hauls in the pelagic drift gillnet fishery increased from 714 in 1989 to 1,144

in 1990; thereafter, with the introduction of quotas, effort was severely reduced. The estimated number of hauls in

1991, 1992, 1993, 1994, 1995, 1996, and 1998 were 233, 243, 232, 197, 164, 149, and 113 respectively. In 1996

and 1997, NMFS issued management regulations which prohibited the operation of this fishery in 1997. Further, in

January 1999 NMFS issued a Final Rule to prohibit the use of driftnets (i.e., permanent closure) in the North

Atlantic swordfish fishery (50 CFR Part 630). Fifty-nine different vessels participated in this fishery at one time or

another between 1989 and 1993. Since 1994, between 10 and 13 vessels have participated in the fishery (Table 1). 

Observer coverage, expressed as percent of sets observed, was 8% in 1989, 6% in 1990, 20% in 1991, 40% in 1992,

42% in 1993, 87% in 1994, 99% in 1995, 64% in 1996, and 99% in 1998. Effort was concentrated along the

southern edge of Georges Bank and off Cape Hatteras. Examination of the species composition of the catch and

locations of the fishery throughout the year, suggested that the pelagic drift gillnet fishery be stratified into two

strata, a southern or winter stratum, and a northern or summer stratum. Estimates of the total bycatch from 1989 to

1993 were obtained using the aggregated (pooled 1989-1993) catch rates, by strata (Northridge 1996). Estimates of

total annual bycatch for 1994 and 1995 were estimated from the sum of the observed caught and the product of the

average bycatch per haul and the number of unobserved hauls as recorded in self-reported fisheries information. 

Variances were estimated using bootstrap re-sampling techniques. There was one report of mortality or serious

injury to dwarf sperm whales attributable to this fishery. Estimated annual fishery-related mortality and serious

injury (CV in parentheses) was 0 dwarf sperm whales from 1991-1994, 1.0 in 1995 (CV=0), and 0 from 1996-1998. 
151

Estimated average annual mortality and serious injury related to this fishery during 1994-1998 was 0.25 dwarf sperm

whales (CV=0). 

Other Mortality

Historical stranding records (1883-1988) of dwarf sperm whales in the southeastern USA (Credle 1988),

and strandings recorded during 1988-1997 (Barros et al. 1998) indicate that this species accounts for about 17% of

all Kogia strandings in this area. During the period 1990-October 1998, 3 dwarf sperm whale strandings occurred in

the northeastern USA (Maryland, Massachusetts, and Rhode Island), whereas 43 strandings were documented along

the USA Atlantic coast between North Carolina and the Florida Keys in the same period. A pair of latex

examination gloves was retrieved from the stomach of a dwarf sperm whale stranded in Miami in 1987 (Barros et al.

1990). In the period 1987-1994, 1 animal had possible propeller cuts on or near the flukes. 

STATUS OF STOCK

The status of this stock relative to OSP in the US Atlantic EEZ is unknown. This species is not listed as

endangered or threatened under the Endangered Species Act. There is insufficient information with which to assess

population trends. Total fishery-related mortality and serious injury for this stock is less than 10% of PBR and

therefore can be considered insignificant and approaching zero mortality and serious injury rate.

REFERENCES

Barlow, J., S. L. Swartz, T. C. Eagle and P. R. Wade. 1995. U.S. Marine Mammal Stock Assessments: Guidelines

for Preparation, Background, and a Summary of the 1995 Assessments. U.S. Dep. Commer., NOAA Tech.

Memo. NMFS-OPR-6, 73 pp.

Barros, N. B., D. A. Duffield, P. H. Ostrom, D. K. Odell and V. R. Cornish. 1998. Nearshore vs. offshore ecotype

differentiation of Kogia breviceps and K. simus based on hemoglobin, morphometric and dietary analyses.

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of biological populations. Chapman and Hall, London, 446 pp. 

Caldwell, D. K. and M. C. Caldwell. 1989. Pygmy sperm whale Kogia breviceps (de Blainville, 1838): dwarf

sperm whale Kogia simus Owen, 1866. Pp. 235-260 in: S. H. Ridgway and R. Harrison, Handbook of

marine mammals, Vol. 4: river dolphins and the larger toothed whales. Academic Press, San Diego. 

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breviceps. MSc. Thesis. University of Miami. Coral Gables, FL.

Hansen, L. J., K. D. Mullin and C. L. Roden. 1994. Preliminary estimates of cetacean abundance in the U.S.

Atlantic Exclusive Economic Zone from 1992 vessel surveys. Southeast Fisheries Science Center, Miami

Laboratory, Contribution No. MIA-93/94-58.

Laake, J. L., S. T. Buckland, D. R. Anderson and K. P. Burnham. 1993. DISTANCE user’s guide, V2.0. Colorado

Cooperative Fish & Wildlife Research Unit, Colorado State University, Ft. Collins, Colorado, 

72 pp.

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summer 1998. Fish. Bull., U.S.

Northridge, S. 1996. Estimation of cetacean mortality in the U.S. Atlantic swordfish and tuna drift gillnet and pair

trawl fisheries. Final report to the Northeast Fisheries Science Center, Contract No.40ENNF500045. 18

pp. 

Palka, D. 1995. Abundance estimate of the Gulf of Maine harbor porpoise. Rep. int Whal. Commn. Special Issue

16: 27-50.

Palka, D., G. Waring, and D. Potter. (in review). Abundances of cetaceans and sea turtles in the northwest Atlantic

during summer 1995 and 1998. Fish. Bull., U.S.

Wade P. R. and R. P. Angliss. 1997. Guidelines for assessing marine mammal stocks: Report of the GAMMS

Workshop April 3-5, 1996, Seattle, Washington. U.S. Dep. Commer., NOAA Tech. Memo. NMFS-OPR12, 93 pp.
152

Waring, G. T., D. L. Palka, P. J. Clapham, S. Swartz, M. C. Rossman, T. V. N. Cole, L. J. Hansen, K. D. Bisack, K.

D. Mullin, R. S. Wells, D. K. Odell, and N. B. Barros. 1999. U.S. Atlantic and Gulf of Mexico marine

mammal stock assessments — 1999. U.S. Dep. Commer., NOAA Tech. Memo NMFS-NE-153, 196pp. 

Willis, P. M., and R. W. Baird. 1998. Status of the dwarf sperm whale, Kogia simus, with special reference to

Canada. Can. Field Nat., 112:114-125.
153

Figure 1. Distribution of Kogia sp. whale sightings from

NEFSC and SEFSC shipboard and aerial surveys during the

summer 1990-1998. Isobaths are at 100 m and 1,000 m.

January 2002

PYGMY SPERM WHALE (Kogia breviceps):

Western North Atlantic Stock

STOCK DEFINITION AND GEOGRAPHIC RANGE

The pygmy sperm whale (Kogia breviceps) appears to be distributed worldwide in temperate to tropical

waters (Caldwell and Caldwell 1989). Sightings of these animals in the Western North Atlantic occur primarily

along the continental shelf edge and over the deeper waters off the continental shelf (Hansen et al. 1994; Southeast

Fisheries Science Center unpublished data). Pygmy sperm whales and dwarf sperm whales are difficult to

distinguish and sightings of either species are often categorized as Kogia sp. There is no information on stock

differentiation for the Atlantic population. In a recent study using hematological and stable-isotope data, Barros et

al. (1998) speculated that dwarf sperm whales may have a more pelagic distribution than pygmy sperm whales,

and/or dive deeper during feeding bouts. 

POPULATION SIZE

An abundance of 115 (CV=0.61) for

Kogia sp. was estimated from a line transect

sighting survey conducted during July 6 to

September 6, 1998 by a ship and plane that

surveyed 15,900 km of track line in waters north of

Maryland (38° N) (Figure 1; Palka et al. in

review). Shipboard data were analyzed using the

modified direct duplicate method (Palka 1995) that

accounts for school size bias and g(0), the

probability of detecting a group on the track line. 

Aerial data were not corrected for g(0).

An abundance of 421 (CV=0.55) for

Kogia sp. was estimated from a shipboard line

transect sighting survey conducted between 8 July

and 17 August 1998 that surveyed 5,570 km of

track line in waters south of Maryland (38°N)

(Figure 1; Mullin in review). Abundance estimates

were made using the program DISTANCE

(Buckland et al. 1993; Laake et al. 1993) where

school size bias and ship attraction were accounted

for.

The best available abundance estimate for

Kogia sp. is the sum of the estimates from the two

1998 USA Atlantic surveys, 536 (CV=0.45), where

the estimate from the northern USA Atlantic is 115

(CV=0.61) and from the southern USA Atlantic is

421 (CV=0.55). This joint estimate is considered

best because together these two surveys have the

most complete coverage of the species’ habitat.

Minimum Population Estimate

The minimum population estimate is the lower limit of the two-tailed 60% confidence interval of the lognormally distributed best abundance estimate. This is equivalent to the 20th percentile of the log-normal distribution

as specified by Wade and Angliss (1997). The best estimate of abundance for Kogia sp. is 536 (CV=0.45). The

minimum population estimate for Kogia sp. is 373.
154

Current Population Trend

The available information is insufficient to evaluate trends in population size for this species in the western

North Atlantic. 

CURRENT AND MAXIMUM NET PRODUCTIVITY RATES

Current and maximum net productivity rates are unknown for this stock. For purposes of this assessment,

the maximum net productivity rate was assumed to be 0.04. This value is based on theoretical modeling showing

that cetacean populations may not grow at rates much greater than 4% given the constraints of their reproductive life

history (Barlow et al. 1995). 

POTENTIAL BIOLOGICAL REMOVAL

Potential Biological Removal (PBR) is the product of minimum population size, one-half the maximum

productivity rate, and a “recovery” factor (Wade and Angliss 1997). The minimum population size is 373. The

maximum productivity rate is 0.04, the default value for cetaceans. The “recovery” factor, which accounts for

endangered, depleted, threatened stocks, or stocks of unknown status relative to optimum sustainable population

(OSP) is assumed to be 0.5 because this stock is of unknown status. PBR for the western North Atlantic Kogia sp. is

3.7. 

ANNUAL HUMAN-CAUSED MORTALITY AND SERIOUS INJURY

There has been one logbook report of fishery-related serious injury recorded off the east coast of Florida in

2000 (Table 1) (Yeung, 2001). The resultant estimated mean annual mortality is 6 pygmy sperm whales (CV=1.0)

for the years 1996-2000.

Fishery Information

 Data on current incidental takes in USA fisheries are available from several sources. In 1986, NMFS

established a mandatory self-reporting fisheries information system for large pelagic fisheries. The Northeast

Fisheries Science Center (NEFSC) Sea Sampling Observer Program was initiated in 1989, and since that year

several fisheries have been covered by the program. In late 1992 and in 1993, the SEFSC provided observer

coverage of pelagic longline vessels fishing off the Grand Banks (Tail of the Banks) and provides observer coverage

of vessels fishing south of Cape Hatteras. There have been no observed mortalities or serious injuries by NMFS Sea

Samplers in the pelagic drift gillnet, pelagic longline, pelagic pair trawl, Northeast multispecies sink gillnet, midAtlantic coastal sink gillnet, nor North Atlantic bottom trawl fisheries. One observed serious injury was reported in

2000 in the pelagic longline fishery (Table 1).
155

Table 1. Summary of the incidental mortality of pygmy sperm whale (Kogia breviceps) by commercial fishery

including the years sampled (Years), the number of vessels active within the fishery (Vessels), the type of

data used (Data Type), the annual observer coverage (Observer Coverage), the observed mortalities and

serious injuries recorded by on-board observers, the estimated annual mortality and serious injury, the

combined annual estimates of mortality and serious injury (Estimated Combined Mortality), the estimated

CV of the combined estimates (Estimated CVs) and the mean of the combined estimates (CV in

parentheses).

Fishery Years Vessels 3 Data Type 1 Observer

Coverage 

Observed

Serious

Injury

Observed

Mortality

Estimated

Serious

Injury

Estimated

Mortality 

Estimated

Combined

Mortality

Estimated

CVs 

Mean

Annual

Mortality

Pelagic

Longline2

96-00 253, 245,

205, 193,

186

Obs. Data

Logbook

.03, .03,

.03, .04,

.04

0, 0, 0, 0, 1 0, 0, 0, 0, 0 0, 0, 0, 0,

28

 0, 0 ,0 ,0,

0

0, 0, 0, 0,

 28 2

0, 0, 0, 0,

1.0

6

(1.0)

TOTAL 6

(1.0)

1 Observer data (Obs. Data) are used to measure bycatch rates, and the data are collected within the Southeast

Fisheries Science Center (SEFSC) Observer Program. NEFSC collects landings data (Weighout), and total

landings are used as a measure of total effort for the coastal gillnet fishery. Observed bycatch rates are

raised to total fishing effort reported to the SEFSC Atlantic Large Pelagic Logbook. 2 The 2000 mortality estimates were taken from Table 10 in Yeung 2001(NMFS Miami Laboratory PRD

00/01-17), and exclude the Gulf of Mexico. 3 Number of vessels in the fishery are based on vessels reporting effort to the pelagic longline logbook.

There were no documented strandings of pygmy sperm whales along the USA Atlantic coast during 1987-

present which were classified as likely caused by fishery interactions. Stranding data probably underestimate the

extent of fishery-related mortality and serious injury because not all of the marine mammals which die or are

seriously injured may wash ashore, nor will all of those that do wash ashore necessarily show signs of entanglement

or other fishery-interaction. Finally, the level of technical expertise among stranding network personnel varies

widely as does the ability to recognize signs of fishery interaction.

Other Mortality

Historical stranding records (1883-1988) of pygmy sperm whales in the southeastern USA (Credle 1988),

and strandings recorded during 1988-1997 (Barros et al. 1998) indicate that this species accounts for about 83% of

all Kogia strandings in this area. During the period 1990-October 1998, 21 pygmy sperm whale strandings occurred

in the northeastern USA (Delaware, New Jersey, New York and Virginia), whereas 194 strandings were documented

along the USA Atlantic coast between North Carolina and the Florida Keys in the same period. Remains of plastic

bags and other marine debris have been retrieved from the stomachs of 13 stranded pygmy sperm whales in the

southeastern USA (Barros et al. 1990, 1998), and at least on one occasion the ingestion of plastic debris is believed

to have been the cause of death. During the period 1987-1994, 1 animal had possible propeller cuts on its flukes. 

STATUS OF STOCK

The status of the pygmy sperm whale to OSP in the US Atlantic EEZ is unknown. This species is not listed

as endangered or threatened under the Endangered Species Act. There is insufficient information with which to

assess population trends. Total fishery-related mortality and serious injury for this stock is not less than 10% of the

calculated PBR and therefore, cannot be considered to be insignificant and approaching zero mortality and serious

injury rate. This is a strategic stock because the 1996-2000 estimated average annual fishery-related mortality to

pygmy sperm whales, (Kogia breviceps), exceeds PBR.
156

REFERENCES

Barlow, J., S. L. Swartz, T. C. Eagle and P. R. Wade. 1995. U.S. Marine Mammal Stock Assessments: Guidelines

for Preparation, Background, and a Summary of the 1995 Assessments. U.S. Dep. Commer., NOAA Tech.

Memo. NMFS-OPR-6, 73 pp.

Barros, N. B., D. A. Duffield, P. H. Ostrom, D.K . Odell and V. R. Cornish. 1998. Nearshore vs. offshore ecotype

differentiation of Kogia breviceps and K. simus based on hemoglobin, morphometric and dietary analyses.

Abstracts. World Marine Mammal Science Conference. Monaco. 20-24 January. 

Barros, N. B., D. K. Odell and G. W. Patton. 1990. Ingestion of plastic debris by stranded marine mammals from

Florida. Page 746 in Shomura, R.S. and M.L. Godfrey (eds). Proceedings of the Second International

Conference on Marine Debris. NOAA Tech. Memo. NOAA-TM-NMFS-SWFSC-154.

Buckland, S. T., D. R. Anderson, K. P. Burnham and J. L. Laake. 1993. Distance Sampling: estimating abundance

of biological populations. Chapman & Hall, London, 446 pp. 

Caldwell, D. K. and M. C. Caldwell. 1989. Pygmy sperm whale Kogia breviceps (de Blainville 1838): dwarf sperm

whale Kogia simus Owen, 1866. Pp. 235-260 in: S. H. Ridgway and R. Harrison, Handbook of marine

mammals, Vol. 4: river dolphins and the larger toothed whales. Academic Press, San Diego. 

Credle, V. R. 1988. Magnetite and magnetoreception in dwarf and pygmy sperm whales, Kogia simus and Kogia

breviceps. MSc. Thesis. University of Miami. Coral Gables, FL.

Hansen, L. J., K. D. Mullin and C. L. Roden. 1994. Preliminary estimates of cetacean abundance in the U.S.

Atlantic Exclusive Economic Zones from 1992 vessel surveys. Southeast Fisheries Science Center, Miami

Laboratory, Contribution No. MIA-93/94-58.

Laake, J. L., S. T. Buckland, D. R. Anderson and K. P. Burnham. 1993. DISTANCE user’s guide, V2.0. Colorado

Cooperative Fish & Wildlife Research Unit, Colorado State University, Ft. Collins, Colorado, 72 pp. 

Mullin, K. D. (in review). Abundance and distribution of cetaceans in the southern U.S. Atlantic Ocean during

summer 1998. Fish. Bull.

Palka, D. 1995. Abundance estimate of the Gulf of Maine harbor porpoise. Rep. int Whal. Commn. Special Issue

16: 27-50

Palka, D., G. Waring, and D. Potter. (in review). Abundances of cetaceans and sea turtles in the northwest Atlantic

during summer 1995 and 1998. Fish. Bull., U.S.

Wade P. R. and R. P. Angliss. 1997. Guidelines for assessing marine mammal stocks: Report of the GAMMS

Workshop April 3-5, 1996, Seattle, Washington. U.S. Dep. Commer., NOAA Tech. Memo. NMFS-OPR12, 93 pp.

Yeung, C. 2001. Estimates of marine mammal and marine turtle bycatch by the U.S. Atlantic pelagic longline fleet

in 1999-2000. NOAA Tech. Memo. NOAA-TM-SEFSC-467, 42 pp. NMFS, Southeast Fisheries Science

Center, Miami, FL.
157

Figure 1. Distribution of spotted dolphin sightings from

NEFSC and SEFSC shipboard and aerial surveys during

the summer in 1990-1998. Isobaths are at 100 m and

1,000 m. 

January 2002

PANTROPICAL SPOTTED DOLPHIN (Stenella attenuata):

Western North Atlantic Stock

STOCK DEFINITION AND GEOGRAPHIC RANGE

There are two species of spotted dolphin in the Western Atlantic — the Atlantic spotted dolphin, Stenella

frontalis, formerly S. plagiodon (Perrin et al. 1987), and the pantropical spotted dolphin, S. attenuata. These species

are difficult to differentiate at sea. 

The pantropical spotted dolphin is distributed worldwide in tropical and some sub-tropical oceans (Perrin et

al. 1987; Perrin and Hohn 1994). Sightings of this species in the northern Gulf of Mexico occur over the deeper

waters, and rarely over the continental shelf or continental shelf edge (Mullin et al. 1991; SEFSC, unpublished

data). Pantropical spotted dolphins were seen in all seasons during recent seasonal aerial surveys of the northern

Gulf of Mexico, and during recent winter aerial surveys offshore of the southeastern USA Atlantic coast (SEFSC

unpublished data). Some of the Pacific populations have been divided into different geographic stocks based on

morphological characteristics (Perrin et al. 1987; Perrin and Hohn 1994); however, there is no information on stock

differentiation in the Atlantic population. 

POPULATION SIZE

Total numbers of pantropical spotted

dolphins off the USA or Canadian Atlantic coast are

unknown, although three estimates from selected

regions of the habitat do exist for select time periods. 

Because S. frontalis and S. attenuata are difficult to

differentiate at sea, the reported abundance estimates,

prior to 1998, are for both species of spotted dolphins

combined. Sightings were almost exclusively in the

continental shelf edge and continental slope areas

west of Georges Bank (Figure 1). An abundance of

6,107 undifferentiated spotted dolphins (CV=0.27)

was estimated from an aerial survey program

conducted from 1978 to 1982 on the continental, shelf

and shelf edge waters between Cape Hatteras, North

Carolina and Nova Scotia (CETAP 1982). As

recommended in the GAMS Workshop Report (Wade

and Angliss 1997), estimates older than eight years

are deemed unreliable, therefore should not be used

for PBR determinations. Further, due to changes in

survey methodology these data should not be used to

make comparisons to more current estimates.

An abundance of 4,772 (CV=1.27)

undifferentiated spotted dolphins was estimated from

a July to September 1995 sighting survey conducted

by two ships and an airplane that covered waters from

Virginia to the mouth of the Gulf of St. Lawrence

(Table 1; Palka et al. in review). Total track line

length was 32,600 km. The ships covered waters

between the 50 and 1000 fathom depth contour lines,

the northern edge of the Gulf Stream, and the northern Gulf of Maine/Bay of Fundy region. The airplane covered

waters in the mid-Atlantic from the coastline to the 50 fathom depth contour line, the southern Gulf of Maine, and
158

shelf waters off Nova Scotia from the coastline to the 1000 fathom depth contour line. Data collection and analysis

methods used were described in Palka (1996). 

An abundance of 343 (CV=1.03) for pantropical spotted dolphins was estimated from a line transect

sighting survey conducted during July 6 to September 6, 1998 by a ship and plane that surveyed 15,900 km of track

line in waters north of Maryland (38° N) (Figure 1; Palka et al. in review). Shipboard data were analyzed using the

modified direct duplicate method (Palka 1995) that accounts for school size bias and g(0), the probability of

detecting a group on the track line. Aerial data were not corrected for g(0).

An abundance of 12,774 (CV=0.57) for pantropical spotted dolphins was estimated from a shipboard line

transect sighting survey conducted between 8 July and 17 August 1998 that surveyed 5,570 km of track line in

waters south of Maryland (38°N) (Figure 1; Mullin in review). Abundance estimates were made using the program

DISTANCE (Buckland et al. 1993; Laake et al. 1993) where school size bias and ship attraction were accounted for.

The best available abundance estimate for pantropical spotted dolphins is the sum of the estimates from the

two 1998 USA Atlantic surveys, 13,117 (CV=0.56), where the estimate from the northern USA Atlantic is 343

(CV=1.03) and from the southern USA Atlantic is 12,774 (CV=0.57). This joint estimate is considered best because

together these two surveys have the most complete coverage of the species’ habitat.

Table 1. Summary of abundance estimates for both undifferentiated spotted dolphins (1995) and differentiated

pantropical spotted dolphins (1998). Month, year, and area covered during each abundance survey, and

resulting abundance estimate (Nbest) and coefficient of variation (CV).

Month/Year Area Nbest CV

Jul-Sep 1995 Virginia to Gulf of St. Lawrence 4,7721 1.27

Jul-Sep 1998 Maryland to Gulf of St. Lawrence 3432 1.03

Jul-Aug 1998 Florida to Maryland 12,7742 0.57

Jul-Aug 1998 Gulf of St. Lawrence to Florida (COMBINED) 13,1173 0.56

1

 Because of uncertain species identification in the 1995 survey, all spotted dolphins were lumped together. 2

 This represents the first estimates for pantropical spotted dolphin. 3

 This represents the combined estimates for both regions.

Minimum Population Estimate

The minimum population estimate is the lower limit of the two-tailed 60% confidence interval of the lognormally distributed best abundance estimate. This is equivalent to the 20th percentile of the log-normal distribution

as specified by Wade and Angliss (1997). The best estimate of abundance for pantropical spotted dolphins is 13,117

(CV=0.56). The minimum population estimate for pantropical spotted dolphins is 8,450 (CV=0.56).

Current Population Trend

There are insufficient data to determine the population trends for this species, because prior to 1998 spotted

dolphins (Stenella spp) were not differentiated during surveys. 

CURRENT AND MAXIMUM NET PRODUCTIVITY RATES

Current and maximum net productivity rates are unknown for this stock. For purposes of this assessment,

the maximum net productivity rate was assumed to be 0.04. This value is based on theoretical modeling showing

that cetacean populations may not grow at rates much greater than 4% given the constraints of their reproductive life

history (Barlow et al. 1995). 

POTENTIAL BIOLOGICAL REMOVAL

Potential Biological Removal (PBR) is the product of minimum population size, one-half the maximum

productivity rate, and a “recovery” factor (MMPA Sec. 3. 16 U.S.C. 1362; Wade and Angliss 1997). The minimum

population size for pantropical spotted dolphins is 8,450 (CV=0.56). The maximum productivity rate is 0.04, the
159

default value for cetaceans. The “recovery” factor, which accounts for endangered, depleted, threatened stocks, or

stocks of unknown status relative to optimum sustainable population (OSP) is assumed to be 0.5 because this stock is

of unknown status. PBR for pantropical dolphins is 84.

ANNUAL HUMAN-CAUSED MORTALITY AND SERIOUS INJURY

Total annual estimated average fishery-related mortality or serious injury to this stock during 1996-2000

was 0 undifferentiated spotted dolphin (Stenella sp.). 

Fisheries Information

No spotted dolphin mortalities were observed in 1977-1991 foreign fishing activities. Data on current

incidental takes in USA fisheries are available from several sources. In 1986, NMFS established a mandatory selfreported fisheries information system for large pelagic fisheries. Data files are maintained at the Southeast Fisheries

Science Center (SEFSC). The Northeast Fisheries Science Center (NEFSC) Sea Sampling Observer Program was

initiated in 1989 and since that year several fisheries have been covered by the program. In late 1992 and in 1993,

the SEFSC provided observer coverage of pelagic longline vessels fishing off the Grand Banks (Tail of the Banks)

and provides observer coverage of vessels fishing south of Cape Hatteras. Total fishery-related mortality and serious

injury cannot be estimated separately for the two species of spotted dolphins in the USA Atlantic Exclusive

Economic Zone (EEZ) because of the uncertainty in species identification by fishery observers. The Atlantic

Scientific Review Group advised adopting the risk-averse strategy of assuming that either species might have been

subject to the observed fishery-related mortality and serious injury.

Bycatch has been observed by NMFS Sea Samplers in the pelagic drift gillnet and pelagic longline

fisheries, but no mortalities or serious injuries have been documented in the pelagic pair trawl, Northeast

multispecies sink gillnet, mid-Atlantic coastal gillnet, and North Atlantic bottom trawl fisheries; and no takes have

been documented in a review of Canadian gillnet and trap fisheries (Read 1994).

Pelagic Drift Gillnet

The estimated total number of hauls in the pelagic drift gillnet fishery increased from 714 in 1989 to 1,144

in 1990; thereafter, with the introduction of quotas, effort was severely reduced. The estimated number of hauls in

1991, 1992, 1993, 1994, 1995, 1996, and 1998 were 233, 243, 232, 197, 164, 149, 113 respectively. In 1996 and

1997, NMFS issued management regulations which prohibited the operation of this fishery in 1997. Further, in

January 1999 NMFS issued a Final Rule to prohibit the use of driftnets (i.e., permanent closure) in the North

Atlantic swordfish fishery (50 CFR Part 630). Fifty-nine different vessels participated in this fishery at one time or

another between 1989 and 1993. Since 1994, between 10 and 13 vessels have participated in the fishery. Observer

coverage, expressed as percent of sets observed, was 8% in 1989, 6% in 1990, 20% in 1991, 40% in 1992, 42% in

1993, 87% in 1994, 99% in 1995, 64% in 1996, and 99% in 1998. Effort was concentrated along the southern edge

of Georges Bank and off Cape Hatteras. Examination of the species composition of the catch and locations of the

fishery throughout the year, suggested that the pelagic drift gillnet fishery be stratified into two strata, a southern or

winter stratum, and a northern or summer stratum. Estimates of the total bycatch from 1989 to 1993 were obtained

using the aggregated (pooled 1989-1993) catch rates, by strata (Northridge 1996). Estimates of total annual bycatch

for 1994 and 1995 were estimated from the sum of the observed caught and the product of the average bycatch per

haul and the number of unobserved hauls as recorded in self-reported fisheries information. Variances were

estimated using bootstrap re-sampling techniques. Forty-nine spotted dolphin mortalities were observed in the drift

gillnet fishery between 1989 and 1998 and occurred northeast of Cape Hatteras within the 183 m isobath in

February-April, and near Lydonia Canyon in October. Six whole animal carcasses that were sent to the Smithsonian

were identified as Pantropical spotted dolphins (S. attenuata). The remaining animals were not identified to species. 

Estimated annual mortality and serious injury attributable to this fishery (CV in parentheses) was 25 in 1989 (.65),

51 in 1990 (.49), 11 in 1991 (.41), 20 in 1992 (0.18), 8.4 in 1993 (0.40), 29 in 1994 (0.01), 0 in 1995, 2 in 1996

(0.06), no fishery in 1997, and 0 in 1998. 

Pelagic Longline

 The pelagic longline fishery operates in the USA Atlantic ( including Caribbean) and Gulf of Mexico EEZ

(SEFSC unpublished data). Interactions between the pelagic longline fishery and spotted dolphins have been

reported; however, a vessel may fish in more than one statistical reporting area and it is not possible to separate

estimates of fishing effort other than to subtract Gulf of Mexico effort from Atlantic fishing effort, which includes

the Caribbean Sea. This fishery has been monitored with about 5% observer coverage, in terms of trips observed,
160

since 1992. Total effort, excluding the Gulf of Mexico, for the pelagic longline fishery, based on mandatory selfreported fisheries information, was 11,279 sets in 1991, 9,869 sets in 1992, 9,862 sets in 1993, 9,481 sets in 1994,

10,129 sets in 1995, 9,885 sets in 1996, 8,023 sets in 1997, and 6,675 sets in 1998 (Cramer 1994; Scott and Brown

1997; Johnson et al.1999; Yeung, 1999a). Since 1992, this fishery has been monitored with about 5% observer

coverage, in terms of trips observed, within every statistical reporting area within the US Atlantic EEZ and beyond. 

Off the US Atlantic coast, the fishery has been observed from January to March off Cape Hatteras, in May and June

in the entire mid-Atlantic, and in July through December in the mid-Atlantic Bight and off Nova Scotia. The 1994-

1998, estimated take was based on a revised analysis of the observed incidental take and self-reported incidental take

and effort data, and replaces previous estimates for the 1992-1993 and 1994-1995 periods (Cramer 1994; Scott and

Brown 1997; Johnson et al. 1999; Yeung 1999b). Further, Yeung (1999b) revised the 1992-1997 fishery mortality

estimates in Johnson et al. (1999) to include seriously injured animals. The 1998 bycatch estimates were from

Yeung (1999a). Most of the estimated marine mammal bycatch was from US Atlantic EEZ waters between South

Carolina and Cape Cod (Johnson et al. 1999). Excluding the Gulf of Mexico where one animal was hooked and

released alive, no pantropical spotted dolphin bycatches were observed for 1992-1998. 

Other Mortality

From 1995-1998, 15 pantropical spotted dolphins were stranded between North Carolina and Florida

(NMFS unpublished data). The 15 mortalities includes the 1996 mass stranding of 11 animals in Florida (NMFS

unpublished data).

STATUS OF STOCK

The status of pantropical spotted dolphins, relative to OSP in the US Atlantic EEZ is unknown. The species

is not listed as threatened or endangered under the Endangered Species Act. There are insufficient data to determine

the population trends for this species. Total fishery-related mortality and serious injury for this stock is less than

10% of the calculated PBR and, therefore, can be considered to be insignificant and approaching zero mortality and

serious injury rate. Average annual fishery-related mortality and serious injury does not exceed the PBR; therefore,

this is not a strategic stock

REFERENCES

Barlow, J., S. L. Swartz, T. C. Eagle, and P. R. Wade. 1995. U.S. Marine Mammal Stock Assessments: Guidelines

for Preparation, Background, and a Summary of the 1995 Assessments. U.S. Dep. Commer., NOAA Tech.

Memo. NMFS-OPR-6, 73 pp.

Buckland, S. T., D. R. Anderson, K. P. Burnham and J. L. Laake. 1993. Distance sampling: estimating abundance

of biological populations. Chapman and Hall, New York, NY. 442 pp.

CETAP. 1 982. A characterization of marine mammals and turtles in the mid- and north Atlantic areas of the U.S.

outer continental shelf. Cetacean and Turtle Assessment Program, University of Rhode Island. Final

Report, Contract AA51-C78-48, Bureau of Land Management, Washington, DC. 538 pp. 

Cramer, J. 1994. Large pelagic logbook newsletter - 1993. NOAA Tech. Mem. NMFS-SEFSC-352, 19 pp. NMFS,

Southeast Fisheries Science Center, Miami, FL.

Johnson, D. R., C. A. Brown, and C. Yeung. 1999. Estimates of marine mammal and marine turtle catch by the

U.S. Atlantic pelagic longline fleet in 1992-1997. SEFSC PRD-98/99-03. 68 pp.

Laake, J. L., S. T. Buckland, D. R. Anderson and K. P. Burnham. 1993. DISTANCE user’s guide, V2.0. Colorado

Cooperative Fish & Wildlife Research Unit, Colorado State University, Ft. Collins, Colorado, 72 pp. 

Mullin, K. D. (in review). Abundance and distribution of cetaceans in the southern U.S. Atlantic Ocean during

summer 1998. Fish. Bull., U.S.

Mullin, K., W. Hoggard, C. Roden, R. Lohoefener, C. Rogers and B. Taggart. 1991. Cetaceans on the upper

continental slope in the north-central Gulf of Mexico. OCS Study/MMS 91-0027. U.S. Dept. of the

Interior, Minerals Management Service, Gulf of Mexico OCS Regional Office, New Orleans, Louisiana,

108 pp. 

Northridge, S. 1996. Estimation of cetacean mortality in the U.S. Atlantic swordfish and tuna drift gillnet and pair

trawl fisheries. Final report to the Northeast Fisheries Science Center, Contract No. 40ENNF500160.

Palka, D. 1995. Abundance estimate of the Gulf of Maine harbor porpoise. Rep. int Whal. Commn. Special Issue

16:27-50.
161

Palka, D. 1996. Update on abundance of Gulf of Maine/Bay of Fundy harbor porpoises. NOAA-NMFS-NEFSC.

Ref. Doc. 96-04; 37p. Available from: National Marine Fisheries Service, 166 Water Street, Woods Hole,

MA 02543-1026.

Palka, D., G. Waring, and D. Potter. (in review). Abundances of cetaceans and sea turtles in the northwest Atlantic

during summer 1995 and 1998. Fish. Bull., U.S.

Perrin, W. F.,E. D. Mitchell, J. G. Mead, D. K. Caldwell, M. C. Caldwell, P. J. H. van Bree, and W. H. Dawbin.

1987. Revision of the spotted dolphins, Stenella sp. Mar. Mammal Sci. 3(2): 99-170.

Perrin, W. F. and A. A. Hohn. 1994. Pantropical spotted dolphin Stenella attenuata. Pp. 71-98 in: S. H. Ridgway

and R. Harrison (eds.). Handbook of marine mammals, Vol. 5: The first book of dolphins. Academic

Press, San Diego, 418 pp. 

Scott, G. P. and C. A. Brown. 1997. Estimates of marine mammal and marine turtle catch by the U.S. Atlantic

pelagic longline fleet in 1994-1995. Miami Laboratory Contribution MIA-96/97-28

Wade, P. R., and R. P. Angliss. 1997. Guidelines for assessing marine mammal stocks: Report of the GAMMS

Workshop April 3-5, 1996, Seattle, Washington. U.S. Dep. Commer., NOAA Tech. Memo. NMFS-OPR012, 93 pp.

Waring, G. T., D. L. Palka, P. J. Clapham, S. Swartz, M. C. Rossman, T. V. N. Cole, L. J. Hansen, K. D. Bisack, K.

D. Mullin, R. S. Wells, D. K. Odell, and N. B. Barros. 1999. U.S. Atlantic and Gulf of Mexico marine

mammal stock assessments — 1999. U.S. Dep. Commer., NOAA Tech. Memo NMFS-NE-153, 196pp. 

Yeung, C. 1999a. Estimates of marine mammal and marine turtle bycatch by the U.S. Atlantic pelagic longline fleet

in 1998. NOAA Tech. Memo. NMFS-SEFSC-430, 26 pp. NMFS, Southeast Fisheries Science Center,

Miami, FL.

Yeung, C. 1999b. Revised Mortality Estimates of Marine Mammal Bycatch in 1992-1997 based on Serious Injury

Guidelines. NOAA Tech. Memo. NMFS-SEFSC-429, 23 pp. NMFS, Southeast Fisheries Science Center,

Miami, FL.
162

Figure 1. Distribution of bottlenose dolphin sightings

from NEFSC and SEFSC shipboard and aerial surveys

during the summer in 1990-1998. Isobaths are at 100 m

and 1,000 m. 

January 2002

BOTTLENOSE DOLPHIN (Tursiops truncatus):

Western North Atlantic Offshore Stock

STOCK DEFINITION AND GEOGRAPHIC RANGE

There are two hematologically and morphologically distinct bottlenose dolphin ecotypes (Duffield et al.

1983; Duffield 1986) which correspond to a shallow water ecotype and a deep water ecotype; both ecotypes have

been shown to inhabit waters in the western North Atlantic Ocean (Hersh and Duffield 1990; Mead and Potter 1995;

Curry and Smith 1997). 

Bottlenose dolphins which had stranded alive in the western North Atlantic in areas with direct access to

deep oceanic waters had hemoglobin profiles which matched that of the deep, cold water ecotype (Hersh and

Duffield 1990). Hersh and Duffield (1990) also

described morphological differences between the

deep, cold water ecotype dolphins and dolphins with

hematological profiles matching the shallow, warm

water ecotype which had stranded in the

Indian/Banana River in Florida. Based on the

distribution of sightings during ship-based surveys

(Figure 1) and survey personnel observations (NMFS

unpublished data), the western North Atlantic

offshore stock is believed to consist of bottlenose

dolphins corresponding to the hematologically and

morphologically distinct deep, cold water ecotype.

Extensive aerial surveys in 1979-1981

indicated that the stock extended along the entire

continental shelf break from Georges Bank to Cape

Hatteras during spring and summer (CETAP 1982;

Kenney 1990). The distribution of sightings

contracted towards the south in the fall and the

central portion of the survey area was almost devoid

of sightings in the winter, although there were still

sightings as far north as the southern edge of Georges

Bank. The offshore stock is concentrated along the

continental shelf break in waters of depths >25 m and

extends beyond the continental shelf into continental

slope waters in lower concentration (Figure 1) 

consistent with Kenney 1990. In Canadian waters,

bottlenose dolphins have occasionally been sighted

on the Scotian Shelf, particularly in the Gully

(Gowans and Whitehead 1995; NMFS unpublished

data). Recent information from Wells et al. (1999)

indicates that the range of the offshore bottlenose

dolphin may include waters beyond the continental

slope and that offshore bottlenose dolphins may move between the Gulf of Mexico and the Atlantic. Dolphins with

characteristics of the offshore type have been stranded as far south as the Florida Keys, but there are no abundance

or distribution estimates available for this stock in USA Exclusive Economic Zone (EEZ) waters south of Cape

Hatteras. 

POPULATION SIZE

An abundance of 16,689 (CV=0.32) for bottlenose dolphins was estimated from a line transect sighting

survey conducted during July 6 to September 6, 1998 by a ship and plane that surveyed 15,900 km of track line in
163

waters north of Maryland (38° N) (Figure 1; Palka et al. in review). Shipboard data were analyzed using the

modified direct duplicate method (Palka 1995) that accounts for school size bias and g(0), the probability of

detecting a group on the track line. Aerial data were not corrected for g(0).

An abundance of 13,944 (CV=0.38) for bottlenose dolphins was estimated from a shipboard line transect

sighting survey conducted between 8 July and 17 August 1998 that surveyed 5,570 km of track line in waters south

of Maryland (38°N) (Figure 1; Mullin in review). Abundance estimates were made using the program DISTANCE

(Buckland et al. 1993; Laake et al. 1993) where school size bias and ship attraction were accounted for.

The best available abundance estimate for bottlenose dolphins is the sum of the estimates from the two

1998 USA Atlantic surveys, 30,633 (CV=0.25), where the estimate from the northern USA Atlantic is 16,689

(CV=0.32) and from the southern USA Atlantic is 13,944 (CV=0.38). This joint estimate is considered best because

together these two surveys have the most complete coverage of the species’ habitat.

Minimum Population Estimate

The minimum population estimate is the lower limit of the two-tailed 60% confidence interval of the lognormally distributed best abundance estimate. This is equivalent to the 20th percentile of the log-normal distribution

as specified by Wade and Angliss (1997). The best estimate of abundance for offshore bottlenose dolphins is 30,633

(CV=0.25). The minimum population estimate for the western North Atlantic offshore bottlenose is 24,897.

Current Population Trend

The data are insufficient to determine population trends. Previous estimates cannot be applied to this

process because previous survey coverage of the species’ habitat was incomplete.

CURRENT AND MAXIMUM NET PRODUCTIVITY RATES

Current and maximum net productivity rates are unknown for this stock. For purposes of this assessment,

the maximum net productivity rate was assumed to be 0.04. This value is based on theoretical modeling showing

that cetacean populations may not grow at rates much greater than 4% given the constraints of their reproductive life

history (Barlow et al. 1995). 

POTENTIAL BIOLOGICAL REMOVAL

Potential Biological Removal (PBR) is the product of minimum population size, one-half the maximum

productivity rate, and a “recovery” factor (MMPA Sec. 3. 16 U.S.C. 1362; Wade and Angliss 1997). The minimum

population size for offshore bottlenose dolphins is 24,897. The maximum productivity rate is 0.04, the default value

for cetaceans. The “recovery” factor, which accounts for endangered, depleted, threatened stocks, or stocks of

unknown status relative to optimum sustainable population (OSP) is assumed to be 0.5 because this stock is of

unknown status. PBR for the western North Atlantic offshore bottlenose dolphin is 249.

ANNUAL HUMAN-CAUSED MORTALITY AND SERIOUS INJURY

 Total estimated mean annual fishery-related mortality to this stock during 1996-2000 was 27 (CV=1.12)

bottlenose dolphins. 

Fishery Information

There was no documentation of marine mammal mortality or serious injury in distant-water fleet (DWF)

activities off the northeast coast of the USA prior to 1977. A fisheries observer program which recorded fishery data

and information on incidental bycatch of marine mammals was established with implementation of the Magnuson

Fisheries Conservation and Management Act (MFCMA) in 1977. DWF effort in the US Atlantic EEZ under

MFCMA was directed primarily towards Atlantic mackerel and squid. An average of 120 different foreign vessels

per year (range 102-161) operated within the US Atlantic EEZ from 1977 through 1982. In 1982, the first year that

NMFS Northeast Regional Observer Program assumed responsibility for observer coverage of the longline vessels,

there were 112 different foreign vessels, eighteen (16%) of which were Japanese tuna longline vessels operating

along the USA east coast. Between 1983 and 1991, the number of foreign fishing vessels operating within the US

Atlantic EEZ each year declined from 67 to 9. Between 1983 and 1988, the numbers of DWF vessels included 3, 5,

7, 6, 8, and 8, respectively, Japanese longline vessels. Observer coverage on DWF vessels was 25-35% during

1977-82, and increased to 58%, 86%, 95%, and 98%, respectively, in 1983-86. From 1987-91, 100% observer
164

coverage was maintained. Foreign fishing operations for squid ceased at the end of the 1986 fishing season and for

mackerel at the end of the 1991 season. Observers in this program recorded 9 bottlenose dolphin mortalities in

foreign-fishing activities during 1977-1988 (Waring et al. 1990). Seven takes occurred in the mackerel fishery, and

1 bottlenose dolphin each was caught in both the squid and hake trawl fisheries. 

Data on current incidental takes in USA fisheries are available from several sources. In 1986, NMFS

established a mandatory self-reported fisheries information system for large pelagic fisheries. Data files are

maintained at the Southeast Fisheries Science Center (SEFSC). The Northeast Fisheries Science Center (NEFSC)

Sea Sampling Observer Program was initiated in 1989, and since that year several fisheries have been covered by the

program. In late 1992 and in 1993, the SEFSC provided observer coverage of pelagic longline vessels fishing off the

Grand Banks (Tail of the Banks) and provides observer coverage of vessels fishing south of Cape Hatteras. 

Bycatch has been observed by NMFS Sea Samplers in the pelagic drift gillnet, pelagic pair trawl, New

England multispecies sink gillnet, North Atlantic bottom trawl fisheries, and pelagic longline fisheries.

Pelagic Longline

The pelagic longline fishery operates in the USA Atlantic (including Caribbean) and Gulf of Mexico EEZ

(SEFSC unpublished data). Interactions between the pelagic longline fishery and bottlenose dolphins have been

reported; however, a vessel may fish in more than one statistical reporting area and it is not possible to separate

estimates of fishing effort other than to subtract Gulf of Mexico effort from Atlantic fishing effort, which includes

the Caribbean Sea. Total effort, excluding the Gulf of Mexico, for the pelagic longline fishery, based on mandatory

self-reported fisheries information, was 11,279 sets in 1991, 9,869 sets in 1992, 9,862 sets in 1993, 9,481 sets in

1994, 10,129 sets in 1995, 9,885 sets in 1996, 8,023 sets in 1997, 6,765 in 1998, 6770 sets in 1999, and 6,582 sets in

2000 (Cramer 1994; Scott and Brown 1997; Johnson et al. 1999; Yeung 1999a; and Yeung, 2001). Since 1992, this

fishery has been monitored with about 5% observer coverage, in terms of trips observed, within every statistical

reporting area within the US Atlantic EEZ and beyond. Off the USA Atlantic coast, the fishery has been observed

from January to March off Cape Hatteras, in May and June in the entire mid-Atlantic, and in July through December

in the mid-Atlantic Bight and off Nova Scotia. Yeung (1999a) provides estimates of mortality for 1998, based on a

treatment which includes seriously injured animals as mortalities, following guidelines proposed by the NOAA

Fisheries Office of Protected Resources (Federal Register Docket No., I.D. 051398C). Yeung (1999b) provides

revised estimates of mortality for 1993-1997. These estimates, which treat seriously injured animals as mortalities,

replace the 1993-1997 estimates which were based on a revised analysis of the observed incidental take and selfreported incidental take and effort data (Johnson et al. 1999), and which replaced previous estimates for the 1992-

1993 (Cramer 1994) and 1994-1995 periods (Scott and Brown 1997). Most of the estimated marine mammal

bycatch was from US Atlantic EEZ waters between South Carolina and Cape Cod (Johnson et al. 1999). During

1993-1998, in waters not including the Gulf of Mexico, 1 bottlenose dolphin was caught and released alive during

1993, and 1 was caught and released alive during 1998.

Pelagic Drift Gillnet

The estimated total number of hauls in the pelagic drift gillnet fishery increased from 714 in 1989 to 1,144

in 1990; thereafter, with the introduction of quotas, effort was severely reduced. The estimated number of hauls in

1991, 1992, 1993, 1994, 1995, 1996, and 1998 were 233, 243, 232, 197, 164, 149, and 113, respectively. In 1996

and 1997, NMFS issued management regulations which prohibited the operation of this fishery in 1997. Further, in

January 1999 NMFS issued a Final Rule to prohibit the use of driftnets (i.e., permanent closure) in the North 

Atlantic swordfish fishery (50 CFR Part 630). Fifty-nine different vessels participated in this fishery at one time or

another between 1989 and 1993. Since 1994, between 10- 13 vessels have participated in the fishery (Table 1). 

Observer coverage, expressed as percent of sets observed, was 8% in 1989, 6% in 1990, 20% in 1991, 40% in 1992,

42% in 1993, 87% in 1994, 99% in 1995, 64% in 1996, no fishery in 1997, and 99% in 1998. 

Effort was concentrated along the southern edge of Georges Bank and off Cape Hatteras. Examination of

the species composition of the catch and locations of the fishery throughout the year, suggested that the pelagic drift

gillnet fishery be stratified into two strata, a southern or winter stratum, and a northern or summer stratum. 

Estimates of the total bycatch, from 1989 to 1993, were obtained using the aggregated (pooled 1989-1993) catch

rates, by strata (Northridge 1996). Estimates of total annual bycatch for 1994 and 1995 were estimated from the sum

of the observed caught and the product of the average bycatch per haul and the number of unobserved hauls as

recorded in self-reported fisheries information. Variances were estimated using bootstrap re-sampling techniques. 

Sixty bottlenose dolphin mortalities have been observed between 1989 and 1998. Estimated bottlenose dolphin

mortalities (CV in parentheses) extrapolated for each year were 72 in 1989 (0.18), 115 in 1990 (0.18), 26 in 1991
165

(0.15), 28 in 1992 (0.10), 22 in 1993 (0.13), 14 in 1994 (0.04), 5 in 1995 (0), 0 in 1996, and 3 in 1998 (0). Since this

fishery no longer exists, it has been excluded from Table 1.

Pelagic Pair Trawl

Effort in the pelagic pair trawl fishery increased during the period 1989 to 1993, from zero hauls in 1989

and 1990, to an estimated 171 hauls in 1991, and then to an estimated 536 hauls in 1992, 586 in 1993, 407 in 1994,

and 440 in 1995, respectively. This fishery ceased operations in 1996, when NMFS rejected a petition to consider

pair trawl gear as an authorized gear type in Atlantic tunas fishery. The fishery operated from August-November in

1991, from June-November in 1992, from June-October in 1993 (Northridge 1996), and from mid-summer to

November in 1994 and 1995. Sea sampling began in October 1992 (Gerrior et al. 1994), and 48 sets (9% of the

total) were sampled in that season, 102 hauls (17% of the total) were sampled in 1993. In 1994 and 1995, 52% and

55%, respectively, of the sets were observed. Nineteen vessels have operated in this fishery. The fishery extends

from 35o

N to 41oN, and from 69°W to 72°W. Approximately 50% of the total effort was within a one degree square

at 39o

N, 72oW, around Hudson Canyon. Examination of the 1991-1993 locations and species composition of the

bycatch, showed little seasonal change for the six months of operation and did not warrant any seasonal or areal

stratification of this fishery (Northridge 1996). Thirty-two bottlenose dolphin mortalities were observed between

1991 and 1995. Estimated annual fishery-related mortality (CV in parentheses) was 13 dolphins in 1991 (0.52), 73

in 1992 (0.49), 85 in 1993 (0.41), 4 in 1994 (0.40) and 17 in 1995 (0.26). Since this fishery no longer exists, it has

been excluded from Table 1. During the 1994 and 1995 experimental fishing seasons, fishing gear experiments were

conducted to collect data on environmental parameters, gear behavior, and gear handling practices to evaluate factors

affecting catch and bycatch (Goudey 1995, 1996). Results of these studies have been presented at Offshore

Cetacean Take Reduction Team Meetings.

North Atlantic Bottom Trawl:

Vessels in the North Atlantic bottom trawl fishery, a Category III fishery under the MMPA, were observed

in order to meet fishery management needs, rather than marine mammal management needs. An average of 970

(CV=0.04) vessels (full and part time) participated annually in the fishery during 1989-1993. The fishery is active in

New England waters in all seasons. One bottlenose dolphin mortality was documented in 1991 and the total

estimated mortality in this fishery in 1991 was 91 (CV=0.97). Since 1992 there were no bottlenose mortalities

observed in this fishery.

Squid, Mackerel and Butterfish:

The mid-Atlantic mackerel and squid trawl fisheries were combined into the Atlantic squid, mackerel and

butterfish trawl fishery in 1996. These fisheries operate seasonally, principally in the USA mid-Atlantic and

southern New England continental shelf region. The mackerel trawl fishery was classified as a Category II fishery

since 1990 and the squid fishery was originally classified as a Category II fishery in 1990, but was reclassified as a

Category III fishery in 1992. The combined fishery has been proposed for classification as a Category II fishery. In

1996, mackerel, squid, and butterfish trawl fisheries were combined into the Atlantic squid, mackerel, and butterfish

trawl fishery, and maintained a Category II classification. Although there were reports of bottlenose dolphin

mortalities in the foreign fishery during 1977-1988, there were no fishery-related mortalities of bottlenose dolphins

reported in the self-reported fisheries information from the mackerel trawl fishery between 1990-1992.

New England Multispecies Sink Gillnet

In 1993, there were approximately 349 full and part-time vessels in the Northeast multispecies sink gillnet

fishery, which covered the Gulf of Maine and southern New England (Table 1). An additional 187 vessels were

reported to occasionally fish with gillnets in the Gulf of Maine for bait or personal use; however these vessels were

not covered by the observer program (Walden 1996) and their fishing effort was not used in estimating mortality. 

Observer coverage in terms of trips has been 1%, 6%, 7%, 5%, 7%, 5%, 4%, 6%, 5%, 6%, and 6% for 1990 to 2000

respectively. The fishery has been observed in the Gulf of Maine and in Southern New England. In 2000, the first

observed mortality of bottlenose dolphins was recorded. This was genetically identified as an offshore, deep-water

ecotype. The estimated annual fishery-related serious injury and mortality attributable to this fishery (CV in

parentheses) was 0 from 1996-1999, and 132 (CV=1.16) in 2000 (Table 1). 

Mid-Atlantic Coastal Gillnet

Observer coverage of the USA Atlantic coastal gillnet fishery was initiated by the NEFSC Sea Sampling

program in July 1993, and from July to December 1993, 20 trips were observed. During 1994 and 1995, 221 and

382 trips were observed, respectively. This fishery, which extends from North Carolina to New York, is actually a

combination of small vessel fisheries that target a variety of fish species, some of which operate right off the beach. 
166

The number of vessels in this fishery is unknown, because records which are held by both state and federal agencies

have not been centralized and standardized. Observer coverage, expressed as percent of tons of fish landed, was 5%,

4%, 3%, 5%, 2%, and 2% for 1995, 1996, 1997, 1998, 1999 and 2000, respectively (Table 1).

Bottlenose dolphins were only reported during the trips in 1998, when 1 mortality was observed as a result

of this fishery. Though this dolphin was not genetically identified, it is being treated as an offshore, deep-water

ecotype because it was caught in the offshore habitat and statistical analyses of all biopsied bottlenose dolphins

caught in this offshore habitat indicate this animal has a high probability of being the offshore ecotype. Observed

effort was concentrated off NJ and scattered between DE and NC from 1 to 50 miles off the beach. All bycatches

were documented during January to April. Using the observed takes, the estimated annual mortality attributed to this

fishery was 0 in 1995 through 1997, 4 (CV=0.7) in 1998, and 0 from 1999 through 2000 (Table1).

Table 1. Summary of the incidental mortality of bottlenose dolphins (Tursiops truncatus) by commercial fishery

including the years sampled (Years), the number of vessels active within the fishery (Vessels), the type of

data used (Data Type), the annual observer coverage (Observer Coverage), the mortalities recorded by onboard observers (Observed Mortality), the estimated annual mortality (Estimated Mortality), the estimated

CV of the annual mortality (Estimated CVs) and the mean annual mortality (CV in parentheses).

Fishery Years Vessels Data Type 1 Observer

 Coverage 2

Observed

Serious

Injury

Observed

Mortality

Estimated

 Mortality 

Estimated

 CVs 

Mean

 Annual

Mortality

New

England 

Multisp.

 Sink

Gillnet

96-00 301 Obs. Data

 Dealer

Reports,

 Logbooks

.04, .06, 

.05, .06,

.06

0, 0, 0,

0, 0

0, 0,

0, 0,

1

0, 0,

0, 0,

132

0, 0,

0, 0

1.16

26

(1.16 )

midAtlantic

Coastal 

Gillnet 

96-00 Unk3 Obs. Data

Dealer

Reports

 .04, .03, 

.05, .02, 

.02

0, 0, 0,

0, 0

0, 0,

1, 0,

 0

 0, 0,

4, 0,

0

0, 0,

0.7, 0,

0

1

(0.7 )

TOTAL 27

(1.12 )

1 Observer data (Obs. Data) are used to measure bycatch rates, and the data are collected within the Northeast

Fisheries Science Center (NEFSC) Sea Sampling Program. Mandatory logbook (logbook) data collected by

the Southeast Fisheries Science Center (SEFSC) are used to measure total effort for the pelagic drift gillnet

fishery. The NEFSC collects landings data (Dealer Reports), and total landings are used as a measure of

total effort for the gillnet fisheries. Mandatory vessel trip reports (Logbook) data are used to determine the

spatial distribution of fishing effort in the Northeast multispecies sink gillnet fishery. 2 Observer coverage of the Northeast multispecies sink gillnet fishery is measured as the percentage of trips

observed. Observer coverage of the mid-Atlantic coastal gillnet fishery is measured as the percentage of 

tons of fish landed. 3 Number of vessels is not known.

Other Mortality

 Bottlenose dolphins are one of the most frequently stranded small cetaceans along the Atlantic coast. 

Many of the animals show signs of human interaction (i.e., net marks, mutilation, etc.). The estimated number of

animals that represent the offshore stock is presently under evaluation.

STATUS OF STOCK

The status of this stock relative to OSP in the US Atlantic EEZ is unknown. The western North Atlantic

offshore bottlenose dolphin is not listed as threatened or endangered under the Endangered Species Act. There are

insufficient data to determine the population trends for this species. This level is not less than 10% of the calculated
167

PBR and, therefore, cannot be considered to be insignificant and approaching zero mortality and serious injury 

rate. Average 1996-2000 annual fishery-related mortality and serious injury does not exceed the PBR; therefore, 

this is not a strategic stock.

REFERENCES

Barlow, J., S. L. Swartz, T. C. Eagle and P. R. Wade. 1995. U.S. Marine Mammal Stock Assessments: Guidelines

for Preparation, Background, and a Summary of the 1995 Assessments. U.S. Dep. Commer., NOAA Tech.

Memo. NMFS-OPR-6, 73 pp. 

Buckland, S. T., D. R. Andersen, K. P. Burnham and J. L. Laake. 1993. Distance sampling: Estimating abundance

of biological populations. Chapman and Hall, New York, 446 pp. 

CETAP (Cetacean and Turtle Assessment Program). 1982. A Characterization of Marine Mammals and Turtles in

the Mid- and North Atlantic Areas of the U.S. Outer Continental Shelf, Final Report, Contract AA551-CT8-

48, U.S. NTIS PB83-215855, Bureau of Land Management, Washington, DC, 576 pp. 

Cramer J. 1994. Large pelagic logbook newsletter - 1993. NOAA Tech. Mem. NMFS-SEFSC-352, 19 pp. NMFS,

Southeast Fisheries Science Center, Miami, FL.

Curry, B. E. and J. Smith. 1997. Phylogeographic structure of the bottlenose dolphin (Tursiops truncatus): stock

identification and implications for management. Pp. 327-247 in: A.E. Dizon, S.J. Chivers and W.F. Perrin

(eds.), Molecular genetics of marine mammals. Spec. Publ. 3 Society for Marine Mammalogy.

Duffield, D. A. 1986. Investigation of genetic variability in stocks of the bottlenose dolphin (Tursiops truncatus). 

Final report to the NMFS/SEFSC, Contract No. NA83-GA-00036, 53 pp. 

Duffield, D. A., S. H. Ridgway and L. H. Cornell. 1983. Hematology distinguishes coastal and offshore forms of

dolphins (Tursiops). Can. J. Zool. 61: 930-933. 

Gerrior, P., A. S. Williams and D. J. Christensen. 1994. Observations of the 1992 U.S. pelagic pair trawl fishery in

the Northwest Atlantic. U.S. Mar. Fish. Rev. 56(3): 24-27.

Goudey, C.A. 1995. The 1994 experimental pair trawl fishery for tuna in the northwest Atlantic, Massachusetts

Institute of Technology, Sea Grant, MITSG 95-6, Cambridge, MA. 10 pp.

Goudey, C.A. 1996. The 1995 experimental pair trawl fishery for tuna in the northwest Atlantic, Massachusetts

Institute of Technology, Sea Grant, MITSG 95-6, Cambridge, MA. 13 pp.

Gowans S. and H. Whitehead. 1995. Distribution and habitat partitioning by small odontocetes in the Gully, a

submarine canyon on the Scotian Shelf. Can. J. Zool. 73: 1599-1608.

Hersh, S. L. and D. A. Duffield. 1990. Distinction between northwest Atlantic offshore and coastal bottlenose

dolphins based on hemoglobin profile and morphometry. Pp. 129-139 in: S. Leatherwood and R. R. Reeves

(eds), The bottlenose dolphin, Academic Press, San Diego, 653 pp.

Johnson, D. R., C. A. Brown and C. Yeung. 1999. Estimates of marine mammal and marine turtle catch by the U.S.

Atlantic pelagic longline fleet in 1992-1997. NOAA Tech. Mem. NOAA-SEFSC-418, 70 pp. NMFS,

Southeast Fisheries Science Center, Miami, FL.

Kenney, R. D. 1990. Bottlenose dolphins off the northeastern United States. Pages 369-386 in: S. Leatherwood

and R. R. Reeves (eds), The bottlenose dolphin, Academic Press, San Diego, 653 pp. 

Laake, J. L., S. T. Buckland, D. R. Anderson and K. P. Burnham. 1993. DISTANCE user’s guide, V2.0. Colorado

Cooperative Fish & Wildlife Research Unit, Colorado State University, Ft. Collins, Colorado, 72 pp. 

Mead, J. G. and C. W . Potter. 1995. Recognizing two populations for the bottlenose dolphin (Tursiops truncatus)

off the Atlantic coast of North America: morphologic and ecologic considerations. International Biological

Research Institute Reports 5:31-43. 

Mullin, K. D. (in review). Abundance and distribution of cetaceans in the southern U.S. Atlantic Ocean during

summer 1998. Fish. Bull., U.S.

Northridge, S. 1996. Estimation of cetacean mortality in the U.S. Atlantic swordfish and tuna drift gillnet and pair

trawl fisheries. Final report to the Northeast Fisheries Science Center, Contract No. 40ENNF500045.

Palka, D. 1995. Abundance estimate of the Gulf of Maine harbor porpoise. Rep. int Whal. Commn. Special Issue

16:27-50

Palka, D., G. Waring and D. Potter. (in review). Abundances of cetaceans and sea turtles in the northwest Atlantic

during summer 1995 and 1998. Fish. Bull., U.S.

Scott, G.P. and C.A. Brown. 1997. Estimates of marine mammal and marine turtle catch by the U.S. Atlantic

pelagic longline fleet in 1994-1995. Miami Laboratory Contribution MIA - 96/97-28.
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Wade, P. R. and R. P. Angliss. 1997. Guidelines for assessing marine mammal stocks: Report of the GAMMS

Workshop April 3-5, 1996, Seattle, Washington. U.S. Dep. Commer., NOAA Tech. Memo. NMFS-OPR12, 93 pp.

Waring, G. T., P. Gerrior, P. M. Payne, B. L. Parry and J. R. Nicolas. 1990. Incidental take of marine mammals in

foreign fishery activities off the northeast United States, 1977-1988. Fish. Bull., U.S. 88(2): 347-360.

Wells, R.S., H.L. Rhinehart, P. Cunningham, J. Whaley, M. Baran, C. Koberna and D.P. Costa. 1999. Long

distance offshore movements of bottlenose dolphins. Mar. Mammal Sci. 15(4):1098-1114.

Yeung, C. 1999a. Estimates of marine mammal and marine turtle bycatch by the U.S. Atlantic pelagic longline fleet

in 1998. NOAA Tech. Memo. NMFS-SEFSC-430, 26 pp. NMFS, Southeast Fisheries Science Center,

Miami, FL.

Yeung, C. 1999b. Revised Mortality Estimates of Marine Mammal Bycatch in 1992-1997 based on Serious Injury

Guidelines. NOAA Tech. Memo. NMFS-SEFSC-429, 23 pp. NMFS, Southeast Fisheries Science Center,

Miami, FL.

Yeung, C. 2001. Estimates of marine mammal and marine turtle bycatch by the U.S. Atlantic pelagic longline fleet

in 1999-2000. NOAA Tech. Memo. NMFS-SEFSC-467, 43 pp. NMFS, Southeast Fisheries Science

Center, Miami, FL.
169

January 2002

BOTTLENOSE DOLPHIN (Tursiops truncatus):

Western North Atlantic Coastal Stock

STOCK DEFINITION AND GEOGRAPHIC RANGE

Stock Structure of the Coastal Morphotype

A. Latitudinal distribution and structure along the coast

The coastal morphotype is continuously distributed along the Atlantic coast south of Long Island, around

peninsula Florida and along the Gulf of Mexico coast. On the basis of differences in mtDNA haplotype frequencies,

however, Curry (1997) concluded that the nearshore animals in the northern Gulf of Mexico and the western North

Atlantic were significantly different and represent separate stocks.

Within the western North Atlantic, the stock structure of coastal bottlenose dolphins is complex. Scott et

al. (1988) hypothesized a single coastal migratory stock ranging seasonally from as far north as Long Island, NY, to

as far south as central Florida, citing stranding patterns during a high mortality event in 1987-88 and observed

density patterns along the US Atlantic coast. The continuous distribution of dolphins along the coast seemed to

support this hypothesis. It was recognized that bottlenose dolphins were resident in some estuaries; these were

considered to be separate from the coastal migratory animals. More recent studies suggest that the single coastal

migratory stock hypothesis is incorrect and that there is likely a complex mosaic of stocks. For example, year-round

resident populations have been reported at a variety of sites in the southern part of the range, from Charleston, South

Carolina (Zolman 1996) to central Florida (Odell and Asper 1990); seasonal residents and migratory or transient

animals also occur in these areas (summarized in Hohn 1997). In the northern part of the range the patterns reported

include seasonal residency, year-round residency with large home ranges, and migratory or transient movements

(Barco and Swingle 1996, Sayigh et al. 1997). Communities of dolphins have been recognized in embayments and

coastal areas of the Gulf of Mexico (Wells et al. 1996; Scott et al. 1990; Weller 1998) so it is not surprising to find

similar situations along the Atlantic coast. 

Recent genetic analyses of samples from Jacksonville, FL, southern South Carolina (primarily the estuaries

around Charleston), southern North Carolina, and coastal Virginia, using both mitochondrial DNA and nuclear

microsatellite markers, indicate that a significant amount of the overall genetic variation can be explained by

differences between the groups (NMFS 2001). The degree of population subdivision, estimated using the parameter

FST, between each of the groups was statistically significant. These results indicate a minimum of four populations

of coastal bottlenose dolphins in the Northwest Atlantic and reject the null hypothesis of one homogeneous

population of bottlenose dolphins.

Another potential population has been identified from stable isotope ratios of oxygen (NMFS 2001). 

Animals sampled along the beaches of North Carolina between Cape Hatteras and Bogue Inlet during the months of

February and March show very low stable isotope ratios of 18O relative to 16O (referred to as depleted 18O or depleted

oxygen) (Cortese 2000). One possible explanation for the depleted oxygen signature is that there is a resident group

of dolphins in Pamlico Sound. Alternatively, these animals may represent a component of the migratory animals that

spend their summers at the northernmost end of the range of bottlenose dolphins and winter in North Carolina. 

Either possibility suggests they represent a separate stock. Stable isotope ratios of 18O from samples taken in

estuarine waters around Charleston, SC, showed little variation and none were at depleted levels.

Photo-identification studies also support the existence of multiple stocks (NMFS 2001). A coastwide

photographic catalogue has been established using contributions from 15 sites from Cape May, NJ, to Cape

Canaveral, FL (Urian et al. 1999). No matches have been found between the northernmost and southernmost sites. 

However, there appears to be a high rate of exchange among northern field sites, where dolphins occur only

seasonally, and central North Carolina including the Beaufort area. Other areas of frequent exchange include

Beaufort and Wilmington, NC. In contrast to the patterns found in the northern end of the range, there appears to be

less movement between southern field sites – there are only two confirmed matches between the relatively large

catalogs of Jacksonville, FL, and Hilton Head, SC, for example, and no matches between the Charleston, SC site and

other sites. 

