NOAA TECHNICAL MEMORANDUM

NMFS-NE-153

U.S. ATLANTIC AND GULF OF MEXICO 

MARINE MAMMAL STOCK ASSESSMENTS -- 1999

By

Gordon T. Waring1, Debra L. Palka1, Phillip J. Clapham1,

Steven Swartz2, Marjorie C. Rossman1, Timothy V.N. Cole1,

Larry J. Hansen3, Kathryn D. Bisack1, Keith D. Mullin4,

Randall S. Wells5, Daniel K. Odell6, and Neilo B. Barros6

1

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

2

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

3

 National Marine Fisheries Service, 219 Fort Johnson Road, Charleston, SC 29412

4 National Marine Fisheries Service, PO Drawer 1207, Pascagoula, MS 39568-1207

5

 Mote Marine Laboratory, 1600 Ken Thompson Parkway, Sarasota, FL 34236

6

 SeaWorld Inc., 7007 Sea World Drive, Orlando, FL 32821-8097

U.S. Department of Commerce

National Oceanic and Atmospheric Administration

National Marine Fisheries Service

Northeast Fisheries Science Center

Woods Hole, Massachusetts 02543-1026

October 1999
iii

TABLE OF CONTENTS

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

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

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

TABLE 1. A summary of Atlantic and Gulf of Mexico marine mammal stock assessment reports

for stocks of marine mammals under NMFS authority that occupy waters under U.S.

jurisdiction. ....................................................... 2

NORTH ATLANTIC RIGHT WHALE (Eubalaena glacialis):

Western North Atlantic Stock ............................................... 5

HUMPBACK WHALE (Megaptera novaeangliae):

North Atlantic Stock ..................................................... 14

FIN WHALE (Balaenoptera physalus):

Western North Atlantic Stock .............................................. 25

SEI WHALE (Balaenoptera borealis):

Nova Scotia Stock ....................................................... 30

BLUE WHALE (Balaenoptera musculus):

Western North Atlantic Stock .............................................. 33

MINKE WHALE (Balaenoptera acutorostrata):

Canadian East Coast Stock ................................................ 36

SPERM WHALE (Physeter macrocephalus):

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

DWARF SPERM WHALE (Kogia simus): 

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

PYGMY SPERM WHALE (Kogia breviceps):

Western North Atlantic Stock .............................................. 56

CUVIER'S BEAKED WHALE (Ziphius cavirostris):

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

MESOPLODON BEAKED WHALES (Mesoplodon spp.):

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

RISSO'S DOLPHIN (Grampus griseus):

Western North Atlantic Stock .............................................. 73

LONG-FINNED PILOT WHALE (Globicephala melas):

Western North Atlantic Stock .............................................. 80

SHORT-FINNED PILOT WHALE (Globicephala macrorhynchus): 

Western North Atlantic Stock .............................................. 91

WHITE-SIDED DOLPHIN (Lagenorhynchus acutus):

Western North Atlantic Stock .............................................. 99

COMMON DOLPHIN (Delphinus delphis):

Western North Atlantic Stock ............................................. 107

ATLANTIC SPOTTED DOLPHIN (Stenella frontalis):

Western North Atlantic Stock ............................................. 116

PANTROPICAL SPOTTED DOLPHIN (Stenella attenuata):

Western North Atlantic Stock ............................................. 122

BOTTLENOSE DOLPHIN (Tursiops truncatus):

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

BOTTLENOSE DOLPHIN (Tursiops truncatus):

Western North Atlantic Coastal Stock ....................................... 136

HARBOR PORPOISE (Phocoena phocoena):

Gulf of Maine/Bay of Fundy Stock .......................................... 145

HARBOR SEAL (Phoca vitulina):

Western North Atlantic Stock ............................................. 156

GRAY SEAL (Halichoerus grypus):

Western North Atlantic Stock ............................................. 162
v

HARP SEAL (Phoca groenlandica):

Western North Atlantic Stock ............................................. 166

HOODED SEAL (Cystophora cristata):

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

BOTTLENOSE DOLPHIN (Tursiops truncatus):

Gulf of Mexico Bay, Sound, and Estuarine Stocks .............................. 176

DWARF SPERM WHALE (Kogia simus):

Northern Gulf of Mexico Stock ............................................ 185

PYGMY SPERM WHALE (Kogia breviceps):

Northern Gulf of Mexico Stock ............................................ 188

Appendix I. Observer comments relating to condition of marine mammals observed caught in 1994-

1997 by US pelagic longline vessels operating in the Atlantic. Listing includes unique

trip identifier (TRIP #), date of capture, species taken, latitude (Lat), longitude (Lon),

and comments. ................................................... 191

INDEX .................................................................... 194
vi

ACKNOWLEDGMENTS

The authors wish to thank and acknowledge Janeen Quintal for her technical assistance throughout the preparation of

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

Sampling Investigation, Dana Hartley and Kim Thounhurst (Northeast Regional Office, NER), and Blair Mase, (Southeast

Fisheries Science Center, SEFSC). Also, we acknowledge advice and comments provided by: Richard Merrick and Fred Serchuk

(NEFSC), Cynthia Yeung (SEFSC), Doug Beach (NER), Kathy Wang (Southeast Regional Office), and the Atlantic Scientific

Review Group which included among its members: Donald Baltz, Solange Brault, Joseph DeAlteris, James Gilbert, Robert

Kenney, James Mead, and Andrew Read. We also thank Paul Wade, NMFS Office of Protected Species, for his comments and

guidance at the SRG review meeting.
vii

EXECUTIVE SUMMARY

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

(NMFS) and the U.S. Fish and Wildlife Service (USFWS) were required to generate stock assessment reports (SAR) for all marine

mammal stocks in waters within the U.S. Exclusive Economic Zone (EEZ). The first reports for the Atlantic (includes the Gulf of

Mexico) were published in July 1995 (Blaylock et al. 1995). The MMPA requires NMFS and USFWS to review these reports

annually for strategic stocks of marine mammals and at least every 3 years for stocks determined to be non-strategic. The second

edition of the SARs (1996 assessments) was published in October 1997 and contained all the previous reports, but major revisions

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

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

Atlantic stocks, and updated reports were identified by a 1998 date-stamp (Waring et al. 1999). The current report contains only

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 1999 date-stamp at the beginning of each report. 

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

Center (SEFSC). NMFS staff presented the reports at the November 1998 meeting of the Atlantic Scientific Review Group (ASRG),

and subsequent revisions were based on their contributions and constructive criticism. 

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

have been revised since the 1998 publication. A total of 28 of the 60 Atlantic and Gulf of Mexico stock assessment reports were

revised for 1999. Most proposed changes incorporate new information into mortality estimates. The revised SARs include 14

strategic and 14 non-strategic stocks. Information on human interactions (fishery and ship strikes) between the North Atlantic right

whale, North Atlantic humpback whale, and Canadian east coast minke whale stocks were re-reviewed and updated. The Western

North Atlantic stocks of Atlantic spotted dolphin, pantropical spotted dolphin, and dwarf sperm whale are now considered “nonstrategic” based on 5-year (1993-1997) annual estimates of incidental mortality in commercial fisheries. The Western North Atlantic

stock of long-finned pilot whales was changed to “strategic” based on the annual incidental mortality estimate. Further, the stock

definitions were changed for four Atlantic stocks (Sei whale, gray, harp and hooded seal) based on stock areas definitions used by

international scientific organizations (i.e., IWC, ICES). 

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 U.S. 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 MMPA requires that each SAR contain several items, including: (1) a description of the stock, including its geographic

range; (2) a minimum population estimate, a maximum net productivity rate, and a description of current population trend, including

a description of the information upon which these are based; (3) an estimate of the annual human-caused mortality and serious injury

of the stock, and, for a strategic stock, other factors that may be causing a decline or impeding recovery of the stock, including effects

on marine mammal habitat and prey; (4) a description of the commercial fisheries that interact with the stock, including the estimated

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

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

biological removal (PBR) level for the stock, describing the information used to calculate it. The MMPA also requires that SARs

be updated annually for stocks which are specified as strategic stocks, or for which significant new information is available, and once

every three years for 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 (Waring et al. 1997) and 1998 (Waring et al. 1999) SARs. A 1997 SAR was not

produced.

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

Atlantic Coast and Gulf of Mexico stocks for which significant new information were available. These are identified by the 1999

date-stamp at the top right corner at the beginning of each report. The stock definitions were changed for four Atlantic stocks (Sei

whale, gray, harp and hooded seal) based on stock areas definitions used by international scientific organizations (i.e., IWC, ICES).

Further, the status of three western North Atlantic stocks (Atlantic spotted dolphin, pantropical spotted dolphin, and

dwarf sperm whale) were changed to non-strategic because the 5-year (1993-1997) mean annual mortalities in fishing operations were

below PBR. 

REFERENCES

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

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

Wade, P. R. and R. P. Angliss. 1997. Guidelines for assessing marine mammal stocks: Report of the GAMMS workshop April 3-5,

1996, Seattle, Washington. NOAA Tech. Memo. NMFS-OPR-12, 93 pp.

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

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

Waring, G. T., D. L. Palka, P, J. Clapham, S. Swartz, M. Rossman, T.V.N. Cole, K. D. Bisack, and L. J. Hansen. 1999. U.S.

Atlantic marine mammal stock assessments-1998. NOAA Tech. Memo. NMFS-NE-116, 182 pp.
2

October 1999

TABLE 1. A summary of Atlantic and Gulf of Mexico marine mammal stock assessment reports for stocks of marine mammals

under NMFS authority that occupy waters under U.S. jurisdiction. (A “Y” under the heading “SAR revised” indicates

which 1999 stock assessment reports have been revised relative to the 1998 reports.)

Species Stock

Area

SRG

Region

NMFS

Center Nmin Rmax Fr PBR

Total

Annual

Mort.

Annua

l

Fish.

Mort.

Strategic

Status

SAR

Revised

Harbor seal Western

North

Atlantic

ATL NEC 30,990 0.12 1.0 1,859 943 943 N Y

Gray seal Western

North

Atlantic

ATL NEC NA NA NA NA 67 67 N Y

Harp seal Western

North

Atlantic

ATL NEC N/A N/A N/A N/A 383 383 N Y

Hooded seal Western

North

Atlantic

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

Harbor porpoise Gulf of

Maine/Bay

of Fundy

ATL NEC 48,289 0.04 0.5 483 1,850 1,850 Y Y

Risso's dolphin Western

North

Atlantic

ATL NEC 11,140 0.04 0.48 107 7.4 7.4 N Y

Atlantic whitesided dolphinWestern

North

Atlantic

ATL NEC 19,196 0.04 0.48 184 287 287 Y Y

White-beaked

dolphin

Western

North

Atlantic

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

Common

dolphin

Western

North

Atlantic

ATL NEC 16,060 0.04 0.48 154 780 780 Y Y

Atlantic spotted

dolphin

Western

North

Atlantic

ATL NEC 1,6171 0.04 0.5 16 9.92 9.92 N Y

Pantropical

spotted dolphin

Western

North

Atlantic

ATL NEC 1,6171 0.04 0.5 16 9.92 9.92 N Y

Striped dolphin Western

North

Atlantic

ATL NEC 18,220 0.04 0.5 182 11 11 N N
Species Stock

Area

SRG

Region

NMFS

Center Nmin Rmax Fr PBR

Total

Annual

Mort.

Annua

l

Fish.

Mort.

Strategic

Status

SAR

Revised

3

Spinner dolphin Western

North

Atlantic

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

Bottlenose

dolphin

Western

North

Atlantic,

offshore

ATL NEC 8,7943 0.04 0.5 88 10 10 N Y

Bottlenose

dolphin

Western

North

Atlantic,

coastal

ATL SEC 2,482 0.04 0.5 25 29 29 Y Y

Dwarf sperm

whale

Western

North

Atlantic

ATL SEC N/A 0.04 N/A N/A 0.20 0.20 N Y

Pygmy sperm

whale

Western

North

Atlantic

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

Killer whale Western

North

Atlantic

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

Pygmy killer

whale

Western

North

Atlantic

ATL SEC 6 0.04 0.5 0.1 0.00 0.00 N N

Northern

bottlenose whale

Western

North

Atlantic 

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

Cuvier's beaked

whale

Western

North

Atlantic

ATL NEC 8954 0.04 0.5 8.9 9.7 9.75 Y Y

Mesoplodon 

beaked whale

Western

North

Atlantic

ATL NEC 8954 0.04 0.5 8.9 9.7 9.75 Y Y

Pilot whale,

long-finned

(Globicephala

sp.)

Western

North

Atlantic

ATL NEC 4,9686 0.04 0.45 45 40 407 N Y

Pilot whale,

short-finned

Western

North

Atlantic

ATL NEC 457 0.04 0.45 4.4 40 407 Y Y

Sperm whale North

Atlantic

ATL NEC 1,617 0.04 0.1 3.2 0.00 0.00 Y Y

North Atlantic

right whale

Western

North

Atlantic

ATL NEC 295 0.025 0.1 0.4 2.0 1.08 Y Y
Species Stock

Area

SRG

Region

NMFS

Center Nmin Rmax Fr PBR

Total

Annual

Mort.

Annua

l

Fish.

Mort.

Strategic

Status

SAR

Revised

4

Humpback whale Western

North

Atlantic

ATL NEC 10,019 0.065 0.1 32.6 4.4 3.29 Y Y

Fin whale Western

North

Atlantic

ATL NEC 1,803 0.04 0.1 3.6 0.6 0.20 Y Y

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

Minke whale Canadian

east coast

ATL NEC 2,145 0.04 0.5 21 5.8 4.8 N Y

Blue whale Western

North

Atlantic

ATL NEC 308 0.04 0.1 0.6 0.00 0.00 Y Y

Bottlenose

dolphin

Gulf of

Mexico

bay, sound,

and

estuarine

ATL SEC 3,933 0.04 0.5 39.7 N/A N/A Y Y

Dwarf sperm

whale

Northern

Gulf of

Mexico

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

Pygmy sperm

whale

Northern

Gulf of

Mexico

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

1. This value includes either or both of Stenella frontalis or Stenella attenuata.

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

Atlantic and Pantropical spotted dolphins.

3. Estimates may include sightings of the coastal form.

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

5. This is the average mortality of beaked whales (Mesoplodon spp.) based on 5 years of observer data. This annual mortality rate includes an

unknown number of Cuvier’s beaked whales.

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

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

long-finned and short-finned pilot whales. 

8. This is the average mortality of right whales based on 5 years of observer data (0.0) and additional fishery impact records (1.0).

9. This is the average mortality of humpback whales based on 5 years of observer data (0.6) and additional fishery impact records (2.6).
5

October 1999

NORTH ATLANTIC RIGHT WHALE (Eubalaena glacialis):

Western North Atlantic 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, nursery, and presumed mating 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, indicating an extended range for at least some individuals and perhaps

the existence of important habitat areas not presently well described. Likewise, a calving and wintering ground has been described

for coastal waters of the southeastern USA; sightings from the Gulf of Mexico (Moore and Clark 1963; Schmidly et al. 1972), are

either geographic anomalies or indicate a more extensive historic range. Whichever the case, 85% of the population is unaccounted

for during the winter. A small offshore survey effort in February 1996 reported three sightings in waters east of northeastern Florida

and southeastern Georgia: a mother/calf pair, a single individual, and a group of four juveniles. These sightings suggest a distribution

further offshore than previously reported.

Research results to date suggest five major habitats or congregation areas (southeastern United States coastal waters, Great

South Channel, Cape Cod Bay, Bay of Fundy, and Scotian Shelf) for western North Atlantic right whales. However, movements

within and between habitats may be more extensive than sometimes thought. Results from a few successfully attached satellite

telemetry tags suggest that sightings separated by perhaps two weeks should not 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 cast new light on movements and habitat use, and raise questions about the

purpose or strategies for such excursions. 

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

of the genera Calanus and Pseudocalanus) in this area. Research suggests that right whales must locate and exploit extremely

dense patches of zooplankton to feed efficiently. These dense zooplankton patches are likely a primary characteristic of the spring,

summer, and fall right whale habitat (Kenney et al. 1986). Acceptable surface copepod resources are limited to perhaps 3% of the

region during the peak feeding season in Cape Cod and Massachusetts Bays (Mayo and Goldman, pers. comm.). While feeding in

the coastal waters off Massachusetts has been better studied, feeding by right whales has been observed elsewhere over Georges Bank,

in the Gulf of Maine, in the Bay of Fundy, and over the Scotian Shelf. The characteristics of acceptable prey distribution in these

areas are not well known. New England waters also serve as a nursery for calves and, in some cases, for mating. 

Genetic analyses of tissue samples are providing insights into stock definition. Schaeff et al. (1993) used Restriction

Fragment Length Polymorphism (RFLP) analysis to suggest that western North Atlantic right whales represent a single breeding

population that may be based on as few as three matrilines. However, more recent analyses based upon direct sequencing of

mitochondrial DNA (mtDNA) have identified five mtDNA haplotypes (Malik, 1997). Schaeff et al. (1997) compared the genetic

variability of northern and southern (E. australis) right whales, and found the former to be significantly less diverse. They suggested

that this 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 specimens of

baleen and bone, is also underway (Rosenbaum et al. 1997). Preliminary results suggest that the eastern and western North Atlantic

populations were not genetically distinct (Rosenbaum et al., submitted). However, the virtual extirpation of the eastern stock and

its lack of recovery this century strongly suggests population subdivision over a protracted (but not evolutionary) timescale.

To date, skin biopsy sampling has resulted in the compilation of a DNA library of more than 200 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 reproductive 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 photoidentified and catalogued population (through December of 1995) is 137 females and 132 males (1.04:1), not significantly different

from parity (P<0.001) (M.W. Brown, pers. comm.). Analyses based on sighting histories of photographically identified individuals

also suggest that, in addition to the Bay of Fundy, there exists an additional and undescribed summer nursery area utilized by

approximately one-third of the population. As described above, a related question is where individuals other than calving females
6

and a few juveniles overwinter. One or more additional wintering and summering grounds may exist in unsurveyed locations, although

it is also possible that “missing” animals simply disperse over a wide area at these times.

POPULATION SIZE

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

population size was estimated to be 295 individuals in 1992 (Knowlton et al. 1994). Because this was a nearly complete census,

it is assumed that this represents a minimum population size estimate. However, no estimate of abundance with an associated

coefficient of variation has been calculated for this population and its status remains uncertain (IWC 1998). Calculation of a reliable

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

Historical Population Estimate

An estimate of pre-exploitation population size is not available. Basque whalers may have taken as many as 200 right

whales a year at times during the 1500s in the Strait of Belle Isle region, 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 eastern USA lasted three centuries, and the records include one report of 29 whales

killed in Cape Cod Bay in a single day during January 1700. Based on incomplete historical whaling data, these authors could only

conclude that there were at least some hundreds of right whales present in the western North Atlantic during the late 1600s. In a later

study (Reeves et al. 1992), a series of population trajectories using historical data and an estimated present population size of 350

were plotted. The results suggest that there may have been at least 1,000 right whales in this population during the early to mid1600s, with the greatest population decline occurring in the early 1700s. The authors cautioned, however, that the record of removals

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

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

whales came into effect in 1935 (Hain 1975; Reeves et al. 1992; Kenney et al. 1995).

Minimum Population Estimate

The western North Atlantic population size was estimated to be 295 individuals in 1992 (Knowlton et al. 1994), based

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

whales that had not been seen for an extended period of time and therefore might be dead, was addressed by assuming that an

individual whale not sighted for five 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 1992 may have been higher if: 1) there

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

Current Population Trend

The population growth rate reported for the period 1986-92 by Knowlton et al. (1994) was 2.5% (CV = 0.12); this

suggested that the stock was showing signs of slow recovery. However, work by Caswell et al. (1999) has suggested that crude

survival probability declined from about 0.99 in the early 1980's to about 0.94 in the late 1990's. The decline was statistically

significant, a finding which (if confirmed) is of grave concern. The impact of heterogeneity of capture on survival estimates remains

unclear, and further research is urgently required; in addition, ongoing work by Caswell and colleagues, as well as by NMFS scientists,

is incorporating age-specific factors into the survival analysis. As noted by the IWC (1998), determination of the status of this

population is a high priority, notably in light of the known high levels of anthropogenic mortality in this population. The status and

trends of the western North Atlantic right whale population will be addressed in an IWC workshop in October 1999.

CURRENT AND MAXIMUM NET PRODUCTIVITY RATES

During 1980-1992, 145 calves were born to 65 identified cows. The number of calves born annually ranged from 5 to 17,

with a mean of 11.2 (SE = 0.90). There was no detectable trend in the number of calves produced per year. 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) (Knowltonet al. 1994). Since that report, total reported calf production in 92/93 was 6; 93/94, 9; 94/95, 7; 95/96, 21; and

96/97, 19. The total calf production was reduced by reported calf mortalities: 2 mortalities in 1993, 3 in 1996, and 1 in 1997. Of

the three calf mortalities in 1996, available data suggested one was not included in the reported 20 mother/calf pairs, resulting in a
7

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 10 years old or younger, two were 9 years old, and six were of unknown age. In 95/96, more mothers gave

birth after a 5-year interval than in previous years (L. Conger, pers. comm.). An updated analysis of calving interval through the

95/96 season suggests that calving interval is increasing (P<0.001) (R. Kenney and A. Knowlton, pers. comm.).

The annual population growth rate during 1986-1992 was estimated to be 2.5% (CV = 0.12) using photo-identification

techniques (Knowlton et al. 1994). A population increase rate of 3.8% was estimated from the annual increase in aerial sighting rates

in the Great South Channel, 1979-1989 (Kenney et al. 1995). The current estimated population growth rate of the western North

Atlantic stock is lower than that of the four stocks of southern-hemisphere right whales for which data are available: western

Australia, 12.7%; Argentina, 7.3%; east and west Africa, 6.8% (Best 1993). This difference could be attributable in part to

reproductive females in the population--only 38% of the females in the North Atlantic population are known to have given birth

compared with 54% in the western South Atlantic population (Brown et al. 1994). In addition, as noted above recent work has

suggested that the population may be in decline (Caswell et al. 1999).

The relatively low population size indicates that this stock is well below its optimum sustainable population (OSP);

therefore, the current population growth rate should reflect the maximum net productivity rate for this stock. The current 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 this assessment. This rate is no longer current and may reflect underlying methodological problems;

nonetheless, it is used here in the absence of better information because a risk-averse approach is appropriate for this critically

endangered population. The alternative default rate of 0.04 is not species-specific and, being higher, is less conservative. 

POTENTIAL BIOLOGICAL REMOVAL

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

productivity rate (1⁄2 of 2.5%), 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 was 0.10 because this species is listed

as endangered under the Endangered Species Act (ESA). PBR for the northern right whale is 0.4 whales. If confirmed by ongoing

work, the suggestion by Caswell et al. (1999) that the population is in decline will warrant a resetting to zero of the recovery factor

in future SARs.

ANNUAL HUMAN-CAUSED SERIOUS INJURY AND MORTALITY

For the period 1993 through 1997, the total estimated human-caused mortality and serious injury to right whales in USA

waters is estimated as 2.0 per year. This is derived from two components: 1) non-observed fishery impact records, 1.0; and 2) ship

strike records, 1.0. Note that in past stock assessment reports, a six-year time frame was used to calculate these averages. A five

year period was used for this report to be consistent with the time frames used for calculating the averages for other species. It is

also important to stress that serious injury determinations are made based upon the best available information; these determinations

may change with the availability of new information.

Background

Approximately one-third of all right whale mortality is caused by human activities (Kraus 1990). Further, the small

population size and low annual reproductive rate suggest that human sources of mortality may have a greater effect relative to

population growth rates than for other whales. The principal factors believed to be retarding growth, and perhaps recovery, of the

population are ship strikes and entanglement with fishing gear. An updated summary of right whale mortalities reports a total of

30 mortalities (29 if one eliminates a record with some doubt about species identification) for the period 1970 to early 1993 (Kenney

and Kraus 1993). Eight (27%) were due to ship collisions, and two (7%) were due to entanglement with fishing gear. (Note that this

report corrects one of the published records from the Kraus 1990 report, where a fishing vessel caught an already-dead carcass, making

the actual cause of death unknown and possibly unrelated to fishing activity. Further, there was uncertainty about the species

identification.) Both entanglements involved fixed fishing gear, and there was no evidence for right whale mortality from encounters

with mobile fishing gear. The total of ten confirmed anthropogenic mortalities is one-third of all known mortalities for the period

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

entanglement or minor vessel collisions may not kill an animal directly, but may weaken or otherwise affect it so that it is more likely

to become vulnerable. Such was apparently the case with the two-year old right whale killed by a ship off Amelia Island, Florida,

in March 1991 after having carried gillnet gear wrapped around its tail region since the previous summer (Kenney and Kraus 1993).
8

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

in Massachusetts and Cape Cod Bays due to a Boston sewage outfall now under construction. Timetables for levels of treatment

are under discussion. 

Awareness and mitigation programs for reducing anthropogenic injury and mortalities to right whales have been set up in

two areas of concern. The first was initiated in 1992 off the coastal waters of the southeastern USA, and it has been upgraded and

expanded annually. It involves both government and non-government organizations, including the Navy, Army Corps of Engineers,

US Coast Guard, and Florida and Georgia state agencies. In 1996, a program was established in the northeastern USA, largely in

cooperation with the US Coast Guard and the State of Massachusetts. 

Fishery-Related Serious Injury and Mortality

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

records maintained by the New England Aquarium and the Northeast Regional Office/NMFS (Table 1). From 1993-97, 5 of 10

records of mortality or serious injury involved entanglement or fishery interactions. The reports often do not contain the detail

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

right whale observed entangled in pelagic drift gillnet in July 1993, which included the observer’s documentation of lobster gear on

the whale’s tail stock and subsequent entanglement reports of this whale, the suspected mortality of this whale was reassigned to

the Gulf of Maine and USA Mid-Atlantic lobster pot fisheries In this case, the pre-existing entanglement of lobster gear was judged

to have been sufficient cause of eventual mortality independent of the drift net entanglement. Although some drift net gear was left

on the tail by the fishing vessel, the entanglement in the drift net gear would likely not have occurred had the lobster gear not

compromised the whale’s mobility. In another instance, a 2 year-old dead male right whale with lobster line through the mouth and

deeply embedded at the base of the right flipper beached in Rhode Island in July 1995. This individual had been sighted previously,

entangled, east of Georgia in December 1993, and again in August 1994 in Cape Cod Bay. In this case, the entanglement became a

serious injury, and, directly or indirectly, the cause of the mortality. 

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 the right whale records of 9 July 1993 and 17 July 1995, shown in Table 1 ). 

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 1992 and in 1993, the SEFSC provided observer

coverage of pelagic longline vessels fishing off the Grand Banks (Tail of the Banks), and currently provides observer coverage of

vessels fishing south of Cape Hatteras. 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 either the pelagic longline, pelagic pair trawl, or other fisheries monitored

by NMFS. The only documented by-catch of a right whale by NMFS Sea Samplers was a 11⁄2 year-old female that was released

from a pelagic drift gillnet along the southern edge of Georges Bank (mentioned above). At the time of the release, it was discovered

that the animal was also entangled in lobster gear. After recent review of the evidence, the serious injury to the whale has since been

attributed to the non-observed Gulf of Maine and USA Mid-Atlantic lobster pot fisheries (see 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. 1998). Entanglement records maintained by NMFS Northeast Regional Office (NMFS, unpublished

data) from 1970-1996, included 42 right whale entanglements or possible entanglements, including right whales in weirs, entangled

in gillnets, and trailing line and buoys. An additional record (M. J. Harris, pers. comm.) reported a 9.1-10.6 m right whale entangled

and released south of Ft. Pierce, Florida, in March 1982 (this event occurred in the course of a sampling program and was not related

to a commercial fishery). Incidents of entanglements in groundfish gillnet gear, cod traps, and herring weirs in waters of Atlantic

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

gillnet gear in the Bay of Fundy and Gulf of Maine between 1975 and 1990, the right whales were either released or escaped on their

own, although several whales have been observed carrying net or line fragments. A right whale mother and calf were released alive

from a herring weir in the Bay of Fundy in 1976. For all areas, specific details of right whale entanglement in fishing gear are often

lacking. When direct or indirect mortality occurs, some carcasses come ashore and are subsequently examined, or are reported as
9

"floaters" at sea; however, the number of unreported and unexamined carcasses is unknown, but may be significant in the case of

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

Other Mortality

Ship strikes are a major cause of mortality and injury to right whales (Kraus 1990). Records from 1993 through 1997 have

been summarized in Table 1. For this time frame, the average reported mortality and serious injury to right whales due to ship strikes

in USA waters was 1.0 whales per year.

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

waters. Five mortalities were reported, at least one of which (on 1/30/96) was attributable to ship strike. A second mortality (on

2/22/96) showed evidence of barotrauma but no proximate cause of death could be determined. Of the remaining three mortalities,

two were calves (1/2/96 and 2/19/96), one of which may have died from birthing trauma (inconclusive). The third (2/7/96) was

decomposed and could not be towed in for examination. The five mortalities in the southeast were followed by a sixth at Cape Cod,

Massachusetts (3/9/96); this involved an animal killed by ship strike, with the possibility that an existing entanglement (first reported

in 1995) may have impeded its mobility. 
10

Table 1. Summarized records of mortality and serious injury likely to result in mortality, North Atlantic right whales, January 1993

- December 1997. This listing includes only records related to USA commercial fisheries and/or 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

Unknown

uncertain

1/5/93 mortality,

offshore

calf St. Augustine,

FL

P vessel reported striking

whale, carcass

recovered 1/8/93, deep

propeller gashes

7/9/93 serious

injury

1 y.o.

female

#2233

120 miles SE

of Nantucket

P lobster gear constricted

on tail stock,

subsequently became

entangled in pelagic

drift gillnet

12/6/93 mortality,

offshore

female offshore VA P S photos show gash

2/22/94 serious

injury

calf

#2404

offshore

NE FL

S P deep wounds from line

or cable on head,

probable propeller

gashes on flukes

11/17/94 serious

injury

3 y.o. juv.,

#2151

nr. Plum I.,

MA

P line tightly wrapped

around rostrum and

deeply embedded in

gums

7/17/95 mortality,

beached

2 y.o. male

#2366

Middletown,

RI

P lobster line through

mouth, embedded

deeply into bone at

base of right flipper

8/13/95 serious

injury,

offshore

adult

female,

#1045

S. Georges

Bank

P S large head wound

exposing bone

1/30/96 mortality,

offshore

adult male,

#1623

offshore

GA

P S shattered skull, broken

vertebrae and ribs

3/9/96 mortality,

beached

adult male

#2220

Cape Cod

MA

P S 3.3 meter gash on back,

broken skull, lobster

line through mouth and

around tail

8/5/96 serious

injury

unknown SE of

Gloucester, 

MA

P unknown type of gear

entangled around head

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

is based on the best judgement of the available data; additional information may result in revisions. When reviewing Table 1, several

factors should be considered: 1) a ship strike or entanglement may occur at some distance from the report location, 2) the mortality
11

or injury may involve multiple factors--struck and entangled whales 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 the most susceptible to revision. There are several records where a struck and injured

whale is re-sighted later, apparently healthy, or, an entangled or partially disentangled whale is re-sighted later free of gear. The

inverse of this 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.

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

(including fishery and non-fishery related causes) was 2.0 right whales per year. As with entanglements, some injury or mortality

due to ship strikes, particularly in offshore waters, may go undetected. 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

2.0 estimate must be regarded as a minimum estimate. 

While this assessment relates to USA fisheries and/or USA waters, there are additional records for Canadian waters within

the same time frame. Six records are noteworthy: 1) whale #1247 was sighted 21 September 1994 in the Bay of Fundy entangled

with line of an unknown gear type tightly wrapped around its tail stock and has not been sighted since--this is considered a serious

injury (A.R. Knowlton, pers. comm.); 2) whale #2250 was found dead on Long Island, Nova Scotia, probably the result of a ship

strike–it had a large gash on its back and broken vertebral disks; 3) whale #2220, which came ashore on Cape Cod on 9 March 1996,

was entangled in Canadian lobster gear set in the Bay of Fundy and noticed missing in mid-December 1995--while the primary cause

of death was probably a ship strike, the entanglement may have played some role in the whale’s death; 4) whale #2450 was found

dead in the Bay of Fundy on 19 August 1997--ship strike was identified as the cause; 5) whale #2212 was initially reported entangled

in the Bay of Fundy on 23 August 1997, was mostly disentangled on 24 July 1998, but considered seriously injured due to

subsequent evidence of it having ingested gear; and 6) whale # 2557, sighted on 29 August 1997, which was considered seriously

injured due to line being tightly wrapped on the body, its emaciated appearance, and evidence of a necrotic left flipper.

 In addition to these records, there was one Canadian record examined this year for which there was insufficient information

to make a serious injury determination. This animal, #1705, was initially seen in mid-July 1997 in the Bay of Fundy with a small

amount of line with several small, oval black buoys attached coming out of the right side of its mouth. The whale was also seen on

7/18/97, 8/25/97, and 9/6/97, still trailing the line and floats in each sighting. Although the injury resulting from the gear appeared

minimal, it may have the potential to impair the animal’s feeding. Future observations of the whale may provide an indication of

whether the gear has resulted in serious injury.

Lastly, there was one USA record of a right whale serious injury that did not fall into the 1993-97 time frame, but is

mentioned here since it was neglected in previous stock assessment reports. The whale was a juvenile sighted off the southeastern

USA on 11 January 1992, apparently the victim of an entanglement. It had a long, deep gash on its fluke and entanglement scars on

its tail. It appeared emaciated and in poor health.

STATUS OF STOCK

The size of this stock is considered to be low relative to OSP in the USA Atlantic EEZ, and this species is listed as

endangered under the ESA. A Recovery Plan has been published and is in effect (NMFS 1991). Three critical habitats, Cape Cod

Bay/Massachusetts Bay, Great South Channel, and the Southeastern USA, were designated by NMFS (59 FR 28793, June 3, 1994).

The NMFS ESA 1996 Northern Right Whale Status Review concludes that the status of the western North Atlantic population of

the northern right whale remains endangered. 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 2.0 right whales per year since 1993. The total fishery-related

mortality and serious injury for this stock is not less than 10% of the calculated PBR and, therefore, cannot be considered to be

insignificant and approaching a zero mortality and serious injury rate. This is a strategic stock because the average annual fisheryrelated mortality and serious injury exceeds PBR, and because the North Atlantic right whale is an endangered species. Relative to

other populations of right whales, there are also concerns about growth rate, percentage of reproductive females, and calving intervals

in this population.

REFERENCES

Best, P. B. 1993. Increase rates in severely depleted stocks of baleen whales. ICES J. Mar. Sci. 50: 169-186.

Brown, M.W., S.D. Kraus, D.E. Gaskin, and B.N. White. 1994. Sexual composition and analysis of reproductive females in the

North Atlantic right whale, (Eubalaena glacialis), population. Mar. Mamm. Sci. 10(3): 253-265.
12

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

Acad. Sci. USA 96: 3308-3313.

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

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

as a method of assessing human impacts. Final report to the Northeast Fisheries Science Center, Contract No. 4EANF-6-

0004.

International Whaling Commission. 1999. Report of the workshop on the comprehensive assessment of right whales: a worldwide

comparison. Rep. int. Whal. Commn. (in press).

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

North Atlantic right whales. Mar. Mamm. Sci. 2(1): 1-13. 

Kenney, R. D. and S. D. Kraus. 1993. Right whale mortality — a correction and an update. Mar. Mamm. Sci. 9:445-446. 

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

glacialis). Cont. Shelf Res. 15: 385-414.

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

(Eubalaena glacialis). Mar. Mamm. Sci. 8(4): 397-405.

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

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

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

Sci. 6(4): 278-291.

Malik, S. 1997. Assessment of genetic structuring and habitat philopatry in the North Atlantic right whale (Eubalaena glacialis).

M.Sc. thesis, McMaster University, Hamilton, Ontario. 133 pp.

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

61: 1393-1405.

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

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

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

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

Special Issue 15: 133-147. 

Reeves, R. R. and E. Mitchell. 1987. Shore whaling for right whales in the northeastern United States. Contract Report No. NA85-

WCC-06194, SEFSC/NMFS, Miami, FL, 108 pp. 

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

Pages 5-7. In: J. Hain (ed.), The right whale in the western North Atlantic: A science and management workshop, 14-15

April 1992, Silver Spring, Maryland. Northeast Fisheries Science Center Reference Document No. 92-05. NEFSC/NMFS,

Woods Hole, Massachusetts, 88 pp. 

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

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

Rosenbaum, H.C., Egam M.G., Clapham, P.J., Brownell, R.L. Jr., Malik, S., Brown, M., White, B. Walsh, P. and DeSalle, R.

Submitted. Levels of historic genetic diversity and population structure in North Atlantic right whales detected by an

effective technique to isolate DNA from museum specimens. Rep. int. Whal. Commn. (in review).

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

and South Atlantic right whales (Eubalaena) using DNA fingerprinting. Can. J. Zool. 75: 1073-1080.

Schaeff, C. M., S. D. Kraus, M. W. Brown, and B. N. White. 1993. Assessment of the population structure of the western North

Atlantic right whales (Eubalaena glacialis) based on sighting and mtDNA data. Can. J. Zool. 71: 339-345. 

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

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

Wade, P.R., and R.P. Angliss. 1997. Guidelines for assessing marine mammal stocks: Report of the GAMMS Workshop, April 3-5,

1996, Seattle, Washington. NOAA Technical Memorandum NMFS-OPR-12. U.S. Dept. of Commerce, Washington, D.C.

93 pp. 
13

October 1999

HUMPBACK WHALE (Megaptera novaeangliae):

North Atlantic Stock

STOCK DEFINITION AND GEOGRAPHIC RANGE

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

eastern coast of the United States (including the Gulf of Maine), the Gulf of St Lawrence, Newfoundland/Labrador, and western

Greenland (Katona and Beard, 1990). Other North Atlantic feeding grounds occur off Iceland and northern Norway, including off

Bear Island and Jan Mayen (Christensen et al., 1992; Palsbøll et al., 1997). These six regions represent relatively discrete

subpopulations, fidelity to which is determined matrilineally (Clapham and Mayo 1987). Recent genetic analysis of mitochondrial

DNA (mtDNA) has indicated that this fidelity has persisted over an evolutionary timescale in at least the Icelandic and Norwegian

feeding grounds (Palsbøll et al. 1995, Larsen et al. 1996). Genetic partitioning is not evident in the western North Atlantic, however;

thus these four subpopulations (Gulf of Maine, Gulf of St Lawrence, Newfoundland/Labrador and western Greenland) are treated

as a single stock in this report. However, given that fidelity to each feeding area is known to be high, it is possible that each of the

four regions should be managed separately, an approach which requires further investigation.

In winter, whales from all six feeding areas mate and calve primarily in the West Indies, where spatial and genetic mixing

among subpopulations occurs (Clapham et al. 1993; Katona and Beard, 1990; Palsbøll et al. 1997, Stevick et al. 1998). A few

whales of unknown northern origin migrate to the Cape Verde Islands (Reiner et al., 1996). In the West Indies, the majority of

whales are found in the waters of the Dominican Republic, notably on Silver Bank, on Navidad Bank, and in Samana Bay (Balcomb

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

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

1978, Price 1985, Mattila and Clapham 1989).

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

in mid- and high-latitude regions at this time (Swingle et al. 1993, Clapham et al. 1993). An increased number of sightings of young

humpback whales in the vicinity of the Chesapeake and Delaware bays occurred in 1992 (Swingle et al. 1993). Wiley et al. (1995)

reported 38 humpback whale strandings which occurred during 1985-1992 in the USA mid-Atlantic and southeastern states.

Humpback whale strandings increased, particularly along the Virginia and North Carolina coasts, and most stranded animals were

sexually immature; in addition, the small size of many of these whales strongly suggests that they had only recently separated from

their mothers. Wiley et al. (1995) concluded that these areas are becoming an increasingly important habitat for juvenile humpback

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

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

Florida DEP, unpublished data). Whether the increased sightings represent a distributional change, or are simply due to an increase

in sighting effort and/or whale abundance, is presently unknown. 

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

has been largely correlated to prey species and abundance, although behavior and bottom topography are factors in foraging strategy

(Payne et al. 1986, 1990). Humpback whales are frequently piscivorus when in these waters, feeding on herring (Clupea

harengus), sand lance (Ammodytes dubius), and other small fishes. In the northern Gulf of Maine, euphausiids are also frequently

taken (Paquet et al. 1997). Commercial depletion of herring and mackerel led to an increase in sand lance in the southwestern Gulf

of Maine in the mid 1970s with a concurrent decrease in humpback whale abundance in the northern Gulf of Maine. Humpback

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

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

in the mid 1980s, and herring and mackerel increased as sand lance again decreased (Fogarty et al. 1991). Humpback whale abundance

in the northern Gulf of Maine increased dramatically during 1992-93 , along with a major influx of herring (P. Stevick, pers. comm.).

Humpback whales were few in nearshore Massachusetts waters in the 1992-93 summer seasons. They were more abundant in the

offshore waters of Cultivator Shoal and the Northeast Peak on Georges Bank, and on Jeffreys Ledge; these latter areas are more

traditional locations of herring occurrence. In 1996 and 1997, sand lance, and thus humpback whales, were once again abundant in

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

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

of the habitat, where they also fed on euphausiids (unpublished data, Center for Coastal Studies and College of the Atlantic).
14

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

1993) was initiated. This project is a large-scale, intensive study of humpback whales throughout almost their entire North Atlantic

range, from the West Indies to the Arctic. During two primary years of field work, photographs for individual identification and

biopsy samples for genetic analysis were collected from summer feeding areas and from the breeding grounds in the West Indies.

Additional samples were collected from certain areas in other years. Results pertaining to the estimation of abundance and to genetic

population structure are summarized below.

POPULATION SIZE

The North Atlantic population was recently estimated from genetic tagging data collected by the YONAH project in the

breeding range at 4,894 males (95% c.i. 3,374-7,123) and 2,804 females (95% c.i. 1,776-4,463) (Palsbøll et al. 1997). Since the sex

ratio in this population is known to be even (Palsbøll et al. 1997), the excess of males is presumed to be a result of sampling bias,

lower rates of migration among females or sex-specific habitat partitioning in the West Indies; whatever the reason, the combined total

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

an ocean-basin-wide estimate of 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.

A population size of 294 humpback whales (CV=0.45) was estimated from an aerial survey program conducted from 1978

to 1982 on the continental shelf and shelf edge waters between Cape Hatteras, North Carolina and Nova Scotia (Table 1; CETAP

1982). The estimate is based on an inverse variance weighted pooling of spring and summer data. An average of these seasons was

chosen because the greatest proportion of the population off the northeast USA coast appeared in the study area during these

seasons. This estimate includes a dive-time scale-up correction of 3.6 but was not corrected for g(0), the probability of detecting an

animal group on the track line. This estimate clearly does not reflect the current true population size because of its high degree of

uncertainty (e.g., large CV), and its age. Furthermore, it is considerably smaller than the size of the existing catalog of identified

individuals in the Gulf of Maine, and it was estimated just after cessation of extensive foreign fishing operations in the region.

Minimum Population Estimate

The minimum population estimate is the lower limit of the two-tailed 60% confidence interval of the log-normally

distributed best abundance estimate. This is equivalent to the 20th percentile of the log-normal distribution as specified by Wade

and Angliss (1997). The best estimate of abundance for North Atlantic humpback whales is 10,600 (CV = 0.067, Smith et al. 1999).

The minimum population estimate for this stock is 10,019 humpback whales (CV=0.067).
15

Table 1. Summary of abundance estimates for North Atlantic humpback whales. Period and area covered during each abundance

survey, and resulting abundance estimate (Nbest) and coefficient of variation (CV). MR = Mark-recapture.

Month/Year Area Type Nbest CV Source

spring/summer

1978-82

Cape Hatteras, NC to

Nova Scotia Transect 294 0.45 CETAP 1982

1979-90 N. Atlantic Ocean W

and SW of Iceland Photo MR 5,543 0.16 Katona et al. 1994

1992-93 N. Atlantic Ocean Photo MR 10,600 0.067 Smith et al. 1999

1992-93 N. Atlantic Ocean Genotype

MR 10,400 0.138 Smith et al. 1999

1992-93 West Indies Genotype

MR

4,894 males

2,804 females

0.180

0.218 Palsbøll et al. 1997

Current Population Trend

The rates of growth cited below, together with recent estimates of abundance that are larger than previous figures, appear

to indicate that the humpback whale population in the North Atlantic is increasing. It is not known whether this increase is oceanwide in nature or confined to specific feeding grounds. An increasing trend is apparent in the Gulf of Maine (Barlow and Clapham

1997); by contrast, the population which summers off western Greenland appears small and is perhaps static (F. Larsen, pers.

comm.)

CURRENT AND MAXIMUM NET PRODUCTIVITY RATES

Current and maximum net productivity rates are unknown for this stock. Katona and Beard (1990) suggest an annual rate

of increase of 9%; however, the lower 95% confidence level was less than zero. The difference between the estimates of abundance

calculated by Katona and Beard (1990) and by Smith et al. (1999) were interpreted by the latter as probably being due to population

growth in the years between the two estimates. This assumed growth rate would be very similar to the growth rate of 6.5% calculated

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

Other life history parameters that could be used to estimate net productivity include the following: mean birth rate for

identified humpbacks in the southwestern Gulf of Maine during 1979-87 was 8% (CV = 0.25), with no significant inter-annual

differences; calving interval was 2.35 years (CV = 0.30); and the average age at attainment of sexual maturity for both males and

females was five years (Clapham and Mayo 1990; Clapham 1992).

For purposes of this assessment, the maximum net productivity rate was set at 0.065, as calculated for the Gulf of Maine

population by 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; Wade and Angliss 1997). The minimum population size is 10,019 (based

on an estimate of abundance of 10,400 with a CV of 0.067). The maximum productivity rate is 0.065 from Barlow and Clapham

(1997). The “recovery” factor, which accounts for endangered, depleted, threatened stocks, or stocks of unknown status relative to

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

Endangered Species Act (ESA). PBR for the North Atlantic humpback whale stock is 32.6 whales. 

ANNUAL HUMAN-CAUSED SERIOUS INJURY AND MORTALITY

For the period 1993 through 1997, the total estimated human-caused mortality and serious injury to humpback whales is

estimated as 4.4 per year. This average is derived from three components: 1) the 1993-1997 observed fishery, 0. 6; 2) additional
16

fishery interaction records, 2.6; and 3) vessel collisions, 1.2. For the reasons described below, the additional records (from other than

the observed fishery) cannot provide a quantitative estimate, but suggest that a number of additional serious injuries and mortalities

do occur. Note that in past 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 was used for this report to be consistent with the time frames used for

calculating the averages for the observed fishery and for other species. It is also important to stress that serious injury determinations

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

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). In addition,

of 20 dead humpback whales, principally in the mid-Atlantic, where decomposition state did not preclude examination for human

impacts, Wiley 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 scars that may have been caused by both ship

strike and entanglement. Thus, 60% of the whale carcasses which were suitable for examination showed signs that anthropogenic

factors may have contributed to, or been responsible for, their death. Wiley et al. (1995) further reported that all stranded animals

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

impacts. Humpback whale entanglements also occur in relatively high numbers in Canadian waters. Reports of collisions with fixed

fishing gear set for groundfish around Newfoundland averaged 365 annually from 1979 to 1987 (range 174-813). An average of 50

humpback whale entanglements (range 26-66) were reported annually between 1979 and 1988, and 12 of 66 humpback whales that

were entangled in 1988 died (Lien et al. 1988). Volgenau et al. (1995) also summarized existing data and concluded that in

Newfoundland and Labrador, cod traps caused the most entanglements and entanglement mortalities (21%) of humpbacks between

1979 and 1992. They also reported that gillnets are the gear that has been the primary cause of entanglements and entanglement

mortalities (20%) of humpbacks in the Gulf of Maine between 1975 and 1990.

Fishery-Related Serious Injuries and Mortalities

 Two mortalities were observed in the pelagic drift gillnet fishery since 1989. In winter 1993, a juvenile humpback was

observed entangled dead in a pelagic drift gillnet along the 200 m isobath northeast of Cape Hatteras; in early summer 1995, a

humpback was entangled and dead in a pelagic drift gillnet on southwestern Georges Bank (see below).

Additional reports of mortality and serious injury relevant to comparison to PBR, as well as description of total human

impacts, are contained in records maintained by the Northeast Regional Office/NMFS. A number of these records (11 entanglements

involving lobster gear) from the 1990-94 period were used in the 1997 List of Fisheries classification (62 FR 33, Jan. 2, 1997). For

this report, the records of dead, injured, and/or entangled humpbacks (either found stranded or at sea) for the period 1993 to 1997

were reviewed. More than half of these records were eliminated from further consideration due to an absence of any evidence of

human impact or, in the case of an entangled whale, it was documented that the animal had become disentangled. Of the remaining

records, there was one mortality where fishery interaction was probable, and 12 records where serious injury attributable to fishery

interaction was probable—for a total of 13 records in the five-year period (Table 3). While these records are not statistically

quantifiable in the same way as the observed fishery records, they are suggestive of the frequency of entanglements. 

Fishery Information

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

mandatory self-reported fisheries information system for large pelagic fisheries. Data files are maintained at the Southeast Fisheries

Science Center (SEFSC). The Northeast Fisheries Science Center (NEFSC) Sea Sampling Observer Program was initiated in 1989,

and several fisheries have been covered by the program. In late 1992 and in 1993, the SEFSC provided coverage of pelagic longline

vessels fishing off the Grand Banks (Tail of the Banks) and provides observer coverage of vessels fishing south of Cape Hatteras.

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, or other fisheries monitored by NMFS. 

Pelagic Drift Gillnet

The estimated total number of hauls in the Atlantic pelagic drift gillnet fishery increased from 714 in 1989 to 1144 in 1990;

thereafter, with the introduction of quotas, effort was severely reduced. The estimated number of hauls in 1991, 1992, 1993, 1994,

1995, and 1996 were 233, 243, 232, 197, 164, and 149 respectively. In 1996 and 1997, the NMFS issued management regulations
17

which prohibited the operation of this fishery in 1997. Further, in January 1999 the 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. In 1994, 1995, and 1996 there were 12, 11, and 10 vessels, respectively, in the fishery (Table

2). Observer coverage (percent of sets observed) was 20% in 1991, 40% in 1992, 42% in 1993, 87% in 1994, 99% in 1995, and 64%

in 1996. The greatest concentrations of effort were located along the southern edge of Georges Bank and off Cape Hatteras.

Examination of the species composition of the catch and locations of the fishery throughout the year suggested that the drift gillnet

fishery be stratified into two strata, a southern or winter stratum, and a northern or summer stratum. Estimates of the total by-catch,

from 1989 to 1993, were obtained using the aggregated catch rates, by strata (Northridge 1996). Estimates of the total annual bycatch

for 1994, 1995, and 1996 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.

Estimated annual mortality (CV in parentheses), extrapolated from fishery observer data, was 1.5 in 1993 (0.34), 0 in 1994 (0), 1.0

in 1995 (0), and 0 in 1996 (0). The total average annual estimated fishery-related mortality and serious injury in fisheries monitored

by NMFS in 1993-1997 was 0.6 humpback whale (CV = 0.34) (Table 2).

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). 

Table 2. Summary of the incidental mortality of the humpback whale (Megaptera novaeangliae), by commercial fishery

including the years sampled (Years), the number of vessels active within the fishery (Vessels), the type of data used (Data

Type), the annual observer coverage (Observer Coverage), the mortalities recorded by on-board observers (Observed

Mortality), the estimated annual mortality (Estimated Mortality), the estimated CV of the annual mortality (Estimated

CVs) and the mean annual mortality (CV in parentheses).

Fishery Years Vessels 1 Data Type 2 Observer

Coverage 3 

Observed

Mortality

Estimated

Mortality 4

Estimated

CVs 4

Mean Annual

Mortality

Pelagic

Drift

Gillnet

93-97

1994=12

1995=11

1996=10

Obs. Data

Logbook

.42, .87, .99,

.64, NA

 1, 

0, 1, 0,

NA

 1.5, 0, 1.05,

0,

NA

 0.34, 0, 0,

0, NA 0.6 (0.34)

TOTAL 0.6 (0.34)

1

1994, 1995, and 1996 shown, other years not available on an annual basis.

2 Observer data (Obs. Data) are used to measure bycatch rates, and the data are collected within the Northeast Fisheries

Science Center (NEFSC) Sea Sampling Program. Mandatory logbook (Logbook) data are used to measure total effort, and

the data are collected at the Southeast Fisheries Science Center (SEFSC).

3 The observer coverage and unit of effort for the pelagic drift gillnet fishery is a set.

4 For 1993, pooled bycatch rates were used to estimate bycatch in months that had fishing effort but did not have observer

coverage. This method is described in Northridge (1996). In 1994 and 1995, observer coverage increased substantially,

and bycatch rates were not pooled for this period.

5 One vessel was not observed and recorded 1 set in a 10 day trip in the SEFSC mandatory logbook. If you assume the vessel

fished 1.4 sets per day as estimated from the 1995 SS data, the point estimate may increase by 0.08 animals. However,

the SEFSC mandatory logbook data were 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.

Table 3. Summarized records of mortality and serious injury likely to result in mortality, North Atlantic humpback whales, January

1993 - December 1997. This listing includes only records related to USA commercial fisheries and/or USA waters. Cause

of mortality or injury, assigned as primary or secondary, are based on records maintained by NMFS/NER and NMFS/SER.
18

Date Report 

Type

Sex, age, ID Location Assigned Cause: P=primary, 

S=secondary

Notes

Ship

strike

Entang./

Fsh.inter

Unknownu

ncertain

4/22/93 serious

injury

age and sex

unknown

4 mi SE of

Provincetown, Mass.

(42E 01'

 70E 06')

P line around tail region and

flukes, whale thin;

unknown if gear trailing;

same whale disentangled

on 4/24/93??; thin and

weak; healing around line

5/5/93 serious

injury

age estimated 

2-3 y.o.

NW part

Stellwagen

Bank

(42E 26'

 70E 27')

P buoy warp wrapped

around base of flipper;

anchored and very

fatigued; whale freed

itself; unknown whether

carrying gear

7/26/93 serious

injury

unknown 30 mi SE of

Bar Harbor,

Maine

(44E 00'

 67E 38')

P entangled; line wrapped

around head and behind

blowhole

8/8/93 serious

injury

unknown 11 mi SE of

Bar Harbor,

Maine

(44E 17'

 68E 00')

P net & buoys on head,

dorsal fin, flippers;

trailing gear; stressed

behavior; cuts and blood

reported, netting was

removed, line remained

on tail

10/7/93 serious

injury

unknown Atlantic City,

New Jersey

P boat collision with 33 ‘

sport fishing vessel;

extent of injuries

undetermined

7/14/94 serious

injury

unknown 15 mi SE of

Cape

Elizabeth,

Maine

(43E 23'

 68E 59')

P CG helicopter crew

reported animal with

gillnet wrapped around

head and swimming at

surface

2/28/95 mortality unknown Cape

Hatteras,

North

Carolina

(35E 17'

 75E 31')

P stranded dead with gear

wrapped around tail

region
Date Report 

Type

Sex, age, ID Location Assigned Cause: P=primary, 

S=secondary

Notes

Ship

strike

Entang./

Fsh.inter

Unknownu

ncertain

19

5/26/95 serious

injury

length (est.) = 

10 m

Great South

Channel

(41E 16'

 69E 20')

P net and monofilament

around tail region; whale

anchored; mesh visible

and gear trailing

6/4/95 mortality 8.9 m male Virginia

Beach,

Virginia

P floater off inlet;

lacerations along

peduncle, probable ship

strike

1/30/96 serious

injury

juvenile Northern

Edge of

Georges Bank 

(42E 26'

 67E 30')

P gear wrapped on body,

some gear removed

2/22/96 serious

injury

length (est.) = 

8 m

Florida Keys P heavy line extending

around maximum girth,

pinning both pectorals;

grooves/healed scars on

dorsal ridge and on leading

edge of both pectorals;

fairly emaciated;

disentangled

4/2/96 mortality 7.2 m female Cape Story,

Virginia

Beach,

Virginia

P fresh dead; fractured left

mandible; emaciated

5/9/96 mortality 6.7 m female mouth of

Delaware Bay

P propeller cuts behind

blowhole, moderate

decomposition; ship

strike

7/18/96 serious

injury

length (est.) = 

10 m

25 mi S of Bar

Harbor Maine

(44E 01'

 68E 00')

P disentanglement

unsuccessful; weighted

gear wrapped around tail

stock; whale swimming

abnormally

7/28/96 serious

injury

length (est.) = 

10m

SW corner of

Stellwagen

Bank, MA

P entanglement involved

mouth or flipper and line

over tail; recent

entanglement; extent of

trailing gear unknown
Date Report 

Type

Sex, age, ID Location Assigned Cause: P=primary, 

S=secondary

Notes

Ship

strike

Entang./

Fsh.inter

Unknownu

ncertain

20

10/7/96 serious

Injury

unknown Great South

Channel

(41E 04'

 69E 10')

P gear wrapped around tail

and trailing 30 m behind

whale

10/18/96 serious

injury

unknown Great South

Channel

(41E 00'

69E 10')

P Whale entangled in steel

cable

11/3/96 mortality 8.4 m male Carrituck,

North

Carolina

P acute trauma to skull

found by necropsy

12/10/97 mortality 9.0 m male Beaufort

Inlet, North

Carolina

P massive hemorrhage

consistent with forceful

blunt trauma

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 reported beached, entangled, or injured. 

