NOAA Technical Memorandum NMFS-NE-168

U.S. Atlantic and Gulf of Mexico

Marine Mammal

Stock Assessments -- 2001

U. S. DEPARTMENT OF COMMERCE

National Oceanic and Atmospheric Administration

National Marine Fisheries Service

Northeast Region

Northeast Fisheries Science Center

Woods Hole, Massachusetts

December 2001

Erratum: Please note that in Table 1 on page 4, the Gulf of Mexico dwarf sperm whale and pygmy sperm whale 

are incorrectly listed as strategic.
149. Essential Fish Habitat Source Document: Scup, Stenotomus chrysops, Life History and Habitat Characteristics.

By Frank W. Steimle, Christine A. Zetlin, Peter L. Berrien, Donna L. Johnson, and Sukwoo Chang. September 1999.

v + 39 p., 18 figs., 1 table. NTIS Access. No. PB2001-100144.

150. Essential Fish Habitat Source Document: Spiny Dogfish, Squalus acanthias, Life History and Habitat

Characteristics. By Donald G. McMillan and Wallace W. Morse. September 1999. v + 19 p., 10 figs., 3 tables. NTIS

Access. No. PB2001-100148.

151. Essential Fish Habitat Source Document: Summer Flounder, Paralichthys dentatus, Life History and Habitat

Characteristics. By David B. Packer, Sara J. Griesbach, Peter L. Berrien, Christine A. Zetlin, Donna L. Johnson, and

Wallace W. Morse. September 1999. vi + 88 p., 38 figs., 6 tables. NTIS Access. No. PB2001-100149.

152. Essential Fish Habitat Source Document: Tilefish, Lopholatilus chamaeleonticeps, Life History and Habitat

Characteristics. By Frank W. Steimle, Christine A. Zetlin, Peter L. Berrien, Donna L. Johnson, and Sukwoo Chang.

September 1999. v + 30 p., 12 figs., 2 tables. NTIS Access. No. PB2001-100143.

153. U.S. Atlantic and Gulf of Mexico Marine Mammal Stock Assessments -- 1999. By Gordon T. Waring, Debra

L. Palka, Phillip J. Clapham, Steven Swartz, Marjorie C. Rossman, Timothy V.N. Cole, Larry J. Hansen, Kathryn D.

Bisack, Keith D. Mullin, Randall S. Wells, and Neilo B. Barros. October 1999. vii + 196 p., 17 figs., 59 tables, 1 app.

NTIS Access. No. PB2000-102497.

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.

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

December 2001

NOAA Technical Memorandum NMFS-NE-168

U.S. Atlantic and Gulf of Mexico

Marine Mammal Stock Assessments -- 2001

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.

1

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

2

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

3

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

Gordon T. Waring1, Janeen M. Quintal1, and Steven L. Swartz2, Editors

with contributions from (listed alphabetically)

Phillip J. Clapham1, Timothy V.N. Cole1, Carol P. Fairfield2, Aleta Hohn3,

Debra L. Palka1, Marjorie C. Rossman1, U.S. Fish & Wildlife Service,

and Cynthia Yeung2
About This Report:

Report History: This report is the sixth 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 five 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) editor 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 (AFS) 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-throughfifth 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 six reports are available (as of the publication date of this issue) online in PDF format at:

http://www.nefsc.nmfs.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.
iii

TABLE OF CONTENTS

ACKNOWLEDGMENTS .................................. .................................. . vi

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 (Euba laena g lacialis):

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

HUMPBACK WHALE (Megaptera novaeangliae):

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

FIN WHALE (Balaenoptera physalus):

Western North Atlantic Stock .................................. ........................ 26

BLUE WHALE (Balaenoptera musculus):

Western North Atlantic Stock .................................. ........................ 31

MINKE WHALE (Balaen optera a cutorostra ta):

Canadian East Coast Stock .................................. ........................... 34

SPERM WHALE (Physeter macrocephalus):

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

CUVIER'S BEAKED WHALE (Ziphius c avirostris):

Western North Atlantic Stock .................................. ........................ 53

MESOPLODO N BEAKED W HALES (Mesoplodon spp.):

Western North Atlantic Stock .................................. ........................ 60

RISSO'S DOLPHIN (Grampus griseus):

Western North Atlantic Stock .................................. ........................ 67

LONG-FINNED PILOT WHALE (Globicephala melas):

Western North Atlantic Stock .................................. ........................ 74

SHORT-FINNED PILOT WHALE (Globicephala macrorhynchus): 

Western North Atlantic Stock .................................. ........................ 85

WHITE-SIDED DOLPHIN (Lagenorhynchus acutus):

Western North Atlantic Stock .................................. ........................ 94

COMMON DOLPHIN (Delphin us delph is):

Western North Atlantic Stock .................................. ....................... 105
iv

BOTTLENOSE DOLPHIN (Tursiops truncatus):

Western North Atlantic Coastal Stock .................................. ................. 114

HARBOR PORPOISE (Phocoena phocoena):

Gulf of Maine/Bay of Fundy Stock .................................. ................... 124

HARBOR SEAL (Phoca vitulina):

Western North Atlantic Stock .................................. ....................... 140

GRAY SEAL (Halichoerus grypus):

Western North Atlantic Stock .................................. ....................... 146

HARP SEAL (Phoca groenlandica):

Western North Atlantic Stock .................................. ....................... 151

APPEN DIX I. West Indian Manatees Stock Assessments - Florida and Antilles Stocks ................... 157

WEST INDIAN MANATEE (Trichechus ma natus latirostris)

FLORIDA STOCK .................................. ........................ 157

WEST INDIAN MANATEE ((Trichechus ma natus man atus)

ANTILLEAN STOCK .................................. ...................... 161

APPENDIX II. Stock assessment reports not updated in the year 2001. ................................ 164

SEI WHALE (Balaen optera b orealis):

Nova Scotia Stock .................................. ......................... 164

DWARF SPERM WHALE (Kogia simus): 

Western North Atlantic Stock .................................. ................ 167

PYGMY SPERM WHALE (Kogia breviceps):

Western North Atlantic Stock .................................. ................ 171

KILLER WHALE (Orcinus orca):

Western North Atlantic Stock .................................. ................ 174

PYGMY KILLER WHALE (Feresa a ttenuata ): 

Western North Atlantic Stock .................................. ................ 176

NORTHERN BOTTLENOSE WHALE (Hyperoodon ampullatus):

Western North Atlantic Stock .................................. ................ 178

WHITE-BEAKED DOLPHIN (Lagen orhync hus albiro stris):

Western North Atlantic Stock .................................. ................ 180

ATLANTIC SPOTTED DOLPHIN (Stenella fro ntalis):

Western North Atlantic Stock .................................. ................ 183

PANTROPICAL SPOTTED DOLPHIN (Stenella a ttenuata ):

Western North Atlantic Stock .................................. ................ 189

STRIPED DOLPHIN (Stenella coeruleoalba):

Western North Atlantic Stock .................................. ................ 195

SPINNER DOLPHIN (Stenella lo ngirostris):

Western North Atlantic Stock .................................. ................ 201

BOTTLENOSE DOLPHIN (Tursiops truncatus):

Western North Atlantic Offshore Stock .................................. ......... 204

HOODED SEAL (Cystoph ora cristata ):

Western North Atlantic Stock .................................. ................ 210

SPERM WHALE (Physeter macrocephalus):

Northern Gulf of Mexico Stock .................................. ............... 215

DWARF SPERM WHALE (Kogia simus):

Northern Gulf of Mexico Stock .................................. ............... 218
v

PYGMY SPERM WHALE (Kogia breviceps):

Northern Gulf of Mexico Stock .................................. ............... 221

BRYDE'S WHALE (Balaenoptera edeni):

Northern Gulf of Mexico Stock .................................. ............... 224

CUVIER'S BEAKED WHALE (Ziphius c avirostris):

Northern Gulf of Mexico Stock .................................. ............... 227

BLAINVILLE’S BEAKED WHALE (Mesop lodon d ensirostris):

Northern Gulf of Mexico Stock .................................. ............... 230

GERVAIS' BEAKED WHALE (Mesoplodon europaeus):

Northern Gulf of Mexico Stock .................................. ............... 233

BOTTLENOSE DOLPHIN (Tursiops truncatus):

Gulf of Mexico Outer Continental Shelf Stock .................................. ... 236

BOTTLENOSE DOLPHIN (Tursiops truncatus):

Gulf of Mexico Continental Shelf Edge and Continental Slope Stock ................... 239

BOTTLENOSE DOLPHIN (Tursiops truncatus):

Western Gulf of Mexico Coastal Stock .................................. ......... 242

BOTTLENOSE DOLPHIN (Tursiops truncatus):

Northern Gulf of Mexico Coastal Stock .................................. ........ 246

BOTTLENOSE DOLPHIN (Tursiops truncatus):

Eastern Gulf of Mexico Coastal Stock .................................. .......... 250

BOTTLENOSE DOLPHIN (Tursiops truncatus):

Gulf of Mexico Bay, Sound, and Estuarine Stocks .................................. 253

ATLANTIC SPOTTED DOLPHIN (Stenella fro ntalis):

Northern Gulf of Mexico Stock .................................. ............... 262

PANTROPICAL SPOTTED DOLPHIN (Stenella a ttenuata ):

Northern Gulf of Mexico Stock .................................. ............... 265

STRIPED DOLPHIN (Stenella coeruleoalba):

Northern Gulf of Mexico Stock .................................. ............... 268

SPINNER DOLPHIN (Stenella lo ngirostris):

Northern Gulf of Mexico Stock .................................. ............... 271

ROUGH-TOOTHED DOLPHIN (Steno b redane nsis):

Northern Gulf of Mexico Stock .................................. ............... 274

CLYMENE DOLPHIN (Stenella clymene):

Northern Gulf of Mexico Stock .................................. ............... 277

FRASER'S DOLPHIN (Lagenodelphis hosei):

Northern Gulf of Mexico Stock .................................. ............... 280

KILLER WHALE (Orcinus orca):

Northern Gulf of Mexico Stock .................................. ............... 283

FALSE KILLER WHALE (Pseudorca crassidens):

Northern Gulf of Mexico Stock .................................. ............... 286

PYGMY KILLER WHALE (Feresa a ttenuata ):

Northern Gulf of Mexico Stock .................................. ............... 289

DWARF SPERM WHALE (Kogia simus):

Northern Gulf of Mexico Stock .................................. ............... 292

PYGMY SPERM WHALE (Kogia breviceps):

Northern Gulf of Mexico Stock .................................. ............... 295

MELON-HEADED WHALE (Pepono cephala electra ):

Northern Gulf of Mexico Stock .................................. ............... 298

RISSO'S DOLPHIN (Grampus griseus):

Northern Gulf of Mexico Stock .................................. ............... 301

SHORT-FINNED PILOT WHALE (Globicephala macrorhynchus):

Northern Gulf of Mexico Stock .................................. ............... 304

INDEX .................................. .................................. .............. 307

ACKNOWLEDGMENTS
vi

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

Sampling Investigation, Dana Hartley (Northeast Regional Office), Blair Mase of the Southeast Fisheries Science

Center (SEFSC). Also, we acknowledge advice and comments provided by: Jon Gibson, Richard Merrick, Fred

Serchuk and Fred Wenzel (NE FSC); Patricia Rosel (SEFSC), Kim Thounhurst (NER); Diane Borggaard and Kathy

Wang (Southeast Regional Office); Solange Brault, Joseph DeAlteris, James Gilbert, Robert Kenney, James Mead,

Daniel O dell, Andre w Read, Randall W ells and Sha ron Yo ung of the Atla ntic Scientific Re view Gro up, Tom Eagle

and Emily Me nashes NM FS Office of Protected Resources and G ary Stenson of the Dep t. of Fisheries and Oceans,

St. John’s, Newfoundland. We also thank the Marine Mammal Com mission, the Ocean Conservancy and the

Humane Society of the United States for their constructive comments and advice.
vii

EXECUTIVE SUMMARY

Under the 1994 amendm ents of the Marine Mammal Protection Act (MM PA), the National Marine

Fisheries Service (NMFS) and the U.S. Fish and Wildlife Service (USFWS) were required to generate stock

assessment re ports (SA R) for all marine mamm al stocks in wate rs within the U.S . Exclusive E conomic Zone (E EZ). 

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

The M MPA requires N MFS and US FWS to review these reports ann ually for strategic sto cks of marine mamma ls

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 S ARs (19 98 assessm ents) 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 edition of the SARs contains all NMFS reports for the

Atlantic (includes the Gulf of Mexico), and the USFW S West Indian manatee assessments. Updated reports were

identified by a 2000 date-stamp (Waring et al. 2000). The current (2001) report contains updated assessments for

Atlantic strategic stocks, and for Atlantic and Gulf of Mexico stocks for which significant new information was

available. These reports are identified by a November 200 1 date-stamp at the beginning of each report. Further,

appendices I and II contain the West Indian Manatees stock assessments and stock assessments not updated in the

year 200 , respectively. 

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

Science Center (SEF SC) and United Sta tes Fish and W ildlife Service (U SFWS). NM FS staff prese nted the rep orts

at the November 2000 meeting of the Atlantic Scientific Review Group (ASRG), and subsequent revisions were

based o n their contrib utions and c onstructive criticism. 

Table 1 co ntains a summary, by species, of the information inc luded in the stock assessments, and a lso

indicates those that have been revised since the 2000 publication. A total of 18 of the 60 Atlantic and Gulf of

Mexico stock assessment reports were revised for 2001. Most of the proposed changes incorporate new information

into sections o n popula tion size and mortality estimate s. The revise d SARs include 12 strategic and 6 non-strategic

stocks. Inform ation on hum an interaction s (fishery and ship strikes) betwee n the right whale, h umpba ck 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

(FWS), in consultation with regional Scientific Review Groups (SRG). 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 Assistant Administrator for NMFS. The reports are then

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

The MM PA 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 p otential biolo gical remov al (PBR) level for the stoc k, describing the informatio n used to ca lculate 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 on ce every three years for nonstrategic stocks.

Following enactment of the 1994 amendments, the NMFS and FWS 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 (W aring et

al. 1997), 1998 (W aring et al. 1999), 1999 (W aring et al. 1999), 2000 (W aring et al. 2000) SARs. A 1997 SAR was

not produced.

In this document, major re visions and updating of the SA Rs were only comp leted for Atlantic Coast

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

by the No vember 2 001 da te-stamp at the to p right corne r at the beginnin g of each rep ort. 

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. B isack. 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. Hanse n. 

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.
2

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

REPORTS FOR STOCKS OF MARINE MAMMALS UNDER NMFS AUTHORITY THAT OCCUPY

WAT ERS UN DER US A JURISDICTION. The “SA R revised” column indicates 2001 stock assessment

reports that have been revised relative to the 2000 reports (Y=yes N=no). If abundance, mortality or PBR

estimates have been revised, they are ind icated with the letters “a”, “m” and “p” respe ctively. For those

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

Species Stock Area SRG

Regio

n

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 2.2 1

1.0 1 Y Y

m

Humpback

whale

Gulf of Maine ATL NEC 568 0.065 0.1 1.8 4.2 23.2 2 Y Y

a,m,p

Fin whale Western North

Atlantic

ATL NEC 2,362 0.04 0.1 4.7 1.8 30.6 3 Y Y

a,m,p

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

(2000)

Minke whale Canadian east

coast

ATL NEC 3,515 0.04 0.5 35 2.4 4

2.2 4 N Y

a, m, p

Blue whale Western North

Atlantic

ATL NEC 308 0.04 0.1 0.6 0.00 0.00 Y Y

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

m

Dwarf sperm

whale

Western North

Atlantic

ATL SEC 373 5

0.04 0.5 3.7 0.25 0.25 N N

(2000)

Pygmy sperm

whale

Western North

Atlantic

ATL SEC 373 50.04 0.5 3.7 0.25 0.25 N N

(2000)

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 60.04 0.5 24 0 0 7 Y Y

 m

Mesoplodon

beaked whales

Western North

Atlantic

ATL NEC 2,419 60.04 0.5 24 0 0 7 Y Y

 m

Risso's dolphin Western North

Atlantic

ATL NEC 22,916 0.04 0.40 183 56 56 N Y

 m

Pilot whale,

long-finned 

Western North

Atlantic

ATL NEC 11,343 80.04 0.48 108 245 9245 9 Y Y

 m, p

Pilot whale,

short-finned

Western North

Atlantic

ATL SEC 11,343 80.04 0.48 108 245 9245 9 Y Y

m, p

Atlantic whit esided dolphinWestern North

Atlantic

ATL NEC 37,904 0.04 0.48 364 136 136 N Y

a,m,p
Species Stock Area SRG

Regio

n

NMFS

Center

Nmin Rmax Fr PBR

Total

Annual

Mort.

Annual

Fish.

Mort.

Strategic

Status

SAR

Revised

3

White-beaked

dolphin

Western North

Atlantic

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

(1997)

Common

dolphin

Western North

Atlantic

ATL NEC 23,655 0.04 0.48 227 406 406 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 NEC 8,450 0.04 0.5 84 7.8 11 7.8 11 N N

(2000)

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 5.3 5.3 N N

Bottlenose

dolphin

Western North

Atlantic, coastal

ATL SEC 2,482 0.04 0.5 25 46 46 Y Y

m

Harbor

porpoise

Gulf of Maine/

Bay of Fundy

ATL NEC 74,695 0.04 0.5 747 382 12 381 12 Y Y

a,m,p

Harbor seal Western North

Atlantic

ATL NEC 30,990 0.12 1.0 1,859 916 895 N Y

m

Gray seal Western North

Atlantic

ATL NEC N/A N/A N/A N/A 110 103 N Y

m

Harp seal Western North

Atlantic

ATL NEC N/A N/A N/A N/A 321,356 13 245 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 No. Gulf of

Mexico

ATL SEC 411 0.04 0.1 0.8 0.00 0.00 Y N

(1995)

Bryde’s whale No. Gulf of

Mexico

ATL SEC 17 0.04 0.5 0.2 0.00 0.00 N N

(1995)

Cuvier’s

beaked whale

No. Gulf of

Mexico

ATL SEC 20 0.04 0.5 0.2 0.00 0.00 N N

(1995)

Blaineville’s

beaked whale

No. Gulf of

Mexico

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

(1995)

Gervais’

beaked whale

No. 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 Mex.

Continental shelf

edge and slope

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

(1995)
Species Stock Area SRG

Regio

n

NMFS

Center

Nmin Rmax Fr PBR

Total

Annual

Mort.

Annual

Fish.

Mort.

Strategic

Status

SAR

Revised

4

Bottlenose

dolphin

Western Gulf of

Mexico

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

(1996)

Bottlenose

dolphin

No. 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

No. Gulf of

Mexico

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

(1995)

Pantropical

spotted dolphin

No. Gulf of

Mexico

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

(1995)

Striped dolphin No. Gulf of

Mexico

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

(1995)

Spinner

dolphin

No. Gulf of

Mexico

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

(1995)

Rough-toothed

dolphin

No. Gulf of

Mexico

ATL SEC 660 0.04 0.5 6.6 0.00 0.00 N N

(1995)

Clymene

dolphin

No. Gulf of

Mexico

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

(1995)

Fraser’s

dolphin

No. Gulf of

Mexico

ATL SEC 66 0.04 0.5 0.7 0.00 0.00 N N

(1995)

Killer whale No. Gulf of

Mexico

ATL SEC 197 0.04 0.5 2.0 0.00 0.00 N N

(1995)

False killer

whale

No. Gulf of

Mexico

ATL SEC 236 0.04 0.5 2.4 0.00 0.00 N N

(1995)

Pygmy killer

whale

No. Gulf of

Mexico

ATL SEC 285 0.04 0.05 2.8 0.00 0.00 N N

(1995)

Dwarf sperm

whale

No. Gulf of

Mexico

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

(2000)

Pygmy sperm

whale

No. Gulf of

Mexico

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

(2000)

Melon-headed

whale

No. Gulf of

Mexico

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

(1995)

Risso’s dolphin No. Gulf of

Mexico

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

(1995)

Pilot whale,

short-finned

No. Gulf of

Mexico

ATL SEC 186 0.04 0.5 1.9 0.3 0.3 Y N

(1995)
5

1. The total estimated human-caused mortality and serious injury to right whales is estimated at 2.2 per year (USA waters, 1.4; Canadian waters, 0.8 ). 

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 1.2 per year (USA waters, 0.8 ; Canadi an waters, 0.4).

2. The total estimated human-caused mortality and serious injury to the Gulf of Maine humpback whale stock is estimated as 4.2 per year (USA waters,

3.8; Canadian waters, 0.4). This average is derived from two components: 1) incidental fishery interaction records 3.2 (USA waters, 2.8; Canadian

waters, 0.4); and 2) records of vessel collisions , 1.0 (USA waters, 1.0; Canad ian waters, 0).

3. This is based on a review of NMFS anecdotal records from 1995-1999, that yielded an average of 1.8 human caused mortalit y -1.2 ship strikes (all

USA waters), 0.6 fishery interactions (0.4 USA waters, 0.2 Canadi an waters).

4. During 1995 to 1998, th e USA total annua l estimated avera ge human-cau sed mortality is 2 .4 minke whales per year. This is deri ved from three

components: 0 minke whales per year (CV=0.0) from USA fisheries using observer data, 2.2 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 dat a are not separa ted by species; t herefore, species-specific estimates are not available. This morta lity estimate repres ents both long-finned

and short-finned pilot whales. Total annual mortality includes Nova Scotia 95-96 average of 8 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-cau sed mortality is 382 harbor porpoises per year. This is derived from four components: 32 3 harbor

porpoise per year (CV=0.25) from USA fisheries using observer data, 3 9 per year (unknown CV) from Canadian fisheri es using observer d ata, 19 per

year from USA unknown fisheries using strandings data, an d 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.,356. This is derived from three components: 1) 1995-

1999 average catches of Northwest Atlantic harp seals by Canada and Greenland 301,611; 2) 1995-1999 average bycatches in the Newfoundland

lumpfish fishery (16,000 - 23,000 annually); and 3) the 1995-1999 observed USA fisheries, 245 harp seals CV= 0.20)
6

November 2001

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 p hotograp hically identified ind ividuals have been mad e off Iceland and arctic N orway. Th e latter (in

September 1 999) represents o ne 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

(Moo re and Cla rk 1963 ; Schmidly et al. 1972) re present eithe r geograp hic anoma lies or a mor e extensive histo ric

range beyo nd the sole kn own calving and wintering ground in the waters of the so utheastern U nited States. 

Whate ver the case, the location of a la rge segme nt of the pop ulation is unkno wn during the winter. Offshor e surveys

flown off the coast of northeastern Florida and southeastern Georgia from 1996 to 2000 had three sightings in 1996,

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

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

southeastern USA remains unclear.

Research results to date su ggest the existen ce of six majo r habitats or co ngregation a reas for weste rn North

Atlantic right wha les; these are the c oastal waters o f the southeaste rn United S tates, the Grea t South Cha nnel,

George s Bank/G ulf of Maine , Cape Cod and M assachusetts B ays, the Bay o f Fundy, and the Scotian S helf. 

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

few successfully attached 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 indica te that movem ents and hab itat use are mo re comp lex than prev iously 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 extreme ly dense patches of zoop lankton to feed efficiently (Mayo and Marx 199 0). 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 seas on in Cap e Cod a nd Ma ssachusetts Bays (C. Mayo pers. co mm.). W hile 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 d istribution in these areas are not well known. In add ition, New England wa ters 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 19 99 and 2 000 foun d substantial numbers of rig ht whales alon g the North ern Edge of Georg es Bank, in

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

Basin. The predic tability with which righ t whales occu r in such locatio ns remains un clear, and the se new data

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

Recent 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). S chaeff et al. (1997) compared the

genetic variability of North Atlantic and southe rn right whales (E. austra lis), 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, 2 000). 

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

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

hundred years strongly sug gests popu lation subdiv ision over a p rotracted (b ut not evolutio nary) timesca le. Results

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

to the 20th century.

To da te, skin biopsy sa mpling has re sulted in the compilation o f a DNA library of mo re 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 doe s not differ significantly from parity (M.W. Brown, pers. comm.). An alyses based on both ge netics 

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

populatio n utilizes summer nursery gro unds other than the Ba y of Fundy. A s described above, a re lated questio n is

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

summering grounds m ay exist in unsurve yed location s, although it is also p ossible that “missing” animals sim ply

disperse o ver a wide a rea at these time s. Identification o f such areas, an d the possib le threats to right wh ales there, is

recognized as a prio rity for research efforts.

POPU LATIO N SIZE

Based o n a census o f individual wha les identified using photo-ide ntification techniq ues, the western North

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

using the same method ga ve an estimate of 291 an imals in 1998 (Kra us et al. 2001) B ecause this wa s a nearly

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

abunda nce with an ass ociated co efficient of variatio n has been calculated fo r this popula tion. Calculatio n of a

reliable po int estimate is likely to b e difficult given the k nown pro blem of hete rogeneity of d istribution in this

populatio n. An IW C worksh op on status and trends of western N orth Atlantic righ t whales gave a minimum d irectcount estima te of 263 rig ht whales alive in 1 996 and noted that the true popu lation was unlike ly to be substan tially

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 du ring January 1 700. Based on inc omplete h istorical whaling data, Reev es and M itchell (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 (Reev es 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, an d refinemen ts are require d. Based on back c alculations using the present p opulation siz e and gro wth

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; K enney 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 Po pulation Estimate

The western N orth Atlantic population size was estima ted to be 291 ind ividuals in 1998 (Kra us et al. 2001),

based o n a census o f individual wha les identified using photo-ide ntification techniq ues. A bias tha t 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 pr esumed d ead 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), sugg esting that the stoc k was showin g signs of slow re covery. H owever, wo rk by Casw ell et al. (1999)

has suggested that crude sur vival prob ability declined from abo ut 0.99 in the e arly 1980 's to about 0.9 4 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 po pulation (Best et al. 2001); the workshop concluded based on several

analytical app roaches tha t survival had ind eed dec lined in the 19 90's. Although heterogen eity of capture c ould

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

decline, which appeare d to be particularly marked in adult females.

CURRENT AND M AXIMUM 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 ; and 98/9 9, 4. The total calf prod uction was re duced b y reported calf mortalities: 2 m ortalities in 199 3, 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

1997/9 8 season su ggests that mea n calving interva l increased sin ce 1992 from 3.67 years to mor e 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 po pulation (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. A workshop on possible causes of reproductive failure was held in April 2000 (Reeves 2000). 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 ae rial sighting rates in the Great So uth Channe l, 1979-1 989 (K enney et al. 1995). However, as noted

above, more recen t work indica ted that the po pulation wa s in decline in the 1990's (Caswell et al. 1999, B est et al.

2001).

An analysis of the age structure o f this populatio n suggests that it co ntains a smaller p roportio n 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 c urrent pop ulation grow th rate should reflect the max imum net pr oductivity rate fo r 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 mode ling and othe r work indic ates that the po pulation is no w in decline; co nsequently, no growth rate

can be used for western N orth 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

right whales is 0.10 because this species is listed as endangered under the Endangered Species Act (ESA ). However,
9

in view of the de cline in this pop ulation (Cas well et al. 1999, B est et al. 2001 ), the PBR for this popu lation is set to

zero.

ANNUAL HUM AN-CAUSED SERIOUS INJURY AND M ORTALITY

For the period 1995 through 1999, the total estimated human-caused mortality and serious injury to right

whales is estimated at 2.2 per year (U SA waters, 1.4; Canad ian waters, 0.8 ). This is derived from two components:

1) non-ob served fishery e ntanglemen t records at 1 .0 per year (U SA waters, 0 .6 ; Canad ian waters, 0.4 ), and 2) ship

strike records at 1.2 per year (USA waters, 0.8 ; Canadian waters, 0.4). 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 c onsistent with the time frames used for calculating th e averages for other spe cies. It is also impo rtant 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 con sidered confirmed human-caused mo rtalities or serious injuries.

Background

Approximately one-third of all right whale mortality is caused by human activities (Kraus 1990). The

details of a particular mortality or serious injury record o ften require a degree of interpretation. T he 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 substantial evidence that the

injury, whether from entanglement or vessel collision, was likely to significantly impede the whale’s locomotion or

feeding in the immediate future, or had a high probability of leading to systemic and debilitating infection. There

was no fore casting of how the entanglem ent or injury may increase the whale’s suscep tibility 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 2.2 right whales per year (USA waters 1.4;

Canadian waters, 0.8 ). 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 2.2 rig ht whales per year must be regarded as a minimum estimate. 

Further, the sm all populatio n size and lo w annual rep roductive r ate suggest that hu man sourc es of mortality

may have a greater effect re lative to pop ulation grow th rates than for o ther whales. T he principa l factors believe d 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 remainde r, 16 (35.6 %) were determined to be the resu lt 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, 4 1.3% of the ob served total for the period, and 59.4% of the 3 2 non-calf deaths,

were attributable to human imp acts.

Young animals, ages 0 -4 years, are ap parently the most impacte d portion of the pop ulation (Kra us 1990 ). 

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

it so that it is more likely to become vulnerable. S uch was ap parently the ca se with the two-yea r old right wha le

killed by a ship off Amelia Islan d, Florida, in March 1991 a fter having carried gillnet gear w rapped around its tail
10

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 degr adation in M assachusetts a nd Cap e Cod B ays due to a B oston sewa ge 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 upgrad ed and expand ed annually. It involves both governm ent and non-governm ent organizations,

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

a program was establishe d in the northe astern US A, largely in co operation with the U.S. Coast Gua rd and the S tate

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 oc currence a nd recom mendatio ns on mea sures to avo id collisions with w hales. 

This system is e xpected to provide m uch-neede d informatio n on pattern s of vessel traffic in critica l habitat areas. 

Fishery-Related Serious Injury and Mortality

Reports o f mortality and se rious injury rela tive to PBR as well as tota l human imp acts are con tained in

records maintained by the New England Aquarium and the Northeast Regional Office/NMFS (Table 1). From 1995

through 1999 , 5 of 11 records o f mortality or serious injury (including records from b oth 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 preexisting 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 becam e a serious inju ry and (direc tly or indirectly) the c ause of the mortality. 

During the period of 1995 through 1999, there were at least three documented cases of entanglements for

which the interv ention of dise ntanglemen t teams averte d a likely serious injury determination. Right w hale #21 10, a

four year old female, was relieved of a substantial amount of gillnet gear in the Bay of Fundy on 9/16/95. 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.

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

entangleme nt records o f large whales from 1990 to 1994 . 
11

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 since that year, several fisheries have been covered by

the program. In late 199 2 and in 19 93, the SE FSC pr ovided o bserver co verage of p elagic 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). Entang lement records maintained by NMF S Northeast

Regiona l Office (NM FS, unpub lished data) fro m 1970 through 19 99, include d at least 62 right whale entan glements

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

additiona l record (M . J. Harris, pe rs. comm.) r eported a 9.1-10.6 m right whale e ntangled an d released south of Ft.

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

fishery). Inciden ts of entanglements in ground fish gillnet gear, co d traps, and herring weirs in w aters of Atlantic

Canada and the USA east coast were summarized by Read (19 94). 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. Mo re informatio n is needed about fisherie s interactions an d where the y occur. 

Other M ortality

Ship strikes are a major cause of mortality and injury to right whales (Kraus 1990, Knowlton & K raus

2001). Records from 1995 through 19 99 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 1.2 whales per year (USA waters, 0.8;

Canadian waters, 0.4).

In the period January to M arch 199 6, an ‘unusua l mortality event’ wa s declared for right whales in

southeastern USA wa ters. Five mo rtalities were rep orted, at least o ne of which (o n 1/30/96 ) was attributab le 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.
12

Table 1. Summarized reco rds of mortality and serious injury likely to result in m ortality, North Atlantic right wha les, 

January 19 95 throug h Decem ber 199 9 . Causes o f mortality or injur y, assigned as p rimary or sec ondary,

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

Date Report 

Type

Sex, age,

ID

Location Assigned Cause:

P=prim ary,

S=secondary

Notes

Ship

strike

 Entang./

Fsh inter

7/17/95 mortality,

beached

2 y.o.

male

#2366

Middletown,

RI

P inshore lobster line through

mouth, embedde d deeply into

bone at base of right flipper

8/13/95 serious

injury,

offshore

69+y.o.

female,

#1045

S. Georges

Bank

P large head wound exposing bone

10/20/95 mortality,

beached

male, age

unknown

#2250

Long I., Nova

Scotia

P large gash on back, broken

vertebrae

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

Glouce ster, 

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

observatio ns indicate the w hale

ingested some gear of an unknown

type 

8/29/97 serious

injury

2 yr old

female

#2557

Bay of

Fundy,

Canada

P Line of unkn own origin tigh tly

wrapped on body and one flipper,

whale emaciated
Date Report 

Type

Sex, age,

ID

Location Assigned Cause:

P=prim ary,

S=secondary

Notes

Ship

strike

 Entang./

Fsh inter

13

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

STATUS OF STOCK

The size o f this stock is consid ered to be extremely low relative to OS P in the US A Atlantic EEZ, and th is

species is listed as endangered un der the ESA. T he North Atlantic right whale is considere d 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 in 2001. 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 N MFS 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 Internation al Wha ling Comm ission (Best et al. 2001), w hich expre ssed grave concern re garding the sta tus 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 2.2 right whales per year from 1995 through 1999 . Given that

PBR has b een set to zero, no mortality or serious injury for this stock ca n be considered insignificant. Th is 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 endang ered species. Relative to other p opulations of right whales, there are also

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

REFERENCES

Aguilar, A. 1 986. A re view of old B asque wha ling and its effect o n the right whales of the North Atlantic. Rep. int.

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

Best, P.B., Ban nister, J.L., Brownell, R.L., Dono van, G.P. (eds.) 200 1. Right whales: worldwide status Journal of

Cetacean Research and Management (Special Issue) 2 (in press).

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 enda ngered p opulations. Mammal Review 29: 35-60.

Hain, J. H . W. 19 75. The international re gulation of wh aling. Marine Affairs J. 3: 28-48.

Hamilton , P. K., A. R. Knowlto n, M. K. M arx and S. D . Kraus. 19 98. Age stru cture and lo ngevity in No rth Atlantic

right whales Euba laena g lacialis and their relatio n to repro duction. 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

(Euba laena g lacialis) 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 w orkshop on the com prehensive assessment o f right whales wo rldwide. J. Cetacean R es.

Mana ge. 1 (supplement): 119-120.

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

required b y western No rth Atlantic right wh ales. Mar. M amm al Sci. 2(1): 1-13 . 
14

Kenney, R. D. and S. D . Kraus. 19 93. Right wh ale mortality — a correctio n and an up date. Mar. M amm al Sci.

9:445-4 46. 

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

whale (Euba laena g lacialis). Cont. Shelf Res. 15: 385-414.

Knowlto n, A. R., J. Sigu rjonsson, J. N. Ciano , and S. D. K raus. 1992 . Long-distanc e movem ents of No rth Atlantic

Right whales (Euba laena g lacialis). Mar. M amm al Sci. 8(4): 397-405.

Knowlton, A. R. and S. D. Kraus. 200 1. Mortality and serious injury of N orth Atlantic right whales (Eubalaena

glacialis) in the North Atlantic Oc ean. J. Cetacean Res. Manage. (Special Issue) 2 (in press).

Knowlton, A. R., S. D . Kraus, and R. D. K enney. 1994. Rep roduction in North A tlantic right whales (Eubalaena

glacialis). Can. J. Z ool. 72: 129 7-1305 . 

Kraus, S. D. 199 0. Rates and potential cause s of mortality in North Atlantic right whales (Euba laena g lacialis). 

Mar. M amm al Sci. 6(4): 278-291.

Kraus, S. D., P. K. Hamilton, R. D. Kenney, A. Knowlton and C. K. Slay. 2001. Status and trends in reproduction

of the North Atlantic right wh ale. J. Cetacean Res. Manage. (Special Issue) 2 (in press).

Malik, S., M . W. Br own, S. D . Kraus, A. K nowlton, P . Hamilton a nd B. N . White. 19 99. Assessm ent of genetic

structuring and habitat philopatry in the North Atlantic right whale (Euba laena g lacialis). Can. J. Z ool. 77:

1217-1222.

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

between N orth and S outh Atlantic rig ht whales. Mar. M amm al Sci. 16: 545-558.

Mate, B. M., S. L. N ieukirk and S . D. Krau s. 1997. S atellite-monitor ed move ments of the no rthern right wha le. J.

Wildl. Manage. 61: 139 3-1405 . 

Mayo, C. A. and M .K. Ma rx. 1990 . Surface fora ging behav iour of the N orth Atlantic righ t whale, Eubalaena

glacialis, and assoc iated zoo plankton c haracteristics. Can. J. Z ool. 68: 2214-2220.

Moo re, J. C. and E . Clark. 196 3. Discov ery of right whale s in the Gulf of M exico. Science 141(35 77): 269 . 

NMFS. 1991. Recovery plan for the northern right whale (Euba laena g lacialis). Prepare d by the Righ t Whale

Recove ry Team for the Natio nal Marin e Fisheries Se rvice, Silver S pring, 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. 20 00. Report of th*e wo rkshop on the causes o f reproductive failure in North A tlantic right whales:

new avenues of research. Available from 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 N o. NA8 5-WCC-0619 4, SEFSC/NM FS, Miami, FL, 108 pp. 

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

United S tates. 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. NEFSC Reference Document No. 92-

05. NO AA/NM FS, No rtheast Fisherie s Science Center, Woods H ole, Ma ssachusetts, 88 pp. 

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

isolating DN A from no n-conventio nal museum specimen s. 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 De Salle, R. 20 00. Utility of N orth Atlantic righ t whale museu m specimens for assessin g changes in

genetic dive rsity. Conservation Biology 14: 1837-1842.

Schaeff, C. M ., S. D. Kra us, M. W . Brown, J. Perkins, R. P ayne and B . N. Wh ite. 1997. Compariso n of genetic

variability of North and South A tlantic right whales (Eubalaena) using DN A fingerprintin g. Can. J. Zool.

75: 1073-1080.

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

along the T exas 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 Commerc e, Wash ington, D.C. 93 pp. 
15

November 2001

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; P alsbøll

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

matrilineally (Cla pham and Mayo 1 987). G enetic analysis o f mitochond rial DNA (mtDN A) has indic ated that this

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

(Palsbø ll 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). In deed, earlier genetic ana lyses (Palsbø ll et al. 1995), b ased upo n relatively small

sample size s, had failed to discriminate among the fo ur western N orth Atlantic fee ding areas. H owever, ge netic

analyses often re flect a timescale o f thousands o f years, well beyo nd those co mmonly use d by mana gers. 

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

based up on the strong fidelity by individu al whales to this re gion, and the attendant assumption that, w ere this

subpop ulation wiped out, repop ulation by imm igration from adjacent a reas would not occur o n any reason able

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

much large r collection o f samples than those utilized b y Palsbøll et al. (1995). These analyses have found significant

differences in m tDNA haplotype frequencies of the four weste rn feeding are as, including the Gulf of M aine (Palsb øll

et al. 2001)

 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 a nd New foundland . Photogra phs from the 1998 su rvey have no w been co mpared to both the o verall 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). Only seven of 32 individual humpback

whales identified on the Sco tian Shelf were recognize d in these comparison s, all of them from the Gulf of M aine. 

Preliminary comparisons of Scotian Shelf 1999 photographs (including some taken much further up the coast of

Nova Scotia) revealed a similar rate of exchange with the Gulf of Maine. In contrast, almost all humpback whales

identified elsewhere in the Gulf of Maine (including from the southwestern shore of Nova Scotia and Bay of Fundy

area) have been previously observed in the Gulf of Maine region. Although only one Scotian Shelf match has so far

been made to Newfoundland, 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

bounda ry, it appears tha t the effective rang e of many members o f this stock doe s not extend onto the Sc otian Shelf.

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; P alsbøll 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

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

Levenson & Leapley 1978, Price 198 5, 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 (Swingle et al. 1993; Clapham et al. 1993). An

increased n umber o f sightings of young humpba ck whales in the vicinity of the Che sapeake a nd Delaw are Bays

occurred in 1992 (Swingle et al. 1993). W iley et al. (1995) reported 38 humpback whale strandings which occurred

during 1985-1992 in the USA mid-Atlantic and southeastern states. Humpback whale strandings increased,

particularly alo ng the Virgin ia and No rth Carolina coasts, and m ost stranded animals were sexually imma ture; in
16

addition, the small size of ma ny of these wha les strongly sugge sts that they had o nly recently sepa rated from their

mothers. W iley et al. (1995) conclude d that these are as are bec oming an inc reasingly impo rtant habitat for ju venile

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 unpublishe d data; Flo rida DE P, unpub lished data). W hether the incre ased sightings r epresent a

distributional c hange, or ar e simply due to an increase in sighting effort and /or whale ab undance , is presently

unknown . 

A key question with regard to humpb ack whales o ff the southeaster n and mid -Atlantic states is their

population identity. Given the relative proximity of this region to the Gulf of Maine, a working hypothesis would be

that these whales belong to a single population that ranges from the southeastern USA to Nova Scotia. NMFSfunded contracts to collect photographs and tissue samples from living and stranded humpbacks from this area were

completed in 2000, and comparisons of the resulting materials should help to resolve this issue. Preliminary

comparisons of mid-Atlantic humpback whale photographs with those in other collections have found that some of

the animals concerned were previously observed in the Gulf of Maine. However, a better understanding of the stock

identity of the mid-Atlantic animals awaits completion of the relevant photographic analyses in late 2000; molecular

studies will probably not be completed until the following year.

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, 199 0). Humpba ck whales are frequently piscivorus whe n in these

waters, feeding on herring (Clupea harengus), sand lance (Ammodytes spp.), and other small fishes. In the northern

Gulf of M aine, eupha usiids are also frequently taken (Paque t 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 shoa ls in the southwestern Gulf of M aine favored by the sand lan ce during m uch of the late 1 970s and early

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

began in the mid 198 0s, and herring and ma ckerel increa sed as sand lance again d ecreased (Fogarty et al. 1991). 

Humpback whale abundance in the northern Gulf of Maine increased dramatically during 1992-93 , along with a

major influx o f herring (P. S tevick, pers. co mm.). Hum pback w hales were few in nearshore Massac husetts waters in

the 1992-93 sum mer seasons. They we re more abund ant in the offshore waters of Cultivator Shoal an d the Northeast

Peak on George s Bank, an d on Jeffreys L edge; these la tter areas are m ore tradition al locations o f herring occu rrence. 

In 1996 and 199 7, sand lanc e, and thus humpbac k whales, were once again abundan t in the Stellwagen Bank are a. 

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 area s and from th e breedin g grounds in the We st Indies. Add itional sample s were collec ted from ce rtain

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

summarized below.

POPU LATIO N SIZE

The ov erall North Atlantic pop ulation (includ ing the Gulf of M aine) was rec ently estimated fro m 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. 1,77 6-4,463 ) (Palsbø ll et al. 1997). Since the sex ratio in this population is known to be even

(Palsbø ll 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 10,600 (95% c.i. 9,300 to 12,100), and an additional genotype-based

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 10,600 (CV=0.067) is regarded as the best available estimate for the North Atlantic. In the northeastern

North Atlantic, Øien (1990) estimated from sighting survey data that there were 1,100 humpback whales in the

Barents Sea region.
17

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 he terogeneity o f sampling, whic h was heavily fo cused on the southweste rn Gulf

of Maine. However, an estimate of 652 (CV=0.15) derived from the more extensive and representative YONAH

sampling in 1992 a nd 1993 w as 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 bo th a previou s and subse quent year, it is po ssible to dete rmine that at least 497 hum pbacks w ere 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

conduc ted by a ship a nd airplane covering w aters from G eorges Bank to the mo uth of the Gu lf of St. Lawrenc e. 

Total trac k line length was 8 ,212 km. Howeve r, in light of the information on stoc k identity of Sco tian 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 ). 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, we have chosen to use the latter as the best

estimate of abundance for Gulf of Maine humpback whales. 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 and may need to be adjusted following further clarification of stock definition.

Minimum Po pulation 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 b y Wad e and Ang liss (1997). The best estimate of ab undance for Gulf of M aine hump back wha les is

816 (C.V.=0.45) . The minimum population estimate for this stock is 568 .

Table 1. Summar y of abunda nce estimates for Gulf of M aine hump back wha les. CCS = Center for Coastal Studie s. 

COA = College of the Atlantic.

Month/Year Type N CV Source

1992/93 Mark-re capture estim ate 652 0.15 YON AH da ta

1997 Minimum known to be alive 497 - CCS+COA d ata

July/August 1999 Line transect 816 0.45 Palka 2000

Current Population Trend

As detailed below, curr ent data stron gly suggest that the G ulf of Maine humpba ck whale stoc k is steadily

increasing in size. This is consistent with the trend in the North Atlantic population overall (Smith et al. 1999)

although there are no other feed ing-area-specific estimates.

CURRENT AND M AXIMUM 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). F or the Gulf o f Maine, d ata

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
18

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) is close to the maximum for this stock.

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

and Beard (1990) suggested an annual rate of increase of 9% ; however, the lower 95% confidence level was less

than zero. T he difference between the estimates of ab undance calculated b y Katona a nd Bea rd (199 0) and by S mith

et al. (1999) were interpreted by the latter as probably being due to population growth in the years between the two

estimates. Th is assumed g rowth rate wo uld be very sim ilar to the grow th rate of 6.5% calculated u sing an interbirth

interval model for humpback whales in the Gulf of Maine (Barlow and Clapham 1997).

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; W ade and Angliss 1997). The minimum

populatio n size is 568 . The max imum pro ductivity rate is 0.0 65 from B arlow and Clapham (1997). The “reco very”

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

Endang ered Sp ecies Act (E SA). PB R for the G ulf of Maine humpba ck whale stoc k is 1.8 whale s. 

ANNUAL HUM AN-CAUSED SERIOUS INJURY AND M ORTALITY

For the period 1995 through 1999 , the total estimated human-caused mortality and serious injury to the

Gulf of M aine hump back wha le stock is estima ted as 4.2 p er year (US A waters, 3.8 ; Canadian waters, 0.4). T his

average is derived from two components: 1) incidental fishery interaction records, 3.2 (USA waters, 2.8; Canadian

waters, 0.4); and 2) records of vessel collisions, 1.0 (USA waters, 1.0; Canadian waters, 0). Note that in the 1996

and 1998 stock assessment reports, a six-year time frame was used to calculate the averages for additional 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. For the first time, Canadian records have

been incorporated into the mortality and serious injury rates of this report to reflect the effective range of this stock

as described abo ve. It is also important to stress that serious injury determinations are ma de based upo n 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 mo rtalities or serious injuries.

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

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

timely recovery of carcasses and c omplete necrop sies. The literature and review of reco rds 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 78% had experienced entanglements (Robbins and Mattila 1999). Decomposed

and/or unexamined animals (e.g., carcasses reported but not retrieved or necropsied) represent ‘lost data’, some of

which may re late to human impacts. 

In addition, we have limited the serious injury designation to only those reports that had substantial

evidence that the injury, whether from entanglement or vessel collision, was likely to significantly impede the

whale’s locomotion or feeding in the immediate future, or had a high probability of leading to systemic and

debilitating infection. There was no forec asting of how the entanglement or injury m ay 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 preclud e examina tion for huma n impacts), W iley et al. (1995) reported that six (30%) had

major injuries possibly attributable to ship strikes, and five (25%) had injuries consistent with possible entanglement

in fishing gear. One whale displayed sca rs that may have been caused by both ship strike and entanglem ent. Thus,
19

60% of the whale carcasses which were suitable for examination showed signs that anthropogenic factors may have

contributed to, or been responsib le for, their death . Wiley et al. (1995) further repo rted that all strand ed animals

were sexually immature, suggesting a winter or migratory segregation and/or that juvenile animals are more

susceptible to human impacts. Humpback whale entanglements also occur in relatively high numbers in Canadian

waters. Rep orts of collision s with fixed fishing ge ar set for grou ndfish aroun d Newfo undland a veraged 3 65 annua lly

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 hum pback 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 m ost entanglem ents and enta nglement mortalities (21% ) of humpb acks betwe en 1979 and 199 2. 

They also reported that 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 o bserved in the pelagic d rift gillnet fishery since 19 89. In winter 1 993, a juv enile

humpback wa s observed entangled dead in a pelagic drift gillnet along the 200 m isobath northeast of Cap e 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 foun d stranded or at sea) for the p eriod 1995 to 1999 were re viewed. Out of nearly 60 re cords,

over 40 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 do cumented that the animal had become disentang led. Of the remaining record s,

there were four mortalities attributable to fishery interactions, and 12 records where serious injuries were sustained

from interactions with fisheries —a total of 16 records in the five-year period (Table 2). While these records are not

statistically quantifiable in the same way as the observed fishery records, they provide some indication of the

frequency o f entangleme nts. 

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 lo ngline, pelagic pair trawl, or o ther fisheries mo nitored by N MFS . 

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 NM FS 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, 8 7% in 19 94, 99% in 1995, 6 4% in 19 96, no fisher y in 1997, a nd 99% coverage during 19 98. 
20

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

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 resampling tec hniques. Estimated ann ual fishery-related mortality and se rious injury (C V in pare ntheses) was 0 in

1994 (0 ), 1.0 in 199 5 (0), 0 in 1 996 (0), and 0 in 19 98 (0). Sinc e this fishery no lon ger exists, reco rds of its

incidental take s have bee n excluded from Ta ble 2. 

Table 2. Summarized records of mortality and serious injury likely to result in mortality, Gulf of Maine humpback

whale stock, January 1995 - December 1999 . 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=prim ary,

S=secondary

Notes

Ship

strike

Entang./

Fsh.inter

2/28/95 mortality unknown Cape

Hatteras,

North

Carolina

(35° 17'

 75° 31')

P stranded dead with gear

wrapped around tail region

4/23/95 serious

injury

length (est.) =

7.6m

Beaufo rt,

NC

P Sink gillnet wrapped several

times around flukes

5/26/95 serious

injury

length (est.)=

10m

Great So uth

Channel

(41° 16'

 69° 20')

P net and monofilament around

tail region; whale anchored;

mesh visible and gear trailing

6/4/95 mortality 8.9 m ma le Virginia

Beach, VA

P several major lacerations

indicative of c ollision with

propeller 

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 K eys P heavy line extending around

maximum girth, pinning bo th

pectorals; grooves/healed scars

on dorsal ridge and on leading

edge of b oth pecto rals; fairly

emaciated; disentangled
Date Report 

Type

Sex, age, ID Location Assigned Cause:

P=prim ary,

S=secondary

Notes

Ship

strike

Entang./

Fsh.inter

21

4/2/96 mortality 7.2 m fema le Cape S tory,

Virginia

Beach,

Virginia

P fresh dead ; fractured left

mandible; emaciated

5/9/96 mortality 6.7 m fema le mouth of

Delaware

Bay

P propeller cuts behind

blowhole , modera te

decomposition; ship strike

7/18/96 serious

injury

length (est.) = 

10 m

25 mi S of

Bar Harbor

Maine

(44° 01'

 68° 00')

P disentanglem ent unsucce ssful;

weighted gear wrapped around

tail stock; whale swimming

abnormally

7/28/96 serious

injury

length (est.) = 

10m

SW corner

of

Stellwagen

Bank, MA

P entangleme nt involved m outh

or flipper an d line over tail;

recent entanglement; extent of

trailing gear unknown

10/7/96 serious

Injury

unknown Great So uth

Channel

(41° 04'

 69° 10')

P gear wrapped around tail and

trailing 30 m b ehind whale

10/18/96 serious

injury

unknown Great So uth

Channel

(41° 00'

69° 10')

P Whale entangled in ste el cable

11/3/96 mortality 8.4 m ma le Carrituck,

North

Carolina

P acute trauma to skull found by

necropsy

12/10/97 mortality 9.0 m ma le Beaufort

Inlet, NC

P massive hemorrhage consistent

with forceful blunt trauma

3/4/98 mortality 8.6 m fema le Ocracoke

Island, NC 

(35° 12'

75° 40')

P Coast Guard present when

whale dro wned enta ngled in

croaker gillnet gear

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
Date Report 

Type

Sex, age, ID Location Assigned Cause:

P=prim ary,

S=secondary

Notes

Ship

strike

Entang./

Fsh.inter

22

8/23/98 serious

injury

adult, sex

unknown

Monta uk Pt.,

NY

(40° 36'

70° 43')

P whale anchored by offshore

lobster gea r, struggling to

breathe; not relocated b y Coast

Guard search

11/5/98 mortality 8.9 m ma le Nags Head,

NC (35° 59'

75° 38')

P Deep a brasions ar ound tail

stock with subdermal

hemorrhaging

1/12/99 mortality 9.7m ma le Martha ’s

Vineyard,

MA

P Fresh and extensive rope

marks on c arcass 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 aro und bod y; possibly

anchored

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, o r injured. 

2. National g uidelines for d etermining wh at constitutes a se rious injury hav e not been finalized. Interim

criteria as estab lished by N ERO /NMF S (62 FR 33, Jan. 2, 1 997) ha ve been us ed here. So me assignments

may change as new information becomes available and/or when national standards are established.

3. Assigned cause base d on best judgem ent of available data. Additional inform ation may result in revisions.

4. Entanglements of juvenile wha les may become m ore serious as the whale grows.

Other M ortality

Between November 1987 and January 1988, 14 humpback whales died after consuming Atlantic mackerel

containing a d inoflagellate sax itoxin (Gera ci et al. 1989). T he whales sub sequently stran ded or w ere recov ered in

the vicinity of Cap e Cod B ay and Na ntucket Sou nd, and it is highly like ly that other mo rtalities occurre d during this

event which went unrecorded. During the first six months of 1990, seven dead juvenile (7.6 to 9.1 m long)

humpba ck whales stran ded betw een No rth Carolina and New Jersey. The significance of the se strandings is

unknown, but is a cause for some concern.

As reported by W iley et al. (1995) injuries possibly attributable to ship strikes are more common and

probably more serious than those from entanglements. In the NER/NM FS records for 1995 through 1999, nine

records had some evidence of a collision with a vessel. Of these, five were mortalities as a result of the collision,

three did not have sufficient information to confirm the collision as the cause of death, and for one 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. T he whale wa s sighted after the collision with a lar ge gash in its bac k, but was rep orted as “no t struggling to

breathe”.

STATUS OF STOCK
23

The North Atlantic humpback whale will be the topic of an International Whaling Commission

Comp rehensive A ssessment in Ju ne 2001 ; this meeting will co nduct a de tailed review o f all aspects of this

population. Although the most recent estimates of abundance indicate continued population growth, the size of the

humpback whale stock may be below OSP in the USA 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

(NM FS 199 1). There are insufficient da ta to reliably de termine po pulation trend s for humpb ack whales in th e North

Atlantic overall. The annual rate of population increase was estimated at 9% (Katona and Beard 1990), but with a

lower 95 % confid ence level less th an zero), an d for the G ulf of Maine stock at 6.5% by Barlo w and Cla pham (1 997). 

The total le vel of human -caused mortality and serio us injury is unkno wn, but curre nt data indica te that it is

significant. This is a strategic stock because the average annual fishery-related mortality and serious injury exceeds

PBR, and beca use the No rth Atlantic hum pback w hale is an end angered sp ecies. 

Disturban ce by whalew atching may p rove to be an importa nt habitat issue in so me areas o f this populatio n’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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Palsbøll, P.J., P. J. Clapham, D. K. Mattila, F. Larsen, R. Sears, H. R. Siegismund, J. Sigurjónsson, O. Vásquez and

P. Arctander. 1995. Distribution of mtDNA haplotypes in North Atlantic humpback whales: the influence

of behavio r on pop ulation structure . Marine Ecology Progress Series 116: 1-10.

Palsbøll, P.J., Allen, J. Anderson, T.H., Bérubé, M., Clapham, P.J., Feddersen, T.P., Friday, N., Hammond, P.,

Jørgensen, H., Katona, S.K., Larsen, A.H., Larsen, F., Lien, J., Mattila, D.K., Nygaard, F.B., Robbins, J.,

Sponer, R., Sears, R., Sigurjónsson, J., Smith, T.D., Stevick, P.T., Vikingsson, G. and Øien, N. 2001. 

Stock structure and composition of the North Atlantic humpback whale, Megaptera novaeangliae. Paper

SC/53/NAH11 presented to the International Whaling Commission Scientific Committee. Available from

IWC, 135 Station Road, Impington, Cambridge, UK.

Payne, P. M., J. R. Nicholas, L. O'Brien, and K. D. Powers. 1986. The distribution of the humpback whale,

Megaptera novaeangliae, on Geo rges Ban k and in the G ulf of Maine in relation to de nsities of the sand eel,

Ammodytes americanus. Fish. Bu ll., U.S. 84: 271 -277. 

Payne, P . M., D. N . Wiley, S. B. Young, S . Pittman, P. J. Clapham, and J. W . Jossi. 199 0. Recent fluc tuations in

the abund ance of ba leen whales in the southern G ulf of Maine in relation to ch anges in selec ted prey. Fish.

Bull., U.S. 88(4): 68 7-696. 

Price, W . S. 1985 . Whaling in the Caribb ean: historical p erspective a nd upda te. Rep. int. Whal. Commn. 35: 413-

420.

Reiner, F., M. E. Dos Santos, and F. W. Wenzel. 1996. Cetaceans of the Cape Verde archipelago. Mar. Mammal

Sci. 12: 434-443.

Robbins, J. and D. K. Mattila. 1999. Monitoring entanglement scars on the caudal peduncle of Gulf of Maine

humpback whales. Final Report to the National Marine Fisheries Service. Available from Center for

Coastal Studies, Provincetown, MA.
25

Smith, T. D., J. Allen, P. J. Clapham, P. S. Hammond, S. Katona, F. Larsen, J. Lien, D. Mattila, P. J. Palsbøll, J.

Sigurjónsso n, P. T. Ste vick and N . Øien. 199 9. An oce an-basin-wid e mark-reca pture study o f the North

Atlantic humpback whale (Megaptera novaeangliae). Mar. M amm al Sci. 15(1):1-32.

Stevick, P., N. Øien and D. K. Ma ttila. 1998. Migration of a hum pback whale be tween Norway and the West

Indies. Mar. M amm al Sci. 14: 162-166.

Swingle, W . M., S. G. B arco, T. D . Pitchford, W .A. McL ellan and D .A. Pabst. 1 993. Ap pearance of juvenile

humpba ck whales fee ding in the nea rshore wate rs of Virginia. Mar. M amm al Sci. 9: 309-3 15. 

Volgena u, L., S. D. K raus, and J. Lien. 1995 . The imp act of entanglements on two substocks o f the western N orth

Atlantic hump back wha le, Megaptera novaeangliae. Can. J. Z ool. 73: 1689-1698.

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.

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

1999. U.S. Atlantic marine mammal stock assessment reports — 1998. NOAA Tech. Memo. NMFS-NE116, 182 pp.

Whitehe ad, H. and M.J. M oore. 19 82. Distrib ution and movemen ts of West In dian hump back wha les in winter. 

Can. J. Zool. 60: 2203-2211.

Wiley, D. N., R. A. Asmutis, T. D. Pitchford, and D. P. Gannon. 1995. Stranding and mortality of humpback

whales, Megaptera novaeangliae, in the mid-Atlan tic and southe ast United S tates, 1985 -1992. Fish. Bu ll.,

U.S. 93: 196 -205. 

Winn, H. E., R. K. Edel and A. G. Taruski. 1975. Population estimate of the humpback whale (Megap tera

novaeangliae) in the We st Indies by visua l and acou stic technique s. J. Fish. Res. Bd. Can. 32: 499-506.
26

Figure 1. Distribution of fin whale sightings from

NEFSC and SEFSC shipboard and aerial surveys during

the summ er in 199 0-199 8. Isobaths are at 100 m and

1,000 m . 

November 2001

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 U SA, north to Nov a Scotia and on to the so utheastern coast

of Newfo undland a re believed to constitute a sing le

stock under the present IWC scheme (Donovan

1991). Howev er, the stock id entity of North Atlantic

fin whales has received relatively little attention, and

whether the current stock boundaries define

biologica lly 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 p roposed by Kellog g (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 prop osed that the North A tlantic

populatio n showed recent diver gence du e to climatic

changes (i.e. postglacial expansion), as well as

substructuring over even relatively short d istances. 

The genetic data are consistent with the idea that

different subpopulations use the same feeding

ground, a h ypothesis that w as also origina lly

proposed by Kellogg (1929).

Fin whales are common in waters of the

USA Atlantic Exclusive Economic Zone (EEZ),

principally from Cape H atteras northw ard (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 H atteras and N ova Sco tia during 19 78-82. 

While a great deal remains unknown, the magnitude

of the ecological role of the fin whale is impressive. In this region fin whales are 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 o f any cetacean species (K enney et al. 1997; Hain et al. 1993).

 There is little do ubt that New England w aters repres ent a majo r feeding gro und for the fin w hale. Ther e 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). S eipt et al. (1990) reported that 49% of identified fin wh ales on M assachusetts

Bay area feeding gro unds were resighted within the same yea r, and 45% were resighted in multiple years. W hile

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

humpba ck whales. T his was reinforc ed by Clap ham and S eipt (199 1), who sho wed mate rnally 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
27

Canadia n fishery, 196 5-1971 (Mitchell 1 974). In se ven years, 3,5 28 fin whales were taken a t three whaling sta tions. 

The station at Blandfo rd, Nov a Scotia, too k 1,402 . 

Hain et al. (1993), based on an analysis of neonate stranding data, suggested that calving takes place during

approx imately four mo nths from O ctober to J anuary in latitude s of the USA mid-Atlantic re gion; howe ver, it is

unknown where calving, mating, and wintering for most of the population occurs. Results from the Navy's SOSUS

program (Clark 19 95) indica te a substantial d eep-ocea n compo nent to fin whale d istribution. It is likely that fin

whales occurring in the USA 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 ev idence for large-scale migratory mo vements (Wa tkins et al. 2000).

POPU LATIO N 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 G ulf of Maine /Bay of Fun dy region. T he 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. La wrence. T otal track line len gth was 8,21 2 km. Similar to that used in the above 1 995 V irginia 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 a bundanc e estimate is co nsidered the best availab le for the western North A tlantic 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 b etween surveyed and un surveyed areas.

Minimum Po pulation 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 a re insufficient data to determin e popula tion trends for this species. Ev en at a conse rvatively

estimated ra te of increase, h owever, the numbers o f fin whales may ha ve increased substantially in rece nt years (Ha in

et al. 1993).

CURRENT AND M AXIMUM NET PRODUCTIVITY RATES

Current and maximum net produ ctivity rates are unk nown for this sto ck. Based on photo graphically

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 purp oses of this assessment, the ma ximum net p roductivity rate was assume d to be 0.0 4. This valu e 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). 
28

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; W ade and Angliss 1997). The minimum

populatio n size is 236 2. The maximum p roductivity rate is 0.04, the de fault value for ce taceans. The “recove ry”

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 1995 through 1999 yielded an average of 1.8 human caused mortalities per year– 0.6 per

year resulting from fishery interactio ns/entanglements (USA waters, 0.4; Canadian w aters, 0.2), an d 1.2 due to

vessel collision s (all in USA waters). 

Fishery-Related Serious Injury and Mortality 

No confirmed fishery-related mortality or serious injury of fin whales was reported in the Sea Sampling

bycatch da tabase; there fore, no de tailed fishery inform ation is presen ted here. A r eview of the re cords of stra nded, 

floating or injur ed fin whales fo r the period 1995 thr ough 19 99 on file at N ER/NM FS found three record s with

substantial evidence of fishery interactions causing mortality or serious injury. 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

entangleme nt initiated the wha le’s decline in he alth is unclear, bu t the chronic stre ss of the entangle ment is likely

lethal given the w hale’s depr essed con dition. The second re cord invo lved a whale that was found floating dead off

Lubec, Maine, on 7/31/94. The whale had several wraps of line through the mouth, and about 30 wraps around the

tail stock. The third entanglement was reported off Digby Neck, Nova Scotia on 9/28/98. The whale was found

dead with gear wrapped through the mouth and ten wraps around the tail stock.

 The three substantiated records p rovide a m inimum ann ual rate of serio us injury and m ortality of 0.6 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 eight records within the period that lacked substantial evidence of the

severity of the en tanglement fo r a serious injur y determinatio n, or that did n ot provid e the detail nec essary to

determine if an entanglement had be en a contrib uting factor in the m ortality.

Other M ortality

After reviewing NER/NMFS records for 1995 through 1999, six were found that had sufficient information

to confirm the cause of de ath as collisions w ith vessels. On 8 /1/95, a 16 .8m male w as found o n the bow o f the ship

“Royal M ajesty”. The ship’s captain r eported a major vib ration was felt wh ile transiting off Cap e Cod, M A, enroute

to Boston, Massachusetts. Another record was of a 10m female, found on 11/14/95 near Charleston, SC. The

necropsy found extensive skeletal damage and hemorrhaging. On 12/20/96, a fin whale was found floating near the

shipping docks in Savannah, Georgia. The necropsy found bruising, coagulated blood, and broken ribs on the right

side of the anim al. Another re ported sh ip strike was a m ortality in Salvo, N orth Caro lina, discove red on 3/2 1/98. 

The wha le had a large hematoma, a disarticulate d spine and numerou s broken v ertebrae. O n 2/10/99 , a 15.5m male

was found off Virginia Beach, Virginia, with a large external wound, extensive fractures to the vertebral column, and

hemorrhaging. The sixth record was from Elizabeth, NJ, on 11/5/99, where a 16.2m male was found to have a large

wound an terior of the blo whole, a seve red left flipper, a nd shattered bones. 

The above records constitute an annual rate of serious injury or mortality of 1.2 fin whales from collisions

with vessels. NER/NMFS data holdings include seven 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 mo rtality. Continuing follow-up efforts may yield additional confirmed events from these

records.
29

STATUS OF STOCK

 The status of this stock relative to OSP in the USA 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/NMF S 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 considere d to be insign ificant and ap proachin g a zero mortality and serio us injury rate. T his 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. Scho oley, S. E. Fro hock, S. K . Katona, a nd I. E. Seip t. 1993. Reprodu ction of pho tographica lly

identified fin wha les, Balaenoptera physalus, from the G ulf 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 Mem orandum

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 1 758): ana lysis of mitocho ndrial and n uclear loci. Mol. Ec ol.

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. 199 1. Resightings of indepen dent fin whales, Balaenoptera physalus, on maternal

summer ra nges. J. Mam m. 72: 788-790.

Clark, C. W . 1995. A pplication o f U.S. Nav y underwate r hydroph one arrays fo r scientific researc h on whales. Rep.

int. Whal. Commn. 45: 210-212.

Dono van, G. P . 1991. A review of IW C stock bo undaries. Rep. int. Whal. Commn. Special Issu e 13: 39 -68. 

Hain, J. H . W., M . J. Ratnaswamy, R. D. K enney, and H . E. Winn . 1993. T he fin whale, Balaenoptera physalus, in

waters of the no rtheastern U nited States co ntinental shelf. Rep. int. Whal. Commn. 42: 653 -669. 

Kellogg, R. 1929. W hat is known o f the migration o f some of the w halebone whales. Ann. Rep . Smithsonian In st.

1928: 467-494.

Kenney, R. D., G. P. S cott, T. J. T hompso n, and H. E . Winn. 19 97. Estima tes of prey co nsumption and troph ic

impacts of cetaceans in the USA northeast continental shelf ecosystem. J. Northw. Atl. Fish. Sci. 22: 155-

171.

Mizroc h, A. A., D. W . Rice and J. M. Bre iwick. 1984 . The fin wha le, Balaenoptera physalus. Mar. Fisheries Rev.

46: 20-24.

Mitchell, E . 1974. P resent status of N orthwest Atlan tic fin and other whale stocks. Pages 10 9-169, in W. E.

Schevill (ed), The whale p roblem: A status report. H arvard University Press, Cambridge, M assachusetts,

419 pp.

Palka, D . 1995. A bundanc e estimate of the Gulf of M aine harbo r porpo ise. Rep. int. Whal. Commn. Special Issue

16: 27-5 0. 

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.

Seipt, I. E., P . J. Clapham , C. A. Ma yo and M . P. Hawv ermale. 19 90. Pop ulation chara cteristics of individ ually

identified fin wha les, Balaenoptera physalus, in Massac husetts 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 Commerc e, Wash ington, DC. 93 pp. 

Watkins, W.A., M .A. Dahe r, G.M. Reppucc i, J.E. Geo rge, D.L. M artin, N.A. D iMarzio and D.P . Gannon . 2000. 

Seasona lity and distributio n of whale ca lls in the North P acific. Oceanography 13: 62-67.
30

November 2001

BLUE WHALE (Balaenoptera musculus):

Western North Atlantic Stock

STOCK DEFINITION AND GEOGRAPHIC RANGE

The distrib ution of the blu e whale, Balaenop tera musculus, in the western North Atlantic generally extends

from the Arctic to at least mid-latitudes. Blue whales are most frequently sighted in the waters off eastern Canada,

with the majority of recent records from the Gulf of St. Lawrence (Sea rs 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. Lawrenc e River estua ry to the Strait of B elle Isle and o ff eastern No va Scotia. T he species o ccurs in winter o ff

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, unp ublished d ata), although the extent of exc hange be tween these two areas rema ins unknown . Similarly, a

blue whale p hotograp hed by a N MFS large whale su rvey in August 1999 ha d previou sly been ob served in the G ulf

of St Lawrence in 1985 (R. Sears and P. Clapham, unpublished data).