Satellite-linked radio transmitters have been deployed on dolphins in Virginia Beach, VA, Beaufort, NC,

and Charleston, SC. The movement patterns of animals with satellite tags provided additional information that was
170

F L

G A

S C

N C

V A

Northern

m igratory

management

unit

Northern NC

m anagem ent unit

Southern NC m anagem ent unit

SC m anagem ent unit

SUMMER

DISTRIBUTION

SUMMER

DISTRIBUTION

W INTER

DISTRIBUTION

W INTER

DISTRIBUTION

Northern

m igratory and

northern NC units

Southern NC unit

N J

GA m anagem ent unit

Northern FL m anagem ent unit

Central FL m anagem ent unit

Northern FL unit

GA unit

SC unit

Central FL unit

complementary to the photo-identification, genetic, and stable isotope studies. The results, along with photoidentification of freeze-branded animals, indicate that a significant number of dolphins reside in NC in summer and

do not migrate. Satellite telemetry results reinforced the photo-identification results from Charleston, SC, indicating

a resident population there. Finally, a dolphin tagged in Virginia Beach, VA, spent the winter between Cape

Hatteras and Cape Lookout, NC, rather than migrating to Florida as would have been expected in the single coastalmigratory-stock hypothesis (NMFS 2001).

Stable isotope ratios of oxygen suggested the possibility of a resident group of bottlenose dolphins in

Pamlico Sound, NC (NMFS 2001). Animals sampled along the beaches of North Carolina between Cape Hatteras

and Bogue Inlet during the months of February and March show very low stable isotope ratios of 18O relative to 16O

(referred to as depleted 18O or depleted oxygen) (Cortese 2000). One possible explanation for the depleted oxygen

signature is that there is a resident group of dolphins in Pamlico Sound that move into nearby nearshore areas in the

winter when Pamlico Sound may have an inadequate resource base. The possibility of a resident group of bottlenose

dolphins in Pamlico Sound is supported by the results from satellite telemetry and photo-identification results. 

Alternatively, however, these animals may represent a component of the migratory animals that spend their summers

at the northernmost end of the range of bottlenose dolphins and winter in North Carolina. Either possibility suggests

they represent a separate stock. Stable isotope ratios of 18O from samples taken in estuarine waters around

Charleston, SC, showed little variation and none were at depleted levels.

In summary, integration of the preliminary results from genetics, photo-identification, satellite telemetry,

and stable isotope studies confirms a complex mosaic of stocks of coastal bottlenose dolphins in the western North

Atlantic. As an interim measure, pending additional results, seven management units within the range of the “coastal

migratory stock” have been defined (Figure 1). The true population structure is likely more than the seven units

identified in this report; research efforts continue in an attempt to identify that structure.

 Figure 1. Management units of the coastal morphotype of bottlenose dolphins along the Atlantic coast of the

U.S. as defined from recent results from genetic, stable isotope ratio, photo-identification, and

telemetry studies (per Hohn 1997; NMFS 2001).
171

B. Longitudinal distribution

Earlier aerial (CETAP 1982) and shipboard (NMFS unpublished data) surveys north of Cape Hatteras

identified two concentrations of bottlenose dolphins, one inshore of the 25 m isobath and the other offshore of the 

25 m isobath. The lowest density of bottlenose dolphins was observed over the continental shelf, with higher

densities along the coast and near the continental shelf edge. It was suggested, therefore, that the coastal

morphotype is restricted to waters < 25 m in depth north of Cape Hatteras (Kenney 1990). There was no apparent

longitudinal discontinuity in bottlenose dolphin herd sightings during aerial surveys south of Cape Hatteras in the

winter (Blaylock and Hoggard 1994). NMFS surveys conducted from 1992-1998 show a clustering of bottlenose

dolphins nearshore and then additional bottlenose dolphins in the offshore areas. However, the morphotype of

bottlenose dolphins (WNA offshore or WNA coastal) can not be determined from the air so attributing each sighting

to a specific morphotype cannot be done. There is also a potential for confusing immature spotted dolphins, with

few or no spots dorsally, with bottlenose dolphins where the two species are sympatric.

 In 1995, NMFS conducted two aerial surveys along the Atlantic coast (Blaylock 1995; Garrison and

Yeung 2001). One survey was conducted during summer 1995 between Cape Hatteras, NC, and Sandy Hook, NJ,

and included three replicate surveys. The second survey was conducted during winter 1995 between Cape Hatteras,

NC, and Ft. Pierce, FL. A distributional analysis identified a significant spatial pattern in bottlenose dolphin

sightings as a function of distance from shore (Garrison 2001a). During the northern (summer) surveys, the

significant spatial boundary occurred at 12 km from shore. During the southern (winter) survey, the significant

spatial boundary occurred at 27 km from shore. The gap in sightings best defines, for the time being, the eastern

extent of the coastal morphotype for purposes of habitat definition and abundance estimates. NMFS continues to

collect biopsy samples from Tursiops throughout the possible range of the coastal morphotype so that stock

boundaries can be confirmed or modified on the basis of a more comprehensive data set.

POPULATION SIZE

The 1995 aerial surveys were conducted to estimate population size of the hypothesized single coastal

migratory stock (Blaylock 1995; Garrison and Yeung 2001). The summer aerial survey was conducted between July

1 and August 14, 1995, covering Cape Hatteras, NC, to Sandy Hook, NJ, (35.23o

N-40.5oN), and from the mainland

shore to the 25 m isobath. This survey provided coverage and abundance estimates for the Northern Migratory

(NM) and Northern North Carolina (NNC) management units. However, coverage of the NNC unit was incomplete

as the surveys did not cover the region south of Cape Hatteras, NC, to Cape Lookout, NC. Abundance was

estimated for each stratum pooling across the three replicate surveys. The winter survey was conducted between

January 27 and March 6, covering from Fort Pierce, FL, to Cape Hatteras, NC, (27.30o

N-35.23oN), from the

mainland shore to 9.25 km (5 Nautical Miles) beyond the inshore edge of the Gulf Stream or <200 km offshore. 

This survey included coverage of the NNC, Southern North Carolina (SNC), South Carolina (SC), Georgia (GA),

Northern Florida (NFL) and Central Florida (CFL) management units. However, the coverage of the NNC

management unit was incomplete and did not include the region north of Cape Hatteras, NC. These abundance

estimates also include NM unit animals that have migrated south of the NC/VA border during winter. Abundance

for each management unit was estimated using line transect methods and the program DISTANCE (Buckland et al.

1993) for both the winter and summer surveys (Table 1). There was no significant difference between the

abundance estimates for the combined NM and NNC management units in summer and the combined NM, NNC,

and SNC stocks in winter. 

Another set of aerial surveys was conducted parallel to the coastline from the North Carolina/South

Carolina border to the Maryland/Delaware border during 1998 and 1999 to document the distribution of dolphins

and fishing gear in nearshore waters (Hohn et al. unpubl. data). These strip transect surveys were conducted weekly,

weather permitting, over 12 months in most of North Carolina and for six months (May to December) in Virginia

and Maryland. In retrospect, they provide seasonal coverage of the Southern North Carolina, Northern North

Carolina, and Northern Migratory management units (Figure 1; Hohn et al. unpubl. data). The strip transect surveys

cannot be used directly for abundance estimation because they did not follow the design constraints of line transect

survey methods and covered only a small proportion of the habitat of coastal bottlenose dolphin. The density of

dolphins near the coastline is high relative to habitats further offshore, and the use of density estimates in this region

to calculate overall abundance would likely result in significant positive bias. However, these surveys do provide

information on the relative abundance of dolphins between regions that may be used to supplement the abundance

estimates from the line transect surveys conducted in 1995 (Garrison and Hohn 2001). Both sets of aerial surveys
172

covered ocean coasts only. An abundance estimate was generated for bottlenose dolphins in estuarine waters of

North Carolina using mark-recapture methodology (Read et al. In review). It is possible to post-stratify the markrecapture estimates consistent with management unit definitions (Palka et al. 2001) (Table 1).

Table 1. Estimates of abundance and the associated CV, nmin, and PBR for each management unit of WNA coastal

bottlenose dolphins (from Palka et al. 2001). The PBR for the Northern Migratory, Northern NC, and

Southern NC management units are applied biannually. For management units south of NC, the PBR is

applied annually.

Management Unit

Best Abundance

Nmin

PBR

Estimate CV Annual 1⁄2 Yr

SUMMER (May - October)

Northern migratory 5681 24.4 4,640 (46) 23

Northern NC

oceanic 3,383 41.8 2,413 (24) 12

estuary 919 12.5 828 (8.3) 4.2

BOTH 4,302 33 3,281 (33) 16

Southern NC

oceanic 1,157 50 777 (7.8) 3.9

estuary 141 15.2 124 (1.2) 0.6

BOTH 1,298 44.6 907 (9.1) 4.5

WINTER (November - April)

NC mixed* 6,474 39.7 4,691 (47) 23

South Carolina 3,513 47 2,412 24 na

Georgia 767 78.4 428 4.3 na

Northern Florida 354 56 228 2.3 na

Central Florida 10,652 45.8 7,377 74 na

 NC mixed* = northern migratory, Northern NC, and Southern NC

Abundance estimates for each management unit are the sum of estimates, where appropriate, from the

recent analyses. Estimated overall abundance was 9,206 from summer surveys and 19,459 from winter surveys. 

However, for consistency with achieving the goals of the MMPA, such as maintaining marine mammals as

functioning components of their ecosystems, it is more appropriate to establish abundance estimates for each

management unit. Abundance for each management unit was estimated by post-stratifying sightings and effort data

consistent with geographic and seasonal management unit boundaries (Table 1) (Garrison and Yeung 2001; Palka et

al. 2001). Although these estimates are better than previous abundance estimates for coastal bottlenose dolphins,

there remain potential biases. The aerial survey estimates are not corrected for g(0), the probability of detecting a

group on the track line as a function of perception bias and availability bias. The exclusion of g(0) from the

abundance estimate results in a negative bias of unknown magnitude. The relatively large herd sizes in the summer

surveys north of Cape Hatteras likely reduce this bias; however, herd sizes were smaller south of Cape Hatteras

during winter, likely resulting in greater negative bias (Palka, unpub. data). A positive bias may occur if the

longitudinal boundaries have been extended too far offshore resulting in offshore dolphins being included in the

abundance estimates for the coastal morphotype or if estuarine dolphins were overrepresented in coastal waters

during the time of the survey. Further uncertainties in the abundance estimates result from incomplete coverage of

some seasonal management units during the line transect surveys. While the strip transect surveys were used to

supplement the survey coverage, uncertainties associated with that analysis also introduce uncertainty in the overall
173

abundance estimate (Garrison and Hohn 2001). The SEFSC intends to conduct both winter and summer coastwide

aerial surveys during 2002 to obtain more robust abundance estimates. 

Minimum Population Estimate

The minimum population size (NMIN) for each management was calculated according to Equation 1 from

the PBR Guidelines (Wade and Angliss 1997): NMIN= N/exp(0.842×[ln(1+[CV(N)]2)]1⁄2) (Table 1). It is

recognized that these estimates may be negatively biased because they do not include corrections for g(0) and, for

some of the managements units, do not include the entire spatial range of the unit during that season. The strip

transect surveys compensate for some of the abundance omitted during line-transect survey; nonetheless, for some

management units the entire range was not covered. 

Current Population Trend

There are insufficient data to determine the population trend for this stock.

CURRENT AND MAXIMUM NET PRODUCTIVITY RATES

Current and maximum net productivity rates are not known for the WNA coastal morphotype. The

maximum net productivity rate was assumed to be 0.04. This value is based on theoretical modeling showing that

cetacean populations may not grow at rates much greater than 4% given the constraints of their reproductive life

history (Barlow et al. 1995). 

POTENTIAL BIOLOGICAL REMOVAL

Potential Biological Removal (PBR) is the product of the minimum population size, one-half the maximum

productivity rate, and a “recovery” factor (Wade and Angliss 1997). The “recovery” factor is assumed to be 0.50,

the default for depleted stocks and stocks of unknown status. At least part of the range-wide stock complex is

depleted; for the remainder, status is unknown. For consistency with achieving the goals of the MMPA, such as

maintaining marine mammals as functioning components of their ecosystems, it is more appropriate to establish

separate PBRs for each management unit (Table 1).

ANNUAL HUMAN-CAUSED MORTALITY AND SERIOUS INJURY

Total estimated average annual fishery-related mortality or serious injury resulting from observed fishing

trips during 1996-2000 was 233 bottlenose dolphins (CV=0.16) in the mid-Atlantic coastal gillnet fishery. The

management units affected by this fishery would be the NM, NNC, and SC. An estimated 24 (CV=0.89) were taken

in the shark drift gillnet fishery off the coast of Florida during 1999-2000, affecting the Central and Northern Florida

management units. No estimates of mortality from observed trips are available for any of the other fisheries that

interact with WNA coastal bottlenose dolphins. Therefore, the total average annual mortality estimate is considered

to be a lower bound of the actual annual human-caused mortality and serious injury.

Fishery Information

Bottlenose dolphins are known to interact with commercial fisheries and occasionally are taken in various

kinds of fishing gear including gillnets, seines, long-lines, shrimp trawls, and crab pots (Read 1994; Wang et al.

1994) especially in near-shore areas where dolphin densities and fishery efforts are greatest. There are nine

Category II commercial fisheries that interact with WNA coastal bottlenose dolphins in the 2001 MMPA List Of

Fisheries (LOF), six of which occur in North Carolina waters. Category II fisheries include the mid-Atlantic coastal

gillnet, NC inshore gillnet, mid-Atlantic haul/beach seine, NC long haul seine, NC stop net, Atlantic blue crab

trap/pot, Southeast Atlantic gillnet, Southeastern U.S. Atlantic shark gillnet and the Virginia pound net (Table 1.1)

(see 2001 List of Fisheries, 66 FR 42780, August 15, 2001). The mid-Atlantic haul/beach seine fishery also includes

the haul seine and swipe net fisheries. The term mid-Atlantic refers to the geographic area south of Long Island,

landward to the 72/ 30’ W. line, and north of the line extending due east from the North Carolina/South Carolina

border (66 FR 6545, January 22, 2001).

There are five Category III fisheries that may interact with WNA coastal bottlenose dolphins. Three of

these are inshore gillnet fisheries: the Delaware Bay inshore gillnet, the Long Island Sound inshore gillnet, and the

Rhode Island, southern Massachusetts, and New York Bight inshore gillnet. The remaining two are the shrimp trawl
174

and mid-Atlantic menhaden purse seine fisheries. There are have been no takes observed by the NMFS observer

programs in any of these fisheries.

Mid-Atlantic Coastal Gillnet

The mid-Atlantic coastal gillnet fishery is actually a combination of small-vessel fisheries that target a

variety of fish species, including bluefish, croaker, spiny and smooth dogfish, kingfish, Spanish mackerel, spot,

striped bass, and weakfish (Steve et al. 2001). It operates in different seasons targeting different species in different

states throughout the range of the coastal morphotype. Most nets are set gillnets without anchors and are fished

close to shore. Anchored set gillnets or drift gillnets are used in some fisheries (e.g., monkfish or dogfish). A

comprehensive description of coastal gillnet gear and fishing effort in North Carolina is available in Steve et al.

(2001). This fishery has the highest documented level of mortality of WNA coastal bottlenose dolphins; the North

Carolina sink gillnet fishery is its largest component in terms of fishing effort and observed takes. Bycatch estimates

are available for the past five years, 1996-2000 (Table 2). Of 12 observed mortalities from 1995-2000, 5 occurred in

sets targeting spiny or smooth dogfish and another in a set targeting “shark” species, 2 occurred in striped bass sets,

2 occurred in Spanish mackerel sets, and the remainder were in sets targeting kingfish, weakfish, or finfish

generically (Rossman and Palka 2001). 

Table 2. Summary of the 1996-2000 incidental mortality of bottlenose dolphins (Tursiops truncatus) by

management unit in the commercial mid-Atlantic coastal gillnet fisheries. Data include the years sampled

(Years), the number of vessels active within the fishery (Vessels), type of data used (Data Type), observer

coverage (Observer Coverage), mortalities recorded by on-board observers (Observed Mortality), estimated

annual mortality (Estimated Mortality), estimated CV of the annual mortality (Estimated CVs), and mean

annual mortality (CV in parentheses).

Seasonal

Management

Unit

Years Vessels Data Type1 Observer

Coverage 2 

Observed

Serious Injury

Observed

Mortality

Estimated 

Mortality

Estimated 

CVs 3

Mean Annual

Mortality

Summer

Northern

Migratory

1996-2000 NA Obs. Data,

NER Dealer Data

.05, .03, .02,

.03, .03

0, 0, 0,

0, 0

0, 0, 1,

1, 1

33, 30, 37,

19, 30

0.48 30 

(0.22)

Summer

Northern NC 1996-2000 NA

Obs. Data,

NCDMF Dealer

Data

.01, .00, <.01,

.01, .03

0, 0, 0,

0, 0

1, 0, 0,

0, 0

27, 33, 17,

13, 26

0.61 23 

(0.29)

Summer

Southern NC 1996-2000 NA

Obs. Data,

NCDMF Dealer

Data

.00, .00, .01,

.03, .03

0, 0, 0,

0, 0

0, 0, 0,

0, 0

0, 0, 0,

0, 0 NA 0

(NA)

Winter NC

mixed 1996-2000 NA

Obs. Data,

NCDMF Dealer

Data

.01, .01, .02,

.02, .02

0, 0, 0,

0, 0

1, 0, 1,

2, 2

173, 211, 175,

196, 146 0.46 180 (0.21)

Total 233 (0.16)

NA=Not Available

1 Observer data (Obs. data) are used to measure bycatch rates; the USA data are collected within the

Northeast Fisheries Science Center (NEFSC) Sea Sampling Program. The NEFSC collects weighout

(Weighout) landings data that are used as a measure of total effort for the USA sink gillnet fisheries. 2 The observer coverage for the mid-Atlantic coastal sink gillnet fishery is measured in tons of fish landed. 3 The annual estimates of mortality were generated by applying one bycatch rate per management unit as

estimated by a GLM (Palka and Rossman 2001). The CV does not account for variability that may exist in

the unit of total landings (mt) from each year that are used to expand the bycatch rate. Therefore, the CV is

the same for all five annual estimates.

A sink gillnet fishery for American shad operates seasonally from Connecticut to Georgia, with nets being

moved from coastal ocean waters into fresh water with the shad spawning migration. It has been considered likely

that a few bottlenose dolphins are taken in this fishery each year (Read 1994) but no takes have been observed

(NEFSC observer data). The portion of the fishery which operates along the South Carolina coast was sampled by

observers during 1994 and 1995, and no fishery interactions were observed (McFee et al. 1996).
175

South Atlantic Shark Gillnet

The shark gillnet fishery operates in federal waters from southern Florida to southern Georgia. The fishery

is defined by vessels using relatively large mesh nets (>10 inches) and net lengths typically greater than 1500 feet. 

The fishery primarily uses drifting nets that are set overnight, however recently it has been employing a small

number of shorter duration “strike” sets that encircle targeted schools of sharks. Since 1999, the Atlantic Large

Whale Take Reduction Plan restricted the activities of the fishery to waters south of 27° 51’ N latitude during the

critical right whale season from 15 November – 31 March and mandated 100% observer coverage during this period. 

During the remainder of the year, these vessels generally operate north of Cape Canaveral, FL and there is little

observer coverage of the fleet.

The fishery potentially interacts with the Georgia, Northern Florida, and Central Florida management units

of coastal bottlenose dolphin. During an observer program in 1993 and 1994 and limited observer coverage during

summer 1998, no takes of bottlenose dolphin were observed (Trent et al. 1997; Carlson and Lee, 2000). However,

takes resulting in mortality were observed in the central Florida management unit during 1999 and 2000. Total

bycatch mortality for this management unit has been estimated for 1999 and 2000 (Table 3) (Garrison 2001b).

Table 3. Summary of the 1999-2000 incidental mortality of bottlenose dolphins (Tursiops truncatus) by

management unit in the driftnet fishery in federal waters off the coast of Florida. Data include years

sampled (Years), number of vessels active within the fishery (Vessels), type of data used (Data Type),

annual observer coverage (Observer Coverage), mortalities recorded by on-board observers (Observed

Mortality), estimated annual mortality (Estimated Mortality), estimated CV of the annual mortality

(Estimated CVs), and mean annual mortality (CV in parentheses).

Seasonal

Management

Unit

Years Vessels Data Type 1 Observer

Coverage 2 

Observed

Serious

Injury

Observed

Mortality

Estimated

Mortality

Estimated

CVs

Mean Annual

Mortality

Northern

Florida 1999-2000 6 Obs. Data,

 SEFSC FVL 0.31, 0.05 0, 0 0, 0 0, 0 NA 0

Central Florida 1999-2000 6 Obs. Data,

 SEFSC FVL 0.09, 0.24 0, 0 4, 1 43, 4 0.78, 1 24 (0.89)

NA=Not Available

1 Observer data are used to estimate bycatch rates. The SEFSC Fishing Vessel Logbook (FVL) is used to

estimate effort as total number of vessel trips per bottlenose dolphin management unit. 2 Observer coverage in the central Florida management unit is largely restricted to the period between

January - March south of 27° 51’ N.

Beach Haul Seine

A beach seine fishery operates along northern North Carolina beaches targeting striped bass, mullet, spot,

weakfish, sea trout, and bluefish. The fishery operates on the Outer Banks of North Carolina primarily in the spring

(April through June) and fall (October through December). It uses two primary gear types: a “beach anchored gill

net” and a “beach seine”. Both systems utilize a small net anchored to the beach. The beach seine system also uses

a bunt and a wash net that are attached to the beach and are in the surf (Steve et al. 2001). The North Carolina beach

seine fishery has been observed since April 7, 1998 by the NMFS fisheries sampling program (observer program)

based at the Northeast Fisheries Science Center. Through 2001, there were 101 sets observed during the winter

season (Nov-Apr) and 65 sets observed during the summer season (May-Oct). There were no sets observed during

the summer of 2001. A total of 2 coastal bottlenose dolphin takes were observed, 1 in May 1998 and 1 in December

2000. The beach seine observer data are currently being reviewed but estimates of mortality are not yet available.

Crab Pots

Between 1994 and 1998, 22 bottlenose dolphin carcasses (4.4 dolphins per year on average) recovered by

the Stranding Network between North Carolina and Florida’s Atlantic coast displayed evidence of possible

interaction with a trap/pot fishery (i.e., rope and/or pots attached, or rope marks). Additionally, at least 5 dolphins

were reported to be released alive (condition unknown) from blue crab traps/pots during this time period. In recent

years, reports of strandings with evidence of interactions between bottlenose dolphins and both recreational and
176

commercial crab-pot fisheries have been increasing in the Southeast Region (McFee and Brooks 1998). The

increased reporting may result from increased effort towards documenting these marks or increases in mortality.

Virginia Pound Nets

Data from the Chesapeake Bay suggest that the likelihood of bottlenose dolphin entanglement in pound net

leads may be affected by the mesh size of the lead net (Bellmund et al. 1997), but the information is not conclusive. 

Stranding data for 1993-1997 document interactions between WNA coastal bottlenose dolphins and pound nets in

Virginia. Two bottlenose dolphin carcasses were found entangled in the leads of pound nets in Virginia during

1993-1997, for an average of 0.4 bottlenose dolphin strandings per year. A third record of an entangled bottlenose

dolphin in Virginia in 1997 may have been applicable to this fishery. This entanglement involved a bottlenose

dolphin carcass found near a pound net with twisted line marks consistent with the twine in the nearby pound net

lead rather than with monofilament gillnet gear. Given that other sources of annual serious injury and mortality

estimates (e.g., observer data) are not available, the stranding data (0.4 bottlenose dolphins per year) were used as a

minimum estimate of annual serious injury and mortality and this fishery was classified as a Category II fishery in

the 2001 List of Fisheries. 

Shrimp Trawl

The shrimp trawl fishery operates from North Carolina through northern Florida virtually year around,

moving seasonally up and down the coast. One bottlenose dolphin was recovered dead from a shrimp trawl in

Georgia in 1995 (Southeast USA Marine Mammal Stranding Network unpublished data), and another was taken in

1996 near the mouth of Winyah Bay, SC, during a research survey. No other bottlenose dolphin mortality or serious

injury has been previously reported to NMFS.

Menhaden Purse Seine

The Atlantic menhaden purse seine fishery targets the Atlantic menhaden in Atlantic coastal waters. Smith

(1999) summarized menhaden fishing patterns by the Virginia-North Carolina vessels from 1985-1996. Most of the

catch and sets during that time occurred within three miles of the shore. Between 1994 and 1997, menhaden were

processed at only three facilities, two in Reedville Beach, VA, and one in Beaufort, NC. Each of the Virginia

facilities had a fleet of 9-10 vessels while the Beaufort facility is supported by 2-6 vessels. Since 1998, only one

plant has operated in Virginia and the number of vessels has been reduced to ten in Virginia and two in North

Carolina (Vaughan et al. 2001). The fishery moves seasonally, with most effort occurring off of North Carolina

from November-January and moving northward to southern New England during warmer months. Menhaden purse

seiners have reported an annual incidental take of 1 to 5 bottlenose dolphins (NMFS 1991, pp. 5-73), although

observer data are not available. 

Other Mortality

From 1997-1999, 995 bottlenose dolphins were reported stranded along the Atlantic coast from New York

to Florida (Table 4) (Hohn and Martone 2001; Hohn et al. 2001; Palka et al. 2001). Of these, it was possible to

determine whether a human interaction had occurred for 449 (45%); for the remainder it was not possible to make

that determination. The proportion of carcasses determined to have been involved in a human interaction averaged

34%, but ranged widely from 11-12% in Delaware and Georgia to 49% and 53% in Virginia and North Carolina,

respectively. 

The nearshore habitat occupied by the coastal morphotype is adjacent to areas of high human population

and in the northern portion of its range is highly industrialized. The blubber of stranded dolphins examined during

the 1987-88 mortality event contained anthropogenic contaminants in levels among the highest recorded for a

cetacean (Geraci 1989). There are no estimates of indirect human-caused mortality resulting from pollution or

habitat degradation.
177

Table 4. Summary of bottlenose dolphins stranded along the Atlantic Coast of the US. Total Stranded is further 

stratified into carcasses with signs of human interaction, those without any signs, and those where human

interaction could not be determined (CBD). Human Interaction is stratified into stranded animals with line

or nets marks or gear attached (Fishery Interaction), cleanly removed (cut off) appendages or cuts on the

body (Mutilation), and other indications of human interactions such as propellor wounds. Florida 

strandings include only the Atlantic coast of Florida but extending to Key West.

STATE 1997 1998 1999 STATE 1997 1998 1999

New York Total Stranded 2 3 3 N. Carolina Total Stranded 123 104 94

 Human Interaction Human Interaction

 ---- Fishery Interaction 1 0 0 ---- Fishery Interaction 28 23 24

 ---- Mutilation 0 0 0 ---- Mutilation 5 3 1

 ---- Other 0 0 0 ---- Other 1 0 0

 No Human Interaction 0 2 3 No Human Interaction 21 16 19

 CBD 1 1 0 CBD 68 62 50

New Jersey Total Stranded 10 11 15 S. Carolina Total Stranded 41 41 34

 Human Interaction Human Interaction

 ---- Fishery Interaction 0 1 3 ---- Fishery Interaction 8 4 1

 ---- Mutilation 0 0 0 ---- Mutilation 2 0 1

 ---- Other 0 0 0 ---- Other 0 1 2

 No Human Interaction 2 3 2 No Human Interaction 15 10 10

 CBD 8 7 10 CBD 16 26 20

Delaware Total Stranded 14 8 18 Georgia Total Stranded 18 26 14

 Human Interaction Human Interaction

 ---- Fishery Interaction 1 1 1 ---- Fishery Interaction 1 1 1

 ---- Mutilation 0 0 0 ---- Mutilation 0 0 0

 ---- Other 2 1 0 ---- Other 0 0 0

 No Human Interaction 4 0 4 No Human Interaction 8 6 8

 CBD 7 6 13 CBD 9 19 5

Maryland Total Stranded 2 2 5 Florida Total Stranded 104 80 87

 Human Interaction Human Interaction

 ---- Fishery Interaction 0 0 1 ---- Fishery Interaction 7 3 4

 ---- Mutilation 0 0 0 ---- Mutilation 0 0 0

 ---- Other 0 0 0 ---- Other 0 1 0

 No Human Interaction 1 0 1 No Human Interaction 34 29 28

 CBD 1 2 3 CBD 63 47 55

Virginia Total Stranded 44 42 50 Total 358 317 320

 Human Interaction

 ---- Fishery Interaction 11 8 18

 ---- Mutilation 0 2 3

 ---- Other 0 1 0

 No Human Interaction 15 12 6

 CBD 18 19 23
178

STATUS OF STOCKS

The coastal migratory stock is designated as depleted under the MMPA. From 1995-2001, NMFS

recognized only a single migratory stock of coastal bottlenose dolphins in the WNA and, therefore, the entire stock

was listed as depleted. The management units in this report now replace the single coastal migratory stock. A reanalysis of the depletion designation on a management unit basis needs to be undertaken. In the interim, because

one or more of the management units may be depleted, all management units retain the depleted designation. In

addition, mortality in multiple units exceed PBR (Table 1). There are no rigorous results that would provide reliable

information on current abundance relative to historical abundance. All prior estimates cover only part of the range

of management units spatially or temporally, include the offshore morphotype, or are otherwise compromised. 

Population trends cannot be determined due to insufficient data. 

Over the past five years, estimated average annual mortality exceeded PBR in the mid-Atlantic gillnet

fisheries for the northern migratory and northern NC management units during summer and for the NC mixed

management units in winter (Tables 1 and 2).

The species is not listed as threatened or endangered under the Endangered Species Act, but because, as

noted above, the stock is listed as depleted under the MMPA it is a strategic stock. This stock is also considered

strategic under the MMPA because fishery-related mortality and serious injury exceed the potential biological

removal level.

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APPENDIX I. Estimated serious injury and mortality (SI&M) of Western North Atlantic marine mammals listed by U.S. observed fisheries - 1996-2000.

Fishery Species Yrs. observed Total annual estimated SI&M(CV)

Ave est.

SI&M

(CV)

PBR

CATEGORY I

Gillnet Fisheries:

Northeast sink gillnet Har bor por poise 1996-1998 1200 (.25), 782 (.22), 332 (.46) 771 747

Harbor porpoise - after Take Reduction Plan 1999-2000 270(.28), 507 (.37) 420 (.27) 747

White sided d olphin 1996-2000 114 (.61), 140 (.61), 34 (.92), 69 (.70), 26 (1.0) 77 (.33) 364

Comm on dolphin 1996-2000 63 (1 .39), 0 , 0, 14 6 (.97 ), 0 42 (.78) 227

Risso's dolphin 1996-2000 0, 0, 0, 0, 15 (1.06) 3 (1.06) 220

Bottlenose dolphin (offshore) 1996-2000 0, 0, 0, 0, 132 (1.16) 26 (1.16) 249

Long and short-finned pilot whale 1996-2000 0, 0, 0 , 0, 0 108

1

 No. Atl. R ight whale 1996-2000 0, 0, 0 , 0, 0 0

2

 Hum pback w hale 1996-2000 0, 0, 0 , 0, 0 1.3

Sperm W hale 1996-2000 0, 0, 0 , 0, 0 7

Pygmy sper m whale 1996-2000 0, 0, 0 , 0, 0 3.7

Fin whale 1996-2000 0, 0, 0 , 0, 0 4.7

Sei whale 1996-2000 0, 0, 0 , 0, 0 n/a

Blue w hale 1996-2000 0, 0, 0 , 0, 0 n/a

4Minke whale 1996-2000 0, 0, 0 , 0, 0 35

Cuvier's bea ked wha le 1996-2000 0, 0, 0 , 0, 0 n/a

Mesoplodon beaked w hale 1996-2000 0, 0, 0 , 0, 0 n/a

Harbor seal 1996-2000 911(.27), 5 98(.26), 33 2(.33), 144 6(.34), 917 (.43) 841 (.17) 1859

Gray seal 1996-2000 49(.49), 131(.50), 61(.98), 155(.51), 193(.55) 118 (.35) n/a

Harp seal 1996-2000 89(.55), 26 9(.50), 78(.48 ), 81(.78), 24(1.5 7) 108 (.30) n/a

Longline Fisheries:

Large pelagics longline Har bor por poise 1996-2000 0, 0, 0 , 0, 0 747

White-sided do lphin 1996-2000 0, 0, 0 , 0, 0 364

Comm on dolphin 1996-2000 0, 0, 0 , 0, 0 227

Risso's dolphin 1996-2000 99 (1.0), 0, 57 (1.0), 22 (1.0), 64 (1.0) 48 (.55) 220

Long an d short-finned pilot wha le 1996-2000 0, 0, 0, 381 (.79), 133 (.88) 103 (.63) 108

1

 No. Atl. R ight whale 1996-2000 0, 0, 0 , 0, 0 0
Fishery Species Yrs. observed Total annual estimated SI&M(CV)

Ave est.

SI&M

(CV)

PBR

2

 Hum pback w hale 1996-2000 0, 0, 0 , 0, 0 1.3

Sperm W hale 1996-2000 0, 0, 0 , 0, 0 7

5Pygmy S perm W hale 1996-2000 0, 0, 0, 0, 28(1.0) 6 (1.0) 3.7

Fin whale 1996-2000 0, 0, 0 , 0, 0 4.7

Sei whale 1996-2000 0, 0, 0 , 0, 0 n/a

Blue w hale 1996-2000 0, 0, 0 , 0, 0 n/a

4Minke whale 1996-2000 0, 0, 0 , 0, 0 35

Cuvier's bea ked wha le 1996-2000 0, 0, 0 , 0, 0 n/a

Mesoplodon beaked w hale 1996-2000 0, 0, 0 , 0, 0 n/a

Trap/Pot Fisheries:

American lobster trap/pot Har bor por poise 1996-2000 0, 0, 0 , 0, 0 747

White-sided do lphin 1996-2000 0, 0, 0 , 0, 0 364

Comm on dolphin 1996-2000 0, 0, 0 , 0, 0 227

Risso's dolphin 1996-2000 0, 0, 0 , 0, 0 220

Long an d short-finned pilot wha le 1996-2000 0, 0, 0 , 0, 0 108

1

 No. Atl. R ight whale 1996-2000 0, 0, 0 , 0, 0 0

2

 Hum pback 1996-2000 0, 0, 1 , 0, 0 1.3

Sperm W hale 1996-2000 0, 0, 0 , 0, 0 7

Fin whale 1996-2000 0, 0, 0 , 0, 0 4.7

Sei whale 1996-2000 0, 0, 0 , 0, 0 n/a

Blue w hale 1996-2000 0, 0, 0 , 0, 0 n/a

4Minke whale 1996-2000 0, 1, 0, 0, 0 0.2 (0) 35

Cuvier's bea ked wha le 1996-2000 0, 0, 0 , 0, 0 n/a

Mesoplodon beaked w hale 1996-2000 0, 0, 0 , 0, 0 n/a

Trawl Fisheries:

Atlanti c squid, m acker el, butter fish Har bor por poise 1996-2000 0, 0, 0 , 0, 0 747

White-sided do lphin 1996-2000 0, 16 1(1.5 8), 0, 0 , 0 32 (1.58) 364

Comm on dolphin 1996-2000 940 (.75), 161 (.49), 0, 49 (.78), 273 (.57) 285 (.51) 227

Risso's dolphin 1996-2000 0, 0, 0 , 0, 0 220

Long an d short-finned pilot wha le 1996-2000 45 (1.27, 0, 85 (.65), 49 (.97), 17 (.53) 39 (.47) 108
Fishery Species Yrs. observed Total annual estimated SI&M(CV)

Ave est.

SI&M

(CV)

PBR

1

 No. Atl. R ight whale 1996-2000 0, 0, 0 , 0, 0 0

2

 Hum pback 1996-2000 0, 0, 0 , 0, 0 1.3

Sperm W hale 1996-2000 0, 0, 0 , 0, 0 7

Fin whale 1996-2000 0, 0, 0 , 0, 0 4.7

Sei whale 1996-2000 0, 0, 0 , 0, 0 n/a

Blue w hale 1996-2000 0, 0, 0 , 0, 0 n/a

4Minke whale 1996-2000 0, 0, 0 , 0, 0 35

Cuvier's bea ked wha le 1996-2000 0, 0, 0 , 0, 0 n/a

Mesoplodon beaked w hale 1996-2000 0, 0, 0 , 0, 0 n/a

CATEGO RY II

SE U .S. Atlantic shark gillnet 3 Bottlenose dolp hin (coastal) 1999-2000 No. Florida 0, 0, Central Florida 43 (.78), 4 (1) 24 (0.89) n/a

US Mid-Atlantic coastal sink gillnet Har bor por poise 1996-1998 311(.31), 572 (.35), 446 (.36) 443 747

Harbor porpoise - after Take Reduction Plan 1999-2000 53 (.49), 21 (.76) 37 (.41) 747

White-sided do lphin 1996-2000 0, 45 (.82) , 0, 0, 0 9 (.82) 364

Comm on dolphin 1996-2000 43 (.7 9), 16 (.53) , 0, 0, 0 12 (.59) 227

Risso's dolphin 1996-2000 0, 0, 0 , 0, 0 220

Bottlenose dolphin (offshore) 1996-2000 0, 0, 4 (0.7) , 0, 0 1 (0.7) 249

3

 Bottlenose dolp hin (coastal) 1996-2000 see footnote 3 below 233 (0.16) footnote

Long an d short-finned pilot wha le 1996-2000 0, 0, 7 (1.1) , 0, 0 1 (1.1) 108

1

 No. Atl. R ight whale 1996-2000 0, 0, 0 , 0, 0 0

2

 Hum pback w hale 1996-2000 0, 0, 1 , 0, 0 1.3

Sperm W hale 1996-2000 0, 0, 0 , 0, 0 7

Pygmy sper m whale 1996-2000 0, 0, 0 , 0, 0 3.7

Fin whale 1996-2000 0, 0, 0 , 0, 0 4.7

Sei whale 1996-2000 0, 0, 0 , 0, 0 n/a

Blue w hale 1996-2000 0, 0, 0 , 0, 0 n/a

4Minke whale 1996-2000 0, 0, 1 , 0, 0 0.2 (n/a) 35

Cuvier's bea ked wha le 1996-2000 0, 0, 0 , 0, 0 n/a

Mesoplodon beaked w hale 1996-2000 0, 0, 0 , 0, 0 n/a
Fishery Species Yrs. observed Total annual estimated SI&M(CV)

Ave est.

SI&M

(CV)

PBR

Harbor seal 1996-2000 0, 0, 1 1(.77 ), 0, 0 2 (.77) 1859

Gray seal 1996-2000 0, 0, 0 , 0, 0 n/a

Harp seal 1996-2000 0, 0, 1 7(1.0 2), 0, 0 3 (1.02) n/a

CATEGO RY III

Trawl Fisheries:

North Atlantic bottom trawl Har bor por poise 1996-2000 0, 0, 0 , 0, 0 747

White-sided do lphin 1996-2000 0, 0, 0 , 0, 0 364

Comm on dolphin 1996-2000 0, 93 (1.06 ), 0, 0, 0 19 (1.06) 227

Risso's dolphin 1996-2000 0, 0, 0 , 0, 0 220

Long and short-finned pilot whales 1996-2000 0, 0, 0 , 228 (1.03 ), 0 46 (1.03) 108

1

 No. Atl. R ight whale 1996-2000 0, 0, 0 , 0, 0 0

2

 Hum pback 1996-2000 0, 0, 0 , 0, 0 1.3

Sperm W hale 1996-2000 0, 0, 0 , 0, 0 7

Pygmy sper m whale 1996-2000 0, 0, 0 , 0, 0 3.7

Fin whale 1996-2000 0, 0, 0 , 0, 0 4.7

Sei whale 1996-2000 0, 0, 0 , 0, 0 n/a

Blue w hale 1996-2000 0, 0, 0 , 0, 0 n/a

4Minke whale 1996-2000 0, 0, 0 , 0, 0 35

Cuvier's bea ked wha le 1996-2000 0, 0, 0 , 0, 0 n/a

Mesoplodon beaked w hale 1996-2000 0, 0, 0 , 0, 0 n/a

Notes: Beginn ing with t he 20 01 S tock A ssessment R eport, C anad ian reco rds were in corpora ted into the morta lity and serious in jury ra tes to reflect the effective ran ge of this stock . It is also

important to stress that serious injury determinations are made based upon the best available information; these determinations may change with the availability of new information. Several

factors must be considered: 1) a ship strike or entanglem ent may occur a t some distance from the reported location; 2) the mor tality or injury may invo lve multiple factors; for example,

whales that have been both ship struck and entangled are not uncommon; 3) the actual vessel or gear type/source is often uncertain; and 4) in entanglements, several types of gear may be

involved . For the p urpose s of this repor t, discussion is prima rily limite d to those r ecords con sidered con firmed hu man-ca used m ortalities o r seriou s injuries.

1 No. Atlantic Right Whales - Between 1996-200 0, five of nine records of mortality or serious injury (including both U.S. and Canada) involved entanglement or fishery interaction. There

were three reported serious injuries from unknown gear: 1 sou theast of Gloucester, MA, 1 east of Manomet, MA a nd 1 in Bay of Fundy, Canada . There was 1 serious injury from ingestion of

unknown gear in Bay of Fundy a nd 1 offshore mortality from sink gillnet gear 80 mi. east of Cape Cod. The other 4 were mortalities from injuries indicating ship strike (one record

described a 3.3m gash, a broke n sku ll, and C anad ian lobste r gear w rapped throug h mou th and a round tail. Primary cause of death was ship strike). The total estimated annual average

human-induced mortality and serious injury incurred by this stock was 1.8 right whales per year (USA waters 1.2; Canadian wa ters, 0.6). This is derived from two components: 1) nonobserved fishery enta nglement recor ds at 1.0 p er year (US A waters, 0 .6 ; Can adian w aters, 0.4 ), a nd 2) ship strik e records at 0 .8 per year (USA w aters, 0.6; C anadia n waters, 0.2 ). As with

entanglements, some injury or m ortality due to ship strikes almost certainly passes undetected, particula rly in offshore waters. Decomposed and/or u nexamined anim als (e.g., carcasses
reported but no t retrieved or necro psied) rep resent ‘lost d ata’, so me of wh ich ma y relate to hum an imp acts. For these reaso ns, the figu re of 1.8 right wh ales per y ear mu st be rega rded as a

minim um estim ate. 

2 Hum pback W hales - For the period 199 6 through 2 000, 1 9 of 23 records indicated entan glement or fishery interaction and the remaining 4 records were mortalities from ship strikes . Eleven

serious in juries a nd three m ortalities w ere from u nknow n gear; 2 serious in juries from gillnet gea r in Ba y of Fun dy; 1 ser ious inju ry from o ffshore lobster gear a t Mont auk Point, N Y, 1

serious injury from sea trout sink gillnet gear east of Cape Lookout, NC and 1 m ortality from croaker gillnet gear at Ocracoke Island, NC. Of these 23 anima ls, 15 were counted from the

Gul f of Main e stock (1 4 fishery in teraction s, 1 ship stri ke). T he total e stimated hum an-cau sed mort ality an d seriou s injury to the G ulf of M aine hu mpba ck wh ale stock is estimate d as 3.0

per yea r (USA waters, 2 .4; Ca nadia n waters, 0.6). T his avera ge is derive d from tw o comp onents: 1 ) incidenta l fishery inter action r ecords, 2.8 (USA waters, 2.2; Canadian waters,

0.6); and 2) records of vessel collisions, 0.2 (USA waters, 0.2; Canadian waters, 0). Additional humpback mortalities and serious injuries that occurred in the

southeastern and mid-Atlantic states could not be confirmed as involving members of the Gulf of Maine stock. These records represent an additional minimum annu al average of 1.6 humancaused mortalities and serious injur ies to humpbacks over the tim e period, of which 1.0 per year a re attributable to incidental fishery interactions and 0.6 per y ear are attributable to vessel

collisions. 

3 Coast al Bo ttlenose D olphins - A s an inter im mea sure, pen ding ad ditiona l results, sev eral “m anag ement u nits” of the c oastal m orphoty pe of bottlen ose dolph in along the U.S. A tlantic co ast

have been defined . Annua l estimated m ortality/seriou s injury and PBR for each ma nagemen t unit can be found in the C oastal Bo ttlenose Dolph in section (Ta bles 2 and 3 ) of this report.

4 Minke Whales - There was 1 reported mortality in the mid-Atlantic coastal gillnet fishery in 1998. Confirmed mortalities that were likely a result of a fishery interaction with an unknown

fishery included 3 in 199 7, 5 in 1 999 , 2 in 20 00 an d 0 in other y ears. The ex aminatio n of the mink e entanglem ent records from 1 997 indicate that 4 out of 4 con firmed records of m ortality

were lik ely a resu lt of fishery inte raction s, one attr ibuted t o the lobste r pot fishery , and thr ee not att ributed to any p articu lar fishery becau se the repor ts do not co ntain th e necessary details. 

Of the 5 mortalities in 1999, 2 were attributed to an unknown trawl fishery and 3 to some other fishery. One of the interactions with an unknown fishery in 2000 was a mortality and one was

a serious injury.

5

Pygmy S perm W hales - Twe nty-eight seriously inju red pygmy sperm wha les were reported in 200 0 in the pela gic longline fishery. T he 200 0 morta lity estimates were ta ken from T able 10 in

Yeung 2 001 (N MFS M iami Labora tory PRD 0 0/01-17 ). There have been no ob served mortalities or serious injuries by NM FS Sea Sam plers in the pelagic drift gillnet, pelagic longline,

pelagic p air tra wl, No rtheast m ultispecie s sink gilln et, mid-At lantic co astal sink gillnet, nor North Atlanti c bottom trawl fishe ries. 
APPENDIX II. Numbers of confirmed and unconfirmed large whale mortality and serious injury (‘SI’) events reported along the U.S. Gulf coasts, the U.S. East

coast and adjacent Canadian Maritimes from 1996 - 2000, including a break down of the number of events attributed to entanglement and/orcollision with a vessel.

Species

Total

number

of

events1

Entanglements Vessel Collisions

Total number

of events2

(1996, 1997, 1998,

1999, 2000)

Confirmed

mortalities3

(1996, 1997, 1998,

1999, 2000)

Confirmed

SI’s4

(1996, 1997, 1998,

1999, 2000)

Total number

of events5

(1996, 1997, 1998,

1999, 2000)

Confirmed

mortalities6

(1996, 1997, 1998,

1999, 2000)

Confirmed

SI’s 

Right whale 44 32 (3, 7, 4, 7, 10) 1 (0, 0, 0, 1, 0) 4 (1, 2, 0, 0, 1) 7 (2, 1, 1, 1, 2) 4 (2, 1, 0, 1, 0) 0

Humpback whale7 99 54 (6, 3, 18, 10, 17) 4 (0, 0, 3, 1, 0) 15 (5, 0, 3, 2, 5) 8 (3, 2, 1, 0, 2) 4 (3, 1, 0, 0, 0) 0Fin whale 40 11 (1, 5, 3, 2, 0) 1 (0, 0, 1, 0, 0) 1 (0, 1, 0, 0, 0) 13 (5, 3, 2, 2, 1) 6 (1, 1, 1, 2, 1) 0Sei whale 0 0 0 0 0 00Blue whale 1 0 00 1 (0, 0, 1, 0, 0) 1 (0, 0, 1, 0, 0) 0Minke whale 62 24 (2, 6, 2, 8, 6) 11 (0, 4, 1, 5, 1) 1 (0, 0, 0, 0, 1) 5 (1, 1, 2, 1, 0) 1 (0, 0, 1, 0, 0) 0Unidentified whale 36 15 (0, 4, 6, 4, 2) 0 0 0 00

1 Includes all large whale mortality and serious injury events, both confirmed and unconfirmed, as well as strandings attributed to natural or unknown causes. It

should be noted that the sum of the entanglement and vessel collision totals will not equal the values found in this column because events caused by

natural or unknown causes are included here. In a few instances, a single event was attributed to both entanglement and vessel collision, and wastherefore included in both the entanglement and vessel collision tallies. 2 Includes both confirmed and unconfirmed events of live entangled whales, as well as dead whales found with gear attached or indications that gear had been on

the whale near the time of death. Whales with healed entanglement marks were not included. Numbers in parentheses are tallies for 1996, 1997, 1998,

1999, and 2000, respectively. 3 Includes only events with substantiated evidence that entanglement was the cause of death.

4 Includes only events with substantiated evidence that the injury from entanglement is likely to lead to the whale’s death. 5 Includes both confirmed and unconfirmed reports of vessel collisions with live whales, as well as recovered carcasses with some evidence of collision with a

vessel. 6 Includes only events with substantiated evidence that collision with a vessel was the cause of death. 7 Includes all reported humpback events, including an unknown portion of whales not from the Gulf of Maine stock.
187

APPENDIX III. Marine mammal stock assessment reports not updated in the year 2002.

July 1995

KILLER WHALE (Orcinus orca):

Western North Atlantic Stock

STOCK DEFINITION AND GEOGRAPHIC RANGE

Killer whales are characterized as uncommon or rare in waters of the U.S. Atlantic Exclusive Economic

Zone (EEZ) (Katona et al. 1988). The 12 killer whale sightings constituted 0.1% of the 11,156 cetacean sightings in

the 1978-81 CETAP surveys (CETAP 1982). The same is true for eastern Canadian waters, where the species has

been described as relatively uncommon and numerically few (Mitchell and Reeves 1988). Their distribution,

however, extends from the Arctic ice-edge to the West Indies. They are normally found in small groups, although 40

animals were reported from the southern Gulf of Maine in September 1979, and 29 animals in Massachusetts Bay in

August 1986 (Katona et al. 1988). In the U.S. Atlantic EEZ, while their occurrence is unpredictable, they do occur

in fishing areas, perhaps coincident with tuna, in warm seasons (Katona et al. 1988; NMFS unpublished data). In an

extensive analysis of historical whaling records, Reeves and Mitchell (1988) plotted the distribution of killer whales

in offshore and mid-ocean areas. Their results suggest that the offshore areas need to be considered in present-day

distribution, movements, and stock relationships. 

Stock definition is unknown. Results from other areas (e.g., the Pacific Northwest and Norway) suggest

that social structure and territoriality may be important. 

POPULATION SIZE

The total number of killer whales off the eastern U.S. coast is unknown. 

Minimum Population Estimate

Present data are insufficient to calculate a minimum population estimate. 

Current Population Trend

There are insufficient data to determine the population trends for this species. 

CURRENT AND MAXIMUM NET PRODUCTIVITY RATES

Current and maximum net productivity rates are not known for this stock. The maximum net productivity

rate was assumed to be 0.04 for purposes of this assessment. This value is based on theoretical calculations showing

that cetacean populations may not generally grow at rates much greater than 4% given the constraints of their

reproductive life history (Barlow et al. 1995). 

POTENTIAL BIOLOGICAL REMOVAL

Potential Biological Removal (PBR) is the product of minimum population size, one-half the maximum

productivity rate, and a “recovery” factor (Wade and Angliss 1997). The minimum population size is unknown. 

The maximum productivity rate is 0.04, the default value for cetaceans. The “recovery” factor, which accounts for

endangered, depleted, threatened stocks, or stocks of unknown status relative to optimum sustainable population

(OSP) is assumed to be 0.5 because this stock is of unknown. PBR for the western North Atlantic killer whale is

unknown because the minimum population size cannot be determined. 

ANNUAL HUMAN-CAUSED MORTALITY

In 1994, one killer whale was caught in the New England multispecies sink gillnet fishery but released

alive. No takes were documented in a review of Canadian gillnet and trap fisheries (Read 1994). 

Fishery Information

Data on current incidental takes in U.S. fisheries are available from several sources. In 1986, NMFS

established a mandatory self-reported fishery information system for large pelagic fisheries. Data files are
188

maintained at the Southeast Fisheries Science Center (SEFSC). The Northeast Fisheries Science Center (NEFSC)

Sea Sampling Observer Program was initiated in 1989, and since that year several fisheries have been covered by the

program. In late 1992 and in 1993, the SEFSC provided observer coverage of pelagic longline vessels fishing off the

Grand Banks (Tail of the Banks) and provides observer coverage of vessels fishing south of Cape Hatteras.

There have been no observed mortalities or serious injuries by NMFS Sea Samplers in the pelagic drift

gillnet, pelagic longline, pelagic pair trawl, New England multispecies sink gillnet, mid-Atlantic coastal sink gillnet,

and North Atlantic bottom trawl fisheries. 

STATUS OF STOCK

The status of killer whales relative to OSP in U.S. Atlantic EEZ is unknown. Because there are no

observed mortalities or serious injury between 1990 and 1995, the total fishery-related mortality and serious injury

for this stock is considered insignificant and approaching zero mortality and serious injury rate. The species is not

listed as threatened or endangered under the Endangered Species Act. In Canada, the Cetacean Protection

Regulations of 1982, promulgated under the standing Fisheries Act, prohibit the catching or harassment of all

cetacean species. There are insufficient data to determine the population trends for this species. This is not a

strategic stock because, although PBR could not be calculated, there is no evidence of human-induced mortality. 

REFERENCES

Barlow, J., S.L. Swartz, T.C. Eagle, and P.R. Wade. 1995. U.S. Marine Mammal Stock Assessments: Guidelines for

Preparation, Background, and a Summary of the 1995 Assessments. U.S. Dep. Commer., NOAA Tech.

Memo. NMFS-OPR-6, 73 pp.

CETAP. 1982. A characterization of marine mammals and turtles in the mid- and north Atlantic areas of the U.S.

outer continental shelf. Cetacean and Turtle Assessment Program, University of Rhode Island. Final

Report #AA551-CT8-48 to the Bureau of Land Management, Washington, DC, 538 pp. 

Katona, S. K., J. A. Beard, P. E. Girton, and F. Wenzel. 1988. Killer whales (Orcinus orca) from the Bay of Fundy

to the Equator, including the Gulf of Mexico. Rit. Fiskideild. 9: 205-224. 

Mitchell, E. and R. R. Reeves. 1988. Records of killer whales in the western North Atlantic, with emphasis on

eastern Canadian waters. Rit. Fiskideild. 9: 161-193. 

Read, A. J. 1994. Interactions between cetaceans and gillnet and trap fisheries in the Northwest Atlantic. Rep. int.

Whal. Commn. Special Issue 15: 133-147.

Reeves, R. R. and E. Mitchell. 1988. Killer whale sightings and takes by American pelagic whalers in the North

Atlantic. Rit. Fiskideild. 9: 7-23

Wade P.R., and R.P. Angliss. 1997. Guidelines for assessing marine mammal stocks: Report of the GAMMS

Workshop April 3-5, 1996, Seattle, Washington. U.S. Dep. Commer., NOAA Tech. Memo. NMFS-OPR12, 93 pp.
189

July 1995

PYGMY KILLER WHALE (Feresa attenuata): 

Western North Atlantic Stock

STOCK DEFINITION AND GEOGRAPHIC RANGE

The pygmy killer whale is distributed worldwide in tropical and subtropical waters (Ross and Leatherwood

1994). Sightings of these animals in the northern Gulf of Mexico occur primarily over the deeper waters off the

continental shelf (NMFS unpublished data). There is no information on stock differentiation for the Atlantic

population. 

POPULATION SIZE

A single sighting of this species was made during a 1992 winter, visual sampling, line-transect vessel

survey of the U.S. Atlantic Exclusive Economic Zone (EEZ) from Miami, Florida, to Cape Hatteras, North Carolina

(Hansen et al. 1994). This sighting, of a herd of six animals, was not made during visual sampling effort; therefore,

the sighting could not be used to estimate abundance of pygmy killer whales, but it does confirm the presence of this

species in the U.S. Atlantic EEZ. 

Minimum Population Estimate

The minimum population estimate based on the count of animals in the single sighting, was six pygmy

killer whales (Hansen et al. 1994). 

Current Population Trend

No information was available to evaluate trends in population size. 

CURRENT AND MAXIMUM NET PRODUCTIVITY RATES

Current and maximum net productivity rates are unknown for this stock. For purposes of this assessment,

the maximum net productivity rate was assumed to be 0.04. This value is based on theoretical modeling showing

that cetacean populations may not grow at rates much greater than 4% given the constraints of their reproductive life

history (Barlow et al. 1995). 

POTENTIAL BIOLOGICAL REMOVAL

Potential Biological Removal (PBR) is the product of minimum population size, one-half the maximum

productivity rate, and a “recovery” factor (Wade and Angliss 1997). The minimum population size is six (6). The

maximum productivity rate is 0.04, the default value for cetaceans. The “recovery” factor, which accounts for

endangered, depleted, threatened stocks, or stocks of unknown status relative to optimum sustainable population

(OSP) is assumed to be 0.5 because this stock is of unknown status. PBR for the western North Atlantic pygmy

killer whale is 0.1.

ANNUAL HUMAN-CAUSED MORTALITY AND SERIOUS INJURY

The level of past or current, direct, human-caused mortality of pygmy killer whales in the U.S. Atlantic

EEZ is unknown; however, there has historically been some take of this species in small cetacean fisheries in the

Caribbean (Caldwell and Caldwell 1971). Available information indicates there likely is little, if any, fisheries

interaction with pygmy killer whales in the U.S. Atlantic EEZ. There have been no logbook reports of fisheryrelated mortality or serious injury and no observed fishery-related mortality or serious injury has been observed.

There have been no documented strandings of pygmy killer whales in the along the U.S. Atlantic coast

during 1987-present which have been classified as likely caused by fishery interactions or other human-related

causes. Stranding data probably underestimate the extent of fishery-related mortality and serious injury because not

all of the dolphins which die or are seriously injured in fishery interactions wash ashore, nor will all of those that do

wash ashore necessarily show signs of entanglement or other fishery-interaction. Finally, the level of technical

expertise among stranding network personnel varies widely as does the ability to recognize signs of fishery

interaction.
190

Fishery Information

Data on current incidental takes in U.S. fisheries are available from several sources. In 1986, NMFS

established a mandatory self-reported fishery information system for large pelagic fisheries. Data files are

maintained at the Southeast Fisheries Science Center (SEFSC). The Northeast Fisheries Science Center (NEFSC)

Sea Sampling Observer Program was initiated in 1989, and since that year several fisheries have been covered by the

program. In late 1992 and in 1993, the SEFSC provided observer coverage of pelagic longline vessels fishing off the

Grand Banks (Tail of the Banks) and provides observer coverage of vessels fishing south of Cape Hatteras.

There have been no observed mortalities or serious injuries by NMFS Sea Samplers in the pelagic drift

gillnet, pelagic longline, pelagic pair trawl, New England multispecies sink gillnet, mid-Atlantic coastal sink gillnet,

and North Atlantic bottom trawl fisheries. 

Other Mortality

 This stock may be subjected to human-induced mortality caused by habitat degradation (e.g., industrial and

agricultural pollution) and indirect effects of fisheries on prey. There have been, however, no studies to date which

have determined the amount, if any, of indirect human-induced mortality resulting from habitat degradation or

competition for prey. 

STATUS OF STOCK

The status of pygmy killer whales relative to OSP in U.S. Atlantic EEZ is unknown. The species is not

listed as threatened or endangered under the Endangered Species Act. There are insufficient data to determine the

population trends for this species. The total known fishery-related mortality and serious injury for this stock is less

than 10% of the calculated PBR and, therefore, can be considered insignificant and approaching zero mortality and

serious injury rate. The western North Atlantic pygmy killer whale is considered a non-strategic stock.

REFERENCES

Barlow, J., S.L. Swartz, T.C. Eagle, and P.R. Wade. 1995. U.S. Marine Mammal Stock Assessments: Guidelines for

Preparation, Background, and a Summary of the 1995 Assessments. U.S. Dep. Commer., NOAA Tech.

Memo. NMFS-OPR-6, 73 pp.

Caldwell, D. K. and M. C. Caldwell. 1971. The pygmy killer whale, Feresa attenuata, in the western Atlantic, with a

summary of world records. J. Mamm. 52:206-209. 

Hansen, L. J., K. D. Mullin and C. L. Roden. 1994. Preliminary estimates of cetacean abundance in the northern

Gulf of Mexico from vessel surveys, and of selected cetacean species in the U.S. Atlantic Exclusive

Economic Zone from vessel surveys from vessel surveys. Southeast Fisheries Science Center, Miami

Laboratory, Contribution No. MIA-93/94-58 

Ross, G. J. B. and S. Leatherwood. 1994. Pygmy killer whale Feresa attenuata (Gray 1874). Pages 387-404 in S. H.

Ridgway and R. Harrison (eds), Handbook of marine mammals, Vol. 5: The first book of dolphins.

Academic Press, San Diego, 418 pp. 

Wade P.R., and R.P. Angliss. 1997. Guidelines for assessing marine mammal stocks: Report of the GAMMS

Workshop April 3-5, 1996, Seattle, Washington. U.S. Dep. Commer., NOAA Tech. Memo. NMFS-OPR12, 93 pp.
191

December 1998

NORTHERN BOTTLENOSE WHALE (Hyperoodon ampullatus):

Western North Atlantic Stock

STOCK DEFINITION AND GEOGRAPHIC RANGE

Northern bottlenose whales are characterized as extremely uncommon or rare in waters of the U.S. Atlantic

Exclusive Economic Zone. The two sightings of three individuals constituted less than 0.1% of the 11,156 cetacean

sightings in the 1978-82 CETAP surveys. Both sightings were in the spring, along the 2,000 m isobath (CETAP

1982). In 1993 and 1996, two sightings of single animals, and in 1996, a single sighting of six animals (one

juvenile), were made during summer shipboard surveys conducted along the southern edge of Georges Bank (Anon.

1993; Anon. 1996).

Northern bottlenose whales are distributed in the North Atlantic from Nova Scotia to about 70° in the Davis

Strait, along the east coast of Greenland to 77° and from England to the west coast of Spitzbergen. It is largely a

deep-water species and is very seldom found in waters less than 2,000 m deep (Mead 1989). 

There are two main centers of bottlenose whale distribution in the western north Atlantic, one in the area

called "The Gully" just north of Sable Island, Nova Scotia, and the other in Davis Strait off northern Labrador

(Reeves et al. 1993). Studies at the entrance to the Gully from 1988-1995 identified 237 individuals and estimated

the local population size at about 230 animals (95% C.I. 160-360) (Whitehead et al. 1997). These individuals are

believed to be year-round residents and all age and sex classes are present (Gowans and Whitehead 1998). Mitchell

and Kozicki (1975) documented stranding records in the Bay of Fundy and as far south as Rhode Island. Stock

definition is unknown. 

POPULATION SIZE

The total number of northern bottlenose whales off the eastern U.S. coast is unknown. 

Minimum Population Estimate

Present data are insufficient to calculate a minimum population estimate. 

Current Population Trend

There are insufficient data to determine the population trends for this species. 

CURRENT AND MAXIMUM NET PRODUCTIVITY RATES

Current and maximum net productivity rates are unknown for this stock. For purposes of this assessment,

the maximum net productivity rate was assumed to be 0.04. This value is based on theoretical modeling showing

that cetacean populations may not grow at rates much greater than 4% given the constraints of their reproductive life

history (Barlow et al. 1995). 

POTENTIAL BIOLOGICAL REMOVAL

Potential Biological Removal (PBR) is the product of minimum population size, one-half the maximum

productivity rate, and a “recovery” factor (MMPA Sec. 3. 16 U.S.C. 1362; Wade and Angliss 1997). The minimum

population size is unknown. The maximum productivity rate is 0.04, the default value for cetaceans. The

“recovery” factor, which accounts for endangered, depleted, threatened stocks, or stocks of unknown status relative

to optimum sustainable population (OSP) is assumed to be 0.5 because this stock is of unknown status. PBR for the

western North Atlantic northern bottlenose whale is unknown because the minimum population size cannot be

determined. 

ANNUAL HUMAN-CAUSED MORTALITY

No mortalities have been reported in U.S. waters. A fishery for northern bottlenose whales existed in

Canadian waters during both the 1800s and 1900s. Its development was due to the discovery that bottlenose whales

contained spermaceti. A Norwegian fishery expanded from east to west (Labrador and Newfoundland) in several

episodes. The fishery peaked in 1965. Decreasing catches led to the cessation of the fishery in the 1970s, and
192

provided evidence that the population was depleted. A small fishery operated by Canadian whalers from Nova

Scotia operated in the Gully, and took 87 animals from 1962 to 1967 (Mead 1989; Mitchell 1977). 

Fishery Information

Data on current incidental takes in U.S. fisheries are available from several sources. In 1986, NMFS

established a mandatory self-reported fishery information system for large pelagic fisheries. Data files are

maintained at the Southeast Fisheries Science Center (SEFSC). The Northeast Fisheries Science Center (NEFSC)

Sea Sampling Observer Program was initiated in 1989, and since that year several fisheries have been covered by the

program. In late 1992 and in 1993, the SEFSC provided observer coverage of pelagic longline vessels fishing off the

Grand Banks (Tail of the Banks) and provides observer coverage of vessels fishing south of Cape Hatteras.

There have been no observed mortalities or serious injuries by NMFS Sea Samplers in the pelagic drift

gillnet, pelagic longline, pelagic pair trawl, New England multispecies sink gillnet, mid-Atlantic coastal sink gillnet,

and North Atlantic bottom trawl fisheries. 

STATUS OF STOCK

The status of northern bottlenose whales relative to OSP in U.S. Atlantic EEZ is unknown; however, a

depletion in Canadian waters in the 1970's may have impacted U.S. distribution and may be relevant to current status

in U.S. waters. The species is not listed as threatened or endangered under the Endangered Species Act. There are

insufficient data to determine the population trends for this species. Because there are no observed mortalities or

serious injury, the total fishery-related mortality and serious injury for this stock is considered to be approaching

zero mortality and serious injury rate. This is not a strategic stock because there are no recent records of fisheryrelated mortality or serious injury. 

REFERENCES

Anon. 1993. Cruise results, NOAA ship DELAWARE II, Cruise No. DEL 93-06, Marine Mammal Survey. NOAA

NMFS NEFSC, Woods Hole Laboratory, Woods Hole, MA 5 pp.

Anon. 1996. Cruise results, R/V ABEL-J, Cruise No. AJ-9601, Part III, Marine Mammal Survey. NOAA NMFS

NEFSC, Woods Hole Laboratory, Woods Hole, MA 7 pp.

Barlow, J., S.L. Swartz, T.C. Eagle, and P.R. Wade. 1995. U.S. Marine Mammal Stock Assessments: Guidelines for

Preparation, Background, and a Summary of the 1995 Assessments. U.S. Dep. Commer., NOAA Tech.

Memo. NMFS-OPR-6, 73 pp.

CETAP. 1982. A characterization of marine mammals and turtles in the mid- and north Atlantic areas of the U.S.

outer continental shelf. Cetacean and Turtle Assessment Program, University of Rhode Island. Final

Report #AA551-CT8-48 to the Bureau of Land Management, Washington, DC, 538 pp. 

Gowans, S. and H. Whitehead. 1998. Social organization of northern bottlenose whales. The World Marine

Mammal Science Conference, Monaco, January 1998 (Abstract).

Mead, J. G. 1989. Bottlenose whales. Pages 321-348. In: S. H. Ridgway and R. Harrison (eds), Handbook of

marine mammals, Volume 4: River dolphins and the larger toothed whales. Academic Press, New York. 

Mitchell, E. D. 1977. Evidence that the northern bottlenose whale is depleted. Rep. int. Whal. Commn. 27: 195-

203.