2. National guidelines for determining what constitutes a serious injury have not been finalized. Interim criteria as established

by NERO/NMFS (62 FR 33, Jan. 2, 1997) have been used here. Some assignments may change as new information

becomes available and/or when national standards are established.

3. Assigned cause based on best judgement of available data. Additional information may result in revisions.

4. Entanglements of juvenile whales may become more serious as whale grows.

5. There is no overlap between tables 2 and 3 (the two records from the observed fishery are not included in Table 3).

Other Mortality

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

dinoflagellate saxitoxin. The whales subsequently stranded or were recovered in the vicinity of Cape Cod Bay and Nantucket Sound,

and it is highly likely that other mortalities occurred during this event which went unrecorded. During the first six months of 1990,

seven dead juvenile (7.6 to 9.1 m long) humpback whales stranded between North Carolina and New Jersey. The significance of these

strandings is unknown, but is a cause for some concern.

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

serious than those from entanglements. In the NER/NMFS records examined, several contained notes about wounds or

probable/possible vessel collision. Five of these records were mortalities resulting from the collision. One record, on 7 October 1993,

involving a 33 ft sport-fishing vessel, resulted in a serious injury to the whale.

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

and incompletely or unexamined animals in the records, there needs to be greater emphasis on the timely recovery of carcasses and

complete necropsies. The literature and review of records described above suggest that there are significant human impacts beyond

those in the fishery observer data. 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 human impacts listed in this report must

be considered a minimum estimate.

STATUS OF STOCK
21

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 (NMFS 1991). There are insufficient data to reliably

determine population trends for humpback whales in the North Atlantic overall. The annual rate of population increase was estimated

at 9% (Katona and Beard 1990, but with a lower 95% confidence level less than zero), and for the Gulf of Maine at 6.5% by Barlow

and Clapham (1997). The total level of human-caused mortality and serious injury is unknown, but current data indicate that it is

significant. The total fishery-related mortality and serious injury for this stock is not less than 10% of the calculated PBR and,

therefore, cannot be considered to be insignificant and approaching a zero mortality and serious injury rate. 

Disturbance by whalewatching may prove to be an important habitat issue in some areas of this population’s range, notably

the coastal waters of New England where the density of whalewatching traffic is seasonally high. No studies have been conducted

to address this question, and its impact (if any) on habitat occupancy and reproductive success is unknown.

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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-Atlantic and southeast United States, 1985-1992. Fish. Bull., U.S. 93: 196-205. 

Winn, H.E., Edel, R.K. and Taruski, A.G. 1975. Population estimate of the humpback whale (Megaptera novaeangliae) in the

West Indies by visual and acoustic techniques. J. Fish. Res. Bd. Can. 32: 499-506.
23

Figure 1. Distribution of fin whale sightings from

NEFSC shipboard and aerial surveys during the summer

in 1990-1995. Isobaths are at 100 m and 1,000 m. 

October 1999

FIN WHALE (Balaenoptera physalus):

Western North Atlantic Stock

STOCK DEFINITION AND GEOGRAPHIC RANGE

The Scientific Committee of the International

Whaling Commission (IWC) has proposed stock boundaries

for North Atlantic fin whales. Fin whales off the eastern USA,

north to Nova Scotia and on to the southeast coast of

Newfoundland are believed to constitute a single stock under

the present IWC scheme (Donovan 1991). However, the stock

identity of North Atlantic fin whales has received relatively

little attention, and whether the current stock boundaries

define biologically isolated units has long been uncertain. The

existence of a subpopulation structure was suggested by local

depletions that resulted from commercial overharvesting

(Mizroch et al. 1984).

A genetic study conducted by Bérubé et al. (1998)

using both mitochondrial and nuclear DNA provided strong

support for an earlier population model proposed by Kellogg

(1929) and others. This postulates the existence of several

subpopulations of fin whales in the North Atlantic and

Mediterranean, with limited gene flow among them. Bérubé et

al. (1998) also proposed that the North Atlantic population

showed recent divergence due to climatic changes (i.e.

postglacial expansion), as well as substructuring over even

relatively short distances. The genetic data are consistent with

the idea that different subpopulations use the same feeding

ground, a hypothesis that was also originally proposed by

Kellogg (1929).

Fin whales are common in waters of the USA

Atlantic Exclusive Economic Zone (EEZ), principally from

Cape Hatteras northward (Figure. 1). Fin whales accounted for 46% of the large whales and 24% of all cetaceans sighted over the

continental shelf during aerial surveys (CETAP 1982) between Cape Hatteras and Nova Scotia during 1978-82. While a great deal

remains unknown, the magnitude of the ecological role of the fin whale is impressive. In this region fin whales are the dominant large

cetacean species in all seasons, with the largest standing stock, the largest food requirements, and therefore the largest impact on the

ecosystem of any cetacean species (Hain et al. 1992).

 There is little doubt that New England waters represent a major feeding ground for the fin whale. There is evidence of site

fidelity by females, and perhaps some segregation by sexual, maturational or reproductive class on the feeding range (Agler et al.

1993). Seipt et al. (1990) reported that 49% of identified fin whales on Massachusetts Bay area feeding grounds were resighted

within years, and 45% were resighted in multiple years. While recognizing localized as well as more extensive movements, these

authors suggested that fin whales on these grounds exhibited patterns of seasonal occurrence and annual return that are in some

respects similar to those shown for humpback whales. This was reinforced by Clapham and Seipt (1991), who showed maternally

directed site fidelity by fin whales in the Gulf of Maine. Information on life history and vital rates is also available in data from the

Canadian fishery, 1965-1971 (Mitchell 1974). In seven years, 3,528 fin whales were taken at three whaling stations. The station

at Blandford, Nova Scotia, took 1,402. 

Hainet al. (1992), based on an analysis of neonate stranding data, suggested that calving takes place during approximately

four months from October-January in latitudes of the USA mid-Atlantic region; however, it is unknown where calving, mating, and

wintering for most of the population occurs. Preliminary results from the Navy's IUSS program (Clark 1995) indicate a substantial
24

deep-ocean component to fin whale distribution. 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. 

POPULATION SIZE

Five seasonal abundance estimates for fin whales are available for portions of the western North Atlantic during spring and

summer of 1978-82, June-July 1991, August-September 1991, August-September 1991 and 1992, and July-September 1995 (Table

1; Figure 1).

 A population size of 4,680 fin 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).

The estimate is based on an inverse variance weighted pooling of spring and summer data. An average of these seasons was chosen

because the greatest proportion of the population off the northeast USA coast appeared in the study area during these seasons. This

estimate includes a dive-time scale-up correction of 4.85 but does not correct for g(0), the probability of detecting an animal group

on the track line. This estimate may not reflect the current true population size because of its old age and because it was estimated

just after cessation of extensive foreign fishing operations in the region.

A population size of 35 (CV=0.56) fin 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 (Table 1; Waring et al. 1992).

Data were collected by one team that searched by naked eye and analyzed using DISTANCE (Buckland et al. 1993; Laake et al.

1993). Estimates include school size-bias, if applicable, but no corrections for g(0) or dive-time. Variability was estimated using

bootstrap resampling techniques.

A population size of 194 (CV=0.18) and 529 (CV=0.19) fin whales was estimated from line transect aerial surveys

conducted from August to September 1991 using the Twin Otter and AT-11, respectively (Table 1; Anon. 1991). The study area

included that covered in the CETAP study plus several additional continental slope survey blocks. Due to weather and logistical

constraints, several survey blocks south and east of Georges Bank were not surveyed. The data were analyzed using DISTANCE

(Buckland et al. 1993; Laake et al. 1993), where the CV was estimated using the bootstrap option. The abundance estimates do

not include g(0) and were not pooled over platforms because the inter-platform calibration analysis has not been conducted.

A population size of 2,700 (CV=0.59) fin whales was estimated from two shipboard line transect surveys conducted during

July to September 1991 and 1992 in the northern Gulf of Maine-lower Bay of Fundy region (Palka and Waring, unpublished data).

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

of its variance. The data were collected during surveys designed to estimate abundance of harbor porpoises (Palka 1995). Two

independent teams of observers on the same ship surveyed using naked eye in non-closing mode. Using the product integral

analytical method (Palka 1995) and DISTANCE (Buckland et al. 1993; Laake et al. 1993) the abundance includes an estimate of

school size-bias, if applicable, and an estimate of g(0)–the probability of detecting a group on the track line–but no correction for

dive-time. Variability was estimated using bootstrap resampling techniques.

A population size 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 (Table 1; NMFS/NEFSC

unpublished data). Total track line length was 32,600 km (17,600 nmi). 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. Shipboard data were collected using a two independent sighting team

procedure and were analyzed using the product integral method (Palka 1995) and DISTANCE (Buckland et al. 1993). Shipboard

estimates were corrected for g(0) and, if applicable, also for school size-bias. Standard aerial sighting procedures with two bubble

windows and one belly window observer were used during the aerial survey. An estimate of g(0) was not made for the aerial portion

of the survey. Estimates do not include corrections for dive-time or ship avoidance. Variability was estimated using bootstrap resampling techniques.

The best available current abundance estimate for the western North Atlantic fin whale is 2,200 (CV=0.24) from the 1995

Virginia to Gulf of St Lawrence line transect surveys because it is relatively recent and covers the largest portion of the known habitat.

However, this estimate must be considered conservative in view of the known range of the fin whale in the entire western North

Atlantic, and uncertainties regarding population structure and exchange between surveyed and unsurveyed areas.

Table 1. Summary of abundance estimates for the western North Atlantic fin whale. Month, year, and area covered during

each abundance survey, and resulting abundance estimate (Nbest) and coefficient of variation (CV).
25

Month/Year Area Nbest CV

spring & summer

1978-1982

Cape Hatteras, NC to

Nova Scotia

4,680 0.23

Jun-Jul 1991

Cape Hatteras, NC to

Georges Bank, shelf

edge only

35 0.56

Aug-Sep 1991 Cape Hatteras, NC to

Nova Scotia 194 and 529*

0.18 and 0.19*

Jul-Sep 1991 and 1992 N. Gulf of Maine and

Bay of Fundy 2,700 0.59

Jul-Sept 1995 Virginia to the Gulf of

St Lawrence 2,200 0.24

* From data collected on the Twin Otter and AT-11, respectively.

Minimum Population Estimate

The minimum population estimate is the lower limit of the two-tailed 60% confidence interval of the log-normally

distributed best abundance estimate. This is equivalent to the 20th percentile of the log-normal distribution as specified by Wade

and Angliss (1997). The best estimate of abundance for fin whales is 2,200 (CV=0.24). The minimum population estimate for the

western North Atlantic fin whale is 1803.

Current Population Trend

There are insufficient data to determine population trends for this species. Even at a conservatively estimated rate of

increase, however, the numbers of fin whales may have increased substantially in recent years (Hain et al. 1992). 

CURRENT AND MAXIMUM NET PRODUCTIVITY RATES

Current and maximum net productivity rates are unknown for this stock. Based on photographically identified fin whales,

Agler et al. (1993) estimated that the gross annual reproduction rate was at 8%, with a mean calving interval of 2.7 years.

For purposes of this assessment, the maximum net productivity rate was assumed to be 0.04. This value is based on

theoretical modeling showing that cetacean populations may not grow at rates much greater than 4% given the constraints of their

reproductive life history (Barlow et al. 1995). 

POTENTIAL BIOLOGICAL REMOVAL

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

and a “recovery” factor (MMPA Sec. 3. 16 U.S.C. 1362; Wade and Angliss 1997). The minimum population size is 1803. The

maximum productivity rate is 0.04, the default value for cetaceans. The “recovery” factor, which accounts for endangered, depleted,

threatened stocks, or stocks of unknown status relative to optimum sustainable population (OSP) is assumed to be 0.10 because the

fin whale is listed as endangered under the Endangered Species Act (ESA). PBR for the western North Atlantic fin whale is 3.6. 

ANNUAL HUMAN-CAUSED MORTALITY AND SERIOUS INJURY

The number of fin whales taken at three whaling stations in Canada from 1965-71 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 1993-97. A review of NER/NMFS anecdotal records from 1993-1997 yielded an average of 0.6 human caused

mortalities per year -- 0.2 per year resulting from fishery interactions/entanglements, and 0.4 due to vessel collisions. 

Fishery-Related Serious Injury and Mortality 
26

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

therefore, no detailed fishery information is presented here. A review of the records of stranded, floating or injured fin whales for

the period 1993-1997 on file at NER/NMFS found four records with evidence of fishery interactions. There was a live fin whale

sighted entangled on 6/24/97 with line wrapped over its back. The animal appeared emaciated, but whether this was a result of the

entanglement could not be determined. Two stranded fin whales had net or rope marks, but the evidence on hand was not sufficient

to confirm entanglement as the cause of death. for these cases. The fourth record involved a whale that was found floating 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. This single

confirmed entanglement mortality suggests an annual mortality of 0.2 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. 

Other Mortality

After reviewing NER/NMFS records, two were found that had sufficient information to confirm the cause of death as

collisions with vessels. On 3/12/94, a 16-meter fin whale was found on Virginia Beach with fresh, deep propeller wounds in the

caudal area. The animal’s full stomach indicated it had been feeding not long before the collision. 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 animal. NER/NMFS data holdings include seven additional records of fin whale mortalities that bore evidence of injury

from collisions with vessels, but the available supporting documentation was not conclusive as to whether these constituted serious

injury or were the proximal cause of the mortality.

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 fin whales. The total fishery-related mortality and serious

injury for this stock is less than 10% of the calculated PBR and can be considered insignificant and approaching zero mortality and

serious injury rate. Any fishery-related mortality would be illegal because there is no recovery plan currently in place, although a draft

plan is currently in review. This is a strategic stock because the fin whale is listed as an endangered species under the ESA.

REFERENCES

Agler, B. A., R. L. Schooley, S. E. Frohock, S. K. Katona, and I. E. Seipt. 1993. Reproduction of photographically identified fin

whales, Balaenoptera physalus, from the Gulf of Maine. J. Mamm. 74(3): 577-587.

Anon. 1991. Northeast cetacean aerial survey and interplatform study. NOAA, NMFS, SEFSC & NEFSC, 4 pp. Available from

NEFSC, Woods Hole Laboratory, Woods Hole, MA. 

Barlow, J., S.L. Swartz, T. C. Eagle, and P.R. Wade. 1995. U.S. Marine Mammal Stock Assessments: Guidelines for preparation,

background, and a summary of the 1995 assessments. NOAA Technical Memorandum NMFS-OPR-6. U.S. Department

of Commerce, Washington, D.C. 73 pp.

Bérubé, M., A. Aguilar, D. Dendanto, F. Larsen, G. Notarbartolo di Sciara, R. Sears, J. Sigurjónsson, J. Urban-R. and P.J. Palsbøll.

1998. Population genetic structure of North Atlantic, Mediterranean and Sea of Cortez fin whales, Balaenoptera

physalus (Linnaeus 1758): analysis of mitochondrial and nuclear loci. Mol. Ecol. 15: 585-599.

Buckland, S. T., D. R. Andersen, K. P. Burnham, and J. L. Laake. 1993. Distance sampling: Estimating abundance of biological

populations. Chapman and Hall, New York, 446 pp. 

CETAP. 1982. A characterization of marine mammals and turtles in the mid- and north Atlantic areas of the U.S. outer continental

shelf. Cetacean and Turtle Assessment Program, University of Rhode Island. Final Report #AA551-CT8-48 to the Bureau

of Land Management, Washington, DC, 538 pp.

Clapham, P.J. & Seipt, I.E. 1991. Resightings of independent fin whales, Balaenoptera physalus, on maternal summer ranges.

Journal of Mammalogy 72: 788-790.

Clark, C.W. 1995. Application of U.S. Navy underwater hydrophone arrays for scientific research on whales. Rep. int. Whal.

Commn. 45: 210-212.

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

Hain, J. H. W., M. J. Ratnaswamy, R. D. Kenney, and H. E. Winn. 1993. The fin whale, Balaenoptera physalus, in waters of

the northeastern United States continental shelf. Rep. int Whal. Commn. 42: 653-669.
27

Kellogg, R. 1929. What is known of the migration of some of the whalebone whales. Ann. Rep. Smithsonian Inst. 1928: 467-

494.

Laake, J. L., S. T. Buckland, D. R. Anderson, and K. P. Burnham. DISTANCE user’s guide, V2.0. 1993. Colorado Cooperative Fish

& Wildlife Research Unit, Colorado State University, Ft. Collins, Colorado, 72 pp. 

Mizroch, A. A., D. W. Rice, and J. M. Breiwick. 1984. The fin whale, Balaenoptera physalus. Mar. Fisheries Rev. 46: 20-

24.

Mitchell, E. 1974. Present status of Northwest Atlantic fin and other whale stocks. Pages 109-169, in W. E. Schevill (ed), The

whale problem: A status report. Harvard University Press, Cambridge, Massachusetts, 419 pp.

Palka, D. 1995. Abundance estimate of the Gulf of Maine harbor porpoise. Pp. 27-50, In: A Bjørge and G.P. Donovan (eds).

Biology of the Phocoenids, Rep. int Whal. Commn Special Issue 16.

Seipt, I. E., P. J. Clapham, C. A. Mayo, and M. P. Hawvermale. 1990. Population characteristics of individually identified fin

whales, Balaenoptera physalus, in Massachusetts Bay. Fish. Bull., U.S. 88(2): 271-278

Sissenwine, M. P., W. J. Overholtz, and S. H. Clark. 1984. In search of density dependence. Pages 119-137 in Proceedings of the

workshop on biological interactions among marine mammals and commercial fisheries in the southeastern Bering Sea.

Alaska Sea Grant Report 84-1, Alaska Sea Grant College Program, University of Alaska, Fairbanks, Alaska. 

Wade, P.R., and R.P. Angliss. 1997. Guidelines for assessing marine mammal stocks: Report of the GAMMS Workshop, April 3-5,

1996, Seattle, Washington. NOAA Technical Memorandum NMFS-OPR-12. U.S. Dept. of Commerce, Washington, D.C.

93 pp. 

Waring, G.T., C.P. Fairfield, C.M. Ruhsam, and M. Sano. 1993. Cetaceans associated with Gulf Stream features off the northeastern

USA shelf. ICES Marine Mammals Comm. CM 1993/N: 12. 29 pp.
28

October 1999

SEI WHALE (Balaenoptera borealis):

Nova Scotia Stock

STOCK DEFINITION AND GEOGRAPHIC RANGE

Indications are that, at least during the feeding season, a major portion of the sei whale population is centered in northerly

waters, perhaps on the Scotian Shelf (Mitchell and Chapman 1977). The southern portion of the species' range during spring and

summer includes the northern portions of the USA Atlantic Exclusive Economic Zone (EEZ) — the Gulf of Maine and Georges Bank.

The period of greatest abundance there is in spring, with sightings concentrated along the eastern margin of Georges Bank and into

the Northeast Channel area, and along the southwestern edge of Georges Bank in the area of Hydrographer Canyon (CETAP 1982).

The sei whale is generally 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 contour than were fin

whales. 

This general offshore pattern of sei whale distribution is disrupted during episodic incursions into more shallow and inshore

waters. The sei whale, like the right whale, is largely planktivorous — feeding primarily on euphausiids and copepods. In years of

reduced predation on copepods by other predators, and thus greater abundance of this prey source, sei whales are reported in more

inshore locations, such as the Great South Channel (in 1987 and 1989) and Stellwagen Bank (in 1986) areas (R.D. Kenney, pers.

comm.; Payne et al. 1990). An influx of sei whales into the southern Gulf of Maine occurred in the summer of 1986 (Schilling et

al. 1993). Such episodes, often punctuated by years or even decades of absence from an area, have been reported for sei whales from

various places worldwide.

Based on analysis of records from the Blandford, Nova Scotia, whaling station, where 825 sei whales were taken between

1965 and 1972, Mitchell (1975) described two "runs" of sei whales, in June-July and in September-October. 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 Scotian stock includes the continental shelf waters

of the northeastern USA, and extends northeastward to south of Newfoundland. The Scientific Committee of the IWC, while

adopting these general boundaries, noted that the stock identity of sei whales (and indeed all North Atlantic whales) was a major

research problem (Donovan 1991). In the absence of evidence to the contrary, the proposed IWC stock definition is provisionally

adopted, and the “Nova Scotia stock” is used here as the management unit for this Stock Assessment. The IWC boundaries for this

stock are from the USA east coast to Cape Breton, Nova Scotia, thence east to longitude 42o W.

POPULATION SIZE

The total number of sei whales in the 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 spring of

1978-82.

Mitchell and Chapman (1977), based on tag-recapture data, estimated the Nova Scotia, Canada, stock to contain between

1,393 and 2,248 sei whales (Table 1). Based on census data, they estimated a minimum Nova Scotian population of 870 sei whales.

A population size of 253 sei whales (CV=0.63) was estimated from an aerial survey program conducted from 1978 to 1982

on the continental shelf and shelf edge waters between Cape Hatteras, North Carolina and Nova Scotia (Table 1; CETAP 1982). The

estimate is based on data collected during the spring when the greatest proportion of the population off the northeast USA coast

appeared in the study area. This estimate does not include a correction for dive-time or g(0), the probability of detecting an animal

group on the track line. The CETAP report suggested, however, that correcting the estimated abundance for dive time would increase

the estimate to approximately the same as Mitchell and Chapman’s (1977) tag-recapture estimate. This estimate may not reflect

the current true population size because of its high degree of uncertainty (e.g., large CV), its old age, and it was estimated just after

cessation of extensive foreign fishing operations in the region. There are no recent abundance estimates for the sei whale.

Table 1. Summary of abundance estimates for the Nova Scotia stock of the sei whale. Month, year, and area covered during each

abundance survey, and resulting abundance estimate (Nbest) and coefficient of variation (CV). 
29

Month/Year Area Nbest CV

1966 - 1972 Nova Scotia, Canada 1,393 to 2,248 None reported

spring 1978-82 Cape Hatteras, NC to Nova Scotia 253 0.63

Minimum Population Estimate

The minimum population estimate is the lower limit of the two-tailed 60% confidence interval of the log-normally

distributed best abundance estimate. This is equivalent to the 20th percentile of the log-normal distribution as specified by Wade

and Angliss (1997). A current minimum population size cannot be estimated because there are no current abundance estimates (within

the last 10 years). 

Current Population Trend

There are insufficient data to determine the population trends for this species. 

CURRENT AND MAXIMUM NET PRODUCTIVITY RATES

Current and maximum net productivity rates are unknown for this stock. For purposes of this assessment, the maximum

net productivity rate was assumed to be 0.04. This value is based on theoretical modeling showing that cetacean populations may

not grow at rates much greater than 4% given the constraints of their reproductive life history (Barlow et al. 1995).

POTENTIAL BIOLOGICAL REMOVAL

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

and a “recovery” factor (MMPA Sec. 3. 16 U.S.C. 1362; Wade and Angliss 1997). The minimum population size is unknown. The

maximum productivity rate is 0.04, the default value for cetaceans. The “recovery” factor, which accounts for endangered, depleted,

threatened stocks, or stocks of unknown status relative to optimum sustainable population (OSP) is assumed to be 0.10 because the

sei whale is listed as endangered under the Endangered Species Act (ESA). PBR for the Nova Scotia stock of the sei whale is

unknown because the minimum population size is unknown.

ANNUAL HUMAN-CAUSED MORTALITY AND SERIOUS INJURY

There are few if any data on fishery interactions or human impacts. There was no reported fishery-related mortality or

serious injury to sei whales in fisheries observed by NMFS during 1993-1997. There are no reports of mortality, entanglement, or

injury in the NEFSC or NE Regional Office databases; however, there is a report of a ship strike. The New England Aquarium

documented a sei whale carcass hung on the bow of a container ship as it docked in Boston on November 17, 1994. The crew

estimated that the whale had been hung on the bow for approximately four days prior to the ship’s arriving in port. 

Fishery Information

There have been no reported entanglements or other interactions between sei whales and commercial fishing activities;

therefore there are no descriptions of fisheries.

STATUS OF STOCK

The status of this stock relative to OSP in the 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 level is insignificant and

approaching a zero mortality and serious injury rate. Any fishery-related mortality would be unlawful because there is no recovery

plan currently in place. This is a strategic stock because the sei whale is listed as an endangered species under the ESA.

REFERENCES

Barlow, J., S.L. Swartz, T. C. Eagle, and P.R. Wade. 1995. U.S. Marine Mammal Stock Assessments: Guidelines for preparation,

background, and a summary of the 1995 assessments. NOAA Technical Memorandum NMFS-OPR-6. U.S. Department

of Commerce, Washington, D.C. 73 pp.
30

CETAP. 1982. A characterization of marine mammals and turtles in the mid- and north Atlantic areas of the U.S. outer continental

shelf. Cetacean and Turtle Assessment Program, University of Rhode Island. Final Report #AA551-CT8-48 to the Bureau

of Land Management, Washington, DC, 538 pp. 

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

Hain, J. H. W., M. A. M. Hyman, R. D. Kenney, and H. E. Winn. 1985. The role of cetaceans in the shelf-edge region of the

northeastern United States. Mar. Fish. Rev. 47(1): 13-17.

Mitchell, E. 1975. Preliminary report on Nova Scotia fishery for sei whales (Balaenoptera borealis). Rep. int Whal. Commn.

25: 218-225. 

Mitchell, E. and D. G. Chapman. 1977. Preliminary assessment of stocks of northwest Atlantic sei whales (Balaenoptera

borealis). Rep. int Whal. Commn. Special Issue 1: 117-120.

Payne, P. M., D. N. Wiley, S. B. Young, S. Pittman, P. J. Clapham, and J. W. Jossi. 1990. Recent fluctuations in the abundance of

baleen whales in the southern Gulf of Maine in relation to changes in selected prey. Fish. Bull., U.S. 88: 687-696. 

Schilling, M. R., I. Seipt, M. T. Weinrich, S. E. Frohock, A. E. Kuhlberg, and P. J. Clapham. 1993. Behavior of individually

identified sei whales, Balaenoptera borealis, during an episodic influx into the southern Gulf of Maine in 1986. Fish.

Bull., U.S. 90(4): 749-755. 

Wade, P.R., and R.P. Angliss. 1997. Guidelines for assessing marine mammal stocks: Report of the GAMMS Workshop, April 3-5,

1996, Seattle, Washington. NOAA Technical Memorandum NMFS-OPR-12. U.S. Dept. of Commerce, Washington, D.C.

93 pp.
31

October 1999

BLUE WHALE (Balaenoptera musculus):

Western North Atlantic Stock

STOCK DEFINITION AND GEOGRAPHIC RANGE

The distribution of the blue whale, Balaenoptera musculus, in the western North Atlantic generally extends from the

Arctic to at least mid-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 (Sears et al. 1987). The species was hunted around Newfoundland in the first half of the 20th

century (Sergeant 1966). The present Canadian distribution, broadly described, is spring, summer, and fall in the Gulf of St.

Lawrence, especially along the north shore from the St. Lawrence River estuary to the Strait of Belle Isle and off eastern Nova Scotia.

The species occurs in winter off southern Newfoundland and also in summer in Davis Strait (Mansfield 1985). Individual

identification has confirmed the movement of a blue whale between the Gulf of St Lawrence and western Greenland (R. Sears and

F. Larsen, unpublished data), although the extent of exchange between these two areas remains unknown.

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

may represent the current southern limit of its feeding range (CETAP 1982; Wenzel et al. 1988). All of the five sightings described

in the foregoing two references were in August. Yochem and Leatherwood (1985) summarized records that suggested an occurrence

of this species south to Florida and the Gulf of Mexico, although the actual southern limit of the species’ range is unknown. 

Using the U.S. Navy’s SOSUS program, blue whales have been detected and tracked acoustically in much of the North

Atlantic, including in subtropical waters north of the West Indies and in deep water east of the 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 extent that they remain

rare in some formerly important habitats, notably in the northern and northeastern North Atlantic.

POPULATION SIZE

Little is known about the population size of blue whales except for in the Gulf of St. Lawrence area. Here, 308 individuals

have been catalogued (Sears et al. 1987), but the data were deemed to be unusable for abundance estimation (Hammond et al. 1990).

Mitchell (1974) estimated that the blue whale population in the western North Atlantic may number only in the low hundreds. R.

Sears (pers. comm.) suggests that no present evidence exists to refute this estimate. 

Minimum Population Estimate

The 308 recognizable individuals from the Gulf of St. Lawrence area which were catalogued by Sears et al. (1987) is

considered to be a minimum population estimate for the western North Atlantic stock. 

Current Population Trend

There are insufficient data to determine population trends for this species. Off western and southwestern Iceland, an

increasing trend of 4.9% a year was reported for the period 1969-1988 (Sigurjónsson and Gunnlaugsson 1990), although this estimate

should be treated with caution given the effort biases underlying the sightings data on which it was based.

CURRENT AND MAXIMUM NET PRODUCTIVITY RATES

Current and maximum net productivity rates are unknown for this stock. For purposes of this assessment, the maximum

net productivity rate was assumed to be 0.04. This value is based on theoretical modeling showing that cetacean populations may

not grow at rates much greater than 4% given the constraints of their reproductive life history (Barlow et al. 1995).

POTENTIAL BIOLOGICAL REMOVAL

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

and a “recovery” factor (MMPA Sec. 3. 16 U.S.C. 1362; Wade and Angliss 1997). The minimum population size is 308

(CV=unknown). The maximum productivity rate is 0.04, the default value for cetaceans. The “recovery” factor, which accounts for

endangered, depleted, threatened stocks, or stocks of unknown status relative to optimum sustainable population (OSP) is assumed
32

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 are no confirmed records of mortality or serious injury to blue whales in the USA Atlantic EEZ. However, in March

1998 a dead 66-foot male blue whale was brought into Rhode Island waters on the bow of tanker. The cause of death was determined

to be ship strike, although it was unclear whether the tanker concerned killed the whale or merely picked up the carcass after death.

The location of the strike was also 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. Any fisheryrelated mortality would be unlawful because there is no recovery plan currently in place, although a draft plan is currently in review.

This is a strategic stock because the blue whale is listed as an endangered species under the ESA.

REFERENCES

Barlow, J., S.L. Swartz, T. C. Eagle, and P.R. Wade. 1995. U.S. Marine Mammal Stock Assessments: Guidelines for preparation,

background, and a summary of the 1995 assessments. NOAA Technical Memorandum NMFS-OPR-6. U.S. Department

of Commerce, Washington, D.C. 73 pp.

CETAP. 1982. A characterization of marine mammals and turtles in the mid- and north Atlantic areas of the U.S. outer continental

shelf. Cetacean and Turtle Assessment Program, University of Rhode Island. Final Report #AA551-CT8-48 to the Bureau

of Land Management, Washington, DC, 538 pp. 

Clark, C.W. 1995. Application of U.S. Navy underwater hydrophone arrays for scientific research on whales. Rep. int. Whal.

Commn. 45: 210-212.

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

Lawrence from photo-identification data. Rep. int. Whal. Commn., Special Issue 12: 141-142.

Mansfield, A. W. 1985. Status of the blue whale, Balaenoptera musculus, in Canada. Canadian Field Naturalist 99(3):

417-420.

Mitchell, E. 1974. Present status of northwest Atlantic fin and other whale stocks. Pages 108-169 in W. E. Schevill (ed), The whale

problem: A status report. Harvard University Press, Cambridge, Massachusetts, 419 pp. 

Sears, R., F. Wenzel, and J. M. Williamson. 1987. The blue whale: a catalog of individuals from the western North Atlantic (Gulf

of St. Lawrence). Mingan Island Cetacean Study, St. Lambert, Quebec, Canada, 27 pp. 

Sergeant, D. E. 1966. Populations of large whale species in the western North Atlantic with special reference to the fin whale. Fish.

Res. Board. Canada Circular No. 9, 30 pp.

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

(Megaptera novaeangliae) off west and southwest Iceland, with a note on occurrence of other cetacean species. Rep.

int Whal. Commn. 40: 537-551.

Wade, P.R., and R.P. Angliss. 1997. Guidelines for assessing marine mammal stocks: Report of the GAMMS Workshop, April 3-5,

1996, Seattle, Washington. NOAA Technical Memorandum NMFS-OPR-12. U.S. Dept. of Commerce, Washington, D.C.

93 pp.

Wenzel, F., D. K. Mattila, and P. J. Clapham. 1988. Balaenoptera musculus in the Gulf of Maine. Mar. Mamm. Sci. 4(2):

172-175. 

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

Marine Mammals, Vol. 3: The Sirenians and Baleen Whales, Academic Press, New York. 
33

Figure 1. Distribution of minke whale sightings from

NEFSC shipboard and aerial surveys during the summer

in 1990-1995. Isobaths are at 100 m and 1,000 m. 

October 1999

MINKE WHALE (Balaenoptera acutorostrata):

Canadian East Coast Stock

STOCK DEFINITION AND GEOGRAPHIC RANGE

Minke whales have a cosmopolitan distribution in

polar, temperate and tropical waters. In the North Atlantic

there are four recognized populations — Canadian east coast,

west Greenland, central North Atlantic, and northeastern

North Atlantic (Donovan 1991). These four population

divisions were defined by examining segregation by sex and

length, catch distributions, sightings, marking data and preexisting ICES boundaries; however, there are very few data

from the Canadian east coast population. 

Minke whales off the eastern coast of the United

States are considered to be part of the Canadian east coast

population, which inhabits the area from the eastern half of

Davis Strait out to 45EW and south to the Gulf of Mexico.

The relationship between this and the other three populations

is uncertain. It is also uncertain if there are separate stocks

within the Canadian east coast population.

The minke whale is common and widely distributed

within the USA Atlantic Exclusive Economic Zone (EEZ)

(CETAP 1982). There appears to be a strong seasonal

component to minke whale distribution. Spring and summer

are times of relatively widespread and common occurrence,

and during this time they are most abundant in New England

waters. During fall, in New England waters, there are fewer

minke whales, while during winter, the species appears to be

largely absent. Like most other baleen whales, the minke

whale generally occupies the continental shelf proper, rather

than the continental shelf edge region. Records summarized by Mitchell (1991) hint at a possible winter distribution in the West

Indies and in mid-ocean south and east of Bermuda. As with several other cetacean species, the possibility of a deep-ocean

component to distribution exists but remains unconfirmed. 

POPULATION SIZE

The total number of minke whales in the Canadian East Coast population is unknown. However, four estimates are

available for portions of the habitat — a 1978-1982 estimate, a shipboard survey estimate from the summers of 1991 and 1992, a

shipboard estimate from June-July 1993, and an estimate made from a combination of a shipboard and aerial surveys conducted during

July to September 1995 (Table 1; Figure 1). 

A population size 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).

The estimate is based on spring data because the greatest proportion of the population off the northeast USA coast appeared in the

study area during this season. This estimate does not include a correction for dive-time or g(0), the probability of detecting an animal

group on the track line. This estimate may not reflect the current true population size because of its old age, and it was estimated

just after cessation of extensive foreign fishing operations in the region.

A population size of 2,650 (CV=0.31) minke whales was estimated from two shipboard line transect surveys conducted

during July to September 1991 and 1992 in the northern Gulf of Maine-lower Bay of Fundy region (Table 1). This population size

is a weighted-average of the 1991 and 1992 estimates, where each annual estimate was weighted by the inverse of its variance. The

data were collected during surveys designed to estimate abundance of harbor porpoises (Palka 1995). Two independent teams of

observers on the same ship surveyed using naked eye in non-closing mode. Using the product integral analytical method (Palka 1995)
34

and DISTANCE (Buckland et al. 1993; Laake et al. 1993) the abundance included an estimate of school size-bias, if applicable, an

estimate of g(0), probability of detecting a group on the track line, but no correction for dive-time or ship avoidance. Variability was

estimated using bootstrap re-sampling techniques. 

A population size 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). Data were collected by two alternating teams that

searched with 25x150 binoculars and were analyzed using DISTANCE (Buckland et al. 1993; Laake et al. 1993). Estimates include

school size-bias, if applicable, but do not include corrections for g(0) or dive-time. Variability was estimated using bootstrap resampling techniques.

A population size of 2,790 (CV=0.32) minke whales was estimated from a July to September 1995 sighting survey

conducted by two ships and an airplane that covered waters from Virginia to the mouth of the Gulf of St. Lawrence (Table 1;

NMFS/NEFSC unpublished data). Total track line length was 32,600 km (17,600 nmi). The ships covered waters between the 50

and 1000 fathom depth contour lines, the northern edge of the Gulf Stream, and the northern Gulf of Maine/Bay of Fundy region.

The airplane covered waters in the Mid-Atlantic from the coastline to the 50 fathom depth contour line, the southern Gulf of Maine,

and shelf waters off Nova Scotia from the coastline to the 1000 fathom depth contour line. This survey included the same region as

that covered during the above 1991 and 1992 sighting surveys. Shipboard data were collected using a two independent sighting team

procedure and were analyzed using the product integral method (Palka 1995) and DISTANCE (Buckland et al. 1993). Shipboard

estimates were corrected for g(0) and, if applicable, also for school size-bias. Standard aerial sighting procedures with two bubble

windows and a belly window observer were used during the aerial survey (Palka 1996). An estimate of g(0) was not made for the

aerial portion of the survey. Estimates do not include corrections for dive-time or platform avoidance. Variability was estimated

using bootstrap re-sampling techniques. Minke whales were only detected in the Georges Bank - Gulf of Maine - Bay of Fundy

region by one of the ships and the plane.

There are no estimates of abundance for this species in Canadian waters that lie farther north or east of the above survey’s

study area. 

The best available current abundance estimate for minke whales is 2,790 (CV=0.32) as estimated from the July to September

1995 line transect surveys because this survey is recent and provided the most complete coverage of the known habitat.

Table 1. Summary of abundance estimates for Canadian East Coast minke whales. Month, year, and area covered during

each abundance survey, and resulting abundance estimate (Nbest) and coefficient of variation (CV).

Month/Year Area Nbest CV

spring 1978-82 Cape Hatteras, NC to

Nova Scotia 320 0.23

Jul -Sep 1991-92 N. Gulf of Maine and

Bay of Fundy 2,650 0.31

Jun-Jul 1993

Georges Bank to

Scotian shelf, shelf

edge only

330 0.66

Jul-Sep 1995 Virginia to Gulf of St.

Lawrence 2,790 0.32

Minimum Population Estimate

The minimum population estimate is the lower limit of the two-tailed 60% confidence interval of the log-normally

distributed best abundance estimate. This is equivalent to the 20th percentile of the log-normal distribution as specified by Wade

and Angliss (1997). The best estimate of abundance for minke whales is 2,790 (CV=0.32). The minimum population estimate for

Canadian East Coast minke whale is 2,145 (CV=0.32).

Current Population Trend
35

There are insufficient data to determine population trends for this species. 

CURRENT AND MAXIMUM NET PRODUCTIVITY RATES

Current and maximum net productivity rates are unknown for this stock. Life history parameters that could be used to

estimate net productivity include: females mature when 6-8 years old; pregnancy rates are approximately 0.86 to 0.93; thus, the

calving interval is between 1 and 2 years; calves are probably born during October to March, after 10 to 11 months gestation; nursing

lasts for less than 6 months; maximum ages are not known, but for Southern Hemisphere minke whales the maximum age appears

to be about 50 years (Katona et al. 1993; IWC 1991). 

For purposes of this assessment, the maximum net productivity rate was assumed to be 0.04. This value is based on

theoretical modeling showing that cetacean populations may not grow at rates much greater than 4% given the constraints of their

reproductive life history (Barlow et al. 1995). 

POTENTIAL BIOLOGICAL REMOVAL

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

and a “recovery” factor (MMPA Sec. 3. 16 U.S.C. 1362; Wade and Angliss 1997). The minimum population size is 2,145

(CV=0.32). The maximum productivity rate is 0.04, the default value for cetaceans. The “recovery” factor, which accounts for

endangered, depleted, threatened, or stocks of unknown status relative to optimum sustainable population (OSP) is assumed to be

0.5 because this stock is of unknown status. PBR for the Canadian east coast minke whale is 21.

ANNUAL HUMAN-CAUSED MORTALITY AND INJURY

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 “Unknown Fisheries”

and the lobster trap fishery within the Fishery Information section and under the Other Mortality section (Tables 4 and 5).

 After USA strandings and entanglement records are completely audited the mortality and serious injury estimate will be

updated. Using the data presently available and audited, for 1993 to 1997, the USA total annual estimated average human-caused

mortality is 5.8 minke whales per year. This is derived from three components: 1.1 minke whales per year (CV=0.0) from USA

observed fisheries, 3.7 minke whales per year from USA fisheries not observed using strandings and entanglement data, and one ship

strike in 1996.

Fishery Information

Recent minke whale takes have been observed in USA waters in the Atlantic pelagic drift gillnet, bluefin tuna purse seine,

and Gulf of Maine and mid-Atlantic lobster trap/pot fisheries, and in fish weirs; though all takes have not resulted in a mortality

(Tables 2 and 3).

USA

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

mandatory self-reported fishery information system for large pelagic fisheries. Data files are maintained at the Southeast Fisheries

Science Center (SEFSC). The Northeast Fisheries Science Center (NEFSC) Sea Sampling Observer Program was initiated in 1989,

and since that year several fisheries have been covered by the program. In late 1992, the SEFSC started observer coverage of pelagic

longline vessels fishing off the Grand Banks (Tail of the Banks) south of Cape Hatteras.

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.

Prior to 1977, there was no documentation of marine mammal by-catch in 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 of incidental by-catch of marine mammals. A minke

whale was caught and released alive in the Japanese tuna longline fishery in 3,000 m of water, south of Lydonia Canyon on Georges

Bank, in September 1986 (Waring et al. 1990). In 1982, there were 112 different foreign vessels; 16%, or 18, were Japanese tuna

longline vessels operating along the USA east coast. This was the first year that the Northeast Regional Observer Program assumed
36

responsibility for observer coverage of the longline vessels. Between 1983 and 1988, the number of Japanese longline vessels

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

Two minke whales were observed taken in the New England multispecies sink gillnet fishery between 1989 and the present.

The take in July 1991, south of Penobscot Bay, Maine resulted in a mortality, and the take in October 1992, off the coast of New

Hampshire near Jeffreys Ledge was released alive. There were approximately 349 vessels (full and part time) in the New England

multispecies sink gillnet fishery in 1993 (Walden 1996). Observer coverage as a percentage of trips has been 1%, 6%, 7%, 5%, 7%,

5%, and 4%, and 6% for years 1990 to 1997. Because no mortalities have been observed within the most recent five years (1993 to

1997), the annual estimated average New England multispecies sink gillnet fishery-related mortality for minke whales is zero.

A minke whale was trapped and released alive in 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 western Nova Scotia and northern Maine coasts. In 1990 there were 56 active weirs in Maine (Read 1994). According to

state of Maine officials, in 1998, the number of weirs in Maine waters dropped to nearly nothing due to the limited herring market

(Jean Chenoweth pers. comm.). The actual number of active weirs in the USA is unknown.

New England Multispecies Sink Gillnet

Because no interactions between minke whales and this fishery were observed within the most recent five years (1993 to

1997) this section was moved to the Earlier Interactions section above. 

Pelagic Drift Gillnet

In 1996 and 1997, the NMFS issued management regulations which prohibited the operation of this fishery in 1997.

Further, in January 1999 the NMFS issued a Final Rule to prohibit the use of driftnet gear in the North Atlantic swordfish fishery

(50 CFR Part 630). Four minke whale mortalities were observed in the Atlantic pelagic drift gillnet fishery during 1995 (Table 2).

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, 1995, and 1996 there were 12, 11 and 10 vessels, respectively, in the fishery (Table 2).

Observer coverage, expressed as percent of sets, was 8% in 1989, 6% in 1990, 20% in 1991, 40% in 1992, 42% in 1993, 87% in 1994,

99% in 1995, and 64% in 1996 (Table 2). 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 by-catch, 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 by-catch for 1994 through 1996 were estimated separately for

each year by summing the observed caught with the product of the average by-catch per haul and number of unobserved hauls as

recorded in SEFSC logbooks. Variances were estimated using bootstrap re-sampling techniques. Estimated annual fishery-related

mortality and serious injury (CV in parentheses) was 0 for 1989 to 1994, 4.5 (0) for 1995, and 0 for 1996. The fishery was closed

during 1997. Estimated average annual mortality and serious injury related to this fishery during 1993 to 1996 was 1.1 minke whales

(CV=0.00) (Table 2).

Bluefin Tuna Purse Seine

In a bluefin 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. 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 directed at large medium and giant bluefin tuna (NMFS 1995). The latter fisheries are entirely

separate from any other Atlantic tuna purse seine fishery. Spotter aircraft are used to locate fish schools. The official start date,

set by regulation, is August 15. Individual vessel quotas (IVQs) and a limited access system prevent a derby fishery situation. Catch

rates for large mediums and giant tuna are high and consequently, the season usually only lasts a few weeks. The 1996 regulations

allocated 250 MT (5 IVQs) with a minimum of 90% giants and 10% large mediums.

Limited observer data are available for the 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. No trips were observed during 1997.

Gulf of Maine and Mid-Atlantic Lobster Trap/Pot Fishery
37

The strandings and entanglement database, maintained by the New England Aquarium and the Northeast Regional

Office/NMFS, reported seven minke whale mortalities and serious injuries that were attributed to the lobster fishery during 1990 to

1994, 1 in 1990 (may be serious injury), 2 in 1991 (one mortality and one a 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). Other than these records, only the 1997

entanglements have been completely audited. From the four 1997 records one minke whale mortality was attributed to the lobster

trap fishery (Tables 4 and 5). The fishery attributing to the other three 1997 minke mortalities could not be determined (see unknown

fisheries). 

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

Island Sound, and 3) Georges Bank and South to Cape Hatteras. In 1997, there were 3,431 vessels holding licenses to harvest lobsters

in federal waters, 2,674 vessels licensed to use lobster pot gear in state waters, 675 vessels licensed to use bottom trawls and

approximately 100 licenses to use dredge gear to harvest lobsters. 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 are harvested from state waters. The offshore

fishery in federal waters has developed in the past 10 to 15 years, largely due to technological improvements in equipment and lower

competition in the offshore areas. In January 1997, NMFS changed the classification of the Gulf of Maine and USA Mid-Atlantic

lobster pot fisheries from Category III to Category I (1997 List of Fisheries 62FR33, January 2, 1997) based on examination of 1990

to1994 stranding and entanglement records of large whales (including right whales, humpback and minke whales). 

Annual mortalities due to this fishery, as determined from strandings and entanglement records that have been audited, were

1 in 1991, 2 in 1992, 1 in 1994, and 1 in 1997. Estimated average annual mortality related to this fishery during 1993 to 1997

(excluding 1995 and 1996 because data not audited) was 0.7 minke whales per year (Table 4). The mortality estimate will be updated

when all strandings and entanglement records have been audited.

Unknown Fisheries

The strandings and entanglement database, maintained by the New England Aquarium and the Northeast Regional

Office/NMFS, included 36 records of minke whales within USA waters for 1975-1992. The gear included unspecified fishing net,

unspecified cable or line, fish trap, weirs, seines, gillnets, and lobster gear. A review of these records is not complete. One confirmed

entanglement was an immature female minke whale, entangled with line around the tail stock that came ashore on the Jacksonville,

Florida, jetty on 31 January 1990 (R. Bonde, USFWS, Gainesville, FL, pers. comm.). The NE Regional Office

entanglement/stranding database for 1993 to 1997 also contains records of minke whales. However, at this time only the 1997 records

have been audited (Tables 4 and 5). Other years will be available later. The examination of the minke entanglement records from 1997

indicate that 4 out of 4 records of mortality are likely a result of fishery interactions, one attributed to the lobster pot fishery (see

above), and three could not be attributed to a particular fishery because the reports do not contain the necessary details.

In general, an entangled or stranded cetacean could be an animal that is part of a expanded by-catch 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, there

were no minke whales observed taken in any fishery that participated in the Sea Sampling Program, however, there were three

confirmed minke whale mortalities due to some unknown fishery. Thus, for 1997, three is the best minimum estimate of mortality

due to one or more fisheries.

CANADA

In Canadian waters, information about minke whale interactions with fishing gear is not well quantified or recorded, though

some records are available. Read (1994) reported interactions between minke whales and gillnets in Newfoundland and Labrador, cod

traps in Newfoundland, and herring weirs in the Bay of Fundy.

Herring Weirs

During 1980 and 1990, 15 of 17 minke whales were released alive from herring weirs in the Bay of Fundy. In 1990, ten

minke whales were trapped in the Bay of Fundy weirs, but all were released alive. 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 Bay of Fundy, and scattered along the western Nova Scotia and northern Maine coasts. In 1990 there were 180 active

weirs in western Bay of Fundy (Read 1994). According to Canadian DFO officials, for 1998, there were 225 weir licenses for herring

weirs on the New Brunswick and Nova Scotia sides of the Bay of Fundy (60 from Grand Manan Island, 95 from Deer and

Campobello Islands, 30 from Passamaquoddy Bay, 35 from East Charlotte area, and 5 from the Saint John area). This number has

been fairly consistent since 1985 (Ed Trippel, pers. comm.).
38

Other Fisheries

Six minke whales were reported entangled during 1989 in the now non-operational groundfish gillnet fishery in the

Newfoundland and Labrador (Read 1994). One of these animals escaped towing gear, the rest died. 

Salmon gillnets in Canada, now no longer being used, had taken a few minke whales. In Newfoundland in 1979, one minke

whale died in a salmon net. In Newfoundland and Labrador, between 1979 and 1990, it was estimated that 15% of the Canadian

minke whale takes were in salmon gillnets, where a total of 124 minke whale interactions were documented in cod traps, groundfish

gillnets, salmon gillnets, other gillnets and other traps. This fishery ended in 1993 as a result of an agreement between the fishermen

and North Atlantic Salmon Fund (Read 1994).

Five minke whales were entrapped and died in Newfoundland cod traps during 1989. The cod trap fishery in

Newfoundland closed in 1993 due to the depleted groundfish resources (Read 1994).
39

Table 2. Summary of the incidental mortality of minke whales (Balaenoptera acutorostrata) by commercial fishery including

the years sampled (Years), the number of vessels active within the fishery (Vessels), the type of data used (Data Type),

the annual observer coverage (Observer Coverage), the mortalities recorded by on-board observers (Observed Mortality),

the estimated annual mortality (Estimated Mortality), the estimated CV of the annual mortality (Estimated CV) 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

Pelagic Drift

Gillnet

93-97 1994=123

1995=11

1996=10

1997=NA6

Obs. Data

Logbook

.42, .87, .99,

.64, NA6

0

4

,04,

4

4

,04, NA6

0

4

, 04,

4.55, 04,

NA6

0 1.16

(0)

TOTAL 1.16

(0)

1 Observer data (Obs. Data) are used to measure by-catch rates, and the data are collected within the Northeast Fisheries

Science Center (NEFSC) Sea Sampling Program. 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 unit of effort for the observer coverage of the pelagic drift gillnet fishery is percent of sets.

3 1994-1997 shown, other years not available on an annual basis.

4 For 1991-1993, pooled by-catch rates were used to estimate by-catch in months that had fishing effort but did not have

observer coverage (Northridge 1996). After 1993, observer coverage increased substantially, and bycatch rates were annual

rates (Bisack 1997). There was no fishery in 1997. 

5 One vessel, not observed during 1995, recorded in the SEFSC mandatory logbook 1 set in a 10 day trip. If it is assumed

that the vessel fished 1.4 sets per day, as estimated from the 1995 Sea Sampling data, the point estimate increases by 0.42

animals. However, the SEFSC mandatory logbook data were taken at face value, and therefore it was assumed 1 set was

fished within this trip; thus the point estimate increases by 0.03 animals.

6 Fishery closed during 1997. So average by-catch is for 1993 to 1996.

Table 3. Summary of minke whales (Balaenoptera acutorostrata) released alive, by commercial fishery, years sampled (Years),

ratio of observed mortalities recorded by on-board observers to the estimated mortality (Ratio), the number of observed

animals released alive and injured (Injured), and the number of observed animals released alive and uninjured (Uninjured).

Fishery Years Ratio Injured Uninjured

Tuna purse seine 96-97 0/0, NA20,NA21

1

, NA2

NA=Not Available.

1

 The minke whale escaped by diving beneath the net.

2

 No observer coverage during 1997.
40

Table 4. From strandings and entanglement data, summary of the incidental mortality of minke whales (Balaenoptera

acutorostrata) by commercial fishery: includes years sampled (Years), number of vessels active within the fishery

(Vessels), type of data used (Data Type), mortalities assigned to this fishery (Mortality), and mean annual mortality.

Fishery Years Vessels Data Type 1 Observed Mortality Mean Annual

Mortality

GOM and midAtlantic Lobster

Trap/Pot

93-97 1997=6880

licenses2

Entanglement

& Strandings

0,1,NA3,

NA3,1

0.73

(0)

Unknown Fisheries 97 NA Entanglement

& Strandings 

3 3

(0)

TOTAL 3.7

(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 1995 and 1996 stranding and entanglement records have not been audited, so average by-catch is an average of 1993, 1994 and

1997.

Table 5. Summary of audited records of mortality and serious injury likely to result in mortality for minke whales. This listing

includes only records related to USA commercial fisheries and/or USA waters. Cause of mortality or injury, assigned as

primary or secondary, 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

Unknown

uncertain

7/2/94 mortality NA off NH P Lobster lines (3 pair traps

involved; line through

mouth; one line around

lower jaw; chafing on tail;

whale brought up dead

with traps.

5/15/97 mortality female

5.5m (est)

Gloucester,

MA (42E36 

70E38')

P Deep lacerations around

tail stock, abrasions

around flukes and mouth

5/16/97 mortality female

5.5m (est)

Rockport, MA

(42E40

70E35')

P Abrasions around flukes;

feeding prior to

entanglement

8/14/97 mortality female

2.8m

Jewell Island,

ME (43E39'

70E02')

P Fresh lacerations on

flukes and pectoral fins

8/30/97 mortality female

8m (est)

Cape Small,

ME (43E40'

69E57')

P Observed entangled in

lobster gear by ME

Marine Patrol

Other Mortality
41

Minke whales have been and are still being hunted in the North Atlantic. From the Canadian East Coast population, documented

whaling occurred from 1948 to 1972 with a total kill of 1,103 animals (IWC 1992). Animals from other North Atlantic populations

are presently still being harvested at low levels.

 Minke whales inhabit coastal waters during much of the year and are 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 1992, a juvenile female minke whale with propeller scars was found floating east of the St. Johns channel

entrance (R. Bonde, USFWS, Gainesville, FL, pers. comm.); and on 15 July 1996 the captain of a vessel reported they hit a minke

whale offshore MA .

All entangled and stranded minke whales from 1993 to 1998 that had injuries suggestive of a vessel collision or fishery interactions

will be audited and summarized in the next stock assessment report.

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 not less than 10%

of the calculated PBR and, therefore, cannot be considered to be insignificant and approaching zero mortality and serious injury rate.