The blue whale is best considered as an occasional visitor in USA Atlantic Exclusive Economic Zone (EEZ)

waters, which m ay represen t the current sou thern limit of its feedin g range (CETA P 198 2; Wen zel et al. 1988). A ll

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 sou thern limit of the sp ecies’ range is un known. 

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 USA

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 exten t that they remain ra re in some fo rmerly impo rtant habitats, no tably

in the northern and northeastern North Atlantic.

POPU LATIO N SIZE

Little is known about the population size of blue whales except for in the Gulf of St. Lawrence area. Here,

308 individuals have b een catalogued (Se ars et al. 1987), but the data were deemed to be unusable for abundance

estimation (Hammond et al. 1990). M itchell (1974 ) estimated tha t the blue whale populatio n in the western N orth

Atlantic may nu mber on ly in the low hund reds. R. Sea rs (pers. com m.) suggests tha t no presen t evidence e xists to

refute this estimate. 

Minimum Po pulation Estimate

The 308 recognizable individuals from the Gulf of St. Lawrence area w hich were catalogued b y Sears et al.

(1987 ) is considere d to be a minimum po pulation estimate for the weste rn North A tlantic 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 M AXIMUM NET PRODUCTIVITY RATES

Current and maximum net produ ctivity rates are unk nown for this sto ck. For pu rposes of this a ssessment,

the maximum net productivity rate was assumed to be 0.04. This value is based on theoretical modeling showing

that cetacean populatio ns may not gro w at rates muc h greater than 4% give n the constrain ts of their repro ductive life

history (Barlow et al. 1995).
31

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; W ade and Angliss 1997). The minimum

populatio n size is 308 . The max imum pro ductivity rate is 0.0 4, the default va lue for cetace ans. The “re covery”

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). PBR for the western North Atlantic blue whale is 0.6.

ANNUAL HUMAN-CAUSED MORTALITY AND SERIOUS INJURY

There a re no con firmed reco rds of mortality or serious inju ry to blue wha les in the USA Atlantic EE Z. 

Howev er, in Marc h 1998 a dead 2 0-m (66-ft) male blue wha le was brou ght into Rho de Island w aters on the b ow 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 USA 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 USA EEZ.

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 USA 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 ES A. A Recovery P lan has been published (Reeves et al. 1998) a nd 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 Mem orandum

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 # AA55 1-CT8 -48 to the Bureau of La nd Ma nagemen t, Washing ton, DC, 5 38 pp. 

Clark, C. W . 1995. A pplication o f U.S. Nav y underwate r hydroph one arrays fo r scientific researc h on whales. Rep.

int. Whal. Commn. 45: 210-212.

Hammond, P. S., R. Sears and M. B érubé. 1990. A note on problems in estimating the number of blue whales in the

Gulf of St La wrence from photo-ide ntification data. Rep. int. W hal. Com mn., Special Issue 12: 141-142.

Mansfield , A. W. 19 85. Status o f the blue whale , Balaenoptera musculus, in Canada . Canadia n Field Natura list

99(3): 417-420.

Mitchell, E. 1974. Present status of northwest Atlantic fin and other whale stocks. Pages 108-169 in W. E. S chevill

(ed), The whale problem: A status report. Harvard University Press, Cambridge, MA, 419 pp.

Reeves, R. R., P. J. Clap ham, R. L. B rownell, Jr. an d G. K. S ilber. 1998 . Recover y Plan for the b lue whale

(Balaenoptera musculus). Office of Protected Resources, National Marine Fisheries Service, Silver Spring,

MD 20910. 39 pp.

Sears, R., F. W enzel and J. M. W illiamson. 19 87. The blue whale: a catalog of ind ividuals from the western N orth

Atlantic (Gu lf of St. Lawrenc e). Minga n Island Ce tacean Stud y, St. Lambe rt, Quebe c, Canad a, 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. 

Sigurjonsson, J. and T. Gunnlaugsson. 1990. Recent trends in abundance of blue (Balaenoptera musculus) and

humpback wh ales (Megaptera novaeangliae) off west and southwest Iceland, with a note on occurrence of

other cetacean species. Rep. int. W hal. Com mn. 40: 537-551.
32

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.

Wenz el, F., D. K. M attila and P. J. C lapham. 1 988. Balaenoptera musculus in the Gulf of M aine. Mar. Mammal

Sci. 4(2): 17 2-175. 

Yochem, P. K. and S. Leatherwood. 1985. Blue whale. Pages 193-240 in: S. H. Ridgeway and R. Harrison (eds),

Hand book o f Marine Mam mals, Vol. 3: The Sirenians a nd Balee n Wha les. Academic Press, N ew York . 
33

Figure 1. Distribution of minke whale sightings from

NEFSC and SEFSC shipboard and aerial surveys during

the summ er in 199 0-199 8. Isobaths are at 100 m and

1,000 m . 

November 2001

MINKE WHALE (Balaenoptera acutorostrata):

Canadian East Coast Stock

STOCK DEFINITION AND GEOGRAPHIC RANGE

Minke w hales have a cosmop olitan distributio n in polar, temperate and tropical wate rs. In the North

Atlantic there are four recognized populations — Canadian east coast, west Greenland, central North Atlantic, and

northeastern North A tlantic (Donovan 19 91). These

four population divisions were defined by examining

segregation by sex and length, catch d istributions,

sightings, marking data and pre-existing ICES

boundaries; however, there are very few data from

the Canad ian east coast populatio n. 

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 M exico. Th e 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 min ke whale is common an d widely

distributed within the USA Atlantic Exclusive

Economic Zone (EEZ ) (CETAP 1 982). 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 Ne w England waters,

there are fewer minke whales, while during winter,

the species appears to b e largely absent. Like most

other balee n whales, the minke whale ge nerally

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

unconfirme d. 

POPU LATIO N 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 o f 1991 an d 1992 , a shipboa rd estimate from June-July 1 993, an e stimate mad e from a combination o f a

shipboar d and aerial surveys con ducted d uring July to Se ptember 1995, a n aerial survey e stimate of the en tire Gulf

of St. Lawren ce cond ucted in Au gust to September 19 95, an aerial survey estimate from the northern Gulf o f St.

Lawrence conducte d during Ju ly and Augu st 1996, a nd an aeria l/shipboard survey cond ucted from George s Bank to

the mouth o f the Gulf of St. La wrence du ring July and A ugust 199 9 (Tab le 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 (Table 1; CETAP 1982).
34

An abund ance of 2,6 50 (CV =0.31) minke whale s was estimated from two ship board line transect surveys

conduc ted during J uly to Septem ber 199 1 and 19 92 in the no rthern Gulf o f Maine-low er Bay of F undy region (Table

1). This population size is a weighted-average of the 1991 and 1992 estimates, where each annual estimate was

weighted b y the inverse of its va riance, using methods as d escribed in Palka (19 95). 

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 2,000m 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 cond ucted by two ships and an airplane that c overed w aters from V irginia to the mo uth of the Gu lf 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 1 000 fathom depth c ontour isob aths, the northe rn edge o f the Gulf Stream, and the no rthern 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 de pth contou r line. Data co llection and a nalysis method s were desc ribed in Pa lka (1996 ). 

Kingsley and Reeves (1 998) estim ated there w ere 1,02 0 (CV= 0.27) min ke whales in the entire Gulf of S t.

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 Aug ust and Sep tember. D uring the 19 96 survey,

3,993 km of track lines were flown in an area of 94,665 km2

 during July and August. Data were analyzed using

Queno uille’s jackknife b ias reduction proced ure on line tran sect method s that mode l the left truncated sig hting curve. 

These estimates were unc orrected 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 be st available cu rrent abund ance estima te for minke w hales is the sum o f the 1999 George s 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), be cause these su rveys are rec ent and pro vided the m ost comp lete covera ge of the kno wn habitat.
35

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 N. Gulf of Maine and Bay of Fundy 2,650 0.31

2 Jun-Jul 1993 George s Bank to S cotian shelf, shelf ed ge 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 ROW S 3 and 4) 3,810 0.25

6 Jul-Aug 1996 northern Gulf of St. Lawrence 620 0.52

7 July-Aug 1999 George s Bank to m outh of Gu lf of St.

Lawrence 2,998 0.19

8

Aug-Sep 1995 +

July-Aug 1999

Georges Bank to Gulf of St. Lawrence

(SUM OF ROW S 4 AND 7) 4,018 0.16

Minimum Po pulation 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 b y Wad e and Ang liss (1997). The best estimate of ab undance for minke wh ales 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 a re insufficient data to determin e popula tion trends for this species. 

CURRENT AND M AXIMUM NET PRODUCTIVITY RATES

Current and maximum net produ ctivity rates are unk nown for this sto ck. Life history pa rameters tha t could

be used to estimate net pr oductivity includ e: females ma ture when 6 -8 years old; p regnancy ra tes are app roximately

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; IW C 1991 ). 

For purp oses of this assessment, the ma ximum net p roductivity rate was assume d to be 0.0 4. This valu e 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; W ade and Angliss 1997). The minimum

population size is 3,515 (CV=0.16). The maximum pro ductivity rate is 0.04, the default value for cetaceans. The

“recovery” factor, which a ccounts for e ndangere d, deplete d, threatened , or stocks of un known status r elative 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.
36

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 gill net, 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 gill net fishery, and

“Unkno wn Fisheries” within the Fishery In formation se ction and un der the O ther Mo rtality section (T ables 3 and 4). 

For the purposes of this report, only those strandings and entanglement records considered confirmed human-caused

mortalities or serious injuries are discussed.

 During 1995 to 1998, the USA total annual estimated average human-caused mortality is 2.4 minke whales

per year. This is derived from three components: 0 minke whales per year (CV=0.0) from USA fisheries using

observer data, 2.2 minke whales per year from USA fisheries using strandings and entanglement data, and 0.2 minke

whales per year from ship strikes.

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

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 19 86 (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 v essels. Betwe en 1983 and 198 8, the numb ers of Japa nese longline vessels

operating within the EEZ each year were 3, 5, 7, 6, 8, and 8, respectively. Observer coverage was 100%.

Northeast Sink Gillnet

Two minke whales w ere obser ved taken in the Northe ast sink gillnet fishery be tween 198 9 and the p resent. 

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 No rtheast sink gillnet fisher y in 1993 (Wald en 1996 ) and 301 full and part time vessels in 199 8. 

Observer coverage as a percentage of trips has been 1%, 6%, 7%, 5%, 7%, 5%, 4%, 6%, 5%, and 6% for years 1990

to 1999. Because no mortalities have been observed since 1991, the annual estimated average Northeast sink gillnet

fishery-related mortality for minke whales is zero.

Herrin g We ir

A minke whale was trapped in and 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 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 dro pped to nearly nothing due to the limite d herring market (Jean Chenow eth, pers. com m.) and in 2 000 on ly

11 weirs we re built (Molynequx 2 000). T he numbe r 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 199 7, NM FS issued m anageme nt regulations w hich prohib ited the ope ration 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 pe lagic drift gillnet fishery d uring 199 5. The estimated total number of ha uls in the Atlantic

pelagic drift gillnet fishery increased from 714 in 19 89 to 1,144 in 1990; thereafter, with the introduction of qu otas,
37

effort was severely reduced. The estimated number of hauls in 1991 to 1996 were 233, 243, 232, 197, 164, and 149

respectively. F ifty-nine different vesse ls participated in this fishery at one time or anothe r between 1 989 and 1993. 

In 1994 to 1998, there were 12, 11 10, 0, and 11 vessels, respectively, in the fishery . Observer coverage, expressed

as percen t of sets, was 8% in 1989, 6 % in 199 0, 20% in 1991, 4 0% in 19 92, 42% in 1993, 8 7% in 19 94, 99% in

1995, 64% in 1996, no fishery in 1997, and 99% coverage during 1998. Observer coverage dropped during 1996

because so me vessels we re deeme d too sma ll or unsafe by the contractor that provide d observ er covera ge to NM FS. 

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 19 89 to 1993 , were obtained using the aggreg ated (pooled 1 989-1993 ) catch rates,

by strata (Northridge 1996). Total annual bycatch after 1993 was estimated separately for each year by summing the

observed caught with the p roduct of the average b ycatch per h aul and num ber of uno bserved h auls as recor ded in

SEFSC logboo ks. Varianc es were estima ted using bo otstrap re-sam pling techniq ues. Estimate d annual fisher yrelated 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 1 998. The fishery was clo sed during 1997. E stimated ave rage annua l mortality and se rious injury 

related to this fishery during 1994 to 1996, and 1998 was 1.1 m inke 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

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 skip jack for the canning industry, while the fishery north of

Cape Cod is directe d at large me dium and giant bluefin tuna (NMFS 199 5). These two fisheries are entirely separa te

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. Ca tch rates for large mediums a nd giant tuna a re high and c onseque ntly, the season us ually only

lasts a few weeks. The 1996 regulations allocated 250 MT (5 IVQs) with a minimum of 90% giants and 10% large

mediums.

Limited ob server data are available for the Atlantic tun a purse seine fishery. Out of 45 total trips mad e 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.

Gulf of Maine and Mid-Atlantic Lobster Trap/Pot Fishery

The strandings and e ntanglement database, maintained by the New E ngland 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 199 7 record s, one minke whale mortality was attributed to the lobster tra p 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 (Tables 3 and 4). None o f the five confirmed minke whale mortalities in 1999 were

attributed to this fishery (Tables 3 and 4).

There are three distinctly identified stock areas for the American lobster: 1) Gulf of Maine, 2) south of Cape

Cod to L ong Island Sound, an d 3) Ge orges Ba nk and sou th to Cape Hatteras. In 1 997, there were 3,43 1 vessels

holding licenses to harvest lobsters in federal waters, 2 ,674 vessels licensed to use lob ster 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. T he offshore fishery in federal waters has develop ed in the past 10 to 15 years,

largely due to technological improvements in equipment and lower competition in the offshore areas. In January
38

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 entangleme nt records o f large whales (inc luding right, hum pback a nd minke w hales). This fishe ry is

operating under regulations from the Large Whale Take Reduction Plan (July 22, 1997; 62 FR 391 57) and the

federal American Lobster fishery plan (December 6, 1999; 64 FR 68228). Annual mortalities due to this fishery, as

determine d from stran dings and e ntanglemen t records tha t have been audited, we re 1 in 199 1, 2 in 199 2, 1 in 199 4, 1

in 1995, 0 in 1996, 1 in 1997, and 0 in 1998 and 1999. Estimated average annual mortality related to this fishery

during 1995 to 1999 was 0.4 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 1999. 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, som e of these vesse ls operate rig ht off the beac h, some using drift nets and o thers using sink ne ts. 

During 1998, it was estimated 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 (Weigh out) that repo rt catch from fish eries during 1 998 from the states of Co nnecticut to N orth Caro lina. 

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%, and 2% for 1995 to 1999, 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 mo rtalities due to this fishe ry, as determin ed from stra ndings and entangleme nt records w ere 0 in

1991, 1 992, 19 94, 199 5, 1996 , 1997, an d 1999 and 1 in 19 98. Estima ted averag e annual mo rtality related to this

fishery during 1995 to 1999 was 0.2 minke whales per year (Tables 3 and 4).

Unknown Fisheries

The strandings and e ntanglement database, maintained by the New E ngland 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 rev iew 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, F L, pers. com m.). The au dited NE Regional O ffice entanglement/stranding d atabase for 1995 to

1999contains 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, 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 inte ractions, one attributed to the lobster po t fishery (see abo ve), and thre e 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 a unknown trawl fishery and 3 to some other fishery (Tables 3 and 4).

In general, an entangled o r stranded c etacean co uld be an a nimal that is part o f a expand ed 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 Pro gram, therefo re, the stranding s where mo rtality was due to a fishery interaction can be ad ded into

the human-caused mortality estimate. During 1995 to 1999, as determined from strandings and entanglement

records, the estimated av erage annu al mortality is 0.4 m inke whales p er year in unkn own trawl fisheries, and 1.2

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

recorde d, though so me recor ds are availa ble. Read (1994) reported interactions b etween mink e whales and gillnets

in Newfoundland and Labrador, cod traps in Newfoundland, and herring weirs in the Bay of Fundy. Hooker et al.
39

(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 19 80 and 1 990, 15 of 17 mink e whales wer e released a live 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 (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 B ay of Fundy, a nd scattered along the co asts of western N ova Sco tia and north ern Ma ine. 

In 1990 there we re 180 active weirs in western B ay of Fundy (Read 1 994). Accord ing to Canadian D FO 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 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

rest died. 

Salmon g illnets in Canad a, now no lo nger being u sed, had tak en a few mink e whales. In N ewfoundla nd in

1979, one minke whale died in a salmon net. In Newfoundland and Labrador, between 1979 and 1990, it was

estimated tha t 15% o f the Canad ian minke wh ale takes were in salmon gillne ts, where a total o f 124 mink e whale

interactions we re docum ented in co d traps, gro undfish gillnets, salm on gillnets, other gillnets and othe r 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).
40

Table 2. Summary of minke w hales (Balaen optera a cutorostra ta) released alive, by commercial fishery, years

sampled (Years), ra tio of obser ved mortalities recorde d by on-bo ard obse rvers to the estim ated 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 96-99 0/0, NA2, NA2,

NA2

0, NA2, NA2,

NA2

1

1

, NA2, NA2,

NA2

NA=Not Available.

1 The min ke whale esc aped by d iving benea th the net.

2 No observer coverage during 1997 through 1999.

Table 3. From strandings and entanglement data, summary of confirmed incidental mortality of minke whales

(Balaen optera a cutorostra ta) by comm ercial fishery: includ es years samp led (Yea rs), number of vessels

active within the fishery (Vessels), type of data used (Data Type), mortalities assigned to this fishery

(Mortality), and mean an nual mortality. See Table 4 for details.

Fishery Years Vessels Data Type 1 Observed

Mortality

Mean Annual

Mortality

GOM and mid-A tlantic

Lobster Trap/Pot 95-99

1997=6880

2000=7539

licenses2

Entanglem ent 

& Strandings 1, 0, 1, 0, 0

0.4

(0)

Mid-Atlantic Coastal Gillnet

95-99

1998=3023 Entanglement

& Strandings 0, 0, 0, 1, 0

0.2

Unknown Trawl 95-99 NA Entanglement

& Strandings

0, 0, 0, 0, 2 0.4

Unknown Fisheries

95-99

NA Entanglement

& Strandings 0, 0, 3, 0, 3

1.2

(0)

TOTAL 2.2

(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 o f sink gillnet vessels. Undetermined numb er of sink gillnet vessels.
41

Table 4. Summarized records of mortality and serious injury likely to result in mortality. Canadian East Coast stock

of minke wh ales, January 1 994 - D ecembe r 1999. T his listing includes o nly confirmed records re lated 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 fishe ry. 

Entangled in inshore

lobster gear.

5/15/97 mortality female

5.5m

(est)

Gloucester,

MA

(42 °36 ' N

70° 38' W )

P Unknown fishery. Deep

lacerations a round tail

stock, abrasions around

flukes and mouth

5/16/97 mortality female

5.5m

(est)

Rockport, MA

(42 °40 ' N

70° 35' W )

P Unkno wn fishery. 

Abrasions around flukes;

feeding prio r to

entanglement

8/14/97 mortality female

2.8m

Jewell Island,

ME

(43 °39 ' N

70° 02' W )

P Unknown fishery. Fresh

lacerations on flukes and

pectoral fins

8/30/97 mortality female

8m (est)

Cape Small,

ME

(43 °40 ' N

69° 57' W )

P Lobster fishe ry. 

Observ ed entangle d in

lobster gear by ME

Marine Patrol

6/24/98 mortality male

3.4m

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 Ba y,

MA

P Body o f whale seen in

wake of a wh ale

watching vess el.
Date Report 

Type

Sex,

age, ID

Location Assigned Cause: P=primary, 

 S=secondary

Notes

Ship

strike

 Entang./

Fsh.inter

Unk/

uncertain

42

5/9/99 mortality female

5.6m

Cape Lookout

Bight

(34° 61'N 

76° 54'W )

P Unknown fishery. Fresh

open wounds around

fluke and link marks

from pectoral fins

through mouth.

6/16/99 mortality female

6.9m

Orleans, MA

(41 ° 48 'N

65° 56'W )

P Unkno wn fishery.

Extensive rope markings

with hemorr haging. 

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 Jud ith

Light, RI

(41 °23 'N

71° 28'W )

P Trawl fishery. 6 inch

stretched mesh tightly

wrapped around rostrum.

10/2/99 mortality female

7.2m

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.

Other M ortality

Minke whales have been and are still being hunted in the N orth Atlantic. From the Canad ian East Coast

populatio n, documented wha ling occurre d from 19 48 to 19 72 with a tota l kill of 1,103 a nimals (IW C 1992 ). 

Animals from other N orth Atlantic populations are p resently still being harvested at low levels.

USA

 Minke wh ales inhabit co astal waters du ring much o f the year and a re subject to collision with vessels. 

According to the NE marine mammal entanglement and stranding database, on 7 July 1974, a necropsy on a minke

whale suggested a vessel collision occurred; on 15 March 199 2, 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 19 96 the cap tain of a vessel re ported the y hit a minke wha le offshore o f Massac husetts. After revie wing this

record, it was concluded the animal struck was not a serious injury or mortality. On 12 December 19 98, a minke

whale was struck and presum ed killed by a whale watching vessel in Ca pe Cod B ay off Massachusetts.

During 1995 to 1999, one 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).
43

CANADA

Whales and dolphins stranded between 1991 and 1 996 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 Fisheries and Oceans, Canada (Lucas and Ho oker 2000). Sable Island is approximately 170 km

southeast of mainland Nova Scotia. Lucas and Hooker (2000) report four minke whales stranded on Sable Island

between 1 970 and 1998, o ne in spring 1 982, on e in January 1 992, and a mother/ca lf in December 199 8 (Tab le 5). 

On the ma inland of N ova Sco tia, a total of seven reported minke whale s stranded d uring 199 1 to 199 6 (Tab le 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, one from Minas Basin, one was at an unknown location, and the rest stranded in the vicinity of Halifax,

Nova S cotia. It is unkno wn how many of the strand ings can be a ttributed to fisher y 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 Hoo ker (2000).

Year Month

Number of strandings

Sable Isl. Nova S cotia

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 USA 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 und er the ESA . 

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.

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., NOA A Tech.

Memo. NMFS-OPR-6, 73 pp.

Bisack, K. D. 1997. Marine mamm al 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.
44

Working paper SC/49/SM35 submitted to the IWC Scientific Committee meeting in Bournemouth, UK,

Aug/Sept 1997.

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 AA 51-C78 -48, Bure au of Land Manag ement, W ashington, D C, 538 p p. 

Donovan, G . P. 1991. A review of IWC stock boundaries. Rep. int Whal. Commn Special Issue 13: 39-68.

Hooker, S. K., R. W. Baird and M . A. Showell. 1997. Cetacean strandings and bycatches in Nova Scotia, Eastern

Canada, 1991-1996. M eeting 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 Ann ex F Rep ort of the sub-c ommittee o n North A tlantic Minke whales. Rep. int Whal. Commn

41: 160.

IWC [International Whaling Commission]. 1992. Annex K. Rep ort 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 Newfo undland. Smithsonian Institution Press. Washing ton DC. 3 16 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. Z ool. 76:1529-1550.

Lucas, Z. N . and S. K. H ooker. 20 00. Cetac ean strandin gs on Sab le Island, No va Scotia, 1 970-19 98. Canadian

Field-Naturalist 114(1): 46-61.

Mitchell, E. D. 1991. Winter records of the Minke whale (Balaen optera a cutorostra ta Lacepede 1804) in the

southern North Atlantic. Rep. int Whal. Commn 41: 455-457.

Molyne qux, P. 20 00. Tra dition 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 rep ort to the No rtheast Fisherie s Science Center, Con tract No. 4 0ENN F5001 60. Availa ble

from No rtheast Fisherie s Science Center, Woods H ole, MA . 

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. A bundanc e estimate of the Gulf of M aine harbo r porpo ise. pp. 27-5 0. In: A. Bjørge and G.P.

Dono van (eds.) B iology of the P hocoen ids. Rep. int Whal. Commn Special Issu e 16. 

Palka, D . 1996. U pdate on abundan ce of Gulf o f Maine/B ay of Fundy h arbor po rpoises. N ortheast Fish. S ci. Cent.

Ref. Doc. 96-04; 37p. Available from: National Marine Fisheries Service, 166 Water Street, Woods Hole,

MA 02543-1026.

Palka, D ., G. Wa ring and D . Potter. (in revie w). Abund ances of ce taceans and sea turtles in the no rthwest Atlantic

during summer 199 5 and 19 98. Fish. Bull., U.S.

Read, A . J. 1994. In teractions be tween cetac eans and g illnet and trap fishe ries in the northw est 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-OPR-12,

93 pp.

Walden, J. 1996. The New England gillnet effort study. NOAA, NFS, NEFSC Ref. Doc. No. 96-10, 38pp.

Available fro m North east Fisheries S cience Ce nter, Wo ods Ho le, MA. 

Waring , G. T., P. G errior, P. M . Payne, B. L. Parry and J. R. Nico las. 1990 . Incidental take of marine mammals in

foreign fishery ac tivities off the northea st United Sta tes, 1977 -1988. Fish. Bull., U.S. 88(2): 347-360.
45

Figure 1. Distribution of sperm whale sightings from

NEFSC and SEFSC shipboard and aerial surveys during

the summ er in 199 0-199 8. Isobaths are at 100 m and

1,000 m . 

November 2001

SPERM WHALE (Physeter macrocephalus):

 North Atlantic Stock

STOCK DEFINITION AND GEOGRAPHIC RANGE

The distribution of the sperm whale in the USA EEZ (Exclusive Economic Zone) 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 Stre am edge and other fe atures. 

However, the sperm whales that occur in the eastern

USA EEZ likely represent only a fraction of the total

stock. The nature of linkages of the USA habitat

with those to the south, north, an d 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 Ca ribbean, b oth

large and small adults, as well as calves and juveniles

of different sizes are reported (W atkins et al. 1985). 

Wheth er the northw estern Atlantic p opulation is

discrete from northeastern Atlantic is curren tly

unresolved. The International Whaling Commission

recognizes one stock for the North Atlantic. Based on

reviews of many types of stoc k studies, (i.e., tagging,

genetics, catch data, mark-recapture, biochemical

markers, etc.) Reeves and Whitehead (1997) and

Dufault et al. (1999) suggest that spe rm whale

populatio ns have no c lear geogra phic structure . 

There e xists one tag retu rn of a male tag ged off

Browns Bank (Nova Scotia) in 1966 and returned

from Spa in in 1973 (Mitchell 1 975). An other male

taken off northern Denmark in August 1981 had been

wounded the previous summer by whalers off the

Azores (Reeves and Whitehead 199 7).

In the USA 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 cen ter of distributio n 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) so uth of New England. In the fall, sperm wh ale occurre nce south o f New En gland on the continental she lf is

at its highest level, and there remains a continental shelf edge occurrence in the mid-Atlantic bight. Similar inshore

(<200m) obser vations have been mad e on the sou thwestern (K enney, pers. c omm) an d eastern S cotian She lf,

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 bo th of these facto rs have man agement implications. Se veral basic g roupings o r social units are generally

recognize d — nu rsery schoo ls, harem or m ixed schoo ls, juvenile or immature scho ols, bachelo r schools, bu ll 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 h igher latitudes. M ale sperm w hales are pre sent off and sometimes on the continenta l shelf
46

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). Ho wever 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 bo nds persist for many years.

POPU LATIO N SIZE

Total numbers of sperm whales off the USA or Canadian Atlantic coast are unknown, although eight

estimates from selected reg ions of the hab itat do exist for se lect time perio ds. Sightings we re almost ex clusively 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 wha les was estimate d from an A ugust 199 0 shipbo ard line transe ct sighting survey, c onducted principally

along the Gulf Stream north wall between Cape Hatteras and Georges Bank (Anon. 1990; W aring 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 (W aring 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 con ducted from August to Septemb er 1991 using the Tw in Otter and AT-11 , respectively

(Anon. 1991). As recommended in the GAMMS Workshop Report (Wade and Angliss 1997), estimates older than

eight years are d eemed u nreliable, there fore should not be used for PBR determinatio ns. Further, du e to change s in

survey metho dology thes e data shou ld not be use d to make comparisons to mo re current estim ates. 

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

George s Bank, ac ross the No rtheast Chan nel to the south eastern edg e of the Sco tian Shelf (Table 1; An on. 199 3). 

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 bo otstrap resampling technique s.

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 bo otstrap resampling technique s.

An abundance of 2,698 (CV =0.67) sperm whales was estimated from a July to September 1995 sighting

survey cond ucted by two ships and an airplane that c overed w aters from V irginia to the mo uth of the Gu lf 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 de pth contou r line. Data co llection and a nalysis method s used were described in Palka (19 96). 

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

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
47

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 co verage of the species’ hab itat.

Becaus e all the sperm whale estimate s presented here were n ot correcte d for dive-time, they are likely

downwa rdly biased a nd an und erestimate o f actual abund ance. Th e average d ive-time of spe rm whales is

approximately 45 min (Whitehead et al. 1991; W atkins et al. 1993), therefore, the proportion of time that they are at

the surface an d available to visual obse rvers is assume d to be low . 

Although the stratification schemes used in the 1990-1998 surveys did not always sample the same areas or

encomp ass the entire sp erm whale h abitat, they did fo cus on segm ents of know n or suspec ted high-use ha bitats 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 sou thern USA Atlantic. Spe rm whale ab undance may increase offshore, pa rticularly in

association with Gulf Stream and warm-core ring features; however, at present there is no reliable estimate of total

sperm wha le abunda nce in the weste rn North A tlantic. 

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

Jun-Jul 1993

George s Bank to

Scotian she lf, shelf

edge only

116 0.40

Aug 1994 warm-core ring SE of

Georges Bank 623 0.52

Jul-Sep 1995 Virginia to G ulf of St.

Lawrence 2,698 0.67

Jul-Sep 1998 Marylan d to Gulf o f St.

Lawrence 2,848 0.49

Jul-Aug 1998 Florida to Maryland 1,854 0.53

Jul-Sep 1998 Gulf of St. La wrence to

Florida (COMBINED) 4,702 0.36

1

 As recommended in the GAM MS W orkshop Report (Wad e and Angliss 1997), estimates older than eight

years are deemed unreliable, therefore are not reported in this table.

Minimum Po pulation 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 b y Wad e and Ang liss (1997). The best estimate of ab undance for sperm w hales is 4,70 2 (CV= 0.36). 

The minimum population estimate for the western North Atlantic sperm whale is 3,505 (CV=0.36).

Current Population Trend

There a re insufficient data to determin e the pop ulation trends for this species. 

CURRENT AND M AXIMUM 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 A tlantic. These include: calvin g interval is 4-6 ye ars; lactation p eriod is 24 months; gesta tion 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 11.0-
48

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 ma turity is 45 years for males and 3 0 years for fem ales (Best 1 974; Best et al.

1984; L ockyer 19 81; Rice 1 989). 

For purp oses of this assessment, the ma ximum net p roductivity rate was assume d to be 0.0 4. This valu e 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; W ade and Angliss 1997). The minimum

population size is 3,505 (CV=0.36). The maximum pro ductivity 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 HUM AN-CAUSED MOR TALITY

Four hundred twenty-four sperm whales were harvested in the Newfoundland-Labrador area between 1904-

1972 and 109 m ale and no female sperm whales were taken near Nova Scotia in 1964-1972 (Mitchell and Kozicki

1984) in a Can adian whaling fishery. There was also a well-documented spe rm whale fishery based on the we st

coast of Iceland. Other spe rm whale catches occu rred near W est Greenland, the Azo res, Madeira, Sp ain, Spanish

Morocco, No rway (coastal and pelagic), Faroes, and British coastal. At present, because of their general offshore

distribution, sp erm whales are less likely to be impacted by humans a nd those impacts that do occur are less likely to

be recor ded. Th ere has bee n no complete analysis an d reporting of existing data o n this topic for the western No rth

Atlantic.

Total annual estimated average fishery-related mortality or serious injury to this stock during 1995-1999

was zero sperm whales. Although, in 1995 one sperm whale was entangled in a pelagic drift gillnet and was released

alive with gear a round sev eral body p arts. Presently, this inj ury has not be en used to e stimate morta lity.

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 o f Bermud a. No inform ation on the sta tus of the anima l was provid ed. 

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 pro vided observer coverage of pelagic longline vessels fishing off the

Grand Ba nks (Tail of the Banks) an d currently provides ob server coverage of vesse ls fishing south of Cape Hatteras.

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

serious injurie s have bee n documented in the p elagic longline , pelagic pa ir trawl, Northe ast multispecie s sink gillnet,

mid-Atlantic coastal gillnet, or North Atlantic bo ttom trawl fisheries by NMF S Sea Samp lers.
49

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 num ber of hauls in th e pelagic d rift net fishery increase d from 71 4 in 1989 to 1144 in

1990; the reafter, with the intro duction of q uotas, effort wa s severely red uced. Th e estimated n umber o f hauls in

1991, 1992, 1993, 1994, 1995, 1996, and 1998 were 233, 243, 232, 197, 164, 149, and 113 respectively. In 1996

and 199 7, NM FS issued m anageme nt regulations w hich prohib ited the ope ration of this fishery in 1 997. Further, in

January 1999 NMFS issued a Final Rule to prohib it the use of driftnets (i.e., permane nt closure) in the North A tlantic

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. T he greatest co ncentrations of effort were lo cated alon g the southern edge of G eorges Bank and o ff

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 1989-1 993) ca tch rates, by strata, a ssuming the 1 990 injur y was a morta lity (Northridg e 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. Since this fishery no longer exists, it has been excluded from Tables 2 and 3, (see Waring et al. 1999).

Other M ortality

Fourteen sperm whale strandings have been documented along the USA Atlantic coast between Maine and

Miami, Florida, during 1994-1999 (NMFS unpublished data). One 1998 stranding off Florida showed signs of

human interactions. The animal’s head was severed, but it is unknown if it occurred pre or post-mortem. In October

1999, a live sperm whale calf stranded on eastern Long Island, and was subsequently euthanized.

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 W hitehead 1997; Hooker et al. 1997; Lucas and Hooker 19 97; Lucas and

Hook er 2000 ). Sex was rec orded fo r eleven of the thirteen anima ls, and all were m ale, which is co nsistent with

sperm whale distribution patterns (Lucas and Hooker 2000).

Ship strikes are another source of human induced m ortality. In May 1994 a ship -struck sperm whale was 

observed south of No va Scotia (R eeves and Whitehe ad 199 7), and in M ay 2000 a merchan t ship reported a strike in

Block Canyon (NM FS, 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 ).

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.
50

REFERENCES

Anon. 1990. Cruise results, NOAA Ship CHAPMAN, Cruise No. 90-05. Marine Mammal Sighting Survey. NOAA,

NMFS, NEFSC, Woods Hole Laboratory, Woods Hole, MA 5 pp.

Anon. 1991. Northeast cetacean aerial survey and interplatform study. NOAA, NMFS, SEFSC & NEFSC, 4 pp.

Available from NEFSC, Woods Hole Laboratory, Woods Hole, MA.

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. 1994. Cruise results, NOAA Ship RELE NTLESS , Cruise No. RS 94-02, Marine Ma mmal Survey/Warm

Core Ring Study. NOAA NMFS NEFSC Woods Hole Laboratory, Woods Hole, MA. 8 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. Comm er., NOAA Tech.

Memo. NMFS-OPR-6, 73 pp.

Best, P. B. 1974. Biology of the sp erm whale. P ages 53-8 1. In: W. E. Schevill (ed), The whale problem: A status

report. Harvard U niversity Press, Cambrid ge, Mass achusetts, 41 9 pp. 

Best, P. B. 1979. So cial organiza tion in sperm whales, Physeter macrocephalus. Pages 22 7-289. In: H. E. Winn

and B. L. Olla (eds), B ehavior of m arine anima ls, Vol. 3: Ce taceans. Plenum P ress, New Y ork. 

Best, P. B., P. A. S. Ca nham and N. Ma cleod. 19 84. Pattern s of reprod uction in sperm whales, Physeter

macrocephlus. Rep. int W hal. Com mn. (Special Issue 8):51-79.

Buckland, S. T., D. R. Andersen, K. P. Burnham and J. L. Laake. 1993. Distance sampling: Estimating abundance

of biologic al popula tions. Chap man a nd Ha ll, New Y ork, 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 # AA55 1-CT8 -48 to the Bureau of La nd Ma nagemen t, Washing ton, DC, 5 38 pp. 

Dufault, S., H. Whitehead, and M. Dillon. 1999. An examination of the current knowledge on the stock structure of

sperm whales (Physeter ma crocephalu s) World wide. J. Cetacean Res. Manage. 1(1):1-10.

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

Coop erative Fish & Wildlife Research U nit, Colorad o State U niversity, Ft. Collins, C olorado , 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. H ooker. 20 00. Cetac ean strandin gs on Sab le Island, No va Scotia, 1 970-19 98. Can. Field

Nat.:114 (45-61).

Mitchell, E . 1975. P rogress rep ort on whale research, Canada. Rep. int Whal. Commn. 25:270-272.

Mitchell, E . and V. M . Kozicki. 1 984. Re produc tive conditio n of male spe rm whales, Physeter macrocephalus,

taken off No va Scotia. Rep. int W hal. Com mn. (Special Issue 6):243-252.

Mullin, K. D. (in review). Abundance and distribution of cetaceans in the southern U.S. Atlantic Ocean during

summer 1 998. Fish. Bull., U.S. 

Northrid ge, S. 199 6. Estimatio n of cetacea n mortality in the U .S. Atlantic swo rdfish and tun a drift gillnet and p air

trawl fisheries. Final report to the NMFS, Northeast Fisheries Science Center, Contract

No.40 ENN F5001 60. 

Palka, D . 1995. A bundanc e estimate of the Gulf of M aine harbo r porpo ise. Rep. int W hal. Com mn. (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 199 5 and 19 98. Fish. Bull., U.S.

Reeves, R. R. and H . Whitehe ad. 199 7. Status of spe rm whale, Physeter macrocephalus, in Canada . Can. Field

Nat. 111:293-307.
51

Rice, D. W . 1989. Sp erm whale. Physeter macrocephalus Linnaeus, 1758. Pp. 177-233 in: Handbook of marine

animals. Vo l. 4. Ed. S. H . Ridgway an d R Ha rrison. Academ ic Press, London.

Scott, T. M . and S. S. Sa dove. 19 97. Sperm whale, Physeter macrocephalus, sightings in the shallow shelf waters

off Long Islan d, New Y ork. Mar. M amm al 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 W ildlife Service P ublication FWS/O BS-80 /41, Washington, D C, 166 p p. 

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 northea stern 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 no rtheastern U SA shelf. Fish. Oceanogr. 2:101-105

Waring, G. T. 1998. Results of the summer 1991 R/V Chapman marine mammal sighting survey. NOAA NMFS

NEFSC, Lab. Ref. Doc. N o. 98-09 , 21 pp. N ortheast Fishe ries Science Center, W oods H ole, Ma ssachusetts. 

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

mamma l stock assessm ents — 1 999. U .S. Dep. Commer., N OAA T ech. Memo NM FS-NE -153, 19 6 pp. 

Watkins, W. A., K . E. Mo ore and P . Tyack. 19 85. Sperm whale ac oustic beha vior in the south east Caribb ean. 

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. M amm al Sci. 9:55-67.

Whitehead, H., S. Brennan and D. Grover. 1991. Distribution and behavior of male sperm whales on the Scotian

Shelf, Cana da. Can. J. Z ool. 70:912-918.
52

Figure 1. Distribution of beaked whale sightings from

NEFSC and SEFSC shipboard and aerial surveys during

the summ er in 199 0-199 8. Isobaths are at 100 m and

1,000 m . 

November 2001

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). S trandings hav e been rep orted from Nova S cotia along th e eastern U SA coast south to

Florida, around the Gulf of Mexico, and within the

Caribbean (Leatherwood et al. 1976; CETAP 1982;

Heyning 1 989; H ouston 19 90; Mig nucci-Gian noni et

al. 1999). S tock structure in the North A tlantic 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 1 982; Waring et al. 1992; NMFS

unpublished data). Most sightings were in late spring

or summer. Base d on sighting data, this species is a

rare inhabitant of waters off the northeast US A coast

(CETAP 1982).

POPU LATIO N SIZE

The total number of Cuvier's beaked whales

off the eastern U SA Can adian Atlan tic coast is

unknown . 

However, eight estimates of the

undifferentiated complex o f 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 19 82 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

GAMM S Workshop Report (Wade and Angliss 1997), estimates older than eight years are deemed unreliable,

therefore sho uld not be u sed for PB R determinations. Furthe r, due to cha nges in survey m ethodolo gy these data

should no t be used to m ake comparisons to more curr ent 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 (Table 1;
53

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 bo otstrap resampling technique s.

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 G eorges Bank (Ta ble 1; Ano n. 1994 ). Data were collected b y two alternating te ams that searc hed with

25x15 0 binocu lars and an ind epende nt observe r who searc hed by nak ed eye from a separate p latform 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 fa thom dep th contour line . Data collec tion and ana lysis methods u sed were d escribed in Palka (19 96). 

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=0.4 0) and from the southern USA Atlantic is 596 (CV=0.5 0). This joint estimate is considered best because

together these two surveys ha ve the most c omplete c overage o f the species’ hab itat.

Because the estimates presented here were not dive-time corrected, they are likely negatively biased and

probab ly underestima te actual abu ndance. G iven that Mesoplodon spp. prefers deep-water habitats (Mead 1989) the

bias may be substantial.
54

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

Jun-Jul 1993 George s Bank to S cotian shelf, shelf ed ge only 330 0.66

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

* from data c ollected on the Twin O tter and AT -11, respec tively.

Minimum Po pulation 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 b y Wad e and Ang liss (1997). The best estimate of ab undance for undifferentia ted beake d whales is

3,196 (CV =0.34). The minimum popu lation estimate for the undifferentiated complex of beaked whales (Ziphius

and Mesoplodon spp.) is 2,41 9 (CV= 0.34). It is not p ossible to de termine the minimum po pulation estimate of only

Cuvier’s beaked wha les.

Current Population Trend

There a re insufficient data to determin e the pop ulation trends for this species. 

CURRENT AND M AXIMUM NET PRODUCTIVITY RATES

Current and maximum net produ ctivity rates are unk nown for this sto ck. Life history pa rameters tha t could

be used to estimate net pro ductivity include: length at birth is 2 to 3 m, length at sexual maturity 6.1 m for fema les,

and 5.5 m for ma les, maximum age for females w ere 30 growth layer grou ps (GLG's) and for m ales was 36 GLG 's,

which may b e annual layers (Mitchell 1 975; M ead 198 4; Housto n 1990 ). 

For purp oses of this assessment, the ma ximum net p roductivity rate was assume d to be 0.0 4. This valu e 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; W ade and Angliss 1997). The minimum

populatio n size for the und ifferentiated complex of b eaked wh ales is 2,419 (CV=0 .34). The maximum produc tivity

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 P BR for only Cuv ier’s beaked whales.

ANNUAL HUMAN-CAUSED MORTALITY AND SERIOUS INJURY

 The 1995-1999 total average estimated annual fishery-related mortality of beaked whales in open fisheries

in the USA EEZ (E xclusive Ec onomic Z one) was ze ro. 

Fishery Information
55

There is no historical information available that documents incidental mortality in either USA or Canadian

Atlantic coa st 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 B anks (Ta il of the Bank s) and curre ntly provide s observer coverage of vessels fishing so uth of Cap e Hatteras. 

Total fishery-re lated morta lity and serious inj ury cannot b e estimated se parately for ea ch beake d 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 USA

Atlantic EE Z might have been subj ect to the ob served fishery-re lated morta lity and serious inj ury.

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

serious injurie s have bee n documented in the p elagic longline , pelagic pa ir trawl, Northe ast multispecie s sink gillnet,

mid-Atlantic coastal gillnet, or North Atlantic bo ttom trawl fisheries by NMF S Sea Samp lers.

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 intr oduction of quotas, effo rt was severely re duced. T he estimated number o f hauls in

1991, 1992, 1993, 1994, 1995,1996, and 1998 were 233, 243, 232, 197, 164, 143, and 113 respectively. In 1996

and 199 7, NM FS issued m anageme nt regulations w hich prohib ited the ope ration of this fishery in 1 997. Further, in

January 1999 NMFS issued a Final Rule to prohib it the use of driftnets (i.e., permane nt closure) in the North A tlantic

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 o f sets observe d, was 8% in 1989, 6 % in 199 0, 20% in 1991, 4 0% in 19 92, 42% in

1993, 87% in 199 4, 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 Hydrog rapher Canyon alon g the continen tal shelf break a nd contine ntal slope du ring July to O ctober. 

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 undifferen tiated beak ed whales. T he estimated annual fishery-rela ted mortality (C V in pare ntheses) was 6 0 in

1989 (0 .21), 76 in 1 990 (0.2 6), 13 in 19 91 (0.21 ), 9.7 in 199 2 (0.24), and 12 in 1 993 (0.1 6). 
56

The 1994-1998 estimates by ‘species’ are:

Year Cuvier’s Sowerb y’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. Since this fishery no longer

exists, Tables 2 and 3 have been deleted from this report (see Waring et al. 1999). 

Other M ortality

From 1992- to 1998, a total of 49 beaked whales stranded along the USA Atlantic coast between Florida

and Massac husetts (NMFS unpublished data). T his includes: 28 (includes one tentative iden tification) Gervais'

beaked whales (one 1997 animal had plastics in esophagus and stomach, and Sargassum in esophagus; two 1998

animals that stranded in Septem ber in South Carolina sho wed signs of fishery interactions); 2 True's beaked whales;

5 Blainville’s beaked whales; 1 Sowerby’s beaked whales; 11 Cuvier's beaked whales (one 1996 animal had

propeller marks ) and 4 unidentified animals. The 1999 strandings data are under review.

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 abo ut 20 per e vent) and sm all numbers of Gervais’ b eaked wh ale and Blainville’s beake d whale oc curred 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, thirteen beaked whales

live stranded in the Bahamas; six beaked whales (2 Cuvier’s, 2 Blainville’s, and 2 unidentified) were returned to sea

(NMFS unpublished data). The seven dead animals included: 5 Cuvier’s, 1 Blainville’s and 1 Gervais’ beaked

whales. Necropsy of six dead beaked whales revealed evidence of tissue trauma associated with sound production

(NMFS unpub lished data).

STATUS OF STOCK

The status of Cuvier's beaked whale relative to OSP in USA 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 naval activities. 

REFERENCES

Anon. 19 90. Cruise results, NO AA Ship CHAP MAN , Cruise No . 90-05. M arine Ma mmal Sigh ting Survey. 

NOAA, NMFS, NEFSC, Woods Hole Laboratory, Woods Hole, MA. 5 pp.

Anon. 1991. Northeast cetacean aerial survey and interplatform study. NOAA, NMFS, SEFSC & NEFSC, 4 pp.

Available from NEFSC, Woods Hole Laboratory, Woods Hole, MA.

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.
57

Anon. 1994. Cruise results, NOAA Ship RELE NTLESS , Cruise No. RS 94-02, Marine Ma mmal Survey/Warm

Core Ring Study. NOAA NMFS NEFSC Woods Hole Laboratory, Woods Hole, MA. 8 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. Comm er., NOAA Tech.

Memo . NMF S-OPR-6, 73 pp . 

Buckland, S. T., D. R. Anderson, K. P. Burnham and J. L. Laake. 1993. Distance sampling: estimating abundance

of biologic al popula tions. Chap man a nd Ha ll, 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 c avirostris G. Cuvier, 1823. Pages 289-308 In: S. H. Ridgway

and R. H arrison (ed s), Handb ook of M arine Ma mmals, Vo l. 4: River do lphins and lar ger toothed whales. 

Academ ic Press, London , 442 pp . 

Houston , J. 1990. S tatus of Cuvier's Beaked W hale, Ziphius c avirostris, 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.

Leatherwo od, S., D. K . Caldwell an d H. E. W inn. 1976 . Whales, d olphins, and porpoise s of the western N orth

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 repro ductive data for the beaked whales (Ziphiidae). Rep. int W hal. Com mn. (Special

Issue 6): 91 -96. 

Mead, J.G . 1989. Beak ed whales of the genus Mesoplodon. Pages 34 9-430. In: S.H. Ridgeway and R. Harrison

(eds.), Ha ndboo k of Marine Mam mals, Vol. 4 : River Do lphins and T oothed W hales. Academ ic 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 Island s. 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 cetac eans. Int W hal. Comm n. J. Fish. Res. Bd. Can. 32(7): 875-1240.

Mullin, K. D. (in review). Abundance and distribution of cetaceans in the southern U.S. Atlantic Ocean during

summer 1 998. Fish. Bull., U.S. 

Northrid ge, S. 199 6. Estimation of cetacean mortality in the U .S. Atlantic swo rdfish and tun a drift gillnet and p air

trawl fisheries. Final report to the Northeast Fisheries Science Center, Contract No. 40ENNF500160.

Palka, D . 1995. A bundanc e estimate of the Gulf of M aine harbo r porpo ise. Rep. int W hal. Com mn. (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. Wa ring and D . Potter. (in revie w). Abund ances of ce taceans and sea turtles in the no rthwest Atlantic

during summer 199 5 and 19 98. Fish Bu ll.

Read, A . J. 1994. In teractions be tween cetac eans and g illnet and trap fishe ries in the No rthwest Atlantic. Rep. int

Whal. Commn. (Special Issue 15): 133-147.

Simmon ds, M. P . and L. F. Lo pez-Jurad o. 1991 . Whales a nd 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 northea stern 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. N o. 98-09, 21 p p. Northeast Fisheries Scienc e Center, Wo ods Hole, M assachusetts.
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

mamma l stock assessm ents — 1 999. U .S. Dep. Commer., N OAA T ech. Memo NM FS-NE -153, 19 6 pp. 
59

Figure 1. Distribution of beaked whale sightings from

NEFSC and SEFSC shipboard and aerial surveys during

the summ er in 199 0-199 8. Isobaths are at 100 m and

1,000 m . 

November 2001

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 inc lude Tru e's beaked w hale, Mesoplodon mirus; Gervais' bea ked whale , M. europaeus; Blainville's beaked

whale, M. den sirostris; and Sowerby's beaked whale,

M. bidens (Mead 1989). T hese specie s are difficult

to identify to the species level at sea; therefore, much

of the availab le characteriz ation for bea ked whale s is

to genus level only. Stock structure for each species

is unknown.

The distrib ution of Mesoplodon spp. in the

northwest Atlantic is known principally from

stranding records (Mead 1989; Nawojchik 1994;

Mignuc ci-Gianno ni et al. 1999). Off the northea st

USA coast, beaked whale (Mesoplodon spp.)

sightings have occurred principally along the

southern edge of Georges Bank (CETAP, 1982;

Waring et al. 1992; NM FS unpublished d ata). Most

sightings were in late spring and summer. In

addition, b eaked wh ales were also sighted in Gu lf

Stream featu res during N EFSC 1990-1 995 surv eys

(Waring et al. 1992; Anon 1994; Tove 1995; NMFS

unpublishe d 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; M ead 198 9). It is conside red rare in

Canadia n waters (H ouston 19 90). 

Gervais' beaked whales are believed to be

principally oceanic, and strandings have been

reported from Cape Cod B ay to Florida, into the

Caribbean and the Gulf of Mexico (Leatherwood et

al. 1976; M ead 198 9; NM FS unpu blished da ta). 

This is the mo st commo n species o f Mesoplodon to

strand along the USA Atlantic coast. The

northernmost stranding w as on Cap e 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 standings in Nova Scotia which probably represent strays from the

Gulf Stream (Mead 1989). T hey are con sidered ra re in Canad ian waters (H ouston 19 90). 

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). 

POPU LATIO N SIZE

The total n umber o f Mesoplodon spp. beak ed whales o ff the eastern U SA and C anadian A tlantic coast is

unknown . 
60

However, eight estimates of the und ifferentiated complex of beak ed 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 surve y program conducte d from 19 78 to 19 82 on the continental she lf

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 (C V=0.7 3) undifferen tiated beak ed whales w as estimated fro m line transect a erial surveys

conducted from August to September 1991 using the Twin Otter and AT-11, respectively (Anon. 1991). As

recommended in the GAM MS W orkshop Report (Wad e 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

methodo logy these da ta should no t be used to m ake comparisons to more curr ent 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 (Table 1;

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 bo otstrap resampling technique s.

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 G eorges Bank (Ta ble 1; Ano n. 1994 ). Data were collected b y two alternating te ams that searc hed with

25x15 0 binocu lars and an ind epende nt observe r who searc hed by nak ed eye from a separate p latform 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 fa thom dep th contour line . Data collec tion and ana lysis methods u sed were d escribed in Palka (19 96). 

An abundance of 2,600 (CV=0.40) for 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=0.4 0) and from the southern USA Atlantic is 596 (CV=0.5 0). This joint estimate is considered best because

together these two surveys ha ve the most c omplete c overage o f the species’ hab itat.

Although the 1990-1998 surveys did not sample exactly the same areas or encompass the entire beaked

whale hab itat, they did focu s on segme nts of known or suspecte d high-use ha bitats off the north eastern US A coast. 

The collective 199 0-98 data suggest that, seasonally, at least several thousand beaked whales are o ccupying these

waters, highest lev els of abund ance in the G eorges Bank region. Recent results sug gest that beak ed whale

abunda nce may be highest in assoc iation with Gu lf Stream and warm-core ring features. 
61

Because the estimates presented here were not dive-time corrected, they are likely negatively biased and

probab ly underestima te actual abu ndance. G iven 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

Jun-Jul 1993 George s Bank to S cotian shelf, shelf ed ge only 330 0.66

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

* from data c ollected on the Twin O tter and AT -11, respec tively.

Minimum Po pulation 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 Wa de and Angliss (199 7). The best estimate of ab undance for undifferentiated b eaked whales is 

3,196 (CV =0.34). The minimum popu lation estimate for the undifferentiated complex of beaked whales (Ziphius

and Mesoplodon spp.) is 2,41 9 (CV= 0.34). It is not p ossible to de termine the minimum po pulation estimate of only

Mesoplodon beaked whales.

Current Population Trend

There a re insufficient data to determin e the pop ulation trends for these spec ies. 

CURRENT AND M AXIMUM NET PRODUCTIVITY RATES

Current and maximum net produ ctivity rates are unk nown for this sto ck. Life history pa rameters tha t could

be used to estimate net pro ductivity include: length at birth is 2 to 3 m, length at sexual maturity 6.1 m for fema les,

and 5.5 m for ma les, maximum age for females w ere 30 growth layer grou ps (GLG's) and for m ales was 36 GLG 's,

which may b e annual layers (Mead 1984). 

For purp oses of this assessment, the ma ximum net p roductivity rate was assume d to be 0.0 4. This valu e 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; W ade and Angliss 1997). The minimum

populatio n size for the und ifferentiated complex of b eaked wh ales is 2,419 (CV=0 .34). The maximum produc tivity

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 no t possible to d etermine the P BR for o nly Mesoplodon beaked whales.

ANNUAL HUMAN-CAUSED MORTALITY AND SERIOUS INJURY
62

The 1995-1999 total average estimated annual fishery-related mortality of beaked whales in open fisheries

in the USA EEZ (Exclusive Economic Zone) was zero.

Fishery Information

There is no historical information available that documents incidental mortality in either USA or Canadian

Atlantic coa st 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 Ba nks (Tail of the Banks) an d currently provides ob server coverage of vesse ls fishing south of Cape Hatteras.

 Total fishery-re lated morta lity and serious inj ury cannot b e estimated se parately for ea ch beake d 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 USA

Atlantic EE Z might have been subj ect to the ob served fishery-re lated morta lity and serious inj ury.

Bycatch has been observed by NMFS sea samplers in the pelagic drift gillnet fishery, but no mortalities or

serious injurie s have bee n documented in the p elagic longline , pelagic trawl, N ortheast mu ltispecies sink gillne t,

mid-Atlantic c oastal gillnet, or N orth Atlantic b ottom trawl fishe ries by NM FS sea sam plers. 

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 intr oduction of quotas, effo rt was severely re duced. T he estimated number o f hauls in

1991, 1992, 1993, 1994, 1995, 1996, and 1998 were 233, 243, 232, 197, 164, 143, and 113 respectively. In 1996

and 199 7, NM FS issued m anageme nt regulations w hich prohib ited the ope ration of this fishery 1 997. Further, in

January 1999 NMFS issued a Final Rule to prohib it the use of driftnets (i.e., permane nt closure) in the North

Atlantic swordfish fishery (50 CFR Part 630). Fifty-nine different vessels participated in this fishery at one time or

another be tween 198 9 and 19 93. From 1994 to 1998, b etween 10 and 13 v essels have p articipated in th e 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 . Variance s were estimate d using bo otstrap re-sam pling techniq ues. Bycatc h of beake d whales ha s only

occurred from Georges Canyon to Hydrographer Canyon along the continental shelf break and continental slope

during July to O ctober. Fo rty-six fishery-related b eaked wh ale mortalities w ere obser ved betwe en 1989 and 199 8. 

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 available for the 1994-1998 period. Prior

estimates are for undifferentiated beaked whales. The estimated annu al fishery-related mortality (CV in parentheses)

was 60 in 1 989 (0.2 1), 76 in 19 90 (0.26 ), 13 in 199 1 (0.21), 9.7 in 199 2 (0.24), and 12 in 1 993 (0.1 6). 
63

The 1994-1998 estimates by ‘species’ are:

Year Cuvier’s Sowerb y’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. Since this fishery no longer

exists, Tables 2 and 3 have been deleted from this report (see Waring et al. 1999). 

Other M ortality

From 1992 to 199 8, a total of 49 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; two 1998 animals that

stranded in S eptembe r in South Carolina show ed signs of fisher y interactions); 2 True's bea ked whale s; 5 Blainville’s

beaked whales; 1 Sowerby’s beaked whale; 11 Cuvier's beaked whales (one 1996 animal had propeller marks ) 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 brasilien sis),

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 abo ut 20 per e vent) and sm all numbers of Gervais’ b eaked wh ale and Blainville’s beake d whale oc curred 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, thirteen beaked whales

live stranded in the Bahamas; six beaked whales (2 Cuvier’s, 2 Blainville’s, and 2 unidentified) were returned to sea

(NMFS unpublished data). The seven dead animals included: 5 Cuvier’s, 1 Blainville’s and 1 Gervais’ beaked

whales. Necropsy of six dead beaked whales revealed evidence of tissue trauma associated with sound production

(NMFS unpub lished data).

STATUS OF STOCK

The status o f Mesoplodon beaked whales relative to OSP in USA 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 naval activities. 
64

REFERENCES

Anon. 19 90. Cruise results, NO AA Ship CHAP MAN , Cruise No . 90-05. M arine Ma mmal Sigh ting Survey. 

NOAA, NMFS, NEFSC, Woods Hole Laboratory, Woods Hole, MA. 5 pp.

Anon. 1991. Northeast cetacean aerial survey and interplatform study. NOAA, NMFS, SEFSC & NEFSC, 4 pp.

Available from NEFSC, Woods Hole Laboratory, Woods Hole, MA.

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. 1994. Cruise results, NOAA ship RELEN TLESS, Cruise No. RS 9 402, Marine Mam mal Survey/Warm Core

Ring Study. NOAA NMFS NEFSC W oods Hole Laboratory, Woods Hole, MA. 8 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. Comm er., 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 biologic al popula tions. Chap man a nd Ha ll, New Y ork, 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 # AA55 1-CT8 -48 to the Bureau of La nd Ma nagemen t, Washing ton, DC, 5 38 pp. 

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pp. 

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Lucas, Z. N . and S. K. H ooker. 20 00. Cetac ean strandin gs on Sab le Island, No va Scotia, 1 970-19 98. Can. Field

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Mead, J. G . 1984. Survey of rep roductive data for the bea ked whales (Ziphiidae). Rep. int Whal. Commn. Special

Issue 6:91-96.

Mead, J. G . 1989. Beak ed whales of the genus Mesoplodon. Pages 349-430 in: S. H., Ridgway and R. Harrison

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Diego, 4 42 pp. 

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summer 1 998. Fish. Bull., U.S.

Nawoj chik, R. 199 4. First recor d of Mesoplodon densirostris (Cetacea : Ziphiidae) fro m Rhod e Island. Mar.

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85.

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

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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.

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66

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.

November 2001

RISSO'S DOLPHIN (Grampus griseus):

Western North Atlantic Stock

STOCK DEFINITION AND GEOGRAPHIC RANGE

Risso's dolphin is distributed worldwide in tropical and temperate seas. Risso's dolphins 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). T here is no information on stock differentia tion of Risso's do lphin in the weste rn North A tlantic. 

POPU LATIO N SIZE

Total numbers of Risso’s dolphins off the USA or Canadian Atlantic coast are unknown, although eight

estimates from selected reg ions of the hab itat do exist for se lect time perio ds. Sightings we re almost ex clusively 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 19 82 on the

continental shelf and shelf edge waters between Cape

Hatteras, North Carolina and Nova Scotia (CETAP

1982). An abund ance of 11 ,017 (C V=0.5 8) 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 (W aring 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 GAM S Workshop Re port

(Wade and Angliss 1997), estimates older than eight

years are deemed unreliable, therefore should not be

used for PBR de terminations. F urther, due to

changes in survey methodology these data should not

be used to make comparisons to more current

estimates. 

An abund ance of 21 2 (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 (Table 1; Anon. 1993). Data were

collected b y two alternating te ams that searc hed with

25x150 binoculars and were analyzed using
67

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 bo otstrap resampling technique s.

An abundance of 5,587 (CV =1.16) Risso’s dolphins was estimated from a July to September 1995 sighting

survey cond ucted by two ships and an airplane that c overed w aters from V irginia to the mo uth of the Gu lf 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 de pth contou r line. Data co llection and a nalysis method s used were described in Palka (19 96). 

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) for Risso’s dolphins was estimated from a shipboard line transect

sighting survey co nducted b etween 8 J uly and 17 August 19 98 that surve yed 5,57 0 km of trac k line in waters so uth

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 surv eys have the m ost comp lete covera ge of the spe cies’ 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

Jun-Jul 1993 George s Bank to S cotian shelf, shelf ed ge only 212 0.62

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 Po pulation 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 po pulation estimate for the western North Atlantic Risso’s dolphin is 22,916 (CV=0.29).

Current Population Trend

There a re insufficient data to determin e the pop ulation trends for this species. 

CURRENT AND M AXIMUM NET PRODUCTIVITY RATES

Current and maximum net produ ctivity rates are unk nown for this sto ck. For pu rposes of this a ssessment,

the maximum net productivity rate was assumed to be 0.04. This value is based on theoretical modeling showing

that cetacean populatio ns may not gro w at rates muc h greater than 4% give n the constrain ts of their repro ductive life

history (Barlow et al. 1995).
68

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; W ade and Angliss 1997). The minimum

population size is 22,916 (CV=0.29). The maximum p roductivity 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 0.40 because the CV of the

average m ortality estimate is gre ater than 0.8 (Wad e and Ang liss 1997). P BR for the western No rth Atlantic Risso ’s

dolphin is 183.

ANNUAL HUM AN-CAUSED MOR TALITY

 Total annual estimated average fishery-related mortality or serious injury to this stock during 1995-1999

was 56 Risso's dolphins (C V= 0.8 9; 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 (MFC MA) 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 USA 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 v essels. Betwe en 1983 and 199 1, the numb ers of foreign v essels oper ating within

USA 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 2 5-35% during 19 77-82, an d increased to 58% , 86%, 9 5%, and 98%, re spectively, in 19 83-86. 

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 D ecember 1991 (W aring et al. 1990; NMFS unpublished data). Three

animals were taken by squ id trawlers and a single anima l was killed in long line fishing ope rations. 

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 pro vided observer coverage of pelagic longline vessels fishing off the

Grand B anks (Ta il of the Bank s) and pro vides obse rver cove rage of vesse ls fishing south of Cape Ha tteras. 

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 b een documen ted 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 intr oduction of quotas, effo rt was severely re duced. T he estimated number o f hauls in

1991, 1992, 1993, 1994, 1995, 1996, and 1998 were 233, 243, 232, 197, 164, 149, and 113 respectively. In 1996

and 199 7, NM FS issued m anageme nt regulations w hich prohib ited the ope ration of this fishery in 1 997. Further, in

January 1999 NMFS issued a Final Rule to prohib it the use of driftnets (i.e., permane nt closure) in the North

Atlantic swordfish fishery (50 CFR Part 630). Fifty-nine different vessels participated in this fishery at one time or

another be tween 198 9 and 19 93. From 1994-1 998, be tween 10 a nd 13 ve ssels have pa rticipated 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
69

from 198 9 to 199 3, were ob tained using the aggregated (pooled 1989-1 993) ca tch rates, by strata ( Northrid ge 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 19 98. 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 19 90 (0.46 ), 21 in 199 1 (0.55), 31 in 199 2 (0.27), 14 in 199 3 (0.42), 1.5 in 199 4 (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 (see

Waring et al. 1999).

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 gea r as an autho rized gear typ e in Atlantic tunas fishery. The fishe ry operated from Augu st-Novem ber in

1991, fro m June-N ovemb er in 1992 , from June-O ctober in 1 993 (N orthridge 1 996), and from mid-summer to

November in 1994 and 1995. Sea sampling began in October 1992 (G errior 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 199 5, 52% and

55%, respectively, of the sets were observed. Nineteen vessels have operated in this fishery. The fishery extends

from 35oN to 41oN, and from 69°W to 72 °W. Approximately 50% o f the total effort was within a one degree square

at 39oN, 72oW, around Hudso n Canyon. Examination of the 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 (No rthridge 19 96). One mortality was o bserved in 1992. E stimated ann ual fishery-related 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 M exico, for the p elagic longline fishery, based o n mandato ry selfreported fisheries informa tion, was 11 ,279 sets in 1 991, 10 ,311 sets in 1 992, 10 ,444 sets in 1 993, 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, and 6,786 sets in 1999 (Cramer

1994; Scott and Brown 199 7; Johnson et al. 1999; Yeung 1999 a; 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 ob served, since 1992. T he 1993 -1997 e stimated 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 19 94-1995 periods (Cramer 199 4; 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 b ycatch estimates were from Yeung (1999a) and Yeung et al. (2000), respectively. 

Most o f the estimated m arine mammal bycatch was from E EZ waters between S outh Caro lina and Ca pe Cod . 

Excluding the Gulf of Mexico, from 1992-1999 one mo rtality was observed in 1994 and 0 in other years. The

observed number of seriously-injured but released alive individuals from 1992-1999 was respectively 2, 0, 6, 4, 1, 0,

1, and 1 (Cramer 1994; Scott and Brown 1 997; Johnson et al. 1999; Yeung 1999 a; Yeung et al. 2000) (T able 2). 

Estimated annual fishery-rela ted mortality (C V in pare ntheses) was 1 7 in 1994 (1.0) and 0 in other yea rs (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 (0.6 8) in 199 5, 99 (1.0 ) in 1996 , 0 in 1997 , 57 (1.0) in 1998, a nd 22 (1 .0) in 199 9 (Tab le 2). 
70

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 Vessels Data Type 1 Observer

Coverage 

Observed

Serious Injury

Observed

Mortality

Estimated

Serious

Injury

Estimated

Mortality 

Estimated

Combined

Mortality

Estimate

d CVs 

Mean

Annual

Mortality

Pelagic

Longline2

95-99 277, 253,

245, 205,

1933

Obs. Data

Logbook

 .04, .03,

.03, .03,

.04

 4, 1, 0, 1, 1 0, 0, 0, 0,

0

103, 99, 0, 57,

22

0, 0, 0, 0,

0

103, 99, 0,

57, 22

.68, 1.0,

0, 1.0,

1.0

56 (.89)

TOTAL 56 (.89)

1 Observer data (O bs. Data) are used to m easure bycatch rates and the d ata are collected within the Northe ast

Fisheries Science Center (NEFSC) Sea Sampling Program. NE FSC collects landings data (Weighout) and

total landings a re used as a m easure of tota l effort for the coa stal gillnet fishery.

2

1995-1999 M ortality estimates were taken from Table 9 in Yeung et al. (NMFS Miami Laboratory PRD

99/00-13), and exclude the Gulf of Mexico.

3 Number of vessels in the fishery are based on vessels reporting effort to the pelagic longline logbook.

Other mortality

From 1995-1998, twelve Risso’s dolphins stranding were recorded along the USA Atlantic coast (NMFS 

unpublished data). The 1999 data are under review. In eastern Canada, one Risso’s dolphin stranding was reported

on Sable Island, Nova Scotia from 1970-1998 (Lucas and H ooker 2000).

STATUS OF STOCK

The status of Risso's 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 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 ra te. The 19 95-199 9 average annual fishery-rela ted mortality d oes not exc eed PB R; therefore , this is

not a strategic sto ck. 

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Atlantic. A guide to their identification. U.S. Dept. of Commerce, NOAA Tech. Rep. NMFS Circ. 396, 176

pp. 

Lucas, Z. N . and S. K. H ooker. 20 00. Cetac ean strandin gs on Sab le Island, No va Scotia, 1 970-19 98. Can. Field

Nat.:114 (45-61).

Mullin, K. D. (in review). Abundance and distribution of cetaceans in the southern U.S. Atlantic Ocean during

summer 1 998. Fish. Bull., U.S. 