Mitchell, E. D. and V. M. Kozicki. 1975. Autumn stranding of a northern bottlenose whale (Hyperoodon

ampullatus) in the Bay of Fundy. J. Fish. Res. Bd. Can. 32: 1019-1040.

Reeves, R.R., E. Mitchell and H. Whitehead. 1993. Status of the northern bottlenose whale, Hyperoodon ampullatus.

Can. Fld. Nat. 107:490-508.

Whitehead, H., S. Gowans, A. Faucher, and S.W. McCarrey. 1997. Population analysis of northern bottlenose

whales in the Gully, Nova Scotia. Mar. Mamm. Sci. 13(2): 173-185.

Wade P.R., and R.P. Angliss. 1997. Guidelines for assessing marine mammal stocks: Report of the GAMMS

Workshop April 3-5, 1996, Seattle, Washington. U.S. Dep. Commer., NOAA Tech. Memo. NMFS-OPR12, 93 pp.
193

August 1997

WHITE-BEAKED DOLPHIN (Lagenorhynchus albirostris):

Western North Atlantic Stock

STOCK DEFINITION AND GEOGRAPHIC RANGE

White-beaked dolphins are the more northerly of the two species of Lagenorhynchus in the Northwest

Atlantic (Leatherwood et al. 1976). The species is found in waters from southern New England, north to western

and southern Greenland and Davis Straits (Leatherwood et al. 1976; CETAP 1982), in the Barents Sea and south to

at least Portugal (Reeves et al., in press). Differences in skull features indicate that there are at least two separate

stocks, one in the eastern and one in the western North Atlantic (Mikkelsen and Lund 1994). No genetic analyzes

have been conducted to distinguish the stock structure.

In waters off the northeastern U.S. coast, white-beaked dolphin sightings have been concentrated in the

western Gulf of Maine and around Cape Cod (CETAP 1982). The limited distribution of this species in U.S. waters

has been attributed to opportunistic feeding (CETAP 1982). Prior to the 1970's, white-sided dolphins (L. acutus) in

U.S. waters were found primarily offshore on the continental slope, while white-beaked dolphins were found on the

continental shelf. During the 1970's, there was an apparent switch in habitat use between these two species. This

shift may have been a result of the increase in sand lance in the continental shelf waters (Katona et al. 1993; Kenny

et al. 1996). 

POPULATION SIZE

The total number of white-beaked dolphins in U.S. and Canadian waters is unknown, although one

abundance estimate is available for part of the known habitat in U.S. waters, and two estimates are from Canadian

waters (Table 1).

A population size of 573 white-beaked dolphins (CV=0.69) was estimated from an aerial survey program

conducted from 1978 to 1982 on the continental shelf and shelf edge waters between Cape Hatteras, North Carolina

and Nova Scotia (Table 1; CETAP 1982). The estimate is based on spring data because the greatest proportion of

the population off the northeast U.S. coast appeared in the study area during this season. This estimate does not

include a correction for dive-time or g(0), the probability of detecting an animal group on the track line. This

estimate may not reflect the current true population size because of its high degree of uncertainty (e.g., large CV), its

old age, and it was estimated just after cessation of extensive foreign fishing operations in the region.

A population size of 5,500 white-beaked dolphins was based on an aerial survey off eastern Newfoundland

and southeastern Labrador (Table 1; Alling and Whitehead 1987).

A population size of 3,486 white-beaked dolphins [95% confidence interval (CI) = 2,001-4,971]was

estimated from a ship-based survey of a small segment of the Labrador Shelf in August 1982 (Table 1; Alling and

Whitehead 1987). A CV was not given, but, assuming a symmetric CI, it would be 0.22.

 There are no abundance estimates for this species in waters between the Gulf of Maine and the

Newfoundland/Labrador region. 

Table 1. Summary of abundance estimates for western North Atlantic white-beaked dolphins. Month, year, and area

covered during each abundance survey, and resulting abundance estimate (Nbest) and coefficient of variation

(CV). Unk=unknown.

Month/Year Area Nbest CV

spring 1978-82 Cape Hatteras, NC

to Nova Scotia 573 0.69

1980's E. Newfoundland

and SE Labrador 5,500 None reported

August 1982 Labrador shelf 3,486 0.22
194

Minimum Population Estimate

Present data are insufficient to calculate a minimum population estimate in U.S. Exclusive Economic Zone

(EEZ) waters. 

Current Population Trend

There are insufficient data to determine population trends for this species. 

CURRENT AND MAXIMUM NET PRODUCTIVITY RATES

Current and maximum net productivity rates are unknown for this stock. For purposes of this assessment,

the maximum net productivity rate was assumed to be 0.04. This value is based on theoretical modeling showing

that cetacean populations may not grow at rates much greater than 4% given the constraints of their reproductive life

history (Barlow et al. 1995).

 

POTENTIAL BIOLOGICAL REMOVAL

Potential Biological Removal (PBR) is the product of minimum population size, one-half the maximum

productivity rate, and a “recovery” factor (Wade and Angliss 1997). The minimum population size of white-beaked

dolphins is unknown. The maximum productivity rate is 0.04, the default value for cetaceans. The “recovery”

factor, which accounts for endangered, depleted, threatened stocks, or stocks of unknown status relative to optimum

sustainable population (OSP) is assumed to be 0.5 because this stock is of unknown status. PBR for the western

North Atlantic white-beaked dolphin is unknown.

ANNUAL HUMAN-CAUSED MORTALITY AND SERIOUS INJURY

White-beaked dolphins have been taken in cod traps and the Canadian groundfish gillnet fisheries off

Newfoundland and Labrador and in the Gulf of St. Lawrence (Alling and Whitehead 1987; Read 1994; Hai et al.

1996); however, the total number of animals taken is not known. 

There are no documented reports of fishery-related mortality or serious injury to this stock in the U.S. EEZ. 

Fishery Information

Because of the absence of observed fishery-related mortality and serious injury to this stock in the U.S.

EEZ, no U.S. fishery information is provided. 

The Canadian Atlantic groundfish gillnet fishery is important and widespread. Many fisherman hold

groundfish gillnet licenses but the number of active fishermen is unknown. In 1989, approximately 6,800 licenses

were issued to fishermen along the southern coast of Labrador, and northeast and southern coast of Newfoundland.

About 3,900 licenses were issued in 1989 in the Gulf of St. Lawrence and 659 licenses were issued in the Bay of

Fundy and southwestern Nova Scotia. 

Other Mortality

White-beaked dolphins were hunted for food by residents in Newfoundland and Labrador (Alling and

Whitehead 1987). These authors, based on interview data, estimated that 366 white-beaked dolphins were taken

each year. The same authors reported that 25-50% of the killed dolphins were lost.

STATUS OF STOCK

The status of white-beaked dolphins, relative to OSP, in U.S. Atlantic coast waters is unknown. They are

not listed as threatened or endangered under the Endangered Species Act. There are insufficient data to determine

population trends for this species. Because there are insufficient data to calculate PBR it is not possible to determine

if stock is strategic and if the total fishery-related mortality and serious injury for this stock is significant and

approaching zero mortality and serious injury rate. However, because this stock has a marginal occurrence in U.S.

waters and there are no documented takes in U.S. waters, this stock has been designated as not strategic. 
195

REFERENCES

Alling, A. K. and H. P. Whitehead. 1987. A preliminary study of the status of white-beaked dolphins,

Lagenorhynchus albirostris, and other small cetaceans off the coast of Labrador. Can. Fld. Nat. 101(2):

131-135.

Barlow, J., S. L. Swartz, T. C. Eagle, and P. R. Wade. 1995. U.S. Marine mammal stock assessments: Guidelines for

preparation, background, and a summary of the 1995 assessments. U.S.Dept. Commer., NOAA Tech.

Memo. NMFS-OPR-6, 73 pp.

CETAP. 1982. A characterization of marine mammals and turtles in the mid- and north Atlantic areas of the U.S.

outer continental shelf. Cetacean and Turtle Assessment Program, University of Rhode Island. Final

Report #AA551-CT8-48 to the Bureau of Land Management, Washington, DC, 538 pp. 

Hai, D.J., J. Lein, D. Nelson, and K. Curren. 1996. A contribution to the biology of the white-sided dolphin,

Lagenorhnchus albirostris, in waters off Newfoundland. Can..Fld. Nat. 110(1).

Katona, S. K., V. Rough, and D. T. Richardson. 1993. A field guide to whales, porpoises, and seals from Cape Cod

to Newfoundland. Washington, D. C. : Smithsonian Institution Press. 316 pp. 

Kenney, R. D., P. M. Payne, D. W. Heineman and H. E. Winn. 1996. Shifts in Northeast shelf cetacean distributions

relative to trends in Gulf of Maine/Georges Bank finfish abundance. Pp. 169-196. In: K. Sherman, N.A.

Jaworski and T. Smada (eds.) The northeast shelf ecosystem: assessment, sustainability, and management.

Blackwell Science, Cambridge, MA 02142, USA.

Leatherwood, S., D. K. Caldwell, and H. E. Winn. 1976. Whales, dolphins, and porpoises of the western North

Atlantic. A guide to their identification. U.S. Dept. of Commerce, NOAA Tech. Rep. NMFS Circ. 396, 176

pp. 

Mikkelsen, A.M.H. and A. Lund. 1994. Intraspecific variation in the dolphins Lagenorhnchus albirostris and L.

acutus (Mammalia: Cetacea) in metrical and non-metrical skull characters, with remarks on occurrence. J.

Zool., Lond. 234:289-299.

Read, A. J. 1994. Interactions between cetaceans and gillnet and trap fisheries in the northwest Atlantic. Rep. int.

Whal. Commn. Special Issue 15: 133-147. 

Reeves, R.R., R. L. Brownell Jr., C. C. Kinze, C. Smeenk and J. Lein. (in press). White-beaked dolphin

(Lagenorhnchus albirostris (Gray 1846). In: S.H. Ridgway and R. Harrison (eds.) Handbook of marine

mammals, Vol 6.

Wade, P. R. and R. P. Angliss. 1997. Guidelines for assessing marine mammal stocks: Report of the GAMMS

workshop April 3-5, 1996, Seattle, Washington. U.S. Dep. Commer., NOAA Tech. Memo. NMFS-OPR-12,

93 pp.
196

Figure 1. Distribution of spotted dolphin sightings from

NEFSC and SEFSC shipboard and aerial surveys during

the summer in 1990-1998. Isobaths are at 100 m and

1,000 m. 

September 2000

ATLANTIC SPOTTED DOLPHIN (Stenella frontalis):

Western North Atlantic Stock

STOCK DEFINITION AND GEOGRAPHIC RANGE

There are two species of spotted dolphin in the Western Atlantic — the Atlantic spotted dolphin, Stenella

frontalis, formerly S. plagiodon (Perrin et al. 1987), and the pantropical spotted dolphin, S. attenuata. These species

are difficult to differentiate at sea. 

Atlantic spotted dolphins are distributed in tropical and warm temperate waters of the western North

Atlantic (Leatherwood et al. 1976). Their distribution is from southern New England, south through the Gulf of

Mexico and the Caribbean to Venezuela (Leatherwood et al. 1976; Perrin et al. 1994). The large, heavily spotted

form of the Atlantic spotted dolphin along the southeastern and Gulf coasts of the United States, which may warrant

designation as a distinct sub-species (Rice 1998), ( inhabits the continental shelf, usually being found inside or near

the 200 m isobath (within 250-350 km of the coast) but sometimes coming into very shallow water adjacent to the

beach (Figure 1). Off the northeast USA coast, spotted dolphins are widely distributed on the continental shelf,

along the continental shelf edge, and offshore over the deep ocean south of 40o

 N (CETAP 1982). Atlantic spotted

dolphins regularly occur in the inshore waters south of Chesapeake Bay and near the continental shelf edge and

continental slope waters north of this region (Payne et al. 1984; Mullin in review). Sightings have also been made

along the north wall of the Gulf Stream and warm-core ring features (Waring et al. 1992). Stock structure in the

western North Atlantic is unknown. 

POPULATION SIZE

Total numbers of Atlantic spotted dolphins

off the USA or Canadian Atlantic coast are unknown,

although three estimates from selected regions of the

habitat do exist for select time periods. Because S.

frontalis and S. attenuata are difficult to differentiate

at sea, the reported abundance estimates, prior to

1998, are for both species of spotted dolphins

combined. Sightings were almost exclusively in the

continental shelf edge and continental slope areas

west of Georges Bank (Figure 1). An abundance of

6,107 undifferentiated spotted dolphins (CV=0.27)

was estimated from an aerial survey program

conducted from 1978 to 1982 on the continental, shelf

and shelf edge waters between Cape Hatteras, North

Carolina and Nova Scotia (CETAP 1982). As

recommended in the GAMS Workshop Report (Wade

and Angliss 1997), estimates older than eight years

are deemed unreliable, therefore should not be used

for PBR determinations. Further, due to changes in

survey methodology these data should not be used to

make comparisons to more current estimates. 

An abundance of 4,772 (CV=1.27)

undifferentiated spotted dolphins was estimated from

a July to September 1995 sighting survey conducted

by two ships and an airplane that covered waters from

Virginia to the mouth of the Gulf of St. Lawrence

(Table 1; Palka et al. in review). Total track line

length was 32,600 km. The ships covered waters

between the 50 and 1000 fathom depth contour lines,
197

the northern edge of the Gulf Stream, and the northern Gulf of Maine/Bay of Fundy region. The airplane covered

waters in the mid-Atlantic from the coastline to the 50 fathom depth contour line, the southern Gulf of Maine, and

shelf waters off Nova Scotia from the coastline to the 1000 fathom depth contour line. Data collection and analysis

methods used were described in Palka (1996).

An abundance of 32,043 (CV=1.39) for offshore Atlantic spotted dolphins was estimated from a line

transect sighting survey conducted during July 6 to September 6, 1998 by a ship and plane that surveyed 15,900 km

of track line in waters north of Maryland (38° N) (Figure 1; Palka et al. in review). Shipboard data were analyzed

using the modified direct duplicate method (Palka 1995) that accounts for school size bias and g(0), the probability

of detecting a group on the track line. Aerial data were not corrected for g(0).

An abundance of 4,396 (CV=0.62) for offshore, and 15,840 (CV=0.60) for coastal Atlantic spotted dolphins

was estimated from a shipboard line transect sighting survey conducted between 8 July and 17 August 1998 that

surveyed 5,570 km of track line in waters south of Maryland (38°N) (Figure 1; Mullin in review). Abundance

estimates were made using the program DISTANCE (Buckland et al. 1993; Laake et al. 1993) where school size

bias and ship attraction were accounted for.

The best available abundance estimate for the Atlantic spotted dolphins is the sum of the estimates from the

two 1998 USA Atlantic surveys, 52,279 (CV=0.87), where the estimate from the northern USA Atlantic is 32,043

(CV=1.39) and estimates from the southern USA Atlantic are 4,396 (CV=0.62) and 15,840 (CV=0.60). At their

November 1999 meeting, the Atlantic SRG recommended that, without a genetic determination of stock structure,

the abundance estimates for the coastal and offshore forms should be combined. This joint estimate is considered

best because together these two surveys have the most complete coverage of the species’ habitat.

Table 1. Summary of abundance estimates for both undifferentiated spotted dolphins (1995), and differentiated

Atlantic spotted dolphins (1998). Month, year, and area covered during each abundance survey, and

resulting abundance estimate (Nbest) and coefficient of variation (CV).

Month/Year Area Nbest CV

Jul-Sep 1995 Virginia to Gulf of St. Lawrence 4,7721 1.27

Jul-Sep 1998 Maryland to Gulf of St. Lawrence 32,0432 1.39

Jul-Aug 1998 Florida to Maryland 4,3962 0.62

Jul-Sep 1998 Gulf of St. Lawrence to Florida (COMBINED) 36,4393 1.22

Jul-Aug 1998 Florida to Maryland 15,8404

 0.60

1

 Because of uncertain species identification in the 1995 survey, all spotted dolphins were lumped together. 2

 This represents the first estimate for the offshore Atlantic spotted dolphin. 3

 This is the combined estimate for the two survey regions

4

 This represents the first estimate for the coastal Atlantic spotted dolphin

Minimum Population Estimate

The minimum population estimate is the lower limit of the two-tailed 60% confidence interval of the lognormally distributed best abundance estimate. This is equivalent to the 20th percentile of the log-normal distribution

as specified by Wade and Angliss (1997). Until more definitive stock identification (i.e., genetic analysis) work is

completed, the Atlantic Scientific Review Group recommends that the best estimate of abundance for Atlantic

spotted dolphins is the combined estimates for the offshore 15,840 (CV=0.60) and coastal 36,439 (CV=1.22) forms

of Atlantic spotted dolphins. This estimate is 52,279 (CV=0.87). The minimum population estimates based on the

combined offshore and coastal abundance estimates is 27,785 (CV=0.87).
198

Current Population Trend

There are insufficient data to determine the population trends for this species, given that surveys prior to

1998 did not differentiate between species of spotted dolphins. 

CURRENT AND MAXIMUM NET PRODUCTIVITY RATES

Current and maximum net productivity rates are unknown for this stock. For purposes of this assessment,

the maximum net productivity rate was assumed to be 0.04. This value is based on theoretical modeling showing

that cetacean populations may not grow at rates much greater than 4% given the constraints of their reproductive life

history (Barlow et al. 1995).

POTENTIAL BIOLOGICAL REMOVAL

Potential Biological Removal (PBR) is the product of minimum population size, one-half the maximum

productivity rate, and a “recovery” factor (MMPA Sec. 3. 16 U.S.C. 1362; Wade and Angliss 1997). The minimum

population size for the combined offshore and coastal ‘forms’ of Atlantic spotted dolphins is 52,279 (CV=0.87). 

The maximum productivity rate is 0.04, the default value for cetaceans. The “recovery” factor, which accounts for

endangered, depleted, threatened stocks, or stocks of unknown status relative to optimum sustainable population

(OSP) is set to 0.5 because this stock is of unknown status. PBR for the combined offshore and coastal forms of

Atlantic spotted dolphins is 278 (CV=0.87) .

ANNUAL HUMAN-CAUSED MORTALITY AND SERIOUS INJURY

 Total annual estimated average fishery-related mortality or serious injury to this stock during 1994-1998

was 7.8 undifferentiated spotted dolphins (Stenella spp.) CV=0.01; Table 2). 

Fishery Information

No spotted dolphin mortalities were observed in 1977-1991 foreign fishing activities. Data on current

incidental takes in USA fisheries are available from several sources. In 1986, NMFS established a mandatory selfreported fisheries information system for large pelagic fisheries. Data files are maintained at the Southeast Fisheries

Science Center (SEFSC). The Northeast Fisheries Science Center (NEFSC) Sea Sampling Observer Program was

initiated in 1989 and since that year several fisheries have been covered by the program. In late 1992 and in 1993,

the SEFSC provided observer coverage of pelagic longline vessels fishing off the Grand Banks (Tail of the Banks)

and provides observer coverage of vessels fishing south of Cape Hatteras. Total fishery-related mortality and serious

injury cannot be estimated separately for the two species of spotted dolphins in the USA Atlantic Exclusive

Economic Zone (EEZ) because of the uncertainty in species identification by fishery observers. The Atlantic

Scientific Review Group advised adopting the risk-averse strategy of assuming that either species might have been

subject to the observed fishery-related mortality and serious injury.

Bycatch has been observed by NMFS Sea Samplers in the pelagic drift gillnet and pelagic longline

fisheries, but no mortalities or serious injuries have been documented in the pelagic pair trawl, Northeast

multispecies sink gillnet, mid-Atlantic coastal gillnet, and North Atlantic bottom trawl fisheries; and no takes have

been documented in a review of Canadian gillnet and trap fisheries (Read 1994).

Pelagic Drift Gillnet

The estimated total number of hauls in the pelagic drift gillnet fishery increased from 714 in 1989 to 1,144

in 1990; thereafter, with the introduction of quotas, effort was severely reduced. The estimated number of hauls in

1991, 1992, 1993, 1994, 1995, 1996, and 1998 were 233, 243, 232, 197, 164,149, and 113 respectively. In 1996 and

1997, NMFS issued management regulations which prohibited the operation of this fishery in 1997. Further, in

January 1999 NMFS issued a Final Rule to prohibit the use of driftnets (i.e., permanent closure) in the North

Atlantic swordfish fishery (50 CFR Part 630). Fifty-nine different vessels participated in this fishery at one time or

another between 1989 and 1993. Since 1994, between 10- and 13 vessels have participated in the fishery (Table 2). 

Observer coverage, expressed as percent of sets observed, was 8% in 1989, 6% in 1990, 20% in 1991, 40% in 1992,

42% in 1993, 87% in 1994, 99% in 1995, 64% in 1996, and 99% in 1998. Effort was concentrated along the

southern edge of Georges Bank and off Cape Hatteras. Examination of the species composition of the catch and

locations of the fishery throughout the year, suggested that the pelagic drift gillnet fishery be stratified into two

strata, a southern or winter stratum, and a northern or summer stratum. Estimates of the total bycatch, from 1989 to

1993, were obtained using the aggregated (pooled 1989-1993) catch rates, by strata (Northridge 1996). Estimates of
199

total annual bycatch for 1994 and 1995 were estimated from the sum of the observed caught and the product of the

average bycatch per haul and the number of unobserved hauls as recorded in self-reported fisheries information. 

Variances were estimated using bootstrap re-sampling techniques. Forty-nine undifferentiated spotted dolphins

mortalities were observed in the drift gillnet fishery between 1989 and 1998 and occurred northeast of Cape

Hatteras within the 183 m isobath in February-April, and near Lydonia Canyon in October. Six whole animal

carcasses that were sent to the Smithsonian were identified as Pantropical spotted dolphins (S. attenuata). The

remaining animals were not identified to species. Estimated annual mortality and serious injury attributable to this

fishery (CV in parentheses) was 25 in 1989 (.65), 51 in 1990 (.49), 11 in 1991 (.41), 20 in 1992 (0.18), 8.4 in 1993

(0.40), 29 in 1994 (0.01), 0 in 1995, 2 in 1996 (0.06), NA in 1997, and 0 in 1998; average annual mortality and

serious injury during 1994-1998 was 7.8 (0.01) (Table 2).

Pelagic Longline

 The pelagic longline fishery operates in the USA Atlantic ( including Caribbean) and Gulf of Mexico EEZ

(SEFSC unpublished data). Interactions between the pelagic longline fishery and spotted dolphins have been

reported; however, a vessel may fish in more than one statistical reporting area and it is not possible to separate

estimates of fishing effort other than to subtract Gulf of Mexico effort from Atlantic fishing effort, which includes

the Caribbean Sea. This fishery has been monitored with about 5% observer coverage, in terms of trips observed,

since 1992. Total effort, excluding the Gulf of Mexico, for the pelagic longline fishery, based on mandatory selfreported fisheries information, was11,279 sets in 1991, 9,869 sets in 1992, 9,862 sets in 1993, 9,481 sets in 1994,

10,129 sets in 1995, 9,885 sets in 1996, 8,023 sets in 1997, and 6,675 sets in 1998 (Cramer 1994; Scott and Brown

1997; Johnson et al.1999; Yeung 1999b). Since 1992, this fishery has been monitored with about 5% observer

coverage, in terms of trips observed, within every statistical reporting area within the EEZ and beyond. Off the USA

Atlantic coast, the fishery has been observed from January to March off Cape Hatteras, in May and June in the entire

mid-Atlantic, and in July through December in the mid-Atlantic Bight and off Nova Scotia. The 1994-1998,

estimated take was based on a revised analysis of the observed incidental take and self-reported incidental take and

effort data, and replace previous estimates for the 1992-1993 and 1994-1995 periods (Cramer 1994; Scott and Brown

1997; Johnson et al. 1999; Yeung 1999a). Further, Yeung (1999b), revised the 1992-1997 fishery mortality

estimates in Johnson et al. (1999) to include seriously injured animals. The 1998 bycatch estimates were from

Yeung (1999a). Most of the estimated marine mammal bycatch was from EEZ waters between South Carolina and

Cape Cod (Johnson et al. 1999). Excluding the Gulf of Mexico where one animal was hooked and released alive

(Appendix 1), no Atlantic spotted dolphin bycatches were observed for 1992-1998. 

Table 2. Summary of the incidental mortality of undifferentiated spotted dolphins (Stenella sp.) by commercial

fishery including the years sampled (Years), the number of vessels active within the fishery (Vessels), the

type of data used (Data Type), the annual observer coverage (Observer Coverage), the mortalities recorded

by on-board observers (Observed Mortality), the estimated annual mortality (Estimated Mortality), the

estimated CV of the annual mortality (Estimated CVs) and the mean annual mortality (CV in parentheses).

Fishery Years Vessels Data Type 1 Observed

Serious Injury

Observer

Coverage 2 

Observed

Mortality

Estimated

Mortality5

Estimated

CVs 

Mean

Annual

Mortality

Pelagic

Drift

Gillnet6

 94-98 1994=113

1995=12

1996=10

1998=13

Obs. Data

Logbook

0, 0, 0, 0, 0 .87, .99,

.64, NA, .99

 29, 0, 2,

NA, 0

29, 0, 24

,

NA, 0

 .01, 0, 0,

NA, 0

 7.75

 (0.01)

TOTAL 7.8

 (0.01)

1 Observer data (Obs. Data) are used to measure bycatch rates, and the data are collected within the Northeast Fisheries Science Center

(NEFSC) Sea Sampling Program. Mandatory logbook (Logbook) data are used to measure total effort for the pelagic drift gillnet fishery,

and these data are collected at the Southeast Fisheries Science Center (SEFSC). 2

 The observer coverage for the pelagic drift gillnet and pair trawl fishery is measured in terms of sets, and the longline fishery is in trips. 3

 1994, 1995, 1996, and 1998 shown, other years not available on an annual basis.

4

 Estimates were based on two seasons. The two observed takes were during the winter season when observer coverage was 100%.

5 Annual mortality estimates include animals seriously injured and released alive. 6 The fishery did not operate in 1997; the average annual mortality is based on the number of years (4; 1994-1998) that the fishery

operated.
200

Other Mortality

From 1995-1998, thirteen Atlantic spotted dolphins were stranded between North Carolina and Florida

(NMFS unpublished data).

STATUS OF STOCK

The status of Atlantic spotted dolphins, relative to OSP in the USA Atlantic EEZ is unknown. The species

is not listed as threatened or endangered under the Endangered Species Act. There are insufficient data to determine

the population trends for this species. Total fishery-related mortality and serious injury for this stock is less than

10% of the calculated PBR and, therefore, can be considered to be insignificant and approaching zero mortality and

serious injury rate. Average annual fishery-related mortality and serious injury does not exceed the PBR; therefore,

this is not a strategic stock.

REFERENCES

Barlow, J., S. L. Swartz, T. C. Eagle and P. R. Wade. 1995. U.S. Marine Mammal Stock Assessments: Guidelines

for Preparation, Background, and a Summary of the 1995 Assessments. U.S. Dep. Commer., NOAA Tech.

Memo. NMFS-OPR-6, 73 pp. 

Buckland, S. T., D. R. Andersen, K. P. Burnham and J. L. Laake. 1993. Distance Sampling: Estimating abundance

of biological populations. Chapman and Hall, New York, 446 pp. 

CETAP. 1982. A characterization of marine mammals and turtles in the mid- and north Atlantic areas of the U.S.

outer continental shelf. Cetacean and Turtle Assessment Program, University of Rhode Island. Final

Report, Contract AA51-C78-48, Bureau of Land Management, Washington, DC, 538 pp. 

Cramer, J. 1994. Large pelagic logbook newsletter - 1993. NOAA Tech. Mem. NMFS-SEFSC-352, 19 pp.

Johnson, D. R., C. A. Brown, and C. Yeung. 1999. Estimates of marine mammal and marine turtle catch by the

U.S. Atlantic pelagic longline fleet in 1992-1997. SEFSC PRD-98/99-03. 68 pp.

Laake, J. L., S. T. Buckland, D. R. Anderson and K. P. Burnham. 1993 . DISTANCE user’s guide, V2.0. Colorado

Cooperative Fish & Wildlife Research Unit, Colorado State University, Ft. Collins, Colorado, 72 pp. 

Leatherwood, S., D. K. Caldwell and H. E. Winn. 1976. Whales, dolphins, and porpoises of the western North

Atlantic. A guide to their identification. NOAA Tech. Rep. NMFS Circ. 396, U.S. Dept. Commer.

Washington, DC 176 pp. 

Mullin, K. D. (in review). Abundance and distribution of cetaceans in the southern U.S. Atlantic Ocean during

summer 1998. Fish. Bull., U.S.

Northridge, S. 1996. Estimation of cetacean mortality in the U.S. Atlantic swordfish and tuna drift gillnet and pair

trawl fisheries. Final report to the Northeast Fisheries Science Center, Contract No. 40ENNF500160. 

Palka, D. 1995. Abundance estimate of the Gulf of Maine harbor porpoise. Rep. int Whal. Commn. Special Issue

16:27-50.

Palka, D. 1996. Update on abundance of Gulf of Maine/Bay of Fundy harbor porpoises. NOAA/NMFS/NEFSC.

Ref. Doc. 96-04; 37 pp. Available from: National Marine Fisheries Service, 166 Water Street, Woods

Hole, MA 02543-1026.

Palka, D., G. Waring, and D. Potter. (in review). Abundances of cetaceans and sea turtles in the northwest Atlantic

during summer 1995 and 1998. Fish. Bull., U.S.

Payne, P. M., L. A. Selzer and A. R. Knowlton. 1984. Distribution and density of cetaceans, marine turtles, and

seabirds in the shelf waters of the northeastern United States, June 1980-December 1983, based on

shipboard observations. NOAA/NMFS Contract No. NA-81-FA-C-00023. 

Perrin, W. F.,E. D. Mitchell, J. G. Mead, D. K. Caldwell, M. C. Caldwell, P. J. H. van Bree, and W. H. Dawbin.

1987. Revision of the spotted dolphins, Stenella sp. Mar. Mammal Sci. 3(2): 99-170.

Perrin, W. F., D. K. Caldwell, and M. C. Caldwell. 1994. Atlantic spotted dolphin. Pages 173-190. In: S. H.

Ridgway and R. Harrison (eds.). Handbook of marine mammals, Volume 5: The first book of dolphins. 

Academic Press, San Diego, 418 pp. 

Rice, D. W. 1998. Marine mammals of the world, systematics and distribution. Spec. Publ. No 4. Society for

Marine Mammalogy, Lawrence, KS. 231 pp.

Scott, G. P. and C. A. Brown. 1997. Estimates of marine mammal and marine turtle catch by the U.S. Atlantic

pelagic longline fleet in 1994-1995. Miami Laboratory Contribution MIA-96/97-28
201

Wade, P. R., and R. P. Angliss. 1997. Guidelines for assessing marine mammal stocks: Report of the GAMMS

Workshop April 3-5, 1996, Seattle, Washington. U.S. Dep. Commer., NOAA Tech. Memo. NMFS-OPR12, 93 pp.

Waring, G. T., C. P. Fairfield, C. M. Ruhsam and M. Sano. 1992. Cetaceans associated with Gulf Stream features

off the northeastern USA shelf. ICES Marine Mammals Comm. CM 1992/N:12, 29 pp. 

Yeung, C. 1999a. Estimates of marine mammal and marine turtle bycatch by the U.S. Atlantic pelagic longline fleet

in 1998. NOAA Technical Memorandum NMFS-SEFSC-430, 26 pp.

Yeung, C. 1999b. Revised Mortality Estimates of Marine Mammal Bycatch in 1992-1997 based on Serious Injury

Guidelines. NOAA Technical Memorandum NMFS-SEFSC-429, 23 pp.
202

Figure 1. Distribution of striped dolphin sightings from

NEFSC and SEFSC shipboard and aerial surveys during

the summer in 1990-1998. Isobaths are at 100 m and

1,000 m. 

September 2000

STRIPED DOLPHIN (Stenella coeruleoalba):

Western North Atlantic Stock

STOCK DEFINITION AND GEOGRAPHIC RANGE

The striped dolphin, Stenella coeruleoalba, is distributed worldwide in warm-temperate to tropical seas 

(Archer and Perrin 1997). Striped dolphins are found in the western North Atlantic from Nova Scotia south to at

least Jamaica and in the Gulf of Mexico. In general, striped dolphins appear to prefer continental slope waters

offshore to the Gulf Stream (Leatherwood et al. 1976; Perrin et al. 1994; Schmidly 1981). There is very little

information concerning striped dolphin stock structure in the western North Atlantic (Archer and Perrin 1997). 

In waters off the northeastern USA coast, striped dolphins are distributed along the continental shelf edge

from Cape Hatteras to the southern margin of Georges Bank, and also occur offshore over the continental slope and

rise in the mid-Atlantic region (CETAP 1982). Continental shelf edge sightings in this program were generally

centered along the 1,000 m depth contour in all seasons (CETAP 1982). During 1990 and 1991 cetacean habitat-use

surveys, striped dolphins were associated with the Gulf Stream north wall and warm-core ring features (Waring et al.

1992). Striped dolphins seen in a survey of the New England Sea Mounts (Palka 1997) were in waters that were

between 200

 and 270C and deeper than 900 m. 

Although striped dolphins are considered to be uncommon in Canadian Atlantic waters (Baird et al. 1993), 

recent summer sightings (2-125 individuals) in the deeper and warmer waters of the Gully (submarine canyon off

eastern Nova Scotia shelf) suggest that this region may be an important part of their range (Gowans and Whitehead

1995; Baird et al. 1997). 

POPULATION SIZE

Total numbers of striped dolphins off the

USA or Canadian Atlantic coast are unknown,

although four estimates from selected regions of the

habitat do exist for select time periods. Sightings

were almost exclusively in the continental shelf edge

and continental slope areas west of Georges Bank

(Figure 1). An abundance of 36,780 striped dolphins

(CV=0.27) was estimated from an aerial survey

program conducted from 1978 to 1982 on the

continental, shelf and shelf edge waters between

Cape Hatteras, North Carolina and Nova Scotia

(CETAP 1982). An abundance of 25,939 (CV=0.36)

and 13,157 (CV=0.45) striped dolphins was

estimated from line transect aerial surveys conducted

from August to September 1991 using the Twin Otter

and AT-11, respectively (Anon. 1991). The study

area included that covered in the CETAP study plus

several additional continental slope survey blocks. 

Due to weather and logistical constraints, several

survey blocks south and east of Georges Bank were

not surveyed. As recommended in the GAMS

Workshop Report (Wade and Angliss 1997),

estimates older than eight years are deemed

unreliable, therefore should not be used for PBR

determinations. Further, due to changes in survey

methodology these data should not be used to make

comparisons to more current estimates
203

An abundance of 31,669 (CV=0.73) striped dolphins was estimated from a July to September 1995 sighting

survey conducted by two ships and an airplane that covered waters from Virginia to the mouth of the Gulf of St.

Lawrence (Table 1; Palka et al. in review). Total track line length was 32,600 km. The ships covered waters

between the 50 and 1000 fathom depth contour lines, the northern edge of the Gulf Stream, and the northern Gulf of

Maine/Bay of Fundy region. The airplane covered waters in the mid-Atlantic from the coastline to the 50 fathom

depth contour line, the southern Gulf of Maine, and shelf waters off Nova Scotia from the coastline to the 1000

fathom depth contour line. Data collection and analysis methods used were described in Palka (1996). 

An abundance of 39,720 (CV=0.45) for striped dolphins was estimated from a line transect sighting survey

conducted during July 6 to September 6, 1998 by a ship and plane that surveyed 15,900 km of track line in waters

north of Maryland (38° N) (Figure 1; Palka et al. in review). Shipboard data were analyzed using the modified

direct duplicate method (Palka 1995) that accounts for school size bias and g(0), the probability of detecting a group

on the track line. Aerial data were not corrected for g(0).

An abundance of 21,826 (CV=0.78) for striped dolphins was estimated from a shipboard line transect

sighting survey conducted between 8 July and 17 August 1998 that surveyed 5,570 km of track line in waters south

of Maryland (38°N) (Figure 1; Mullin in review). Abundance estimates were made using the program DISTANCE

(Buckland et al. 1993; Laake et al. 1993) where school size bias and ship attraction were accounted for.

The best available abundance estimate for striped dolphins is the sum of the estimates from the two 1998

USA Atlantic surveys, 61,546 (CV=0.40), where the estimate from the northern USA Atlantic is 39,720 (CV=0.45)

and from the southern USA Atlantic is 21,826 (CV=0.78). This joint estimate is considered best because together

these two surveys have the most complete coverage of the species’ habitat.

Table 1. Summary of abundance estimates for western North Atlantic striped dolphins. Month, year, and area

covered during each abundance survey, and resulting abundance estimate (Nbest) and coefficient of variation

(CV).

Month/Year Area Nbest CV

Jul-Sep 1995 Virginia to Gulf of St. Lawrence 31,669 0.73

Jul-Sep 1998 Maryland to Gulf of St. Lawrence 39,720 0.45

Jul-Aug 1998 Florida to Maryland 21,826 0.78

Jul-Sep 1998 Florida to Gulf of St. Lawrence

(combined) 61,546 0.40

Minimum Population Estimate

The minimum population estimate is the lower limit of the two-tailed 60% confidence interval of the lognormally distributed best abundance estimate. This is equivalent to the 20th percentile of the log-normal distribution

as specified by Wade and Angliss (1997). The best estimate of abundance for striped dolphins is 61,546

(CV=0.40). The minimum population estimate for the western North Atlantic striped dolphin is 44,500 (CV=0.40).

Current Population Trend

There are insufficient data to determine the population trends for this species. 

CURRENT AND MAXIMUM NET PRODUCTIVITY RATES

Current and maximum net productivity rates are unknown for this stock. For purposes of this assessment,

the maximum net productivity rate was assumed to be 0.04. This value is based on theoretical modeling showing

that cetacean populations may not grow at rates much greater than 4% given the constraints of their reproductive life

history (Barlow 1995). 
204

POTENTIAL BIOLOGICAL REMOVAL

Potential Biological Removal (PBR) is the product of minimum population size, one-half the maximum

productivity rate, and a “recovery” factor (MMPA Sec. 3. 16 U.S.C. 1362; Wade and Angliss 1997). The minimum

population size is 44,500 (CV=0.40). The maximum productivity rate is 0.04, the default value for cetaceans. The

“recovery” factor, which accounts for endangered, depleted, threatened stocks, or stocks of unknown status relative

to optimum sustainable population (OSP) is 0.5 because this stock is of unknown status. PBR for the western North

Atlantic striped dolphin is 445.

ANNUAL HUMAN-CAUSED MORTALITY AND SERIOUS INJURY

 Total annual estimated average fishery-related mortality to this stock during 1994-1998 was 7.3 striped

dolphins; CV=0.08)Table 2). 

Fishery Information

USA

No mortalities were observed in 1977-1991 foreign fishing activities off the northeast USA coast. Nineteen

mortalities were documented between 1989 and 1993 (see below) in the pelagic drift gillnet fishery, and two

mortalities were documented in 1991 in the North Atlantic bottom trawl fishery.

 Data on current incidental takes in USA fisheries are available from several sources. In 1986, NMFS

established a mandatory self-reported fishery information system for large pelagic fisheries. Data files are

maintained at the Southeast Fisheries Science Center (SEFSC). The Northeast Fisheries Science Center (NEFSC)

Sea Sampling Observer Program was initiated in 1989 and since that year several fisheries have been covered by the

program. In late 1992 and in 1993, the SEFSC provided observer coverage of pelagic longline vessels fishing off the

Grand Banks (Tail of the Banks) and provides observer coverage of vessels fishing south of Cape Hatteras.

Bycatch has been observed by NMFS Sea Samplers in the pelagic drift gillnet and North Atlantic bottom

trawl fisheries but no mortalities or serious injuries have been documented in the pelagic longline fisheries, pelagic

pair trawl, Northeast multispecies sink gillnet, and mid-Atlantic coastal sink gillnet fisheries.

Pelagic Drift Gillnet

The estimated total number of hauls in the pelagic drift net fishery increased from 714 in 1989 to 1144 in

1990; thereafter, with the introduction of quotas, effort was severely reduced. The estimated number of hauls in

1991, 1992, 1993, 1994, 1995, 1996, and 1998 were 233, 243, 232, 197, 164, 149, and 113 respectively. In 1996

and 1997, NMFS issued management regulations which prohibited the operation of this fishery in 1997. Further, in

January 1999 NMFS issued a Final Rule to prohibit the use of driftnets (i.e., permanent closure) in the North

Atlantic swordfish fishery (50 CFR Part 630). Fifty-nine vessels participated in this fishery between 1989 and 1993. 

Since 1994, between 10 and 13 vessels have participated in the fishery . Observer coverage, percent of sets

observed, was 8% in 1989, 6% in 1990, 20% in 1991, 40% in 1992, 42% in 1993, 87% in 1994, 99% in 1995, 64%

in 1996, NA in 1997, and 99% in 1998. The greatest concentrations of effort were located along the southern edge of

Georges Bank and off Cape Hatteras. Examination of the species composition of the catch and locations of the

fishery throughout the year, suggested that the pelagic drift gillnet fishery be stratified into two strata, a southern or

winter stratum, and a northern or summer stratum. Estimates of total bycatch, for each year from 1989 to 1993, were

obtained using the aggregated (pooled 1989-1993) catch rates, by strata, assuming the 1990 injury was a mortality 

(Northridge 1996). Estimates of total annual bycatch for 1994 and 1995 were estimated from the sum of the

observed caught and the product of the average bycatch per haul and the number of unobserved hauls as recorded in

self-reported fishery information. Variances were estimated using bootstrap re-sampling techniques. Forty striped

dolphin mortalities were observed in this fishery between 1989 and 1998 and occurred east of Cape Hatteras in

January and February, and along the southern margin of Georges Bank in summer and autumn. Estimated annual

mortality and serious injury (CV in parentheses) attributable to this fishery was 39 striped dolphins in 1989 (0.31),

57 in 1990 (0.33), 11 in 1991 (0.28), 7.7 in 1992 (0.31), 21 in 1993 (0.11), 13 in 1994 (0.06), 2 in 1995 (0), 7 in

1996 (CV=0.22), NA in 1997, and 4 in 1998 (CV=0). The 1994-1998 average annual mortality and serious injury

to striped dolphins in the pelagic drift gillnet fishery was 7.25 (CV=0.08) (Table 2). 

North Atlantic Bottom Trawl

Vessels in the North Atlantic bottom trawl fishery, a Category III fishery under the MMPA, were observed

in order to meet fishery management needs, rather than marine mammal management needs. An average of 970 

vessels (full and part time) participated annually in the fishery during 1989-1995. The fishery is active in New
205

England waters in all seasons. The only reported fishery-related mortalities (two) occurred in 1991. Total estimated

mortality and serious injury attributable to this fishery in 1991 was 181 (CV=0.97); average annual mortality and

serious injury during 1994-1998 was zero.

 Total estimated average annual fishery-related mortality and serious injury to this stock in the Atlantic

during 1994-1998 was 7.3 (CV=0.08) (Table 2). 

CANADA

No mortalities were documented in review of Canadian gillnet and trap fisheries (Read 1994). However, in a recent

review of striped dolphins in Atlantic Canada two records of incidental mortality have been reported (Baird et al.

1997) In the late 1960's and early 1970's two mortalities each, were reported in trawl and salmon net fisheries. 

Between January 1993 and December 1994, 36 Spanish deep-water trawlers, covering 74 fishing trips

(4,726 fishing days and 14,211sets), were observed in NAFO Fishing Area 3 (off the Grand Bank) (Lens 1997). A

total of 47 incidental catches were recorded, which included two striped dolphins. The incidental mortality rate for

striped dolphins was 0.014/set.

Table 2. Summary of the incidental mortality of striped dolphins (Stenella coeruleoalba) by commercial fishery

including the years sampled (Years), the number of vessels active within the fishery (Vessels), the type of

data used (Data Type), the annual observer coverage (Observer Coverage), the mortalities recorded by onboard observers (Observed Mortality), the estimated annual mortality (Estimated Mortality), the estimated

CV of the annual mortality (Estimated CVs) and the mean annual mortality (CV in parentheses).

Fishery Years Number

Vessel

Data

Type1

Range of

Observer

Coverage2

Observed

Serious

Injury

Observed

Mortality

Estimated

Mortality

CVs Mean

Annual

Mortality

Pelagic

Drift

Gillnet

94-98 1994=12

1995=11

1996=10

1998=13

Obs

Data

Logbook

 .87, .99,

.64, NA,

.99

0, 0, 0, 0,

0

12, 2, 7,

NA, 4

 13, 2.03

,

10, NA, 4

 .06, 0,

.22, NA,

0

 7.3

 (0.08)

TOTAL 7.3

 (0.08)

1 Observer data (Obs. Data) are used to measure bycatch rates, and the data are collected within the Northeast Fisheries

Science Center (NEFSC) Sea Sampling Program. Mandatory logbook (Logbook) data are used to measure total effort

for the pelagic drift gillnet and longline fishery, and these data are collected at the Southeast Fisheries Science Center

(SEFSC). 2 Observer coverage for the pelagic drift gillnet and bottom trawl fishery are in terms of sets.

3

 One vessel was not observed and recorded 1 set in a 10 day trip (in the logbook). If you assume 1 set, the point

estimate would increase by 0.01 animals.

Other Mortality

From 1995- 1998, seven striped dolphins were stranded between Massachusetts and Florida (NMFS

unpublished data).

In eastern Canada, ten strandings were reported off eastern Canada from 1926-1971, and nineteen from

1991-1996 (Sergeant et al. 1970; Baird et al. 1997; Lucas and Hooker 1997). In both time periods, most of the

strandings were on Sable Island, Nova Scotia.

STATUS OF STOCK

The status of striped dolphins, relative to OSP, in the USA Atlantic EEZ is unknown. The species is not

listed as threatened or endangered under the Endangered Species Act. There are insufficient data to determine the

population trends for this species. The total fishery-related mortality and serious injury for this stock is less than 10%

of the calculated PBR, therefore can be considered to be insignificant and approaching zero mortality and serious

injury rate. Average annual fishery-related mortality and serious injury does not exceed the PBR; therefore, this is

not a strategic stock. 
206

REFERENCES

Anon. 1991. Northeast cetacean aerial survey and interplatform study. NOAA, NMFS, NEFSC & SEFSC, 4 pp.

Available from NEFSC, Woods Hole Laboratory, Woods Hole, MA.

Archer, F. I., II and W. F. Perrin. 1997. Species account of striped dolphins (Stenella coeruleoalba). Paper

SC/49/SM27 presented to the IWC Scientific Committee, September 1997. 27 pp.

Baird, R.W., S. K. Hooker, H. Whitehead, and R. Etcheberry. 1997. A Review of records of striped dolphins

(Stenella coeruleoalba) from Canadian waters. IWC Doc. SC/49/SM4, 10 pp. 

Barlow, J., S. L. Swartz, T. C. Eagle, and P. R. Wade. 1995. U.S. Marine Mammal Stock Assessments: Guidelines

for Preparation, Background, and a Summary of the 1995 Assessments. U.S. Dep. Commer., NOAA Tech.

Memo. NMFS-OPR-6, 73 pp.

Buckland, S. T., D. R. Andersen, K. P. Burnham, and J. L. Laake. 1993. Distance sampling: Estimating abundance

of biological populations. Chapman and Hall, New York, 446 pp. 

CETAP. 1982. A characterization of marine mammals and turtles in the mid- and north Atlantic areas of the U.S.

outer continental shelf. Cetacean and Turtle Assessment Program, University of Rhode Island. Final

Report, Contract AA51-C78-48, Bureau of Land Management, Washington, DC, 538 pp. 

Cramer, J. 1994. Large pelagic logbook newsletter - 1993. NOAA Tech. Mem. NMFS-SEFSC-352, 19 pp.

Gowans, S. and H. Whitehead. 1995. Distribution and habitat partitioning by small odontocetes in the Gully, a

submarine canyon on the Scotian Shelf. Can. J. Zool. 73:1599-1608.

Laake, J. L., S. T. Buckland, D. R. Anderson and K. P. Burnham. 1993. DISTANCE user’s guide, V2.0. Colorado

Cooperative Fish & Wildlife Research Unit, Colorado State University, Ft. Collins, Colorado, 72 pp. 

Leatherwood, S., D. K. Caldwell and H. E. Winn. 1976. Whales, dolphins, and porpoises of the western North

Atlantic. A guide to their identification. U.S. Dept. of Commerce, NOAA Tech. Rep. NMFS Circ. 396, 176

pp. 

Lens, S. 1997. Interactions between marine mammals and deep water trawlers in the NAFO regulatory area. ICES

CM 1997/Q:8. 10 pp.

Lucas, A. N. and S. K. Hooker. 1997. Cetacean strandings on Sable Island, Nova Scotia, 1990-1996. Paper

SC/49/06 presented to the IWC Scientific Committee, September 1997. 10 pp.

Mullin, K. D. (in review). Abundance and distribution of cetaceans in the southern U.S. Atlantic Ocean during

summer 1998. Fish. Bull., U.S.

Northridge, S. 1996. Estimation of cetacean mortality in the U.S. Atlantic swordfish and tuna drift gillnet and pair

trawl fisheries. Final report to the Northeast Fisheries Science Center, Contract No. 40ENNF500160. 

Palka, D. 1995. Abundance estimate of the Gulf of Maine harbor porpoise. Rep. int. Whal. Commn. Special Issue

16:27-50.

Palka, D. 1996. Update on abundance of Gulf of Maine/Bay of Fundy harbor porpoises. NOAA/NMFS/NEFSC.

Ref. Doc. 96-04; 37p. Available from: National Marine Fisheries Service, 166 Water Street, Woods Hole,

MA 02543-1026.

Palka, D.L. 1997. A review of striped dolphins (Stenella coeruleoalba) in U.S. Atlantic waters. IWC Doc.

SC/49/SM26, 13 pp.

Palka, D., G. Waring and D. Potter. (in review). Abundances of cetaceans and sea turtles in the northwest Atlantic

during summer 1995 and 1998. Fish. Bull., U.S.

Perrin, W. F., C. E. Wilson and F. I. Archer II. 1994. Pages 129-159 in: S. H. Ridgway and R. Harrison (eds.),

Handbook of marine mammals, Volume 5: The first book of dolphins, Academic Press, San Diego. 

Read, A. J. 1994. Interactions between cetaceans and gillnet and trap fisheries in the northwest Atlantic. Rep. int.

Whal. Commn. Special Issue 15: 133-147. 

Sergeant, D.E., A.W. Mansfield and B. Beck. 1970. Inshore records of cetacea for eastern Canada, 1949-68. J.

Fish. Res. Brd. of Can. 27: 1903-1915.

Schmidly, D. J. 1981. Marine mammals of the southeastern United States coast and the Gulf of Mexico. Pub. No.

FWS/OBS-80/41, U.S. Fish and Wildlife Service, Office of Biological Services, Washington, DC, 163 pp. 

Wade, P. R. and R. P. Angliss. 1997. Guidelines for assessing marine mammal stocks: Report of the GAMMS

Workshop April 3-5, 1996, Seattle, Washington. U.S. Dep. Commer., NOAA Tech. Memo. NMFS-OPR12, 93 pp.

Waring, G. T., C. P. Fairfield, C. M. Ruhsam and M. Sano. 1992. Cetaceans associated with Gulf Stream features

off the northeastern USA shelf. ICES Marine Mammals Comm. CM 1992/N:12, 29 pp.
207

Waring, G. T. 1998. Results of the summer 1991 R/V Chapman marine mammal sighting survey. NOAA NMFS

NEFSC, Lab. Ref. Doc. No. 98-09, 21 pp. Northeast Fisheries Science Center, Woods Hole, Massachusetts.
208

December 1998

SPINNER DOLPHIN (Stenella longirostris):

Western North Atlantic Stock

STOCK DEFINITION AND GEOGRAPHIC RANGE

Spinner dolphins are distributed in oceanic and coastal tropical waters (Leatherwood et al. 1976). This is

presumably an offshore, deep-water species (Schmidly 1981; Perrin and Gilpatrick 1994), and its distribution in the

Atlantic is very poorly known. In the western North Atlantic, these dolphins occur in deep water along most of the

U.S. coast south to the West Indies and Venezuela, including the Gulf of Mexico. Spinner dolphin sightings have

occurred exclusively in deeper (>2,000 m) oceanic waters (CETAP 1982; Waring et al. 1992) off the northeast U.S.

coast. Stranding records exist from North Carolina, South Carolina, and Florida in the Atlantic and in Texas and

Florida in the Gulf of Mexico. The North Carolina strandings represent the northernmost documented distribution of

this species in the Atlantic. Stock structure in the western North Atlantic is unknown. 

POPULATION SIZE

The number of spinner dolphins inhabiting the U.S. Atlantic Exclusive Economic Zone (EEZ) is unknown

and seasonal abundance estimates are not available for this species since it was rarely seen in any of the surveys. 

Minimum Population Estimate

Present data are insufficient to calculate a minimum population estimate. 

Current Population Trend

There are insufficient data to determine the population trends for this species. 

CURRENT AND MAXIMUM NET PRODUCTIVITY RATES

Current and maximum net productivity rates are unknown for this stock. For purposes of this assessment,

the maximum net productivity rate was assumed to be 0.04. This value is based on theoretical modeling showing

that cetacean populations may not grow at rates much greater than 4% given the constraints of their reproductive life

history (Barlow et al. 1995). 

POTENTIAL BIOLOGICAL REMOVAL

Potential Biological Removal (PBR) is the product of minimum population size, one-half the maximum

productivity rate, and a “recovery” factor (MMPA Sec. 3. 16 U.S.C. 1362; Wade and Angliss 1997). The minimum

population size is unknown. The maximum productivity rate is 0.04, the default value for cetaceans. The

“recovery” factor, which accounts for endangered, depleted, threatened stocks, or stocks of unknown status relative

to optimum sustainable population (OSP) is assumed to be 0.5 because this stock is of unknown status. PBR for the

western North Atlantic spinner dolphin is unknown because the minimum population size is unknown.

ANNUAL HUMAN-CAUSED MORTALITY AND SERIOUS INJURY

Total average annual estimated average fishery-related mortality and serious injury to this stock in the

Atlantic during 1992-1996 was 0.38 spinner dolphin (CV = 0.35).

Fishery Information

 There was no documentation of spinner dolphin mortality or serious injury in distant-water fleet (DWF)

activities off the northeast U.S. coast (Waring et al.. 1990). No takes were documented in a review of Canadian

gillnet and trap fisheries (Read 1994). 

Data on current incidental takes in U.S. fisheries are available from several sources. In 1986, NMFS

established a mandatory self-reported Fishery information system for large pelagic fisheries. Data files are

maintained at the Southeast Fisheries Science Center (SEFSC). The Northeast Fisheries Science Center (NEFSC)

Sea Sampling Observer Program was initiated in 1989 and since that year several fisheries have been covered by the
209

program. In late 1992 and in 1993, the SEFSC provided observer coverage of pelagic longline vessels fishing off the

Grand Banks (Tail of the Banks) and provides observer coverage of vessels fishing south of Cape Hatteras.

By-catch has been observed by NMFS Sea Samplers in the pelagic drift gillnet fishery, but no mortalities or

serious injuries have been documented in the pelagic longline, pelagic pair trawl, Northeast multispecies sink gillnet,

mid-Atlantic coastal gillnet, and North Atlantic bottom trawl fisheries.

The estimated total number of hauls in the pelagic drift gillnet fishery increased from 714 in 1989 to 1,144

in 1990; thereafter, with the introduction of quotas, effort was severely reduced. The estimated number of hauls in

1991, 1992, 1993, 1994, 1995, and 1996 were 233, 243, 232, 197, 164, and 149 respectively. Fifty-nine different

vessels participated in this fishery at one time or another between 1989 and 1993. Since 1994, between 10-12

vessels have participated in the fishery (Table 2). Observer coverage, expressed as percent of sets observed, was 8%

in 1989, 6% in 1990, 20% in 1991, 40% in 1992, 42% in 1993, 87% in 1994, 99% in 1995, and 64% in 1996. Effort

was concentrated along the southern edge of Georges Bank and off Cape Hatteras. Examination of the species

composition of the catch and locations of the fishery throughout the year, suggested that the pelagic drift gillnet

fishery be stratified into two strata, a southern or winter stratum, and a northern or summer stratum. Estimates of the

total by-catch, from 1989 to 1993, were obtained using the aggregated (pooled 1989-1993) catch rates, by strata

(Northridge 1996). Estimates of total annual by-catch for 1994 and 1995 were estimated from the sum of the

observed caught and the product of the average bycatch per haul and the number of unobserved hauls as recorded in

self-reported Fishery information. Variances were estimated using bootstrap re-sampling techniques. One spinner

dolphin mortality was observed between 1989 and 1993 and occurred east of Cape Hatteras in March 1993. 

Estimated annual fishery-related mortality and serious injury attributable to this fishery (CV in parentheses) was 0.7

in 1989 (1. 00), 1.7 in 1990 (1.00), 0.7 in 1991 (1.00), 1.4 in 1992 (0.31), 0.5 in 1993 (1.00), and zero from 1994-

1996. Total average annual estimated average fishery-related mortality and serious injury to this stock in the

Atlantic during 1992-1996 was 0.38 spinner dolphin (CV = 0.35) (Table 1). The 1992-1996 period provides a better

characterization of this fishery (i.e., fewer vessels and increased observer coverage).

Table 1. Summary of the incidental mortality of spinner dolphins (Stenella longirostris) by commercial fishery

including the years sampled (Years), the number of vessels active within the fishery (Vessels), the type of

data used (Data Type), the annual observer coverage (Observer Coverage), the mortalities recorded by onboard observers (Observed Mortality), the estimated annual mortality (Estimated Mortality), the estimated

CV of the annual mortality (Estimated CVs) and the mean annual mortality (CV in parentheses).

Fishery Years Vessels 1 Data Type 2 Observer

Coverage 3 

Observed

Mortality

Estimated

Mortality 4

Estimated

CVs 4

Mean

Annual

Mortality

Pelagic

Drift Gillnet

 92-96 1994=12

1995=11

1996=10

Obs. Data

Logbook

.40, .42,

.87, .99,

.64

1, 0, 0, 0, 0 1.4, 0.5, 0,

05

, 0

 

.31, 1.0, 0,

0, 0

0.31

 (.35)

TOTAL 0.31

(.35)

1

 1994 and 1995 - 1996 shown, other years not available on an annual basis. 2

 Observer data (Obs. Data) are used to measure bycatch rates, and the data are collected within the Northeast

Fisheries Science Center (NEFSC) Sea Sampling Program. Mandatory logbook (Logbook) data are used to

measure total effort, and the data are collected at the Southeast Fisheries Science Center (SEFSC). 3

 The observer coverage and unit of effort for the Pelagic Drift Gillnet is a set. 4

 For 1991-1993, pooled bycatch rates were used to estimate bycatch in months that had fishing effort but did

not have observer coverage. This method is described in Northridge (1996). In 1994 and 1995, observer

coverage increased substantially, and bycatch rates were not pooled for this period. 5

 One vessel was not observed and recorded 1 set in a 10 day trip in the SEFSC mandatory logbook. If you

assume the vessel fished 1.4 sets per day as estimated from the 1995 SS data, the point estimate may

increase by 0.8 animals. However, the SEFSC mandatory logbook data was taken at face value, and

therefore it was assumed that 1 set was fished within this trip, and the point estimate would then increase by

0.1 animals.
210

STATUS OF STOCK

The status of spinner dolphins relative to OSP in the U.S. Atlantic EEZ is unknown. The species is not

listed as threatened or endangered under the Endangered Species Act. There are insufficient data to determine the

population trends for this species. PBR cannot be calculated for this stock, but no fishery-related mortality and

serious injury has been observed since 1992; therefore, total fishery-related mortality and serious injury can be

considered insignificant and approaching zero mortality and serious injury rate. Population size and PBR cannot be

estimated, but fishery-related mortality is very low; therefore, this stock is not a strategic stock. 

REFERENCES

Barlow, J., S.L. Swartz, T.C. Eagle, and P.R. Wade. 1995. U.S. Marine Mammal Stock Assessments: Guidelines for

Preparation, Background, and a Summary of the 1995 Assessments. U.S. Dep. Commer., NOAA Tech.

Memo. NMFS-OPR-6, 73 pp.

CETAP. 1982. A characterization of marine mammals and turtles in the mid- and north Atlantic areas of the U.S.

outer continental shelf. Cetacean and Turtle Assessment Program, University of Rhode Island. Final 

Report, Contract AA51-C78-48, Bureau of Land Management, Washington, DC, 538 pp. 

Leatherwood, S., D.K. Caldwell, and H.E. Winn. 1976. Whales, dolphins, and porpoises of the western North

Atlantic. A guide to their identification. U.S. Dept. of Commerce, NOAA Tech. Rep. NMFS Circ. 396, 176

pp.

Northridge, S. 1996. Estimation of cetacean mortality in the U.S. Atlantic swordfish and tuna drift gillnet and pair

trawl fisheries. Final report to the Northeast Fisheries Science Center, Contract No. 40ENNF500045, 18

pp. 

Perrin, W. F. and J. W. Gilpatrick, Jr. 1994. Spinner dolphin. Pages 99-128 in: S. H. Ridgway and R. Harrison

(eds), Handbook of marine mammals, Volume 5: The first book of dolphins. Academic Press, San Diego,

418 pp. 

Read, A. J. 1994. Interactions between cetaceans and gillnet and trap fisheries in the northwest Atlantic. Rep. int.

Whal. Commn. Special Issue 15: 133-147. 

Reilly, S. B. and J. Barlow. 1986. Rates of increase in dolphin population size. Fish. Bull., U.S. 84(3): 527-533.

Schmidly, D. J. 1981. Marine mammals of the southeastern United States coast and the Gulf of Mexico. Pub. No.

FWS/OBS-80/41, U.S. Fish and Wildlife Service, Office of Biological Services, Washington, DC, 163 pp. 

Wade, P.R., and R.P. Angliss. 1997. Guidelines for assessing marine mammal stocks: Report of the GAMMS

Workshop April 3-5, 1996, Seattle, Washington. U.S. Dep. Commer., NOAA Tech. Memo. NMFS-OPR12, 93 pp.

Waring, G. T., C. P. Fairfield, C. M. Ruhsam and M. Sano. 1992. Cetaceans associated with Gulf Stream features

off the northeastern USA shelf. ICES Marine Mammals Comm. CM 1992/N:12, 29 pp. 
211

December 1998

HOODED SEAL (Cystophora cristata):

Western North Atlantic Stock

STOCK DEFINITION AND GEOGRAPHIC RANGE

The hooded seal occurs throughout much of the North Atlantic and Arctic Oceans (King 1983) preferring

deeper water and occurring farther offshore than harp seals (Lavigne and Kovacs 1988; Stenson et al.. 1996). 

Hooded seals tend to wander far out of their range and have been seen as far south as Puerto Rico, with increased

occurrences from Maine to Florida. These appearances usually occur between January and May. Although it is not

known which stock these seals come from, it is known that during this time frame, the Northwest Atlantic stock of

hooded seals are at their southern most point of migration in the Gulf of St. Lawrence. The worlds' hooded seal

population is divided into three separate stocks, each identified with a specific breeding site (Lavigne and Kovacs

1988). In the northwest Atlantic, whelping occurs in the Davis Strait, off Newfoundland and in Gulf of St. Lawrence

(Stenson et al.. 1996). One stock, which whelps off the coast of eastern Canada, is divided into two breeding herds

(Front and Gulf) which breed on the pack ice. The Front herd (largest) breeds off the coast of Newfoundland and

Labrador and the Gulf herd breeds in the Gulf of St. Lawrence. The second stock breeds in the Davis Strait, and the

third stock occurs on the West Ice off eastern Greenland.

Hooded seals are a highly migratory species. Hooded seals remain on the Newfoundland continental shelf

during winter/spring (Stenson et al.. 1996). Breeding occurs at about the same time in March for each stock. Adults

from all stocks then assemble in the Denmark Strait to molt between late June and August (King 1983; Anon 1995),

and following this, the seals disperse widely. Some move south and west around the southern tip of Greenland, and

then north along the west coast of Greenland. Others move to the east and north between Greenland and Svalbard

during late summer and early fall (Lavigne and Kovacs 1988). Little else is known about the activities of hooded

seals during the rest of the year until they assemble again in February for breeding. 

Hooded seals are rarely found in the U.S. Atlantic Exclusive Economic Zone. Small numbers of hooded

seals at the extreme southern limit of their range occur in the winter and spring seasons. The influx of harp seals and

geographic distribution in New England to mid-Atlantic waters is based on stranding data. 

POPULATION SIZE

The number of hooded seals in the western North Atlantic is unknown. Seasonal abundance estimates are

available based on a variety of analytical methods based on commercial catch data, and including aerial surveys. 

These methods often include surveying the whelping concentrations and modeling the pup production. Several

estimates of pup production at the Front are available. Hooded seal pup production between 1966 and 1977 was

estimated between 25,000 - 32,000 annually (Benjaminsen and Oritsland 1975; Sergeant 1976; Lett 1977; Winters

and Bergflodt 1978; Stenson et al.. 1996). Estimated pup production dropped to 26,000 hooded seal pups in 1978

(Winters and Bergflodt 1978). Pup production estimates began to increase after 1978, reaching 62,000 (95% CI.

43,700 - 89,400) by 1984 (Bowen et al.. 1987). Bowen et al.. (1987) also estimated pup production in the Davis

Strait at 18,600 (95% C.I. 14,000 - 23,000). A 1985 survey at the Front (Hay et al. 1985) produced a estimate of

61,400 (95% C.I. 16,500 - 119,450). Hammill et al. (1992) estimated pup production to be 82,000 (SE=12,636) in

1990. No recent population estimate is available, but assuming a ratio of pups to total population of 1:5, pup

production in the Gulf and Front herds would represent a total population of approximately 400,000-450,000 hooded

seals (Stenson 1993). Based on the 1990 survey, Stenson et al.. (1996) suggests that pup production may have

increased at about 5% per year since 1984. However, because of exchange between the Front and the Davis Strait

stocks, the possibility of a stable or slightly declining level of pup production are also likely (Stenson 1993; Stenson

et al.. 1996). It appears that the number of hooded seals is increasing.
212

Table 1. Summary of pup production estimates for western North Atlantic hooded seals. Year and area covered

during each abundance survey, and resulting abundance estimate (Nmin) and coefficient of variation (CV). 

Month/Year Area Nmin CV

1978 Front herd: Newfoundland/ Labrador 26,000 None reported

1984 Front herd: Newfoundland/Labrador 62,000 None reported

1984 Davis Strait 18,600 None reported

1985 Front herd: Newfoundland/Labrador 61,400 None reported

1990 Front herd: Newfound/Labrador 82,100 None reported

Minimum population estimate

Present data are insufficient to calculate the minimum population estimate for U.S. waters. It is estimated

that there are approximately 400,000 hooded seals (5:1 ratio of adults to pups) in Canadian waters (Stenson et al..

1993). 

Current population trend

The population appears to be increasing in U.S. Atlantic EEZ, judging from stranding records, although the

actual magnitude of this increase is unknown. The Canadian population appears to be increasing but, because

different methods have been used over time to estimate population size, the magnitude of this increase has not been

quantified. 

CURRENT AND MAXIMUM NET PRODUCTIVITY RATES

Current and maximum net productivity rates are unknown for this stock. The most appropriate data are

based on Canadian studies. Pup production in Canada may be increasing slowly (5% per annum), but due to the

wide confidence intervals and lack of understanding regarding stock dynamics, it is possible that pup production is

stable or declining (Stenson 1993). 