This is not a strategic stock because estimated fishery-related mortality and serious injury does not exceed PBR and the minke whale

is not listed as a threatened or endangered species under the ESA. 

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., NOAA Tech. Memo. NMFS-OPR-6, 73 pp.

Bisack, K.D. 1997. Marine mammal bycatch estimates and their sampling distributions in the U.S. New England sink gillnet, pair

trawl, Atlantic pelagic drift gillnet and North Atlantic bottom trawl fisheries: 1994 to 1996. Working paper SC/49/SM35

submitted to the IWC Scientific Committee meeting in Bournemouth, UK, Aug/Sept 1997.

Buckland, S. T., D. R. Anderson, K. P. Burnham, and J. L. Laake. 1993. Distance Sampling: Estimating abundance of biological

populations. Chapman & Hall, New York, 446 pp. 

CETAP. 1982. A characterization of marine mammals and turtles in the mid- and north Atlantic areas of the U.S. outer continental

shelf. Cetacean and Turtle Assessment Program, University of Rhode Island. Final Report, Contract AA51-C78-48, Bureau of

Land Management, Washington, DC, 538 pp. 

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

IWC [International Whaling Commission]. 1991. Appendix 11. Biological parameters of North Atlantic minke whales in Annex F

Report of the sub-committee on North Atlantic Minke whales. Rep. int Whal. Commn. 41: 160.

IWC [International Whaling Commission]. 1992. Annex K. Report of the working group on North Atlantic Minke trials. Rep. int

Whal. Commn. 42: 246-251.

Katona, S. K., V. Rough, and D. T. Richardson. 1993. A field guide to whales, porpoises, and seals from Cape Cod to

Newfoundland. Smithsonian Institution Press. Washington. 316 pp. 

Laake, J. L., S. T. Buckland, D. R. Anderson, and K. P. Burnham. 1993. DISTANCE user’s guide, V2.0. Colorado Cooperative Fish

& Wildlife Research Unit, Colorado State University, Ft. Collins, Colorado, 72 pp. 

Mitchell, E. D. 1991. Winter records of the Minke whale (Balaenoptera acutorostrata Lacepede 1804) in the southern North

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

National Marine Fisheries Service (NMFS). 1995. Final environmental impact statement for a regulatory amendment for the western

Atlantic bluefin tuna fishery. July 20, 1995.

Northridge, S. 1996. Estimation of cetacean mortality in the U.S. Atlantic swordfish and tuna driftnet and pair trawl fisheries. Final

report to the Northeast Fisheries Science Center, Contract No. 40ENNF500045, 18 pp. 

Palka, D. 1996. Update on abundance of Gulf of Maine/Bay of Fundy harbor porpoises. Northeast Fish. Sci. Cent. Ref. Doc. 96-04;

37p. Available from: National Marine Fisheries Service, 166 Water Street, Woods Hole, MA 02543-1026.

Palka, D. 1995. Abundance estimate of the Gulf of Maine harbor porpoise. pp. 27-50. In: A. Bjørge and G.P. Donovan (eds.)

Biology of the Phocoenids. Rep. int Whal. Commn. Special Issue 16. 
42

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

Special Issue 15: 133-147. 

Wade, P. R. and R. P. Angliss. 1997. Guidelines for assessing marine mammal stocks: Report of the GAMMS workshop April 3-5,

1996, Seattle, Washington. U.S. Dep. Commer., NOAA Tech. Memo. NMFS-OPR-12, 93 pp.

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

Science Center, Woods Hole, Massachusetts. 

Waring, G. T., P. Gerrior, P. M. Payne, B. L. Parry, and J. R. Nicolas. 1990. Incidental take of marine mammals in foreign fishery

activities off the northeast United States, 1977-1988. Fish. Bull., U.S. 88(2): 347-360.
43

Figure 1. Distribution of sperm whale sightings from

NEFSC shipboard and aerial surveys during the summer

in 1990-1995. Isobaths are at 100 m and 1,000 m. 

October 1999

SPERM WHALE (Physeter macrocephalus):

 North Atlantic Stock

STOCK DEFINITION AND GEOGRAPHIC RANGE

The distribution of the sperm whale in the USA EEZ

occurs on the continental shelf edge, over the continental slope,

and into mid-ocean regions (Figure 1). Waring et al. (1993)

suggest that this offshore distribution is more commonly

associated with the Gulf Stream edge and other features.

However, the sperm whales that occur in the eastern 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,

and offshore is unknown. Historical whaling records compiled

by Schmidly (1981) suggested an offshore distribution off the

southeast USA, over the Blake Plateau, and into deep ocean.

In the southeast Caribbean, both large and small adults, as well

as calves and juveniles of different sizes are reported (Watkins

et al. 1985). Whether the northwest Atlantic population is

discrete from the northwestern or northeastern Atlantic is

currently unresolved. The International Whaling Commission

recognizes one stock for the North Atlantic. Based on a review

of tagging and genetic studies, Reeves and Whitehead (1997)

suggest that sperm whale populations have no clear geographic

structure. There exists one tag return of a male tagged off

Browns Bank (Nova Scotia) in 1966 and returned from Spain

in 1973 (Mitchell 1975). Another male taken off northern

Denmark in August 1981 had been wounded the previous

summer by whales off the Azores (Reeves and Whitehead

1997).

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 center of distribution shifts northward to east of Delaware and Virginia, and is widespread throughout the central

portion of the mid-Atlantic bight and the southern portion of Georges Bank. In summer, the distribution is similar but now also

includes the area east and north of Georges Bank and into the Northeast Channel region, as well as the continental shelf (inshore of

the 100m isobath) south of New England. In the fall, sperm whale occurrence south of New England on the continental shelf is at

its highest level, and there remains a continental shelf edge occurrence in the mid-Atlantic bight. Similar inshore (<200m) observations

have been made on the southwestern portion (Kenney pers. comm) and the eastern Scotian Shelf, particularly in the region of “the

Gully” (Whitehead et al. 1991).

Geographic distribution of sperm whales may be linked to their social structure and their low reproductive rate and both of these

factors have management implications. Several basic groupings or social units are generally recognized — nursery schools, harem

or mixed schools, juvenile or immature schools, bachelor schools, bull schools or pairs, and solitary bulls (Best 1979; Whitehead et

al. 1991). These groupings have a distinct geographical distribution, with females and juveniles generally based in tropical and

subtropical waters, and males more wide-ranging and occurring in higher latitudes. Male sperm whales are present off and sometimes

on the continental shelf along the entire east coast of Canada south of Hudson Strait, whereas, females rarely migrate north of the

southern limit of the Canadian EEZ (Reeves and Whitehead 1997). However off the northeast U.S, CETAP and NMFS/NEFSC

sightings in shelf-edge and off-shelf waters included many social groups with calves/juveniles (CETAP 1981; Waring et al. 1992,

1993). The basic social unit of the sperm whale appears to be the mixed school of adult females plus their calves and some juveniles

of both sexes, normally numbering 20-40 animals in all. There is evidence that some social bonds persist for many years.
44

POPULATION SIZE

Total number of sperm whales off the USA or Canadian Atlantic coast are unknown, although seven estimates from selected

regions of the habitat do exist for select time periods (Table 1): spring and summer of 1978-82, August 1990, June-July 1991, AugustSeptember 1991, June-July 1993, August 1994, and July-September 1995. These surveys were conducted in continental shelf edge

and/or deeper oceanic waters. Sightings were almost exclusively in the continental shelf edge and continental slope areas (Figure 1).

A population size of 219 sperm whales (CV=0.36) was estimated from an aerial survey program conducted from 1978 to 1982

on the continental shelf and shelf edge waters between Cape Hatteras, North Carolina and Nova Scotia (Table 1; CETAP 1982). The

estimate is based on an inverse variance weighted pooling of spring and summer data. An average of these seasons were chosen

because the greatest proportion of the population off the northeast USA coast appeared in the study area during these seasons. This

estimate does not include corrections for dive-time or g(0), the probability of detecting an animal group on the track line. This

estimate may not reflect the current true population size because of its high degree of uncertainty, its old age, and it was estimated

just after cessation of extensive foreign fishing operations in the region.

A population size of 338 (CV=0.31) sperm whales was estimated from an August 1990 shipboard line transect sighting survey,

conducted principally along the Gulf Stream north wall between Cape Hatteras and Georges Bank (Table 1; Anon. 1990; Waring et

al. 1992). Data were collected by one team that searched by naked eye and 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.

A population size 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 (Table 1; Waring et al. 1992;

Waring 1998). Data were collected by one team that searched by naked eye and analyzed using DISTANCE (Buckland et al. 1993;

Laake et al. 1993). Estimates include school size-bias, if applicable, but no corrections for g(0) or dive-time. Variability was

estimated using bootstrap resampling techniques.

A population size of 705 (CV=0.66) and 337 (CV=0.50) sperm whales was estimated from line transect aerial surveys conducted

from August to September 1991 using the Twin Otter and AT-11, respectively (Table 1; Anon. 1991). The study area included that

covered in the CETAP study plus several additional continental slope survey blocks. Due to weather and logistical constraints,

several survey blocks south and east of Georges Bank were not surveyed. The data were analyzed using DISTANCE (Buckland et

al. 1993; Laake et al. 1993), where the CV was estimated using the bootstrap option. The abundance estimates do not include g(0)

and were not pooled over platforms because the inter-platform calibration analysis has not been conducted.

A population size of 116 (CV=0.40) sperm whales was estimated from a June and July 1993 shipboard line transect sighting

survey conducted principally between the 200 and 2,000m isobaths from the southern edge of Georges Bank, across the Northeast

Channel to the southeastern edge of the Scotian Shelf (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 bootstrap

resampling techniques.

A population size of 623 (CV=0.52) sperm whales was estimated from an August 1994 shipboard line transect survey conducted

within a Gulf Stream warm-core ring located in continental slope waters southeast of Georges Bank (Table 1; Anon. 1994). Data were

collected by two alternating teams that searched with 25x150 binoculars and an independent observer who searched by naked eye

from a separate platform on the bow. Data were analyzed using DISTANCE (Buckland et al. 1993; Laake et al. 1993). Estimates

include school size-bias, if applicable, but do not include corrections for g(0) or dive-time. Variability was estimated using bootstrap

resampling techniques.

A population size of 2,698 (CV=0.67) sperm whales was estimated from a July to September 1995 sighting survey conducted

by two ships and an airplane that covered waters from Virginia to the mouth of the Gulf of St. Lawrence (Table 1; NMFS,

unpublished data). Total track line length was 32,600 km (17,600 nmi). 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. Shipboard data were collected using a two independent sighting team

procedure and were analyzed using the product integral method (Palka 1995) and DISTANCE (Buckland et al. 1993). Shipboard

estimates were corrected for g(0) and, if applicable, also for school size-bias. Standard aerial sighting procedures with two bubble

windows and one belly window observer were used during the aerial survey. An estimate of g(0) was not made for the aerial portion

of the survey. Estimates do not include corrections for dive-time. Variability was estimated using bootstrap resampling techniques.
45

Because all the sperm whale estimates presented here were not corrected for dive-time, they are likely downwardly biased and

an underestimate of actual abundance. Given that the average dive-time of sperm whales is approximately 45 min (Whitehead et al.

1991; Watkins et al. 1993), the bias may be substantial. 

Although the stratification schemes used in the 1990-1995 surveys did not always sample the same areas or encompass the entire

sperm whale habitat, they did focus on segments of known or suspected high-use habitats off the northeastern USA coast. The

collective 1990-95 data suggest that, seasonally, at least several hundred sperm whales are occupying these waters. The 1995

estimate is nearly eight-fold greater than CETAP data from a decade previous. Sperm whale abundance may increase offshore,

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

sperm whale abundance in the western North Atlantic. 

The best available current abundance estimate for the western North Atlantic sperm whale is 2,698 (CV=0.67) as estimated from

the July to September 1995 line transect survey (NMFS, unpublished data) because this survey is recent and provided the most

complete coverage of continental shelf edge and continental slope waters off the northeast USA coast.

Table 1. Summary of abundance estimates 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

spring & summer

1978-82

Cape Hatteras, NC to

Nova Scotia 219 0.36

Aug 1990 Gulf Stream 338 0.31

Jun-Jul 1991

Cape Hatteras, NC to

Georges Bank, shelf

edge only

736 0.33

Aug-Sep 1991 Cape Hatteras, NC to

Nova Scotia 705 and 337*

0.66 and 0.50*

Jun-Jul 1993

Georges Bank to

Scotian shelf, shelf

edge only

116 0.40

Aug 1994 warm-core ring SE of

Georges Bank 623 0.52

Jul-Sep 1995 Virginia to Gulf of St.

Lawrence 2,698 0.67

* From data collected on the Twin Otter and AT-11, respectively.

Minimum Population Estimate

The minimum population estimate is the lower limit of the two-tailed 60% confidence interval of the log-normally distributed

best abundance estimate. This is equivalent to the 20th percentile of the log-normal distribution as specified by Wade and Angliss

(1997). The best estimate of abundance for sperm whales is 2,698 (CV=0.67). The minimum population estimate for the western

North Atlantic sperm whale is 1,617 (CV=0.67).

Current Population Trend

There are insufficient data to determine the population trends for this species. 

CURRENT AND MAXIMUM NET PRODUCTIVITY RATES

Current and maximum net productivity rates are unknown for this stock. While more is probably known about sperm whale life

history in other areas, some life history and vital rates information is available for the northwest Atlantic. These include: calving
46

interval is 4-6 years, lactation period is 24 months, gestation period is 14.5-16.5 months, births occur mainly in July to November,

length at birth is 4.0 m, length at sexual maturity 11.0-12.5 m for males, and 8.3-9.2 m for females, mean age at sexual maturity is 19

years for males and 9 years for females, and mean age at physical maturity is 45 years for males and 30 years for females (Best 1974;

Lockyer 1981; Best et al. 1984). 

For purposes of this assessment, the maximum net productivity rate was assumed to be 0.04. This value is based on theoretical

modeling showing that cetacean populations may not grow at rates much greater than 4% given the constraints of their reproductive

life history (Barlow et al. 1995). 

POTENTIAL BIOLOGICAL REMOVAL

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

a “recovery” factor (MMPA Sec. 3. 16 U.S.C. 1362; Wade and Angliss 1997). The minimum population size is 1,617 (CV=0.67).

The maximum productivity rate is 0.04, the default value for cetaceans. The “recovery” factor, which accounts for endangered,

depleted, threatened stocks, or stocks of unknown status relative to optimum sustainable population (OSP) is assumed to be 0.10

because the sperm whale is listed as endangered under the Endangered Species Act (ESA). PBR for the western North Atlantic sperm

whale is 3.2.

ANNUAL HUMAN-CAUSED MORTALITY

Four hundred twenty-four sperm whales were harvested in the Newfoundland-Labrador area between 1904-1972 and 109 male

and no female sperm whales were taken near Nova Scotia in 1964-1972 (Mitchell and Kozicki 1984) in a Canadian whaling fishery.

There was also a well-documented sperm whale fishery based on the west coast of Iceland. Other sperm whale catches occurred near

West Greenland, the Azores, Madeira, Spain, Spanish Morocco, Norway (coastal and pelagic), Faroes, and British coastal. At

present, because of their general offshore distribution, sperm whales are less likely to be impacted by humans and those impacts that

do occur are less likely to be recorded. There has been no complete analysis and reporting of existing data on this topic for the

western North Atlantic.

Total annual estimated average fishery-related mortality or serious injury to this stock during 1993-1997 was zero sperm whales.

Although, in 1995 one sperm whale was entangled in a pelagic drift gillnet and released alive with gear around several body parts.

Presently, this injury has not been used to estimate mortality.

Fishery Information

Three sperm whale entanglements have been documented from August 1993 to May 1997. 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 nm northwest of Bermuda. No information on the status of the animal was provided. 

Data on current incidental takes in U.S. fisheries are available from several sources. In 1986, NMFS established a mandatory selfreported fisheries information system for large pelagic fisheries. Data files are maintained at the Southeast Fisheries Science Center

(SEFSC). The Northeast Fisheries Science Center (NEFSC) Sea Sampling Observer Program was initiated in 1989, and since that

year several fisheries have been covered by the program. In late 1992 and in 1993, the SEFSC provided observer coverage of pelagic

longline vessels fishing off the Grand Banks (Tail of the Banks) and currently provides observer coverage of vessels fishing south

of Cape Hatteras.

By-catch has been observed by NMFS Sea Samplers in the pelagic drift gillnet fishery, but no mortalities or serious injuries have

been documented in the pelagic longline, pelagic pair trawl, New England multispecies sink gillnet, mid-Atlantic coastal sink gillnet,

or North Atlantic bottom trawl observed fisheries.

Pelagic Drift Gillnet

Only two records exist in the present NEFSC by-catch database. In July 1990, a sperm whale was entangled and subsequently

released (injured) from a pelagic drift gillnet near the continental shelf edge on southern Georges Bank. During June 1995, one sperm

whale was entangled with “gear in/around several body parts” then released injured from a pelagic drift gillnet haul located on the shelf

edge between Oceanographer and Hydrographer Canyons on Georges Bank.

The estimated total number of hauls in the pelagic drift net fishery increased from 714 in 1989 to 1144 in 1990; thereafter, with

the introduction of quotas, effort was severely reduced. The estimated number of hauls in 1991, 1992, 1993, 1994, 1995, and 1996

were 233, 243, 232, 197, 164, and 149 respectively. In 1996 and 1997, the NMFS issued management regulations which prohibited
47

the operation of this fishery in 1997. Further, in January 1999 the 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 to 12 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, and 64% in 1996. The

greatest concentrations of effort were located along the southern edge of Georges Bank and off Cape Hatteras. Examination of the

species composition of the catch and locations of the fishery throughout the year, suggested that the pelagic drift gillnet fishery be

stratified into two strata, a southern or winter stratum, and a northern or summer stratum. Estimates of total by-catch, for each year

from 1989 to 1993, were obtained using the aggregated (pooled 1989-1993) catch rates, by strata, assuming the 1990 injury was a

mortality (Northridge 1996). Estimated annual fishery-related mortality and serious injury (CV in parentheses) was 2.2 sperm

whales in 1989 (2.43), 4.4 in 1990 (1.77), 0 in 1991, 0 in 1992, 0 in 1993, 0 in 1994, 0 in 1995, 0 in 1996, and 0 in 1997. Estimated

average annual mortality and serious injury related to this fishery during 1993-1997 was zero, assuming the 1995 injured sperm whale

was not a serious injury. Table 2 summarizes the number of animals released alive and classified as injured or non-injured. It also

includes the ratio of observed to estimated mortalities for this fishery.

Table 2. Summary of sperm whales (Physeter macrocephalus) released alive, by commercial fishery, years sampled (Years),

ratio of observed mortalities recorded by on-board observers to the estimated mortality (Ratio), the number of observed

animals released alive and injured (Injured), and the number of observed animals released alive and uninjured (Uninjured)

Fishery Years Ratio Injured2 Uninjured

Pelagic Drift Gillnet 93-973 0, 0, 0, 0, NA 0, 0, 11,0, NA 0, 0, 0, 0, NA

 

1 The observer recorded this animal being released alive and having the “gear in/around several body parts”.

 

2 Annual mortality estimates do not include any animals injured and released alive.

 

3 The fishery did not operate in 1997.

Other Mortality

 Ten sperm whale strandings have been documented along the USA Atlantic coast between Maine and Miami, Florida, during

1994-1996 (NMFS unpublished data). 

In eastern Canada, five dead stranding were reported in Newfoundland/Labrador from 1987-1995; nine dead stranding along Nova

Scotia from 1988-1991; seven dead stranding on Prince Edward Island from 1988-1991, and two dead strandings in Quebec in 1992

(Reeves and Whitehead 1997).

Ship strikes are another source of human induced mortality. In May 1994 a ship struck sperm whale was observed south of Nova

Scotia (Reeves and Whitehead 1997).

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.

This is a strategic stock because the species is listed as endangered under the ESA.

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 5pp.

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 RELENTLESS, Cruise No. RS 94-02, Marine Mammal Survey/Warm Core Ring Study.

NOAA NMFS NEFSC Woods Hole Laboratory, Woods Hole, MA. 8pp
48

Barlow, J., S.L. Swartz, T.C. Eagle, and P.R. Wade. 1995. U.S. Marine Mammal Stock Assessments: Guidelines for Preparation,

Background, and a Summary of the 1995 Assessments. U.S. Dep. Commer., NOAA Tech. Memo. NMFS-OPR-6, 73 pp.

Best, P. B. 1974. Biology of the sperm whale. Pages 53-81. In: W. E. Schevill (ed),The whale problem: A status report. Harvard

University Press, Cambridge, Massachusetts, 419 pp. 

Best, P. B. 1979. Social organization in sperm whales, Physeter macrocephalus. Pages 227-289. In: H. E. Winn and B. L. Olla

(eds), Behavior of marine animals, Vol. 3: Cetaceans. Plenum Press, New York. 

Best, P. B., P. A. S. Canham, and N. Macleod. 1984. Patterns of reproduction in sperm whales, Physeter macrocephlus. Rep.

int Whal. Commn. (special issue) 8: 51-79.

Buckland, S. T., D. R. Andersen, K. P. Burnham, and J. L. Laake. 1993. Distance sampling: Estimating abundance of biological

populations. Chapman and Hall, New York, 442 pp. 

CETAP. 1982. A characterization of marine mammals and turtles in the mid- and north Atlantic areas of the U.S. outer continental

shelf. Cetacean and Turtle Assessment Program, University of Rhode Island. Final Report #AA551-CT8-48 to the Bureau of

Land Management, Washington, DC, 538 pp. 

Laake, J. L., S. T. Buckland, D. R. Anderson, and K. P. Burnham. 1993. DISTANCE user’s guide, V2.0. Colorado Cooperative Fish

& Wildlife Research Unit, Colorado State University, Ft. Collins, Colorado, 72 pp. 

Lockyer, C. 1981. Estimates of growth and energy budget for the sperm whale. Pages 491-504 in Mammals in the seas, III. FAO

Fish. Ser. No. 5. FAO, Rome, 504 pp. 

Mitchell, E. and V. M. Kozicki. 1984. Reproductive condition of male sperm whales, Physeter macrocephalus, taken off Nova

Scotia. Rep. int Whal. Commn. (Special Issue 6): 243-252.

Northridge, S. 1996. Estimation of cetacean mortality in the U.S. Atlantic swordfish and tuna drift gillnet and pair trawl fisheries.

Final report to the Northeast Fisheries Science Center, Contract No.

Palka, D. 1995. Abundance estimate of the Gulf of Maine harbor porpoise. pp. 27-50. In: A. Bjørge and G.P. Donovan (eds.)

Biology of the Phocoenids. Rep. int Whal. Commn. Special Issue 16.

Reeves, R. R. and H. Whitehead. 1997. Status of sperm whale, Physeter macrocephalus, in Canada. Can. Fld. Nat.

111(2):293-307.

Rice, D. W. 1989. Sperm whale. Physeter macrocephalus Linnaeus, 1758. PP. 177-233 in Handbook of marine animals. Vol. 4. Ed.

S. H. Ridgway and R Harrison. Academic Press, London.

Scott, T.M. and S.S. Sadove. 1997. Sperm whale, Physeter macrocephalus, sightings in the shallow shelf waters off Long Island,

New York. Mar. Mamm. Sci. 13: 317-321.

Schmidly, D. J. 1981. Marine mammals of the southeastern United States and the Gulf of Mexico. Department of the Interior, U.S.

Fish and Wildlife Service Publication FWS/OBS-80/41, Washington, DC, 166 pp. 

Wade P.R., and R.P. Angliss. 1997. Guidelines for assessing marine mammal stocks: Report of the GAMMS Workshop April 3-5,

1996, Seattle, Washington. U.S. Dep. Commer., NOAA Tech. Memo. NMFS-OPR-12, 93 pp.

Waring, G.T. 1998. Results of the summer 1991 R/V Chapman marine mammal sighting survey. NOAA NMFS NEFSC, Lab. Ref.

Doc. No. 98-09, 21pp. Northeast Fisheries Science Center, Woods Hole, Massachusetts. 

Waring, G.T., C.P. Fairfield, C.M. Ruhsam and M. Sano. 1992. Cetaceans associated with Gulf Stream features off the northeastern

USA shelf. ICES. C.M. 1992/N:12. 29p.

Waring, G.T., C.P. Fairfield, C.M. Ruhsam and M. Sano. 1993. Sperm whales associated with Gulf Stream features off the

northeastern USA shelf. Fish. Oceanogr. 2(2): 101-105

Watkins, W. A., K. E. Moore, and P. Tyack. 1985. Sperm whale acoustic behavior in the southeast Caribbean. Cetology 49: 1-

15.

Watkins, W.A., M.A. Daher, K.M. Fristrup, and T.J. Howald. 1993. Sperm whales tagged with transponders and tracked underwater

by sonar. Mar. Mamm. Sci. 9(1):55-67.

Whitehead, H., S. Brennan, and D. Grover. 1991. Distribution and behavior of male sperm whales on the Scotian Shelf, Canada. Can.

J. Zool. 70: 912-918.
49

October 1999

DWARF SPERM WHALE (Kogia simus): 

Western North Atlantic Stock

STOCK DEFINITION AND GEOGRAPHIC RANGE

The dwarf sperm whale (Kogia simus) appears to be distributed worldwide in temperate to tropical waters (Caldwell and

Caldwell 1989). There are no stranding records for the east Canadian coast (Willis and Baird 1998). Sightings of these animals in the

Western North Atlantic occur primarily along the continental shelf edge and over the deeper waters off the continental shelf (Hansen

et al 1994 NMFS unpublished data). Dwarf sperm whales and pygmy sperm whales are difficult to distinguish and sightings of either

species are often categorized as Kogia sp. There is no information on stock differentiation for the Atlantic population. In a recent

study using hematological and stable-isotope data, Barros et al. (1998) speculated that dwarf sperm whales may have a more pelagic

distribution than pygmy sperm whales, and/or dive deeper during feeding bouts. 

POPULATION SIZE

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 a 1992 winter, visual sampling, line-transect

vessel survey of the U.S. Atlantic Exclusive Economic Zone (EEZ) waters between Miami, Florida, and Cape Hatteras, North

Carolina. Abundance was estimated for both species combined because the majority of sightings were not identified to species, and

both species are known to occur in the area. The estimated abundance of dwarf sperm whales and pygmy sperm whales combined

for the 1992 surveys was 420 animals (coefficient of variation, CV = 0.60) (Hansen et al. 1994). Dwarf sperm whale abundance

alone cannot be estimated due to uncertainty of species identification of sightings. 

Minimum Population Estimate

A best and minimum population size could not be estimated because of the uncertainty in species identification.

Current Population Trend

No information was available evaluate trends in population size for this species in the Western North Atlantic. 

CURRENT AND MAXIMUM NET PRODUCTIVITY RATES

Current and maximum net productivity rates are unknown for this stock. For purposes of this assessment, the maximum net

productivity rate was assumed to be 0.04. This value is based on theoretical modeling showing that cetacean populations may not

grow at rates much greater than 4% given the constraints of their reproductive life history (Barlow et al. 1995). 

POTENTIAL BIOLOGICAL REMOVAL

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

a “recovery” factor (Wade and Angliss 1997). The minimum population size is unknown. The maximum productivity rate is 0.04,

the default value for cetaceans. The “recovery” factor, which accounts for endangered, depleted, threatened stocks, or stocks of

unknown status relative to optimum sustainable population (OSP) is assumed to be 0.5 because this stock is of unknown status.

PBR for the western North Atlantic dwarf sperm whale is unknown because the minimum population size cannot be estimated. 

ANNUAL HUMAN-CAUSED MORTALITY AND SERIOUS INJURY

The level of past or current, direct, human-caused mortality of dwarf sperm whales in the U.S. Atlantic EEZ is unknown.

Available information indicates there is likely little fisheries interaction with dwarf sperm whales in the U.S. Atlantic EEZ. 

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
50

observer coverage of pelagic longline vessels fishing off the Grand Banks (Tail of the Banks) and provides observer coverage of vessels

fishing south of Cape Hatteras.

By-catch has been observed by NMFS Sea Samplers in the pelagic drift gillnet fishery, but no mortalities or serious injuries have

been documented in the pelagic longline, pelagic pair trawl, New England multispecies sink gillnet, mid-Atlantic coastal sink gillnet,

and North Atlantic bottom trawl fisheries. 

Pelagic Drift Gillnet

In 1996 and 1997, the NMFS issued management regulations which prohibited the operation of this fishery in 1997. Further,

in January 1999 the NMFS issued a Final Rule to prohibit the use of driftnets (i.e., permanent closure) in the North Atlantic

swordfish fishery (50 CFR Part 630). Fifty-nine different vessels participated in the pelagic drift gillnet fishery at one time or

another between 1989 and 1993. In 1994 and 1995, respectively, there were 12 and 11 vessels 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

and 99% in 1995. 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. 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, and 1.0 in 1995 (CV = 0); estimated average annual mortality and serious

injury related to this fishery during 1993-1997 was 0.2 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 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 1 Data Type 2 Observer

Coverage 3 

Observed

Mortality

Estimated

Mortality 4

Estimated

CVs 4

Mean

Annual

Mortality

Pelagic

Drift

Gillnet

93-97 1994=12

1995=11

Obs. Data

Logbook

.42, .87, .99,

.64, NA

0, 0, 1, 0,

NA

0, 0, 1.04, 0,

NA

0 0.2

(0)

TOTAL 0.2

(0)

1

 1994 and 1995 shown, other years not available on an annual basis.

2 Observer data (Obs. Data) are used to measure bycatch rates, and the data are collected within the Northeast Fisheries Science

Center (NEFSC) Sea Sampling Program. Logbook (Logbook) data are used to measure total effort, and the data are collected at

the Southeast Fisheries Science Center (SEFSC).

3 The observer coverage and unit of effort for the Pelagic Drift Gillnet is a set.

4 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.

Other Mortality

Historical stranding records (1883-1988) of dwarf sperm whales in the southeastern USA (Credle 1988), and strandings recorded

during 1988-1997 (Barros et al. 1998) indicate that this species accounts for about 17% of all Kogia strandings in this area. During

the period 1990-October 1998, 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
51

Keys in the same period. A pair of latex examination gloves was retrieved from the stomach of a dwarf sperm whale stranded in

Miami in 1987 (Barros et al. 1990). In the period 1987-1994, one animal had possible propeller cuts 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 or

threatened under the Endangered Species Act. There is insufficient information with which to assess population trends. It is not

known whether total fishery-related mortality and serious injury for this stock is less than 10% of PBR and therefore cannot be

considered insignificant and approaching zero mortality and serious injury rate, because PBR cannot be calculated.

REFERENCES

Barlow, J., S.L. Swartz, T.C. Eagle, and P.R. Wade. 1995. U.S. Marine Mammal Stock Assessments: Guidelines for Preparation,

Background, and a Summary of the 1995 Assessments. U.S. Dep. Commer., NOAA Tech. Memo. NMFS-OPR-6, 73 pp.

Barros, N.B., D.A. Duffield, P.H. Ostrom, D.K. Odell, and V.R. Cornish. 1998. Nearshore vs. offshore ecotype differentiation of

Kogia breviceps and K. simus based on hemoglobin, morphometric and dietary analyses. Abstracts. World Marine Mammal

Science Conference. Monaco. 20-24 January. 

Barros, N.B., D.K. Odell, and G.W. Patton. 1990. Ingestion of plastic debris by stranded marine mammals from Florida. Page 746

in: Shomura, R.S. and M.L. Godfrey (eds). Proceedings of the Second International Conference on Marine Debris. NOAA Tech.

Memo. NOAA-TM-NMFS-SWFSC-154.

Buckland, S. T., D. R. Anderson, K. P. Burnham and J. L. Laake. 1993. Distance Sampling: estimating abundance of biological

populations. Chapman & Hall, London, 446 pp. 

Caldwell, D. K. and M. C. Caldwell 1989. Pygmy sperm whale Kogia breviceps (de Blainville, 1838): dwarf sperm whale Kogia

simus Owen, 1866. Pages 235-260 in: S. H. Ridgway and R. Harrison, Handbook of marine mammals, Vol. 4: river dolphins

and the larger toothed whales. Academic Press, San Diego. 

Credle, V.R. 1988. Magnetite and magnetoreception in dwarf and pygmy sperm whales, Kogia simus and Kogia breviceps. MSc.

Thesis. University of Miami. Coral Gables, FL.

Hansen, L. J., K. D. Mullin and C. L. Roden. 1994. Preliminary estimates of cetacean abundance in the U.S. Atlantic Exclusive

Economic 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. 

Northridge, S. 1996. Estimation of cetacean mortality in the U.S. Atlantic swordfish and tuna drift gillnet and pair trawl fisheries.

Final report to the Northeast Fisheries Science Center, Contract No.40ENNF500045. 18p.

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.

Willis, P.M., and R.W. Baird. 1998. Status of the dwarf sperm whale, Kogia simus, with special reference to Canada. Canadian

Field-Naturalist, 112:114-125.
52

October 1999

PYGMY SPERM WHALE (Kogia breviceps):

Western North Atlantic Stock

STOCK DEFINITION AND GEOGRAPHIC RANGE

The pygmy sperm whale (Kogia breviceps) appears to be distributed worldwide in temperate to tropical waters (Caldwell

and Caldwell 1989). Sightings of these animals in the Western North Atlantic occur primarily along the continental shelf edge and

over the deeper waters off the continental shelf (Hansen et al 1994; Southeast Fisheries Science Center unpublished data). Pygmy

sperm whales and dwarf sperm whales are difficult to distinguish and sightings of either species are often categorized as Kogia sp.

There is no information on stock differentiation for the Atlantic population. In a recent study using hematological and stable-isotope

data, Barros et al. (1998) speculated that dwarf sperm whales may have a more pelagic distribution than pygmy sperm whales, and/or

dive deeper during feeding bouts. 

POPULATION SIZE

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 a 1992 winter, visual sampling, line-transect

vessel survey of the USA Atlantic Exclusive Economic Zone (EEZ) waters between Miami, Florida, and Cape Hatteras, North

Carolina. Abundance was estimated for both species combined because the majority of sightings were not identified to species, and

both species are known to occur in the area. The estimated abundance of dwarf sperm whales and pygmy sperm whales combined

for the 1992 surveys was 420 animals (coefficient of variation, CV = 0.60) (Hansen et al. 1994). Pygmy sperm whale abundance

alone cannot be estimated due to uncertainty of species identification of sightings. 

Minimum Population Estimate

A best and minimum population size could not be estimated because of the uncertainty in species identification. 

Current Population Trend

No information was available to evaluate trends in population size for this species in the Western North Atlantic. 

CURRENT AND MAXIMUM NET PRODUCTIVITY RATES

Current and maximum net productivity rates are not known for this stock. For purposes of this assessment, the maximum net

productivity rate was assumed to be 0.04. This value is based on theoretical modeling showing that cetacean populations may not

grow at rates much greater than 4% given the constraints of their reproductive life history (Barlow et al. 1995). 

POTENTIAL BIOLOGICAL REMOVAL

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

a “recovery” factor (Wade and Angliss 1997). The minimum population size is unknown. The maximum productivity rate is 0.04,

the default value for cetaceans. The “recovery” factor, which accounts for endangered, depleted, threatened stocks, or stocks of

unknown status relative to optimum sustainable population (OSP) is assumed to be 0.5 because this stock is of unknown status.

PBR for the western North Atlantic pygmy sperm whale was unknown because the minimum population estimate cannot be

estimated. 

ANNUAL HUMAN-CAUSED MORTALITY AND SERIOUS INJURY

The level of past or current, direct, human-caused mortality of pygmy sperm whales in the USA Atlantic EEZ is unknown.

Available information indicates there is likely little, if any, fisheries interaction with pygmy sperm whales in the USA Atlantic EEZ.

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.
53

Fishery Information

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

self-reporting fisheries information system for large pelagic fisheries. The Northeast Fisheries Science Center (NEFSC) Sea Sampling

Observer Program initiated in 1989, and since that year several fisheries have been covered by the program. In late 1992 and in 1993,

the SEFSC provided observer coverage of pelagic longline vessels fishing off the Grand Banks (Tail of the Banks) and provides

observer coverage of vessels fishing south of Cape Hatteras. There have been no observed mortalities or serious injuries by NMFS

Sea Samplers in the pelagic drift gillnet, pelagic longline, pelagic pair trawl, New England multispecies sink gillnet, mid-Atlantic coastal

sink gillnet, and North Atlantic bottom trawl fisheries. 

Other Mortality

Historical stranding records (1883-1988) of pygmy sperm whales in the southeastern USA (Credle 1988), and strandings recorded

during 1988-1997 (Barros et al. 1998) indicate that this species accounts for about 83% of all Kogia strandings in this area. During

the period 1990-October 1998, 21 pygmy sperm whale strandings occurred in the northeastern USA (Delaware, New Jersey, New

York and Virginia), whereas 194 strandings were documented along the USA Atlantic coast between North Carolina and the Florida

Keys in the same period. Remains of plastic bags and other marine debris have been retrieved from the stomachs of 13 stranded

pygmy sperm whales in the southeastern USA (Barros et al. 1990, 1998), and at least on one occasion the ingestion of plastic debris

is believed to have been the cause of death. During the period 1987-1994 one animal had possible propeller cuts on its 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 or

threatened under the Endangered Species Act. There is insufficient information with which to assess population trends. It is not

known whether total fishery-related mortality and serious injury for this stock is less than 10% of PBR and therefore, cannot be

considered insignificant and approaching zero mortality and serious injury rate, because PBR cannot be calculated.

REFERENCES

Baird, R.W., D. Nelson, J. Lien, and D.W. Nagorsen. 1996. The status of the pygmy sperm whale, Kogia breviceps, in Canada.

Canadian Field-Naturalist, 110:525-532.

Barlow, J., S.L. Swartz, T.C. Eagle, and P.R. Wade. 1995. U.S. Marine Mammal Stock Assessments: Guidelines for Preparation,

Background, and a Summary of the 1995 Assessments. U.S. Dep. Commer., NOAA Tech.Memo. NMFS-OPR-6, 73 pp.

Barros, N.B., D.A. Duffield, P.H. Ostrom, D.K. Odell, and V.R. Cornish. 1998. Nearshore vs. offshore ecotype differentiation of

Kogia breviceps and K. simus based on hemoglobin, morphometric and dietary analyses. Abstracts. World Marine Mammal

Science Conference. Monaco. 20-24 January. 

Barros, N.B., D.K. Odell, and G.W. Patton. 1990. Ingestion of plastic debris by stranded marine mammals from Florida. Page 746

in Shomura, R.S. and M.L. Godfrey (eds). Proceedings of the Second International Conference on Marine Debris. NOAA Tech.

Memo. NOAA-TM-NMFS-SWFSC-154.

Buckland, S. T., D. R. Anderson, K. P. Burnham and J. L. Laake. 1993. Distance Sampling: estimating abundance of biological

populations. Chapman & Hall, London, 446 pp. 

Caldwell, D. K. and M. C. Caldwell 1989. Pygmy sperm whale Kogia breviceps (de Blainville 1838): dwarf sperm whale Kogia

simus Owen, 1866. Pages 235-260 in S. H. Ridgway and R. Harrison, Handbook of marine mammals, Vol. 4: river dolphins and

the larger toothed whales. Academic Press, San Diego. 

Credle, V.R. 1988. Magnetite and magnetoreception in dwarf and pygmy sperm whales, Kogia simus and Kogiabreviceps. MSc.

Thesis. University of Miami. Coral Gables, FL.

Hansen, L. J., K. D. Mullin and C. L. Roden. 1994. Preliminary estimates of cetacean abundance in the U.S. Atlantic Exclusive

Economic Zones from 1992 vessel surveys. Southeast Fisheries Science Center, Miami Laboratory, Contribution No. MIA-93/94-

58.

Laake, J. L., S. T. Buckland, D. R. Anderson, and K. P. Burnham. 1993. DISTANCE user’s guide, V2.0. Colorado Cooperative Fish

& Wildlife Research Unit, Colorado State University, Ft. Collins, Colorado, 72 pp. 

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.
54

Figure 1. Distribution of beaked whale sightings from

NEFSC shipboard and aerial surveys during the summer

in 1990-1995. Isobaths are at 100 m and 1,000 m. 

October 1999

CUVIER'S BEAKED WHALE (Ziphius cavirostris):

Western North Atlantic Stock

STOCK DEFINITION AND GEOGRAPHIC RANGE

The distribution of Cuvier's beaked whales is poorly

known, and is based mainly on stranding records (Leatherwood

et al. 1976). Strandings have been reported from Nova Scotia

along the eastern USA coast south to Florida, around the Gulf

of Mexico, and within the Caribbean (Leatherwood et al.

1976; CETAP 1982; Heyning 1989; Houston 1990). Stock

structure in the western North Atlantic is unknown. 

Cuvier's beaked whale sightings have occurred principally

along the continental shelf edge in the mid-Atlantic region off

the northeast USA coast (CETAP 1982; Waring et al. 1992;

NMFS unpubl. data). Most sightings were in late spring or

summer. Based on sighting data, this species is a rare

inhabitant of waters off the northeast USA coast (CETAP

1982).

POPULATION SIZE

The total number of Cuvier's beaked whales off the eastern

USA coast is unknown. However, seven estimates of the

undifferentiated complex of beaked whales (Ziphius and

Mesoplodon spp.) is available from select regions of the

habitat during summer 1978-82, August 1990, June-July 1991,

August-September 1991, June-July 1993, August 1994, and

July to September 1995 (Table 1; Figure 1).

A population size of 120 undifferentiated beaked whales

(CV=0.71) was estimated from an aerial survey program

conducted from 1978 to 1982 on the continental shelf and shelf

edge waters between Cape Hatteras, North Carolina and Nova

Scotia (Table 1; CETAP 1982). The estimate is based on summer data because the greatest proportion of the population off the

northeast USA coast appeared in the study area during this season. This estimate does not include corrections for dive-time or g(0),

the probability of detecting an animal group on the track line. This estimate may not reflect the current true population size because

of its high degree of uncertainty (e.g., large CV), its old age, and it was estimated just after cessation of extensive foreign fishing

operations in the region.

A population size of 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 (Table 1; Waring

et al. 1992). Data were collected by one team that searched by naked eye and 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.

A population size 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 (Table 1;

Waring et al. 1992; Waring 1998). Data were collected by one team that searched by naked eye and analyzed using DISTANCE

(Buckland et al. 1993; Laakeet al. 1993). Estimates include school size-bias, if applicable, but no corrections for g(0) or dive-time.

Variability was estimated using bootstrap resampling techniques.

A population size 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 (Table 1; Anon. 1991). The study

area included that covered in the CETAP study plus several additional continental slope survey blocks. Due to weather and logistical
55

constraints, several survey blocks south and east of Georges Bank were not surveyed. The data were analyzed using DISTANCE

(Buckland et al. 1993; Laake et al. 1993), where the CV was estimated using the bootstrap option. The abundance estimates do

not include g(0) and were not pooled over platforms because the inter-platform calibration analysis has not been conducted.

A population size 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; Anon. 1993). Data were collected by two alternating

teams that searched with 25x150 binoculars and were analyzed using DISTANCE (Buckland et al. 1993; Laake et al. 1993).

Estimates include school size-bias, if applicable, but do not include corrections for g(0) or dive-time. Variability was estimated using

bootstrap resampling techniques.

A population size of 99 (CV=0.64) undifferentiated beaked whales was estimated from an August 1994 shipboard line transect

survey conducted within a Gulf Stream warm-core ring located in continental slope waters southeast of Georges Bank (Table 1; Anon.

1994). Data were collected by two alternating teams that searched with 25x150 binoculars and an independent observer who searched

by naked eye from a separate platform on the bow. Data were analyzed using DISTANCE (Buckland et al. 1993; Laake et al. 1993).

Estimates include school size-bias, if applicable, but do not include corrections for g(0) or dive-time. Variability was estimated using

bootstrap resampling techniques.

A population size 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; NMFS unpubl. data). Total track line length of this survey was 32,600 km (17,600 nmi). 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. Shipboard data were collected using a two independent

sighting team procedure and were analyzed using the product integral method (Palka 1995) and DISTANCE (Buckland et al. 1993).

Shipboard estimates were corrected for g(0) and, if applicable, also for school size-bias. Standard aerial sighting procedures with two

bubble windows and one belly window observer were used during the aerial survey. An estimate of g(0) was not made for the aerial

portion of the survey. Estimates do not include corrections for dive-time. Variability was estimated using bootstrap resampling

techniques. Because the number of beaked whale sightings in each strata were extremely low (3 to 10), and their sightability and

behavior preclude pooling with other cetaceans, the abundance estimates are based on small sample sizes. Therefore, the above

abundance estimates should be viewed with caution.

Because the estimates presented here were not dive-time corrected, they are likely negatively biased and probably underestimate

actual abundance. Given that Mesoplodon spp. prefers deep-water habitats (Mead 1989) the bias may be substantial.

The best available current abundance estimate for the undifferentiated complex of beaked whales is 1,519 (CV=0.69) as estimated

from the July to September 1995 line transect survey ( NMFS unpubl. data) because this survey provided the most complete

coverage of the known habitat.
56

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

summer 1978-82 Cape Hatteras, NC to

Nova Scotia 120 0.71

Aug 1990 Gulf Stream 442 0.51

Jun-Jul 1991

Cape Hatteras, NC to

Georges Bank, shelf

edge only

262 0.99

Aug-Sep 1991 Cape Hatteras, NC to

Nova Scotia 370 and 612*

0.65 and 0.73*

Jun-Jul 1993

Georges Bank to

Scotian shelf, shelf

edge 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

* From data collected on the Twin Otter and AT-11, respectively.

Minimum Population Estimate

The minimum population estimate is the lower limit of the two-tailed 60% confidence interval of the log-normally distributed

best abundance estimate. This is equivalent to the 20th percentile of the log-normal distribution as specified by Wade and Angliss

(1997). The best estimate of abundance for undifferentiated beaked whales is 1,519 (CV=0.69). The minimum population estimate

for the undifferentiated complex of beaked whales (Ziphius and Mesoplodon spp.) is 895 (CV=0.69). It is not possible to

determine the minimum population estimate of only Cuvier’s beaked whales.

Current Population Trend

There are insufficient data to determine the population trends for this species. 

CURRENT AND MAXIMUM NET PRODUCTIVITY RATES

Current and maximum net productivity rates are unknown for this stock. Life history parameters that could be used to estimate

net productivity include: length at birth is 2 to 3 m, length at sexual maturity 6.1 m for females, and 5.5 m for males, maximum age

for females were 30 growth layer groups (GLG's) and for males was 36 GLG's, which may be annual layers (Mitchell 1975; Mead

1984; Houston 1990). 

For purposes of this assessment, the maximum net productivity rate was assumed to be 0.04. This value is based on theoretical

modeling showing that cetacean populations may not grow at rates much greater than 4% given the constraints of their reproductive

life history (Barlow et al. 1995). 

POTENTIAL BIOLOGICAL REMOVAL

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

a “recovery” factor (MMPA Sec. 3. 16 U.S.C. 1362; Wade and Angliss 1997). The minimum population size for the undifferentiated

complex of beaked whales is 895 (CV=0.69). 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
57

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 8.9. It is not possible to determine the PBR for only Cuvier’s beaked whales.

ANNUAL HUMAN-CAUSED MORTALITY AND SERIOUS INJURY

 The 1993-1997 total average estimated annual fishery-related mortality of beaked whales in the USA EEZ was 9.7 (CV = 0.06).

Fishery Information

There is no historical information available that documents incidental mortality in either USA or Canadian Atlantic coast fisheries

(Read 1994). 

Current data on incidental takes in USA fisheries are available from several sources. In 1986, NMFS established a mandatory

self-reported fisheries information system for large pelagic fisheries. Data files are maintained at Southeast Fisheries Science Center

(SEFSC). The Northeast Fisheries Science Center (NEFSC) Sea Sampling Observer Program was initiated in 1989, and since that

year several fisheries have been covered by the program. In 1986, NMFS established a mandatory self-reported fisheries information

system for large pelagic fisheries. Data files are maintained at Southeast Fisheries Science Center (SEFSC). In late 1992 and in 1993

the SEFSC provided observer coverage of pelagic longline vessels fishing off the Grand Banks (Tail of the Banks) and currently

provides observer coverage of vessels fishing south of Cape Hatteras. 

Total fishery-related mortality and serious injury cannot be estimated separately for each beaked whale species because of the

uncertainty in species identification by fishery observers. The Atlantic Scientific Review Group advised adopting the risk-averse

strategy of assuming that any beaked whale stock which occurred in the USA Atlantic EEZ might have been subject to the observed

fishery-related mortality and serious injury.

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, New England multispecies sink gillnet, mid-Atlantic coastal sink gillnet,

or North Atlantic bottom trawl observed fisheries. 

The estimated total number of hauls in the pelagic drift gillnet fishery increased from 714 in 1989 to 1,144 in 1990; thereafter,

with the introduction of quotas, effort was severely reduced. The estimated number of hauls in 1991, 1992, 1993, 1994, 1995, and

1996 were 233, 243, 232, 197, 164, and 143, respectively. In 1996 and 1997, the NMFS issued management regulations with

prohibited the operation of this fishery 1997. Further, in January 1999 the NMFS issued a Final Rule to prohibit the use of driftnets

(i.e., permanent closure) in the North Atlantic swordfish fishery (50 CFR Part 630). Fifty-nine different vessels participated in this

fishery at one time or another between 1989 and 1993. Since 1994, between 10-12 vessels have participated in the fishery (Table

2). Observer coverage, expressed as percent of sets observed, was 8% in 1989, 6% in 1990, 20% in 1991, 40% in 1992, 42% in 1993,

87% in 1994, 99% in 1995, and 64% in 1996. Effort was concentrated along the southern edge of Georges Bank and off Cape

Hatteras. Examination of the species composition of the catch and locations of the fishery throughout the year, suggested that the

pelagic drift gillnet fishery be stratified into two strata, a southern or winter stratum, and a northern or summer stratum. Estimates

of the total by-catch, 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 by-catch for 1994 and 1995 were estimated from the sum of the observed caught and

the product of the average bycatch per haul and the number of unobserved hauls as recorded in self-reported fisheries information.

Variances were estimated using bootstrap re-sampling techniques. By-catch of beaked whales has only occurred from Georges

Canyon to Hydrographer Canyon along the continental shelf break and continental slope during July to October. Thirty-five fisheryrelated beaked whale mortalities were observed between 1989 and 1996. The estimated annual fishery-related mortality (CV in

parentheses) was 60 in 1989 (0.21), 76 in 1990 (0.26), 13 in 1991 (0.21), 9.7 in 1992 (0.24), 12 in 1993 (0.16) 4.8 in 1994 (0.08),

9.1 in 1995 (0), and 13 in 1996 (0.12) (Table 2). Annual mortality estimates do not include any animals injured and released alive.

The 1993-1997 total average estimated annual fishery-related mortality of beaked whales in the USA EEZ was 9.7 (CV = 0.06) (Table

2). Table 3 summarizes the number of animals released alive and classified as injured or non-injured. It also includes the ratio of

observed to estimated mortalities for this fishery.
58

Table 2. Summary of the incidental mortality for the undifferentiated complex of beaked whales which include Cuvier’s beaked

whale (Ziphius cavirostris), and Mesoplodon beaked whale, by commercial fishery including the years sampled (Years),

the number of vessels active within the fishery (Vessels), the type of data used (Data Type), the annual observer coverage

(Observer Coverage), the mortalities recorded by on-board observers (Observed Mortality), the estimated annual mortality

(Estimated Mortality), the estimated CV of the annual mortality (Estimated CVs) and the mean annual mortality (CV in

parentheses).

Fishery Years Vessels 1 Data Type 2 Observer

Coverage 3 

Observed

Mortality

Estimated

Mortality 4

Estimated

CVs 4

Mean

Annual

Mortality

Pelagic

Drift

Gillnet

93-976

1994=12

1995=11

1996=10

Obs. Data

Logbook

 .42, .87,

.99, .64, NA

 5, 4, 9, 8,

NA

 12, 4.8,

9.15, 13, NA

 .16, .08, 0,

.12, NA

 9.76

 (.06)

TOTAL 9.7

 (.06)

1 1994 - 1996 shown, other years not available on an annual basis.

2 Observer data (Obs. Data) are used to measure bycatch rates, and the data are collected within the Northeast Fisheries Science

Center (NEFSC) Sea Sampling Program. Mandatory logbook (Logbook) data are used to measure total effort, and the data are

collected at the Southeast Fisheries Science Center (SEFSC).

3 The observer coverage and unit of effort for the Pelagic Drift Gillnet is a set.

4 For 1991-1993, pooled bycatch rates were used to estimate bycatch in months that had fishing effort but did not have observer

coverage. This method is described in Northridge (1996). Because observer coverage increased substantially from 1994-1996,

bycatch rates for this period are single year estimates. 

5 One vessel was not observed and recorded 1 set in a 10 day trip in the SEFSC mandatory logbook. If you assume the vessel

fished 1.4 sets per day as estimated from the 1995 SS data, the point estimate may increase by 0.8 animals. However, the SEFSC

mandatory logbook data was taken at face value, and therefore it was assumed that 1 set was fished within this trip, and the point

estimate would then increase by 0.1 animals.

6

 The fishery did not operate in 1997; the average annual mortality is based on the number of years (4; 1993-1996) that the fishery

operated.

Table 3. Summary for the undifferentiated complex of beaked whales which include Cuvier’s beaked whales (Ziphius cavirostris)

andMesoplodon beaked whales released alive, by commercial fishery, years sampled (Years), ratio of observed mortalities

recorded by on-board observers to the estimated mortality (Ratio), the number of observed animals released alive and

injured (Injured), and the number of observed animals released alive and uninjured (Uninjured)

Fishery Years Ratio Injured1 Uninjured

Pelagic Drift Gillnet 93-973 5/12, 4/4.8, 9/9.1, 8/13, NA 0, 0, 12

0, NA

 0, 0, 0, 0, NA

1

Injured and released alive animals are not included in the Table 2 mortality estimates.

2 The observer recorded this animal being released alive and having the “gear in/around a single body part”.

3 The fishery did not operate in 1997.

Other Mortality

From 1992-1997, a total of 32 beaked whales, 17 (includes one tentative identification) Gervais's beaked whales (one 1997 animal

had plastics in esophagus and stomach, and Sargassum in esophagus); 2 True's beaked whales; 3 Blainville’s beaked whales; 7 Cuvier's

beaked whales (one 1996 animal showed signs of human interactions propeller marks ) and 3 unidentified animals stranded along the

USA Atlantic coast between Florida and Massachusetts (NMFS unpublished data).

STATUS OF STOCK
59

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. There are insufficient data to determine population trends and the level of humancaused mortality and serious injury is unknown because of uncertainty regarding species identification in observed fisheries. If one

were to assume that the incidental fisheries mortality of the four Mesoplodon spp. and Z. cavirostris was random with respect

to species (i.e., in proportion to their relative abundance), then the minimum population estimate for all of those stocks would need

to sum to at least 970 in order for an annual mortality of 9.7 animals not to exceed the PBR of any one of these species. Because

an assumption of unselective incidental fishing mortality is probably overly optimistic and represents a best case situation, it is likely

that a combined minimum population estimate of substantially greater than 970 would be necessary for an annual mortality of 9.7

to not exceed the PBR of any one of these five stocks. The largest recent abundance estimate available for beaked whales in the

western North Atlantic was 1,519 (CV = 0.69) which would result in a minimum population estimate of 895 beaked whales; however,

this estimate does not include a correction factor for submerged animals which may be substantial. Although a species specific PBR

cannot be determined, the total fishery mortality and serious injury for this group is not less than 10% of the calculated PBR and,

therefore, cannot be considered to be insignificant and approaching zero mortality and serious injury rate. This is a strategic stock

because of uncertainty regarding stock size and evidence of fishery-related mortality and serious injury. 

REFERENCES

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. 5pp.

Anon. 1994. Cruise results, NOAA Ship RELENTLESS, Cruise No. RS 94-02, Marine Mammal Survey/Warm Core Ring Study.

NOAA NMFS NEFSC Woods Hole Laboratory, Woods Hole, MA. 8pp.