Northrid ge, S. 199 6. Estimatio n of cetacea n mortality in the U .S. Atlantic swo rdfish and tun a drift gillnet and p air

trawl fisheries. Final report to the Northeast Fisheries Science Center, Contract No. 40ENNF500160.

Palka, D . 1995. A bundanc e estimate of the Gulf of M aine harbo r porpo ise. Biology o f the Phoco enids. Rep. int

Whal. Commn. (Special Issue 16):27-50.

Palka, D ., G. Wa ring, and D . Potter. (in revie w). Abund ances of ce taceans and sea turtles in the no rthwest Atlantic

during summer 199 5 and 19 98. 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

shipboar d observ ations. NO AA/NM FS Con tract No. N A-81-FA -C-0002 3. 

Scott, G. P . and C. A. B rown. 19 97. Estima tes of marine m ammal and marine turtle ca tch 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. G errior, P. M . Payne, B. L. Parry and J. R. Nico las. 1990 . Incidental take of marine mammals in

foreign fishery activities off the northeast United States, 1977-1988. Fish. Bull., U .S., 88:347-360.

Waring, G. T., C. P. Fairfield, C. M. Ruhsam and M. Sano. 1992. Cetaceans associated with Gulf Stream features

off the northea stern USA shelf. ICES M arine M amm als Com m. CM 1 992/N :12, 29 p p. 

Waring, G. T. 1993. Spatial patterns of six cetaceans along a linear habitat. Proceedings of the Tenth Biennial

Conferen ce on the Biology of M arine Ma mmals, No v. 11-15, 1 993, G alveston, T X (Abstr act). 

Waring, G.T. 1998. Results of the summer 1991 R/V Chapman marine mammal sighting survey. NOAA NMFS

NEFSC , Lab. Ref. Doc. N o. 98-09, 21 p p. Northeast Fisheries Scienc e Center, Wo ods Hole, M assachusetts.

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

mamma l stock assessm ents — 1 999. U .S. Dep. Commer., N OAA T ech. Memo NM FS-NE -153, 19 6pp. 

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 M ortality Estimates of Marine Mammal Bycatch in 1992-1997 based on Serious Injury

Guidelines. NOAA Technical Memorandum NMFS-SEFSC-429, 23 pp.

Yeung, C., S. Eppe rly, and C. A. B rown. 200 0. Prelimina ry revised estimates of marine mamma l 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.
72

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.

November 2001

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 sho rt-finned pilot wh ale, G. macrorhynchus. These sp ecies are difficu lt to identify to

the species level at sea; therefore, some of the descriptive material below refers to Globice phala sp., and is identified

as such. Th e species b oundary is c onsidered to be in the N ew Jersey to C ape Ha tteras area. Sigh tings north of this

area are likely G. melas. 

Pilot whales (Globice phala 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; N MFS unpublishe d 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 currently unknown (Anon. 1993a); however,

several recently initiated genetic studies and proposed North Atlantic sighting surveys will likely provide information

required to delineate stoc k bound aries. 

POPU LATIO N SIZE

The total number of long-finned pilot whales

off the eastern U SA and C anadian A tlantic 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 deriv ed from ca tch data and populatio n 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

1978-8 2, August 1 990, Jun e-July 199 1, AugustSeptember 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

Globice phala sp., both long-finned and short-finned

pilot whales. One estimate is available from the Gulf of

St. Lawrence.

Mitchell (1 974) use d cumulative catch data

from the 19 51-61 d rive fishery off Ne wfoundlan d to

estimate the initial population size (ca. 50,000 animals).

Merce r (1975 ), used pop ulation mod els 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 con sidered the best estimate. 

An abundance of 11,120 (CV=0.29)

Globice phala sp. was estimated from an aerial survey

program conducted from 1978 to 19 82 on the

continental shelf and shelf edge waters between Cape
73

Hatteras, North Carolina and Nova Scotia (CETAP 1982). An abundance of 3,636 (CV=0.36) Globice phala sp.

was estimated from a June and July 1991 shipboard line transect sighting survey conducted primarily between the

200 and 2,000m isobaths from Cape H atteras to Georges Bank (Waring et al. 1992; Waring 1998). An abundance 

of 3,368 (CV=0.28) and 5,377 (CV=0.53 ) Globice phala sp. was estima ted from line tra nsect aerial surv eys

conducted from August to September 1991 using the Twin Otter and AT-11, respectively (Anon. 1991). As

recommended in the GAM S Workshop Re port (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

methodo logy, these da ta should no t be used to m ake comparisons to more curr ent estimates. 

 An abundance of 668 (CV =0.55) Globice phala sp. 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

George s Bank, ac ross the No rtheast Chan nel to the south eastern edg e of the Sco tian Shelf (Table 1; An on. 199 3b). 

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 bo otstrap resampling technique s.

An abundance of 8,176 (CV =0.65) Globice phala sp. was estimated from a July to September 1995 sighting

survey cond ucted by two ships and an airplane that c overed w aters from V irginia to the mo uth of the Gu lf 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 de pth contou r line. Data co llection and a nalysis method s used were described in Palka (19 96). 

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 summ er survey data. The

best 1995 abundance estimate for Globice phala 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) Globice phala 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) Globice phala 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 Globice phala 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 surv eys have the m ost comp lete covera ge of the spe cies’ habitat.
74

Table 1. Summary of abundance estimates for the western North Atlantic Globice phala 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 George s Bank to S cotian shelf, shelf ed ge 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

Minimum Po pulation 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 Globice phala sp. is 14,524

(CV=0.30). The minimum po pulation estimate for Globice phala sp. is 11,343 (CV=0.30).

Current Population Trend

There a re insufficient data to determin e the pop ulation trends for this species. 

CURRENT AND M AXIMUM NET PRODUCTIVITY RATES

Current and maximum net produ ctivity rates are unk nown for this sto ck. Life history pa rameters tha t could

be used to estimate net productivity include those from animals taken in the Newfoundland drive fishery: calving

interval 3.3 yea rs; lactation pe riod abo ut 21-22 m onths; gestation period 1 2 months; b irths mainly from June to

Novemb er; length at birth is 177 cm; mean length at sexu al maturity is 490 cm for males; and 3 56 cm for females;

age at sexual maturity is 12 years for males and 6 years for females, and 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; Desp ortes et al. 1993; M artin and Ro thery 1993 ). These d ifferences are like ly

related, at least in p art, to larger sam ple sizes and newer analytica l techniques. 

For purp oses of this assessment, the ma ximum net p roductivity rate was assume d to be 0.0 4. This valu e 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; W ade and Angliss 1997). The minimum

population size for Globice phala 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 m ortality estimate is b etween 0.3 -0.6 (Wade and Angliss 199 7) and be cause this stock is of unknown status. 

PBR for the western North Atlantic Globice phala sp. is 108.
75

ANNUAL HUM AN-CAUSED MOR TALITY

Total fishery-related mortality and serious injury cannot be estimated separately for the two species of pilot

whales in the USA Atlantic EEZ (Exclusive Economic Zone) 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 to this stock during 1995-1999 in the USA fisheries

listed below was 237 pilot whales (CV = 0.44) (Table 2). The Canadian average annual mortality estimate for 1995-

1996 from the Nova Scotia trawl fisheries is 8 long-finned pilot whales. It is not possible to estimate variance of the

Canadian estimate. The total average annual mortality estimate for 1995-1999 from the USA and Nova Scotia trawl

fisheries is 245 (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). DW F effort in the Atlantic coast EEZ under

MFCM A has been directed primarily towards Atlantic mackerel and squid. An average of 120 different foreign

vessels per year (range 102-161) operated within the Atlantic coast EEZ during 1977 through 1982 . In 1982, there

were 112 different foreign vessels; 18 (1 6%) we re Japane se tuna longline vessels ope rating along the USA A tlantic

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 USA 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 fishin g season an d, for mack erel, at the end of the 199 1 fishing seaso n. 

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 op erations. This total includes 48 doc umented ta kes by US A vessels

involved in joint venture fishing operations in which USA captains transfer their catches to foreign processing

vessels. Due to tempor al fishing restrictions, th e bycatch o ccurred d uring winter/spring (December to M ay) 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 (Globice phala sp.) are con sidered tog ether. 

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 pro vided observer coverage of pelagic longline vessels fishing off the

Grand Ba nks (Tail of the Banks) an d provides ob server coverage of vesse ls fishing south of Cape Hatteras.

Bycatch h as been o bserved b y NMF S Sea Samplers in the p elagic drift gillnet, pe lagic longline, an d pelagic

pair trawl fisheries, but no mortalities or serious injuries have been documented in the Northeast multispecies sink

gillnet or mid-A tlantic coastal gillne t.
76

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 intr oduction of quotas, effo rt was severely re duced. T he estimated number o f hauls in

1991, 1992, 1993, 1994, 1995, 1996, and 1998 were 233, 243, 232, 197, 164, 149, and 113 respectively. In 1996

and 199 7, NM FS issued m anageme nt regulations w hich prohib ited the ope ration of this fishery in 1 997. Further, in

January 1999 NMFS issued a Final Rule to prohib it 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

(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, 199 7 (No fishery), 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, fro m 1989 to 1993 , were obta ined using the a ggregated (pooled 1989-1 993) ca tch 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 produ ct of the avera ge bycatch p er haul and th e number of unobse rved hauls a s recorde d in

self-reported fisheries information. Variances were estimated using bootstrap re-sampling techniques. Between

1989 a nd 199 8, eighty-seven m ortalities were o bserved in the large pela gic drift gillnet fishery. T he annual fishe ryrelated 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), 1997 (No fishery), 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, respectively. This fishery ceased operations in 1996 when NMFS rejected a petition to consider

pair trawl gea r as an autho rized gear typ e in Atlantic tunas fishery. The fishe ry operated from Augu st-Novem ber in

1991, from June-November in 1992 , from June-October in 1993, and from mid-summer to November in 199 4 and

1995. Sea sampling began in October 1992 (G errior 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% (212) and 54% (23 8),

respectively, of the sets were observed. Twelve vessels have operated in this fishery. The fishery extends from 35oN

to 41oN, and from 69°W to 72°W. Approximately 50% of the total effort was within a one degree square at 39oN,

72oW, aro und Hud son Canyo n. Examina tion of the loca tions and sp ecies composition of the bycatch, sho wed 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 (Globice phala sp.) mortalities were reported in the self-reported fisheries

information in 1993. In 1994 and 1995 observers reported one and twelve mortalities, respectively. The estimated

fishery-related 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 M exico, for the p elagic longline fishery, based o n mandato ry selfreported fisheries informa tion, was 11 ,279 sets in 1 991, 10 ,311 sets in 1 992, 10 ,444 sets in 1 993, 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, and 6,786 sets in 1999 (Cramer

1994; Scott and Brown 199 7; Johnson et al. 1999; Yeung 1999 a; 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
77

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 ob served, since 1992. T he 1993 -1997, estimated take w as based o n a revised a nalysis of 

the observed incidental take and self-reported incidental take and effort data, and replace previous estimates for the

1990-1993 and 19 94-1995 periods (Cramer 199 4; 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 b ycatch estimates were from Yeung (1999a) and Yeung et al. (2000), respectively. 

Most of the estimated marine mammal bycatch was from EEZ waters between 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 1992-1999 sixty-two pilot whales (including two identified as a short-finned pilot

whales) were released alive, including 3 2 that were considered seriously injured (of which one was ide ntified as a

short-finned pilot whale), and two 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 o f Hydrogr apher Ca nyon off the co ntinental shelf in wate r over 1,0 00 fathom s during Ap ril-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)

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, and 288 (CV=0.74) in 1999 (includes 37

estimated short-finned pilot whales in 1995 (CV=1.00)); average annual mortality between 1995 and 1999 was 145

pilot whales (0.66) (Table 2). Seriously injured and released alive animals are combined with mortalities in the

category ‘co mbined m ortality’. 

Bluefin Tuna Purse Seine

The tuna purse seine fishe ry between C ape Ha tteras and Cape Co d is directed at small and m edium blu efin

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 a ircraft are used to locate fish sch ools. The official start date is A ugust 15, set b y 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, five p ilot whales were encircled in a set. The net w as opene d prior to p ursing to let the wh ales swim

free, appa rently uninjured . This set occ urred on th e Cultivator S hoals region on Geo rges Ban k. Since 19 96, this

fishery has not b een obse rved. 

North Atlantic Bottom Traw l 

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. T he estimated fishery-related mortality to pilot wh ales in the US A Atlantic attrib utable to this

fishery was: 0 in 1994-1998, and 228 in 1999. The average annual mortality between 1995-1999 was 46 pilot

whales (CV = 1.03) (Table 2). However, these estimates should be viewed with caution due to the extremely low

(<1% ) observe r coverag e. 
78

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, butterfish trawl fishery, and maintained a Category II classification. Three fishery-related mortalities of

pilot whales w ere repo rted in self-repo rted fisheries info rmation from the macker el trawl fishery betw een 199 0-1992 . 

Six mortalities were observed in 1996, one in 1998, and one in 1999. 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 A tlantic attributable to this fishery was: 45 in 1996 (CV = 1 .27), 0 in 19 97, 85 in 1 998 (C V = 0.6 5), and 49 in

1999 (C V = 0.9 7); average annual mo rtality between 1 996 and 1999 w as 45 pilot w hales (CV =0.52) (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 Sam pling

program in July, 1993; and from July to December 1993, 20 trips were observed. During 1994 and 1995, 221 and

382 trips w ere obser ved, respe ctively. This fishery, w hich extend s from No rth Carolina to New Y ork, is actually a

combina tion of small vessel fisheries that targe t a variety of fish spe cies, some o f which ope rate right off the be ach. 

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%, and 5% for 1995, 1996, 1997, and 19 98 respectively (Table 2).

No pilo t whales were ta ken in obse rved trips d uring 199 3-1997 . One pilot w hale was ob served take n in

1998, and 0 in 1999 (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 1995-1999 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 Atlan tic Canadia n and Gr eenland sa lmon gillnet fishery is se asonal, with the p eak from J une to

Septemb er, depen ding on loc ation. During 1989, in so uthern and e astern New foundland and Lab rador, 2,1 96 nets

91m long were used. There are no effort data available for the Greenland fishery; however, the fishery was

terminated in 1993 u nder an ag reement b etween Ca nada and North A tlantic Salmo n Fund (Read 199 4). 

There were 3,121 cod traps operating in Newfoundland and Labrador during 1979, and about 7,500 in 1980

(Read 1 994). T his fishery was clos ed at the end of 1993 due to colla pse of Can adian grou ndfish resour ces. 

Between January 1993 and December 1994, 36 Spanish deep-water trawlers, covering 74 fishing trips

(4,726 fish ing days and 14,211 sets), were ob served in N AFO F ishing Area 3 (off the Gran d Bank ) (Lens 19 97). A

total of 47 inc idental catch es were reco rded, whic h included one long-finne d pilot whale . The incid ental mortality

rate for pilot wh ales was 0.0 07/set.

In Canada, the fisheries observer program places observers on all foreign fishing vessels, on 25% to 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.

Record ed bycatch es by year wer e: 16 in 19 91, 21 in 1 992, 13 in 1994, 9 in 1995, a nd 6 in 19 96. Pilot wh ale

bycatches occurred in all months except January-March and September (Hooker et al. 1997).
79

Table 2. Summary of the incidental mo rtality of pilot whales (Globicephala sp.) by commercial fishery including the

years samp led (Yea rs), the numb er of vessels ac tive within the fishery (V essels), the type o f data used (D ata

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

96-99 NA Obs. Data

Weighouts

.007, .008,

 .003, .004 

 0, 0, 0, 0 6, 0, 1, 1 45, 0, 

85, 49

 1.27, 0,

 .65, .97

45

(.52)

N. Atlantic 3,5

Bottom Tr awl

95-99 NA Obs. Data

Weighouts

.0114, .002,

 .002, .001,

.003

0, 0, 0, 0, 0 0, 0, 

0, 0, 1

 0, 0,

 0, 0,

228

0, 0, 

0, 0, 1.03

 46

(1.03)

Pelagic 6

Longline 

95-99 277, 253, 

 245, 205, 

 1937

Obs. Data

Logbook

.04, .03,

.03, .03, .04

13, 0, 0,

 0, 4

0, 0, 0, 0, 1 345, 0, 0, 

0, 288

 0, 0, 0,

 0, 93

345, 0, 0, 

0, 381

0.51, 0, 0,

 0, 0.79

145

 (0.66)

Mid-Atlantic

Coastal Gillnet 

95-99 NA Obs. Data

Weighouts

.05, .04,

 .03, .05,

.02

0, 0, 0, 0, 0 0, 0, 0, 1,

0

0, 0, 0, 7,

0

0, 0, 0,

 1.1,

0

1

(1.1)

Nova Scotia

trawl fisheries

95-96 NA Obs. Data NA,

 NA

 0, 0 9, 6 9, 6 NA,

 NA

8

(NA)

TOTAL 245

(0.44)

1 Observer data (O bs. Data) are used to m easure bycatch rates, and the da ta are collected within the Northea st

Fisheries Science Center (NEFSC) Sea Sampling Program. M andatory 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. Th e trawl fisheries are measured in trips.

3

1995 estimate no t available for the squid, mackerel and butterfish sub-fisheries.

4 Observer coverage for the Atlantic bottom trawl fishery in 1995 is based on only January to May data.

5

In 1997 and 1998 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.

6

1995-1999 mortality estimates were taken from Table 9a in Yeung et al. (NMFS Miami Laboratory PRD

99/00-13), and exclude the Gulf of Mexico.

7 Number of vessels in the fishery are based on vessels reporting effort to the pelagic longline logbook.

Other M ortality

Pilot whales have a prop ensity to mass strand throughout their range, bu t the role of human activity in these

events is unkno wn. Betwe en 2 and 1 20 pilot wh ales have stran ded annu ally, either individu ally or in group s, in

NMFS Northeast Region (Anon. 1993b) since 1980. From 1992-1998, 71 long-finned pilot whale stranded between

South Carolina and Maine, including 22 animals that mass stranded in 1992 along the Massachusetts coast (NMFS

unpublishe d data). 

In eastern Canada, 37 strandings of lo ng-finned pilo t whales (17 3 individua ls) were repo rted on Sa ble

Island, No va Scotia fro m 1970 -1998 (L ucas and H ooker 1 997; Luc as and H ooker 2 000). T his included 130 anim als

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 (Ho oker 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
80

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 stand ing group tha n animals of the same sex o r age. Also, hig h 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 ). The po pulation effec t of the observ ed levels of suc h contamin ants is unknow n. 

STATUS OF STOCK

The status of long-finned pilot whales relative to OSP in USA 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 1 971, and increased a bundanc e of herring, mackerel, and squid stock s. There ar e 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 con sidered to be insignificant and app roaching zero mo rtality and serious injury rate. This is a

strategic stock b ecause the 1 995-19 99 estimate d average annual fishery-rela ted mortality, ex cluding N ova Sco tia

bycatches to pilot whales, Globice phala sp., exceeds PBR.

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Institute of Technology, Sea Grant, MITSG 95-6, Cambridge, MA. 10 pp.

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Canada, 1991-1996. Paper SC/49/05 presented to the IWC Scientific Committee, September 1997. 11 pp.
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Kasuya, T., D. E. Sergeant and K. Tanaka. 1988. Re-examination of life history parameters of long-finned pilot

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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.

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pp. 

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Martin, A. R. and P . Rothery. 1993. Re productive param eters of female long-finned pilot whales (Globice phala

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Mercer, M. C. 1975. Modified Leslie-DeLury population models of the long-finned pilot whale (Globice phala

melaena) and annual production of the short-finned squid (Illex illecebrosus) based upon their interactions

at Newfou ndland. J. Fish. Res. Bd. Can. 32(7): 11 45-54. 

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Muir, D. C. G., R. Wagermann, N. P. Grift, R. J. Norstrom, M. Simon and J. Lien. 1988. Organochlorine chemical

and heavy metal contam inants in white-beaked dolphins (Lagen orhync hus albiro stris) and pilot whales

(Globicephala melaena) from the co ast of Newfo undland. Canada. Arch. Environ. Contam. Toxicol. 17:

613-62 9. 

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summer 1 998. Fish. Bull., U.S.

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. 

Northrid ge, S. 199 6. Estimatio n of cetacea n mortality in the U .S. Atlantic swo rdfish and tun a drift gillnet and p air

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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. Wa ring and D . Potter. (in revie w). Abund ances of ce taceans and sea turtles in the no rthwest Atlantic

during summer 199 5 and 19 98. Fish. Bull., U.S.

Payne, P. M. an d D. W. H einemann. 1993 . The distribution of pilot whales (Globice phala sp.) in shelf/shelf edge

and slope waters of the no rtheastern U nited States, 1 978-19 88. Rep. int Whal. Commn. (Special Issue 14):

51-68. 

Read, A . J. 1994. In teractions be tween cetac eans and g illnet and trap fishe ries in the northw est Atlantic. Rep. int

Whal. Commn. (Special Issue 15): 133-147.

Scott, G. P . and C. A. B rown. 19 97. Estima tes of marine m ammal and marine turtle ca tch by the U.S . Atlantic

pelagic longline fleet in 1994-1995. Miami Laboratory Contribution MIA-96/97-28.

Sergeant D. E. 1962. The biology of the pilot or pothead whale (Globicephala melaena (Traill) in Newfoundland

waters. Bull. F ish. Res. Bd . Can. 132 : 1-84. 

Taruski, A . G., C. E. O lney and H . E. Winn . 1975. Chlorinated h ydrocarb ons in cetace ans. J. Fish. Res. Bd. Can.

32(11 ): 2205-9 . 
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.

Waring , G. T., P. G errior, P. M . Payne, B. L. Parry and J. R. Nico las. 1990 . Incidental take of marine mammals in

foreign fishery ac tivities off the northea st United Sta tes, 1977 -1988. Fish. Bu ll., 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 northea stern USA shelf. ICES Marine Mammals Comm. CM 1992/N:12, 29 pp.

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dissertation, University of Massachusetts, Amherst, 260 pp.

Waring, G. T. 1998. Results of the summer 1991 R/V Chapman marine mammal sighting survey. NOAA NMFS

NEFSC, Lab. Ref. Doc. N o. 98-09 , 21pp. N ortheast Fishe ries Science Center, W oods H ole, Ma ssachusetts

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Weisbrod, A. V., D. Shea, M. J. Moore, and J. J. Stegeman. 2000. Bioaccumulation patterns of polychlorinated

biphenyls an d chlorinate d pesticide s in northwest A tlantic pilot whale s. Environ. Toxicol. Chem. 19:667-

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Yeung, C. 1999a. Estimates of marine mammal and marine turtle bycatch by the U.S. Atlantic pelagic longline fleet

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Guidelines. NOAA Technical Memorandum NMFS-SEFSC-429, 23 pp.

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Number 99/00-13. 58 pp.
83

Figure 1. Distribution of pilot whale sightings from

NEFSC and SEF SC shipboard and aerial surveys

during th e summ er in 199 0-199 8. Isobath s are at 

100 m and 1,000 m.

November 2001

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 sho rt-finned pilot wh ale, G. macrorhynchus. These sp ecies are difficu lt to identify to

the species level at sea; therefore, some of the descriptive material below refers to Globice phala sp. and is identified

as such. The species boundary is considered to be in the

New Jersey to Cap e Hatteras a rea. Sightings no rth of this

area are likely G. melas. The short-finned pilot wh ale is

distributed w orldwide in tropical to w arm temp erate

waters (Leatherwood and Reeves 1983). The northern

extent of the range of this species within the USA

Atlantic Exc lusive Eco nomic Zo ne (EEZ ) is generally

thought to be Cape Hatteras, North Carolina

(Leatherwood a nd Reeves 19 83). Sightings of these

animals in USA Atlantic EEZ occur primarily within the

Gulf Stream [Southeast Fisheries Science Center

(SEFSC) unpublished data], and primarily 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 po pulation. 

POPU LATIO N SIZE

An abundance of 9,800 (CV=0.34) for

Globice phala 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 proba bility

of detecting a group on the track line. Aerial data were

not corrected for g(0).

An abundance of 4,724 (CV=0.61) for

Globice phala sp. was estimated from a shipboard line

transect sighting survey conducted between 8 July and 17

August 19 98 that surve yed 5,57 0 km of trac k 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 Globice phala sp. is the sum of the estimates from the two 1998

USA Atlantic surveys, 14,524 (CV=0.30), 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 surv eys have the m ost comp lete covera ge of the spe cies’ habitat.

Minimum Po pulation 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
84

as specified by Wade and Angliss (1997). The best estimate of abundance for Globice phala sp. is 14,524

(CV=0.30). The minimum po pulation estimate for Globice phala sp. is 11,343.

Current Population Trend

There are insufficient data to determ ine the population trends for this species.

CURRENT AND M AXIMUM NET PRODUCTIVITY RATES

Current and maximum net produ ctivity rates are unk nown for this sto ck. For pu rposes of this a ssessment,

the maximum net productivity rate was assumed to be 0.04. This value is based on theoretical modeling showing

that cetacean populatio ns may not gro w at rates muc h greater than 4% give n the constrain ts of their repro ductive 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; W ade and Angliss 1997). The minimum

population size for Globice phala 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 m ortality estimate is b etween 0.3 -0.6 (Wade and Angliss 199 7), and be cause this stock is of unknown status. 

PBR for the western North Atlantic Globice phala sp. is 108.

ANNUAL HUM AN-CAUSED MOR TALITY

Total fishery-related mortality and serious injury cannot be estimated separately for the two species of pilot

whales in the USA 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 to this stock during 1995-1999 in the USA fisheries listed below was 237

pilot whales (CV = 0.44) (Table 2). The Canadian average annual mortality estimate for 1995-1996 from the Nova

Scotia trawl fishe ries is 8 long-finne d pilot whale s. It is not possible to estimate variance of the Canadian estimate. 

The total average annual mortality estimate for 1995-1999 from the USA and Nova Scotia trawl fisheries is 245

(Table 1).

Fishery Information

USA

The leve l of past or current, direct, hum an-caused mortality of sho rt-finned pilot wh ales in the US A Atlantic

EEZ is un known. T he short-finned pilot whale ha s been taken in the pelagic lo ngline fishery in Atla ntic waters off

the southeastern USA (Lee et al. 1994; SEFSC unpublishe d 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). DW F effort in the Atlantic coast EEZ under

MFCM A has been directed primarily towards Atlantic mackerel and squid. An average of 120 different foreign

vessels per year (range 102-161) operated within the Atlantic coast EEZ during 1977 through 1982 . In 1982, there

were 112 different foreign vessels; 18 (1 6%) we re Japane se tuna longline vessels ope rating along the USA A tlantic

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 USA Atlantic EEZ each year

between 1983 and 1991 averaged 33 and ranged from nine to 67. The number of Japanese longline vessels included

among the DWF vessels averaged six and ranged from three to eight between 1983 and 1988. MFCMA o bserver

coverage on DW F vessels was 25-35% during 1977-82, increased to 58%, 86% , 95%, and 98%, respectively, during

1983-86, and 100% observer coverage was maintained from 1987-91. Foreign fishing operations for squid ceased at

the end of the 1986 fishin g season an d, for mack erel, at the end of the 199 1 fishing seaso n. 

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%)
85

occurred during Loligo and Illex squid-fishing op erations. This total includes 48 doc umented ta kes by US A vessels

involved in joint venture fishing operations in which USA captains transfer their catches to foreign processing

vessels. Due to tempor al fishing restrictions, th e bycatch o ccurred d uring winter/spring (December to M ay) 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 (Globice phala sp.) are con sidered tog ether. 

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 pro vided observer coverage of pelagic longline vessels fishing off the

Grand Ba nks (Tail of the Banks) an d provides ob server coverage of vesse ls fishing south of Cape Hatteras.

Bycatch h as been o bserved b y NMF S Sea Samplers in the p elagic drift gillnet, pe lagic longline, an d pelagic

pair trawl fisheries, but no mortalities or serious injuries have documented in the Northeast multispecies sink gillnet

or mid-Atla ntic coastal sink g illnet.

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 intr oduction of quotas, effo rt was severely re duced. T he estimated number o f hauls in

1991, 1992, 1993, 1994, 1995, 1996, and 1998 were 233, 243, 232, 197, 164, 149, and 113 respectively. In 1996

and 199 7, NM FS issued m anageme nt regulations w hich prohib ited the ope ration of this fishery in 1 997. Further, in

January 1999 NMFS issued a Final Rule to prohib it 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

(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, 1997 (NA), 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, fro m 1989 to 1993 , were obta ined using the a ggregated (pooled 1989-1 993) ca tch 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 produ ct of the avera ge bycatch p er haul and th e number of unobse rved hauls a s recorde d in

self-reported fisheries information. Variances were estimated using bootstrap re-sampling techniques. Between

1989 and 1998, eighty-seven mortalities were observed in the large pelagic drift gillnet fishery. The annual

fishery-related mortality (CV in parenthese s) was 77 in 1 989 (0.2 4), 132 in 1990 (0 .24), 30 in 1 991 (0.2 6), 33 in

1992 (0 .16), 31 in 1 993 (0.1 9), 20 in 19 94 (0.06 ), 9.1 in 199 5 (0), 11 in 1996 (.1 7), 1997 (NA), and 12 in 199 8 (0).. 

Since this fishery no longer exists it has been excluded from Table 1. 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 Cap e Charles, V irginia, in June. P ilot whales were taken from H ydrograp her Canyo n along the G reat South

Channel to George s Bank from July-No vember. T akes occu rred at the O ceanogra pher Can yon contine ntal shelf

break and along the continental shelf northeast of Cape Hatteras in October-November.

Pelagic Pair Trawl

Effort in the pe lagic pair trawl fishe ry has increase d during the period 1 989 to 1 993, from zero hauls in

1989 a nd 199 0, to an estima ted 171 hauls in 199 1, and then to an estimated 536 hau ls in 1992, 5 86 in 199 3, 407 in

1994, a nd 440 in 1995, re spectively. This fishery ceased operation s in 1996 , when NM FS rejecte d a petition to

consider p air trawl gear as an authorize d gear type in Atlantic tunas fishe ry. The fishery o perated fro m AugustNovember 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 19 92 (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%,
86

respectively, of the sets were observed. Twelve vessels have operated in this fishery. The fishery extends from 35oN

to 41oN, and from 69°W to 72°W. Approximately 50% of the total effort was within a one degree square at 39oN,

72oW, aro und Hud son Canyo n. Examina tion of the loca tions and sp ecies composition of the bycatch, sho wed 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 (Globice phala sp.) mortalities were reported in the self-reported fisheries

information in 1993. In 1994 a nd 199 5 observ ers reporte d one and twelve morta lities, respectively. Sin ce this

fishery no longe r exists, it has been excluded from Ta ble 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 were inconclusive in identifying factors responsible for

marine mammal bycatch.

Pelagic Longline

Total effort, excluding the Gulf of M exico, for the p elagic longline fishery, based o n mandato ry selfreported fisheries information, was 11,279 sets in 1991, 10311 sets in 1992, 10444 sets in 1993, 11082 sets in 1994,

11493 sets in 1995, 9864 sets in 1996, 9499 sets in 1997, 7589 sets in 1998, and 6786 sets in 1999 (Cramer 1994;

Scott and Brown 1997; Johnson et al. 1999; Yeung 1999 a; 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 ob served, since 1992. T he 1993 -1997, estimated take w as based o n a revised a nalysis of 

the observed incidental take and self-reported incidental take and effort data, and replace previous estimates for the

1990-1993 and 19 94-1995 periods (Cramer 199 4; 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 b ycatch estimates were from Yeung (1999a) and Yeung et al. (2000), respectively. 

Most of the estimated marine mammal bycatch was from EEZ waters between 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 1992-1999 sixty-two pilot whales (including two identified as a short-finned pilot

whales) were released alive, including 3 2 that were considered seriously injured (of which one was ide ntified as a

short-finned pilot whale), and three 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 o f Hydrogr apher Ca nyon off the co ntinental shelf in wate r over 1,0 00 fathom s during Ap ril-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 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, and 288 (CV=0.74) in 1999, (includes 37

estimated short-finned pilot whales) in 1995 (CV=1.00); average annual mortality between 1995 and 1999 was 145

pilot whales (0.66) (Table 1). Seriously injured and released alive animals are combined with mortalities in the

category ‘co mbined m ortality’. 

Bluefin Tuna Purse Seine

The tuna purse seine fishe ry between C ape Ha tteras and Cape Co d is directed at small and m edium blu efin

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 a ircraft are used to locate fish sch ools. The official start date is A ugust 15, set b y 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
87

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, five p ilot whales were encircled in a set. The net w as opene d prior to p ursing to let the wh ales swim

free, appa rently uninjured . This set occ urred on th e Cultivator S hoals region on Geo rges Ban k. Since 19 96, this

fishery has not b een obse rved. 

North Atlantic Bottom Traw l 

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. T he estimated fishery-related mortality to pilot wh ales in the US A Atlantic attrib utable to this

fishery was: 0 in 1994-1998, and 228 in 1999. The average annual mortality between 1995-1999 was 46 pilot

whales (CV = 1.03) (Table 1). However, these estimates should be viewed with caution due to the extremely low

(<1% ) observe r coverag e. 

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, butterfish trawl fishery, and maintained a Category II classification. Three fishery-related mortality of pilot

whales were reported in self-reported fisheries information from the mackerel trawl fishery between 1990-1992. One

mortality was observed in the years 1996, 1998 and, 1999. 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), and 49 in 1999

(CV = 0.97); average annual mortality between 1996 and 1999 was 45 p ilot whales (CV=0.52) (Table 1). 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 Sam pling

program in July, 1993; and from July to December 1993, 20 trips were observed. During 1994 and 1995 221 and

382 trips w ere obser ved, respe ctively. This fishery, w hich extend s from No rth Carolina to New Y ork, is actually a

combina tion of small vessel fisheries that targe t a variety of fish spe cies, some o f which ope rate right off the be ach. 

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%, and 5% for 1995, 1996, 1997, and 19 98 (Table 1).

No pilo t whales were ta ken in obse rved trips d uring 199 3-1997 . One pilot w hale was ob served take n in

1998, and 0 in 1999 (Table 1). 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 1995-1999 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 Atlan tic Canadia n and Gr eenland sa lmon gillnet fishery is se asonal, with the p eak from J une to

September, depending on location. In southern and eastern Newfoundland, and Labrador during 1989, 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 a greement b etween Ca nada and North A tlantic Salmo n Fund (Read 199 4). 

There were 3,121 cod traps operating in Newfoundland and Labrador during 1979, and about 7,500 in 1980

(Read 1 994). T his fishery was clos ed at the end of 1993 due to colla pse of Can adian grou ndfish resour ces. 
88

Between January 1993 and Dece mber 1994, 36 Spanish deep-water trawlers, covering 74 fishing trips, were

observed in NAFO Fishing Area 3 (off the Grand Bank) (Lens 199 7). A total of 47 incidental catches were

recorde d, which includ ed one lo ng-finned pilo t whale. The incidental mo rtality rate for pilot wh ales was 0.0 07/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 N ova Scotia during 19 91-1996 va ried 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. Reco rded byc atches by yea r were: 16 in 1991, 2 1 in 1992 , 13 in 199 4, 9 in 199 5, and 6 in 1 996. Pilo t whale

bycatches occurred in all months except January-March and September (Hooker et al. 1997).
89

Table 1. Summary of the incidental mo rtality of pilot whales (Globicephala sp.) by commercial fishery including the

years samp led (Yea rs), the numb er of vessels ac tive within the fishery (V essels), the type o f data used (D ata

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

Estimate

d

Serious 

Injury

Estimated

 Mortality 

Estimated

Combined

Mortality

Estimat

ed

 CVs 

Mean

 Annual

Mortality

Atlantic 5

squid,

mackerel

, 

butterfish 

trawl

96-99

NA Obs.

 Data

Weighouts

.007, .008,

 .003, .004 

 0, 0, 0, 0 6, 0, 1, 1 45, 0, 

85, 49

 1.27,

0,

 .65,

.97

45

(.52)

N. Atl. 3,5

Bottom

Trawl

95-99 NA Obs.

 Data

Weighouts

.0114

, .002,

 .002, .001,

.003

0, 0, 0, 0,

0

0, 0, 

0, 0, 1

 0, 0,

 0, 0,

228

, 0, 0, 

0, 0,

1.03

46

(1.03)

Pelagic 6

Longline 95-99

277, 253, 

 245, 205, 

 1937

Obs. Data

Logbook

.04, .03,

.03,

 .03, .04

13, 0, 0,

 0, 4

0, 0, 0, 0, 1 345, 0, 0, 

0, 288

 0, 0, 0,

 0, 93

345, 0, 0, 

0, 381

0.51, 0,

0,

 0, 0.79

145

 (0.66)

MidAtlantic

Coastal

Gillnet 

95-99

NA Obs. Data

Weighouts

.05, .04,

 .03, .05,

.02

0, 0, 0, 0,

0

0, 0, 0, 1,

0

0, 0, 0, 7,

0

0, 0, 0,

 1.1,

0

1

(1.1)

Nova

Scotia

trawl

fisheries

95-96

NA Obs. Data NA,

 NA

 0, 0, 0, 0 9, 6 9, 6 NA,

 NA

8

(NA)

TOTAL

245

(0.44)

1 Observer data (O bs. Data) are used to m easure bycatch rates, and the da ta are collected within the Northea st

Fisheries Science Center (NEFSC) Sea Sampling Program. M andatory 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. Th e trawl fisheries are measured in trips.

3

 1995 estimate not av ailable for the squid, mackerel and butterfish subfisheries.

4 Observer coverage for the Atlantic bottom trawl fishery in 1995 is based on only January to May data.

5

In 1997 and 1998 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.

6

 1995-1999 Mortality estimates were taken from Table 9a in Yeung et al. (NMFS Miami Laboratory PRD

99/00-13), and exclude the Gulf of Mexico.

7 Number of vessels in the fishery are based on vessels reporting effort to the pelagic longline logbook.

Other M ortality

Pilot whales have a prop ensity to mass strand throughout their range, bu t the role of human activity in these

events is unkno wn. Betwe en two and 120 pilo t whales have stranded a nnually either ind ividually or in gro ups in

NMFS Northeast Region (Anon. 1993b) since 1980. From 1992-1998, 71 long-finned pilot whale stranded

between South Carolina and Ma ine, including 22 animals that mass stranded in 1992 along the M assachusetts coast

(NM FS unpu blished da ta). 
90

In eastern Canada, 37 strandings of lo ng-finned pilo t whales (17 3 individua ls) were repo rted on Sa ble

Island, No va Scotia fro m 1970 -1998 (L ucas and H ooker 1 997; Luc as and H ooker 2 000). T his included 130 anim als

that mass strand ed in Dec ember 1 976, and two smaller gr oups (<1 0 each) in au tumn 197 9 and sum mer 199 2. 

Fourteen strandings were also recorded along Nova Scotia from 1991-1996 (Ho oker 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 stand ing group tha n animals of the same sex o r age. Also, hig h 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 ). The po pulation effec t of the observ ed levels of suc h contamin ants is unknow n. 

STATUS OF STOCK

The status of long-finned pilot whales relative to OSP in USA 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 1 971, and increased a bundanc e of herring, mackerel, and squid stock s. There ar e 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 con sidered to be insignificant and app roaching zero mo rtality and serious injury rate. This is a

strategic stock b ecause the 1 995-19 99 estimate d average annual fishery-rela ted mortality, ex cluding N ova Sco tia

bycatches to pilot whales, Globice phala sp., exceeds PBR.

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19 pp. 
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Lens, S. 19 97. Interac tions betwee n marine mammals an d deep w ater trawlers in the NAFO regulatory are a. ICES

CM 1997/Q:8. 10 pp.

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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,

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trawl fisheries. Final report to the Northeast Fisheries Science Center, Contract No. 40ENNF500160.

Palka, D . 1995. A bundanc e estimate of the Gulf of M aine harbo r porpo ise. Rep. int Whal. Commn. (Special Issue

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Workshop April 3-5, 1996, Seattle, Washington. U.S. Dep. Commer., NOAA Tech. Memo. NMFS-OPR12, 93 pp.

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off the northea stern USA shelf. ICES Marine M ammals Comm. CM 1992/N :12, 29 p p. 

Waring, G. T. 1998. Results of the summer 1991 R/V Chapman marine mammal sighting survey. NOAA NMFS

NEFSC, Lab. Ref. Doc. N o. 98-09 , 21pp. N ortheast Fishe ries Science Center, W oods H ole, Ma ssachusetts. 

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.

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mamma l stock assessm ents — 1 999. U .S. Dep. Commer., N OAA T ech. Memo NM FS-NE -153, 19 6pp. 

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biphenyls an d chlorinate d pesticide s in northwest A tlantic pilot whale s. Environ. Toxicol. Chem.

19:667-677.

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in 1998. NOAA Technical Memorandum NMFS-SEFSC-430, 26 pp.

Yeung, C. 1999b. Revised M ortality Estimates of Marine Mammal Bycatch in 1992-1997 based on Serious Injury

Guidelines. NOAA Technical Memorandum NMFS-SEFSC-429, 23 pp.

Yeung, C., S. Eppe rly, and C. A. B rown. 200 0. Prelimina ry revised estimates of marine mamma l 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.
92

Figure 1. Distribution of white-sided dolphin sightings

from NEFSC and SEFSC shipboard and aerial surveys

during th e summ er in 199 0-199 8. Isobaths are at 100 m

and 1,0 00 m. 

November 2001

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 she lf waters to the 10 0 m dep th contour. T he species inh abits waters from central we st Greenlan d to

North Carolina (about 35o

 N) and perhaps as far east as 43o

 W (Evans 1987 ). Distribution of sightings, strandings

and incidental takes suggests the possible existence of three stock units: a Gulf of Maine, 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. 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 rep orted in G askin (199 2), is evident in S mithsonian stra nding reco rds, and wa s seen during abundan ce surveys

conduc ted in summers 1995 and 199 9 that cove red waters fro m Virginia to the entrance o f the Gulf of St. La wrence. 

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 reco rded in the waters between these two regions.

The Gulf of Maine stock of white-sided dolphins are most common in continental shelf waters from Hudson

Canyon (a pproxim ately 39°N ) north throu gh Geor ges Bank , and in the G ulf of Maine to the lower B ay 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 (P ayne and H einemann 1990). S ightings 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 do lphins in

USA waters were found primarily offshore on the

continental slope, while white-beaked d olphins (L.

albirostris) were found on the contin ental shelf. 

During the 1 970's, there w as an app arent 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). 

POPU LATIO N SIZE

The total number of white-sided dolphins

along the ea stern USA and Can adian Atlan tic coast is

unknown, although five estimates from select regions

are available: 1) from spring, summer and autumn

1978-8 2, 2) July-Sep tember 1 991-92 , 3) June-July

1993, 4) July-Sep tember 1995 , and 5) July-August

1999 (Table 1; Figure 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
93

continental shelf and shelf edge waters between Cape Hatteras, North Carolina and Nova Scotia (Table 1; CETAP

1982).

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 po pulation size is a weighted-average o f the 1991 and 1 992 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 2,000m 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 collec tion and ana lysis methods u sed were d escribed in Palka (19 96). 

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 cond ucted from a ship and a n airplane co vering waters from Geo rges Ban k to the mou th

of the Gulf of S t. Lawrence (Table 1 ; Figure 1; D . Palka, pers. comm.). T otal track line len gth was 8,21 2 km. 

Similar to that us ed in the abo ve 1995 survey, shipbo ard data w ere analyzed using the mod ified direct du plicate

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 w hite-sided do lphins were se en. 

Kingsley and Reeves (1 998) estim ated there w ere 11,7 40 (CV =0.47) white-sided d olphins in the G ulf of St.

Lawrence during 19 95 and 5 60 (CV =0.89) white-sided d olphins in the n orthern G ulf of St. Lawren ce during 1 996. 

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 an d August. D ata were ana lyzed using Q uenouille’s

jackknife bias reduction pro cedure on line transect metho ds that model the left truncated sighting curve. T hese

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 co verage of the known hab itat.
94

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 N. Gulf of Maine and lower Bay of Fundy 20,400 0.63

Jun-Jul 1993 George s Bank to S cotian shelf, shelf ed ge 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

Minimum Po pulation 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 a re insufficient data to determin e popula tion trends for this species. 

CURRENT AND M AXIMUM NET PRODUCTIVITY RATES

Current and maximum net produ ctivity rates are unk nown for this sto ck. Life history pa rameters tha t 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 sex ual maturity is 23 0-240 cm for males, a nd 201 -222 cm for females; ag e at sexual ma turity 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 maxim um repo rted age for m ales is 22 years and for females, 27 years (Sergean t et al. 1980). 

For purp oses of this assessment, the ma ximum net p roductivity rate was assume d to be 0.0 4. This valu e 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; W ade and Angliss 1997). The minimum

population size is 37,904 (CV=0.38). The maximum p roductivity rate is 0.04, the default value for cetaceans. The

“recovery” factor, which a ccounts for e ndangere d, deplete d, threatened , or stocks of un known status r elative 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.
95

ANNUAL HUMAN-CAUSED MORTALITY AND SERIOUS INJURY

Fishery Information

Recently, within USA waters, white-sided dolphins have been caught in the Northeast sink gillnet, midAtlantic 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 1995-1999 was 136

(CV=0.52) 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 six takes of white-sided dolphins of which two carcasses were necropsied for biological studies (Gilbert and

Wynne 1987; G askin 199 2). 

Atlantic foreign mackerel

NMF S foreign fisher y observers have repo rted 44 tak es of Atlantic wh ite-sided do lphins inciden tal to

fishing activities in the continental shelf and continental slope waters between March 1977 and December 1991

(Waring et al. 1990; N MFS unpublishe d data). O f these animals, 9 6% wer e taken in the A tlantic macke rel fishery. 

This total includes nine 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 w hich record ed fishery data and information of incide ntal bycatch o f marine mam mals. DW F effort in

the USA Atlantic Exc lusive Eco nomic Zo ne (EEZ ) under M FCM A had be en directed primarily towa rds Atlantic

mackerel and squid. From 1977 through 1982, an average of 120 different foreign vessels per year (range 102-161)

operated within the Atlantic coast EEZ. In 1982, there were 112 different foreign vessels; 16%, or 18, were

Japanese tuna longline vessels o perating 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 Atlantic coast 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; 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 199 7, NM FS issued m anageme nt regulations w hich prohib ited the ope ration 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 1998, two 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 1 990; there after, with the introd uction of qu otas, effort was se verely

reduced . The estima ted numb er of hauls in 19 91 to 19 96 were 2 33, 243 , 232, 19 7, 164, an d 149 re spectively. 

Fifty-nine different ve ssels participa ted in this fishery at on e time or ano ther betwee n 1989 and 199 3. In 199 4 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 19 96, no fishery in 1997, and 99% cov erage during 199 8. Observer cov erage dropp ed during 199 6 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

compo sition of the catch and locatio ns of the fishery thro ughout the yea r, suggested tha t 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 p roduct of the average b ycatch per h aul and the number of un observed hauls as reco rded in

logbooks. Variances were estimated using bootstrap re-sampling techniques (Bisack 1997b). Estimated annual
96

fishery-related mortality and serio us injury (CV in parenthese s) was 4.4 (.7 1) in 198 9, 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.

USA

Northeast Sink Gillnet 

Between 1990 a nd 199 9 there were 44 morta lities observed in the Northe ast sink gillnet fishery (T able 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

time) in the No rtheast sink gillnet fisher y (Wald en 1996 ). During 19 98 it was estimated there w ere 301 full and parttime vessels participating in this fishery. This is the number of unique vessels in the com mercial 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 num ber was missing. Observe r coverage, expressed as a

percentage of the number of trips, has been 1%, 6%, 7%, 5%, 7%, 5%, 4%, 6%, 5%, and 6% for years 1990 to 1999,

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 (0.6 1) in 199 6 (Bisack 1997a ), 140 (0.6 1) in 199 7, 34 (0.9 2) in 199 8, and 69 (0.70) in 1 999. 

Average annual estimated fishery-related mortality during 1995-1999 was 87 (0.35) white-sided dolphins per year

(Table 2).

Mid-Atlantic Coastal Gillnet

One white-sid ed dolp hin was obs erved take n in this fishery during 1997 (T able 2). N one were ta ken in

observed trips during 1 993 to 1 996, and none in 19 98 and 1 999. In Ju ly 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 Ca rolina to New Yo rk, is actually a combination of small vessel fisheries that target a variety of fish

species, som e of the vessels o perate right o ff the beach, some using drift nets, and others using sink nets attac hed to

the bottom. During 1998, it was estimated 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 da tabase (W eighout) that re ported ca tch from this fishery d uring 199 8 from the sta tes of Conn ecticut to

North Carolina. Th is does not inc lude a small p ercentage o f records wh ere the vessel n umber wa s missing. 

Observer coverage, expressed as percent of tons of fish landed, was 5%, 4%, 3%, 5%, and 2% for 1995 to 1999,

respectively (Table 2). Observed fishing effort was concentrated off New Jersey and scattered between Delaware

and 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 mo rtality (CV in parentheses)

attributed to this fishery was 0 for 1993 to 1996, 1998, and 1999 , and 45 (0.82) for 1997. However, because the

spatial-tempo ral distribution o f observer c overage d id not cove r all types of gillnet fisheries in the mid-A tlantic

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 1995 to 1 999 was 9

(CV=0.82) (Tab le 2).

North Atlantic Bottom Trawl

Becaus e there have been no o bserved ta kes of white-side d dolph ins in this fishery during 1995 to 1999, in

the next report this section will be moved to the “Earlier Interactions” section above. Three mortalities were

documented between 1991 and 1999 in the North Atlantic bottom trawl 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, though at a low level. The observer coverage was 0.4% in 1994, 1.1% in 1995, 0.2%

in 1996 , 0.2% in 1 997, 0.1 % in 199 8, and 0.3 % in 199 9. Vessels in th e North A tlantic 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 1 989-19 93. The fishery is active in N ew Englan d waters in all sea sons. The one white-side d dolph in

taken in 1992 was taken in a haul that was composed of 43% cod, 20% silver hake, and 17% p ollock. 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 ha ul that kept seve n species o f which none were dom inant. The e stimated fishery-re lated morta lity in
97

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 1995-1999 was 0 white-sided dolphins (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-fishe ry is mostly in southe rn New E ngland, N ew York and mid-A tlantic

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-fishe ry is primarily on th e continenta l slope durin g June to

September. The mackerel sub-fishery during January to May is primarily in the southern New England and midAtlantic waters, while during M ay to Dece mber, it is primarily in the Gulf of M aine. Butterfish is p rimarily a

bycatch of the squid and mackerel su b-fisheries. Bu tterfish migrate no rth and insho re during the su mmer, and south

and offshore during the winter. In 1995, the squid, mackerel, butterfish trawl fishery was classified as a Category II

fishery. Obse rver cove rage was ve ry low; expre ssed as per centage of trip s observed , it was 0.7% in 1996, 0 .8% in

1997, 0.3% in 1998, and 0.4% in 1999. The bycatch, stratified by sub-fishery, 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, 1 61 (CV =1.58) in 1997, a nd 0 in 19 98 and 1 999. The average annual estima ted fisheryrelated mortality during 1996 to 1999 was 40 (CV=1.58) (T able 2).
98

Table 2. Summary of the incidental mo rtality 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 Mo rtality), 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 95-99

1993=349

1998=301

Obs. D ata

 Weighout

Trip Logbook

 .05, .04,

.06,.05, .06

 23, 23,,

4

3

, 13, 43

 803,1143,

1403,343, 693

 1.16,.61,

.61,.92,.70

87

(0.35)

Mid-A tlantic

Coastal Gillnet

95-99 1998=3027 Obs. D ata

 Weighout

.05, .04, 

.03, .05, .02

0, 0,

1 ,0, 0

0, 0, 

45, 0, 0

0 , 0 ,

.82, 0, 0

9

(0.82)

North A tlantic

Bottom Trawl 95-99 1993=970

Obs. D ata

 Weighout

.0114,.002,

.002, .001,

.003

0, 0,

 0, 0, 

0

 0, 0, 

0, 0, 

0

 0, 0,

 0, 0,

 0

0

(0.0)

Squid, M ackerel,

 Butterfish

 Trawl

96-99 Unk6 Obs. D ata

 Weighout

.007, .008,

.003, .004

0, 15

,

0, 0

0, 1615

,

0, 0

0, 1.585

,

0, 0

40

(1.58)

Total 136

.52

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 (Trip Logbook) data are used to determine the spatial

distribution o f fishing effort in the sink gillne t 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 th at year. Durin g 1998 and 199 9, a weighted bycatch rate w as applied to effort from b oth

pingered and non-p ingered ha uls within the stratum where white-sid ed dolp hins were ob served take n..

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, and 1998.

4 Observer coverage for the Atlantic bottom trawl fishery in 1995 is based on only January to May data (the

only time takes w ere obser ved). 

5 The ob served take was in the mac kerel sub-fisher y.

6 Number of vessels is unknown.

7 Number o f sink gillnet vessels, undetermined number o f drift gillnet vessels.

CANADA

There is little info rmation ava ilable which q uantifies fishery interac tions involving w hite-sided do lphins in

Canadian waters. Two white-sided dolphins were reported caught in groundfish gillnet sets in the Bay of Fundy

during 1985 to 1989, and nine were reported taken in West Greenland between 19 64 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-o perationa l Newfoun dland and Labrad or ground fish gillnets. A few wer e taken in an ex perimenta l drift

gillnet fishery for salmon off West Greenla nd which to ok place fro m 1965 to 1982 (Read 1 994). 

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 (gre ater than 10 0 feet long), an d on app roximately 5 % of sma ller Canad ian fishing vessels. B y-
99

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 eac h species. D uring 199 1 through 1 996, it was e stimated six wh ite-sided do lphins were o bserved ta ken. 

One take was from a long line trip south of the Grand Banks (43° 10'N 53 ° 08'W) in November 199 6. The other five

were taken in the bottom trawl fishery off No va Scotia in the Atlantic Oc ean: 1 in July 1 991, 1 in A pril 1992 , 1 in

May 1992,1 in April 1993, 1 in June 1993 and 0 in 1994 to 1996.

Other M ortality

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 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.

During 1997, there were 17 recorded stranded white-sided dolphins, of which 16 died and one was released

alive (from Rhode Island during February), according to the NE Regional Office/NMFS strandings and entanglement

database . One strand ing was in Virg inia during M arch, the rest we re from M aryland to M aine during J anuary 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, 1 and 4 were recorded

during January, Februa ry, April, May, and No vember, respectively. The re were 70 animals found in a mass

stranding, near Wellfleet, Massachusetts, during the week of January 29 to February 3. Of these, two were released

alive. Of the four found during the November mass stranding, one was released alive.

The NE Regional O ffice/NMFS strandings and entanglement records of small cetaceans are currently being

audited. When this is complete, updates will be provided.

CANADA

Whales and dolphins stranded during 1991 and 19 96 on the coast of Nova Scotia were documented by the

Nova Scotia Stranding Network (Hooker et al. 1997). S trandings on the beache s of Sable Isla nd during 1 970 to

1998 w ere documented b y researchers from De pt. of Fisheries a nd Oce ans, Canad a (Lucas an d Hoo ker 200 0). Sable

Island is app roximately 1 70 km so utheast of ma inland No va Scotia. T he white-sided dolphins stra nded at ne arly all

times of the year on the mainland and on Sable Island. On the mainland of Nova Scotia, a total of 34 stranded

white-sided dolphins were recorded between 1991 and 1996 (T able 3). During July 1992, 26 white-sided dolphins

stranded o n the Atlantic sid e of Cape Breton. O f these 26, 11 were release d alive and the rest were fo und dead . 

Among the rest of the Nova Scotia strandings, one was found in Minas Basin, two near Yarmouth and the rest near

Halifax. On Sable Island, 10 stranded white-sided dolphins were documented between 1991and 1998. All were

males, seven were young males (< 200 cm) (Table 3).
100

Table 3. Docum ented number of strand ed white-side d dolph ins, by month a nd year, alon g the coast o f Nova S cotia

(Hooker et al. 1997), and on Sable Island (Lucas and Hooker 20 00).

Year Month Number of strandings

Nova

Scotia

Sable

Island

1991 Aug 1 0

Oct 1 0

1992 Jul 26 0

1993 Jan 0 1

Mar 0 5

Nov 1 0

1994 Feb 1 0

Nov 1 0

1995 Apr 1 0

Aug 1 1

1996 Oct 1 0

Dec 0 1

1997 April NA 1

1998 Feb NA 1

TOTAL 34 10

NA = Not available.

STATUS OF STOCK

The status o f white-sided d olphins, relative to OSP , in the USA Atlantic EE Z is unknow n. The spe cies 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% o f the calculated PBR and, therefo re, cannot b e consider ed to be insig nificant and ap proachin g zero mo rtality

and serious injury rate. This is a non-strategic stock because estimated average annual fishery-related mortality and

serious injury d oes not exc eed PB R. 

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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.

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 199 5. Rep. int Whal. Comm 47: 705-14.

Bisack, K. D. 1997b. Marine mam mal bycatch estimates and their sampling distributions in the U.S. New England

sink gillnet, pair traw l, Atlantic pelagic drift gillnet and N orth Atlantic b ottom trawl fishe ries - 1994 to
101

1996. NOA A, NMFS, N EFSC. Wo ods Hole, MA. W orking 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 AA 51-C78 -48, Bure au of Land Manag ement, W ashington, D C, 538 p p. 

Evans, P . G. H. 19 87. The natural history o f whales and d olphins. Facts on File Publications, New Y ork, 343 pp. 

Gaskin, D . E. 1992 . Status of Atlantic w hite-sided do lphin, 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, National Marine Fisheries Service, Northeast Fisheries Science

Center, W oods H ole, Ma ssachusetts, 12 pp. 

Hain, J. H. W . and G. T. W aring. 1994. Status of and hu man effects upon marine m ammals. 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. N MFS -NE-10 6, Northe ast Fisheries Sc ience Cen ter, Wo ods Ho le, Massac husetts. 

Hooker, S. K., R. W. Baird and M . A. Showell. 1997. Cetacean strandings and bycatches in Nova Scotia, Eastern

Canada, 1991-1996. M eeting 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 Newfo undland. Smithsonian Institution Press, Washin gton, 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.

Sherman, N.A. Jaworski and T. Smada (eds.). The northeast shelf ecosystem: assessment, sustainability, and

managem ent. 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. Z ool. 76:1529-1550.

Lucas, Z. N . and S. K. H ooker. 20 00. Cetac ean strandin gs on Sab le Island, No va Scotia, 1 970-19 98. 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 Northeast Fisheries Science Center, 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 n orthwest Eu ropean a nd U.S. N orth

Atlantic waters. Rep. int.Whal. Commn 47:797-805.

Palka, D. 1995. Abundance estimate of the Gulf of Maine harbor porpoise. pp. 27-50 In: A. Bjørge and G.P.

Dono van (eds.) B iology of the P hocoen ids. Rep. int Whal. Commn Special Issu e 16. 

Palka, D . 1996. U pdate on abundan ce of Gulf o f Maine/B ay of Fundy h arbor po rpoises. N OAA/N MFS /NEFSC Ref.

Doc. 96-04; 37 pp. Available from: National Marine Fisheries Service, 166 Water Street, Woods Hole,

MA 02543-1026.

Palka, D., A. Read and C. Potter. 199 7. Summary of kno wledge of white-sided dolp hins (Lagenorhynchus acutus)

from the U .S. and Ca nadian N orth Atlantic w aters. Rep. int Whal. Commn 47: 729-34.

Palka, D. 2000. Abundance of the Gulf of Maine/Bay of Fundy harbor porpoise based on shipboard and aerial

surveys during 1999. NOAA/NM FS/NEFSC Ref. Doc. 00-07; 29 pp. Available from: National Marine

Fisheries Service, 166 Water Street, Woods Hole, MA 02543-1026.

Palka, D ., G. Wa ring and D . Potter. (in revie w). Abund ances of ce taceans and sea turtles in the no rthwest Atlantic

during summer 199 5 and 19 98. 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 Scie nce Cente r, Woo ds Hole, M assachusetts. 
102

Read, A . J. 1994. In teractions be tween cetac eans and g illnet and trap fishe ries in the northw est Atlantic. Rep. int

Whal. Commn Special Issue 15: 133-147. 

Sergeant, D . E., D. J. St. A ubin and J. R. Gerac i. 1980. Life h istory and no rthwest Atlantic sta tus of the Atlantic

white-sided d olphin, Lagenorhynchus acutus. Cetolog y 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.

Wald en, J. 1996 . The Ne w England gillnet effort study. N OAA, N MFS , NEFSC Ref. Do c. No. 96 -10, 38 p p. 

Northea st Fisheries Scie nce Cente r, Woo ds Hole, M assachusetts. 

Waring , G. T., P. G errior, P. M . Payne, B. L. Parry, and J. R. Nico las. 1990 . Incidental take of marine mammals in

foreign fishery ac tivities off the northea st United Sta tes, 1977 -1988. Fish. Bu ll., U.S. 88(2): 347-360.
103

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 . 

November 2001

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 200-300 m 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 1 994). Info rmation reg arding com mon do lphin stock stru cture in the weste rn North A tlantic does no t exist. 

However, a high variance in skull morphometric measurements suggests the existence of more than a single stock (J.

G. Me ad, pers. co mm.). 

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 (CET AP 1982; Selzer and Payne 19 88; 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 midJanuary to May (Hain et al. 1981; CETAP 1982;

Payne et al. 1984). Common dolphins move

northward onto Ge orges Ba nk and the S cotian She lf

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 M aine, 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 (S ergeant et al. 1970; Gowans and Whitehead

1995).

POPU LATIO N 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

conduc ted from 1 978 to 1 982 on the continenta l,

shelf and shelf edge waters between Cape Hatteras,

North Carolina and Nova Scotia (CETAP 1982). An

abundance of 22,215 (CV =0.40) common do lphins

was estimated from a June and July 1991 shipboard line transect sighting survey conducted primarily between the

200 and 2,000m isobaths from Cape H atteras to Georges Bank (Waring et al. 1992; Waring 1998). As

recommended in the GAM S Workshop Re port (Wade and Angliss 1997), estimates older than eight years are
104

deemed unreliable, therefore should not be used for PBR determinations. Further, due to changes in survey

methodo logy these da ta should no t be used to m ake comparisons to more curr ent estimates. 

 An abundance of 1,645 (CV =0.47) common do lphins 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

George s Bank, ac ross the No rtheast Chan nel to the south eastern edg e of the Sco tian Shelf (Table 1; An on. 199 3). 

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 bo otstrap resampling technique s.

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 de pth contou r line. Data co llection and a nalysis method s used were described in Palka (19 96). 

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 d olphins 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 Maryla nd (38°N ) (Mullin in re view). 

Although the 1991, 1993, 1995, and 19 98 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 hab itats off the northea stern USA coast. The 1993, 1 995, and 1998 d ata suggest that, se asonally,

at least several thousand comm on dolphins are oc cupying continental shelf edge waters, with perha ps highest

abunda nce in the G eorges 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 A tlantic 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

Jun-Jul 1993 George s Bank to S cotian shelf, shelf ed ge only 1,645 0.47

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 Po pulation 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).
105

Current Population Trend

There a re insufficient data to determin e the pop ulation trends for this species. 

CURRENT AND M AXIMUM NET PRODUCTIVITY RATES

Current and maximum net produ ctivity rates are unk nown for this sto ck. For pu rposes of this a ssessment,

the maximum net productivity rate was assumed to be 0.04. This value is based on theoretical modeling showing

that cetacean populatio ns may not gro w at rates muc h greater than 4% give n the constrain ts of their repro ductive 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; W ade and Angliss 1997). The minimum

population size is 23,655 (CV=0.32). The maximum p roductivity 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 p opulation ( OSP) is assumed to be 0.48 because the CV of the average mortality estimate is

between 0 .3-0.6 (W ade and Angliss 199 7) , and be cause 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 1995-1999

was 406 common do lphins CV=0.45; 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 Atlantic coast EEZ. In 1982, there were

112 differe nt foreign vesse ls; 16%, o r 18, were J apanese tu na longline ve ssels opera ting along the U SA east co ast. 

This was the first year that the Northeast Regional Observer Program assumed responsibility for observer coverage

of the longline vessels. Between 19 83 and 199 1, the numbers of foreign vessels op erating within the Atlantic coast

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 1983-1986. From

1987-1991, 100% observer coverage was maintained. Foreign fishing operations for squid and mackerel ceased at

the end of the 1986 a nd 199 1 fishing seaso ns, respective ly. 

During the period 1977-1986, observers recorded 12 3 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 continenta l shelf edge (1 00 m) isob ath during win ter (December to F ebruary). 

From 1977-1991 , observers recorded 110 mortalities in foreign mackerel-fishing operations (Waring et al.

1990; NM FS 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/sp ring (Dece mber to M ay). 

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 pro vided observer coverage of pelagic longline vessels fishing off the

Grand B anks (Ta il of the Bank s) and pro vides obse rver cove rage of vesse ls fishing south of Cape Ha tteras. 
106

Bycatch h as been o bserved b y NMF S Sea Samplers in the p elagic drift gillnet, pe lagic pair trawl, p elagic

longline fishery, mid-Atlantic coastal gillnet, North Atlantic bottom trawl, Northeast multispecies sink gillnet, and

Atlantic squid , mackerel, b utterfish trawl 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 intr oduction of quotas, effo rt was severely re duced. T he estimated number o f hauls in

1991, 1992, 1993, 1994, 1995, 1996, and 1998 were 233, 243, 232, 197, 164, 149, and 113 respectively. In 1996

and 199 7, NM FS issued m anageme nt regulations w hich prohib ited the ope ration of this fishery in 1 997. Further, in

January 1999 NMFS issued a Final Rule to prohib it the use of driftnets (i.e., permane nt closure) in the North A tlantic

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 o f sets observe d, was 8% in 1989, 6 % in 199 0, 20% in 1991, 4 0% in 19 92, 42% in

1993, 87% in 199 4, 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 1 989 and 1998 in th is fishery. Mortalities were ob served in all sea sons and a reas. 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 Tables 2 and 3 (see W aring 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 199 0, to an estima ted 171 hauls in 199 1 and then to an estimated 536 hau ls in 1992 a nd 586 in 1993, 4 07 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 to November in 1991,

from June to November in 19 92, from J une to Oc tober in 19 93 (No rthridge 19 96), and fro m mid-summer to

December in 1994 & 1995. Sea sampling began in October of 1992 (G errior 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. Twelve mortalities were observed between 1991

and 199 5. The estimated ann ual fishery-related mortality and se rious injury attrib utable to this fisher y (CV in

parenthese s) was 5.6 in 1 991 (0.5 3), 32 in 19 92 (0.48 ), 35 in 199 3 (0.43), 0 in 1994 (0), 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 b een prese nted at Offsho re Cetace an Take Reductio n Team Meetings. 

Pelagic Longline

 Total effort, excluding the Gulf of M exico and fishing regions ea st 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,

and 5,832 sets in 1999 (Cramer 1994; Sco tt and Brown 1997; Johnson et al. 1999; Yeung 1999 a; Yeung et al. 2000).

 Since 19 92, this fishery has been mo nitored with a bout 5% observer coverage , in terms of trips o bserved, w ithin

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. This fishery has been monitored with about 5% observer
107

coverage, in terms of trips observed, since 1992. 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 19 94-1995 periods (Cramer 199 4; 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 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). Between 1990-1999 fifteen common

dolphins were hooked and released alive (Yeung et al. 2000).

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 covere d by the ob server pro gram (W alden 19 96) 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%, and 6% for 1990 to 1999,

respectively. The fishery has been o bserved in the Gulf of M aine and in Southern N ew England. In 19 96, the first

observed mortality of common d olphins in this fisher y was record ed. The e stimated ann ual fishery-related mortality

and seriou s injury attributab le to this fishery (CV in parenthese s) was 0 in 19 95 (0), 63 in 1996 (CV=1 .39), 0 in

1997 (0), 0 in 1998 (0) and 146 in 1999 (0.97); estimated annual mortality (1995-1999) was 42 common dolphins

(CV=0.78) (Table 2). Annual estimates of common dolphin bycatch in the Northeast multispecies sink gillnet

fishery reflect seaso nal distribution of the species and of fishing effo rt.

Mid-Atlantic Coastal Gillnet

Observer coverage of the USA Atlantic coastal gillnet fishery was initiated by the NEFSC Sea Sam pling

program in July, 1993; and from July to December 1993, 20 trips were observed. During 1994 and 1995, 221 and

382 trips w ere obser ved, respe ctively. This fishery, w hich extend s from No rth Carolina to New Y ork, is actually a

combina tion of small vessel fisheries that targe t a variety of fish spe cies, some o f which ope rate right off the be ach. 

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% , and 2% for 1995, 1996 , 1997, 1998, and 1999 respectively (Table 2).

No common d olphins were taken in observed trips during 1993 and 1994. Two commo n dolphin were

observed taken in 1995, 1996, and 1997 , and no takes were observed in 1998 and 1999 (T able 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 o bserved takes, the estimated ann ual mortality (CV in parentheses)

attributed to this fish ery was 7.4 in 1 995 (C V=0.6 9), 43 in 19 96 (0.79 ), 16 in 199 7 (0.53), and 0 in 19 98-199 9. 