For purposes of this assessment, the maximum net productivity rate was assumed to be 0.12. This value is

based on theoretical modeling showing that pinniped populations may not grow at rates much greater than 12%

given the constraints of their reproductive life history (Barlow et al. 1995). 

POTENTIAL BIOLOGICAL REMOVAL

Potential Biological Removal (PBR) is the product of minimum population size, one-half the maximum

productivity rate, and a “recovery” factor (MMPA Sec. 3. 16 U.S.C. 1362; Wade and Angliss 1997). The minimum

population size is unknown. The maximum productivity rate is 0.12, the default value for pinnipeds. The recover

factor (FR ) for this stock is 1.0, the value for stocks with unknown population status, but know to be increasing. 

PBR for the western North Atlantic hooded seal in U.S. waters is unknown. Applying the formula to abundance

estimates (400,000) in Canadian waters results in a PBR= 24,000 hooded seals. 

ANNUAL HUMAN-CAUSED MORTALITY AND SERIOUS INJURY

In Atlantic Canada, hooded seals have been commercially hunted at the Front since the late 1800's. In 1974

total allowable catch (TAC) was set at 15,000, and reduced to 12,000 in 1983 and to 2,340 in 1984 (Stenson 1993;

Anon 1998). From 1991- 1992 the TAC was increased to 15,000. A TAC of 8,000 was set for 1993, and held at

that level through 1997. From 1974 through 1982, the average catch was 12,800 animals, mainly pups. Since 1983

catches ranged from 33 in 1986 to 6,425 in 1991, with a mean catch of 1,001 between 1983 and 1995. In 1996

catches (25,754) were more than three times the allowable quota (Anon 1998). The high catch was attributable to

good ice conditions and strong market demand. Catches in 1997 were 7,058, slightly below the TAC.

 Hunting in the Gulf of St. Lawrence (below 500

N) has been prohibited since 1964. No commercial hunting

of hooded seals is permitted in the Davis Strait. 
213

 Total annual estimated average fishery-related mortality or serious injury to this stock in U.S. waters

during 1992-1996 was 5.6 hooded seals (CV = 0.96; Table 2). 

Fishery Information

USA

Data on current incidental takes in U.S. fisheries are available from several sources. In 1986, NMFS

established a mandatory self-reported fishery information system for large pelagic fisheries. Data files are

maintained at the Southeast Fisheries Science Center (SEFSC). The Northeast Fisheries Science Center (NEFSC)

Sea Sampling Observer Program was initiated in 1989, and since that year several fisheries have been covered by the

program. In late 1992 and in 1993, the SEFSC provided observer coverage of pelagic longline vessels fishing off the

Grand Banks (Tail of the Banks) and provides observer coverage of vessels fishing south of Cape Hatteras. 

Recent by-catch has been observed by NMFS Sea Samplers in the New England multispecies sink gillnet

fisheries, but no mortalities have been documented in the mid-Atlantic coastal gillnet, Atlantic drift gillnet, pelagic

pair trawl or pelagic longline fisheries. 

In 1993, there were approximately 349 full and part-time vessels in the New England multispecies sink

gillnet fishery, which covered the Gulf of Maine and southern New England (Table 2). An additional 187 vessels

were reported to occasionally fish in the Gulf of Maine with gillnets for bait or personal use; however, these vessels

were not covered by the observer program (Walden 1996) and their fishing effort was not used in estimating

mortality. Observer coverage in terms of trips has been 1%, 6%, 7%, 5%, 7%, 5%, and 4% for 1990 to 1996,

respectively. The fishery has been observed in the Gulf of Maine and in Southern New England. There was one

hooded seal mortality observed in the New England multispecies sink gillnet fishery between 1990 and 1996. 

Annual estimates of hooded seal by-catch in the New England multispecies sink gillnet fishery reflect seasonal

distribution of the species and of fishing effort. Estimated annual mortalities (CV in parentheses) from this fishery

during 1990-1996 was zero (1990-1994), and 28 in 1995 (0.96), and zero in 1996. The 1995 by-catch includes five

animals from the estimated number of unknown seals (based on observed mortalities of seals that could not be

identified to species). The unknown seals were prorated, based on spatial/temporal patterns of by-catch of harbor

seals, gray seals, harp seals, and hooded seals. Average annual estimated fishery-related mortality and serious injury

to this stock attributable to this fishery during 1992-1996 was 5.6 hooded seals (CV = 0.96). The stratification

design used is the same as that for harbor porpoise (Bravington and Bisack 1996). The by-catch occurred only in

winter (January-May) and was in waters between Cape Ann and New Hampshire.

CANADA

An unknown number of hooded seals have been taken in Newfoundland and Labrador groundfish gillnets

(Read 1994).

There were 3,121 cod traps operating in Newfoundland and Labrador during 1979, and about 7,500 in 1980

(Read 1994). This fishery was closed at the end of 1993 due to collapse of Canadian groundfish resources. 

Hooded seals are being taken in Canadian lumpfish and groundfish gillnets and trawls; however, estimates

of total removals have not been calculated to date. 
214

Table 2. Summary of the incidental mortality of hooded seal (Cystophora cristata) by commercial fishery including

the years sampled (Years), the number of vessels active within the fishery (Vessels), the type of data used

(Data Type), the annual observer coverage (Observer Coverage), the mortalities recorded by on-board

observers (Observed Mortality), the estimated annual mortality (Estimated Mortality), the estimated CV of

the annual mortality (Estimated CVs) and the mean annual mortality (CV in parentheses).

Fishery Years Vessels Data Type 1 Observer

Coverage 2

Observed

Mortality

Estimated

Mortality 

Estimated

CVs 

Mean

Annual

Mortality

New England

Multispecies

Sink Gillnet

92-96 349 Obs. Data

Weighout,

Logbooks

 .07, .05,

.07, .05,

.04

 0, 0, 0, 1,

0

 0, 0, 0, 28, 0 0, 0, 0,

.96, 0

5.6

(.96)

TOTAL 5.6

(.96)

1 Observer data (Obs. Data) are used to measure by-catch rates, and the data are collected within the

Northeast Fisheries Science Center (NEFSC) Sea Sampling Program. NEFSC collects Weighout

(Weighout) landings data, and total landings are used as a measure of total effort for the sink gillnet fishery. 

Mandatory logbook (Logbook) data are used to determine the spatial distribution of some fishing effort in

the New England multispecies sink gillnet fishery. 2 The observer coverage for the New England multispecies sink gillnet fishery is measured in trips.

Other Mortality

 In 1988-93, strandings were less than 20 per year, and from 1994-1996 they increased to about 50 per

annum (Rubinstein 1994; Rubinstein, pers. comm). Carcasses were recovered from Massachusetts, Connecticut, and

New York (Rubinstein 1994), North Carolina and U.S. Virgin Islands (NMFS, unpubl. data). The increased

number of strandings may indicate a possible shift in distribution or range expansion southward into U.S. waters; if

so, fishery interactions may increase. 

STATUS OF STOCK

The status of hooded seals relative to OSP in U.S. Atlantic EEZ is unknown, but the population appears to

be increasing in Canada. They are not listed as threatened or endangered under the Endangered Species Act. The

total fishery-related mortality and serious injury for this stock is believed to be very low relative to the population

size in Canadian waters and can be considered insignificant and approaching zero mortality and serious injury rate.

This is not a strategic stock because the level of human-caused mortality and serious injury is believed to be very

low relative to overall stock size.

REFERENCES

Anon. 1995. Report of the Joint ICES/NAFO Working Group on Harp and Hooded Seals. 5-9 June 1995,

Dartmouth, Nova Scotia Canada. NAFO SCS Doc. 95/16. Serial No. N2569. 40 pp.

Anon. 1998. Report of the Joint ICES/NAFO Working Group on Harp and Hooded Seals. 28 August - 3 September

1997, Copenhagen, Denmark. ICES CM 1998/Assess:3. 35 pp.

Barlow, J., S.L. Swartz, T.C. Eagle, and P.R. Wade. 1995. U.S. Marine Mammal Stock Assessments: Guidelines for

Preparation, Background, and a Summary of the 1995 Assessments. U.S. Dep. Commer., NOAA Tech.

Memo. NMFS-OPR-6, 73 pp. 

Benjaminsen, T., and T. Oritsland. 1975. The survival of year-classes and estimates of production and sustainable

yield of northwest Atlantic harp seals. Int. Comm. Northwest Atl. Fish. Res. Doc. 75/121.

Bowen, W.D., R.A. Myers and K. Hay. 1987. Abundance estimation of a dispersed, dynamic population: Hooded

seals (Cystophora cristata) in the Northwest Atlantic. Can. J. Fish. Aquat. Sci. 44: 282-295.

Bravington, M. V. and K. D. Bisack. 1996. Estimates of harbor porpoise by-catch in the Gulf of Maine sink gillnet

fishery, 1990-93. Rep. int. Whal. Commn. 46:567-574.
215

Hammill, M. O., G. B. Stenson, and R. A. Myers. 1992. Hooded seal (Cystophora cristata) pup production in the

Gulf of St. Lawrence. Can. J. Fish. Aquat. Sci. 49: 2546-2550.

Hay, K., G. B. Stenson, D. Wakeham, and R. A. Myers. 1985. Estimation of pup production of hooded seals

(Cystophora cristata) at Newfoundland during March 1985. Con. Atl. Fish. Sci. Adv. Comm. 85/96. 

King, J. E. 1983. Seals of the World. Cornell University Press, Ithaca, NY, 240 pp. 

Lavigne, D. M. and K. M. Kovacs. 1988. Harps and Hoods Ice Breeding Seals of the Northwest Atlantic. University

of Waterloo Press, Waterloo, Ontario, Canada, 174 pp. 

Lett, P.F. 1977. A model to determine stock size and management options for the Newfoundland hooded seal stock. 

Can. Atl. Fish. Sci. Adv. Comm. Res. Doc. 77/25.

Read, A. J. 1994. Interactions between cetaceans and gillnet and trap fisheries in the northwest Atlantic. Rep. int.

Whal. Commn. Special Issue 15: 133-147. 

Rubinstein, B. 1994. An apparent shift in distribution of ice seals, Phoca groenlandica, Cystophora cristata, and

Phoca hispida, toward the east coast of the United States. M.A. Thesis, Boston University, Boston, MA, 45

pp. 

Sergeant, D.E. 1976. Research on hooded seals Cystophora cristata Erxleben in 1976. International Commission

for the Northwest Atlantic Fisheries Research Document 76/X/126.

Stenson, G. B. 1993. The status of pinnipeds in the Newfoundland region. NAFO SCR Doc. 93/34. 

Stenson, G.B., R.A. Myers, I-H Ni and W.G. Warren. 1996. Pup production of hooded seals (Cystophora cristata)

in the northwest Atlantic. NAFO Sci. Coun. Studies 26:105-114.

Wade, P.R., and R.P. Angliss. 1997. Guidelines for assessing marine mammal stocks: Report of the GAMMS

Workshop April 3-5, 1996, Seattle, Washington. U.S. Dep. Commer., NOAA Tech. Memo. NMFS-OPR12, 93 pp.

Walden, J. 1996. The New England gillnet effort survey. NOAA, NMFS, NEFSC, Woods Hole, Massachusetts.

NEFSC [Northeast Fisheries Science Center] Ref. Doc. 99-10. 38p.

Winters, G. H. And B. Bergflodt. 1978. Mortality and productivity of the Newfoundland hooded seal stock.

International Commission for the Northwest Atlantic Fisheries Res. Doc. 78/XI/91.
216

Figure 1. Distribution of sperm whale sightings during NOAA Ship Oregon II

marine mammal surveys during 1991-1994. The straight lines show transects

during two ship surveys and are examples of typical ship survey transects.

Isobaths are in 183 m (100 fm) intervals.

July 1995

SPERM WHALE (Physeter macrocephalus):

Northern Gulf of Mexico Stock

STOCK DEFINITION AND GEOGRAPHIC RANGE

Sperm whales are found throughout the world's oceans in deep waters from between about 60° N and 60° S

latitudes (Leatherwood and Reeves 1983; Rice 1989). There has been speculation, based on year round occurrence

of strandings, opportunistic sightings, and whaling catches, that sperm whales in the Gulf of Mexico may constitute

a distinct stock (Schmidly 1981), but there is no information on stock differentiation. Seasonal aerial surveys

confirm that sperm whales are present in the northern Gulf of Mexico in all seasons, but sightings are more common

during the summer months (Mullin et al. 1991; Davis et al., in preparation).

POPULATION SIZE

Estimates of abundance were derived through the application of distance sampling analysis (Buckland et al.

1993) and the computer program DISTANCE (Laake et al. 1993) to sighting data collected during 1991-1994 springsummer, visual sampling, line-transect vessel surveys of the northern Gulf of Mexico (Hansen et al. 1995) (Fig. 1),

which includes data collected as part of the GulfCet program (Davis et al., in preparation). These surveys were

conducted throughout the area from approximately the 200 m isobath along the U.S. coast to the seaward extent of

the U.S. Exclusive Economic Zone. The seasonal GulfCet aerial surveys included only a small portion of the stock

range and these data were not

used for abundance estimation. 

Estimated abundance of sperm

whales by survey year

[coefficient of variation (CV) in

parentheses] was 143 in 1991

(0.58), 931 in 1992 (0.48), 229

in 1993 (0.52), and 771 in 1994

(0.42) (Hansen et al. 1995). 

Survey effort-weighted

estimated average abundance of

sperm whales for all surveys

combined was 530 (CV = 0.31)

(Hansen et al. 1995).

Minimum Population Estimate

The minimum

population estimate is the lower

limit of the two-tailed 60%

confidence interval of the log-normal distributed abundance estimate, which is equivalent to the 20th percentile of

the log-normal distributed abundance estimate as specified by NMFS (Anon. 1994). The minimum population

estimate was calculated from the 1991-1994 average abundance estimate of 530 sperm whales (CV = 0.31) (Hansen

et al. 1995) and is 411 sperm whales. 

Current Population Trend

No trend was discernable in the average annual abundance estimates. All of the log-normal 95%

confidence intervals of the annual estimates overlap, indicating that the estimates were not significantly different at

that level. The variation in abundance estimates may represent inter-annual variation in distribution, rather than a

change in abundance. 
217

CURRENT AND MAXIMUM NET PRODUCTIVITY RATES

Current and maximum net productivity rates are not known for this stock; therefore, the default maximum

net productivity rate of 0.04 (Anon. 1994) was used for purposes of this assessment. 

POTENTIAL BIOLOGICAL REMOVAL

Potential biological removal level (PBR) was specified as the product of the minimum population size, one

half the maximum net productivity rate, and a recovery factor for endangered, threatened, or depleted stocks, or

stocks of unknown status relative to optimum sustainable population (OSP) (Anon. 1994). The recovery factor was

0.10 because sperm whales are an endangered species. The resulting PBR for this stock is 0.8 sperm whales. 

ANNUAL HUMAN-CAUSED MORTALITY AND SERIOUS INJURY

A commercial fishery for sperm whales operated in the Gulf of Mexico during the late 1700's to the early

1900's, but the exact number of whales taken is not known (Townsend 1935). 

The level of current, direct, human-caused mortality and serious injury of sperm whales in the northern Gulf

of Mexico is unknown, but available information indicates there likely is little, if any, fisheries interaction with

sperm whales in the northern Gulf of Mexico. 

There were no documented strandings of sperm whales in the northern Gulf of Mexico during 1987-1994

which were classified as likely caused by fishery interactions or other human-related causes. Stranding data

probably underestimate the extent of fishery-related mortality and serious injury because not all of the marine

mammals which die or are seriously injured may wash ashore, nor will all of those that do wash ashore necessarily

show signs of entanglement or other fishery-interaction. Finally, the level of technical expertise among stranding

network personnel varies widely as does the ability to recognize signs of fishery interaction. 

The total known fishery-related mortality and serious injury for this stock is less than 10% of the calculated

PBR and, therefore, can be considered insignificant and approaching zero mortality and serious injury rate. This

determination cannot be made for specific fisheries until the implementing regulations for Section 118 of the MMPA

have been reviewed by the public and finalized. 

Fisheries Information

Pelagic swordfish, tunas, and billfish are the targets of the longline fishery operating in the U.S. Gulf of

Mexico. Total longline effort for the Gulf of Mexico pelagic fishery, including OCS edge, continental slope, and

Mexican territorial waters, based on mandatory logbook reporting, was 4,400 sets in 1991, 4,850 sets in 1992, and

3,260 sets in 1993 (Cramer 1994). This fishery has been monitored with about 5% observer coverage, in terms of

trips observed, since 1992. There were no reports of mortality or serious injury to sperm whales by this fishery. 

Pair trawl fishing gear has the potential to capture marine mammals, but there have been no reports of

mortality or serious injury to marine mammals in the Gulf of Mexico. This fishery has not been observed by NMFS

observers, and there are no other data available as to the extent of this fishery in the Gulf of Mexico. It is assumed

that it is very limited in scope and duration. 

Other Mortality

A total of nine sperm whale strandings were documented in the northern Gulf of Mexico during 1987-1994. 

One of the whales had deep, parallel cuts posterior to the dorsal ridge that were believed to be caused by the

propeller of a large vessel. This trauma was assumed to be the proximate cause of this stranding. 

 Stranding data probably underestimate the extent of fishery-related mortality and serious injury because

not all of the marine mammals which die or are seriously injured may wash ashore, nor will all of those that do wash

ashore necessarily show signs of entanglement or other fishery-interaction. Finally, the level of technical expertise

among stranding network personnel varies widely as does the ability to recognize signs of fishery interaction.

 

STATUS OF STOCK

Stock size is considered to be low relative to OSP and the species is therefore listed as endangered under

the Endangered Species Act (ESA). There are insufficient data to determine population trends. The total level of

human-caused mortality and serious injury is unknown, but it is believed to be insignificant; however, because this
218

species is listed as endangered and there is presently no recovery plan in place, any fishery-related mortality would

be unlawful. This is a strategic stock because the sperm whale is listed as an endangered species under the ESA.

REFERENCES

Anon. 1994. Report of the PBR (Potential Biological Removal) workshop. June 27-29, 1994. NOAA, NMFS

Southwest Fisheries Science Center, La Jolla, California, 13 pp. + Appendices. 

Buckland, S. T., D. R. Anderson, K. P. Burnham and J. L. Laake. 1993. Distance Sampling: estimating abundance

of biological populations. Chapman & Hall, London, 446 pp. 

Cramer, J. 1994. Large pelagic logbook newsletter - 1993. NOAA Tech. Mem. NMFS-SEFSC-352, 19 pp. 

Davis, R., G. Scott, B. Würsig, W. Evans, G. Fargion, L. Hansen, K. Mullin, N. May, T. Leming, B. Mate, J. Norris,

and T. Jefferson. In preparation. Distribution and abundance of marine mammals in the north-central and

western Gulf of Mexico: Final Report. OCS Study #MMS 94-0003. Texas Institute of Oceanography and

the National Marine Fisheries Service. U.S. Dept. of the Interior, Minerals Mgmt. Service, Gulf of Mexico

OCS Region, New Orleans, Louisiana. 

Hansen, L. J., K. D. Mullin and C. L. Roden. 1995. Estimates of cetacean abundance in the northern Gulf of

Mexico from vessel surveys. Southeast Fisheries Science Center, Miami Laboratory, Contribution No.

MIA-94/95-25, 9 pp. + tables and figures.

Laake, J. L., S. T. Buckland, D. R. Anderson, and K. P. Burnham. DISTANCE user’s guide, V2.0. Colorado

Cooperative Fish & Wildlife Research Unit, Colorado State University, Ft. Collins, Colorado, 72 pp. 

Leatherwood, S. and R. R. Reeves. 1983. The Sierra Club handbook of whales and dolphins. Sierra Club Books,

San Francisco, 302 pp. 

Mullin, K., W. Hoggard, C. Roden, R. Lohoefener, C. Rogers and B. Taggart. 1991. Cetaceans on the upper

continental slope in the north-central Gulf of Mexico. OCS Study/MMS 91-0027. U.S. Dept. of the

Interior, Minerals Management Service, Gulf of Mexico OCS Regional Office, New Orleans, Louisiana,

108 pp. 

Rice, D. W. 1989. Sperm whale, Physeter macrocephalus Linnaeus, 1758. Pages 177-233 in S. H. Ridgway and R.

Harrison (editors), Handbook of marine mammals, Vol. 4: river dolphins and the larger toothed whales. 

Academic Press, London, 442 pp. 

Schmidly, D. J. 1981. Marine mammals of the southeastern United States and the Gulf of Mexico. U.S. Fish and

Wildlife Service, Office of Biological Services, Washington, DC, FWS/OBS-80/41, 165 pp. 

Townsend, C. H. 1935. The distribution of certain whales as shown by logbook records of American whale ships.

Zoologica 19: 1-50.
219

September 2000 

DWARF SPERM WHALE (Kogia simus):

Northern Gulf of Mexico Stock

STOCK DEFINITION AND GEOGRAPHIC RANGE

The dwarf sperm whale appears to be distributed worldwide in temperate to tropical waters (Caldwell and

Caldwell 1989). Sightings of these animals in the northern Gulf of Mexico occur primarily along the continental

shelf edge and over the deeper waters off the continental shelf (Mullin et al. 1991; Southeast Fisheries Science

Center, SEFSC, unpublished data). Dwarf sperm whales and pygmy sperm whales (Kogia breviceps) are difficult to

distinguish and sightings of either species are often categorized as Kogia sp. Sightings of this category were

documented in all seasons during seasonal GulfCet aerial surveys of the northern Gulf of Mexico during 1993-1995

(Hansen et al. 1996). The few reliable sightings of dwarf sperm whales during those surveys were more numerous

in spring, probably a result of greater survey efforts in that season (Jefferson and Shapiro 1997). Pygmy and dwarf

sperm whales have been sighted in the northwestern Gulf of Mexico in waters 1000 m deep, on average (Davis et al.

1998). However, these authors cautioned that inferences on preferred bottom depths should await surveys for the

entire Gulf of Mexico. The difficulty in sighting pygmy and dwarf sperm whales may be exacerbated by their

avoidance reaction towards ships, and change in behavior towards approaching survey aircraft (Würsig et al. 1998).

In a recent study using hematological and stable-isotope data, Barros et al. (1998) speculated that dwarf sperm

whales may have a more pelagic distribution than pygmy sperm whales, and/or dive deeper during feeding bouts.

There is no information on stock differentiation. 

POPULATION SIZE

Estimates of abundance of Kogia sp. were derived through the application of distance sampling analysis

(Buckland et al. 1993) and the computer program DISTANCE (Laake et al. 1993) to sighting data collected during

1991-1994 spring-summer, visual sampling, line-transect vessel surveys of the northern Gulf of Mexico (Fig. 1 in

Hansen et al. 1995), which includes data collected as part of the GulfCet program (Hansen et al. 1996). These

surveys were conducted throughout the area from approximately the 200 m isobath along the USA coast to the

seaward extent of the USA Exclusive Economic Zone. The seasonal GulfCet aerial surveys included only a small

portion of the species’ range and therefore, these data were not used to estimate population size. Estimated

abundance of Kogia sp. by survey year [coefficient of variation (CV) in parentheses] was 109 in 1991 (0.68), 1,010

in 1992 (0.40), 580 in 1993 (0.45), and 162 in 1994 (0.61) (Hansen et al. 1995). Survey effort-weighted estimated

average abundance of Kogia sp. for all surveys combined was 547 (CV=0.28) (Hansen et al. 1995). Estimates of

dwarf sperm whale abundance cannot be provided due to uncertainty of species identification at sea. 

Minimum Population Estimate

A minimum population estimate was not calculated because of uncertainty of species identification at sea. 

Current Population Trend

There is insufficient information to describe any population trend of this species in the Gulf of Mexico.

CURRENT AND MAXIMUM NET PRODUCTIVITY RATES

Current and maximum net productivity rates are not known for this stock. The maximum net productivity

rate was assumed to be 0.04. This value is based on theoretical modeling showing that cetacean populations may not

grow at rates much greater than 4% given the constraints of their reproductive life history (Barlow et al. 1995).

POTENTIAL BIOLOGICAL REMOVAL

Potential Biological Removal (PBR) is the product of the minimum population size, one half the maximum

net productivity rate, and a “recovery” factor (Wade and Angliss 1997). The “recovery “ factor, which accounts for

endangered, depleted, and threatened stocks, or stocks of unknown status relative to optimum sustainable population

(OSP) is assumed to be 0.5 because this stock is of unknown status. PBR for the dwarf sperm whale is unknown

because the minimum population estimate cannot be estimated.
220

ANNUAL HUMAN-CAUSED MORTALITY AND SERIOUS INJURY

The level of past or current, direct, human-caused mortality of dwarf sperm whales in the northern Gulf of

Mexico is unknown. Available information indicates there likely is little, if any, fisheries interaction with dwarf

sperm whales in the northern Gulf of Mexico. There have been no logbook reports of fishery-related mortality or

serious injury and no fishery-related mortality or serious injury has been observed.

There were no documented strandings of dwarf sperm whales in the northern Gulf of Mexico during 1987-

October 1998 which were classified as likely caused by fishery interactions, but there have been stranding

investigation reports of dwarf sperm whales which may have died as a result of other human-related causes. 

Stranding data probably underestimate the extent of fishery-related mortality and serious injury because not all of the

marine mammals which die or are seriously injured may wash ashore, nor will all of those that do wash ashore

necessarily show signs of entanglement or other fishery-interaction. Finally, the level of technical expertise among

stranding network personnel varies widely as does the ability to recognize signs of fishery interaction. 

Fisheries Information

Pelagic swordfish, tunas, and billfish are the targets of the longline fishery operating in the USA Gulf of

Mexico. Total longline effort for the Gulf of Mexico pelagic fishery, including OCS edge, continental slope, and

Mexican territorial waters, based on mandatory logbook reporting, was 4,400 sets in 1991, 4,850 sets in 1992, and

3,260 sets in 1993 (Cramer 1994). This fishery has been monitored with about 5% observer coverage, in terms of

trips observed, since 1992. There were no reports of mortality or serious injury of dwarf sperm whales by this

fishery. 

Pair trawl fishing gear has the potential to capture marine mammals, but there have been no reports of

mortality or serious injury to marine mammals in the Gulf of Mexico. This fishery has not been observed by NMFS

observers, and there are no other data available as to the extent of this fishery in the Gulf of Mexico. It is assumed

that it is very limited in scope and duration. 

Other Mortality

A total of at least 16 dwarf sperm whale strandings were documented in the northern Gulf of Mexico from

1990 through October 1998. 

STATUS OF STOCK

The status of this stock relative to OSP is unknown and there are insufficient data to determine population

trends. This species is not listed under the Endangered Species Act. Although the PBR cannot be calculated, there is

no known fishery-related mortality or serious injury to this stock and, therefore, total fishery-related mortality and

serious injury can be considered insignificant and approaching zero mortality and serious injury rate. The total level

of fishery-related mortality and serious injury is unknown, but it is believed to be insignificant.

REFERENCES

Barlow, J., S. L. Swartz, T. C. Eagle and P. R. Wade. 1995. U.S. Marine Mammal Stock Assessments: Guidelines

for Preparation, Background and a Summary of the 1995 Assessments. U.S. Dep. Commer., NOAA Tech.

Memo. NMFS-OPR-6, 73 pp.

Barros, N. B., D. A. Duffield, P. H. Ostrom, D. K. Odell and V. R. Cornish. 1998. Nearshore vs. offshore ecotype

differentiation of Kogia breviceps and K. simus based on hemoglobin, morphometric and dietary analyses.

Abstracts. World Marine Mammal Science Conference. Monaco. 20-24 January. 

Buckland, S. T., D. R. Anderson, K. P. Burnham and J. L. Laake. 1993. Distance Sampling: estimating abundance

of biological populations. Chapman & Hall, London, 446 pp. 

Caldwell, D. K. and M. C. Caldwell. 1989. Pygmy sperm whale Kogia breviceps (de Blainville, 1838): dwarf

sperm whale Kogia simus Owen, 1866. Pages 235-260 in: S. H. Ridgway and R. Harrison (eds), Handbook

of marine mammals, Vol. 4: River dolphins and the larger toothed whales. Academic Press, San Diego. 

Cramer, J. 1994. Large pelagic logbook newsletter - 1993. NOAA Tech. Mem. NMFS-SEFSC-352, 19 pp. 

Davis, R. W., G. S. Fargion, N. May, T. D. Leming, M. Baumgartner, W. E. Evans, L. J. Hansen and K. Mullin. 

1998. Physical habitats of cetaceans along the continental slope of the north-central and western Gulf of

Mexico. Mar. Mammal. Sci., 14:490-507.
221

Hansen, L. J., K. D. Mullin, T. A. Jefferson and G. P. Scott. 1996. Visual surveys aboard ships and aircraft. Pages

55-132. In: R.W. Davis and G.S. Fargion (eds). Distribution and abundance of marine mammals in the

north-central and western Gulf of Mexico: Final Report. Volume II: Technical Report. OCS Study MMS

96-0027. Prepared by the Texas Institute of Oceanography and the National Marine Fisheries Service. U.S.

Dept. of the Interior, Minerals Mgmt. Service, Gulf of Mexico OCS Region, New Orleans, LA. 357 pp.

Hansen, L. J., K. D. Mullin and C. L. Roden. 1995. Estimates of cetacean abundance in the northern Gulf of

Mexico from vessel surveys. Southeast Fisheries Science Center, Miami Laboratory, Contribution No.

MIA-94/95-25, 9 pp. + tables and figures.

Jefferson, T. J. and A. Schiro. 1997. Distribution of cetaceans in the northern Gulf of Mexico. Mammal Rev., 27:27-

50. 

Laake, J. L., S. T. Buckland, D. R. Anderson and K. P. Burnham. 1993. DISTANCE user’s guide, V2.0. Colorado

Cooperative Fish & Wildlife Research Unit, Colorado State University, Ft. Collins, Colorado, 72 pp. 

Mullin, K., W. Hoggard, C. Roden, R. Lohoefener, C. Rogers and B. Taggart. 1991. Cetaceans on the upper

continental slope in the north-central Gulf of Mexico. OCS Study/MMS 91-0027. U.S. Dept. of the

Interior, Minerals Management Service, Gulf of Mexico OCS Regional Office, New Orleans, Louisiana 108

pp. 

Wade, P.R., and R.P. Angliss. 1997. Guidelines for assessing marine mammal stocks: Report of the GAMMS

Workshop April 3-5, Seattle, Washington. U.S. Dep. Commer., NOAA Tech. Memo. NMFS-OPR-12, 93

pp.

Würsig, B., S.K. Lynn, T.A. Jefferson, and K.D. Mullin. 1998. Behavior of cetaceans in the northern Gulf of Mexico

relative to survey ships and aircraft. Aquat. Mammals, 24:41-50.
222

September 2000 

PYGMY SPERM WHALE (Kogia breviceps):

Northern Gulf of Mexico Stock

STOCK DEFINITION AND GEOGRAPHIC RANGE

The pygmy sperm whale appears to be distributed worldwide in temperate to tropical waters (Caldwell and

Caldwell 1989). Sightings of these animals in the northern Gulf of Mexico occur primarily along the continental

shelf edge and over the deeper waters off the continental shelf (Mullin et al. 1991; Southeast Fisheries Science

Center, SEFSC, unpublished data). Pygmy sperm whales and dwarf sperm whales (Kogia simus) are difficult to

distinguish and sightings of either species are often categorized as Kogia sp. Sightings of this category were

documented in all seasons during seasonal GulfCet aerial surveys of the northern Gulf of Mexico during 1993-1995

(Hansen et al. 1996). Pygmy and dwarf sperm whales have been sighted in the northwestern Gulf of Mexico in

waters 1000 m deep, on average (Davis et al. 1998). However, these authors cautioned that inferences on preferred

bottom depths should await surveys for the entire Gulf of Mexico. The difficulty in sighting pygmy and dwarf sperm

whales may be exacerbated by their avoidance reaction towards ships, and change in behavior towards approaching

survey aircraft (Würsig et al. 1998) In a recent study using hematological and stable-isotope data, Barros et al.

(1998) speculated that dwarf sperm whales may have a more pelagic distribution than pygmy sperm whales, and/or

dive deeper during feeding bouts. There is no information on stock differentiation. 

POPULATION SIZE

Estimates of abundance of Kogia sp. were derived through the application of distance sampling analysis

(Buckland et al. 1993) and the computer program DISTANCE (Laake et al. 1993) to sighting data collected during

1991-1994 spring-summer, visual sampling, line-transect vessel surveys of the northern Gulf of Mexico (Hansen et

al. 1995) (Fig. 1), which includes data collected as part of the GulfCet program (Hansen et al. 1996). These surveys

were conducted throughout the area from approximately the 200 m isobath along the USA coast to the seaward

extent of the USA Exclusive Economic Zone. The seasonal GulfCet aerial surveys included only a small portion of

the species’ range and therefore, these data were not used to estimate population size. Estimated abundance of Kogia

sp. by survey year [coefficient of variation (CV) in parentheses] was 109 in 1991 (0.68), 1,010 in 1992 (0.40), 580 in

1993 (0.45), and 162 in 1994 (0.61) (Hansen et al. 1995). Survey effort-weighted estimated abundance of Kogia sp.

for all surveys combined was 547 (CV = 0.28) (Hansen et al. 1995). Estimates of pygmy sperm whale abundance

cannot be provided due to uncertainty of species identification at sea. 

Minimum Population Estimate

A minimum population estimate could not be calculated because of uncertainty of species identification at

sea. 

Current Population Trend

There is insufficient information to describe any population trend for this species in the Gulf of Mexico.

CURRENT AND MAXIMUM NET PRODUCTIVITY RATES

Current and maximum net productivity rates are not known for this stock. The maximum net productivity

rate was assumed to be 0.04. This value is based on theoretical modeling showing that cetacean populations may not

grow at rates much greater than 4% given the constraints of their reproductive life history (Barlow et al. 1995).

POTENTIAL BIOLOGICAL REMOVAL

Potential Biological Removal (PBR) is the product of the minimum population size, one half the maximum

net productivity rate, and a “recovery” factor (Wade and Angliss 1997). The “recovery “ factor, which accounts for

endangered, depleted, and threatened stocks, or stocks of unknown status relative to optimum sustainable population

(OSP) is assumed to be 0.5 because this stock is of unknown status. PBR for the pygmy sperm whale is unknown

because the minimum population estimate cannot be estimated.
223

ANNUAL HUMAN-CAUSED MORTALITY AND SERIOUS INJURY

The level of past or current, direct, human-caused mortality of pygmy sperm whales in the northern Gulf of

Mexico is unknown. Available information indicates there likely is little, if any, fisheries interaction with pygmy

sperm whales in the northern Gulf of Mexico. There have been no logbook reports of fishery-related mortality or

serious injury and no fishery-related mortality or serious injury has been observed.

There have been no documented strandings of pygmy sperm whales in the northern Gulf of Mexico during

1987-October 1998 which have been classified as likely caused by fishery interactions, but there have been stranding

investigation reports of pygmy sperm whales which may have died as a result of other human-related causes. 

Stranding data probably underestimate the extent of fishery-related mortality and serious injury because not all of the

marine mammals which die or are seriously injured may wash ashore, nor will all of those that do wash ashore

necessarily show signs of entanglement or other fishery-interaction. Finally, the level of technical expertise among

stranding network personnel varies widely as does the ability to recognize signs of fishery interaction.

Fisheries Information

Pelagic swordfish, tunas, and billfish are the targets of the longline fishery operating in the USA Gulf of

Mexico. Total longline effort for the Gulf of Mexico pelagic fishery, including OCS edge, continental slope, and

Mexican territorial waters, based on mandatory logbook reporting, was 4,400 sets in 1991, 4,850 sets in 1992, and

3,260 sets in 1993 (Cramer 1994). This fishery has been monitored with about 5% observer coverage, in terms of

trips observed, since 1992. There were no reports of mortality or serious injury of pygmy sperm whales by this

fishery. 

Pair trawl fishing gear has the potential to capture marine mammals, but there have been no reports of

mortality or serious injury to marine mammals in the Gulf of Mexico. This fishery has not been observed by NMFS

observers, and there are no other data available as to the extent of this fishery in the Gulf of Mexico. It is assumed

that it is very limited in scope and duration. 

Other Mortality

At least 20 pygmy sperm whale strandings were documented in the northern Gulf of Mexico from 1990 

through October 1998. Two of these animals had a plastic bag or pieces thereof in their stomachs (Tarpley and

Marwitz 1993, Barros, unpublished data). Another animal stranded apparently due to injuries inflicted by impact,

possibly with a vessel. 

STATUS OF STOCK

The status of this stock relative to OSP is unknown and there are insufficient data to determine population

trends. This species is not listed under the Endangered Species Act. Although the PBR cannot be calculated, the

total known fishery-related mortality and serious injury for this stock is zero and, therefore, can be considered

insignificant and approaching zero mortality and serious injury rate. The total level of fishery-related mortality and

serious injury is unknown, but it is believed to be insignificant.

REFERENCES

Barlow, J., S.L. Swartz, T.C. Eagle, and P.R. Wade. 1995. U.S. Marine Mammal Stock Assessments: Guidelines for

Preparation, Background and a Summary of the 1995 Assessments. U.S. Dep. Commer., NOAA Tech.

Memo. NMFS-OPR-6, 73 pp.

Barros, N.B., D.A. Duffield, P.H. Ostrom, D.K. Odell, and V.R. Cornish. 1998. Nearshore vs. offshore ecotype

differentiation of Kogia breviceps and K. simus based on hemoglobin, morphometric and dietary analyses.

Abstract. World Marine Mammal Science Conference. Monaco. 20-24 January.

Buckland, S. T., D. R. Anderson, K. P. Burnham and J. L. Laake. 1993. Distance Sampling: estimating abundance

of biological populations. Chapman & Hall, London, 446 pp. 

Caldwell, D. K. and M. C. Caldwell 1989. Pygmy sperm whale Kogia breviceps (de Blainville, 1838): dwarf sperm

whale Kogia simus Owen, 1866. Pages 235-260 in: S. H. Ridgway and R. Harrison (eds), Handbook of

marine mammals, Vol. 4: River dolphins and the larger toothed whales. Academic Press, San Diego. 

Cramer, J. 1994. Large pelagic logbook newsletter - 1993. NOAA Tech. Mem. NMFS-SEFSC-352, 19 pp. 
224

Davis, R.W., G.S. Fargion, N. May, T.D. Leming, M. Baumgartner, W.E. Evans, L.J. Hansen, and K. Mullin. 1998.

Physical habitats of cetaceans along the continental slope of the north-central and western Gulf of Mexico.

Mar. Mamm. Sci., 14:490-507.

Hansen, L.J., K.D. Mullin, T.A. Jefferson and G.P. Scott. 1996. Visual surveys aboard ships and aircraft. Pages 55-

132. In: R.W. Davis and G.S. Fargion (eds). Distribution and abundance of marine mammals in the northcentral and western Gulf of Mexico: Final Report. Volume II: Technical Report. OCS Study MMS 96-

0027. Prepared by the Texas Institute of Oceanography and the National Marine Fisheries Service. U.S.

Dept. of the Interior, Minerals Mgmt. Service, Gulf of Mexico OCS Region, New Orleans, LA. 357 pp.

Hansen, L. J., K. D. Mullin and C. L. Roden. 1995. Estimates of cetacean abundance in the northern Gulf of

Mexico from vessel surveys. Southeast Fisheries Science Center, Miami Laboratory, Contribution No.

MIA-94/95-25, 9 pp. + tables and figures. 

Laake, J. L., S. T. Buckland, D. R. Anderson, and K. P. Burnham. 1993. DISTANCE user’s guide, V2.0. Colorado

Cooperative Fish & Wildlife Research Unit, Colorado State University, Ft. Collins, Colorado, 72 pp. 

Mullin, K., W. Hoggard, C. Roden, R. Lohoefener, C. Rogers and B. Taggart. 1991. Cetaceans on the upper

continental slope in the north-central Gulf of Mexico. OCS Study/MMS 91-0027. U.S. Dept. of the

Interior, Minerals Management Service, Gulf of Mexico OCS Regional Office, New Orleans, Louisiana 108

pp. 

Tarpley, R. J., and S. Marwitz. 1993. Plastic debris ingestion by cetaceans along the Texas coast: two case studies.

Aquat. Mammals, 14:93-98.

Wade, P. R. and R. P. Angliss. 1997. Guidelines for assessing marine mammal stocks: Report of the GAMMS

Workshop April 3-5, Seattle, Washington. U.S. Dep. Commer., NOAA Tech. Memo. NMFS-OPR-12, 93

pp.

Würsig, B., S. K. Lynn, T. A. Jefferson and K. D. Mullin. 1998. Behavior of cetaceans in the northern Gulf of

Mexico relative to survey ships and aircraft. Aquat. Mammals, 24:41-50.
225

Figure 1. Distribution of Bryde’s whale sightings (filled circles) and

unidentified balaenopterid whales (unfilled circles) during NOAA Ship Oregon

II marine mammal surveys during 1991-1994. The straight lines show transects

during two ship surveys and are examples of typical ship survey transects. 

Isobaths are in 183 m (100 fm) intervals.

July 1995

BRYDE'S WHALE (Balaenoptera edeni):

Northern Gulf of Mexico Stock

STOCK DEFINITION AND GEOGRAPHIC RANGE

Bryde's whales are considered the tropical and sub-tropical baleen whale of the world's oceans. In the 

western Atlantic, Bryde's whales are reported from off the southeastern United States and the southern West Indies

to Cabo Frio, Brazil (Leatherwood and Reeves 1983). It is postulated that the Bryde's whales found in the Gulf of

Mexico may represent a resident stock (Schmidly 1981; Leatherwood and Reeves 1983), but there is no information

on stock differentiation. Most sightings of Bryde's whales have occurred during the spring-summer months (Hansen

et al. 1995; Davis et al., in preparation), but strandings have occurred throughout the year (Jefferson et al. 1992). 

POPULATION SIZE

Estimates of abundance were derived through the application of distance sampling analysis (Buckland et al.

1993) and the computer program DISTANCE (Laake et al. 1993) to sighting data collected during 1991-1994 springsummer, visual sampling, line-transect vessel surveys of the northern Gulf of Mexico (Hansen et al. 1995) (Fig. 1),

which includes data collected as part of the GulfCet program (Davis et al., in preparation). These surveys were

conducted throughout the area from approximately the 200 m isobath along the U.S. coast to the seaward extent of

the U.S. Exclusive Economic

Zone. The seasonal GulfCet

aerial surveys included only a

small portion of the stock range

and these data were not used for

abundance estimation. The

estimated abundance of Bryde’s

whales by survey year was 218

in 1991 (coefficient of variation,

CV = 1.01) and zero in 1992,

1993, and 1994 (Hansen et al.

1995). Survey effort-weighted

estimated average abundance of

Bryde's whales for all surveys

combined was 35 (CV = 1.10)

(Hansen et al. 1995) and was

based on only three sightings,

all of which occurred in 1991. 

Minimum Population

Estimate

 The minimum population estimate is the lower limit of the two-tailed 60% confidence interval of the lognormal distributed abundance estimate, which is equivalent to the 20th percentile of the log-normal distributed

abundance estimate as specified by NMFS (Anon. 1994). The minimum population estimate was based on the 1991-

1994 average estimated abundance of Bryde's whales which was 35 (CV = 1.10) (Hansen et al. 1995) and is 17

Bryde’s whales. 

Current Population Trend

The abundance estimates decreased to zero for survey years 1992-1994 because Bryde's whales were not

sighted during vessel surveys those years. This could be due to chance rather than to a decrease in population size

and the result of a relatively small population size and low sampling intensity or it could be due to inter-annual

variation in distribution. 
226

CURRENT AND MAXIMUM NET PRODUCTIVITY RATES

Current and maximum net productivity rates are not known for this stock; therefore, the default maximum

net productivity rate of 0.04 (Anon. 1994) was used for purposes of this assessment. 

POTENTIAL BIOLOGICAL REMOVAL

Potential biological removal level (PBR) was specified as the product of the minimum population size, one

half the maximum net productivity rate, and a recovery factor for endangered, threatened, or depleted stocks, or

stocks of unknown status relative to optimum sustainable population (OSP) (Anon. 1994). The recovery factor was

set at 0.50 because the status of the stock relative to OSP is unknown. The resulting PBR for this stock is 0.2

Bryde’s whales. 

ANNUAL HUMAN-CAUSED MORTALITY AND SERIOUS INJURY

The level of past or current, direct, human-caused mortality of Bryde's whales in the northern Gulf of

Mexico is unknown, but available information indicates there is little fisheries interaction with Bryde's whales in the

northern Gulf of Mexico. There was one report of a Bryde’s whale entangled in line, but the line was removed and

the animal released alive. 

There were no documented strandings of Bryde’s whales in the northern Gulf of Mexico during 1987-1994

which were classified as likely caused by fishery interactions or other human-related causes. Stranding data

probably underestimate the extent of fishery-related mortality and serious injury because not all of the marine

mammals which die or are seriously injured may wash ashore, nor will all of those that do wash ashore necessarily

show signs of entanglement or other fishery-interaction. Finally, the level of technical expertise among stranding

network personnel varies widely as does the ability to recognize signs of fishery interaction. 

The total known fishery-related mortality and serious injury for this stock is less than 10% of the calculated

PBR and, therefore, can be considered insignificant and approaching zero mortality and serious injury rate. This

determination cannot be made for specific fisheries until the implementing regulations for Section 118 of the MMPA

have been reviewed by the public and finalized. 

Fisheries Information

Pelagic swordfish, tunas, and billfish are the targets of the longline fishery operating in the U.S. Gulf of

Mexico. Total longline effort for the Gulf of Mexico pelagic fishery, including OCS edge, continental slope, and

Mexican territorial waters, based on mandatory logbook reporting, was 4,400 sets in 1991, 4,850 sets in 1992, and

3,260 sets in 1993 (Cramer 1994). This fishery has been monitored with about 5% observer coverage, in terms of

trips observed, since 1992. There were no reports of mortality or serious injury to Bryde’s whales by this fishery. 

Pair trawl fishing gear has the potential to capture marine mammals, but there have been no reports of

mortality or serious injury to marine mammals in the Gulf of Mexico. This fishery has not been observed by NMFS

observers, and there are no other data available as to the extent of this fishery in the Gulf of Mexico. It is assumed

that it is very limited in scope and duration. 

Other Mortality

No human-caused mortality has been reported for this stock. 

STATUS OF STOCK

The status of this stock relative to OSP is unknown and there are insufficient data to determine population

trends. This species is not listed under the Endangered Species Act. The total level of human-caused mortality and

serious injury is unknown, but it is believed to be insignificant; therefore, this is not a strategic stock.

REFERENCES

Anon. 1994. Report of the PBR (Potential Biological Removal) workshop. June 27-29, 1994. NOAA, NMFS

Southwest Fisheries Science Center, La Jolla, California, 13 pp. + Appendices. 

Buckland, S. T., D. R. Anderson, K. P. Burnham and J. L. Laake. 1993. Distance Sampling: estimating abundance

of biological populations. Chapman & Hall, London, 446 pp. 

Cramer, J. 1994. Large pelagic logbook newsletter - 1993. NOAA Tech. Mem. NMFS-SEFSC-352, 19 pp. 
227

Davis, R., G. Scott, B. Würsig, W. Evans, G. Fargion, L. Hansen, K. Mullin, N. May, T. Leming, B. Mate, J. Norris

and T. Jefferson. In preparation. Distribution and abundance of marine mammals in the north-central and

western Gulf of Mexico: Final Report. OCS Study #MMS 94-0003. Texas Institute of Oceanography and

the National Marine Fisheries Service. U.S. Dept. of the Interior, Minerals Mgmt. Service, Gulf of Mexico

OCS Region, New Orleans, Louisiana. 

Hansen, L. J., K. D. Mullin and C. L. Roden. 1995. Estimates of cetacean abundance in the northern Gulf of

Mexico from vessel surveys. Southeast Fisheries Science Center, Miami Laboratory, Contribution No.

MIA-94/95-25, 9 pp. + tables and figures.

Jefferson, T. A., S. Leatherwood, L. K. M. Shoda and R. L. Pitman. 1992. Marine mammals of the Gulf of Mexico:

a field guide for aerial and shipboard observers. Texas A&M University Printing Center, College Station,

Texas, 92 pp.

Laake, J. L., S. T. Buckland, D. R. Anderson, and K. P. Burnham. DISTANCE user’s guide, V2.0. Colorado

Cooperative Fish & Wildlife Research Unit, Colorado State University, Ft. Collins, Colorado, 72 pp. 

Leatherwood, S. and R. R. Reeves. 1983. The Sierra Club handbook of whales and dolphins. Sierra Club Books,

San Francisco, 302 pp. 

Schmidly, D. J. 1981. Marine mammals of the southeastern United States and the Gulf of Mexico. U.S. Fish and

Wildlife Service, Office of Biological Services, Washington, DC, FWS/OBS-80/41, 165 pp. 
228

Figure 1. Distribution of Curvier’s beaked whale sightings (filled circles) and

unidentified beaked whale sightings (unfilled circles) during NOAA Ship Oregon

II marine mammal surveys during 1991-1994. The straight lines show transects

during two surveys and are examples of typical ship survey transects. Isobaths

are in 183 m (100 fm) intervals.

July 1995

CUVIER'S BEAKED WHALE (Ziphius cavirostris):

Northern Gulf of Mexico Stock

STOCK DEFINITION AND GEOGRAPHIC RANGE

Cuvier's beaked whales are distributed throughout the world's oceans except for the polar regions

(Leatherwood and Reeves 1983; Heyning 1989). Strandings have occurred in all months along the United States east

coast (Schmidly 1981) and have been documented throughout the year in the Gulf of Mexico. Strandings of Cuvier's

beaked whales along the west coast of North America, based on skull characteristics, are thought to represent

members of a panmictic population (Mitchell 1968), but there is no information on stock differentiation in the Gulf

of Mexico and nearby waters. 

Beaked whales were seen in all seasons during recent seasonal GulfCet aerial surveys of the northern Gulf

of Mexico (Davis et al., in preparation). Some of the aerial survey sightings may have included Curvier’s beaked

whale, but identification of beaked whale species from aerial surveys is problematic.

POPULATION SIZE

Estimates of abundance were derived through the application of distance sampling analysis (Buckland et al.

1993) and the computer program DISTANCE (Laake et al. 1993) to sighting data collected during 1991-1994 springsummer, visual sampling, line-transect vessel surveys of the northern Gulf of Mexico (Hansen et al. 1995) (Fig. 1),

which includes data collected as part of the GulfCet program (Davis et al., in preparation). These surveys were

conducted throughout the area from approximately the 200 m isobath along the U.S. coast to the seaward extent of

the U.S. Exclusive Economic Zone. The seasonal GulfCet aerial surveys included only a small portion of the stock

range and these data were not used for abundance estimation. The estimated abundance [coefficient of variation

(CV) in parentheses] by survey

year was zero in 1991and 1992,

70 in 1993 (0.63), and 38 in

1994 (0.80) (Hansen et al.

1995). Survey effort-weighted

estimated average abundance

average abundance of Cuvier's

beaked whales was 30 (CV =

0.50) (Hansen et al. 1995). The

estimated abundance of

Curvier’s beaked whales is

probably low because only

sightings of beaked whales

which could be positively

identified to species were used. 

Minimum Population

Estimate

The minimum

population estimate was based

on average estimated abundance of Cuvier's beaked whales for all surveys combined which was 30 whales (CV =

0.50) (Hansen et al. 1995). The minimum population estimate is the lower limit of the two-tailed 60% confidence

interval of the log-normal distributed abundance estimate, which is equivalent to the 20th percentile of the lognormal distributed abundance estimate as specified by NMFS (Anon. 1994). The minimum population estimate is

20 Cuvier's beaked whales. 

Current Population Trend

The abundance estimates were zero in 1991 and 1992, and then increased for 1993 and 1994. Cuvier's

beaked whales were not sighted during the 1991 and 1992 vessel surveys. This could be due to chance given the
229

small estimated population size and sampling intensity or inter-annual variation in distribution, rather than a change

in population size. 

CURRENT AND MAXIMUM NET PRODUCTIVITY RATES

Current and maximum net productivity rates are not known for this stock; therefore, the default maximum

net productivity rate of 0.04 (Anon. 1994) was used for purposes of this assessment. 

POTENTIAL BIOLOGICAL REMOVAL

Potential biological removal level (PBR) was specified as the product of the minimum population size, one

half the maximum net productivity rate, and a recovery factor for endangered, threatened, or depleted stocks, or

stocks of unknown status relative to optimum sustainable population (OSP) (Anon. 1994). The recovery factor was

set at 0.50 because the status of the stock relative to OSP is unknown. PBR for this stock is 0.2 Cuvier's beaked

whales. 

ANNUAL HUMAN-CAUSED MORTALITY AND SERIOUS INJURY

Cuvier's beaked whales were taken occasionally in a small, directed fishery for cetaceans that operated out

of the Lesser Antilles (Caldwell and Caldwell 1971). 

The actual level of past or current, direct, human-caused mortality of Cuvier's beaked whales in the

northern Gulf of Mexico is unknown, but there have been no reports of fishery-related mortality or serious injury to

beaked whales by U.S. fisheries in the Gulf of Mexico. Available information indicates there likely is little, if any,

fisheries interaction with Cuvier's beaked whales in the northern Gulf of Mexico. 

There were no documented strandings of Cuvier's beaked whales in the northern Gulf of Mexico during

1987-1994 which were classified as likely caused by fishery interactions or other human-related causes. Stranding

data probably underestimate the extent of fishery-related mortality and serious injury because not all of the marine

mammals which die or are seriously injured may wash ashore, nor will all of those that do wash ashore necessarily

show signs of entanglement or other fishery-interaction. Finally, the level of technical expertise among stranding

network personnel varies widely as does the ability to recognize signs of fishery interaction. 

Total fishery-related mortality and serious injury for this stock is less than 10% of the calculated PBR and,

therefore, can be considered insignificant and approaching zero mortality and serious injury rate. This determination

cannot be made for specific fisheries until the implementing regulations for Section 118 of the MMPA have been

reviewed by the public and finalized. 

Fisheries Information

Pelagic swordfish, tunas, and billfish are the targets of the longline fishery operating in the U.S. Gulf of

Mexico. Total longline effort for the Gulf of Mexico pelagic fishery, including OCS edge, continental slope, and

Mexican territorial waters, based on mandatory logbook reporting, was 4,400 sets in 1991, 4,850 sets in 1992, and

3,260 sets in 1993 (Cramer 1994). This fishery has been monitored with about 5% observer coverage, in terms of

trips observed, since 1992. There were no reports of mortality or serious injury to Cuvier's or any beaked whales by

this fishery. 

Pair trawl fishing gear has the potential to capture marine mammals, but there have been no reports of

mortality or serious injury to marine mammals in the Gulf of Mexico. This fishery has not been observed by NMFS

observers, and there are no other data available as to the extent of this fishery in the Gulf of Mexico. It is assumed

that it is very limited in scope and duration. 

STATUS OF STOCK

The status of this stock relative to OSP is unknown and there are insufficient data to determine population

trends. This species is not listed under the Endangered Species Act. The total level of human-caused mortality and

serious injury is unknown, but it is believed to be insignificant; therefore, this is not a strategic stock. 
230

REFERENCES

Anon. 1994. Report of the PBR (Potential Biological Removal) workshop. June 27-29, 1994. NOAA, NMFS

Southwest Fisheries Science Center, La Jolla, California, 13 pp. + Appendices. 

Buckland, S. T., D. R. Anderson, K. P. Burnham and J. L. Laake. 1993. Distance Sampling: estimating abundance

of biological populations. Chapman & Hall, London, 446 pp. 

Caldwell, D. K. and M. C. Caldwell. 1971. Beaked whales, Ziphius cavirostris, in the Bahamas. Florida Academy of

Science Quarterly Journal. 34: 157-160.

Cramer, J. 1994. Large pelagic logbook newsletter - 1993. NOAA Tech. Mem. NMFS-SEFSC-352, 19 pp. 

Davis, R., G. Scott, B. Würsig, W. Evans, G. Fargion, L. Hansen, K. Mullin, N. May, T. Leming, B. Mate, J. Norris

and T. Jefferson. In preparation. Distribution and abundance of marine mammals in the north-central and

western Gulf of Mexico: Final Report. OCS Study #MMS 94-0003. Texas Institute of Oceanography and

the National Marine Fisheries Service. U.S. Dept. of the Interior, Minerals Mgmt. Service, Gulf of Mexico

OCS Region, New Orleans, Louisiana. 

Hansen, L. J., K. D. Mullin and C. L. Roden. 1995. Estimates of cetacean abundance in the northern Gulf of

Mexico from vessel surveys. Southeast Fisheries Science Center, Miami Laboratory, Contribution No.

MIA-94/95-25, 9 pp. + tables and figures.

Heyning, J. E. 1989. Cuvier's beaked whale Ziphius cavirostris G. Cuvier, 1923. Pages 289-308 in S. H. Ridgway

and R. Harrison (editors), Handbook of marine mammals, Vol. 4: River dolphins and the larger toothed

whales, Academic Press, London, 442 pp. 

Jefferson, T. A., S. Leatherwood, L. K. M. Shoda and R. L. Pitman. 1992. Marine mammals of the Gulf of Mexico:

a field guide for aerial and shipboard observers. Texas A&M University Printing Center, College Station,

92 pp. 

Laake, J. L., S. T. Buckland, D. R. Anderson, and K. P. Burnham. DISTANCE user’s guide, V2.0. Colorado

Cooperative Fish & Wildlife Research Unit, Colorado State University, Ft. Collins, Colorado, 72 pp. 

Leatherwood, S. and R. R. Reeves. 1983. The Sierra Club handbook of whales and dolphins. Sierra Club Books,

San Francisco, 302 pp. 

Schmidly, D. J. 1981. Marine mammals of the southeastern United States and the Gulf of Mexico. U.S. Fish and

Wildlife Service, Office of Biological Services, Washington, DC, FWS/OBS-80/41, 165 pp. 
231

Figure 1. Distribution of beaked whale sightings during NOAA Ship Oregon II

marine mammal surveys during 1991-1994. The straight lines show transects

during two surveys and are examples of typical survey transects. Isobaths are in

183 m (100 fm) intervals.

July 1995

BLAINVILLE’S BEAKED WHALE (Mesoplodon densirostris):

Northern Gulf of Mexico Stock

STOCK DEFINITION AND GEOGRAPHIC RANGE

Only three species of Mesoplodon are known, from strandings and/or sightings, to occur in the Gulf of

Mexico (Jefferson et al. 1992; Hansen et al. 1995). These are Blainville's beaked whale (M. densirostris), Gervais'

beaked whale (M. europaeus), and Sowerby's beaked whale (M. bidens). The occurrence of Sowerby’s beaked whale

in the Gulf of Mexico is considered extralimital because there is only one known stranding of this species in the Gulf

of Mexico (Bonde and O’Shea 1989) and because it normally occurs in northern temperate waters of the North

Atlantic (Mead 1989).

Identification of Mesoplodon species at sea is problematic; therefore, nearly all sightings of these species

are identified as beaked whales and may include sightings of Ziphius cavirostris that were not identified as such.

Beaked whales were seen in all seasons during recent seasonal GulfCet aerial surveys of the northern Gulf of

Mexico (Davis et al., in preparation). 

Blainville’s beaked whales appear to be widely but sparsely distributed in warm temperate and tropical

waters of the world’s oceans (Leatherwood et al. 1976; Leatherwood and Reeves 1983). Strandings have occurred

along the northwestern Atlantic coast from Florida to Nova Scotia (Schmidly 1981), and there have been two

documented strandings of this species in the northern Gulf of Mexico and one sighting (Jefferson et al. 1992; Hansen

et al. 1995). There is no information on stock differentiation. 

POPULATION SIZE

Estimates of abundance of beaked whales were derived through the application of distance sampling

analysis (Buckland et al. 1993) and the computer program DISTANCE (Laake et al. 1993) to sighting data collected

during 1991-1994 spring-summer, visual sampling, line-transect vessel surveys of the northern Gulf of Mexico

(Hansen et al. 1995) (Fig. 1), which includes data collected as part of the GulfCet program (Davis et al., in

preparation). These surveys were conducted throughout the area from approximately the 200 m isobath along the

U.S. coast to the seaward extent of the U.S. Exclusive Economic Zone. The seasonal GulfCet aerial surveys

included only a small portion of the stock range and these data were not used for abundance estimation. Survey

effort-weighted estimated

average abundance of beaked

whales not identified to species

for all surveys combined was

117 (coefficient of variation, CV 

= 0.38) (Hansen et al. 1995). 

Estimated beaked whale

abundance (CV in parentheses)

by survey year was 129 in 1991

(0.78),18 in 1992 (1.27), 53 in

1993 (0.78), and 287 in 1994

(0.48) (Hansen et al. 1995). 

These estimates may also

include an unknown number of

Cuvier’s beaked whales (Ziphius

cavirostris) and abundance of

Blainville’s beaked whale

cannot be estimated due to

uncertainty of species

identification at sea.
232

Minimum Population Estimate

A minimum population estimate was not calculated because of uncertainty of species identification of

sightings. 

Current Population Trend

The abundance estimates of beaked whales for 1991-1993 were lower than 1994, but there was

considerable overlap of the log-normal 95% confidence intervals, which indicates the estimates were not

significantly different at that level. Any differences in abundance estimates could be due to chance given the small

estimated population size and sampling intensity or a change in distribution, rather than a change in population size. 

CURRENT AND MAXIMUM NET PRODUCTIVITY RATES

Current and maximum net productivity rates are not known for this stock; therefore, the default maximum

net productivity rate of 0.04 (Anon. 1994) was used for purposes of this assessment. 

POTENTIAL BIOLOGICAL REMOVAL

Potential biological removal level (PBR) was not calculated because the minimum population size cannot

be calculated. 

ANNUAL HUMAN-CAUSED MORTALITY AND SERIOUS INJURY

The level of past or current, direct, human-caused mortality of beaked whales in the northern Gulf of

Mexico is unknown, but there have been no documented reports of fishery-related mortality or serious injury to

beaked whales by U.S. fisheries in the Gulf of Mexico. Available information indicates there likely is little, if any,

fisheries interaction with beaked whales in the northern Gulf of Mexico. 

There were no documented strandings of beaked whales in the northern Gulf of Mexico during 1987-1994

which were classified as likely caused by fishery interactions or other human-related causes. Stranding data

probably underestimate the extent of fishery-related mortality and serious injury because not all of the marine

mammals which die or are seriously injured may wash ashore, nor will all of those that do wash ashore necessarily

show signs of entanglement or other fishery-interaction. Finally, the level of technical expertise among stranding

network personnel varies widely as does the ability to recognize signs of fishery interaction. 

Although PBR cannot be calculated, the total known fishery-related mortality and serious injury for this

stock is zero and, therefore, can be considered insignificant and approaching zero mortality and serious injury rate.

This determination cannot be made for specific fisheries until the implementing regulations for Section 118 of the

MMPA have been reviewed by the public and finalized. 

Fisheries Information

Pelagic swordfish, tunas, and billfish are the targets of the longline fishery operating in the U.S. Gulf of

Mexico. Total longline effort for the Gulf of Mexico pelagic fishery, including OCS edge, continental slope, and

Mexican territorial waters, based on mandatory logbook reporting, was 4,400 sets in 1991, 4,850 sets in 1992, and

3,260 sets in 1993 (Cramer 1994). This fishery has been monitored with about 5% observer coverage, in terms of

trips observed, since 1992. 

Pair trawl fishing gear has the potential to capture marine mammals, but there have been no reports of

mortality or serious injury to marine mammals in the Gulf of Mexico. This fishery has not been observed by NMFS

observers, and there are no other data available as to the extent of this fishery in the Gulf of Mexico. It is assumed

that it is very limited in scope and duration. 

STATUS OF STOCK

The status of this stock relative to OSP is unknown and there are insufficient data to determine population

trends. This species is not listed under the Endangered Species Act. The total level of human-caused mortality and

serious injury is unknown, but it is believed to be insignificant; therefore, this is not a strategic stock. 
233

REFERENCES

Anon. 1994. Report of the PBR (Potential Biological Removal) workshop. June 27-29, 1994. NOAA, NMFS

Southwest Fisheries Science Center, La Jolla, California, 13 pp. + Appendices. 

Bonde, R. K. and T. J. O’Shea. 1989. Sowerby’s beaked whale (Mesoplodon bidens) in the Gulf of Mexico. J.

Mammal. 70: 447-449. 

Buckland, S. T., D. R. Anderson, K. P. Burnham and J. L. Laake. 1993. Distance Sampling: estimating abundance

of biological populations. Chapman & Hall, London, 446 pp. 

Cramer, J. 1994. Large pelagic logbook newsletter - 1993. NOAA Tech. Mem. NMFS-SEFSC-352, 19 pp. 

Davis, R., G. Scott, B. Würsig, W. Evans, G. Fargion, L. Hansen, K. Mullin, N. May, T. Leming, B. Mate, J. Norris

and T. Jefferson. In preparation. Distribution and abundance of marine mammals in the north-central and

western Gulf of Mexico: Final Report. OCS Study #MMS 94-0003. Texas Institute of Oceanography and

the National Marine Fisheries Service. U.S. Dept. of the Interior, Minerals Mgmt. Service, Gulf of Mexico

OCS Region, New Orleans, Louisiana. 

Hansen, L. J., K. D. Mullin and C. L. Roden. 1995. Estimates of cetacean abundance in the northern Gulf of

Mexico from vessel surveys. Southeast Fisheries Science Center, Miami Laboratory, Contribution No.

MIA-94/95-25, 9 pp. + tables and figures.

Jefferson, T. A., S. Leatherwood, L. K. M. Shoda and R. L. Pitman. 1992. Marine mammals of the Gulf of Mexico:

a field guide for aerial and shipboard observers. Texas A&M University Printing Center, College Station,

TX. 92 pp. 

Laake, J. L., S. T. Buckland, D. R. Anderson, and K. P. Burnham. DISTANCE user’s guide, V2.0. Colorado

Cooperative Fish & Wildlife Research Unit, Colorado State University, Ft. Collins, Colorado, 72 pp. 

Leatherwood, S., D. K. Caldwell and H. E. Winn. 1976. Whales, dolphins, and porpoises of the western North

Atlantic. NOAA Tech. Rep. NMFS CIRC-396, 176 pp. 

Leatherwood, S. and R. R. Reeves. 1983. The Sierra Club handbook of whales and dolphins. Sierra Club Books,

San Francisco, 302 pp. 

Mead, J. G. 1989. Beaked whales of the genus Mesoplodon. Pages 349-430 in S. H. Ridgway and R. Harrison

(editors), Handbook of marine mammals, Vol. 4: River dolphins and the larger toothed whales. Academic

Press, London, 442 pp. 
234

Figure 1. Distribution of beaked whale sightings during NOAA Ship Oregon II

marine mammal surveys during 1991-1994. The straight lines show transects

during two surveys and are examples of typical survey transects. Isobaths are in

183 m (100 fm) intervals.

July 1995

GERVAIS' BEAKED WHALE (Mesoplodon europaeus):

Northern Gulf of Mexico Stock

STOCK DEFINITION AND GEOGRAPHIC RANGE

Only three species of Mesoplodon are known, from strandings and/or sightings, to have occurred in the

Gulf of Mexico (Jefferson et al. 1992; Hansen et al. 1995). These are Blainville's beaked whale (M. densirostris),

Gervais' beaked whale (M. europaeus), and Sowerby's beaked whale (M. bidens). The occurrence of Sowerby’s

beaked whale in the Gulf of Mexico is considered extralimital because there is only one known stranding of this

species in the Gulf of Mexico (Bonde and O’Shea 1989), and because it normally occurs in northern temperate

waters of the North Atlantic (Mead 1989). Identification of Mesoplodon species at sea is problematic. Therefore,

nearly all sightings of these species are identified as beaked whales and may include sightings of Ziphius cavirostris

which were not identified as such. Beaked whales were seen in all seasons during recent seasonal GulfCet aerial

surveys of the northern Gulf of Mexico (Davis et al., in preparation). 