Barlow, J., S.L. Swartz, T.C. Eagle, and P.R. Wade. 1995. U.S. Marine Mammal Stock Assessments: Guidelines for Preparation,

Background, and a Summary of the 1995 Assessments. U.S. Dep. Commer., NOAA Tech. Memo. NMFS-OPR-6, 73 pp. 

Buckland, S.T., D.R. Anderson, K.P. Burnham and J.L. Laake. 1993. Distance sampling: estimating abundance of biological

populations. Chapman and Hall, New York, NY, 442 pp.

CETAP. 1982. A characterization of marine mammals and turtles in the mid- and north Atlantic areas of the U.S. outer continental

shelf. Cetacean and Turtle Assessment Program, University of Rhode Island. Final Report #AA551-CT8-48 to the Bureau of

Land Management, Washington, DC, 538 pp. 

Heyning, J. E. 1989. Cuvier's beaked whale, Ziphius cavirostris G. Cuvier, 1823. Pages 289-308. In: S. H. Ridgway and R.

Harrison (eds), Handbook of Marine Mammals, Vol. 4: River dolphins and larger toothed whales. Academic Press, London,

442 pp. 

Houston, J. 1990. Status of Cuvier's Beaked Whale, Ziphius cavirostris, in Canada. Can. Fld. Nat. 105(2): 215-218.

Laake, J.L., S.T. Buckland, D.R. Anderson and K.P. Burnham. 1993. DISTANCE user’s guide, V2.0. Colorado Cooperative Fish

and Wildlife Research Unit, Colorado State University, Ft. Collins, Colorado. 72pp.

Leatherwood, S., D. K. Caldwell and H. E. Winn. 1976. Whales, dolphins, and porpoises of the western North Atlantic. A guide

to their identification. U.S. Dept. of Commerce, NOAA Tech. Rep. NMFS Circ. 396, 176 pp. 

Mead, J. G. 1984. Survey of reproductive data for the beaked whales (Ziphiidae). Rep. int Whal. Commn. (Special Issue 6):

91-96. 

Mitchell, E. D. (ed). 1975. Review of the biology and fisheries for smaller cetaceans. Report of the meeting on smaller cetaceans.

Int Whal. Commn. J. Fish. Res. Bd. Can. 32(7): 875-1240.

Northridge, S. 1996. Estimation of cetacean mortality in the U.S. Atlantic swordfish and tuna drift gillnet and pair trawl fisheries.

Final report to the Northeast Fisheries Science Center, Contract No. 40ENNF500045, 18 pp. 

Palka, D. 1995. Abundance estimate of the Gulf of Maine harbor porpoise. pp. 27-50. In: A. Bjørge and G.P. Donovan

 (eds.) Biology of the Phocoenids. Rep. int Whal. Commn. Special Issue 16.

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

Special Issue 15: 133-147.

Wade, P.R., and R.P. Angliss. 1997. Guidelines for assessing marine mammal stocks: Report of the GAMMS Workshop April 3-5,

1996, Seattle, Washington. U.S. Dep. Commer., NOAA Tech. Memo. NMFS-OPR-12, 93 pp.

Waring, G.T. 1998. Results of the summer 1991 R/V Chapman marine mammal sighting survey. NOAA NMFS NEFSC, Lab. Ref.

Doc. No. 98-09, 21pp. Northeast Fisheries Science Center, Woods Hole, Massachusetts.
60

Waring, G.T., C.P. Fairfield, C.M. Ruhsam, and M. Sano. 1992. Cetaceans associated with Gulf Stream features off the northeastern

USA shelf. ICES C.M. 1992/N:12 29 pp.
61

Figure 1. Distribution of beaked whale sightings from

NEFSC shipboard and aerial surveys during the summer

in 1990-1995. Isobaths are at 100 m and 1,000 m. 

October 1999

MESOPLODON BEAKED WHALES (Mesoplodon spp.):

Western North Atlantic Stock

STOCK DEFINITION AND GEOGRAPHIC RANGE

Within the genus Mesoplodon, there are four species of

beaked whales that reside in the northwest Atlantic. These

include True's beaked whale, Mesoplodon mirus; Gervais'

beaked whale, M. europaeus; Blainville's beaked whale, M.

densirostris; and Sowerby's beaked whale, M. bidens. These

species are difficult to identify to the species level at sea;

therefore, much of the available characterization for beaked

whales is to genus level only. Stock structure for each species

is unknown.

The distribution of Mesoplodon spp. in the northwest

Atlantic is known principally from stranding records (Mead

1989; Nawojchik 1994). Off the northeast USA coast, beaked

whale (Mesoplodon spp.) sightings have occurred principally

along the southern edge of Georges Bank (CETAP, 1982;

Waring et al. 1992; NMFS unpubl. data). Most sightings

were in late spring and summer. In addition, beaked whales

were also sighted in Gulf Stream features during NEFSC 1990-

1995 surveys (Waring et al. 1992; Anon 1994; Tove 1995;

NMFS unpubl. data). 

True's beaked whale is a temperate-water species that has

been reported from Cape Breton Island, Nova Scotia, to the

Bahamas (Leatherwood et al. 1976, Mead 1989). It is

considered rare in Canadian waters (Houston 1990). 

Gervais's beaked whales are believed to be principally

oceanic, and strandings have been reported from the midAtlantic Bight to Florida, into the Caribbean and the Gulf of

Mexico (Leatherwood et al. 1976; Mead 1989). This is the commonest species of Mesoplodon stranded along the USA Atlantic

coast. The northernmost stranding was off New York (Mead 1989). 

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). There are two records of standings

in Nova Scotia which probably represent strays from the Gulf Stream (Mead 1989). They are considered rare in Canadian waters

(Houston 1990). 

Sowerby's beaked whales have been reported from New England waters north to the ice pack, and individuals are seen along the

Newfoundland coast in summer (Leatherwood et al. 1976; Mead 1989). Furthermore, a single stranding occurred off the Florida west

coast (Mead 1989). This species is considered rare in Canadian waters (Lien et al. 1990). 

POPULATION SIZE

The total number of Mesoplodon spp. beaked whales off the eastern USA coast is unknown. However, seven estimates of the

undifferentiated complex of beaked whales (Ziphius and Mesoplodon spp.) is available from select regions of the habitat during

summer 1978-82, August 1990, June-July 1991, August-September 1991, June-July 1993, August 1994, and July to September 1995

(Table 1; Figure 1).

A population size of 120 undifferentiated beaked whales (CV=0.71) was estimated from an aerial survey program conducted from

1978 to 1982 on the continental shelf and shelf edge waters between Cape Hatteras, North Carolina and Nova Scotia (Table 1;

CETAP 1982). The estimate is based on summer data because the greatest proportion of the population off the northeast USA coast

appeared in the study area during this season. This estimate does not include corrections for dive-time or g(0), the probability of
62

detecting an animal group on the track line. This estimate may not reflect the current true population size because of its high degree

of uncertainty (e.g., large CV), its old age, and it was estimated just after cessation of extensive foreign fishing operations in the region.

A population size of 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 (Table 1; Waring

et al. 1992). Data were collected by one team that searched by naked eye and analyzed using DISTANCE (Buckland et al. 1993;

Laakeet 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.

A population size 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 (Table 1;

Waring et al. 1992; Waring 1998). Data were collected by one team that searched by naked eye and analyzed using DISTANCE

(Buckland et al. 1993; Laake et al. 1993). Estimates include school size-bias, if applicable, but no corrections for g(0) or dive-time.

Variability was estimated using bootstrap resampling techniques.

A population size 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 (Table 1; Anon. 1991). The study

area included that covered in the CETAP study plus several additional continental slope survey blocks. Due to weather and logistical

constraints, several survey blocks south and east of Georges Bank were not surveyed. The data were analyzed using DISTANCE

(Buckland et al. 1993; Laake et al. 1993), where the CV was estimated using the bootstrap option. The abundance estimates do

not include g(0) and were not pooled over platforms because the inter-platform calibration analysis has not been conducted.

A population size 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

bootstrap resampling techniques.

A population size of 99 (CV=0.64) undifferentiated beaked whales was estimated from an August 1994 shipboard line transect

survey conducted within a Gulf Stream warm-core ring located in continental slope waters southeast of Georges Bank (Table 1; Anon.

1994). Data were collected by two alternating teams that searched with 25x150 binoculars and an independent observer who searched

by naked eye from a separate platform on the bow. Data were analyzed using DISTANCE (Buckland et al. 1993; Laake et al. 1993).

Estimates include school size-bias, if applicable, but do not include corrections for g(0) or dive-time. Variability was estimated using

bootstrap resampling techniques.

A population size 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; NMFS unpubl. data). Total track line length was 32,600 km (17,600 nmi). 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. Shipboard data were collected using a two independent sighting

team procedure and were analyzed using the product integral method (Palka 1995) and DISTANCE (Buckland et al. 1993).

Shipboard estimates were corrected for g(0) and, if applicable, also for school size-bias. Standard aerial sighting procedures with two

bubble windows and one belly window observer were used during the aerial survey. An estimate of g(0) was not made for the aerial

portion of the survey. Estimates do not include corrections for dive-time. Variability was estimated using bootstrap resampling

techniques. Because the number of beaked whale sightings in each survey were extremely low (3 to 10), and their sightability and

behavior preclude pooling with other cetaceans, the abundance estimates are based on small sample sizes. Therefore, the above

abundance estimates should be viewed with caution. 

Although the 1990-1995 surveys did not sample exactly the same areas or encompass the entire beaked whale habitat, they did

focus on segments of known or suspected high-use habitats off the northeastern USA coast. The collective 1990-95 data suggest that,

seasonally, at least several hundred beaked whales are occupying these waters, highest levels of abundance in the Georges Bank region.

This is consistent with the earlier CETAP results. Recent results suggest that beaked whale abundance may be highest in association

with Gulf Stream and warm-core ring features. 

Because the estimates presented here were not dive-time corrected, they are likely negatively biased and probably underestimate

actual abundance. Given that Mesoplodon spp. prefers deep-water habitats (Mead 1989) the bias may be substantial. 
63

The best available current abundance estimate for the undifferentiated complex of beaked whales is 1,519 (CV=0.69) as estimated

from the July to September 1995 line transect survey ( NMFS unpubl. data) because this survey provided the most complete

coverage of the known habitat.

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

summer 1978-82 Cape Hatteras, NC to

Nova Scotia 120 0.71

Aug 1990 Gulf Stream 442 0.51

Jun-Jul 1991

Cape Hatteras, NC to

Georges Bank, shelf

edge only

262 0.99

Aug-Sep 1991 Cape Hatteras, NC to

Nova Scotia 370 and 612*

0.65 and 0.73*

Jun-Jul 1993

Georges Bank to

Scotian shelf, shelf

edge 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

* From data collected on the Twin Otter and AT-11, respectively.

Minimum Population Estimate

The minimum population estimate is the lower limit of the two-tailed 60% confidence interval of the log-normally distributed

best abundance estimate. This is equivalent to the 20th percentile of the log-normal distribution as specified by Wade and Angliss

(1997). The best estimate of abundance for undifferentiated beaked whales is 1,519 (CV=0.69). The minimum population estimate

for the undifferentiated complex of beaked whales (Ziphius and Mesoplodon spp.) is 895 (CV=0.69). It is not possible to

determine the minimum population estimate of only Mesoplodont beaked whales.

Current Population Trend

There are insufficient data to determine the population trends for this species. 

CURRENT AND MAXIMUM NET PRODUCTIVITY RATES

Current and maximum net productivity rates are unknown for this stock. Life history parameters that could be used to estimate

net productivity include: length at birth is 2 to 3 m, length at sexual maturity 6.1 m for females, and 5.5 m for males, maximum age

for females were 30 growth layer groups (GLG's) and for males was 36 GLG's, which may be annual layers (Mead 1984). 

For purposes of this assessment, the maximum net productivity rate was assumed to be 0.04. This value is based on theoretical

modeling showing that cetacean populations may not grow at rates much greater than 4% given the constraints of their reproductive

life history (Barlow et al. 1995). 

POTENTIAL BIOLOGICAL REMOVAL
64

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

a “recovery” factor (MMPA Sec. 3. 16 U.S.C. 1362; Wade and Angliss 1997). The minimum population size for the undifferentiated

complex of beaked whales is 895 (CV=0.69). The maximum productivity rate is 0.04, the default value for cetaceans. The “recovery”

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

population (OSP) is assumed to be 0.5 because this stock is of unknown status. PBR for all species in the undifferentiated complex

of beaked whales (Ziphius and Mesoplodon spp.) is 8.9. It is not possible to determine the PBR for only Mesoplodon beaked

whales.

ANNUAL HUMAN-CAUSED MORTALITY AND SERIOUS INJURY

The 1993-1997 total average estimated annual fishery-related mortality of beaked whales in the USA EEZ was 9.7 (CV = 0.06).

Fishery Information

There is no historical information available that documents incidental mortality in either USA or Canadian Atlantic coast fisheries

(Read 1994). 

Current data on incidental takes in USA fisheries are available from several sources. In 1986, NMFS established a mandatory

self-reported fisheries information system for large pelagic fisheries. Data files are maintained at Southeast Fisheries Science Center

(SEFSC). The Northeast Fisheries Science Center (NEFSC) Sea Sampling Observer Program was initiated in 1989, and since that

year several fisheries have been covered by the program. In late 1992 and in 1993 the SEFSC provided observer coverage of pelagic

longline vessels fishing off the Grand Banks (Tail of the Banks) and currently provides observer coverage of vessels fishing south

of Cape Hatteras.

 Total fishery-related mortality and serious injury cannot be estimated separately for each beaked whale species because of the

uncertainty in species identification by fishery observers. The Atlantic Scientific Review Group advised adopting the risk-averse

strategy of assuming that any beaked whale stock which occurred in the USA Atlantic EEZ might have been subject to the observed

fishery-related mortality and serious injury.

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 trawl, New England multispecies sink gillnet, mid-Atlantic coastal sink gillnet, or

North Atlantic bottom trawl observed fisheries. 

The estimated total number of hauls in the pelagic drift gillnet fishery increased from 714 in 1989 to 1,144 in 1990; thereafter,

with the introduction of quotas, effort was severely reduced. The estimated number of hauls in 1991, 1992, 1993, 1994, 1995, and

1996 were 233, 243, 232, 197, 164, and 143, respectively. In 1996 and 1997, the NMFS issued management regulations with

prohibited the operation of this fishery 1997. Further, in January 1999 the NMFS issued a Final Rule to prohibit the use of driftnets

(i.e., permanent closure) in the North Atlantic swordfish fishery (50 CFR Part 630). Fifty-nine different vessels participated in this

fishery at one time or another between 1989 and 1993. Since 1994, between 10-12 vessels have participated in the fishery (Table

2). Observer coverage, expressed as percent of sets observed, was 8% in 1989, 6% in 1990, 20% in 1991, 40% in 1992, 42% in 1993,

87% in 1994, 99% in 1995, and 64% in 1996. Effort was concentrated along the southern edge of Georges Bank and off Cape

Hatteras. Examination of the species composition of the catch and locations of the fishery throughout the year, suggested that the

pelagic drift gillnet fishery be stratified into two strata, a southern or winter stratum, and a northern or summer stratum. Estimates

of the total by-catch, 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 by-catch for 1994 and 1995 were estimated from the sum of the observed caught and

the product of the average bycatch per haul and the number of unobserved hauls as recorded in self-reported fisheries information.

Variances were estimated using bootstrap re-sampling techniques. By-catch of beaked whales has only occurred from Georges

Canyon to Hydrographer Canyon along the continental shelf break and continental slope during July to October. Thirty-five fisheryrelated beaked whale mortalities were observed between 1989 and 1996. The estimated annual fishery-related mortality (CV in

parentheses) was 60 in 1989 (0.21), 76 in 1990 (0.26), 13 in 1991 (0.21), 9.7 in 1992 (0.24), 12 in 1993 (0.16) 4.8 in 1994 (0.08),

9.1 in 1995 (0), and 13 in 1996 (0.12) (Table 2). Annual mortality estimates do not include any animals injured and released alive.

The 1993-1997 total average estimated annual fishery-related mortality of beaked whales in the USA EEZ was 9.7 (CV = 0.06) (Table

2). Table 3 summarizes the number of animals released alive and classified as injured or non-injured. It also includes the ratio of

observed to estimated mortalities for this fishery.

Table 2. Summary of the incidental mortality for the undifferentiated complex of beaked whales which include Cuvier’s beaked

whale (Ziphius cavirostris), and Mesoplodon beaked whale, by commercial fishery including the years sampled (Years),
65

the number of vessels active within the fishery (Vessels), the type of data used (Data Type), the annual observer coverage

(Observer Coverage), the mortalities recorded by on-board observers (Observed Mortality), the estimated annual mortality

(Estimated Mortality), the estimated CV of the annual mortality (Estimated CVs) and the mean annual mortality (CV in

parentheses).

Fishery Years Vessels 1 Data Type 2 Observer

Coverage 3 

Observed

Mortality

Estimated

Mortality 4

Estimated

CVs 4

Mean

Annual

Mortality

Pelagic

Drift

Gillnet

93-976

1994=12

1995=11

1996=10

Obs. Data

Logbook

 .42, .87,

.99, .64, NA

 5, 4, 9, 8,

NA

 12, 4.8,

9.15, 13, NA

 .16, .08, 0,

.12, NA

 9.76

 (.06)

TOTAL 9.7

 (.06)

1 1994 - 1996 shown, other years not available on an annual basis.

2 Observer data (Obs. Data) are used to measure bycatch rates, and the data are collected within the Northeast Fisheries Science

Center (NEFSC) Sea Sampling Program. Mandatory logbook (Logbook) data are used to measure total effort, and the data are

collected at the Southeast Fisheries Science Center (SEFSC).

3 The observer coverage and unit of effort for the Pelagic Drift Gillnet is a set.

4 For 1991-1993, pooled bycatch rates were used to estimate bycatch in months that had fishing effort but did not have observer

coverage. This method is described in Northridge (1996). Because observer coverage increased substantially from 1994-1996,

bycatch rates for this period are single year estimates. 

5 One vessel was not observed and recorded 1 set in a 10 day trip in the SEFSC mandatory logbook. If you assume the vessel fished

1.4 sets per day as estimated from the 1995 SS data, the point estimate may increase by 0.8 animals. However, the SEFSC

mandatory logbook data was taken at face value, and therefore it was assumed that 1 set was fished within this trip, and the point

estimate would then increase by 0.1 animals.

6 The fishery did not operate in 1997; the average mortality is based on the number of years (4; 1993-1996) that the fishery

operated.

Table 3. Summary for the undifferentiated complex of beaked whales which include Cuvier’s Beak Whales (Ziphius cavirostris)

and Mesoplodon beaked whales released alive, by commercial fishery, years sampled (Years), ratio of observed

mortalities recorded by on-board observers to the estimated mortality (Ratio), the number of observed animals released alive

and injured (Injured), and the number of observed animals released alive and uninjured (Uninjured)

Fishery Years Ratio Injured1 Uninjured

Pelagic Drift Gillnet 93-973 5/12, 4/4.8, 9/9.1, 8/13, NA 0, 0, 12, 0,

NA

 0, 0, 0, 0, NA

1

Injured and released alive animals are not included in the Table 2 mortality estimates.

2 The observer recorded this animal being released alive and having the “gear in/around a single body part”.

3 The fishery did not operate in 1997.

Other Mortality

From 1992-1997, a total of 32 beaked whales, 17 (includes one tentative identification) Gervais's beaked whales (one 1997 animal

had plastics in esophagus and stomach, and Sargassum in esophagus); 2 True's beaked whales; 3 Blainville’s beaked whales; 7 Cuvier's

beaked whales (one 1996 animal showed signs of human interactions propeller marks ) and 3 unidentified animals stranded along the

USA Atlantic coast between Florida and Massachusetts (NMFS unpublished data).

STATUS OF STOCK

The status of Mesoplodont 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. There are insufficient data to determine population trends and the level

of human-caused mortality and serious injury is unknown because of uncertainty regarding species identification in observed fisheries.
66

If one were to assume that the incidental fisheries mortality of the four Mesoplodon spp. and Z. cavirostris was random with

respect to species (i.e., in proportion to their relative abundance), then the minimum population estimate for all of those stocks would

need to sum to at least 970 in order for an annual mortality of 9.7 animals not to exceed the PBR of any one of these species.

Because an assumption of unselective incidental fishing mortality is probably overly optimistic and represents a best case situation,

it is likely that a combined minimum population estimate of substantially greater than 970 would be necessary for an annual mortality

of 9.7 to not exceed the PBR of any one of these five stocks. The largest recent abundance estimate available for beaked whales in

the western North Atlantic was 1,519 (CV = 0.69), which would result in a minimum population estimate of 895 beaked whales;

however, this estimate does not include a correction factor for submerged animals which may be substantial. Although a species

specific PBR cannot be determined, the total fishery mortality and serious injury for this group is not less than 10% of the calculated

PBR and, therefore, cannot be considered to be insignificant and approaching zero mortality and serious injury rate. This is a strategic

stock because of uncertainty regarding stock size and evidence of fishery-related mortality and serious injury. 

REFERENCES

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 RELENTLESS, Cruise No. RS 9402, Marine Mammal Survey/Warm Core Ring Study.

NOAA NMFS NEFSC Woods Hole Laboratory, Woods Hole, MA. 8pp.

Barlow, J., S.L. Swartz, T.C. Eagle, and P.R. Wade. 1995. U.S. Marine Mammal Stock Assessments: Guidelines for Preparation,

Background, and a Summary of the 1995 Assessments. U.S. Dep. Commer., NOAA Tech. Memo. NMFS-OPR-6, 73 pp.

Buckland, S. T., D. R. Andersen, K. P. Burnham, and J. L. Laake. 1993. Distance sampling: Estimating abundance of biological

populations. Chapman and Hall, New York, 446 pp. 

CETAP. 1982. A characterization of marine mammals and turtles in the mid- and north Atlantic areas of the U.S. outer continental

shelf. Cetacean and Turtle Assessment Program, University of Rhode Island. Final Report #AA551-CT8-48 to the Bureau of

Land Management, Washington, DC, 538 pp. 

Houston, J. 1990. Status of Blainville’s beaked whale, Mesoplodon densirostris, in Canada. Can. Fld. Nat. 104(1): 117-120.

Laake, J. L., S. T. Buckland, D. R. Anderson, and K. P. Burnham. 1993. DISTANCE user’s guide, V2.0. Colorado Cooperative Fish

& Wildlife Research Unit, Colorado State University, Ft. Collins, Colorado, 72 pp. 

Leatherwood, S., D. K. Caldwell and H. E. Winn. 1976. Whales, dolphins, and porpoises of the western North Atlantic. A guide

to their identification. U.S. Dept. of Commerce, NOAA Tech. Rep. NMFS Circ. 396, 176 pp. 

Lien J., F. Barry, K. Breeck, and U. Zuschlag. 1990. Status of Sowerby's Beaked Whale, Mesoplodon bidens, in Canada. Can.

Fld. Nat. 104(1): 125-130.

Mead, J.G. 1984. Survey of reproductive data for the beaked whales (Ziphiidae). Rep. int Whal. Commn. (Special Issue 6):91-

96.

Mead, J. G. 1989. Beaked whales of the genus Mesoplodon. Pages 349-430. In: S. H., Ridgway and R. Harrison (eds), Handbook

of marine mammals, Vol. 4: River Dolphins and toothed whales. Academic press, San Diego, 442 pp. 

Nawojchik, R. 1994. First record of Mesoplodon densirostris (Cetacea: Ziphiidae) from Rhode Island. Mar. Mamm. Sci. 10: 477-

480.

Nicolas, J., A. Williams, G. Repucci. 1993. Observations of beaked whales (Mesoplodon spp.) in the western North Atlantic

Ocean. Proceedings of the Tenth Biennial Conference on the Biology of Marine Mammals, Nov. 11-15, 1993, Galveston, TX

(Abstract). 

Palka, D. 1995. Abundance estimate of the Gulf of Maine harbor porpoise. Pp. 27-50. In: A. Bjørge and G.P. Donovan (eds.).

Biology of the Phocoenids. Rep. int Whal. Commn. Special Issue 16.

Northridge, S. 1996. Estimation of cetacean mortality in the U.S. Atlantic swordfish and tuna drift gillnet and pair trawl fisheries.

Final report to the Northeast Fisheries Science Center, Contract No. 40ENNF500045, 18 pp. 

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.

Trove, M. 1995. Live sighting of Mesoplodon CF. M. Mirus, True’s Beaked Whale. Mar. Mamm. Sci. 11(1): 80-85.

Wade, P.R., and R.P. Angliss. 1997. Guidelines for assessing marine mammal stocks: Report of the GAMMS Workshop April 3-5,

1996, Seattle, Washington. U.S. Dep. Commer., NOAA Tech. Memo. NMFS-OPR-12, 93 pp.
67

Waring, G.T. 1998. Results of the summer 1991 R/V Chapman marine mammal sighting survey. NOAA NMFS NEFSC, Lab. Ref.

Doc. No. 98-09, 21pp. Northeast Fisheries Science Center, Woods Hole, Massachusetts.

Waring, G.T., C.P. Fairfield, C.M. Ruhsam, and M. Sano. 1992. Cetaceans associated with Gulf Stream features off the northeastern

USA shelf. ICES C.M. 1992/N:12 29 pp.
68

Figure 1. Distribution of Risso’s dolphin sightings from

NEFSC shipboard and aerial surveys during the summer

in 1990-1995. Isobaths are at 100 m and 1,000 m. 

October 1999

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 dolphin is 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 midAtlantic bight and extends further into oceanic waters (Payne et al. 1984). In general, the population occupies the mid-Atlantic

continental shelf edge year round, and is rarely seen in the Gulf of Maine (Payne et al. 1984). During 1990, 1991 and 1993,

spring/summer surveys conducted in continental shelf edge and deeper oceanic waters had sightings of Risso's dolphins associated

with strong bathymetric features, Gulf Stream warm-core rings, and the Gulf Stream north wall (Waring et al. 1992; Waring 1993).

There is no information on stock differentiation of Risso's dolphin in the western North Atlantic. 

POPULATION SIZE

The total number of Risso's dolphins off the eastern

USA and Canadian Atlantic coast is unknown, although four

estimates are available from selected regions during spring

and summer 1978-82, June-July 1991, August-September

1991, and June-July 1993.

A population size of 4,980 (CV = 0.34) Risso’s dolphins

was estimated from an aerial survey program conducted from

1978 to 1982 on the continental shelf and shelf edge waters

between Cape Hatteras, North Carolina and Nova Scotia

(Table 1; CETAP 1982). The estimate is based on an

inverse variance weighted pooling of spring and summer

data. An average of these seasons were chosen because the

greatest proportion of the population off the northeast USA

coast appeared in the study area during these seasons. This

estimate does not include a correction for dive-time or g(0),

the probability of detecting an animal group on the track line.

This estimate may not reflect the current true population

size because of its old age, and it was estimated just after

cessation of extensive foreign fishing operations in the

region.

A population size of 11,017 (CV=0.58) Risso’s

dolphins was estimated from a June and July 1991

shipboard line transect sighting survey conducted primarily

between the 200 and 2,000m isobaths from Cape Hatteras to

Georges Bank (Table 1; Waring et al. 1992; Waring 1998).

Data were collected by one team that searched by naked eye and analyzed using DISTANCE (Buckland et al. 1993; Laake et al.

1993). Estimates include school size-bias, if applicable, but no corrections for g(0) or dive-time. Variability was estimated using

bootstrap resampling techniques.

A population size 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 (Table 1; Anon. 1991). The study area

included that covered in the CETAP study plus several additional continental slope survey blocks. Due to weather and logistical

constraints, several survey blocks south and east of Georges Bank were not surveyed. The data were analyzed using DISTANCE

(Buckland et al. 1993; Laake et al. 1993), where the CV was estimated using the bootstrap option. The abundance estimates do

not include g(0) and were not pooled over platforms because the inter-platform calibration analysis has not been conducted.
69

A population size of 212 (CV=0.62) Risso’s dolphins was estimated from a June and July 1993 shipboard line transect sighting

survey conducted principally between the 200 and 2,000m isobaths from the southern edge of Georges Bank, across the Northeast

Channel to the southeastern edge of the Scotian Shelf (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 bootstrap

resampling techniques.

The few Risso's dolphin sightings made during August 1990 and 1994 were widely scattered, and therefore were not used to

obtain abundance estimates. It should be noted, however, that nearly all of the sightings in these two years were in deeper oceanic

waters (Waring 1993; Anon. 1994).

A population size of 5,587 (CV=1.16) Risso’s dolphins was estimated from a July to September 1995 sighting survey conducted

by two ships and an airplane that covered waters from Virginia to the mouth of the Gulf of St. Lawrence (Table 1; NMFS

unpublished data). Total track line length was 32,600 km (17,600 nmi). 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. Shipboard data were collected using a two independent sighting team

procedure and were analyzed using the product integral method (Palka 1995) and DISTANCE (Buckland et al. 1993). Shipboard

estimates were corrected for g(0) and, if applicable, also for school size-bias. Standard aerial sighting procedures with two bubble

windows and one belly window observer were used during the aerial survey. An estimate of g(0) was not made for the aerial portion

of the survey. Estimates do not include corrections for dive-time. Variability was estimated using bootstrap resampling techniques.

Although the 1991, 1993, and 1995 surveys did not sample exactly the same areas or encompass the entire Risso's dolphin habitat,

they did focus on segments of known or suspected high-use habitats off the northeastern USA coast. The collective data suggest that

at least several thousand Risso's dolphins occupy these waters seasonally; however, survey coverage to date was not judged adequate

to provide a definitive estimate of Risso's dolphin abundance in the western North Atlantic. 

The best available current abundance estimate for Risso’s dolphins is 16,818 (CV=0.52) as estimated from the August to

September 1991 aerial line transect survey in the AT-11 because this survey provided the most complete coverage of the known

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

spring & summer

1978-82 Cape Hatteras, NC to Nova Scotia 4,980 0.34

Jun-Jul 1991 Cape Hatteras, NC to Georges Bank, shelf edge only 11,017 0.58

Aug-Sep 1991 Cape Hatteras, NC to Nova Scotia 6,496 and 16,818*0.74 and 0.52*

Jun-Jul 1993 Georges Bank to Scotian shelf, shelf edge only 212 0.62

Jul-Sep 1995 Virginia to Gulf of St. Lawrence 5587 1.16

* From data collected on the Twin Otter and AT-11, respectively.

Minimum Population Estimate

The minimum population estimate is the lower limit of the two-tailed 60% confidence interval of the log-normally distributed

best abundance estimate. This is equivalent to the 20th percentile of the log-normal distribution as specified by Wade and Angliss

(1997). The best estimate of abundance for Risso’s dolphins is 16,818 (CV=0.52). The minimum population estimate for the

western North Atlantic Risso’s dolphin is 11,140 (CV=0.52).

Current Population Trend

There are insufficient data to determine the population trends for this species. 
70

CURRENT AND MAXIMUM NET PRODUCTIVITY RATES

Current and maximum net productivity rates are unknown for this stock. For purposes of this assessment, the maximum net

productivity rate was assumed to be 0.04. This value is based on theoretical modeling showing that cetacean populations may not

grow at rates much greater than 4% given the constraints of their reproductive life history (Barlow et al. 1995).

 

POTENTIAL BIOLOGICAL REMOVAL

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

a “recovery” factor (MMPA Sec. 3. 16 U.S.C. 1362; Wade and Angliss 1997). The minimum population size is 11,140 (CV=0.52).

The maximum productivity rate is 0.04 , the default value for cetaceans (Barlow et al. 1995). The “recovery” factor, which accounts

for endangered, depleted, threatened stocks, or stocks of unknown status relative to optimum sustainable population (OSP) is

assumed to be 0.48 because the CV of the average mortality estimate is between 0.3-0.6; Wade and Angliss 1997), because this stock

is of unknown status. PBR for the western North Atlantic Risso’s dolphin is 107.

ANNUAL HUMAN-CAUSED MORTALITY

 Total annual estimated average fishery-related mortality or serious injury to this stock during 1993-1997 was 7.4 Risso's

dolphins (CV = 0.33; Table 2). 

Fishery Information

Prior to 1977, there was no documentation of marine mammal by-catch in distant-water fleet (DWF) activities off the northeast

coast of the USA With implementation of the Magnuson Fisheries Conservation and Management Act (MFCMA) in that year, an

observer program was established which has recorded fishery data and information of incidental by-catch 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 vessels. Between 1983 and 1991, the numbers of foreign vessels operating 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 25-35% during 1977-82, and increased to 58%,

86%, 95%, and 98%, respectively, in 1983-86. From 1987-91, 100% observer coverage was maintained. Foreign fishing operations

for squid and mackerel ceased at the end of the 1986 and 1991 fishing seasons, respectively. NMFS foreign-fishery observers have

reported four deaths of Risso's dolphins incidental to squid and mackerel fishing activities in the continental shelf and continental

slope waters between March 1977 and December 1991 (Waring et al. 1990; NMFS unpublished data). Three animals were taken

by squid trawlers and a single animal was killed in longline fishing operations. 

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

self-reported fisheries information system for large pelagic fisheries. Data files are maintained at the Southeast Fisheries Science

Center (SEFSC). The Northeast Fisheries Science Center (NEFSC) Sea Sampling Observer Program was initiated in 1989, and since

that year several fisheries have been covered by the program. In late 1992 and in 1993, the SEFSC provided observer coverage of

pelagic longline vessels fishing off the Grand Banks (Tail of the Banks) and provides observer coverage of vessels fishing south of

Cape Hatteras. 

Pelagic Drift Gillnet

By-catch has been observed by NMFS Sea Samplers in the pelagic drift gillnet fishery, pelagic pair trawl fishery, and pelagic

longline fishery, but no mortalities or serious injuries have been documented in the New England multispecies sink gillnet, midAtlantic coastal sink gillnet, or North Atlantic bottom trawl observed fisheries.

The estimated total number of hauls in the pelagic drift gillnet fishery increased from 714 in 1989 to 1,144 in 1990; thereafter,

with the introduction of quotas, effort was severely reduced. The estimated number of hauls in 1991, 1992, 1993, 1994, 1995, and

1996 were 233, 243, 232, 197, 164, and 149 respectively. In 1996 and 1997, the NMFS issued management regulations which

prohibited the operation of this fishery in 1997. Further, in January 1999 the NMFS issued a Final Rule to prohibit the use of

driftnets (i.e., permanent closure) in the North Atlantic swordfish fishery (50 CFR Part 630). Fifty-nine different vessels participated

in this fishery at one time or another between 1989 and 1993. Since 1994, between 10 and 12 vessels have participated in the fishery

(Table 2). Observer coverage, expressed as percent of sets observed, was 8% in 1989, 6% in 1990, 20% in 1991, 40% in 1992, 42%

in 1993, 87% in 1994, 99% in 1995, and 64% in 1996. Effort was concentrated along the southern edge of Georges Bank and off
71

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, 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 by-catch for 1994 and 1995 were estimated from the sum of the observed

caught and the product of the average bycatch per haul and the number of unobserved hauls as recorded in self-reported fisheries

information. Variances were estimated using bootstrap re-sampling techniques. Forty two Risso's dolphin mortalities were observed

between 1989 and 1996. One animal was entangled and released alive. By-catch occurred during July, September and October along

continental shelf edge canyons off the southern New England coast. Estimated annual mortality and serious injury (CV in

parentheses) attributable to the drift gillnet fishery was 87 in 1989 (0.52), 144 in 1990 (0.46), 21 in 1991 (0.55), 31 in 1992 (0.27),

14 in 1993 (0.42), 1.5 in 1994 (0.16), 6 in 1995 (0), and 0 in 1996. The 1993-1997 average mortality for this fishery was 5.4 (CV

= 0.27) (Table 2). 

Pelagic Pair Trawl

 Effort in the pelagic pair trawl fishery increased during the period 1989 to 1993, from zero hauls in 1989 and 1990, to an

estimated 171 hauls in 1991, and then to an estimated 536 hauls in 1992, 586 in 1993, 407 in 1994, and 440 in 1995, respectively.

This fishery ceased operations in 1996, when NMFS rejected a petition to consider pair trawl gear as an authorized gear type in

Atlantic tunas fishery. The fishery operated from August-November in 1991, from June-November in 1992, from June-October in

1993 (Northridge 1996), and from mid-summer to November in 1994 and 1995. Sea sampling began in October 1992 (Gerrior et al.

1994), and 48 sets (9% of the total) were sampled in that season, 102 hauls (17% of the total) were sampled in 1993. In 1994 and

1995, 52% and 55%, respectively, of the sets were observed. Nineteen vessels have operated in this fishery. The fishery extends

from 35oN to 41oN, and from 69EW to 72EW. Approximately 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 by-catch, showed little seasonal change for

the six months of operation and did not warrant any seasonal or areal stratification of this fishery (Northridge 1996). One mortality

was observed in 1992. Estimated annual 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 is no longer exists, it has been excluded from Tables 2

and 3.

During the 1994 and 1995 experimental fishing seasons, fishing gear experiments were conducted to collect data on environmental

parameters, gear behavior, and gear handling practices to evaluate factors affecting catch and bycatch (Goudey 1995, 1996). Results

of these studies were inconclusive in identifying factors responsible for marine mammal bycatch.

Pelagic Longline

Total effort, excluding the Gulf of Mexico, for the pelagic longline fishery, based on mandatory 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 sets in 1996, and 8,023

sets in 1997 (Cramer 1994; Scott and Brown 1997; Johnson et al. 1999). 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 coverage, in terms of trips observed, since 1992. The 1993-1997,

estimated take was based on a revised analysis of the observed incidental take and self-reported incidental take and effort data, and

replace previous estimates for the 1990-1993 and 1994-1995 periods (Cramer 1994; Scott and Brown 1997; Johnson et al. 1999).

Most of the estimated marine mammal by-catch was from EEZ waters between South Carolina and Cape Cod. Excluding the Gulf

of Mexico, from 1992- 1997 one mortality was observed in 1994 (Cramer 1994; Scott and Brown 1997; Johnson et al. 1999) (Table

2). Estimated annual fishery-related mortality (CV in parentheses) was 0 in 1992 (0), 0 1993 (0), 10 in 1994 (1.0) 0 in 1995-1997.

The 1993-1997 estimated mean annual Risso’s dolphin mortality attributable to this fishery is 2.0 (CV = 1.0) (Table 2). Injured and

released alive animals are not included in the Table 2 mortality estimates. Table 3 summarizes the number of animals released alive

and classified as injured or non-injured. It also includes the ratio of observed to estimated mortalities for this fishery. 

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 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

Estimated5

Mortality 

Estimated

CVs 

Mean

Annual

Mortality
72

Pelagic Drift

Gillnet 93-97

1994=123

1995=11

1996=10

Obs. Data

Logbook

 .42, .87,

.99, .64,

NA

 1, 1, 6, 0,

NA

 14, 1.5 64,

0, NA

 .42, .16, 0,

0, NA

 5.46

 (.27)

Pelagic Longline7 93-97 Obs. Data

Logbook

 .06, .05,

.06, .03, .04

 0, 1, 0, 0,

0

 0, 10, 0, 0,

0

 0, 1.0, 0, 0,

0

 2.0

 (1.0)

TOTAL 7.4

 (0.33)

1 Observer data (Obs. Data) are used to measure bycatch rates, and the data are collected within the Northeast Fisheries Science

Center (NEFSC) Sea Sampling Program. NEFSC collects weighout (Weighout) landings data, 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 North Atlantic bottom trawl

fishery. 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 North Atlantic

bottom trawl fishery is in days fished. Assessments for the coastal gillnet fishery have not been completed. The number of trips

sampled by the NEFSC Sea Sampling Program are reported here.

3 1994 -1996 shown, other years not available on an annual basis.

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 0.42 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 increase by 0.03 animals.

5

Injured and released alive animals are not included in the Table 2 mortality estimates.

6 The average is based on the number of years (4; 1993-1996) that the fishery operated.

7 Mortality estimates were taken from Table 12 in Johnson et al. (1999), and exclude the Gulf of Mexico.
73

Table 3. Summary of Risso’s dolphin (Grampus griseus) released alive, by commercial fishery, years sampled (Years), ratio of

observed mortalities recorded by on-board observers to the estimated mortality (Ratio), the number of observed animals

released alive and injured (Injured), and the number of observed animals released alive and uninjured (Uninjured). 

Fishery Years Ratio Injured2 Uninjured

Pelagic Longline3 93-97 0, 1/10, 0, 0, 0 0, 5 1 , 21, 1, 0 24, 1, 21, 2, 0 

1 See Appendix 1.

2

Injured and released alive animals are not included in the Table 2 mortality estimates.

3 Excludes the Gulf of Mexico.

4 Data from Table 6 (Johnson et al. 1999). Information on status of released animals was not reported.

Other mortality

From 1995- 1997, eight Risso’s dolphins stranding were recorded along the USA Atlantic coast (NMFS unpublished data).

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, cannot be considered

to be insignificant and approaching a zero mortality and serious injury rate. The 1993-1997 average annual fishery-related mortality

does not exceed PBR; therefore, this is not a strategic stock. 

REFERENCES

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 RELENTLESS, Cruise No. RS 9402, Marine Mammal 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. Commer., NOAA Tech. Memo. NMFS-OPR-6, 73 pp. 

Baird, R. W. and P. J. Stacey. 1990. Status of Risso's dolphin, Grampus griseus, in Canada. Can. Fld. Nat. 105:233-242. 

Buckland, S.T., D.R. Anderson, K.P. Burnham and S.L. Laake. 1993. Distance sampling: estimating abundance of biological

populations. Chapman and Hall, New York, NY, 446 pp.

CETAP. 1982. A characterization of marine mammals and turtles in the mid- and north Atlantic areas of the U.S. outer continental

shelf. Cetacean and Turtle Assessment Program, University of Rhode Island. Final Report #AA551-CT8-48 to the Bureau of

Land Management, Washington, DC, 538 pp. 

Cramer J. 1994. Large pelagic logbook newsletter - 1993. NOAA Tech. Mem. NMFS-SEFSC-352, 19 pp. 

Gerrior, P., A.S. Williams, and D.J. Christensen. 1994. Observations of the 1992 U.S. pelagic pair trawl fishery in the Northwest

Atlantic. U.S. Mar. Fish. Rev. 56(3): 24-27.

Goudy, C.A. 1995. The 1994 experimental pair trawl fishery for tuna in the northwest Atlantic, MITSG 95-6,Cambridge, MA. 10

pp.

Goudy, C.A. 1996. The 1995 experimental pair trawl fishery for tuna in the northwest Atlantic, MITSG 95-6, Cambridge,

MA. 13 pp.

Johnson, D.R., C. Yeung and C.A. Brown . 1999. Estimates of marine mammal and marine turtle catch by the U.S. Atlantic pelagic

longline fleet in 1992-1997. NOAA Tech. Mem. NMFS-SEFSC-418, 70p.

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. 72pp.

Leatherwood, S., D. K. Caldwell and H. E. Winn. 1976. Whales, dolphins, and porpoises of the western North Atlantic. A guide

to their identification. U.S. Dept. of Commerce, NOAA Tech. Rep. NMFS Circ. 396, 176 pp. 

Northridge, S. 1996. Estimation of cetacean mortality in the U.S. Atlantic swordfish and tuna drift gillnet and pair trawl fisheries.

Final report to the Northeast Fisheries Science Center, Contract No. 40ENNF500045, 18 pp.
74

Palka, D. 1995. Abundance estimate of the Gulf of Maine harbor porpoise. Pp. 27-50. In: A. Bjørge and G.P. Donovan (eds.).

Biology of the Phocoenids. Rep. int Whal. Commn. Special Issue 16.

Payne, P. M., L. A. Selzer and A. R. Knowlton. 1984. Distribution and density of cetaceans, marine turtles, and seabirds in the shelf

waters of the northeastern United States, June 1980-December 1983, based on shipboard observations. NOAA/NMFS Contract

No. NA-81-FA-C-00023. 

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

Special Issue 15: 133-147. 

Scott, G.P. and C.A. Brown. 1997. Estimates of marine mammal and marine turtle catch by the US 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-OPR-12, 93 pp.

Waring, G.T. 1998. Results of the summer 1991 R/V Chapman marine mammal sighting survey. NOAA NMFS NEFSC, Lab. Ref.

Doc. No. 98-09, 21pp. Northeast Fisheries Science Center, Woods Hole, Massachusetts.

Waring, G. T. 1993. Spatial patterns of six cetaceans along a linear habitat. Proceedings of the Tenth Biennial Conference on the

Biology of Marine Mammals, Nov. 11-15, 1993, Galveston, TX (Abstract). 

Waring, G. T., C. P. Fairfield, C. M. Ruhsam and M. Sano. 1992. Cetaceans associated with Gulf Stream features off the

northeastern USA shelf. ICES Marine Mammals Comm. CM 1992/N:12, 29 pp.

Waring, G. T., P. Gerrior, P. M. Payne, B. L. Parry and J. R. Nicolas. 1990. Incidental take of marine mammals in foreign fishery

activities off the northeast United States, 1977-1988. Fish. Bull., U.S., 88:347-360.
75

Figure 1. Distribution of pilot whale sightings from

NEFSC shipboard and aerial surveys during the summer

in 1990-1995. Isobaths are at 100 m and 1,000 m. 

October 1999

LONG-FINNED PILOT WHALE (Globicephala melas):

Western North Atlantic Stock

STOCK DEFINITION AND GEOGRAPHIC RANGE

There are two species of pilot whales in the Western Atlantic — the Atlantic or long-finned pilot whale, Globicephala melas,

and the short-finned pilot whale, G. macrorhynchus. These species are difficult to identify to the species level at sea; therefore,

some of the descriptive material below refers to Globicephala sp., and is identified as such. The species boundary is considered

to be in the New Jersey to Cape Hatteras area. Sightings north of this area are likely G. melas. 

Pilot whales (Globicephala sp.) are distributed principally along the continental shelf edge in the winter and early spring off

the northeast USA coast, (CETAP 1982; Payne and Heinemann 1993). In late spring, pilot whales move onto Georges Bank and

into the Gulf of Maine and more northern waters, and remain in these areas through late autumn (CETAP 1982; Payne and Heinemann

1993). In general, pilot whales generally occupy areas of high relief or submerged banks. They are also associated with the Gulf

Stream north wall and thermal fronts along the continental shelf edge (Waring et al. 1992; NMFS unpublished data). 

The long-finned pilot whale is distributed from North Carolina to Iceland and possibly the Baltic Sea (Sergeant 1962; Leatherwood

et al. 1976; Abend 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 stock boundaries. 

POPULATION SIZE

The total number of long-finned pilot whales off the

eastern USA and Canadian Atlantic coast is unknown,

however, eight estimates are available (Table 1; Figure 1).

Two estimates were derived from catch data and population

models that estimated the abundance of the entire stock. Six

seasonal estimates are available from selected regions in USA

waters during spring, summer and autumn 1978-82, August

1990, June-July 1991, August-September 1991, June-July

1993, and July-September 1995. Because long-finned and

short-finned pilot whales are difficult to identify at sea,

seasonal abundance estimates were reported for

Globicephala sp., both long-finned and short-finned pilot

whales.

Mitchell (1974) used cumulative catch data from the 1951-

61 drive fishery off Newfoundland to estimate the initial

population size (ca. 50,000 animals).

Mercer (1975), used population models to estimate a

population in the same region of between 43,000-96,000 longfinned pilot whales, with a range of 50,000-60,000 being

considered the best estimate. 

A population size of 11,120 (CV=0.29) Globicephala

sp. was estimated from an aerial survey program conducted

from 1978 to 1982 on the continental shelf and shelf edge

waters between Cape Hatteras, North Carolina and Nova

Scotia (Table 1; CETAP 1982). The estimate is based on an inverse variance weighted pooling of spring, summer and autumn data.

An average of these seasons were chosen because the greatest proportion of the population off the northeast USA coast appeared

in the study area during these seasons. This estimate does not include a correction for dive-time or g(0), the probability of detecting

an animal group on the track line. This estimate may not reflect the current true population size because of its high degree of

uncertainty , its old age, and it was estimated just after cessation of extensive foreign fishing operations in the region.
76

A population size of 1,043 (CV=0.78) Globicephala sp. 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 (Table 1; Waring et al.

1992). Data were collected by one team that searched by naked eye and 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.

A population size of 3,636 (CV = 0.36) Globicephala sp. was estimated from a June and July 1991 shipboard line transect

sighting survey conducted primarily between the 200 and 2,000m isobaths from Cape Hatteras to Georges Bank (Table 1; Waring

et al. 1992; Waring 1998). Data were collected by one team that searched by naked eye and analyzed using DISTANCE (Buckland

et al. 1993; Laakeet al. 1993). Estimates include school size-bias, if applicable, but no corrections for g(0) or dive-time. Variability

was estimated using bootstrap resampling techniques.

A population size of 3,668 (CV=0.28) and 5,377 (CV=0.53)Globicephala sp. was estimated from line transect aerial surveys

conducted from August to September 1991 using the Twin Otter and AT-11, respectively (Table 1; Anon. 1991). The study area

included that covered in the CETAP study plus several additional continental slope survey blocks. Due to weather and logistical

constraints, several survey blocks south and east of Georges Bank were not surveyed. The data were analyzed using DISTANCE

(Buckland et al. 1993; Laake et al. 1993), where the CV was estimated using the bootstrap option. The abundance estimates do

not include g(0) and were not pooled over platforms because the inter-platform calibration analysis has not been conducted.

A population size of 668 (CV=0.55) Globicephala sp. was estimated from a June and July 1993 shipboard line transect sighting

survey conducted principally between the 200 and 2,000m 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 bootstrap

resampling techniques.

A population size of 8,176 (CV=0.65) Globicephala sp. was estimated from a July to September 1995 sighting survey

conducted by two ships and an airplane that covered waters from Virginia to the mouth of the Gulf of St. Lawrence (Table 1; NMFS

unpublished data.). Total track line length was 32,600 km (17,600 nmi). 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. Shipboard data were collected using a two independent sighting team

procedure and were analyzed using the product integral method (Palka 1995) and DISTANCE (Buckland et al. 1993). Shipboard

estimates were corrected for g(0) and, if applicable, also for school size-bias. Standard aerial sighting procedures with two bubble

windows and one belly window observer were used during the aerial survey. An estimate of g(0) was not made for the aerial portion

of the survey. Estimates do not include corrections for dive-time. Variability was estimated using bootstrap resampling techniques.

Although the 1990-1995 surveys did not sample the same areas or encompass the entire pilot whale habitat, they did focus on

segments of known or suspected high-use habitats off the northeastern USA coast. The collective 1990-95 data suggest that,

seasonally, at least several thousand pilot whales are occupying these waters; however, survey coverage to date is not judged adequate

to provide a definitive estimate of pilot whale abundance in the western North Atlantic. 

The best available current abundance estimate for Globicephala sp. is 8,176 (CV=0.65) as estimated from the July to September

1995 line transect survey (NMFS unpublished data.) because this survey is recent and provided the most complete coverage of the

known habitat.
77

Table 1. Summary of abundance estimates for the western North Atlantic Globicephala sp. Month, year, and area covered during

each abundance survey, and resulting abundance estimate (Nbest) and coefficient of variation (CV).

Month/Year Area Nbest CV

1951-1961 Newfoundland 50,000 None reported

1951-1961 Newfoundland 50,000-60,000 None reported

spring, summer &

autumn 1978-82

Cape Hatteras, NC to Nova Scotia 11,120 0.29

Aug 1990 Gulf Stream 1,043 0.78

Jun-Jul 1991 Cape Hatteras, NC to Georges Bank, shelf edge only 3,636 0.36

Aug-Sep 1991 Cape Hatteras, NC to Nova Scotia 3,668 and 5,377*0.28 and 0.53*

Jun-Jul 1993 Georges Bank to Scotian shelf, shelf edge only 668 0.55

Jul-Sep 1995 Virginia to Gulf of St. Lawrence 8,176 0.65

* From data collected on the Twin Otter and AT-11, respectively.

Minimum Population Estimate

The minimum population estimate is the lower limit of the two-tailed 60% confidence interval of the log-normally distributed

best abundance estimate. This is equivalent to the 20th percentile of the log-normal distribution as specified by Wade and Angliss

(1997). The best estimate of abundance for Globicephala sp. is 8,176 (CV=0.65). The minimum population estimate for

Globicephala sp. is 4,968 (CV=0.65).

Current Population Trend

There are insufficient data to determine the population trends for this species. 

CURRENT AND MAXIMUM NET PRODUCTIVITY RATES

Current and maximum net productivity rates are unknown for this stock. Life history parameters that could be used to estimate

net productivity include those from animals taken in the Newfoundland drive fishery: calving interval 3.3 years; lactation period about

21-22 months; gestation period 12 months; births mainly from June to November; length at birth is 177 cm; mean length at sexual

maturity, 490 cm, males; and 356 cm, 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; Desportes et al. 1993; Martin and Rothery 1993). These differences are likely related, at least

in part, to larger sample sizes and newer analytical techniques. 

For purposes of this assessment, the maximum net productivity rate was assumed to be 0.04. This value is based on theoretical

modeling showing that cetacean populations may not grow at rates much greater than 4% given the constraints of their reproductive

life history (Barlow et al. 1995). 

POTENTIAL BIOLOGICAL REMOVAL

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

a “recovery” factor (MMPA Sec. 3. 16 U.S.C. 1362; Wade and Angliss 1997). The minimum population size for Globicephala

sp. is 4,968 (CV=0.65). 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 0.45 because the CV of the average mortality estimate is between 0.6-0.8; Wade and Angliss 1997) , and because

this stock is of unknown status. PBR for the western North Atlantic Globicephala sp. is 45.

ANNUAL HUMAN-CAUSED MORTALITY
78

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 1993-1997 was 40.3

pilot whales (CV = 0.71; Table 2).

Fishery Information

USA

Prior to 1977, there was no documentation of marine mammal by-catch 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 by-catch of marine

mammals, was established in 1977 with the implementation of the Magnuson Fisheries Conservation and Management Act

(MFCMA). DWF effort in the Atlantic coast EEZ under MFCMA has been directed primarily towards Atlantic mackerel and squid.

An average of 120 different foreign vessels per year (range 102-161) operated within the Atlantic coast EEZ during 1977 through

1982. In 1982, there were 112 different foreign vessels; 18 (16%) were Japanese tuna longline vessels operating along the USA

Atlantic coast. This was the first year that the Northeast Regional Observer Program assumed responsibility for observer coverage

of the longline vessels. The number of foreign vessels operating within the 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 observer coverage on DWF 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 fishing season and, for mackerel, at the end of the 1991 fishing

season. 

During 1977-1991, observers in this program recorded 436 pilot whale mortalities in foreign-fishing activities (Waring et al. 1990;

Waring 1995). A total of 391 (90%) were taken in the mackerel fishery, and 41 (9%) occurred during Loligo and Illex squid-fishing

operations. This total includes 48 documented takes by USA vessels involved in joint venture fishing operations in which USA

captains transfer their catches to foreign processing vessels. Due to temporal fishing restrictions, the by-catch occurred during

winter/spring (December to May) in continental shelf and continental shelf edge waters (Fairfield et al. 1993; Waring 1995); however,

the majority of the takes occurred in late spring along the 100 m isobath. Two animals were also caught in both the hake fishery and

tuna longline fisheries (Waring et al. 1990). 

The distribution of long-finned pilot whale, a northern species, overlaps with that of the short-finned pilot whale, a predominantly

southern species, between 35E30'N to 38E00'N (Leatherwood et al. 1976). Although long-finned 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 by-catch does occur in the

overlap area. In this summary, therefore, long-finned pilot whales (Globicephala melas) and unidentified pilot whales

(Globicephala sp.) are considered together. 

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

self-reported fisheries information system for large pelagic fisheries. Data files are maintained at the Southeast Fisheries Science

Center (SEFSC). The Northeast Fisheries Science Center (NEFSC) Sea Sampling Observer Program was initiated in 1989, and since

that year several fisheries have been covered by the program. In late 1992 and in 1993, the SEFSC provided observer coverage of

pelagic longline vessels fishing off the Grand Banks (Tail of the Banks) and provides observer coverage of vessels fishing south of

Cape Hatteras.