Average annual estimated fishery-related mortality attributable to this fishery during 1995-1999 was 13 common

dolphins (CV=0.53)

North Atlantic Bottom Trawl

Vessels in the North A tlantic bottom trawl fishery, a Cate gory III fishery un der MM PA, were observed in

order to m eet fishery mana gement nee ds, rather than marine mammal man agement ne eds. An ave rage of 97 0 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- 1998. Observer coverage, expressed as number of

trips, was < 1% from 1994-1998 (T able 2). The estimated annual fishery-related mortality and serious injury

attributable to this fishery (CV in parenthese s) was 0 in 19 91, 0 in 19 92, 0 in 19 93, 0 in 19 94, 142 in 1995 ( 0.77), 0

in 1996 , 93 in 199 7 (1.06), and 0 in 19 98 and 1 999. Av erage annu al estimated fishe ry-related mo rtality attributable

to this fishery during 1995-1 999 was 47 common do lphins (CV =0.63) (Table 2 ). Howev er, these estima tes should

be viewed with caution due to the extremely low (<1%) observer coverage.
108

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 1996-1999 (Table 2). Three common dolphin mortalities were observed in 1996,

one in 1997, zero in 1998, one in 1999 (T able 2). The 1996 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 (0.49), 0 in 1998, and 49

in 1999 (0.78). Average annual estimated fishery-related mortality attributable to this fishery during 1996-1999 was

287 common do lphins (CV=0.62) (Table 2). However, these estimates should be viewed with caution due to the

extremely low (<1% ) observe r coverag e and unce rtainties regard ing numbe r of vessels pa rticipating in this "fishe ry". 

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. Seven teen common d olphin mortalities were observe d in March. T he 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 fish ing days and 14,211 sets), were ob served in N AFO F ishing Area 3 (off the Gran d Bank ) (Lens 19 97). A

total of 47 incidental catches were recorded, which included one common dolphin. The incidental mortality rate for

commo n dolphins was 0.007 /set.
109

Table 2. Summary of the incidental mo rtality of common dolphins (Delphin us delph is) 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

 95-99 349 Obs. D ata

 Weigho ut,

 Logbooks

0, 0, 0, 0,

 0

.05, .04,

.06, .05,

.06

 0, 1, 

 0, 0, 2

 0, 63, 0,

0, 146

 0, 1.39, 0,

0, .97

42

(.78)

Mid-A tlantic

Coastal G illnet 95-99

NA Obs. D ata

Weighout

0, 0, 0, 0,

 0

 .05, .04,

 .03, .05,

.02

2, 2, 2, 

0, 0

 7.4, 43, 

16, 0, 0

.69, .79,

 .53, 0, 0

13

 (.53) 

Atlantic squid,

mackere l,

butterfish trawl

96-99 NA Obs. D ata

 Weighout

0, 0, 0, 0 .007, .008,

 .003, .004

3 3, 1 3, 

0, 1 3

 940, 161,

 0, 49

 .75, .49,

 0, .78

287

(.62)

North A tlantic

Bottom Trawl

95-99 970 Obs. D ata

Weighout

0, 0, 0, 0,

 0

 .0114

 .002, .002,

 .001, .003

 3, 0,

 1, 0, 0

 142, 0,

 93, 0,

0

 .77, 0,

 1.06, 0,

0

 47

 (.63)

Mackerel

joint venture

98 4 Obs. D ata 0 1.00 17 17 0 17

(0)

TOTAL 406

(.45)

 1 Observer data (O bs. Data) are used to m easure bycatch rates, and the da ta are collected within the Northea st

Fisheries Science Center (NEFSC) Sea Sampling Program. NE FSC collects landings data (Weighout), and

total landings are used as a measure of total effort for the coastal gillnet fishery and days fished are used as

total effort for the N orth Atlantic b ottom trawl fishe ry.

2 The ob server cov erage for the North A tlantic bottom trawl fishery is in trips. 

3

 During 1996 and 1999 the observed common dolphins were taken in the Loligo squid otter trawl

subfisheries, and during 1997 the observed common dolphin was taken in the Atlantic mackerel otter trawl

subfishery. 

4 Observer coverage for the North Atlantic bottom trawl fishery in 1995 is based on January to May data.

Other M ortality

From 199 2-1998, 94 common d olphins were stranded b etween North Ca rolina and Massa chusetts,

predominantly along beaches in the latter state (NMFS unpublished data). The total includes ten and nine common

dolphins that, respectively mass stranded in November 1997 and January 1998 on Cape Cod.

Four common dolphin strandings (6 individuals) were reported on Sable Island, Nova Scotia from 1970-

1998, a nd all strandin gs have oc curred sinc e 1996 (Lucas and Hooke r 1997; L ucas and H ooker 2 000.) ). 

STATUS OF STOCK

The status of common 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 not less than

10% o f the calculated PBR and, therefo re, cannot b e consider ed to be insig nificant and ap proachin g zero mo rtality

and serious injury rate. This is a strategic stock because the 1995-1999 average annual fishery-related mortality and

serious injury e xceeds PBR. 
110

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112

Figure 1. Sightings of bottlenose dolphins during aerial

surveys from shore to the 25 m isobath north of Cape

Hatteras during summer 1994, shore to 9 km past the

western Gulf Stream wall south of Cape Hatteras during

winter 1992, three coastal surveys within o ne km of sho re

from New Jersey to mid-Flo rida durin g the sum mer in

1994, and during vessel surveys from about the 30 m

isobath to the offshore extent of the USA EEZ in 1998.

November 2001

BOTTLENOSE DOLPHIN (Tursiops truncatus):

Western North Atlantic Coastal Stock

STOCK DEFINITION AND GEOGRAPHIC RANGE

There are two distinct bottlenose dolphin ecotypes (Duffield et al. 1983; Duffield 1986; Mead and Potter

1995; Walker et al. 1999); a shallow water ecotype and a deep water ecotype which correspond to nearshore and

offshore forms, respectively. Both ecotypes have

been sho wn to inhab it waters in the weste rn North

Atlantic Ocean (Hersh and Duffield 1990; Mead and

Potter 19 95; Ho elzel et al. 1998; Walker et al. 1999). 

The inshore and offshore forms, of all age classes,

can be po sitively identified ba sed on differ ences in

morphometrics, parasite loads, and prey (Mead and

Potter 19 95). Ho elzel et al. (1998) found significant

differentiation between the nearshore and offshore

forms in both nuclear and mtDNA markers, and

concluded the two forms were distinct. Curry (1997)

concluded that, based on differences in mtDNA

haplotypes, the nearshore animals in the northern

Gulf of Mexico and the western North Atlantic were

significantly different stocks. Bottlenose dolphins

which had str anded a live in the western North

Atlantic in area s with direct acc ess to deep oceanic

waters had hemoglobin profiles matching that of the

deep, cold water ecotype (Hersh and Duffield 1990).

Hersh and Duffield (1990) also described

morpho logical differen ces betwee n the deep , cold

water ecotyp e dolphins and dolp hins with

hematological profiles matching the shallow, warm

water ecotype which had stranded in the

Indian/Banana Riv er in Florida . Because of their

occurrence in shallow, relatively warm waters along

the USA Atlantic coast and beca use their

morphological characteristics are similar to the

shallow, warm water ecotype described by Hersh and

Duffield (1990), the A tlantic coastal bottlenose

dolphin stock is believed to consist of this ecotype or

nearshore form. Furthe rmore, H oelzel et al. (1998)

genetically identified a sample of animals captured or

incidentally caught in nearshore waters as the

nearshore form. Curre ntly, data are insufficie nt to

allow separation of locally resident bo ttlenose

dolphins found in bays, sounds and estuaries (such as

those from the Indian/Banana River) from the coastal

stock in the we stern North Atlantic; Ho elzel et al.

(1998) found less variation in nuclear and mtDNA

markers am ong their sam ple of nearsh ore anima ls, which likely includ ed residen t and coasta l animals, than the ir

sample of offshore animals.

The structu re of the coa stal bottlenose dolphin sto ck in the western North A tlantic is uncertain, b ut what is

known about it suggests that the structure is complex. Some portion of the coastal stock migrates north of Cape

Hatteras, N orth Caro lina, to New J ersey during th e summer ( Scott et al. 1988). It has been suggested that this stock
113

Figure 5. Illustration of stock structure hypotheses of Atlantic coastal

bottlenose dolphins: one stock ranging from New Jersey to Florida or

multiple sto cks which may inc lude: 1) ye ar-roun d residen ts with sma ll

home ranges; 2 ) multiple, co ntiguou s, seasona lly resident g roups with

relatively large hom e ranges; and 3) groups with lon g-range m igratory

pattern. (Su = sum mer, Wi = win ter)

Location Year-round

Residents

Seasonal

Residents

Migratory/

Transient

Virginia Beach, VA No Jun-Sept Jun-Sept

Beaufort, NC, “coastal” No Oct-Apr ?

Beaufort, NC,

“estuarine” Possible large home

range

Wilmington, NC

Charleston, SC Yes fallwinter spring, fall

Bull Creek, SC Yes Yes

Table 1. Residency and movement patterns of

bottlenose dolphins documented from photoidentification (from Ho hn 199 7).

is restricted to waters < 25 m in depth within the northern portion of its range (Kenney 1990) because there are two

concentrations of animals north of Cape Hatteras, one inshore of the 25m isobath and the other offshore of the 25m

isobath, which were observed during

aerial surveys of the region (CETAP

1982) and vessel surveys (NMFS

unpublished data). The lowest density of

bottlenose dolphins was observed over

the continental shelf, with higher

densities along the coast and near the

continental shelf edge. The coastal stock

is believed to reside south of Cape

Hatteras in the late winter (Mead 1975;

Kenney 1 990); ho wever, the d epth

distribution of the stock south of Cape

Hatteras is uncertain and the coastal and

offshore stocks may overlap there. 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 ).

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 den sity patterns along the USA A tlantic coast. Figure 1 illustrates the distribution of 696 bottlenose

dolphin herd sightings during aerial and vessel surveys conducted during 1992-1998. The proportion of the

sightings illustrated w hich might be of bottlenos e dolphins from other th an the coasta l stock is unkno wn; howeve r, it

is reasonab le to assume th at the coastal su rveys within one km of shore minimized inclusion of the o ffshore stock. 

Gathering information to distinguish between coastal and offshore ecotypes is currently an active area of research by

NMF S Southeast Fisheries Science Center (SEFSC), as is research to determine the relationsh ip between bottlenose

dolphin that inhabit bays, sounds and estuaries and those

that are believed to comprise the coastal stock (Hohn

1997).

A multi-disciplinary, multi-investigator research

program to understan d the stock stru cture of Atlan tic

coastal bottlenose dolphins was initiated in late 1996.

Several different hypotheses about stock structure are

being considered (Figure 2). The experimental design for

the program is based on: 1) obtaining samples from live

captures, photo-identification, projectile biopsy, and

incidental take (strandings and observer programs); 2)

conducting indepe ndent analyses including genetics,

isotope ratios, contaminants, mo vement patterns,

morphometrics, telemetry, and life history; and 3) merging

of the disassociated results to describe stock structure

(Hohn 1997). Based on current information, it is expected

that multiple stocks exist and include year-round residents,

seasonal re sidents, and m igratory grou ps. Site-specific,

year-round residents have been reported only in the
114

southern part of the range, from Charleston, South Carolina (Zolman 1996) and Georgia (Petricig 1995) to central

Florida (Odell and Asper 1990);

 seasonal residents and migratory or transient animals also occur in these areas. In the northern part of the range the

patterns reported include seasonal residency, year-round residency with large home range, and migratory or transient

movements (Barco and Swingle 1996, Sayigh et al. 1997). Table I lists the locations and the patterns of residency

and movement that have been documented through photo-identification of naturally-marked animals, and of 31

individuals an imals that were live -captured a nd freeze-b randed in B eaufort, NC in 1995 ( Hansen a nd Wells 1996 ). 

Comp lex patterns o f moveme nt and reside ncy were ob served in a sample of 10 of the animals live -captured in

Beaufort that were radio-tagged and tracked for up to 31 days: some left the area immediately, some were located up

to 120 km distant within a few days of tagging, and others remained in the area (Read et al. 1996). 

The observed patterns of year-round residency and seasonal residency, and migratory and transient

movements likely represent a population that consists of a complex mosaic of biologically-meaningful stocks. The

patterns are in some cases essentially identical or very similar to patterns observed in recognized stocks or

commu nities identified in em bayments a nd coastal a reas in the northern Gulf o f Mexico (e.g. Scott et al. 1990;

Weller 199 8; Wells et al. 1996). Sufficient information exists to identify year-round resident communities in several

bay and estuarine areas; however, much of the suitable bay and estuarine habitats along the Atlantic coast have not

yet been studied sufficiently. Although numerous research efforts are underway, it will require several years of

photographic identification, genetic and radio-tracking research to provide sufficient information for interpretation.

The entire range(s) and number of migratory and transient stocks are unknown, but much of the current research

effort is directed towards d etermining sto ck structure, movemen ts, and degre e of mixing o f these presum ed stocks. 

As the research efforts are completed, it is likely that a number of stocks or communities will be identified, including

year-round and resident stocks in embayments, and transient or migratory stocks. This will necessitate a revision of

the stock assessment report of the western North Atlantic Coastal Stock of bottlenose dolphins to reflect the number

of stocks described.

POPU LATIO N SIZE

 Mitchell (1975) estimated that the coastal bottlenose dolphin population which was exploited by a shorebased net fishery until 1925 (Mead 1 975) numbered at least 13,748 bottlenose dolphins in the 1800s. Recent

estimates of bottlenose dolphin abundance in the USA Atlantic coastal area were made from two types of aerial

surveys. The first type was aerial su rvey using stand ard line transe ct sampling w ith perpend icular distance data

analysis (Buckland et al. 1993) and the computer program DISTANCE (Laake et al. 1993). The alternate survey

method consisted of a simple count of all bottlenose dolphins seen from aerial surveys within one km of shore.

An aerial line-transect survey was conducted during February-March 1992 in the coastal area south of Cape

Hatteras. Sampling transects extended orthogonally from shore out to approximately 9 km past the western wall of

the Gulf Stream into waters as deep as 140 m, and the area surveyed extended from Cape Hatteras to mid-Florida

(Blaylock and Ho ggard 19 94). Systematic transects we re placed randomly with respect to b ottlenose d olphin

distribution and approximately 3.3% of the total survey area of about 89,900 km2 was visually searched. Survey

transects, area, and dates were chosen utilizing the known winter distribution of the stocks in order to sample the

entire coastal population; however, the offshore stock may represent some unknown proportion of the resulting

population size estimates. Preliminary 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 the

perpend icular distance sighting data. Bottlenose d olphin abu ndance w as estimated to be 12,4 35 dolp hins with

coefficient of variation (CV) = 0.18 and the log-normal 95% co nfidence interval was 9,684-15,967 (Blaylock and

Hogga rd 1994 ). 

An aerial survey was conducted during late January-early March 1995, following nearly the same design as

the 1992 survey. Preliminary analysis (following the same procedures described above) resulted in an abundance

estimate of 21,128 dolphins (CV=0.22) with a long-normal 95% confidence interval of 13,815-32,312.

Perpendicular sighting distance analysis (Buckland et al. 1983) of line transect data from an aerial survey

throughout the northern portion of the range in July 1994, from Cape Hatteras to Sandy Hook, New Jersey, and from

shore to the 25 m isobath, resulted in an abundance estimate of 25,841 bottlenose dolphins (CV=0.40) (Blaylock

1995) within the approximately 25,600 km2

 area. These data were collected during a pilot study for designing

future surveys an d are con sidered to b e preliminar y in nature. 
115

An aerial survey of this area was conducted during mid July-mid August 1995. Data from the pilot study

was used to design this survey; survey sampling was designed to produce an abundance estimate with a CV of 0.20

or less. Preliminary analysis (following the same procedures described above for the surveys south of Cape

Hatteras) resulted in an abundance estimate of 12,570 dolphins (CV=0.19) with a log-normal 95% confidence

interval of 8,6 95-18,1 73. 

An aerial surv ey of the coastal waters within a o ne km strip alo ng the shore from Sand y Hook to

approximately Vero Beach, Florida, was also conducted during July 1994 (Blaylock 1995). Dolphins from the

offshore stock are believed unlikely to occur in this area. Observers counted all bottlenose dolphins seen within the

one km strip alongshore from Cape Hatteras to Sandy Hook (northern area) and within the one km strip alongshore

south of Cape H atteras to approximately V ero Beach (so uthern area). The avera ge of three counts of bottlenose

dolphins in the northern area wa s 927 dolphins (ran ge = 303-1,66 7) and the average o f three counts of bottlenose

dolphins in the southern area was 630 dolphins (range = 497-815). The sum of the highest counts in both areas was

2,482 d olphins. 

A vessel survey to obtain abundance, distribution, and biopsy information from pelagic cetaceans in USA

waters south of Delaware Bay was conducted during July and August 1998 (NMFS unpublished data). The survey

included waters from approximately the 30 m isobath out to the offshore extent of the USA EEZ. A total of 56 herds

or groups of bottlenose dolphins were sighted; an unkno wn number of these herd s were likely the offshore bottlenose

dolphin ec otype. On e of the herd s sighted was e xceptiona lly large and wa s estimated to consist of 25 1 individua ls. 

The data from the survey are currently being analyzed; abundance estimates should be available in late 1999.

It is not currently possible to distinguish the two bottlenose dolphin ecotypes with certainty during visual

aerial and vessel surveys, as the distribution of the two eco types in USA Atlantic EE Z waters is uncertain. Because

of this difficulty, the resulting abundance estimates may include dolphins from the offshore stock. Until additional

research provides information to determine the range of habitat utilized by both ecotypes and their degree of mixing

along the Atlantic coast, it will not be possible to assess the abundance of either type with any certainty. Determining

the degree of geograp hic mixing of the se two eco types is currently a n active area of research b y NMF S, SEFSC. 

Minimum Po pulation Estimate

Reasona ble assuranc e of a minimum popu lation estimate c an not be p rovided by line transect su rveys

because the prop ortion of dolphins from the o ffshore stock which might have bee n observed is unkno wn. The risk

averse approach is to assume that the minimum population size is the highest count of bottlenose dolphins within the

one km strip from shore between Sandy Hook and Vero B each obtained during the July 1994 survey. The maximum

count within one km of shore between Sandy Hook and Cape Hatteras was 1,667 bottlenose dolphins and it was 815

bottlenose dolphins within one km of shore between Cape Hatteras and Vero Beach. The resulting minimum

populatio n size estimate fo r the western N orth Atlantic co astal bottleno se dolphin stock is 2,48 2 dolph ins. 

Current Population Trend

 Kenney (1 990) rep orted an estimated 40 0-700 b ottlenose d olphins from the inshore stra ta of aerial surve ys

conducted along the USA Atlantic coast north of Cape Hatteras in the summer during 1979-1981. These estimates

resulted from line transect ana lyses; thus, they cann ot be used in compa rison with the dir ect count d ata collected in

1994 to assess pop ulation trends. 

There was no significant difference in bottlenose dolphin abundance estimated from aerial line transect

surveys conducted south of Cape Hatteras in the winter of 1983 and the winter of 1992 using comparable survey

designs (NMFS unpublished data; Blaylock and Hoggard 1 994) in spite of the 1987-88 mortality incident during

which it was estimated that the co astal migrator y populatio n may have b een reduc ed by up to 53% (S cott et al.

1988). 
116

CURRENT AND M AXIMUM NET PRODUCTIVITY RATES

Current and maximum net produ ctivity rates are no t known for this sto ck. The m aximum ne t productiv ity

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, which accounts for

endangered, depleted, and threatened stocks, or stocks of unknown status relative to optimum sustainable population

(OSP ) is assumed to be 0.50 because this sto ck is listed as de pleted und er the Ma rine Mam mal Prote ction Act. 

Therefo re, PBR for the USA Atlantic coastal bottlenose dolphin sto ck is 25 do lphins. 

ANNUAL HUMAN-CAUSED MORTALITY AND SERIOUS INJURY

 Total annual estimated average fishery-related mortality or serious injury to this stock during 1994-1998

was 45.8 bottlenose dolphins (C V=0.6 7). 

Fishery Information

Menhaden Purse Seine

The Atla ntic menhad en purse sein e fishery targets the A tlantic menhad en, Brevortia tyrannus, in Atlantic

coastal waters approximately 3-18 m in depth. Twenty-two vessels operate off northern Florida to New England

from April-January (NMFS 1991, pp. 5-73). M enhaden purse seiners have reported an annual incidental take of one

to five bottleno se dolphin s (NM FS 199 1, pp. 5-7 3), although observer data are no t available. 

Mid-Atlantic Coastal Gillnet

Coastal gillnets operate in different seasons targeting different species in different states throughout the

range of this stoc k. Most ne ts are ancho red close to shore, but some are allow ed to drift, and nets range in len gth

from 91 m to 914 m. A gillnet fishery for American sha d, Alosa sapidissima, operates seasonally from Connecticut

to Georgia, with nets being moved from coastal ocean waters into fresh water with the shad spawning migration

(Read 1 994). It is co nsidered like ly that a few bottlen ose dolp hins are taken in this fishery each yea r (Read 1 994). 

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). The North Carolina sink gillnet fishery

operates in October-May targeting weakfish, croaker, spot, bluefish, and dogfish. Another gillnet fishery along the

North Carolina Ou ter Banks ta rgets bluefish in Ja nuary-Ma rch. Similar mixed-specie s gillnet fisheries, und er state

jurisdiction, operate seasonally along the coast from Florida to New Jersey, with the exclusion of Georgia.

The mid -Atlantic coastal gillnet fishery is actually a c ombinatio n of small vesse l fisheries that target a

variety of fish species. Some of the fishery operates right off the beach. Although observer coverage of the fishery

was initiated in Ju ly, 1993, the re was no co verage in 19 94 and b ycatch estimate s are availab le only for 19 95-199 8. 

Observer coverage of the fishery ranged from 3% in 1997 to 5% in 1995 and 1998. One take of a bottlenose dolphin 

was observed in 1995 and 1996, none in 1997, and three in 1998. The annual estimated mortalities with associated

CVs in parentheses by year are as follows: 1995, 56 (1.66); 1996, 64 (0.83); 1997, 0; 1998, 63 (0.94); estimated

1995-1 998 me an annual estim ated take is 45 .8, CV= 0.67 (T able 2). 

Shrimp Trawl

The shrimp trawl fishery operates from North Carolina through northern Florida virtually year around,

moving sea sonally up an d down th e coast. On e bottlenos e dolphin w as recove red dead from a shrimp trawl in

Georgia in 1995 ( Southeast U SA M arine Ma mmal Stran ding Netw ork unpub lished data), b ut no bottleno se dolphin

mortality or serious injury has been previously reported to NMFS.

Beach Seine

A beach seine fishery operates along northern North Carolina beaches during the spring and fall targeting

mullet, spot, weakfish, sea trout, and bluefish. The North Carolina beach seine has been observed since April 7,

1998. The fishery, based on the Outer Banks of North Carolina, occurs primarily in the spring (April through June)

and fall (October through December). This fishery has two types of setup systems: a “beach anchored gill net” and a

“beach seine”. Both systems utilize a gill net anchored to the beach. The beach seine system also uses a bunt and

wash net that are attached to the beach and are in the surf. This fishery was observed by patrolling the beaches on a

daily basis. During April 1998, 12 hauls were observed: 9 were the gill net system and 3 were the beach seine
117

system. Durin g May 1 998, 26 hauls were o bserved: 1 4 gill net and 1 2 beach seine hauls. D uring Octo ber 199 8, 7

hauls were observed, all the gill net system. During November 1998, 1 gillnet system haul was observed. During

December 199 8, 14 hau ls were obse rved: 12 g ill net and 2 be ach seine ha uls. The on ly observed take was a fresh ly

killed bottleno se dolphin during M ay 1998 . The bea ch seine ob server data is currently being audited an d is

unavailable for analysis. The beach seine fishery bycatch mortality estimate will be available for the 2001 stock

assessment re port.

Table 2. Summary of the incidental mo rtality 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

Mid-Atlantic

Coastal Sink

Gillnet 

94-98 NA Obs. Data

Weighout

NA, .05, .04,

.03, .05

NA, 0, 0, 0,

0

NA, 1, 1, 0,

3

 NA, 56,

64, 0, 63

NA, 1.66,

.83, 0, .94

45.8

(0.67)

 

TOTAL 45.8

(0.67)

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.

Other Mortality

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. These interactions are

due in part to the species’ gregarious nature and habits of feeding on discarded bycatch and from baited gear (e.g.,

long-line and crab pots). However, 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 may wash ashore, nor will all of

those that do wash ashore necessarily show signs of entanglement or other fishery-interaction. In addition, the level

of technical expertise among stranding network personnel varies widely as does the ability to recognize signs of

fishery interaction. Due to the extent of decomposition and/or the level of experience of the examiner, a

determination cannot always be made as to whether or not a stranding occurred due to human interaction

From 1993-1997, two hundred and eighty-eight bottlenose dolphins were reported stranded in waters north

of Cape Hatteras (Virginia to Massachusetts, NE Region) (NMFS, unpublished data). The majority of the

strandings within this northern area occurred in Virginia (n = 182, 63%). An unknown number of the animals

reported stranded during 1993-1995 have shown signs of entanglement with fishing gear or interactions with fishing

activities; however, limited information was available for 1993, and complete information was available for 1996-

1999. In 1993, eight bottlenose dolphins in Virginia and one in Maryland were reported as entangled in fishing

gear, but the gear type was not reported (NMFS unpublished data). In 1996, seventy-four bottlenose dolphins were

reported stranded in the NE Region. The cause of death could be determined for 44 animals and of these, 16 or

36% were reported due to human interactions (including 13 gear entanglements). In 1997, seventy-four bottlenose

dolphins were also reported stranded in the NE Region. The cause of death could be determined for 54 animals and

of these, 14 or 26% were reported due to human interactions. If the percentages are consistent for animals for

which cause of death could not be determined, it is likely that during 1996 about 27 (36%), and during 1997 about

19 (26%), of the stranded animals in the NE Region died due to human interactions.

Evidence of interaction with fisheries (entanglement, net marks, mutilations, gun shots, etc.) were present

in 178 of 1353 of the bottlenose dolphin strandings investigated in the USA Southeast Atlantic region (North
118

STATE 1997 1998 1999

NEW YORK Total Stranded 2 3 3

 Human Interaction

 ---- Fishery Interaction 1 0 0

 ---- Mutilation 0 0 0

 ---- Other 0 0 0

 No Human Interaction 0 2 3

 Could Not Be Determined 1 1 0

NEW JERSEY Total Stranded 10 11 15

 Human Interaction

 ---- Fishery Interaction 0 1 3

 ---- Mutilation 0 0 0

 ---- Other 0 0 0

 No Human Interaction 2 3 2

 Could Not Be Determined 8 7 10

DELAWARE Total Stranded 14 8 18

 Human Interaction

 --- Fishery Interaction 1 1 1

 --- Mutilation 0 0 0

 ---- Other 2 1 0

 No Human Interaction 4 0 4

 Could Not Be Determined 7 6 13

MARYLAND Total Stranded 2 2 2

 Human Interaction

 ---- Fishery Interaction 0 0 1

 ---- Mutilation 0 0 0

 ---- Other 0 0 0

 No Human Interaction 1 0 1

 Could Not Be Determined 1 2 3

VIRGINIA Total Stranded 44 42 50

 Human Interaction

 ---- Fishery Interaction 11 8 18

 ---- Mutilation 0 2 3

 ---- Other 0 1 0

 No Human Interaction 15 12 6

 Could Not Be Determined 18 19 23

N. CAROLINA Total Stranded 123 103 94

 Human Interaction

 ---- Fishery Interaction 28 22 24

 ---- Mutilation 5 3 1

 ---- Other 1 0 0

 No Human Interaction 21 16 19

 Could Not Be Determined 68 62 50

S. CAROLINA Total Stranded 41 41 34

 Human Interaction

 ---- Fishery Interaction 8 4 1

 ---- Mutilation 2 0 1

 ---- Other 0 1 2

 No Human Interaction 15 10 10

 Could Not Be Determined 16 26 20

GEORGIA Total Stranded 18 26 14

 Human Interaction

 ---- Fishery Interaction 1 1 1

 ---- Mutilation 0 0 0

 ---- Other 0 0 0

 No Human Interaction 8 6 8

 Could Not Be Determined 9 19 5

FLORIDA Total Stranded 104 80 87

 Human Interaction

 ---- Fishery Interaction 7 3 4

 ---- Mutilation 0 0 0

 ---- Other 0 1 0

 No Human Interaction 34 29 28

Table 3. Bottlenose dolphin strandings from New York to

Florida during 1997 through 1999. Data from Southeast

and Northeast Marine Mammal Stranding Databases.

Carolina to Florida) from 1993 to 1998, as determined from

evidence of entanglement in fishing gear and/or other human

related causes (e.g., net marks, entanglement, mutilations,

boat strikes, gunshot wounds) (NMFS unpublished

information). This does not take into account those animals

for which cause of death could not be determined so the

number of animals that stranded due to human interaction is

likely greater. Table 3 provides coastal bottlenose dolphin

strandings observed from New York to Florida during 1997

through 1999 (unpublished data from Southeast and Northeast

Marine Mammal Stranding Databases). This data is presently

under analysis and additional information on stock structure

and fishery interactions is expected for the next Status of the

Stocks review. As the table illustrates, there is considerable

variability in strandings between these states during this time

period. 

In recent years reports of strandings with evidence of

interactions between bottlenose dolphins and both recreational

and commercial crab-pot fisheries have been increasing in the

Southeast Region (McFee and Brooks 1998).

The nearshore habitat occupied by this stock 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, but a recent assessment of the

health of live-captured bottlenose dolphins from Matagorda

Bay, Texas, associated high levels of certain chlorinated

hydrocarbons with low health assessment scores (Reif et al. in

review). 

STATUS OF STOCK

This stock is considered to be depleted relative to

OSP and it is listed as depleted under the Marine Mammal

Protection Act (MMPA). There are data suggesting that the

population was at an historically high level immediately prior

to the 1987-88 mortality event (Keinath and Musick 1988);

however, the 1987-88 anomalous mortality event was

estimated to have decreased the population by as much as 53%

(Scott et al. 1988). A comparison of historical and recent

winter aerial survey data in the area south of Cape Hatteras

found no statistically significant difference between

population size estimates (Student's t-test, P > 0.10), but these

estimates may have included an unknown proportion of the

offshore stock. Population trends cannot be determined due to

insufficient data. 

Although there are limited observer data directly

linking serious injury and mortality to fisheries (e.g., in the

coastal gillnet fishery complex in the mid-Atlantic), the total

number of bottlenose dolphin assumed from this stock which

stranded showing signs of fishery or human-related mortality

exceeded PBR in 1993, 1996, 1997, and by the end of October

in 1998. In North Carolina alone, human-related mortality
119

approached PBR in each of the intervening years. 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.

The species is not listed as threatened or endangered under the Endangered Species Act, but because this

stock is listed as depleted under the MMPA it is a strategic stock. 

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

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Contract No. 40-GENF-500160, Southeast Fisheries Science Center, Miami, FL, 36 pp.

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Diego. 653 pp.

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Workshop April 3-5, Seattle, Washington. U.S. Dep. Commer., NOAA Tech. Memo. NMFS-OPR-12, 93

pp.

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thesis. University of Charleston, South Carolina, USA. 128 pp.
122

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 . 

November 2001

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 sigh ting surveys, strand ings, and take s reported by NM FS obse rvers in the Sea Sampling P rogram. 

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 dee p (Gaskin 197 7; Kraus et al. 1983; Palka 1995a, b),

with a few sightings in th e upper B ay of Fundy a nd on the no rthern edge of Georg es Bank (P alka 200 0). During fa ll

(Octob er-Decem ber) and sp ring (April-Ju ne), harbo r porpo ises are widely d ispersed from New J ersey to M aine, 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 fo und in waters off New Y ork to Ne w Brunsw ick, Canad a. There d oes not ap pear to be a tempora lly

coordin ated migratio n or a spec ific migratory ro ute to and from the Bay o f Fundy regio n. Thoug h, during the fall,

several satellite tag ged harb or porp oises did fav or the waters a round the 9 2m isoba th, which is consistent with

observations of high rates of incidental catches in this depth range (Read and Westgate 1997). There were two

stranding rec ords from Florida (Smithsonian stra ndings data base). 

Gaskin (1984, 1992) propo sed 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 pop ulations. 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 19 99), heav y metals (Joh nston 199 5), 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 G ulf of St. Lawren ce males ac cording to

studies com paring mtD NA (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-Atlan tic states suggest tha t this

aggregatio n of harbo r porpo ises consists of an imals

from more than just the Gulf of Maine/Bay of Fundy

stock (Ro sel et al. 1999a). However, the majority of

the samples used in the Rosel et al. (1999a) study were

from strand ed juvenile a nimals. Furthe r work is

underway to examine ad ult animals from this region. 

Nuclear microsatellite markers have also been applied

to samples fro m these four p opulations, but this

analysis failed to detect significant population subdivision in either sex (Rose l et al. 1999a). This pattern

may be ind icative of fema le philopatry c oupled w ith

dispersal of male harbor porpoises. This report follows Gaskin's hypothesis on harbor porpoise stock structure in the
123

western North Atlantic; Gulf of Maine and Bay of Fundy harbor porpoises are recognized as a single management

stock sepa rate from ha rbor po rpoise po pulations in the Gulf of St. Law rence, Ne wfoundlan d, and G reenland. 

POPU LATIO N SIZE

To estimate the population size of harbor porpoises in the Gulf of Maine/Bay of Fundy region, four linetransect sighting su rveys were co nducted d uring the summ ers of 199 1, 1992 , 1995, an d 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 = 40,90 0-109,100) (Palka 1996), and 89 ,700 in 1999 (CV=0 .22, 95% CI =

53,400 - 150,900) (Palka 200 0). 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

temperatu re and ava ilability of primary p rey species (P alka 199 5b), and m ovemen t among p opulation u nits (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, for the first time, during 1999, the upper Bay of Fundy and northern Georges Bank were surveyed and

harbor porpoises were seen. 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 re gion was surv eyed by airp lane while the re st of the region w as 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. Law rence were surveyed an d harbo r porpo ises were seen only in the vicinity

of the Gulf of M aine/Bay o f Fundy. Du ring 1999 , waters from so uth of Cap e Cod to the mouth o f 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 curren t, and this survey d iscovered portions o f the harbor p orpoise ra nge not co vered pre viously. 

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 an d August. D ata were ana lyzed using Q uenouille’s

jackknife bias reduction pro cedure on line transect metho ds that modeled the left truncated sighting curve . These

estimates were not corrected for visibility biases, such as g(0).
124

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 M aine to

upper Bay of Fundy 89,700 0.22 67,600

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 de termine if trend information can be o btained from the four N EFSC 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, Gask in 1977, and 1 5,800 animals, K raus 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 no t incorpora te an estimate o f g(0) (NEFSC 199 2).

CURRENT AND M AXIMUM 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 Bo veng (19 91), who used a re-sca led human life table, estimated the upper b ound of the annual po tential 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 su rvivorship a nd repro duction, Caswell et al. (1998) used a Monte Carlo method to calculate a

probab ility distribution of gro wth rates. Th e median p otential annua l rate of increase was appro ximately 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

observatio ns of maximum rate of inc rease are no t available, and following a rec ommen dation 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).
125

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; W ade and Angliss 1997). The minimum

population size is 74,695 (CV=0.22). The maximum p roductivity 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 HUM AN-CAUSED MOR TALITY

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 (T able 3) and unde r the Other Mo rtality 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 council fishery management plans that

apply to parts of the gillnet fisheries were also implemented during 1999. Because these plans changed the USA

gillnet fisheries, only 1999 USA mortality estimates are representative of the current USA mortality. The total

annual estimated average human-caused mortality is 382 harbor porpoises per year. This is derived from four

components: 323 harbor porpoise per year (CV=0.25) from USA fisheries using observer data, 39 per year

(unknown CV) from Canadian fisheries using observer data, 19 per year from USA unknown fisheries using

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

Fishery Information

Recently, G ulf of Maine /Bay of Fun dy harbo r porpo ise takes have been do cumented in the USA Northea st 

sink gillnet, mid-A tlantic coastal gillne t, and in the Ca nadian Bay of Fundy g roundfish sink gillnet and herring weir

fisheries (Table 2).

EARLIER INTERACTIONS

Pelagic Drift Gillnet 

In 1996 and 199 7, NM FS issued m anageme nt regulations w hich prohib ited the ope ration 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 Atla ntic pelagic d rift gillnet fishery during 1 991-19 98. The estimated tota l number o f hauls in the Atlantic

pelagic drift gillnet fishery increased from 714 in 19 89 to 1,144 in 1990; thereafter, with the introduction of qu otas,

effort was severely reduced. Fifty-nine different vessels participated in this fishery at one time or another between

1989 a nd 199 3. In 199 4 to 199 8 there were 11, 12, 1 0, 0, and 1 1 vessels, resp ectively, in the fishery (T able 2). 

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 o f the fishing vessel. Fish ing effort was co ncentrated along the sou thern edge of Georg es Bank a nd 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 parenthe ses)

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 (Table 2).
126

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 Hamp shire, 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

porpo ises were killed annually in this fishery (G ilbert and W ynne 198 5, 1987 ). 

In 1990 , an observ er program was started by NM FS to investiga te marine ma mmal takes in the Northe ast 

sink gillnet fishery. There have been 437 harbor porpoise mortalities related to this fishery observed between 1990

and 1999 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 ad ditional 187 vessels were rep orted 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, 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 to M aine. This d oes not includ e a small per centage of re cords whe re the vessel number was missing. 

Observer coverage in terms of trips was 1%, 6%, 7%, 5%, 7%, 5%, 4%, 6%, 5%, and 6% for 1990 to 1999,

respectively. Bycatch in the northern Gulf of Maine occurs primarily from June to September; while in the southern

Gulf of Maine bycatch occurs from January to May and September to December. Annual estimates of harbor

porpo ise bycatch in the Northea st sink gillnet fishery reflect se asonal distrib ution of the spe cies and of fishin g 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 unob served hau ls were lower than that for ob served hau ls. Further analytica l details are give n in Palka (1 994), 

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 1990-1999 was 2,900 in 1990 (0 .32), 2,000 in 1991 (0.35),

1,200 in 1 992 (0.2 1), 1,400 in 1993 ( 0.18) (B ravington an d Bisack 1996; C UD 1 994), 21 00 in 199 4 (0.18), 1400 in

1995 (0.27) (Bisack 1997a), 1200 (0.25) in 1996, 782 (0.22) in 1997, 332 (0.46) in 1998, and 270 (0.28) in 1999

(Rossma n and M errick 199 9). The inc rease in the 19 98 CV is mainly due to the small numb er of obser ved 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

compo sition of the byca tch (Read and Ho hn 1995 ). Using ob server data collected d uring 199 0 to 199 8 and a log it

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 a nd broug ht back to lan d were no t significantly different (Lamb 20 00). 

Two p reliminary exp eriments, using a coustic alarm s (pingers) attac hed to gillnets, tha t were cond ucted in

the Gulf of M aine during 1 992 and 1993 a nd took 1 0 and 33 harbor p orpoises, re spectively. D uring fall 199 4, a

controlled scientific experiment was conducted in the southern Gulf of Maine, where all nets with and without active

pingers were observe d (Kraus et al. 1997). In this experime nt 25 harb or porp oises were tak en in 423 strings with

non-active pingers (controls) and two harbor porpoises were taken in 421 strings with active pingers. In addition, 17

other harb or porp oises were tak en in nets that did not follow the e xperimen tal protoco l (Table 2 ). From 19 95 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, the experimental fishery was

conduc ted in the south ern Gulf of M aine (Jeffreys Ledge) reg ion, where no harbor p orpoises w ere obser ved 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, three other experimental fisheries occurred. In the Jeffreys Ledge area, in 88 observed

hauls using ping ered nets nine harbor p orpoises w ere taken. In the Massac husetts Bay re gion, in 171 observed hauls
127

using pingere d nets, two ha rbor po rpoises wer e taken. And , in a region just so uth of Cap e Cod, in 5 3 observ ed hauls

using pingered nets no harbor porpoises were taken. During 1997, experimental fisheries were allowed in the midcoast 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 differe nce betwe en the catch ra te in nets with pinge rs and silent nets (K raus and B rault 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 Decemb er 1989-94, Atlantic herring (Clupea harengus) was the most important prey. Pearlsides

(Maurolicus weitzmani), silver hake (Merluc cius bilinea ris) and red and white hake (Uroph ycis 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

1994-1 998 be fore the Ta ke Redu ction Plan w as 1,163 (0.11). Because the T ake Red uction Plan to reduce ta kes in

USA Atlantic gillnets, and the NEFMC fish management plans to manage groundfish changed fishing practices

during 1999, the current average annual harbor porpoise mortality and serious injury in the Northeast sink gillnet

fishery is from 1999 only: 270 (0.28).

Mid-Atlantic Co astal Gillnet 

Before an observer program was in place, Polacheck et al. (1995) reported one harb or porp oise inciden tally

taken in shad nets in the Yo rk River, V irginia. In July 19 93 an ob server pro gram was initiate d in the mid-A tlantic

coastal gillnet fisher y by the NE FSC Se a Samplin g program . This fishery, whic h extends from North Carolina to

New Y ork, is actually a co mbination o f small vessel fisherie s that target a varie ty of fish species, some of the vessels

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 an d an unde termined number of d rift gillnet vessels partic ipating in

this fishery. This is the number of unique vessels in the commercial landings database (Weighout) that reported

catch from th is fishery during 1 998 from the states of Co nnecticut to N orth Caro lina. This do es 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 38 2 trips were observed , respectively. Observer cove rage, expressed as pe rcent of tons of fish

landed, was 5% for 1995, 4% for 1996, 3% for 1997, 5% for 1998, and 6% for 1999 (Table 2). No harbor

porpoises were taken in observed trips during 1993 and 1994. During 1995 to 199 9, respectively, 6, 19, 32, 53, and

3 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 subfisheries. 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, and 53 (0.49) for 1999. 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 the Take Reduction Plan to reduce takes in USA

Atlantic gillnets, and the fish management plans to manage groundfish changed fishing practices during 1999, the

current average annual harbor porpoise mortality and serious injury in the Mid-Atlantic coastal gillnet fishery is from

1999 o nly, 53 (0.49 ). 

Unknown Fishery

The strandings and e ntanglement database, maintained by the New E ngland Aquarium and the Northeast

Regional Office/NMFS, reported 228 stranded harbor p orpoises during 1999 (see Other Mortality section for more

details). Of these 228, it was d etermined that the cause o f death of 19 stranded h arbor po rpoises was due to gillnets

and these animals were in areas and times that were not included in the above mortality estimate derived from

observer program data (Table 3).

North Atlantic Bottom Traw l 

One harbor porpoise mortality was observed in the North Atlantic bottom trawl fishery between 1989 and

1999. Vessels in this fishery, a Category III fishery under the MMP A, 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) pa rticipated an nually in the fishery du ring 1989 -1993. T his fishery is active in N ew Englan d waters in all
128

seasons. T he one take occurred in Februar y 1992 e ast of Barn egatt Inlet, Ne w York a t the continenta l shelf break. 

The animal was clearly dead prior to being taken by the trawl, because it was severely decomposed and the tow

duration o f 3.3 hours w as insufficient to allow extensive de compo sition; therefore , the estimated b ycatch 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 Fund y Sink Gillnet 

During the early 1980's, Canadian harbor porpoise bycatch in the Bay of Fundy sink gillnet fishery, based

on casual observations a nd discussions with fishermen, was thought to b e low. The estimated harb or porpoise

bycatch in 1 986 was 94-116 and in 198 9 it was 130 (Trippe l 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 ob server pro gram imp lemented 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) (Trippe l et al. 1996).

During 19 94, the ob server pro gram was e xpande d to cove r 49% o f the gillnet trips (17 1 observ ed trips). 

The bycatch was estimated to be 101 harbor porpoises (95% confidence limit: 80-122), and the fishing fleet

consisted o f 28 vessels (T rippel et al. 1996). 

During 19 95, due to groundfish q uotas being exceede d, the gillnet fishery wa s closed from July 21 to

August 31 , 1995. D uring the op en fishing perio d of 199 5, 89% of the trips were observed , all in the Swallow tail

region. Approximately 30% of these observed trips used pingered nets. The estimated bycatch was 87 harbor

porpo ises (Tripp el 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 Ju ly 20-31 and Aug ust 16-31 due to gro undfish

quotas. Fro m the 107 monitored trips, the bycatch in 1996 w as estimated to be 20 ha rbor po rpoises (T rippel et al.

1999; D FO 19 98). Trip pel et al. (1999) estimated that during 1996, gill nets equipped with acoustic alarms reduced

harbor p orpoise b ycatch rates b y 68% o ver nets withou t alarms in the Sw allowtail area o f 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, gill nets equipped with acoustic alarms reduced harbor porpoise bycatch

rates by 85 % over nets without alarm s in the Swallow tail area of the low er Bay of F undy.

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 one

harbor porpoise mortality was observed. Fishers independently reported an additional four porpoises. The Wolves

and Head Harbour area had seven 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.

 Average estimated harbor porpoise mortality in the Canadian groundfish sink gillnet fishery during 1995-

1999 was 36 (Table 2). An estimate of variance is not possible.

Herring Weirs

Harbo r porpo ises are taken fre quently in Can adian herrin g weirs, but there have been no recent effo rts to

observe takes in the USA component of this fishery. Weirs operate from May to September each year along the
129

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 Ba y of Fundy an d 56 active weirs in Ma ine (Read 1994). A ccording 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 (Molynequx 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 o f Fundy (in N ew Bruns wick: 60 from Grand Manan Island, 95 fro m Deer a nd 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 tha t, in 1980, ap proxima tely 70 harb or porp oises beco me trapp ed annua lly

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 2 06 of 26 3 harbo r porpo ises caught in he rring weirs. M ortalities (and re leases) were 11 (and 5 0) in

1992, 33 (a nd 113) in 19 93, and 13 (an d 43) in 1994 (Neimanis et al. 1995). Since that time, an additional 217

harbor porpoises have been documented in Canadian herring weirs, of which 203 were released or escaped and 14

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;

and 3 (and 89) in 1999 (A. Read, pers. comm .).

Clinical hematology values were obtained from 29 harbor porpoises released from Bay of Fundy herring

weirs (Koopman et al. 1999). Th ese data represent a base line for free-ranging harbor porp oises 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 1995-1999 was

2.8 (Table 2). An estimate of variance is not possible.
130

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 C V of the ann ual mortality (E stimated CV s) and the me an 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

(.11)

After

TRP6

99

1998=301 Obs. Data,

Weighout,

Trip Logbook

.06 1432703.28 270

(.28)

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

1998=3028 Obs. Data

Weighout

.06 3 53 .49 53

(.49)

USA TOTAL 323

(0.25)

CANADA

Groundfish Sink

Gillnet 

95-99 1994=28 Obs. Data

Can. Trips

.89, .8, .8, .8,

NA7

25,13, 19, 1,

3

87, 20, 43,

10, 207

NA 36

(NA)

Herring Weir 95-99 1998=255

licenses5

Coop. Data NA 5,

2,2,2,3

5,

2,2,2,3

NA 2.8

(NA)

CANADIAN

TOTAL

39

(NA)

TOTAL 362

(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 (Trip Logbook) data are

used to determine the spatial 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 mid-Atlantic

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. During1997, 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; and during 1999, harbor porpoises were taken on pingered strings within strata that required
131

pingers but that stratum also had observed strings without pingers. For 1998 and 1999 estimates, a weighted bycatch

rate was applied to effort from both pingered and non-pingered hauls within the above stratum. The weighted bycatch

rate was:

There were 10, 33, 44, 0, 11, 0, 2, and 8 observed harbor porpoise takes on pinger trips from 1992 to 1999,

respectively, that are included in the observed mortality column. In addition, there were 9, 0, 2, 1, and 1 observed

harbor porpoise takes in 1995 to 1999, 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 M anageme nt Measu res Take n to Redu ce Bycatc h” for mor e 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.

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 (Mortality), and mean

annual mo rtality.

Fishery Years Vessels Data Type 1 Observed

Mortality

Mean Annual

Mortality

Unknown gillnet fishery 99 NA Entanglement

& Strandings

19 19

TOTAL 19

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 M ortality

USA

There is evidence that harb or porpoises were harvested by natives in Ma ine and Canada before the 1960 's,

and the me at was used fo r human co nsumption , oil, and fish bait (N EFSC 1992). T he extent of the se past harve sts is

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 Passamoquoddy 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 19 93, seventy-thr ee harbo r porpo ises were rep orted strand ed on be aches 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 eight carcasses and fifteen 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 an d along the New J ersey coast and reports o f apparent mutilation of harbor p orpoise

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 1 993). Betwee n 1994 and 1996, one hun dred and seven h arbor porpo ise
132

carcasses w ere recov ered from beaches in M aryland, V irginia, and N orth Caro lina and investigated by scien tists. 

Only juven ile harbor p orpoises w ere presen t in this sample. O f the 40 harb or porp oises for which cause of de ath

could be established, twenty-five displayed definitive evidence of entanglement in fishing gear. In four 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/NMF S 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 1999 were 106, 86, 94, 118, 59, and 228, respectively (Table 4). Of these,

three stranded alive on a Massachusetts beach in 1996, were tagged, and subsequently released. In 1998, two

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, six 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 o f Massac husetts and N orth Caro lina. The state s with the next large st numbers w ere Virginia , New Jers ey,

and M aryland , in that o rder. The cause of de ath was investiga ted for all the 19 99 strand ings (Tab le 5). Of these , it

was possib le to determine that the cause of death of 3 6 animals wa s fishery interaction s. Of these 36 , 19 anima ls

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 wa s cut off). This an imal was attribu ted to an unk nown hum an-caused mortality.

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 wa sh ashore, nor will all of those that do wash

ashore necessarily show signs of entanglem ent 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.
133

Table 4. Summar y of numbe r of stranded harbor p orpoises d uring Janua ry 1, 1994 to Decem ber 31, 1 999, by sta te

and year.

State Year Total

1994 1995 1996 1997 1998 1999

Maine 0 0 5 6 5 3 19

New Hampshire 0 0 2 0 0 0 2

Massac husetts1,3 9 26 31 28 18 60 172

Rhode Island 3 0 1 1 0 3 8

Connecticut 0 0 1 0 0 0 1

New York47 6 3 10 5 10 41

New Jersey217 18 12 21 16 23 107

Delaware 3 5 4 4 7 9 32

Maryland 10 4 3 10 1 21 49

Virginia 42 18 20 12 3 40 135

North Carolina 15 9 12 26 4 59 125

TOTAL 106 86 94 118 59 228 691

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 ob served mid -Atlantic coastal gill net fishing vessel.

3

Five animals stranded alive in 1999 and were tagged and released.

4 One anim al stranded alive in 199 9, rehabilitated at Mystic Aq uarium and died at the aq uarium in Ap ril

2000.

Table 5. Cause of mortality of USA stranded harbor porpoises during January 1, 1999 to December 31, 1999.

“Unique FI” is a fishery intera ction that is in a time a nd area tha t could not b e 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

determine d not to be related to a fishe ry interaction. “A live” is stranded animal not d ead. “CB D/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

1 Attributed to an unknow n gillnet fishery.

2 Attributed to an unknow n human-ca used mo rtality.

CANADA

Whales and dolphins stranded between 1991 and 1 996 on the coast of Nova Scotia were documented by the

Nova Scotia Stranding Network (Hooker et al. 1997). S trandings on the beache s of Sable Isla nd during 1 970 to

1998 w ere documented b y researchers with Fisheries an d Ocea ns, Canad a (Lucas an d Hoo ker 200 0). Sable Isla nd is

approximately 170 km southeast of mainland Nova Scotia. On the mainland of Nova Scotia, a total of eight stranded

harbor p orpoises w ere record ed betwe en 1991 and 199 6 (Tab le 6); of these, two were release d alive. On S able

Island, eight stranded dead harbor porpoises were documented, most in January and February (Table 6). 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
134

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.

Table 6. Docum ented number of strand ed harbo r porpo ises, by month and year, alo ng the coast o f Nova S cotia

(Hooker et al. 1997), a nd on Sa ble Island (L ucas and H ooker 2 000). 

Year Month Number of strandings

Nova

Scotia

Sable

Island

1991 May 1 1

1992 Jan 0 1

1993 Jan 0 1

July 1 0

Sep 1 0

1994 Aug 1* 0

1995 Aug 1 0

1996 Mar 1 0

Apr 1 0

Jul 1* 0

1997 Feb NA 3

May NA 1

June NA 1

TOTAL 8 8

* Released alive.

NA : not a vailable

USA M anagement 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 N ew England waters,

from Maine through Rhode Island. This portion of the rule includes time and area closures, some of which are

complete closures; othe rs are closed to multispecie s gillnet fishing unless p ingers are use d in the presc ribed ma nner. 

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 midAtlantic shore line from New York to North Carolina. This portion of the rule includes time and area closures, some

of which are complete c losures; others are closed to gillnet fishing unless the gear meets certain sp ecifications.

STATUS OF STOCK

The status o f harbor po rpoises, relativ e to OSP , in the USA Atlantic EE Z (Exclusiv e Econo mic Zone ) is

unknown. On January 7, 1993, the National Marine Fisheries Service (NMFS) propo sed 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
135

review of the biological status of the Gulf of Maine/Bay of Fundy harbor porpoise population and made a

preliminary determination that listing to the Endangered Species Act (ESA) is not warranted at this time and they

intend to remove this stock from the ESA candidate species list. Comments to this preliminary determination were

due September 4, 2001. 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 considere d to be insign ificant and ap proachin g zero mo rtality and seriou s injury rate. Th is is a strategic

stock because average annual fishery-related mortality and serious injury exceeded PBR for many years before 1999

and the takes have been below PBR for only one year.

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Ecology 8: S41-S54.

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in herring weirs in Charlotte County, New Brunswick , Canada . Fish. Bu ll., U.S. 81(3):6 60-2. 

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phocoena, subpop ulations in No rth America n waters. Can J Fish A quat Science s 53:1632-45.

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138

November 2001

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 Yo rk, and occasionally to the Carolinas (Boulva and

McLaren 1979; Katona et al. 1993; G ilbert and G uldager 19 98). Altho ugh the stock structure of the w estern No rth

Atlantic pop ulation is unkno wn, it is thought that ha rbor seals fo und along the eastern U SA and C anadian co asts

represent o ne popu lation (Tem te et al. 1991). Breeding and pupping normally occur in waters north of the New

Hamp shire/Ma ine borde r, although br eeding oc curred as far south as Ca pe Cod in the early part o f 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 occu r seasonally alo ng the southe rn New E ngland and New Y ork coasts fro m Septem ber throug h 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 M aine and eastern

Canada occ urs prior to the pupping sea son, which takes place from m id-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 Ne w England has not chan ged significantly d uring the last cen tury (Payne a nd Selzer 1 989). 

The majority of animals 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). W hitman and Payne (1 990) suggest

that the age-rela ted dispers al may reflect the h igher energy re quiremen ts of younger a nimals. 

POPU LATIO N 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 G ilbert and Guldager 1 998). These n umbers are conside red to be a minimum abundance estimate b ecause

they are uncorrected for animals in the water or outside the survey area. 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 p opulation e stimate. 

Table 1. Summary of abundance estimates for the western Atlantic harbor seal. Month, year, and area covered

during each abundance survey, and resulting abundance estimate (Nmin) and coe fficient of variation (CV). 

Month/Year Area Nmin CV

May/June 1993 Maine coast 28,810 (4,250) None reported

May/June 1997 Maine coast 30,990 (5,359) None reported

 

1

Pup counts are in bra ckets 
139

Minimum Po pulation Estimate

A minimum population estimate is 30,990 seals, based on uncorrected total counts along the Maine coast in 

1997. 

Current Population Trend

 The annual increase since 1993 has been 1.8 % (Gilbert and Guldager 199 8). Since 1981, the average

increase 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. Similarly, the number of pups along the Maine coast has increased at an

annual rate o f 12.9% over the 19 81-199 7 period (Gilbert and Guldage r 1998). Possible fac tors contribu ting to

harbor se al popula tion increase include M MPA protection and increa sed prey.

CURRENT AND M AXIMUM NET PRODUCTIVITY RATES

Current and maximum net produ ctivity rates are unk nown for this sto ck. For pu rposes of this a ssessment,

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; W ade 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 HUM AN-CAUSED MOR TALITY

For the pe riod 199 5-1999 , the total estimated human cau sed morta lity and serious inj ury to harbo r seals is

estimated to be 916 per year. The average is derived from two components: 1) the 1995-1999 observed fishery 895

(CV=0.14; Tab le 2); and 2) average 1997-1998 stranding mortalities resulting from boat strikes, power plant

entrainmen ts, and other so urces, 21. 

 Research ers and fishery o bservers ha ve docum ented incide ntal mortality in sev eral fisheries, pa rticularly

within the Gulf o f Maine (se e below). A n unknown level of morta lity also occurre d in the maric ulture industry (i.e.,

salmon farm ing), and by d eliberate sho oting (NM FS unpu blished da ta). Howe ver, there are no recent d ata to

indicate that sho oting aroun d aquac ulture sites still takes plac e. 

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 pro vided observer coverage of pelagic longline vessels fishing off the

Grand B anks (Ta il of the Bank s) and pro vides obse rver cove rage of vesse ls fishing south of Cape Ha tteras. 

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 an d Wyn ne 1987 ). All seals were yo ung of the year and were c aught from la te June throu gh August, an d in

early October. Interviews with a limited number of mackerel gillnetters indicated only one harbor seal entanglement

and a neglig ible loss of fish to se als. Net dam age and fish ro bbing wer e not repo rted to be a major ec onomic

concern to gillnetters interviewe d (Gilbert and Wynne 198 7). 

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

halibut tub traw ls are rare. O ne vessel cap tain indicted tha t he took on e or two sea ls a year. The se seals were a ll

hooked through the skin and released alive, indicating they were snagged as they followed baited hooks. Infrequent
140

reports suggest seals may rob bait off longlines, although this loss is considered negligible (Gilbert and Wynne

1985). 

Incidental tak es in lobster trap s in inshore wa ters off Main e are repo rtedly rare. Ca ptures of ap proxima tely

two seal pup s per port p er year were recorde d by mid-co astal lobsterm en off Ma ine (Gilbert and Wynne 198 5). 

Seals have b een repo rted to rob bait from insho re lobster trap s, especially in the sp ring, when fresh bait is used. 

These inc idents may invo lve only a few ind ividual anima ls. Lobstermen claim that sea ls consume shedding lo bsters. 

Northeast M ultispecies 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 199 6) 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%, and 6% for 1990 to 1999, respectively. The fishery has been

observed in the Gulf of Maine and in Southern New England. There were 336 harbo r 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 1999. 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- 1999 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), and 1446 in 1999 (0.34). The 1 994 and 1995 b ycatches, respectively, include 14 and 179 animals from the

estimated number of un known sea ls (based o n observe d mortalities o f seals that could not be iden tified to specie s). 

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 1995-1999 was 893 harbor seals (CV=0.14). The stratification design used is the

same as that fo r harbor p orpoise (B ravington an d Bisack 1996). T he bycatch o ccurred in M assachusetts B ay, 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 M assachusetts B ay during July-S eptembe r. In inshore wa ters, the takes we re aggrega ted while

offshore takes were more dispersed. Incidental takes were confined from Cape Elizabeth out to Jeffreys Ledge and

south to N antucket So und during Octobe r-December. 

Mid-Atlantic Coastal Gillnet

Observer coverage of the USA Atlantic coastal gillnet fishery was initiated by the NEFSC Sea Sam pling

program in July, 1993; and from July to December 1993, 20 trips were observed. During 1994 and 1995 221 and

382 trips w ere obser ved, respe ctively. This fishery, w hich extend s from No rth Carolina to New Y ork, is actually a

combina tion of small vessel fisheries that targe t a variety of fish spe cies, some o f which ope rate right off the be ach. 

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%, and 3%, 5% , and 2% for 1995, 1996 , 1997, 1998, and 1999 (Table 2).

No harbor seals were taken in observed trips during 1993-1997, and in 1999. Two harbo r 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 an nual mortality (C V in pare ntheses) attribu ted to this fishery wa s 0 in 1995 -1997 a nd 199 9 and 11 in

1998 (0.77 ). Average annual estimated fishery-related mortality attributable to this fishery during 1995-1999 was 2

harbor seals (CV=0.77)

CANADA

An unknown number of harbor seals have been taken in Newfoundland and Labrador, Gulf of St. Lawrence

and Bay of Fund y groundfish gillnets, Atlantic Canada and G reenland salmon gillnets, Atlantic Canad a cod traps,

and in Ba y of Fundy he rring weirs (Re ad 199 4). Furtherm ore, some of these mortalities (e.g., seals trapp ed in

herring weirs) a re the result of d irect shooting . 

There were 3,121 cod traps operating in Newfoundland and Labrador during 1979, and about 7,500 in 1980

(Read 1 994). T his fishery was clos ed at the end of 1993 due to colla pse of Can adian grou ndfish resour ces. 
141

Herring weirs are also distributed throughout the Bay of Fundy; it has been reported that 180 weirs were

operating in the Bay of F undy in 199 0 (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 A reas 3) (Lens, 1997). Seal bycatches occurred year-round, but

interactions we re highest during April-Jun e. Many o f the seals that died during fishing ac tivities were unide ntified. 

The proportion of sets with mortality (all seals) was 2.7 per 1,000 hauls (0.003).

Table 2. Summar y of the incidenta l mortality of harb or seal (Phoca vitulina) by commercial fishery including the

years samp led (Yea rs), the numb er of vessels ac tive within the fishery (V essels), the type o f data used (D ata

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 England3

Multispecies

 Sink Gillnet

95-99 301 Obs. D ata

 Weigho ut,

 Logbooks

.05, .04, .06,

.05, .06

56, 36,

 48, 15,

49

 1179, 911,

 598, 332,

1446

.21, .27,

.26, .33,

.34

893

(.14)

Mid-Atlantic

 Coastal Sink

 Gillnet 

95-99 Unk4 Obs. D ata

Weighout

 .05, .04,

 .03, .05,

.02

0, 0, 0, 2,

0

 0, 0, 0, 11,

0

0, 0, 0, .77,

0

2

 (.77) 

TOTAL 895

(.14)

1 Observer data (O bs. Data) are used to m easure bycatch rates, and the da ta are collected within the Northea st

Fisheries Science Center (NEFSC) Sea Sampling Program. NE FSC 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 1995, 1996, 1997, 1998 and 1999 respectively, observed mortality on “marine mammal trips” was 41,

37, 14, 13 and 45 animals. Only these mortalities were used to estimate total harbor seal bycatch. See

Bisack (1997) for “trip” type definitions. In 1995, 15 mortalities were recorded on “fish trips”. In 1996

two mortalities were recorded on “pinger trips” and three on “fish trips”. In 1997, one animal was taken on

a “fish trip,” and 14 harbor seals were taken on pingered trips. In 1998 two observed animals were taken of

“fish trips” and one harbor seal was taken on pingered trip. In 1999 four observed animals were taken on

“fish trips” and five harbor seals were taken o n pingered trips.

4 Number of vessels is not known.

Other M ortality

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 unpub lished data), oil, shooting (around salmon aquaculture sites and fixed fishing gear),

storms, abandonment by the mother, and disease (Katona et al. 1993; N MFS unpublishe d data). Inter actions 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 a n influenza ou tbreak (G eraci et al. 1981). 
142

The 1992-1996 , and 1999 harbor seal strandings data are currently under review. In 1995 one stranding

was in South Carolina. In 1 997 and 1998, 1 53 and 2 56, respe ctively, harbo r seal stranding were repo rted. 

Strandings were reported in all states between Maine and North Carolina, and in 1997 one each was in Geo rgia and

Florida. Maine (174/409), Massachusetts (83/409), New York (53/409) and New Jersey (25/409) accounted for

most of the stra ndings, reflecting both long c oastlines and habitat use. Fo rty-one of the stran ded animals during this

two year pe riod show ed signs of hum an interaction s: fishery (10), ve ssel strike (3), po wer plant (1 6), and oth er (12). 

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 wa sh ashore, nor will all of those that do wash

ashore nec essarily show sign s of entanglem ent or other fish ery-interaction. 

STATUS OF STOCK

The status o f harbor sea ls, relative to OS P, in the US A Atlantic EEZ is unkno wn, but the po pulation 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, 1 993, 19 97 surveys c onducted along the M aine coast. T he popu lation is increasin g 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. 19 99. The distribution and abundance of harb or seals (Phoca vitulina concolor) and gray sea ls

(Halichoerus grypus) in southern New England, winter 1998- summer 1999. MA Thesis, Boston

University, G raduate Sc hool of Arts and Scien ces., Bosto n, MA. 5 2 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. Comm er., NOAA Tech.

Memo . NMF S-OPR-6, 73 pp . 

Bisack, K. D. 1997. Harbor porpoise bycatch estimates in the New England multispecies sink gillnet fishery: 1994

and 199 5. Rep. int Whal. Commn. 47:705-14.

Boulva, J. and I. A. M cLaren. 19 79. Bio logy of the harb or seal, Phoca vitulina, in eastern Ca nada. Bull. Fish. Res.

Bd. Can. 200:1-2 4. 

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. Aub in and I. K. B arker. 198 1. Mass m ortality of harbo r seals: pneum onia assoc iated with

influenza A vir us. Science 215: 11 29-113 1. 

Gilbert, J. R. and N. Guldager. 1998. Status of harbor and gray seal populations in northern New England. Final

Report to : National M arine Fisherie s Service, N ortheast Fishe ries Science Center, W oods H ole, MA . 

Under NMFS/NER Cooperative Agreement 14-16-009-1557. 13 pp.

Gilbert, J. R. and J. L. Stein. 1981. Harbor seal populations and marine mammal fisheries interactions, 1981.

Annual report. Northeast Fisheries Science Center. Contract NA-80-FA-C-00029.

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.

Gilbert, J. R. and K. M. Wynne. 1984. Harbor seal populations and marine mammal fisheries interactions, 1983.

Third an nual report. Northeast Fisheries Scie nce Cente r. Contract N A-80-FA -C-0002 9. 

Gilbert, J. R. and K. M . Wynne . 1985. H arbor sea l populatio ns and fisheries interactions with m arine mammals in

New En gland, 19 84. Interim R ep., NO AA NA -84-EAC -00070 , NMF S, NEF SC., Woods H ole, MA , 15 pp. 

Gilbert, J. R. and K. M. Wynne. 1987. Marine mammal interactions with New England gillnet fisheries. Final

Report C ontract No . NA-84 -EAC-0 0070, N OAA, N MFS , NEFSC, Wo ods Ho le, MA. 1 2 pp. 

Hoov er, K., S. Sad ove and P . Forestell. 19 99. Tre nds of harb or seal, Phoca vitulina, abundan ce from ae rial surveys

in New York waters: 1985-1999. Proceedings of the 13th Biennial Conference on the Biology of Marine

Mamm als, Wailea , Hawaii, N ov. 28 - D ec. 3, 199 9. (Abstrac t). 
143

Katona, S. K., V. Rough and D. T. Richardson. 1993. A field guide to whales, porpoises, and seals from Cape Cod

to Newfo undland. Smithsonian Institution Press: Washing ton, DC, 3 16 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 N o. 50-EA NF-2-00 064, N OAA, N MFS , NEFSC, Wo ods Ho le, MA. 1 9 pp. 

Lens, S. 19 97. Interac tions betwee n marine mammals an d deep w ater trawlers in the NAFO regulatory are a. ICES

C.M. 8/Q. 10 pp.

Payne. P . M. and D . C. Schneid er. 1984 . Yearly chan ges in abund ance of har bor seals, Phoca vitulina, at a winter

haul-out site in M assachusetts. Fish. Bull., U.S. 82: 440 -442. 

Payne, P . M. and L . A. Selzer. 19 89. The distribution, ab undance and selected prey of the har bor seal, Phoca

vitulina concolor, in southern New England. Mar. M amm al 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. 

Richards on, D. T . 1976. A ssessment of h arbor and gray seal po pulations in M aine 197 4-1975 . Final report to

Marine Mammal Commission. Contract No. MM4AC009.

Rosenfeld M., M . George and J. M . Terhune . 1988. E vidence o f autumnal har bour seal, Phoca vitulina, movement

from Can ada to the U nited States. Can. Field-Nat. 102(3): 527-52 9. 

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

Massac husetts. J. Mamm. 64(3): 518-520.

Slocum, C.J., R. Schoe lkopf, S. Tulevech, M . Stevens, S. E vert and M . Moyer. 1 999. Sea l populatio ns wintering in

New Jersey (USA) have increased in abundance and diversity. Proceedings of the 13th Biennial Conference

on the Biology of Marine Mammals, W ailea, Hawaii, Nov. 28 - Dec. 3, 1999. (Abstract).

Stobo, W. T. and G. M. Fowler. 1994. Aerial surveys of seals in the Bay of Fundy and off southwest Nova Scotia.

Can. Te ch. Rep . Fish. Aqu at. Sci. 1943:57 pp.

Temte, J. L., M. A. B igg and O. Wiig. 19 91. Clines re visited: the timing o f pupping in th e harbou r 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. 19 96. The N ew England gillnet effort survey. NO AA, NM FS, NEFSC, Woo ds Hole, M assachusetts.