Strandings of Gervais' beaked whales have occurred along the northwestern Atlantic coast from Florida to

New York (Mead 1989), and there have been at least ten documented strandings of this species in the Gulf of

Mexico (Jefferson et al. 1992). There is no information on stock differentiation. 

POPULATION SIZE

Estimates of abundance of beaked whales were derived through the application of distance sampling

analysis (Buckland et al. 1993) and the computer program DISTANCE (Laake et al. 1993) to sighting data collected

during 1991-1994 spring-summer, visual sampling, line-transect vessel surveys of the northern Gulf of Mexico

(Hansen et al. 1995) (Fig. 1), which includes data collected as part of the GulfCet program (Davis et al., in

preparation). These surveys were conducted throughout the area from approximately the 200 m isobath along the

U.S. coast to the seaward extent of the U.S. Exclusive Economic Zone. The seasonal GulfCet aerial surveys

included only a small portion of the stock range and these data were not used for abundance estimation. Survey

effort-weighted estimated

average abundance of beaked

whales not identified to species

for all surveys combined was

117 (coefficient of variation, CV 

= 0.38) (Hansen et al. 1995). 

Estimated beaked whale

abundance (CV in parentheses)

by survey year was 129 in 1991

(0.78),18 in 1992 (1.27), 53 in

1993 (0.78), and 287 in 1994

(0.48) (Hansen et al. 1995). 

These estimates may also

include an unknown number of

Cuvier’s beaked whales (Ziphius

cavirostris) and abundance of

Gervais’ beaked whale cannot

be estimated due to uncertainty

of species identification at sea.

Minimum Population Estimate

A minimum population estimate could not be not calculated because of uncertainty of species identification

of sightings. 
235

Current Population Trend

The abundance estimates of beaked whales for 1991-1993 were lower than 1994, but there was

considerable overlap of the log-normal 95% confidence intervals, which indicates the estimates were not

significantly different at that level. Any differences in abundance estimates could be due to chance given the small

estimated population size and sampling intensity or a change in distribution, rather than a change in population size. 

CURRENT AND MAXIMUM NET PRODUCTIVITY RATES

Current and maximum net productivity rates are not known for this stock; therefore, the default maximum

net productivity rate of 0.04 (Anon. 1994) was used for purposes of this assessment. 

POTENTIAL BIOLOGICAL REMOVAL

Potential biological removal level (PBR) was not calculated because the minimum population size cannot

be calculated. 

ANNUAL HUMAN-CAUSED MORTALITY AND SERIOUS INJURY

The level of past or current, direct, human-caused mortality of beaked whales in the northern Gulf of

Mexico is unknown, but there have been no documented reports of fishery-related mortality or serious injury to

beaked whales by U.S. fisheries in the Gulf of Mexico. Available information indicates there likely is little, if any,

fisheries interaction with beaked whales in the northern Gulf of Mexico. 

There were no documented strandings of beaked whales in the northern Gulf of Mexico during 1987-1994

which were classified as likely caused by fishery interactions or other human-related causes. Stranding data

probably underestimate the extent of fishery-related mortality and serious injury because not all of the marine

mammals which die or are seriously injured may wash ashore, nor will all of those that do wash ashore necessarily

show signs of entanglement or other fishery-interaction. Finally, the level of technical expertise among stranding

network personnel varies widely as does the ability to recognize signs of fishery interaction. 

Although PBR cannot be calculated, the total known fishery-related mortality and serious injury for this

stock is zero and, therefore, can be considered insignificant and approaching zero mortality and serious injury rate.

This determination cannot be made for specific fisheries until the implementing regulations for Section 118 of the

MMPA have been reviewed by the public and finalized. 

Fisheries Information

 Pelagic swordfish, tunas, and billfish are the targets of the longline fishery operating in the U.S. Gulf of

Mexico. Total longline effort for the Gulf of Mexico pelagic fishery, including OCS edge, continental slope, and

Mexican territorial waters, based on mandatory logbook reporting, was 4,400 sets in 1991, 4,850 sets in 1992, and

3,260 sets in 1993 (Cramer 1994). This fishery has been monitored with about 5% observer coverage, in terms of

trips observed, since 1992. 

Pair trawl fishing gear has the potential to capture marine mammals, but there have been no reports of

mortality or serious injury to marine mammals in the Gulf of Mexico. This fishery has not been observed by NMFS

observers, and there are no other data available as to the extent of this fishery in the Gulf of Mexico. It is assumed

that it is very limited in scope and duration. 

STATUS OF STOCK

 The status of this stock relative to OSP is unknown and there are insufficient data to determine population

trends. This species is not listed under the Endangered Species Act. The total level of human-caused mortality and

serious injury is unknown, but it is believed to be insignificant; therefore, this is not a strategic stock. 
236

REFERENCES

Anon. 1994. Report of the PBR (Potential Biological Removal) workshop. June 27-29, 1994. NOAA, NMFS

Southwest Fisheries Science Center, La Jolla, California, 13 pp. + Appendices. 

Bonde, R. K. and T. J. O’Shea. 1989. Sowerby’s beaked whale (Mesoplodon bidens) in the Gulf of Mexico. J.

Mammal. 70: 447-449. 

Buckland, S. T., D. R. Anderson, K. P. Burnham and J. L. Laake. 1993. Distance Sampling: estimating abundance

of biological populations. Chapman & Hall, London, 446 pp. 

Cramer, J. 1994. Large pelagic logbook newsletter - 1993. NOAA Tech. Mem. NMFS-SEFSC-352, 19 pp. 

Davis, R., G. Scott, B. Würsig, W. Evans, G. Fargion, L. Hansen, K. Mullin, N. May, T. Leming, B. Mate, J. Norris

and T. Jefferson. In preparation. Distribution and abundance of marine mammals in the north-central and

western Gulf of Mexico: Final Report. OCS Study #MMS 94-0003. Texas Institute of Oceanography and

the National Marine Fisheries Service. U.S. Dept. of the Interior, Minerals Mgmt. Service, Gulf of Mexico

OCS Region, New Orleans, Louisiana. 

Hansen, L. J., K. D. Mullin and C. L. Roden. 1995. Estimates of cetacean abundance in the northern Gulf of

Mexico from vessel surveys. Southeast Fisheries Science Center, Miami Laboratory, Contribution No.

MIA-94/95-25, 9 pp. + tables and figures.

Jefferson, T. A., S. Leatherwood, L. K. M. Shoda and R. L. Pitman. 1992. Marine mammals of the Gulf of Mexico:

a field guide for aerial and shipboard observers. Texas A&M University Printing Center, College Station,

92 pp. 

Laake, J. L., S. T. Buckland, D. R. Anderson, and K. P. Burnham. DISTANCE user’s guide, V2.0. Colorado

Cooperative Fish & Wildlife Research Unit, Colorado State University, Ft. Collins, Colorado, 72 pp. 

Mead, J. G. 1989. Beaked whales of the genus Mesoplodon. Pages 349-430 in S. H. Ridgway and R. Harrison

(editors), Handbook of marine mammals, Vol. 4: River dolphins and the larger toothed whales. Academic

Press, London, 442 pp. 
237

Figure 1. Sightings of U.S. Gulf of Mexico outer continental shelf (OCS)

bottlenose dolphin stock during GOMEX regional aerial surveys (filled circles).

Bottlenose dolphin sightings along the OCS edge and continental slope during

NOAA Ship Oregon II surveys (unfilled circles), shown for comparison, are

believed to be a separate stock. The straight lines show transects during two

ship surveys and are examples of typical ship survey transects. Isobaths are in

183 m (100 fm) intervals.

July 1995

BOTTLENOSE DOLPHIN (Tursiops truncatus):

Gulf of Mexico Outer Continental Shelf Stock

STOCK DEFINITION AND GEOGRAPHIC RANGE

The Gulf of Mexico Outer Continental Shelf (OCS) bottlenose dolphin stock is assumed to consist of the

shallow, warm water bottlenose dolphin ecotype hypothesized by Hersh and Duffield (1990) inhabiting waters over

the U.S. OCS in the northern Gulf of Mexico from approximately 9 km seaward of the 18 m isobath to

approximately 9 km seaward of the 183 m isobath and from the U.S.-Mexican border to the Florida Keys. The stock

range may extend into Mexican and Cuban territorial waters; however, there are no available estimates of either

abundance or mortality from those countries. As a working hypothesis, the bottlenose dolphins inhabiting the 0-18

m depth stratum are believed to constitute coastal stocks in the western, northern, and eastern U.S. Gulf of Mexico

separate from the OCS stock; however, the OCS stock may overlap with coastal stocks in some areas and may be

genetically indistinguishable from those stocks. The OCS stock may be combined with some or all of the coastal

stocks when additional data become available. 

In addition, the aerial surveys from which the current abundance estimates were derived overlapped the

outer continental shelf edge which is believed to be inhabited by the OCS edge and continental slope stock (Fig. 1). 

This stock is believed to consist of the deep, cold water ecotype described by Hersh and Duffield for the Atlantic

(1990). It is not currently possible to differentiate the two ecotypes visually during aerial surveys.

POPULATION SIZE

Preliminary estimates of abundance were derived using distance sampling analysis (Buckland et al. 1993)

and the computer program DISTANCE (Laake et al. 1993) with sighting data collected during Gulf of Mexico

regional aerial line-transect surveys in September-October 1992 and 1993 (Blaylock and Hoggard 1994) and 1994

(NMFS unpublished data). Transects providing systematic coverage of the area and assumed to be randomly placed

with respect to bottlenose dolphin distribution extended orthogonally from approximately 9 km past the 18 m isobath

to approximately 9 km past the

183 m isobath. Approximately

3.3% of the total area was

visually sampled. Preliminary

analyses provided a bottlenose

dolphin abundance estimate of

50,247 dolphins with coefficient

of variation (CV) = 0.18. The

survey area overlapped with a

portion of the area occupied by

the OCS edge and continental

slope stock which was assumed

to occur in waters over the OCS

edge and beyond to the seaward

limits of the U.S. Exclusive

Economic Zone. This would

tend to inflate the abundance

estimate, but it is not currently

possible to estimate the amount

of potential bias.

Minimum Population Estimate

The minimum population estimate was based on the abundance estimate of 50,247 dolphins (CV = 0.18). 

The minimum population estimate is the lower limit of the two-tailed 60% confidence interval of the log-normal

distributed abundance estimate, which is equivalent to the 20th percentile of the log-normal distribution as specified

by NMFS (Anon. 1994). The minimum population estimate is 43,233 bottlenose dolphins. 
238

Current Population Trend

The data are insufficient to determine population trends. Aerial surveys conducted during autumn 1983 and

1985 by the Southeast Fisheries Science Center (SEFSC) produced an abundance estimate of 31,519 bottlenose

dolphins (CV = 0.08) for this stock (Scott et al. 1989). This population thus appears to have increased from earlier

estimated levels; however, a valid statistical comparison of the historical and present estimated population sizes is

not presently possible because of the preliminary nature of the recent population size estimate and the possible biases

caused by overlap of the survey area with the OCS edge and continental slope stock. 

CURRENT AND MAXIMUM NET PRODUCTIVITY RATES

Current and maximum net productivity rates are not known for this stock. The maximum net productivity

rate was assumed to be 0.04 for purposes of this assessment. This value is based on theoretical calculations showing

that cetacean populations may not generally grow at rates much greater than 4% given the constraints of their

reproductive life history (Reilly and Barlow 1986). 

POTENTIAL BIOLOGICAL REMOVAL

Potential biological removal (PBR) was specified as the product of minimum population size, one-half the

maximum productivity rate, and a "recovery" factor for endangered, depleted, threatened stocks, or stocks of

unknown status relative to optimum sustainable population (OSP) (Anon. 1994). The recovery factor was set at 0.50

because of the stock's status relative to its OSP level is unknown. PBR for this stock is 432 bottlenose dolphins. 

ANNUAL HUMAN-CAUSED MORTALITY AND SERIOUS INJURY

There are no observed cases of human-caused mortality and serious injury in this stock; however, based on

an observed non-lethal take in U.S. Atlantic waters in 1993 in the pelagic longline fishery, this stock may be subject

to incidental take resulting in serious injury or mortality. Fishery interactions have been reported to occur between

bottlenose dolphins and the longline swordfish/tuna fishery in the Gulf of Mexico (SEFSC unpublished logbook

data) and annual fishery-related mortality and serious injury to bottlenose dolphins is estimated to be 2.8 per year

(CV = 0.74) during 1992-1993. This could include bottlenose dolphins from the outer continental shelf edge and

continental slope stock.

 Total fishery-related mortality and serious injury for this stock is less than 10% of the calculated PBR and,

therefore, can be considered to be insignificant and approaching zero mortality and serious injury rate. This

determination cannot be made for specific fisheries until the implementing regulations for Section 118 of the MMPA

have been reviewed by the public and finalized. 

Fishery Information

Annual fishing effort for the shrimp trawl fishery in the U.S. Gulf of Mexico OCS during 1988-1993

averaged approximately 2.58 million hours of tows (CV = 0.07) (NMFS unpublished data). This fishery was

monitored by NMFS observers in 1992 and 1993, but less than 1% of the fishing effort was observed (NMFS

unpublished data). There have been no reports of incidental mortality or injury associated with the shrimp trawl

fishery in this area. 

Pelagic swordfish, tunas, and billfish are the targets of the longline fishery operating in the U.S. Gulf of

Mexico. Total longline effort for the Gulf of Mexico pelagic fishery, including OCS edge, continental slope, and

Mexican territorial waters, based on mandatory logbook reporting, was 4,400 sets in 1991, 4,850 sets in 1992, and

3,260 sets in 1993 (Cramer 1994). This fishery has been monitored with about 5% observer coverage, in terms of

trips observed, since 1992. Estimated take was based on a generalized linear model (Poisson error assumption) fit to

the available observed incidental take and self-reported incidental take and effort data for the fishery. The following

estimates were based on observed takes across the Atlantic longline swordfish/tuna fishery (which includes the Gulf

of Mexico). All observed takes were used because the species occurs generally throughout the area of the fishery,

but observed takes were infrequent in any given region of the fishery. There were no lethal takes of bottlenose

dolphins observed or reported in 1992 and 1993, and only one non-lethal take was reported in 1993, which is

assumed to have caused serious injury. The estimated level of fishery-related mortality and serious injury for the

entire fishery, including waters outside of the Gulf of Mexico, in 1993 was 16 bottlenose dolphins (CV = 0.19). No

take was observed in the Gulf of Mexico, but interactions between bottlenose dolphins and this fishery in the Gulf of

Mexico have been reported under the Marine Mammal Protection Act Interim Exemption Program (NMFS 1993).
239

Given the fact that fishery interactions have been reported to occur between bottlenose dolphins and the

longline swordfish/tuna fishery in the Gulf of Mexico, a probable level of fishery-related mortality and serious injury

rate can be estimated. Under the assumption that the probability of an incidental take is proportional to fishing effort

(number of sets), the estimated level of incidental mortality and serious injury partitioned to include only the Gulf of

Mexico stock would be 5.5 bottlenose dolphins in 1993 (CV = 0.19). Average annual fishery-related mortality and

serious injury during 1992-1993 would be 2.8 bottlenose dolphins (CV= 0.74). This estimate could include dolphins

from the OCS edge and continental slope stock.

Pair trawl fishing gear has the potential to capture marine mammals, but there have been no reports of

mortality or serious injury to marine mammals in the Gulf of Mexico. This fishery has not been observed by NMFS

observers, and there are no other data available as to the extent of this fishery in the Gulf of Mexico. It is assumed

that it is very limited in scope and duration in the Gulf of Mexico. 

A trawl fishery for butterfish was monitored by NMFS observers for a short period in the 1980's with no

records of incidental take of marine mammals (Burn and Scott 1988; NMFS unpublished data), although an

experimental set by NMFS resulted in the death of two bottlenose dolphins (Burn and Scott 1988). There are no

other data available. 

Other Human-Related Mortality or Serious Injury

The use of explosives to remove oil rigs in the portions of the OCS in the western Gulf of Mexico has the

potential to cause serious injury or mortality to marine mammals. These activities have been closely monitored by

NMFS observers since 1987 (Gitschlag and Hale, in press) and Gitschlag and Herczeg (in press) described the

monitoring activities that occurred in 1992. There have been no reports of either serious injury or mortality to

bottlenose dolphins (NMFS unpublished data). 

STATUS OF STOCK

The status of this stock relative to OSP is not known and the population trend cannot be determined due to

insufficient data. This species is not listed as threatened or endangered under the Endangered Species Act. This is

not a strategic stock because fishery-related mortality and serious injury does not exceed PBR. 

REFERENCES

Anon. 1994. Report of the PBR (Potential Biological Removal) workshop. June 27-29, 1994. NOAA, NMFS

Southwest Fisheries Science Center, La Jolla, California, 13 pp. + Appendices. 

Blaylock, R. A. and W. Hoggard. 1994. Preliminary estimates of bottlenose dolphin abundance in southern U.S.

Atlantic and Gulf of Mexico continental shelf waters. NOAA Tech. Mem. NMFS-SEFSC-356, 10 pp. 

Buckland, S. T., D. R. Anderson, K. P. Burnham, and J. L. Laake. 1993. Distance sampling: Estimating abundance

of biological populations. Chapman & Hall, London, 446 pp. 

Burn, D. And G. P. Scott. 1988. Synopsis of available information on marine mammal-fisheries interactions in the

southeastern United States: preliminary report. NMFS/SEFC, Miami Laboratory, Coastal resources

Division, Contribution ML-CRG-87/88-26, 37 pp. 

Gitschlag, G. R. and J. K. Hale. In press. Susceptibility of sea turtles to underwater explosives at offshore energy

structure removals. Submitted to N. E. Gulf Science. 

Gitschlag, G. R. and B. A. Herczeg. In press. Sea turtle observations at explosive removals of energy structures. 

Submitted to Mar. Fish. Rev. 

Hersh, S. L. and D. A. Duffield. 1990. Distinction between northwest Atlantic offshore and coastal bottlenose

dolphins based on hemoglobin profile and morphometry. Pages 129-139 in S. Leatherwood and R. R.

Reeves (editors), The bottlenose dolphin, Academic Press, San Diego, 653 pp. 

Laake, J. L., S. T. Buckland, D. R. Anderson, and K. P. Burnham. DISTANCE user’s guide, V2.0. Colorado

Cooperative Fish & Wildlife Research Unit, Colorado State University, Ft. Collins, Colorado, 72 pp. 

Northridge, S. In review. Estimation of cetacean mortality in the U.S. Atlantic swordfish and tuna driftnet and pair

trawl fisheries. Draft final report to the Northeast Fisheries Science Center, Contract No. 40ENNF500045. 

18 pp. 

Reilly, S. B. and J. Barlow. 1986. Rates of increase in dolphin population size. Fish. Bull., U.S. 84(3): 527-533. 
240

Figure 1. Distribution of sightings of bottlenose dolphins during NOAA Ship

Oregon II marine mammal surveys in the Gulf of Mexico outer continental shelf

(OCS) edge and continental slope waters (filled circles). Sightings of the OCS

bottlenose dolphin stock made during GOMEX regional aerial surveys (unfilled

circles) are shown for comparison. The bottlenose dolphin on the OCS are

believed to be a separate stock. The straight lines show transects during two

ship surveys and are examples of typical ship survey transects. Isobaths are in

183 m (100 fm) intervals.

July 1995

BOTTLENOSE DOLPHIN (Tursiops truncatus):

Gulf of Mexico Continental Shelf Edge and Continental Slope Stock

STOCK DEFINITION AND GEOGRAPHIC RANGE

This bottlenose dolphin stock is defined as the stock which occupies the outer edge of the U.S. Gulf of

Mexico Outer Continental Shelf (OCS) and waters over the continental slope within the U.S. Exclusive Economic

Zone (EEZ), from the latitude and longitude of the U.S. EEZ off the U.S.-Mexico border to the latitude of the U.S.

EEZ south of Key West, Florida. Close observation by experienced NMFS observers from shipboard surveys

conducted throughout much of its range (Fig. 1) indicates that most of the dolphins sighted during ship-based

surveys over the continental shelf edge and continental slope were the relatively large and robust dolphins assumed

to be of the deep water ecotype hypothesized by Hersh and Duffield (1990). These dolphins were reported to be

larger and darker in color than bottlenose dolphins seen over the continental shelf closer to shore (NMFS

unpublished data). This stock’s range may extend into Mexican and Cuban waters; however, there are no estimates

available for bottlenose dolphin abundance or mortality from those countries.

POPULATION SIZE

Preliminary estimates of abundance were derived using distance sampling analysis (Buckland et al. 1993)

and the computer program DISTANCE (Laake et al. 1993) with sighting data collected during shipboard linetransect surveys conducted during the spring of 1992-1994 (Fig. 1). These surveys were conducted throughout the

area from approximately the 200 m isobath along the U.S. coast to the seaward extent of the U.S. Exclusive

Economic Zone. The seasonal GulfCet aerial surveys included only a small portion of the stock range and these data

were not used for abundance

estimation. Average bottlenose

dolphin abundance over six

surveys was estimated at 5,618

dolphins with coefficient of

variation (CV) = 0.26. In this

analysis, it was assumed that

all of the bottlenose dolphins

sighted during the ship-based

surveys were of this stock. The

survey area overlapped in some

areas with the OCS stock

which was assumed to occur

from approximately 9 km

seaward of the 18 m isobath to

approximately 9 km seaward of

the 183 m isobath; however,

the amount of overlap is

considered insignificant and its

effect on the abundance

estimate is not known. 

Minimum Population

Estimate

The minimum population estimate was based on the average bottlenose dolphin abundance estimate of

5,618 bottlenose dolphins (CV = 0.26). The minimum population estimate is the lower limit of the two-tailed 60%

confidence interval of the log-normal distributed abundance estimate, which is equivalent to the 20th percentile of
241

the log-normal distribution as specified by NMFS (Anon. 1994). The minimum population estimate is 4,530

bottlenose dolphins. 

Current Population Trend

The data are insufficient to determine population trends. 

CURRENT AND MAXIMUM NET PRODUCTIVITY RATES

Current and maximum net productivity rates for this stock are unknown. The maximum net productivity

rate for purposes of this assessment, was assumed to be 0.04. This value is based on theoretical calculations

showing that cetacean populations may not generally grow at rates much greater than 4% given the constraints of

their reproductive life history (Reilly and Barlow, 1986). 

POTENTIAL BIOLOGICAL REMOVAL

Potential biological removal (PBR) has been specified as the product of minimum population size, one-half

the maximum productivity rate, and a "recovery" factor for endangered, depleted, threatened stocks, or stocks of

unknown status relative to optimum sustainable population (OSP). The recovery factor was 0.50 because of the

stock's unknown status relative to OSP. PBR for this stock is 45 bottlenose dolphins. 

ANNUAL HUMAN-CAUSED MORTALITY AND SERIOUS INJURY

There are no observed cases of human-caused mortality and serious injury in this stock; however, based on

an observed non-lethal take in U.S. Atlantic waters in 1993 in the pelagic longline fishery, this stock may be subject

to incidental take resulting in serious injury or mortality. Fishery interactions have been reported to occur between

bottlenose dolphins and the longline swordfish/tuna fishery in the Gulf of Mexico [Southeast Fisheries Science

Center (SEFSC) unpublished logbook data] and annual fishery-related mortality and serious injury to bottlenose

dolphins is estimated to be 2.8 per year (CV = 0.74) during 1992-1993. This estimate could include bottlenose

dolphins from the OCS stock.

The total fishery-related mortality and serious injury for this stock is less than 10% of the calculated PBR

and, therefore, can be considered to be insignificant and approaching zero mortality and serious injury rate. This

determination cannot be made for specific fisheries until the implementing regulations for Section 118 of the MMPA

have been reviewed by the public and finalized. 

Fishery Interaction

Pelagic swordfish, tunas, and billfish are the targets of the longline fishery operating in the U.S. Gulf of

Mexico. Total longline effort for the Gulf of Mexico pelagic fishery, including OCS edge, continental slope, and

Mexican territorial waters, based on mandatory logbook reporting, was 4,400 sets in 1991, 4,850 sets in 1992, and

3,260 sets in 1993 (Cramer 1994). This fishery has been monitored with about 5% observer coverage, in terms of

trips observed, since 1992. Estimated take was based on a generalized linear model (Poisson error assumption) fit to

the available observed incidental take and self-reported incidental take and effort data for the fishery. The following

estimates were based on observed takes across the Atlantic longline swordfish/tuna fishery (which includes the Gulf

of Mexico). All observed takes were used because the species occurs generally throughout the area of the fishery,

but observed takes were infrequent in any given region of the fishery. There were no lethal takes of bottlenose

dolphins observed or reported in 1992 and 1993, and only one non-lethal take was reported in 1993, which is

assumed to have caused serious injury. The estimated level of fishery-related mortality and serious injury for the

entire fishery, including waters outside of the Gulf of Mexico, in 1993 was 16 bottlenose dolphins (CV = 0.19). No

take was observed in the Gulf of Mexico, but there are logbook reports of interactions between bottlenose dolphins

and this fishery (SEFSC unpublished logbook data).

Given the fact that fishery interactions have been reported to occur between bottlenose dolphins and the

longline swordfish/tuna fishery in the Gulf of Mexico, a probable level of fishery-related mortality and serious injury

rate can be estimated. Under the assumption that the probability of an incidental take is proportional to fishing effort

(number of sets), the estimated level of incidental mortality and serious injury partitioned to include only the Gulf of

Mexico stock would be 5.5 bottlenose dolphins in 1993 (CV = 0.19). Average annual fishery-related mortality and

serious injury during 1992-1993 would be 2.8 bottlenose dolphins (CV= 0.74). This estimate could include dolphins

from the OCS stock. 
242

Pair trawl fishing gear has the potential to capture marine mammals, but there have been no reports of

mortality or serious injury to marine mammals in the Gulf of Mexico. This fishery has not been observed by NMFS

observers, and there are no other data available as to the extent of this fishery in the Gulf of Mexico. It is assumed

that it is very limited in scope and duration. 

A trawl fishery for butterfish was monitored by NMFS observers for a short period in the 1980's with no

records of incidental take of marine mammals (Burn and Scott 1988; NMFS unpublished data), although an

experimental NMFS set resulted in the death of two bottlenose dolphins (Burn and Scott 1988). There are no other

data available. 

Other Mortality

No direct or indirect human-caused mortality has been reported for this stock. 

STATUS OF STOCK

The status of this stock relative to OSP is not known and the population trend cannot be determined due to

insufficient data. This species is not listed as threatened or endangered under the Endangered Species Act. This is

not a strategic stock because fishery-related mortality or serious injury does not exceed PBR. 

REFERENCES

Anon. 1994. Report of the PBR (Potential Biological Removal) workshop. June 27-29, 1994. NOAA, NMFS

Southwest Fisheries Science Center, La Jolla, California, 13 pp. + Appendices. 

Buckland, S. T., D. R. Anderson, K. P. Burnham, and J. L. Laake. 1993. Distance sampling: Estimating abundance

of biological populations. Chapman & Hall, London, 446 pp. 

Burn, D. And G. P. Scott. 1988. Synopsis of available information on marine mammal-fisheries interactions in the

southeastern United States: preliminary report. NMFS/SEFC, Miami Laboratory, Coastal resources

Division, Contribution ML-CRG-87/88-26, 37 pp. 

Cramer, J. 1994. Large pelagic logbook newsletter - 1993. NOAA Tech. Mem. NMFS-SEFSC-352, 19 pp. 

Hersh, S. L. and D. A. Duffield. 1990. Distinction between northwest Atlantic offshore and coastal bottlenose

dolphins based on hemoglobin profile and morphometry. Pages 129-139 in S. Leatherwood and R. R.

Reeves (editors), The bottlenose dolphin, Academic Press, San Diego, 653 pp. 

Laake, J. L., S. T. Buckland, D. R. Anderson, and K. P. Burnham. DISTANCE user’s guide, V2.0. Colorado

Cooperative Fish & Wildlife Research Unit, Colorado State University, Ft. Collins, Colorado, 72 pp. 

Northridge, S. In review. Estimation of cetacean mortality in the U.S. Atlantic swordfish and tuna driftnet and pair

trawl fisheries. Draft final report to the Northeast Fisheries Science Center, Contract No. 40ENNF500045. 

18 pp. 

Reilly, S. B. and J. Barlow. 1986. Rates of increase in dolphin population size. Fish. Bull., U.S. 84(3): 527-533.
243

Figure 1. Sightings of coastal bottlenose dolphins during GOMEX aerial

surveys of the Gulf of Mexico in 1992-1994. Western Gulf of Mexico coastal

bottlenose dolphin stock is shown with filled circles. Isobaths are in 183 m

(100 fm) intervals.

August 1997

BOTTLENOSE DOLPHIN (Tursiops truncatus):

Western Gulf of Mexico Coastal Stock

STOCK DEFINITION AND GEOGRAPHIC RANGE

The western Gulf of Mexico coastal bottlenose dolphin stock has been defined for management purposes as

the bottlenose dolphins inhabiting the nearshore coastal waters in the U.S. Gulf of Mexico from the Texas border to

the Mississippi River mouth, from shore or presumed bay boundaries to 9.3 km seaward of the 18.3 m isobath (Fig.

1). As a working hypothesis, it is assumed that the dolphins occupying habitats with dissimilar climactic, coastal,

and oceanographic characteristics might be restricted in their movements between habitats and, thus, constitute

separate stocks. The western coastal area is characterized by an arid to temperate climate, sand beaches, and low

fresh water input. The northern coastal stock area which is characterized by a temperate climate, barrier islands,

sand beaches, coastal marshes and marsh islands, and has a relatively high level of fresh water input from rivers and

streams. The eastern coastal stock area is temperate to subtropical in climate, is bordered by a mixture of coastal

marshes, sand beaches, marsh and mangrove islands, and has an intermediate level of freshwater input.

The stock occurs trans-boundary with Mexico; however, there is no information available for abundance

estimation, nor for estimating

fishery-related mortality in

Mexican waters. The ratio of

DDE to DDT was extraordinarily

high in tissues of one bottlenose

dolphin stranded on the Texas

coast (Varanasi et al. 1992),

suggesting recent exposure to

DDT which is still in use in

Mexico. 

The Mississippi River

outflow may constitute an

effective ecological barrier to

stock migration at the eastern

boundary. This assumption has

not been tested and interbreeding

may, in fact, occur between this

and the northern coastal stock at

this boundary; therefore, the

definition of this stock may be

revised and the stock may be incorporated with the northern coastal stock when more data become available. There

are data which suggest that there is considerable alongshore movement by some members of the western coastal

stock (NMFS unpublished data), but the extent of this movement is unknown. 

Some of this stock may co-occur with the resident bay, sound, and estuarine stocks, and breeding may

occur among these stocks. For instance, two bottlenose dolphins previously seen in the South Padre Island area in

Texas were seen in Matagorda Bay, 285 km north, in May 1992 and May 1993 (Lynn 1995). These sightings

suggest that some bay stocks dolphins occasionally traverse the coastal stock area. 

Portions of this stock may co-occur with the U.S. Gulf of Mexico outer continental shelf (OCS) stock. The

seaward boundary for this stock corresponds to aerial survey strata (NMFS unpublished data) and thus, represents a

management boundary rather than an ecological boundary. Anecdotal evidence suggests that both the coastal and

OCS stocks consist of the shallow, warm water ecotype described by Hersh and Duffield (1990). Data are not

currently available to determine genetically if the two stocks should be separated or, if so, where; and interbreeding

may occur at the boundary interface. 
244

POPULATION SIZE

Preliminary abundance estimates were derived using distance sampling analysis (Buckland et al. 1993) and

the computer program DISTANCE (Laake et al. 1993) with sighting data collected during aerial line-transect

surveys in September-October 1992 (Blaylock and Hoggard 1994). Sampling transects extended orthogonally from

shore out to approximately 9 km past the 18 m isobath. The 1992 coastal survey area extended from the U.S. -

Mexican border to the Mississippi River mouth. Systematic transects were placed randomly with respect to

bottlenose dolphin distribution and provided approximately 5% visual coverage of the survey area. Bottlenose

dolphin abundance was estimated to be 3,499 dolphins (CV = 0.21) (Blaylock and Hoggard 1994). 

Minimum Population Estimate

The minimum population estimate was based on the 1992 abundance estimate of 3,499 bottlenose dolphins

(CV = 0.21) (Blaylock and Hoggard 1994). The minimum population estimate is the lower limit of the two-tailed

60% confidence interval of the log-normally distributed abundance estimate. This is equivalent to the 20th

percentile of the log-normal distribution as specified by Wade and Angliss (1997). The minimum population

estimate is 2,938 bottlenose dolphins. 

Current Population Trend

 Aerial surveys of this area conducted by NMFS in autumn 1983 resulted in an estimated bottlenose

dolphin abundance of 4,718 (CV = 0.10). The data are not sufficient to conduct a statistical trend analysis, but the

current population size estimate is significantly lower than the 1983 estimate (Student's t-test, P < 0.001) and

suggests a decline in stock abundance. 

This stock was subject to higher than usual mortality levels in 1990, 1992, and 1993-94, and the incidence

of bottlenose dolphin strandings along the Texas coast in those years was significantly higher than the 1984-94 mean

stranding rate (Southeast U.S. Marine Mammal Stranding Network unpublished data). Some of these mortalities

may have been related to accumulation of anthropogenic hydrocarbon contaminants. A recent study indicated an

inverse relationship between hydrocarbon contaminant levels and certain bacterial and viral antigen titers in

bottlenose dolphins from Matagorda Bay, Texas (Reif et al., in review). 

CURRENT AND MAXIMUM NET PRODUCTIVITY RATES

Current and maximum net productivity rates are not known for this stock. The maximum net productivity

rate was assumed to be 0.04. This value is based on theoretical modeling showing that cetacean populations may not

grow at rates much greater than 4% given the constraints of their reproductive life history (Barlow et al. 1995). 

POTENTIAL BIOLOGICAL REMOVAL

Potential Biological Removal (PBR) is the product of minimum population size, one-half the maximum

productivity rate, and a “recovery” factor (Wade and Angliss 1997). The “recovery “ factor, which accounts for

endangered, depleted, and threatened stocks, or stocks of unknown status relative to optimum sustainable population

(OSP)is assumed to be 0.5 because this stock is of unknown status, because of an undetermined level of fisheryrelated mortality, and because of the recent occurrence of three anomalous mortality events. PBR for this stock is 29

dolphins. 

ANNUAL HUMAN-CAUSED MORTALITY AND SERIOUS INJURY

The level of direct human-caused mortality in this stock is unknown. An annual mean of 13 (CV = 0.46)

bottlenose dolphins stranded on the Texas coast during the period 1988-1993, showing signs of fishery interactions

such as net entanglement, mutilation, gunshot wounds, etc. (Southeast U.S. Marine Mammal Stranding Network

unpublished data). This was 10.3% of the total bottlenose dolphin strandings reported for this area. There were 283

reported bottlenose dolphin strandings in Texas (1994), of these 7 (2%) showed signs of human interaction. Three

had evidence of fishery entanglement, one of which was found in a shrimp trawl, three were mutilated and one was

shot. In 1995 the total number of reported bottlenose dolphins in Texas for 1995 was 110 and 3 (3%) were human

interactions. One was found in a shrimp trawl. The total bottlenose dolphin strandings from January through August

31, 1996 was 175 and 1 (0.5%) had evidence of human interaction (entanglement).

 There are a number of difficulties associated with the interpretation of stranding data. It is possible that

some or all of the stranded dolphins may have been from a bay, sound or estuarine stock; however, the proportion of
245

the stranded dolphins belonging to another stock cannot be determined because of the difficulty of determining from

where the stranded carcass originated. Stranding data probably underestimate the extent of fishery-related mortality

and serious injury because not all of the dolphins which die or are seriously injured in fishery interactions wash

ashore, nor will all of those that do wash ashore necessarily show signs of entanglement or other fishery-interaction. 

Finally, the level of technical expertise among stranding network personnel varies widely as does the ability to

recognize signs of fishery interaction.

Fisheries Information

Annual fishing effort for the shrimp trawl fishery in the western Gulf of Mexico coastal stock area during

1988-1993 averaged approximately 0.35 million hours of tows (CV = 0.16) (NMFS unpublished data). This fishery

was monitored by NMFS observers in 1992 and 1993, but less than 1% of the fishing effort was observed (NMFS

unpublished data). There have been no reports of incidental mortality or injury in the western Gulf of Mexico

coastal bottlenose dolphin stock associated with the shrimp trawl fishery in this area. 

 The menhaden purse seine fishery targets the Gulf menhaden, Brevoortia patronus, in Gulf of Mexico

coastal waters approximately 3-18 m in depth (NMFS 1991). Seventy-five menhaden vessels operate within 1.6 km

of shore from Apalachicola, Florida to Freeport, Texas, from April-October. Lethal takes of bottlenose dolphins

reported by the menhaden fishery during the period 1982-1988 ranged between 0-4 dolphins annually (NMFS

unpublished data). 

Gillnets are not used in Texas, and gillnets over 46 m3

 in area will not be allowed in Florida past July 1995,

but fixed and runaround gillnets are currently in use in Louisiana, Mississippi, and Alabama. These fisheries, for the

most part, operate year around. They are state-controlled and licensed, and vary widely in intensity and target

species. No marine mammal mortalities associated with gillnet fisheries have been reported in these states, but

stranding data suggest that gillnet and marine mammal interaction does occur, causing mortality and serious injury. 

The fishery for blue crabs operates in estuarine areas throughout the Gulf coast employing traps attached to

a buoy with rope. Bottlenose dolphins have been reported stranded in Mississippi with polypropylene rope around

their flukes indicating the possibility of entanglement with crab pot lines (NMFS 1991); however, this fishery has

not been monitored by observers. 

Two bottlenose dolphins were entangled and died in a scientific research net fishery for sea turtles in Sabine

Pass in 1993 (A. Landry, Texas A&M University, report to Texas Marine Mammal Stranding Network, August

1993). The nets used in this Endangered Species Act (ESA) permitted research activity were two 4.9 m deep x 91.5

m in length stationary entanglement nets adjacent to each other. They were fished in shallow water (0.9-2.5 m

depth), monitored continuously throughout the day, and removed at night. 

Other Mortality

The coast adjacent to the nearshore habitat occupied by this stock varies from agricultural to industrial and,

in some places, such as Galveston Island, is dense in human population. Concentrations of chlorinated hydrocarbons

and metals were relatively low in most of the bottlenose dolphins examined in conjunction with an anomalous

mortality event in Texas bays in 1990; however, some had concentrations at levels of possible toxicological concern

(Varanasi et al. 1992). Agricultural runoff following periods of high rainfall in 1992 was implicated in a high level

of bottlenose dolphin mortalities in Matagorda Bay, which is adjacent to the western coastal stock area (NMFS

unpublished data). A recent study of hydrocarbon contaminant levels was conducted in conjunction with a health

assessment study of 35 live-captured bottlenose dolphins in Matagorda Bay which adjoins the coastal stock area. 

Alpha-HCB, p,p,DDE, and PCB concentrations were inversely related to the magnitude of the serum antibody titer

to Erysipelas spp. and Staphylococcus spp. bacteria (Reif et al., in review.). A similar and more pronounced trend

was seen in relationship to the pseudorabies virus; however, since pseudorabies virus is not known to infect

bottlenose dolphins, the significance of this finding is not clear. Concentrations of contaminants were higher in

dolphins having evidence of exposure to the cetacean morbillivirus. The reason for the difference in the relationship

between antibody titers to bacteria and pseudorabies and antibody titers to cetacean morbillivirus is not understood. 

STATUS OF STOCK

The status of this stock relative to OSP is unknown. A population trend analysis is not available due to

insufficient information. This species is not listed as threatened or endangered under the ESA. The occurrence of

three anomalous mortality events among bottlenose dolphins along the Texas coast since 1990 (NMFS unpublished

data) is cause for concern and the available evidence suggests that bottlenose dolphin stocks in the northern and
246

western portion of the U.S. Gulf of Mexico may have experienced a morbillivirus epidemic in 1993 (Lipscomb

1993); however, the effects of these events on stock abundance has yet to be determined. The total fishery-related

mortality and serious injury for this stock is not less than 10% of the calculated PBR and, therefore, cannot be

considered to be insignificant and approaching zero mortality and serious injury rate. This is not a strategic stock

because the known level of fishery-related mortality or serious injury does not exceed PBR. 

REFERENCES

Barlow, J., S.L. Swartz, T.C. Eagle, and P.R. Wade. 1995. U.S. Marine Mammal Stock Assessments: Guidelines for

Preparation, Background and a Summary of the 1995 Assessments. U.S. Dep. Commer., NOAA Tech.

Memo. NMFS-OPR-6, 73 pp.

Blaylock R. A. and W. Hoggard. 1994. Preliminary estimates of bottlenose dolphin abundance in southern U.S.

Atlantic and Gulf of Mexico continental shelf waters. NOAA Tech. Mem. NMFS-SEFSC-356, 10 pp. 

Buckland, S. T., D. R. Anderson, K. P. Burnham, and J. L. Laake. 1993. Distance sampling: Estimating abundance

of biological populations. Chapman & Hall, London, 446 pp. 

Hersh, S. L. and D. A. Duffield. 1990. Distinction between northwest Atlantic offshore and coastal bottlenose

dolphins based on hemoglobin profile and morphometry. Pages 129-139 in S. Leatherwood and R. R.

Reeves (editors), The bottlenose dolphin, Academic Press, San Diego, 653 pp. 

Laake, J. L., S. T. Buckland, D. R. Anderson, and K. P. Burnham. 1993. DISTANCE user’s guide, V2.0. Colorado

Cooperative Fish & Wildlife Research Unit, Colorado State University, Ft. Collins, Colorado, 72 pp. 

Lipscomb, T. P. 1993. Some answers to questions about morbillivirus. Pages 4-5 in R. A. Blaylock, B. Mase, and

D. K. Odell (editors), Strandings - Newsletter of the Southeast U.S. Marine Mammal Stranding Network,

Vol. 2 No. 3, Southeast Fisheries Science Center, Miami Laboratory, Miami, Florida, 8 pp. 

NMFS. 1991. Proposed regime to govern the interactions between marine mammals and commercial fishing

operations after October 1, 1993. Draft Environmental Impact Statement. June 1991. 

Reif, J. S., L. J. Hansen, S. Galloway, G. Mitchum, T. L. Schmitt. In review. The relationship between chlorinated

hydrocarbon contaminants and selected health parameters in bottlenose dolphins (Tursiops truncatus) from

Matagorda Bay, Texas, 1992. Colorado State University, Fort Collins, and NMFS, Southeast Fisheries

Science Center, Miami, Florida. 

Varanasi, U., K. L. Tilbury, D. W. Brown, M. M. Krahn, C. A. Wigren, R. C. Clark, and S-L. Chan. 1992. Pages

56-86 in L. J. Hansen (editor), Report on investigation of 1990 Gulf of Mexico bottlenose dolphin

strandings, Southeast Fisheries Science Center Contribution MIA-92/93-21, 219 pp. 

Wade, P.R., and R.P. Angliss. 1997. Guidelines for assessing marine mammal stocks: Report of the GAMMS

Workshop April 3-5, Seattle, Washington. U.S. Dep. Commer., NOAA Tech. Memo. NMFS-OPR-12, 93

pp.
247

Figure 1. Sightings of coastal bottlenose dolphins during GOMEX aerial

surveys of the Gulf of Mexico in 1992-1994. Northern Gulf of Mexico coastal

bottlenose dolphin stock is shown with filled circles. Isobaths are in 183 m (100

fm) intervals.

August 1997

BOTTLENOSE DOLPHIN (Tursiops truncatus):

Northern Gulf of Mexico Coastal Stock

STOCK DEFINITION AND GEOGRAPHIC RANGE

The northern Gulf of Mexico coastal bottlenose dolphin stock has been defined for management purposes

as those bottlenose dolphins occupying the nearshore coastal waters in the U.S. Gulf of Mexico from the Mississippi

River mouth to approximately 84o

 W longitude, from shore, barrier islands, or presumed bay boundaries to 9.3 km

seaward of the 18.3 m isobath (Fig. 1). As a working hypothesis, it is assumed that the dolphins occupying habitats

with dissimilar climactic, coastal, and oceanographic characteristics might be restricted in their movements between

habitats and, thus, constitute separate stocks. The northern coastal stock area is characterized by a temperate

climate, barrier islands, sand beaches, coastal marshes and marsh islands, and has a relatively high level of fresh

water input from rivers and streams. It is bordered on the east by an extensive area of coastal marsh and marsh

islands typical of Florida’s Apalachee Bay. The western coastal area is characterized by an arid to temperate

climate, sand beaches, and low fresh water input. The eastern coastal stock area is temperate to subtropical in

climate, is bordered by a mixture of coastal marshes, sand beaches, marsh and mangrove islands, and has an

intermediate level of freshwater

input.

The definition of this

stock may be changed and it

may be incorporated with other

Gulf of Mexico stocks when

more data become available. 

Seasonal changes in bottlenose

dolphin abundance in

Mississippi Sound (NMFS

unpublished data) suggests that

there is interchange with at least

that portion of the Gulf of

Mexico bay and sound stocks;

however, its extent and

significance is not presently

known. Portions of this stock

may co-occur with the U.S. Gulf

of Mexico outer continental

shelf (OCS) stock. The seaward

boundary for this stock corresponds to aerial survey strata (NMFS unpublished data) and thus, represents a

management boundary rather than an ecological boundary. Anecdotal evidence suggests that both the coastal and

OCS stocks consist of the shallow, warm water ecotype described by Hersh and Duffield (1990). Data are not

currently available to determine genetically if the stocks should be separated or, if so, where; and interbreeding may

occur at the boundary interface. 

POPULATION SIZE

Preliminary estimates of abundance were derived using distance sampling analysis (Buckland et al.1993)

and the computer program DISTANCE (Laake et al. 1993) with sighting data collected during aerial line-transect

surveys in September-October 1993 (Blaylock and Hoggard 1994). Systematic sampling transects, placed randomly

with respect to the bottlenose dolphin distribution, extended orthogonally from shore out to approximately 9 km past

the 18 m isobath. The area surveyed extended from the Mississippi River mouth to approximately 84o

 W Longitude,

and approximately 5% of the total area was visually searched. Bottlenose dolphin abundance was estimated to be

4,191 dolphins with coefficient of variation (CV) = 0.21 (Blaylock and Hoggard 1994). 
248

Minimum Population Estimate

The minimum population estimate was based on the 1993 abundance estimate of 4,191 dolphins (CV =

0.21) (Blaylock and Hoggard 1994). The minimum population estimate is the lower limit of the two-tailed 60%

confidence interval of the log-normally distributed abundance estimate. This is equivalent to the 20th percentile of

the log-normal distribution as specified by Wade and Angliss (1997). The minimum population estimate is 3,518

bottlenose dolphins. 

Current Population Trend

 Aerial surveys of this area conducted partly in autumn 1983 and partly in autumn 1985, by NMFS resulted

in an estimated bottlenose dolphin abundance of 1,319 (CV = 0.10). The data are not sufficient to conduct a

statistical trend analysis, but the current population size estimate is significantly higher than the 1983-85 estimate

(Student's t-test, P < 0.005). 

CURRENT AND MAXIMUM NET PRODUCTIVITY RATES

Current and maximum net productivity rates are not known for this stock. The maximum net productivity

rate was assumed to be 0.04. This value is based on theoretical modeling showing that cetacean populations may not

grow at rates much greater than 4% given the constraints of their reproductive life history (Barlow et al. 1995).

POTENTIAL BIOLOGICAL REMOVAL

Potential Biological Removal (PBR) is the product of minimum population size, one-half the maximum

productivity rate, and a “recovery” factor (Wade and Angliss 1997). The “recovery “ factor, which accounts for

endangered, depleted, and threatened stocks, or stocks of unknown status relative to optimum sustainable population

(OSP)is assumed to be 0.5 because this stock is of unknown status, because the stock apparently sustains some

unknown level of fishery-related mortality, and because of the unknown effects of the 1993 mortality event. PBR

for this stock is 35 dolphins. 

ANNUAL HUMAN-CAUSED MORTALITY AND SERIOUS INJURY

The level of direct human-caused mortality in this stock is unknown. An annual average of ten bottlenose

dolphins (CV = 0.41) stranded on the coast of Louisiana, Mississippi, or Alabama during the period 1988-1993,

showing signs of fishery interactions such as net entanglement, mutilation, gunshot wounds, etc. (Southeast U.S.

Marine Mammal Stranding Network unpublished data). This was 8.2% of the total bottlenose dolphin strandings

reported for this area. In 1994, the Stranding Network reported a total of 92 bottlenose dolphins in Mississippi,

Louisiana and Alabama, four (4%) were reported as showing signs of human interaction. One was a boat strike, one

entangled in fishing gear and 2 had gun shot wounds. There were 78 strandings reported in 1995 in the northern

Gulf and 10 (12%) had evidence of human interaction; 6 were entanglements (2 were found wrapped in a square

gillnet), two mutilations and 2 had gunshot wounds. A total of 120 bottlenose dolphin strandings was reported from

January through August 31, 1996, and four (3%) of these were reported as human interactions (2 net entanglements,

1 boat strike and one mutilation).

 There are a number of difficulties associated with the interpretation of stranding data. It is possible that

some or all of the stranded dolphins may have been from a bay, sound or estuarine stock; however, the proportion of

the stranded dolphins belonging to another stock cannot be determined because of the difficulty of determining from

where the stranded carcass originated. Stranding data probably underestimate the extent of fishery-related mortality

and serious injury because not all of the dolphins which die or are seriously injured in fishery interactions wash

ashore, nor will all of those that do wash ashore necessarily show signs of entanglement or other fishery-interaction. 

Finally, the level of technical expertise among stranding network personnel varies widely as does the ability to

recognize signs of fishery interaction.

Fisheries Information

Annual fishing effort for the shrimp trawl fishery in the northern Gulf of Mexico coastal stock area during

1988-1993 averaged approximately 2.17 million hours of tows (CV = 0.13) (NMFS unpublished data). This fishery

was monitored by NMFS observers in 1992 and 1993, but less than 1% of the fishing effort was observed (NMFS

unpublished data). There have been no reports of incidental mortality or injury in the northern Gulf of Mexico

coastal bottlenose dolphin stock associated with the shrimp trawl fishery in this area. 
249

 The menhaden purse seine fishery targets the Gulf menhaden, Brevoortia patronus, in Gulf of Mexico

coastal waters approximately 3-18 m in depth (NMFS 1991). Seventy-five menhaden vessels operate within 1.6 km

of shore from Apalachicola, Florida to Freeport, Texas, from April-October. Lethal takes of bottlenose dolphins

reported by the menhaden fishery during the period 1982-1988 ranged between 0-4 dolphins annually (NMFS

unpublished data). 

Other clupeid purse seiners opportunistically target Spanish sardine, thread herring, ladyfish, cigarfish, and

blue runners. Single boat purse seiners, fishing for sardines and herrings, operate in coastal waters between the

Mississippi River delta and Pascagoula, Mississippi and in the Florida panhandle between Pensacola and

Apalachicola. It is estimated that ten vessels participate in this fishery between May-October. There are no

estimates of dolphin mortality associated with this fishery. 

Gillnets are not used in Texas, and gillnets over 46 m3

 in area will not be allowed in Florida past July 1995,

but fixed and runaround gillnets are currently in use in Louisiana, Mississippi, and Alabama. These fisheries, for the

most part, operate year around. They are state-controlled and licensed, and vary widely in intensity and target

species. No marine mammal mortalities associated with gillnet fisheries have been reported in these states, but

stranding data suggest that gillnet and marine mammal interaction does occur, causing mortality and serious injury. 

The fishery for blue crabs operates in estuarine areas throughout the Gulf coast employing traps attached to

a buoy with rope. Bottlenose dolphins have been reported stranded in Mississippi with polypropylene rope around

their flukes indicating the possibility of entanglement with crab pot lines (NMFS 1991); however, this fishery has

not been monitored by observers. 

Other Mortality

The nearshore habitat occupied by this stock is adjacent to areas of high human population. Two stranded

dolphins from the northern Gulf coastal area (one from Mississippi and one from Alabama) had the highest levels of

DDT derivatives of any of the bottlenose dolphin liver samples analyzed in conjunction with the 1990 mortality

investigation conducted by NMFS (Varanasi et al. 1992). The significance of these findings are unclear, but there is

some evidence that increased exposure to anthropogenic compounds may reduce immune function in bottlenose

dolphins. A recent study found the magnitude of the serum antibody titer to Erysipelas spp. and Staphylococcus spp.

bacteria in bottlenose dolphins was inversely related to "-HCB, p,p,DDE, and PCB's concentrations (Reif et al., in

review). 

This stock was subject to a high incidence of mortality in 1993, which was suspected to have been the result

of a morbillivirus epidemic. The effect of this mortality event on the stock cannot be determined, in part, because

the mortality may have also affected the bay, sound and estuarine stock and the stock identity of the stranded

animals could not be determined. The increase in mortalities began in the Florida panhandle area and moved

westward during that period (NMFS unpublished data). Concentrations of contaminants were found to be higher in

dolphins having evidence of exposure to the cetacean morbillivirus (Reif et al., in review). The reason for the

relationship between cetacean morbillivirus antibody titers and high contaminant levels is not understood and the

effect of the epidemic on this stock has not been determined. 

STATUS OF STOCK

The status of this stock relative to OSP is not known and population trends cannot be determined due to

insufficient data. This species is not listed as threatened or endangered under the Endangered Species Act. The total

fishery-related mortality and serious injury for this stock is unknown, but considering the evidence from stranding

data, it may not be less than 10% of the calculated PBR and, therefore, cannot be considered to be insignificant and

approaching zero mortality and serious injury rate. This is not a strategic stock because the known level of fisheryrelated mortality or serious injury does not exceed PBR. 
250

REFERENCES

Barlow, J., S.L. Swartz, T.C. Eagle, and P.R. Wade. 1995. U.S. Marine Mammal Stock Assessments: Guidelines for

Preparation, Background and a Summary of the 1995 Assessments. U.S. Dep. Commer., NOAA Tech.

Memo. NMFS-OPR-6, 73 pp.. 

Blaylock, R. A. and W. Hoggard. 1994. Preliminary estimates of bottlenose dolphin abundance in southern U.S.

Atlantic and Gulf of Mexico continental shelf waters. NOAA Tech. Mem. NMFS-SEFSC-356, 10 pp.

Buckland, S. T., D. R. Anderson, K. P. Burnham, and J. L. Laake. 1993. Distance sampling: Estimating abundance

of biological populations. Chapman & Hall, London, 446 pp. 

Hersh, S. L. and D. A. Duffield. 1990. Distinction between northwest Atlantic offshore and coastal bottlenose

dolphins based on hemoglobin profile and morphometry. Pages 129-139 in S. Leatherwood and R. R.

Reeves (editors), The bottlenose dolphin, Academic Press, San Diego, 653 pp. 

Laake, J. L., S. T. Buckland, D. R. Anderson, and K. P. Burnham. 1993. DISTANCE user’s guide, V2.0. Colorado

Cooperative Fish & Wildlife Research Unit, Colorado State University, Ft. Collins, Colorado, 72 pp. 

Lipscomb, T. P. 1993. Some answers to questions about morbillivirus. Pages 4-5 in R. A. Blaylock, B. Mase, and

D. K. Odell (editors), Strandings - Newsletter of the Southeast U.S. Marine Mammal Stranding Network,

Vol. 2 No. 3, Southeast Fisheries Science Center, Miami Laboratory, Miami, Florida, 8 pp. 

NMFS. 1991. Proposed regime to govern the interactions between marine mammals and commercial fishing

operations after October 1, 1993. Draft Environmental Impact Statement. June 1991. 

Reif, J. S., L. J. Hansen, S. Galloway, G. Mitchum, T. L. Schmitt. In review. The relationship between chlorinated

hydrocarbon contaminants and selected health parameters in bottlenose dolphins (Tursiops truncatus) from

Matagorda Bay, Texas, 1992. Colorado State University, Fort Collins, and NMFS, Southeast Fisheries

Science Center, Miami, Florida. 

Wade, P.R., and R.P. Angliss. 1997. Guidelines for assessing marine mammal stocks: Report of the GAMMS

Workshop April 3-5, Seattle, Washington. U.S. Dep. Commer., NOAA Tech. Memo. NMFS-OPR-12, 93

pp.
251

0

0

0

0

0

Figure 1. Sightings of coastal bottlenose dolphins during GOMEX aerial

surveys of the Gulf of Mexico in 1992-1994. Eastern Gulf of Mexico coastal

bottlenose dolphin stock is shown with filled circles. Isobaths are in 183 m (100

fm) intervals.

August 1997

BOTTLENOSE DOLPHIN (Tursiops truncatus):

Eastern Gulf of Mexico Coastal Stock

STOCK DEFINITION AND GEOGRAPHIC RANGE

 The eastern Gulf of Mexico coastal bottlenose dolphin stock has been defined for management purposes as

the bottlenose dolphins occupying the area which extends from approximately 84o

 W Longitude to Key West,

Florida, from shore, barrier islands, or presumed bay boundaries to 9.3 km seaward of the 18.3 m isobath (Fig. 1). 

As a working hypothesis, it is assumed that the dolphins occupying habitats with dissimilar climactic, coastal, and

oceanographic characteristics might be restricted in their movements between habitats and, thus, constitute separate

stocks. The eastern coastal stock area is temperate to subtropical in climate, is bordered by a mixture of coastal

marshes, sand beaches, marsh

and mangrove islands, and has

an intermediate level of

freshwater input. It is bordered

on the north by an extensive area

of coastal marsh and marsh

islands typical of Florida’s

Apalachee Bay. The western

coastal area is characterized by

an arid to temperate climate,

sand beaches, and low fresh

water input. The northern

coastal stock area is

characterized by a temperate

climate, barrier islands, sand

beaches, coastal marshes and

marsh islands, and has a

relatively high level of fresh

water input from rivers and

streams.

 Portions of this stock may co-occur with the U.S. Gulf of Mexico outer continental shelf (OCS) stock. The

seaward boundary for this stock corresponds to aerial survey strata (NMFS unpublished data) and thus, represents a

management boundary rather than an ecological boundary. Anecdotal evidence suggests that both the coastal and

OCS stocks consist of the shallow, warm water ecotype described by Hersh and Duffield (1990). Data are not

currently available to determine genetically if the two stocks should be separated or, if so, where; and interbreeding

may occur at the boundary interface. 

POPULATION SIZE

Preliminary estimates of abundance were derived using distance sampling analysis (Buckland et al. 1993)

and the computer program DISTANCE (Laake et al. 1993) with sighting data collected during aerial line-transect

surveys conducted during autumn 1994 (NMFS unpublished data). Systematic sampling transects, placed randomly

with respect to the bottlenose dolphin distribution, extended orthogonally from shore out to approximately 9 km past

the 18 m isobath. Approximately 5% of the total survey area was visually searched. Bottlenose dolphin abundance

was estimated to be 9,912 dolphins with coefficient of variation (CV) = 0.12. 

Minimum Population Estimate

The minimum population estimate was based on the 1994 abundance estimate of 9,912 (CV = 0.12) (NMFS

unpublished data). The minimum population estimate is the lower limit of the two-tailed 60% confidence interval of

the log-normally distributed abundance estimate. This is equivalent to the 20th percentile of the log-normal
252

distribution as specified by Wade and Angliss (1997). The minimum population estimate is 8,963 bottlenose

dolphins. 

Current Population Trend

Aerial surveys of this area conducted by NMFS in autumn 1985, resulted in an estimated bottlenose dolphin

abundance of 4,711 (CV = 0.05). The data are not sufficient to conduct a statistical trend analysis, but the current

population size estimate is significantly higher than the 1985 estimate (Student's t-test, P < 0.0005). 

CURRENT AND MAXIMUM NET PRODUCTIVITY RATES

Current and maximum net productivity rates are not known for this stock. The maximum net productivity

rate was assumed to be 0.04. This value is based on theoretical modeling showing that cetacean populations may not

grow at rates much greater than 4% given the constraints of their reproductive life history (Barlow et al. 1995). 

POTENTIAL BIOLOGICAL REMOVAL

Potential Biological Removal (PBR) is the product of minimum population size, one-half the maximum

productivity rate, and a “recovery” factor (Wade and Angliss 1997). The “recovery “ factor, which accounts for

endangered, depleted, and threatened stocks, or stocks of unknown status relative to optimum sustainable population

(OSP) is assumed to be 0.5 because this stock is of unknown status. PBR for this stock is 90 dolphins. 

ANNUAL HUMAN-CAUSED MORTALITY AND SERIOUS INJURY

The level of direct human-caused mortality in this stock is unknown. An annual mean of eight bottlenose

dolphins (CV = 0.41) stranded on the Florida Gulf coast during the period 1988-1993, showing signs of fishery

interactions such as net entanglement, mutilation, gunshot wounds, etc. (Southeast U.S. Marine Mammal Stranding

Network unpublished data). This was 8.9% of the total bottlenose dolphin strandings reported for this area. 

Morgan and Patton (1990) reported that 12.9% of 116 cetaceans examined by Mote Marine Laboratory's marine

mammal stranding response program on the west coast of Florida between 1984 and 1990 exhibited evidence of

human-caused mortality or serious injury. The stranding networks reported a total of 62 bottlenose dolphin

strandings in 1994 with only one reported human interaction. Eighty-three strandings were reported in 1995 and 2

had evidence of human interactions. One was found entangled in a gillnet, and one was a boat strike. The network

reported 111 bottlenose dolphins from January through August 31, 1996. Three showed signs of human interaction

(one entanglement-gillnet, one boat strike and one mutilation).

 There are a number of difficulties associated with the interpretation of stranding data. It is possible that

some or all of the stranded dolphins may have been from a bay, sound or estuarine stock; however, the proportion of

the stranded dolphins belonging to another stock cannot be determined because of the difficulty of determining from

where the stranded carcass originated. Stranding data probably underestimate the extent of fishery-related mortality

and serious injury because not all of the dolphins which die or are seriously injured in fishery interactions wash

ashore, nor will all of those that do wash ashore necessarily show signs of entanglement or other fishery-interaction. 

Finally, the level of technical expertise among stranding network personnel varies widely as does the ability to

recognize signs of fishery interaction.

Fisheries Information

Annual fishing effort for the shrimp trawl fishery in the eastern Gulf of Mexico coastal stock area during

1988-1993 averaged approximately 0.102 million hours of tows (CV = 0.30) (NMFS unpublished data). This fishery

was monitored by NMFS observers in 1992 and 1993, but less than 1% of the fishing effort was observed (NMFS

unpublished data). There was one report in 1992 of an incidental mortality in the eastern Gulf of Mexico coastal

bottlenose dolphin stock which was associated with the shrimp trawl fishery in this area. 

Gillnets are not used in Texas, and gillnets over 46 m3

 in area will not be allowed in Florida past July 1995,

but fixed and runaround gillnets are currently in use in Louisiana, Mississippi, and Alabama. These fisheries, for the

most part, operate year around. They are state-controlled and licensed, and vary widely in intensity and target

species. No marine mammal mortalities associated with gillnet fisheries have been reported in these states, but

stranding data suggest that gillnet and marine mammal interaction does occur, causing mortality and serious injury. 

A coastal gillnet fishery for menhaden was reported to have taken one bottlenose dolphin in 1991 (NMFS

unpublished data). There are no effort data available for this fishery. 
253

The menhaden purse seine fishery targets the Gulf menhaden, Brevoortia patronus, in Gulf of Mexico

coastal waters approximately 3-18 m in depth (NMFS 1991). Seventy-five menhaden vessels operate within 1.6 km

of shore from Apalachicola, Florida to Freeport, Texas, from April-October. Lethal takes of bottlenose dolphins

reported by the menhaden fishery during the period 1982-1988 ranged between 0-4 dolphins annually (NMFS

unpublished data). 

Other clupeid purse seiners opportunistically target Spanish sardine, thread herring, ladyfish, cigarfish, and

blue runners. There are no effort data available for this fishery and there are no estimates of dolphin mortality

associated with this fishery. 

A fishery for blue crabs operates in estuarine areas throughout the Gulf coast employing traps attached to a

buoy with rope. Bottlenose dolphins have been reported stranded in other coastal locations in the Gulf of Mexico

with polypropylene rope around their flukes indicating the possibility of entanglement with crab pot lines (NMFS

1991); however, this fishery has not been monitored by observers. 

Other Mortality

The nearshore habitat occupied by this stock is adjacent to areas of high human population and in some

areas of Florida, such as the Tampa Bay area, is highly industrialized. PCB concentrations in three stranded

dolphins sampled from this stock ranged from 16-46 μg/g wet weight. Concentrations of "-HCB, p,p,DDE, and

PCB's were inversely related to the magnitude of the serum antibody titer to Erysipelas spp. and Staphylococcus spp.

bacteria in a study of bottlenose dolphins in Texas (Reif et al., in review). A similar and more pronounced trend was

seen in relationship to the pseudorabies virus; however, since pseudorabies virus is not known to infect bottlenose

dolphins, the significance of this finding is not clear. Concentrations of contaminants were higher in dolphins

having evidence of exposure to the cetacean morbillivirus. The reason for the difference in the relationship between

antibody titers to bacteria and pseudorabies and antibody titers to cetacean morbillivirus is not understood. 

STATUS OF STOCK

The status of this stock relative to OSP is not known and population trends cannot be determined due to

insufficient data. This species is not listed as threatened or endangered under the Endangered Species Act. The total

known fishery-related mortality and serious injury for this stock is less than 10% of the calculated PBR and,

therefore, can be considered to be insignificant and approaching zero mortality and serious injury rate. This is not a

strategic stock because the known level of fishery-related mortality or serious injury does not exceed PBR. 

REFERENCES

Barlow, J., S.L. Swartz, T.C. Eagle, and P.R. Wade. 1995. U.S. Marine Mammal Stock Assessments: Guidelines for

Preparation, Background and a Summary of the 1995 Assessments. U.S. Dep. Commer., NOAA Tech.

Memo. NMFS-OPR-6, 73 pp.

Buckland, S. T., D. R. Anderson, K. P. Burnham, and J. L. Laake. 1993. Distance sampling: Estimating abundance

of biological populations. Chapman & Hall, London, 446 pp. 

Laake, J. L., S. T. Buckland, D. R. Anderson, and K. P. Burnham. 1993. DISTANCE user’s guide, V2.0. Colorado

Cooperative Fish & Wildlife Research Unit, Colorado State University, Ft. Collins, Colorado, 72 pp. 

Morgan, M. A. and G. W. Patton. 199 0. Human dolphin interactions on the west coast of Florida: Documentation

from MML's marine mammal response program. MML Technical Report #191, 9 pp. 

NMFS. 1991. Proposed regime to govern the interactions between marine mammals and commercial fishing

operations after October 1, 1993. Draft Environmental Impact Statement. June 1991. 

Wade, P.R., and R.P. Angliss. 1997. Guidelines for assessing marine mammal stocks: Report of the GAMMS

Workshop April 3-5, Seattle, Washington. U.S. Dep. Commer., NOAA Tech. Memo. NMFS-OPR-12, 93

pp.
254

September 2000

BOTTLENOSE DOLPHIN (Tursiops truncatus):

Gulf of Mexico Bay, Sound, and Estuarine Stocks

STOCK DEFINITION AND GEOGRAPHIC RANGE

Bottlenose dolphins are distributed throughout the bays, sounds, and estuaries of the Gulf of Mexico

(Mullin 1988). The identification of biologically-meaningful “stocks” of bottlenose dolphins in these waters is

complicated by the high degree of behavioral variability exhibited by this species (Shane et al. 1986; Wells and Scott

1999), and by the lack of requisite information for much of the region. 