Pelagic Drift Gillnet

By-catch has been observed by NMFS Sea Samplers in the pelagic drift gillnet, pelagic longline, and pelagic pair trawl fisheries,

but no mortalities or serious injuries have documented in the New England multispecies sink gillnet or mid-Atlantic coastal sink

gillnet.

The estimated total number of hauls in the pelagic drift gillnet fishery increased from 714 in 1989 to 1,144 in 1990; thereafter,

with the introduction of quotas, effort was severely reduced. The estimated number of hauls in 1991, 1992, 1993, 1994, 1995, and

1996 were 233, 243, 232, 197, 164, and 149 respectively. In 1996 and 1997, the NMFS issued management regulations which

prohibited the operation of this fishery in 1997. Further, in January 1999 the NMFS issued a Final Rule to prohibit the use of

driftnets (i.e., permanent closure) in the North Atlantic swordfish fishery (50 CFR Part 630). Fifty-nine different vessels

participated in this fishery at one time or another between 1989 and 1993. Since 1994, between 10-12 vessels have participated in

the fishery (Table 2). Observer coverage, expressed as percent of sets observed, was 8% in 1989, 6% in 1990, 20% in 1991, 40%

in 1992, 42% in 1993, 87% in 1994, 99% in 1995, and 64% in 1996. Effort was concentrated along the southern edge of Georges
79

Bank and off Cape Hatteras. Examination of the species composition of the catch and locations of the fishery throughout the year,

suggested that the pelagic drift gillnet fishery be stratified into two strata, a southern or winter stratum, and a northern or summer

stratum. Estimates of the total by-catch, from 1989 to 1993, were obtained using the aggregated (pooled 1989-1993) catch rates, by

strata (Northridge 1996). Estimates of total annual by-catch for 1994 and 1995 were estimated from the sum of the observed caught

and the product of the average bycatch per haul and the number of unobserved hauls as recorded in self-reported fisheries information.

Variances were estimated using bootstrap re-sampling techniques. Between 1989 and 1995, sixty -eight mortalities were observed

in the large pelagic drift gillnet fishery. The annual fishery-related mortality (CV in parentheses) was 77 in 1989 (0.24), 132 in 1990

(0.24), 30 in 1991 (0.26), 33 in 1992 (0.16), 31 in 1993 (0.19), 20 in 1994 (0.06), 9.1 in 1995 (0), and 11 in 1996 (.17); average annual

mortality between 1993-1997 was 17.8 pilot whales (0.09) (Table 2). Table 3 summarizes the number of animals released alive and

classified as injured or non-injured. It also includes the ratio of observed to estimated mortalities for this fishery. Because animals

released alive may have subsequently died due to injuries received during entanglement, pilot whales that were released were included

in the mortality estimates. Pilot whales were taken along the continental shelf edge, northeast of Cape Hatteras in January and

February. Takes were recorded at the continental shelf edge east of Cape Charles, Virginia, in June. Pilot whales were taken from

Hydrographer Canyon along the Great South Channel to Georges Bank from July-November. Takes occurred at the Oceanographer

Canyon continental shelf break and along the continental shelf northeast of Cape Hatteras in October-November.

Pelagic Pair Trawl

Effort in the pelagic pair trawl fishery has increased during the period 1989 to 1993, from zero hauls in 1989 and 1990, to an

estimated 171 hauls in 1991, and then to an estimated 536 hauls in 1992, 586 in 1993, 407 in 1994, and 440 in 1995, respectively.

This fishery ceased operations in 1996, when NMFS rejected a petition to consider pair trawl gear as an authorized gear type in

Atlantic tunas fishery. The fishery operated from August-November in 1991, from June-November in 1992, from June-October in

1993, 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% (212) and

54% (238), respectively, of the sets were observed. Twelve vessels have operated in this fishery. The fishery extends from 35oN

to 41oN, and from 69EW to 72EW. Approximately 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 by-catch, showed little seasonal change for the six

months of operation and did not warrant any seasonal or areal stratification of this fishery (Northridge 1996). Five pilot whale

(Globicephala sp.) mortalities were reported in the self-reported fisheries information in 1993. In 1994 and 1995 observers

reported 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 is no longer exists, it has been

excluded from Tables 2 and 3.

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

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 pilot whales have been reported; however, a vessel may fish in more than

one statistical reporting area and it is not possible to separate estimates of fishing effort other than to subtract Gulf of Mexico effort

from Atlantic fishing effort, which includes the Caribbean Sea. This fishery has been monitored with about 5% observer coverage,

in terms of trips observed, since 1992. Total effort, excluding the Gulf of Mexico, for the pelagic longline fishery, based on mandatory

self-reported fisheries information, was 11,279 sets in 1991, 9,869 sets in 1992, 9,862 sets in 1993, 9,481 sets in 1994, 10,129 sets

in 1995, 9,885 sets in 1996, and 8,023 sets in 1997 (Cramer 1994; Scott and Brown 1997; Johnson et al., 1999). Since 1992, this

fishery has been monitored with about 5% observer coverage, in terms of trips observed, within every statistical reporting area within

the EEZ and beyond. Off the USA Atlantic coast, the fishery has been observed from January to March off Cape Hatteras, in May

and June in the entire Mid-Atlantic, and in July through December in the Mid-Atlantic Bight and off Nova Scotia. This fishery has

been monitored with about 5% observer coverage, in terms of trips observed, since 1992. The 1992-1997, estimated take was based

on a revised analysis of the observed incidental take and self-reported incidental take and effort data, and replace previous estimates

for the 1992-1993 and 1994-1995 periods (Cramer 1994; Scott and Brown 1997; Johnson et al. 1999). Most of the estimated marine

mammal by-catch 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 1990-1997 fifty- eight pilot whales

(including two identified as a short-fin pilot whale) were released alive, and one mortality was observed. The condition codes that

the observers assigned to the disentangled animals were: alive (41 animals); unknown (10 animals); and dead (5 animals). January-
80

March by-catch was concentrated on the continental shelf edge northeast of Cape Hatteras. By-catch was recorded in this area during

April-June, and takes also occurred north of Hydrographer Canyon off the continental shelf in water over 1,000 fathoms during AprilJune. 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 by-catch 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: 40 in 1992 (CV = 1.00), and zero in 1993-1997; average annual mortality between 1993-

1997 was 0 pilot whales (Table 2). Injured and released alive animals are not included in the Table 2 mortality estimates. Table 3

summarizes the number of animals released alive and classified as injured or non-injured. It also includes the ratio of observed to

estimated mortalities for this fishery.

Bluefin Tuna Purse Seine

The tuna purse seine fishery between Cape Hatteras and Cape Cod is directed at small and medium bluefin and skip jack for the

canning industry, while north of Cape Cod purse seine vessels are directed at large medium and giant bluefin tuna (NMFS, 1995).

The latter fishery is entirely separate from any other Atlantic tuna purse seine fishery. Spotter aircraft are used to locate fish

schools. The official start date is August 15, set by regulation. Individual vessel quotas (IVQs) and a limited access system prevent

a derby fishery situation. Catch rates are high with this gear and consequently, the season usually only lasts a few weeks for large

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

Limited observer data are available for the bluefin tuna purse seine fishery. Out of 45 total trips made in 1996, 43 trips (95.6%) were

observed. Forty-four sets were made on the 43 observed trips and all sets were observed. A total of 136 days were covered. Two

interactions with pilot whales were observed in 1996. In one interaction, the net was actually pursed around one pilot whale, the

rings were released and the animal escaped alive, condition unknown. This set occurred east of the Great South Channel and just north

of the Cultivator Shoals region on Georges Bank. In a second interaction, five pilot whales were encircled in a set. The net was

opened prior to pursing to let the whales swim free, apparently uninjured. This set occurred on the Cultivator Shoals region on

Georges Bank. This fishery was not observed in 1997.

North Atlantic Bottom Trawl 

Vessels in the North Atlantic bottom trawl fishery, a Category III fishery under the MMPA, were observed in order to meet

fishery management needs, rather than marine mammal management needs. An average of 970 (CV = 0.04) vessels (full and part time)

participated annually in the fishery during 1989-1993. The fishery is active in New England in all seasons. One mortality was

documented in 1990, and one animal was released alive and uninjured in 1993. The estimated fishery-related mortality to pilot whales

in the USA Atlantic attributable to this fishery was: 0 in 1993-1997; average annual mortality between 1993-1997 was 0 pilot whales

(Table 2). However, these estimates should be viewed with caution due to the extremely low (<1%) observer coverage. Table 3

summarizes the number of animals released alive and classified as injured or non-injured. It also includes the ratio of observed to

estimated mortalities for this fishery.

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 1996 Illex squid fishery. The estimated fishery-related mortality to pilot whales in the USA Atlantic attributable

to this fishery was: 45 in 1996 and 0 in 1997; average annual mortality between 1996-1997 was 22.5 pilot whales (CV = 1.27) (Table

2). However, these estimates should be viewed with caution due to the extremely low (<1%) observer coverage.

CANADA

An unknown number of pilot whales have also been taken in Newfoundland and Labrador, and Bay of Fundy, groundfish gillnets,

Atlantic Canada and Greenland salmon gillnets, and Atlantic Canada cod traps (Read 1994). The Atlantic Canadian and Greenland

salmon gillnet fishery is seasonal, with the peak from June to September, depending on location. 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
81

fishery; however, the fishery was terminated in 1993 under an agreement between Canada and North Atlantic Salmon Fund (Read

1994). 

There were 3,121 cod traps operating in Newfoundland and Labrador during 1979, and about 7,500 in 1980 (Read 1994). This

fishery was closed at the end of 1993 due to collapse of Canadian groundfish resources. 

Between January 1993 and December 1994, 36 Spanish deep water trawlers, covering 74 fishing trips (4,726 fishing days and

14,211 sets), were observed in NAFO Fishing Area 3 (off the Grand Bank) (Lens 1997). A total of 47 incidental catches were

recorded, which included one long-finned pilot whale. The incidental mortality rate for pilot whales was (0.007/set).
82

Table 2. Summary of the incidental mortality of pilot whales (Globicephala sp.) by commercial fishery including the years

sampled (Years), the number of vessels active within the fishery (Vessels), the type of data used (Data Type), the annual

observer coverage (Observer Coverage), the 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 6

Estimated

CVs 

Mean

Annual

Mortality

Pelagic7

Drift Gillnet 93-97

1994=123

1995=11

1996=10

Obs. Data

Logbook

 .42, .87, .99,

.64, NA

 114, 17,

9, 7, NA

 31, 20, 9.15,

11, NA

 .19, .06, 0,

.17, NA

 17.87

 (0.09)

Atlantic

squid,

mackerel,

butterfish

trawl

96-97 NA Obs. Data 

Weighouts

 .007, .008 6, 0 45, 0 1.27, 0 22.5

(1.27)

N. Atl.

Otter Trawl

93-97 NA Obs. Data

Weighouts

.004, .004,

.0118,.002,

.002

0, 0, 0, 0,

0

0, 0, 0, 0, 0 0, 0, 0, 0, 0 0

(0)

Pelagic9

Longline 

 93-97 Obs. Data

Logbook

 .06, .05, .06,

.03, .04

0, 0, 0, 0,

0

 0, 0, 0, 0, 0 0, 0, 0, 0,

0

 0

 (0)

TOTAL 40.3

 (0.71)

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, pair trawl and longline fishery are in terms of sets. The trawl fisheries are measured

in trips.

3 1994, 1995 and 1996 shown, other years not available on an annual basis.

4 For 1991-1993, pooled bycatch rates were used to estimate bycatch in months that had fishing effort but did not have observer

coverage. This method is described in Northridge (1996). In 1994 and 1995, observer coverage increased substantially, and

bycatch rates were not pooled for this period. 

5 One vessel was not observed and recorded 1 set in a 10 day trip in the SEFSC mandatory logbook. If you assume the vessel fished

1.4 sets per day as estimated from the 1995 SS data, the point estimate may increase by 0.84 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 0.06 animals.

6 Annual mortality estimates do not include any animals injured and released alive.

7 The fishery did not operate in 1997; the average annual mortality is based on the number of years (4; 1993-1996) that the fishery

operated.

8 Observer coverage for the Atlantic bottom trawl fishery in 1995 is based on only January to May data.

9 Mortality estimates were taken from Table 12 in Johnson et al. (1999), and exclude the Gulf of Mexico.
83

Table 3. Summary of pilot whales (Globicephala sp.) released alive, by commercial fishery, years sampled (Years), ratio of

observed mortalities recorded by on-board observers to the estimated mortality (Ratio), the number of observed animals

released alive and injured (Injured), and the number of observed animals released alive and uninjured (Uninjured).

Fishery Years Ratio Injured3 Uninjured

Pelagic Drift Gillnet 93-97 11/31, 17/20,9/9.1,7/11,

NA

 11, 0, 0, 0, NA 0

Pelagic Long Line 93-97 0, 0, 0, 0, 0 NA, 52, 42, 0, 12 164, 92,102, 0, 0

North Atlantic Bottom Trawl 93-97 0, 0, 0, 0, 0 0, 0, 0, 0, 0 0, 1, 0, 0, 0

1 Released alive with condition unknown.

2 See Appendix 1.

3

Injured and released alive animals are not included in the Table 2 mortality estimates.

4 Data from Table 6 (Johnson et al. 1999). Information on status of released animals was not reported.

Other Mortality

Pilot whales have a propensity to mass strand throughout their range, but the role of human activity in these events is unknown.

Between two and 120 pilot whales have stranded annually either individually or in groups in the NMFS Northeast Region (Anon.

1993b) since 1980. From 1992-1997, 65 long-finned pilot whale stranded between South Carolina and Maine, including 22 animals

that mass stranded in 1992 along the Massachusetts coast (NMFS unpublished data). 

A potential human-caused source of mortality is from polychlorinated biphenyls (PCBs) and DDT, moderate levels of which

have been found in pilot whale blubber (Taruski 1975; Muir et al. 1988). The effect of the observed levels of such contaminants

is unknown. 

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 1971, and increased

abundance of herring, mackerel, and squid stocks. There are insufficient data to determine the population trends for this species.

The species is not listed under the Endangered Species Act. The total fishery-related mortality and serious injury for this stock is

not less than 10% of the calculated PBR and, therefore, cannot be considered to be insignificant and approaching zero mortality and

serious injury rate. The 1993-1997 estimated average annual fishery-related mortality to pilot whales, Globicephala sp., did not

exceed PBR, therefore, this is not a strategic stock. 

REFERENCES

Abend, A. 1993. Long-finned pilot whale distribution and diet as determined from stable carbon and nitrogen ratio isotope tracers.

M.S. Thesis, University of Massachusetts, Amherst. 

Anon. 1991. Northeast cetacean aerial survey and interplatform study. NOAA, NMFS, SEFSC & NEFSC. Available from NEFSC,

Woods Hole Laboratory, Woods Hole, MA. 4 pp.

Anon. 1993a. 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. 1993b. Status of fishery resources off the northeastern United States for 1993. NOAA Tech. Mem. NMFS-F/NEC-101,

140 pp.

Anon. 1994. Cruise results, NOAA ship RELENTLESS, Cruise No. RS 9402, Marine Mammal 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. Commer., NOAA Tech. Memo. NMFS-OPR-6, 73 pp. 

Bloch, D., M. Zachariassen and P. Zachariassen. 1993. Some external characters of the long-finned pilot whale off Faroe Island and

a comparison with the short-finned pilot whale. Rep. int Whal. Commn. Special Issue 14:117-135.
84

Buckland, S.T., D.R. Anderson, K.P. Burnham and S.L. Laake. 1993. Distance sampling: estimating abundance of biological

populations. Chapman and Hall, New York, NY, 446 pp.

CETAP. 1982. A characterization of marine mammals and turtles in the mid- and north Atlantic areas of the U.S. outer continental

shelf. Cetacean and Turtle Assessment Program, University of Rhode Island. Final Report, Contract AA51-C78-48, Bureau of

Land Management, Washington, DC. 538 pp.

Cramer J. 1994. Large pelagic logbook newsletter - 1993. NOAA Tech. Mem. NMFS-SEFSC-352, 19 pp. 

Desportes, G., M. Saboureau and A. Lacroix. 1993. Reproductive maturity and seasonality of male pilot long-finned whales off the

Faroe Islands. Rep. int Whal. Commn. Special Issue 14: 233-262.

Fairfield, C. P., G. T. Waring and M. H. Sano. 1993. Pilot whales incidentally taken during the distant water fleet Atlantic mackerel

fishery in the mid-Atlantic Bight, 1984-88. Rep. int Whal. Commn. Special Issue 14: 107-116.

Gerrior, P., A.S. Williams, and D.J. Christensen. 1994. Observations of the 1992 U.S. pelagic pair trawl fishery in the Northwest

Atlantic. Mar. Fish. Rev. 56(3): 24-27.

Goudy, C.A. 1995. The 1994 experimental pair trawl fishery for tuna in the northwest Atlantic, MITSG 95-6, Cambridge, MA. 10

pp.

Goudy, C.A. 1996. The 1995 experimental pair trawl fishery for tuna in the northwest Atlantic, MITSG 95-6, Cambridge, MA. 13

pp.

Kasuya, T., D. E. Sergeant and K. Tanaka. 1988. Re-examination of life history parameters of long-finned pilot whales in the

Newfoundland waters. Sci. Rep. Whales Res. Inst. No. 39: 103-119.

Johnson, D.R., C.A. Brown, and C. Yeung. 1999. Estimates of marine mammal and marine turtle catch by the US Atlantic pelagic

longline fleet in 1992-1997. NOAA Tech. Mem. NMFS-SEFSC-418, 70p.

Laake, J.L., S.T. Buckland, D.R. Anderson and K.P. Burnham. 1993. DISTANCE user’s guide, V2.0. Colorado Cooperative Fish

and Wildlife Research Unit, Colorado State University, Ft. Collins, Colorado. 72 pp.

Leatherwood, S., D. K. Caldwell and H. E. Winn. 1976. Whales, dolphins, and porpoises of the western North Atlantic. A guide

to their identification. U.S. Dept. of Commerce, NOAA Tech. Rep. NMFS Circ. 396, 176 pp. 

Lens, S. 1997. Interactions between marine mammals and deep water trawlers in the NAFO regulatory area. ICES CM 1997/Q:8.

10 pp.

Martin, A. R. and P. Rothery. 1993. Reproductive parameters of female long-finned pilot whales (Globicephala melas) around

the Faroe Islands. Rep. int Whal. Commn. Special Issue 14: 263-304.

Mercer, M. C. 1975. Modified Leslie-DeLury population models of the long-finned pilot whale (Globicephala melaena) and

annual production of the short-finned squid (Illex illecebrosus) based upon their interactions at Newfoundland. J. Fish. Res.

Bd. Can. 32(7): 1145-54. 

Mitchell, E. 1974. Present status of northwest Atlantic fin and other whale stocks. Pages 108-169. In: W. E. Schevill (ed.), The

whale problem: A status report. Harvard University Press, Cambridge, Massachusetts, 419 pp.

Muir, D. C. G., R. Wagermann, N. P. Grift, R. J. Norstrom, M. Simon, and J. Lien. 1988. Organochlorine chemical and heavy metal

contaminants in white-beaked dolphins (Lagenorhynchus albirostris) and pilot whales (Globicephala melaena) from the

coast of Newfoundland. Canada. Arch. Environ. Contam. Toxicol. 17: 613-29. 

Northridge, S. 1996. Estimation of cetacean mortality in the U.S. Atlantic swordfish and tuna drift gillnet and pair trawl fisheries.

Final report to the Northeast Fisheries Science Center, Contract No. 40ENNF500045, 18 pp.

Palka, D. 1995. Abundance estimate of the Gulf of Maine harbor porpoise. Pp. 27-50. In: A. Bjørge and G.P. Donovan (eds.)

Biology of the Phocoenids. Rep. int Whal. Commn. Special Issue 16.

Payne, P. M. and D. W. Heinemann. 1993. The distribution of pilot whales (Globicephala sp.) in shelf/shelf edge and slope waters

of the northeastern United States, 1978-1988. Rep. int Whal. Commn. Special Issue 14: 51-68.

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

Special Issue 15: 133-147.

Scott, G.P. and C.A. Brown. 1997. Estimates of marine mammal and marine turtle catch by the US 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.

Fish. Res. Bd. Can. 132: 1-84. 

Taruski, A. G., C. E. Olney, and H. E. Winn. 1975. Chlorinated hydrocarbons in cetaceans. J. Fish. Res. Bd. Can. 32(11): 2205-

9. 
85

Wade, P.R., and R.P. Angliss. 1997. Guidelines for assessing marine mammal stocks: Report of the GAMMS Workshop April 3-5,

1996, Seattle, Washington. U.S. Dep. Commer., NOAA Tech. Memo. NMFS-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 northeast United States, 1977-1988. Fish. Bull., U.S. 88(2): 347-360.

Waring, G. T., C. P. Fairfield, C. M. Ruhsam and M. Sano. 1992. Cetaceans associated with Gulf Stream features off the

northeastern USA shelf. ICES Marine Mammals Comm. CM 1992/N:12, 29 pp.

Waring, G.T. 1998. Results of the summer 1991 R/V Chapman marine mammal sighting survey. NOAA NMFS NEFSC, Lab. Ref.

Doc. No. 98-09, 21pp. Northeast Fisheries Science Center, Woods Hole, Massachusetts. 

Waring, G. T. 1995. Fishery and ecological interactions for selected cetaceans off the northeast USA. Ph.D. dissertation, University

of Massachusetts, Amherst, 260 pp. 
86

Cape Hatteras

Cape Canaveral

Figure 1. Sightings of short-finned pilot

whales (filled circles) and unidentified pilot

whales (unfilled circles) during NOAA Ship

Oregon II marine mammal survey cruise in

winter 1992.

October 1999

SHORT-FINNED PILOT WHALE (Globicephala macrorhynchus): 

Western North Atlantic Stock

STOCK DEFINITION AND GEOGRAPHIC RANGE

There are two species of pilot whales in the Western Atlantic: the Atlantic or long-finned pilot whale, Globicephala melas,

and the short-finned pilot whale, G. macrorhynchus. These species are difficult to identify to the species level at sea; therefore,

some of the descriptive material below refers to Globicephala sp. and is identified as such. The species boundary is considered

to be in the New Jersey to Cape Hatteras area. Sightings north of this area are likely G. melas. The short-finned pilot whale is

distributed worldwide in tropical to warm temperate waters (Leatherwood and Reeves 1983). The northern extent of the range of this

species within the USA Atlantic Exclusive Economic Zone (EEZ) is generally thought to be Cape Hatteras, North Carolina

(Leatherwood and Reeves 1983). Sightings of these animals in 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 population. 

POPULATION SIZE

Estimates of abundance were derived through the application of

distance sampling analysis (Buckland et al. 1993) and the computer

program DISTANCE (Laake et al. 1993) to sighting data collected during

a 1992 winter, visual sampling, line-transect vessel survey of the USA

Atlantic EEZ waters between Miami, Florida, and Cape Hatteras, North

Carolina. The estimated abundance of short-finned pilot whales for the

1992 survey was 749 (coefficient of variation, CV = 0.64) (Hansen et

al. 1994). 

Minimum Population Estimate

The minimum population estimate is the lower limit of the two-tailed

60% confidence interval of the log-normally distributed best abundance

estimate. This is equivalent to the 20th percentile of the log-normal

distribution as specified by Wade and Angliss (1997). The best estimate

of abundance for short-finned pilot whales is 749 (CV=0.64). The

minimum population estimate for the western North Atlantic shortfinned pilot whale is 457 (CV=0.64).

Current Population Trend

There are insufficient data to determine the population trends for this

species.

CURRENT AND MAXIMUM NET PRODUCTIVITY RATES

Current and maximum net productivity rates are unknown for this

stock. For purposes of this assessment, the maximum net productivity rate was assumed to be 0.04. This value is based on

theoretical modeling showing that cetacean populations may not grow at rates much greater than 4% given the constraints of their

reproductive life history (Barlow et al. 1995). 

POTENTIAL BIOLOGICAL REMOVAL

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

a “recovery” factor (MMPA Sec. 3. 16 U.S.C. 1362; Wade and Angliss 1997). The minimum population size is 457 (CV=0.64).
87

The maximum productivity rate is 0.04, the default value for cetaceans. The “recovery” factor, which accounts for endangered,

depleted, threatened stocks, or stocks of unknown status relative to optimum sustainable population (OSP) was set at 0.45 because

of the high variance associated with the estimate of total annual fishery-related mortality and serious injury for Globicephala sp.

PBR for the western North Atlantic short-finned pilot whales is 4.4. 

ANNUAL HUMAN-CAUSED MORTALITY AND SERIOUS INJURY

 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 1993-1997 was 40

pilot whales (CV = 0.71; Table 2).

Fishery Information

USA

The level of past or current, direct, human-caused mortality of short-finned pilot whales in the USA Atlantic EEZ is unknown.

The short-finned pilot whale has been taken in the pelagic longline fishery in Atlantic waters off the southeastern USA (Lee et al.

1994; SEFSC unpublished data). 

Prior to 1977, there was no documentation of marine mammal by-catch 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 by-catch of marine

mammals, was established in 1977 with the implementation of the Magnuson Fisheries Conservation and Management Act

(MFCMA). DWF effort in the Atlantic coast EEZ under MFCMA has been directed primarily towards Atlantic mackerel and squid.

An average of 120 different foreign vessels per year (range 102-161) operated within the Atlantic coast EEZ during 1977 through

1982. In 1982, there were 112 different foreign vessels; 18 (16%) were Japanese tuna longline vessels operating along the USA

Atlantic coast. This was the first year that the Northeast Regional Observer Program assumed responsibility for observer coverage

of the longline vessels. The number of foreign vessels operating within the 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 observer coverage on DWF 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 fishing season and, for mackerel, at the end of the 1991 fishing

season. 

During 1977-1991, observers in this program recorded 436 pilot whale mortalities in foreign-fishing activities (Waring et al. 1990;

Waring 1995). A total of 391 (90%) were taken in the mackerel fishery, and 41 (9%) occurred during Loligo and Illex squid-fishing

operations. This total includes 48 documented takes by USA vessels involved in joint venture fishing operations in which USA

captains transfer their catches to foreign processing vessels. Due to temporal fishing restrictions, the by-catch occurred during

winter/spring (December to May) in continental shelf and continental shelf edge waters (Fairfield et al. 1993; Waring 1995); however,

the majority of the takes occurred in late spring along the 100 m isobath. Two animals were also caught in both the hake fishery and

tuna longline fisheries (Waring et al. 1990). 

The distribution of long-finned pilot whale, a northern species, overlaps with that of the short-finned pilot whale, a predominantly

southern species, between 35E30'N to 38E00'N (Leatherwoodet al. 1976). Although long-finned 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 by-catch does occur in the

overlap area. In this summary, therefore, long-finned pilot whales (Globicephala melas) and unidentified pilot whales

(Globicephala sp.) are considered together. 

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

self-reported fisheries information system for large pelagic fisheries. Data files are maintained at the Southeast Fisheries Science

Center (SEFSC). The Northeast Fisheries Science Center (NEFSC) Sea Sampling Observer Program was initiated in 1989, and since

that year several fisheries have been covered by the program. In late 1992 and in 1993, the SEFSC provided observer coverage of

pelagic longline vessels fishing off the Grand Banks (Tail of the Banks) and provides observer coverage of vessels fishing south of

Cape Hatteras.

Pelagic Drift Gillnet
88

By-catch has been observed by NMFS Sea Samplers in the pelagic drift gillnet, pelagic longline, and pelagic pair trawl fisheries,

but no mortalities or serious injuries have documented in the New England multispecies sink gillnet or mid-Atlantic coastal sink

gillnet.

The estimated total number of hauls in the pelagic drift gillnet fishery increased from 714 in 1989 to 1,144 in 1990; thereafter,

with the introduction of quotas, effort was severely reduced. The estimated number of hauls in 1991, 1992, 1993, 1994, 1995, and

1996 were 233, 243, 232, 197, 164, and 149 respectively. In 1996 and 1997, the NMFS issued management regulations with

prohibited the operation of this fishery 1997. Further, in January 1999 the NMFS issued a Final Rule to prohibit the use of driftnets

(i.e., permanent closure) in the North Atlantic swordfish fishery (50 CFR Part 630). Fifty-nine different vessels participated in this

fishery at one time or another between 1989 and 1993. Since 1994, between 10-12 vessels have participated in the fishery (Table

2). Observer coverage, expressed as percent of sets observed, was 8% in 1989, 6% in 1990, 20% in 1991, 40% in 1992, 42% in 1993,

87% in 1994, 99% in 1995, and 64% in 1996. Effort was concentrated along the southern edge of Georges Bank and off Cape

Hatteras. Examination of the species composition of the catch and locations of the fishery throughout the year, suggested that the

pelagic drift gillnet fishery be stratified into two strata, a southern or winter stratum, and a northern or summer stratum. Estimates

of the total by-catch, from 1989 to 1993, were obtained using the aggregated (pooled 1989-1993) catch rates, by strata (Northridge

1996). Estimates of total annual by-catch for 1994 and 1995 were estimated from the sum of the observed caught and the product

of the average bycatch per haul and the number of unobserved hauls as recorded in self-reported fisheries information. Variances were

estimated using bootstrap re-sampling techniques. Between 1989 and 1995, sixty -eight mortalities were observed in the large pelagic

drift gillnet fishery. The annual fishery-related mortality (CV in parentheses) was 77 in 1989 (0.24), 132 in 1990 (0.24), 30 in 1991

(0.26), 33 in 1992 (0.16), 31 in 1993 (0.19), 20 in 1994 (0.06), 9.1 in 1995 (0), and 11 in 1996 (.17); average annual mortality between

1993-1997 was 17.8 pilot whales (0.09) (Table 2). Table 3 summarizes the number of animals released alive and classified as injured

or non-injured. It also includes the ratio of observed to estimated mortalities for this fishery. Because animals released alive may

have subsequently died due to injuries received during entanglement, pilot whales that were released were included in the mortality

estimates. Pilot whales were taken along the continental shelf edge, northeast of Cape Hatteras in January and February. Takes were

recorded at the continental shelf edge east of Cape Charles, Virginia, in June. Pilot whales were taken from Hydrographer Canyon

along the Great South Channel to Georges Bank from July-November. Takes occurred at the Oceanographer Canyon continental shelf

break and along the continental shelf northeast of Cape Hatteras in October-November.

Pelagic Pair Trawl

Effort in the pelagic pair trawl fishery has increased during the period 1989 to 1993, from zero hauls in 1989 and 1990, to an

estimated 171 hauls in 1991, and then to an estimated 536 hauls in 1992, 586 in 1993, 407 in 1994, and 440 in 1995, respectively.

This fishery ceased operations in 1996, when NMFS rejected a petition to consider pair trawl gear as an authorized gear type in

Atlantic tunas fishery. The fishery operated from August-November in 1991, from June-November in 1992, from June-October in

1993, and from mid-summer to November in 1994 and 1995. Sea sampling began in October 1992 (Gerrior et al. 1994), and 48 sets

(9% of the total) were sampled in that season, 102 hauls (17% of the total) were sampled in 1993. In 1994 and 1995, 52% and 54%,

respectively, of the sets were observed. Twelve vessels have operated in this fishery. The fishery extends from 35oN to 41oN, and

from 69EW to 72EW. Approximately 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 by-catch, showed little seasonal change for the six months of operation

and did not warrant any seasonal or areal stratification of this fishery (Northridge 1996). Five pilot whale (Globicephala sp.)

mortalities were reported in the self-reported fisheries information in 1993. In 1994 and 1995 observers reported one and twelve

mortalities, respectively. Since this fishery no longer exists, it has been excluded from Tables 2 and 3. 

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

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 pilot whales have been reported; however, a vessel may fish in more than

one statistical reporting area and it is not possible to separate estimates of fishing effort other than to subtract Gulf of Mexico effort

from Atlantic fishing effort, which includes the Caribbean Sea. This fishery has been monitored with about 5% observer coverage,

in terms of trips observed, since 1992. Total effort, excluding the Gulf of Mexico, for the pelagic longline fishery, based on mandatory

self-reported fisheries information, was 11,279 sets in 1991, 9,869 sets in 1992, 9,862 sets in 1993, 9,481 sets in 1994, 10,129 sets

in 1995, 9,885 sets in 1996, and 8,023 sets in 1997 (Cramer 1994; Scott and Brown 1997; Johnson et al. 1999). Since 1992, this

fishery has been monitored with about 5% observer coverage, in terms of trips observed, within every statistical reporting area within
89

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 coverage, in terms of trips observed, since 1992. The 1993-1997, estimated take was based

on a revised analysis of the observed incidental take and self-reported incidental take and effort data, and replace previous estimates

for the 1992-1993 and 1994-1995 periods (Cramer 1994; Scott and Brown 1997; Johnson et al. 1999). Most of the estimated marine

mammal by-catch 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 1990-1997 fifty eight pilot whales

(including two identified as a short-fin pilot whale) were released alive, and one mortality was observed. The condition codes that

the observers assigned to the disentangled animals were: alive (41 animals); unknown (10 animals); and dead (5 animals). JanuaryMarch by-catch was concentrated on the continental shelf edge northeast of Cape Hatteras. By-catch was recorded in this area during

April-June, and takes also occurred north of Hydrographer Canyon off the continental shelf in water over 1,000 fathoms during AprilJune. 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 by-catch occurred along the 20 to 50 fathom contour lines between

Barnegatt Bay and Cape Hatteras. The 1992-1997, estimated take was based on a revised analysis of the observed incidental take

and self-reported incidental take and effort data, and replace previous estimates for the 1990-1993 and 1994-1995 periods (Scott and

Brown 1997; Johnson et al. 1999). The estimated fishery-related mortality to pilot whales in the USA Atlantic (excluding the Gulf

of Mexico) attributable to this fishery was: 40 in 1992 (CV = 1.00), and zero in 1993-1997; average annual mortality between 1993-

1997 was zero pilot whales (Table 2). Injured and released alive animals are not included in the Table 2 mortality estimates. Table

3 summarizes the number of animals released alive and classified as injured or non-injured. It also includes the ratio of observed to

estimated mortalities for this fishery.

North Atlantic Bottom Trawl 

Vessels in the North Atlantic bottom trawl fishery, a Category III fishery under the MMPA, were observed in order to meet

fishery management needs, rather than marine mammal management needs. An average of 970 (CV = 0.04) vessels (full and part time)

participated annually in the fishery during 1989-1993. The fishery is active in New England in all seasons. One mortality each was

documented in 1990 and 1997, and one animal was released alive and uninjured in 1993. The 1997 mortality occurred within the midAtlantic region. The estimated fishery-related mortality to pilot whales in the USA Atlantic attributable to this fishery was: 0 in

1996 and 93 in 1997; average annual mortality between 1996-1997 was 46.5 pilot whales (CV = 0.96) (Table 2). Table 3 summarizes

the number of animals released alive and classified as injured or non-injured. It also includes the ratio of observed to estimated

mortalities for this fishery.

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 1996 Illex squid fishery. The estimated fishery-related mortality to pilot whales in the USA Atlantic attributable

to this fishery was: 45 in 1996 and 0 in 1997; average annual mortality between 1996-1997 was 22.5 pilot whales (CV = 1.27) (Table

2).

CANADA

An unknown number of pilot whales have also been taken in Newfoundland and Labrador, and Bay of Fundy, groundfish gillnets,

Atlantic Canada and Greenland salmon gillnets, and Atlantic Canada cod traps (Read 1994). The Atlantic Canadian and Greenland

salmon gillnet fishery is seasonal, with the peak from June to September, depending on location. 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 agreement between Canada and North Atlantic Salmon Fund (Read

1994). 

There were 3,121 cod traps operating in Newfoundland and Labrador during 1979, and about 7,500 in 1980 (Read 1994). This

fishery was closed at the end of 1993 due to collapse of Canadian groundfish resources. 
90

Between January 1993 and December 1994, 36 Spanish deep water trawlers, covering 74 fishing trips, were observed in NAFO

Fishing Area 3 (off the Grand Bank) (Lens 1997). A total of 47 incidental catches were recorded, which included one long-finned pilot

whale. The incidental mortality rate for pilot whales was (0.007/set).
91

Table 2. Summary of the incidental mortality of pilot whales (Globicephala sp) by commercial fishery including the years sampled

(Years), the number of vessels active within the fishery (Vessels), the type of data used (Data Type), the annual observer

coverage (Observer Coverage), the 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 6

Estimated

CVs 

Mean

Annual

Mortality

Pelagic7

Drift Gillnet 93-97

1994=123

1995=11

1996=10

Obs. Data

Logbook

 .42, .87, .99,

.64, NA

 114, 17,

9, 7, NA

 31, 20, 9.15,

11, NA

 .19, .06, 0,

.17, NA

 17.87

 (0.09)

Atlantic

squid,

mackerel,

butterfish

trawl

96-97 NA Obs. Data 

Weighouts

 .007, .008 6, 0 45, 0 1.27, 0 22.5

(1.27)

N. Atl.

Otter Trawl

93-97 NA Obs. Data

Weighouts

.004, .004,

.0118,.002,

.002

0, 0, 0, 0,

0

0, 0, 0, 0, 0 0, 0, 0, 0, 0 0

(0)

Pelagic9

Longline 

 93-97 Obs. Data

Logbook

 .06, .05, .06,

.03, .04

0, 0, 0, 0,

0

 0, 0, 0, 0, 0 0, 0, 0, 0,

0

 0

 (0)

TOTAL 40.3

 (0.71)

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, pair trawl and longline fishery are in terms of sets. The trawl fisheries are measured

in trips.

3 1994, 1995 and 1996 shown, other years not available on an annual basis.

4 For 1991-1993, pooled bycatch rates were used to estimate bycatch in months that had fishing effort but did not have observer

coverage. This method is described in Northridge (1996). In 1994 and 1995, observer coverage increased substantially, and

bycatch rates were not pooled for this period. 

5 One vessel was not observed and recorded 1 set in a 10 day trip in the SEFSC mandatory logbook. If you assume the vessel fished

1.4 sets per day as estimated from the 1995 SS data, the point estimate may increase by 0.84 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 0.06 animals.

6 Annual mortality estimates do not include any animals injured and released alive.

7 The fishery did not operate in 1997; the average annual mortality is based on the number of years (4; 1993-1996) that the fishery

operated.

8 Observer coverage for the Atlantic bottom trawl fishery in 1995 is based on only January to May data.

9 Mortality estimates were taken from Table 12 in Johnson et al. (1999), and exclude the Gulf of Mexico.
92

Table 3. Summary of pilot whales (Globicephala sp) released alive, by commercial fishery, years sampled (Years), ratio of

observed mortalities recorded by on-board observers to the estimated mortality (Ratio), the number of observed animals

released alive and injured (Injured), and the number of observed animals released alive and uninjured (Uninjured).

Fishery Years Ratio Injured4 Uninjured

Pelagic Drift Gillnet 93-97 11/31, 17/20,9/9.1,7/11, NA 1

2

, 0, 0, 0, NA 0

Pelagic Long Line 93-97 4/38, 0, 0, 0, 0 NA, 53, 44, 0, 1 NA, 93,113, 0,

0

North Atlantic Bottom Trawl 93-97 0, 0, 0, 0, 0 0, 0, 0, 0, 0 0, 1, 0, 0, 0

2 Released alive with condition unknown.

3 See Appendix 1.

4

Injured and released alive animals are not included in the Table 2 mortality estimates.

Other Mortality

There were 193 short-finned pilot whale strandings documented during 1987- 1997along the USA Atlantic coast between Cape

Hatteras, North Carolina, and Miami, Florida; five of these were classified as likely caused by fishery interactions. From 1992-1995,

eight short-finned pilot whales stranded along beaches north of Cape Hatteras (Virginia to New Jersey) (NMFS unpublished data).

STATUS OF STOCK

The status of the short-finned pilot whale relative to OSP in USA Atlantic EEZ is unknown. There are insufficient data to

determine the population trends for this stock. They are not listed under the Endangered Species Act. The total fishery-related

mortality and serious injury for this stock is not less than 10% of the calculated PBR and, therefore, cannot be considered to be

insignificant and approaching zero mortality and serious injury rate. This is a strategic stock because the 1993-1997 estimated average

annual fishery-related mortality to pilot whales, Globicephala sp., exceeds PBR.

REFERENCES

Barlow, J., S.L. Swartz, T.C. Eagle, and P.R. Wade. 1995. U.S. Marine Mammal Stock Assessments: Guidelines for Preparation,

Background, and a Summary of the 1995 Assessments. U.S. Dep. Commer., NOAA Tech. Memo. NMFS-OPR-6, 73 pp. 

Buckland, S. T., D. R. Anderson, K. P. Burnham and J. L. Laake. 1993. Distance Sampling: estimating abundance of biological

populations. Chapman & Hall, London, 446 pp. 

Cramer J. 1994. Large pelagic logbook newsletter - 1993. NOAA Tech. Mem. NMFS-SEFSC-352, 19pp.

Gerrior, P., A.S. Williams, and D.J. Christensen. 1994. Observations of the 1992 U.S. pelagic pair trawl fishery in the Northwest

Atlantic. Mar. Fish. Rev. 56(3): 24-27.

Goudy, C.A. 1995. The 1994 experimental pair trawl fishery for tuna in the northwest Atlantic, MITSG 95-6, Cambridge, MA. 10

pp.

Goudy, C.A. 1996. The 1995 experimental pair trawl fishery for tuna in the northwest Atlantic, MITSG 95-6, Cambridge, MA. 13

pp.

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.

Johnson, D.R., C. Yeung and C.A. Brown,. 1999. Estimates of marine mammal and marine turtle catch by the US Atlantic pelagic

longline fleet in 1992-1997. NOAA Tech. Mem. NMFS-SEFSC-418. 70pp.

Laake, J. L., S. T. Buckland, D. R. Anderson, and K. P. Burnham. 1993. DISTANCE user’s guide, V2.0. Colorado Cooperative Fish

& Wildlife Research Unit, Colorado State University, Ft. Collins, Colorado, 72 pp.

Leatherwood, S. and R. R. Reeves. 1983. The Sierra Club handbook of whales and dolphins. Sierra Club Books, San Francisco,

302 pp. 

Lee, D. W., C. J. Brown, A. J. Catalano, J. R. Grubich, T. W. Greig, R. J. Miller and M. T. Judge. 1994. SEFSC pelagic longline

observer program data summary for 1992-1993. NOAA Tech. Mem. NMFS-SEFSC-347. 19 pp. 
93

Mullin, K., W. Hoggard, C. Roden, R. Lohoefener, C. Rogers and B. Taggart. 1991. Cetaceans on the upper continental slope in the

north-central Gulf of Mexico. OCS Study/MMS 91-0027. U.S. Dept. of the Interior, Minerals Management Service, Gulf of

Mexico OCS Regional Office, New Orleans, Louisiana, 108 pp. 

Northridge, S. 1996. Estimation of cetacean mortality in the U.S. Atlantic swordfish and tuna drift gillnet and pair trawl fisheries.

Final report to the Northeast Fisheries Science Center, Contract No. 40ENNF500045, 18 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-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 northeast United States, 1977-1988. Fish. Bull., U.S. 88(2): 347-360.

Waring, G. T. 1995. Fishery and ecological interactions for selected cetaceans off the northeast USA. Ph.D. dissertation, University

of Massachusetts, Amherst, 260 pp. 
94

Figure 1. Distribution of white-sided dolphin sightings from NEFSC

shipboard and aerial surveys during the summer in 1990-1995. 

Isobaths are at 100 m and 1,000 m. 

October 1999

WHITE-SIDED DOLPHIN (Lagenorhynchus acutus):

Western North Atlantic Stock

STOCK DEFINITION AND GEOGRAPHIC RANGE

White-sided dolphins are found in temperate and sub-polar waters of the North Atlantic, primarily on continental shelf waters

to the 100 m depth contour. The species inhabits waters from central west Greenland to North Carolina (about 35EN) and perhaps

as far east as 43o W (Evans 1987). Distribution of sightings, strandings and incidental takes suggests the possibly existence of three

stocks units: a Gulf of Maine, Gulf of St. Lawrence, and a Labrador Sea stock (Palka et al. 1997). No genetic studies have been

conducted to test this proposed population structure, although some samples are available to initiate such a study (about 25

specimens). Evidence for a separation between the well documented unit in the southern Gulf of Maine and a Gulf of St. Lawrence

population comes from a hiatus of summer sightings along the Atlantic side of Nova Scotia. This has been reported in Gaskin (1992),

is evident in Smithsonian stranding records, and was seen during an abundance survey conducted in summer 1995 that covered waters

from Virginia to the entrance of the Gulf of St. Lawrence. White-sided dolphins were seen frequently in eastern Gulf of Maine waters

and in waters at the mouth of the Gulf of St. Lawrence, but only one sighting was recorded 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

(approximately 39EN) north through Georges Bank, and in the Gulf of Maine to the lower Bay of Fundy. Sightings data indicate

seasonal shifts in distribution. During January to April, low numbers of white-sided dolphins are found from Georges Bank to

Jeffreys Ledge (off New Hampshire), and even lower numbers are south of Georges Bank, as documented by a few strandings

collected on beaches of Virginia and North Carolina. From June through September, large numbers of white-sided dolphins are found

from Georges Bank to lower Bay of Fundy. From October to December, white-sided dolphins occur at intermediate densities from

southern Georges Bank to southern Gulf of Maine (Payne and Heinemann 1990). Sightings south of Georges Bank and around

Hudson Canyon have been seen at all times of the year but at low densities. The Virginia and North Carolina observations appear

to represent the southern extent of the species range.

Prior to the 1970's, white-sided dolphins in

USA waters were found primarily offshore on the

continental slope, while white-beaked dolphins

(L. albirostris) were found on the continental

shelf. During the 1970's, there was an apparent

switch in habitat use between these two species.

This shift may of been a result of the increase in

sand lance in the continental shelf waters (Katona

et al. 1993; Kenney et al. 1996). 

POPULATION SIZE

The total number of white-sided dolphins

along the eastern USA and Canadian Atlantic

coast is unknown, although four estimates from

select regions are available from spring, summer

and autumn 1978-82, July-September 1991-92,

and July-September 1995 (Table 1; Figure 1).

A population size of 28,600 white-sided

dolphins (CV=0.21) was estimated from an aerial

survey program conducted from 1978 to 1982 on

the continental shelf and shelf edge waters

between Cape Hatteras, North Carolina and Nova

Scotia (Table 1; CETAP 1982). The estimate

was based on an inverse variance weighted

pooling of spring, summer and autumn data. An average of these seasons were chosen because the greatest proportion of the

population off the northeast USA coast appeared in the study area during these seasons. This estimate does not include a correction
95

for dive-time or g(0), the probability of detecting an animal group on the track line. This estimate may not reflect the current true

population size because of its old age, and it was estimated just after cessation of extensive foreign fishing operations in the region.

A population size of 20,400 (CV=0.63) white-sided dolphins was estimated from two shipboard line transect surveys conducted

during July to September 1991 and 1992 in the northern Gulf of Maine-lower Bay of Fundy region (Table 1; Palka et al. 1997). This

population size is a weighted-average of the 1991 and 1992 estimates, where each annual estimate was weighted by the inverse of

its variance. The data were collected during surveys designed to estimate abundance of harbor porpoises (Palka 1995). Two

independent teams of observers on the same ship surveyed using naked eye in non-closing mode. Using the product integral

analytical method (Palka 1995) and DISTANCE (Buckland et al. 1993; Laake et al. 1993) the abundance included an estimate of

school size-bias, if applicable, an estimate of g(0), probability of detecting a group on the track line, but no correction for dive-time

or ship avoidance. Variability was estimated using bootstrap re-sampling.

A population size 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). 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), dive-time or ship avoidance. Variability was estimated

using bootstrap re-sampling techniques.

A population size 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;

NMFS/NEFSC unpublished data). Total track line length was 32,600 km (17,600 nmi). 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. Shipboard data were collected using a two independent

sighting team procedure and were analyzed using the product integral method (Palka 1995) and DISTANCE (Buckland et al. 1993).

Shipboard estimates were corrected for g(0) and, if applicable, also for school size-bias. Standard aerial sighting procedures with two

bubble windows and one belly window observer were used during the aerial survey (Palka 1996). An estimate of g(0) was not made

for the aerial portion of the survey. Estimates do not include corrections for dive-time or ship avoidance. Variability was estimated

using bootstrap re-sampling techniques.

There are no published abundance estimates for this species in Canadian waters which lie farther north or east of the above

surveys (Gaskin 1992). 

The best available current abundance estimate for white-sided dolphins in USA waters is 27,200 (CV=0.43) as estimated from

the July to September 1995 line transect survey because this survey is recent and provided the most complete coverage of the known

habitat.

Table 1. Summary of abundance estimates for western North Atlantic white-sided dolphins. Month, year, and area covered during

each abundance survey, and resulting abundance estimate (Nbest) and coefficient of variation (CV).

Month/Year Area Nbest CV

spring, summer &

autumn 1978-82 Cape Hatteras, NC to Nova Scotia 28,600 0.21

Jul-Sep 1991-92 N. Gulf of Maine and Bay of Fundy 20,400 0.63

Jun-Jul 1993 Georges Bank to Scotian shelf, shelf edge only 729 0.47

Jul-Sep 1995 Virginia to Gulf of St. Lawrence 27,200 0.43

Minimum Population Estimate

The minimum population estimate is the lower limit of the two-tailed 60% confidence interval of the log-normally distributed

best abundance estimate. This is equivalent to the 20th percentile of the log-normal distribution as specified by Wade and Angliss

(1997). The best estimate of abundance for white-sided dolphins is 27,200 (CV=0.43). The minimum population estimate for the

western North Atlantic white-sided dolphins is 19,196 (CV=0.43).

Current Population Trend
96

There are insufficient data to determine population trends for this species. 

CURRENT AND MAXIMUM NET PRODUCTIVITY RATES

Current and maximum net productivity rates are unknown for this stock. Life history parameters that could be used to estimate

net productivity include: calving interval is 2-3 years; lactation period is 18 months; gestation period is 10-12 months and births occur

from May to early August, mainly in June and July; length at birth is 110 cm; length at sexual maturity is 230-240 cm for males, and

201-222 cm for females; age at sexual maturity is 8-9 years for males and 6-8 years for females; mean adult length is 250 cm for males

and 224 cm for females (Evans 1987); and maximum reported age for males is 22 years and for females, 27 years (Sergeant et al.

1980). 

For purposes of this assessment, the maximum net productivity rate was assumed to be 0.04. This value is based on theoretical

modeling showing that cetacean populations may not grow at rates much greater than 4% given the constraints of their reproductive

life history (Barlow et al. 1995).

POTENTIAL BIOLOGICAL REMOVAL

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

a “recovery” factor (MMPA Sec. 3. 16 U.S.C. 1362; Wade and Angliss 1997). The minimum population size is 19,196 (CV=0.43).

The maximum productivity rate is 0.04, the default value for cetaceans. The “recovery” factor, which accounts for endangered,

depleted, threatened, or stocks of unknown status relative to optimum sustainable population (OSP) is assumed to be 0.48 because

this stock is of unknown status and the CV of the mortality estimate is between 0.3 and 0.6. PBR for the western North Atlantic

white-sided dolphin is 184.

ANNUAL HUMAN-CAUSED MORTALITY AND SERIOUS INJURY

Fishery Information

Recently, within USA waters, white-sided dolphins have been caught in the New England multispecies sink gillnet, Mid-Atlantic

coastal gillnet, pelagic drift gillnet, North Atlantic bottom trawl, and Atlantic squid, mackerel, butterfish trawl fisheries (Table 2).

Estimated average annual fishery-related mortality and serious injury to the western North Atlantic white-sided dolphin stock from

these USA fisheries during 1993-1997 was 287 dolphins per year (CV = 0.47).

Earlier Interactions

In the past, incidental takes of white-sided dolphins have been recorded in the New England and Bay of Fundy multispecies gillnet

fisheries and the Atlantic foreign mackerel 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; Gaskin

1992). NMFS foreign fishery observers have reported 44 takes of Atlantic white-sided dolphins incidental to fishing activities in

the continental shelf and continental slope waters between March 1977 and December 1991 (Waring et al. 1990; NMFS unpublished

data). Of these animals, 96% were taken in the Atlantic mackerel fishery. This total includes 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 by-catch in distant-water fleet (DWF) activities off the northeast coast of the USA

With implementation of the Magnuson Fisheries Conservation and Management Act (MFCMA) in that year, an observer program

was established which has recorded fishery data and information of incidental by-catch 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 Atlantic coast EEZ. In

1982, there were 112 different foreign vessels; 16%, or 18, were Japanese tuna longline vessels operating along the USA east coast.

This was the first year that the Northeast Regional Observer Program assumed responsibility for observer coverage of the longline

vessels. Between 1983 and 1991, the numbers of foreign vessels operating within the 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.

USA

New England Multispecies Sink Gillnet 
97

Between 1990 and 1997 there were 39 mortalities observed in the New England multispecies sink gillnet fishery (Table 2). The

Northeast Fisheries Science Center (NEFSC) Sea Sampling Observer Program was initiated in 1989, and since that year this fishery

has been covered by the program. In 1993 there were approximately 349 vessels (full and part time) in the New England multispecies

sink gillnet fishery (Walden 1996). Observer coverage, expressed as a percentage of the number of trips, has been 1%, 6%, 7%, 5%,

7%, 5%, 4%, and 6% for years 1990 to 1997, respectively. The fishery has been observed in the Gulf of Maine and in Southern New

England. Most white-sided dolphins have been taken in waters south of Cape Ann during April to December. In recent years, the

majority are east and south of Cape Cod. Estimated annual fishery-related mortalities (CV in parentheses) were 49 in 1991 (0.46),

154 in 1992 (0.35), 205 in 1993 (0.31), 240 in 1994 (0.51), 80 in 1995 (1.16), 114 in 1996 (0.61) (Bisack 1997a), and 140 (0.61) in

1997. Average annual estimated fishery-related mortality during 1993-1997 was 156 white-sided dolphins per year (0.26) (Table

2).

Mid-Atlantic Coastal Gillnet

One white-sided dolphin was observed taken in this fishery during 1997 (Table 2). None were taken in observed trips during 1993

to 1996. In July 1993, an observer program was initiated in the USA Atlantic coastal gillnet fishery by the NEFSC Sea Sampling

program. Twenty trips were observed during 1993. During 1994 and 1995 221 and 382 trips were observed, respectively. This

fishery, which extends from North Carolina to New York, is actually a combination of small vessel fisheries that target a variety of

fish species, some of which operate right off the beach. The number of vessels in this fishery is unknown because records, which

are held by both state and federal agencies, have not been centralized and standardized. Observer coverage, expressed as percent of

tons of fish landed, was 5%, 4%, and 3% for 1995, 1996, and 1997, respectively (Table 2). During 1995 and 1996, observed fishing

effort was concentrated off NJ and scattered between DE and NC from 1 to 50 miles off the beach. By-catch estimates were

determined using methods similar to that used for by-catch estimates in the New England multispecies gillnet fishery (Bravington

and Bisack 1996; Bisack 1997a). Using the observed takes of white-sided dolphins, the estimated annual mortality (CV in

parentheses) attributed to this fishery was 0 for 1995 and 1996, and 45 (0.82) for 1997. However, because the spatial-temporal

distribution of observer coverage did not cover all types of gillnet fisheries in the mid-Atlantic region during all times of the year, it

is likely that the estimated numbers are under-estimates. Average estimated white-sided dolphin mortality and serious injury from

the Mid-Atlantic coastal gillnet fishery during 1995 to 1997 was 15 (CV=0.82) (Table 2).