NEFSC [Northeast Fisheries Science Center] Ref. D oc. 99-10 . 38 pp. 

Whitma n, A. A. and P. M. P ayne. 199 0. Age of ha rbour sea ls, Phoca vitulina concolor, wintering in southern New

England . Can. Field-Nat. 104(4 ): 579-58 2. 

Wilson, S . C. 1978 . Social orga nization and behavior o f harbor sea ls, Phoca concolor, in Maine. F inal Repo rt to

Marine Mamm al Comm ission, Contra ct MM 6ACO 13, GP O-PB-280-18 8. 
144

November 2001

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: in 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 se parated b y both geo graphy and differences in the breeding s eason from the eastern A tlantic

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 tha t breeds o n the pack ic e in the Gulf of S t. Lawrence (Hammill et al. 1998). Tagging studies indicate that

there is little intermixing between the two breeding groups (Zwanenberg and Bowe n 1990), and for management

purpose s, they are treated as separate p opulations (Mohn and Bo wen 199 6). How ever, small num bers of animals

and pupping have been observed on several isolated islands along the Maine coast and in Nantucket-Vineyard

Sound, Massachusetts (Katona et al. 1993; Rough 1995; J. R. Gilbert, pers. comm., University of Maine, Orono,

ME). In recent years, a year-round breeding population of approximately 400 animals has been documented on outer

Cape Cod and N antucket Island (Dennis Murley, pers. comm., Mass. Audubon Society, Wellfleet, MA). Gilbert

(pers. com m.) has also d ocumen ted a reside nt colony in M aine. 

POPU LATIO N SIZE

Estimates of the total western Atlantic gray seal population are not available; however, four estimates of

portions of the stock are available for Sable Island, the Maine coast, and Muskeget Island (Nantucket) and

Monomoy, (Cape Cod) Massachusetts (Table 1). The 1993 estimate of the Sable Island and Gulf of St. Lawrence

stocks was 143,000 animals (Mohn and Bo wen 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. 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 at a winter breeding colony on

Muskeget Island, west of Nantucket Island obtained during the spring molt 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). 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). No gray seals were recorded at

haulout sites be tween Ne wport, Rh ode Island and Montauk P t., New Yo rk (Barlas 1 999). T he 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 Nantuc ket Sound . Fifty-four percen t of the seasona l count was o n Muske get Island and adjacent sa nd 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, and resulting abundance estimate (Nmin) and coe fficient of variation (CV). 

Month/Year Area Nmin CV

1993 Sable Island and Gulf of St. Lawrence 143,000 none reported

Apr-May 1994 Muskeget Island and Monomoy, MA12,010 none reported

Spring 1999 Muskeget Island and Monomoy, MA1

5,611 none reported 

 

1 These c ounts repre sent pertain to animals seen in USA w aters, and the sto ck relationship to animals in

Canadian waters is unknown.
145

Minimum Po pulation 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 14 3,000 g ray seals in Can ada (M ohn and B owen 19 96). 

Current Population Trend

Gray seal ab undance is likely increasing in the USA A tlantic Exclusive Economic Zone (EEZ), b ut 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; M ohn and

Bowen 1996); w hereas, in the G ulf of St. Lawren ce it is increasing a t a slower rate o f 7.4% (H ammill et al. 1998). 

Appro ximately 57% of the western N orth Atlantic p opulation is fro m the Sab le 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 1998/99 winter surveys (26 January, 9 February, and 10 March). On 9 February, 77 gray seal

pups (59 on Muskeget Island and 18 on So uth Monomoy) were recorded (B arlas 1999). 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 d etermined what prop ortion of the inc rease repr esents growth or immigra tion. 

CURRENT AND M AXIMUM 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 1 994).

For purp oses of this assessment, the ma ximum net p roductivity rate was assume d to be 0.1 2. This valu e 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; W ade 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 known to be increasing. PBR for the

western North Atlantic gray seals in USA waters is unknown. Applying the formula to the minimum population

estimate for Canadian waters resu lts in a “PBR” of 8,85 0 gray seals.

ANNUAL HUMAN-CAUSED MORTALITY AND SERIOUS INJURY

For the pe riod 199 5-1999 , the total estimated human cau sed morta lity and serious inj ury to gray seals is

estimated to be 110 per year. The average is derived from two components: 1) the 1995-1999 observed fishery 103

(CV= 0.25; Table 2); and 2) average 1997-1 998 stran ding morta lities resulting from p ower plan t entrainments, o il

spill, shooting, an d other sou rces, 6.5. 

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 pro vided observer coverage of pelagic longline vessels fishing off the

Grand B anks (Ta il of the Bank s) and pro vides obse rver cove rage of vesse ls fishing south of Cape Ha tteras. 
146

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 199 6) 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%, and 6%, respectively. The fishery has been observed in the Gulf of

Maine and in Southern New England. There were 40 gray seal mortalities observed in the Northeast multispecies

sink gillnet fishery between 1993- 1999 (Table 2). Twenty-one of the observed mortalities occurred in winter

(January - May), 9 in the southern Gulf of Maine, two in the "mid-coast closed area,” and two in the South Cape

closure. Only one mortality was observed in northern Maine waters, which occurred in autumn (SeptemberDecember) 199 5. One o f the 1993 observed mortalities was in May, and was from SE of Block Island. 

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 zero 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), and 155 in 1999 (0.51). The 1995 bycatch includes 28 animals from

the estimated number o f unknown se als (based o n observe d mortalities o f seals that could not be iden tified to

species). The unkno wn seals were prorated, b ased on spatial/tempora l patterns of bycatch of harbor sea ls, 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 1995-1999 was

103 gray seals (CV=0.25). 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 Fund y groundfish gillnets, Atlantic Canada and G reenland salmon gillnets, Atlantic Canad a cod traps,

and in Ba y of Fundy he rring weirs (Re ad 199 4). In additio n to incidenta l catches, some mortalities (e.g ., seals

trapped in herring weirs) were the resu lt of direct shoo ting, and there w ere culls of ab out 1,700 animals annu ally

during the 1 970's and e arly 1980 's on Sable Islan d (Anon . 1986). 

There were 3,121 cod traps operating in Newfoundland and Labrador during 1979, and about 7,500 in 1980

(Read 1 994). T his fishery was clos ed at the end of 1993 due to colla pse of Can adian grou ndfish resour ces. 

Herring weirs are also distributed throughout the Bay of Fundy; it has been reported that 180 weirs were

operating in the Bay of F undy in 199 0 (Read 1994). 

In 1996, observers recorded three gray 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 we re highest during April-Jun e. Many o f the seals that died during fishing ac tivities were unide ntified. 

The proportion of sets with mortality (all seals) was 2.7 per 1,000 hauls (0.003).
147

Table 2. Summar y of the incidenta l mortality of gray se al (Halichoerus grypus) by commercial fishery including the

years samp led (Yea rs), the numb er of vessels ac tive within the fishery (V essels), the type o f data used (D ata

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 3

Estimated

 Mortality 3

Estimated

 CVs 

Mean

 Annual

 Mortality

 Northeast

Multispecies

 Sink Gillnet

95-99 301 Obs. D ata

 Weigho ut,

 Logbooks

.05, .04,

.06, .05,

.06

7, 3, 16,

4, 5

117, 49,

131, 61,

155

.42, .49,

 .50, .98,

.51

103

(.25)

 TOTAL 103

(.25)

1 Observer data (O bs. Data) are used to m easure bycatch rates, and the da ta are collected within the Northea st

Fisheries Science Center (NEFSC) Sea Sampling Program. NE FSC 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 observe r coverage for the No rtheast multispecies sink gillnet fishery is measured in trips.

3

In 1995 and 199 8 respectiv ely, observe d mortality on “marine mammal trips” w as 6 and 3 animals. On ly

these mortalities were used to estimate total gray seal byca tch. See Bisack (19 97) for “trip” type definitions.

In 1995 and 1998 o ne mortality in each year was recorded on a “fish trip.” In 1997 all observed takes were

on marine mammal trips, including 12 taken on pingered trips. In 1998 and 1999 takes from nonpingered

nets within a marine mammal time/area closure that required pingers and takes from pingered nets not

within a marine mamma l time/area clo sure that requ ired pingers were poo led with the take s 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 one take was observed in a net

without a pinger that was within a marine mammal closure that required pingers. In 1999 two takes were

observed in nets with pingers.

Other M ortality

 Gray seals, like h arbor sea ls, were hunted for bounty in N ew Englan d waters until the la te 1960 's. This

hunt may have severely depleted this stock in USA waters (Rough 1995). In addition, V. Rough (pers. comm.) has

documented several animals with netting around their necks in the Cape Cod/Nantucket area. An unknown level of

mortality also o ccurs in the ma riculture industry (i.e., salmon farming) and by deliberate shooting (NMFS

unpublishe d data). 

The 1992-1996 gray seal strandings data are currently under review. In 1997-1998, 103 gray seal stranding

were recorded, extending from Maine (17) to Maryland (2). Most of the stranding were in Massachusetts (28), New

York (2 8), and M aine (17). T hirteen anima ls showed sign s of human inte ractions: fishery (3 ), power p lant (2), oil

spill (4), shot (1), mutilated (1), other (2). 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 wash ashore,

nor will all of those that do wash ashore nec essarily show sign s of entanglem ent or other fish ery interaction. 

 STATUS OF STOCK

The status of the gray seal population, relative to OSP, in USA 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 serio us injury for this stoc k is believed to be very low relative to the p opulation siz e in

Canadian waters and can be considered insignificant and approaching zero mortality and serious injury rate. The
148

level of human-caused mortality and serious injury in the USA Atlantic EEZ is unknown, but believed to be very low

relative to the to tal stock size; there fore, this is not a strate gic 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.

Bonne r, W. N . 1981. G rey seal, Halichoerus grypus. In: S. H. Ridgway and R. J. Harrison (eds.), Handbook of

Marine Mamm als, Vol. 2. P p. 111-1 44. Lond on: Academ ic Press.

Barlas, M. E. 19 99. The distribution and abundance of harb or seals (Phoca vitulina concolor) and gray sea ls

(Halichoerus grypus) in southern New England, winter 1998- summer 1999. MA Thesis, Boston

University, G raduate Sc hool of Arts and Scien ces., Bosto n, MA. 5 2 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. Comm er., 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 199 5. 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), H andbook o f Marine Ma mmals,

Vol. 2: Se als. Academ ic Press, London , 359 pp . 

Davies, J. L. 1957. T he geogra phy of the gra y seal. J. Mamm. 38: 297-310.

Hammill, M.O., G.B. Stenson, R.A. Myers and W .T. Stobo. 1998. Pup production and po pulation trends of the

grey seal (Halichoerus grypus) in the Gulf of S t. Lawrence . Can. J. F ish. Aqua t. 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 Newfo undland. Smithsonian Institution Press, Washin gton, DC. 316 pp . 

Lens, S. 19 97. Interac tions betwee n marine mammals an d deep w ater trawlers in the NAFO regulatory are a. ICES

C.M. 8/Q. 10 pp.

Mansfield , A.W. 1 966. The grey seal in ea stern Canad ian 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. A quat. Sc i. 53:2722-2738.

Payne, P . M. and L . A. Selzer. 19 89. The distribution, ab undance and selected prey of the har bor seal, Phoca

vitulina concolor, in southern New England. Mar. M amm al Sci. 5(2): 173 -192. 

Read, A . J. 1994. In teractions be tween cetac eans and g illnet and trap fishe ries in the northw est Atlantic. Rep. int

Whal. Commn. Special Issu e 15: 13 3-147. 

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. Zwa nenburg. 1 990. G rey 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

biology of sealworm (Pseudoterranova decipiens) in relation to its interm ediate 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. 19 96. The N ew England gillnet effort survey. NO AA, NM FS, NEFSC, Woo ds Hole, M assachusetts.

NEFSC [Northeast Fisheries Science Center] Ref. D oc. 99-10 . 38 pp. 

Zwanenb erg, K.C.T . and W.D. Bow en. 1990 . Populatio n trends of the g rey 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 H osts. Can. Bull. Fish. and Aq. Sci. 222.
149

November 2001

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 an d Kova cs 1988 ); however, in recent years, numbers of sigh tings and strand ings have be en 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). These appearances usually occur in January-May, when the

western North Atlantic stock of harp seals is at its most southern point of migration. The worlds' harp seal

population is divided into three separate stocks, each identified with a specific breeding site (Bonner 1990; Lavigne

and Ko vacs 198 8). The lar gest stock is loc ated in the we stern North Atlantic off easter n Canad a and is divid ed 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 198 8). The second stock breeds in the White Sea off the coast of the Soviet Union, and

the third stock breeds o n the We st Ice off of easter n Greenla nd (Lavign e and Ko vacs 198 8; Anon 1 998). H arp seals

are highly migratory (Sergeant 1965; Stenson and Sjare 1997). Breeding occurs at different times between midFebruary a nd April for each stock. A dults then assem ble north o f their whelping p atches to und ergo the ann ual 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 rem aining off the co ast of Newfo undland. F ollowing ma ting, the seals disp erse to feed, a nd in late Ap ril

they again co ncentrate in larg e numbers on the ice to m olt.

The extre me souther n limit of the harp seal's habitat exten ds into the U SA Atlantic E xclusive Ec onomic

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).

POPU LATIO N SIZE

The total population size of harp seals is unknown; however, three seasonal abundance estimates are

available which used a variety of metho ds including aerial surveys and mark -recapture (Table 1 ). Generally, these

methods in clude surve ying the whelpin g concen trations and m odeling pu p produ ction. Harp seal pup p roduction 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) 57 7,900 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

populatio n. This techn ique incorp orates rece nt pregnanc y rates and estim ates of age-sp ecific hunting mortality

(CAFSAC 19 92). 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 estimates was 4.8 million (95% CI =

4.1-5.5) million harp seals (Warren et al. 1997; T able1). T he 1999 populatio n estimate is 5.2 million (95% CI = 4.0

- 6.4) million harp seals (Healey and Stenson 2000) (Table 1).
150

Table 1. Summary of abundance estimates (pups and total) for western North Atlantic harp seals. Year and area

covered during each abundance survey, and 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 pop ulation estimate

Present data are insufficient to calculate the minimum population estimate for USA waters. It is estimated

there are at lea st 5.2 million (± 1.2 million) h arp seals in Canada (H ealey and S tenson 20 00). 

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 m illion; ±1.2 million), due to lar ge harvests o f young anima ls in recent years (H ealey and S tenson 20 00). 

CURRENT AND M AXIMUM NET PRODUCTIVITY RATES

Current and maximum net productivity rates are unknown for this stock. The best data are based on

Canadian studies. Rece nt studies indicate that pup produ ction has increased, but the rate of po pulation 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 purp oses of this assessment, the ma ximum net p roductivity rate was assume d to be 0.1 2. This valu e 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; W ade and Angliss 1997). The minimum

populatio n size in US A waters is unk nown. Th e maximum produc tivity rate is 0.12, the default value fo r pinniped s. 

The “recovery” factor, which accounts for endangered, depleted, threatened stocks, or stocks of unknown status

relative to op timum sustaina ble pop ulation (OS P) was set at 1 .0 becaus e it was believe d that harp se als 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 312,00 0 harp seals. However, Johnston et

al. (2000), suggest that catch statistics from the Canadian hunt are negatively biased due to under reporting, therefore

an FR 0.5 would be appropriate. Using the lower FR results in a “PBR” of 15 6,000 h arp seals. 

ANNUAL HUMAN-CAUSED MORTALITY AND SERIOUS INJURY

For the period 1995-1999, the total estimated human caused mortality and serious injury to harp seals was

321,356. This is derived from three components: 1) 1995-1999 average catches of Northwest Atlantic harp seals by

Canada and Greenland 301,611; 2) 1995-1999 average bycatches in the Newfoundland lumpfish fishery (16,000 -

23,000 annually); and 3) the 1995-1999 observed U SA fisheries, 245 harp seals CV= 0.20; Table 2).
151

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 pro vided observer coverage of pelagic longline vessels fishing off the

Grand B anks (Ta il of the Bank s) and pro vides obse rver cove rage of vesse ls fishing south of Cape Ha tteras. 

Recent bycatch has been observed by NMFS Sea Samplers in the Northeast multispecies sink gillnet

fisheries, but no m ortalities have b een doc umented in the mid-Atlan tic coastal gillnet, A tlantic drift gillnet, pelag ic

pair trawl or p elagic longline fisheries. 

Northeast M ultispecies 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 199 6) 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%, and 6% for 1990 to 1999, respectively. The fishery has been

observed in the Gulf of Maine and in Southern New England. There were 118 harp seal mortalities observed in the

Northeast multispecies sink gillnet fishery between 1990 and 1999. 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 was zero (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), and 81 in 1999 (0.78). The

1994 a nd 199 5 bycatche s, respectively, inc lude 16 a nd 153 animals from the estimated number o f unknown se als

(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 1995-

1999 was 2 42 harp seals (CV =0.20). The stratification design used is the same as that for harbor p orpoise

(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 Co astal Gillnet:

Observer coverage of the USA Atlantic coastal gillnet fishery was initiated by the NEFSC Sea Sam pling

program in July, 1993; and from July to December 1993, 20 trips were observed. During 1994 and 1995 221 and

382 trips w ere obser ved, respe ctively. This fishery, w hich extend s from No rth Carolina to New Y ork, is actually a

combina tion of small vessel fisheries that targe t a variety of fish spe cies, some o f which ope rate right off the be ach. 

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%, and 3%, 5% , and 2% for 1995, 1996 , 1997, 1998, and 1999 , 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 mo rtality (CV in p arentheses) a ttributed to this fishe ry was 0 in 19 95-199 7 (0), 17 in 1998 (1 .02), and 0 in

1999 (0 ). Average a nnual estimate d fishery-related mortality attributa ble to this fishery d uring 199 5-1999 was 3.0

harp seals (CV=1.02)

CANADA

An unkno wn numbe r of harp sea ls have been taken in Ne wfoundlan d and La brador g roundfish gillne ts

(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 ind icates that fewer th an 10,00 0 seals were taken annua lly 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 23,00 0 seals annually (DFO 2000).
152

There were 3,121 cod traps operating in Newfoundland and Labrador during 1979, and about 7,500 in 1980

(Read 199 4). This fishery was closed at the end o f 1993 due to co llapse of Canadian gro undfish resources.

In 1996, observers recorded four harp 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 we re highest during April-Jun e. Many o f the seals that died during fishing ac tivities were unide ntified. 

The proportion of sets with mortality (all seals) was 2.7 per 1,000 hauls (0.003).

Table 2. Summar y of the incidenta l mortality of harp seal (Phoca groenlandica) by commercial fishery including the

years samp led (Yea rs), the numb er of vessels ac tive within the fishery (V essels), the type o f data used (D ata

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 3

Estimated

 Mortality 

Estimated

 CVs 

Mean

 Annual

 Mortality

 Northeast

Multispecies

 Sink Gillnet

95-99 301 Obs. D ata

 Weigho ut,

 Logbooks

.05, .04, .06,

.05, .06

 27, 9,

 40, 4,

4

694, 89,

269, 78, 81

.27, .55,

.50, .48,

.78

242

(.20)

Mid Atlantic

Coastal Sink

Gillnet

95-99 Unk4 Obs. D ata

Weighout

.05, .04, 

.03, .05,

.02

0, 0, 

0, 1,

0

0, 0, 

0,17,

0

0, 0, 0,

 1.02,

0

3

(1.02)

TOTAL 245

(.20)

1 Observer data (O bs. Data) are used to m easure bycatch rates, and the da ta are collected within the Northea st

Fisheries Science Center (NEFSC) Sea Sampling Program. NE FSC 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 thirty-one and zero harp seals were taken on pingered trips during

1997 and 1998, respectively. During 1997, 1998 and 1999 there were 31, 4 and 2 harp seals observed on

"mamm al trips", respe ctively. See Bisack (199 7) for “trip” typ e definitions. D uring 199 9 two harp seals

were observed o n “fish trips” and three were observe d taken from pingered nets.

4 Number of vessels is not known.

Other M ortality

 Harp sea ls have been comme rcially hunted sinc e the mid-18 00's in the Can adian Atlan tic (Stenson 1 993). 

A total allowa ble catch (T AC) of 2 00,000 harp seals wa s set for the large v essel hunt in 19 71. The TAC v aried until

1982 when it was set at 186,000 seals, and remained at this level through 1995 (Stenson 1993; Anon 1 998). The

TAC was increased to 250,000 and 275,000, respectively in 1996 and 1997 (Anon 1998). Catches ranged from

124,000 to 231,000 from 1971-1982, declining to a range of 19,000 to 94,000 between 1983-1995, and increased

dramatically to 242,000 (1996) and 261,000 (1 997) (Stenson 1993; Anon 199 8). Harp seals are also hunted in the

Canadian Arctic and in Greenland (DFO 200 0). 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 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 loss es of older se als is higher (ap proxima tely 50%) (DFO 2000). 
153

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 stra nding in No rth Carolina . From 19 97-199 8 224 stra ndings were recorde d, including o ne in North

Carolina. M ost of the strand ings occurre d in Main e (27), M assachusetts (5 1), New J ersey (21), a nd New York (9 2). 

Few animals showed signs of human interactions, and except for one shot animal the interactions were classified as

other. The increased n umber o f strandings ma y indicate a po ssible shift in distributio n or expa nsion southw ard into

USA waters.

STATUS OF STOCK

The status of the harp seal stock, relative to OSP, in the USA 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

endange red unde r the Enda ngered S pecies Ac t. The total fisher y-related mo rtality and seriou s 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

USA A tlantic EEZ is unknown, b ut believed to be very low r elative to the tota l stock size; there fore, 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, Copenha gen, Denm ark. 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. Comm er., NOAA Tech.

Memo . NMF S-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 199 5. Rep. int Whal. Commn. 47:705 -14. 

Bonne r, W. N . 1990. T he natural histo ry of seals. Fact on File, New Y ork, 196 pp. 

Bowen, W. D. and D. E. Sergeant. 1983. Mark-recapture estimates of harp seal pup (Phoca groenlandica)

produc tion in the northw est Atlantic. Can. J. F ish. Aqua t. Sci. 40: 728-742.

Bowen, W. D. and D . E. Sergeant. 1985. A Mark-recapture estimate of 1983 Harp seal Pup Production in the

Northwe st Atlantic. NAFO SCR. Doc. 85 /I/1. 

CAFS AC. 199 2. Upd ate on po pulation estimates of Har p seal in the N orthwest Atlan tic. Canadia n Atlantic

Fisheries Sc ientific Adviso ry Committee, CAFSAC Adv. Doc. 92/8.

DFO. 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. Stenso n. 2000. E stimating pup produc tion and po pulation size o f the northwest A tlantic

harp seal (Phoca groenlandica). Can. Stock Assess. Sec. Res. Doc. 2000/081.

Johnston, D . W., P., M eisenheime r, and D. M . Lavigne. An evaluation o f managem ent objec tives for Cana da’s

comme rcial harp sea l 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 Newfo undland. Smithsonian Institution Press, Washin gton, DC. 316 pp . 

Lavigne, D . M. 199 9. Estimating to tal kill of Northw est Atlantic harp seals, 1994 -1998. Mar. Mammal Sci.,

15(3):8 71-878 . 

Lavigne, D . M. and K . M. Ko vacs. 198 8. Harps and Ho ods Ice B reeding Se als of the No rthwest Atlantic. 

University of Waterloo Press, Waterlo o, Ontario , Canada , 174 pp . 

Lens, S. 1997. Interactions between marine mammals and deep water trawlers in the NAFO regulatory area. ICES

C.M. 8/Q. 10 pp.

McA lpine , D. F. an d R. H. W alker. 199 0. Extralimital re cords of the harp seal, Phoca groenlandica, from the

western N orth Atlantic: a re view. Mar. M amm al 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 Issu e 15: 13 3-147. 
154

Roff, D. A. a nd W. D. Bow en. 1983 . Populatio n dynamics a nd manag ement of the N orthwest Atlan tic harp seal.

Can. J. F ish. Aqua t. 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, V ol. 2: Seals. Academ ic Press, New Y ork, 359 pp. 

Rubinstein, B . 1994. A n appare nt shift in distribution o f ice seals, Phoca groenlandica, Cystoph ora 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 . Migration s of harp sea l Pagophilus groenlandicus (Erxlebe n) in the No rthwest Atlantic. J.

Fish. Res. Bd. Can. 22:433-464.

Sergeant, D . E. 1975 . Estimating num bers of H arp seals. Rapp. P. -v. R eun. Cons. int Ex plor. Mer. 169: 274-280.

Shelton, P. A., N. G. Caddigan and G. B. Stenson. 1992. Mo del estimates of harp seal population trajectories in the

Northwe st Atlantic. CAFSAC Res. Doc. 92/89, 2 3 pp. 

Shelton, P. A., G. B. Stenson, B. Sjare and W. G. Warren. 1996. Model estimates of harp seal numbers-at-age for

the Northw est Atlantic. NAFO Sci. Coun. Studies 26:1-14.

Sjare, B., G. B. Stenson and W. G. W arren. 1996. Summary of female harp seal reproductive parameters in the

Northwe st 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. 20 00. Rece nt estimates of re produc tive rates for har p seals in the N orthwest Atlan tic. 

Can. Stock Assess. Sec. Res. Doc. 2000/077.

Stenson, G . B. 1993 . The status o f pinnipeds in the Newfo undland re gion. 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 S eals, Phoca groenlandica, in the Northw est Atlantic. Can. J. F ish. Aqua t. Sci. 50: 2429-2439.

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.

Stenson, G. B., M. O. Hammill, M. C. S. Kingsley, B. Sjare, W. G. W arren and R. A. Myers. 1996. 1994 pup

production of N orthwest 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.

Stevick, P. T . and T. W . Fernald. 19 98. Increa se in extralimital rec ords of har p seals in M aine. 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. 19 96. The N ew England gillnet effort survey. NO AA, NM FS, NEFSC, Woo ds Hole, M assachusetts.

NEFSC [Northeast Fisheries Science Center] Ref. Doc. 99-10. 38 pp.

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.

Warre n, W. G ., P. A. Shelto n and G. B . Stenson. 19 97. Qua ntifying some o f the major so urces of unc ertainty

associated with estimates of harp seal prey consumption. Part 1: Uncertainty in the estimates of harp seal

populatio n size. J. Northwest Atl. Fish. Sci., 22: 289-302.
155

APPEN DIX I. 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 prese nt, manatees of the genus Trichechus are represented

by three allop atric species: T. senega lensis, the West A frican mana tee, T. inung uis, 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 (Trichech us man atus latirostris) (U.S. Fish and

Wildlife S ervice, 198 9). Such sub speciation m ay reflect repro ductive isolatio n brought o n by the intemp erate

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 (Trichech us man atus 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 Florid a's east coast. Ex tralimital movements occ urred and were typically sea sonal, with animals travelling north

during warm er period s and travelling south as temp eratures de clined. W hile most ma natees wintere d 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 subm erged aquatic vegetation, and increased protective me asures,

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. D ocumen tation of man atee move ments betwe en Gulf and Atlantic coast populatio ns in far south Flo rida 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 ou tside of Florida has increased in rec ent years.

POPU LATIO N SIZE

Minimum Po pulation 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 increa sed by an av erage of 5.9 percent pe r year in Florid a from 19 76 throug h 1992 (Ackerman et al. In press). 

Garrott et a l.'s (1994) an alysis of trends at w inter aggrega tion sites suggest a mean annu al increase o f 7-12 perc ent 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 m aterial collecte d by the carc ass recove ry program . This study yield ed informa tion on age-re lated aspec ts

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

value. When adult mortality was reduced by 10 percent in the model, population growth improved considerably, but
156

when adu lt mortality was incre ased by 10 percent the p opulation q uickly dwindle d. These results clearly indic ate

that the Florida manatee population is still at high risk of extinction in the long term. Any negative change in the

population param eters, caused by environmental changes or a catastroph e, might tip the balance towards grea ter risk

of extinction.

ANNUAL HUM AN-CAUSED MOR TALITY

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,

entangleme nt in, and ingestio n of marine d ebris (e.g., mo nofilament), an d others (A ckerman e t al., In press). 

From 1974 through 1994, 2,456 manatee carcasses were recovered in the southeastern U.S. Eight hundred

and two (3 3 percen t) were attribute d to huma n-related cau ses. Of these, 6 13 were c aused by c ollisions with

watercraft, 11 1 were floo d gate/cana l lock-related, a nd anothe r 78 were c ategorized as other hum an-related. 

In Florida, human-related mortality accounted for the greatest proportion of deaths with identifiable causes

(45 perc ent, with anothe r 24 perc ent of deaths r esulting from un determine d causes) fro m 1986 -1992. Collisions with

watercraft acc ounted for 83 perc ent of human -related caus es of death d uring this perio d (Ackerman et al. 19 94, 

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 app roximately 25% o f 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, 19 92; Bec k, C.A. and N.B. Barros, 199 1). Recre ational fishing ac tivities have also b een implica ted in

manatee deaths; manatees have died as a result of ingesting monofilament line and fishing tackle and from

entanglement in monofilame nt line, crab trap lines, and cast nets. Non-lethal entangleme nt associated with these

gear types, sometimes resu lting in the loss of a flipp er due to co nstriction, is also kn own to oc cur. Collision s with

fishing boats probably occ ur; 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 (F DEP Manate e Morta lity Database , 1994). F ishing gear is susp ected in three additional d eaths. 

"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 ma jority of the ma natee dea ths attributed to comme rcial fisheries invo lve the shrimp ing industry. 

Mortalities have occurred in northeast Florida (Duval County), east central Florida (Volusia County), and the Florida

Panhand le area (Fra nklin Coun ty), as well as in coa stal waters of G eorgia and South Ca rolina 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 M ortality 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 (natura l and huma n-related) rela tive to the estima ted pop ulation level an d continuing , severe threats to

critical manatee habitats in the southeastern U.S.

POTENTIAL BIOLOGICAL REMOVAL
157

Because of its endang ered 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 R max (maximum net productivity rate) of

0.04, the Potential Bio logical Removal (PBR) rate for mana tees is as follows:

PBR = (1822)(.02, or 1/2 Rmax)(.1) = 3

The calc ulated PB R level is greatly e xceeded by known h uman-related manatee m ortality (primarily

watercraft collisions and water control structure deaths) every year in Florida. For this reason, and because current

efforts of the Flo rida Ma natee Rec overy Te am focus inte nsively on the re duction of the se major typ es 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 m anatees a d ifficult exercise. M armontel's (19 94) estima te of net prod uctivity 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. W right, R.K. Bonde, D .K. Ode ll, and D.J. B anowetz. (In press). Tre nds and p atterns in

mortality in Florida, 197 4-1992 . In T.J. O'Shea, B.B. Ackerman, and H. F. Percival, editors. Population

Biology of the Florida manatee (Trichech us man atus latirostris). National Biological Service, Biological

Report.

Ackerman, B.B. 1992. O ngoing ma natee aerial su rvey progr ams: a prog ress 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 Southea stern United States: a compilation and review of rec ent informatio n. Natl. Te ch. Inf. Ser.,

PB88-207980/AS: Springfield, VA. Two volumes, 613 pp.

Domn ing, D.P. an d L.C. H ayek. 198 6. Interspec ific and intraspe cific morph ological variation in mana tees (Sirenia: 

Trichechus)," Marine Mammal Sci. 2:87-144.

Florida Department of Environmental Protection. 1995. Manatee mortality database, 1974-1994. Florida Marine

Research Institute, Marine Mam mal Patho biology La boratory.

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. 197 4. Distributio n, status, and co nservation o f the manatee in the United States. Natl. T ech. Inf.

Ser., PB81-140725, Springfield, VA. 246 pp.

Marmontel, M. (In press). Age and repro ductive pa rameter estim ates in female F lorida man atees. In T.J. O'Shea,

B.B. Ackerman, and H.F. Percival, eds. Population biology of the Florida manatee (Trichechus manatus

latirostris). National B iological Se rvice, Biolo gical Repo rt.

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 M ammals 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.

Packard, J.M. 1985. Preliminary assessment of uncertainty involved in modeling manatee populations. Manatee

populatio n Researc h Repo rt No. 9. T echnical Re port No . 8-9. Florida Coope rative Fish and Wildlife

Research Unit. University of Florida, Gainesville, Florida. 19 pp.
158

Reynolds, J.E., III and J.R. Wilcox. 199 4. Observations of Flo rida manatees (Trichech us man atus latirostris)

around selected power plants in winter. Marine Mammal Sci. 10(2): 143-177.

U.S. Fish and Wildlife Service. 1989. Florida Manatee (Trichech us man atus 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 Flo rida, 197 9-1991 . In T.J. O'She a, B.B. A ckerman, a nd H. F. P ercival, edito rs. 

Population Biology of the Florida manatee (Trichech us man atus latirostris). National Biological Service,

Biologic al 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.
159

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 prese nt, manatees of the genus Trichechus are represented

by three allop atric species: T. senega lensis, the West A frican mana tee, T. inung uis, 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

mana tus 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.

POPU LATIO N SIZE

The exact number of Antillean manatees known to occur in Puerto Rico is unknown but, based on aerial

surveys cond ucted on J uly 16 and 17, 199 4, this popu lation include s at least 86 ind ividuals (Ola nd, pers. co mm.). 

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

sporadic ally to the prese nt. Carcass sa lvage efforts we re initiated in Ap ril 1974, b y the U.S. Fish and W ildlife

Service (Rathbun et al., 1986). In 1989, the Caribbean Stranding Network initiated a dedicated salvage, rescue, and

rehabilitation program and has assumed respo nsibility for all carcass recovery efforts in Puerto Rico. D espite these

assessments, limited information exists by which to determ ine trends in this population of manatee s.

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 HUM AN-CAUSED MOR TALITY

Since the inception of Puerto Rico's manatee carcass salvage program, 70 manatee deaths have been

recorde d from that ar ea (Carib bean Stran ding Netw ork, unpub l. data). Ma ny of the death s have bee n attributed to

human-rela ted causes. Carcass collec tion efforts have docume nted morta lities associated with nets and w atercraft

(N=37). M any net-related mortalities involve poaching a nd are not substantiated by the pre sence of a carcass

(Rathbun et al., 1985 ). From 19 74 until 19 88, 41.5 percent of the docume nted morta lity 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).
160

FISHERIES INFORMATION

In Puerto Rico, fisheries in teractions ha ve been d ocumen ted through the carcass re covery pro gram 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 unk nown (M ignucci et al., 19 93). Give n the scarcity of d etailed information, little is

known about capture sites, seasonality of occurrence, etc. (Rathbun et al., 1985). Because these deaths account for a

substantial pro portion o f known hum an-related mortalities (and b ecause of the prevalenc e of fishery repo rts), 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 populatio n level and c ontinuing, seve re threats to critica l manatee ha bitats

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 Popula tion. Inadeq uate informa tion on po pulation size a nd net pro ductivity rate for m anatees in P uerto

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 datase t for that pop ulation, suggested that the net p roductivity wa s essentially zero (-0.003). W hen the defa ult

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 p lans.

REFERENCES

Ackerman, B.B., S.D. W right, R.K. Bonde, D .K. Ode ll, and D.J. B anowetz.(I n press). Trends and patterns in

mortality in Florida, 197 4-1992 . In T.J. O'Shea, B.B. Ackerman, and H. F. Percival, editors. Population

Biology of the Florida manatee (Trichech us man atus latirostris). National Biological Service, Biological

Report.

Domn ing, D.P. an d L.C. H ayek. 198 6. Interspec ific and intraspe cific morph ological variation in mana tees (Sirenia: 

Trichechus). Marine Mammal Sci. 2:87-144.

Freeman, J. and H . Quintero. 1990. T he distribution of West Ind ian 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. B est. 1989. Distribution, status,and bioge ography of the W est

Indian manatee. Biogeography of the West Indies, 1989: 567-610.

Marmontel, M. (In press). Age and repro ductive pa rameter estim ates in female F lorida man atees. In T.J. O'Shea,

B.B. Ackerman, and H.F. Percival, eds. Population biology of the Florida manatee (Trichechus manatus

latirostris). National B iological Se rvice, Biolo gical Repo rt.

Mignuc ci Gianno ni, A.A. 198 9. Zooge ography o f marine mam mals in Pue rto Rico an d 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.
161

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.

Mignuc ci Gianno ni, A.A., B. P into-Rodriguez, R.A. M ontoya-O spina, D.P . Moor e, and E.H . Williams. 1 993. 

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 M ammals 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 , Boque ron, PR. T o: Robe rt O. Turn er, Mana tee Reco very Coo rdinator, FW S Jackso nville

Field Office, Jacksonville, FL.

Rathbun, G .B., Carr, N ., Carr, T., an d C.A. W oods. 19 85. The distribution o f manatees an d sea turtles in P uerto

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.
162

APPENDIX II. Stock assessment reports not updated in the year 2001.

September 2000

SEI WHALE (Balaenoptera borealis):

Nova Scotia Stock

STOCK DEFINITION AND GEOGRAPHIC RANGE

Indications a re that, at least during the feeding season, a major portion of the sei wha le popula tion is

centered in northerly waters, perhaps on the Scotian Shelf (Mitchell and Chapman 1977). The southern portion of

the species' rang e during spring and summer include s the northern portions o f the USA Atlantic Exc lusive Eco nomic

Zone (EEZ) — the Gulf of M aine and G eorges Bank. The p eriod of gre atest abund ance there is in sp ring, with

sightings concentrated along the eastern margin of Georges Bank and into the Northeast Channel area, and along the

southwestern edge of G eorges Bank in the area of Hydro grapher Canyon (CE TAP 1982). N MFS aerial surveys in

1999 a nd 200 0 found co ncentrations of sei and right w hales along th e Northe rn Edge o f George s 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). Mitchell (1975) similarly reported that sei whales off Nova Scotia were often distributed closer to the 2,000

m depth c ontour than were fin whales. 

This general offshore pattern of sei whale distribution is disrupted during episodic incursions into more

shallow and inshore wate rs. Although k nown to tak e piscine pre y, sei whales (like righ t whales) are lar gely

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 S outh Chan nel (in 198 7 and 19 89) and Stellwagen B ank (in 198 6) areas (R.D. Kenn ey, pers. com m.;

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, M itchell (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 indee d all North Atlantic whales) was a majo r research p roblem (D onovan 1 991). In the absence o f evidence to

the contrary, the proposed IWC stock definition is provisionally adopted, and the “Nova Scotia stock” is used here as

the manage ment unit for this sto ck assessme nt. The IW C bound aries for this stock are from the U SA east co ast to

Cape Breton, Nova Scotia, thence east to longitude 42o W.

POPU LATIO N SIZE

The total number of sei whales in the USA 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 USA

Atlantic EEZ during the springs of 1979-81.

Mitchell an d Chapman (19 77), base d on tag-rec apture da ta, estimated the Nova S cotia, Cana da, stock to

contain between 1,393 and 2,248 sei whales (Table 1). Based on census data, they estimated a minimum Nova

Scotian po pulation of 8 70 sei whale s. 

An abundance of 253 sei whales (CV=0.63) was estimated from an aerial survey program conducted from

1978 to 1982 o n the continen tal shelf and shelf ed ge waters be tween Cap e Hatteras, N orth Caro lina and N ova Sco tia

(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
163

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 ce ssation of exten sive foreign fishing operation s 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 coe fficient 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 Po pulation 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 a bundanc e estimates (within the last 10 years). 

Current Population Trend

There a re insufficient data to determin e the pop ulation trends for this species. 

CURRENT AND M AXIMUM NET PRODUCTIVITY RATES

Current and maximum net produ ctivity rates are unk nown for this sto ck. For pu rposes of this a ssessment,

the maximum net productivity rate was assumed to be 0.04. This value is based on theoretical modeling showing

that cetacean populatio ns may not gro w at rates muc h greater than 4% give n the constrain ts of their repro ductive 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; W ade and Angliss 1997). The minimum

populatio n size is unkno wn. The m aximum p roductivity rate is 0.04, the de fault value for ce taceans. The “recove ry”

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). PB R 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, entang lement, or inju ry in the NEF SC or N E Regio nal Office da tabases; how ever, there is a re port of a

ship strike. Th e New E ngland Aq uarium do cumented a sei whale car cass hung o n the bow o f a container sh ip 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.
164

STATUS OF STOCK

The status of this stock relative to OSP in the USA 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

level of human-caused mortality and serious injury is unknown, but the rarity of mortality reports for this species

suggests that this leve l is insignificant and a pproac hing a zero m ortality and serio us injury rate. T his 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 Mem orandum

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 # AA55 1-CT8 -48 to the Bureau of La nd Ma nagemen t, Washing ton, DC, 5 38 pp. 

Dono van, G. P . 1991. A review of IW C stock bo undaries. Rep. int. Whal. Commn. Special Issu e 13: 39 -68. 

Hain, J. H. W., M. A. M. Hyma n, R. D. Kenney and H. E. Winn. 1985 . The role of cetaceans in the shelf-edge

region of the n ortheastern U nited States. Mar. Fish. Rev. 47(1): 13 -17. 

Mitchell, E. 1975 . Preliminary report on N ova Scotia fishery for sei whales (Balaen optera b orealis). Rep. int.

Whal. Commn. 25: 218 -225. 

Mitchell, E. and D. G. Chapman. 1977. Preliminary assessment of stocks of northwest Atlantic sei whales

(Balaen optera b orealis). 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

abunda nce of bale en whales in the southern G ulf of Maine in relation to ch anges in selec ted 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 ide ntified sei whales, Balaen optera b orealis, during an ep isodic influx into the southern G ulf

of Maine in 1986. Fish. Bull., U.S. 90(4): 74 9-755. 

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.
165

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 pu rposes of th is assessme nt. 

September 2000

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; NMF S 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, B arros et al. (1998) speculated that dwarf spe rm whales may have a mo re pelagic

distribution tha n pygmy spe rm whales, an d/or dive d eeper du ring feeding b outs. 

POPU LATIO N 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 19 98 that surve yed 5,57 0 km of trac k line in

waters south o f Maryland (38°N) (Figure 1; M ullin 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=0.5 5). This joint estimate is considered best

because together these two surveys have the most

complete coverage of the species’ habitat.

Minimum Po pulation Estimate

The minimum population estimate is the lower

limit of the two-tailed 60% confidence interval of the

log-norma lly distributed b est abunda nce estimate. T his

is equivalent to the 20th percentile of the log-normal

distribution as specified by W ade and Angliss (199 7). 

The best estimate of abundance for Kogia sp. is 536

(CV=0.45). The minimum population estimate for

Kogia sp. is 373.
166

Current Population Trend

The available information is insufficient to evaluate trends in population size for this species in the western

North A tlantic. 

CURRENT AND M AXIMUM NET PRODUCTIVITY RATES

Current and maximum net produ ctivity rates are unk nown for this sto ck. For pu rposes of this a ssessment,

the maximum net productivity rate was assumed to be 0.04. This value is based on theoretical modeling showing

that cetacean populatio ns may not gro w at rates muc h greater than 4% give n the constrain ts of their repro ductive 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 p opulation 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 be cause this stock is of unknown status. PBR for the western North A tlantic Kogia sp. is

3.7. 

ANNUAL HUMAN-CAUSED MORTALITY AND SERIOUS INJURY

The leve l of past or current, direct, hum an-caused mortality of dw arf sperm wh ales in the US A Atlantic

EEZ is unknown. Available information indicates there is likely little fisheries interaction with dwarf sperm whales

in the USA Atlantic EEZ. Total annual estimated average fishery-related mortality or serious injury to this stock

during 1994-1998 was 0.25 dwarf sperm whales (CV =0); 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 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 Ba nks (Tail of the Banks) an d provides ob server coverage of vesse ls fishing south of Cape Hatteras.

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

serious injurie s have bee n documented in othe r 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 intr oduction of quotas, effo rt was severely re duced. T he estimated number o f hauls in

1991, 1992, 1993, 1994, 1995, 1996, and 1998 were 233, 243, 232, 197, 164,149, and 113 respectively. In 1996

and 199 7, NM FS issued m anageme nt regulations w hich prohib ited the ope ration of this fishery in 1 997. Further, in

January 1999 NMFS issued a Final Rule to prohib it the use of driftnets (i.e., permane nt closure) in the North A tlantic

swordfish fishery (50 CFR Part 630). Fifty-nine different vessels participated in this fishery at one time or another

between 1 989 and 1993. S ince 199 4, between 10- and 1 3 vessels hav e participate d in the fishery (T able 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 souther n or winter stratum, and a no rthern or sum mer stratum. E stimates of the to tal 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 b ycatch per h aul and the number of un observed hauls as reco rded in self-rep orted 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;
167

estimated average annual mortality and serious injury related to this fishery during 1994-1998 was 0.25 dwarf sperm

whales (CV =0) (Table 1). 

Table 1. Summary of the incidental mortality of the dwarf sperm whale (Kogia simus), 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

Serious

Injury

Observe

d

Mortality

Estimated

Mortality 

Estimated

CVs

Mean

Annual

Mortality

Pelagic 5

Drift

Gillnet

94-98

1994=11

1995=12

1996=10

1998=13

Obs.

Data

Logbook

 .87, .99,

.64, NA,

.99

0, 0, 0, 0,

0

 0, 1, 0,

NA, 0

 0, 1.04

, 0,

NA, 0

0 0.25

(0)

TOTAL 0.25

(0)

1

1994, 199 5, 1996 and 1998 shown , other years not available on an ann ual basis.

2 Observer data (O bs. Data) are used to m easure bycatch rates, and the da ta are collected within the Northea st

Fisheries Science Center (NEFSC) Sea Sampling Program. Logbo ok (Logbook) data are used to measure

total effort, and the data are collected at the Southeast Fisheries Science Center (SEFSC).

3 The ob server cov erage and unit of effort for the P elagic Drift G illnet is a set.

4 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 0.08 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

0.01 animals.

5 The fishery did not operate in 1997; the average annual mortality is based on the number of years (4; 1994-

1996, 1998) that the fishery operated.

Other M ortality

Historical stranding records (1883-1988) of dwarf sperm whales in the southeastern USA (Credle 1988),

and strandings recorde d during 1988 -1997 (Ba rros et al. 1998) indicate that this species accounts for about 17% of

all Kogia strandings in this area. During the period 1990-October 1998, three 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 dw arf sperm whale stranded in Miami in 1987 (Barros et al.

1990). In the period 1987-1 994, on e animal had possible p ropeller cu ts on or near the flukes. 

STATUS OF STOCK

The status of this stock relative to OSP in the USA Atlantic EEZ is unknown. This species is not listed as

endangered o r threatened under the Endangered Sp ecies 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.
168

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. Comm er., 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 o f Kogia breviceps and K. simus based on hemoglobin, morpho metric and dietary analyses.

Abstracts. W orld M arine Ma mmal Scie nce Con ference. M onaco. 2 0-24 Jan uary. 

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 biologic al popula tions. Chapman & H all, Londo n, 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, Handbook of marine

mamma ls, Vol. 4: river d olphins and the larger too thed whales. Academ ic Press, San Dieg o. 

Credle, V . R. 1988 . Magne tite and magn etorecep tion in dwarf an d pygmy sp erm 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 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.

Mullin, K. D. (in review). Abundance and distribution of cetaceans in the southern U.S. Atlantic Ocean during

summer 1 998. Fish. Bull., U.S.

Northrid ge, S. 199 6. Estimatio n of cetacea n mortality in the U .S. Atlantic swo rdfish and tun a drift gillnet and p air

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. Wa ring, and D . Potter. (in revie w). Abund ances of ce taceans and sea turtles in the no rthwest Atlantic

during summer 199 5 and 19 98. 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.

Willis, P. M ., and R. W . Baird. 19 98. Status o f the dwarf spe rm whale, Kogia simus, with special refer ence to

Canada . Can. Field Nat., 112:114-125.
169

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.

September 2000

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 (Cald well and Ca ldwell 198 9). Sightings o f these animals in th e Weste rn North A tlantic occur p rimarily

along the continental shelf edge and over the deeper waters off the continental shelf (Hansen et al. 1994; Southea st

Fisheries Sc ience Cen ter unpublish ed data). P ygmy sperm whales and dwarf sperm whales are d ifficult to

distinguish and sightings of either species are often categorize d as Kogia sp. There is no information on stock

differentiation for the Atlantic population. In a recent study using hem atological and stable-isotope d ata, Barros et al.

(1998) speculated that dwarf sperm whales may have a more pelagic distribution than pygmy sperm whales, and/or

dive deep er during feed ing bouts. 

POPU LATIO N SIZE

An abundance of 115 (CV=0.61) for

Kogia sp.was estimated from a line transect

sighting survey co nducted d uring 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

probab ility of detecting a gr oup 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 su rvey cond ucted betw een 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 A tlantic surveys, 536 (CV=0.45 ), where

the estimate from the northern USA Atlantic is 115

(CV= 0.61) and from the sou thern USA Atlantic is

421 (CV=0.55). This joint estimate is considered

best because together these two surveys have the

most com plete cove rage of the sp ecies’ habitat.

Minimum Po pulation 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). T he

minimum population estimate for Kogia sp. is 373.
170

Current Population Trend

The available information is insufficient to evaluate trends in population size for this species in the western

North A tlantic. 

CURRENT AND M AXIMUM NET PRODUCTIVITY RATES

Current and maximum net produ ctivity rates are unk nown for this sto ck. For pu rposes of this a ssessment,

the maximum net productivity rate was assumed to be 0.04. This value is based on theoretical modeling showing

that cetacean populatio ns may not gro w at rates muc h greater than 4% give n the constrain ts of their repro ductive 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 p opulation 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 be cause this stock is of unknown status. PBR for the western North A tlantic Kogia sp. is

3.7. 

ANNUAL HUMAN-CAUSED MORTALITY AND SERIOUS INJURY

The leve l of past or current, direct, hum an-caused mortality of pygm y sperm wha les in the USA Atlantic

EEZ is unknown. Available information indicates there is likely little, if any, fisheries interaction with pygmy sperm

whales in the U SA Atlantic E EZ. 

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.

Fishery Information

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

established a mandato ry self-reporting fisheries information system for large pelagic fisheries. The N ortheast

Fisheries Science Center (NEFSC) Sea Sampling Observer Program 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 long line vessels fishing o ff the Grand Banks (T ail of the Ban ks) and pro vides obse rver cove rage of vesse ls

fishing south of Cape Hatteras. There have been no observed mortalities or serious injuries by NMFS Sea Samplers

in the pelagic d rift gillnet, pelagic lon gline, pelagic p air trawl, No rtheast multispe cies sink gillnet, mid -Atlantic

coastal sink gillne t, nor North Atlantic bottom trawl fisheries. 

Other M ortality

Historical stranding records (1883-1988) of pygmy sperm whales in the southeastern USA (Credle 1988),

and strandings recorde d during 1988 -1997 (Ba rros 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 U SA Atlantic c oast betwee n North Carolina and the Florida K eys in the same p eriod. 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 be en the cause of death. D uring the perio d 1987 -1994 o ne animal ha d possible propeller cuts on its flukes. 
171

STATUS OF STOCK

The status of this stock relative to OSP in the USA Atlantic EEZ is unknown. This species is not listed as

endangered o r threatened under the Endangered Sp ecies 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, cant 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 o f Kogia breviceps and K. simus based on hemoglobin, morpho metric and dietary analyses.

Abstracts. W orld M arine Ma mmal Scie nce Con ference. M onaco. 2 0-24 Jan uary. 

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. Chapm an & Ha ll, 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, Handbook of marine

mamma ls, Vol. 4: river d olphins and the larger too thed whales. Academ ic Press, San Dieg o. 

Credle, V . R. 1988 . Magne tite and magn etorecep tion in dwarf an d pygmy sp erm whales, Kogia simus and Ko gia

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

Coop erative Fish & Wildlife Research U nit, Colorad o State U niversity, Ft. Collins, C olorado , 72 pp. 

Mullin, K. D. (in review). Abundance and distribution of cetaceans in the southern U.S. Atlantic Ocean during

summer 1 998. Fish. Bu ll.

Palka, D . 1995. A bundanc e estimate of the Gulf of M aine harbo r porpo ise. Rep. int W hal. Com mn. Special Issue 16:

27-50

Palka, D ., G. Wa ring, and D . Potter. (in revie w). Abund ances of ce taceans and sea turtles in the no rthwest Atlantic

during summer 199 5 and 19 98. 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.
172

July 1995

KILLER WHALE (Orcinus orca):

Western North Atlantic Stock

STOCK DEFINITION AND GEOGRAPHIC RANGE

Killer whales are charac terized as un commo n or rare in wa ters of the U.S . Atlantic Exc lusive Eco nomic

Zone (EEZ) (Katona et al. 1988). T he 12 killer w hale sightings co nstituted 0.1% of the 11,1 56 cetace an 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 sou thern Gulf o f Maine in S eptembe r 1979, a nd 29 an imals in Ma ssachusetts 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, movemen ts, and stock re lationships. 

Stock definition is unknown. Results from other areas (e.g., the Pacific Northwe st and Norway) sugge st

that social structu re and territo riality may be imp ortant. 

POPU LATIO N SIZE

The total n umber o f killer whales off the e astern U.S . coast is unkno wn. 

Minimum Po pulation Estimate

Present d ata are insufficient to calculate a minimum po pulation estimate. 

Current Population Trend

There a re insufficient data to determin e the pop ulation trends for this species. 

CURRENT AND M AXIMUM NET PRODUCTIVITY RATES

Current and maximum net produ ctivity rates are no t known for this sto ck. The m aximum ne t productiv ity

rate was assumed to be 0.04 for purposes of this assessment. This value is based on theoretical calculations showing

that cetacean populatio ns may not ge nerally grow a t rates much gr eater than 4% given the con straints 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

produc tivity rate, and a “rec overy” facto r (Wad e and Ang liss 1997). T he minimum populatio n size is unkno wn. 

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 be cause this stock is of unknown . PBR fo r the western N orth Atlantic killer whale is

unknown because the minimum p opulation siz e cannot b e determine d. 

ANNUAL HUM AN-CAUSED MOR TALITY

In 1994 , one killer wha le was caugh t in the New E ngland mu ltispecies sink gillne t fishery but release d alive. 

No takes were doc umented in a review of Canadian gillne t and trap fisheries (Read 1 994). 

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
173

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

Grand Ba nks (Tail of the Banks) an d provides ob server coverage of vesse ls fishing south of Cape Hatteras.

There h ave been no obser ved mortalities or serious in juries by NM FS Sea S amplers in the pelagic drift

gillnet, pelagic lo ngline, pelagic pair trawl, Ne w England multispecies sin k gillnet, mid-Atlan tic coastal sink gillne t,

and No rth Atlantic bo ttom trawl fisherie s. 

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

Regulation s of 1982 , promulga ted under th e standing Fish eries Act, pro hibit the catching or harassment of all

cetacean sp ecies. The re are insufficient d ata to determ ine the pop ulation trends for this species. T his is not a

strategic stock b ecause, altho ugh PBR could n ot be calcu lated, there is no evidence o f human-indu ced 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. Com mer., NOAA Tec h.

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 # AA55 1-CT8 -48 to the Bureau of La nd Ma nagemen t, Washing ton, DC, 5 38 pp. 

Katona, S. K., J. A. Beard, P. E. Girton, and F. Wenzel. 19 88. Killer whales (Orcinus orca) from the Bay of Fundy

to the Equ ator, including the Gulf of M exico. Rit. Fiskideild . 9: 205-2 24. 

Mitchell, E. and R. R. Reeves. 1988. Records of killer whales in the western North Atlantic, with emphasis on

eastern Ca nadian wa ters. Rit. Fiskideild . 9: 161-1 93. 

Read, A . J. 1994. In teractions be tween cetac eans and g illnet and trap fishe ries in the No rthwest Atlantic. Rep. int.

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

Reeves, R. R. and E. M itchell. 1988 . Killer whale sigh tings and take s by Americ an pelagic w halers in the N orth

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.
174

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 she lf (NMF S unpub lished data). T here is no information on stock differentia tion for the Atlan tic

populatio n. 

POPU LATIO N 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 cou ld not be use d to estimate a bundanc e of pygmy killer whales, but it do es confirm the presence of this

species in the U .S. Atlantic EE Z. 

Minimum Po pulation 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 inform ation was ava ilable to evalu ate trends in p opulation siz e. 

CURRENT AND M AXIMUM NET PRODUCTIVITY RATES

Current and maximum net produ ctivity rates are unk nown for this sto ck. For pur poses of this a ssessment,

the maximum net productivity rate was assumed to be 0.04. This value is based on theoretical modeling showing

that cetacean populatio ns may not gro w at rates muc h greater than 4% give n the constrain ts of their repro ductive 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 p opulation 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 p ygmy killer whale s in the U.S. A tlantic EEZ. There ha ve been no logboo k reports o f fisheryrelated mortality or serious injury and no observed fishery-related mortality or serious injury has been observed.

There have b een no docum ented 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. 
175

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 pro vided observer coverage of pelagic longline vessels fishing off the

Grand Ba nks (Tail of the Banks) an d provides ob server coverage of vesse ls fishing south of Cape Hatteras.

There h ave been no obser ved mortalities or serious in juries by NM FS Sea S amplers in the pelagic drift

gillnet, pelagic lo ngline, pelagic pair trawl, Ne w England multispecies sin k gillnet, mid-Atlan tic coastal sink gillne t,

and No rth Atlantic bo ttom trawl fisherie s. 

Other M ortality

 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

compe tition 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. T he 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. Com mer., NOAA Tec h.

Memo. NMFS-OPR-6, 73 pp.

Caldwell, D . K. and M . C. Caldwe ll. 1971. T he pygmy killer whale, Feresa attenua ta, in the western Atlantic, with a

summary o f world reco rds. 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 a ttenuata (Gray 1874). Pages 387-404 in S. H.

Ridgway and R. Harrison (eds), Han dbook of ma rine mammals, Vo l. 5: The first book of dolph ins.

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.
176

December 1998

NORTHERN BOTTLENOSE WHALE (Hyperoodon ampullatus):

Western North Atlantic Stock

STOCK DEFINITION AND GEOGRAPHIC RANGE

Northern bottlenose whales a re characte rized as extre mely uncom mon or ra re 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 (CETA P 1982).

In 1993 a nd 199 6, two sightings o f 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. 199 6).

Northern bottlenose whales are d istributed in the N orth Atlantic from Nova Scotia to ab out 70° in the Davis

Strait, along the east coast of Green land to 77° and from England to the west coast of Spitzbe rgen. It is largely a deepwater spec ies and is very se ldom foun d in waters less tha n 2,000 m deep (M ead 198 9). 

There are two ma in centers of b ottlenose wh ale distribution in the western no rth Atlantic, one in the area called

"The G ully" just north o f Sable Island, Nova Sco tia, and the other in Davis Strait off northern Lab rador (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 strand ing record s in the Bay o f Fundy and as far south as Rhode Islan d. Stock d efinition is unkno wn. 

POPU LATIO N SIZE

The total n umber o f northern bo ttlenose whale s off the eastern U .S. coast is unkn own. 

Minimum Po pulation Estimate

Present d ata are insufficient to calculate a minimum po pulation estimate. 

Current Population Trend

There a re insufficient data to determin e the pop ulation trends for this species. 

CURRENT AND M AXIMUM 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 Biologic al Remo val (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 A ngliss 1997). The minimum

population size is unknown. The maximum productivity rate is 0.04, the default value for cetaceans. T he “recove ry”

factor, which acco unts for enda ngered, depleted, threatened stocks, or stocks of unknown status relative to optimum

sustainable populatio n (OSP ) is assumed to be 0.5 because this stock is of unkn own status. PB R for the western North

Atlantic northe rn bottleno se whale is unkn own bec ause the minim um pop ulation size ca nnot be d etermined . 

ANNUAL HUM AN-CAUSED MOR TALITY

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

spermac eti. A Norwegian fishery expand ed from ea st to west (Lab rador and Newfoun dland) in several episodes. The

fishery peaked in 1965. Decreasing catches led to the cessation of the fishery in the 1970s, and provided evidence that

the population was depleted. A small fishery op erated by Canadian w halers from N ova Sco tia operated in the Gully, and

took 87 animals from 1962 to 1967 (M ead 198 9; Mitche ll 1977). 
177

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 (SE FSC). 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 pro vides observer cov erage of vessels fishing south of Cape H atteras.

There have been no observed mortalities or serious injuries by NM FS Sea S amplers in the pelagic drift gillne t,

pelagic longline, pelagic pair trawl, New England multispecies sink gillnet, mid-Atlantic coastal sink gillne t, and No rth

Atlantic botto m trawl fisheries. 

STATUS OF STOCK

The status of norther n bottlenose whales relative to OSP in U .S. Atlantic EE Z is unknow n; 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 fishery-related 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. Ea gle, and P.R . Wad e. 1995 . U.S. M arine Ma mmal Sto ck 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

#AA5 51-CT 8-48 to the Bureau o f Land M anageme nt, Wash ington, DC, 538 pp . 

Gowans, S. and H. Whitehead. 1998. Social organization of northern bottlenose whales. The World Marine Mammal

Science Conference, Monaco, January 1998 (Ab stract).

Mead, J. G. 198 9. Bottleno se whales. Pa ges 321-3 48. In: S. H. Ridgway and R. Harrison (eds), Handbook of marine

mamma ls, Volume 4: River do lphins and the larger toothe d whales. Academ ic Press, New Y ork. 

Mitchell, E. D. 1977. Evidence that the northern bottlenose whale is dep leted. Rep. int. Whal. Commn. 27: 195-203.

Mitchell, E. D. and V. M. K ozicki. 1975. Autumn stranding of a northern bottlenose whale (Hyperoo don am pullatus)

in the Bay o f Fundy. J. Fish. Res. Bd. Can. 32: 1019-1040.

Reeves, R.R., E. Mitchell and H. Whitehead. 1993. Status of the northern b ottlenose wh ale, Hyperoodon ampullatus.

Can. Fld. Nat. 107:490-508.

Whitehead, H., S. Gowans, A. Faucher, a nd S.W . McCarrey. 1997. Population analysis of northern bottlenose whales

in the Gully, N ova Sco tia. Mar. Mamm. Sci. 13(2): 173-185.

Wade P.R., and R.P. A ngliss. 1997. Guidelines for assessing marine mammal stocks: Report of the GAMMS W orkshop

April 3-5, 1996, Seattle, Washington. U.S. Dep. Commer., NOAA Tech. Memo. NMFS-OPR-12, 93 pp.
178

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 Northw est Atlantic

(Leatherwood et al. 1976). The spe cies is found in waters from southern New England, north to western and southern

Greenland and Dav is Straits (Leatherwood et al. 1976; CETA P 198 2), 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 concentra ted 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; K enny et al. 1996). 

POPU LATIO N SIZE

The total number o f white-beaked dolphins in U.S. and Canadian waters is unknown, although one abundance

estimate is available for p art of the know n habitat in U.S. waters, and tw o estimates ar e from Ca nadian wa ters (Tab le

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 (T able 1; CE TAP 1982). T he estimate is b ased on sp ring data be cause the greatest proportion of the

population off the northea st U.S. coa st appeare d in the study are a during this sea son. 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 populatio n size beca use 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 abundan ce estimates for this species in waters betw een the Gu lf of Maine and the

Newfou ndland/La brador r egion. 

Table 1. Summary of abundance estimates for we stern North Atlantic white-be aked do lphins. Month, year, and

area covered during each abundance survey, and resulting abun dance estim ate (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

198 0's E. Newfoundland

and SE Labrador 5,500 None reported

August 1982 Labrad or shelf 3,486 0.22

Minimum Po pulation Estimate
179

Present data are insufficient to calculate a minimum population estimate in U.S. Exclusive Economic Zone

(EEZ) w aters. 

Current Population Trend

There a re insufficient data to determin e popula tion trends for this species. 

CURRENT AND M AXIMUM NET PRODUCTIVITY RATES

Current and maxim um net pro ductivity 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

produc tivity 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 unknow n status relative to o ptimum susta inable

population (OSP) is assumed to be 0.5 be cause this stock is of unknown status. PBR for the western North A tlantic

white-beaked dolphin is unknown.

ANNUAL HUMAN-CAUSED MORTALITY AND SERIOUS INJURY

White-beaked dolphins have been taken in cod traps and the Canad ian ground fish gillnet fisheries off

Newfoundland and Lab rador and in the Gulf of St. Lawrence (Alling and W hitehead 1 987; Re ad 199 4; Hai et al. 1996);

however, th e total numb er of animals ta ken is not kno wn. 

There a re no doc umented r eports of fishe ry-related mo rtality or serious inj ury to this stock in the U.S. EE Z. 

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. fishe ry 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 unk nown. In 19 89, app roximately 6 ,800 licens es 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 th e Gulf of St. Lawrence and 659 licenses were issued in the Bay of Fundy and southwestern Nova

Scotia. 

Other M ortality

W hite-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 sa me authors reported that 25-50 % of the killed dolphins w ere lost.

STATUS OF STOCK

The status of white-be aked do lphins, 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 calcu late PBR it is not possible to d etermine 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 tak es in U.S. wa ters, this stock has b een designa ted as not strate gic. 
180

REFERENCES

Alling, A. K. and H. P. Whitehead. 1987. A prelimina ry study of the status o f 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 a ssessments. 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 P rogram, University of Rhode Island. Final Report

#AA5 51-CT 8-48 to the Bureau o f Land M anageme nt, Wash ington, DC, 538 pp . 

Hai, D.J., J. Lein, D. Nelson, and K. Curren. 1996. A contribution to the biology of the white-sided dolphin,

Lagen orhnch us albirostris, in waters off Ne wfoundlan d. Can..Fld. Nat. 110(1).

Katona, S. K., V. Rough, an d D. T. R ichardson . 1993. A field guide to w hales, porp oises, and se als from Ca pe Cod to

Newfou ndland. W ashington, D . C. : Smithsonian Institution Press. 316 pp . 

Kenney, R. D., P. M . Payne, D . W. He ineman and H. E. W inn. 1996 . Shifts in Northeast shelf cetacean distributions

relative to trends in Gulf o f Maine/G eorges Bank finfish abun dance. P p. 169-1 96. In: K. Sherman, N.A.

Jaworski and T. Smada (eds.) The northeast shelf ecosystem: assessment, su stainability, a nd ma nagem ent.

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. Dep t. of Comm erce, NO AA Te ch. Rep. N MFS Circ. 396 , 176 pp . 

Mikkelsen, A.M.H. and A. Lund. 1994. Intraspecific variation in the do lphins Lagen orhnch us 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.

Comm n. Specia l Issue 15: 1 33-14 7. 

Reeves, R.R., R. L. Brownell Jr., C. C. Kinze, C. Smeenk and J. Lein. (in press). White-beaked dolphin (Lagenorhnchus

albirostris (Gray 18 46). In: S.H. Ridgway and R. Harrison (eds.) Hand book o f marine m amm als, 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.
181

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 spe cies of spotted dolphin in the Wester n Atlantic — the Atlantic spo tted dolph in, Stenella

frontalis, formerly S. plagiodon (Perrin et al. 1987), a nd the pan tropical spo tted dolph in, S. attenuata . These species

are difficult to differe ntiate at sea. 

Atlantic spotted dolphins are distributed in tropical and warm temperate waters of the western N orth Atlantic

(Leatherwood et al. 1976). Their distribution is from southern New England, south through the Gulf of Mexico and the

Caribbean to Venez uela (Leatherwood et al. 1976; Perrin et al. 1994). T he large, hea vily spotted form of the Atlan tic

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 nea r 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). A tlantic spotted dolphins re gularly 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; M ullin in review). Sightings have also been made along the north wall of the Gulf Stream and warmcore ring features (Waring et al. 1992). S tock structure in the western N orth Atlantic is un known. 

POPU LATIO N SIZE

Total numbers o f Atlantic spotted dolphins o ff

the USA o r Canadia n Atlantic coast are unknown,

although three estimates from selected regions of the

habitat do exist for se lect time perio ds. Because S.

frontalis and S. attenuata are difficult to differentiate at

sea, the reported abund ance 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 continenta l, shelf and shelf

edge waters between Cape Hatteras, North Carolina and

Nova Scotia (CE TAP 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 methodo logy these

data should not be used to make comparisons to more

current estima tes. 

An abundance of 4,772 (CV=1.27)

undifferentiated spotted dolphins was estimated from a

July to September 199 5 sighting surve y conducte d 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
182

Maine/Bay of Fundy region. The airplane covered waters in the mid-Atlantic from the coastline to the 50 fatho m depth

contour line, the southern G ulf of Maine , and shelf waters off Nova Scotia from the coastline to the 1000 fathom dep th

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 cond ucted durin g July 6 to Se ptember 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 shipbo ard line transect sighting survey conducted b etween 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 availab le abunda nce 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 bec ause together these two

surveys have the most complete co verage of the species’ hab itat.

Table 1. Summary of abundance estimates for both undifferentiated spotted dolphins (1995), and differentia ted 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 4,77211.27

Jul-Sep 1998 Maryland to Gulf of St. Lawrence 32,0432

1.39

Jul-Aug 1998 Florida to Maryland 4,39620.62

Jul-Sep 1998 Gulf of St. Lawrence to Florida (COMBINED) 36,4393

1.22

Jul-Aug 1998 Florida to Maryland 15,84040.60

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 repre sents the first estimate fo r the coastal A tlantic spotted dolphin

Minimum Po pulation Estimate

The minimum p opulation e stimate is the lowe r 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 e stimate 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).
183

Current Population Trend

There are insufficient data to determine the population trends for this species, given that surveys prior to 1998

did not differe ntiate betwee n species o f spotted do lphins. 