Previous stock assessment reports have provisionally identified distinct stocks in each of 33 areas of

contiguous, enclosed, or semi-enclosed bodies of water adjacent to the Gulf of Mexico (Table 1, Waring et al.

1997), based on descriptions of relatively discrete dolphin “communities” in some of these areas. A “community”

includes resident dolphins that regularly share large portions of their ranges, exhibit similar distinct genetic profiles,

and interact with each other to a much greater extent than with dolphins in adjacent waters. The term, as adapted

from Wells et al. (1987), emphasizes geographic, genetic, and social relationships of dolphins. Bottlenose dolphin

communities do not constitute closed demographic populations, as individuals from adjacent communities are known

to interbreed. Nevertheless, the geographic nature of these areas and long-term stability of residency patterns suggest

that many of these communities exist as functioning units of their ecosystems and, under the Marine Mammal

Protection Act, must be maintained as such. Also, the stable patterns of residency observed within communities

suggest that long periods would be required to repopulate the home range of a community were it eradicated or

severely depleted. Thus, in the absence of information supporting management on a larger scale, it is appropriate to

adopt a risk-averse approach and focus management efforts at the level of the community rather than at some larger

demographic scale. Support for this risk-averse approach derives from several sources. Long-term (year-round,

multi-year) residency by at least some individuals has been reported from nearly every site where photographic

identification or tagging studies have been conducted in the Gulf of Mexico. In Texas, some of the dolphins in the

Matagorda-Espiritu Santo Bay area (Gruber 1981; Lynn 1995; Würsig and Lynn 1996), Aransas Pass (Shane 1977;

Weller 1998), San Luis Pass (Maze 1997), and Galveston Bay (Bräger 1993; Bräger et al. 1994; Fertl 1994) have

been reported as long-term residents. Hubard (1998) reported sightings of dolphins tagged 12-15 years previously

in Mississippi Sound. In Florida, long-term residency has been reported from Choctawhatchee Bay (1989-1993, F.

Townsend unpublished data), Tampa Bay (Wells 1986a; Wells et al. 1996a), Sarasota Bay (Irvine and Wells 1972;

Irvine et al. 1981; Wells 1986a, 1991; Scott et al. 1990; Wells et al. 1987), Lemon Bay (Wells et al. 1996b), and

Charlotte Harbor/Pine Island Sound (Shane 1990; Wells et al. 1996b, 1997). In many cases, residents emphasize

use of the bay, sound, or estuary waters, with limited movements through passes to the Gulf of Mexico (Shane 1977,

1990; Gruber 1981; Irvine et al. 1981; Lynn 1995, Maze 1997). These habitat use patterns are reflected in the

ecology of the dolphins in some areas; for example, residents of Sarasota Bay, Florida lacked squid in their diet,

unlike non-resident dolphins stranded on nearby Gulf beaches (Barros and Wells 1998). 

Genetic data also support the concept of relatively discrete bay, sound, and estuary stocks. Analyses of

mitochondrial DNA haplotype distributions indicate the existence of clinal variations along the Gulf of Mexico

coastline (Duffield and Wells In press). Differences in reproductive seasonality from site to site also suggest

genetic-based distinctions between communities (Urian et al. 1996). Mitochondrial DNA analyses suggest finerscale structural levels as well. For example, Matagorda Bay, Texas dolphins appear to be a localized population

(NMFS unpublished data), and differences in haplotype frequencies distinguish between adjacent communities in

Tampa Bay, Sarasota Bay, and Charlotte Harbor/Pine Island Sound, along the central west coast of Florida (Duffield

and Wells 1991; in press). Examination of protein electrophoretic data resulted in similar conclusions for the Florida

dolphins (Duffield and Wells 1986).

The long-term structure and stability of at least some of these communities is exemplified by the residents

of Sarasota Bay, Florida. This community has been observed since 1970 (Irvine and Wells 1972; Scott et al. 1990;

Wells 1991). The number of dolphins regularly occupying the Sarasota Bay area has remained consistently at about

100. At least four generations of identifiable residents currently inhabit the region, including half of those first

identified in 1970. Maximum immigration and emigration rates of about 2-3% have been estimated (Wells and Scott

1990).
255

Genetic exchange occurs between resident communities; hence the application of the demographically and

behaviorally-based term “community” rather than “population” (Wells 1986a). Some of the calves in Sarasota Bay

apparently have been sired by non-residents (Duffield and Wells, in press). A variety of potential exchange

mechanisms occur in the Gulf. Small numbers of inshore dolphins traveling between regions have been reported,

with patterns ranging from traveling through adjacent communities (Wells 1986b; Wells et al. 1996a,b) to

movements over distances of several hundred km in Texas waters (Gruber 1981; Würsig and Lynn 1996; Würsig

unpublished data). In many areas year-round residents co-occur with non-resident dolphins, providing potential

opportunities for genetic exchange. About 17% of group sightings involving resident Sarasota Bay dolphins include

at least one non-resident as well (Wells et al. 1987). Similar mixing of inshore residents and non-residents is seen

off San Luis Pass, Texas (Maze 1997). Non-residents exhibit a variety of patterns, ranging from apparent nomadism

recorded as transience in a given area, to apparent seasonal or non-seasonal migrations. Passes, especially the

mouths of the larger estuaries, serve as mixing areas. For example, several communities mix at the mouth of Tampa

Bay, Florida (Wells 1986a), and most of the dolphins identified in the mouths of Galveston Bay and Aransas Pass,

Texas were considered transients (Henningsen 1991; Bräger 1993; Weller 1998). 

Seasonal movements of dolphins into and out of some of the bays, sounds, and estuaries provide additional

opportunities for genetic exchange with residents, and complicate the identification of stocks in coastal and inshore

waters. In small bay systems such as Sarasota Bay, Florida and San Luis Pass, Texas residents move into Gulf

coastal waters in fall/winter, and return inshore in spring/summer (Irvine et al. 1981; Maze 1997). In larger bay

systems, seasonal changes in abundance suggest possible migrations, with increases in more northerly bay systems

in summer, and in more southerly systems in winter. Fall/winter increases in abundance have been noted for

Matagorda Bay (Gruber 1981; Lynn 1995; Würsig and Lynn 1996), Aransas Pass (Shane 1977; Weller 1998),

Tampa Bay (Scott et al. 1989), and Charlotte Harbor/Pine Island Sound (Thompson 1981; Scott et al. 1989). 

Spring/summer increases in abundance have been reported for Galveston Bay (Henningsen 1991; Bräger 1993; Fertl

1994) and Mississippi Sound (Hubard 1998). 

Much uncertainty remains regarding the structure of bottlenose dolphin stocks in many of the Gulf of

Mexico bays, sounds, and estuaries. Given the apparent co-occurrence of resident and non-resident dolphins in these

areas, and the demonstrated variations in abundance, it appears that consideration should be given to the existence of

a complex of stocks, and to the roles of bays, sounds, and estuaries for stocks emphasizing Gulf of Mexico coastal

waters. A starting point for management strategy should be the protection of the long-term resident communities,

with their multi-generational geographic, genetic, demographic, and social stability. These localized units would be

at greatest risk from geographically-localized impacts. Complete characterization of many of these basic units

would benefit from additional photo-identification, telemetry, and genetic research (Wells 1994). 

The current provisional stocks follow the designations in Table 1, with a few revisions. Available

information suggests that Block B35, Little Sarasota Bay, can be subsumed under Sarasota Bay, and B36,

Caloosahatchee River, can be considered a part of Pine Island Sound. As more information becomes available,

additional combination or division may be warranted. For example, a number of geographically and socially distinct

subgroupings of dolphins in regions such as Tampa Bay, Charlotte Harbor, Pine Island Sound, Aransas Pass, and

Matagorda Bay have been identified, but the importance of these distinctions to stock designations remain

undetermined (Shane 1977; Gruber 1981; Wells et al. 1996a,b, 1997; Würsig and Lynn 1996).

Understanding the full complement of the stock complex using the bay, sound, and estuarine waters of the

Gulf of Mexico will require much additional information. The development of biologically-based criteria to better

define and manage stocks in this region should integrate multiple approaches, including studies of ranging patterns,

genetics, morphology, social patterns, distribution, life history, stomach contents, isozyme analyses, and contaminant

concentrations. Spatially-explicit population modeling could aid in evaluating the implications of community-based

stock definition. As these studies provide new information on what constitutes a bottlenose dolphin "biological

stock," current provisional definitions will likely need to be revised. As stocks are more clearly identified, it will be

possible to conduct abundance estimates using standardized methodology across sites (thereby avoiding some of the

previous problems of mixing results of aerial and boat-based surveys), identify fisheries and other human impacts

relative to specific stocks, and perform individual stock assessments. As recommended by the Atlantic Scientific

Review Group (November 1998, Portland, Maine), a workshop was held from March 13-15, 2000 in Sarasota, FL to

review current information pertaining to bottlenose dolphin stock structure in Gulf of Mexico bays, sounds, and

estuaries. As a result of this, efforts are being made to conduct simulations of alternative stock structure and, if

warranted, propose a new stock structure.
256

Table 1. Bottlenose dolphin abundance (NBEST), coefficient of variation (CV), minimum population estimate (NMIN),

and Potential Biological Removal (PBR) in USA Gulf of Mexico bays, sounds, and other estuaries. Blocks

refer to aerial survey blocks illustrated in Fig. 1. Blocks with an abundance of zero were surveyed but not

considered stocks at this time (but see Note 1 below).

Blocks Gulf of Mexico Estuary NBEST CV NMIN PBR Year Reference

B51 Laguna Madre 80 1.57 31 0.3 1992 A

B52 Nueces Bay, Corpus Christi Bay 58 0.61 36 0.4 1992 A

B50 Compano Bay, Aransas Bay, San Antonio Bay,

Redfish Bay, Espiritu Santo Bay

55 0.82 30 0.3 1992 A

B54 Matagorda Bay, Tres Palacios Bay, Lavaca Bay 61 0.45 42 0.4 1992 A

B55 West Bay 29 1.10 14 0.1 1992 A

B56 Galveston Bay, East Bay, Trinity Bay 152 0.43 107 1.1 1992 A

B57 Sabine Lake 01 - 1992 A

B58 Calcasieu Lake 01 - 1992 A

B59 Vermillion Bay, West Cote Blanche Bay,

Atchafalaya Bay

01 - 1992 A

B60 TerreBonne Bay, Timbalier Bay 100 0.53 66 0.7 1993 A

B61 Barataria Bay 219 0.55 142 1.4 1993 A

B30 Mississippi River Delta 01 - 1993 A

B02-05,

29,31

Bay Boudreau, Mississippi Sound 1,401 0.13 1,256 13 1993 A

B06 Mobile Bay, Bonsecour Bay 122 0.34 92 0.9 1993 A

B07 Perdido Bay 01 - 1993 A

B08 Pensacola Bay, East Bay 33 0.80 18 0.2 1993 A

B09 Choctawhatchee Bay 242 0.31 188 1.9 1993 A

B10 St. Andrew Bay 124 0.57 79 0.8 1993 A

B11 St. Joseph Bay 01 - 1993 A

B12-13 St. Vincent Sound, Apalachicola Bay, St.

Georges Sound

387 0.34 293 2.9 1993 A

B14-15 Apalachee Bay 491 0.39 358 3.6 1993 A

B16 Waccasassa Bay, Withlacoochee Bay, Crystal

Bay

100 0.85 54 0.5 1994 A

B17 St. John’s Sound, Clearwater Harbor 37 1.06 18 0.2 1994 A

B32-34 Tampa Bay 559 0.24 458 4.6 1994 A

B20 Sarasota Bay 97 na3 97 1.0 1992 B

B35 Little Sarasota Bay 22 0.24 2 0.0 1985 C

B21 Lemon Bay 01 - 1994 A

B22-23 Pine Sound, Charlotte Harbor, Gasparilla Sound 209 0.38 153 1.5 1994 A

B36 Caloosahatchee River 01,2 - 1985 C

B24 Estero Bay 104 0.67 62 0.6 1994 A

B25 Chokoloskee Bay, Ten Thousand Islands,

Gullivan Bay

208 0.46 144 1.4 1994 A

B27 Whitewater Bay 242 0.37 179 1.8 1994 A

B28 Florida Keys (Bahia Honda to Key West) 29 1.00 14 0.1 1994 A

References: A- Blaylock and Hoggard 1994; B- Wells 1992; C- Scott et al. 1989

Notes:

1 During earlier surveys (Scott et al. 1989), the range of seasonal abundances was as follows: B57, 0-2 (CV=

0.38); B58, 0-6 (0.34); B59, 0-0; B30, 0-182(0.14); B07, 0-0; B21, 0-15(0.43); and B36, 0-0. 2 Block not surveyed during surveys reported in Blaylock and Hoggard 1994. 3 No CV because NBEST was a direct count of known individuals.
257

Figure 1. USA Gulf of Mexico bays and sounds. Each of the alpha-numerically designated blocks corresponds

to one of the NMFS Southeast Fisheries Science Center logistical aerial survey areas listed in Table 1. The

bottlenose dolphins inhabiting each bay and sound are considered to comprise a unique stock for purposes of this

assessment. 

POPULATION SIZE

Population size (Table 1) for all of the stocks except Sarasota Bay, Florida, was estimated from preliminary

analyses of line-transect data collected during aerial surveys conducted in September-October 1992 in Texas and

Louisiana; in September-October 1993 in Louisiana, Mississippi, Alabama, and the Florida panhandle (Blaylock and

Hoggard 1994); and in September-November 1994 along the west coast of Florida (NMFS unpublished data). 

Standard line-transect perpendicular sighting distance analytical methods (Buckland et al. 1993) and the computer

program DISTANCE (Laake et al. 1993) were used. Stock size in Sarasota Bay, Florida, was obtained through

direct count of known individuals (Wells 1992). 

Minimum Population Estimate

The minimum population estimate (Table 1) is the lower limit of the two-tailed 60% confidence interval of

the log-normally distributed abundance estimate. This is equivalent to the 20th percentile of the log-normal

distribution as specified by Wade and Angliss (1997). The minimum population estimate was calculated for each

block from the estimated population size and its associated coefficient of variation. Where the population size

resulted from a direct count of known individuals, the minimum population size was identical to the estimated

population size. 

Current Population Trend

The data are insufficient to determine population trends for all of the Gulf of Mexico bay, sound, and

estuary bottlenose dolphin communities. The Sarasota Bay community, however, has been monitored since 1970

and has remained relatively constant over the last 20+ years at approximately 105 animals (Wells 1998). Three

anomalous mortality events have occurred among portions of these dolphin communities between 1990 and 1994;

however, it is not possible to accurately partition the mortalities between bay and coastal stocks, thus the impact of

these mortality events on communities is not known. 

CURRENT AND MAXIMUM NET PRODUCTIVITY RATES

Current and maximum net productivity rates are not known for the dolphin communities that comprise these

stocks. While productivity rates may be estimated for individual females within communities, such estimates are

confounded at the stock level due to the influx of dolphins from adjacent areas which balance losses, and the

unexplained loss of some individuals which offset births and recruitment (Wells 1998). Continued monitoring and

expanded survey coverage will be required to address and develop estimates of productivity for these dolphin
258

communities. The maximum net productivity rate was assumed to be 0.04. This value is based on theoretical

modeling showing that cetacean populations may not grow at rates much greater than 4% given the constraints of

their reproductive life history (Barlow et al. 1995).

POTENTIAL BIOLOGICAL REMOVAL

Potential Biological Removal (PBR) is the product of minimum population size, one-half the maximum

productivity rate, and a “recovery” factor (Wade and Angliss 1997). The “recovery” factor, which accounts for

endangered, depleted, and threatened stocks, or stocks of unknown status relative to optimum sustainable population

(OSP), is assumed to be 0.5 because these stocks are of unknown status. PBR for each stock is given in Table 1. 

ANNUAL HUMAN-CAUSED MORTALITY AND SERIOUS INJURY

There are a number of difficulties associated with the interpretation of stranding data. It is possible that

some or all of the stranded dolphins may have been from a nearby coastal stock; however, the proportion of stranded

dolphins belonging to another stock cannot be determined because of the difficulty of determining from where the

stranded carcass originated. Stranding data probably underestimate the extent of fishery-related mortality and

serious injury because not all of the dolphins which die or are seriously injured in fishery interactions wash ashore,

nor will all of those that do wash ashore necessarily show signs of entanglement or other fishery-interaction. 

Finally, the level of technical expertise among stranding network personnel varies widely as does the ability to

recognize signs of fishery interaction, and the condition of the carcass if badly decomposed can inhibit the

interpretation of cause of death.

A total of 1,881 bottlenose dolphins were found stranded in the USA Southeast Gulf of Mexico from 1993

to 1997 (Table 2) (NMFS unpublished data). Of these, 57 or 3% showed evidence of human interactions as the

cause of death (e.g., gear entanglement, mutilation, gunshot wounds). Bottlenose dolphin are known to become

entangled in recreational and commercial fishing gear (Wells et al. 1998; Gorzelany 1998; Wells and Scott 1994)

and some are struck by recreational and commercial vessels (Wells and Scott 1997). In 1998 alone, two resident

bottlenose dolphins and an associated calf were killed by vessel strikes and a resident young-of-the-year died from

entanglement in a crab-pot float line (R.S. Wells, pers. comm.).

The Gulf of Mexico menhaden fishery was observed to take 9 bottlenose dolphins (three fatally) between

1992 and 1995 (NMFS unpublished data). There were 1,366 sets observed out of 26,097 total sets, which if

extrapolated for all years suggests that as many as 172 bottlenose dolphins could have been taken in this fishery with

up to 57 animals killed. An observer program is urgently needed to obtain statistically reliable information for this

fishery on the number of sets annually, the incidental take and mortality rates, and the communities from which

bottlenose dolphins are being taken.

Some of the bay, sound and estuarine communities were the focus of a live-capture fishery for bottlenose

dolphins which supplied dolphins to the U.S. Navy and to oceanaria for research and public display for almost two

decades (NMFS unpublished data). During the period between 1972-89, 490 bottlenose dolphins, an average of 29

dolphins annually, were removed from a few locations in the Gulf of Mexico, including the Florida Keys. 

Mississippi Sound sustained the highest level of removals with 202 dolphins taken from this stock during this period,

representing 41% of the total and an annual average of 12 dolphins (compared to a current PBR of 13). The annual

average number of removals never exceeded current PBR levels, but it may be biologically significant that 73% of

the dolphins removed during 1982-88 were females. The impact of those removals on the stocks is unknown. 

Fishery Information

Annual fishing effort for the shrimp trawl fishery in the USA Gulf of Mexico bays, sounds, and estuaries

during 1988-1993 averaged approximately 2.20 million hours of tows (CV=0.11) (NMFS unpublished data). There

have been very low numbers of incidental mortality or injury in the stocks associated with the shrimp trawl fishery. 

A fishery for blue crabs operates in estuarine areas throughout the Gulf of Mexico coast employing traps

attached to a buoy with rope. Bottlenose dolphins have been reported stranded with polypropylene rope around their

flukes (NMFS 1991; McFee and Brooks, Jr. 1998; NMFS unpublished data), indicating the possibility of

entanglement with crab pot lines. This fishery has not been monitored by observers and there are no estimates of

bottlenose dolphin mortality or serious injury for this fishery. 

Gillnets are not used in Texas, and gillnets over 46 m3

 in area were not allowed in Florida past July 1995,

but fixed and runaround gillnets are currently in use in Louisiana, Mississippi, and Alabama. These fisheries, for the
259

most part, operate year around. They are state-controlled and licensed, and vary widely in intensity and target

species. No marine mammal mortalities associated with gillnet fisheries have been reported in these states, but

stranding data suggest that gillnet and marine mammal interaction does occur, causing mortality and serious injury.

Table 2. Bottlenose dolphin strandings in the USA Gulf of Mexico (West Florida to Texas) from 1993 to 1997. Data

are from the Southeast Marine Mammal Stranding Database (SESUS).

State 1993 1994 1995 1996 1997 Total

Florida

No. Stranded 134 51 101 133 63 482

No. Human Interactions 4 2 3 2 0 11

% With Human Interactions 3% 4% 3% 2% 0% 2%

Alabama

No. Stranded 48 16 15 17 14 110

No. Human Interactions 1 0 1 0 1 3

% With Human Interactions 2% 0% 7% 0% 7% 3%

Mississippi

No. Stranded 64 25 32 59 42 222

No. Human Interactions 4 0 4 2 2 12

% With Human Interactions 6% 0% 12% 3% 5% 5%

Louisiana

No. Stranded 14 74 31 92 42 253

No. Human Interactions 0 0 1 3 1 5

% With Human Interactions 0% 0% 3% 3% 2% 2%

Texas

No. Stranded 133 227 110 208 136 814

No. Human Interactions 4 6 7 7 2 26

% With Human Interactions 0% 3% 6% 3% 0% 3%

Totals

No. Stranded 393 393 289 509 297 1881

No. Human Interactions 13 8 16 14 6 57

% With Human Interactions 3% 2% 6% 3% 2% 3%

Other Mortality

The near shore habitat occupied by many of these stocks is adjacent to areas of high human population, and

in some bays, such as Mobile Bay in Alabama and Galveston Bay in Texas, is highly industrialized. The area

surrounding Galveston Bay, for example, has a coastal population of over 3 million people. More than 50% of all

chemical products manufactured in the USA are produced there and 17% of the oil produced in the Gulf of Mexico

is refined there (Henningsen and Würsig 1991). Many of the enclosed bays in Texas are surrounded by agricultural

lands which receive periodic pesticide applications. 

Concentrations of chlorinated hydrocarbons and metals were examined in conjunction with an anomalous

mortality event of bottlenose dolphins in Texas bays in 1990 and found to be relatively low in most; however, some

had concentrations at levels of possible toxicological concern (Varanasi et al. 1992). No studies to date have

determined the amount, if any, of indirect human-induced mortality resulting from pollution or habitat degradation. 
260

However, a recent health assessment of 35 bottlenose dolphins from Matagorda Bay, Texas associated high levels of

chlorinated hydrocarbons with low health assessment scores (Reif et al. in review). Morbillivirus has also been

implicated in the deaths of bottlenose dolphins in some of these communities (Duignan et al. 1996).

STATUS OF STOCK

The status of these stocks relative to OSP is unknown and this species is not listed as threatened or

endangered under the Endangered Species Act. The occurrence of three anomalous mortality events among

bottlenose dolphins along the USA Gulf of Mexico coast since 1990 (NMFS unpublished data) is cause for concern;

however, the effects of the mortality events on stock abundance have not yet been determined. The available

evidence suggests that bottlenose dolphin stocks in the northern and western coastal portion of the USA Gulf of

Mexico may have experienced a morbillivirus epidemic in 1993 (Lipscomb 1993; Lipscomb et al. 1994). Seven of

35 live-captured bottlenose dolphins (20%) from Matagorda Bay, Texas, in 1992, tested positive for previous

exposure to cetacean morbillivirus (Reif et al. in review), and it is possible that other estuarine resident stocks have

been exposed to the morbillivirus (Duignan et al. 1996). 

The relatively high number of bottlenose dolphin deaths which occurred during the mortality events in the

last decade suggests that some of these stocks may be stressed. Fishery-related mortality and serious injury for each

of these stocks is not known, but considering the evidence from stranding data, the total fishery-related mortality and

serious injury exceeds 10% of the total PBR, and, therefore, it is not insignificant and approaching the zero

mortality and serious injury rate. For these reasons, and because the PBR for most of these stocks would be

exceeded with the incidental capture of a single dolphin, each of these stocks is a strategic stock. 

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40-WCNF601958

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and 6 Appendices. 
263

Figure 1. Distribution of Atlantic spotted dolphin sightings during NOAA Ship

Oregon II marine mammal surveys during 1991-1994 (filled circles) and during

GOMEX regional aerial surveys during 1992-1994 (unfilled circles). The

straight lines show transects during two ship surveys and are examples of

typical ship survey transects. Isobaths are in 183 m (100 fm) intervals.

July 1995

ATLANTIC SPOTTED DOLPHIN (Stenella frontalis):

Northern Gulf of Mexico Stock

STOCK DEFINITION AND GEOGRAPHIC RANGE

The Atlantic spotted dolphin is endemic to the Atlantic Ocean in warm temperate to tropical waters (Perrin

et al. 1987, 1994). Sightings of this species are concentrated along the continental shelf edge and also occur over the

continental shelf in the northern Gulf of Mexico [Fritts et al. 1983; Mullin et al. 1991; Southeast Fisheries Science

Center (SEFSC) unpublished data], but they have been reported as occurring around oceanic islands and far offshore

in other areas (Perrin et al. 1994). The island and offshore animals may be a different stock than those occurring on

the continental shelf (Perrin et al. 1994). Atlantic spotted dolphins were seen in all seasons during seasonal recent

GulfCet aerial surveys of the northern Gulf of Mexico during 1993-1995 (Davis et al., in preparation). Atlantic

spotted dolphins were seen in 1992 during regional aerial surveys conducted in the autumn of 1992-1994 over the

U.S. continental shelf [see Blaylock and Hoggard (1994) for a description of the areas surveyed in 1992-1993]. 

These surveys were designed to estimate abundance of bottlenose dolphins and spotted dolphin abundance was not

estimated. It has been suggested that there may be a seasonal movement of this species onto the continental shelf in

the spring, but data supporting this hypothesis are limited (Caldwell and Caldwell 1966; Fritts et al. 1983). 

POPULATION SIZE

Estimates of abundance were derived through the application of distance sampling analysis (Buckland et al.

1993) and the computer program DISTANCE (Laake et al. 1993) to sighting data collected during 1991-1994 springsummer, visual sampling, line-transect vessel surveys of the northern Gulf of Mexico (Hansen et al. 1995) (Fig. 1),

which includes data collected as part of the GulfCet program (Davis et al., in preparation). These surveys were

conducted throughout the area from approximately the 200 m isobath along the U.S. coast to the seaward extent of

the U.S. Exclusive Economic Zone. The seasonal GulfCet aerial surveys included only a small portion of the stock

range and these data were not

used for abundance estimation.

Estimated abundance of Atlantic

spotted dolphins [coefficient of

variation (CV) in parentheses]

by survey year was zero in 1991,

4,527 in 1992 (0.65), 4,618 in

1993 (0.62), and 2,186 in 1994

(0.85) (Hansen et al. 1995). 

Survey effort-weighted

estimated average abundance of

Atlantic spotted dolphins for all

surveys combined was 3,213

(CV = 0.44) (Hansen et al.

1995). This is probably an

underestimate and should be

considered a partial stock

estimate because the continental

shelf areas were not generally

covered by either the vessel or

GulfCet aerial surveys. 

Minimum Population Estimate

 The minimum population size was estimated using the average abundance estimate of Atlantic spotted

dolphins for all surveys combined which was 3,213 (CV = 0.44) (Hansen et al. 1995). The minimum population

estimate is the lower limit of the two-tailed 60% confidence interval of the log-normal distributed abundance
264

estimate, which is equivalent to the 20th percentile of the log-normal distributed abundance estimate as specified by

NMFS (Anon. 1994). The minimum population estimate is 2,255 Atlantic spotted dolphins. 

Current Population Trend

No trend was identified in the annual abundance estimates. There were no sightings of this stock during

1991. The lack of sightings during 1991 may have been due to less sampling that year along the continental shelf

edge where sightings of this species were concentrated. The difference in abundance estimates during 1992-1994

were not significant using the criteria of no overlap of log-normal 95 % confidence intervals. 

CURRENT AND MAXIMUM NET PRODUCTIVITY RATES

Current and maximum net productivity rates are not known for this stock; therefore, the default maximum

net productivity rate of 0.04 (Anon. 1994) was used for purposes of this assessment. 

POTENTIAL BIOLOGICAL REMOVAL

Potential biological removal level (PBR) was specified as the product of the minimum population size, one

half the maximum net productivity rate, and a recovery factor for endangered, threatened, or depleted stocks, or

stocks of unknown status relative to optimum sustainable population (OSP) (Anon. 1994). The recovery factor was

set at 0.50 because the status of the stock relative to OSP is unknown. The resulting PBR, based on the partial

estimate, for this stock is 23 dolphins.

ANNUAL HUMAN-CAUSED MORTALITY AND SERIOUS INJURY

The level of past or current, direct, human-caused mortality of Atlantic spotted dolphins in the northern

Gulf of Mexico is unknown; however, interactions between spotted dolphins and fisheries have been observed in the

northern Gulf of Mexico.

There were two documented strandings of Atlantic spotted dolphins in the northern Gulf of Mexico during

1987-1994 which were classified as likely caused by fishery interactions. Stranding data probably underestimate the

extent of fishery-related mortality and serious injury because not all of the dolphins which die or are seriously

injured in fishery interactions wash ashore, nor will all of those that do wash ashore necessarily show signs of

entanglement or other fishery-interaction. Finally, the level of technical expertise among stranding network

personnel varies widely as does the ability to recognize signs of fishery interaction. 

Total estimated average annual fishing-related mortality and serious injury of spotted dolphins (both

species) is 1.5 spotted dolphins annually (CV = 0.33). Observed fishery-related mortality and serious injury for

spotted dolphins is less than 10% of PBR and can be considered insignificant and approaching zero mortality and

serious injury rate for this stock. This determination cannot be made for specific fisheries until the implementing

regulations for Section 118 of the MMPA have been reviewed by the public and finalized. 

Fisheries Information

Pelagic swordfish, tunas, and billfish are the targets of the longline fishery operating in the U.S. Gulf of

Mexico. Total longline effort for the Gulf of Mexico pelagic fishery, including OCS edge, continental slope, and

Mexican territorial waters, based on mandatory logbook reporting, was 4,400 sets in 1991, 4,850 sets in 1992, and

3,260 sets in 1993 (Cramer 1994). This fishery has been monitored with about 5% observer coverage, in terms of

trips observed, since 1992. There were two observed incidental takes and releases of spotted dolphins in the Gulf of

Mexico during 1994, but no observed lethal takes of Atlantic spotted dolphins by this fishery in the Gulf of Mexico. 

Estimates of fishery-related mortality and serious injury were based on a generalized linear model (Poisson

error assumption) fit to the available observed incidental take for the entire Atlantic longline swordfish/tuna fishery

(which includes the Gulf of Mexico) (SEFSC, unpublished data). Takes observed throughout the range of this

fishery were used because the species occurs generally throughout the area of the fishery, but observed takes were

infrequent in any given region. Either spotted dolphin species may have been involved in the observed fisheryrelated mortality and serious injury incidents, but because of the difficulty of species identification by fishery

observers, they cannot currently be separated. Estimated mortality and serious injury to spotted dolphins attributable

to the longline fishery for the entire fishery (including waters outside of the Gulf of Mexico) for 1993 was 16 (CV =

0.19). Estimated fishery-related mortality and serious injury for the Gulf of Mexico, based on proportionality of

fishing
265

effort (number of sets) in 1993 was 4.4 spotted dolphins. Estimated average annual fishing-related mortality and

serious injury of spotted dolphins attributable to this fishery during 1991-1993 was 1.5 annually (CV = 0.33).

Pair trawl fishing gear has the potential to capture marine mammals, but there have been no reports of

mortality or serious injury to marine mammals in the Gulf of Mexico. This fishery has not been observed by NMFS

observers, and there are no other data available as to the extent of this fishery in the Gulf of Mexico. It is assumed

that it is very limited in scope and duration. 

STATUS OF STOCK

The status of this stock relative to OSP is unknown and there are insufficient data to determine population

trends. This species is not listed under the Endangered Species Act. The total level of human-caused mortality and

serious injury is unknown, but it is believed to be low relative to PBR; therefore, this is not a strategic stock.

REFERENCES

Anon. 1994. Report of the PBR (Potential Biological Removal) workshop. June 27-29, 1994. NOAA, NMFS

Southwest Fisheries Science Center, La Jolla, California, 13 pp. + Appendices. 

Blaylock, R. A. and W. Hoggard. 1994. Preliminary estimates of bottlenose dolphin abundance in southern U.S.

Atlantic and Gulf of Mexico continental shelf waters. NOAA Tech. Mem. NMFS-SEFSC-356, 10 pp. 

Buckland, S. T., D. R. Anderson, K. P. Burnham and J. L. Laake. 1993. Distance Sampling: estimating abundance

of biological populations. Chapman & Hall, London, 446 pp. 

Caldwell, D. K. and M. C. Caldwell. 1966. Observations on the distribution, coloration, behavior and audible sound

production of the spotted dolphin, Stenella plagiodon (Cope). Los Angeles County Museum Contribution to

Science, 104:1-28. 

Cramer, J. 1994. Large pelagic logbook newsletter - 1993. NOAA Tech. Mem. NMFS-SEFSC-352, 19 pp. 

Davis, R., G. Scott, B. Würsig, W. Evans, G. Fargion, L. Hansen, K. Mullin, N. May, T. Leming, B. Mate, J. Norris

and T. Jefferson. In preparation. Distribution and abundance of marine mammals in the north-central and

western Gulf of Mexico: Final Report. OCS Study #MMS 94-0003. Texas Institute of Oceanography and

the National Marine Fisheries Service. U.S. Dept. of the Interior, Minerals Mgmt. Service, Gulf of Mexico

OCS Region, New Orleans, Louisiana. 

Fritts, T. H., A. B. Irvine, R. D. Jennings, L. A. Collum, W. Hoffman and M. A. McGehee. 1983. Turtles, birds, and

mammals in the northern Gulf of Mexico and nearby Atlantic waters. U.S. Fish and Wildlife Service,

Division of Biological Services, Washington, D. C., FWS/OBS-82/65, 455 pp. 

Hansen, L. J., K. D. Mullin and C. L. Roden. 1995. Estimates of cetacean abundance in the northern Gulf of

Mexico from vessel surveys. Southeast Fisheries Science Center, Miami Laboratory, Contribution No.

MIA-94/95-25, 9 pp. + tables and figures.

Laake, J. L., S. T. Buckland, D. R. Anderson, and K. P. Burnham. DISTANCE user’s guide, V2.0. Colorado

Cooperative Fish & Wildlife Research Unit, Colorado State University, Ft. Collins, Colorado, 72 pp. 

Mullin, K., W. Hoggard, C. Roden, R. Lohoefener, C. Rogers and B. Taggart. 1991. Cetaceans on the upper

continental slope in the north-central Gulf of Mexico. OCS Study/MMS 91-0027. U.S. Dept. of the

Interior, Minerals Management Service, Gulf of Mexico OCS Regional Office, New Orleans, 108 pp. 

Perrin, W. F., E. D. Mitchell, J. G. Mead, D. K. Caldwell, M. C. Caldwell, P. J. H. van Bree and W. H. Dawbin.

1987. Revision of the spotted dolphins, Stenella spp. Mar. Mam. Sci. 3(2):99-170.

Perrin, W. F., D. K. Caldwell and M. C. Caldwell. 1994. Atlantic spotted dolphin Stenella frontalis (G. Cuvier,

1829). Pages 173-190 in S. H. Ridgway and R. Harrison (editors), Handbook of marine mammals, Vol. 5: 

The first book of dolphins. Academic Press, London, 416 pp. 
266

Figure 1. Distribution of pantropical spotted dolphin sightings during NOAA

Ship Oregon II marine mammal surveys during 1991-1994. The straight lines

show transects during two surveys and are examples of typical survey transects. 

Isobaths are in 183 m (100 fm) intervals.

July 1995

PANTROPICAL SPOTTED DOLPHIN (Stenella attenuata):

Northern Gulf of Mexico Stock

STOCK DEFINITION AND GEOGRAPHIC RANGE

The pantropical spotted dolphin is distributed worldwide in tropical and some sub-tropical oceans (Perrin et

al. 1987; Perrin and Hohn 1994). Sightings of this species occurred over the deeper waters of the northern Gulf of

Mexico, and rarely over the continental shelf or continental shelf edge [Mullin et al. 1991; Southeast Fisheries

Science Center (SEFSC) unpublished data]. Pantropical spotted dolphins were seen in all seasons during recent

seasonal GulfCet aerial surveys of the northern Gulf of Mexico during 1993-1995 (Davis et al., in preparation). 

Some of the Pacific populations have been divided into different geographic stocks based on morphological

characteristics (Perrin et al. 1987; Perrin and Hohn 1994); however, there is no information on stock differentiation

for the Atlantic population. 

POPULATION SIZE

Estimates of abundance were derived through the application of distance sampling analysis (Buckland et al.

1993) and the computer program DISTANCE (Laake et al. 1993) to sighting data collected during 1991-1994 springsummer, visual sampling, line-transect vessel surveys of the northern Gulf of Mexico (Hansen et al. 1995) (Fig. 1),

which includes data collected as part of the GulfCet program (Davis et al., in preparation). These surveys were

conducted throughout the area from approximately the 200 m isobath along the U.S. coast to the seaward extent of

the U.S. Exclusive Economic

Zone. The seasonal GulfCet

aerial surveys included only a

small portion of the stock range

and these data were not used for

abundance estimation.

Estimated abundance of

pantropical spotted dolphins by

survey year [coefficient of

variation (CV) in parentheses]

was 19,767 in 1991 (0.45),

15,280 in 1992 (0.36), 29,414 in

1993 (0.29), and 71,847 in 1994

(0.31) (Hansen et al. 1995). 

Survey effort-weighted

estimated average abundance of

pantropical spotted dolphins for

all surveys combined was

31,320 (CV = 0.20) (Hansen et

al. 1995).

Minimum Population Estimate

The minimum population size was estimated from the average estimated abundance of pantropical spotted

dolphins which was 31,320 (CV = 0.20) (Hansen et al. 1995). The minimum population estimate is the lower limit

of the two-tailed 60% confidence interval of the log-normal distributed abundance estimate, which is equivalent to

the 20th percentile of the log-normal distributed abundance estimate as specified by NMFS (Anon. 1994). The

minimum population estimate is 26,510 pantropical spotted dolphins. 

Current Population Trend

The 1994 abundance estimate was larger than the estimates for 1991-1993. The 1992 and 1994 estimates

were significantly different using the criteria of no overlap of log-normal 95% confidence intervals, but differences

within 1991-1993 estimates and differences between 1991, 1993, and 1994 were not significant. The observed
267

differences in abundance estimates may have been caused by inter-annual variation in distribution patterns and

spatial sampling, rather than changes in population size. 

CURRENT AND MAXIMUM NET PRODUCTIVITY RATES

Current and maximum net productivity rates are not known for this stock; therefore, the default maximum

net productivity rate of 0.04 (Anon. 1994) was used for purposes of this assessment. 

POTENTIAL BIOLOGICAL REMOVAL

Potential biological removal level (PBR) was specified as the product of the minimum population size, one

half the maximum net productivity rate, and a recovery factor for endangered, threatened, or depleted stocks, or

stocks of unknown status relative to optimum sustainable population (OSP) (Anon. 1994). The recovery factor was

set at 0.50 because the status of the stock relative to OSP is unknown. The resulting PBR for this stock is 265

animals. 

ANNUAL HUMAN-CAUSED MORTALITY AND SERIOUS INJURY

The level of past or current, direct, human-caused mortality of pantropical spotted dolphins in the northern

Gulf of Mexico is unknown; however, interactions between spotted dolphins and fisheries have been observed in the

northern Gulf of Mexico.

There was one documented stranding of a pantropical spotted dolphin in the northern Gulf of Mexico

during 1987-1994 which was classified as likely caused by fishery interactions. Stranding data probably

underestimate the extent of fishery-related mortality and serious injury because not all of the dolphins which die or

are seriously injured in fishery interactions wash ashore, nor will all of those that do wash ashore necessarily show

signs of entanglement or other fishery-interaction. Finally, the level of technical expertise among stranding network

personnel varies widely as does the ability to recognize signs of fishery interaction. 

Total estimated average annual fishing-related mortality and serious injury of spotted dolphins (both

species) is 1.5 spotted dolphins annually (CV = 0.33). Observed fishery-related mortality and serious injury for

spotted dolphins is less than 10% of PBR and can be considered insignificant and approaching zero mortality and

serious injury rate for this stock. This determination cannot be made for specific fisheries until the implementing

regulations for Section 118 of the MMPA have been reviewed by the public and finalized. 

Fisheries Information

Pelagic swordfish, tunas, and billfish are the targets of the longline fishery operating in the U.S. Gulf of

Mexico. Total longline effort for the Gulf of Mexico pelagic fishery, including OCS edge, continental slope, and

Mexican territorial waters, based on mandatory logbook reporting, was 4,400 sets in 1991, 4,850 sets in 1992, and

3,260 sets in 1993 (Cramer 1994). This fishery has been monitored with about 5% observer coverage, in terms of

trips observed, since 1992. There were two observed incidental takes and releases of spotted dolphins in the Gulf of

Mexico during 1994, but no observed lethal takes of Atlantic spotted dolphins by this fishery in the Gulf of Mexico. 

Estimates of fishery-related mortality and serious injury were based on a generalized linear model (Poisson

error assumption) fit to the available observed incidental take for the entire Atlantic longline swordfish/tuna fishery

(which includes the Gulf of Mexico) (SEFSC, unpublished data). Takes observed throughout the range of this

fishery were used because the species occurs generally throughout the area of the fishery, but observed takes were

infrequent in any given region. Either spotted dolphin species may have been involved in the observed fisheryrelated mortality and serious injury incidents, but because of the difficulty of species identification by fishery

observers, they cannot currently be separated. Estimated mortality and serious injury to spotted dolphins attributable

to the longline fishery for the entire fishery (including waters outside of the Gulf of Mexico) for 1993 was 16 (CV =

0.19). Estimated fishery-related mortality and serious injury for the Gulf of Mexico, based on proportionality of

fishing effort (number of sets) in 1993 was 4.4 spotted dolphins. Estimated average annual fishing-related mortality

and serious injury of spotted dolphins attributable to this fishery during 1991-1993 was 1.5 annually (CV = 0.33).

Pair trawl fishing gear has the potential to capture marine mammals, but there have been no reports of

mortality or serious injury to marine mammals in the Gulf of Mexico. This fishery has not been observed by NMFS

observers, and there are no other data available as to the extent of this fishery in the Gulf of Mexico. It is assumed

that it is very limited in scope and duration. 
268

STATUS OF STOCK

The status of this stock relative to OSP is unknown and there are insufficient data to determine population

trends. This species is not listed under the Endangered Species Act. The total level of human-caused mortality and

serious injury is unknown, but it is believed to be insignificant relative to PBR; therefore, this is not a strategic stock. 

REFERENCES

Anon. 1994. Report of the PBR (Potential Biological Removal) workshop. June 27-29, 1994. NOAA, NMFS

Southwest Fisheries Science Center, La Jolla, California, 13 pp. + Appendices. 

Buckland, S. T., D. R. Anderson, K. P. Burnham and J. L. Laake. 1993. Distance Sampling: estimating abundance

of biological populations. Chapman & Hall, London, 446 pp. 

Cramer, J. 1994. Large pelagic logbook newsletter - 1993. NOAA Tech. Mem. NMFS-SEFSC-352, 19 pp. 

Davis, R., G. Scott, B. Würsig, W. Evans, G. Fargion, L. Hansen, K. Mullin, N. May, T. Leming, B. Mate, J. Norris

and T. Jefferson. In preparation. Distribution and abundance of marine mammals in the north-central and

western Gulf of Mexico: Final Report. OCS Study #MMS 94-0003. Texas Institute of Oceanography and

the National Marine Fisheries Service. U.S. Dept. of the Interior, Minerals Mgmt. Service, Gulf of Mexico

OCS Region, New Orleans, Louisiana. 

Hansen, L. J., K. D. Mullin and C. L. Roden. 1995. Estimates of cetacean abundance in the northern Gulf of

Mexico from vessel surveys. Southeast Fisheries Science Center, Miami Laboratory, Contribution No.

MIA-94/95-25, 9 pp. + tables and figures.

Laake, J. L., S. T. Buckland, D. R. Anderson, and K. P. Burnham. DISTANCE user’s guide, V2.0. Colorado

Cooperative Fish & Wildlife Research Unit, Colorado State University, Ft. Collins, Colorado, 72 pp. 

Mullin, K., W. Hoggard, C. Roden, R. Lohoefener, C. Rogers and B. Taggart. 1991. Cetaceans on the upper

continental slope in the north-central Gulf of Mexico. OCS Study/MMS 91-0027. U.S. Dept. of the

Interior, Minerals Management Service, Gulf of Mexico OCS Regional Office, New Orleans, 108 pp. 

Perrin, W. F., E. D. Mitchell, J. G. Mead, D. K. Caldwell, M. C. Caldwell, P. J. H. van Bree, and W. H. Dawbin.

1987. Revision of the spotted dolphins, Stenella spp. Mar. Mam. Sci. 3(2): 99-170.

Perrin, W. F. and A. A. Hohn. 1994. Pantropical spotted dolphin Stenella attenuata. Pages 71-98 in S. H. Ridgway

and R. Harrison (editors), Handbook of marine mammals, Vol. 5: The first book of dolphins. Academic

Press, London, 416 pp. 
269

Figure 1. Distribution of striped dolphin sightings during NOAA Ship Oregon II

marine mammal surveys during 1991-1994. The straight lines show transects

during two surveys and are examples of typical survey transects. Isobaths are in

183 m (100 fm) intervals.

July 1995

STRIPED DOLPHIN (Stenella coeruleoalba):

Northern Gulf of Mexico Stock

STOCK DEFINITION AND GEOGRAPHIC RANGE

The striped dolphin is distributed worldwide in tropical to warm temperate oceanic waters (Leatherwood

and Reeves 1983; Perrin et al. 1994). Sightings of these animals in the northern Gulf of Mexico occur primarily over

the deeper waters off the continental shelf [Mullin et al. 1991; Southeast Fisheries Science Center (SEFSC)

unpublished data]. Striped dolphins were seen in fall, winter, and spring during recent seasonal GulfCet aerial

surveys of the northern Gulf of Mexico during 1993-1995 (Davis et al., in preparation). There is no information on

stock differentiation for the Atlantic population. 

POPULATION SIZE

Estimates of abundance were derived through the application of distance sampling analysis (Buckland et al.

1993) and the computer program DISTANCE (Laake et al. 1993) to sighting data collected during 1991-1994 springsummer, visual sampling, line-transect vessel surveys of the northern Gulf of Mexico (Hansen et al. 1995) (Fig. 1),

which includes data collected as part of the GulfCet program (Davis et al., in preparation). These surveys were

conducted throughout the area from approximately the 200 m isobath along the U.S. coast to the seaward extent of

the U.S. Exclusive Economic

Zone. The seasonal GulfCet

aerial surveys included only a

small portion of the stock range

and these data were not used for

abundance estimation.

Estimated abundance of striped

dolphins by survey year

[coefficient of variation (CV) in

parentheses] was 3,483 in 1991

(0.76), 2,574 in 1992 (0.52),

4,160 in 1993 (0.63), and 8,147

in 1994 (0.60) (Hansen et al.

1995). Survey effort-weighted

estimated average abundance of

striped dolphins for all surveys

combined was 4,858 (CV =

0.44) (Hansen et al. 1995).

Minimum Population

Estimate

The minimum population size was estimated from the average estimate abundance which was 4,858 striped

dolphins (CV = 0.44) (Hansen et al. 1995). The minimum population estimate is the lower limit of the two-tailed

60% confidence interval of the log-normal distributed abundance estimate, which is equivalent to the 20th percentile

of the log-normal distributed abundance estimate as specified by NMFS (Anon. 1994). The minimum population

estimate is 3,409 striped dolphins. 

Current Population Trend

The abundance estimates for 1991-1993 were less than the 1994 estimate. The abundance estimates were

not significantly different using the criteria of no overlap of log-normal 95% confidence intervals. The apparent

differences in abundance estimates may have been caused by small sample sizes; only 29 observations of herds of

striped dolphins were used in the distance sampling analysis. The differences in the estimates may also have been

caused by inter-annual variation in distribution patterns and spatial sampling, rather than changes in population size.
270

CURRENT AND MAXIMUM NET PRODUCTIVITY RATES

Current and maximum net productivity rates are not known for this stock; therefore, the default maximum

net productivity rate of 0.04 (Anon. 1994) was used for purposes of this assessment. 

POTENTIAL BIOLOGICAL REMOVAL

Potential biological removal level (PBR) was specified as the product of the minimum population size, one

half the maximum net productivity rate, and a recovery factor for endangered, threatened, or depleted stocks, or

stocks of unknown status relative to optimum sustainable population (OSP) (Anon. 1994). The recovery factor was

set at 0.50 because the status of the stock relative to OSP is unknown. PBR for this stock is 34 striped dolphins. 

ANNUAL HUMAN-CAUSED MORTALITY AND SERIOUS INJURY

The level of past or current, direct, human-caused mortality of striped dolphins in the northern Gulf of

Mexico is unknown. Available information indicates there likely is little, if any, fisheries interaction with striped

dolphins in the northern Gulf of Mexico. There have been no logbook reports of fishery-related mortality or serious

injury and no fishery-related mortality or serious injury has been observed.

There were no documented strandings of striped dolphins in the northern Gulf of Mexico during 1987-1994

which were classified as likely caused by fishery interactions or other human-related causes. Stranding data

probably underestimate the extent of fishery-related mortality and serious injury because not all of the dolphins

which die or are seriously injured in fishery interactions wash ashore, nor will all of those that do wash ashore

necessarily show signs of entanglement or other fishery-interaction. Finally, the level of technical expertise among

stranding network personnel varies widely as does the ability to recognize signs of fishery interaction. 

Total known fishery-related mortality and serious injury for this stock is less than 10% of the calculated

PBR and, therefore, can be considered insignificant and approaching zero mortality and serious injury rate. This

determination cannot be made for specific fisheries until the implementing regulations for Section 118 of the MMPA

have been reviewed by the public and finalized. 

Fisheries Information

 Pelagic swordfish, tunas, and billfish are the targets of the longline fishery operating in the U.S. Gulf of

Mexico. Total longline effort for the Gulf of Mexico pelagic fishery, including OCS edge, continental slope, and

Mexican territorial waters, based on mandatory logbook reporting, was 4,400 sets in 1991, 4,850 sets in 1992, and

3,260 sets in 1993 (Cramer 1994). This fishery has been monitored with about 5% observer coverage, in terms of

trips observed, since 1992. There were no reports of mortality or serious injury to striped dolphins by this fishery. 

Pair trawl fishing gear has the potential to capture marine mammals, but there have been no reports of

mortality or serious injury to marine mammals in the Gulf of Mexico. This fishery has not been observed by NMFS

observers, and there are no other data available as to the extent of this fishery in the Gulf of Mexico. It is assumed

that it is very limited in scope and duration. 

STATUS OF STOCK

The status of this stock relative to OSP is unknown and there are insufficient data to determine population

trends. This species is not listed under the Endangered Species Act. The total level of human-caused mortality and

serious injury is unknown, but it is believed to be insignificant relative to PBR; therefore, this is not a strategic stock. 

REFERENCES

Anon. 1994. Report of the PBR (Potential Biological Removal) workshop. June 27-29, 1994. NOAA, NMFS

Southwest Fisheries Science Center, La Jolla, California, 13 pp. + Appendices. 

Buckland, S. T., D. R. Anderson, K. P. Burnham and J. L. Laake. 1993. Distance Sampling: estimating abundance

of biological populations. Chapman & Hall, London, 446 pp. 

Cramer, J. 1994. Large pelagic logbook newsletter - 1993. NOAA Tech. Mem. NMFS-SEFSC-352, 19 pp.

Davis, R., G. Scott, B. Würsig, W. Evans, G. Fargion, L. Hansen, K. Mullin, N. May, T. Leming, B. Mate, J. Norris

and T. Jefferson. In preparation. Distribution and abundance of marine mammals in the north-central and

western Gulf of Mexico: Final Report. OCS Study #MMS 94-0003. Texas Institute of Oceanography and

the National Marine Fisheries Service. U.S. Dept. of the Interior, Minerals Mgmt. Service, Gulf of Mexico

OCS Region, New Orleans, Louisiana. 
271

Hansen, L. J., K. D. Mullin and C. L. Roden. 1995. Estimates of cetacean abundance in the northern Gulf of

Mexico from vessel surveys. Southeast Fisheries Science Center, Miami Laboratory, Contribution No.

MIA-94/95-25, 9 pp. + tables and figures.

Laake, J. L., S. T. Buckland, D. R. Anderson, and K. P. Burnham. DISTANCE user’s guide, V2.0. Colorado

Cooperative Fish & Wildlife Research Unit, Colorado State University, Ft. Collins, Colorado, 72 pp. 

Leatherwood, S. and R. R. Reeves. 1983. The Sierra Club handbook of whales and dolphins. Sierra Club Books,

San Francisco, 302 pp. 

Mullin, K., W. Hoggard, C. Roden, R. Lohoefener, C. Rogers and B. Taggart. 1991. Cetaceans on the upper

continental slope in the north-central Gulf of Mexico. OCS Study/MMS 91-0027. U.S. Dept. of the

Interior, Minerals Management Service, Gulf of Mexico OCS Regional Office, New Orleans, 108 pp. 

Perrin, W. F., C. E. Wilson and F. I. Archer II. 1994. Striped dolphin Stenella coeruleoalba (Meyen, 1833). Pages

129-159 in S. H. Ridgway and R. Harrison (editors), Handbook of marine mammals, Vol. 5: The first book

of dolphins. Academic Press, London, 416 pp. 
272

Figure 1. Distribution of spinner dolphin sightings during NOAA Ship Oregon

II marine mammal surveys during 1991-1994. The straight lines show transects

during two surveys and are examples of typical survey transects. Isobaths are in

183 m (100 fm) intervals.

July 1995

SPINNER DOLPHIN (Stenella longirostris):

Northern Gulf of Mexico Stock

STOCK DEFINITION AND GEOGRAPHIC RANGE

The spinner dolphin is distributed worldwide in tropical to warm temperate waters in the world's oceans

(Leatherwood and Reeves 1983; Perrin and Gilpatrick 1994). Sightings of these animals in the northern Gulf of

Mexico occur primarily over the deeper waters off the continental shelf [Southeast Fisheries Science Center

(SEFSC) unpublished data]. Spinner dolphins were seen in winter, spring and summer during recent seasonal

GulfCet aerial surveys of the northern Gulf of Mexico during 1993-1995 (Davis et al., in preparation). Different

geographic stocks have been identified in the Pacific based on morphological characteristics (Perrin and Gilpatrick

1994); however, there is no information on stock differentiation for the Atlantic population. 

POPULATION SIZE

Estimates of abundance were derived through the application of distance sampling analysis (Buckland et al.

1993) and the computer program DISTANCE (Laake et al. 1993) to sighting data collected during 1991-1994 springsummer, visual sampling, line-transect vessel surveys of the northern Gulf of Mexico (Hansen et al. 1995) (Fig. 1),

which includes data collected as part of the GulfCet program (Davis et al., in preparation). These surveys were

conducted throughout the area from approximately the 200 m isobath along the U.S. coast to the seaward extent of

the U.S. Exclusive Economic

Zone. The seasonal GulfCet

aerial surveys included only a

small portion of the stock range

and these data were not used for

abundance estimation. 

Estimated abundance of spinner

dolphins by survey year

[coefficient of variation (CV) in

parentheses] was zero in 1991, 

2,593 in 1992 (0.63), 2,336 in

1993 (0.62), and 15,995 in 1994

(0.67) (Hansen et al. 1995). 

Survey effort-weighted

estimated average abundance of

spinner dolphins for all surveys

combined was 6,316 (CV =

0.43) (Hansen et al. 1995).

Minimum Population

Estimate

The minimum population size was estimated from the average estimate abundance which was 6,316 spinner

dolphins (CV = 0.43) (Hansen et al. 1995). The minimum population estimate is the lower limit of the two-tailed

60% confidence interval of the log-normal distributed abundance estimate, which is equivalent to the 20th percentile

of the log-normal distributed abundance estimate as specified by NMFS (Anon. 1994). The minimum population

estimate is 4,465 spinner dolphins. 

Current Population Trend

The abundance estimates for 1992 and 1993 were approximately the same and the 1994 estimate was

considerably larger; however, the estimates were not significantly different using the criteria of no overlap of lognormal 95% confidence intervals. The apparent differences in abundance estimates may have been caused by less

sampling effort during 1991 (Hansen et al. 1995), or by inter-annual variation in distribution patterns or spatial

sampling patterns, rather than changes in population size. 
273

CURRENT AND MAXIMUM NET PRODUCTIVITY RATES

Current and maximum net productivity rates for this stock are not known; therefore, the default maximum

net productivity rate of 0.04 (Anon. 1994) was used for purposes of this assessment. 

POTENTIAL BIOLOGICAL REMOVAL

Potential biological removal level (PBR) was specified as the product of the minimum population size, one

half the maximum net productivity rate, and a recovery factor for endangered, threatened, or depleted stocks, or

stocks of unknown status relative to optimum sustainable population (OSP) (Anon. 1994). The recovery factor was

set at 0.50 because the status of the stock relative to OSP is unknown. PBR for this stock is 45 spinner dolphins. 

 

ANNUAL HUMAN-CAUSED MORTALITY AND SERIOUS INJURY

The level of past or current, direct, human-caused mortality of spinner dolphins in the northern Gulf of

Mexico is unknown. Available information indicates there likely is little, if any, fisheries interaction with spinner 

dolphins in the northern Gulf of Mexico. There have been no logbook reports of fishery-related mortality or serious

injury and no fishery-related mortality or serious injury has been observed.

There were no documented strandings of spinner dolphins in the northern Gulf of Mexico during 1987-1994

which were classified as likely caused by fishery interactions or other human-related causes. Stranding data

probably underestimate the extent of fishery-related mortality and serious injury because not all of the dolphins

which die or are seriously injured in fishery interactions wash ashore, nor will all of those that do wash ashore

necessarily show signs of entanglement or other fishery-interaction. Finally, the level of technical expertise among

stranding network personnel varies widely as does the ability to recognize signs of fishery interaction. 

The total known fishery-related mortality and serious injury for this stock is less than 10% of the calculated

PBR and, therefore, can be considered insignificant and approaching zero mortality and serious injury rate. This

determination cannot be made for specific fisheries until the implementing regulations for Section 118 of the MMPA

have been reviewed by the public and finalized. 

Fisheries Information

Pelagic swordfish, tunas, and billfish are the targets of the longline fishery operating in the U.S. Gulf of

Mexico. Total longline effort for the Gulf of Mexico pelagic fishery, including OCS edge, continental slope, and

Mexican territorial waters, based on mandatory logbook reporting, was 4,400 sets in 1991, 4,850 sets in 1992, and

3,260 sets in 1993 (Cramer 1994). This fishery has been monitored with about 5% observer coverage, in terms of

trips observed, since 1992. There were no reports of mortality or serious injury of spinner dolphins by this fishery. 

Pair trawl fishing gear has the potential to capture marine mammals, but there have been no reports of

mortality or serious injury to marine mammals in the Gulf of Mexico. This fishery has not been observed by NMFS

observers, and there are no other data available as to the extent of this fishery in the Gulf of Mexico. It is assumed

that it is very limited in scope and duration. 

STATUS OF STOCK

The status of this stock relative to OSP is unknown and there are insufficient data to determine population

trends. This species is not listed under the Endangered Species Act. The total level of human-caused mortality and

serious injury is unknown, but it is believed to be insignificant relative to PBR; therefore, this is not a strategic stock. 

REFERENCES

Anon. 1994. Report of the PBR (Potential Biological Removal) workshop. June 27-29, 1994. NOAA, NMFS

Southwest Fisheries Science Center, La Jolla, California, 13 pp. + Appendices. 

Buckland, S. T., D. R. Anderson, K. P. Burnham and J. L. Laake. 1993. Distance Sampling: estimating abundance

of biological populations. Chapman & Hall, London, 446 pp. 

Cramer, J. 1994. Large pelagic logbook newsletter - 1993. NOAA Tech. Mem. NMFS-SEFSC-352, 19 pp.

Davis, R., G. Scott, B. Würsig, W. Evans, G. Fargion, L. Hansen, K. Mullin, N. May, T. Leming, B. Mate, J. Norris

and T. Jefferson. In preparation. Distribution and abundance of marine mammals in the north-central and

western Gulf of Mexico: Final Report, OCS Study #MMS 94-0003. Texas Institute of Oceanography

andthe National Marine Fisheries Service. U.S. Dept. of the Interior, Minerals Mgmt. Service, Gulf of

Mexico OCS Region, New Orleans, Louisiana. 
274

Hansen, L. J., K. D. Mullin and C. L. Roden. 1995. Estimates of cetacean abundance in the northern Gulf of

Mexico from vessel surveys. Southeast Fisheries Science Center, Miami Laboratory, Contribution No.

MIA-94/95-25, 9 pp + tables and figures. 

Laake, J. L., S. T. Buckland, D. R. Anderson, and K. P. Burnham. DISTANCE user’s guide, V2.0. Colorado

Cooperative Fish & Wildlife Research Unit, Colorado State University, Ft. Collins, Colorado, 72 pp. 

Leatherwood, S. and R. R. Reeves. 1983. The Sierra Club handbook of whales and dolphins. Sierra Club Books,

San Francisco, 302 pp. 

Perrin, W. F. and J. W. Gilpatrick, Jr. 1994. Spinner dolphin Stenella longirostris (Gray, 1828). Pages 99-128 in S.

H. Ridgway and R. Harrison (editors), Handbook of marine mammals, Vol. 5: The first book of dolphins. 

Academic Press, London, 416 pp.
275

Figure 1. Distribution of rough-toothed dolphin sightings during NOAA Ship

Oregon II marine mammal surveys during 1991-1994. The straight lines show

transects during two surveys and are examples of typical survey transects. 

Isobaths are in 183 m (100 fm) intervals.

July 1995

ROUGH-TOOTHED DOLPHIN (Steno bredanensis):

Northern Gulf of Mexico Stock

STOCK DEFINITION AND GEOGRAPHIC RANGE

The rough-toothed dolphin is distributed worldwide in tropical to warm temperate waters (Leatherwood

and Reeves 1983; Miyazaki and Perrin 1994). Sightings of these animals in the northern Gulf of Mexico occur

primarily over the deeper waters off the continental shelf [Southeast Fisheries Science Center (SEFSC) unpublished

data]. Rough-toothed dolphins were seen in all seasons during recent seasonal GulfCet aerial surveys of the northern

Gulf of Mexico during 1993-1995 (Davis et al., in preparation). There is no information on stock differentiation for

the Atlantic population. 

POPULATION SIZE

Estimates of abundance were derived through the application of distance sampling analysis (Buckland et al.

1993) and the computer program DISTANCE (Laake et al. 1993) to sighting data collected during 1991-1994 springsummer, visual sampling, line-transect vessel surveys of the northern Gulf of Mexico (Hansen et al. 1995), which

includes data collected as part of the GulfCet program (Davis et al., in preparation). These surveys were conducted

throughout the area from approximately the 200 m isobath along the U.S. coast to the seaward extent of the U.S.

Exclusive Economic Zone. The

seasonal GulfCet aerial surveys

included only a small portion of

the stock range and these data

were not used for abundance

estimation. Estimated abundance

of rough-toothed dolphins by

survey year [coefficient of

variation (CV) in parentheses]

was 545 in 1991 (1.15), 758 in

1992 (0.58), 1,192 in 1993

(0.48), and 527 in 1994 (0.86)

(Hansen et al. 1995). Survey

effort-weighted estimated

average abundance of roughtoothed dolphins for all surveys

combined was 852 (CV = 0.31)

(Hansen et al. 1995).

Minimum Population Estimate

The minimum population size was estimated from the average estimate abundance which was 852 roughtoothed dolphins (CV = 0.31) (Hansen et al. 1995). The minimum population estimate is the lower limit of the twotailed 60% confidence interval of the log-normal distributed abundance estimate, which is equivalent to the 20th

percentile of the log-normal distributed abundance estimate as specified by NMFS (Anon. 1994). The minimum

population estimate is 660 rough-toothed dolphins. 

Current Population Trend

The 1993 abundance estimate was greater than the 1991, 1993, and 1994 estimates; however, the

abundance estimates were not significantly different using the criteria of no overlap of log-normal 95% confidence

intervals. The apparent differences in abundance estimates may have been caused by small sample sizes (Hansen et

al. 1995) or by inter-annual variation in distribution patterns or spatial sampling patterns, rather than changes in

population size. 
276

CURRENT AND MAXIMUM NET PRODUCTIVITY RATES

Current and maximum net productivity rates are not known for this stock; therefore, the default maximum

net productivity rate of 0.04 (Anon. 1994) was used for purposes of this assessment. 

POTENTIAL BIOLOGICAL REMOVAL

Potential biological removal level (PBR) was specified as the product of the minimum population size, one

half the maximum net productivity rate, and a recovery factor for endangered, threatened, or depleted stocks, or

stocks of unknown status relative to optimum sustainable population (OSP) (Anon. 1994). The recovery factor was

set at 0.50 because the status of the stock relative to OSP is unknown. The resulting PBR for this stock is 6.6 roughtoothed dolphins. 

ANNUAL HUMAN-CAUSED MORTALITY AND SERIOUS INJURY

The level of past or current, direct, human-caused mortality of rough-toothed dolphins in the northern Gulf

of Mexico is unknown. Available information indicates there likely is little, if any, fisheries interaction with roughtoothed dolphins in the northern Gulf of Mexico. There have been no logbook reports of fishery-related mortality or

serious injury and no fishery-related mortality or serious injury has been observed.

There were no documented strandings of rough-toothed dolphins in the northern Gulf of Mexico during

1987-1994 which were classified as likely caused by fishery interactions or other human-related causes. Stranding

data probably underestimate the extent of fishery-related mortality and serious injury because not all of the marine

mammals which die or are seriously injured may wash ashore, nor will all of those that do wash ashore necessarily

show signs of entanglement or other fishery-interaction. Finally, the level of technical expertise among stranding

network personnel varies widely as does the ability to recognize signs of fishery interaction. 

Total fishery-related mortality and serious injury for this stock is less than 10% of the calculated PBR and,

therefore, can be considered insignificant and approaching zero mortality and serious injury rate. This determination

cannot be made for specific fisheries until the implementing regulations for Section 118 of the MMPA have been

reviewed by the public and finalized. 

Fisheries Information

Pelagic swordfish, tunas, and billfish are the targets of the longline fishery operating in the U.S. Gulf of

Mexico. Total longline effort for the Gulf of Mexico pelagic fishery, including OCS edge, continental slope, and

Mexican territorial waters, based on mandatory logbook reporting, was 4,400 sets in 1991, 4,850 sets in 1992, and

3,260 sets in 1993 (Cramer 1994). This fishery has been monitored with about 5% observer coverage, in terms of

trips observed, since 1992. There were no reports of mortality or serious injury of rough-toothed dolphins by this

fishery. 

Pair trawl fishing gear has the potential to capture marine mammals, but there have been no reports of

mortality or serious injury to marine mammals in the Gulf of Mexico. This fishery has not been observed by NMFS

observers, and there are no other data available as to the extent of this fishery in the Gulf of Mexico. It is assumed

that it is very limited in scope and duration. 

STATUS OF STOCK

The status of this stock relative to OSP is unknown and there are insufficient data to determine population

trends. This species is not listed under the Endangered Species Act. The total level of human-caused mortality and

serious injury is unknown, but it is believed to be insignificant relative to PBR; therefore, this is not a strategic stock. 

REFERENCES

Anon. 1994. Report of the PBR (Potential Biological Removal) workshop. June 27-29, 1994. NOAA, NMFS

Southwest Fisheries Science Center, La Jolla, California, 13 pp. + Appendices. 