Pelagic Drift Gillnet 

In 1996 and 1997, the NMFS issued management regulations which prohibited the operation of this fishery in 1997. Further,

in January 1999 the NMFS issued a Final Rule to prohibit the use of driftnet gear in the North Atlantic swordfish fishery (50 CFR

Part 630). During 1991 to 1996, two white-sided dolphins were observed taken in the Atlantic pelagic drift gillnet fishery. In 1986,

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

the Southeast Fisheries Science Center (SEFSC). The estimated total number of hauls in the Atlantic pelagic drift gillnet fishery

increased from 714 in 1989 to 1,144 in 1990; thereafter, with the introduction of quotas, effort was severely reduced. The estimated

number of hauls in 1991, 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, 1995, and 1996 there were 11, 12, and

10 vessels, respectively, in the fishery (Table 2). Observer coverage, expressed as percent of sets observed was 8% in 1989, 6%

in 1990, 20% in 1991, 40% in 1992, 42% in 1993, 87% in 1994, 99% in 1995, and 64% in 1996. 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 is stratified into two strata, a

southern or winter stratum, and a northern or summer stratum. Estimates of the total by-catch, 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 by-catch

for 1994 through 1996 were estimated for each year separately by summing the observed caught with the product of the average bycatch per haul and the number of unobserved hauls as recorded in logbooks. Variances were estimated using bootstrap re-sampling

techniques (Bisack 1997b). Estimated annual fishery-related mortality and serious injury (CV in parentheses) was 4.4 in 1989 (.71),

6.8 in 1990 (.71), 0.9 in 1991 (.71), 0.8 in 1992 (.71), 2.7 in 1993 (0.17), 0 in 1994, 1995, and 1996. There was no fishery during

1997. Estimated average annual mortality and serious injury related to this fishery during 1993-1996 was 0.7 white-sided dolphins

(0.17) (Table 2).

North Atlantic Bottom Trawl

Three mortalities were documented between 1991 and 1997 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. Vessels in the North Atlantic bottom trawl fishery, a Category III fishery under the
98

MMPA, were observed in order to meet fishery management needs, rather than marine mammal management needs. An average of

970 (CV = 0.04) vessels (full and part time) participated annually in the fishery during 1989-1993. The fishery is active in New

England waters in all seasons. The one white-sided dolphin taken in 1992 was taken in a haul that was composed of 43% cod, 20%

silver hake, and 17% pollock. One of the 1994 takes was in a haul that was composed of 42% white hake, 19% pollock, and 16%

monkfish. The other 1994 take was in a haul that kept seven species of which none were dominant. The estimated fishery-related

mortality from 1992 was 110 (CV = 0.97), from 1994 it was 182 (CV=0.71), and it was 0 in the other years (Bisack 1997b). The

average annual estimate fishery-related mortality during 1993-1997 was 36.4 white-sided dolphins (CV = 0.71) (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 FMP by the Mid-Atlantic Fisheries Management Council, is actually three independent

fisheries operating in different areas during different times of the year (NMFS 1998). The Loligo squid sub-fishery is mostly in

southern New England, New York and Mid-Atlantic waters, where fishing patterns reflect the seasonal migration of the Loligo

(offshore during October to March and inshore during April to September). The Illex sub-fishery is primarily on the continental slope

during June to September. The mackerel sub-fishery during January to May is primarily in the southern New England and MidAtlantic waters, while during May to December, it is primarily in the Gulf of Maine. The butterfish sub-fishery is primarily a bycatch of the squid and mackerel sub-fisheries. Butterfish migrate north and inshore during the summer, and south and offshore during

the winter. In 1995, the squid, mackerel, butterfish trawl fishery was classified as a Category II fishery. Observer coverage was

very low; as expressed as percentage of trips observed, it was 0.07% in 1996 and 0.08% in 1997. The by-catch, stratified by subfishery, season and geographical area, was estimated using the ratio estimator method, as was documented in Bisack (1997b). The

estimated fishery-related mortality was 0 in 1996 and 161 (CV=1.58) in 1997. The average annual estimated fishery-related mortality

during 1996 and 1997 was 80.5 (CV=1.58) (Table 2).

CANADA

There is little information available which quantifies fishery interactions involving white-sided dolphins in Canadian waters. Two

white-sided dolphins were reported caught in groundfish gillnet sets in the Bay of Fundy during 1985 to 1989, and nine were taken

in West Greenland between 1964 and 1966 in the now non-operational salmon drift nets (Gaskin 1992). Several (number not

specified) were also taken during the 1960's in the now non-operational Newfoundland and Labrador groundfish gillnets. A few were

taken in an experimental drift gillnet fishery for salmon off West Greenland which took place from 1965 to 1982 (Read 1994). More

recent information on Canadian white-sided dolphin takes were not available.
99

Table 2. Summary of the incidental mortality of white-sided dolphins (Lagenorhynchus acutus) by commercial fishery including

the years sampled (Years), the number of vessels active within the fishery (Vessels), the type of data used (Data Type),

the annual observer coverage (Observer Coverage), the mortalities recorded by on-board observers (Observed Mortality),

the estimated annual mortality (Estimated Mortality), the estimated CV of the annual mortality (Estimated CVs) and the

mean annual mortality (CV in parentheses).

Fishery Years Vessels Data Type 1 Observer

Coverage 2 

Observed

Mortality

Estimated

Mortality 

Estimated

CVs 

Mean

Annual

Mortality

New England

Multispecies Sink

Gillnet

93-97 1993=349 Obs. Data

Weighout

Trip Logbook

.05, 

.07, .05,

.04,.06

7,

103, 23,

2

3,,43

205, 

2403, 803,

1143,1403

.31, 

.51, 1.16,

.61,.61

156.0

(.0.26)

Mid-Atlantic

Coastal Sink

Gillnet

95-97 Unk8 Obs. Data

Weighout

.05, .04, .03 0, 0, 1 0, 0, 45 0 , 0 ,.82 15

(0.82)

Pelagic Drift

Gillnet

93-9771994=114

1995=12

1996=10

1997=NA7

Obs. Data

Logbook

.42, .87, 

.99,.64, NA7

2

5

,05, 

0

5

, 05,

NA7

2.75, 05, 

0

5

, 05,

NA7

0.17, 0, 

0, 0,

NA7

0.77

(0.17)

North Atlantic

Bottom Trawl

93-97 1993=970 Obs. Data

Weighout

.004,

.004,.0116,

,.002,

.002

0, 

2, 0,

 0, 

0

0,

182, 0,

 0, 

0

0,

 .71, 0,

 0,

 0

36.4 

(0.71)

Squid, Mackerel,

Butterfish Trawl

96-97 Unk8 Obs. Data

Weighout

.007, .008 0, 190, 16190, 1.58980.5

(1.58)

Total 287

(0.47)

1 Observer data (Obs. Data) are used to measure bycatch rates, and the data are collected within the Northeast Fisheries Science

Center (NEFSC) Sea Sampling Program. NEFSC collects Weighout (Weighout) landings data which is used as a measure of total

effort. Mandatory trip logbook (Trip Logbook) data are used to determine the spatial distribution of some fishing effort in the

sink gillnet fishery. 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 Observer coverage for the New England sink gillnet and Atlantic bottom trawl fisheries are measured in trips, the pelagic drift

gillnet fishery is measured in sets, and the Mid-Atlantic coastal sink gillnet fishery is measured in tons of fish landed.

3 White-sided dolphins taken on observed pinger trips were added directly to the estimated total by-catch for that year when there

was no closure in effect. There was one observed white-sided dolphin take on a pinger trip in 1994, which was not included in

the observed mortality count, no takes observed in pinger trips during 1995 and 1996, and two takes, not included in the observed

mortality count, were observed in pingered trips during 1997.

4 1994 to 1997 shown, other years not available on an annual basis.

5 For 1991-1993, pooled bycatch rates were used to estimate bycatch in months that had fishing effort but did not have observer

coverage (Northridge 1996). After 1993, observer coverage increased substantially, and by-catch rates were annual rates (Bisack

1997b). There was no fishery in 1997.

6 Observer coverage for the Atlantic bottom trawl fishery in 1995 is based on only January to May data (the only time takes were

observed). 

7 Fishery closed during 1997. So average by-catch is from 1993 to 1996.

8 Number of vessels is not known.

9 The observed take was in the mackerel sub-fishery.

Other Mortality
100

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 fisheryrelated 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.

From the NE Regional Office/NMFS strandings and entanglement database, there were 17 recorded stranded white-sided dolphins

during 1997, of which 16 died and one was released alive (from RI during Feb). One stranding was in VA during March, the rest were

from MD to ME during January to August, where 10 were from MA. The cause of death of these strandings were not determined.

STATUS OF STOCK

The status of white-sided 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 population trends for this species. The

total fishery-related mortality and serious injury for this stock is not less than 10% of the calculated PBR and, therefore, cannot be

considered to be insignificant and approaching zero mortality and serious injury rate. This is a strategic stock because estimated

average annual fishery-related mortality and serious injury exceeds PBR. 

REFERENCES

Anon. 1993. Cruise results, NOAA ship DELAWARE II, Cruise No. DEL 93-06, Marine Mammal Survey. 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 1995. Rep.

int Whal. Comm 47: 705-14.

Bisack, K.D. 1997b. Marine mammal bycatch estimates and their sampling distributions in the U.S. New England sink gillnet, pair

trawl, Atlantic pelagic drift gillnet and North Atlantic bottom trawl fisheries - 1994 to 1996. NOAA, NMFS, NEFSC. Woods

Hole, MA. Working paper SC/49/SM35 submitted to the IWC Scientific Committee meeting in Bournemouth, UK, Aug/Sept

1997.

Bravington, M. V. and K. D. Bisack. 1996. Estimates of harbor porpoise by-catch in the Gulf of Maine sink gillnet fishery, 1990-

1993. Rep. int Whal. Comm 46: 567-74.

Buckland, S. T., D. R. Anderson, K. P. Burnham, and J. L. Laake. 1993. Distance Sampling: Estimating abundance of biological

populations. Chapman & Hall, New York, 446 pp. 

CETAP. 1982. A characterization of marine mammals and turtles in the mid- and north Atlantic areas of the U.S. outer continental

shelf. Cetacean and Turtle Assessment Program, University of Rhode Island. Final Report, Contract AA51-C78-48, Bureau of

Land Management, Washington, DC, 538 pp. 

Evans, P. G. H. 1987. The natural history of whales and dolphins. Facts on File Publications, New York, 343 pp. 

Gaskin, D. E. 1992. Status of Atlantic white-sided dolphin, Lagenorhynchus acutus, in Canada. Can. Fld. Nat. 106: 64-72.

Gilbert, J. R. and K. M. Wynne. 1987. Marine mammal interactions with New England gillnet fisheries. Final Report, Contract No.

NA-84-EAC-00070, National Marine Fisheries Service, Northeast Fisheries Science Center, Woods Hole, Massachusetts, 12 pp.

Hain, J. H. W. and G. T. Waring. 1994. Status of and human effects upon marine mammals. In: R. W. Langton , J. B. Pearce, and

J.A. Gibson (eds), Selected living resources, habitat conditions, and human perturbations of the Gulf of Maine: Environmental

and ecological considerations for fishery managements. NOAA Tech. Mem. NMFS-NE-106, Northeast Fisheries Science Center,

Woods Hole, Massachusetts. 

Katona, S. K., V. Rough, and D. T. Richardson. 1993. A field guide to whales, porpoises, and seals from Cape Cod to

Newfoundland. Smithsonian Institution Press, Washington, DC, 316 pp. 
101

Kenney, R.D., Payne, P.M., Heinemann, D.W. and Winn, H.E. 1996. Shifts in Northeast shelf cetacean distributions relative to trends

in Gulf of Maine/Georges Bank finfish abundance. Pp. 169-196. In: K. Sherman, N.A. Jaworski and T. Smada (eds.). The

northeast shelf ecosystem: assessment, sustainability, and management. Blackwell Science, Cambridge, MA 02142, USA.

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. 

NMFS (National Marine Fisheries Service). 1998 (in press). 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. 40ENNF500045, 18 pp.

Palka, D. 1996. Update on abundance of Gulf of Maine/Bay of Fundy harbor porpoises. Northeast Fish. Sci. Cent. Ref. Doc. 96-04;

37p. Available from: National Marine Fisheries Service, 166 Water Street, Woods Hole, MA 02543-1026.

Palka, D. 1995. Abundance estimate of the Gulf of Maine harbor porpoise. Pp. 27-50. In: A. Bjørge and G.P. Donovan (eds.).

Biology of the Phocoenids. Rep. int Whal. Commn. Special Issue 16.

Palka, D., Read, A. and Potter, C. 1997. Summary of knowledge of white-sided dolphins (Lagenorhynchus acutus) from the U.S.

and Canadian North Atlantic waters. Rep. int Whal. Commn. 47: 729-34.

Payne, M. and D. W. Heinemann. 1990. A distributional assessment of cetaceans in the shelf and shelf edge waters of the

northeastern United States based on aerial and shipboard surveys, 1978-1988. Report to National Marine Fisheries Science

Center, Woods Hole, Massachusetts. 

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

Special Issue 15: 133-147. 

Sergeant, D. E., D. J. St. Aubin, and J. R. Geraci. 1980. Life history and northwest Atlantic status of the Atlantic white-sided

dolphin, Lagenorhynchus acutus. Cetology No. 37: 1-12.

Wade, P. R. and R. P. Angliss. 1997. Guidelines for assessing marine mammal stocks: Report of the GAMMS workshop April 3-5,

1996, Seattle, Washington. U.S. Dep. Commer., NOAA Tech. Memo. NMFS-OPR-12, 93 pp.

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

Science Center, Woods Hole, Massachusetts. 

Waring, G. T., P. Gerrior, P. M. Payne, B. L. Parry, and J. R. Nicolas. 1990. Incidental take of marine mammals in foreign fishery

activities off the northeast United States, 1977-1988. Fish. Bull., U.S. 88(2): 347-360.
102

Figure 1. Distribution of common dolphin sightings from

NEFSC shipboard and aerial surveys during the summer

in 1990-1995. Isobaths are at 100 m and 1,000 m. 

October 1999

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 world-wide in temperate,

tropical, and subtropical seas. In the North Atlantic, common dolphins appears to be present along the coast over the continental

shelf along the 200-300 m isobaths or over prominent underwater topography from 50E N to 40ES latitude (Evans 1994). The

species is less common south of Cape Hatteras, although schools have been reported as far south as eastern Florida (Gaskin 1992).

At least some of the reported sightings of common dolphins in the Gulf of Mexico may have been Stenella clymene, which has a

color pattern similar to that of common dolphins (Evans 1994). Information regarding common dolphin stock structure in the western

North Atlantic does not exist. However, a high variance in skull morphometric measurements suggests the existence of more than

a single stock (J. G. Mead, pers. comm.). 

Common dolphins are distributed in broad bands along the continental slope (100 to 2,000 meters), and are associated with other

Gulf Stream features in waters off the northeastern USA coast (CETAP 1982; Selzer and Payne 1988; Waring et al. 1992). They

are widespread from Cape Hatteras northeast to Georges Bank (35o to 42o North latitude) in outer continental shelf waters from midJanuary to May (Hain et al. 1981; CETAP 1982; Payne et al. 1984). Common dolphins move northward onto Georges Bank and

the Scotian Shelf from mid-summer to autumn. Selzer and Payne (1988) reported very large aggregations (greater than 3,000 animals)

on Georges Bank in autumn. Common dolphins are rarely found in the Gulf of Maine, where temperature and salinity regimes are

lower than on the continental slope of the Georges Bank/mid-Atlantic region (Selzer and Payne 1988). Migration onto the Scotian

Shelf and continental shelf off Newfoundland occurs during summer and autumn when water temperatures exceed 11EC (Sergeant

et al. 1970; Gowans and Whitehead 1995).

POPULATION SIZE

The total number of common dolphins off the eastern

USA and Canadian Atlantic coast is unknown, although four

estimates are available from selected regions during June-July

1991, June-July 1993, and July-September 1995 (Table 1;

Figure 1).

A population size of 29,610 (CV = 0.39) common

dolphins 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). R. Kenney (pers.

comm.) provided abundance estimates that accounted for

survey effort in two continental slope survey blocks and

uncertainties resulting from sightings of unidentified small

dolphins. The estimate is based on an inverse variance

weighted pooling of spring and summer data. An average of

these seasons were chosen because the greatest proportion of

the population off the northeast USA coast appeared in the

study area during these seasons. This estimate does not

include a correction for dive-time or g(0), the probability of

detecting an animal group on the track line. This estimate

may not reflect the current true population size because of

its high degree of uncertainty, its old age, and it was

estimated just after cessation of extensive foreign fishing

operations in the region.

A population size of 22,215 (CV=0.40) common dolphins was estimated from a June and July 1991 shipboard line transect

sighting survey conducted primarily between the 200 and 2,000m isobaths from Cape Hatteras to Georges Bank (Table 1; Waring
103

et al. 1992; Waring 1998). Data were collected by one team that searched by naked eye and analyzed using DISTANCE (Buckland

et al. 1993; Laake et al. 1993). Estimates include school size-bias, if applicable, but no corrections for g(0) or dive-time. Variability

was estimated using bootstrap resampling techniques.

A population size of 1,645 (CV=0.47) common dolphins was estimated from a June and July 1993 shipboard line transect sighting

survey conducted principally between the 200 and 2,000m 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 bootstrap

resampling techniques.

A population size 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; NMFS,

unpublished data). Total track line length was 32,600 km (17,600 nmi). 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. However, the August 1995

ship survey on Georges Bank was greatly hindered by hurricane events. 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. Shipboard data were collected using a two independent sighting team procedure and were analyzed using the

product integral method (Palka 1995) and DISTANCE (Buckland et al. 1993). Shipboard estimates were corrected for g(0) and, if

applicable, also for school size-bias. Standard aerial sighting procedures with two bubble windows and one belly window observer

were used during the aerial survey. An estimate of g(0) was not made for the aerial portion of the survey. Estimates do not include

corrections for dive-time. Variability was estimated using bootstrap resampling techniques.

Although the 1991, 1993, and 1995 surveys did not sample the same areas or encompass the entire common dolphin habitat (e.

g., little effort in Scotian shelf edge waters), they did focus on segments of known or suspected high-use habitats off the northeastern

USA coast. The 1991, 1993, and 1995 data suggest that, seasonally, at least several thousand common dolphins are occupying

continental shelf edge waters, with perhaps highest abundance in the Georges Bank region. This is consistent with the earlier CETAP

data from a decade previous. Survey coverage to date is not adequate to provide a definitive estimate of common dolphin abundance

for the western North Atlantic.

The best available current abundance estimate for common dolphins is 22,215 (CV=0.40) as estimated from the June to July 1991

line transect survey because this survey provided the most complete coverage of the known habitat, particularly Georges Bank which

was inadequately surveyed in 1995 (see above).

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

spring & summer

1978-82 Cape Hatteras, NC to Nova Scotia 29,610 0.39

Jun-Jul 1991 Cape Hatteras, NC to Georges Bank, shelf edge only 22,215 0.40

Jun-Jul 1993 Georges Bank to Scotian shelf, shelf edge only 1,645 0.47

Jul-Sep 1995 Virginia to Gulf of St. Lawrence 6,741 0.69

Minimum Population Estimate

The minimum population estimate is the lower limit of the two-tailed 60% confidence interval of the log-normally distributed

best abundance estimate. This is equivalent to the 20th percentile of the log-normal distribution as specified by Wade and Angliss

(1997). The best estimate of abundance for common dolphins is 22,215 (CV=0.40). The minimum population estimate for the

western North Atlantic common dolphin is 16,060 (CV=0.40).

Current Population Trend

There are insufficient data to determine the population trends for this species. 
104

CURRENT AND MAXIMUM NET PRODUCTIVITY RATES

Current and maximum net productivity rates are unknown for this stock. For purposes of this assessment, the maximum net

productivity rate was assumed to be 0.04. This value is based on theoretical modeling showing that cetacean populations may not

grow at rates much greater than 4% given the constraints of their reproductive life history (Barlow et al. 1995). 

POTENTIAL BIOLOGICAL REMOVAL

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

a “recovery” factor (MMPA Sec. 3. 16 U.S.C. 1362; Wade and Angliss 1997). The minimum population size is 16,060 (CV=0.40).

The maximum productivity rate is 0.04, the default value for cetaceans. The “recovery” factor, which accounts for endangered,

depleted, threatened stocks, or stocks of unknown status relative to optimum sustainable population (OSP) is assumed to be 0.48

because the CV of the average mortality estimate is between 0.3-0.6; Wade and Angliss 1997) , and because this stock is of unknown

status. PBR for the western North Atlantic common dolphin is 154.

ANNUAL HUMAN-CAUSED MORTALITY AND SERIOUS INJURY

 Total annual estimated average fishery-related mortality or serious injury to this stock during 1993-1997 was 780 common

dolphins CV = 0.45; Table 2).

Fishery Information

USA

Prior to 1977, there was no documentation of marine mammal by-catch 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 by-catch 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 different foreign vessels; 16%, or 18, were Japanese tuna longline vessels operating along the

USA east coast. This was the first year that the Northeast Regional Observer Program assumed responsibility for observer coverage

of the longline vessels. Between 1983 and 1991, the numbers of foreign vessels operating within the 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. From 1987-91, 100% observer coverage was maintained. Foreign fishing

operations for squid and mackerel ceased at the end of the 1986 and 1991 fishing seasons, respectively. 

During the period 1977-1986, observers recorded 123 mortalities in foreign Loligo squid-fishing activities (Waring et al. 1990).

In 1985 and 1986, Italian vessels took 56 and 54 animals, respectively, which accounts for 89% (n = 110) of the total takes in foreign

Loligo squid-fishing operations. No mortalities were reported in foreign Illex squid fishing operations. Because of spatial/temporal

fishing restrictions, most of the by-catch occurred along the continental shelf edge (100 m) isobath during winter (December to

February). 

From 1977-1991, observers recorded 110 mortalities in foreign mackerel-fishing operations (Waring et al. 1990; NMFS

unpublished data). This total includes one documented take by a USA vessel involved in joint-venture fishing operations in which

USA captains transfer their catches to foreign processing vessels. The by-catch occurred during winter/spring (December to May).

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

self-reported fisheries information system for large pelagic fisheries. Data files are maintained at the Southeast Fisheries Science

Center (SEFSC). The Northeast Fisheries Science Center (NEFSC) Sea Sampling Observer Program was initiated in 1989, and since

that year several fisheries have been covered by the program. In late 1992 and in 1993, the SEFSC provided observer coverage of

pelagic longline vessels fishing off the Grand Banks (Tail of the Banks) and provides observer coverage of vessels fishing south of

Cape Hatteras. 

By-catch has been observed by NMFS Sea Samplers in the pelagic drift gillnet, pelagic pair trawl, pelagic longline fishery, midAtlantic coastal sink gillnet, North Atlantic bottom trawl, New England multispecies sink gillnet, and Atlantic squid, mackerel,

butterfish 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 introduction of quotas, effort was severely reduced. The estimated number of hauls in 1991, 1992, 1993, 1994, 1995, and
105

1996 were 233, 243, 232, 197, 164, and 149 respectively. In 1996 and 1997, the NMFS issued management regulations which

prohibited the operation of this fishery in 1997. Further, in January 1999 the NMFS issued a Final Rule to prohibit the use of

driftnets (i.e., permanent closure) in the North Atlantic swordfish fishery (50 CFR Part 630). Fifty-nine different vessels participated

in this fishery at one time or another between 1989 and 1993. Since 1994, between 10-12 vessels have participated in the fishery

(Table 2). Observer coverage, expressed as percent of sets observed, was 8% in 1989, 6% in 1990, 20% in 1991, 40% in 1992, 42%

in 1993, 87% in 1994, 99% in 1995, and 64% in 1996. Effort was concentrated along the southern edge of Georges Bank and off

Cape Hatteras. Examination of the species composition of the catch and locations of the fishery throughout the year, suggested that

the pelagic drift gillnet fishery be stratified into two strata, a southern or winter stratum, and a northern or summer stratum.

Estimates of the total by-catch, from 1989 to 1993, were obtained using the aggregated (pooled 1989-1993) catch rates, by strata

(Northridge 1996). Estimates of total annual by-catch for 1994 and 1995 were estimated from the sum of the observed caught and

the product of the average bycatch per haul and the number of unobserved hauls as recorded in self-reported fisheries information.

Variances were estimated using bootstrap re-sampling techniques. Six hundred and six common dolphin mortalities were observed

between 1989 and 1996 in this fishery. Mortalities were observed in all seasons and areas. Seven animals were released alive, but

six were injured. Estimated annual mortality and serious injury attributable to this fishery (CV in parentheses) was 540 in 1989

(0.19), 893 in 1990 (0.18), 223 in 1991 (0.12), 227 in 1992 (0.09), 238 in 1993 (0.08), 163 in 1994 (0.02), 83 in 1995 (0), and 106

in 1996 (0.07); average annual estimated fishery-related mortality during 1993-1997 attributable to this fishery was 148 common

dolphins (CV = 0.04) (Table 2). Injured and released alive animals are not included in the Table 2 mortality estimates. Table 3

summarizes the number of animals released alive and classified as injured or non-injured. It also includes the ratio of observed to

estimated mortalities for this fishery.

Pelagic Pair Trawl

During the period 1989 to 1993, effort in the pelagic pair trawl fishery increased from zero hauls in 1989 and 1990, to an

estimated 171 hauls in 1991 and then to an estimated 536 hauls in 1992 and 586 in 1993, 407 in 1994 and 440 in 1995. This fishery

ceased operations in 1996, when NMFS rejected a petition to consider pair trawl gear as an authorized gear type in Atlantic tunas

fishery. The fishery operated from August to November in 1991, from June to November in 1992, from June to October in 1993

(Northridge 1996), and from mid-summer to December in 1994 & 1995. Sea sampling began in October of 1992 (Gerrior et al. 1994)

where 48 sets (9% of the total) were sampled. In 1993, 102 hauls (17% of the total) were sampled. In 1994 and 1995, 52% (212)

and 55% (238), respectively, of the sets were observed. Nineteen vessels have operated in this fishery. The fishery operates in the

area between 35EN to 41EN and 69EW to 72EW. Approximately 50% of the total effort was within a one degree square at 39EN,

72EW, 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 1995. The estimated annual fishery-related mortality and serious

injury attributable to this fishery (CV in parentheses) was 5.6 in 1991 (0.53), 32 in 1992 (0.48), 35 in 1993 (0.43), 0 in 1994 (0), and

5.6 in 1995 (0.35). Since this fishery is no longer in operation it has been deleted from Tables 2 and 3.

During the 1994 and 1995 experimental pelagic pair trawl fishing seasons, fishing gear experiments were conducted to collect data

on environmental parameters, gear behavior, and gear handling practices to evaluate factors affecting catch and bycatch (Goudey 1995,

1996). Results of these studies have been presented at Offshore Cetacean Take Reduction Team Meetings. 

Pelagic Longline

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 pilot whales have been reported; however, a vessel may fish in more than

one statistical reporting area and it is not possible to separate estimates of fishing effort other than to subtract Gulf of Mexico effort

from Atlantic fishing effort, which includes the Caribbean Sea. This fishery has been monitored with about 5% observer coverage,

in terms of trips observed, since 1992. Total effort, excluding the Gulf of Mexico, for the pelagic longline fishery, based on mandatory

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 sets in 1996, and 8,023 sets in 1997 (Cramer 1994; Scott and Brown 1997; Johnson et al. 1999). Since 1992, this

fishery has been monitored with about 5% observer coverage, in terms of trips observed, within every statistical reporting area within

the EEZ and beyond. Off the USA Atlantic coast, the fishery has been observed from January to March off Cape Hatteras, in May

and June in the entire Mid-Atlantic, and in July through December in the Mid-Atlantic Bight and off Nova Scotia. This fishery has

been monitored with about 5% observer coverage, in terms of trips observed, since 1992. The 1993-1997, estimated take was based

on a revised analysis of the observed incidental take and self-reported incidental take and effort data, and replace previous estimates

for the 1992-1993 and 1994-1995 periods (Cramer 1994; Scott and Brown 1997; Johnson et al. 1999). Most of the estimated marine
106

mammal by-catch was from EEZ waters between South Carolina and Cape Cod (Johnson et al. 1999). Between 1990-1997 one

common dolphin was hooked and released alive.

New England Multispecies Sink Gillnet

 In 1993, there were approximately 349 full and part-time vessels in the New England multispecies sink gillnet fishery, which

covered the Gulf of Maine and southern New England (Table 2). An additional 187 vessels were reported to occasionally fish in the

Gulf of Maine with gillnets for bait or personal use; however, these vessels were not covered by the observer program (Walden 1996)

and their fishing effort was not used in estimating mortality. Observer coverage in terms of trips has been 1%, 6%, 7%, 5%, 7%, 5%,

4%, and 6% for 1990 to 1997, respectively. The fishery has been observed in the Gulf of Maine and in Southern New England. In

1996, the first observed mortality of common dolphins in this fishery was recorded. The estimated mortality was 63 common

dolphins (CV = 1.39); estimated annual mortality (1993-1997) was 12.6 common dolphins (CV = 1.39) (Table 2). Annual estimates

of common dolphin by-catch in the New England multispecies sink gillnet fishery reflect seasonal distribution of the species and of

fishing effort.

Mid-Atlantic Coastal Gillnet

Observer coverage of the USA Atlantic coastal gillnet fishery was initiated by the NEFSC Sea Sampling program in July, 1993;

and from July to December 1993, 20 trips were observed. During 1994 and 1995 221 and 382 trips were observed, respectively.

This fishery, which extends from North Carolina to New York, is actually a combination of small vessel fisheries that target a variety

of fish species, some of which operate right off the beach. The number of vessels in this fishery is unknown, because records which

are held by both state and federal agencies have not been centralized and standardized. Observer coverage, expressed as percent of

tons of fish landed, was 5% 4%, and 3% for 1995, 1996, and 1997 (Table 2).

No common dolphins were taken in observed trips during 1993 and 1994. Two common dolphin were observed taken in 1995

and 1996 , and no takes were observed in 1997 (Table 2). Observed effort was concentrated off NJ and scattered between DE and

NC from 1 to 50 miles off the beach. All by-catches were documented during January to April. Using the observed takes, the

estimated annual mortality (CV in parentheses) attributed to this fishery was 7.4 in 1995 (CV = 0.69), 43 in 1996 (0.79), and 16 in

1997 (0.53). Average annual estimated fishery-related mortality attributable to this fishery during 1995-1997 was 22 common

dolphins (CV = 0.53)

North Atlantic Bottom Trawl

Vessels in the North Atlantic bottom trawl fishery, a Category III fishery under MMPA, were observed in order to meet fishery

management needs, rather than marine mammal management needs. An average of 970 vessels (full and part time) participated

annually in the fishery during 1991-1995. The fishery is active in all seasons in New England waters. Four mortalities were observed

between 1991-1997. The estimated annual fishery-related mortality and serious injury attributable to this fishery (CV in parentheses)

was 0 in 1991, 0 in 1992, 0 in 1993, 0 in 1994 (0), 142 in 1995 (0.77), 0 in 1996 (0), and 93 in 1997 (1.06). Average annual estimated

fishery-related mortality attributable to this fishery during 1993-1997 was 47 common dolphins (CV = 0.63) (Table 2). However,

these estimates should be viewed with caution due to the extremely low (<1%) observer coverage.

Squid, Mackerel, Butterfish Trawl

The mid-Atlantic mackerel and squid trawl fisheries were combined into the Atlantic mid-water trawl fishery in the revised

proposed list of fisheries in 1995. The fishery occurs along the USA mid-Atlantic continental shelf region between New Brunswick,

Canada, and Cape Hatteras year around. The mackerel trawl fishery was classified as a Category II fishery since 1990 and the squid

fishery was originally classified as a Category II fishery in 1990, but was reclassified as a Category III fishery in 1992. The combined

fishery was reclassified as a Category II fishery in 1995. In 1996, mackerel, squid, and butterfish trawl fisheries were combined into

the Atlantic squid, mackerel, and butterfish trawl fishery, and maintained a Category II classification. Three common dolphin

mortalities were observed in 1996 and one in 1997 (Table 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), and 161 in 1997 (0.49). Average annual estimated fishery-related

mortality attributable to this fishery during 1996-1997 was 551 common dolphins (CV = 0.64) (Table 2). However, these estimates

should be viewed with caution due to the extremely low (<1%) observer coverage and uncertainties regarding number of vessels

participating in this "fishery". 

CANADA

Between January 1993 and December 1994, 36 Spanish deep water trawlers, covering 74 fishing trips (4,726 fishing days and

14,211 sets), were observed in NAFO Fishing Area 3 (off the Grand Bank) (Lens 1997). A total of 47 incidental catches were

recorded, which included one common dolphin. The incidental mortality rate for common dolphins was (0.007/set).
107

Table 2. Summary of the incidental mortality of common dolphins (Delphinus delphis) by commercial fishery including the years

sampled (Years), the number of vessels active within the fishery (Vessels), the type of data used (Data Type), the annual

observer coverage (Observer Coverage), the mortalities recorded by 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

Estimated6

Mortality 

Estimated

CVs 

Mean

Annual

Mortality

Pelagic Drift

Gillnet893-97

1994=11

1995=12

1996=103

Obs. Data 

Logbook

 .42, .87, .99,

.64, NA

 113, 142,

82, 74, NA

 227, 238,

163,

834,106,

NA

 .09, .08,

.02, 0, .07,

NA

 147.58

(.04)

(.04)

New England

Multispecies

Sink Gillnet

93-97 349 Obs. Data

Weighout,

Logbooks

 .05, .07, .05,

.04, .06

 0, 0, 0, 1, 

0

 0, 0, 0, 63,

0

 0, 0, 0,

1.39, 0

 12.6 

(1.39)

Mid-Atlantic

Coastal Sink

Gillnet 

95-97 NA Obs. Data

Weighout

 .05, .04, .03 2, 2, 2 7.4, 43, 16 .69, .79, .53 22.0

 (.53)

 

Atlantic squid,

mackerel,

butterfish trawl

96-97 NA Obs. Data

Weighout

 .007, .008 3, 1 940, 161 .75, .49 551

(.64)

North Atlantic

Bottom Trawl

93-97 970 Obs. Data

Weighout

 .004, .004,

.0115, .002,

.002

 0, 0, 3, 0, 1 0, 0, 142,

0, 93

 0, 0, .77, 0,

1.06

 47

 (.63)

TOTAL 780

 (.45)

1 Observer data (Obs. Data) are used to measure bycatch rates, and the data are collected within the Northeast Fisheries Science

Center (NEFSC) Sea Sampling Program. NEFSC collects weighout (Weighout) landings data, 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 North Atlantic bottom trawl

fishery. 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 North Atlantic

bottom trawl fishery is in trips. Assessments for the coastal gillnet fishery have not been completed. The number of trips sampled

by the NEFSC Sea Sampling Program are reported here.

3

1994 - 1996 shown, other years not available on an annual basis.

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 7.0 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 0.50 animals.

5 Observer coverage for the North Atlantic bottom trawl fishery in 1995 is based on January to May data.

6

Injured and released alive animals are not included in the Table 2 mortality estimates.

8 The fishery did not operate in 1997; the average annual mortality is based on the number of years (4; 1993-1996) that the fishery

operated.
108

Table 3. Summary of common dolphins (Delphinus delphis) released alive, by commercial fishery, years sampled (Years), ratio

of observed mortalities recorded by on-board observers to the estimated mortality (Ratio), the number of observed animals

released alive and injured (Injured), and the number of observed animals released alive and uninjured (Uninjured)

Fishery Years Ratio Injured4 Uninjured

Pelagic Drift Gillnet 93-97 113/238, 142/163, 82/83, 74/106, NA 31, 12, 0, 33,

NA

 0, 0, 0, 0, NA

1

 Released alive, 2 were moderately injured and 1 common dolphin was severely injured.

2

 Released alive and gear was “in/around several body parts”.

3

 Released alive, one animal “seemed tired,” but had few wounds, little bleeding from fluke. Both animals were smaller as compared

to other common dolphins taken in the same set.

4

 Injured and released alive animals are not included in the Table 2 mortality estimates.

Other Mortality

From 1992-1997, 69 common dolphins were stranded between North Carolina and Massachusetts, predominantly along beaches

in the latter state (NMFS unpublished data). The total includes ten common dolphins that mass stranded in November 1997 on Cape

Cod.

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% of the calculated PBR and, therefore, cannot be

considered to be insignificant and approaching zero mortality and serious injury rate. This is a strategic stock because the 1993-1997

average annual fishery-related mortality and serious injury exceeds PBR. 

REFERENCES

Anon. 1993. Cruise results, NOAA ship DELAWARE II, Cruise No. DEL 93-06, Marine mammal Survey. NOAA NMFS NEFSC,

Woods Hole Laboratory, Woods Hole, MA. 5 pp.

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Background, and a Summary of the 1995 Assessments. U.S. Dep. Commer., NOAA Tech. Memo. NMFS-OPR-6, 73 pp. 

Buckland, S. T., D. R. Andersen, K. P. Burnham, and J. L. Laake. 1993. Distance Sampling: Estimating abundance of biological

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CETAP. 1982. A characterization of marine mammals and turtles in the mid- and north Atlantic areas of the U.S. outer continental

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Evans, W. E. 1994. Common dolphin, white-bellied porpoise. Pages 191-224. In: S. H. Ridgway and R. Harrison (eds.). Handbook

of marine mammals, Volume 5: The first book of dolphins. Academic Press, San Diego

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Gerrior, P., A.S. Williams, and D.J. Christensen. 1994. Observations of the 1992 U.S. pelagic pair trawl fishery in the Northwest

Atlantic. Mar. Fish. Rev. 56(3): 24-27.

Goudy, C.A. 1995. The 1994 experimental pair trawl fishery for tuna in the northwest Atlantic, MITSG 95-6, Cambridge, MA. 10

pp.

Goudy, C.A. 1996. The 1995 experimental pair trawl fishery for tuna in the northwest Atlantic, MITSG 96-17, Cambridge, MA.

13 pp.

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on the Scotian Shelf. Can. J. Zool. 73: 1599-1608.

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of marine mammals and turtles in the mid- and north Atlantic areas of the U.S. outer continental shelf, Annual Report for 1979.

Contract No. AA551-CT8-48, U.S. Dept. of Interior, Bureau of Land Management, Washington, DC. 
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Johnson, D.R., C.A. Brown, and C. Yeung. 1999. Estimates of marine mammal and marine turtle catch by the US Atlantic pelagic

longline fleet in 1992-1997. NOAA Tech. Mem. NMFS-SEFSC-418, 70p.

Laake, J. L., S. T. Buckland, D. R. Anderson, and K. P. Burnham. 1993 . DISTANCE user’s guide, V2.0. Colorado Cooperative Fish

& Wildlife Research Unit, Colorado State University, Ft. Collins, Colorado, 72 pp. 

Leatherwood, S., D. K. Caldwell, and H. E. Winn. 1976. Whales, dolphins, and porpoises of the western North Atlantic. A guide

to their identification. U.S. Dept. of Commerce, NOAA Tech. Rep. NMFS Circ. 396, 176 pp.

Lens, S. 1997. Interactions between marine mammals and deep water trawlers in the NAFO regulatory area. ICES CM 1997/Q:8.

10 pp.

Northridge, S. 1996. Estimation of cetacean mortality in the U.S. Atlantic swordfish and tuna drift gillnet and pair trawl fisheries.

Final report to the Northeast Fisheries Science Center, Contract No. 40ENNF500045, 18 pp.

Palka, D. 1995. Abundance estimate of the Gulf of Maine harbor porpoise. Pp. 27-50. In: A. Bjørge and G.P. Donovan (eds.).

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Payne, P. M., L. A. Selzer, and A. R. Knowlton. 1984. Distribution and density of cetaceans, marine turtles, and seabirds in the shelf

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No. NA-81-FA-C-00023. 

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

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Reilly, S. B. and J. Barlow. 1986. Rates of increase in dolphin population size. Fish. Bull., U.S. 84(3): 527-533.

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Wade, P.R., and R.P. Angliss. 1997. Guidelines for assessing marine mammal stocks: Report of the GAMMS Workshop April 3-5,

1996, Seattle, Washington. U.S. Dep. Commer., NOAA Tech. Memo. NMFS-OPR-12, 93 pp.

Waring, G.T. 1998. Results of the summer 1991 R/V Chapman marine mammal sighting survey. NOAA NMFS NEFSC, Lab. Ref.

Doc. No. 98-09, 21pp. Northeast Fisheries Science Center, Woods Hole, Massachusetts.

Waring, G. T., P. Gerrior, P. M. Payne, B. L. Parry and J. R. Nicolas. 1990. Incidental take of marine mammals in foreign fishery

activities off the northeast United States, 1977-1988. Fish. Bull., U.S. 88(2): 347-360.

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110

Figure 1. Distribution of spotted dolphin sightings from

NEFSC shipboard and aerial surveys during the summer

in 1990-1995. Isobaths are at 100 m and 1,000 m. 

October 1999

ATLANTIC SPOTTED DOLPHIN (Stenella frontalis):

Western North Atlantic Stock

STOCK DEFINITION AND GEOGRAPHIC RANGE

There are two species of spotted dolphin in the Western Atlantic — the Atlantic spotted dolphin, Stenella frontalis, formerly

S. plagiodon (Perrin et al. 1987), and the pantropical spotted dolphin, S. attenuata. These species are difficult to differentiate

at sea. 

Atlantic spotted dolphins are distributed in tropical and warm temperate waters of the western North Atlantic (Leatherwood et

al. 1976). Their distribution is from southern New England, south through the Gulf of Mexico and the Caribbean to Venezuela

(Leatherwoodet al. 1976; Perrin et al. 1987). The large, heavily spotted form of the Atlantic spotted dolphin along the southeastern

and Gulf coasts of the United States inhabits the continental shelf, usually being found inside or near the 200 m isobath (within 250-

350 km of the coast) but sometimes coming into very shallow water adjacent to the beach. Off the northeast USA coast, spotted

dolphins are widely distributed on the continental shelf, along the continental shelf edge, and offshore over the deep ocean south of

40o N (CETAP 1982). Atlantic spotted dolphins regularly occur in the inshore waters south of Chesapeake Bay and near the

continental shelf edge and continental slope waters north of this region (Payne et al. 1984). Sightings have also been made along the

north wall of the Gulf Stream and warm-core ring features (Waring et al. 1992). Stock structure in the western North Atlantic is

unknown. 

POPULATION SIZE

The total number of Atlantic spotted dolphins off the

eastern USA coast is unknown. However, two population sizes

are available for select regions from spring and summer 1978-82

and July-September 1995 (Table 1; Figure 1). Because S.

frontalis and S. attenuata are difficult to differentiate at sea,

the reported abundance estimates are for both species of

spotted dolphins.

A population size of 6,107 (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 (Table 1; CETAP 1982). R.

Kenney (pers. comm.) provided abundance estimates for both

species of spotted dolphins combined that accounted for survey

effort in two continental slope survey blocks and uncertainties

resulting from sightings of unidentified small dolphins. The

estimate is based on an inverse variance weighted pooling of

spring and summer data. An average of these seasons were

chosen because the greatest proportion of the population off the

northeast USA coast appeared in the study area during these

seasons. This estimate does not include a correction for divetime or g(0), the probability of detecting an animal group on the

track line. Furthermore, this survey did not cover important

spotted dolphin habitat in the continental shelf between Cape

Hatteras and Florida, and Atlantic deep oceanic waters. This

estimate may not reflect the current true population size because of its high degree of uncertainty , its old age, and it was estimated

just after cessation of extensive foreign fishing operations in the region.

A population size of undifferentiated 4,772 (CV=1.27) 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; NMFS, unpublished data). Total track line length was 32,600 km (17,600 nmi). 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
111

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. Shipboard data were collected using a two independent sighting

team procedure and were analyzed using the product integral method (Palka 1995) and DISTANCE (Buckland et al. 1993).

Shipboard estimates were corrected for g(0) and, if applicable, also for school size-bias. Standard aerial sighting procedures with two

bubble windows and one belly window observer were used during the aerial survey. An estimate of g(0) was not made for the aerial

portion of the survey. Estimates do not include corrections for dive-time. Variability was estimated using bootstrap resampling

techniques.

The best available current abundance estimate for the undifferentiated group of spotted dolphins is 4,772 (CV=1.27) as estimated

from the July to September 1995 line transect survey (NMFS, unpublished data) because this survey is recent and provided the most

complete coverage of the known habitat.

Table 1. Summary of abundance estimates for a combination of the Atlantic and pantropical spotted 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

spring & summer

1978-82

Cape Hatteras, NC to

Nova Scotia 6,107 0.27

Jul-Sep 1995 Virginia to Gulf of St.

Lawrence 4,772 1.27

Minimum Population Estimate

The minimum population estimate is the lower limit of the two-tailed 60% confidence interval of the log-normally distributed

best abundance estimate. This is equivalent to the 20th percentile of the log-normal distribution as specified by Wade and Angliss

(1997). The best estimate of abundance for the undifferentiated group of spotted dolphins is 4,772 (CV=1.27). The minimum

population estimate for the undifferentiated group of spotted dolphins is 1,617 (CV=1.27).

Current Population Trend

There are insufficient data to determine the population trends for this species. 

CURRENT AND MAXIMUM NET PRODUCTIVITY RATES

Current and maximum net productivity rates are unknown for this stock. For purposes of this assessment, the maximum net

productivity rate was assumed to be 0.04. This value is based on theoretical modeling showing that cetacean populations may not

grow at rates much greater than 4% given the constraints of their reproductive life history (Barlow et al. 1995).

POTENTIAL BIOLOGICAL REMOVAL

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

a “recovery” factor (MMPA Sec. 3. 16 U.S.C. 1362; Wade and Angliss 1997). The minimum population size for the undifferentiated

group of spotted dolphins is 1,617 (CV=1.27). The maximum productivity rate is 0.04, the default value for cetaceans. The

“recovery” factor, which accounts for endangered, depleted, threatened stocks, or stocks of unknown status relative to optimum

sustainable population (OSP) is set to 0.5 because this stock is of unknown status. PBR for the undifferentiated group of spotted

dolphins combined is 16. However, it is not reasonable to calculate a PBR for the Atlantic spotted dolphin alone, because it was

impossible to separately identify the two species.

ANNUAL HUMAN-CAUSED MORTALITY AND SERIOUS INJURY

 Total annual estimated average fishery-related mortality or serious injury to this stock during 1993-1997 was 9.9 spotted

dolphins (Stenella sp.) CV = 0.09; Table 2). 

Fishery Information
112

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

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

(Tail of the Banks) and provides observer coverage of vessels fishing south of Cape Hatteras. Total fishery-related mortality and

serious injury cannot be estimated separately for the two species of spotted dolphins in the USA Atlantic Exclusive Economic Zone

(EEZ) because of the uncertainty in species identification by fishery observers. The Atlantic Scientific Review Group advised

adopting the risk-averse strategy of assuming that either species might have been subject to the observed fishery-related mortality

and serious injury.

By-catch has been observed by NMFS Sea Samplers in the pelagic drift gillnet and pelagic longline fisheries, but no mortalities

or serious injuries have been documented in the pelagic pair trawl, New England multispecies sink gillnet, mid-Atlantic coastal gillnet,

and North Atlantic bottom trawl fisheries; and no takes have been documented in a review of Canadian gillnet and trap fisheries (Read

1994).

Pelagic Drift Gillnet

The estimated total number of hauls in the pelagic drift gillnet fishery increased from 714 in 1989 to 1,144 in 1990; thereafter,

with the introduction of quotas, effort was severely reduced. The estimated number of hauls in 1991, 1992, 1993, 1994, 1995, and

1996 were 233, 243, 232, 197, 164, and 149 respectively. In 1996 and 1997, the NMFS issued management regulations which

prohibited the operation of this fishery in 1997. Further, in January 1999 the NMFS issued a Final Rule to prohibit the use of

driftnets (i.e., permanent closure) in the North Atlantic swordfish fishery (50 CFR Part 630). Fifty-nine different vessels participated

in this fishery at one time or another between 1989 and 1993. Since 1994, between 10-12 vessels have participated in the fishery

(Table 2). Observer coverage, expressed as percent of sets observed, was 8% in 1989, 6% in 1990, 20% in 1991, 40% in 1992, 42%

in 1993, 87% in 1994, 99% in 1995, and 64% in 1996. Effort was concentrated along the southern edge of Georges Bank and off Cape

Hatteras. Examination of the species composition of the catch and locations of the fishery throughout the year, suggested that the

pelagic drift gillnet fishery be stratified into two strata, a southern or winter stratum, and a northern or summer stratum. Estimates

of the total by-catch, from 1989 to 1993, were obtained using the aggregated (pooled 1989-1993) catch rates, by strata (Northridge

1996). Estimates of total annual by-catch for 1994 and 1995 were estimated from the sum of the observed caught and the product

of the average bycatch per haul and the number of unobserved hauls as recorded in self-reported 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 1996 and occurred northeast of Cape Hatteras within the 183 m isobath in February-April, and near Lydonia

Canyon in October. Six whole animal carcasses that were sent to the Smithsonian were identified as Pantropical spotted dolphins

(S. attenuata). The remaining animals were not identified to species. Estimated annual mortality and serious injury attributable to

this fishery (CV in parentheses) was 25 in 1989 (.65), 51 in 1990 (.49), 11 in 1991 (.41), 20 in 1992 (0.18), 8.4 in 1993 (0.40), 29

in 1994 (0.01), 0 in 1995, and 2 in 1996 (0.06); average annual mortality and serious injury during 1993-1997 was 9.9 (0.09) (Table

2). 

Pelagic Longline

 Interactions between the pelagic longline fishery and spotted dolphins have been reported; however, a vessel may fish in more

than one statistical reporting area and it is not possible to separate estimates of fishing effort other than to subtract Gulf of Mexico

effort from Atlantic fishing effort, which includes the Caribbean Sea. This fishery has been monitored with about 5% observer

coverage, in terms of trips observed, since 1992. Total effort, excluding the Gulf of Mexico, for the pelagic longline fishery, based

on mandatory self-reported fisheries information, was 11,279 sets in 1991, 9,869 sets in 1992, 9,862 sets in 1993, 9,481 sets in 1994,

10,129 sets in 1995, 9,885 sets in 1996, and 8,023 sets in 1997 (Cramer 1994; Scott and Brown 1997; Johnson et al. 1999). Since

1992, this fishery has been monitored with about 5% observer coverage, in terms of trips observed, within every statistical reporting

area within the EEZ and beyond. Off the USA Atlantic coast, the fishery has been observed from January to March off Cape

Hatteras, in May and June in the entire Mid-Atlantic, and in July through December in the Mid-Atlantic Bight and off Nova Scotia.

This fishery has been monitored with about 5% observer coverage, in terms of trips observed, since 1992. Most of the estimated

marine mammal by-catch was from EEZ waters between South Carolina and Cape Cod (Johnson et al. 1999). The 1992-1997,

estimated take was based on a revised analysis of the observed incidental take and self-reported incidental take and effort data, and

replace previous estimates for the 1992-1993 and 1994-1995 periods (Scott and Brown 1997; Johnson et al. 1999). Excluding the

Gulf of Mexico where one animal was hooked and released alive (Appendix 1), no Atlantic spotted dolphin bycatches were observed
113

for 1992-1997. Table 3 summarizes the number of animals released alive and classified as injured or non-injured. It also includes

the ratio of observed to estimated mortalities for this fishery.

Table 2. Summary of the incidental mortality of spotted dolphins (Stenella sp.) by commercial fishery including the years sampled

(Years), the number of vessels active within the fishery (Vessels), the type of data used (Data Type), the annual observer

coverage (Observer Coverage), the mortalities recorded by on-board observers (Observed Mortality), the estimated annual

mortality (Estimated Mortality), the estimated CV of the annual mortality (Estimated CVs) and the mean annual mortality

(CV in parentheses).

Fishery Years Vessels Data Type 1 Observer

Coverage 2 

Observed

Mortality

Estimated6

Mortality 

Estimated

CVs 

Mean

Annual

Mortality

Pelagic

Drift

Gillnet7

93-96 1994=113

1995=12

1996=10

Obs. Data

Logbook

 .42, .87,

.99, .64, NA

 0, 29, 0, 2,

NA

 8.44, 29, 0,

2, NA

 .40, .01, 0,

0

5

, NA

 9.9

 (.09)

Pelagic

Longline

93-97 NA Obs. Data

Logbook

 .06, .05,

.06, .03, .04

 0, 0, 0, 0,

0

 0, 0, 0, 0, 0 0, 0, 0, 0,

0

0 

TOTAL 9.9

 (.09)

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 and 1995 shown, other years not available on an annual basis.

4 For 1991-1993, pooled bycatch rates were used to estimate bycatch in months that had fishing effort but did not have observer

coverage. This method is described in Northridge (1996). In 1994 and 1995, observer coverage increased substantially, and

bycatch rates were not pooled for this period . 

5 Estimates were based on 2 seasons. The two observed takes were during the winter season when observer coverage was 100%.

6 Annual mortality estimates do not include any animals injured and released alive.

7 The fishery did not operate in 1997; the average annual mortality is based on the number of years (4; 1993-1996) that the fishery

operated.
114

Table 3. Summary of spotted dolphins (Stenella sp.) released alive, by commercial fishery, years sampled (Years), ratio of

observed mortalities recorded by on-board observers to the estimated mortality (Ratio), the number of observed animals

released alive and injured (Injured), and the number of observed animals released alive and uninjured (Uninjured)

Fishery Years Ratio Injured2 Uninjured

Pelagic longline 93-97 0, 0, 0, 0, 0 0,11, 0, 0, 0 0, 11, 0, 0, 0

1 See Appendix 1.

2 Annual mortality estimates do not include any animals injured and released alive.

Other Mortality

From 1995-1997, eight 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 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 status of this stock has been

changed from strategic to non-strategic because the estimated annual fishery-related mortality and serious injury are below 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. Andersen, K. P. Burnham, and J. L. Laake. 1993. Distance Sampling: Estimating abundance of biological

populations. Chapman and Hall, New York, 446 pp. 

CETAP. 1982. A characterization of marine mammals and turtles in the mid- and north Atlantic areas of the U.S. outer continental

shelf. Cetacean and Turtle Assessment Program, University of Rhode Island. Final Report, Contract AA51-C78-48, Bureau of

Land Management, Washington, DC, 538 pp. 

Cramer, J. Large pelagic logbook newsletter - 1993. NOAA Tech. Mem. NMFS-SEFSC-352, 19 pp.

Johnson, D.R., C.A. Brown, and C. Yeung. 1999. Estimates of marine mammal and marine turtle catch by the US Atlantic pelagic

longline fleet in 1992-1997. NOAA Tech. Mem. NMFS-SEFSC-418, 70p.

Leatherwood, S., D. K. Caldwell and H. E. Winn. 1976. Whales, dolphins, and porpoises of the western North Atlantic. A guide to

their identification. U.S. Dept. of Commerce, NOAA Tech. Rep. NMFS Circ. 396, 176 pp. 

Northridge, S. 1996. Estimation of cetacean mortality in the U.S. Atlantic swordfish and tuna drift gillnet and pair trawl fisheries.

Final report to the Northeast Fisheries Science Center, Contract No. 40ENNF500045, 18 pp. 

Palka, D. 1995. Abundance estimate of the Gulf of Maine harbor porpoise. Pp. 27-50. In: A. Bjørge and G.P. Donovan (eds.).

Biology of the Phocoenids. Rep. int Whal. Commn. Special Issue 16.

Payne, P. M., L. A. Selzer and A. R. Knowlton. 1984. Distribution and density of cetaceans, marine turtles, and seabirds in the shelf

waters of the northeastern United States, June 1980-December 1983, based on shipboard observations. NOAA/NMFS Contract

No. NA-81-FA-C-00023. 

Perrin, W. F.,E. D. Mitchell, J. G. Mead, D. K. Caldwell, M. C. Caldwell, P. J. H. van Bree, and W. H. Dawbin. 1987. Revision of

the spotted dolphins, Stenella sp. Mar. Mamm. Sci. 3(2): 99-170.

Perrin, W. F., D. K. Caldwell, and M. C. Caldwell. 1994. Atlantic spotted dolphin. Pages 173-190. In: S. H. Ridgway and R.

Harrison (eds.). Handbook of marine mammals, Volume 5: The first book of dolphins. Academic Press, San Diego, 418 pp.

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

Special Issue 15: 133-147. 

Scott, G.P. and C.A. Brown. 1997. Estimates of marine mammal and marine turtle catch by the US 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-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 shelf. ICES Marine Mammals Comm. CM 1992/N:12, 29 pp.
115

Figure 1. Distribution of spotted dolphin sightings from

NEFSC shipboard and aerial surveys during the summer

in 1990-1995. Isobaths are at 100 m and 1,000 m. 