CURRENT AND M AXIMUM NET PRODUCTIVITY RATES

Current and maximum net productivity rates are unknown for this stock. For purpose s of this assessment, the

maximum net productivity rate was assumed to be 0.04. This value is based on theoretical modelin g 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

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

population size for the com bined offsho re and co astal ‘forms’ of A tlantic spotted dolphins is 52,279 (CV=0.87). The

maximum produc tivity 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 offsho re and co astal forms of A tlantic

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 do lphins (Stenella spp.) CV =0.01; T able 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 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 Ob server 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 A tlantic 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 e ither species m ight have be en subject to the observed fishery-related mortality and

serious injury.

Bycatch has been o bserved b y NMF S Sea Samplers in the p elagic drift gillnet and pelagic longline fisheries,

but no mortalities o r serious injurie s have bee n documented in the p elagic pair traw l, 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 o f hauls in 1991,

1992, 1993, 1994, 1995, 1996, and 1998 were 233, 243, 23 2, 197, 1 64,149 , 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 Fina l Rule to pro hibit the use of d riftnets (i.e., permane nt closure) in the North A tlantic swordfish fishery

(50 CFR Part 630). Fifty-nine different vessels p articipated 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 d rift 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
184

of the observ ed caugh t and the pro duct of the av erage byca tch per haul a nd the number of uno bserved h auls 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.

attenua ta). 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 d uring 199 4-1998 was 7.8 (0 .01) (Ta ble 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 Caribbe an Sea. T his

fishery has been monitored with about 5% o bserver covera ge, in terms of trip s observed , since 199 2. Total e ffort,

excluding the Gulf of Mexico, for the pelagic longline fishery, based on mandatory self-reported 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 se ts 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 observ ed, within

every statistical reporting area within the EEZ and beyond. Off the USA Atlantic coast, the fishery has been observed

from January to Marc h off Cape Hatteras, in M ay and June in the entire mid-A tlantic, and in July thr ough De cember 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 199 4-1995 periods (C ramer 19 94; Sco tt and Brown 1997; Johnson et al. 1999; Yeung 1999 a). Further, Yeung

(1999b), revised the 1 992-19 97 fishery mo rtality estimates in Johnson et al. (1999) to include seriously injured animals.

The 1998 b ycatch estimate s were from Y eung (19 99a). 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 do lphin bycatch es were ob served for 1 992-19 98. 

Table 2. Summary of the incidental mo rtality of undifferentiated spotted dolphins (Stenella sp.) by commercial fishery

including the years samp led (Yea rs), the numb er of vessels ac tive 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 an nual mortality (E stimated 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 u sed to measur e total effort for the p elagic drift gillnet fishery,

and these data are collected at the Southeast Fisheries Scien ce 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 inc lude animals s eriously 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.

Other M ortality
185

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. Ea gle 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.

NMF S-OPR-6, 73 pp . 

Buckland, S. T., D. R. Andersen, K. P. Burnham and J. L. Laake. 1993. Distance Sampling: Estimating abundance of

biologica l populatio ns. Chap man a nd Ha ll, New Y ork, 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. Cetacea n and Turtle Assessment Progr am, Unive rsity of Rhode Island. Final Report,

Contract A A51-C78-48, B ureau of La nd Ma nagemen t, Washing ton, DC, 5 38 pp. 

Cramer, J. 1994. Large pelagic logbook newsletter - 1993. NOAA Tech. Mem. NMFS-SEFSC-352, 19 pp.

Johnson , D. R., C. A . Brown, a nd C. Ye ung. 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

Coop erative Fish & Wildlife Research U nit, Colorad o State U niversity, Ft. Collins, C olorado , 72 pp. 

Leatherwood, S., D. K. Caldw ell and H. E . Winn. 1 976. W hales, dolp hins, and po rpoises of the western No rth Atlantic.

A guide to their identificatio n. NOA A Tech . Rep. NM FS Circ. 3 96, U.S. D ept. 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 rep ort to the No rtheast Fisherie s Science Center, Con tract No. 4 0ENN F5001 60. 

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 p p. Available from: Natio nal Marin e Fisheries Se rvice, 166 Water S treet, Woods Hole, MA

02543-1026.

Palka, D., G. W aring, and D . Potter. (in revie w). Abund ances of ce taceans and sea turtles in the no rthwest Atlantic

during summer 199 5 and 19 98. Fish. Bull., U.S.

Payne, P. M., L. A. Selzer and A. R. Knowlton. 19 84. Distribution and de nsity of cetaceans, marine turtles, and seabirds

in the shelf wate rs of the northeastern United States, June 1980-December 19 83, based on shipboard

observatio ns. NOA A/NM FS Con tract No. N A-81-FA -C-0002 3. 

Perrin, W. F.,E. D. Mitch ell, J. G. Mead, D. K. Caldwell, M. C. Caldwell, P. J. H. van Bree, and W. H. Dawbin. 1987.

Revision o f the spotted d olphins, Stenella sp. Mar. Mammal Sci. 3(2): 99-170.

Perrin, W. F., D. K. Caldwell, and M. C. Caldwell. 199 4. Atlantic spo tted dolph in. Pages 17 3-190. In: S. H. Ridgway

and R. Harrison (eds.). Handbook of marine mammals, Volume 5: The first book of do lphins. Academic P ress,

San Dieg o, 418 p p. 

Rice, D. W. 19 98. Ma rine mamm als of the world , systematics and distribution. Sp ec. Publ. No 4. Society for Marine

Mammalogy, Lawrence, KS. 231 pp.

Scott, G. P. and C. A. Bro wn. 1997 . Estimates of m arine mammal and marine turtle catch by the U.S. A tlantic pelagic

longline fleet in 1994-1995. Miami Laboratory Contribution MIA-96/97-28
186

Wade, P. R., and R. P. An gliss. 1997. G uidelines for assessing marine mammal stocks: Report of the GAMMS

Workshop April 3-5, 1996, Seattle, Washington. U.S. De p. Comm er., NOA A Tech . Memo . NMFS-OPR-12,

93 pp.

Waring, G. T., C. P. Fairfield, C. M. Ruhsam and M. Sano. 1992. Cetacean s associated with Gulf Stream features off

the northeastern USA shelf. ICES Marine M ammals Comm. CM 1992/N :12, 29 p p. 

Yeung, C. 1999a. Estimates of marine mammal and marine turtle bycatch by the U.S. Atlantic pelagic long line 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.
187

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

PANTROPICAL SPOTTED DOLPHIN (Stenella attenuata):

Western North Atlantic Stock

STOCK DEFINITION AND GEOGRAPHIC RANGE

There are two spe cies of spotted dolphin in the Wester n Atlantic — the Atlantic spo tted dolph in, Stenella

frontalis, formerly S. plagiodon (Perrin et al. 1987), and the pantropical spotted dolphin, S. attenua ta. These species

are difficult to differe ntiate 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 oc cur over the deepe r waters,

and rarely over the continental s helf 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; P errin and H ohn 199 4); howev er, there is no informa tion on stock differentiation in

the Atlantic po pulation. 

POPU LATIO N 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 conducte d from 19 78 to 1982 on

the continental, shelf and shelf edge waters between

Cape Hatteras, North Carolina and N ova Sco tia

(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 PB R 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,
188

and shelf waters off Nova Scotia from the coastline to the 1000 fathom depth contour line. Data collection and analysis

methods u sed were d escribed in Palka (19 96). 

An abundance of 343 (CV=1.03) for pantropical spotted dolphins was estimated from a line transect sighting

survey conducte d during Ju ly 6 to September 6, 1 998 by a ship and p lane that surveye d 15,90 0 km of trac k 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 spott ed 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=0.36), 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 ha ve the most c omplete c overage o f the species’ hab itat.

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 12,77420.57

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 com bined estimates for both region s.

Minimum Po pulation 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 W ade and Angliss (199 7). The best estimate of abundance for pantropical spotted dolphins is 13,117

(CV=0.56). The minimum po pulation 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 surve ys. 

CURRENT AND M AXIMUM 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

produc tivity rate, and a “recovery” factor (MMP A Sec. 3. 16 U.S.C. 1362; W ade and Angliss 1997). The minimum

population size for the pantropical spotted dolphins is 8,450 (CV=0.56). The maximum productivity rate is 0.04, the
189

default value for cetaceans. The “recovery” factor, which acco unts for endangered, de pleted, 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 1994-1998 was

7.8 undifferentiated spotted do lphins (Stenella sp.) CV= 0.01; Table 2). 

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 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 Ob server 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 observ ers. The A tlantic 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 o bserved b y NMF S Sea Samplers in the pelagic drift gillnet and pelagic longline fisheries,

but no mortalities o r serious injurie s have bee n documented in the p elagic pair traw l, 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 19 89 to 1,1 44 in

1990; thereafter, with the introduction of quotas, effort was sever ely 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 managem ent regulation s which pro hibited the o peration o f this fishery in 1997. Further, in January 1999

NMFS issued a Final Rule to prohib it the use of driftnets (i.e., permanent closure) in the North Atlantic swordfish fishery

(50 CFR P art 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 observ ed, was 8% in 1989, 6 % in 1990, 2 0% in 19 91, 40% in 1992, 4 2% in 19 93, 87% in 1994, 9 9% in

1995, 64% in 1 996, and 99% 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 d rift 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 P antropical spotted do lphins (S. attenua ta). 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 19 98; average annual mortality and serious injury during

1994-1 998 was 7.8 (0.01 ) (Table 2). 
190

Pelagic Longline

 The pelagic longline fishery operates in the USA Atlantic ( including Caribbean) and Gulf of Mexico EEZ

(SEFSC unpublishe d data). Interactions b etween the p elagic longline fishery and spotted dolphins have been reported;

however, a vessel may fish in m ore than on e statistical repo rting 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 o bserved, sin ce 1992 . Total effort,

excluding the Gulf of Mexico, for the pelagic longline fishery, based on mandatory self-reported fisheries information,

was11,279 sets in 1991, 9,869 se ts in 1992, 9 ,862 sets in 1 993, 9,4 81 sets in 19 94, 10,1 29 sets in 19 95, 9,88 5 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 199 2, this fishery has been monitored with about 5% observer coverage , in terms of trips o bserved, w ithin

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 D ecembe r 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 1999 b). Further, Yeung

(1999b), revised the 1 992-19 97 fishery mo rtality 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 pantropical spotted dolphin bycatches were observed for 1992-1998.

 

Table 2. Summa ry of the inciden tal mortality of undifferentiated spotted dolphins (Stenella sp.) by commercial fishery

including the years sampled (Years), the number of vessels active within the fishery (Ve ssels), the type of d ata

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

Pelagic6

Drift

Gillnet

 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

 7.8

 (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.
191

Other M ortality

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 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 P BR and , therefore, can be consid ered to be insignificant and approaching zero mortality and serious

injury rate. Average annual fishery-related mortality and se rious injury do es not excee d 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. Anderso n, K. P. Burnham an d J. L. Laak e. 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 Rhod e Island. Fina l Report,

Contract A A51-C78-48, B ureau of La nd Ma nagemen t, Washing ton, DC, 5 38 pp. 

Cramer, J. 1994. La rge pelagic logboo k newsletter - 19 93. NO AA Te ch. Mem . NMF S-SEFSC-352, 1 9 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

Coop erative Fish & Wildlife Research U nit, Colorad o State U niversity, Ft. Collins, C olorado , 

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, Minera ls

Manag ement Ser vice, Gulf of M exico OC S Region al Office, Ne w Orleans, Louisiana, 1 08 pp. 

Northridge, S. 1996. Estimation of cetacean mortality in the U.S. Atlantic swordfish and tuna drift gillnet and pair trawl

fisheries. Final rep ort to the No rtheast Fisherie s Science Center, Con tract No. 4 0ENN F5001 60. 

Palka, D. 1995. Abunda nce estimate of the Gulf of Maine harbor porpoise. Rep. int Whal. Commn. Special Issue 16:27-

50.

Palka, D. 199 6. Update on abundance of Gulf of M aine/Bay o f Fundy harb or porp oises. NO AA/NM FS/NE FSC. Re f.

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 o f cetaceans a nd sea turtles in the northwest A tlantic

during summer 199 5 and 19 98. 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 o f the spotted d olphins, Stenella sp. Mar. Mammal Sci. 3(2): 99-170.

Perrin, W. F., D . K. Caldw ell, and M . C. Caldwe ll. 1994. Atla ntic spotted d olphin. Pa ges 173-1 90. In: S. H. Ridgway

and R. Harrison (eds.). Ha ndbook of m arine mammals, Volume 5: The first book of d olphins. Academ ic Press,

San Dieg o, 418 p p. 

Perrin, W. F. and A. A. Hohn. 1994. Pantropical spotted dolphin Stenella a ttenuata . Pages 71 -98. In: S. H. Ridgway

and R. Harrison (eds.). Ha ndbook of m arine mammals, Vol. 5: T he first book of dolphins. Academ ic Press,

San Dieg o, 418 p p. 

Scott, G. P. and C. A. Brown. 1997. Estimates of marine mammal and marine turtle ca tch by the U.S . Atlantic pelag ic

longline fleet in 1994-1995. Miami Laboratory Contribution MIA-96/97-28
192

Wade, P. R., and R. P. An gliss. 1997. G uidelines for assessing marine mammal stocks: Report of the GAMMS

Workshop April 3-5, 199 6, Seattle, W ashington. U .S. Dep. Commer., NOAA Tech. Memo. NMFS-OPR-012,

93 pp.

Yeung, C. 1999a. Estimates of marine mammal and marine turtle bycatch b y the U.S. Atla ntic pelagic long line fleet in

1998. NOAA Technical Memorandum NMFS-SEFSC-430, 26 pp.

Yeung, C. 1999 b. Revised Mortality E stimates of M arine Ma mmal Bycatch in 1992-1997 based on Serious Injury

Guidelines. NOAA Technical Memorandum NMFS-SEFSC-429, 23 pp.
193

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 do lphin, Stenella coeruleoalba, is distributed worldwide in warm-temperate to tropicalseas (Archer

and Perrin 1997). Striped dolphins are found in the western N orth 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; Schmid ly 1981). There is very little information concerning striped

dolphin sto ck structure in the western No rth Atlantic (Ar cher and P errin 199 7). 

In waters off the northeastern USA coast, striped dolphins are distributed along the continental shelf edge from

Cape Hatteras to the southern margin of G eorges Bank, and also occur offsho re over the c ontinental slop e 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 co ntour 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 surve y of the New England S ea Mo unts (Palka 1997) were in waters that were between 200

 and 270C

and dee per than 90 0 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). 

POPU LATIO N SIZE

Total numbers of striped dolphins off the USA

or Canadia n Atlantic coast are unknown, although four

estimates from selected regions of the habitat do exist

for select time periods. Sightings were almo st

exclusively in the continen tal shelf edge an d 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 slo pe survey b locks. Due to

weather and logisticalconstraints, 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 determinatio ns. Further, du e to changes in survey

methodology these data should not be used to make

comparisons to more current estimates
194

An abundance of 3 1,669 (CV =0.73) striped do lphins was estimated from a July to September 1995 sighting

survey conducted by two ships and an airplane that covere d 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 regio n. The airp lane cover ed waters in the mid-Atlan tic from the coastline to the 50 fathom depth contour line,

the southern G ulf of Maine , and shelf waters off Nova Scotia from the coastline to the 1000 fathom depth contour line.

Data co llection and a nalysis method s used were described in Palka (19 96). 

An abundan ce of 39,7 20 (CV =0.45) for striped d olphins was e stimated from a line transect sig hting survey

conducted during July 6 to September 6, 1998 by a ship and plane that surveyed 15,900 km of track line in wa ters north

of Maryland (38° N) (Figure 1; Palka et al. in review). Shipboa rd data we re analyzed using the mod ified direct du plicate

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; M ullin 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 availab le 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 co verage of the species’ hab itat.

Table 1. Summar y of abunda nce estimates for western N orth 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 Po pulation 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 (1 997). T he best estima te of abund ance for stripe d dolph ins 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 a re insufficient data to determin e the pop ulation trends for this species. 

CURRENT AND M AXIMUM NET PRODUCTIVITY RATES

Current and maximum net produ ctivity 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 gro w at rates muc h greater than 4% give n the constrain ts of their repro ductive life history

(Barlow 1995). 

POTENTIAL BIOLOGICAL REMOVAL

Potential Biological Remo val (PBR) is the pro duct of minimum po pulation size, one-half the maximum

produc tivity rate, and a “re covery” factor (MMPA Sec. 3. 16 U.S.C. 1362; W ade 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
195

“recovery” factor, which a ccounts for e ndangere d, deplete d, threatened stocks, or stoc ks of unkno wn status relative to

optimum sustainable population (OSP) is 0.5 because this stock is of un known status. P BR for the western No rth

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; C V=0.0 8)Tab le 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 doc umented in 1991 in th e North A tlantic 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 Sam pling

Observer Program was initiated in 1989 and since that year severa l fisheries have b een cove red by the p rogram. In la te

1992 and in 1993, the SEFSC provided observer coverage of pelagic lon gline vessels fishing o ff the Grand Banks (T ail

of the Banks) and p rovides observer co verage of vessels fishing south of Cape H atteras.

Bycatch has been observed by NMF S 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 lo ngline fisheries, pe lagic pair trawl,

Northeast multispecies sink gillnet, and mid-A tlantic coastal sink gillnet fisheries.

Pelagic Drift Gillnet

The estimated tota l number o f hauls in the pelag ic drift net fishery increa sed from 7 14 in 1989 to 1144 in 1990;

thereafter, with the introduction of quotas, effo rt 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 particip ated in the fishery . Observer coverage, percent of sets observed, was 8% in 1989, 6% in 1990, 20%

in 1991, 40% in 199 2, 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 Ban k and off Cape H atteras.

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, b y strata, assuming the 1990 injury was a mo rtality (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 Ja nuary and F ebruary, and along the sou thern margin of Georg es Bank in summer

and autumn. Estim ated annua l mortality and seriou s 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 199 6 (CV= 0.22), N A in 199 7, and 4 in 1998 (CV=0). The 199 4-1998 average annual mortality and

serious injury to striped do lphins in the pe lagic drift gillnet fishery w as 7.25 (C V=0.0 8) (Tab le 2). 

North Atlantic Bottom Trawl

Vessels in the North Atlantic bottom trawl fishery, a Cate gory III fishery un der the M MPA , were obse rved in

order to meet fishery management needs, rather than marine mammal managem ent needs. A n average o f 970 vesse ls

(full and part time) participated annually in the fishery during 1989-1995. The fishery is active in New 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

1994-1 998 was 7.3 (CV =0.08) (Table 2 ). 
196

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 196 0's and early 1 970's two mortalities each, w ere repo rted in trawl and salmon net fishe ries. 

Between January 1993 and December 1994, 36 Spanish deep-water trawlers, covering 74 fishing trips (4,726

fishing days and 14,211sets), were obse rved in NAFO Fishing Area 3 (off the Grand Bank) (Lens 1997). A total of 47

incidental catches wer e record ed, which inc luded two striped do lphins. The incidental mortality rate for striped dolphins

was 0.01 4/set.

Table 2. Summary of the incidental mo rtality of striped dolphins (Stenella coeruleoalba) by commercial fishery

including the years sampled (Years), the number of vessels active within the fishery (Ve ssels), the type of d ata

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 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 M ortality

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 (S ergeant et al. 1970; Baird et al. 1997; Lucas and H ooker 1 997). 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. 

REFERENCES

Anon. 1991. N ortheast ceta cean aerial su rvey and inter platform study. NOAA, NMFS, NEFSC & SEFSC, 4 pp.

Available from NEFSC, Woods Hole Laboratory, Woods Hole, MA.

Archer, F. I., II and W. F. P errin. 1997. Spec ies account of striped dolp hins (Stenella coeruleoalba). Paper SC/49/SM27

presented to the IWC Scientific Committee, September 1997. 27 pp.
197

Baird, R.W., S. K. Hooke r, H. Whitehead , and R. Etcheberry. 19 97. A Review o f records of striped dolph ins (Stenella

coeruleoalba) from Can adian waters. IWC Doc. SC /49/SM 4, 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 o f the 1995 Assessme nts. 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

biologica l populatio ns. Chap man a nd Ha ll, New Y ork, 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 Tu rtle Assessme nt Program, University of Rhode Island. Final Report,

Contract A A51-C78-48, B ureau of La nd Ma nagemen t, Washing ton, DC, 5 38 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 S helf. 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

Coop erative Fish & Wildlife Research U nit, Colorad o State U niversity, Ft. Collins, C olorado , 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. Dep t. of Comm erce, NO AA Te ch. Rep. N MFS Circ. 396 , 176 pp . 

Lens, S. 1997. Interactions between marine mammals and deep water trawlers in the NAF O regulato ry 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 rep ort to the No rtheast Fisherie s Science Center, Con tract No. 4 0ENN F5001 60. 

Palka, D. 199 5. Abund ance estima te of the Gulf of M aine harbo r porpo ise. Rep. int. Whal. Commn. Special Issue 16:27-

50.

Palka, D. 199 6. Upd ate on abu ndance o f Gulf of M aine/Bay o f Fundy harb or porp oises. NO AA/NM FS/NE FSC. Re f.

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 1 995 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, V olume 5: T he first book of dolphins, Acade mic Press, San Dieg o. 

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

Commn. Special Issue 15: 133 -147. 

Sergeant, D.E., A.W . Mansfield and B. Bec k. 1970. In shore reco rds of cetace a for eastern C anada, 19 49-68. 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-8 0/41, U .S. Fish and W ildlife Service, O ffice of Biolo gical Service s, Washin gton, DC, 163 pp . 

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

April 3-5, 1996, Seattle, Washington. U.S. Dep. Commer., NOAA Tech. Memo. NMFS-OPR-12, 93 pp.

Waring, G. T., C. P. Fairfield , C. M. Ru hsam and M. Sano . 1992. Cetaceans ass ociated with Gulf Stream features off the

northeastern USA she lf. ICES Marine Mammals Comm. CM 1992/N:12, 29 pp.

Waring, G. T. 19 98. Results o f the summer 1 991 R/V Chapman marine mammal sighting survey. NOAA NMFS NEFSC,

Lab. Ref. Doc. N o. 98-09, 21 p p. Northeast Fisheries Scienc e Center, Wo ods Hole, M assachusetts.
198

December 1998

SPINNER DOLPHIN (Stenella longirostris):

Western North Atlantic Stock

STOCK DEFINITION AND GEOGRAPHIC RANGE

Spinner dolphins ar e distributed in oceanic a nd coastal tro pical waters (Leatherwood et al. 1976). T his is

presumably an offshore, d eep-water sp ecies (Schm idly 1981 ; Perrin and Gilpatrick 1 994), and its distribution in the A tlantic

is very poorly known. In the w estern No rth Atlantic, these d olphins oc cur in deep water along m ost of the U.S. co ast south

to the West Indies and Ven ezuela, includ ing the Gulf of M exico. Spin ner dolph in sightings have o ccurred e xclusively 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 stra ndings rep resent the northernmost documented distribution of this species in the Atlantic. Stock

structure in the we stern North Atlantic is unkno wn. 

POPU LATIO N SIZE

The number o f spinner do lphins inhabiting the U.S. Atla ntic Exclusive Economic Zone (EEZ) is unknown and

seasonal ab undance estimates are n ot available fo r this species sinc e it was rarely seen in any of the surve ys. 

Minimum Po pulation Estimate

Present d ata are insufficient to calculate a minimum po pulation estimate. 

Current Population Trend

There a re insufficient data to determin e the pop ulation trends for this species. 

CURRENT AND M AXIMUM NET PRODUCTIVITY RATES

Current and maxim um net pro ductivity rates are unknown fo r this stock. For purposes of this assessment, the

maximum net produ ctivity 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 Biologic al Removal (PBR) is the product of minimum population size, one-half the maximum

produc tivity rate, and a “re covery” fac tor (MM PA Sec . 3. 16 U.S.C. 1362; Wade and Angliss 1997). The minimum

population size is unknown. The ma ximum produc tivity 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 b e 0.5 bec ause this stock is o f unknown sta tus. 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 ave rage annua l estimated av erage fishery-re lated morta lity and seriou s injury to this stock in the A tlantic

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 (W aring et al.. 1990). No takes were documented in a review of Canadian gillnet and trap

fisheries (Rea d 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 Southea st

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,
199

the SEFSC provided observer coverage of pelagic longline vessels fishing off the Grand Banks (Tail of the Banks) and

provides observ er coverage of vessels fishing south of Ca pe 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, midAtlantic 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 in troduction of quotas, effo rt was severely re duced. The estimated number of hauls in 1991,

1992, 1993, 1 994, 19 95, and 1 996 wer e 233, 243, 232, 197, 164, an d 149 re spectively. Fifty-nine different vessels

participated in this fishery at one time or another between 1989 and 1993. Since 199 4, between 10-12 vessels have

participated in the fishery (Table 2). Observer coverage, expressed as percent o f sets observe d, 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 aggre gated (po oled 19 89-199 3) catch rate s, by strata (No rthridge 19 96). Estima tes of total annua l 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. 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 attributab le 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 1994-1 996. 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 provide s 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 lo ngirostris) by commercial fishery including

the years sampled (Years), the number of vessels active within the fishery (Vessels), the type of data used (Da ta

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 Yea

rs

 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. D ata

Logbook

.40, .42,

.87, .99,

.64

1, 0, 0, 0,

0

1.4, 0.5, 0,

0

5

, 0

 

.31, 1.0, 0,

0, 0

0.31

 (.35)

TOTAL 0.31

(.35)

1

1994 and 1995 - 199 6 shown, other years not ava ilable 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 (N EFSC) Se a Sampling Pro gram. Mand atory logbook (Lo gbook) data are used to

measure total effort, and the data are collected at the Southeast Fisheries Science Center (SEFSC).

3 The ob server cov erage and unit of effort for the P elagic Drift G illnet is a set.

4

For 1991-1993, pooled b ycatch 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 s ubstantially, and bycatch rates were not po oled for this p eriod. 

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, th e point estima te may increa se by 0.8

animals. However, the SEFSC mandatory logbook data was taken at face value, and the refore it was assumed that

1 set was fished within this trip, and the point estimate would then increa se by 0.1 animals.
200

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 mo rtality and serious injury rate. Population size and PBR cannot be estimated, but fishery-related

mortality is very low ; therefore, this stoc k is not a strategic sto ck. 

REFERENCES

Barlow, J., S.L. Swartz , T.C. Ea gle, and P.R . Wad e. 1995 . U.S. M arine Mammal Stock Assessments: Guidelines for

Preparation, Background, and a Summa ry of the 1995 Assessm ents. 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 she lf. Cetacean a nd Turtle Assessmen t Program , University of Rhode Islan d. Final R e port ,

Contract A A51-C78-48, B ureau of La nd Ma nagemen t, Washing ton, DC, 5 38 pp. 

Leatherwood, S., D.K. Caldwell, and H .E. Winn. 197 6. Whales, do lphins, and porp oises of the we stern 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 rep ort to the No rtheast Fisherie s Science Center, Con tract No. 4 0ENN F5000 45, 18 p p. 

Perrin, W. F. an d J. W. G ilpatrick, Jr. 1994. Spinner dolphin. Pages 99-128 in: S. H. Ridgway and R. Harrison (eds),

Handb ook of ma rine mamm als, Volume 5: The first b ook of do lphins. Academ ic Press, San Dieg o, 418 p p. 

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

Comm n. Specia l Issue 15: 1 33-14 7. 

Reilly, S. B. an d J. Barlo w. 1986 . Rates of incre ase in dolp hin popu lation size. Fish. Bu ll., 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-8 0/41, U .S. Fish and W ildlife Service, O ffice of Biolo gical Service s, Washin gton, DC, 163 pp . 

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

April 3-5, 1996, Seattle, Washington. U.S. Dep. Commer., NOAA Tech. Memo. NMFS-OPR-12, 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 she lf. ICES M arine M amm als Com m. CM 1992/N:12, 29 p p. 
201

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 1,0 00 m. 

September 2000

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 19 86) which correspo nd to a shallow water ecotype and a deep water ecotype; both ecotypes have been shown

to inhabit waters in th e western N orth Atlantic Ocean (H ersh and D uffield 1990; M ead and Potter 19 95; Curry a nd 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 unpub lished data),

the western North Atlantic offshore sto ck is believed to

consist of bottlenose dolphins corresponding to the

hematolo gically and mo rphologic ally distinct deep , cold

water ecotype.

Extensive aerial surveys in 1979-1981 indicated

that the stock extended along the entire continental she lf

break from Georges Bank to Cape Hatteras during spring

and summer (CETA P 198 2; Kenney 1990). The

distribution of sightings con tracted towa rds 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 E xclusive Ec onomic Z one (EE Z) waters sou th of Cape Hatteras. 

POPU LATIO N 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 surv eyed 15,9 00 km o f track line in waters north

of Maryland (38° N) (Figure 1; Palka et al. in review). Shipboard data were analyzed using the modified d irect duplica te
202

method (Palka 1995) that accounts for school size bias and g(0), the proba bility 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 U SA Atlantic is 16,689 (CV=0 .32) and from

the southern U SA Atlantic is 1 3,944 (C V=0.3 8). This jo int estimate is considered best because together these two surveys

have the mo st complete coverage of the species’ habitat.

Minimum Po pulation Estimate

The minimum population estimate is the lower limit of the two-tailed 60% c onfidence 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 an d 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 canno t be applied to this process

because previous survey coverage of the species’ habitat was incomplete.

CURRENT AND M AXIMUM NET PRODUCTIVITY RATES

Current and maximum ne t productivity rates are unknown for this stock. Fo r 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

produc tivity 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 p opulation ( 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 ann ual estimated average fishe ry-related mo rtality or serious inju ry to this stock during 1994-1998 was

5.3 bottlen ose dolp hins (CV= 0.03). 

Fishery Information

There was no documentation of marine mammal mortality or serious injury in distant-water fleet (DWF) activities

off the northeast c oast of the U SA prior to 1977 . A fisheries observer program which recorded fishery data and information

on incidental byc atch of marin e mammals was established with implementation of the Magnuson Fisheries Conservation

and Management Act (MFCMA) in 1977. DWF effort in the USA Atlantic EEZ under MFC MA wa s directed p rimarily

towards Atlantic mackerel and squid. An average of 120 different foreign vessels per yea r (range 10 2-161) o perated w ithin

the Atlantic coast EEZ from 1977 through 1982. In 1982, the first year that NMFS Northeast Regional Observer Program

assumed responsib ility for observer coverage of the longline vessels, there were 112 different foreign vessels, eighteen

(16%) of which were Japanese tuna longline ve ssels opera ting along the USA east coast. Between 1983 and 19 91, the

number of foreign fishing vessels operating within the USA Atlantic EEZ each year declined from 67 to nine. 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 ceased at the end of

the 1986 fishing season and for mackerel at the end of the 19 91 season. Ob servers in this program record ed nine bottlenose
203

dolphin mortalities in foreign-fishing activities during 1977-1988 (Waring et al. 1990). Seven takes occurred in the

mackere l fishery, and one bottlenose dolphin ea ch was caug ht in both the sq uid and ha ke 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 Sc ience Cen ter (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

provide s observer coverage of vessels fishing so uth of Cap e Hatteras. 

Bycatch has been observe d by NM FS Sea Samplers in the pelagic d rift gillnet, pelagic pa ir trawl, and N orth

Atlantic bottom tr awl fisheries, but no mortalities have been documented in the Northeast multispecies sink gillnet 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 includ es the Carib bean 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 1 992, 9,8 62 sets in 19 93, 9,48 1 sets in 1994, 10,129 sets in 1995, 9,885 sets in 1996,

8,023 sets in 1997 , and 6,76 5 in 1998 (Cramer 1994; S cott and Brown 1997; Johnson et al. 1999, Yeung 1999 a). Since

1992, this fishery has bee n monitore d 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. 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 serious injured animals as mortalities, replace the 1993-1997 estimates which were

based on a revised analysis of the observed incidental take and self-reported 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 EEZ waters between South Carolina and Cape Cod

(Johnson et al. 1999). D uring 199 3-1998 , in waters not inclu ding the G ulf of Mexic o, one bo ttlenose do lphin was caught

and released alive during 1993, and one was caught and released alive during 1998.

Pelagic Drift Gillnet

The estimated total number of hauls in the pelagic drift gillnet fishery increase d from 71 4 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 Fina l Rule to pro hibit the use of driftnets (i.e., permane nt closure) in the North Atla ntic swordfish fishery

(50 CFR P art 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 199 0, 20% in 1991, 4 0% in 19 92, 42% in 1993, 8 7% in 19 94, 99% in 1995, 64%

in 1996, 1997 (NA), 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 n umber o f unobserve d hauls as rec orded in

self-reported fisheries information. Variances were estimated using bootstrap re-sam pling techniques. Sixty bottlenose

dolphin mortalities have been observed between 1989 and 1998. Estimated bottlenose dolphin kills (CV in parentheses)

extrapolated for each year were 72 in 1989 (0.18), 115 in 1990 (0.18), 26 in 1991 (0.15), 28 in 1992 (0.10), 22 in 1993

(0.13), 14 in 1994 (0.04), 5 in 1995 (0), zero in 19 96, and 3 in 1998 ( 0). Mea n annual estimated fishery-relate d mortality

for this fishery in 19 94-199 8 was 5.3 b ottlenose d olphins (C V=0.0 3) (Tab le 1). 

Pelagic Pair Trawl
204

Effort in the pelagic p air trawl fishery incre ased durin g 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 199 2, 586 in 1993, 407 in 1994, and 440

in 1995, respectively. This fishery ceased operations in 1996, when NMFS rejected a p etition to consider pair trawl gear

as an authorized gear type in Atlantic tunas fishery. The fishery operated from August-November in 1991, from JuneNovember 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 35oN to 41oN, and from 69°W to 72°W.

Appro ximately 50% of the total effort was within a one degree square at 39oN, 72oW, around Hudson Canyon.

Examination of the 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 obse rved betw een 199 1 and 19 95. Estima ted annual fishe ry-related mo rtality (CV in parentheses)

was 13 dolphins in 1991 (0.52), 73 in 1992 ( 0.49), 85 in 1993 ( 0.41), 4 in 1 994 (0.4 0) and 17 in 1995 ( 0.26). Sinc e this

fishery no longer exists, it has been excluded from T able 1. During the 19 94 and 199 5 experimental fishing seasons,

fishing gear experiments were co nducted to collect data o n environmental param eters, gear behavior, and gear handling

practices to evaluate facto rs affecting catch and bycatc h (Goud ey 1995 , 1996). Results of these studies have been presented

at Offshore Cetacean T ake Reduction T eam Mee tings.

North Atlantic Bottom Traw l:

Vessels in the North A tlantic bottom trawl fishery, a Category III fishery under th e MM PA, were observed in order

to meet fishery management needs, rather than marine mamma l managem ent needs. An averag e 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 wate rs in

all seasons. O ne bottleno se dolphin mortality was documented in 1991 and the total estimated mortality in this fishery in

1991 w as 91 (CV =0.97). Since 199 2 there were no bottleno se mortalities o bserved 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 origina lly classified as a Ca tegory II fishery in 1 990, bu t was reclassified as a Catego ry 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.
205

Table 1. Summary of the incidental mortality of bottlenose dolphins (Tursiops truncatus) by commercial fishery including

the years sampled (Years), the number o f vessels active with in the fishery (Ve ssels), the type of d ata used (D ata

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

Serious

Injury

Observed

Mortality

Estimated

Mortality4 

Estimated

CVs 

Mean

Annual

Mortality

Pelagic Drift

Gillnet5 94-98

1994=12

1995=11

1996=10

1997=N/A

1998=13

Obs. Data

Logbook

.87, .99,

.64, NA,

.99

0, 0, 0,

NA, 0

12, 5, 0 , NA,

3

13, 5.03

, 0, NA,

3

 .05, 0, 0,

NA, 0

5.3

(0.03)

TOTAL 5.3

(0.03)

1 Observer data (Obs. Data) are used to measure bycatch rates, and the data are collected w ithin the Northeast

Fisheries Science Center (NE FSC) Se a Samplin g Program. Man datory logb ook (Lo gbook) data are use d to

measure total effort for the p elagic drift gillnet fishery, and these data are collected at the Southeast Fisheries

Science Center (SEFSC).

2 The observer coverage for the pelagic drift gillnet is measured in terms of sets. The proportion of trips sampled

by the NEFSC Sea Sampling Program are reported here.

3

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 0.42

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 increa se by 0.03 animals.

4 Annual mortality estimates do not include any animals injured and released alive.

5 The fishery did not operate in 1997; the average annual mortality is based on the number of years (4; 1994-1996,

1998) that the fishery operated.

Other M ortality

 Bottlenose dolphins are one of the most frequently-stra nded small cetaceans along the Atla ntic 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 Atlantic EEZ is unknown. The western north Atlantic offshore

bottlenose dolphin is not listed as threatened or endangered under the Endan gered Sp ecies Act. T here are insufficie nt data

to determine the population trends for this species. This level is less than 10% of the calculated PBR and, therefore, can

be considere d to be insign ificant and ap proachin g zero mo rtality and seriou s injury rate. Average 1994-1998 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. Wa de. 1995. U.S. Marine Mammal Stock Assessments: Guidelines for

Preparation, Background, and a Summa ry of the 1995 Assessm ents. U.S. Dep. Commer., NOAA Tech. Memo.

NMF S-OPR-6, 73 pp . 

Buckland, S. T., D. R. Andersen, K. P. Burnham and J. L. Laake. 1993. Distance samplin g: Estimating abundance of

biologica l populatio ns. Chap man a nd Ha ll, New Y ork, 446 pp. 

CETAP (Cetacean and Turtle Assessment Program). 1982. A Characterization of Marine Mammals and T urtles in the

Mid- and North Atlantic Areas of the U.S. Outer Continental Shelf, Final Report, Contract AA551-CT8-48, U.S.

NTIS PB83 -21585 5, Burea u of Land M anageme nt, Wash ington, DC, 576 pp . 

Cramer J. 1994. Large pelagic logbook newsletter - 1993. NOAA Tech. Mem. NMFS-SEFSC-352, 19 pp.
206

Curry, B. E. and J. Smith. 1997. Phylogeographic structure of the bottlenose dolphin (Tursiops truncatus): stock

identification and implications for management. Pages 327-247 in: A.E. Dizon, S.J. Chivers and W .F. Perrin

(eds.), Molecu lar genetic s of marin e mam mals. Spec. Pu bl. 3 Socie ty for Marin e Mammalogy.

Duffield, D. A. 1986. Investigation of genetic variab ility in stocks of the bottlenose dolphin (Tursiops truncatus). Final

report to the NMF S/SEFSC, Contra ct No. N A83-G A-0003 6, 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

Northwe st Atlantic. U.S. Mar. Fish. Rev. 56(3): 24-27.

Goud ey, C.A. 199 5. The 1 994 exp erimental pa ir trawl fishery for tuna in the northwest Atlantic, Ma ssachusetts Institute

of Technology, Sea Grant, MITSG 95-6, Cambridge, MA. 10 pp.

Goudey, C.A. 1996. The 1995 experime ntal pair trawl fisher y for tuna in the no rthwest Atlantic, M assachusetts Institute

of Technology, Sea Grant, MITSG 95-6, Cambridge, MA. 13 pp.

Gowans S. and H . Whitehe ad. 199 5. Distributio n and hab itat partitioning b y small odo ntocetes in the Gully, a submarine

canyon on the Scotian S helf. Can. J. Zool. 73: 1599-1608.

Hersh, S. L. and D. A. Du ffield. 1990. Distinction between no rthwest Atlantic offshore and coastal bottlenose dolphins

based on hemoglobin profile and morphometry. Pages 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.

Kenney, R. D. 1990. Bottlenose dolphins off the northeastern United States. Pages 369-386 in: S. Leatherwood and R.

R. Reeve s (eds), Th e bottlenos e dolphin, Academ ic Press, San Dieg o, 653 p p. 

Laake, J. L., S. T. Buckland, D . R. Anderson and K . P. Burnham. 1993. DISTANCE user’s guide, V2.0. Colorado

Coop erative Fish & Wildlife Research U nit, Colorad o State U niversity, Ft. Collins, C olorado , 72 pp. 

Mead, J. G. and C. W . Po tter. 1995 . Recognizing two populations for the bottlenose dolphin (Tursiopstruncatus) off the

Atlantic coast of North America: morphologic and ecologic considerations. International Biological Research

Institute Rep orts 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 rep ort to the No rtheast Fisherie s Science Center, Con tract No. 4 0ENN F5000 45. 18 p p. 

Palka, D. 1995. Abundance estimate of the Gulf of Maine harbor porpoise. Rep. int W hal. 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 1 995 and 1998. Fish. Bull., U.S.

Scott, G.P. and C.A. Bro wn. 1997 . Estimates of m arine mamm al and marine turtle catch b y the U.S A tlantic 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-OPR-12, 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 no rtheast United States, 197 7-1988 . 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 mo vements of b ottlenose d olphins. Marine Mammal Science, 15(4):1098-1114.

Yeung, C. 1999a. Estimates of marine mammal and marine turtle bycatch by the U.S. Atla ntic pelagic lo ngline 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.
207

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 occu rring farther offsho re 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. T hese app earances u sually occur b etween Jan uary and M ay. 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 a t their southern most

point of migration in the Gulf of St. Lawrence. T he worlds' ho oded se al popula tion is divided into three separate stoc ks,

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 stoc k, 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 o ff the coast of N ewfoundla nd and Labrado r and the G ulf herd bree ds in the Gu lf 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. A dults 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 sum mer and e arly

fall (Lavigne an d Kova cs 1988 ). Little else is known about the activities of hooded seals during the rest of the year until

they assemb le again in Feb ruary for bre eding. 

Hooded seals are rarely fo und in the U .S. Atlantic Exclusive E conomic Zone. Sm all numbers of hoode d seals

at the extreme s outhern limit o f their range oc cur in the winter and spring seasons. The influx of harp seals an d geogra phic

distribution in N ew Englan d to mid-A tlantic waters is ba sed on stran ding data. 

POPU LATIO N 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 commerc ial catch data, and including aerial surveys. Th ese

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; W inters and Bergflodt 1978; Stenson et al..

1996). Estimated pup production dropped to 2 6,000 hooded seal pups in 1978 (W inters 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 produc tion in the Da vis Strait at 18,6 00 (95% C.I. 14,00 0 - 23,00 0). A

1985 survey at the Front (H ay et al. 1985) p roduced a estimate of 6 1,400 (9 5% C.I. 16,500 - 119,45 0). 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 appro ximately 400 ,000-45 0,000 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 S trait stocks, the po ssibility 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.
208

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 coe fficient 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 Stra it 18,600 None reported

1985 Front herd: Newfoundland/Labrador 61,400 None reported

1990 Front herd: Newfound/Labrador 82,100 None reported

Minimum pop ulation estimate

Present data are insufficient to calculate the minimum po pulation 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 Canadia n popula tion appe ars to be increasing but, because different methods

have bee n used ove r time to estimate populatio n size, the mag nitude of this incre ase has not b een quan tified. 

CURRENT AND M AXIMUM 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 1 993). 

For purposes of this assessment, the maximum net productivity rate was assumed to be 0.12. This value is based

on theoretical modeling sho wing that pinnip ed pop ulations may no t grow at rates much greater than 12% given the

constraints of their reproductive life history (Barlow et al. 1995). 

POTENTIAL BIOLOGICAL REMOVAL

Potential Biologic al Remo val (PBR) is the pro duct of minimum population size, one-half the maximum

produc tivity rate, and a “recovery” factor (M MPA Sec. 3. 16 U.S.C. 1362; W ade and Angliss 1997). The minimum

population size is unknown. The maximum produc tivity rate is 0.12, the default value fo r pinniped s. 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 hoo ded seal in U .S. waters is unknown. Applying the formula to abundance estimates (400,000)

in Canadia n waters results in a PBR= 24,00 0 hood ed 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- 1 992 the T AC was inc reased to 1 5,000. 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 1 991, with a m ean catch o f 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 500N) has been prohibited since 1964. No comm ercial hunting of

hooded seals is permitted in the Davis S trait. 

 Total ann ual estimated average fishe ry-related mo rtality or serious inj ury to this stock in U.S. waters during

1992-1 996 was 5.6 hood ed seals (C V = 0.9 6; Table 2). 
209

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 Sou theast

Fisheries Science Center (SEFSC). The No rtheast 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 provid ed observer coverage of pelagic longline vessels fishing off the Grand Banks (Tail of the Banks) and

provide s observer coverage of vessels fishing so uth of Cap e Hatteras. 

Recent by-catch has been observed by NMFS Sea Samplers in the New England multispecies sink gillnet fisheries,

but no mortalities h ave been docume nted in the M id-Atlantic co astal gillnet, Atlanti c drift gillnet, pelagic pair trawl or

pelagic long line fisheries. 

In 1993, there were ap proximately 349 full and p art-time vessels in the New England multispecies sink gillnet

fishery, which covered the Gulf of M aine and so uthern Ne w England (Table 2). An additional 187 vessels were reported

to occasionally fish in the Gulf of Maine w ith 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-catc h 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 o f harbor sea ls, 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). T he by-catch occurred

only in winter (January-May) and was in waters between Cape Ann and New Hampshire.

CANADA

An unknown n umber o f hooded seals have b een taken in N ewfoundla nd and Labrado r groundfish g illnets (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 e nd of 199 3 due to co llapse of Ca nadian gro undfish resou rces. 

Hooded seals are being taken in Canadian lumpfish and groundfish gillnets and trawls; however, estimates of total

removals h ave not be en calculated to date. 
210

Table 2. Summary of the incidenta l mortality of hoo ded seal (C ystophora cristata) by commercial fis hery including the

years sampled (Yea rs), the number of vessels active within the fishe ry (Vessels), the type of data u sed (Da ta

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. D ata

Weigh out,

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 co llected 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 observe r coverage for the Ne w England multispecies sink gillnet fishery is measured in trips.

Other M ortality

 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 po ssible shift in distributio n or range e xpansion so uthward 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 th e popula tion size in

Canadian waters and can be considered insignificant and approaching zero mortality and serious injury rate. This is not

a strategic stock b ecause the lev el of human-c aused mo rtality and seriou s injury is believed to be very low relative to

overall stock size.

REFERENCES

Anon. 1995. Report of the Joint ICES/NAFO W orking Group on Harp and H ooded Seals. 5-9 June 1995, Dartmouth,

Nova Scotia Canada. NAFO SCS Doc. 95/16. Serial No. N2569. 40 pp.

Anon. 1998. Rep ort of the Joint ICES/N AFO W orking Group o n Harp and H ooded Se als. 28 August - 3 September 1997,

Copen hagen, De nmark. ICES CM 1998/Assess:3. 35 pp.

Barlow, J., S.L. Swartz, T.C. Ea gle, 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.

NMF S-OPR-6, 73 pp . 

Benjaminsen, T., and T . Oritsland. 19 75. The survival of year-c lasses and estim ates of prod uction 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. Abunda nce estimatio n of a dispersed, dynam ic popula tion: Hoo ded seals

(Cystophora cristata) in the North west 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.
211

Hammill, M. O., G. B. Stenson, and R. A. Myers. 1992 . Hood ed seal (Cystoph ora cristata ) pup production in the Gulf

of St. Lawren ce. Can. J. Fish. Aquat. Sci. 49: 2546-2550.

Hay, K., G. B. Stenson, D. Wakeham, and R. A. M yers. 1985. Estimation of pu p production o f hooded seals (Cystophora

cristata) at Newfou ndland d uring Ma rch 198 5. Con. A tl. Fish. Sci. Adv . Comm. 8 5/96. 

King, J. E. 1 983. Sea ls of the Wo rld. Cornell Unive rsity Press, Ithaca, NY , 240 pp . 

Lavigne, D . M. and K . M. Ko vacs. 198 8. Harps and Hood s Ice Bree ding Seals o f the Northw est Atlantic. University of

Waterloo Press, Waterlo o, 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 A tlantic. Rep. int. W hal.

Comm n. Specia l Issue 15: 1 33-14 7. 

Rubinstein, B. 199 4. An app arent shift in distribu tion of ice seals, Phoca groenlandica, Cystoph ora cristata , and Phoca

hispida, toward the e ast coast of the U nited States. M .A. Thesis, B oston Un iversity, Bosto n, MA, 4 5 pp. 

Sergeant, D.E. 1976. Research on hoo ded seals Cystophora cristata Erxleben in 1976. International Commission for the

Northwest Atlantic Fisheries Research Document 76/X/126.

Stenson, G . B. 199 3. The statu s of pinniped s in the Newfo undland re gion. NA FO SCR Doc . 93/34. 

Stenson, G.B., R.A. M yers, I-H Ni and W.G . Warre n. 1996 . Pup pro duction of h ooded 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 W orkshop

April 3-5, 1996, Seattle, Washington. U.S. Dep. Commer., NOAA Tech. Memo. NMFS-OPR-12, 93 pp.

Walden, J. 1996. T he New E ngland gillnet e ffort survey. NOAA, NMF S, NEFSC, Woods Hole, Massachusetts. NEFSC

[Northeast Fisheries Science Center] Ref. Doc. 99-10. 38p.

Winters, G. H. And B. Bergflodt. 1978. M ortality and productivity of the Newfoundland hooded seal stock. International

Commission for the Northwest Atlantic Fisheries Res. Doc. 78/XI/91.
212

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 wo rld's oceans in deep waters from b etween 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).

POPU LATIO N 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 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 e xtent of the U .S. Exclusive Economic

Zone. The seasonal GulfCet aerial

surveys included o nly a small

portion of the stock range and these

data were not use d for abundance

estimation. Estimated abundance of

sperm whales by survey year

[coefficient of variation (C V) 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 effortweighted estimated average

abundance of sperm wh ales for all

surveys combined was 5 30 (CV =

0.31) (Hansen et al. 1995).

Minimum Po pulation 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 a bundanc e 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 wha les. 

Current Population Trend

No trend was discernable in the average annual abundance estimates. All of the log-normal 95% confidence

intervals of the annual e stimates overlap, indicating that the estimates w ere not significantly different at that level. The

variation in abundance estimates may represent inter-annual variation in distribution, rather than a change in abundance.

CURRENT AND M AXIMUM NET PRODUCTIVITY RATES

Current and maximum net productivity rates are not known for this stock; therefore, the default maximum net

produc tivity rate of 0.04 (Anon. 19 94) was use d for purp oses of this assessment. 

POTENTIAL BIOLOGICAL REMOVAL
213

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 wha les are an end angered sp ecies. The resulting PBR for this stock is 0.8 sperm whales. 

ANNUAL HUMAN-CAUSED MORTALITY AND SERIOUS INJURY

A commercial fishery for sperm wha les operate d in the Gulf o f Mexico during the late 1 700's to the ea rly 1900's,

but the exac t number o f whales taken is no t known (T ownsend 1935). 

The leve l of current, dire ct, 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 M exico. 

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 ma rine mamm als 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 ab ility to recognize signs of fishery interac tion. 

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 pub lic 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 se ts in 1991, 4 ,850 sets in 1992, and 3,260 sets in 1993 (Cramer

1994). This fishery has been mo nitored with a bout 5% observer coverage , in terms of trips o bserved, sin ce 1992 . There

were no re ports of mo rtality or serious inj ury to sperm whales by this fisher y. 

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 ob servers, and

there are no othe r data available as to the extent of this fisher y in the Gulf of M exico. It is assumed that it is very limited

in scope an d duration . 

Other M ortality

A total of nine spe rm whale stran dings were d ocumen ted in the northern G ulf of Mexic o during 1 987-19 94. 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 tra uma was ass umed to b e the proxim ate cause o f this stranding. 

 Stranding d ata proba bly 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 e ntanglemen t or other fishery-inte raction. 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 to tal level of humancaused mortality and serious injury is unknown, but it is believed to be insignificant; however, because this species is listed

as endangered and there is presently no recovery plan in place , any fishery-related mortality would be unlawful. T his is

a strategic stock because the sperm whale is listed as an endangered species under the ESA.

REFERENCES
214

Anon. 1994. Report of the PBR (Potential Biological Removal) workshop. June 27-29, 19 94. NOA A, NMF S Southwest

Fisheries Sc ience Cen ter, La Jolla, California, 13 p p. + App endices. 

Buckland, S. T., D. R. Anderson, K. P. Burnham and J. L. Laake. 1993. Distance Sampling: estimating abundance of

biologica l populatio ns. Chapm an & Ha ll, London , 446 pp . 

Cramer, J. 1994. Large pelag ic logboo k newsletter - 19 93. NO AA Te ch. Mem . NMF S-SEFSC-352, 1 9 pp. 

Davis, R., G. Sco tt, B. Wü rsig, 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 Ser vice. U.S. D ept. of the Interio r, Minera ls 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 Labo ratory, Con tribution No . MIA-9 4/95-25 , 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 & W ildlife Researc h Unit, Co lorado S tate University, Ft. Collins, Co lorado, 7 2 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 S tudy/MM S 91-00 27. U.S. D ept. of the Interio r, Minera ls

Manag ement Ser vice, Gulf of M exico OC S Region al Office, Ne w Orleans, Louisiana, 1 08 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 mamma ls, Vol. 4: river d olphins and the larger too thed whales. A cademic

Press, Lo ndon, 44 2 pp. 

Schmidly, D. J. 1981. Marine mammals of the southeastern United States and the G ulf of Mexic o. U.S. Fish an d Wild life

Service, O ffice of Biolo gical Service s, Washin gton, DC, FWS /OBS-8 0/41, 16 5 pp. 

Townsend, C. H. 1935. The distribution of certain whales as shown by logbook records of American whale ships.

Zoologica 19: 1-50.
215

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 no rthern Gulf o f Mexico occur prim arily along the co ntinental shelf edge

and over the deeper waters off the continental shelf (Mullin et al. 1991; South east Fisheries Science Center, SEFSC,

unpublished data). Dwarf sperm whales and pygmy sperm w hales (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 m ore nume rous in spring , probab ly 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 d eep, on average (D avis et al. 1998). However, these authors cautioned

that inferences on preferred bottom depths should await surveys for the entire Gulf of M exico. Th e 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 div e deepe r during feed ing bouts. T here is no information on stock differentia tion. 

POPU LATIO N SIZE

Estimates of abunda nce 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 springsummer, 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 E conomic

Zone. The seasonal GulfCet ae rial surveys includ ed only a small portion of the species’ range and th erefore, these data

were not used to e stimate pop ulation size. Estimated ab undance of Kogia sp. by survey year [coefficient of variation (CV)

in parenthes es] was 10 9 in 1991 (0.68), 1,0 10 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 se a. 

Minimum Po pulation Estimate

A minimum populatio n estimate was not calculated because o f uncertainty of sp ecies identificatio n at sea. 

Current Population Trend

There is insufficient information to describe any population trend of this species in the Gulf of Mexico.

CURRENT AND M AXIMUM NET PRODUCTIVITY RATES

Current and maximum net produc tivity rates are not kn own for this stoc k. The ma ximum net p roductivity 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

produc tivity 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.
216

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 wha les 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 c lassified as likely caused by fishery interactions, but there have been stranding investigation reports of

dwarf sperm whales which may have died as a res ult of other hum an-related ca uses. Strandin g data pro bably und erestimate

the extent of fishery-related mortality and serious injury because not all of the marine mamma ls 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 fisheryinteraction. Finally, the level of te chnical exp ertise amon g stranding ne twork perso nnel varies wid ely as does the a bility

to recogniz e signs of fishery intera ction. 

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 re ports of mo rtality or serious inj ury of dwarf sp erm 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 ob servers, and

there are no other data available as to the extent of this fish ery in the Gulf o f Mexico . It is assumed that it is very limited

in scope an d duration . 

Other M ortality

A total of at least 16 dwarf sperm whale strandings were documented in the northern Gulf of Mexico from 1990

through O ctober 19 98. 

STATUS OF STOCK

The status of this stock relative to OSP is unknown and there are insufficient data to determine population trend s.

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 un known, bu t it is believed to b e insignificant.

REFERENCES

Barlow, J., S. L. Swartz , T. C. Ea gle and P . R. Wa de. 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 hemo globin, morphom etric and dietary analyses.

Abstracts. W orld M arine Ma mmal Scie nce Con ference. M onaco. 2 0-24 Jan uary. 

Buckland, S. T., D. R. Anderson, K. P. Burnham and J. L. Laake. 1993. Distance Sampling: estimating abundance of

biological populations. Chapm an & Ha ll, London , 446 pp . 

Caldwell, D. K. and M. C. Caldwell. 1989. Pygmy sperm whale Kogia breviceps (de Blainv ille, 1838): d warf sperm whale

Kogia simus Owen, 1866. Pages 235-260 in: S. H. Ridgway and R. Harrison (eds), Handbook of marine

mamma ls, Vol. 4: Rive r dolphins a nd the larger toothed w hales. Academ ic Press, San Dieg o. 

Cramer, J. 1994. La rge pelagic logboo k newsletter - 19 93. NO AA Te ch. Mem . NMF S-SEFSC-352, 1 9 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 cetacean s along the co ntinental slope of the north-ce ntral and western Gulf of M exico. Mar.

Mam mal. 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. D avis and G .S. Fargion ( eds). Distrib ution and ab undance of marine mammals in the north-central and
217

western Gulf of Mexico: Final Report. Volume II: Technical Report. OCS Study MMS 9 6-0027. Prepared by the

Texas Institute of Oce anograp hy and the N ational M arine Fisherie s Service. U .S. Dept. o f the Interior, M inerals

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. 19 97. Distrib ution of cetac eans in the no rthern Gulf o f 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

Coop erative Fish & Wildlife Research U nit, Colorad o State U niversity, Ft. Collins, C olorado , 72 pp. 

Mullin, K., W. Hoggard, C. Rod en, 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, M inerals

Manag ement Ser vice, Gulf of M exico OC S Region al Office, Ne w Orleans, Louisiana 1 08 pp. 

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

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 surve y ships and airc raft. Aquat. Mammals, 24:41-50.
218

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 no rthern Gulf o f Mexico occur prim arily along the co ntinental shelf edge

and over the deeper waters off the continental shelf (Mullin et al. 1991; South east Fisheries Science Center, SEFSC,

unpublished data). Pygmy sperm wh ales and dwarf sperm w hales (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 M exico in waters 1000 m deep, on avera ge (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 pe lagic

distribution than pygmy sperm whales, and/or dive deeper during feeding bouts. There is no information on stock

differentiation. 

POPU LATIO N SIZE

Estimates of abunda nce 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 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 (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 E conomic

Zone. The seasona l GulfCet ae rial surveys included o nly a small portion of the spe cies’ range an d therefore , these data

were not used to estimate population size. Estimated abundan ce 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-we ighted estima ted abund ance 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 Po pulation Estimate

A minimum p opulation e stimate 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 M AXIMUM NET PRODUCTIVITY RATES

Current and maximum net productivity rates are not known for this stock. The maximum net produ ctivity 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

produc tivity 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.
219

ANNUAL HUMAN-CAUSED MORTALITY AND SERIOUS INJURY

The level of past or curren t, direct, human -caused mortality of pygmy sperm wha les in the norther n Gulf of

Mexico is unknown. A vailable inform ation indicate s there likely is little, if any, fisheries interaction with pygmy sperm

whales in the northern Gulf of M exico. Th ere have b een no log book re ports 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 re ports 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

mamma ls which die or are seriously injured may wash ashore, nor will all of those that do wash ashore nec essarily 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 re ports of mo rtality or serious inj ury of pygmy sp erm 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 ob servers, and

there are no other data available as to the extent of this fish ery in the Gulf o f Mexico . It is assumed that it is very limited

in scope an d duration . 

Other M ortality

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). Ano ther animal stra nded ap parently due to injuries inflicted by impact, p ossibly with a vessel.

STATUS OF STOCK

The status of this stock relative to OSP is unknow n and there are insufficient data to determine p opulation trends.

This species is not listed under the Enda ngered Species A ct. Although th e 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 insignifican t.

REFERENCES

Barlow, J., S.L. Swartz , T.C. Ea gle, and P.R . Wad e. 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 hemo globin, morphom etric and dietary analyses.

Abstract. W orld M arine Ma mmal Scie nce Con ference. M onaco. 2 0-24 Jan uary.

Buckland, S. T., D. R. Anderson, K. P. Burnham and J. L. Laake. 1993. Distance Sampling: estimating abundance of

biologica l populatio ns. Chap man & H all, London , 446 pp . 

Caldwell, D. K. and M. C. Caldwe ll 1989. Pygmy sperm whale Kogia breviceps (de Blainv ille, 1838): d warf sperm whale

Kogia simus Owen, 1866. Pages 235-260 in: S. H. Ridgway and R. Harrison (eds), Handbook of marine

mamma ls, Vol. 4: Riv er dolphin s and the large r toothed w hales. Academ ic Press, San Dieg o. 

Cramer, J. 1994. Large pelag ic logboo k newsletter - 19 93. NO AA Te ch. Mem . NMF S-SEFSC-352, 1 9 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 ceta ceans alon g the continen tal slope of the n orth-central an d western G ulf of Mexic o. Mar.

Mamm. Sci., 14:490-507.
220

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 mamma ls 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 Oce anograp hy and the N ational M arine Fisherie s Service. U .S. Dept. o f the Interior, M inerals

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

Coop erative Fish & Wildlife Research U nit, Colorad o State U niversity, Ft. Collins, C olorado , 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-cen tral Gulf of M exico. OC S Study/M MS 9 1-0027 . U.S. Dep t. of the Interior, Mine rals

Manag ement Ser vice, Gulf of M exico OC S Region al Office, Ne w Orleans, Louisiana 1 08 pp. 

Tarpley, R. J., and S. Marwitz. 1993. Plastic debris ingestion by cetaceans along the T exas coast: two case studies. Aqua t.

Mam mals, 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 surve y ships and airc raft. Aqua t. Mam mals, 24:41-50.
221

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

Bry de's whales are considered the tropical and sub-tropical baleen whale of the world's oceans. In the western

Atlantic, Bryde's wha les are repo rted from o ff 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 19 83), but there is no information on stock differentiation. Most

sightings of Bryde's whales have oc curred du ring the spring-summer mo nths (Hanse n et al. 1995 ; Davis et al., in

prepara tion), but strand ings have oc curred thro ughout the yea r (Jefferson e t al. 1992). 

POPU LATIO N 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 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 e xtent of the U .S. Exclusive Economic

Zone. The seaso nal GulfCet aerial

surveys included only a small

portion of the stock range and these

data were not used for abundance

estimati on. The estim ate d

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 effortweighted 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 occ urred in 19 91. 

Minimum Po pulation 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 20 th

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 B ryde’s whales. 

Current Population Trend

The abundance estimates decreased to zero for survey years 199 2-1994 be cause 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 p opulation siz e and low sa mpling intensity or it could be due to inter-annual variation in distribution.

CURRENT AND M AXIMUM NET PRODUCTIVITY RATES

Current and maximum net productivity rates are not known for this stock; therefore, the default maximum net

produc tivity rate of 0.04 (Anon. 19 94) was use d for purp oses of this assessment. 
222

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 pop ulation (OSP) (A non. 1994). T he recovery factor was set at 0.50

because th e status of the stoc k relative to O SP is unkno wn. The re sulting PBR for this stock is 0.2 Bryde’s wh ales. 

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

unk now n, but av aila ble info rma tion indicat es th ere is little fishe ries inte rac tion with Bry de's whales in the no rthern 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 ab ility to recognize signs of fishery interac tion. 

The total known fishery-related mortality and serious injury for this stock is less than 10% of the calculated PBR

and, therefore, can be co nsidered insignificant and a pproac hing zero m ortality 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 pub lic 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 re ports of mo rtality or serious inj ury to Bryd e’s whales by this fishe ry. 

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 NMF S 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 an d duration . 

Other M ortality

No hum an-caused mortality has be en reporte d for this stock. 

STATUS OF STOCK

The status of this stock relative to OSP is unknow n and there are insufficient data to determine p opulation 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 P BR (P otential Bio logical Rem oval) workshop . June 27-2 9, 1994 . NOAA , NMFS Southwest

Fisheries Sc ience Cen ter, La Jolla, California, 13 p p. + App endices. 

Buckland, S. T., D. R. Anderson, K. P. Burnham and J. L. Laake. 1993. Distance Sampling: estimating abundance of

biologica l populatio ns. Chapm an & Ha ll, London , 446 pp . 

Cramer, J. 1994. Large pelag ic logboo k newsletter - 19 93. NO AA Te ch. Mem . NMF S-SEFSC-352, 1 9 pp. 

Davis, R., G. Scott, B. Würsig, W. Evans, G. Fargion, L. Hansen, K. Mullin, N. May, T. Leming, B. M ate, 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 #M MS 9 4-0003 . 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. 
223

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 Labora tory, Contrib ution No . MIA-9 4/95-25 , 9 pp.

+ tables and figures.

Jefferson, T. A., S. Leatherwood, L. K. M. Shoda and R. L. Pitman. 1992. M arine mammals of the G ulf of Mexic o: 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 . DIST ANCE user’s guide, V2.0. Colorado Cooperative

Fish & W ildlife Researc h Unit, Co lorado S tate University, Ft. Collins, Co lorado, 7 2 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 Mexic o. U.S. Fish and W ildlife

Service, O ffice of Biolo gical Service s, Washin gton, DC, FWS /OBS-8 0/41, 16 5 pp. 
224

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

Cuv ier's bea ked wha les a re d istri but ed thro ugh out the w orld '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 N orth Ame rica, based on skull characteristics, a re thought to r epresent members o f a panmictic population

(Mitchell 1 968), bu t there is no inform ation on stoc k differentiation in the Gulf of M exico and nearby wate rs. 

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.

POPU LATIO N SIZE

Estimates of abundance were derived through the applicatio n of distance sa mpling ana lysis (Bucklan d et al. 1993)

and the computer program DIST ANCE (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 seaso nal GulfCe t aerial surveys inc luded on ly a small portion of the stock range and these d ata 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

Cuv ier's beaked whales was 30 (CV

= 0.50) (H ansen et al. 1995). The

estimated abundan ce of Curv ier’s

beaked whales is probably low

because only sightings of beaked

whales which could be p ositively

identified to sp ecies were u sed. 

Minimum Po pulation 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 log-normal

distributed abundance estimate as specified by N MF S (A non . 19 94). Th e minimum p opu latio n est ima te is 20 Cuvie r'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 small estimated

populatio n size and sampling intensity o r inter-annual va riation in distribu tion, rather than a change in p opulation siz e. 

CURRENT AND M AXIMUM NET PRODUCTIVITY RATES
225

Current and maxim um net pro ductivity rates are not known for this stock; there fore, the defau lt maximum net

produc tivity rate of 0.04 (Anon. 19 94) was use d for purp oses of this assessment. 

POTENTIAL BIOLOGICAL REMOVAL

Potential biological removal level (PBR) was specified as the produc t of the minimum populatio n size, one ha lf

the maximum net produ ctivity 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 th e status of the stoc k relative to O SP is unkno wn. PBR for this stock is 0.2 Cuvier's beak ed whales. 

ANNUAL HUMAN-CAUSED MORTALITY AND SERIOUS INJURY

Cuv ier's beaked whales were taken occasionally in a small, directed fishery for cetaceans that operated out of the

Lesser An tilles (Caldwell a nd Caldw ell 1971). 

The actual level of past or current, d irect, human-c aused mo rtality of Cuvier's bea ked whale s 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 Gu lf of Mexico . Available information indicates there likely is little, if any, fisheries interaction with

Cuvier's beak ed whales in th e northern G ulf of Mexic o. 

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-r elated mo rtality and serious injury because not all of the marine mamma ls 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 ab ility to recognize signs of fishery interac tion. 

Total fishery-related mortality and serio us 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 re ports of mo rtality or serious inj ury to Cuvier's or any beake d whales by th is fishery. 

Pair trawl fishing gear has the potential to capture marine mamma ls, but there hav e been no reports of mortality

or serious injury to marine mammals in the G ulf of Mexico. This fishery has not been observed by NMFS observers, and

there are no othe r data availab le as to the exten t of this fishery in the Gulf of Mexico. It is assumed that it is very limited

in scope an d duration . 

STATUS OF STOCK

The status of this stock relative to OSP is unknow n and there are insufficient data to determine p opulation trends.

This species is not listed under the Endangered Species Act. The total level of human-caused mortality and serious injury

is unknown, b ut it is believed to be insignificant; the refore, this is not a str ategic stock. 

REFERENCES

Anon. 1994. Report of the PBR (Potential Biological Removal) workshop. June 27-29, 1994. NOAA, NMFS Southwest

Fisheries Sc ience Cen ter, La Jolla, California, 13 p p. + App endices. 

Buckland, S. T., D. R. Anderson, K. P. Burnham and J. L. Laake. 1993. Distance Sampli ng: estimating abundance of

biologica l populatio ns. Chapm an & Ha ll, 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 pelag ic logboo k newsletter - 19 93. NO AA Te ch. Mem . NMF S-SEFSC-352, 1 9 pp. 

Davis, R., G. Scott, B. Würsig, W. Evans, G. Fargion, L. Hansen, K. Mullin, N. May, T. Leming, B. M ate, J. Norris and

T. Jefferson. In preparation. Distribution and abundance of marine mammals in the north-central and western
226

Gulf of Mexico: Final Report. OCS Study #MMS 94-0003. Texas Institute of Oceanography and the National

Marine Fisheries Ser vice. U.S. D ept. of the Interio r, Minera ls Mgmt. S ervice, Gu lf 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 c avirostris G. Cuvier, 1923. Pages 289-308 in S. H. Ridgway and

R. Harrison ( editors), H andboo k of marine m ammals, V ol. 4: River dolphins and the larger toothed w hales,

Academ ic Press, Lo ndon, 44 2 pp. 