Buckland, S. T., D. R. Anderson, K. P. Burnham and J. L. Laake. 1993. Distance Sampling: estimating abundance

of biological populations. Chapman & Hall, London, 446 pp. 

Cramer, J. 1994. Large pelagic logbook newsletter - 1993. NOAA Tech. Mem. NMFS-SEFSC-352, 19 pp. 

Davis, R., G. Scott, B. Würsig, W. Evans, G. Fargion, L. Hansen, K. Mullin, N. May, T. Leming, B. Mate, J. Norris

and T. Jefferson. In preparation. Distribution and abundance of marine mammals in the north-central and

western Gulf of Mexico: Final Report. OCS Study #MMS 94-0003. Texas Institute of Oceanography and
277

the National Marine Fisheries Service. U.S. Dept. of the Interior, Minerals Mgmt. Service, Gulf of Mexico

OCS Region, New Orleans, Louisiana. 

Hansen, L. J., K. D. Mullin and C. L. Roden. 1995. Estimates of cetacean abundance in the northern Gulf of

Mexico from vessel surveys. Southeast Fisheries Science Center, Miami Laboratory, Contribution No.

MIA-94/95-25, 9 pp. + tables and figures. 

Laake, J. L., S. T. Buckland, D. R. Anderson, and K. P. Burnham. DISTANCE user’s guide, V2.0. Colorado

Cooperative Fish & Wildlife Research Unit, Colorado State University, Ft. Collins, Colorado, 72 pp. 

Leatherwood, S. and R. R. Reeves. 1983. The Sierra Club handbook of whales and dolphins. Sierra Club Books,

San Francisco, 302 pp. 

Miyazaki, N. and W. F. Perrin. 1994. Rough-toothed dolphin Steno bredanensis (Lesson, 1828). Pages 1-21 in S.

H. Ridgway and R. Harrison (editors), Handbook of marine mammals, Vol. 5: The first book of dolphins. 

Academic Press, London, 416 pp.
278

Figure 1. Distribution of clymene dolphin sightings during NOAA Ship Oregon

II marine mammal surveys during 1991-1994. The straight lines show transects

during two surveys and are examples of typical survey transects. Isobaths are in

183 m (100 fm) intervals.

July 1995

CLYMENE DOLPHIN (Stenella clymene):

Northern Gulf of Mexico Stock

STOCK DEFINITION AND GEOGRAPHIC RANGE

The Clymene dolphin is endemic to tropical and sub-tropical waters of the Atlantic (Leatherwood and

Reeves 1983; Perrin and Mead 1994). Sightings of these animals in the northern Gulf of Mexico occur primarily

over the deeper waters off the continental shelf (Mullin et al. 1994). Clymene dolphins were seen in the winter,

spring and summer during recent seasonal GulfCet aerial surveys of the northern Gulf of Mexico during 1993-1995

(Davis et al., in preparation). There is no information on stock differentiation for the Atlantic population. 

POPULATION SIZE

Estimates of abundance were derived through the application of distance sampling analysis (Buckland et al.

1993) and the computer program DISTANCE (Laake et al. 1993) to sighting data collected during 1991-1994 springsummer, visual sampling, line-transect vessel surveys of the northern Gulf of Mexico (Hansen et al. 1995) (Fig. 1),

which includes data collected as part of the GulfCet program (Davis et al., in preparation). These surveys were

conducted throughout the area from approximately the 200 m isobath along the U.S. coast to the seaward extent of

the U.S. Exclusive Economic

Zone. The seasonal GulfCet

aerial surveys included only a

small portion of the stock range

and these data were not used for

abundance estimation. Estimated

abundance of Clymene dolphins

by survey year [coefficient of

variation (CV) in parentheses]

was 1,936 in 1991 (0.69), 3,390

in 1992 (0.48), 6,486 in 1993

(0.46), and 12,255 in 1994

(0.62) (Hansen et al. 1995). 

Survey effort-weighted

estimated average abundance of

Clymene dolphins for all

surveys combined was 5,571

(CV = 0.37) (Hansen et al.

1995). 

Minimum Population Estimate

The minimum population size was estimated from the average estimate abundance which was 5,571

Clymene dolphins (CV = 0.37) (Hansen et al. 1995). The minimum population estimate is the lower limit of the

two-tailed 60% confidence interval of the log-normal distributed abundance estimate, which is equivalent to the 20th

percentile of the log-normal distributed abundance estimate as specified by NMFS (Anon. 1994). The minimum

population estimate is 4,120 Clymene dolphins. 

Current Population Trend

The abundance estimates showed an increasing trend during 1991-1994; however, the estimates were not

significantly different using the criteria of no overlap of log-normal 95% confidence intervals. The apparent

differences in abundance estimates may have been caused by small sample sizes (Hansen et al. 1995) or by interannual variation in distribution patterns or spatial sampling patterns, rather than changes in population size. 

CURRENT AND MAXIMUM NET PRODUCTIVITY RATES

Current and maximum net productivity rates are not known for this stock; therefore, the default maximum

net productivity rate of 0.04 (Anon. 1994) was used for purposes of this assessment. 
279

POTENTIAL BIOLOGICAL REMOVAL

Potential biological removal level (PBR) was specified as the product of the minimum population size, one

half the maximum net productivity rate, and a recovery factor for endangered, threatened, or depleted stocks, or

stocks of unknown status relative to optimum sustainable population (OSP) (Anon. 1994). The recovery factor was

set at 0.50 because the status of the stock relative to OSP is unknown. PBR for this stock is 41 Clymene dolphins. 

ANNUAL HUMAN-CAUSED MORTALITY AND SERIOUS INJURY

The level of past or current, direct, human-caused mortality of Clymene dolphins in the northern Gulf of

Mexico is unknown. Available information indicates there likely is little, if any, fisheries interaction with Clymene

dolphins in the northern Gulf of Mexico. There have been no logbook reports of fishery-related mortality or serious

injury and no fishery-related mortality or serious injury has been observed.

There were no documented strandings of Clymene dolphins in the northern Gulf of Mexico during 1987-

1994 which were classified as likely caused by fishery interactions or other human-related causes. Stranding data

probably underestimate the extent of fishery-related mortality and serious injury because not all of the marine

mammals which die or are seriously injured may wash ashore, nor will all of those that do wash ashore necessarily

show signs of entanglement or other fishery-interaction. Finally, the level of technical expertise among stranding

network personnel varies widely as does the ability to recognize signs of fishery interaction. 

The total known fishery-related mortality and serious injury for this stock is less than 10% of the calculated

PBR and, therefore, can be considered insignificant and approaching zero mortality and serious injury rate. This

determination cannot be made for specific fisheries until the implementing regulations for Section 118 of the MMPA

have been reviewed by the public and finalized. 

Fisheries Information

Pelagic swordfish, tunas, and billfish are the targets of the longline fishery operating in the U.S. Gulf of

Mexico. Total longline effort for the Gulf of Mexico pelagic fishery, including OCS edge, continental slope, and

Mexican territorial waters, based on mandatory logbook reporting, was 4,400 sets in 1991, 4,850 sets in 1992, and

3,260 sets in 1993 (Cramer 1994). This fishery has been monitored with about 5% observer coverage, in terms of

trips observed, since 1992. There were no reports of mortality or serious injury to Clymene dolphins by this fishery. 

Pair trawl fishing gear has the potential to capture marine mammals, but there have been no reports of

mortality or serious injury to marine mammals in the Gulf of Mexico. This fishery has not been observed by NMFS

observers, and there are no other data available as to the extent of this fishery in the Gulf of Mexico.

STATUS OF STOCK

The status of this stock relative to OSP is unknown and there are insufficient data to determine population

trends. This species is not listed under the Endangered Species Act. The total level of human-caused mortality and

serious injury is unknown, but it is believed to be insignificant relative to PBR; therefore, this is not a strategic stock. 

REFERENCES

Anon. 1994. Report of the PBR (Potential Biological Removal) workshop. June 27-29, 1994. NOAA, NMFS

Southwest Fisheries Science Center, La Jolla, California, 13 pp. + Appendices. 

Buckland, S. T., D. R. Anderson, K. P. Burnham and J. L. Laake. 1993. Distance Sampling: estimating abundance

of biological populations. Chapman & Hall, London, 446 pp. 

Cramer, J. 1994. Large pelagic logbook newsletter - 1993. NOAA Tech. Mem. NMFS-SEFSC-352, 19 pp. 

Davis, R., G. Scott, B. Würsig, W. Evans, G. Fargion, L. Hansen, K. Mullin, N. May, T. Leming, B. Mate, J. Norris

and T. Jefferson. In preparation. Distribution and abundance of marine mammals in the north-central and

western Gulf of Mexico: Final Report. OCS Study #MMS 94-0003. Texas Institute of Oceanography and

the National Marine Fisheries Service. U.S. Dept. of the Interior, Minerals Mgmt. Service, Gulf of Mexico

OCS Region, New Orleans, Louisiana. 

Hansen, L. J., K. D. Mullin and C. L. Roden. 1995. Estimates of cetacean abundance in the northern Gulf of

Mexico from vessel surveys. Southeast Fisheries Science Center, Miami Laboratory, Contribution No.

MIA-94/95-25, 9 pp. + tables and figures. 

Laake, J. L., S. T. Buckland, D. R. Anderson, and K. P. Burnham. DISTANCE user’s guide, V2.0. Colorado

Cooperative Fish & Wildlife Research Unit, Colorado State University, Ft. Collins, Colorado, 72 pp. 
280

Leatherwood, S. and R. R. Reeves. 1983. The Sierra Club handbook of whales and dolphins. Sierra Club Books,

San Francisco, 302 pp. 

Mullin, K. D., L V. Higgins, T. A. Jefferson, and L. J. Hansen. 1994. Sightings of the Clymene dolphin (Stenella

clymene) in the Gulf of Mexico. Mar. Mam. Sci. 10(4): 464-470.

Perrin, W. F. and J. G. Mead. 1994. Clymene dolphin Stenella clymene (Gray, 1846). Pages 161-171 in S. H.

Ridgway and R. Harrison (editors), Handbook of marine mammals, Vol. 5: The first book of dolphins. 

Academic Press, London, 416 pp.
281

Figure 1. Distribution of Fraser’s dolphin sightings during NOAA Ship Oregon

II surveys during 1991-1994 (filled circle) and during GulfCet seasonal aerial

surveys (unfilled circles). The straight lines show transects during two ship

surveys and are examples of typical survey transects. Isobaths are in 183 m

(100 fm) intervals.

July 1995

FRASER'S DOLPHIN (Lagenodelphis hosei):

Northern Gulf of Mexico Stock

STOCK DEFINITION AND GEOGRAPHIC RANGE

Fraser's dolphin is distributed worldwide in tropical waters (Perrin et al. 1994). Sightings of these animals

in the northern Gulf of Mexico occur primarily over the deeper waters off the continental shelf (Leatherwood et al.

1993). Fraser's dolphins have been observed recently in the northern Gulf of Mexico during the spring, summer, and

fall (Leatherwood et al. 1993), and also were seen in the winter during recent seasonal GulfCet aerial surveys of the

northern Gulf of Mexico during 1993-1995 (Davis et al., in preparation). There is no information on stock

differentiation for the Atlantic population. 

POPULATION SIZE

Estimates of abundance were derived through the application of distance sampling analysis (Buckland et al.

1993) and the computer program DISTANCE (Laake et al. 1993) to sighting data collected during 1991-1994 springsummer, visual sampling, line-transect vessel surveys of the northern Gulf of Mexico (Hansen et al. 1995) (Fig. 1),

which includes data collected as part of the GulfCet program (Davis et al., in preparation). These surveys were

conducted throughout the area from approximately the 200 m isobath along the U.S. coast to the seaward extent of

the U.S. Exclusive Economic

Zone. The seasonal GulfCet

aerial surveys included only a

small portion of the stock range

and these data were not used for

abundance estimation. Estimated

abundance of Fraser’s dolphins

by survey year [coefficient of

variation (CV) in parentheses]

was zero in 1991, 443 in 1992

(0.92), and zero in 1993 and

1994 (Hansen et al. 1995). 

Survey effort-weighted

estimated average abundance of

Fraser's dolphins for all vessel

surveys combined was 127 (CV 

= 0.90) (Hansen et al. 1995).

Minimum Population Estimate

The minimum

population size was estimated from the average estimate abundance which was 127 Fraser’s dolphins (CV = 0.90)

(Hansen et al. 1995). The minimum population estimate is the lower limit of the two-tailed 60% confidence interval

of the log-normal distributed abundance estimate, which is equivalent to the 20th percentile of the log-normal

distributed abundance estimate as specified by NMFS (Anon. 1994). The minimum population estimate is 66

Fraser’s dolphins. 

Current Population Trend

No trend was identified in the annual abundance estimates. There were no observations of Fraser's dolphins

during 1991 and 1993 vessel surveys, and the 1992 estimate is based on only one observation (Hansen et al. 1995);

however, five other sightings of Fraser's dolphins were documented in the northern Gulf of Mexico during other

surveys in 1992, 1993 and 1994 (Leatherwood et al. 1993, SEFSC unpublished data). The apparent differences in

abundance estimates may have been caused by low sampling intensity relative to population size (Hansen et al.

1995) or by inter-annual variation in distribution patterns or spatial sampling patterns, rather than changes in

population size. 
282

CURRENT AND MAXIMUM NET PRODUCTIVITY RATES

Current and maximum net productivity rates are not known; therefore, the default maximum net

productivity rate of 0.04 (Anon. 1994) was used for purposes of this assessment. 

POTENTIAL BIOLOGICAL REMOVAL

Potential biological removal level (PBR) was specified as the product of the minimum population size, one

half the maximum net productivity rate, and a recovery factor for endangered, threatened, or depleted stocks, or

stocks of unknown status relative to optimum sustainable population (OSP) (Anon. 1994). The recovery factor was

set at 0.50 because the status of the stock relative to OSP is unknown. PBR for this stock is 0.7 Fraser’s dolphins. 

ANNUAL HUMAN-CAUSED MORTALITY AND SERIOUS INJURY

The level of past or current, direct, human-caused mortality of Fraser's dolphins in the northern Gulf of

Mexico is unknown. Available information indicates there likely is little, if any, fisheries interaction with Fraser’s

dolphins in the northern Gulf of Mexico. There have been no logbook reports of fishery-related mortality or serious

injury and no fishery-related mortality or serious injury has been observed.

There were no documented strandings of Fraser's dolphins in the northern Gulf of Mexico during 1987-

1994 which were classified as likely caused by fishery interactions or other human-related causes. Stranding data

probably underestimate the extent of fishery-related mortality and serious injury because not all of the marine

mammals which die or are seriously injured may wash ashore, nor will all of those that do wash ashore necessarily

show signs of entanglement or other fishery-interaction. Finally, the level of technical expertise among stranding

network personnel varies widely as does the ability to recognize signs of fishery interaction. 

 Available information indicates there likely is little, if any, fisheries interaction with Fraser's dolphins in

the northern Gulf of Mexico. The total known fishery-related mortality and serious injury for this stock is less than

10% of the calculated PBR and, therefore, can be considered insignificant and approaching zero mortality and

serious injury rate. This determination cannot be made for specific fisheries until the implementing regulations for

Section 118 of the MMPA have been reviewed by the public and finalized. 

Fisheries Information

Pelagic swordfish, tunas, and billfish are the targets of the longline fishery operating in the U.S. Gulf of

Mexico. Total longline effort for the Gulf of Mexico pelagic fishery, including OCS edge, continental slope, and

Mexican territorial waters, based on mandatory logbook reporting, was 4,400 sets in 1991, 4,850 sets in 1992, and

3,260 sets in 1993 (Cramer 1994). This fishery has been monitored with about 5% observer coverage, in terms of

trips observed, since 1992. There were no reports of mortality or serious injury of Fraser’s dolphins by this fishery. 

Pair trawl fishing gear has the potential to capture marine mammals, but there have been no reports of

mortality or serious injury to marine mammals in the Gulf of Mexico. This fishery has not been observed by NMFS

observers, and there are no other data available as to the extent of this fishery in the Gulf of Mexico.

STATUS OF STOCK

The status of this stock relative to OSP is unknown and there are insufficient data to determine population

trends. This species is not listed under the Endangered Species Act. The total level of human-caused mortality and

serious injury is unknown, but it is believed to be insignificant relative to PBR; therefore this is not a strategic stock. 

REFERENCES

Anon. 1994. Report of the PBR (Potential Biological Removal) workshop. June 27-29, 1994. NOAA, NMFS

Southwest Fisheries Science Center, La Jolla, California, 13 pp. + Appendices. 

Buckland, S. T., D. R. Anderson, K. P. Burnham and J. L. Laake. 1993. Distance Sampling: estimating abundance

of biological populations. Chapman & Hall, London, 446 pp. 

Cramer, J. 1994. Large pelagic logbook newsletter - 1993. NOAA Tech. Mem. NMFS-SEFSC-352, 19 pp. 

Davis, R., G. Scott, B. Würsig, W. Evans, G. Fargion, L. Hansen, K. Mullin, N. May, T. Leming, B. Mate, J. Norris

and T. Jefferson. In preparation. Distribution and abundance of marine mammals in the north-central and

western Gulf of Mexico: Final Report. OCS Study #MMS 94-0003. Texas Institute of Oceanography and

the National Marine Fisheries Service. U.S. Dept. of the Interior, Minerals Mgmt. Service, Gulf of Mexico

OCS Region, New Orleans, Louisiana. 
283

Hansen, L. J., K. D. Mullin and C. L. Roden. 1995. Estimates of cetacean abundance in the northern Gulf of

Mexico from vessel surveys. Southeast Fisheries Science Center, Miami Laboratory, Contribution No.

MIA-94/95-25, 9 pp. + tables and figures. 

Laake, J. L., S. T. Buckland, D. R. Anderson, and K. P. Burnham. DISTANCE user’s guide, V2.0. Colorado

Cooperative Fish & Wildlife Research Unit, Colorado State University, Ft. Collins, Colorado, 72 pp. 

Leatherwood, S., T. A. Jefferson, J. C. Norris, W. E. Stevens, L. J. Hansen, and K. D. Mullin. 1993. Occurrence and

sounds of Fraser's dolphin in the Gulf of Mexico. The Texas Journal of Science, 45(4):349-354. 

Perrin, W. F., S. Leatherwood and A. Collet. 1994. Fraser's dolphin Lagenodelphis hosei (Fraser 1956). Pages 225-

240 in S. H. Ridgway and R. Harrison (editors), Handbook of marine mammals, Vol. 5: The first book of

dolphins. Academic Press, London, 416 pp.
284

Figure 1. Distribution of killer whale sightings during NOAA Ship Oregon II

marine mammal surveys during 1991-1994. The straight lines show transects

during two surveys and are examples of typical survey transects. Isobaths are in

183 m (100 fm) intervals.

July 1995

KILLER WHALE (Orcinus orca):

Northern Gulf of Mexico Stock

STOCK DEFINITION AND GEOGRAPHIC RANGE

The killer whale is distributed worldwide from tropical to polar regions (Leatherwood and Reeves 1983).

Sightings of these animals in the northern Gulf of Mexico occur primarily over the deeper waters off the continental

shelf [Southeast Fisheries Science Center (SEFSC) unpublished data]. Killer whales were seen only in the summer

during recent seasonal GulfCet aerial surveys of the northern Gulf of Mexico during 1993-1995 (Davis et al., in

preparation) and in the late spring during vessel surveys (SEFSC unpublished data). Different stocks have been

identified in the northeastern Pacific based on morphological, behavioral, and genetic characteristics (Bigg et al.

1990; Hoelzel 1991). There is no information on stock differentiation for the Atlantic population, although an

analysis of vocalizations of killer whales from Iceland and Norway indicated that stocks from these areas may

represent different stocks (Moore et al. 1988). 

POPULATION SIZE

Estimates of abundance were derived through the application of distance sampling analysis (Buckland et al.

1993) and the computer program DISTANCE (Laake et al. 1993) to sighting data collected during 1991-1994 springsummer, visual sampling, line-transect vessel surveys of the northern Gulf of Mexico (Hansen et al. 1995), which

includes data collected as part of the GulfCet program (Davis et al., in preparation). These surveys were conducted

throughout the area from approximately the 200 m isobath along the U.S. coast to the seaward extent of the U.S.

Exclusive Economic Zone. The seasonal GulfCet aerial surveys included only a small portion of the stock range and

these data were not used for

abundance estimation. Estimated

killer whale abundance by

survey year [coefficient of

variation (CV) in parentheses]

was zero in 1991, 138 in 1992

(0.96), 641 in 1993 (0.50), and

193 in 1994 (1.12) (Hansen et al.

1995). Survey effort-weighted

estimated average abundance of

killer whales for all surveys

combined was 277 (CV = 0.42)

(Hansen et al. 1995).

Minimum Population Estimate

The minimum

population size was estimated

from the average estimate

abundance which was 277 killer

whales (CV = 0.42) (Hansen et al. 1995). The minimum population estimate is the lower limit of the two-tailed 60%

confidence interval of the log-normal distributed abundance estimate, which is equivalent to the 20th percentile of

the log-normal distributed abundance estimate as specified by NMFS (Anon. 1994). The minimum population

estimate is 197 killer whales. 

Current Population Trend

The abundance estimates were highest during 1993; however, there were no observations of this species

during 1991, and the 1992-1994 estimates were not significantly different using the criteria of no overlap of lognormal 95% confidence intervals. The apparent differences in abundance estimates may have been caused by lower

sampling effort during 1991, and by low sampling intensity relative to population size (Hansen et al. 1995) or by
285

inter-annual variation in distribution patterns or spatial sampling patterns, rather than changes in population size. 

Preliminary analysis of existing photo-identification data shows that some individual whales have been seen during

more than one survey (SEFSC unpublished data). 

CURRENT AND MAXIMUM NET PRODUCTIVITY RATES

Current and maximum net productivity rates for this stock are not known; therefore, the default maximum

net productivity rate of 0.04 (Anon. 1994) was used for purposes of this assessment. 

POTENTIAL BIOLOGICAL REMOVAL

Potential biological removal level (PBR) was specified as the product of the minimum population size, one

half the maximum net productivity rate, and a recovery factor for endangered, threatened, or depleted stocks, or

stocks of unknown status relative to optimum sustainable population (OSP) (Anon. 1994). The recovery factor was

set at 0.50 because the status of the stock relative to OSP is unknown. PBR for this stock is 2.0 killer whales. 

ANNUAL HUMAN-CAUSED MORTALITY AND SERIOUS INJURY

The level of past or current, direct, human-caused mortality of killer whales in the northern Gulf of Mexico

is unknown. Available information indicates there likely is little, if any, fisheries interaction with killer whales in

the northern Gulf of Mexico. There have been no logbook reports of fishery-related mortality or serious injury and

no fishery-related mortality or serious injury has been observed.

There were no documented strandings of killer whales in the northern Gulf of Mexico during 1987-1994

which were classified as likely caused by fishery interactions or other human-related causes. Stranding data

probably underestimate the extent of fishery-related mortality and serious injury because not all of the marine

mammals which die or are seriously injured may wash ashore, nor will all of those that do wash ashore necessarily

show signs of entanglement or other fishery-interaction. Finally, the level of technical expertise among stranding

network personnel varies widely as does the ability to recognize signs of fishery interaction. 

The total known fishery-related mortality and serious injury for this stock is less than 10% of the calculated

PBR and, therefore, can be considered insignificant and approaching zero mortality and serious injury rate. This

determination cannot be made for specific fisheries until the implementing regulations for Section 118 of the MMPA

have been reviewed by the public and finalized. 

Fisheries Information

Pelagic swordfish, tunas, and billfish are the targets of the longline fishery operating in the U.S. Gulf of

Mexico. Total longline effort for the Gulf of Mexico pelagic fishery, including OCS edge, continental slope, and

Mexican territorial waters, based on mandatory logbook reporting, was 4,400 sets in 1991, 4,850 sets in 1992, and

3,260 sets in 1993 (Cramer 1994). This fishery has been monitored with about 5% observer coverage, in terms of

trips observed, since 1992. There were no reports of mortality or serious injury of killer whales by this fishery. 

Pair trawl fishing gear has the potential to capture marine mammals, but there have been no reports of

mortality or serious injury to marine mammals in the Gulf of Mexico. This fishery has not been observed by NMFS

observers, and there are no other data available as to the extent of this fishery in the Gulf of Mexico. It is assumed

that it is very limited in scope and duration. 

STATUS OF STOCK

The status of this stock relative to OSP is unknown and there are insufficient data to determine population

trends. This species is not listed under the Endangered Species Act. The total level of human-caused mortality and

serious injury is unknown, but it is believed to be insignificant relative to PBR; therefore, this is not a strategic stock. 
286

REFERENCES

Anon. 1994. Report of the PBR (Potential Biological Removal) workshop. June 27-29, 1994. NOAA, NMFS

Southwest Fisheries Science Center, La Jolla, California, 13 pp. + Appendices. 

Bigg, M. A., P. F. Olesiuk, G. M. Ellis, J. K. B. Ford and K. C. Balcomb. 1990. Social organization and genealogy

of resident killer whales (Orcinus orca) in the coastal waters of British Columbia and Washington State. 

Pages 383-405 in P. S. Hammond, S. A. Mizroch and G. P. Donovan (editors), Individual recognition of

cetaceans: Use of photoidentification and other techniques to estimate population parameters, Rep. Int.

Whal. Commn., Special Issue 12, Cambridge, 440 pp. 

Buckland, S. T., D. R. Anderson, K. P. Burnham and J. L. Laake. 1993. Distance Sampling: estimating abundance

of biological populations. Chapman & Hall, London, 446 pp. 

Cramer, J. 1994. Large pelagic logbook newsletter - 1993. NOAA Tech. Mem. NMFS-SEFSC-352, 19 pp. 

Davis, R., G. Scott, B. Würsig, W. Evans, G. Fargion, L. Hansen, K. Mullin, N. May, T. Leming, B. Mate, J. Norris

and T. Jefferson. In preparation. Distribution and abundance of marine mammals in the north-central and

western Gulf of Mexico: Final Report. OCS Study #MMS 94-0003. Texas Institute of Oceanography and

the National Marine Fisheries Service. U.S. Dept. of the Interior, Minerals Mgmt. Service, Gulf of Mexico

OCS Region, New Orleans, Louisiana. 

Hansen, L. J., K. D. Mullin and C. L. Roden. 1995. Estimates of cetacean abundance in the northern Gulf of

Mexico from vessel surveys. Southeast Fisheries Science Center, Miami Laboratory, Contribution No.

MIA-94/95-25, 9 pp. + tables and figures. 

Hoelzel, A. R. 1991. Analysis of regional mitochondrial DNA variation in the killer whale; implications for

conservation. Pages 225-233 in A. R. Hoelzel (editor), Genetic ecology of whales and dolphins, Rep. Int.

Whal. Commn. Special Issue 13, Cambridge, 311 pp. 

Laake, J. L., S. T. Buckland, D. R. Anderson, and K. P. Burnham. DISTANCE user’s guide, V2.0. Colorado

Cooperative Fish & Wildlife Research Unit, Colorado State University, Ft. Collins, Colorado, 72 pp. 

Leatherwood, S. and R. R. Reeves. 1983. The Sierra Club handbook of whales and dolphins. Sierra Club Books,

San Francisco, 302 pp. 

Moore, S. E., J. K. Francine, A. E. Bowles and K. B. Ford. 1988. Analysis of calls of killer whales, Orcinus orca,

from Iceland and Norway. Rit. Fiskideild. 11:225-250.
287

Figure 1. Distribution of false killer whale sightings during NOAA Ship Oregon

II marine mammal surveys during 1991-1994 (filled circles) and during GulfCet

seasonal aerial surveys (filled circles). The straight lines show transects during

two surveys and are examples of typical survey transects. Isobaths are in 183 m

(100 fm) intervals.

July 1995

FALSE KILLER WHALE (Pseudorca crassidens):

Northern Gulf of Mexico Stock

STOCK DEFINITION AND GEOGRAPHIC RANGE

The false killer whale is distributed worldwide throughout warm temperate and tropical oceans

(Leatherwood and Reeves 1983). Sightings of this species in the northern Gulf of Mexico occur primarily over the

deeper waters off the continental shelf [Southeast Fisheries Science Center (SEFSC) unpublished data]. False killer

whales were seen only in the summer during recent seasonal GulfCet aerial surveys of the northern Gulf of Mexico

during 1993-1995 (Davis et al., in preparation) and in the late spring during vessel surveys (NMFS unpublished

data). There is no information on stock differentiation for the Atlantic population. 

POPULATION SIZE

Estimates of abundance were derived through the application of distance sampling analysis (Buckland et al.

1993) and the computer program DISTANCE (Laake et al. 1993) to sighting data collected during 1991-1994 springsummer, visual sampling, line-transect vessel surveys of the northern Gulf of Mexico (Hansen et al. 1995) (Fig. 1),

which includes data collected as part of the GulfCet program (Davis et al., in preparation). These surveys were

conducted throughout the area from approximately the 200 m isobath along the U.S. coast to the seaward extent of

the U.S. Exclusive Economic

Zone. The seasonal GulfCet

aerial surveys included only a

small portion of the stock range

and these data were not used for

abundance estimation. 

Estimated abundance of false

killer whales by survey year

[coefficient of variation (CV) in

parentheses] was 661 in 1991

(0.88), 196 in 1992 (1.00), 77 in

1993 (1.08), and 744 in 1994

(1.14) (Hansen et al. 1995). 

Survey effort-weighted

estimated average abundance of

false killer whales for all

surveys combined was 381 (CV 

= 0.62) (Hansen et al. 1995). 

Minimum Population

Estimate

The minimum population size was estimated from the average estimate abundance which was 381 false

killer whales (CV = 0.62) (Hansen et al. 1995). The minimum population estimate is the lower limit of the twotailed 60% confidence interval of the log-normal distributed abundance estimate, which is equivalent to the 20th

percentile of the log-normal distributed abundance estimate as specified by NMFS (Anon. 1994). The minimum

population estimate is 236 false killer whales. 

Current Population Trend

No trend was identified in the annual abundance estimates, and the differences in the abundance estimates

were not significant using the criteria of no overlap of log-normal 95% confidence intervals. The apparent

differences in abundance estimates may have been caused by lower sampling effort during 1991, by low sampling

intensity relative to population size (Hansen et al. 1995), or by inter-annual variation in distribution patterns or

spatial sampling patterns, rather than changes in population size. 
288

CURRENT AND MAXIMUM NET PRODUCTIVITY RATES

Current and maximum net productivity rates are not known; therefore, the default maximum net

productivity rate of 0.04 (Anon. 1994) was used for purposes of this assessment. 

POTENTIAL BIOLOGICAL REMOVAL

Potential biological removal level (PBR) was specified as the product of the minimum population size, one

half the maximum net productivity rate, and a recovery factor for endangered, threatened, or depleted stocks, or

stocks of unknown status relative to optimum sustainable population (OSP) (Anon. 1994). The recovery factor was

set at 0.50 because the status of the stock relative to OSP is unknown. PBR for this stock is 2.4 false killer whales.

 

ANNUAL HUMAN-CAUSED MORTALITY AND SERIOUS INJURY

The level of past or current, direct, human-caused mortality of false killer whales in the northern Gulf of

Mexico is unknown. Available information indicates there likely is little, if any, fisheries interaction with false killer

whales in the northern Gulf of Mexico. There have been no logbook reports of fishery-related mortality or serious

injury and no fishery-related mortality or serious injury has been observed.

There were no documented strandings of false killer whales in the northern Gulf of Mexico during 1987-

1994 which were classified as likely caused by fishery interactions or other human-related causes. Stranding data

probably underestimate the extent of fishery-related mortality and serious injury because not all of the marine

mammals which die or are seriously injured may wash ashore, nor will all of those that do wash ashore necessarily

show signs of entanglement or other fishery-interaction. Finally, the level of technical expertise among stranding

network personnel varies widely as does the ability to recognize signs of fishery interaction. 

The total known fishery-related mortality and serious injury for this stock is less than 10% of the calculated

PBR and, therefore, can be considered insignificant and approaching zero mortality and serious injury rate. This

determination cannot be made for specific fisheries until the implementing regulations for Section 118 of the MMPA

have been reviewed by the public and finalized. 

Fisheries Information

Pelagic swordfish, tunas, and billfish are the targets of the longline fishery operating in the U.S. Gulf of

Mexico. Total longline effort for the Gulf of Mexico pelagic fishery, including OCS edge, continental slope, and

Mexican territorial waters, based on mandatory logbook reporting, was 4,400 sets in 1991, 4,850 sets in 1992, and

3,260 sets in 1993 (Cramer 1994). This fishery has been monitored with about 5% observer coverage, in terms of

trips observed, since 1992. There were no reports of mortality or serious injury of false killer whales by this fishery. 

Pair trawl fishing gear has the potential to capture marine mammals, but there have been no reports of

mortality or serious injury to marine mammals in the Gulf of Mexico. This fishery has not been observed by NMFS

observers, and there are no other data available as to the extent of this fishery in the Gulf of Mexico. It is assumed

that it is very limited in scope and duration. 

STATUS OF STOCK

The status of this stock relative to OSP is unknown and there are insufficient data to determine population

trends. This species is not listed under the Endangered Species Act. The total level of human-caused mortality and

serious injury is unknown, but it is believed to be insignificant relative to PBR; therefore, this is not a strategic stock. 

REFERENCES

Anon. 1994. Report of the PBR (Potential Biological Removal) workshop. June 27-29, 1994. NOAA, NMFS

Southwest Fisheries Science Center, La Jolla, California, 13 pp. + Appendices. 

Buckland, S. T., D. R. Anderson, K. P. Burnham and J. L. Laake. 1993. Distance Sampling: estimating abundance

of biological populations. Chapman & Hall, London, 446 pp. 

Cramer, J. 1994. Large pelagic logbook newsletter - 1993. NOAA Tech. Mem. NMFS-SEFSC-352, 19 pp. 

Davis, R., G. Scott, B. Würsig, W. Evans, G. Fargion, L. Hansen, K. Mullin, N. May, T. Leming, B. Mate, J. Norris

and T. Jefferson. In preparation. Distribution and abundance of marine mammals in the north-central and

western Gulf of Mexico: Final Report. OCS Study #MMS 94-0003. Texas Institute of Oceanography and

the National Marine Fisheries Service. U.S. Dept. of the Interior, Minerals Mgmt. Service, Gulf of Mexico

OCS Region, New Orleans, Louisiana. 
289

Hansen, L. J., K. D. Mullin and C. L. Roden. 1995. Estimates of cetacean abundance in the northern Gulf of

Mexico from vessel surveys. Southeast Fisheries Science Center, Miami Laboratory, Contribution No.

MIA-94/95-25, 9 pp. + tables and figures. 

Laake, J. L., S. T. Buckland, D. R. Anderson, and K. P. Burnham. DISTANCE user’s guide, V2.0. Colorado

Cooperative Fish & Wildlife Research Unit, Colorado State University, Ft. Collins, Colorado, 72 pp.

Leatherwood, S. and R. R. Reeves. 1983. The Sierra Club handbook of whales and dolphins. Sierra Club Books,

San Francisco, 302 pp.
290

Figure 1. Distribution of pygmy killer whale sightings during NOAA Ship

Oregon II marine mammal surveys during 1991-1994. The straight lines show

transects during two surveys and are examples of typical survey transects. 

Isobaths are in 183 m (100 fm) intervals.

July 1995

PYGMY KILLER WHALE (Feresa attenuata):

Northern Gulf of Mexico Stock

STOCK DEFINITION AND GEOGRAPHIC RANGE

The pygmy killer whale is distributed worldwide in tropical and subtropical waters (Ross and Leatherwood

1994). Sightings of these animals in the northern Gulf of Mexico occur primarily over the deeper waters off the

continental shelf [Southeast Fisheries Science Center (SEFSC) unpublished data]. Pygmy killer whales and melonheaded whales (Peponocephala electra) are difficult to distinguish and sightings of either species are often

categorized as pygmy killer/melon-headed whales. Sightings of this category were documented in all seasons during

recent seasonal GulfCet aerial surveys of the northern Gulf of Mexico during 1993-1995 (Davis et al., in

preparation). There is no information on stock differentiation for the Atlantic population. 

POPULATION SIZE

Estimates of abundance were derived through the application of distance sampling analysis (Buckland et al.

1993) and the computer program DISTANCE (Laake et al. 1993) to sighting data collected during 1991-1994 springsummer, visual sampling, line-transect vessel surveys of the northern Gulf of Mexico (Hansen et al. 1995) (Fig. 1),

which includes data collected as part of the GulfCet program (Davis et al., in preparation). These surveys were

conducted throughout the area from approximately the 200 m isobath along the U.S. coast to the seaward extent of

the U.S. Exclusive Economic

Zone. The seasonal GulfCet

aerial surveys included only a

small portion of the stock range

and these data were not used for

abundance estimation. 

Estimated abundance of pygmy

killer whales by survey year

[coefficient of variation (CV) in

parentheses] was 2,347 in

(0.81), 356 in 1992 (0.73), 153

in 1993 (1.13), and zero in 1994

(Hansen et al. 1995). Survey

effort-weighted estimated

average abundance of pygmy

killer whales for all surveys

combined was 518 (CV = 0.81)

(Hansen et al. 1995).

Minimum Population

Estimate

The minimum population size was estimated from the average estimated abundance which was 518 pygmy

killer whales (CV = 0.81) (Hansen et al. 1995). The minimum population estimate is the lower limit of the twotailed 60% confidence interval of the log-normal distributed abundance estimate, which is equivalent to the 20th

percentile of the log-normal distributed abundance estimate as specified by NMFS (Anon. 1994). The minimum

population estimate is 285 pygmy killer whales. 

Current Population Trend

A declining trend was identified in the annual abundance estimates; however, the 1991-1993 abundance

estimates were not significantly different using the criteria of no overlap of log-normal 95% confidence intervals.

There were no observations of this species during the 1994 survey. The apparent differences in abundance estimates

may have been caused by lower sampling effort during 1991, by low sampling intensity relative to population size

(Hansen et al. 1995), or by inter-annual variation in distribution patterns or spatial sampling patterns, rather than

changes in population size. 
291

CURRENT AND MAXIMUM NET PRODUCTIVITY RATES

Current and maximum net productivity rates are not known; therefore, the default maximum net

productivity rate of 0.04 (Anon. 1994) was used for purposes of this assessment. 

POTENTIAL BIOLOGICAL REMOVAL

Potential biological removal level (PBR) was specified as the product of the minimum population size, one

half the maximum net productivity rate, and a recovery factor for endangered, threatened, or depleted stocks, or

stocks of unknown status relative to optimum sustainable population (OSP) (Anon. 1994). The recovery factor was

set at 0.50 because the status of the stock relative to OSP is unknown. PBR for this stock is 2.8 pygmy killer whales. 

ANNUAL HUMAN-CAUSED MORTALITY AND SERIOUS INJURY

There has historically been some take of this species in small cetacean fisheries in the Caribbean (Caldwell

and Caldwell 1971); however, the level of past or current, direct, human-caused mortality of pygmy killer whales in

the northern Gulf of Mexico is unknown. Available information indicates there likely is little, if any, fisheries

interaction with pygmy killer whales in the northern Gulf of Mexico. There have been no logbook reports of fisheryrelated mortality or serious injury and no fishery-related mortality or serious injury has been observed.

There were no documented strandings of pygmy killer whales in the northern Gulf of Mexico during 1987-

1994 which were classified as likely caused by fishery interactions or other human-related causes. Stranding data

probably underestimate the extent of fishery-related mortality and serious injury because not all of the marine

mammals which die or are seriously injured may wash ashore, nor will all of those that do wash ashore necessarily

show signs of entanglement or other fishery-interaction. Finally, the level of technical expertise among stranding

network personnel varies widely as does the ability to recognize signs of fishery interaction.

The total known fishery-related mortality and serious injury for this stock is less than 10% of the calculated

PBR and, therefore, can be considered insignificant and approaching zero mortality and serious injury rate. This

determination cannot be made for specific fisheries until the implementing regulations for Section 118 of the MMPA

have been reviewed by the public and finalized. 

Fisheries Information

Pelagic swordfish, tunas, and billfish are the targets of the longline fishery operating in the U.S. Gulf of

Mexico. Total longline effort for the Gulf of Mexico pelagic fishery, including OCS edge, continental slope, and

Mexican territorial waters, based on mandatory logbook reporting, was 4,400 sets in 1991, 4,850 sets in 1992, and

3,260 sets in 1993 (Cramer 1994). This fishery has been monitored with about 5% observer coverage, in terms of

trips observed, since 1992. There were no reports of mortality or serious injury of pygmy killer whales by this

fishery. 

Pair trawl fishing gear has the potential to capture marine mammals, but there have been no reports of

mortality or serious injury to marine mammals in the Gulf of Mexico. This fishery has not been observed by NMFS

observers, and there are no other data available as to the extent of this fishery in the Gulf of Mexico. It is assumed

that it is very limited in scope and duration. 

STATUS OF STOCK

The status of this stock relative to OSP is unknown and there are insufficient data to determine population

trends. This species is not listed under the Endangered Species Act. The total level of human-caused mortality and

serious injury is unknown, but it is believed to be insignificant relative to PBR; therefore, this is not a strategic stock. 

REFERENCES

Anon. 1994. Report of the PBR (Potential Biological Removal) workshop. June 27-29, 1994. NOAA, NMFS

Southwest Fisheries Science Center, La Jolla, California, 13 pp. + Appendices. 

Buckland, S. T., D. R. Anderson, K. P. Burnham and J. L. Laake. 1993. Distance Sampling: estimating abundance

of biological populations. Chapman & Hall, London, 446 pp. 

Caldwell, D. K. and M. C. Caldwell. 1971. The pygmy killer whale, Feresa attenuata, in the western Atlantic, with a

summary of world records. J. Mamm. 52:206-209. 

Cramer, J. 1994. Large pelagic logbook newsletter - 1993. NOAA Tech. Mem. NMFS-SEFSC-352, 19 pp.
292

Davis, R., G. Scott, B. Würsig, W. Evans, G. Fargion, L. Hansen, K. Mullin, N. May, T. Leming, B. Mate, J. Norris

and T. Jefferson. In preparation. Distribution and abundance of marine mammals in the north-central and

western Gulf of Mexico: Final Report. OCS Study #MMS 94-0003. Texas Institute of Oceanography and

the National Marine Fisheries Service. U.S. Dept. of the Interior, Minerals Mgmt. Service, Gulf of Mexico

OCS Region, New Orleans, Louisiana. 

Hansen, L. J., K. D. Mullin and C. L. Roden. 1995. Estimates of cetacean abundance in the northern Gulf of

Mexico from vessel surveys. Southeast Fisheries Science Center, Miami Laboratory, Contribution No.

MIA-94/95-25, 9 pp. + tables and figures. 

Laake, J. L., S. T. Buckland, D. R. Anderson, and K. P. Burnham. DISTANCE user’s guide, V2.0. Colorado

Cooperative Fish & Wildlife Research Unit, Colorado State University, Ft. Collins, Colorado, 72 pp. 

Ross, G. J. B. and S. Leatherwood. 1994. Pygmy killer whale Feresa attenuata (Gray, 1874). Pages 387-404 in S.

H. Ridgway and R. Harrison (editors), Handbook of marine mammals, Vol. 5: The first book of dolphins. 

Academic Press, London, 416 pp. 
293

September 2000 

DWARF SPERM WHALE (Kogia simus):

Northern Gulf of Mexico Stock

STOCK DEFINITION AND GEOGRAPHIC RANGE

The dwarf sperm whale appears to be distributed worldwide in temperate to tropical waters (Caldwell and

Caldwell 1989). Sightings of these animals in the northern Gulf of Mexico occur primarily along the continental

shelf edge and over the deeper waters off the continental shelf (Mullin et al. 1991; Southeast Fisheries Science

Center, SEFSC, unpublished data). Dwarf sperm whales and pygmy sperm whales (Kogia breviceps) are difficult to

distinguish and sightings of either species are often categorized as Kogia sp. Sightings of this category were

documented in all seasons during seasonal GulfCet aerial surveys of the northern Gulf of Mexico during 1993-1995

(Hansen et al. 1996). The few reliable sightings of dwarf sperm whales during those surveys were more numerous

in spring, probably a result of greater survey efforts in that season (Jefferson and Shapiro 1997). Pygmy and dwarf

sperm whales have been sighted in the northwestern Gulf of Mexico in waters 1000 m deep, on average (Davis et al.

1998). However, these authors cautioned that inferences on preferred bottom depths should await surveys for the

entire Gulf of Mexico. The difficulty in sighting pygmy and dwarf sperm whales may be exacerbated by their

avoidance reaction towards ships, and change in behavior towards approaching survey aircraft (Würsig et al. 1998).

In a recent study using hematological and stable-isotope data, Barros et al. (1998) speculated that dwarf sperm

whales may have a more pelagic distribution than pygmy sperm whales, and/or dive deeper during feeding bouts.

There is no information on stock differentiation. 

POPULATION SIZE

Estimates of abundance of Kogia sp. were derived through the application of distance sampling analysis

(Buckland et al. 1993) and the computer program DISTANCE (Laake et al. 1993) to sighting data collected during

1991-1994 spring-summer, visual sampling, line-transect vessel surveys of the northern Gulf of Mexico (Fig. 1 in

Hansen et al. 1995), which includes data collected as part of the GulfCet program (Hansen et al. 1996). These

surveys were conducted throughout the area from approximately the 200 m isobath along the USA coast to the

seaward extent of the USA Exclusive Economic Zone. The seasonal GulfCet aerial surveys included only a small

portion of the species’ range and therefore, these data were not used to estimate population size. Estimated

abundance of Kogia sp. by survey year [coefficient of variation (CV) in parentheses] was 109 in 1991 (0.68), 1,010

in 1992 (0.40), 580 in 1993 (0.45), and 162 in 1994 (0.61) (Hansen et al. 1995). Survey effort-weighted estimated

average abundance of Kogia sp. for all surveys combined was 547 (CV=0.28) (Hansen et al. 1995). Estimates of

dwarf sperm whale abundance cannot be provided due to uncertainty of species identification at sea. 

Minimum Population Estimate

A minimum population estimate was not calculated because of uncertainty of species identification at sea. 

Current Population Trend

There is insufficient information to describe any population trend of this species in the Gulf of Mexico.

CURRENT AND MAXIMUM NET PRODUCTIVITY RATES

Current and maximum net productivity rates are not known for this stock. The maximum net productivity

rate was assumed to be 0.04. This value is based on theoretical modeling showing that cetacean populations may not

grow at rates much greater than 4% given the constraints of their reproductive life history (Barlow et al. 1995).

POTENTIAL BIOLOGICAL REMOVAL

Potential Biological Removal (PBR) is the product of the minimum population size, one half the maximum

net productivity rate, and a “recovery” factor (Wade and Angliss 1997). The “recovery “ factor, which accounts for

endangered, depleted, and threatened stocks, or stocks of unknown status relative to optimum sustainable population

(OSP) is assumed to be 0.5 because this stock is of unknown status. PBR for the dwarf sperm whale is unknown

because the minimum population estimate cannot be estimated.
294

ANNUAL HUMAN-CAUSED MORTALITY AND SERIOUS INJURY

The level of past or current, direct, human-caused mortality of dwarf sperm whales in the northern Gulf of

Mexico is unknown. Available information indicates there likely is little, if any, fisheries interaction with dwarf

sperm whales in the northern Gulf of Mexico. There have been no logbook reports of fishery-related mortality or

serious injury and no fishery-related mortality or serious injury has been observed.

There were no documented strandings of dwarf sperm whales in the northern Gulf of Mexico during 1987-

October 1998 which were classified as likely caused by fishery interactions, but there have been stranding

investigation reports of dwarf sperm whales which may have died as a result of other human-related causes. 

Stranding data probably underestimate the extent of fishery-related mortality and serious injury because not all of the

marine mammals which die or are seriously injured may wash ashore, nor will all of those that do wash ashore

necessarily show signs of entanglement or other fishery-interaction. Finally, the level of technical expertise among

stranding network personnel varies widely as does the ability to recognize signs of fishery interaction. 

Fisheries Information

Pelagic swordfish, tunas, and billfish are the targets of the longline fishery operating in the USA Gulf of

Mexico. Total longline effort for the Gulf of Mexico pelagic fishery, including OCS edge, continental slope, and

Mexican territorial waters, based on mandatory logbook reporting, was 4,400 sets in 1991, 4,850 sets in 1992, and

3,260 sets in 1993 (Cramer 1994). This fishery has been monitored with about 5% observer coverage, in terms of

trips observed, since 1992. There were no reports of mortality or serious injury of dwarf sperm whales by this

fishery. 

Pair trawl fishing gear has the potential to capture marine mammals, but there have been no reports of

mortality or serious injury to marine mammals in the Gulf of Mexico. This fishery has not been observed by NMFS

observers, and there are no other data available as to the extent of this fishery in the Gulf of Mexico. It is assumed

that it is very limited in scope and duration. 

Other Mortality

A total of at least 16 dwarf sperm whale strandings were documented in the northern Gulf of Mexico from

1990 through October 1998. 

STATUS OF STOCK

The status of this stock relative to OSP is unknown and there are insufficient data to determine population

trends. This species is not listed under the Endangered Species Act. Although the PBR cannot be calculated, there is

no known fishery-related mortality or serious injury to this stock and, therefore, total fishery-related mortality and

serious injury can be considered insignificant and approaching zero mortality and serious injury rate. The total level

of fishery-related mortality and serious injury is unknown, but it is believed to be insignificant.

REFERENCES

Barlow, J., S. L. Swartz, T. C. Eagle and P. R. Wade. 1995. U.S. Marine Mammal Stock Assessments: Guidelines

for Preparation, Background and a Summary of the 1995 Assessments. U.S. Dep. Commer., NOAA Tech.

Memo. NMFS-OPR-6, 73 pp.

Barros, N. B., D. A. Duffield, P. H. Ostrom, D. K. Odell and V. R. Cornish. 1998. Nearshore vs. offshore ecotype

differentiation of Kogia breviceps and K. simus based on hemoglobin, morphometric and dietary analyses.

Abstracts. World Marine Mammal Science Conference. Monaco. 20-24 January. 

Buckland, S. T., D. R. Anderson, K. P. Burnham and J. L. Laake. 1993. Distance Sampling: estimating abundance

of biological populations. Chapman & Hall, London, 446 pp. 

Caldwell, D. K. and M. C. Caldwell. 1989. Pygmy sperm whale Kogia breviceps (de Blainville, 1838): dwarf

sperm whale Kogia simus Owen, 1866. Pages 235-260 in: S. H. Ridgway and R. Harrison (eds), Handbook

of marine mammals, Vol. 4: River dolphins and the larger toothed whales. Academic Press, San Diego. 

Cramer, J. 1994. Large pelagic logbook newsletter - 1993. NOAA Tech. Mem. NMFS-SEFSC-352, 19 pp. 

Davis, R. W., G. S. Fargion, N. May, T. D. Leming, M. Baumgartner, W. E. Evans, L. J. Hansen and K. Mullin. 

1998. Physical habitats of cetaceans along the continental slope of the north-central and western Gulf of

Mexico. Mar. Mammal. Sci., 14:490-507.
295

Hansen, L. J., K. D. Mullin, T. A. Jefferson and G. P. Scott. 1996. Visual surveys aboard ships and aircraft. Pages

55-132. In: R.W. Davis and G.S. Fargion (eds). Distribution and abundance of marine mammals in the

north-central and western Gulf of Mexico: Final Report. Volume II: Technical Report. OCS Study MMS

96-0027. Prepared by the Texas Institute of Oceanography and the National Marine Fisheries Service. U.S.

Dept. of the Interior, Minerals Mgmt. Service, Gulf of Mexico OCS Region, New Orleans, LA. 357 pp.

Hansen, L. J., K. D. Mullin and C. L. Roden. 1995. Estimates of cetacean abundance in the northern Gulf of

Mexico from vessel surveys. Southeast Fisheries Science Center, Miami Laboratory, Contribution No.

MIA-94/95-25, 9 pp. + tables and figures.

Jefferson, T. J. and A. Schiro. 1997. Distribution of cetaceans in the northern Gulf of Mexico. Mammal Rev., 27:27-

50. 

Laake, J. L., S. T. Buckland, D. R. Anderson and K. P. Burnham. 1993. DISTANCE user’s guide, V2.0. Colorado

Cooperative Fish & Wildlife Research Unit, Colorado State University, Ft. Collins, Colorado, 72 pp. 

Mullin, K., W. Hoggard, C. Roden, R. Lohoefener, C. Rogers and B. Taggart. 1991. Cetaceans on the upper

continental slope in the north-central Gulf of Mexico. OCS Study/MMS 91-0027. U.S. Dept. of the

Interior, Minerals Management Service, Gulf of Mexico OCS Regional Office, New Orleans, Louisiana 108

pp. 

Wade, P.R., and R.P. Angliss. 1997. Guidelines for assessing marine mammal stocks: Report of the GAMMS

Workshop April 3-5, Seattle, Washington. U.S. Dep. Commer., NOAA Tech. Memo. NMFS-OPR-12, 93

pp.

Würsig, B., S.K. Lynn, T.A. Jefferson, and K.D. Mullin. 1998. Behavior of cetaceans in the northern Gulf of Mexico

relative to survey ships and aircraft. Aquat. Mammals, 24:41-50.
296

September 2000 

PYGMY SPERM WHALE (Kogia breviceps):

Northern Gulf of Mexico Stock

STOCK DEFINITION AND GEOGRAPHIC RANGE

The pygmy sperm whale appears to be distributed worldwide in temperate to tropical waters (Caldwell and

Caldwell 1989). Sightings of these animals in the northern Gulf of Mexico occur primarily along the continental

shelf edge and over the deeper waters off the continental shelf (Mullin et al. 1991; Southeast Fisheries Science

Center, SEFSC, unpublished data). Pygmy sperm whales and dwarf sperm whales (Kogia simus) are difficult to

distinguish and sightings of either species are often categorized as Kogia sp. Sightings of this category were

documented in all seasons during seasonal GulfCet aerial surveys of the northern Gulf of Mexico during 1993-1995

(Hansen et al. 1996). Pygmy and dwarf sperm whales have been sighted in the northwestern Gulf of Mexico in

waters 1000 m deep, on average (Davis et al. 1998). However, these authors cautioned that inferences on preferred

bottom depths should await surveys for the entire Gulf of Mexico. The difficulty in sighting pygmy and dwarf sperm

whales may be exacerbated by their avoidance reaction towards ships, and change in behavior towards approaching

survey aircraft (Würsig et al. 1998) In a recent study using hematological and stable-isotope data, Barros et al.

(1998) speculated that dwarf sperm whales may have a more pelagic distribution than pygmy sperm whales, and/or

dive deeper during feeding bouts. There is no information on stock differentiation. 

POPULATION SIZE

Estimates of abundance of Kogia sp. were derived through the application of distance sampling analysis

(Buckland et al. 1993) and the computer program DISTANCE (Laake et al. 1993) to sighting data collected during

1991-1994 spring-summer, visual sampling, line-transect vessel surveys of the northern Gulf of Mexico (Hansen et

al. 1995) (Fig. 1), which includes data collected as part of the GulfCet program (Hansen et al. 1996). These surveys

were conducted throughout the area from approximately the 200 m isobath along the USA coast to the seaward

extent of the USA Exclusive Economic Zone. The seasonal GulfCet aerial surveys included only a small portion of

the species’ range and therefore, these data were not used to estimate population size. Estimated abundance of Kogia

sp. by survey year [coefficient of variation (CV) in parentheses] was 109 in 1991 (0.68), 1,010 in 1992 (0.40), 580 in

1993 (0.45), and 162 in 1994 (0.61) (Hansen et al. 1995). Survey effort-weighted estimated abundance of Kogia sp.

for all surveys combined was 547 (CV = 0.28) (Hansen et al. 1995). Estimates of pygmy sperm whale abundance

cannot be provided due to uncertainty of species identification at sea. 

Minimum Population Estimate

A minimum population estimate could not be calculated because of uncertainty of species identification at

sea. 

Current Population Trend

There is insufficient information to describe any population trend for this species in the Gulf of Mexico.

CURRENT AND MAXIMUM NET PRODUCTIVITY RATES

Current and maximum net productivity rates are not known for this stock. The maximum net productivity

rate was assumed to be 0.04. This value is based on theoretical modeling showing that cetacean populations may not

grow at rates much greater than 4% given the constraints of their reproductive life history (Barlow et al. 1995).

POTENTIAL BIOLOGICAL REMOVAL

Potential Biological Removal (PBR) is the product of the minimum population size, one half the maximum

net productivity rate, and a “recovery” factor (Wade and Angliss 1997). The “recovery “ factor, which accounts for

endangered, depleted, and threatened stocks, or stocks of unknown status relative to optimum sustainable population

(OSP) is assumed to be 0.5 because this stock is of unknown status. PBR for the pygmy sperm whale is unknown

because the minimum population estimate cannot be estimated.
297

ANNUAL HUMAN-CAUSED MORTALITY AND SERIOUS INJURY

The level of past or current, direct, human-caused mortality of pygmy sperm whales in the northern Gulf of

Mexico is unknown. Available information indicates there likely is little, if any, fisheries interaction with pygmy

sperm whales in the northern Gulf of Mexico. There have been no logbook reports of fishery-related mortality or

serious injury and no fishery-related mortality or serious injury has been observed.

There have been no documented strandings of pygmy sperm whales in the northern Gulf of Mexico during

1987-October 1998 which have been classified as likely caused by fishery interactions, but there have been stranding

investigation reports of pygmy sperm whales which may have died as a result of other human-related causes. 

Stranding data probably underestimate the extent of fishery-related mortality and serious injury because not all of the

marine mammals which die or are seriously injured may wash ashore, nor will all of those that do wash ashore

necessarily show signs of entanglement or other fishery-interaction. Finally, the level of technical expertise among

stranding network personnel varies widely as does the ability to recognize signs of fishery interaction.

Fisheries Information

Pelagic swordfish, tunas, and billfish are the targets of the longline fishery operating in the USA Gulf of

Mexico. Total longline effort for the Gulf of Mexico pelagic fishery, including OCS edge, continental slope, and

Mexican territorial waters, based on mandatory logbook reporting, was 4,400 sets in 1991, 4,850 sets in 1992, and

3,260 sets in 1993 (Cramer 1994). This fishery has been monitored with about 5% observer coverage, in terms of

trips observed, since 1992. There were no reports of mortality or serious injury of pygmy sperm whales by this

fishery. 

Pair trawl fishing gear has the potential to capture marine mammals, but there have been no reports of

mortality or serious injury to marine mammals in the Gulf of Mexico. This fishery has not been observed by NMFS

observers, and there are no other data available as to the extent of this fishery in the Gulf of Mexico. It is assumed

that it is very limited in scope and duration. 

Other Mortality

At least 20 pygmy sperm whale strandings were documented in the northern Gulf of Mexico from 1990 

through October 1998. Two of these animals had a plastic bag or pieces thereof in their stomachs (Tarpley and

Marwitz 1993, Barros, unpublished data). Another animal stranded apparently due to injuries inflicted by impact,

possibly with a vessel. 

STATUS OF STOCK

The status of this stock relative to OSP is unknown and there are insufficient data to determine population

trends. This species is not listed under the Endangered Species Act. Although the PBR cannot be calculated, the

total known fishery-related mortality and serious injury for this stock is zero and, therefore, can be considered

insignificant and approaching zero mortality and serious injury rate. The total level of fishery-related mortality and

serious injury is unknown, but it is believed to be insignificant.

REFERENCES

Barlow, J., S.L. Swartz, T.C. Eagle, and P.R. Wade. 1995. U.S. Marine Mammal Stock Assessments: Guidelines for

Preparation, Background and a Summary of the 1995 Assessments. U.S. Dep. Commer., NOAA Tech.

Memo. NMFS-OPR-6, 73 pp.

Barros, N.B., D.A. Duffield, P.H. Ostrom, D.K. Odell, and V.R. Cornish. 1998. Nearshore vs. offshore ecotype

differentiation of Kogia breviceps and K. simus based on hemoglobin, morphometric and dietary analyses.

Abstract. World Marine Mammal Science Conference. Monaco. 20-24 January.

Buckland, S. T., D. R. Anderson, K. P. Burnham and J. L. Laake. 1993. Distance Sampling: estimating abundance

of biological populations. Chapman & Hall, London, 446 pp. 

Caldwell, D. K. and M. C. Caldwell 1989. Pygmy sperm whale Kogia breviceps (de Blainville, 1838): dwarf sperm

whale Kogia simus Owen, 1866. Pages 235-260 in: S. H. Ridgway and R. Harrison (eds), Handbook of

marine mammals, Vol. 4: River dolphins and the larger toothed whales. Academic Press, San Diego. 

Cramer, J. 1994. Large pelagic logbook newsletter - 1993. NOAA Tech. Mem. NMFS-SEFSC-352, 19 pp. 
298

Davis, R.W., G.S. Fargion, N. May, T.D. Leming, M. Baumgartner, W.E. Evans, L.J. Hansen, and K. Mullin. 1998.

Physical habitats of cetaceans along the continental slope of the north-central and western Gulf of Mexico.

Mar. Mamm. Sci., 14:490-507.

Hansen, L.J., K.D. Mullin, T.A. Jefferson and G.P. Scott. 1996. Visual surveys aboard ships and aircraft. Pages 55-

132. In: R.W. Davis and G.S. Fargion (eds). Distribution and abundance of marine mammals in the northcentral and western Gulf of Mexico: Final Report. Volume II: Technical Report. OCS Study MMS 96-

0027. Prepared by the Texas Institute of Oceanography and the National Marine Fisheries Service. U.S.

Dept. of the Interior, Minerals Mgmt. Service, Gulf of Mexico OCS Region, New Orleans, LA. 357 pp.

Hansen, L. J., K. D. Mullin and C. L. Roden. 1995. Estimates of cetacean abundance in the northern Gulf of

Mexico from vessel surveys. Southeast Fisheries Science Center, Miami Laboratory, Contribution No.

MIA-94/95-25, 9 pp. + tables and figures. 

Laake, J. L., S. T. Buckland, D. R. Anderson, and K. P. Burnham. 1993. DISTANCE user’s guide, V2.0. Colorado

Cooperative Fish & Wildlife Research Unit, Colorado State University, Ft. Collins, Colorado, 72 pp. 

Mullin, K., W. Hoggard, C. Roden, R. Lohoefener, C. Rogers and B. Taggart. 1991. Cetaceans on the upper

continental slope in the north-central Gulf of Mexico. OCS Study/MMS 91-0027. U.S. Dept. of the

Interior, Minerals Management Service, Gulf of Mexico OCS Regional Office, New Orleans, Louisiana 108

pp. 

Tarpley, R. J., and S. Marwitz. 1993. Plastic debris ingestion by cetaceans along the Texas coast: two case studies.

Aquat. Mammals, 14:93-98.

Wade, P. R. and R. P. Angliss. 1997. Guidelines for assessing marine mammal stocks: Report of the GAMMS

Workshop April 3-5, Seattle, Washington. U.S. Dep. Commer., NOAA Tech. Memo. NMFS-OPR-12, 93

pp.

Würsig, B., S. K. Lynn, T. A. Jefferson and K. D. Mullin. 1998. Behavior of cetaceans in the northern Gulf of

Mexico relative to survey ships and aircraft. Aquat. Mammals, 24:41-50.
299

Figure 1. Distribution of melon-headed whale sightings during NOAA Ship

Oregon II marine mammal surveys in 1991-1994. The straight lines show

transects during two surveys and are examples of typical survey transects. 

Isobaths are in 183 m (100 fm) depth intervals.

July 1995

MELON-HEADED WHALE (Peponocephala electra):

Northern Gulf of Mexico Stock

STOCK DEFINITION AND GEOGRAPHIC RANGE

The melon-headed whale appears to be distributed worldwide in tropical to sub-tropical waters (Perryman

et al. 1994). Sightings of these animals in the northern Gulf of Mexico occur primarily over the deeper waters off the

continental shelf (Mullin et al. 1994). Melon-headed whales and pygmy killer whales (Feresa attenuata) are difficult

to distinguish and sightings of either species are often categorized as pygmy killer/melon-headed whales. Sightings

of this category were documented in all seasons during recent seasonal GulfCet aerial surveys of the northern Gulf

of Mexico during 1993-1995 (Davis et al., in preparation). There is no information on stock differentiation for the

Atlantic population. 

POPULATION SIZE

Seasonal aerial survey data were insufficient for estimating abundance. Estimates of abundance were

derived through the application of distance sampling analysis (Buckland et al. 1993) and the computer program

DISTANCE (Laake et al. 1993) to sighting data collected during 1991-1994 spring-summer, visual sampling, linetransect vessel surveys of the northern Gulf of Mexico (Hansen et al. 1995) (Fig.1), which includes data collected as

part of the GulfCet program (Davis et al., in preparation). These surveys were conducted throughout the area from

approximately the 200 m isobath along the U.S. coast to the seaward extent of the U.S. Exclusive Economic Zone. 

The seasonal GulfCet aerial

surveys included only a small

portion of the stock range and

these data were not used for

abundance estimation. 

Estimated abundance of melonheaded whales by survey year

[coefficient of variation (CV) in

parentheses] was zero in 1991,

3,174 in 1992 (0.54), 827 in

1993 (0.70) and 10,586 in 1994

(0.48) (Hansen et al. 1995). 

The survey effort-weighted

estimated average abundance of

melon-headed whales for all

surveys combined was 3,965

(CV = 0.39) (Hansen et al.

1995).

Minimum Population

Estimate

The minimum population size was estimated from the average abundance estimate which was 3,965 (CV =

0.39) (Hansen et al. 1995). The minimum population estimate is the lower limit of the two-tailed 60% confidence

interval of the log-normal distributed abundance estimate, which is equivalent to the 20th percentile of the lognormal distributed abundance estimate as specified by NMFS (Anon. 1994). The minimum population estimate is

2,888 melon-headed whales.

Current Population Trend

No trend was identified in the annual abundance estimates; however, the 1994 estimate was more than ten

times larger than the 1993 estimate and the difference was significant using the criteria of no overlap of log-normal

95% confidence intervals. No melon-headed whales were sighted during 1991, and the differences between the

1992 and 1993 estimates and between the 1993 and 1994 estimates were not significant. The apparent differences in

abundance estimates may have been caused by lower sampling effort during 1991, and by low sampling intensity
300

relative to population size (Hansen et al. 1995), or by inter-annual variation in distribution patterns or spatial

sampling patterns, rather than changes in population size. 

CURRENT AND MAXIMUM NET PRODUCTIVITY RATES

Current and maximum net productivity rates are not known; therefore, the default maximum net

productivity rate of 0.04 (Anon. 1994) was used for purposes of this assessment. 

POTENTIAL BIOLOGICAL REMOVAL

Potential biological removal level (PBR) was specified as the product of the minimum population size, one

half the maximum net productivity rate, and a recovery factor for endangered, threatened, or depleted stocks, or

stocks of unknown status relative to optimum sustainable population (OSP) (Anon. 1994). The recovery factor was

set at 0.50 because the status of the stock relative to OSP is unknown. PBR for this stock is 29 melon-headed

whales. 

ANNUAL HUMAN-CAUSED MORTALITY AND SERIOUS INJURY

There has historically been some take of this species in small cetacean fisheries in the Caribbean (Caldwell

et al. 1976); however, the level of past or current, direct, human-caused mortality of melon-headed whales in the

northern Gulf of Mexico is unknown. Available information indicates there likely is little, if any, fisheries

interaction with melon-headed whales in the northern Gulf of Mexico. There have been no logbook reports of

fishery-related mortality or serious injury and no fishery-related mortality or serious injury has been observed.