October 1999

PANTROPICAL SPOTTED DOLPHIN (Stenella attenuata):

Western North Atlantic Stock

STOCK DEFINITION AND GEOGRAPHIC RANGE

There are two species of spotted dolphin in the Western Atlantic — the Atlantic spotted dolphin, Stenella frontalis, formerly

S. plagiodon (Perrin et al. 1987), and the pantropical spotted dolphin, S. attenuata. These species are difficult to differentiate

at sea. 

The pantropical spotted dolphin is distributed worldwide in tropical and some sub-tropical oceans (Perrin et al. 1987; Perrin

and Hohn 1994). Sightings of this species in the northern Gulf of Mexico occur over the deeper waters, and rarely over the

continental shelf or continental shelf edge (Mullin et al. 1991; SEFSC, unpublished data). Pantropical spotted dolphins were seen

in all seasons during recent seasonal aerial surveys of the northern Gulf of Mexico, and during recent winter aerial surveys offshore

of the southeastern USA Atlantic coast (SEFSC unpublished data). Some of the Pacific populations have been divided into different

geographic stocks based on morphological characteristics (Perrin et al. 1987; Perrin and Hohn 1994); however, there is no information

on stock differentiation in the Atlantic population. 

POPULATION SIZE

The total number of pantropical spotted dolphins off the

eastern USA coast is unknown; however, two abundance

estimates are available for the combination of both spotted

dolphin species within portions of the northeastern USA

Atlantic during spring and summer of 1978-82, and JulySeptember 1995 (Table 1; Figure 1). Neither survey

distinguishes between the two species or covers important

spotted dolphin habitat in the continental shelf between Cape

Hatteras and Florida, or in oceanic waters.

A population size of 6,107 spotted dolphins (CV=0.27)

was estimated from an aerial survey program conducted from

1978 to 1982 on the continental shelf and shelf edge waters

between Cape Hatteras, North Carolina and Nova Scotia

(Table 1; CETAP 1982). R. Kenney (pers. comm.) provided

abundance estimates for both species of spotted dolphins

combined that accounted for survey effort in two continental

slope survey blocks and uncertainties resulting from sightings

of unidentified small dolphins. The estimate is based on

inverse variance-weighted pooling of the revised CETAP

(1982) spring and summer data. An average of these seasons

were chosen because the greatest proportion of the population

off the northeast USA coast appeared in the study area during

these seasons. This estimate does not include a correction for

dive-time or g(0), the probability of detecting an animal group

on the track line. This estimate may not reflect the current true

population size because of its high degree of uncertainty, its

old age, and it was estimated just after cessation of extensive foreign fishing operations in the region.

Due to insufficient numbers of spotted dolphin sightings collected during the August 1990, June-July 1991, August-September

1991 and June-July 1993 sighting surveys spotted dolphin abundance was not estimated.

A population size of undifferentiated 4,772 (CV = 1.27) 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; NMFS, unpublished data). Total track line length was 32,600 km (17,600 nmi). 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
116

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. Shipboard data were collected using a two independent sighting

team procedure and were analyzed using the product integral method (Palka 1995) and DISTANCE (Buckland et al. 1993).

Shipboard estimates were corrected for g(0) and, if applicable, also for school size-bias. Standard aerial sighting procedures with two

bubble windows and one belly window observer were used during the aerial survey. An estimate of g(0) was not made for the aerial

portion of the survey. Estimates do not include corrections for dive-time. Variability was estimated using bootstrap resampling

techniques.

The best available current abundance estimate for the undifferentiated group of spotted dolphins is 4,772 (CV=1.27) as estimated

from the July to September 1995 line transect survey (NMFS, unpublished data) because this survey is recent and provided the most

complete coverage of the known habitat.

Table 1. Summary of abundance estimates for both species of spotted 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

spring & summer

1978-82

Cape Hatteras, NC to

Nova Scotia 6,107 0.27

Jul-Sep 1995 Virginia to Gulf of St.

Lawrence 4,772 1.27

Minimum Population Estimate

The minimum population estimate is the lower limit of the two-tailed 60% confidence interval of the log-normally distributed

best abundance estimate. This is equivalent to the 20th percentile of the log-normal distribution as specified by Wade and Angliss

(1997). The best estimate of abundance for spotted dolphins is 4,772 (CV=1.27). The minimum population estimate for spotted

dolphins is 1,617 (CV=1.27).

Current Population Trend

There are insufficient data to determine the population trends for this species. 

CURRENT AND MAXIMUM NET PRODUCTIVITY RATES

Current and maximum net productivity rates are unknown for this stock. For purposes of this assessment, the maximum net

productivity rate was assumed to be 0.04. This value is based on theoretical modeling showing that cetacean populations may not

grow at rates much greater than 4% given the constraints of their reproductive life history (Barlow et al. 1995). 

POTENTIAL BIOLOGICAL REMOVAL

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

a “recovery” factor (MMPA Sec. 3. 16 U.S.C. 1362; Wade and Angliss 1997). The minimum population size for the undifferentiated

group of spotted dolphins is 1,617 (CV=1.27). 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 undifferentiated group of

spotted dolphins combined is 16. However, it is not reasonable to calculate a PBR for the pantropical spotted dolphin alone, because

it was impossible to separately identify the two species.

ANNUAL HUMAN-CAUSED MORTALITY AND SERIOUS INJURY

 Total annual estimated average fishery-related mortality or serious injury to this stock during 1993-1997 was 9.9 spotted

dolphins (Stenella sp.) CV = 0.09; 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
117

large pelagic fisheries. Data files are maintained at the Southeast Fisheries Science Center (SEFSC). The Northeast Fisheries Science

Center (NEFSC) Sea Sampling Observer Program was initiated in 1989 and since that year several fisheries have been covered by the

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

(Tail of the Banks) and provides observer coverage of vessels fishing south of Cape Hatteras. Total fishery-related mortality and

serious injury cannot be estimated separately for the two species of spotted dolphins in the USA Atlantic Exclusive Economic Zone

(EEZ) because of the uncertainty in species identification by fishery observers. The Atlantic Scientific Review Group advised

adopting the risk-averse strategy of assuming that either species might have been subject to the observed fishery-related mortality

and serious injury.

By-catch has been observed by NMFS Sea Samplers in the pelagic drift gillnet and pelagic longline fisheries, but no mortalities

or serious injuries have been documented in the pelagic pair trawl, New England multispecies sink gillnet, mid-Atlantic coastal gillnet,

and North Atlantic bottom trawl fisheries; and no takes have been documented in a review of Canadian gillnet and trap fisheries (Read

1994).

Pelagic Drift Gillnet

The estimated total number of hauls in the pelagic drift gillnet fishery increased from 714 in 1989 to 1,144 in 1990; thereafter,

with the introduction of quotas, effort was severely reduced. The estimated number of hauls in 1991, 1992, 1993, 1994, 1995, and

1996 were 233, 243, 232, 197, 164, and 149 respectively. In 1996 and 1997, the NMFS issued management regulations which

prohibited the operation of this fishery in 1997. Further, in January 1999 the NMFS issued a Final Rule to prohibit the use of

driftnets (i.e., permanent closure) in the North Atlantic swordfish fishery (50 CFR Part 630). Fifty-nine different vessels participated

in this fishery at one time or another between 1989 and 1993. Since 1994, between 10-12 vessels have participated in the fishery

(Table 2). Observer coverage, expressed as percent of sets observed, was 8% in 1989, 6% in 1990, 20% in 1991, 40% in 1992, 42%

in 1993, 87% in 1994, 99% in 1995, and 64% in 1996. Effort was concentrated along the southern edge of Georges Bank and off Cape

Hatteras. Examination of the species composition of the catch and locations of the fishery throughout the year, suggested that the

pelagic drift gillnet fishery be stratified into two strata, a southern or winter stratum, and a northern or summer stratum. Estimates

of the total by-catch, from 1989 to 1993, were obtained using the aggregated (pooled 1989-1993) catch rates, by strata (Northridge

1996). Estimates of total annual by-catch for 1994 and 1995 were estimated from the sum of the observed caught and the product

of the average bycatch per haul and the number of unobserved hauls as recorded in self-reported 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 1996 and occurred northeast of Cape Hatteras within the 183 m isobath in February-April, and near Lydonia

Canyon in October. Six whole animal carcasses that were sent to the Smithsonian were identified as Pantropical spotted dolphins

(S. attenuata). The remaining animals were not identified to species. Estimated annual mortality and serious injury attributable

to this fishery (CV in parentheses) was 25 in 1989 (.65), 51 in 1990 (.49), 11 in 1991 (.41), 20 in 1992 (0.18), 8.4 in 1993 (0.40),

29 in 1994 (0.01), 0 in 1995, and 2 in 1996 (0.06); average annual mortality and serious injury during 1993-1997 was 9.9 (0.09) (Table

2). 

Pelagic Longline

 Interactions between the pelagic longline fishery and spotted dolphins have been reported; however, a vessel may fish in more

than one statistical reporting area and it is not possible to separate estimates of fishing effort other than to subtract Gulf of Mexico

effort from Atlantic fishing effort, which includes the Caribbean Sea. Total effort, excluding the Gulf of Mexico, for the pelagic

longline fishery, based on mandatory self-reported fisheries information, was 11,279 sets in 1991, 9,869 sets in 1992, 9,862 sets in

1993, 9,481 sets in 1994, 10,129 sets in 1995, 9,885 sets in 1996, and 8,023 sets in 1997 (Cramer 1994; Scott and Brown 1997;

Johnson et al. 1999). Since 1992, this fishery has been monitored with about 5% observer coverage, in terms of trips observed,

within every statistical reporting area within the EEZ and beyond. Off the USA Atlantic coast, the fishery has been observed from

January to March off Cape Hatteras, in May and June in the entire Mid-Atlantic, and in July through December in the Mid-Atlantic

Bight and off Nova Scotia. This fishery has been monitored with about 5% observer coverage, in terms of trips observed, since 1992.

Most of the estimated marine mammal by-catch was from EEZ waters between South Carolina and Cape Cod (Johnson et al. 1999).

The 1992-1997, estimated take was based on a revised analysis of the observed incidental take and self-reported incidental take and

effort data, and replace previous estimates for the 1992-1993 and 1994-1995 periods (Scott and Brown 1997; 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 1992-1997. Table 3 summarizes the number of animals released alive and classified as injured or noninjured. It also includes the ratio of observed to estimated mortalities for this fishery.
118

Table 2. Summary of the incidental mortality of spotted dolphins (Stenella sp.) by commercial fishery including the years sampled

(Years), the number of vessels active within the fishery (Vessels), the type of data used (Data Type), the annual observer

coverage (Observer Coverage), the mortalities recorded by on-board observers (Observed Mortality), the estimated annual

mortality (Estimated Mortality), the estimated CV of the annual mortality (Estimated CVs) and the mean annual mortality

(CV in parentheses).

Fishery Years Vessels Data Type 1 Observer

Coverage 2 

Observed

Mortality

Estimated6

Mortality 

Estimated

CVs 

Mean

Annual

Mortality

Pelagic7

Drift

Gillnet

93-97 1994=113

1995=12

1996=10

Obs. Data

Logbook

 .42, .87,

.99, .64, NA

 0, 29, 0, 2,

NA

4

, 8.4, 29, 0,

2, NA

 .40, .01, 0,

0

5

, NA

 9.97

(.09)

 Pelagic

Longline

93-97 NA Obs. Data

Logbook

 .06, .05,

.06, .03, .04

 0, 0, 0, 0,

0

 0, 0, 0, 0, 0 0, 0, 0, 0,

0, 0, 0 0 

TOTAL 9.9

 (.09)

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 and 1995 shown, other years not available on an annual basis.

4 For 1991-1993, pooled bycatch rates were used to estimate bycatch in months that had fishing effort but did not have observer

coverage. This method is described in Northridge (1996). In 1994 and 1995, observer coverage increased substantially, and

bycatch rates were not pooled for this period . 

5 Estimates were based on 2 seasons. The two observed takes were during the winter season when observer coverage was 100%.

6 Annual mortality estimates do not include any animals injured and released alive.

7 The fishery did not operate in 1997; the average annual mortality is based on the number of years (4; 1993- 1996) that

the fishery operated.
119

Table 3. Summary of spotted dolphins (Stenella sp.) released alive, by commercial fishery, years sampled (Years), ratio of

observed mortalities recorded by on-board observers to the estimated mortality (Ratio), the number of observed animals

released alive and injured (Injured), and the number of observed animals released alive and uninjured (Uninjured)

Fishery Years Ratio Injured2 Uninjured

Pelagic longline 93-97 0, 0, 0, 0, 0 0,11, 0, 0, 0 0, 11, 0, 0, 0

1 See Appendix 1.

2 Annual mortality estimates do not include any animals injured and released alive.

Other Mortality

From 1995-1997, 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 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 status of this stock has been

changed from strategic to non-strategic because the estimated annual fishery-related mortality and serious injury are below PBR.

REFERENCES

Barlow, J., S.L. Swartz, T.C. Eagle, and P.R. Wade. 1995. U.S. Marine Mammal Stock Assessments: Guidelines for Preparation,

Background, and a Summary of the 1995 Assessments. U.S. Dep. Commer., NOAA Tech. Memo. NMFS-OPR-6, 73 pp.

Buckland, S.T., D.R. Anderson, K.P. Burnham and J.L. Laake. 1993. Distance sampling: estimating abundance of biological

populations. Chapman and Hall, New York, NY, 442 pp.

CETAP. 1982. A characterization of marine mammals and turtles in the mid- and north Atlantic areas of the U.S. outer continental

shelf. Cetacean and Turtle Assessment Program, University of Rhode Island. Final Report, Contract AA51-C78-48, Bureau of

Land Management, Washington, DC, 538 pp. 

Cramer, J. 1994. Large pelagic logbook newsletter - 1993. NOAA Tech. Mem. NMFS-SEFSC-352, 19 pp. 

Johnson, D.R., C.A. Brown, and C. Yeung. 1999. Estimates of marine mammal and marine turtle catch by the US Atlantic pelagic

longline fleet in 1992-1997. NOAA Tech. Mem. NMFS-SEFSC-418, 70p.

Mullin, K., W. Hoggard, C. Roden, R. Lohoefener, C. Rogers and B. Taggart. 1991. Cetaceans on the upper continental slope in the

north-central Gulf of Mexico. OCS Study/MMS 91-0027. U.S. Dept. of the Interior, Minerals Management Service, Gulf of

Mexico OCS Regional Office, New Orleans, Louisiana, 108 pp. 

Northridge, S. 1996. Estimation of cetacean mortality in the U.S. Atlantic swordfish and tuna drift gillnet and pair trawl fisheries.

Final report to the Northeast Fisheries Science Center, Contract No. 40ENNF500045, 18 pp. 

Palka, D. 1995. Abundance estimate of the Gulf of Maine harbor porpoise. Pp. 27-50. In: A. Bjørge and G.P. Donovan (eds.).

Biology of the Phocoenids. Rep. int Whal. Commn. Special Issue 16.

Perrin, W. F.,E. D. Mitchell, J. G. Mead, D. K. Caldwell, M. C. Caldwell, P. J. H. van Bree, and W. H. Dawbin. 1987. Revision of

the spotted dolphins, Stenella sp. Mar. Mamm. Sci. 3(2): 99-170.

Perrin, W. F., D. K. Caldwell, and M. C. Caldwell. 1994. Atlantic spotted dolphin. Pages 173-190. In: S. H. Ridgway and R.

Harrison (eds.). Handbook of marine mammals, Volume 5: The first book of dolphins. Academic Press, San Diego, 418 pp.

Perrin, W. F. and A. A. Hohn. 1994. Pantropical spotted dolphin Stenella attenuata. Pages 71-98. In: S. H. Ridgway and R.

Harrison (eds.). Handbook of marine mammals, Vol. 5: The first book of dolphins. Academic Press, San Diego, 418 pp. 

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

Special Issue 15: 133-147. 

Scott, G.P. and C.A. Brown. 1997. Estimates of marine mammal and marine turtle catch by the US 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-OPR-012, 93 pp.
120

Figure 1. Distribution of bottlenose dolphin sightings

from NEFSC shipboard and aerial surveys during the

summer in 1990-1995. Isobaths are at 100 m and 1,000

m. 

October 1999

BOTTLENOSE DOLPHIN (Tursiops truncatus):

Western North Atlantic Offshore Stock

STOCK DEFINITION AND GEOGRAPHIC RANGE

There are two hematologically and morphologically distinct bottlenose dolphin ecotypes (Duffield et al. 1983; Duffield 1986)

which correspond to a shallow, warm water ecotype and a deep, cold water ecotype; both ecotypes have been shown to inhabit

waters in the western North Atlantic Ocean (Hersh and Duffield 1990; Mead and Potter 1995; Curry and Smith 1997). 

Bottlenose dolphins which had stranded alive in the western North Atlantic in areas with direct access to deep oceanic waters

had hemoglobin profiles which matched that of the deep, cold water ecotype (Hersh and Duffield 1990). Hersh and Duffield (1990)

also described morphological differences between the deep, cold water ecotype dolphins and dolphins with hematological profiles

matching the shallow, warm water ecotype which had

stranded in the Indian/Banana River in Florida. Based on the

distribution of sightings during ship-based surveys (Figure 1)

and survey personnel observations (NMFS unpublished data),

the western North Atlantic offshore stock is believed to

consist of bottlenose dolphins corresponding to the

hematologically and morphologically distinct deep, cold water

ecotype.

Extensive aerial surveys in 1979-1981 indicated that the

stock extended along the entire continental shelf break from

Georges Bank to Cape Hatteras during spring and summer

(CETAP 1982; Kenney 1990). The distribution of sightings

contracted towards the south in the fall and the central portion

of the survey area was almost devoid of sightings in the

winter, although there were still sightings as far north as the

southern edge of Georges Bank. The offshore stock is

concentrated along the continental shelf break in waters of

depths > 25 m and extends beyond the continental shelf into

continental slope waters in lower concentration (Figure 1)

consistent with Kenney 1990. In Canadian waters, bottlenose

dolphins have occasionally been sighted on the Scotian Shelf,

particularly in the Gully (Gowans and Whitehead 1995;

NMFS unpublished data). Dolphins with characteristics of

the offshore type have been stranded as far south as the

Florida Keys, but there are no abundance or distribution

estimates available for this stock in USA Exclusive Economic

Zone (EEZ) waters south of Cape Hatteras. 

POPULATION SIZE

The total number of bottlenose dolphins off the Atlantic USA coast is unknown; however, six abundance estimates are available

for portions of the northeastern USA Atlantic during fall of 1978-82, August 1990, June - July 1991, August-September 1991, JuneJuly 1993, and July - September 1995 (Table 1 and Figure 1).

A population size of 7,696 offshore bottlenose dolphins (CV=0.58) was estimated from an aerial survey program conducted from

1978 to 1982 on the continental shelf and shelf edge waters between Cape Hatteras, North Carolina and Nova Scotia (Table 1;

CETAP 1982). The estimate is based on fall data only, because the greatest proportion of the population off the northeast USA coast

appeared in the study area the fall. This estimate does not include a correction for dive-time or g(0), the probability of detecting an

animal group on the track line. This estimate may not reflect the current true population size because of its high degree of uncertainty

(e.g., large CV), its old age, and it was estimated just after cessation of extensive foreign fishing operations in the region.
121

A population size of 2,903 offshore bottlenose dolphins (CV=0.66) 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 (Table 1; Waring

et al. 1992). Data were collected by one team that searched by naked eye and 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.

A population size of 9,106 offshore bottlenose dolphins (CV=0.36) 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 (Table 1;

Waring et al. 1992; Waring 1998). Data were collected by one team that searched by naked eye and analyzed using DISTANCE

(Bucklandet al. 1993; Laake et al. 1993). Estimates include school size-bias, if applicable, but no corrections for g(0) or dive-time.

Variability was estimated using bootstrap resampling techniques.

A population size of 12,090 (CV=0.38) and 12,760 (CV=0.84) offshore bottlenose dolphins was estimated from line transect

aerial surveys conducted from August to September 1991 using the Twin Otter and AT-11, respectively (Table 1; Anon. 1991). The

study area included that covered in the CETAP study plus several additional continental slope survey blocks. Due to weather and

logistical constraints, several survey blocks south and east of Georges Bank were not surveyed. The data were analyzed using

DISTANCE (Buckland et al. 1993; Laake et al. 1993), where the CV was estimated using the bootstrap option. The abundance

estimates do not include g(0) and were not pooled over platforms because the inter-platform calibration analysis has not been

conducted.

A population size of 716 offshore bottlenose dolphins (CV=0.44) 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

bootstrap resampling techniques.

A population size of 13,453 offshore bottlenose dolphins (CV=0.54) 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; NMFS unpublished data). Total track line length was 32,600 km (17,600 nmi). 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. Shipboard data were collected using a two independent sighting

team procedure and were analyzed using the product integral method (Palka 1995) and DISTANCE (Buckland et al. 1993).

Shipboard estimates were corrected for g(0) and, if applicable, also for school size-bias. Standard aerial sighting procedures with two

bubble windows and one belly window observer were used during the aerial survey. An estimate of g(0) was not made for the aerial

portion of the survey. Estimates do not include corrections for dive-time. Variability was estimated using bootstrap resampling

techniques.

Although the 1990-1995 surveys did not sample the same areas or encompass the entire offshore bottlenose dolphin habitat, they

did focus on segments of known or suspected high-use habitats off the northeastern USA coast. The collective 1990-95 data suggest

that, seasonally, at least several thousand bottlenose dolphins are occupying these waters; however, survey coverage to date is not

judged adequate to provide a definitive estimate of bottlenose dolphin abundance in the western North Atlantic because of the limited

scope of the shipboard surveys. The best available current abundance estimate for offshore bottlenose dolphins is 13,453 (CV=0.54)

as estimated from the July to September 1995 line transect survey (NMFS unpublished data) because this survey is recent and

provided the most complete coverage of the known habitat.
122

Table 1. Summary of abundance estimates for the western North Atlantic offshore bottlenose 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

fall 1978-82 Cape Hatteras, NC to Nova Scotia 7,676 0.58

Aug 1990 Gulf Stream 2,903 0.66

Jun-Jul 1991 Cape Hatteras, NC to Georges Bank,

shelf edge only

9,106 0.36

Aug-Sep 1991 Cape Hatteras, NC to Nova Scotia 12,090 and

12,760*

0.38 and

0.84*

Jun-Jul 1993 Georges Bank to Scotian shelf, shelf

edge only

716 0.44

Jul-Sep 1995 Virginia to Gulf of St. Lawrence 13,453 0.54

* From data collected on the Twin Otter and AT-11, respectively.

Minimum Population Estimate

The minimum population estimate is the lower limit of the two-tailed 60% confidence interval of the log-normally distributed

best abundance estimate. This is equivalent to the 20th percentile of the log-normal distribution as specified by Wade and Angliss

(1997). The best estimate of abundance for offshore bottlenose dolphins is 13,453 (CV=0.54). The minimum population estimate

for the western North Atlantic offshore bottlenose is 8,794 (CV=0.54).

Current Population Trend

The data are insufficient to determine population trends.

CURRENT AND MAXIMUM NET PRODUCTIVITY RATES

Current and maximum net productivity rates are unknown for this stock. For purposes of this assessment, the maximum net

productivity rate was assumed to be 0.04. This value is based on theoretical modeling showing that cetacean populations may not

grow at rates much greater than 4% given the constraints of their reproductive life history (Barlow et al. 1995). 

POTENTIAL BIOLOGICAL REMOVAL

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

a “recovery” factor (MMPA Sec. 3. 16 U.S.C. 1362; Wade and Angliss 1997). The minimum population size for offshore bottlenose

dolphins is 8,794 (CV=0.54). The maximum productivity rate is 0.04, the default value for cetaceans. The “recovery” factor, which

accounts for endangered, depleted, threatened stocks, or stocks of unknown status relative to optimum sustainable population (OSP)

is assumed to be 0.5 because this stock is of unknown status. PBR for the western North Atlantic offshore bottlenose dolphin is

88.

ANNUAL HUMAN-CAUSED MORTALITY AND SERIOUS INJURY

 Total annual estimated average fishery-related mortality or serious injury to this stock during 1993-1997 was 10 bottlenose

dolphins (CV = 0.07). 

Fishery Information

There was no documentation of marine mammal mortality or serious injury in distant-water fleet (DWF) activities off the

northeast coast of the USA prior to 1977. A fisheries observer program which recorded fishery data and information on incidental

by-catch of marine mammals was established with implementation of the Magnuson Fisheries Conservation and Management Act

(MFCMA) in 1977. DWF effort in the USA Atlantic EEZ under MFCMA was directed primarily towards Atlantic mackerel and

squid. An average of 120 different foreign vessels per year (range 102-161) operated within the Atlantic coast EEZ from 1977
123

through 1982. In 1982, the first year that the NMFS Northeast Regional Observer Program assumed responsibility for observer

coverage of the longline vessels, there were 112 different foreign vessels, eighteen (16%) of which were Japanese tuna longline vessels

operating along the USA east coast. Between 1983 and 1991, the number of foreign fishing vessels operating within the 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 1991 season. Observers in this program recorded

nine bottlenose dolphin mortalities in foreign-fishing activities during 1977-1988 (Waring et al. 1990). Seven takes occurred in the

mackerel fishery, and one bottlenose dolphin each was caught in both the squid and hake trawl fisheries. 

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

self-reported fisheries information system for large pelagic fisheries. Data files are maintained at the Southeast Fisheries Science

Center (SEFSC). The Northeast Fisheries Science Center (NEFSC) Sea Sampling Observer Program was initiated in 1989, and since

that year several fisheries have been covered by the program. In late 1992 and in 1993, the SEFSC provided observer coverage of

pelagic longline vessels fishing off the Grand Banks (Tail of the Banks) and provides observer coverage of vessels fishing south of

Cape Hatteras. 

By-catch has been observed by NMFS Sea Samplers in the pelagic drift gillnet, pelagic pair trawl, and North Atlantic bottom trawl

fisheries, but no mortalities have 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 pilot whales have been reported; however, a vessel may fish in more than

one statistical reporting area and it is not possible to separate estimates of fishing effort other than to subtract Gulf of Mexico effort

from Atlantic fishing effort, which includes the Caribbean Sea. Total effort, excluding the Gulf of Mexico, for the pelagic longline

fishery, based on mandatory self-reported fisheries information, was 11,279 sets in 1991, 9,869 sets in 1992, 9,862 sets in 1993,

9,481 sets in 1994, 10,129 sets in 1995, 9,885 sets in 1996, and 8,023 sets in 1997 (Cramer 1994; Scott and Brown 1997; Johnson

et al. 1999). Since 1992, this fishery has been monitored with about 5% observer coverage, in terms of trips observed, within every

statistical reporting area within the EEZ and beyond. Off the USA Atlantic coast, the fishery has been observed from January to

March off Cape Hatteras, in May and June in the entire Mid-Atlantic, and in July through December in the Mid-Atlantic Bight and

off Nova Scotia. This fishery has been monitored with about 5% observer coverage, in terms of trips observed, since 1992. The

1993-1997, estimated take was based on a revised analysis of the observed incidental take and self-reported incidental take and effort

data, and replace previous estimates for the 1992-1993 and 1994-1995 periods (Cramer 1994; Scott and Brown 1997; Johnson et

al. 1999). Most of the estimated marine mammal by-catch was from EEZ waters between South Carolina and Cape Cod (Johnson

et al. 1999). In 1993 two bottlenose dolphins were hooked and released alive (Table 3). The 1992-1997, estimated take was based

on a revised analysis of the observed incidental take and self-reported incidental take and effort data, and replace previous estimates

for the 1992-1993 and 1994-1995 periods (Scott and Brown 1997; Johnson et al. 1999).

Pelagic Drift Gillnet

The estimated total number of hauls in the pelagic drift gillnet fishery increased from 714 in 1989 to 1,144 in 1990; thereafter,

with the introduction of quotas, effort was severely reduced. The estimated number of hauls in 1991, 1992, 1993, 1994, 1995, and

1996 were 233, 243, 232, 197,164, and 149 respectively. In 1996 and 1997, the NMFS issued management regulations which

prohibited the operation of this fishery in 1997. Further, in January 1999 the NMFS issued a Final Rule to prohibit the use of

driftnets (i.e., permanent closure) in the North Atlantic swordfish fishery (50 CFR Part 630). Fifty-nine different vessels participated

in this fishery at one time or another between 1989 and 1993. Since 1994, between 10-12 vessels have participated in the fishery

(Table 2). Observer coverage, expressed as percent of sets observed, was 8% in 1989, 6% in 1990, 20% in 1991, 40% in 1992, 42%

in 1993, 87% in 1994, 99% in 1995, and 64% in 1996. Effort was concentrated along the southern edge of Georges Bank and off Cape

Hatteras. Examination of the species composition of the catch and locations of the fishery throughout the year, suggested that the

pelagic drift gillnet fishery be stratified into two strata, a southern or winter stratum, and a northern or summer stratum. Estimates

of the total by-catch, from 1989 to 1993, were obtained using the aggregated (pooled 1989-1993) catch rates, by strata (Northridge

1996). Estimates of total annual by-catch for 1994 and 1995 were estimated from the sum of the observed caught and the product

of the average bycatch per haul and the number of unobserved hauls as recorded in self-reported fisheries information. Variances were

estimated using bootstrap re-sampling techniques. Fifty-seven bottlenose dolphin mortalities have been observed between 1989 and

1996. Estimated bottlenose dolphin kills (CV in parentheses) extrapolated for each year were 72 in 1989 (0.18), 115 in 1990 (0.18),
124

26 in 1991 (0.15), 28 in 1992 (0.10), 22 in 1993 (0.13), 14 in 1994 (0.04), 5 in 1995 (0), and zero in 1996. Mean annual estimated

fishery-related mortality for this fishery in 1993-1997 was 10 bottlenose dolphins (CV = 0.07) (Table 2). 

Pelagic Pair Trawl

Effort in the pelagic pair trawl fishery increased during the period 1989 to 1993, from zero hauls in 1989 and 1990, to an

estimated 171 hauls in 1991, and then to an estimated 536 hauls in 1992, 586 in 1993, 407 in 1994, and 440 in 1995, respectively.

This fishery ceased operations in 1996, when NMFS rejected a petition to consider pair trawl gear as an authorized gear type in

Atlantic tunas fishery. The fishery operated from August-November in 1991, from June-November in 1992, from June-October in

1993 (Northridge 1996), and from mid-summer to November in 1994 and 1995. Sea sampling began in October 1992 (Gerrior et al.

1994), and 48 sets (9% of the total) were sampled in that season, 102 hauls (17% of the total) were sampled in 1993. In 1994 and

1995, 52% and 55%, respectively, of the sets were observed. Nineteen vessels have operated in this fishery. The fishery extends

from 35oN to 41oN, and from 69EW to 72EW. Approximately 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 by-catch, showed little seasonal change for

the six months of operation and did not warrant any seasonal or areal stratification of this fishery (Northridge 1996). Thirty-two

bottlenose dolphin mortalities were observed between 1991 and 1995. Estimated annual fishery-related mortality (CV in parentheses)

was 13 dolphins in 1991 (0.52), 73 in 1992 (0.49), 85 in 1993 (0.41), 4 in 1994 (0.40) and 17 in 1995 (0.26). Since this fishery no

longer exists, it has been excluded from Tables 2 and 3. During the 1994 and 1995 experimental fishing seasons, fishing gear

experiments were conducted to collect data on environmental parameters, gear behavior, and gear handling practices to evaluate factors

affecting catch and bycatch (Goudey 1995, 1996). Results of these studies have been presented at Offshore Cetacean Take Reduction

Team Meetings.

North Atlantic Bottom Trawl:

Vessels in the North Atlantic bottom trawl fishery, a Category III fishery under the MMPA, were observed in order to meet

fishery management needs, rather than marine mammal management needs. An average of 970 (CV = 0.04) vessels (full and part time)

participated annually in the fishery during 1989-1993. The fishery is active in New England waters in all seasons. One bottlenose

dolphin mortality was documented in 1991 and the total estimated mortality in this fishery in 1991 was 91 (CV=0.97). Since 1992

there were no bottlenose mortalities observed in this fishery.

Squid, Mackerel and Butterfish:

The mid-Atlantic mackerel and squid trawl fisheries were combined into the Atlantic squid, mackerel and butterfish trawl fishery

in 1996. These fisheries operate seasonally, principally in the USA mid-Atlantic and southern New England continental shelf region.

The mackerel trawl fishery was classified as a Category II fishery since 1990 and the squid fishery was originally classified as a

Category II fishery in 1990, but was reclassified as a Category III fishery in 1992. The combined fishery has been proposed for

classification as a Category II fishery. In 1996, mackerel, squid, and butterfish trawl fisheries were combined into the Atlantic squid,

mackerel, and butterfish trawl fishery, and maintained a Category II classification. Although there were reports of bottlenose dolphin

mortalities in the foreign fishery during 1977-1988, there were no fishery-related mortalities of bottlenose dolphins reported in the

self-reported fisheries information from the mackerel trawl fishery between 1990-1992.
125

Table 2. Summary of the incidental mortality of bottlenose dolphins (Tursiops truncatus) by commercial fishery including the

years sampled (Years), the number of vessels active within the fishery (Vessels), the type of data used (Data Type), the

annual observer coverage (Observer Coverage), the mortalities recorded by 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

Pelagic Drift

Gillnet693-97

1994=123

1995=11

1996=10

Obs. Data

Logbook

 .42, .87,

.99, .64,

NA

 6, 12, 5,

0, NA

 22, 13, 5.04,

0, NA

 .13, .05, 0,

0, NA

(10)

(0.07)

TOTAL (10)

(0.07)

1 Observer data (Obs. Data) are used to measure bycatch rates, and the data are collected within the Northeast Fisheries Science

Center (NEFSC) Sea Sampling Program. NEFSC collects weighout (Weighout) landings data, and total landings are used as a

measure of total effort for the coastal gillnet fishery and trips are used as total effort for the North Atlantic bottom trawl fishery.

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 North Atlantic

bottom trawl fishery is in days fished. Assessments for the coastal gillnet fishery have not been completed. The number of trips

sampled by the NEFSC Sea Sampling Program are reported here.

3 1994-1996 shown, other years not available on an annual basis.

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 0.42 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 increase by 0.03 animals.

5 Annual mortality estimates do not include any animals injured and released alive.

6 The fishery did not operate in 1997; the average annual mortality is based on the number of years (4; 1993-1996) that the fishery

operated.

Table 3. Summary of bottlenose dolphins (Tursiops truncatus) released alive, by commercial fishery, years sampled (Years), ratio

of observed mortalities recorded by on-board observers to the estimated mortality (Ratio), the number of observed animals

released alive and injured (Injured), and the number of observed animals released alive and uninjured (Uninjured)

Fishery Years Ratio Injured1 Uninjured

 Pelagic Longline 93-97 0, 0, 0, 0, 0 0, 0, 0, 0, 0 0, 0, 0, 0, 0

1 Injured and released alive animals are not included in the Table 2 mortality estimates.

Other Mortality

 Bottlenose dolphins are one of the most frequently stranded small cetacean along the Atlantic coast. Many of the animals show

signs of human interaction (i.e., net marks, mutilation, etc.). The estimated number of animals that represent the offshore stock are

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 Endangered Species Act. There are insufficient data to determine the population

trends for this species. This level is not less than 10% of the calculated PBR and, therefore, cannot be considered to be insignificant
126

and approaching zero mortality and serious injury rate. Average 1993-1997 annual fishery-related mortality and serious injury does

not exceed the PBR; therefore, this is not a strategic stock.

REFERENCES

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.

Barlow, J., S.L. Swartz, T.C. Eagle, and P.R. Wade. 1995. U.S. Marine Mammal Stock Assessments: Guidelines for Preparation,

Background, and a Summary of the 1995 Assessments. U.S. Dep. Commer., NOAA Tech. Memo. NMFS-OPR-6, 73 pp.

Buckland, S. T., D. R. Andersen, K. P. Burnham, and J. L. Laake. 1993. Distance sampling: Estimating abundance of biological

populations. Chapman and Hall, New York, 446 pp. 

CETAP (Cetacean and Turtle Assessment Program). 1982. A Characterization of Marine Mammals and Turtles in the Mid- and

North Atlantic Areas of the U.S. Outer Continental Shelf, Final Report, Contract AA551-CT8-48, U.S. NTIS PB83-215855,

Bureau of Land Management, Washington, DC, 576 pp. 

Cramer J. 1994. Large pelagic logbook newsletter - 1993. NOAA Tech. Mem. NMFS-SEFSC-352, 19 pp.

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.), Molecular genetics of

marine mammals. Spec. Publ. 3 Society for Marine Mammalogy.

Duffield, D. A. 1986. Investigation of genetic variability in stocks of the bottlenose dolphin (Tursiops truncatus). Final report

to the NMFS/SEFSC, Contract No. NA83-GA-00036, 53 pp. 

Duffield, D. A., Ridgway, S. H., and Cornell, L. H. 1983. Hematology distinguishes coastal and offshore forms of dolphins

(Tursiops). Can. J. Zool. 61: 930-933.

Gerrior, P., A.S. Williams, and D.J. Christensen. 1994. Observations of the 1992 U.S. pelagic pair trawl fishery in the Northwest

Atlantic. U.S. Mar. Fish. Rev. 56(3): 24-27.

Goudy, C.A. 1995. The 1994 experimental pair trawl fishery for tuna in the northwest Atlantic, MITSG 95-6, Cambridge, MA. 10

pp.

Goudy, C.A. 1996. The 1995 experimental pair trawl fishery for tuna in the northwest Atlantic, MITSG 95-6, Cambridge, MA. 13

pp.

Gowans S. and H. Whitehead. 1995. Distribution and habitat partitioning by small odontocetes in the Gully, a submarine canyon

on the Scotian Shelf. Can. J. Zool. 73: 1599-1608.

Hersh, S. L. and D. A. Duffield. 1990. Distinction between northwest Atlantic offshore and coastal bottlenose dolphins based on

hemoglobin profile and morphometry. 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 US Atlantic pelagic

longline fleet in 1992-1997. NOAA Tech. Mem. NOAA-SEFSC-418, 70p.

Kenney, R. D. 1990. Bottlenose dolphins off the northeastern United States. Pages 369-386 in S. Leatherwood and R. R. Reeves

(eds), The bottlenose dolphin, Academic Press, San Diego, 653 pp. 

Laake, J. L., S. T. Buckland, D. R. Anderson, and K. P. Burnham. 1993. DISTANCE user’s guide, V2.0. Colorado Cooperative Fish

& Wildlife Research Unit, Colorado State University, Ft. Collins, Colorado, 72 pp. 

Mead, J.G. and C.W. Potter. 1995. Recognizing two populations for the bottlenose dolphin (Tursiopstruncatus) off the Atlantic

coast of North America: morphologic and ecologic considerations. International Biological Research Institute Reports

5:31-43. 

Northridge, S. 1996. Estimation of cetacean mortality in the U.S. Atlantic swordfish and tuna drift gillnet and pair trawl fisheries.

Final report to the Northeast Fisheries Science Center, Contract No. 40ENNF500045. 18 pp. 

Palka, D. 1995. Abundance estimate of the Gulf of Maine harbor porpoise. pp. 27-50 in: A. Bjørge and G.P. Donovan (eds.) Biology

of the Phocoenids. Rep. int Whal. Commn. Special Issue 16.

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. 1998. Results of the summer 1991 R/V Chapman marine mammal sighting survey. NOAA NMFS NEFSC, Lab. Ref.

Doc. No. 98-09, 21pp. Northeast Fisheries Science Center, Woods Hole, Massachusetts. 
127

Waring, G. T., P. Gerrior, P. M. Payne, B. L. Parry and J. R. Nicolas. 1990. Incidental take of marine mammals in foreign fishery

activities off the northeast United States, 1977-1988. Fish. Bull., U.S. 88(2): 347-360.

Waring, G. T., C. P. Fairfield, C. M. Ruhsam and M. Sano. 1992. Cetaceans associated with Gulf Stream features off the

northeastern USA shelf. ICES Marine Mammals Comm. CM 1992/N: 12, 29 pp.
128

8 0 7 5

3 0

3 5

4 0

Cape Hatteras

Cape Canaveral

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 one km of

shore from New Jersey to mid-Florida during the summer in 1994,

and during vessel surveys from about the 30 m isobath to the offshore

extent of the US EEZ in 1998.

October 1999

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. in press); a shallow, warm water ecotype and a

deep, cold water ecotype which correspond to nearshore and

offshore forms, respectively. Both ecotypes have been shown

to inhabit waters in the western North Atlantic Ocean (Hersh

and Duffield 1990; Mead and Potter 1995; Hoelzel et al.

1998; Walker et al. in press). The inshore and offshore forms,

of all age classes, can be positively identified based on

differences in morphometrics, parasite loads, and prey (Mead

and Potter 1995). Hoelzel 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 stranded alive in the western North Atlantic in areas with

direct access 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

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. Because of their

occurrence in shallow, relatively warm waters along the USA

Atlantic coast and because their morphological characteristics

are similar to the shallow, warm water ecotype described by

Hersh and Duffield (1990), the Atlantic coastal bottlenose

dolphin stock is believed to consist of this ecotype or

nearshore form. Furthermore, Hoelzel et al. (1998)

genetically identified a sample of animals captured or

incidentally caught in nearshore waters as the nearshore form.

Currently, data are insufficient to allow separation of locally

resident bottlenose dolphins found in bays, sounds and

estuaries (such as those from the Indian/Banana River) from

the coastal stock in the western North Atlantic; Hoelzel et al.

(1998) found less variation in nuclear and mtDNA markers

among their sample of nearshore animals, which likely included resident and coastal animals, than their sample of offshore animals.

The structure of the coastal bottlenose dolphin stock in the western North Atlantic is uncertain, but what is known about it

suggests that the structure is complex. Some portion of the coastal stock migrates north of Cape Hatteras, North Carolina, to New

Jersey during the summer (Scott et al. 1988). It has been suggested that this stock is restricted to waters < 25 m in depth within

the northern portion of its range (Kenney 1990) because of an apparent concentration of bottlenose dolphins centered on the 25 m

isobath which was 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
129

Year-round

residents

Small 

home

ranges

Seasonal

residents

Su

Wi

Su

Wi

Su

Wi

Large

home 

ranges

Large

range

Multiple Stocks

Migratory

groups

Stock

Su

Wi

Long-range

movements

Cape

May

Virginia

Beach

Beaufort

Wilmington

Charleston

Jacksonville

One

Figure 2. Illustration of stock structure hypotheses of Atlantic coastal bottlenose

dolphins: one stock ranging from New Jersey to Florida or multiple stocks which may

include: 1) year-round residents with small home ranges; 2) multiple, contiguous,

seasonally resident groups with relatively large home ranges; and 3) groups with

long-range migratory pattern.

Location

Yearround

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

Table I. Residency and movement patterns of bottlenose

dolphins documented from photo-identification (from Hohn

1997).

continental shelf edge. The coastal stock is believed to reside south of Cape Hatteras in the late winter (Mead 1975; Kenney 1990);

however, the depth 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 density patterns along

the USA Atlantic coast. Figure 1 illustrates the distribution of 696 bottlenose dolphin herd sightings during aerial surveys from shore

to approximately 9 km past the Gulf Stream edge south of Cape Hatteras in the winter in 1992 (Blaylock and Hoggard 1994), from

shore seaward to the 25 m isobath during the summer north of Cape Hatteras in 1994 (Blaylock 1995), within one km of the shore

from New Jersey to mid-Florida during three replicate coastal surveys conducted during the summer in 1994 (Blaylock 1995), and

from about the 30 m isobath to the offshore extent of the USA Exclusive Economic Zone (EEZ) during a vessel survey for pelagic

cetaceans in 1998 (NMFS unpublished data).

The proportion of the sightings illustrated

which might be of bottlenose dolphins from

other than the coastal stock is unknown;

however, it is reasonable to assume that the

coastal surveys within one km of shore

minimized inclusion of the offshore stock.

Gathering information to distinguish between

coastal and offshore ecotypes is currently an

active area of research by the NMFS

Southeast Fisheries Science Center (SEFSC),

as is research to determine the relationship

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 determine the stock

structure of Atlantic coastal bottlenose

dolphins was initiated in late 1996. Figure 2

illustrates the stock structure hypotheses

that are being considered. 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 independent analyses including genetics,

isotope ratios, contaminants, movement 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 residents, and migratory groups. 

Site-specific, year-round residents have been reported only in

the southern part of the range, from Charleston, SC (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
130

through photo-identification of naturally-marked animals, and of 31 individuals animals that were live-captured and freeze-branded

in Beaufort, NC in 1995 (Hansen and Wells 1996). Complex patterns of movement and residency were observed 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 communities identified in embayments and coastal areas in the northern

Gulf of Mexico (e.g. Scott et al. 1990; Weller 1998; 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 determining stock

structure, movements, and degree of mixing of these presumed 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 report of Western North Atlantic Coastal Stock of bottlenose dolphins to reflect the

number of stocks described.

POPULATION SIZE

 Mitchell (1975) estimated that the coastal bottlenose dolphin population which was exploited by a shore-based net fishery until

1925 (Mead 1975) 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 survey using standard line

transect sampling with perpendicular 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 Hoggard 1994). Systematic transects

were placed randomly with respect to bottlenose dolphin 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 perpendicular distance sighting

data. Bottlenose dolphin abundance was estimated to be 12,435 dolphins with coefficient of variation (CV) = 0.18 and the log-normal

95% confidence interval was 9,684-15,967 (Blaylock and Hoggard 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 and are considered to be preliminary in nature. 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 8,695-18,173.

An aerial survey of the coastal waters within a one km strip along the shore from Sandy 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 Hatteras to approximately Vero Beach (southern area). The

average of three counts of bottlenose dolphins in the northern area was 927 dolphins (range = 303-1,667) and the average of three
131

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 dolphins. 

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 unknown number of these herds were likely the offshore bottlenose dolphin ecotype. One of the herds sighted was

exceptionally large and was estimated to consist of 251 individuals. 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 ecotypes in USA Atlantic EEZ 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 geographic mixing of these two ecotypes is currently an active

area of research by the NMFS, SEFSC. 

Minimum Population Estimate

Reasonable assurance of a minimum population estimate can not be provided by line transect surveys because the proportion

of dolphins from the offshore stock which might have been observed is unknown. 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 Beach 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 population size estimate for the western North Atlantic coastal bottlenose dolphin stock is 2,482

dolphins. 

Current Population Trend

 Kenney (1990) reported an estimated 400-700 bottlenose dolphins from the inshore strata of aerial surveys conducted along the

USA Atlantic coast north of Cape Hatteras in the summer during 1979-1981. These estimates resulted from line transect analyses;

thus, they cannot be used in comparison with the direct count data collected in 1994 to assess population 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 1994) in spite of the 1987-88 mortality incident during which it was estimated that the coastal migratory population

may have been reduced by up to 53% (Scott et al. 1988). 

CURRENT AND MAXIMUM NET PRODUCTIVITY RATES

Current and maximum net productivity rates are not known for this stock. The maximum net productivity rate was assumed to

be 0.04. This value is based on theoretical modeling showing that cetacean populations may not grow at rates much greater than 4%

given the constraints of their reproductive life history (Barlow et al. 1995). 

POTENTIAL BIOLOGICAL REMOVAL

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

listed as depleted under the Marine Mammal Protection Act. Therefore, PBR for the USA Atlantic coastal bottlenose dolphin stock

is 25 dolphins. 

ANNUAL HUMAN-CAUSED MORTALITY AND SERIOUS INJURY

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
132

Gear Type Effort

Haul seines 222

Purse seines 11,962

Otter trawls, bottom 22,550

Otter trawls, midwater 70

Gillnets, anchored or staked 22,252

Gillnets, drift and runaround 11,792

Table III. Roughly estimated average annual fishing

effort (number deployed) by gear type for U.S. Atlantic

coastal fisheries from New Jersey to Key West, Florida, in

1992-1993, having the potential for causing serious

injury or mortality to bottlenose dolphins (NMFS

unpublished data).

Table II. Bottlenose dolphin strandings in the U.S. Southeast

Atlantic (North Carolina to Florida) from 1993 to 1997. 

Data from Southeast Marine Mammal Stranding Database

(SEUS).

State 1993 1994 1995 1996 1997

Tota

l

North Carolina

No. Stranded 78 51 80 70 127 406

No. Human Interactions 18 14 18 14 36 100

% With Human

Interactions 23% 27% 22% 20% 28% 25%

South Carolina

No. Stranded 33 19 32 29 41 154

No. Human Interactions 1 1 3 5 9 19

% With Human

Interactions 3% 5% 9% 17% 22% 12%

Georgia

No. Stranded 29 13 17 17 18 94

No. Human Interactions 0 3 1 2 1 7

% With Human

Interactions 0% 23% 6% 12% 6% 7%

Florida

No. Stranded 111 62 91 104 104 472

No. Human Interactions 6 6 2 1 7 22

% With Human

Interactions 5% 10% 2% 1% 7% 5%

Puerto Rico

No. Stranded 0 1 1 1 0 3

No. Human Interactions 0 0 0 1 0 1

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 1996-1997. 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 149 of 1,129 (13%)

of the bottlenose dolphin strandings investigated in the USA Southeast Atlantic region (North Carolina to Florida) from 1993 to 1997

(Table II) 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. 

North Carolina stranding records show the highest incidence of fishery interactions from the SE Atlantic Region. North Carolina

data from 1993 through 1997 indicate that 100 of 406 animals, or 25% showed evidence of human interactions. In 1997, 127

bottlenose dolphin stranded in North Carolina. Cause of death could be determined for only 58 of these animals, and of these 36 or

62.1% exhibited positive signs of fisheries interactions. If this percentage is consistent for all North Carolina stranded animals, it

is possible that approximately 78 or 62% of the stranded animals died

from human interactions in 1997. 

Fishery Information

The Atlantic menhaden purse seine fishery targets the Atlantic

menhaden, 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). Menhaden purse seiners have reported an annual incidental take of

one to five bottlenose dolphins (NMFS 1991, pp. 5-73), although

observer data are not available. 

Coastal gillnets operate in different seasons targeting different species

in different states throughout the range of this stock. Most nets are
133

staked close to shore, but some are allowed to drift, and nets range in length from 91 m to 914 m. A gillnet fishery for American shad,

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 1994). It is considered likely that a few bottlenose dolphins are taken in this fishery

each year (Read 1994). 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 Outer Banks

targets bluefish in January-March. Similar mixed-species gillnet fisheries, under state jurisdiction, operate seasonally along the coast

from Florida to New Jersey, with the exclusion of Georgia. There are no estimates of bottlenose dolphin mortality or serious injury

available for these fisheries. A rough estimate of the average total annual coastal gillnet fishing effort is given in Table III.

Observer coverage of the USA Atlantic coastal gillnet fisheries for monkfish and dogfish, primarily, was initiated by the NEFSC

Sea Sampling program in July, 1993. From July to December 1993, 20 trips were observed. By 1996, 350 trips were observed,

representing about less than 5% coverage. This coastal gillnet fishery, which extends from North Carolina to New York, is actually

a combination of small vessel fisheries that target a variety of fish species, some of which operate right off the beach. The number

of vessels in this fishery is unknown, because records are held by both state and federal agencies, and have not, as of yet, been

centralized and standardized. Still, only one bottlenose dolphins has been taken in the observed trips, despite large numbers of

stranded dolphins with signs of fishery interactions indicative of gillnets. 

Because this observer program was not covering those components of the coastal gillnet complex believed to be responsible for

most of the interactions with coastal bottlenose dolphins, the NMFS initiated an observer program in 1997 to better define the

various components of the coastal gillnet fisheries and place observers on representative fishing vessels to obtain statistically reliable

information on takes of bottlenose dolphin. Although no takes of bottlenose dolphin were observed in 1997, three dolphins were

observed taken in fisheries operating off Virginia and North Carolina in 1998 (NMFS unpublished data). 

The shrimp trawl fishery operates from North Carolina through northern Florida virtually year around, moving seasonally up

and down the coast. Estimated total fishing effort is given in Table III. One bottlenose dolphin was recovered dead from a shrimp

trawl in Georgia in 1995 (Southeast USA Marine Mammal Stranding Network unpublished data), but no bottlenose dolphin mortality

or serious injury has been previously reported to NMFS. 

A haul seine fishery operates along northern North Carolina beaches during the spring and fall targeting mullet, spot, sea trout,

and bluefish. No by-catch of marine mammals has been reported to NMFS. In recent years reports of strandings with evidence of

interactions between bottlenose dolphin and both recreational and commercial crab-pot fisheries have been increasing in the Southeast

region (McFee and Brooks 1998). 

Other Mortality

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, humanrelated mortality approached PBR in each of the intervening years. The total fishery-related mortality and serious injury for this
134

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. 

REFERENCES

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Management Program through Grant #NA47OZ0287-01 from NOAA, Office of Ocean and Coastal Resource Management. 32

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Background and a Summary of the 1995 Assessments. U.S. Dep. Commer., NOAA Tech. Memo. NMFS-OPR-6, 73 pp.

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Blaylock, R. A. and W. Hoggard. 1994. Preliminary estimates of bottlenose dolphin abundance in southern U.S. Atlantic and Gulf

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Curry, B. E. 1997. Phylogenetic relationships among bottlenose dolphins (genus Tursiops) in a world-wide context. Ph.D.

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Commission, 63 pp. 

Hansen, L. J. and R.S. Wells. 1996. Bottlenose dolphin health assessment: Field report on sampling in and around Beaufort, North

Carolina, during July, 1995. NOAA Tech. Memo. NMFS-SEFSC-382, 24pp.

Hersh, S. L. and D. A. Duffield. 1990. Distinction between northwest Atlantic offshore and coastal bottlenose dolphins based on

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of the bottlenose dolphin. Proceedings of the Royal Society of London. 265:1177-1183.

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NOAA Technical Memorandum NMFS-SEFSC-401, 22 pp.

Keinath, J. A. and J. A. Musick. 1988. Population trends of the bottlenose dolphin (Tursiops truncatus) in Virginia. Final

Contract Report, Contract No. 40-GENF-800564, Southeast Fisheries Science Center, Miami, FL, 36 pp. 

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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

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McFee, W. E., D. L. Wolf, D. E. Parshley, and P. A. Fair. 1996. Investigation of marine mammal entanglement associated with a

seasonal coastal net fishery. NOAA Technical Memo. NMFS-SEFSC-38, 22pp. + 8 Tables, 5 Figures, 6 Appendices.

McFee, W. E. and W. Brooks, Jr. 1998. Fact finding meeting of marine mammal entanglement in the crab pot fishery: a summary.

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Mead, J. G. 1975. Preliminary report on the former net fisheries for Tursiops truncatus in the western North Atlantic. J. Fish.

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135

Mead, J. G. and C.W. Potter. 1995. Recognizing two populations of the bottlenose dolphin (Tursiops truncatus) off the Atlantic

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5:31-43.

Mitchell, E. 1975. Porpoise, dolphin and small whale fisheries of the world. Status and problems. int Union Conserv. Natur.

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NMFS. 1991. Proposed regime to govern the interactions between marine mammals and commercial fishing operations after October

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Odell, D. K. and E. D. Asper. 1990. Distribution and movements of freeze-branded bottlenose dolphins in the Indian and Banana

Rivers, Florida. Pages 515-540 in S. Leatherwood and R. R. Reeves (eds), The bottlenose dolphin, Academic Press, San Diego,

653 pp. 

Petricig, R. O. 1995. Bottlenose dolphins (Tursiops truncatus) in Bull Creek, South Carolina. Ph.D. Dissertation. University

of Rhode Island, USA. 298 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. 

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of bottlenose dolphins in Beaufort, NC using radio telemetry. Final Contract Report, Contract No. 40-GENF-500160, Southeast

Fisheries Science Center, Miami, FL, 36 pp.

Reif, J. S., L. J. Hansen, S. Galloway, G. Mitchum, T. L. Schmitt. In review. The relationship between chlorinated hydrocarbon

contaminants and selected health parameters in bottlenose dolphins (Tursiops truncatus) from Matagorda Bay, Texas, 1992.

Colorado State University, Fort Collins, and NMFS, Southeast Fisheries Science Center, Miami, Florida.

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near Wilmington, NC. Abstract. Fifth Annual Atlantic Coastal Dolphin Conference.

Scott, G. P., D. M. Burn, and L. J. Hansen. 1988. The dolphin dieoff: long term effects and recovery of the population.