Jefferson, T. A., S. Le atherwoo d, L. K. M . Shoda a nd R. L. P itman. 1992. M arine mammals of the G ulf of Mexic o: a field

guide for ae rial and shipb oard ob servers. Te xas A&M University P rinting Center, C ollege Statio n, 92 pp. 

Laake, J. L., S. T. Buckland, D. R. Anderson, and K. P. Burnham. DISTANCE user’s guide, V2.0. Colorado Coop erative

Fish & W ildlife Researc h Unit, Co lorado S tate University, Ft. Collins, Co lorado, 7 2 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 M exico. U.S . Fish and W ildlife

Service, O ffice of Biolo gical Service s, Washin gton, DC, FWS /OBS-8 0/41, 16 5 pp. 
227

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 sp ecies of Mesoplodon are known, from strandings and/or sightings, to occur in the Gulf of Mexico

(Jefferson et al. 1992 ; Hansen e t al. 1995). These are Blainville's beaked whale (M. den sirostris), Gervais' bea ked 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 kno wn stranding of this species in the Gulf of Mexico (Bonde

and O’Shea 1989) and bec ause 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 c avirostris that were not identified as such. Beaked

whales were seen in all seasons during recent seasonal GulfCet aerial surveys of the northern G ulf of Mexic o (Davis e t al.,

in prepara tion). 

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 198 3). 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 d ifferentiation. 

POPU LATIO N SIZE

Estimates of abundance of beaked whales were derived thro ugh the app lication of distan ce 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 da ta collected as part of the G ulfCet prog ram (Da vis et al., in prepa ration). Th ese surveys were

conducted throughout the area from approx imately the 200 m isobath along the U.S. coast to the seaward extent of the U.S.

Exclusive Economic Zone . The seaso nal GulfCe t aerial surveys included o nly a small portion of the stock range an d 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) (Ha nsen et al.

1995). Estimated beake d 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 abundan ce of Blain ville’s

beaked whale cannot be estimated

due to uncertainty of species

identification at sea.

Minimum Po pulation Estimate

A minimum population

estimate was n ot calculated because o f uncertainty of sp ecies identificatio n of sightings. 

Current Population Trend
228

The abundance estimates o f beaked whales for 1991-1 993 wer e lower than 1 994, bu t there was co nsiderable

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 inten sity or a change in distribution, ra ther than a cha nge in pop ulation size. 

CURRENT AND M AXIMUM NET PRODUCTIVITY RATES

Current and maximum net productivity rates are not known for this stock; therefore, the default maximum net

produc tivity rate of 0.04 (Anon. 19 94) was use d for purp oses 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, d irect, human-c aused mo rtality of beaked whales in the no rthern Gulf o f 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 no rthern Gulf o f Mexico . 

There were no d ocumen ted stranding s of beaked whales in the no rthern Gulf of Mexico during 1987-1994 which

were classified as likely caus ed by fishery inter actions or o ther human -related caus es. Stranding data prob ably

underestimate the extent of fishery-r elated mo rtality and serious injury because not all of the marine mammals whic h 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 ab ility to recognize signs of fishery interac tion. 

Although PBR cannot be calculated, the total known fishery-related mortality and serious injury for this stock is

zero and, therefore , can be co nsidered insignificant and a pproac hing zero m ortality and serio us injury rate. This

determination cannot be made for specific fisheries until the implementing regulations for Section 118 of the MMPA have

been revie wed by the p ublic and fina lized. 

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 fo r the Gulf of M exico pela gic 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 b een monito red with abo ut 5% ob server cov erage, in terms of trips obse rved, since 1 992. 

Pair trawl fishing gear has the potential to capture marine mamma ls, but there hav e been no reports of mortality

or serious injury to marine mammals in the Gulf of Mexico. This fishery has not been observed by NMF S observers, and

there are no other data available as to the extent of this fish ery in the Gulf o f Mexico . It is assumed that it is very limited

in scope an d duration . 

STATUS OF STOCK

The status of this stock re lative to OS P is unknown and there are insufficient data to determine p opulation trends.

This species is not listed under the Endan gered Sp ecies Act. The total level of human-caused mortality and serious injury

is unknown, b ut it is believed to be insignificant; the refore, this is not a str ategic stock. 

REFERENCES

Anon. 1994. Report of the PBR (Potential Biological Re moval) workshop . June 27-29, 199 4. NOAA , NMFS Southwest

Fisheries Sc ience Cen ter, La Jolla, California, 13 p p. + App endices. 

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

biologica l populatio ns. Chapm an & Ha ll, London , 446 pp . 

Cramer, J. 1994. Large pelag ic logboo k newsletter - 19 93. NO AA Te ch. Mem . NMF S-SEFSC-352, 1 9 pp. 
229

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 abun dance o f marine mam mals in the north-central and western

Gulf of Mexic o: Final Rep ort. OCS Study #MM S 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. And erson, and K. P. Burnham. D ISTA NCE user’s guide, V 2.0. Colorado Cooperative

Fish & W ildlife Researc h Unit, Co lorado S tate University, Ft. Collins, Co lorado, 7 2 pp. 

Leatherwood, S., D. K. Caldwell and H. E. Winn. 1976. Whales, dolphins, and porpoises of the western North Atlantic.

NOA A Tech . Rep. NM FS CIRC-396, 1 76 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. 198 9. Beake d whales of the genus M esoplod on. Pages 349-430 in S. H. Ridgway and R. Harrison (editors),

Handbook of marine mammals, Vo l. 4: River do lphins and the larger toothe d whales. Academic Press, London,

442 pp . 
230

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 an d/or sightings, to have occurred in the Gulf of

Mexico (Jefferson et al. 1992; Ha nsen et al. 1995). The se are Blainville's beaked whale (M. den sirostris), Gervais' beaked

whale (M. europaeus), and Sowerby's beaked whale (M. bidens). The oc currence o f Sowerby’s b eaked wh ale 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’S hea 198 9), and be cause it normally oc curs 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 ca virostris which were not identified as such. Beaked whales were

seen in all seasons during recent seasonal G ulfCet aerial surv eys of the northe rn Gulf of M exico (D avis et al., in

prepara tion). 

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 doc umented str andings of this species in the Gulf of Mexico (Jefferson

et al. 1992 ). There is no information o n stock differen tiation. 

POPU LATIO N SIZE

Estimates of abundance of beaked whales were deriv ed through the applicatio n of distance sa mpling ana lysis

(Buckland et al. 1993) and the computer program DISTA NCE (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 o f 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 include d only a small portion of the stock ran ge and these

data were not use d for abun dance estim ation. Survey e ffort-weighted e stimated ave rage abun dance o f beaked whales not

identified to species for all surveys

combined was 117 (coefficient of

variation, CV = 0 .38) (Ha nsen 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 Po pulation Estimate

A minimum population

estimate cou ld not be no t calculated b ecause of un certainty of spe cies identification of sightings. 

Current Population Trend

The abundance estimates of beaked whales for 1991 -1993 w ere lower tha n 1994 , but there was co nsiderable

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 inten sity or a change in distribution, ra ther than a cha nge in pop ulation size. 
231

CURRENT AND M AXIMUM NET PRODUCTIVITY RATES

Current and maximum net productivity rates are not known for this stock; therefore, the default maximum net

produc tivity rate of 0.04 (Anon. 19 94) was use d for purp oses 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 no rthern Gulf o f 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. Strand ing data pro bably

underestimate the extent of fishery-related mortality and serious injury becau se 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 ab ility to recognize signs of fishery interac tion. 

Although PBR cannot be calculated, the total known fishery-related mortality and serious injury fo r this stock is

zero and, therefore, can be considered insignificant and approaching zero morta lity and serious inj ury rate. This

determination cannot be made for specific fisheries until the implementing regulations for Section 118 of the MMPA have

been revie wed by the p ublic and fina lized. 

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 b een monito red with abo ut 5% ob server cov erage, in terms of trips obse rved, since 1 992. 

Pair trawl fishing gear has the potential to capture marine mammals, but there have b een no rep orts of morta lity

or serious injury to marine mammals in the G ulf 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 an d duration . 

STATUS OF STOCK

 The status of this stock relative to OS P is unknown and there ar e insufficient data to determine popu lation trends.

This species is not listed under the Endangered Species Act. The total level of human-caused mortality and serious injury

is unknown, b ut it is believed to be insignificant; the refore, this is not a str ategic stock. 

REFERENCES

Anon. 1994. Report of the PBR (Pote ntial Biolog ical Remo val) workshop. June 2 7-29, 1994 . NOAA, N MFS So uthwest

Fisheries Sc ience Cen ter, La Jolla, California, 13 p p. + App endices. 

Bonde, R. K. and T. J. O’Shea. 1989. Sowerby’s beaked whale (M esoplod on biden s) in the Gulf of M exico. J. M ammal.

70: 447 -449. 

Buckland, S. T., D. R. Anderson, K. P. Burnham and J. L. Laake. 1993. Distance Sampling: estimating abundance of

biologica l populatio ns. Chapm an & Ha ll, London , 446 pp . 

Cramer, J. 1994. Large pelag ic logboo k newsletter - 19 93. NO AA Te ch. Mem . NMF S-SEFSC-352, 1 9 pp. 

Davis, R., G. Scott, B. Würsig, W. Evans, G. Fargion, L. Hansen, K. Mullin, N. May, T. Leming, B. M ate, 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 #M MS 9 4-0003 . 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. 
232

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. M arine mammals of the G ulf of Mexic o: a field

guide for ae rial and shipb oard ob servers. Te xas A&M University P rinting Center, C ollege Statio n, 92 pp. 

Laake, J. L., S. T. Buckland, D. R. Anderson, and K. P . Burnham . DIST ANCE user’s guide, V2.0. Colorado Cooperative

Fish & W ildlife Researc h Unit, Co lorado S tate University, Ft. Collins, Co lorado, 7 2 pp. 

Mead, J. G. 198 9. Beake d whales of the genus M esoplod on. Pages 349-430 in S. H. Ridgway and R. Harrison (editors),

Handbook of marine mamma ls, Vol. 4: River dolph ins and the larger toothed wha les. Academic Press, London,

442 pp . 
233

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 iso bath and from the U.S.-M exican bo rder to the F lorida Ke ys. The stoc k range ma y 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 w ith coastal stock s in some area s and may b e genetically indistinguishable from those stocks. The OCS stock

may be co mbined w ith some or a ll of the coastal sto cks when ad ditional 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 d eep, cold water ecotyp e describe d by Hersh and D uffield for the Atla ntic (1990 ). It is not

currently possible to differentiate the two ecotypes visually during ae rial surveys.

POPU LATIO N 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 linetransect surveys in September-October 1992 and 19 93 (Blaylock and Hoggard 199 4) and 1994 (NM FS unpublished data).

Transec ts providing systematic coverage of the area and assumed to be rando mly placed with respect to bottlenose dolphin

distribution extended orthogon ally from app roximately 9 km past the 1 8 m isoba th to appro ximately 9 km past the 183 m

isobath. Ap proxima tely 3.3% of the

total area was visually sampled.

Preliminary analyses provided a

bottlenose dolphin abundance

estimate of 50,24 7 dolph ins 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 Po pulation Estimate

The minimum population

estimate was based on the abundance estimate of 50,247 dolphins (CV = 0.18). The minimum p opulation 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 bo ttlenose do lphins. 

Current Population Trend
234

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) fo r this stock (Scott et al. 1989). T his population thus appea rs to have increased from e arlier 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 w ith the OCS edge and continental slo pe stock. 

CURRENT AND M AXIMUM NET PRODUCTIVITY RATES

Current and maximum net produc tivity rates are not k nown for this sto ck. The m aximum ne t productiv ity 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 o f their reprod uctive life

history (Reilly and Barlow 1 986). 

POTENTIAL BIOLOGICAL REMOVAL

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

maximum produc tivity rate, and a "r ecovery" factor for end angered, d epleted, 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 lev el is unknown . PBR fo r 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 19 93 in the pe lagic longline fishe ry, this stock may b e subject to

incidental take resulting in serious injury or mortality. Fishery interactions have been reported to occur between bo ttlenose

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 pub lic and finalized . 

Fishery Information

Annual fishing effort for the shrimp trawl fishery in the U.S. Gulf of Mexico OCS during 1988-1993 averaged

approx imately 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 unp ublished data). There have

been no r eports of inc idental mortality or injury assoc iated with the shrim p trawl fishery in this ar ea. 

Pelagic swordfish, tuna s, and billfish are the targets of the lon gline fishery ope rating 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 logboo k reporting, w as 4,400 sets in 1991 , 4,850 se ts in 1992, a nd 3,26 0 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 fisheryrelated 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 wa s observed in the Gu lf of Mexico, but interactions betwe en bottlenose

dolphins and this fishery in the Gulf of Mexico have been reported under the Marine Mammal Protection Act Inte rim

Exemption Program (NM FS 1993).

Given the fact that fishery interactions have been reported to occur between bottlenose dolphins and the longline

swordfish/tuna fishery in the Gulf o f 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),
235

the estimated level of incidental mortality and se rious injury pa rtitioned to inclu de only the G ulf of Mexic o stock wo uld

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 b ottlenose dolphins (CV = 0.74). This e stimate could include dolphins from the OCS edge and

continental slope stock.

Pair trawl fishing gear h as the poten tial to capture marine mammals, but there have been no reports of mortality

or serious injury to marine mammals in the Gulf of M exico. This fishery has not been o bserved by NM FS observers, and

there are no other data available as to the extent of this fishery in the Gulf of M exico. It is assumed that it is very limited

in scope an d duration in the Gulf of M exico. 

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

NMF S resulted in the death of two bottlenose dolphins (B urn and Sc ott 1988 ). There ar e no other d ata available . 

Other Human-Related M ortality 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 mo rtality to marine mammals. T hese activities ha ve been clo sely monitored by NMFS o bservers

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

unpublishe d data). 

STATUS OF STOCK

The status of this stock relative to OSP is not known and the popu lation trend ca nnot be d etermined due to

insufficient data. This species is not listed as threatened or endangered under the Endangered Species A ct. This is not a

strategic stock b ecause fishery-re lated morta lity and serious inj ury does no t exceed PBR. 

REFERENCES

Anon. 1994. Report of the PBR (Potential Biological Removal) workshop. June 27-29, 1994. NOAA, NMFS Southwest

Fisheries Sc ience Cen ter, La Jolla, California, 13 p p. + App endices. 

Blaylock, R. A. and W. Ho ggard. 19 94. Prelim inary estimates o f bottlenose d olphin abundan ce in southern U.S. Atlantic

and Gulf o f Mexico continental she lf waters. NO AA Te ch. Mem . NMF S-SEFSC-356, 1 0 pp. 

Buckland, S. T., D. R. Anderson, K. P. Burnham, and J. L. Laake. 1993. Distance sampling: Estimating abundance of

biologica l populatio ns. Chapm an & Ha ll, London , 446 pp . 

Burn, D. And G . P. Scott. 19 88. Synop sis of available in formation o n marine mammal-fisherie s interactions in the

southeastern United States: preliminary report. NMFS/SEFC, Miami Laboratory, Coastal resources Division,

Contributio n ML-CRG-87 /88-26, 3 7 pp. 

Gitschlag, G. R. and J. K. Hale. In press. Susceptibility of sea turtles to underwater explosives at offshore energy structure

removals. S ubmitted to N. E. Gu lf Science. 

Gitschlag, G. R. and B. A. Herczeg. In press. Sea turtle observations at explosive removals of energy structures.

Submitted to Mar. F ish. Rev. 

Hersh, S. L. and D. A. Duffield. 1990. Distinction between northwest A tlantic offshore and coastal bottlenose dolphins

based o n hemoglo bin profile and mor phome try. Pages 129-139 in S. Leatherwood and R. R. Reeves (editors),

The bo ttlenose do lphin, Acad emic Pre ss, San Dieg o, 653 p p. 

Laake, J. L., S. T. Buckland, D. R. Anderson, and K. P. Burnham . DIST ANCE user’s guide, V 2.0. Colorado Cooperative

Fish & W ildlife Researc h Unit, Co lorado S tate University, Ft. Collins, Co lorado, 7 2 pp. 

Northridge, S. In review. Estimation of cetacean mortality in the U.S. Atlantic swordfish and tuna driftnet and pair trawl

fisheries. Draft final re port to the N ortheast Fishe ries Science Center, Co ntract No. 4 0ENN F5000 45. 18 p p. 

Reilly, S. B. an d J. Barlo w. 1986 . Rates of incre ase in dolp hin popu lation size. Fish. B ull., U.S. 84( 3): 527-5 33. 
236

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 an d Duffield (1990). The se dolphins were repo rted to be larger and da rker 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 abund ance or mortality from those

countries.

POPU LATIO N 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 durin g shipboa rd line-transec t surveys

conducted during the spring of 1992-1 994 (Fig . 1). These sur veys were co nducted th roughou t the area from approx imately

the 200 m iso bath along the U.S. co ast to the seawa rd extent of the U.S. Exc lusive Eco nomic Zo ne. The seasonal GulfCet

aerial surveys includ ed 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

a t 5,618 dolp hins wi th

coefficient of variation (CV) =

0.26. In this analysis, it was

assumed that all of the

bottlenose dolphins sigh ted

during the ship-base d surveys

were of this stock. The survey

area overlapp ed in some areas

with the OCS stock which was

assumed to occur from

approx imately 9 km seaward of

the 18 m isobath t o

approx imately 9 km seaward of

the 183 m isobath; however, the

amount of overlap is considered

insignificant and its effect on the

abunda nce estimate is n ot known. 

Minimum Po pulation Estimate

The minimum p opulation e stimate was based on the average bottlenose dolphin abundance estimate of 5,618

bottlenose dolphins (C V = 0.2 6). The min imum po pulation 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 N MFS (Anon. 19 94). Th e minimum populatio n estimate is 4,5 30 bottlen ose dolp hins. 
237

Current Population Trend

The da ta are insufficient to d etermine po pulation trend s. 

CURRENT AND M AXIMUM NET PRODUCTIVITY RATES

Current and maximum net productivity rates for this stock are unknown. The maximum net productivity rate for

purposes of this assessme nt, was assume d to be 0.0 4. This valu e 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 B arlow, 198 6). 

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 po pulation (OSP ). The recovery factor wa s 0.50 because o f the stock's unknown

status relative to O SP. PB R for this stock is 45 bottlen ose dolp hins. 

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 bo ttlenose

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 bottlen ose dolp hins 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 pub lic 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 mandato ry logboo k reporting, w as 4,400 sets in 1991 , 4,850 se ts in 1992, a nd 3,26 0 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 th e species o ccurs gene rally 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 reporte d in 1992 and 199 3, and on ly

one non-lethal take was reported in 1993, which is assumed to have caused serious injury. The estimated level of fisheryrelated 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 prob ability of an incide ntal take is prop ortional to fishing effort (number of sets),

the estimated level of incidental mortality and serious injury partitioned to include only the Gulf of M exico stock would

be 5.5 bottlenose dolphins in 1993 (CV = 0.19). Average annual fishery-related mortality and serious injury during 1992-

1993 w ould be 2 .8 bottleno se dolphin s (CV= 0.74). This estimate co uld include d olphins from the OCS stock. 

Pair trawl fishing gear has the potential to capture marine m ammals, but there hav e been no reports of mortality

or serious injury to marine mammals in the Gulf of M exico. Th is fishery has not been observed by NMFS observers, and

there are no othe r data available as to the extent of this fishery in the Gulf of Mexico. It is assumed that it is very limited

in scope an d duration . 
238

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 (B urn and Sc ott 1988 ). There ar e no other d ata available . 

Other M ortality

No dire ct or indirect h uman-caus ed morta lity has been rep orted for this sto ck. 

STATUS OF STOCK

The status of this stock relative to OSP is not known and the popu lation trend ca nnot be d etermined due to

insufficient data. This species is not listed as threatened or endangered under the Endangered Species A ct. This is not a

strategic stock b ecause fishery-re lated morta lity or serious injur y does not e xceed PBR. 

REFERENCES

Anon. 1994. Report of the PBR (P otential Biological Remo val) workshop. June 2 7-29, 1994 . NOAA, N MFS So uthwest

Fisheries Sc ience Cen ter, La Jolla, California, 13 p p. + App endices. 

Buckland, S. T., D. R. Anderson, K. P. Burnham, and J. L. Laake. 1993. Distance sampling: Estimating abundance of

biologica l populatio ns. Chapm an & Ha ll, London , 446 pp . 

Burn, D. And G . P. Scott. 19 88. Synop sis of available in formation o n marine mammal-fisheries interactio ns in the

southeastern United States: preliminary report. NMFS/SEFC, Miami Laboratory, Coastal resources Division,

Contributio n ML-CRG-87 /88-26, 3 7 pp. 

Cramer, J. 1994. La rge pelagic logboo k newsletter - 19 93. NO AA Te ch. Mem . NMF S-SEFSC-352, 1 9 pp. 

Hersh, S. L. and D. A. Duffield. 1990. Distinction between northwest Atlantic offshore and coastal bottlenose dolphins

based on hemo globin profile and morphometry. Pages 129-139 in S. Leatherwood and R. R. Reeves (editors),

The bo ttlenose do lphin, Acad emic Pre ss, San Dieg o, 653 p p. 

Laake, J. L., S. T. Buckland, D. R. Anderson, and K. P. Burnham. DISTAN CE user’s guide, V2.0. Colorado Cooperative

Fish & W ildlife Researc h Unit, Co lorado S tate University, Ft. Collins, Co lorado, 7 2 pp. 

Northridge, S. In review. Estimation of cetacean mortality in the U.S. Atlantic swordfish and tuna driftnet and pair trawl

fisheries. Draft final re port to the N ortheast Fishe ries Science Center, Co ntract No. 4 0ENN F5000 45. 18 p p. 

Reilly, S. B. and J. Barlow. 1986. Rates of increase in dolphin population size. Fish. Bull., U.S. 84(3): 527-533.
239

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

oceano graphic characteristics m ight be restricted in their movem ents betwee n habitats and, thus, con stitute separate stocks.

The western coastal area is characterized by an arid to temperate climate, sand be aches, and low fresh water input. The

northern coastal stock area which is c haracterize d by a temp erate 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 h as an interme diate level of fre shwater inpu t.

The stock occurs transboundary with Mexico; however,

there is no information available for

abundance estimation, nor for

estimating fishery-relatedmortality in

Mexican waters. The ratio of DDE

to DDT was extraordinarily high in

tissues of one bottlenose d olphin

stranded on the Texas coast

(Varanasi et al. 1992), suggesting

recent exposure to DDT which is still

in use in Me xico. 

The Mississippi River

outflow may constitute an effective

ecologica l barrier to stock migration

at the eastern boun dary. This

assumption has not been tested and

interbreeding may, in fact, occur

between this and the northern coastal

stock at this bound ary; therefore, the

definition of this stock may be revised and the stock may be incorpor ated with the no rthern coastal stock when more da ta

become available. There are data which suggest that there is considerable alongshore movement by some members of the

western coa stal stock (NMFS unpublishe d data), bu t the extent of this mo vement is unk nown. 

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 dolp hins occasio nally 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 bounda ry for this stock co rrespond s to aerial surve y strata (NM FS unpu blished da ta) 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 (19 90). Data are not curre ntly available

to determine genetically if the two stocks should be separated or, if so, where; and interbreeding may occur at the boundary

interface. 

POPU LATIO N SIZE
240

Preliminary abundance estimates were derived using distance sampling analysis (Buckland et al. 1993) and the

computer program DISTANCE (Laake et al. 19 93) with sighting data collec ted during a erial line-transect su rveys in

September-October 1992 (Blaylock and Hogga rd 1994 ). Sampling tra nsects extend ed orthog onally from sh ore out to

approx imately 9 km past the 18 m isobath. The 1992 coastal survey area extended from the U.S. -Mexican border to the

Mississippi River mo uth. Systematic tra nsects were place d randomly with respec t to bottlenose dolphin distribution and

provided approximately 5% visual coverage of the survey area. Bottlenose dolphin abundance was estimated to be 3,499

dolphins (C V = 0.2 1) (Blaylo ck and H oggard 1 994). 

Minimum Po pulation 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 distrib uted abun dance estim ate. This is equivalent to the 20th pe rcentile of the lognormal distribution as specified by W ade and Angliss (19 97). The minimum population estimate is 2,93 8 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 significan tly lower than the 1 983 estimate (Studen t's t-test, P < 0.001 ) and sugge sts a decline

in stock abu ndance. 

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. M arine Ma mmal Stran ding Netw ork unpub lished data). Some o f these mortalities may have been

related to accumulation of anthropogenic hydrocarbon contaminants. A recen t study indicated an inverse rela tionship

between hydrocarbon contaminant levels and certain bacterial and viral antigen titers in bottlenose dolphins from

Matago rda Bay, T exas (Reif et a l., in review). 

CURRENT AND M AXIMUM NET PRODUCTIVITY RATES

Current and maximum net productivity rates are not known for this stock. The maximum net produ ctivity 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

produc tivity rate, and a “recovery” factor (Wade and Angliss 1997). The “recovery “ factor, which accounts for

endangered, depleted , and threaten ed stocks, o r stocks of unk nown status re lative to optimum sustainab le popula tion

(OSP )is assumed to be 0.5 because this stock is of unknown status, because of an undetermined level of fishery-related

mortality, and because of the recent occurrence of three anomalo us mortality eve nts. 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 bottleno se dolphin strandings rep orted for th is 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 traw l. The total b ottlenose d olphin strand ings from Jan uary 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 the stranded

dolphins belonging to another stock cannot be determined because of the difficulty of determining from where the stranded

carcass originated. S tranding da ta probably underestimate the extent of fishery-related mortality and serious injury because
241

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 appr oximately 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 re ports of incid ental mortality o r injury in the weste rn Gulf of M exico coa stal bottlenose dolphin

stock assoc iated with the shrim p trawl fishery in this ar ea. 

 The me nhaden p urse seine fishery ta rgets the Gu lf menhade n, Brevoortia patronus, in Gulf of Mexico coastal

waters approx imately 3-18 m in depth (N MFS 1991). S eventy-five men haden ve ssels opera te within 1.6 km of shore from

Apalachicola, Florida to Freeport, Texas, from April-October. Lethal ta kes of bottlenose dolphins reported by the

menhad en fishery during the period 1982-1 988 ran ged betwe en 0-4 do lphins annua lly (NMF S unpub lished 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 curre ntly in use in Louisiana, M ississippi, and Alab ama. Th ese fisheries, for the most part,

operate ye ar around . They are sta te-controlled and licensed , and vary wid ely 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 ma rine mamm al interaction d oes occu r, causing mo rtality and seriou s injury. 

The fishery for blue cr abs ope rates 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 observ ers. 

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 U niversity, report to Texas Marine Mamm al Stranding Network , August 19 93). Th e 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

throughou t the day, and re moved at night. 

Other M ortality

The coast adjacent to the nearshore habitat occupied by this stock varies fro m agricultura l to industrial and , in

some places, such as Galvesto n 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 period s of high rainfall in 19 92 was imp licated in a high le vel of bottleno se 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 Matago rda Bay which ad joins 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 cetacea n morbillivirus.

The reason for the difference in the relationship between antibody titers to bacteria and pseudorabies and antibody titers

to cetacean morbillivirus is no t understoo d. 

STATUS OF STOCK

The status of this stock relative to OS P is unknow n. 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 western portion of the U.S.

Gulf of Mexico may have experienced a morbillivirus epidemic in 1993 (Lipsco mb 1993 ); however, the effects of these

events on sto ck abund ance has yet to be determ ined. The total fishery-related mortality and se rious injury for this stock

is not less than 10 % of the ca lculated PB R and, there fore, canno t be considered to be insignificant and approaching zero
242

mortality and serious injury rate. This is not a strategic stock because the known leve l of fishery-related m ortality or serious

injury does n ot 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. P reliminary estima tes of bottleno se dolphin abundan ce in southern U.S. Atlantic

and Gulf o f Mexico continental she lf waters. NO AA Te ch. Mem . NMF S-SEFSC-356, 1 0 pp. 

Buckland, S. T., D. R. Anderson, K. P. Burnham, and J. L. Laake. 1993. Distance sampling: Estimating abundance of

biologica l populatio ns. Chapm an & Ha ll, London , 446 pp . 

Hersh, S. L. and D. A. Duffield. 1990. Distinction between northwest Atlantic offshore and coastal bottlenose dolphins

based on hemo globin profile and morphometry. Pages 129-139 in S. Leatherwood and R. R. Reeves (editors),

The bo ttlenose do lphin, Acad emic Pre ss, San Dieg o, 653 p p. 

Laake, J. L., S. T. Buckland, D. R. Anderson, and K. P. Burnham. 1993. DISTANCE user’s guide, V2.0. Colorado

Coop erative Fish & Wildlife Research U nit, Colorad o State U niversity, Ft. Collins, C olorado , 72 pp. 

Lipscomb, T. P. 1993 . Some answers to que stions about morbillivirus. Pages 4-5 in R. A. Blaylock, B. Mase, and D. K.

Odell (editors), Strandings - Newsletter o f the Southea st U.S. M arine Ma mmal Stran ding Netw ork, Vo l. 2 No.

3, Southea st Fisheries Scie nce Cente r, Miami Laborato ry, Miami, F lorida, 8 pp . 

NMFS. 1991. Proposed regime to govern the interactions between marine mammals and commercial fishing operations

after Octob er 1, 199 3. Draft En vironmen tal Impact S tatement. 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 d olphins (Tursiops truncatus) from

Matagorda Bay, Texas, 1992. Colorado State University, Fort Collins, and NMFS, Southeast Fisheries Science

Center, M iami, Florida . 

Varana si, U., K. L. T ilbury, D. W . Brown, M. M. K rahn, 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 Sc ience Cen ter Contrib ution MI A-92/93 -21, 219 pp. 

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

April 3-5, Seattle, Washington. U.S. Dep. Commer., NOAA Tech. Memo. NMFS-OPR-12, 93 pp.
243

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 Me xico 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 o f 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 hab itats and, thus, co nstitute

separate stocks. The northern co astal stock area is characterized by a temp erate climate, barrier islands, sand beac hes,

coastal marshes and marsh islands, and has a relatively high level o f fresh water inpu t from rivers an d streams. It is

bordered on the east by a n extensive ar ea of coasta l 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 tem perate to subtropical in climate, is bordered by a mixture of coastal marshes, sand b eaches, marsh

and mang rove islands, and has an inte rmediate lev el of freshwater input.

The definition of this stock

may be change d and it may be

incorporated with other Gulf of

Mexico stocks when more da ta

become available. Seasonal

changes in bottlenose dolphin

abundance in Mississippi Sound

(NMFS unpublished data) su ggests

that there is interchange with at least

that portion of the Gulf of Mexico

bay and sound stocks; howe ver, 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 a nd Duffield (1990). Data are no t currently

available to determin e genetically if the stocks should be separated or, if so, where; and interbreeding may occur at the

bounda ry interface. 

POPU LATIO N SIZE

Preliminary estimates of abundance were derived using distance sampling analysis (Buckland et al.1993) and the

computer program DISTA NCE (Laake et al. 1993) with sighting data co llected durin g aerial line-transe ct surveys in

September-October 1993 (Blaylock and Hoggard 1994). Systematic sampling transects, placed randomly with respect to

the bottlenose dolphin distribution, extended orthogon ally 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. Bo ttlenose dolphin abundance was estimated to be 4,191 dolphins with coefficient

of variation (C V) = 0.2 1 (Blayloc k and Ho ggard 19 94). 

Minimum Po pulation Estimate
244

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 W ade and Angliss (199 7). The m inimum po pulation 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 NM FS resulted in

an estimated bottlenose dolphin abundance of 1,319 (CV = 0 .10). The data are no t 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 M AXIMUM NET PRODUCTIVITY RATES

Current and maximum net produc tivity rates are not k nown for this sto ck. The m aximum ne t productiv ity 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

produc tivity rate, and a “re covery” fac tor (Wa de and A ngliss 1997 ). The “recove ry “ 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-relate d mortality, and because o f the unknown effects of the 19 93 mortality event. PBR for this stock is

35 dolp hins. 

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 nec essarily show signs of e ntanglemen t or other fishery-inte raction. 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 approx imately 2.17 million hours of tows (CV = 0.13) (NMFS unpublished data). This fishery was

monitored by NM FS obse rvers 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 sto ck associate d with the shrimp trawl fishery in this ar ea. 

 The menhaden purse seine fishery targets the Gu lf menhade n, Brevoo rtia 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

menhad en fishery during the period 1982-1 988 ran ged betwe en 0-4 do lphins annua lly (NMF S unpub lished data). 
245

Other clupeid pu rse seiners op portunistically target Spanish sardine, thread herring, ladyfish, cigarfish, and blue

runners. Single boat purse seiners, fishing for sardin es 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 L ouisiana, M ississippi, and A labama. T hese fisheries, for the most pa rt,

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 ma rine mamm al interaction d oes occu r, causing mo rtality and seriou s 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 observ ers. 

Other M ortality

The nearshore habitat occupied by this stock is adjacent to areas of high human population. Two stranded

dolphins from the northern Gulf co astal area (on e from M ississippi and o ne from Ala bama) ha d the highest lev els of DDT

derivatives of any of the bo ttlenose do lphin liver samples analyze d in conjun ction 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 anthrop ogenic compound s 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,DD E, and PCB's conc entrations (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 morbillivir us epidemic. The effect of this mortality event on the stock cannot be determined, in part, because the

mortality may have also affected the b ay, sound and estuarine stoc k and the stoc k identity of the stran ded animals could

not be determ ined. The increase in mortalities began in the Florida panhandle area and moved westward during that period

(NMFS unpublishe d data). Co ncentratio ns of contaminants were found to be higher in dolphins having evidence of

exposure to the cetace an morb illivirus (Reif et al., in review). The reason for the relationship between cetacean

morbillivirus antibody titers a nd high co ntaminant leve ls is not understo od and th e effect of the ep idemic on this stock has

not been d etermined . 

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 fishery-related mortality or

serious injury d oes not exc eed PB R. 

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.

NMF S-OPR-6, 73 pp .. 

Blaylock, R. A. and W. Hoggard. 1994. Preliminary e stimates of bo ttlenose do lphin abund ance in southern U .S. Atlantic

and Gulf o f Mexico continental she lf waters. NO AA Te ch. Mem . NMF S-SEFSC-356, 1 0 pp. 

Buckland, S. T., D. R. Anderson, K. P. Burnham, and J. L. Laake. 1993. Distance sampling: Estimating abundance of

biologica l populatio ns. Chapm an & Ha ll, 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 bo ttlenose do lphin, Acad emic Pre ss, San Dieg o, 653 p p. 

Laake, J. L., S. T. Buckland, D . R. Anderson, and K . P. Burnham. 1993. DISTANCE user’s guide, V2.0. Colorado

Coop erative Fish & Wildlife Research U nit, Colorad o State U niversity, Ft. Collins, C olorado , 72 pp. 
246

Lipscomb, T. P. 1993. Some answers to questions about morbillivirus. Pages 4-5 in R. A. Blaylock, B. Mase, and D. K.

Odell (ed itors), Strandings - Newsletter of the Southeast U.S. Marine Mammal Stranding Network, Vol. 2 No.

3, Southea st Fisheries Scie nce Cente r, Miami Laborato ry, Miami, F lorida, 8 pp . 

NMFS. 1991. Proposed regime to govern the interactions between marine mammals and commercial fishing operations

after Octob er 1, 199 3. Draft En vironmen tal Impact S tatement. June 1991. 

Reif, J. S., L. J. Han sen, S. Galloway, G . Mitchum, T. L. Schmitt. In review. The relationship between chlorinated

hydrocarbon contaminants and selected health parameters in bottlenose d olphins (Tursiops truncatus) from

Matagorda Bay, Texas, 1992. Colorado State University, Fort Collins, and NMFS, Southeast Fisheries Science

Center, M iami, Florida . 

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

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. 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 o ccupying the area which e xtends from approx imately 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 occup ying habitats with dissimilar climactic , coastal, and oceano graphic

characteristics might be restric ted 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 bea ches, 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 tem perate climate,

sand beaches, and low fresh water

input. The northern coastal stock

area is characterized by a tempera te

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 contin ental 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 ecologica l bounda ry. Anecdo tal evidence suggests that both the coastal and OCS stocks co nsist

of the shallow, wa rm water ec otype desc ribed by H ersh and D uffield (199 0). 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.

POPU LATIO N 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 autum n 1994 (NMFS unpu blished da ta). 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.

Appro ximately 5% of the total survey are a was visually sea rched. Bottlenose d olphin abundance was estimated to be 9,912

dolphins w ith coefficient of va riation (CV ) = 0.12. 

Minimum Po pulation Estimate

The minimum population estimate was based on the 1994 abundance estimate of 9,912 (CV = 0.12) (NMFS

unpublished data). The minimum p opulation e stimate is the lower limit of the two-tailed 60% confidence interval of the

log-norma lly distributed a bundanc e estimate. This is equivalen t to the 20th percentile of the log-normal distribution as

specified b y Wad e and Ang liss (1997). The minim um pop ulation estimate is 8,963 b ottlenose d olphins. 

Current Population Trend
248

Aerial surveys of this area c onducted by NM FS in autumn 1985 , resulted in an e stimated bo ttlenose do lphin

abundance of 4,711 (CV = 0.05). The data are not sufficient to conduct a statistical trend analysis, but the current

populatio n size estimate is sig nificantly higher than the 1985 estimate (Stud ent's t-test, P < 0.00 05). 

CURRENT AND M AXIMUM NET PRODUCTIVITY RATES

Current and maximum net produ ctivity rates are no t known for this sto ck. The m aximum ne t productiv ity 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

produc tivity 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 be cause this stock is of unknown status. PBR for this stock is 90 dolphins. 

ANNUAL HUMAN-CAUSED MORTALITY AND SERIOUS INJURY

The level of direct huma n-caused m ortality 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 tota l bottlenose d olphin strand ings reporte d 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 m ortality 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 we re reporte d in 1995 a nd 2 had evidence o f human intera ctions. One was found e ntangled 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 nec essarily show signs of e ntanglemen t or other fishery-inte raction. 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 app roximately 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 w as 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 runaro und gillnets are currently in use in L ouisiana, M ississippi, and Alab ama. These fishe ries, for the mo st 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 unp ublished data). There are no effort data

available for this fishery. 

The menhade n purse seine fishery targets the Gulf menhaden , Brevoortia patronus, in Gulf of Mexico coastal

waters approx imately 3-18 m in depth (N MFS 1991). S eventy-five men haden ve ssels opera te within 1.6 km of shore from

Apalachicola, Florida to Freeport, Texas, from April-October. Lethal takes of bottlenose dolphins reported by the

menhad en fishery during the period 1982-1 988 ran ged betwe en 0-4 do lphins annua lly (NMF S unpub lished data). 
249

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 estima tes of dolph in mortality asso ciated with

this fishery. 

A fishery for blue crabs operates in estuarine areas throughout the Gulf coast employing traps attached to a buoy

with rope. Bo ttlenose do lphins have b een repo rted strande d in other co astal locations in the Gulf of M exico with

polypropylene rope around their flukes indicating the possibility of entanglement with crab pot lines (NMFS 1 991);

however, th is fishery has not b een monito red by ob servers. 

Other M ortality

The nearshore habitat occu pied by this sto ck is adjace nt to areas of hig h human p opulation a nd in some areas of

Florida, such as the T ampa Bay area, is highly industrialize d. PCB concentrations in three stranded dolphins sampled from

this stock ranged from 16-46 μg/g wet weight. Conc entrations of "-HCB, p,p,DD E, and PCB's were in versely related to

the magnitude of the serum antibody titer to Erysipelas spp. and Staphylococcus spp. bacte ria 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 m orbillivirus is not u nderstoo d. 

STATUS OF STOCK

The status of this stock relative to OSP is not known a nd pop ulation 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. Th is is not a strategic stock because

the known le vel of fishery-related mortality or serio us injury doe s 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

biologica l populatio ns. Chapm an & Ha ll, London , 446 pp . 

Laake, J. L., S. T. Buckland, D . R. Anderson, and K . P. Burnh am. 1993. DISTANCE user’s guide, V2.0. Colorado

Coop erative Fish & Wildlife Research U nit, Colorad o State U niversity, Ft. Collins, C olorado , 72 pp. 

Morgan, M. A. and G. W. Patton. 199 0. Human dolphin interactions on the west coast of Florida: Documentation from

MM L's marine mammal resp onse pro gram. M ML T echnical Re port #19 1, 9 pp. 

NMFS. 1991. Proposed regime to govern the interactions between marine mammals and commercial fishing operations

after Octob er 1, 199 3. Draft En vironmen tal Impact S tatement. June 1991. 

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

April 3-5, Seattle, Washington. U.S. Dep. Commer., NOAA Tech. Memo. NMFS-OPR-12, 93 pp.
250

September 2000

BOTTLENOSE DOLPHIN (Tursiops truncatus):

Gulf of Mexico Bay, Sound, and Estuarine Stocks

STOCK DEFINITION AND GEOGRAPHIC RANGE

Bottlenose dolphins are distributed through out the bays, so unds, and e stuaries of the G ulf of Mexic o (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 info rmation for m uch of the reg ion. 

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

descriptio ns of relatively discrete dolphin “communities” in some of these areas. A “community” includes resident dolphins

that regularly share large portio ns of their range s, exhibit similar d istinct genetic pro files, and interact w ith each other to

a much greater exten t than with dolp hins in adjac ent waters. The term, as ad apted from Wells et al. (1987), emphasizes

geographic, genetic, and social relationships of dolphins. Bottlenose dolphin communities do not constitute closed

demog raphic populations, as individuals from adjacent commun ities are known to interbreed . Neverthe less, the geogra phic

nature of these areas and long-term stability of residency pa tterns 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 pattern s of residenc y observed within comm unities suggest that lo ng period s would be required to repopu late

the home ra nge of a community wer e it eradicated or severely d epleted. T hus, 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 d emograp hic scale. Support for this risk-averse approach derives from several

sources. Long-term (year-round , multi-year) reside ncy by at least some individu als 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 19 95; Würsig and Lynn 1996), Ara nsas 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 yea rs previously

in Mississipp i Sound. In F lorida, 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; W ells 1986 a, 1991 ; Scott et al. 1990; Wells et al. 1987), Lemo n Bay (Wells et al. 1996b ), and Cha rlotte

Harbor/Pine Island Sound (Shane 1990 ; Wells et al. 1996b , 1997). In many cases, re sidents emphasiz e use of the ba y,

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 1 997). These habitat use patterns are reflected in the ecology of the dolphins in some

areas; for examp le, residents of Sarasota Bay, Florid a lacked sq uid in their diet, unlike non-resident dolphins stranded on

nearby G ulf beaches (B arros and Wells 19 98). 

Genetic data also support the co ncept 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 W ells In press). D ifferences in rep roductive se asonality from site to site also suggest genetic-based

distinctions between communities (Urian et al. 1996). Mitochondrial DNA analyses suggest finer-scale 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 betw een adjac ent communities in Tam pa Bay, Sarasota B ay, and Cha rlotte

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 struc ture and stab ility of at least some o f these comm unities is exemp lified by the residents of

Sarasota Bay, Florida. This community has been observed since 1970 (Irvine and Wells 1972; S cott et al. 1990; W ells

1991). The num ber of do lphins regularly occupying the Sarasota Bay area has remained consistently at about 10 0. 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).

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
251

apparen tly 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 commun ities (Wells 1986b; W ells 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 (W ells 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 recorde d as transienc e in a given area, to apparent seasonal or nonseasonal 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 (W ells 1986a), and most of the dolphins identified in the mouths of

Galvesto n Bay and Aransas P ass, Texa s were considered tran sients (Henn ingsen 199 1; Bräge r 1993; W eller 1998 ). 

Seasonal movements of do lphins into and out of some of the bays, sounds, and estuaries provide additional

opportunities for genetic exchange with residents, an d comp licate the identification of stocks in coastal and inshore waters.

In small bay systems such as Sarasota Bay, Florid a and San Luis Pass, T exas reside nts 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 sou therly

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 ), Tamp a Bay (Sc ott et al. 1989), a nd Charlo tte

Harbor/Pine Island Sound (Thompson 1981; S cott et al. 1989). Spring/summer increases in abundance have been reported

for Galveston Bay (H enningsen 1 991; Bräger 199 3; Fertl 199 4) and M ississippi Sou nd (Hub ard 199 8). 

Much uncertainty remains regarding the structure of bottlenose dolphin sto cks in many of the Gulf of Me xico bays,

sounds, and estuaries. Given the apparent co-occurrence of resident and non-resident dolphins in these areas, and the

demonstrated variations in ab undance , it appears tha t considera tion 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, demogr aphic, and social stability. These loc alized units wo uld be at gre atest risk from ge ographic allylocalized impacts. Co mplete cha racterization of many of these basic units would benefit from additional photoidentification, telem etry, and gene tic research (W ells 1994 ). 

The current provisio nal stocks follo w the designa tions in Table 1, with a few revisions. Available information

suggests that Block B 35, Little Sara sota 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; W ells et al.

1996a,b, 1997; W ürsig and Lynn 1996).

Understanding the full complem ent of the stock complex using the bay, so und, and e stuarine 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,

morpho logy, social patterns, distribution,life history, stomach contents, isozyme analyses, and co ntaminant concentrations.

Spatially-exp licit populatio n modelin g 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 b e revised. A s stocks are more clearly ide ntified, it will be possible to conduct abundance

estimates using standardized methodology across sites (thereby avoiding some of the previou s problem s of mixing resu lts

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 pertain ing to

bottlenose dolphin sto ck structure in G ulf of Mexic o bays, soun ds, and estua ries. As a result of this, efforts are being made

to conduct simulations of alternative stock structure and, if warranted, propose a new stock structure.

Table 1. Bottlenose dolphin abundance (NBEST), coefficient of variation (CV), minimum population estimate (NMIN), and

Potential Biological Removal (PBR) in USA G ulf of Mexic o bays, soun ds, and oth er estuaries. Blocks refer to
252

aerial survey bloc ks 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 Comp ano Ba y, Aransas Bay, San Anto nio 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 0

1

- 1992 A

B58 Calcasieu Lake 0

1

- 1992 A

B59 Vermillion Bay, W est Cote Blanche Bay,

Atchafalaya Bay

0

1

- 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 Mississipp i River De lta 0

1

- 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 0

1

- 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 0

1

- 1993 A

B12-13 St. Vincen t Sound, A palachico la 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 na397 1.0 1992 B

B35 Little Sarasota Bay 2

2

0.24 2 0.0 1985 C

B21 Lemon Bay 0

1

- 1994 A

B22-23 Pine Sou nd, Charlo tte Harbo r, Gasparilla

Sound

209 0.38 153 1.5 1994 A

B36 Caloosahatchee River 0

1,2

- 1985 C

B24 Estero Bay 104 0.67 62 0.6 1994 A

B25 Chokoloskee Bay, Ten T housand Islands,

Gullivan Bay

208 0.46 144 1.4 1994 A

B27 Whitewater Bay 242 0.37 179 1.8 1994 A

B28 Florida K eys (Bahia H onda to K ey West) 29 1.00 14 0.1 1994 A

Reference s: A- Blayloc k and Ho ggard 19 94; B- W ells 1992 ; C- Scott et al. 1989

Notes:

1 During earlier surveys (S cott 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.
253

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

bottlenos e dolph ins inhab iting each bay an d sound are considered to c omprise a uniqu e stock for p urposes o f this

assessme nt. 

POPU LATIO N 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 aerialsurveys 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 D ISTANCE (Laake

et al. 1993) were used. Stock size in Sarasota Bay, Florida, was obtaine d through d irect count o f known indiv iduals (W ells

1992). 

Minimum Po pulation Estimate

The minimum population estimate (Table 1) is the lower limit of the two-tailed 60% confidence interval of the

log-normally distributed a bundanc e estimate. This is equivalen t to the 20th p ercentile of the lo g-normal d istribution as

specified by Wa de and A ngliss (1997 ). The min imum po pulation 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 p opulation siz e was identica l to the estimated populatio n 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 appro ximately 105 animals (W ells 1998 ). Three an omalous m ortality events

have occurred among portions of these dolphin communities betwee n 1990 and 199 4; howeve r, it is not possible to

accurately partition the mortalities betwe en bay and coastal stock s, thus the impac t of these mortality events on

commu nities is not know n. 

CURRENT AND M AXIMUM NET PRODUCTIVITY RATES

Current and maxim um net pro ductivity rates are not known for the dolp hin communities that comp rise 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 require d to add ress and de velop estimates of prod uctivity for these d olphin
254

communities. The maximum net produ ctivity 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 Biologic al Remo val (PBR) is the pro duct of minim um pop ulation size, on e-half the maximum

produc tivity 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 be cause these sto cks are of unk nown status. PBR for e ach stock is giv en in Tab le 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 determ ined because of the difficulty of determining from where the stranded carca ss

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 asho re, 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 th e USA Southeast G ulf of Mexico from 1993 to 1997

(Table 2) (NM FS unpu blished da ta). 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; W ells and Scott 1994) and some are struck by recreational

and commercial vessels (W ells and Scott 1997 ). In 1998 alone, two resid ent bottlenose dolphins an d an assoc iated calf

were killed by vessel strikes and a resident young-of-the-year died from entanglement in a crab-pot float line (R.S. W ells,

pers. comm.).

The G ulf of Mexico menhaden fishery was observed to take 9 bottlenose dolphins (three fatally) between 1992

and 1995 (NM FS 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 oce anaria for research and p ublic 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 remova ls with 202 d olphins take n 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 we re females.

The imp act of those removals on the stocks is unkn own. 

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) (NM FS unpublished data). There have been

very low num bers of incid ental mortality o r injury in the stock s 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 rep orted strand ed with polypropylene rope around their flukes (NMFS

1991; McFee and Brooks, Jr. 1998; NMFS unpublished data), indicating the po ssibility 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 n ot allowed in Florida past July 1995, but fixed

and runaround gillnets are currently in use in Louisiana, M ississippi, and A labama. T hese fisheries, for the most pa rt,

operate year around. They are state-controlled and licensed, and vary widely in intensity and target species. No marine
255

mammal mortalities associated with gillnet fisheries have been reported in these states, but stranding data suggest that

gillnet and ma rine mamm al interaction d oes occu r, causing mo rtality and seriou s injury.

Table 2. Bottlenose dolphin strandings in the US A Gulf of Mex ico (West Florid a to Texas) from 199 3 to 199 7. Data are

from the Southeast Marine Mammal Stranding Database (SESU S).

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 M ortality

The near shore habitat occu pied by many of these stoc ks is adjacen t to areas of high human po pulation, 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% o f all chemical p roducts

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 p esticide app lications. 

Concentrations of chlorinatedhydrocarbons and metals w ere examin ed in conju nction with an a nomalou s mortality

event of bottlenose dolphins in Texas bays in 1990 and fo und to be relatively low in most; however, some had

concentrations at levels of po ssible toxicologic al concern (Varana si et al. 1992). No studies to date have determined the

amount, if any, of indirect hum an-induced mortality resulting from pollution or habitat degradation. However, a recent
256

health assessment of 35 bottlenose dolphins from Matagorda Bay, Texas associated high levels of chlorinated hydrocarbons

with low health asse ssment scor es (Reif et al. in review). M orbillivirus has a lso 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 (N MFS unp ublished 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 bo ttlenose do lphin

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 d eaths which occurred d uring 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 b ecause the PBR for most of these stocks would be exceeded with the incidental capture of

a single dolp hin, each of the se stocks is a strate gic stock. 

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and capture-release techniques. Pages 407-415 in: P. S. Hammond, S. A. Mizroch and G. P. Donovan (eds),

Individual Recognition of Cetace ans: Use of Photo-Identification and Other Techniques to Estimate Population

Parame ters. Rep. int. Whal. Commn., Special Issue 12, Cambridge, U.K. 440 pp.

Wells, R. S. and M.D . Scott. 1999. Bottlenose dolphins. Pages 137-182 in S.H. Ridgway and R. Harrison (eds),

Handbook of Marine Mammals, Vol. 6, the Second Book of Dolphins and Porpoises. Academ ic Press, San

Diego. 

Wells, R. S., M. D. Scott and A. B. Irvine. 1987. The so cial structure of free-ranging bottlenose dolphins. Pages 247-305

in: Genowa ys, H. (ed), Current Mammalo gy, Vol. 1. N ew York , Plenum P ress.

Wells, R. S., K. W. U rian, A. J. Read, M. K . Bassos, W. J. Carr and M. D. Scott. 1996a. Low-level monitoring of

bottlenose dolphins, Tursiops truncatus, in Tamp a Bay, Florida: 1988-1993. NOAA Technical Memorandum.

NMF S-SEFSC-385, 25 pp. + 6 Tables, 8 Figure s, and 4 Appen dices.

Wells, R. S., M. K. Bassos, K. W. Urian, W. J. Carr and M. D . Scott. 1996b. Lo w-level monitoring of bottlenose

dolphins, Tursiops truncatus, in Charlotte Harbor, Florida: 1990-1994. NOAA Technical Memorandum. NMFSSEFSC -384, 36 pp. + 8 T ables, 10 F igures, and 5 Append ices. 

Wells, R. S., M. K. Bassos, K. W. Urian, S. H. Shane, E. C. G. Owen, C. F. Weiss, W. J. Carr and M . D. Scott. 19 97. 

Low-level monitoring of bottlenos e dolphins, Tursiops truncatus, in Pine Island Sound, Florida: 1996. Contract

report to National Marine Fisheries Service, Southeast Fisheries Center. Contribution No. 40-WCNF601958

Würsig, B. and S. K. Lynn. 1 996. M ovemen ts, site fidelity, and respiration patterns of bottlenose dolphins on the central

Texas coast. NOAA Technical Memorandum. NMFS-SEFSC-383, 43 pp. + 10 Tables, 15 Figures, and 6

Appen dices. 
259

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 spotte d dolph in is endemic to the Atlantic O cean 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 northe rn Gulf of M exico [Fritts et a l. 1983; M ullin 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 (Pe rrin

et al. 1994). The island and offshore animals may be a different stock than tho se occurrin g on the con tinental shelf (Pe rrin

et al. 1994). Atlantic spotted dolphins w ere seen in all sea sons during seasonal rec ent 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 con ducted in the autumn of 1 992-19 94 over the U.S. continental shelf [see Blaylock and

Hoggard (1994) for a descriptio n of the areas su rveyed in 19 92-199 3]. 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 sup porting this hyp othesis are limite d (Caldw ell

and Cald well 1966 ; Fritts et al. 1983 ). 

POPU LATIO N SIZE

Estimates of abundance were derived through the application of distance sampling analysis (Buckland et al. 1993)

and the computer program DIST ANCE (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 a s part of the G ulfCet prog ram (Da vis et al., in prepara tion). These surveys were conducted throughout the

area from approximately the 200 m isobath along the U.S. coa st to the seawar d 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 abundan ce 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 do lphins for all

surveys combined was 3,213 (CV =

0.44) (Hansen et al. 1995). This is

probab ly an undere stimate and

should be considered a partial stock

estimate because the continental

shelf areas were not generally

covered by either the vessel or

GulfCet ae rial surveys. 

Minimum Po pulation 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 estimate, which is equivalent

to the 20th percentile of the log-normal distributed abundance estimate as specified by NMFS (Anon. 1994 ). The minimum

populatio n estimate is 2,2 55 Atlantic sp otted dolp hins. 

Current Population Trend
260

No trend was identified in the annual abund ance 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 o f no overlap of log-normal 95 % confidenc e intervals. 

CURRENT AND M AXIMUM NET PRODUCTIVITY RATES

Current and maximum net productivity rates are not known for this stock; therefore, the default maximum net

produc tivity rate of 0.04 (Anon. 19 94) was use d for purp oses 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 productiv ity rate, and a recovery factor for endangered, threatened, or depleted stocks, or stocks of

unknown status relative to o ptimum susta inable po pulation (O SP) (An on. 199 4). 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 ashor e, nor will all of thos e that do wa sh ashore ne cessarily show signs of entanglement or other fish eryinteraction. Finally, the level of technical expertise among stranding network personnel varies widely as does the ab ility

to recogniz e signs of fishery intera ction. 

Total estimated average annual fishing-related mortality and serious injury of spotted do lphins (both species) is

1.5 spotted do lphins annua lly (CV = 0 .33). Ob served fishery-re lated morta lity and serious inj ury 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

MM PA have been revie wed by the p ublic and fina lized. 

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 A tlantic spotted dolphins b y this fishery in the Gu lf 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 sp ecies may ha ve been inv olved in the o bserved fish ery-related 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 (C V = 0.1 9). Estimated fishery-related mortality and

serious injury for the G ulf of Mexic o, based o n propo rtionality of fishing effort (number of sets) in 1993 was 4.4 spotted

dolphins. Estimated average annual fishing-related mortality and serio us injury of spo tted dolph ins 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 b een no rep orts of morta lity

or serious injury to marine mammals in the Gulf of Mexico. This fishery has not been observed by NMF S observers, and
261

there are no othe r data available as to the extent of this fisher y in the Gulf of M exico. It is assumed that it is very limited

in scope an d duration . 

STATUS OF STOCK

The status of this stock relative to OSP is unknown and there are insufficient data to determine population trend s.

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 Sc ience Cen ter, La Jolla, California, 13 p p. + App endices. 

Blaylock, R. A. and W. H oggard. 1994 . Preliminary estimates of bottlenose dolphin ab undance in southern U .S. Atlantic

and Gulf o f Mexico continental she lf waters. NO AA Te ch. Mem . NMF S-SEFSC-356, 1 0 pp. 

Buckland, S. T., D. R. Anderso n, K. P. Burnham and J. L. Laake. 1993. Distance Sampling: estimating abundance of

biologica l populatio ns. Chapm an & Ha ll, 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 Ange les County M useum Co ntribution to

Science, 1 04:1-28 . 

Cramer, J. 1994. Large pelag ic logboo k newsletter - 19 93. NO AA Te ch. Mem . NMF S-SEFSC-352, 1 9 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. J ennings, L. A. C ollum, W . Hoffman and M. A. McG ehee. 1983. Turtles, birds, and

mamma ls in the northern Gulf of Mexico and nearby Atlantic waters. U.S. Fish and Wildlife Service, Division

of Biolog ical Services, Washin gton, D. C., FWS /OBS-8 2/65, 45 5 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 & W ildlife Researc h Unit, Co lorado S tate University, Ft. Collins, Co lorado, 7 2 pp. 

Mullin, K., W. Hoggard, C. Roden, R. Lohoefener, C. Rogers and B. Taggart. 1991. Cetaceans on the upper continental

slope in the north-cen tral Gulf of M exico. OC S Study/M MS 9 1-0027 . U.S. Dept. of the Interior, M inerals

Manag ement Ser vice, Gulf of M exico OC S Region al Office, Ne w 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 o f the spotted d olphins, Stenella spp. Mar. Mam. Sci. 3(2):99-170.

Perrin, W. F., D. K. Caldwell and M. C. Caldwell. 1994. Atlantic spotted dolphin Stenella fro ntalis (G. Cuvier, 1829).

Pages 173-190 in S. H. Ridgway and R. H arrison (ed itors), Hand book o f marine mam mals, Vol. 5 : The first book

of dolphin s. Academ ic Press, Lo ndon, 41 6 pp. 
262

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 norther n Gulf of M exico durin g 1993 -1995 (D avis 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 1 994); ho wever, there is no informatio n on stock d ifferentiation for the Atlantic pop ulation. 

POPU LATIO N SIZE

Estimates of abundance were derived through the application of distance sampling analysis (Buckland et al. 1993)

and the computer program DIST ANCE (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 a s part of the G ulfCet prog ram (Da vis et al., in prepa ration). Th ese surveys were conducted throughout the

area from approximately the 200 m isobath alon g the U.S. co ast to the seawa rd extent of the U.S. Exc lusive Eco nomic

Zone. The seaso nal GulfCet aerial

surveys included on ly 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 Po pulation 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 spe cified by NM FS (Ano n. 1994 ). The minim um pop ulation 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 o verlap of log-normal 95% confidence intervals, but differences within 1991-

1993 estimates and differences between 1991, 1993, and 1994 were not significant. The observed differences in abundance

estimates may have b een caused by inter-annua l variation in distribution patterns and spatial sampling, rather than changes

in populatio n size. 

CURRENT AND M AXIMUM NET PRODUCTIVITY RATES
263

Current and maxim um net pro ductivity rates are not known for this stock; there fore, the defau lt maximum net

produc tivity rate of 0.04 (Anon. 19 94) was use d for purp oses of this assessment. 

POTENTIAL BIOLOGICAL REMOVAL

Potential biological removal level (PBR) was specified as the produc t of the minimum populatio n size, one ha lf

the maximum net produ ctivity 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 th e status of the stoc k relative to O SP is unkno wn. The re sulting PBR for this stock is 26 5 animals. 

ANNUAL HUMAN-CAUSED MORTALITY AND SERIOUS INJURY

The level of past or curre nt, direct, huma n-caused m ortality of pantro pical spotted do lphins in the no rthern 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 se rious injury be cause 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 nec essarily show signs of e ntanglemen t or other fisheryinteraction. Finally, the level of technical exp ertise amon g stranding ne twork perso nnel varies wid ely as does the ability

to recogniz e signs of fishery intera ction. 

Total estimated average annual fishing-related mortality and serious injury of spotted do lphins (both species) is

1.5 spotted do lphins annua lly (CV = 0 .33). Ob served fishery-re lated morta lity and serious inj ury 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

MM PA have been revie wed by the p ublic and fina lized. 

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, wa s 4,400 se ts in 1991, 4 ,850 sets in 1 992, and 3,260 se ts 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 A tlantic spotted dolphins b y this fishery in the Gu lf 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 fishery-related 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 a verage ann ual fishing-related mortality and se rious injury of sp otted dolphins attribu table to this

fishery during 1991-1993 was 1.5 annually (CV = 0.33).

Pair trawl fishing gear has the potential to capture marine mamma ls, but there hav e been no reports of mortality

or serious injury to marine mammals in the Gulf of Mexico. This fishery has not been observed by NMF S observers, and

there are no othe r data available as to the extent of this fishery in the Gulf of Mexico. It is assumed that it is very limited

in scope an d duration . 
264

STATUS OF STOCK

The status of this stock re lative to OSP is unknown and there are insufficient data to d etermine population trend s.

This species is not listed under the Endang ered Sp ecies Act. The total level of human-caused mortality and serious injury

is unknown, b ut it is believed to be insignificant re lative to PBR; therefore , this is not a strategic sto ck. 

REFERENCES

Anon. 1994. Report of the PBR (Potential Biological Remo val) workshop. June 2 7-29, 1994 . NOAA, N MFS So uthwest

Fisheries Sc ience Cen ter, La Jolla, California, 13 p p. + App endices. 

Buckland, S. T., D. R. Anderson, K. P. Burnham and J. L. Laake. 1993. Distance Sampling: estimating abundance of

biologica l populatio ns. Chapm an & Ha ll, London , 446 pp . 

Cramer, J. 1994. Large pelag ic logboo k newsletter - 19 93. NO AA Te ch. Mem . NMF S-SEFSC-352, 1 9 pp. 

Davis, R., G. Sco tt, B. Wü rsig, W. Evans, G. Fa rgion, L. Ha nsen, K. M ullin, N. Ma y, T. Lemin g, B. Ma te, 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. And erson, and K. P. Burnham. D ISTA NCE user’s guide, V 2.0. Colorado Cooperative

Fish & W ildlife Researc h Unit, Co lorado S tate University, Ft. Collins, Co lorado, 7 2 pp. 

Mullin, K., W. Hoggard, C. Roden, R. Lohoefener, C. Rogers and B. Taggart. 1991. Cetaceans on the upper continental

slope in the north-cen tral Gulf of Mexico . OCS S tudy/MM S 91-00 27. U.S. D ept. of the Interio r, Minera ls

Manag ement Ser vice, Gulf of M exico OC S Region al Office, Ne w 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 o f the spotted d olphins, 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. Academ ic Press,

Londo n, 416 pp . 
265

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 she lf [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.

POPU LATIO N SIZE

Estimates of abundance were derived through the applicatio n of distance sa mpling ana lysis (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-tra nsect vessel sur veys 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 prepara tion). These surveys were conducted throughout the

area from approximately the 200 m isobath along the U.S. coast to the se award exte nt of the U.S. E xclusive Ec onomic

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 (C V) 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 Po pulation 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 perc entile of the log-no rmal distribute d abund ance estima te

as specified b y NMF S (Anon . 1994). T he minimum populatio n estimate is 3,4 09 striped dolphins. 

Current Population Trend

The abundan ce estimates fo r 1991-1 993 wer e less than the 1 994 estimate. The abundance estimates were not

significantly different using the criteria of no o verlap of log -normal 95 % confid ence interva ls. 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 samp ling analysis. The differences in the estimates may also have been caused by inter-annual

variation in distrib ution patterns and spatial sampling, rathe r than change s in populatio n size. 

CURRENT AND M AXIMUM NET PRODUCTIVITY RATES

Current and maximum net productivity rates are not known for this stock; therefore, the default maximum net

produc tivity rate of 0.04 (Anon. 19 94) was use d for purp oses of this assessment. 
266

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 pop ulation (OSP) (A non. 1994). T he recovery factor was set at 0.50

because th e status of the stoc k relative to O SP is unkno wn. PBR for this stock is 34 striped do lphins. 

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. A vailable inform ation indicate s 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 seriou s injury and no fisheryrelated 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 a s does the ab ility to recognize signs of fishery interac tion. 

Total known fishery-re lated morta lity and serious inj ury 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 sp ecific fisheries until the implementing regulations for Section 118 of the MMPA have been reviewed by the

public and finalized. 

Fisheries Information

 Pelagic swo rdfish, tunas, and billfish are the targe ts of the longline fishe ry operating in the U.S. G ulf 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 re ports of mo rtality or serious inj ury to striped d olphins by this fishe ry. 

Pair trawl fishing gear has the potential to ca pture marin e mammals, but there ha ve been no reports of mortality

or serious injury to marine mammals in the Gulf of Mexico. This fishery has not been observed by NMFS ob servers, 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 an d duration . 

STATUS OF STOCK

The status of this stock re lative to OS P is unknow n and there a re 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, b ut it is believed to be insignificant re lative to PBR; therefore , this is not a strategic sto ck. 

REFERENCES

Anon. 1994. Report of the PBR (Potential B iological Re moval) wo rkshop. June 27-29, 19 94. NOA A, NMF S Southwest

Fisheries Sc ience Cen ter, La Jolla, California, 13 p p. + App endices. 

Buckland, S. T., D. R. Anderson, K. P. Burnham and J. L. Laake. 1993. Distance Sampling: estimating abundance of

biologica l populatio ns. Chapm an & Ha ll, London , 446 pp . 

Cramer, J. 1994. Large pelag ic logboo k newsletter - 19 93. NO AA Te ch. Mem . NMF S-SEFSC-352, 1 9 pp. 

Davis, R., G. Sco tt, B. Wü rsig, W. Evans, G. Fargion, L. Hansen, K. Mullin, N. May, T. Leming, B. Mate, J. Norris and

T. Jefferson. In prepara tion. Distributio n and abu ndance o f marine mam mals in the north-central and western

Gulf of Mexico: Final Report. O CS Stud y #MM S 94-00 03. Texas Institute of Oceanography and the National

Marine Fisheries Ser vice. U.S. D ept. 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.
267

Laake, J. L., S. T. Buckland, D. R. And erson, and K. P. Burnham. D ISTA NCE user’s guide, V 2.0. Colorado Cooperative

Fish & W ildlife Researc h Unit, Co lorado S tate University, Ft. Collins, Co lorado, 7 2 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 o f Mexico . OCS S tudy/MM S 91-00 27. U.S. D ept. of the Interio r, Minera ls

Manag ement Ser vice, Gulf of M exico OC S Region al Office, Ne w 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. Rid gway and R. Harrison (editors), Handbook of marine mammals, Vol. 5: The first book of

dolphins. A cademic Press, Lon don, 41 6 pp. 
268

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 Ree ves 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 ba sed on mo rphologic al characteristic s (Perrin and Gilpatrick 1994); however, there is no information on

stock differen tiation for the Atla ntic popula tion. 

POPU LATIO N SIZE

Estimates of abundance were derived through the application of distance sampling analysis (Buckland et al. 1993)

and the computer program DIST ANCE (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 a s part of the G ulfCet prog ram (Da vis et al., in prepa ration). Th ese surveys were conducted throughout the

area from approximately the 200 m isobath alon g the U.S. co ast to the seawa rd extent of the U.S. Exc lusive Eco nomic

Zone. The seasonal GulfCet aerial

surveys included o nly 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 (C V) in

parentheses] was zero in 1991,

2,593 in 1992 ( 0.63), 2,3 36 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 Po pulation Estimate

The minimum p opulation

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 minim um pop ulation estimate is 4,465 sp inner dolp hins. 

Current Population Trend

The abundance estimates for 1992 and 199 3 were ap proxima tely the same an d the 199 4 estimate wa s considera bly

larger; 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 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 populatio n size. 