There were no documented strandings of melon-headed whales in the northern Gulf of Mexico during

1987-1994 which were classified as likely caused by fishery interactions or other human-related causes. Stranding

data probably underestimate the extent of fishery-related mortality and serious injury because not all of the marine

mammals which die or are seriously injured may wash ashore, nor will all of those that do wash ashore necessarily

show signs of entanglement or other fishery-interaction. Finally, the level of technical expertise among stranding

network personnel varies widely as does the ability to recognize signs of fishery interaction.

The total known fishery-related mortality and serious injury for this stock is less than 10% of the calculated

PBR and, therefore, can be considered insignificant and approaching zero mortality and serious injury rate. This

determination cannot be made for specific fisheries until the implementing regulations for Section 118 of the MMPA

have been reviewed by the public and finalized. 

Fisheries Information

Pelagic swordfish, tunas, and billfish are the targets of the longline fishery operating in the U.S. Gulf of

Mexico. Total longline effort for the Gulf of Mexico pelagic fishery, including OCS edge, continental slope, and

Mexican territorial waters, based on mandatory logbook reporting, was 4,400 sets in 1991, 4,850 sets in 1992, and

3,260 sets in 1993 (Cramer 1994). This fishery has been monitored with about 5% observer coverage, in terms of

trips observed, since 1992. There were no reports of mortality or serious injury to melon-headed whales by this

fishery. 

Pair trawl fishing gear has the potential to capture marine mammals, but there have been no reports of

mortality or serious injury to marine mammals in the Gulf of Mexico. This fishery has not been observed by NMFS

observers, and there are no other data available as to the extent of this fishery in the Gulf of Mexico. It is assumed

that it is very limited in scope and duration. 

STATUS OF STOCK

The status of this stock relative to OSP is unknown. This species is not listed under the Endangered

Species Act. There are insufficient data to determine population trends. The total level of fishery-related mortality

and serious injury is unknown, but it is believed to be insignificant relative to PBR; therefore, this is not a strategic

stock. 
301

REFERENCES

Anon. 1994. Report of the PBR (Potential Biological Removal) workshop. June 27-29, 1994. NOAA, NMFS

Southwest Fisheries Science Center, La Jolla, California, 13 pp. + Appendices. 

Buckland, S. T., D. R. Anderson, K. P. Burnham and J. L. Laake. 1993. Distance Sampling: estimating abundance

of biological populations. Chapman & Hall, London, 446 pp. 

Caldwell, D. K., M. C. Caldwell and R. V. Walker. 1976. First records for Fraser's dolphin (Lagenodelphis hosei)

in the Atlantic and the melon-headed whale (Peponocephala electra) in the western Atlantic. Cetology 25:

1-4. 

Cramer, J. 1994. Large pelagic logbook newsletter - 1993. NOAA Tech. Mem. NMFS-SEFSC-352, 19 pp. 

Davis, R., G. Scott, B. Würsig, W. Evans, G. Fargion, L. Hansen, K. Mullin, N. May, T. Leming, B. Mate, J. Norris

and T. Jefferson. In preparation. Distribution and abundance of marine mammals in the north-central and

western Gulf of Mexico: Final Report. OCS Study #MMS 94-0003. Texas Institute of Oceanography and

the National Marine Fisheries Service. U.S. Dept. of the Interior, Minerals Mgmt. Service, Gulf of Mexico

OCS Region, New Orleans, Louisiana. 

Hansen, L. J., K. D. Mullin and C. L. Roden. 1995. Estimates of cetacean abundance in the northern Gulf of

Mexico from vessel surveys. Southeast Fisheries Science Center, Miami Laboratory, Contribution No.

MIA-94/95-25, 9 pp. + tables and figures. 

Laake, J. L., S. T. Buckland, D. R. Anderson, and K. P. Burnham. DISTANCE user’s guide, V2.0. Colorado

Cooperative Fish & Wildlife Research Unit, Colorado State University, Ft. Collins, Colorado, 72 pp. 

Mullin, K. D., T. A. Jefferson, L. J. Hansen and W. Hoggard. 1994. First sightings of melon-headed whales

(Peponocephala electra) in the Gulf of Mexico. Mar. Mam. Sci. 10(3): 342-348. 
302

Figure 1. Distribution of Risso’s dolphin sightings during NOAA Ship Oregon

II marine mammal surveys during 1991-1994. The straight lines show transects

during two surveys and are examples of typical survey transects. Isobaths are in

183 m (100 fm) intervals.

July 1995

RISSO'S DOLPHIN (Grampus griseus):

Northern Gulf of Mexico Stock

STOCK DEFINITION AND GEOGRAPHIC RANGE

Risso's dolphin is distributed worldwide in tropical to warm temperate waters (Leatherwood and Reeves

1983). Sightings of these animals in the northern Gulf of Mexico occur primarily along the continental shelf and

continental slope (Mullin et al. 1991; Southeast Fisheries Science Center, SEFSC, unpublished data). Risso's

dolphin were seen in all seasons during recent seasonal GulfCet aerial surveys of the northern Gulf of Mexico during

1993-1995 (Davis et al., in preparation) and in the late spring during vessel surveys (SEFSC, unpublished data).

There is no information on stock differentiation for the Atlantic population. 

POPULATION SIZE

Seasonal aerial survey data were insufficient for abundance estimation. Estimates of abundance were

derived through the application of distance sampling analysis (Buckland et al. 1993) and the computer program

DISTANCE (Laake et al. 1993) to sighting data collected during 1991-1994 spring-summer, visual sampling, linetransect vessel surveys of the northern Gulf of Mexico (Hansen et al. 1995) (Fig.1), which includes data collected as

part of the GulfCet program (Davis et al., in preparation). These surveys were conducted throughout the area from

approximately the 200 m isobath

along the U.S. coast to the

seaward extent of the U.S.

Exclusive Economic Zone. The

seasonal GulfCet aerial surveys

included only a small portion of

the stock range and these data

were not used for abundance

estimation. Estimated

abundance of Risso’s dolphins

by survey year [coefficient of

variation (CV) in parentheses]

was 667 in 1991 (0.95), 2,325 in

1992 (0.34), 1,408 in 1993

(0.41), and 6,332 in 1994 (0.45)

(Hansen et al. 1995). Survey

effort-weighted average

abundance of Risso's dolphins

estimated for all surveys

combined was 2,749 (CV = 

0.27) (Hansen et al. 1995). 

Minimum Population Estimate

The minimum population size was estimated from the average abundance estimate which was 2,749 Risso’s

dolphins (CV = 0.27) (Hansen et al. 1995). The minimum population estimate is the lower limit of the two-tailed

60% confidence interval of the log-normal distributed abundance estimate, which is equivalent to the 20th percentile

of the log-normal distributed abundance estimate as specified by NMFS (Anon. 1994). The minimum population

estimate is 2,199 Risso’s dolphins. 

Current Population Trend

No trend was identified in the annual abundance estimates. The 1994 abundance estimate was greater than

the other annual estimates, but no annual estimates differed significantly using the criteria of no overlap of lognormal 95% confidence intervals. The apparent differences in abundance estimates may have been caused by lower
303

sampling effort during 1991 (Hansen et al. 1995) or by inter-annual variation in distribution patterns or spatial

sampling patterns, rather than changes in population size. 

CURRENT AND MAXIMUM NET PRODUCTIVITY RATES

Current and maximum net productivity rates for this stock are not known; therefore, the default maximum

net productivity rate of 0.04 (Anon. 1994) was used for purposes of this assessment. 

POTENTIAL BIOLOGICAL REMOVAL

Potential biological removal level (PBR) was specified as the product of the minimum population size, one

half the maximum net productivity rate, and a recovery factor for endangered, threatened, or depleted stocks, or

stocks of unknown status relative to optimum sustainable population (OSP) (Anon. 1994). The recovery factor was

set at 0.50 because the status of the stock relative to OSP is unknown. PBR for this stock is 22 Risso’s dolphins. 

ANNUAL HUMAN-CAUSED MORTALITY AND SERIOUS INJURY

The level of past or current, direct, human-caused mortality of Risso's dolphins in the northern Gulf of

Mexico is unknown. This species has been taken in the U.S. longline swordfish/tuna fishery in the northern Gulf of

Mexico and in the U.S. Atlantic (Lee et al. 1994). Estimated average annual fishery-related mortality and serious

injury attributable to the longline swordfish/tuna fishery in the Gulf of Mexico during 1992-1993 was 19 Risso’s

dolphins annually (CV = 0.20). 

There were no documented strandings of Risso' dolphins in the northern Gulf of Mexico during 1987-1994

which were classified as likely caused by fishery interactions or other human-related causes. Stranding data

probably underestimate the extent of fishery-related mortality and serious injury because not all of the marine

mammals which die or are seriously injured may wash ashore, nor will all of those that do wash ashore necessarily

show signs of entanglement or other fishery-interaction. Finally, the level of technical expertise among stranding

network personnel varies widely as does the ability to recognize signs of fishery interaction.

The total estimated fishery-related mortality and serious injury for this stock is not less than 10% of the

calculated PBR and, therefore, cannot be considered insignificant and approaching zero mortality and serious injury

rate. This determination cannot be made for specific fisheries until the implementing regulations for Section 118 of

the MMPA have been reviewed by the public and finalized. 

Fisheries Information

Interactions between the U.S. longline swordfish/tuna fishery and Risso' dolphins have been documented in

the northern Gulf of Mexico (Lee et al. 1994). Pelagic swordfish, tunas, and billfish are the targets of the longline

fishery operating in the U.S. Gulf of Mexico. Total longline effort for the Gulf of Mexico pelagic fishery, including

OCS edge, continental slope, and Mexican territorial waters, based on mandatory logbook reporting, was 4,400 sets

in 1991, 4,850 sets in 1992, and 3,260 sets in 1993 (Cramer 1994). This fishery has been monitored with about 5%

observer coverage, in terms of trips observed, since 1992. One Risso's dolphin was observed taken and released

alive during 1992; the extent of injury to the animal was unknown (SEFSC, unpublished data). One lethal take of a

Risso's dolphin by the fishery was observed in the Gulf of Mexico during 1993 (SEFSC, unpublished data). Annual

fishery-related mortality and incidental injury was estimated using a generalized linear model (Poisson error

assumption) fit to the available observed incidental take data for the entire fishery and partitioned on the fishery

effort (number of sets) in the Gulf of Mexico. Estimated total mortality and serious injury to Risso’s dolphins (CV

in parentheses) in the Gulf of Mexico in 1992 was 24 (0.19), and in 1993 it was 13 (0.20). Estimated average annual

fishery-related mortality and serious injury attributable to the longline swordfish/tuna fishery in the Gulf of Mexico

during 1992-1993 was 19 Risso’s dolphins annually (CV = 0.20). 

Pair trawl fishing gear has the potential to capture marine mammals, but there have been no reports of

mortality or serious injury to marine mammals in the Gulf of Mexico. This fishery has not been observed by NMFS

observers, and there are no other data available as to the extent of this fishery in the Gulf of Mexico. It is assumed

that it is very limited in scope and duration. 

STATUS OF STOCK

The status of this stock relative to OSP is unknown. This species is not listed under the Endangered

Species Act and there are insufficient data to determine population trends. This is not a strategic stock because

fishery-
304

related mortality and serious injury does not exceed PBR; however, fishery-related mortality and serious injury is

very close to PBR and requires close monitoring. 

REFERENCES

Anon. 1994. Report of the PBR (Potential Biological Removal) workshop. June 27-29, 1994. NOAA, NMFS

Southwest Fisheries Science Center, La Jolla, California, 13 pp. + Appendices. 

Buckland, S. T., D. R. Anderson, K. P. Burnham and J. L. Laake. 1993. Distance Sampling: estimating abundance

of biological populations. Chapman & Hall, London, 446 pp. 

Cramer, J. 1994. Large pelagic logbook newsletter - 1993. NOAA Tech. Mem. NMFS-SEFSC-352, 19 pp. 

Davis, R., G. Scott, B. Würsig, W. Evans, G. Fargion, L. Hansen, K. Mullin, N. May, T. Leming, B. Mate, J. Norris

and T. Jefferson. In preparation. Distribution and abundance of marine mammals in the north-central and

western Gulf of Mexico: Final Report. OCS Study #MMS 94-0003. Texas Institute of Oceanography and

the National Marine Fisheries Service. U.S. Dept. of the Interior, Minerals Mgmt. Service, Gulf of Mexico

OCS Region, New Orleans, Louisiana. 

Hansen, L. J., K. D. Mullin and C. L. Roden. 1995. Estimates of cetacean abundance in the northern Gulf of

Mexico from vessel surveys. Southeast Fisheries Science Center, Miami Laboratory, Contribution No.

MIA-94/95-25, 9 pp. + tables and figures. 

Laake, J. L., S. T. Buckland, D. R. Anderson, and K. P. Burnham. DISTANCE user’s guide, V2.0. Colorado

Cooperative Fish & Wildlife Research Unit, Colorado State University, Ft. Collins, Colorado, 72 pp. 

Leatherwood, S. and R. R. Reeves. 1983. The Sierra Club handbook of whales and dolphins. Sierra Club Books,

San Francisco, 302 pp. 

Mullin, K., W. Hoggard, C. Roden, R. Lohoefener, C. Rogers and B. Taggart. 1991. Cetaceans on the upper

continental slope in the north-central Gulf of Mexico. OCS Study/MMS 91-0027. U.S. Dept. of the

Interior, Minerals Management Service, Gulf of Mexico OCS Regional Office, New Orleans, Louisiana,

108 pp. 
305

Figure 1. Distribution of short-finned pilot whale sightings during NOAA Ship

Oregon II surveys during 1991-1994. The straight lines show transects during

two surveys and are examples of typical survey transects. Isobaths are in 183 m

(100 fm) intervals.

July 1995

SHORT-FINNED PILOT WHALE (Globicephala macrorhynchus):

Northern Gulf of Mexico Stock

STOCK DEFINITION AND GEOGRAPHIC RANGE

The short-finned pilot whale is distributed worldwide in tropical to warm temperate waters (Leatherwood

and Reeves 1983). Sightings of these animals in the northern Gulf of Mexico occur primarily along the continental

shelf and continental slope [Mullin et al. 1991; Southeast Fisheries Science Center (SEFSC) unpublished data]. 

Short-finned pilot whales were seen in all seasons during recent seasonal GulfCet aerial surveys of the northern Gulf

of Mexico during 1993-1995 (Davis et al., in preparation). There is no information on stock differentiation for the

Atlantic population. 

POPULATION SIZE

Abundance was estimated using distance sampling analysis (Buckland et al. 1993) and the computer

program DISTANCE (Laake et al. 1993) with sighting data collected during 1991-1994 spring-summer, visual

sampling, line-transect vessel surveys of the northern Gulf of Mexico (Hansen et al. 1995) (Fig. 1), which includes

data collected as part of the GulfCet program (Davis et al., in preparation). These surveys were conducted

throughout the area from approximately the 200 m isobath along the U.S. coast to the seaward extent of the U.S.

Exclusive Economic Zone. The seasonal GulfCet aerial surveys included only a small portion of the stock range, so

those data were not used for

abundance estimation. 

Estimated abundance of shortfinned pilot whales by survey

year [coefficient of variation

(CV) in parentheses] was zero

in 1991, 909 in 1992 (0.62),

103 in 1993 (1.20), and 240 in

1994 (1.03) (Hansen et al.

1995). Survey effort-weighted

estimated average abundance

of short-finned pilot whales for

all surveys combined was 353

(CV = 0.89) (Hansen et al.

1995). 

Minimum Population

Estimate

The minimum

population size was estimated from the average abundance estimate which was 353 pilot whales (CV = 0.89)

(Hansen et al. 1995). The minimum population estimate is the lower limit of the two-tailed 60% confidence interval

of the log-normal distributed average abundance estimate, which is equivalent to the 20th percentile of the lognormal distributed abundance estimate as specified by NMFS (Anon. 1994). The minimum population estimate is

186 pilot whales. 

Current Population Trend

The annual abundance estimates were not significantly different using the criteria of no overlap of lognormal 95% confidence intervals. The variation in abundance estimates that was observed may have been caused by

lower sampling effort during 1991, by low sampling intensity relative to population size (Hansen et al. 1995), or by

inter-annual variation in distribution patterns or spatial sampling patterns, rather than changes in population size. 
306

CURRENT AND MAXIMUM NET PRODUCTIVITY RATES

Current and maximum net productivity rates are not known for this stock; therefore, the default maximum

net productivity rate of 0.04 (Anon. 1994) was used for purposes of this assessment. 

POTENTIAL BIOLOGICAL REMOVAL

Potential biological removal level (PBR) was specified as the product of the minimum population size, one

half the maximum net productivity rate, and a recovery factor for endangered, threatened, or depleted stocks, or

stocks of unknown status relative to optimum sustainable population (OSP) (Anon. 1994). The recovery factor was

set at 0.50 because the status of the stock relative to OSP is unknown. PBR for this stock is 1.9 short-finned pilot

whales. 

ANNUAL HUMAN-CAUSED MORTALITY AND SERIOUS INJURY

The level of past or current, direct, human-caused mortality of short-finned pilot whales in the northern

Gulf of Mexico is unknown. This species has been taken in the U.S. longline swordfish/tuna fishery in U.S. Atlantic

waters (Lee et al. 1994) and there is a logbook report of a fishery-related mortality or serious injury in the northern

Gulf of Mexico (NMFS unpublished data); however, fishery-related mortality or serious injury has not been

observed. Total known fishery-related mortality or serious injury is estimated to be 0.3 short-finned pilot whales per

year based upon the logbook report. 

There were no documented strandings of short-finned pilot whales in the northern Gulf of Mexico during

1987-1994 which were classified as likely caused by fishery interactions or other human-related causes. Stranding

data probably underestimate the extent of fishery-related mortality and serious injury because not all of the marine

mammals which die or are seriously injured may wash ashore, nor will all of those that do wash ashore necessarily

show signs of entanglement or other fishery-interaction. Finally, the level of technical expertise among stranding

network personnel varies widely as does the ability to recognize signs of fishery interaction.

 The total known fishery-related mortality and serious injury for this stock is greater than 10% of the

calculated PBR and, therefore, cannot be considered insignificant and approaching zero mortality and serious injury

rate. This determination cannot be made for specific fisheries until the implementing regulations for Section 118 of

the MMPA have been reviewed by the public and finalized. 

Fisheries Information

Pelagic swordfish, tunas, and billfish are the targets of the longline fishery operating in the U.S. Gulf of

Mexico. Interactions between the U.S. longline swordfish/tuna fishery and short-finned pilot whales have been

reported in the northern Gulf of Mexico (SEFSC, unpublished logbook data), but have not been observed by NMFS

fishery observers. Total longline effort for the Gulf of Mexico pelagic fishery, including OCS edge, continental

slope, and Mexican territorial waters, based on mandatory logbook reporting, was 4,400 sets in 1991, 4,850 sets in

1992, and 3,260 sets in 1993 (Cramer 1994). This fishery was been monitored with about 5% observer coverage in

both the Atlantic Ocean and the Gulf of Mexico, in terms of trips observed, in 1992-1993. There was one logbook

report of a fishery-related injury of a pilot whale in the northern Gulf of Mexico in 1991, but no fishery interactions

were observed during 1992-1993. Total known fishery-related mortality or serious injury is estimated to be 0.3

short-finned pilot whales per year based upon the logbook report. 

Pair trawl fishing gear has the potential to capture marine mammals, but there have been no reports of

mortality or serious injury to marine mammals in the Gulf of Mexico. This fishery has not been observed by NMFS

observers, and there are no other data available as to the extent of this fishery in the Gulf of Mexico. It is assumed

that it is very limited in scope and duration. 

STATUS OF STOCK

The status of this stock relative to OSP is unknown and there are insufficient data to determine population

trends. This species is not listed under the Endangered Species Act. The total level of estimated fishery-related

mortality and serious injury is unknown, but because there is a record of a fishery-related mortality or serious injury

and because of the extremely low estimated stock size, this is a strategic stock.
307

REFERENCES

Anon. 1994. Report of the PBR (Potential Biological Removal) workshop. June 27-29, 1994. NOAA, NMFS

Southwest Fisheries Science Center, La Jolla, California, 13 pp. + Appendices. 

Buckland, S. T., D. R. Anderson, K. P. Burnham and J. L. Laake. 1993. Distance Sampling: estimating abundance

of biological populations. Chapman & Hall, London, 446 pp. 

Cramer, J. 1994. Large pelagic logbook newsletter - 1993. NOAA Tech. Mem. NMFS-SEFSC-352, 19 pp. 

Davis, R., G. Scott, B. Würsig, W. Evans, G. Fargion, L. Hansen, K. Mullin, N. May, T. Leming, B. Mate, J. Norris

and T. Jefferson. In preparation. Distribution and abundance of marine mammals in the north-central and

western Gulf of Mexico: Final Report. OCS Study #MMS 94-0003. Texas Institute of Oceanography and

the National Marine Fisheries Service. U.S. Dept. of the Interior, Minerals Mgmt. Service, Gulf of Mexico

OCS Region, New Orleans, Louisiana. 

Hansen, L. J., K. D. Mullin and C. L. Roden. 1995. Estimates of cetacean abundance in the northern Gulf of

Mexico from vessel surveys. Southeast Fisheries Science Center, Miami Laboratory, Contribution No.

MIA-94/95-25, 9 pp. + tables and figures. 

Laake, J. L., S. T. Buckland, D. R. Anderson, and K. P. Burnham. DISTANCE user’s guide, V2.0. Colorado

Cooperative Fish & Wildlife Research Unit, Colorado State University, Ft. Collins, Colorado, 72 pp. 

Leatherwood, S. and R. R. Reeves. 1983. The Sierra Club handbook of whales and dolphins. Sierra Club Books,

San Francisco, 302 pp. 

Lee, D. W., C. J. Brown, A. J. Catalano, J. R. Grubich, T. W. Greig, R. J. Miller and M. T. Judge. 1994. SEFSC

pelagic longline observer program data summary for 1992-1993. NOAA Tech. Mem. NMFS-SEFSC-347,

19 pp. 

Mullin, K., W. Hoggard, C. Roden, R. Lohoefener, C. Rogers and B. Taggart. 1991. Cetaceans on the upper

continental slope in the north-central Gulf of Mexico. OCS Study/MMS 91-0027. U.S. Dept. of the

Interior, Minerals Management Service, Gulf of Mexico OCS Regional Office, New Orleans, Louisiana,

108 pp. 
308

APPENDIX IV. West Indian manatees stock assessments - Florida and Antilles stocks.

WEST INDIAN MANATEE (Trichechus manatus latirostris)

FLORIDA STOCK

U.S. Fish and Wildlife Service, Jacksonville, Florida

STOCK DEFINITION AND GEOGRAPHIC RANGE

Manatees are typically found in the temperate and equatorial waters of the southeastern U.S., the Caribbean

basin, northern and northeastern South America, and equatorial West Africa. Their near relative, the dugong

(Dugong dugon), is found in the Indo-Pacific region. At present, manatees of the genus Trichechus are represented

by three allopatric species: T. senegalensis, the West African manatee, T. inunguis, the Amazonian manatee, and T.

manatus, the West Indian manatee. The West Indian species is subdivided into two subspecies, the Antillean

manatee (Trichechus manatus manatus) and the Florida manatee (Trichechus manatus latirostris) (U.S. Fish and

Wildlife Service, 1989). Such subspeciation may reflect reproductive isolation brought on by the intemperate

northern coast of the Gulf of Mexico and characteristically strong currents found in the Straits of Florida (Domning

and Hayek, 1986).

Historically, the winter range of the Florida manatee (Trichechus manatus latirostris) was thought to focus

on south Florida, with some animals ranging north of Charlotte Harbor on Florida's west coast and north of Sebastian

on Florida's east coast. Extralimital movements occurred and were typically seasonal, with animals travelling north

during warmer periods and travelling south as temperatures declined. While most manatees wintered in south

Florida, some were known to winter in natural spring areas to the north (Hartman, 1974). With the advent of

artificial warm water refugia, the spread of exotic submerged aquatic vegetation, and increased protective measures,

the manatee's winter range has expanded significantly (Beeler and O'Shea, 1988). On the east coast, manatees are

now known to winter as far north as southeastern Georgia and, on the west coast, as far north as Crystal River,

Florida. Documentation of manatee movements between Gulf and Atlantic coast populations in far south Florida is

lacking, presumably because lack of suitable habitat in Florida Bay is not conducive to such movements, but

significant genetic variation between coastal populations has not been demonstrated (McClenaghan and O'Shea

1988). Range extremes extend north to Virginia on the Atlantic coast and west to Louisiana on the Gulf coast. The

number of sighting reports outside of Florida has increased in recent years.

POPULATION SIZE

Minimum Population Estimate

The exact population size for Florida manatees is unknown but the minimum population is estimated at

1,822 animals, based on intensive statewide winter aerial surveys at warm-water refuges coordinated by the Florida

Department of Environmental Protection in early February of 1995 (FDEP 1995). A previous high count of 1856

manatees was obtained in a survey conducted in 1992 (Ackerman, 1992). While not a statistical estimate, this count

provides the best available data on the minimum size of the population.

Population Trends

Manatee population trends are poorly known but, based on the results of a carcass recovery program, deaths

have increased by an average of 5.9 percent per year in Florida from 1976 through 1992 (Ackerman et al. In press). 

Garrott et al.'s (1994) analysis of trends at winter aggregation sites suggest a mean annual increase of 7-12 percent in

adjusted counts at sites on the east coast from 1978-1992, noting that this figure exceeds Packard's conservative

estimate of maximum potential rate of increase for manatees of 2-7 percent annually (Packard 1985). Reynolds and

Wilcox (1994) reported a decline in the percentage and number of calves seen at power plant aggregation sites

during recent winter aerial surveys. It is not clear at this time whether this is related to increases in perinatal

mortality or to some other factor.

Marmontel (1994) conducted a population viability analysis through computer simulations using 16 years of

data and material collected by the carcass recovery program. This study yielded information on age-related aspects

of mortality and reproduction for the Florida manatee population. A scenario, calculated from the data, having an

initial population size of 2,000 individuals resulted in a gradually declining population (r = -0.003), a probability of

persistence of 44 percent in 1,000 years, and a mean final population size of less than 10 percent of the original
309

value. When adult mortality was reduced by 10 percent in the model, population growth improved considerably, but

when adult mortality was increased by 10 percent the population quickly dwindled. These results clearly indicate

that the Florida manatee population is still at high risk of extinction in the long term. Any negative change in the

population parameters, caused by environmental changes or a catastrophe, might tip the balance towards greater risk

of extinction.

ANNUAL HUMAN-CAUSED MORTALITY

Manatee deaths resulting from human activities are well documented through a carcass recovery program,

initiated in 1974. Causes of death include collisions with large and small boats, crushing by barges and man made

water control structures (flood gates/canal locks), entanglement in nets and lines, entrapment in culverts, poaching,

entanglement in, and ingestion of marine debris (e.g., monofilament), and others (Ackerman et al., In press). 

From 1974 through 1994, 2,456 manatee carcasses were recovered in the southeastern U.S. Eight hundred

and two (33 percent) were attributed to human-related causes. Of these, 613 were caused by collisions with

watercraft, 111 were flood gate/canal lock-related, and another 78 were categorized as other human-related. 

In Florida, human-related mortality accounted for the greatest proportion of deaths with identifiable causes

(45 percent, with another 24 percent of deaths resulting from undetermined causes) from 1986-1992. Collisions with

watercraft accounted for 83 percent of human-related causes of death during this period (Ackerman et al. 1994, 

Wright et al. 1994). Watercraft-related deaths increased by an average of 9.3 percent per year from 1974 to 1992,

increasing as a percentage of total deaths from 21 percent in 1976-1980 to 28 percent from 1986-1992 (Ackerman et

al., In press). Overall, watercraft collisions account for approximately 25% of all manatee deaths.

The highest known annual mortality for the Florida manatee in any given year occurred in 1990 when 214

deaths (206 of which occurred in Florida) were recorded (Ackerman et al. 1994). In 1994, the second highest annual

level of mortality on record occurred, when 193 carcasses were recovered (FDEP 1995).

FISHERIES INFORMATION

Manatee deaths have been attributed to inshore and nearshore commercial fishing activity. Fisheries gear

involved in these incidents include shrimp nets, crab trap lines, hoop nets, and a trotline (National Marine Fisheries

Service, 1992; Beck, C.A. and N.B. Barros, 1991). Recreational fishing activities have also been implicated in

manatee deaths; manatees have died as a result of ingesting monofilament line and fishing tackle and from

entanglement in monofilament line, crab trap lines, and cast nets. Non-lethal entanglement associated with these

gear types, sometimes resulting in the loss of a flipper due to constriction, is also known to occur. Collisions with

fishing boats probably occur; however, it is not possible to determine the extent to which this occurs.

While fisheries have been implicated in the deaths of manatees, the number of such incidents is low. The

manatee carcass recovery program has identified 17 manatee deaths which are directly attributable to commercial

fisheries gear (FDEP Manatee Mortality Database, 1994). Fishing gear is suspected in three additional deaths. 

"Because total annual manatee mortality is increasing, the population is small, and reproduction is low, incidental

mortality from commercial fisheries, when added to other human-related mortality, could be significant if not critical

to the manatee population" (Young et al., 1993).

The majority of the manatee deaths attributed to commercial fisheries involve the shrimping industry. 

Mortalities have occurred in northeast Florida (Duval County), east central Florida (Volusia County), and the Florida

Panhandle area (Franklin County), as well as in coastal waters of Georgia and South Carolina where shrimping is

permitted. Other fishery interactions have occurred throughout the manatee's range in Florida. No distinct

seasonality has been associated with these events (FDEP Manatee Mortality Database, 1994).

STATUS OF STOCK

The Florida manatee is listed as "endangered" under provisions of the Endangered Species Act of 1973 (16

U.S.C. 1531 et seq.), as amended. The manatee is considered a "strategic stock" as defined in Section 12 of the

Marine Mammal Protection Act of 1972, as amended. The basis for this designation is the high level of documented

mortality (natural and human-related) relative to the estimated population level and continuing, severe threats to

critical manatee habitats in the southeastern U.S.
310

POTENTIAL BIOLOGICAL REMOVAL

Because of its endangered status, the recovery factor for the Florida manatee should be 0.1, the lowest

allowable figure. Given a minimum population estimate of 1,822 and an Rmax (maximum net productivity rate) of

0.04, the Potential Biological Removal (PBR) rate for manatees is as follows:

PBR = (1822)(.02, or 1/2 Rmax)(.1) = 3

The calculated PBR level is greatly exceeded by known human-related manatee mortality (primarily

watercraft collisions and water control structure deaths) every year in Florida. For this reason, and because current

efforts of the Florida Manatee Recovery Team focus intensively on the reduction of these major types of mortality,

the determination of the PBR level for manatees is of limited value. The excessive level of documented manatee

mortality and the resulting unlikelihood of attaining Optimum Sustainable Population (OSP) make the calculation of

meaningful PBR for manatees a difficult exercise. Marmontel's (1994) estimate of net productivity is essentially

zero (-0.003). Substituting this value for the default value for maximum net productivity rate (0.04) in the above

equation results in a PBR level of 0.

The U.S. Fish and Wildlife Service has consistently concluded in Section 7 Biological Opinions, pursuant

to the Endangered Species Act, that the take of a single manatee would "jeopardize the continued existence" of the

species. We therefore believe that designating any level of take for manatees would be inappropriate and

inconsistent with the revised Florida Manatee Recovery Plan.

REFERENCES

Ackerman, B.B., S.D. Wright, R.K. Bonde, D.K. Odell, and D.J. Banowetz. (In press). Trends and patterns in

mortality in Florida, 1974-1992. In T.J. O'Shea, B.B. Ackerman, and H. F. Percival, editors. Population

Biology of the Florida manatee (Trichechus manatus latirostris). National Biological Service, Biological

Report.

Ackerman, B.B. 1992. Ongoing manatee aerial survey programs: a progress report. In: O'Shea, T.J., B.B.

Ackerman, and H.F. Percival (eds.). 1992. Interim report of the technical workshop on manatee population

biology. Manatee Population Research Report No. 10. Florida Cooperative Fish and Wildlife Research

Unit. University of Florida, Gainesville, FL 83 pp.

Beck, C.A. and N.B. Barros. 1991. The impact of debris on the Florida manatee. Marine Pollution Bulletin 22(10):

508-510.

Beeler, I.E. and T.J. O'Shea. 1988. Distribution and mortality of the West Indian Manatee (Trichechus manatus) in

the Southeastern United States: a compilation and review of recent information. Natl. Tech. Inf. Ser.,

PB88-207980/AS: Springfield, VA. Two volumes, 613 pp.

Domning, D.P. and L.C. Hayek. 1986. Interspecific and intraspecific morphological variation in manatees (Sirenia: 

Trichechus)," Marine Mammal Sci. 2:87-144.

Florida Department of Environmental Protection. 1995. Manatee mortality database, 1974-1994. Florida Marine

Research Institute, Marine Mammal Pathobiology Laboratory.

Florida Department of Environmental Protection. Press Release, February 9, 1995.

Garrott, R.A., B.B. Ackerman, J.R. Cary, D. M. Heisey, J.E. Reynolds, III, P.M. Rose, and J.R. Wilcox. 1994. 15-

year trends in counts of Florida manatees at winter aggregation sites. Journal of Wildlife Management 58

(4):642-654. 

Hartman, D.S. 1974. Distribution, status, and conservation of the manatee in the United States. Natl. Tech. Inf.

Ser., PB81-140725, Springfield, VA. 246 pp.

Marmontel, M. (In press). Age and reproductive parameter estimates in female Florida manatees. In T.J. O'Shea,

B.B. Ackerman, and H.F. Percival, eds. Population biology of the Florida manatee (Trichechus manatus

latirostris). National Biological Service, Biological Report.

McClenaghan, L.R. and T.J. O'Shea. 1988. Genetic variability in the Florida manatee (Trichechus manatus). J. 

Mamm., 69 (3):481-488.

National Marine Fisheries Service. 1992. Proposed Regime to Govern Interactions Between Marine Mammals and

Commercial Fishing Operations. Silver Spring, MD. 96 pp.

O'Shea, T.J., G.B. Rathbun, R.K. Bonde, C.D. Buergelt, and D.K. Odell. 1991. An epizootic of Florida manatees

associated with a dinoflagellate bloom. Marine Mammal Sci. 7(2): 165-179.
311

Packard, J.M. 1985. Preliminary assessment of uncertainty involved in modeling manatee populations. Manatee

population Research Report No. 9. Technical Report No. 8-9. Florida Cooperative Fish and Wildlife

Research Unit. University of Florida, Gainesville, Florida. 19 pp.

Reynolds, J.E., III and J.R. Wilcox. 1994. Observations of Florida manatees (Trichechus manatus latirostris)

around selected power plants in winter. Marine Mammal Sci. 10(2): 143-177.

U.S. Fish and Wildlife Service. 1989. Florida Manatee (Trichechus manatus latirostris) Recovery Plan. Prepared

by the Florida Manatee Recovery Team for the U.S. Fish and Wildlife Service, Atlanta, GA. 98 pp.

Wright, S.D., B.B. Ackerman, R.K. Bonde, C.A. Beck, and D.J. Banowetz. (In press). Analysis of watercraft-related

mortalities of manatees in Florida, 1979-1991. In T.J. O'Shea, B.B. Ackerman, and H. F. Percival, editors. 

Population Biology of the Florida manatee (Trichechus manatus latirostris). National Biological Service,

Biological Report.

Young, N.M., S. Iudicello, K. Evans, and D. Baur. 1993. The incidental capture of marine mammals in U.S.

fisheries: problems and solutions. Center for Marine Conservation, Washington, D.C. 415 pp.
312

WEST INDIAN MANATEE ((Trichechus manatus manatus)

ANTILLEAN STOCK

U.S. Fish and Wildlife Service, Jacksonville, Florida

STOCK DEFINITION AND GEOGRAPHIC RANGE

Manatees are typically found in the temperate and equatorial waters of the southeastern U.S., the Caribbean

basin, northern and northeastern South America, and equatorial West Africa. Their nearest relative, the dugong

(Dugong dugon), is found in the Indo-Pacific region. At present, manatees of the genus Trichechus are represented

by three allopatric species: T. senegalensis, the West African manatee, T. inunguis, the Amazonian manatee, and T.

manatus, the West Indian manatee (U.S. Fish and Wildlife Service, 1986). The West Indian species is subdivided

into two subspecies, the Antillean manatee (Trichechus manatus manatus) and the Florida manatee (Trichechus

manatus latirostris). Such subspeciation may reflect reproductive isolation brought on by the intemperate northern

coast of the Gulf of Mexico and characteristically strong currents found in the Straits of Florida (Domning and

Hayek, 1986).

The Antillean manatee is found in eastern Mexico, Central America, northern and eastern South America,

and in the Greater Antilles (Lefebvre et al., 1989). In Puerto Rico, the manatee is most abundant along the south and

east coasts, particularly in the area of Fajardo and Ceiba (Roosevelt Roads Naval Station) and in the Jobos Bay area

between Guayama and Salinas. In general, manatees are not abundant on the north coast although they are

infrequently seen in areas immediately to the west of San Juan (Mignucci Giannoni, 1989, Caribbean Stranding

Network, unpubl. data). Manatees are rarely seen near Culebra Island and are generally absent from Mona Island

and the Virgin Islands (Caribbean Stranding Network, unpubl. data). The U.S. has jurisdictional responsibilities for

the Antillean subspecies only in Puerto Rico and the U.S. Virgin Islands.

POPULATION SIZE

The exact number of Antillean manatees known to occur in Puerto Rico is unknown but, based on aerial

surveys conducted on July 16 and 17, 1994, this population includes at least 86 individuals (Oland, pers. comm.). 

Manatees are virtually unknown from the U.S. Virgin Islands (Lefebvre et al., 1989). A rare sighting and stranding

was reported here in 1988 (Caribbean Stranding Network, unpubl. data).

Population Trends

Quantitative information is limited regarding trends in the abundance of the Antillean manatee, although

"[h]istorical accounts indicate that manatees were once more common and that hunting has been responsible for

declining numbers throughout much of their range" (Lefebvre et al., 1989).

In Puerto Rico, efforts have been made to assess the status of the Antillean manatee by conducting aerial

surveys and by means of a carcass salvage program. Aerial surveys were initiated in 1978 and have continued

sporadically to the present. Carcass salvage efforts were initiated in April 1974, by the U.S. Fish and Wildlife

Service (Rathbun et al., 1986). In 1989, the Caribbean Stranding Network initiated a dedicated salvage, rescue, and

rehabilitation program and has assumed responsibility for all carcass recovery efforts in Puerto Rico. Despite these

assessments, limited information exists by which to determine trends in this population of manatees.

Based largely on historical accounts and increasing human pressures, the Antillean manatee as a subspecies

appears to be in decline. However, efforts to quantify population levels and trends are preliminary and there are no

conclusive indications as to whether or not the population of Antillean manatees is stable, increasing, or decreasing

either in Puerto Rico or throughout its range.

ANNUAL HUMAN-CAUSED MORTALITY

Since the inception of Puerto Rico's manatee carcass salvage program, 70 manatee deaths have been

recorded from that area (Caribbean Stranding Network, unpubl. data). Many of the deaths have been attributed to

human-related causes. Carcass collection efforts have documented mortalities associated with nets and watercraft

(N=37). Many net-related mortalities involve poaching and are not substantiated by the presence of a carcass

(Rathbun et al., 1985). From 1974 until 1988, 41.5 percent of the documented mortality was attributed to poaching. 

Watercraft-related mortalities are increasing. During the period 1988 to 1991, watercraft-related mortalities

accounted for 43 percent of the known mortalities (U.S. Fish and Wildlife Service, 1992).
313

FISHERIES INFORMATION

In Puerto Rico, fisheries interactions have been documented through the carcass recovery program and in

numerous anecdotal reports. Manatees are captured primarily in gill and/or turtle nets either intentionally or

inadvertently during fishing activities. Reports indicate that manatee meat is sold to ready buyers, although the

extent to which this occurs is unknown (Mignucci et al., 1993). Given the scarcity of detailed information, little is

known about capture sites, seasonality of occurrence, etc. (Rathbun et al., 1985). Because these deaths account for a

substantial proportion of known human-related mortalities (and because of the prevalence of fishery reports), it is

apparent that fisheries interactions significantly affect the status of the manatee in Puerto Rico.

STATUS OF STOCK

The manatee is listed as "endangered" under provisions of the Endangered Species Act of 1973 (16 U.S.C.

1531 et seq.), as amended. The manatee is considered a "strategic stock" as defined in Section 12 of the Marine

Mammal Protection Act of 1972, as amended. The basis for this designation is the high level of documented

mortality relative to the estimated population level and continuing, severe threats to critical manatee habitats

throughout its range.

POTENTIAL BIOLOGICAL REMOVAL

Because of its endangered status, the recovery factor for the Antillean manatee in Puerto Rico should be

0.1, the lowest allowable figure. Given a minimum population estimate of 86 and an Rmax (maximum net

productivity rate) of 0.04, the Potential Biological Removal (PBR) rate for Antillean manatees in Puerto Rico and

the U.S. Virgin Islands is as follows:

PBR = (86)(.02, or 1/2 Rmax)(.1) =0

We currently have insufficient knowledge of the Puerto Rican manatee population to determine the Optimum

Sustainable Population. Inadequate information on population size and net productivity rate for manatees in Puerto

Rico render the calculation of a PBR level for this population an exercise of limited value. Marmontel (1994)

estimated net productivity for the Florida manatee population. This estimate, based largely on a long term sex and

age dataset for that population, suggested that the net productivity was essentially zero (-0.003). When the default

value above (0.2) is replaced with this empirical value, the equation results in a PBR level of zero.

The U.S. Fish and Wildlife Service has consistently concluded in Section 7 Biological Opinions, pursuant

to the Endangered Species Act, that the take of a single manatee would "jeopardize the continued existence" of the

species. We therefore believe that designating any level of take for Antillean manatees would be inappropriate and

inconsistent with manatee recovery plans.

REFERENCES

Ackerman, B.B., S.D. Wright, R.K. Bonde, D.K. Odell, and D.J. Banowetz.(In press). Trends and patterns in

mortality in Florida, 1974-1992. In T.J. O'Shea, B.B. Ackerman, and H. F. Percival, editors. Population

Biology of the Florida manatee (Trichechus manatus latirostris). National Biological Service, Biological

Report.

Domning, D.P. and L.C. Hayek. 1986. Interspecific and intraspecific morphological variation in manatees (Sirenia: 

Trichechus). Marine Mammal Sci. 2:87-144.

Freeman, J. and H. Quintero. 1990. The distribution of West Indian manatees (Trichechus manatus)

in Puerto Rico: 1988-1989. NTIS PB91-137240. Springfield, VA. 43 pp.

Lefebvre, L.W., T.J. O'Shea, G.B. Rathbun and R.C. Best. 1989. Distribution, status,and biogeography of the West

Indian manatee. Biogeography of the West Indies, 1989: 567-610.

Marmontel, M. (In press). Age and reproductive parameter estimates in female Florida manatees. In T.J. O'Shea,

B.B. Ackerman, and H.F. Percival, eds. Population biology of the Florida manatee (Trichechus manatus

latirostris). National Biological Service, Biological Report.

Mignucci Giannoni, A.A. 1989. Zoogeography of marine mammals in Puerto Rico and the Virgin Islands. 

Unpublished master's thesis, The University of Rhode Island, Kingston, RI.

Mignucci Giannoni, A.A. 1990. Manatee mortality in Puerto Rico: urgent need for assessment and preventive

action. Whalewatcher, Journal of the American Cetacean Society, 24(1):10-12.
314

Mignucci Giannoni, A.A., E.H. Williams, B. Pinto Rodríguez and R.A. Montoya Ospina. 1991. Marine mammal

mortality assessment in the Caribbean and the established Caribbean Stranding Network. Presented at the

Ninth Biennial Conference on the Biology of Marine Mammals, Chicago, IL, 7 December.

Mignucci Giannoni, A.A., B. Pinto-Rodriguez, R.A. Montoya-Ospina, D.P. Moore, and E.H. Williams. 1993. 

Stranding and mortality assessment of marine mammals in Puerto Rico and the Virgin Islands. Presented at

the Tenth Biennial Conference on the Biology of Marine Mammals, Galveston, TX, 11-16 November.

National Marine Fisheries Service. 1992. Proposed Regime to Govern Interactions Between Marine Mammals and

Commercial Fishing Operations. Silver Spring, MD. 96 pp.

Oland, J.P. 1994. Personal communication, July 19, 1994. From: James P. Oland, Supervisor, FWS Caribbean

Field Office, Boqueron, PR. To: Robert O. Turner, Manatee Recovery Coordinator, FWS Jacksonville

Field Office, Jacksonville, FL.

Rathbun, G.B., Carr, N., Carr, T., and C.A. Woods. 1985. The distribution of manatees and sea turtles in Puerto

Rico, with emphasis on Roosevelt Roads Naval Station. NTIS PB 85-151847 AS. Springfield, VA. 83 pp.

U.S. Fish and Wildlife Service. 1986. Recovery plan for the Puerto Rico population of the West Indian manatee

(Trichechus manatus manatus L.). Prepared by: G.B. Rathbun and E. Possardt for the U.S. Fish and

Wildlife Service, Atlanta, GA. 28 pp.

U.S. Fish and Wildlife Service. 1992. Letter dated June 4, 1992, to the U.S. Army Corps of Engineers from the

FWS Caribbean Field Office, Boqueron, PR.

Young, N.M., S. Iudicello, K. Evans, and D. Baur. 1993. The incidental capture of marine mammals in U.S.

fisheries: problems and solutions. Center for Marine Conservation, Washington, D.C. 415 pp.
315

INDEX

Note: Species are indexed under both common and scientific names. The reader should refer to both when seeking

information within the text of this document.

agricultural runoff . . . . . . . . . . . . . . . . . . . . . . . . 245

arctic . . . . . . . . . . . . . . 6, 16, 36, 75, 87, 90, 187, 211

area closure . . . . . . . . . . . . . . . . . . . . . . . . . . . 84, 119

Atlantic spotted dolphin . . . 3, 4, 157, 196, 197, 199,

200, 263, 265

Balaenoptera acutorostrata . . . . . . . . . . . 93, 99, 103

Balaenoptera borealis . . . . . . . . . . . . . . . . . . . . 33, 35

Balaenoptera musculus . . . . . . . . . . . . . . . . . . . . 36-38

Barataria Bay . . . . . . . . . . . . . . . . . . . . . . . . . . . . 256

Basque whalers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

Bay Boudreau . . . . . . . . . . . . . . . . . . . . . . . . . . . . 256

Bay of Fundy . . 3, 6, 7, 11, 12, 15, 19, 22, 25, 28, 31,

40, 45, 47, 51, 53, 60, 67, 73, 75,

77, 78, 80, 83, 94, 96, 98, 103-105,

109, 110, 112-116, 118-121, 124-

127, 129, 134, 137, 140, 144, 157,

161, 184, 188, 191, 192, 194, 197,

200, 203, 206

billfish ..... 217, 220, 223, 226, 229, 232, 235, 238,

241, 264, 267, 270, 273, 276, 279,

282, 285, 288, 291, 294, 297, 300,

303, 306

biopsy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7, 16, 171

Blainville’s beaked whale . . . . . . . . 3, 49, 56, 57, 231

blue runners .......................... 249, 253

blue whale . . . . . . . . . . . . . . . 2, 36-38, 181-184, 186

Bonsecour Bay . . . . . . . . . . . . . . . . . . . . . . . . . . . 256

bottlenose dolphin . . . . . 3-5, 162-167, 169, 171, 175,

176, 178-181, 183, 185, 237, 239,

240, 242-262, 265

Bryde’s whale . . . . . . . . . . . . . . . . . . . . . . 3, 225, 226

Calcasieu Lake . . . . . . . . . . . . . . . . . . . . . . . . . . . 256

Canada . 5, 11, 12, 22, 29, 33, 34, 36, 37, 40, 43-45,

50, 57, 63, 70-73, 75, 77, 79-89, 91,

98, 99, 102, 103, 109-111, 113,

118, 120, 121, 124-126, 133-135,

137, 144-146, 152, 184, 188, 205,

206, 211-215

Canadian East Coast . . . . . . . . . . 2, 93-95, 100, 101

Canadian fisheries . . . . . . . . . . . . . . . . . 98, 109, 118

Cape Cod Bay . . . . . . . . . . 7, 10, 13, 23, 52, 100, 101

Cape Hatteras . 20, 27, 33, 34, 39, 40, 42, 43, 46, 48,

49, 53, 55, 59, 61, 62, 66, 68-70,

76, 83, 89, 93, 96, 97, 105, 107,

116, 128, 129, 131-133, 139, 142-

144, 150, 154, 157, 159, 160, 162,

164, 169-172, 188-190, 192, 193,

196, 198, 199, 202, 204, 209, 213

Chesapeake Bay . . . . . . . . . . . . . . . . . . 122, 176, 196

chlorinated hydrocarbons ...... 138, 245, 259, 260

cigarfish . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 249, 253

Clearwater Harbor . . . . . . . . . . . . . . . . . . . . . . . . 256

clymene dolphin . . . . . . . . . . . . . . . . . . . . 4, 278, 280

coastal gillnet . 42, 48, 55, 61, 63, 68, 70, 71, 77, 78,

89, 95, 97, 99, 100, 106, 108, 109,

116-118, 120-122, 126, 131, 134,

135, 142, 144, 145, 155, 159, 165,

166, 173, 174, 185, 198, 213, 253

cod traps . . . 11, 19, 77, 78, 83, 90, 98, 99, 134, 144,

145, 194, 213

common dolphin . . . . . . . . . . . . . . . 3, 66-72, 181-184

Compano Bay . . . . . . . . . . . . . . . . . . . . . . . . . . . . 256

Connecticut . . . . . . . . . . . 97, 108, 118, 123, 174, 214

contaminants . . 8, 113, 127, 136, 137, 146, 176, 244-

246, 249, 250, 253, 261

Crystal Bay . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 256

Cystophora cristata . . . . . . . . . . . . . 92, 211, 214, 215

DDE . . . . . . . . . . . . . 43, 136, 146, 243, 245, 249, 253

DDT . . . . . . . . . . . . . . . . . . . . . 43, 136, 146, 243, 249

Delaware . . . . 16, 21, 39, 44, 50, 56, 63, 72, 98, 102,

110, 111, 123, 131, 136, 142, 155,

171, 173, 176, 177, 192

Delphinus delphis . . . . . . . . . . . . . . . . . . . . . 66, 71-73

drift gillnet . . 10, 11, 20, 25, 42-44, 48-51, 55-57, 61,

62, 64, 68, 69, 73, 89, 96, 97, 102,

106-109, 111, 116, 118, 121, 124,

131, 132, 137, 142, 147, 150, 151,

154, 159, 160, 164, 166, 167, 173,

178, 180, 185, 188, 190, 192, 198-

200, 204-206, 209, 210, 213

dwarf sperm whale . . . 2, 4, 149, 151, 152, 156, 219,

220, 223, 293, 294, 297

East Bay . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 256

ecotype . . . . . 151, 156, 162, 165, 166, 220, 223, 237,

240, 243, 247, 251, 294, 297

entanglement . . 4, 5, 9-11, 13, 19, 20, 22, 23, 29, 30,

34, 76, 79, 85, 95, 97-101, 110,

118, 121, 122, 155, 176, 179, 184-

186, 189, 217, 220, 223, 226, 229,

232, 235, 244, 245, 248, 249, 252,

253, 258, 261, 264, 267, 270, 273,

276, 279, 282, 285, 288, 291, 294,

297, 300, 303, 306, 309

epidemic . . . . . . . . . . . . . . . . . . . . . . . . . 246, 249, 260

Erysipelas spp. . . . . . . . . . . . . . . . . . . . 245, 249, 253

estuaries . . . . . . . . . . . . . . . . . . . . . 169, 254-256, 258

Eubalaena glacialis . . . . . . . . . . . . . . . . . . . 6, 13, 14

false killer whale . . . . . . . . . . . . . . . . . . . . . . . . 4, 287

Feresa attenuata .......... 189, 190, 290-292, 299

fin whale . . . . . . . . . . vii, 2, 27-31, 37, 181-184, 186
316

foreign fishing . . . 34, 61, 68, 98, 107, 109, 118, 131,

134, 136, 142, 145, 146, 159, 163,

164, 193, 198, 204

Fraser’s dolphin . . . . . . . . . . . . . . . . . . . . . . . . 4, 281

Georges Bank . . 6, 16, 17, 20, 21, 26, 28, 33, 39-43,

46, 47, 49, 52-55, 59, 61, 66, 67,

69, 93, 94, 96, 97, 104, 105, 107,

111, 113, 114, 116, 128, 129, 132,

133, 139, 140, 142, 144, 150, 157,

159, 162, 164, 191, 195, 196, 198,

202, 204, 209

Georgia . . . . . vii, 6, 10, 79, 171, 172, 174-178, 180,

308, 309

Gervais’ beaked whale . . . . . . . . . . . . . 3, 49, 56, 234

gillnet . . . . 9-12, 14, 20, 22, 25, 42-44, 48-51, 55-57,

61-64, 68-71, 73, 76-80, 83-86, 89-

92, 95-97, 99, 100, 102, 103, 106-

109, 111, 112, 115-127, 131, 132,

134, 135, 137, 138, 142, 144, 145,

147, 150, 151, 154, 155, 159, 160,

164-167, 173, 174, 176, 178-181,

183-185, 187, 188, 190, 192, 194,

195, 198-200, 204-206, 208-210,

213-215, 245, 248, 249, 252, 253,

259

Globicephala macrorhynchus ........... 139, 305

Globicephala melas . . 128, 131, 136-139, 142, 146,

147

Grampus griseus . . . . . . . . . . . . . . . . . . . . 59, 63, 302

gray seal . . . . . . . . . . . . . . . . . . . . 3, 80-85, 181, 182

Great South Channel . . 6, 8, 10, 13, 21, 33, 97, 132,

133, 142, 144

Greenland . . . 5, 6, 15, 36, 42, 75, 77, 83, 87, 88, 90,

93, 104, 109, 113, 114, 128, 134,

144, 145, 191, 193, 211

groundfish . . 11, 19, 76-78, 83, 89, 90, 99, 109, 116-

120, 134, 144, 145, 194, 213

Gulf of Maine . . 2-4, 6, 10, 11, 15-21, 23-28, 31, 33,

35, 38, 40, 44, 45, 47, 51, 53, 57,

59, 60, 64, 66, 67, 70, 73, 76, 77,

79, 83, 85, 89, 91, 94, 95, 97, 103-

106, 108, 111-117, 124-129, 137,

140, 147, 151, 156, 157, 160, 161,

165, 167, 184-187, 193, 195, 197,

200, 203, 206, 213, 214

Gulf of Mexico . . . . . . . . 1, 3, 4, 6, 14, 36, 45, 46, 51,

52, 58, 62-64, 66, 69, 73, 93, 132,

133, 135, 138, 143, 145, 147, 152,

155, 157, 159-162, 164, 169, 178,

188-190, 196, 199, 202, 206, 208,

210, 216-243, 245-249, 251-308,

312

Gulf Stream . . . . 28, 39-41, 45-47, 51-53, 57, 59, 60,

64, 66, 67, 73, 94, 105, 128, 129,

138-140, 147, 157, 171, 196, 197,

201-203, 206, 210

Gullivan Bay . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 256

gunshot wounds ............... 244, 248, 252, 258

Halichoerus grypus . . . . . . . . . . . . . . . . 79, 81, 84-86

harbor porpoise . 3, 5, 25, 31, 44, 51, 57, 64, 73, 77,

79, 83, 85, 89, 91, 103, 111-122,

124-127, 137, 147, 151, 156, 160,

167, 181-184, 200, 206, 213, 214

harbor seal . . . . . . . . . . . 3, 75-80, 85, 125, 181, 182

harp seal . . . . . . . . . . . . . . . . . . . . 3, 87-92, 181, 182

haul seine ............................ 173, 175

health assessment . . . . . . . . . . . . . . . . . . . . . 245, 260

herring weirs . 11, 77, 78, 83, 98, 110, 119-121, 125,

126

hooded seal . . . . . . . . . . . . . . . . . . . . . . . . 3, 211-215

humpback whale . . vii, 2, 4, 15, 16, 18, 19, 21, 23-26,

181, 182, 184, 186

Hyperoodon ampullatus ................ 191, 192

Indian/Banana River . . . . . . . . . . . . . . . . . . . . . . . 162

Key West . . . . . . . . . . . . . . . . . . . . 177, 240, 251, 256

killer whale . . 2, 4, 187-190, 284, 286, 287, 290-292

Kogia breviceps . . 151, 153, 155, 156, 219, 220, 222,

223, 293, 294, 296, 297

Kogia simus . . . . . 149, 151, 152, 156, 219, 220, 222,

223, 293, 294, 296, 297

ladyfish . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 249, 253

Lagenorhynchus acutus . . . . . 73, 104, 109, 111, 112

Long Island . . . . . . . . . . . . . . 43, 45, 75, 97, 169, 173

longline fishery . . . 61, 62, 68, 69, 96, 132, 135, 141,

143, 145, 154, 159, 160, 164, 185,

199, 205, 217, 220, 223, 226, 229,

232, 235, 238, 241, 264, 267, 270,

273, 276, 279, 282, 285, 288, 291,

294, 297, 300, 303, 306

long-finned pilot whale ..... 128, 129, 134-137, 139,

140, 142, 145, 146

mackerel . . . 16, 23, 61, 68, 70, 71, 76, 106-109, 131,

133, 135, 136, 141, 142, 144-146,

163-165, 174, 183

Maine . . . 2-4, 6, 10, 11, 15-21, 23-28, 31, 33, 35, 38,

40, 42-45, 47, 51, 53, 57, 59, 60,

64, 66, 67, 70, 73, 75-85, 87, 89,

91, 92, 94-98, 103-106, 108, 110-

117, 119, 121-129, 135, 137, 140,

146, 147, 151, 156, 157, 160, 161,

165, 167, 184-187, 193, 195, 197,

200, 203, 206, 211, 213, 214, 256

mark-recapture . . . . . 17, 18, 26, 39, 87, 91, 172, 179

Maryland . . . 14, 40, 41, 47, 53, 54, 60, 67, 110, 122,

123, 129, 130, 140, 149, 151, 153,

158, 163, 171, 177, 197, 203

Massachusetts . . . 1, 6, 10, 13, 14, 16, 24, 27, 31, 32,

44, 49, 51, 56, 64, 72, 77, 79-82,
317

84, 85, 91, 101, 110-112, 116, 117,

122, 123, 125, 135-138, 146, 147,

151, 167, 173, 187, 205, 207, 214,

215

Megaptera novaeangliae . . . . . . . . . . . 15, 24-26, 38

melon-headed whale . . . . . . . . . . . . . . . . . 4, 299, 301

menhaden . . 173, 176, 179, 180, 245, 249, 253, 258

Mesoplodon bidens . . . . . . . . . . . . . . . . . 57, 233, 235

Mesoplodon densirostris . . . . . . . . . . . . . . . . . 57, 231

Mesoplodon europaeus . . . . . . . . . . . . . . . . . . . . . 234

Mesoplodon mirus . . . . . . . . . . . . . . . . . . . . . . . . . . 52

metals . . . . 43, 44, 113, 136, 137, 146, 147, 245, 259

minke whale . . . . . . . . vii, 2, 93, 95-99, 101-103, 186

morbillivirus .... 245, 246, 249, 250, 253, 260, 261

mutilation ....... 122, 166, 177, 244, 248, 252, 258

net entanglement . . . . . . . . . . . . 10, 19, 244, 248, 252

New England . . . 6, 10, 13, 16, 24, 27, 34, 39, 43, 52,

62, 70, 75, 77-87, 89-93, 97-99,

102, 103, 107, 108, 110-112, 115,

118, 121, 124, 125, 127, 133, 144,

164-166, 176, 179, 187, 188, 190,

192, 193, 196, 202, 205, 211, 213-

215

New Jersey . . 23, 72, 75, 79, 80, 87, 91, 98, 110, 113,

122, 123, 128, 139, 155, 177

New York . . 19, 30, 38, 44, 45, 50, 57, 64, 70, 72, 75,

77, 79-81, 84, 89, 91, 92, 97, 108,

111, 113, 117, 118, 122, 124, 134,

136, 144, 155, 160, 165, 167, 173,

176, 177, 179, 192, 200, 206, 214,

234, 262

North Carolina . . . 16, 21, 23, 33, 40, 46, 53, 59, 66,

70, 72, 77, 79, 89, 91, 93, 97, 98,

104, 105, 108, 113, 117, 118, 122-

124, 126, 128, 129, 134, 139, 144,

151, 155, 157, 160, 165, 169-176,

178-180, 189, 193, 196, 200, 202,

208, 214

Orcinus orca . . . . . . . . . . . . . . . . . 187, 188, 284-286

organochlorines . . . . . . . . . . . . . . . . . . . . . . . . . . . 44

pair trawl . . 11, 20, 25, 42, 44, 48, 51, 57, 61, 62, 64,

68, 69, 72, 73, 89, 102, 103, 111,

112, 124, 126, 131, 132, 137, 142,

143, 146, 147, 151, 154, 159, 160,

164, 165, 167, 185, 188, 190, 192,

198-200, 204, 206, 209, 210, 213,

217, 220, 223, 226, 229, 232, 235,

239, 242, 265, 267, 270, 273, 276,

279, 282, 285, 288, 291, 294, 297,

300, 303, 306

pantropical spotted dolphin . . . . 3, 4, 157, 158, 160,

161, 196, 266-268

PCBs . . . . . . . . . . . . . . see polychlorinated biphenyls

Peponocephala electra ............. 290, 299, 301

Perdido Bay . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 256

Phoca groenlandica . . . . . . . . . . . . . . 87, 90-92, 215

Phoca vitulina . . . . . . . . . . . . . . . . . . . . 75, 78-80, 85

Phocoena phocoena ....... 113, 120, 121, 125-127

photo-identification . . . . . 7, 8, 17, 37, 169, 170, 180,

255, 262, 285

Physeter macrocephalus . . . . 24, 39, 44, 45, 216, 218

Pine Sound . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 256

pinger . . . . . . . . . . . . . . . . . . . . . . . . . 77, 84, 109, 121

Plymouth . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

polychlorinated biphenyls.43, 113, 136, 138, 146, 147

population growth rate . . . . . . . . . . . . . . . . 8, 18, 115

pound net ............................ 173, 176

pseudorabies virus .................... 245, 253

Pseudorca crassidens . . . . . . . . . . . . . . . . . . . . . . 287

pygmy killer whale . . . . . . . . . 2, 4, 189, 190, 290-292

pygmy sperm whale . . . 2, 4, 151, 153, 155, 156, 181,

182, 184, 220, 222, 223, 294, 296,

297

Redfish Bay . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 256

right whale . vii, 2, 6, 9-11, 13, 14, 175, 181-184, 186

Risso’s dolphin . . . . . . . . . . . . . . . . 4, 59-61, 63, 302

Sabine Lake . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 256

salmon gillnets . . . . . . . . . . . . . . . 77, 83, 99, 134, 144

Scotian Shelf . . . 6, 15, 17, 33, 39, 40, 45, 46, 53, 59,

66, 67, 72, 85, 94, 105, 129, 140,

162, 167, 206

sei whale . . . . . . . . . . . . . . . . 2, 33-35, 181-184, 186

shark . . . . . . . . . 56, 79, 80, 173, 174, 178, 180, 183

ship strikes . . . . . vii, 5, 9, 11, 19, 23, 43, 95, 100, 184

short-finned pilot whale . . . 128, 133, 136, 139, 141-

143, 305

sink gillnet . . . . 12, 22, 42, 48, 55, 61, 63, 68, 70, 71,

77-79, 83-85, 89-91, 96, 97, 99,

102, 106-109, 111, 116-121, 124-

126, 131, 142, 154, 159, 164-166,

174, 181, 184, 185, 187, 188, 190,

192, 198, 204, 209, 213, 214

South Carolina . . . 49, 56, 62, 70, 79, 133, 135, 143,

146, 160, 164, 169, 171-174, 179,

180, 199, 208, 309

Sowerby’s beaked whale . . . . . . . . . 56, 231, 233-235

sperm whale . . . . 2, 4, 39-45, 149, 151-153, 155, 156,

181-184, 216-220, 222, 223, 293,

294, 296, 297

spinner dolphin . . . . . . . . . . . 3, 4, 208-210, 272, 274

squid . . . . 43, 61, 68, 70, 71, 106-109, 131, 133, 135-

137, 141, 142, 144-146, 163-165,

183, 254

St. Andrew Bay . . . . . . . . . . . . . . . . . . . . . . . . . . . 256

St. Joseph Bay . . . . . . . . . . . . . . . . . . . . . . . . . . . . 256

Staphylococcus spp. ............... 245, 249, 253

Stellwagen Bank . . . . . . . . . . . . . . . 16, 23, 33, 77, 96

Stenella attenuata ............. 157, 161, 266, 268
318

Stenella clymene . . . . . . . . . . . . . . . . . . . 66, 278, 280

Stenella frontalis . . . . . . . . . . . . . . 157, 196, 263, 265

Stenella longirostris ........... 208, 209, 272, 274

Strait of Belle Isle . . . . . . . . . . . . . . . . . . . . . . . . 7, 36

striped dolphin . . . . . . . . . . . 3, 4, 202-204, 269, 271

swordfish . . 20, 25, 43, 44, 48, 51, 55, 57, 61, 62, 64,

69, 73, 96, 103, 107, 112, 116, 126,

131, 132, 137, 142, 143, 147, 150,

151, 159, 160, 164, 167, 198, 200,

204, 206, 210, 217, 220, 223, 226,

229, 232, 235, 238, 239, 241, 242,

264, 267, 270, 273, 276, 279, 282,

285, 288, 291, 294, 297, 300, 303,

306

take reduction plan . . . . 97, 115, 117, 118, 121, 175,

181

telemetry . . . . . . . . . . . . . . . . . . 6, 126, 127, 170, 255

Ten Thousand Islands . . . . . . . . . . . . . . . . . . . . . . 256

TerreBonne Bay . . . . . . . . . . . . . . . . . . . . . . . . . . 256

thread herring . . . . . . . . . . . . . . . . . . . . . . . . 249, 253

Trinity Bay . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 256

tunas . . . 132, 143, 165, 217, 220, 223, 226, 229, 232,

235, 238, 241, 264, 267, 270, 273,

276, 279, 282, 285, 288, 291, 294,

297, 300, 303, 306

Vermillion Bay . . . . . . . . . . . . . . . . . . . . . . . . . . . . 256

West Bay . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 256

West Cote Blanche Bay . . . . . . . . . . . . . . . . . . . . . 256

Whitewater Bay . . . . . . . . . . . . . . . . . . . . . . . . . . . 256

white-beaked dolphin . . . . . . . . . . . . . . . . 2, 193-195

white-sided dolphin . . 2, 104, 106-108, 111, 112, 195

Ziphius cavirostris . . . . . . . 46, 50, 228, 230, 231, 234
Publishing in NOAA Technical Memorandum NMFS-NE

Jon A. Gibson, Biological Sciences Editor & Laura S. Garner, Editor

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NORTHEAST FISHERIES SCIENCE CENTER

Dr. Michael P. Sissenwine, Science & Research Director

Capt. John T. Moakley, Operations, Management & Information Services Chief

Teri L. Frady, Research Communications Chief
Research Communications Unit

Northeast Fisheries Science Center

National Marine Fisheries Service, NOAA

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