CURRENT AND M AXIMUM NET PRODUCTIVITY RATES
269

Current and maxim um net pro ductivity rates for th is stock are no t known; there fore, the defau lt maximum net

produc tivity rate of 0.04 (Anon. 19 94) was use d for purp oses of this assessment. 

POTENTIAL BIOLOGICAL REMOVAL

Potential biological removal level (PBR) was specified as the produc t of the minimum populatio n size, one ha lf

the maximum net produ ctivity 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 th e status of the stoc k relative to O SP is unkno wn. PBR for this stock is 45 spinner do lphins. 

 

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 an d no fisheryrelated 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. Stran ding data p robably

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 a s does the ab ility to recognize signs of fishery interac tion. 

The total known fishe ry-related mo rtality and seriou s 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 pub lic 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, wa s 4,400 se ts in 1991, 4 ,850 sets in 1 992, and 3,260 se ts in 1993 (Cramer

1994). This fishery has been monitored with about 5% observer coverage, in terms of trips observed, since 1992. There

were no re ports of mo rtality or serious inj ury of spinner d olphins by this fishe ry. 

Pair trawl fishing gear has the potential to capture marine m ammals, but there hav e been no reports of mortality

or serious injury to marine mammals in the Gulf of Mexico. This fishery has not been observed by NMF S observers, and

there are no other data available as to the extent of this fishery in the Gu lf of Mexico . It is assumed tha t it is very limited

in scope an d duration . 

STATUS OF STOCK

The status of this stock relative to OSP is unkno wn 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, b ut it is believed to be insignificant re lative to PBR; therefore , this is not a strategic sto ck. 

REFERENCES

Anon. 1994. Report of the PBR (Potential Biological Removal) workshop. June 27-29, 1994. NOAA, NMFS Southwest

Fisheries Sc ience Cen ter, La Jolla, California, 13 p p. + App endices. 

Buckland, S. T., D. R. Anderson, K. P. Burnham and J. L. Laake. 1993. Distance Sampling: estimating abundance of

biologica l populatio ns. Chapm an & Ha ll, London , 446 pp . 

Cramer, J. 1994. Large pelag ic logboo k newsletter - 19 93. NO AA Te ch. Mem . NMF S-SEFSC-352, 1 9 pp. 

Davis, R., G. Sco tt, B. Würsig, W. Evans, G. Fargion, L. Hansen, K. Mullin, N. May, T. Leming, B. M ate, 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. 
270

Hansen, L. J., K. D. Mullin and C. L. Roden. 1995. Estimates of cetacean abundance in the northern Gulf of Mexico from

vessel surveys. Sou theast Fisheries Science Center, Miami Labo ratory, Contribution No. MIA-94/95-25, 9 pp +

tables and figu res. 

Laake, J. L., S. T. Buckland, D. R. Anderson, and K. P. Burnham. DISTANCE user’s guide, V2.0. Colorado Cooperative

Fish & W ildlife Researc h Unit, Co lorado S tate University, Ft. Collins, Co lorado, 7 2 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. S pinner do lphin Stenella lo ngirostris (Gray, 18 28). Pages 99-128 in S. H.

Ridgway and R. H arrison (ed itors), Hand book o f marine mam mals, Vol. 5 : The first boo k of dolph ins. Academ ic

Press, London, 416 pp.
271

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-too thed dolp hin is distributed worldwide in tropical to warm temperate waters (Leatherwood and

Reeves 1983; Miyazaki and Perrin 19 94). 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 G ulf of Mexico during 1993-

1995 (D avis et al., in prep aration). There is no information on stock differentia tion for the Atlan tic populatio n. 

POPU LATIO N SIZE

Estimates of abundance were derived through the applicatio n of distance sa mpling ana lysis (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 vesse l surveys of the no rthern Gulf o f Mexico (Hansen et al. 1995 ), which includ es data

collected as part of the G ulfCet prog ram (Da vis 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 roughtoothed 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 effortweighted estimate d ave rage

abundance of rough-tooth ed

dolphins for all surveys combined

was 852 (CV = 0.31) (Hansen et al.

1995).

Minimum Po pulation Estimate

The minimum population

size was estimated from the average estimate abundance which was 852 rough-toothed dolphins (CV = 0.31) (Hansen et

al. 1995). The minimum population estimate is the lower limit of the two-tailed 60% confidence interval of the log-normal

distributed abundan ce estimate, wh ich is equivalen t to the 20th percentile o f the log-normal distributed a bundanc e estimate

as specified b y NMF S (Anon . 1994). T he minimum populatio n estimate is 66 0 rough-to othed do lphins. 

Current Population Trend

The 1993 abundanc e estimate was greater than the 1991, 1993, and 1994 estimates; however, the abundance

estimates were not significa ntly different using the criteria of no overlap of log-normal 95% confidence intervals. The

apparent differences in abundance estimates may h ave been caused b y small sample sizes (Hansen et al. 1995) or by interannual varia tion in distributio n patterns or spatial samp ling patterns, rath er than chan ges in pop ulation size. 

CURRENT AND M AXIMUM NET PRODUCTIVITY RATES

Current and maximum net productivity rates are not known for this stock; therefore, the default maximum net

produc tivity rate of 0.04 (Anon. 19 94) was use d for purp oses of this assessment. 
272

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 unkno wn. The resulting PBR for this stock is 6.6 rough-toothed 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 inter action with rough-toothed

dolphins in the northern Gulf of Mexic o. There have been no logbo ok repo rts 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-tootheddolphins in the northern Gulf of Mexico during 1987-1994

which were classified as likely caused by fishery interactions or other hum an-related ca uses. Strandin g data pro bably

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 ab ility to recognize signs of fishery interac tion. 

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 lon gline fishery ope rating 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 re ports of mo rtality or serious inj ury of rough-to othed do lphins by this fishery. 

Pair trawl fishing gear has the potential to capture marine mammals, but there have been no re ports of mo rtality

or serious injury to marine mammals in the Gulf of Mexico. This fishery has not been observed by NMFS observers, and

there are no othe r data available as to the extent of this fishery in the Gulf of Mexico. It is assumed that it is very limited

in scope an d duration . 

STATUS OF STOCK

The status of this stock relative to OSP is unknown and there are insufficient data to determine po pulation trends.

This species is not listed under the Endangered Species Act. The total level of huma n-caused m ortality and serious injury

is unknown, b ut it is believed to be insignificant re lative to PBR; therefore , this is not a strategic sto ck. 

REFERENCES

Anon. 1994. Report of the PBR (Potential Biological Removal) workshop. June 27-29, 1994. NO AA, NM FS Southwest

Fisheries Sc ience Cen ter, La Jolla, California, 13 p p. + App endices. 

Buckland, S. T., D. R. Anderson, K. P. Burnham and J. L. Laake. 1993. Distance Sampling: estimating abundance of

biologica l populatio ns. Chapm an & Ha ll, London , 446 pp . 

Cramer, J. 1994. Large pelag ic logboo k newsletter - 19 93. NO AA Te ch. Mem . NMF S-SEFSC-352, 1 9 pp. 

Davis, R., G. Sco tt, B. Wü rsig, W. Evans, G. Fa rgion, L. Ha nsen, K. M ullin, N. Ma y, T. Leming, B. Mate, J. Norris and

T. Jefferso n. In prepar ation. Distribu tion and ab undance of marine mammals in the north-central and western

Gulf of M exico: 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. 
273

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 & W ildlife Researc h Unit, Co lorado S tate University, Ft. Collins, Co lorado, 7 2 pp. 

Leatherwood, S. and R. R. Reeves. 1983. The Sierra Club handbook of whales and dolphins. Sierra Club Books, San

Francisco , 302 pp . 

Miyazak i, N. and W. F. Perrin. 1994. Rough-toothed dolphin Steno b redane nsis (Lesson, 1828). Pages 1-21 in S. H.

Ridgway and R. H arrison (ed itors), Hand book o f marine mam mals, Vol. 5 : The first boo k of dolph ins. Academ ic

Press, London, 416 pp.
274

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 d olphin is end emic to trop ical and sub-tropical waters of the Atlantic (Leatherwood and Reeves

1983; Perrin and Mead 199 4). 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 o n stock differen tiation for the Atla ntic popula tion. 

POPU LATIO N SIZE

Estimates of abundance were derived through the applicatio n of distance sa mpling ana lysis (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-tra nsect vessel sur veys 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 prepara tion). These surveys were conducted throughout the

area from approximately the 200 m isobath along the U.S. coast to the se award exte nt of the U.S. E xclusive Ec onomic

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 (C V) 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) (Ha nsen et al. 199 5). 

Minimum Po pulation Estimate

The minimum population

size was estimated from the average

estimate abundan ce which wa s 5,571 C lymene do lphins (CV = 0.37) (H ansen et al. 19 95). The minimum population

estimate is the lower limit of the two-tailed 60% confidence interval of the log-normal distributed abundanc e estimate,

which is equivalent to the 20th pe rcentile of the lo g-normal d istributed ab undance estimate as specified by NMFS (Anon.

1994). The minim um pop ulation estimate is 4,120 Clymene do lphins. 

Current Population Trend

The abundan ce estimates sh owed an increasing tren d during 1 991-19 94; 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 inter-ann ual variation in

distribution p atterns or spa tial sampling p atterns, rather tha n changes in p opulation siz e. 

CURRENT AND M AXIMUM NET PRODUCTIVITY RATES

Current and maximum net productivity rates are not known for this stock; therefore, the default maximum net

produc tivity rate of 0.04 (Anon. 19 94) was use d for purp oses of this assessment. 

POTENTIAL BIOLOGICAL REMOVAL
275

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 th e status of the stoc k relative to O SP is unkno wn. PBR for this stock is 41 Clymene d olphins. 

ANNUAL HUMAN-CAUSED MORTALITY AND SERIOUS INJURY

The level of past o r current, direc t, human-cau sed morta lity of Clymene d olphins in the northern Gulf of Mexico

is unknown. Available info rmation ind icates there likely is little, if any, fisheries interaction w ith Clymene d olphins in the

northern Gulf of M exico. There have been no logbook reports of fishe ry-related mo rtality or serious inj ury and no fish eryrelated 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-r elated mo rtality and serious injury because not all of the marine mammals whic h die

or are seriously inju red may wa sh ashore, no r 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 ab ility to recognize signs of fishery interac tion. 

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 pub lic and finalized . 

Fisheries Information

Pelagic swordfish, tunas, and billfish are the targets of the longline fishery operating in the U.S. G ulf of Mexico.

Total longline effort fo r the Gulf of M exico pela gic fishery, including OCS edge, continental slope, and Mexican territorial

waters, based on mandato ry logboo k reporting, w as 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 re ports of mo rtality or serious inj ury to Clymen e dolphins by this fishery. 

Pair trawl fishing gear has the potential to capture marine mamma ls, but there hav e been no reports of mortality

or serious injury to marine mammals in the Gulf of Mexico. This fishery has not been observed by NMFS ob servers, 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 unkno wn 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, b ut it is believed to be insignificant re lative to PBR; therefore , this is not a strategic sto ck. 

REFERENCES

Anon. 1994. Report of the PBR (Potential Biological Removal) workshop. June 27-29, 1994. NOAA, NMFS Southwest

Fisheries Sc ience Cen ter, La Jolla, California, 13 p p. + App endices. 

Buckland, S. T., D. R. Anderson, K. P. Burnham and J. L. Laake. 1993. Distance Sampling: estimating abundance of

biologica l populatio ns. Chapm an & Ha ll, London , 446 pp . 

Cramer, J. 1994. Large pelag ic logboo k newsletter - 19 93. NO AA Te ch. Mem . NMF S-SEFSC-352, 1 9 pp. 

Davis, R., G. Sco tt, B. Wü rsig, W. Evans, G. Fa rgion, L. Ha nsen, K. M ullin, N. Ma y, T. Lemin g, B. Ma te, J. Norris and

T. Jefferson. In preparation. Distribution and abun dance o f marine mam mals in the north-central and western

Gulf of Mexic o: Final Rep ort. OCS Study #MM S 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 & W ildlife Researc h Unit, Co lorado S tate University, Ft. Collins, Co lorado, 7 2 pp. 
276

Leatherwood, S. and R. R. Reeves. 1 983. 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 do lphin Stenella clymene (Gray, 1846). Pages 161-171 in S. H. Ridgway

and R. Harrison (editors), H andbook o f marine mammals, Vol. 5: T he first book of dolphins. Academic P ress,

London, 416 pp.
277

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

Fra ser's dolphin is d istributed wo rldwide in tro pical waters (P errin 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).

Fra ser's dolphins have been observed recently in the northe rn Gulf of M exico durin g the spring, sum mer, 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 pop ulation. 

POPU LATIO N 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 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 e xtent 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 use d for abundance

estimation. Estimated abundance of

Fraser’s dolphins by survey year

[coefficient of variation (C V) 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 abu nda nce of Frase r's

dolphins for all vessel surveys

combined was 127 (CV = 0.90)

(Hansen et al. 1995).

Minimum Po pulation Estimate

The minimum population

size was estimated from the average

estimate abundance which was 127 Fraser’s do lphins (CV = 0.90) (H ansen et al. 1995). T he minimum populatio n estimate

is the lower limit of the two-tailed 60 % confid ence interva l of the log-norm al distributed abunda nce estimate, w hich is

equivalent to the 20th percentile of the log-normal distributed abundance estimate as specified by NMFS (Anon. 1994 ).

The min imum po pulation estimate is 66 Fra ser’s dolphin s. 

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 sigh ting s of F rase r's dolphins were documented in the northern Gulf of Mexico during other surveys in 1992, 1993

and 1994 (Leatherwood et al. 1993, S EFSC unpublishe d data). T he appa rent difference s in abundance estimates may have

been caused b y low samplin g intensity relative to p opulatio n size (Hansen et al. 199 5) or by inter-a nnual variatio n in

distribution p atterns or spa tial sampling p atterns, rather tha n changes in p opulation siz e. 

CURRENT AND M AXIMUM NET PRODUCTIVITY RATES
278

Current and maxim um net pro ductivity rates are not known ; therefore, the d efault maximum net prod uctivity rate

of 0.04 (A non. 199 4) was used for purpo ses of this assessment. 

POTENTIAL BIOLOGICAL REMOVAL

Potential biological removal level (PBR) was specified as the produc t of the minimum populatio n size, one ha lf

the maximum net produ ctivity 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 th e status of the stoc k relative to O SP is unkno wn. PBR for this stock is 0.7 Fraser’s do lphins. 

ANNUAL HUMAN-CAUSED MORTALITY AND SERIOUS INJURY

The level of past o r current, direc t, human-caused mo rtality of Fraser's dolphins in the northern Gulf of Mexico

is unknown. Available info rmation ind icates there likely is little, if any, fisheries interaction w ith Fraser’s dolphins in the

northern Gulf of Mexico. There have been no logbook rep orts of fishery-related mortality or serious injury and no fisheryrelated 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 ca uses. Strandin g data pro bably

underestimate the extent of fishery-r elated mo rtality and serious injury because not all of the marine mammals whic h 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 ab ility to recognize signs of fishery interac tion. 

 Available information indicates there likely is little, if any, fisheries interaction with Fraser's dolphins in the

northern Gulf of Mexico . The total kn own fishery-rela ted mortality an d serious inju ry 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 bee n 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 logboo k reporting, w as 4,400 sets in 1991 , 4,850 se ts in 1992, a nd 3,26 0 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 re ports of mo rtality or serious inj ury of Fraser’s d olphins by this fishe ry. 

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 NM FS 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 unkno wn and there are insufficient data to determine population trends.

This species is not listed unde r the Enda ngered S pecies Ac t. The total leve l of human-ca used mo rtality and serious injury

is unknown, b ut it is believed to be insignificant re lative to PBR; therefore this is not a strategic sto ck. 
279

REFERENCES

Anon. 1994. Report of the PBR (Potential Biological Removal) workshop. June 27-29, 1994 . NOAA, N MFS So uthwest

Fisheries Sc ience Cen ter, La Jolla, California, 13 p p. + App endices. 

Buckland, S. T., D. R. Anderson, K. P. Burnham and J. L. Laake. 1993. Distance Sampling: estimating abundance of

biologica l populatio ns. Chapm an & Ha ll, London , 446 pp . 

Cramer, J. 1994. Large pelag ic logboo k newsletter - 19 93. NO AA Te ch. Mem . NMF S-SEFSC-352, 1 9 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 M exico: Final Report. OC S Study #M MS 9 4-0003 . 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 Coop erative

Fish & W ildlife Researc h Unit, Co lorado S tate University, Ft. Collins, Co lorado, 7 2 pp. 

Leatherwood, S., T. A. Jefferson, J. C. Norris, W. E. Stevens, L. J. Hansen, and K. D. Mullin. 1993. Occurrence and

sounds o f Fraser's dolp hin in the Gulf o f Mexico . The Texas Journ al of Science , 45(4):34 9-354. 

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), Handbo ok of marine mammals, Vol. 5: The first boo k of dolphins.

Academic Press, London, 416 pp.
280

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 tropicalto polar regions (Leatherwood and Reeves 1983). Sightings

of these animals in the northern G ulf of Mexico oc cur primarily over the deep er 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 (D avis 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

Norwa y indicated tha t stocks from the se areas ma y represent d ifferent stocks (M oore et al. 1 988). 

POPU LATIO N SIZE

Estimates of abundance were derived through the applicatio n of distance sa mpling ana lysis (Bucklan d et al. 1993)

and the computer program DIST ANCE (Laake et al. 1993) to sighting data collected during 1991-1994 spring-summer,

visual sampling, line-tra nsect vessel sur veys of the northern Gulf o f Mexico (Hansen et al. 199 5), which inclu des 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 [co efficient 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 fo r all

surveys combined was 277 (CV =

0.42) (Hansen et al. 1995).

Minimum Po pulation 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 lognormal distributed a bundanc e estimate as sp ecified by N MFS (Anon. 19 94). Th e minimum populatio n 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 log-normal 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 inter-annua l 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

unpublishe d data). 
281

CURRENT AND M AXIMUM NET PRODUCTIVITY RATES

Current and maximum net productivity rates for this stock are not known; therefore, the default maximum net

produc tivity rate of 0.04 (Anon. 19 94) was use d for purp oses of this assessment. 

POTENTIAL BIOLOGICAL REMOVAL

Potential biological removal level (PBR) was specified as the produc t of the minimum populatio n size, one ha lf

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

unknown status relative to o ptimum susta inable population (OSP) (Anon. 1994). The recovery factor was set at 0.50

because th e status of the stoc k relative to O SP is unkno wn. PBR for this stock is 2.0 killer whales. 

ANNUAL HUMAN-CAUSED MORTALITY AND SERIOUS INJURY

The level of past or current, direct, huma n-caused m ortality of killer whale s in the northern Gulf of M exico 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 othe r human-rela ted causes. S tranding da ta probab ly

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 ab ility to recognize signs of fishery interac tion. 

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 pub lic and finalized . 

Fisheries Information

Pelagic swordfish, tuna s, and billfish are the targets of the lon gline fishery ope rating 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 re ports of mo rtality or serious inj ury of killer whale s by this fishery. 

Pair trawl fishing gear has the potential to capture marine m ammals, but there have been no reports of mortality

or serious injury to marine mammals in the G ulf 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 an d duration . 

STATUS OF STOCK

The status of this stock relative to OSP is unknown and there are insufficient data to determine pop ulation trends.

This species is not listed under the Endangered Species Act. The total level of human-caused mortality and serious injury

is unknown, b ut it is believed to be insignificant re lative to PBR; therefore , this is not a strategic sto ck. 

REFERENCES

Anon. 1994. Report of the PBR (Po tential Biological Removal) workshop. June 27-29, 1994 . NOAA, N MFS So uthwest

Fisheries Sc ience Cen ter, La Jolla, California, 13 p p. + App endices. 

Bigg, M. A., P . F. Olesiuk, G . M. Ellis, J. K . B. Ford and K. C. Balcom b. 1990 . Socia l 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. Hammon d, S. A. Mizroch and G. P. Do novan (editors), Individual reco gnition of cetaceans: Use of

photoidentification and other techniques to estimate population parameters, Rep. Int. Whal. Commn., Special

Issue 12, Cambridg e, 440 p p. 

Buckland, S. T., D. R. Anderson, K. P. Burnham and J. L. Laake. 1993. Distance Sampling: estimating abundance of

biologica l populatio ns. Chapm an & Ha ll, London , 446 pp . 

Cramer, J. 1994. Large pelag ic logboo k newsletter - 19 93. NO AA Te ch. Mem . NMF S-SEFSC-352, 1 9 pp. 
282

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 abun dance o f marine mam mals in the north-central and western

Gulf of Mexic o: Final Rep ort. OCS Study #MM S 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. 

Hoelze l, A. R. 1991. Analysis of regional mitochondrial DNA variation in the killer whale; implications for conservation.

Pages 225-233 in A. R. Ho elzel (editor), Genetic ec ology of wha les and do lphins, Rep . Int. Whal. Commn.

Special Issu e 13, Cam bridge, 31 1 pp. 

Laake, J. L., S. T. Buckland, D. R. Anderson, and K. P. Burnham. DISTANCE user’s guide, V2.0. Colorado Coop erative

Fish & W ildlife Researc h Unit, Co lorado S tate University, Ft. Collins, Co lorado, 7 2 pp. 

Leatherwood, S. and R. R. Reeves. 1983. The Sierra Club handboo k 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.
283

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 (SE FSC) unpub lished data]. False killer whales wer e seen only in

the summer during rece nt seasonal G ulfCet aerial surv eys of the northe rn Gulf of M exico durin g 1993 -1995 (D avis et al.,

in preparation) and in the late spring during vessel surveys (NMFS unpublished data). There is no information on stock

differentiation fo r the Atlantic po pulation. 

POPU LATIO N 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 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 e xtent of the U .S. Exclusive Economic

Zone. The seaso nal 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 (C V) 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 effortweighted e stimated average

abundance of false killer whales for

all surveys combined was 381 (CV

= 0.62) ( Hansen e t al. 1995). 

Minimum Po pulation 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 minim um pop ulation estimate

is the lower limit of the two-tailed 60 % confid ence interva l of the log-norm al distributed abunda nce estimate, w hich is

equivalent to the 20th percentile of the log-normal distributed abundance estimate as specified by NMFS (Anon. 1994 ).

The min imum po pulation 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 c riteria of no ov erlap of log-n ormal 95 % confid ence interva ls. The app arent differenc es in

abundance estimates may have been caused by lower sampling effort during 1991, by low samplin g intensity relative to

population size (Hansen et al. 1995), or by inter-annual variation in distribution patterns or spatial sampling patterns, rather

than change s in populatio n size. 

CURRENT AND M AXIMUM NET PRODUCTIVITY RATES
284

Current and maxim um net pro ductivity rates are not known ; therefore, the d efault maximum net prod uctivity rate

of 0.04 (A non. 199 4) was used for purpo ses of this assessment. 

POTENTIAL BIOLOGICAL REMOVAL

Potential biological removal level (PBR) was specified as the prod uct of the minimum pop ulation size, on e half

the maximum net produ ctivity rate, and a recovery factor for endangered, threatened, or depleted stocks, or stocks of

unknown status relative to o ptimum susta inable po pulation (OSP) (Anon. 1994). The recovery factor was set at 0.50

because the status of the stock relative to OS P is unknown. PB R for this stock is 2.4 false killer whales.

 

ANNUAL HUMAN-CAUSED MORTALITY AND SERIOUS INJURY

The level of past o r current, direct, human-caused mortality of false killer whales in the northern Gulf of Mexico

is unknown. A vailable inform ation indicate s 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 an d no fisheryrelated mortality or serious injury has been observed.

There were no documented stra ndings of false k iller whales in the no rthern Gulf o f Mexico during 19 87-1994

which were classified as likely caused b y fishery interaction s or other human-related causes. Stran ding data p robably

underestimate the extent of fishery-related mortality and serious injury because not all of the marine mammals wh ich 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 ab ility to recognize signs of fishery interac tion. 

The total known fishe ry-related mo rtality and seriou s 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 pub lic 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, wa s 4,400 se ts in 1991, 4 ,850 sets in 1 992, and 3,260 se ts in 1993 (Cramer

1994). This fishery has been monitored with about 5% observer coverage, in terms of trips observed, since 1992. There

were no re ports of mo rtality or serious inj ury of false killer wha les by this fishery. 

Pair trawl fishing gear has the potential to capture marine m ammals, but there hav e been no reports of mortality

or serious injury to marine mammals in the Gulf of Mexico. This fishery has not been observed by NMF S observers, and

there are no other data available as to the extent of this fishery in the Gu lf of Mexico . It is assumed tha t it is very limited

in scope an d duration . 

STATUS OF STOCK

The status of this stock relative to OSP is unkno wn 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, b ut it is believed to be insignificant re lative to PBR; therefore , this is not a strategic sto ck. 

REFERENCES

Anon. 1994. Report of the PBR (Potential Biological Removal) workshop. June 27-29, 1994. NOAA, NMFS Southwest

Fisheries Sc ience Cen ter, La Jolla, California, 13 p p. + App endices. 

Buckland, S. T., D. R. Anderson, K. P. Burnham and J. L. Laake. 1993. Distance Sampling: estimating abundance of

biologica l populatio ns. Chapm an & Ha ll, London , 446 pp . 

Cramer, J. 1994. Large pelag ic logboo k newsletter - 19 93. NO AA Te ch. Mem . NMF S-SEFSC-352, 1 9 pp. 

Davis, R., G. Sco tt, B. Würsig, W. Evans, G. Fargion, L. Hansen, K. Mullin, N. May, T. Leming, B. M ate, 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. 
285

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.
286

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 anima ls in the northern Gulf of M exico occ ur primarily o ver the dee per waters o ff the continental sh elf

[Southeast Fisheries Science Center (SEFSC) unpublished data]. Pygmy killer whales and melon-headed whales

(Pepon oceph ala electra) are difficult to disting uish and sighting s 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 differen tiation for the Atla ntic popula tion. 

POPU LATIO N SIZE

Estimates of abundance were derived through the application of distance sampling analysis (Buckland et al. 1993)

and the computer program DIST ANCE (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 a s part of the G ulfCet prog ram (Da vis et al., in prepa ration). Th ese surveys were conducted throughout the

area from approximately the 200 m isobath alon g the U.S. co ast to the seawa rd extent of the U.S. Exc lusive Eco nomic

Zone. The seasonal GulfCet aerial

surveys included o nly 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 (C V) 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 Po pulation Estimate

The minimum p opulation

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 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 minim um pop ulation estimate is 285 pygm y killer whales. 

Current Population Trend

A declining trend was identified in the annual abu ndance estimates; however, the 1991-1993 abundance estimates

were not significantly differe nt 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 va riation in distribu tion patterns o r spatial samp ling patterns, rath er than chan ges in pop ulation size. 

CURRENT AND M AXIMUM NET PRODUCTIVITY RATES
287

Current and maxim um net pro ductivity rates are not known ; therefore, the d efault maximum net prod uctivity rate

of 0.04 (A non. 199 4) was used for purpo ses of this assessment. 

POTENTIAL BIOLOGICAL REMOVAL

Potential biological removal level (PBR) was specified as the produc t of the minimum populatio n size, one ha lf

the maximum net produ ctivity 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 th e status of the stoc k relative to O SP is unkno wn. PBR for this stock is 2.8 pygmy killer wh ales. 

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 M exico is unknown. Available information indicates there likely is little, if any, fisheries interactio n with

pygmy 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 pygmy killer whales in the northern Gulf of Mexico during 1987-1994

which were classified as likely caused b y fishery interaction s or other human-related causes. Stran ding data p robably

underestimate the extent of fishery-related mortality and serious injury because not all of the ma rine mamm als 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 pub lic 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 logboo k reporting, w as 4,400 sets in 1991 , 4,850 se ts in 1992, a nd 3,26 0 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 re ports of mo rtality or serious inj ury of pygmy k iller whales by this fishe ry. 

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 NM FS observers, and

there are no othe r data availab le as to the extent of this fishery in the Gulf of Mexico. It is assumed that it is very limited

in scope an d duration . 

STATUS OF STOCK

The status of this stock relative to OSP is unknown and there are insufficient data to determine population trend s.

This species is not listed under the Endangered Species Act. The total level of human-caused mortality and serious injury

is unknown, b ut it is believed to be insignificant re lative to PBR; therefore , this is not a strategic sto ck. 

REFERENCES

Anon. 1994. Report of the PBR (Potential Biological Removal) workshop. June 27-29, 1994. NO AA, NM FS Southwest

Fisheries Sc ience Cen ter, La Jolla, California, 13 p p. + App endices. 

Buckland, S. T., D. R. Anderso n, K. P. Burnham an d J. L. Laak e. 1993 . Distance S ampling: estimating abundance of

biologica l populatio ns. Chapm an & Ha ll, London , 446 pp . 

Caldwell, D. K. and M . C. Caldwell. 197 1. The p ygmy killer whale , Feresa attenua ta, in the western Atlantic, with a

summary o f world reco rds. J. Ma mm. 52:2 06-209 . 

Cramer, J. 1994. Large pelag ic logboo k newsletter - 19 93. NO AA Te ch. Mem . NMF S-SEFSC-352, 1 9 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
288

Marine Fisheries Ser vice. U.S. D ept. of the Interio r, Minera ls 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. Sou theast Fisheries Science Center, Miami Labo ratory, Contribution No. MIA-94/95-25, 9 pp.

+ tables and figures. 

Laake, J. L., S. T. Buckland, D. R. Anderson, and K. P . Burnham . DIST ANCE user’s guide, V2.0. Colorado Cooperative

Fish & W ildlife Researc h Unit, Co lorado S tate University, Ft. Collins, Co lorado, 7 2 pp. 

Ross, G. J. B. and S. Leatherwood. 1994. Pygmy killer whale Feresa a ttenuata (Gray, 1874). Pages 387-404 in S. H.

Ridgway and R. H arrison (ed itors), Hand book o f marine mam mals, Vol. 5 : The first boo k of dolph ins. Academ ic

Press, Lo ndon, 41 6 pp. 
289

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 no rthern Gulf o f Mexico occur prim arily along the co ntinental shelf edge

and over the deeper waters off the continental shelf (Mullin et al. 1991; South east Fisheries Science Center, SEFSC,

unpublished data). Dwarf sperm whales and pygmy sperm w hales (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 m ore nume rous in spring , probab ly 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 d eep, on average (D avis et al. 1998). However, these authors cautioned

that inferences on preferred bottom depths should await surveys for the entire Gulf of M exico. Th e 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 div e deepe r during feed ing bouts. T here is no information on stock differentia tion. 

POPU LATIO N SIZE

Estimates of abunda nce 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 springsummer, 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 E conomic

Zone. The seasonal GulfCet ae rial surveys includ ed only a small portion of the species’ range and th erefore, these data

were not used to e stimate pop ulation size. Estimated ab undance of Kogia sp. by survey year [coefficient of variation (CV)

in parenthes es] was 10 9 in 1991 (0.68), 1,0 10 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 se a. 

Minimum Po pulation Estimate

A minimum populatio n estimate was not calculated because o f uncertainty of sp ecies identificatio n at sea. 

Current Population Trend

There is insufficient information to describe any population trend of this species in the Gulf of Mexico.

CURRENT AND M AXIMUM NET PRODUCTIVITY RATES

Current and maximum net produc tivity rates are not kn own for this stoc k. The ma ximum net p roductivity 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

produc tivity 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.
290

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 wha les 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 c lassified as likely caused by fishery interactions, but there have been stranding investigation reports of

dwarf sperm whales which may have died as a res ult of other hum an-related ca uses. Strandin g data pro bably und erestimate

the extent of fishery-related mortality and serious injury because not all of the marine mamma ls 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 fisheryinteraction. Finally, the level of te chnical exp ertise amon g stranding ne twork perso nnel varies wid ely as does the a bility

to recogniz e signs of fishery intera ction. 

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 re ports of mo rtality or serious inj ury of dwarf sp erm 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 ob servers, and

there are no other data available as to the extent of this fish ery in the Gulf o f Mexico . It is assumed that it is very limited

in scope an d duration . 

Other M ortality

A total of at least 16 dwarf sperm whale strandings were documented in the northern Gulf of Mexico from 1990

through O ctober 19 98. 

STATUS OF STOCK

The status of this stock relative to OSP is unknown and there are insufficient data to determine population trend s.

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 un known, bu t it is believed to b e insignificant.

REFERENCES

Barlow, J., S. L. Swartz , T. C. Ea gle and P . R. Wa de. 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 hemo globin, morphom etric and dietary analyses.

Abstracts. W orld M arine Ma mmal Scie nce Con ference. M onaco. 2 0-24 Jan uary. 

Buckland, S. T., D. R. Anderson, K. P. Burnham and J. L. Laake. 1993. Distance Sampling: estimating abundance of

biological populations. Chapm an & Ha ll, London , 446 pp . 

Caldwell, D. K. and M. C. Caldwell. 1989. Pygmy sperm whale Kogia breviceps (de Blainv ille, 1838): d warf sperm whale

Kogia simus Owen, 1866. Pages 235-260 in: S. H. Ridgway and R. Harrison (eds), Handbook of marine

mamma ls, Vol. 4: Rive r dolphins a nd the larger toothed w hales. Academ ic Press, San Dieg o. 

Cramer, J. 1994. La rge pelagic logboo k newsletter - 19 93. NO AA Te ch. Mem . NMF S-SEFSC-352, 1 9 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 cetacean s along the co ntinental slope of the north-ce ntral and western Gulf of M exico. Mar.

Mam mal. 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. D avis and G .S. Fargion ( eds). Distrib ution and ab undance of marine mammals in the north-central and
291

western Gulf of Mexico: Final Report. Volume II: Technical Report. OCS Study MMS 9 6-0027. Prepared by the

Texas Institute of Oce anograp hy and the N ational M arine Fisherie s Service. U .S. Dept. o f the Interior, M inerals

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. 19 97. Distrib ution of cetac eans in the no rthern Gulf o f 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

Coop erative Fish & Wildlife Research U nit, Colorad o State U niversity, Ft. Collins, C olorado , 72 pp. 

Mullin, K., W. Hoggard, C. Rod en, 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, M inerals

Manag ement Ser vice, Gulf of M exico OC S Region al Office, Ne w Orleans, Louisiana 1 08 pp. 

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

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 surve y ships and airc raft. Aquat. Mammals, 24:41-50.
292

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 no rthern Gulf o f Mexico occur prim arily along the co ntinental shelf edge

and over the deeper waters off the continental shelf (Mullin et al. 1991; South east Fisheries Science Center, SEFSC,

unpublished data). Pygmy sperm wh ales and dwarf sperm w hales (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 M exico in waters 1000 m deep, on avera ge (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 pe lagic

distribution than pygmy sperm whales, and/or dive deeper during feeding bouts. There is no information on stock

differentiation. 

POPU LATIO N SIZE

Estimates of abunda nce 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 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 (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 E conomic

Zone. The seasona l GulfCet ae rial surveys included o nly a small portion of the spe cies’ range an d therefore , these data

were not used to estimate population size. Estimated abundan ce 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-we ighted estima ted abund ance 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 Po pulation Estimate

A minimum p opulation e stimate 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 M AXIMUM NET PRODUCTIVITY RATES

Current and maximum net productivity rates are not known for this stock. The maximum net produ ctivity 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

produc tivity 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.

ANNUAL HUMAN-CAUSED MORTALITY AND SERIOUS INJURY
293

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 p ygmy sperm whales in the northern Gulf of Mexico during 1987-

Octo ber 1998 which have been classified as likely caused by fishery interactions, but there have been stranding

investigation reports of pygmy spe rm whales wh ich may have died as a res ult of other human-related causes. Stranding

data probab ly underestima te the extent of fishe ry-related mo rtality and seriou s injury becau se not all of the marine

mamma ls which die or are seriously injured may wash ash ore, 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, tuna s, and billfish are the targets of the lon gline fishery ope rating 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 se ts 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 re ports of mo rtality or serious inj ury of pygmy sp erm whales by this fishery. 

Pair trawl fishing gear has the potential to capture marine m ammals, 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 d ata available as to the extent o f this fishery in the Gulf of Mexico. It is assumed that it is very limited

in scope an d duration . 

Other M ortality

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, unpublishe d data). An other anima l stranded ap parently due to injuries inflicted by impact, possibly with a v essel.

STATUS OF STOCK

The status of this stock relative to OSP is unknown and there are insufficient data to determine po pulation 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 seriou s injury rate. Th e total level of fisher y-related mo rtality and seriou s injury is

unknown , but it is believed to be insignifican t.

REFERENCES

Barlow, J., S.L. Swartz, T.C. Eagle, and P.R. Wade. 1995. U.S. Marine Mammal Stock Ass essments: 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 hemo globin, morphom etric and dietary analyses.

Abstract. W orld M arine Ma mmal Scie nce Con ference. M onaco. 2 0-24 Jan uary.

Buckland, S. T., D. R. Anderson, K. P. Burnham and J. L. Laake. 1993. Distance Sampling: estimating abundance of

biologica l populatio ns. Chap man & H all, London , 446 pp . 

Caldwell, D. K. and M. C. Caldwell 1989. Pygmy sperm whale Kogia breviceps (de Blainv ille, 1838): d warf sperm whale

Kogia simus Owen, 1866. Pages 235-260 in: S. H. Ridgway and R. Harrison (eds), Handbook of marine

mamma ls, Vol. 4: Riv er dolphin s and the large r toothed w hales. Academ ic Press, San Dieg o. 

Cramer, J. 1994. Large pelag ic logboo k newsletter - 19 93. NO AA Te ch. Mem . NMF S-SEFSC-352, 1 9 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 ceta ceans alon g the continen tal slope of the n orth-central an d western G ulf of Mexic o. 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. D avis and G .S. Fargion ( eds). Distrib ution and ab undance of marine mammals in the north-central and
294

western Gulf of Mexico: Final Report. Volume II: Technical Report. OCS Study MMS 9 6-0027. Prepared by the

Texas Institute of Oce anograp hy and the N ational M arine Fisherie s Service. U .S. Dept. o f the Interior, M inerals

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. 19 93. DIST ANCE user’s guide, V2.0. Colorado

Coop erative Fish & Wildlife Research U nit, Colorad o State U niversity, Ft. Collins, C olorado , 72 pp. 

Mullin, K., W. Hoggar d, C. Rod en, R. Loh oefener, C. Rogers an d B. Taggart. 199 1. Cetaceans on the upper continental

slope in the north-central Gulf of Mexico. OCS Study/MM S 91-0027. U.S. Dept. of the Interior, Minerals

Manag ement Ser vice, Gulf of M exico OC S Region al Office, Ne w Orleans, Louisiana 1 08 pp. 

Tarpley, R. J., and S. Marwitz. 1993. Plastic debris ingestion by cetaceans along the Texas co ast: two case stud ies. Aqua t.

Mam mals, 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 surve y ships and airc raft. Aqua t. Mam mals, 24:41-50.
295

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 wate rs (Perryma n 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-head ed whales and pygm y killer whales (Feresa a ttenuata ) are difficult to distinguish

and sightings of either species are often categorized a s pygmy killer/melon-headed w hales. 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 p reparation ). There is no information o n stock differen tiation for the Atla ntic popula tion. 

POPU LATIO N SIZE

Seasonal aerial survey data were insufficient for estimating abundance. Estimates of abundance were derived

through the application of distance sampling ana lysis (Bucklan d et al. 1993) and the computer program D ISTANCE (Laake

et al. 1993) to sighting data collected during 1991-1994 spring-summer, visual sampling, line-transect vessel surveys of

the northern G ulf of Mexic o (Hanse n 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 iso bath

along the U.S. coast to the seaward extent of the U.S. Exclusive Economic Zone. The se asonal G ulfCet aerial surv eys

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 (C V) 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 Po pulation 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 w hales.

Current Population Trend

No trend was identified in the annual abundance estimates; however, the 1994 estimate was more than ten times

larger than the 199 3 estimate an d 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 relative to population siz e

(Hansen et al. 1995), or by inter-annual variation in distribution patterns or spatial sampling patterns, rather than changes

in populatio n size. 
296

CURRENT AND M AXIMUM NET PRODUCTIVITY RATES

Current and maxim um net pro ductivity rates are not known ; therefore, the d efault maximum net prod uctivity rate

of 0.04 (A non. 199 4) was used for purpo ses 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 th e status of the stoc k relative to O SP is unkno wn. PBR for this stock is 29 melon-hea ded wha les. 

ANNUAL HUMAN-CAUSED MORTALITY AND SERIOUS INJURY

There has historically been some take of this species in small cetacean fisheries in the Ca ribbean (C aldwell et al.

1976); however, the level of past o r current, direc t, human-cau sed morta lity of melon-hea ded wha les in the northern Gulf

of Mexico is unknown. A vailable information in dicates 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-rela ted causes. S tranding da ta probab ly

underestimate the extent of fishery-related mortality and serious injury because not all of the ma rine mamm als which die

or are seriously inju red may wa sh ashore, no r will all of those that d o wash asho re 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 pub lic 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 re ports of mo rtality or serious inj ury to melon -headed w hales 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 M exico. 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 an d duration . 

STATUS OF STOCK

The status of this stock relative to OSP is unknown. This species is not listed under the Endang ered Sp ecies Act.

There a re insufficient data to determine population trends. The total level of fishery-related mortality and serious injury

is unknown, b ut it is believed to be insignificant re lative to PBR; therefore , this is not a strategic sto ck. 

REFERENCES

Anon. 1994. Report o f the PBR (Potential B iological Re moval) wo rkshop. Ju ne 27-29 , 1994. NOAA , NMFS Southwest

Fisheries Sc ience Cen ter, La Jolla, California, 13 p p. + App endices. 

Buckland, S. T., D. R. Anderson, K. P. Burnham and J. L. Laake. 1993. Distance Sampling: estimating abundance of

biologica l populatio ns. Chapm an & Ha ll, London , 446 pp . 

Caldwell, D. K., M. C. Caldwell and R. V. W alker. 1976. First records for Fraser's dolphin (Lagenodelphis hosei) in the

Atlantic and the melon-headed whale (Pepono cephala electra ) in the western A tlantic. Cetolog y 25: 1-4. 

Cramer, J. 1994. Large pelag ic logboo k newsletter - 19 93. NO AA Te ch. Mem . NMF S-SEFSC-352, 1 9 pp. 

Davis, R., G. Scott, B. Würsig, W. Evans, G. Fargion, L. Hansen, K. Mullin, N. May, T. Leming, B. M ate, J. Norris and

T. Jefferso n. In prepa ration. Distribution and abundance of marine mammals in the north-central and western
297

Gulf of M exico: 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 . DIST ANCE user’s guide, V2.0. Colorado Cooperative

Fish & W ildlife Researc h Unit, Co lorado S tate University, Ft. Collins, Co lorado, 7 2 pp. 

Mullin, K. D., T. A. Jefferson, L. J. Hansen and W. Hoggard. 1994. First sightings of melon-headed whales

(Pepono cephala electra ) in the Gulf of M exico. M ar. Mam . Sci. 10(3): 342-34 8. 
298

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 F isheries Science Center, S EFSC, 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 (SE FSC, unpublish ed data). There is no information on stock

differentiation fo r the Atlantic po pulation. 

POPU LATIO N SIZE

Seasonal aerial survey data were insufficient for abundance estimation. Estimates of abundance were derived

through the application of distance sampling ana lysis (Bucklan d et al. 1993) and the computer program D ISTANCE (Laake

et al. 1993) to sighting data collected during 1991-1994 spring-summer, visual sampling, line-transect vessel surveys of

the northern G ulf of Mexic o (Hanse n 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 iso bath

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 abundan ce estim ation.

Estimated abundan ce 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 abu nda nce of Risso 's

dolphins estimated for all surveys

combined was 2,749 (CV = 0.27)

(Hansen et al. 1995 ). 

Minimum Po pulation Estimate

The minimum p opulation siz e was estimate d from the a verage ab undance 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 lognormal distributed a bundanc e estimate as specified by NMFS (Anon. 1994). The minimum population estimate is 2,199

Risso’s do lphins. 

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 log-normal 95%

confidence intervals. The apparent differences in abundance estimates may have been caused by lower sampling effort

during 1991 (Hansen et al. 1995) or by inter-annual variation in distribution patterns or spatial sampling patterns, rather

than change s in populatio n size. 

CURRENT AND M AXIMUM NET PRODUCTIVITY RATES
299

Current and maximum net productivity rates for this stock are not known; t herefore, the default maximum net

produc tivity rate of 0.04 (Anon. 19 94) was use d for purp oses 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 th e status of the stoc k relative to O SP is unkno wn. PBR for this stock is 22 Risso’s dolp hins. 

ANNUAL HUMAN-CAUSED MORTALITY AND SERIOUS INJURY

The leve l of past or current, direct, human-c aus ed morta lity o f Risso's dolphins in the northern Gulf of Mexico

is unknown. T his species ha s been taken in the U.S. lon gline sword fish/tuna fishery in the northern Gulf of Mexico and

in the U.S. Atla ntic (Lee et al. 1994). Estimated average annual fishery-related mortality and serious injury attributab le

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 interactio ns or other h uman-related causes. Stran ding data p robably

underestimate the extent of fishery-related mortality and serious injury because not all of the marine mammals wh ich 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 m ortality and serio us injury rate. T his

determination cannot be made for specific fisheries until the implementing regulations for Section 118 of the MMPA have

been revie wed by the p ublic and fina lized. 

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 fo r the Gulf of M exico pela gic fishery, including OCS edge,

continental slope, and Me xican territorial waters, based on mandatory logbook reporting, was 4,400 sets in 1991, 4,850

sets in 1992, a nd 3,26 0 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 un known (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 seriou s injury to Risso ’s dolphins (C V in pare ntheses) in the Gulf of M exico in 1992 w as 24 (0.1 9), 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 o f Mexico during 19 92-199 3 was 19 Risso’s dolp hins annually (C V = 0.2 0). 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. T his fishery has not been observed by NMF S observers, and there are no other

data available as to the extent of this fisher y in the Gulf of M exico. 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 pop ulation trends. This is not a strategic stock because fishe ry-related mo rtality

and serious injury does not exceed PBR; however, fishery-related mortality and serious injury is very close to PBR and

requires clo se monitorin g. 

REFERENCES
300

Anon. 1994. Report of the PBR (Potential Biological Removal) workshop. June 27-29, 19 94. NOA A, NMF S Southwest

Fisheries Sc ience Cen ter, La Jolla, California, 13 p p. + App endices. 

Buckland, S. T., D. R. Anderson, K. P. Burnham and J. L. Laake. 1993. Distance Sampling: estimating abundance of

biologica l populatio ns. Chapm an & Ha ll, London , 446 pp . 

Cramer, J. 1994. Large pelag ic logboo k newsletter - 19 93. NO AA Te ch. Mem . NMF S-SEFSC-352, 1 9 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 & W ildlife Researc h Unit, Co lorado S tate University, Ft. Collins, Co lorado, 7 2 pp. 

Leatherwood, S. and R. R. Reeves. 1 983. The Sierra Club handb ook of wh ales and do lphins. Sierra Club Boo ks, San

Francisco , 302 pp . 

Mullin, K., W. H oggard, C. Roden, R . Lohoefen er, C. Rog ers and B. Taggart. 1991. Cetaceans on the upper continental

slope in the north-central Gulf o f Mexico . OCS S tudy/MM S 91-00 27. U.S. D ept. of the Interio r, Minera ls

Manag ement Ser vice, Gulf of M exico OC S Region al Office, Ne w Orleans, Louisiana, 1 08 pp. 
301

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). S ightings of these a nimals in the northern Gulf of M exico occ ur primarily alo ng the contine ntal 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 (D avis et al., in prep aration). There is no information on stock differentia tion for the Atlan tic populatio n. 

POPU LATIO N 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, 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 ae rial surveys

included only a small portion of

the stock range, so tho se data were

not used for abundance estimation.

Estimated abundance of shortfinned pilot whales by survey year

[coefficient of variation (C V) 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 Po pulation 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 p opulation e stimate 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 log-normal distributed abundance estimate

as specified b y NMF S (Anon . 1994). T he minimum populatio n estimate is 18 6 pilot whale s. 

Current Population Trend

The annual abundance estimates were not significantly different using the criteria of no overlap of log-normal 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 p atterns or spa tial sampling p atterns, rather tha n changes in p opulation siz e. 

CURRENT AND M AXIMUM NET PRODUCTIVITY RATES

Current and maximum net productivity rates are not known for this stock; therefore, the default maximum net

produc tivity rate of 0.04 (Anon. 19 94) was use d for purp oses of this assessment. 

POTENTIAL BIOLOGICAL REMOVAL
302

Potential biological removal level (PBR) was specified as the produc t of the minimum populatio n size, one ha lf

the maximum net produ ctivity rate, and a re covery 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 th e status of the stoc k relative to O SP is unkno wn. PBR for this stock is 1.9 short-finned p ilot whales. 

ANNUAL HUMAN-CAUSED MORTALITY AND SERIOUS INJURY

The level of past or curre nt, direct, huma n-caused m ortality 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 lo gbook re port of a fisher y-related mo rtality or serious injury in the northern Gulf of Mexico

(NMFS unpublished data); however, fishery-related mortality or serious injur y has not bee n observe d. Total kn own fisheryrelated mortality or serious injury is estimated to be 0.3 short-finned pilot whales per year based upon the lo gbook re port.

There were no d ocumen ted stranding s of short-finned pilot whales in the northern G ulf of Mexico during 1987-

1994 which were classified as likely caused by fishery interactions or other hum an-related ca uses. Stranding d ata proba bly

underestimate the extent of fishery-related mortality and serious injury because not all of the marine mamma ls 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, c annot be c onsidered insignificant and a pproac hing zero m ortality and serio us injury rate. This

determination cannot be made for specific fisheries until the implementing regulations for Section 118 of the MMPA have

been revie wed by the p ublic and fina lized. 

Fisheries Information

Pelagic swordfish, tuna s, 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 M exico (SE FSC, unp ublished log book d ata), but have not been o bserved b y NMF S 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 o bserved, in 1992-1 993. There was on e logboo k report o f 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 kno wn fisheryrelated mortality or serious injury is estimated to be 0.3 sho rt-finned pilot wh ales per year based up on the logb ook rep ort.

Pair trawl fishing gear h as the poten tial to capture marine mammals, but there have been no reports of mortality

or serious injury to marine mammals in the Gulf of M exico. Th is fishery has not been observed by NMFS observers, and

there are no other d ata available as to the extent o f this fishery in the Gulf of Mexico. It is assumed that it is very limited

in scope an d 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 E ndangere d Specie s Act. The total level of estimated fishery-relate d 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.

REFERENCES

Anon. 1994. Report of the PBR (Potential Biological Re moval) workshop . June 27-29, 199 4. NOAA , NMFS Southwest

Fisheries Sc ience Cen ter, La Jolla, California, 13 p p. + App endices. 

Buckland, S. T., D. R. Anderson, K. P. Burnham and J. L. Laake. 1993. Distance Sampling: estimating abundance of

biologica l populatio ns. Chapm an & Ha ll, London , 446 pp . 

Cramer, J. 1994. Large pelag ic logboo k newsletter - 19 93. NO AA Te ch. Mem . NMF S-SEFSC-352, 1 9 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
303

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 & W ildlife Researc h Unit, Co lorado S tate University, Ft. Collins, Co lorado, 7 2 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. J udge. 19 94. SEF SC pelag ic

longline ob server pro gram data summary fo r 1992-1 993. N OAA T ech. Mem. NM FS-SEF SC-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/MM S 91-00 27. U.S. D ept. of the Interio r, Minera ls

Manag ement Ser vice, Gulf of M exico OC S Region al Office, Ne w Orleans, Louisiana, 1 08 pp. 
304

INDEX

Agricultural ru noff ........................ 244

Antilles ......................... 157, 161, 228

Arctic .......... 6, 16, 31, 140, 151, 154, 174, 210

Atlantic spo tted dolph in .... 3, 4, 183, 184, 186, 187,

189, 193, 262, 264

Balaen optera a cutorostra ta ............ 34, 41, 45

Balaen optera b orealis ................. 164, 166

Balaenoptera musculus ................... 31-33

Barataria Bay ............................ 255

Basque whalers ............................. 7

Bay Boudreau ............................ 255

Bay of Fundy . . 3, 6, 7, 10-12, 15, 22, 24, 27, 29, 35-

37, 40, 45, 47, 51, 54, 58, 61, 68, 75,

80, 83, 89, 94-96, 100, 103, 106,

113, 124-127, 130, 131, 133, 135-

140, 142, 143, 145, 148, 175, 178,

179, 181, 184, 187, 189, 193, 196,

199

billfish . 216, 219, 222, 225, 228, 231, 234, 237, 240,

263, 266, 269, 272, 275, 278, 281,

284, 287, 290, 293, 296, 299, 302,

305

Blainville’s be aked wha le .......... 57, 64, 65, 230

blue runners ......................... 248, 252

blue whale ........................... 2, 31-33

Bonsecour Bay ........................... 255

bottlenose dolphin .... 3, 4, 114-122, 204-209, 236,

238, 239, 241-251, 253-261, 264

Brevortia tyrannus ........................ 118

Bryde’s wh ale ...................... 3, 224, 225

Calcasieu Lake ........................... 255

Canada . . 5, 11, 12, 22, 28, 31, 32, 40, 44, 45, 47, 50-

52, 58, 65, 71, 80, 81, 83, 89, 90, 92,

100, 101, 103, 110, 112, 113, 124,

130, 132, 133, 135, 137-140, 142,

144-148, 150-153, 155, 164, 165,

170, 175, 198, 199, 210-214

Canadian Ea st Coast ............. 2, 34, 36, 42, 43

Canadian fisheries ................. 40, 101, 130

Cape Cod Bay ........... 7, 10, 13, 23, 42, 43, 60

Cape Hatteras . . 11, 19, 20, 26, 35, 38, 46, 47, 49, 50,

53, 56, 61, 63, 67, 69, 70, 74, 75, 77-

80, 85, 87-89, 95, 97, 105, 108-110,

114-117, 119, 120, 127, 141, 147,

153, 164, 165, 168, 172, 175-177,

179, 180, 183, 185, 186, 189, 191,

192, 195, 197, 202, 204, 206, 212

Chesapeake Bay ...................... 134, 183

chlorinated hydrocarbons ........ 84, 120, 244, 259

cigarfish ............................ 248, 252

Clearwater Harbor ........................ 255

clymene do lphin .................... 4, 277, 279

coastal gillnet . . 39, 41, 42, 49, 56, 63, 69, 71, 77, 80,

81, 89, 91, 97, 98, 100, 108, 109,

111, 118, 121, 127, 129, 132, 134,

139, 142, 143, 153, 185, 191, 212,

251

cod traps . . 11, 19, 40, 80, 89, 90, 143, 148, 154, 181,

212

commo n dolphin ..................... 3, 105-112

Compano Bay ............................ 255

Connecticut ........... 39, 98, 118, 129, 135, 213

contamina nts . . 8, 82, 83, 92, 115, 120, 122, 124, 139,

243-245, 248, 249, 252, 260

Crystal Bay .............................. 255

Cystoph ora cristata ........... 156, 210, 213, 214

DDE ................. 81, 92, 242, 244, 248, 252

DDT ......................... 81, 92, 242, 248

Delaware . . 15, 21, 39, 44, 46, 51, 57, 65, 71, 77, 82,

87, 98, 101, 102, 112, 117, 120, 135,

172, 179

Delphin us delph is .................. 105, 111-113

drift gillnet . 10, 11, 19, 20, 24, 37-39, 45, 49-51, 56-

58, 63-65, 69, 70, 72, 77, 78, 83, 87,

93, 97, 98, 100, 103, 108, 112, 127-

129, 133, 137, 153, 168-170, 172,

175, 177, 179, 185-187, 191-193,

197-199, 202, 203, 206, 208, 209,

212

dwarf sperm whale .... 2, 4, 167, 169, 170, 173, 218,

219, 222, 292, 293, 296

East Bay ................................ 255

ecotype ..... 114, 117, 170, 173, 204, 219, 222, 236,

239, 242, 246, 250, 293, 296

entanglement . 4, 9-11, 18, 19, 21, 25, 28, 37-39, 41-

43, 101, 119, 120, 122, 129, 133,

134, 141, 144, 149, 158, 165, 172,

176, 216, 219, 222, 225, 228, 231,

234, 243, 244, 247, 248, 251, 252,

257, 260, 263, 266, 269, 272, 275,

278, 281, 284, 287, 290, 293, 296,

299, 302, 305

epidemic ........................ 245, 248, 259

Erysipelas spp. ................... 244, 248, 252

estuaries ................. 114, 115, 253-255, 257

Euba laena g lacialis ................... 6, 13, 14

false killer whale ....................... 4, 286

Feresa a ttenuata .......... 176, 177, 289-291, 298

fin whale .......................... 2, 26-29, 32

foreign fishing .... 40, 69, 77, 80, 82, 86, 90, 92, 97,

101, 107, 130, 165, 180, 185, 191,

197, 205

Fraser’s do lphin ........................ 4, 280
305

Georges Bank ... 6, 12, 16, 17, 19-21, 25, 27, 34-38,

46-48, 50, 53-56, 60-63, 67, 68, 70,

74-76, 78, 79, 87, 89, 94-97, 103,

105, 106, 108, 124, 125, 127, 164,

168, 178, 182, 183, 185, 189, 191,

195, 197, 202, 204, 206

Georgia ..... 6, 10, 28, 116, 118, 120, 144, 157, 158

Gervais’ b eaked wh ale ............. 3, 57, 64, 233

gillnet ... 9-11, 13, 14, 19, 20, 22, 24, 37-42, 45, 49-

51, 56-58, 63-66, 69-72, 77, 78, 80,

81, 83, 87, 89, 91, 93, 97, 98, 100,

102-104, 108, 109, 111, 112, 118,

119, 121, 122, 127-139, 141-145,

148-150, 153-156, 168-170, 172,

174, 175, 177, 179, 181, 182, 185-

187, 191-193, 197-199, 201-203,

206, 208, 209, 212-214, 244, 247,

248, 251, 258

Globicephala macrorhynchus ............ 85, 304

Globicephala melas ......... 74, 77, 83, 85, 87, 93

Grampus griseus ................... 67, 71, 301

gray seal ........................... 3, 144-150

Great South Channel .... 6, 8, 10, 13, 14, 20, 21, 78,

79, 87, 89, 164

Greenland .... 5, 6, 15, 31, 34, 49, 74, 80, 89, 90, 94,

100, 124, 125, 140, 142, 148, 151,

152, 154, 178, 180, 210

groundfish .... 11, 19, 40, 80, 89, 90, 100, 127, 129-

132, 141-143, 148, 153, 154, 181,

212

Gulf of Maine ... 2-4, 6, 10, 11, 15-20, 23-25, 27, 29,

33, 35-39, 45, 47, 51, 54, 58, 61, 65,

67, 68, 72, 74, 75, 83, 93-97, 99,

103, 105, 106, 109, 112, 113, 124-

129, 136-139, 141, 142, 144, 148,

150, 153, 155, 164, 166, 170, 173,

174, 180, 182, 184, 187, 189, 190,

193, 196, 199, 209, 212, 213

Gulf of Mexico ....... 1, 3, 4, 6, 14, 31, 34, 52, 53,

59, 60, 66, 70-72, 78, 79, 81, 84, 85,

88, 91, 93, 105, 108, 113, 114, 116,

121, 157, 161, 167, 175-177, 183,

186, 189, 192, 193, 195, 199, 201,

203, 204, 206, 215-242, 244-248,

250-306

Gulf Stream . 27, 35, 46-48, 52-54, 58, 60-62, 66-68,

72, 74, 75, 84, 85, 93, 95, 105, 106,

113, 114, 116, 183, 184, 188, 189,

195, 196, 199, 203

Gullivan Bay ............................ 255

gunshot wounds .......... 120, 243, 247, 251, 257

Halichoerus grypus ........... 144, 146, 149, 150

harbor porp oise . . 3, 5, 24, 29, 45, 51, 58, 65, 72, 83,

93, 102, 103, 112, 124-134, 136-

139, 142, 144, 148, 150, 153, 155,

170, 173, 187, 193, 199, 209, 212,

213

harbor seal ................. 3, 137, 140-145, 150

harp seal ........................... 3, 151-156

health assessment ............. 120, 121, 244, 259

herring weirs .... 11, 40, 131-133, 138, 139, 143, 148

hooded seal ......................... 3, 210-214

humpba ck whale .............. 2, 4, 15-20, 23-25

Hyperoodon ampullatus ................ 178, 179

Indian/Banana River ................... 114, 204

Key We st ....................... 239, 250, 255

killer whale ... 2, 4, 174-177, 283, 285, 286, 289-291

Kogia breviceps . . 170, 171, 173, 218, 219, 221, 222,

292, 293, 295, 296

Kogia simus ..... 167, 169, 170, 173, 218, 219, 221,

222, 292, 293, 295, 296

ladyfish ............................. 248, 252

Lagenorhynchus acutus ..... 94, 100, 103, 104, 113

Long Island .............. 38, 39, 50, 52, 115, 140

longline fishery ... 37, 69, 70, 78, 81, 86, 88, 91, 108,

186, 192, 198, 206, 216, 219, 222,

225, 228, 231, 234, 237, 240, 263,

266, 269, 272, 275, 278, 281, 284,

287, 290, 293, 296, 299, 302, 305

long-finned p ilot whale .... 74, 75, 77, 80-83, 85, 87,

90, 91

mackerel ... 16, 23, 69, 77, 80-82, 86, 87, 89, 91, 92,

97, 99, 100, 107, 108, 110, 111, 141,

205-207

Maine ... 2-4, 6, 10, 11, 15-21, 23-25, 27-29, 33, 35-

40, 45, 47, 49-51, 54, 58, 61, 65, 67,

68, 72, 74, 75, 81, 83, 91, 93-97, 99,

101, 103, 105, 106, 109, 112, 113,

124-129, 131, 133-142, 144-151,

153, 155, 156, 164, 166, 170, 173,

174, 180, 182, 184, 187, 189, 190,

193, 196, 199, 209, 210, 212, 213,

254

mark-recapture ........... 16, 17, 25, 46, 151, 155

Maryland . . 14, 47, 48, 54, 55, 61, 62, 68, 75, 76, 85,

101, 106, 119, 120, 134, 135, 149,

167, 169, 171, 184, 190, 196, 204,

205

Massac husetts ... 6, 10, 13, 14, 16, 23, 26, 28, 29, 43,

51, 52, 57, 59, 64, 66, 72, 81-84, 91-

93, 101, 103, 104, 111-113, 119,

128, 129, 134, 135, 137-139, 142,

144-147, 149, 150, 155, 156, 169,

174, 198, 200, 209, 213, 214

Megaptera novaeangliae ............ 15, 23-25, 33
306

melon-hea ded wha le ................. 4, 298, 300

menhaden ........... 118, 244, 248, 251, 252, 257

Mesoplodon bidens ................ 65, 231, 234

Mesop lodon d ensirostris ................ 65, 230

Mesoplodon europaeus .................... 233

Mesoplodon mirus ......................... 60

metals .............. 82, 83, 92, 93, 124, 244, 259

minke whale ................ 2, 34, 36-41, 43-45

morbillivirus ..... 244, 245, 248, 249, 252, 259, 260

mutilation ....... 120, 134, 208, 243, 247, 251, 257

net entanglement ............ 10, 18, 243, 247, 251

New England ... 6, 10, 16, 23, 26, 34, 38, 39, 41, 45,

46, 50, 60, 70, 79, 89, 98, 99, 101-

104, 109, 118, 127, 129, 130, 133,

136, 137, 139, 140, 142-151, 153-

156, 165, 174, 175, 177, 179, 180,

183, 195, 197, 207, 210, 212-214

New Jersey ... 23, 39, 74, 85, 98, 114-116, 118, 120,

124, 134, 135, 140, 144, 145, 151,

155, 172

New York . . 33, 39, 51, 52, 58, 65, 72, 80, 82, 89, 98,

99, 103, 109, 112, 120, 124, 129,

130, 133, 136, 140, 142, 144-146,

149, 153, 155, 156, 172, 179, 187,

193, 199, 208, 213, 233, 261

North Carolina .... 16, 20, 22, 23, 28, 35, 39, 47, 53,

61, 67, 74, 75, 80, 85, 89, 94, 95, 98,

105, 109, 111, 114, 118, 120-122,

124, 129, 133-136, 139, 142, 144,

153, 155, 164, 169, 172, 176, 180,

183, 187, 189, 193, 195, 201, 213

Orcinus orca ................. 174, 175, 283-285

pair trawl . . 11, 19, 24, 45, 49, 51, 56, 58, 65, 69, 70,

72, 77, 78, 82, 83, 87, 92, 93, 103,

108, 112, 137, 138, 153, 170, 172,

175, 177, 179, 185-187, 191-193,

197, 199, 202, 203, 206, 207, 209,

212, 216, 219, 222, 225, 228, 231,

234, 238, 240, 241, 264, 266, 269,

272, 275, 278, 281, 284, 287, 290,

293, 296, 299, 302, 305

pantrop ical spotted d olphin . 3, 4, 183, 189, 190, 192,

193, 265-267

PCBs ............................ 81, 92, 124

Pepono cephala electra ............. 289, 298, 300

Perdido Bay ............................. 255

Phoca groenlandica ............ 151, 154-156, 214

Phoca vitulina ................ 140, 143-145, 150

Phocoena phocoena ........ 124, 132, 133, 137-139

photo-identification . 7, 8, 17, 32, 115, 116, 122, 254,

261, 284

Physeter macrocephalus ... 23, 46, 51, 52, 215, 217

Pine Sound .............................. 255

Plymouth ................................. 7

polychlorin ated biph enyls .......... 81, 84, 92, 93

populatio n growth rate ............. 8, 17, 18, 126

pseudorabies virus .................... 244, 252

Pseudorca crassidens ...................... 286

pygmy killer wh ale ......... 2, 4, 176, 177, 289-291

pygmy spe rm whale ... 2, 4, 170-173, 219, 221, 222,

293, 295, 296

Redfish Bay ............................. 255

right whale ................... 2, 6, 9-11, 13, 14

Risso’s do lphin ................. 4, 67-69, 71, 301

Sabine Lake ............................. 255

salmon gillnets .............. 40, 80, 89, 142, 148

Scotian Sh elf ... 6, 15, 17, 35, 36, 46-48, 52, 54, 55,

61, 62, 67, 68, 75, 76, 95, 96, 105,

106, 112, 150, 164, 199, 204, 209

sei whale ........................... 2, 164-166

shark .................................. . . 64

ship strikes ............ 4, 9, 11, 19, 23, 37, 42, 50

short-finned p ilot whale ... 74, 77, 79, 82, 85-88, 304

sink gillnet .... 13, 20, 37, 39, 41, 45, 49, 56, 63, 69,

77, 87, 97, 98, 100, 102, 103, 108,

109, 111, 118, 119, 127-133, 137-

139, 142-144, 148-150, 153-155,

172, 174, 175, 177, 179, 185, 191,

197, 202, 206, 212, 213

South Carolina . . 57, 64, 70, 79, 81, 88, 91, 109, 116,

118, 122, 123, 144, 158, 186, 192,

201, 206

Sowerb y’s beaked w hale .... 64, 230, 231, 233, 234

sperm wha le .... 2, 4, 46-52, 167, 169-173, 215-219,

221, 222, 292, 293, 295, 296

spinner do lphin ............ 3, 4, 201-203, 271, 273

squid ... 50, 69, 77, 80-83, 86, 87, 89, 91, 92, 97, 99,

100, 107, 108, 110, 111, 205-207,

253

St. Andrew Bay .......................... 255

St. Joseph Bay ........................... 255

Staphylococcus spp. ............... 244, 248, 252

Stellwagen Bank ............. 16, 21, 38, 142, 164

Stenella a ttenuata ............. 189, 193, 265, 267

Stenella clymene .................. 105, 277, 279

Stenella fro ntalis ............. 183, 189, 262, 264

Stenella lo ngirostris ........... 201, 202, 271, 273

Strait of Belle Isle ........................ 7, 31

striped do lphin ............ 3, 4, 195-197, 268, 270

swordfish . . 19, 24, 37, 45, 50, 51, 56, 58, 63, 65, 69,

70, 72, 78, 79, 83, 87, 88, 93, 97,

103, 108, 112, 127, 138, 168, 170,

185, 187, 191, 193, 197, 199, 203,

206, 209, 216, 219, 222, 225, 228,

231, 234, 237, 238, 240, 241, 263,
307

266, 269, 272, 275, 278, 281, 284,

287, 290, 293, 296, 299, 302, 305

Ten Thousand Islands ...................... 255

TerreBonne Bay .......................... 255

thread herring ........................ 248, 252

Trichech us man atus latirostris ........ 157, 159-162

Trichechus manatus manatus ........ 157, 161, 163

Trinity Bay .............................. 255

tunas . . 70, 78, 87, 108, 207, 216, 219, 222, 225, 228,

231, 234, 237, 240, 263, 266, 269,

272, 275, 278, 281, 284, 287, 290,

293, 296, 299, 302, 305

Vermillion Bay ........................... 255

West Bay ............................... 255

West Cote Blanche Bay .................... 255

Whitewater Bay .......................... 255

white-beake d dolph in ................. 2, 180-182

white-sided d olphin ..... 2, 94, 96-99, 103, 104, 182

Ziphius c avirostris ........... 53, 58, 227-230, 233
Publishing in NOAA Technical Memorandum NMFS-NE

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