Proceedings: Oceans '88, IEEE Cat. No. 88-CH2585-8,Vol. 3: 819-823.

Scott, M. D., R. S. Wells and A. B. Irvine. 1990. A long-term study of bottlenose dolphins on the west coast of Florida. Pp. 235-

244 In: S. Leatherwood and R. R. Reeves. The Bottlenose Dolphin. Academic Press, San Diego. 653 pp.

Wade, P. R., and R. P. Angliss. 1997. Guidelines for assessing marine mammal stocks: Report of the GAMMS Workshop April 3-5,

Seattle, Washington. U.S. Dep. Commer., NOAA Tech. Memo. NMFS-OPR-12, 93 pp.

Walker, J. L., C. W. Potter, and S. A. Macko. 1999. The diets of modern and historic bottlenose dolphin populations reflected

through stable isotopes. Marine Mammal Science 15(2): 335-350.

Wang, K. R., P. M. Payne, and V. G. Thayer. 1994. Coastal stock(s) of Atlantic bottlenose dolphin: status review and management:

Proceedings and recommendations from a workshop held in Beaufort, North carolina, 13-14 September 1993. U.S. Department

of Commerce, NOAA, NMFS Tech. Mem NMFS-OPR-4, 120 pp.

Weller, D. W. 1998. Global and regional variation in the biology and behavior of bottlenose dolphins. Ph.D. dissertation, Texas

A&M University, Galveston, TX. 142 pp.

Wells, R. S., K. W. Urian, A. J. Read, M. K. Bassos, W. J. Carr and M. D. Scott. 1996. Low-level monitoring of bottlenose dolphins

(Tursiops truncatus), in Tampa Bay, Florida: 1998-1993. NOAA Tech. Mem. NMFS-SEFSC-385, 25 pp. + 6 Tables, 8

Figures, and 4 Appendices.

Zolman, E. S. 1996. Residency patterns, relative abundance and population ecology of bottlenose dolphins (Tursiops truncatus)

in the Stono River Estuary, Charleston County, South Carolina. Master of Science thesis. University of Charleston, South

Carolina, USA. 128 pp.
136

Figure 1. Distribution of harbor porpoise sightings from

NEFSC shipboard and aerial surveys during the summer in

1990-1995. Isobaths are at 100 m and 1,000 m. 

October 1999

HARBOR PORPOISE (Phocoena phocoena):

Gulf of Maine/Bay of Fundy Stock

STOCK DEFINITION AND GEOGRAPHIC RANGE

This stock is found in USA and Canadian Atlantic waters. The distribution of harbor porpoises has been documented by sighting

surveys, strandings, and takes reported by NMFS observers in the Sea Sampling Program. During summer (July to September),

harbor porpoises are concentrated in the northern Gulf of Maine and southern Bay of Fundy region, generally in waters less than 150

m deep (Gaskin 1977; Kraus et al. 1983; Palka 1995a, b). During fall (October-December) and spring (April-June), harbor porpoises

are widely dispersed from New Jersey to Maine, with lower densities farther north and south. They are seen from the coastline into

the middle of the Gulf of Maine (> 200 m deep). During winter (January to March), intermediate densities of harbor porpoises can

be found in waters off New Jersey to North Carolina, and lower densities are found in waters off New York to New Brunswick,

Canada. There does not appear to be a temporally coordinated migration or a specific migratory route to and from the Bay of Fundy

region. Though, during the fall, several satellite tagged harbor porpoises did favor the waters around the 92m isobath, which is

consistent with observations of high rates of incidental catches in this depth range (Read and Westgate 1997). There were two

stranding records from Florida (Smithsonian strandings data base). 

Gaskin (1984, 1992) proposed that there were four separate populations in the western North Atlantic: the Gulf of Maine/Bay

of Fundy, Gulf of St. Lawrence, Newfoundland and Greenland populations. Recent analyzes involving mtDNA (Wang et al. 1996),

organochlorine contaminants (Westgate et al.1997), heavy metals (Johnston 1995), and life history parameters (Read and Hohn 1995)

support Gaskin’s proposal. In particular, there is a suggestion that the Gulf of Maine/Bay of Fundy females are different than Gulf

of St. Lawrence females, but males were statistically indistinguishable (Palka et al. 1996). Research on microsatellites, a potentially

powerful genetic tool, is currently being conducted to re-analyze existing genetic data and analyze new samples in order to resolve

the larger scale stock structure question. This report follows Gaskin's hypothesis on harbor porpoise stock structure in the western

North Atlantic; Gulf of Maine and Bay of Fundy harbor porpoises are recognized as a single management stock separate from harbor

porpoise populations in the Gulf of St. Lawrence, Newfoundland, and Greenland. 

POPULATION SIZE

To estimate the absolute population size of harbor

porpoises aggregated in the Gulf of Maine/Bay of Fundy

region, three line-transect sighting surveys were conducted

during the summers of 1991, 1992 and 1995 (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), and 74,000 harbor

porpoises in 1995 (CV=0.20, 95% CI = 40,900-109,100)

(Palka 1996). The inverse variance weighted-average

abundance estimate (Smith et al. 1993) 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 and inter-annual

changes in water temperature and availability of primary

prey species (Palka 1995b). 

The shipboard sighting survey procedure used in all

three 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
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estimated using bootstrap re-sampling methods. Potential biases not explicitly accounted for are ship avoidance and time of

submergence. During 1995 a small section of the region was surveyed by airplane while the rest of the region was surveyed by ship,

as in previous years. An abundance estimate including g(0) was estimated for both the plane and ship (Palka 1996). During 1995,

in addition to the Gulf of Maine/Bay of Fundy area, waters from Virginia to the mouth of the Gulf of St. Lawrence were surveyed

and no harbor porpoises were seen except in the vicinity of the Gulf of Maine/Bay of Fundy.

Table 1. Summary of abundance estimates for the Gulf of Maine/Bay of Fundy harbor porpoise. 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-Aug 1991 N. Gulf of Maine &

lower Bay of Fundy 37,500 0.29

Jul-Sep 1992 N. Gulf of Maine &

lower Bay of Fundy 67,500 0.23

Jul-Sep 1995 N. Gulf of Maine &

lower Bay of Fundy 74,000 0.20

Inverse variance-weighted average of above

1991, 1992 and 1995 estimates 54,300 0.14

Minimum Population Estimate 

The minimum population estimate is the lower limit of the two-tailed 60% confidence interval of the log-normally distributed

best abundance estimate. This is equivalent to the 20th percentile of the log-normal distribution as specified by Wade and Angliss

(1997). The best estimate of abundance for harbor porpoises is 54,300 (CV=0.14). The minimum population estimate for the Gulf

of Maine/Bay of Fundy harbor porpoise is 48,289 (CV=0.14).

Current Population Trend

There are insufficient data to determine the population trends for this species. Previous abundance estimates for harbor porpoises

in the Gulf of Maine/Bay of Fundy are available from earlier studies, (e. g. 4,000 animals, Gaskin 1977, and 15,800 animals, Kraus

et al. 1983). These estimates cannot be used in a trends analysis because they were for selected small regions within the entire

known summer range and, in some cases, did not incorporate any estimate of g(0) (NEFSC 1992). 

CURRENT AND MAXIMUM NET PRODUCTIVITY RATES

Although current population growth rates of Gulf of Maine/Bay of Fundy harbor porpoises have not been estimated due to lack

of data, several attempts have been made to estimate potential population growth rates. Barlow and Boveng (1991), who used a rescaled human life table, estimated the upper bound of the annual potential growth rate to be 9.4%. Woodley and Read (1991) used

a re-scaled Himalayan tahr life table to estimate a likely annual growth rate of 4%. In an attempt to estimate the potential population

growth rate which incorporated many of the uncertainties in survivorship and reproduction, Caswell et al. (1998), using a Monte

Carlo method to calculate a probability distribution of growth rates, estimated the median potential annual rate of increase is be

approximately 10%, with a 90% confidence interval of 3-15%. This analysis underscored the considerable uncertainty that exists

regarding the potential rate of increase in this population. Consequently, for the purposes of this assessment, the maximum net

productivity rate was assumed to be 0.04, consistent with values used for other cetaceans for which direct observations of maximum

rate of increase are not available. The 0.04 value is based on theoretical modeling showing that cetacean populations may not grow

at rates much greater than 4% given the constraints of their reproductive life history (Barlow et al. 1995). 

POTENTIAL BIOLOGICAL REMOVAL

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

a “recovery” factor (MMPA Sec. 3. 16 U.S.C. 1362; Wade and Angliss 1997). The minimum population size is 48,289 (CV=0.14).

The maximum productivity rate is 0.04, the default value for cetaceans. The “recovery” factor, which accounts for endangered,
138

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 483.

ANNUAL HUMAN-CAUSED MORTALITY

Fishery Information

Gulf of Maine/Bay of Fundy harbor porpoise takes have been documented in the USA New England multispecies sink gillnet,

Mid-Atlantic coastal gillnet, Atlantic pelagic drift gillnet fisheries, and in the Canadian Bay of Fundy groundfish sink gillnet and

herring weir fisheries. The USA average annual mortality estimate for 1993 to 1997 from the above USA fisheries is 1,704 (CV=0.09)

harbor porpoises (Table 2). The Canadian average annual mortality estimate for 1993 to 1997 from the above Canadian fisheries

is 146 harbor porpoises. It was not possible to estimate variance of the Canadian estimate. The total average annual mortality

estimate for 1993 to 1997 from the USA and Canadian fisheries is 1,850 (Table 2).

USA

Recent data on incidental takes in USA fisheries are available from several sources. In 1986, NMFS established a mandatory selfreported fisheries information system for large pelagic fisheries. Data files are maintained at the Southeast Fisheries Science Center

(SEFSC). The Northeast Fisheries Science Center (NEFSC) Sea Sampling Observer Program was initiated in 1989, and since that

year several fisheries have been covered by the program. From late 1992, the SEFSC provided observer coverage of pelagic long line

vessels fishing off the Grand Banks (Tail of the Banks) and south of Cape Hatteras. 

New England Multispecies Sink Gillnet 

Most of the harbor porpoise takes from USA fisheries are from the New England multispecies sink gillnet fishery. In 1984 the

New England multispecies sink gillnet fishery was investigated by a sampling program that collected information concerning marine

mammal by-catch. Approximately 10% of the vessels fishing in Maine, New Hampshire, and Massachusetts were sampled. Among

the eleven gillnetters who received permits and logbooks, 30 harbor porpoises were reported caught. It was estimated, using rough

estimates of fishing effort, that a maximum of 600 harbor porpoises were killed annually in this fishery (Gilbert and Wynne 1985,

1987). 

In 1990, an observer program was started by the NMFS to investigate marine mammal takes in the New England multispecies

sink gillnet fishery. There have been 411 harbor porpoise mortalities related to this fishery observed between 1990 and 1997 and

one was released alive uninjured. In 1993, there were approximately 349 full and part-time vessels in the New England multispecies

sink gillnet fishery, which covered the Gulf of Maine and southern New England (Table 2). An additional 187 vessels were reported

to occasionally fish in the Gulf of Maine with gillnets for bait or personal use; however, these vessels were not covered by the

observer program (Walden 1996) and their fishing effort was not used in estimating mortality. Observer coverage in terms of trips

has been 1%, 6%, 7%, 5%, 7%, 5% 4%, and 6% for years 1990 to 1997, respectively. By-catch in the northern Gulf of Maine occurs

primarily from June to September; while in the southern Gulf of Maine by-catch occurs from January to May and September to

December. Annual estimates of harbor porpoise by-catch in the New England multispecies sink gillnet fishery reflect seasonal

distribution of the species and of fishing effort. By-catch 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 by-catch rates

from unobserved hauls were lower than that for observed hauls. Further analytical details are given in Palka (1994), CUD (1994),

and Bravington and Bisack (1996). These revised by-catch estimates replace those published earlier (Smith et al. 1993). These

estimates 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 by-catch (CV in parentheses) from this fishery during 1990-1997 was 2,900

in 1990 (0.32), 2,000 in 1991 (0.35), 1,200 in 1992 (0.21), 1,400 in 1993 (0.18) (Bravington and Bisack 1996; CUD 1994), 2100 in

1994 (0.18), 1400 in 1995 (0.27) (Bisack 1997a), 1200 (0.25) in 1996, and 775 (0.24) in 1997. Average estimated harbor porpoise

mortality and serious injury in the New England multispecies sink gillnet fishery during 1993-1997 was 1,375 (0.10).

There appeared to be no evidence of differential mortality in USA or Canadian gillnet fisheries by age or sex in animals collected

before 1994, although there was substantial inter-annual variation in the age and sex composition of the by-catch (Read and Hohn

1995). However, with a larger sample, from harbor porpoises examined by necropsy or from tissues received from sea sampling

observers (n=171 between 1989 and 1997), the sex ratio is now 58 females and 113 males (A. Read, pers com). Investigations are

currently underway to determine spatial-temporal patterns in the sex ratio.
139

Two preliminary experiments, using acoustic alarms (pingers) attached to gillnets, that were conducted in the Gulf of Maine during

1992 and 1993 took 10 and 33 harbor porpoises, respectively. During fall 1994, a controlled scientific experiment was conducted

in the southern Gulf of Maine, where all nets with and without active pingers were observed (Kraus et al. 1997). In this experiment

25 harbor porpoises were taken in 423 strings with non-active pingers (controls) and two harbor porpoises were taken in 421 strings

with active pingers. In addition, 17 other harbor porpoises were taken in nets that did not follow the experimental protocol (Table

2). From 1995 to 1997, experimental fisheries were conducted where all nets in a designated area were required to used pingers and

only a sample of the nets were observed. During November-December 1995, the experimental fishery was conducted in the southern

Gulf of Maine (Jeffreys Ledge) region, where no harbor porpoises were observed taken in 225 pingered nets. During 1995, all takes

from pingered nets were added directly to the estimated total by-catch for that year. During April 1996, three other experimental

fisheries occurred. In the Jeffreys Ledge area, in 88 observed hauls using pingered nets nine harbor porpoises were taken. In the

Massachusetts Bay region, in 171 observed hauls using pingered nets two harbor porpoises were taken. And, in a region just south

of Cape Cod, in 53 observed hauls using pingered nets no harbor porpoises were taken. During 1997, experimental fisheries were

allowed in the midcoast region during March 25 to April 25 and November 1 to December 31. During the 1997 spring experimental

fishery, out of 538 observed hauls using pingered nets five harbor porpoises were taken. During the 1997 fall experimental fishery,

out of 125 observed hauls using pingered nets no harbor porpoises were taken.

From 95 stomachs of harbor porpoises collected in groundfish gillnets in the Gulf of Maine between September and December

1989-94, Atlantic herring (Clupea harengus) was the most important prey. Pearlsides (Maurolicus weitzmani), silver hake

(Merluccisu bilinearis) and red and white hake (Urophycis spp.) were the next most common prey species (Gannon et al. 1998).

Mid-Atlantic Coastal Gillnet 

Before an observer program was in place, Polacheck et al. (1995) reported one harbor porpoise incidentally taken in shad nets

in the York River, Virginia. In July 1993 an observer program was initiated in the USA Atlantic coastal gillnet fishery by the NEFSC

Sea Sampling program. This fishery, which extends from North Carolina to New York, is actually a combination of small vessel

fisheries that target a variety of fish species, some of which operate right off the beach. The number of vessels in this fishery is

unknown, because records which are held by both state and federal agencies have not been centralized and standardized. Twenty

trips were observed during 1993. During 1994 and 1995, 221 and 382 trips were observed, respectively. Observer coverage,

expressed as percent of tons of fish landed, was 5% for 1995, 4% for 1996, and 3% for 1997 (Table 2). No harbor porpoises were

taken in observed trips during 1993 and 1994. During 1995 to 1997, respectively, 6, 19, and 32 harbor porpoises were observed taken

(Table 2). Observed fishing effort has been concentrated off NJ and scattered between DE and NC from the beach to 50 miles off

the beach. Documented by-catches during 1995 and 1997 were mostly from January to April, with the exception of one taken during

May 1997, and one taken during December 1997. By-catch estimates were calculated using methods similar to that used for by-catch

estimates in the New England multispecies gillnet fishery (Bravington and Bisack 1996; Bisack 1997a). Using the observed takes,

the estimated annual mortality (CV in parentheses) attributed to this fishery was 103 (0.57) for 1995, 311 (0.31) for 1996, and 572

(0.35) for 1997. Average estimated harbor porpoise mortality and serious injury from the Mid-Atlantic coastal gillnet fishery during

1995 to 1997 was 329 (CV=0.23) (Table 2). 

Pelagic Drift Gillnet 

In 1996 and 1997, the NMFS issued management regulations which prohibited the operation of this fishery in 1997. Further,

in January 1999 the NMFS issued a Final Rule to prohibit the use of driftnet gear in the North Atlantic swordfish fishery (50 CFR

Part 630). One harbor porpoise was observed taken from the 1991-1996 Atlantic pelagic drift gillnet fishery. The estimated total

number of hauls in the Atlantic pelagic drift gillnet fishery increased from 714 in 1989 to 1,144 in 1990; thereafter, with the

introduction of quotas, effort was severely reduced. Fifty-nine different vessels participated in this fishery at one time or another

between 1989 and 1993. In 1994, 1995, and 1996 there were 11, 12, and 10 vessels, respectively, in the fishery (Table 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, and 64% in 1996. The decline in observer coverage in 1996 is attributable to trips made by vessels that were deemed

unsafe for observers due to the size or condition of the fishing vessel. Fishing effort was concentrated along the southern edge of

Georges Bank and off Cape Hatteras. Examination of the species composition of the catch and locations of the fishery throughout

the year suggested that the drift gillnet fishery be stratified into two strata, a southern or winter stratum, and a northern or summer

stratum. Estimates of the total by-catch, 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 by-catch after 1993 were estimated from the sum of the observed

caught and the product of the average by-catch per haul and the number of unobserved hauls as recorded in logbooks. Variances were
140

estimated using bootstrap re-sampling techniques (Bisack 1997b). The one observed by-catch was notable because it occurred in

continental shelf edge waters adjacent to Cape Hatteras (Read et al. 1996). Estimated annual fishery-related mortality (CV in

parentheses) attributable to this fishery was 0.7 in 1989 (7. 00), 1.7 in 1990 (2.65), 0.7 in 1991 (1.00), 0.4 in 1992 (1.00), 1.5 in 1993

(0.34), and 0 in 1994 to1996. The fishery was closed during 1997. Average estimated harbor porpoise mortality and serious injury

in the Atlantic pelagic drift gillnet fishery during 1993-1996 was 0.4 (0.34) (Table 2).

North Atlantic Bottom Trawl 

One harbor porpoise mortality was observed in the North Atlantic bottom trawl fishery between 1989 and 1997. Vessels in this

fishery, a Category III fishery under the MMPA, were observed in order to meet fishery management needs, rather than marine

mammal management needs. An average of 970 (CV = 0.04) vessels (full and part time) participated annually in the fishery during

1989-1993. This fishery is active in New England waters in all seasons. The one take occurred in February 1992 east of Barnegatt

Inlet, New York at the continental shelf break. The animal was clearly dead prior to being taken by the trawl, because it was severely

decomposed and the tow duration of 3.3 hours was insufficient to allow extensive decomposition; therefore, there is no estimated

by-catch for this fishery.

CANADA

Bay of Fundy Sink Gillnet 

During the 1980's, Canadian harbor porpoise by-catch in the Bay of Fundy sink gillnet fishery, based on casual observations and

discussions with fishermen, was thought to be low. The estimated harbor porpoise by-catch in 1986 was 94-116 and in 1989 it was

130 (Trippel et al. 1996). The Canadian gillnet fishery occurs mostly in the western portion of the Bay of Fundy during the summer

and early autumn months, when the density of harbor porpoises is highest. Polacheck (1989) reported there were 19 gillnetters active

in 1986, 28 active in 1987, and 21 in 1988. 

More recently, an observer program implemented in the summer of 1993 provided a total by-catch estimate of 424 harbor

porpoises (± 1 SE: 200-648) from 62 observed trips, which is an 11.3% coverage of the Bay of Fundy trips (Trippel et al. 1996).

This estimate is not considered to be as accurate as more recent estimates because of low observer coverage and the absence of

temporal stratification (Trippel et al. 1996). 

During 1994, the observer program was expanded to cover 49.4% of the gillnet trips (171 observed trips). The by-catch was

estimated to be 101 harbor porpoises (95% confidence limit: 80-122), where the fishing fleet consisted of 28 vessels (Trippel et al.

1996). 

During 1995, due to groundfish quotas being exceeded, the gillnet fishery was closed during July 21 to August 31, 1995. During

the open fishing period of 1995, 89% of the fishing trips were observed, all in the Swallowtail region. Approximately 30% of these

observed trips used pingered nets. The estimated by-catch was 87 harbor porpoises (Trippel et al. 1996). No confidence interval

was able to be computed due to lack of coverage in the Wolves fishing grounds.

During 1996, the Canadian gillnet fishery was closed from July 20-31 and August 16-31 due to reduced groundfish quotas. From

the 107 monitored trips, the by-catch from 1996 was estimated to be 20 harbor porpoises (Trippel et al. 1999; DFO 1998).

During 1997, the fishery was closed to the majority of the gillnet fleet from July 18-31 and August 16-31, due to reduced

groundfish quotas. In addition a time-area closure to reduce porpoise by-catch 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 by-catch in 1997 was 43 animals (DFO 1998). 

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 throughout 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 coverage. A preliminary total by-catch for Bay of Fundy in 1998 was estimated at 10 porpoises.

No estimates of variability are available (DFO 1998).

 Average estimated harbor porpoise mortality in the Canadian groundfish sink gillnet fishery during 1993-1997 was 135 (Table

2). No estimate of variability is possible.

Herring Weirs

Harbor porpoises takes have been observed in Canadian fishing weirs, though not in USA fishing weirs. However, no program

has been set up to observer USA fishing weirs. In the Bay of Fundy, weirs are operating from May to September each year. Weirs

are found along the southwestern shore of the Bay of Fundy, and scattered along the western Nova Scotia and northern Maine coasts.

There were 180 active weirs in the western Bay of Fundy and 56 active weirs in Maine in 1990 (Read 1994). According to state of

Maine officials, in 1998, the number of weirs in Maine waters has dropped to nearly zero due to the limited herring market (Jean
141

Chenoweth pers. comm.). According to Canadian DFO officials, for 1998, there were 225 licenses for herring weirs on the New

Brunswick side and 30 from the Nova Scotia side of the Bay of Fundy (In New Brunswick: 60 from Grand Manan Island, 95 from

Deer and Campobello Islands, 30 from Passamaquoddy Bay, 35 from East Charlotte area, and 5 from the Saint John area). This

number has been fairly consistent since 1985 (Ed Trippel, pers. comm.) The actual number of active weirs in the USA is not known.

Smith et al. (1983) estimated approximately 70 harbor porpoises become trapped annually and, on average, 27 died annually,

and the rest were released alive. At least 43 harbor porpoises were trapped in Bay of Fundy weirs in 1990, but the number killed

is unknown. In 1993, after a cooperative program between fishermen and Canadian biologists began, over 100 harbor porpoises were

released alive and an unknown number died (Read 1994). Due to the cooperative program, out of 263 documented harbor porpoises

caught in herring weirs during 1992 to 1994, 57 died while the rest were either released or escaped. The numbers that died during the

seining process (and were released alive) were 11 (and 50) in 1992, 33 (and 113) in 1993, and 13 (and 43) in 1994 (Neimanis et al.

1995). Out of 125 documented harbor porpoises caught in herring weirs during 1995 to 1998, 11 died while the rest were either

released or escaped. The numbers that died (and were released alive or escaped) were 5 (and 60) in 1995; 2 (and 4) in 1996; 2 (and

24) in 1997; and 2 (and 26) in 1998 (Westgate, per. comm.).

 Average estimated harbor porpoise mortality in the Canadian herring weir fishery during 1993-1997 was 11 (Table 2). No

estimate of variance is possible.
142

Table 2. Summary of the incidental mortality of harbor porpoise (Phocoena phocoena) by commercial fishery including the years

sampled (Years), the number of vessels active within the fishery (Vessels), the type of data used (Data Type), the annual

observer coverage (Observer Coverage), the mortalities recorded by on-board observers (Observed Mortality), the estimated

annual mortality (Estimated Mortality), the estimated CV of the annual mortality (Estimated CVs) and the mean annual

mortality (CV in parentheses).

Fishery Years Vessels Data Type 1 Observer

Coverage 2 

Observed

Mortality

Estimated

Mortality 

Estimated

CVs 

Mean

Annual

Mortality

USA

New England

Multispecies

Sink Gillnet

93-97 1993=349 Obs. Data

Weighout, Trip

Logbook

.05, .07, .05,

.04, .06

533,993,

433,523,

473

14003,21003,1

4003,12003,77

5

3

.18, .18,

.27, .25, .24

1375

(.10)

Mid-Atlantic

Coastal Sink

Gillnet

95-976 Unk7 Obs. Data

Weighout

.05, .04, .03 6, 19, 

32

103, 311,

572

.57, .31,

.35

329

(0.23)

Pelagic Drift

Gillnet

93-97 1994=114

1995=12 

1996=10 

1997=NA8 

Obs. Data

Logbook

.42, .87, .99,

.64, NA8

1,0, 

0, 0, 

NA8

1.55, 0, 

0, 0, 

NA8

.34, 0, 

0, 0, 

NA8

0.48

(.34)

USA TOTAL 1704

(0.09)

CANADA

Groundfish Sink

Gillnet 

93-98 1994=28 Obs. Data

Can. Trips

.11,.49,.89,

.8,.8,.8

25,49,25,

13,19,1

424,101,87,20

,43,10

NA 1359

(NA)

Herring Weir 93-98 1998=255

licenses10

Coop. Data NA 33,13,5,

2,2,2

33,13,5,

2,2,2

NA 119

(NA)

CANADIAN

TOTAL

146

(NA)

TOTAL 1850

(NA)

NA = Not available.

1 Observer data (Obs. Data) are used to measure by-catch rates; the USA data are collected within the Northeast Fisheries Science

Center (NEFSC) Sea Sampling Program, the Canadian data are collected by DFO. NEFSC collects Weighout (Weighout) landings

data, and total landings are used as a measure of total effort for the USA sink 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 some fishing effort in the New England multispecies sink gillnet fishery. 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). Observed mortalities from herring weirs are collected by a cooperative program between fishermen and Canadian

biologists (Coop. Data).
143

 2 The observer coverage for the USA and Canadian sink gillnet fishery is measured in trips, for the pelagic drift gillnet fishery the

unit of effort is a set, and for the Mid-Atlantic coastal sink gillnet fishery the unit of effort is tons of fish landed.

3 Harbor porpoise taken during and before 1997 in observed pinger trips were added directly to the estimated total by-catch for

that year. There were 10, 33, 44, 0, 11, and 8 observed harbor porpoise takes on pinger trips from 1992 to 1997, respectively.

In addition, there were 9 and 2 observed harbor porpoise takes in 1995 and 1997, respectively on trips dedicated to fish sampling

versus marine mammals (Bisack 1997a).

4 1994, 1995, and 1996 shown, other years not available on an annual basis.

5 For 1991-1993, pooled by-catch rates were used to estimate by-catch in months that had fishing effort but did not have observer

coverage (Northridge 1996). After 1993, observer coverage increased substantially, and by-catch rates were annual rates (Bisack

1997b). The fishery was closed during 1997. 

6 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.

7 The number of vessels in the Mid-Atlantic coastal sink gillnet fishery is presently not available.

8 Fishery closed during 1997. So average by-catch is from 1993 to 1996.

9 To be consistent with years in USA calculations, average is calculated from 1993 to 1997 estimates.

10 There were 255 licenses for herring weirs in the Canadian Bay of Fundy region.

Other Mortality

There is evidence that harbor porpoises were harvested by natives in Maine and Canada before the 1960's, and the meat was used

for human consumption, oil, and fish bait (NEFSC 1992). The extent of these past harvests is unknown, though it is believed to be

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.

Sixty-four harbor porpoise strandings were reported from Maine to North Carolina between January and June, 1993. Fifty of

those harbor porpoises were reported stranded in the USA Atlantic region from New York to North Carolina between February and

May. Many of the 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 and along the New Jersey coast and

reports of apparent mutilation of harbor porpoise carcasses, raised concern that the 1993 strandings were related to a coastal net

fishery, such as the American shad coastal gillnet fishery (Haley and Read 1993). 

Between 1994 and 1996, 107 harbor porpoise carcasses were recovered from beaches in Maryland, Virginia, and North Carolina.

Only juvenile harbor porpoises were present in this sample. Of the 40 harbor porpoises for which cause of death could be

established, 25 displayed definitive evidence of entanglement in fishing gear. In four cases it was possible to determine that the animal

was entangled in monofilament nets (Cox et al. 1998).

During 1996 and 1997, the NE Regional Office/NMFS strandings and entanglement database recorded 211 harbor porpoises that

stranded on beaches from North Carolina to Maine (Table 3). Of these, three stranded alive on a Massachusetts beach and were

tagged and subsequently released. The largest number of recorded strandings were on Massachusetts beaches. The states with the

next largest numbers were North Carolina, New Jersey and Virginia, in that order. The number of these strandings that show signs

of human interactions is presently being investigated.

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.
144

Table 3. Summary of number of stranded harbor porpoises during January 1, 1996 to December 31, 1997, by state and year.

State Year Total

1996 1997

Maine 5 6 11

New Hampshire 2 0 2

Massachusetts128 28 56

Rhode Island 1 1 2

Connecticut 1 0 1

New York 3 10 13

New Jersey 12 21 33

Delaware 4 3 7

Maryland 3 10 13

Virginia 20 12 32

North Carolina 12 26 38

TOTAL 91 117 208

1 During 1996, an additional three animals stranded alive on a Massachusetts beach. They were tagged and released.

STATUS OF STOCK

The status of harbor porpoises, relative to OSP, in the USA Atlantic EEZ is unknown. On January 7, 1993, the National Marine

Fisheries Service (NMFS) proposed listing the Gulf of Maine harbor porpoise as threatened under the Endangered Species Act

(NMFS 1993). On January 5, 1999, the NMFS determined the proposed listing was not warranted (NMFS 1999). There are

insufficient data to determine population trends for this species. The total fishery-related mortality and serious injury for this stock

is not less than 10% of the calculated PBR and, therefore, cannot be considered to be insignificant and approaching zero mortality

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

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147

October 1999

HARBOR SEAL (Phoca vitulina):

Western North Atlantic Stock

STOCK DEFINITION AND GEOGRAPHIC RANGE

The harbor seal is found in the western North Atlantic, from the eastern Canadian Arctic and Greenland south to southern New

England and New York, and occasionally to the Carolinas (Boulva and McLaren 1979; Katona et al. 1993; Gilbert and Guldager

1998). Although the stock structure of the western North Atlantic population is unknown, it is thought that harbor seals found along

the eastern USA and Canadian coasts represent one population (Temte et al. 1991). Breeding and pupping normally occurs in waters

north of the New Hampshire/Maine border, although breeding occurred as far south as Cape Cod in the early part of the twentieth

century (Temte et al. 1991; Katona et al. 1993). 

Harbor seals are year-round inhabitants of the coastal waters of eastern Canada and Maine (Katona et al. 1993), and occur

seasonally along the southern New England and New York coasts from September through late May (Schneider and Payne 1983).

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). A northward movement from southern New England to Maine and eastern Canada occurs prior to the

pupping season, which takes place from mid-May through June along the Maine Coast (Richardson 1976; Wilson 1978; Whitman

and Payne 1990; Kenney 1994). No pupping areas have been identified in southern New England (Payne and Schneider 1984). The

overall geographic range throughout coastal New England has not changed significantly during the last century (Payne and Selzer

1989). 

The majority of animals moving into southern New England waters are juveniles. Whitman and Payne (1990) suggest that the

age-related dispersal may reflect the higher energy requirements of younger animals. 

POPULATION SIZE

 Since passage of the MMPA in 1972, the number of seals along the New England coast has increased nearly five-fold. Coastwide aerial surveys along the Maine coast have been conducted in May/June during pupping in 1981, 1982, 1986, 1993, and 1997

(Table 1; Gilbert and Stein 1981; Gilbert and Wynne 1983, 1984; Kenney 1994; and Gilbert and Guldager 1998). These numbers

are considered to be a minimum abundance estimate because 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 southern New England and eastern Long Island (Payne and Selzer 1989; Rough 1995). Canadian scientists counted 3,600

harbor seals during an August 1992 aerial survey in the Bay of Fundy (Stobo and Fowler 1994), but noted that the survey was not

designed to obtain a population estimate. 

Table 1. Summary of abundance estimates for the western Atlantic harbor seal. Month, year, and area covered during each

abundance survey, and resulting abundance estimate (Nmin) and coefficient of variation (CV). 

Month/Year Area Nmin CV

May/June 1981 Maine coast 10,540 (676)1 None reported

May/June 1982 Maine coast 9,331 (1,198) None reported

May/June 1986 Maine coast 12,940 (1,713) None reported

May/June 1993 Maine coast 28,810 (4,250) None reported

May/June 1997 Maine coast 30,990 (5,359) None reported

August 1992 Bay of Fundy 3,600 None reported

1Pup counts are in brackets 

Minimum Population Estimate
148

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 1998). Since 1981, the average increase has been 4.2 %

(Gilbert and Gualdager 1998), about 50% of the 8.9 percent annual increase estimated Kenney (1994) from counts through 1993.

Similarly, the number of pups along the Maine coast has increased at an annual rate of 12.9% over the 1981-1997 period (Gilbert

and Guldager 1998). Possible factors contributing to this increase include MMPA protection and increased prey. There are no

indications that population growth has slowed or that it is at or near its potential maximum level. The rapid increase observed during

the past two decades may reflect past reduction of the population by historical bounty hunting, possibly to a very low level. 

CURRENT AND MAXIMUM NET PRODUCTIVITY RATES

Current and maximum net productivity rates are unknown for this stock. For purposes of this assessment, the maximum net

productivity rate was assumed to be 0.12. This value is based on theoretical modeling showing that pinniped populations may not

grow at rates much greater than 12% given the constraints of their reproductive life history (Barlow et al. 1995). 

POTENTIAL BIOLOGICAL REMOVAL

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

a “recovery” factor (MMPA Sec. 3. 16 U.S.C. 1362; Wade and Angliss 1997). The minimum population size is 30,990. The

maximum productivity rate is 0.12, the default value for pinnipeds. The recovery factor (FR) for this stock is 1.0, the value for stocks

of unknown status, but known to be increasing. PBR for counts in USA waters is 1,859.

ANNUAL HUMAN-CAUSED MORTALITY

Total annual estimated average fishery-related mortality or serious injury to this stock during 1993-1997 was 943 harbor seals

(CV = 0.11; Table 2). 

Harbor seals were bounty hunted in New England waters until the late 1960's. This hunt may have caused the demise of this

stock in USA waters (Katona et al. 1993). Researchers and fishery observers have documented incidental mortality in several

fisheries, particularly within the Gulf of Maine (see below). An unknown level of mortality also occurs in the mariculture industry

(i.e., salmon farming), and by deliberate shooting (NMFS unpublished data). 

Fishery Information

USA

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

self-reported fisheries information system for large pelagic fisheries. Data files are maintained at the Southeast Fisheries Science

Center (SEFSC). The Northeast Fisheries Science Center (NEFSC) Sea Sampling Observer Program was initiated in 1989, and since

that year several fisheries have been covered by the program. In late 1992 and in 1993, the SEFSC provided observer coverage of

pelagic longline vessels fishing off the Grand Banks (Tail of the Banks) and provides observer coverage of vessels fishing south of

Cape Hatteras. 

Incidental takes of harbor seals have been recorded in groundfish gillnet, herring purse seine, halibut tub trawl, and lobster fisheries

(Gilbert and Wynne, 1985 and 1987). A study conducted by the University of Maine reported a combined average of 22 seals

entangled annually by 17 groundfish gillnetters off the coast of Maine (Gilbert and Wynne 1987). All seals were young of the year

and were caught from late June through August, and in early October. Interviews with a limited number of mackerel gillnetters

indicated only one harbor seal entanglement and a negligible loss of fish to seals. Net damage and fish robbing were not reported to

be a major economic concern to gillnetters interviewed (Gilbert and Wynne 1987). 

Herring purse seiners have reported accidentally entrapping seals off the mid-coast of Maine, but indicated that the seals were

rarely drowned before the seine was emptied (Gilbert and Wynne 1985). Capture of seals by halibut tub trawls are rare. One vessel

captain indicted that he took one or two seals a year. These seals were all hooked through the skin and released alive, indicating they

were snagged as they followed baited hooks. Infrequent reports suggest seals may rob bait off longlines, although this loss is

considered negligible (Gilbert and Wynne 1985). 

Incidental takes in lobster traps in inshore waters off Maine are reportedly rare. Captures of approximately two seal pups per

port per year were recorded by mid-coastal lobstermen off Maine (Gilbert and Wynne 1985). Seals have been reported to rob bait
149

from inshore lobster traps, especially in the spring, when fresh bait is used. These incidents may involve only a few individual

animals. Lobstermen claim that seals consume shedding lobsters. 

New England Multispecies Sink Gillnet:

In 1993, there were approximately 349 full and part-time vessels in the New England multispecies sink gillnet fishery, which

covered the Gulf of Maine and southern New England (Table 2). An additional 187 vessels were reported to occasionally fish in the

Gulf of Maine with gillnets for bait or personal use; however, these vessels were not covered by the observer program (Walden 1996)

and their fishing effort was not used in estimating mortality. Observer coverage in terms of trips has been 1%, 6%, 7%, 5%, 7%, 5%,

4%, and 6% for 1990 to 1997, respectively. The fishery has been observed in the Gulf of Maine and in Southern New England.

There were 272 harbor seal mortalities, excluding three animals taken in the 1994 pinger experiment (NMFS unpublished data),

observed in the New England multispecies sink gillnet fishery between 1990 and 1997. Annual estimates of harbor 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 1990-1997 was 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), and 598 in 1997 (0.26). The 1994 and 1995 bycatches, respectively, include 14 and 179 animals from the estimated number of unknown seals (based on observed mortalities of seals

that could not be identified to species). The unknown seals were prorated, based on spatial/temporal patterns of by-catch of harbor

seals, gray seals, harp seals, and hooded seals. Average annual estimated fishery-related mortality and serious injury to this stock

attributable to this fishery during 1993-1997 was 943 harbor seals (CV = 0.11). The stratification design used is the same as that

for harbor porpoise (Bravington and Bisack 1996). The by-catch occurred in Massachusetts Bay, south of Cape Ann and west of

Stellwagen Bank during January-March. By-catch locations became more dispersed during April-June from Casco Bay to Cape Ann,

along the 30 fathom contour out to Jeffreys Ledge, with one take location near Cultivator Shoal and one off southern New England

near Block Island. Incidental takes occurred from Frenchman's Bay to Massachusetts Bay during July-September. In inshore waters,

the takes were aggregated while offshore takes were more dispersed. Incidental takes were confined from Cape Elizabeth out to

Jeffreys Ledge and south to Nantucket Sound during October-December. 

CANADA

An unknown number of harbor seals have been taken in Newfoundland and Labrador, Gulf of St. Lawrence and Bay of Fundy

groundfish gillnets, Atlantic Canada and Greenland salmon gillnets, Atlantic Canada cod traps, and in Bay of Fundy herring weirs

(Read 1994). Furthermore, some of these mortalities (e.g., seals trapped in herring weirs) are the result of direct shooting. The

Canadian government has recently implemented a pilot program that permits mariculture operators to use acoustic deterrents or shoot

problem seals. 

There were 3,121 cod traps operating in Newfoundland and Labrador during 1979, and about 7,500 in 1980 (Read 1994). This

fishery was closed at the end of 1993 due to collapse of Canadian groundfish resources. 

Herring weirs are also distributed throughout the Bay of Fundy; it has been reported that 180 weirs were operating in the Bay

of Fundy in 1990 (Read 1994). 

In 1996, observers recorded seven harbor seals (one released alive) in Spanish deep water trawl fishing on the southern edge of

the Grand Bank (NAFO Areas 3) (Lens, 1997). Seal by-catches occurred year-round, but interactions were highest during April-June.

Many of the seals that died during fishing activities were unidentified. The proportion of sets with mortality (all seals) was 2.7 per

1,000 hauls (0.003). 
150

Table 2. Summary of the incidental mortality of harbor seal (Phoca vitulina) by commercial fishery including the years sampled

(Years), the number of vessels active within the fishery (Vessels), the type of data used (Data Type), the annual observer

coverage (Observer Coverage), the mortalities recorded by on-board observers (Observed Mortality), the estimated annual

mortality (Estimated Mortality), the estimated CV of the annual mortality (Estimated CVs) and the mean annual mortality

(CV in parentheses).

Fishery Years Vessels Data Type 1 Observer

Coverage 2 

Observed

Mortality3

Estimated

Mortality3

Estimated

CVs 

Mean

Annual

Mortality

New England

Multispecies

Sink Gillnet

 93-97 349 Obs. Data

Weighout,

Logbooks

 .05, .07,

.05, .04, .06

 22, 86,

56,36, 48

 698, 1330,

1179, 911, 598

 .19, .25,

.21, .27,

.26

 943

 (.11)

TOTAL 943

(.11)

1 Observer data (Obs. Data) are used to measure by-catch rates, and the data are collected within the Northeast Fisheries Science

Center (NEFSC) Sea Sampling Program. NEFSC collects Weighout (Weighout) landings data, and total landings are used as a

measure of total effort for the sink gillnet fishery. Mandatory logbook (Logbook) data are used to determine the spatial

distribution of some fishing effort in the New England multispecies sink gillnet fishery.

2 The observer coverage for the New England multispecies sink gillnet fishery is measured in trips.

3

In 1994, 1995, 1996, and 1997 respectively, observed mortality on “marine mammal trips” was 59, 41, 37, and 14 animals. Only

these mortalities were used to estimate total harbor seal by-catch. In 1994, 3 mortalities were observed on “fish trips” and 24 on

“pinger trips.” 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. See

Bisack (1997) for “trip” type definitions.

Other Mortality

Annually, small numbers of harbor seals regularly strand throughout their migratory range. Most stranding, 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 unpubl. Data), oil, shooting), storms,

abandonment by the mother, and disease (Katona et al. 1993; NMFS unpublished data). Interactions with Maine salmon aquaculture

operations appears to be increasing, although the magnitude of interactions and seal mortalities has not been quantified (Anon 1996).

In 1980, more than 350 seals were found dead in the Cape Cod area from an influenza outbreak (Geraci et al. 1981).

The 1992-1996 harbor seal strandings data are currently under review. In 1995 one stranding was in South Carolina. In 1997, there

were 153 stranding , including one each was in Georgia and Florida. The majority of the strandings were in New England, Maine

(71/153) and Massachusetts (32/153). In the mid-Atlantic region, most of the stranding events occurred in New York (17/153) and

New Jersey (11/153). Eighteen animals showed signs of human interactions: fishery (4), vessel strike (2), power plant (8), and other

(4). 

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. 

STATUS OF STOCK

The status of harbor seals, relative to OSP, in the USA Atlantic EEZ is unknown, but the population is increasing. The species

is not listed as threatened or endangered under the Endangered Species Act. Gilbert and Guldager (1998) estimated a 4.4% annual

rate of increase of this stock in Maine coastal waters based on 1981, 1982, 1986, 1993, 1997 surveys conducted along the Maine

coast. The population is increasing despite the known fishery-related 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
151

Anon. 1996. Report of the Gulf of Maine Aquaculture-Pinniped Interaction task Force. Available from NMFS, Office of Protected

Resources. Silver Springs. MC. 70 pp.

Barlow, J., S.L. Swartz, T.C. Eagle, and P.R. Wade. 1995. U.S. Marine Mammal Stock Assessments: Guidelines for Preparation,

Background, and a Summary of the 1995 Assessments. U.S. Dep. Commer., NOAA Tech. Memo. NMFS-OPR-6, 73 pp. 

Bisack, K.D. 1997. Harbor porpoise bycatch estimates in the New England multispecies sink gillnet fishery: 1994 and 1995. Rep.

int Whal. Comm. 47:705-14.

Boulva, J. and I. A. McLaren. 1979. Biology of the harbor seal, Phoca vitulina, in eastern Canada. Bull. Fish. Res. Bd. Can.

200:1-24. 

Bravington, M. V. and K. D. Bisack. 1996. Estimates of harbor porpoise by-catch in the Gulf of Maine sink gillnet fishery, 1990-93.

Rep. int Whal. Commn. 46:567-574.

Geraci, R., D. J. St. Aubin and I. K. Barker. 1981. Mass mortality of harbor seals: pneumonia associated with influenza A virus.

Science 215: 1129-1131.

Gilbert, J.R. and N. Guldager. 1998. Status of harbor and gray seal populations in northern New England. Final Report to: National

Marine Fisheries Service, Northeast Fisheries Science Center, Woods Hole, MA. Under NMFS/NER Cooperative Agreement

14-16-009-1557. 13 pp.

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 annual report.

Northeast Fisheries Science Center. Contract NA-80-FA-C-00029. 

Gilbert, J. R. and K. M. Wynne. 1985. Harbor seal populations and fisheries interactions with marine mammals in New England,

1984. Interim Rep., NOAA NA-84-EAC-00070, NMFS, NEFSC., Woods Hole, MA, 15 pp. 

Gilbert, J. R. and K. M. Wynne. 1987. Marine mammal interactions with New England gillnet fisheries. Final Report Contract No.

NA-84-EAC-00070, NOAA, NMFS, NEFSC, Woods Hole, MA, 12 pp. 

Katona, S. K., V. Rough, and D. T. Richardson. 1993. A field guide to whales, porpoises, and seals from Cape Cod to

Newfoundland. Smithsonian Institution Press: Washington, DC, 316 pp. 

Kenney, M.K. 1994. Harbor seal population trends and habitat use in Maine. M.S. Thesis. University of Maine, Orono, ME. 55

pp.

Kenney, M. K. and J. R. Gilbert. 1994. Increase in harbor and gray seal populations in Maine. Dept. of Commerce, NOAA-NMFS

Contract Rep. 50-EANF-2-00064, 19 pp. 

Lens, S. 1997. Interactions between marine mammals and deep water trawlers in the NAFO regulatory area. ICES C.M. 8/Q. 10

pp.

Payne. P. M. and D. C. Schneider. 1984. Yearly changes in abundance of harbor seals, Phoca vitulina, at a winter haul-out site

in Massachusetts. Fish. Bull., U.S. 82: 440-442.

Payne, P. M. and L. A. Selzer. 1989. The distribution, abundance and selected prey of the harbor seal, Phoca vitulina concolor,

in southern New England. Mar. Mamm. Sci. 5(2): 173-192. 

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

Special Issue 15: 133-147. 

Richardson, D.T. 1976. Assessment of harbor and gray seal populations in Maine 1974-1975. Final report to Marine Mammal

Commission. Contract No. MM4AC009.

Rosenfeld M., M. George and J. M. Terhune. 1988. Evidence of autumnal harbour seal, Phoca vitulina, movement from Canada

to the United States. Can. Field-Nat. 102(3): 527-529.

Rough, V. 1995. Gray seals in Nantucket Sound, Massachusetts, winter and spring, 1994. Final report to Marine Mammal

Commission, Contract T10155615, 28 pp. NTIS Pub. PB95-191391.

Schneider, D. C. and P. M. Payne. 1983. Factors affecting haul-out of harbor seals at a site in southeastern Massachusetts. J.

Mamm. 64(3): 518-520.

Stobo, W.T. and G.M. Fowler. 1994. Aerial surveys of seals in the Bay of Fundy and off southwest Nova Scotia. Can. Tech. Rep.

Fish. Aquat. Sci. 1943:57 pp.

Temte, J.L., M.A. Bigg and O. Wiig. 1991. Clines revisited: the timing of pupping in the harbour seal (Phoca vitulina). J. Zool.

Lond. 224: 617-632.
152

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 survey. NOAA, NMFS, NEFSC, Woods Hole, Massachusetts. NEFSC [Northeast

Fisheries Science Center] Ref. Doc. 99-10. 38p. 

Whitman, A. A. and P. M. Payne. 1990. Age of harbour seals, Phoca vitulina concolor, wintering in southern New England.

Can. Field-Nat. 104(4): 579-582.

Wilson, S. C. 1978. Social organization and behavior of harbor seals, Phoca concolor, in Maine. Final Report to Marine Mammal

Commission, Contract MM6ACO13, GPO-PB-280-188. 
153

October 1999

GRAY SEAL (Halichoerus grypus):

Western North Atlantic Stock

STOCK DEFINITION AND GEOGRAPHIC RANGE

The gray seal is found in the western North Atlantic from New England to Labrador and is centered in the Sable Island region

of Nova Scotia (Katona et al. 1993; Davies 1957). This stock is separated by both geography and differences in the breeding season

from the eastern Atlantic stock (Bonner 1981). The western Atlantic stock is distributed and breeds principally in eastern Canadian

waters; however, small numbers 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 the outer

Cape Cod and Nantucket Island (Dennis Murley, pers. comm., Mass. Audubon Society, Wellfleet, MA). Gilbert (pers. comm) has

also documented a resident colony in Maine. 

POPULATION 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 1986 population estimate for individuals on Sable Island, Nova Scotia that are one year old and older was between 100,000

and 130,000 animals (Stobo and Zwanenburg 1990). The 1993 estimate of the Sable Island and Gulf of St. Lawrence stocks was

143,000 animals (Mohn and Bowen 1994). The population in waters off Maine has increased from about 30 in the early 1980's to

between 500-1,000 animals in 1993; recently 29-49 pups/year have been recorded in Penobscot Bay (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). 

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 coefficient of variation (CV). 

Month/Year Area Nmin CV

1986 Sable Island 100,000 to 130,000 none reported

1993 Sable Island and Gulf of

St. Lawrence 143,000 none reported

1993 Maine coast 500-1000 none reported

Apr-May 1994

Muskeget Island and

Monomoy, MA (only US

portion of stock)

2,010 none reported

Minimum Population Estimate

At the November 1998 meeting of the Atlantic Scientific Review Group (SRG), the SRG recommended that the minimum estimate

(2,010) used in previous assessments be discontinued, because it did not account for the unknown fraction of the Sable Island gray

seal stock that overwinters in the Nantucket Sound region. Therefore, present data are insufficient to calculate the minimum

population estimate for USA waters. It is estimated that there are at least 143,000 gray seals in Canada (Mohn and Bowen 1993).

Current Population Trend

Gray seal abundance is likely increasing in the USA Atlantic Exclusive Economic Zone (EEZ), but the percent increase is

unknown. The population has been increasing for several decades in Canadian waters. 
154

Pup production on Sable Island, Nova Scotia, has been about 13% per year since 1962 (Mohn and Bowen 1994). Approximately

57% of the western North Atlantic population is from the Sable Island stock. 

 Winter breeding colonies in Maine and on Muskeget Island may provide some measure of gray seal population trends and

expansion in distribution. Sightings in New England increased during the 1980s as the gray seal population and range expanded in

eastern Canada. Five pups were born at Muskeget in 1988. The number of pups increased to 12 in 1992, 30 in 1993, and 59 in 1994

(Rough 1995).

CURRENT AND MAXIMUM NET PRODUCTIVITY RATES

Current and maximum net productivity rates are unknown for this stock. One study that estimated pup production on Sable

Island estimated the annual production rate was 13% (Mohn and Bowen 1994).

For purposes of this assessment, the maximum net productivity rate was assumed to be 0.12. This value is based on theoretical

modeling showing that pinniped populations may not grow at rates much greater than 12% given the constraints of their reproductive

life history (Barlow et al. 1995). 

POTENTIAL BIOLOGICAL REMOVAL

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

a “recovery” factor (MMPA Sec. 3. 16 U.S.C. 1362; Wade and Angliss 1997). The minimum population size is unknown. The

maximum productivity rate is 0.12, the default value for pinnipeds. The recovery factor (FR) for this stock is 1.0, the value for stocks

of unknown status, but 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 results in a “PBR” of 8,850 gray seals.

ANNUAL HUMAN-CAUSED MORTALITY AND SERIOUS INJURY

Gray seals, like harbor seals, were hunted for bounty in New England waters until the late 1960's. This hunt may have severely

depleted this stock in USA waters (Rough 1995).

 Total annual estimated average fishery-related mortality or serious injury to this stock during 1993- 1997 was 67 gray seals (CV

= 0.27; Table 2). 

Fishery Information

USA

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

self-reported fisheries information system for large pelagic fisheries. Data files are maintained at the Southeast Fisheries Science

Center (SEFSC). The Northeast Fisheries Science Center (NEFSC) Sea Sampling Observer Program was initiated in 1989, and since

that year several fisheries have been covered by the program. In late 1992 and in 1993, the SEFSC provided observer coverage of

pelagic longline vessels fishing off the Grand Banks (Tail of the Banks) and provides observer coverage of vessels fishing south of

Cape Hatteras. 

New England Multispecies Sink Gillnet:

In 1993, there were approximately 349 full and part-time vessels in the New England multispecies sink gillnet fishery, which

covered the Gulf of Maine and southern New England (Table 2). An additional 187 vessels were reported to occasionally fish in the

Gulf of Maine with gillnets for bait or personal use; however, these vessels were not covered by the observer program (Walden 1996)

and their fishing effort was not used in estimating mortality. Observer coverage in terms of trips has been 1%, 6%, 7%, 5%, 7%, 5%,

4%, and 6% for 1990 to 1997, respectively. The fishery has been observed in the Gulf of Maine and in Southern New England. There

were 31 gray seal mortalities observed in the New England multispecies sink gillnet fishery between 1993-1997 (Table 2). Nineteen

of the observed mortalities occurred in winter (January - May), 7 in the southern Gulf of Maine and one in the "mid-coast closed

area." Only one mortality was observed in northern Maine waters, which occurred in autumn (September-December) 1995. One

of the 1993 observed mortalities was in May, and was from SE of Block Island. 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 occurs in the

mariculture industry (i.e., salmon farming) and by deliberate shooting (NMFS unpublished data). 

Annual estimates of gray 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 in 1990-

1992, 18 in 1993 (1.00), 19 in 1994 (0.95), 117 in 1995 (0.42), 49 in 1996 (0.49), and 131 in 1997 (0.50). The 1995 by-catch includes

28 animals from the estimated number of unknown seals (based on observed mortalities of seals that could not be identified to
155

species). The unknown seals were prorated, based on spatial/temporal patterns of by-catch of harbor seals, gray seals, harp seals,

and hooded seals. Further, they will likely have little impact on the estimates presented. Average annual estimated fishery-related

mortality and serious injury to this stock attributable to this fishery during 1993-1997 was 67 gray seals (CV = 0.27). The

stratification design used is the same as that for harbor porpoise (Bravington and Bisack 1996).

CANADA

An unknown number of gray seals have been taken in Newfoundland and Labrador, Gulf of St. Lawrence, and Bay of Fundy

groundfish gillnets, Atlantic Canada and Greenland salmon gillnets, Atlantic Canada cod traps, and in Bay of Fundy herring weirs

(Read 1994). In addition to incidental catches, some mortalities (e.g., seals trapped in herring weirs) were the result of direct shooting,

and there were culls of about 1,700 animals annually during the 1970's and early 1980's on Sable Island (Anon. 1986). 

There were 3,121 cod traps operating in Newfoundland and Labrador during 1979, and about 7,500 in 1980 (Read 1994). This

fishery was closed at the end of 1993 due to collapse of Canadian groundfish resources. 

Herring weirs are also distributed throughout the Bay of Fundy; it has been reported that 180 weirs were operating in the Bay

of Fundy in 1990 (Read 1994). 

In 1996, observers recorded 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 by-catches occurred year-round, but interactions were highest during April-June.

Many of the seals that died during fishing activities were unidentified. The proportion of sets with mortality (all seals) was 2.7 per

1,000 hauls (0.003).

Table 2. Summary of the incidental mortality of gray seal (Halichoerus grypus) by commercial fishery including the years

sampled (Years), the number of vessels active within the fishery (Vessels), the type of data used (Data Type), the annual

observer coverage (Observer Coverage), the mortalities recorded by on-board observers (Observed Mortality), the estimated

annual mortality (Estimated Mortality), the estimated CV of the annual mortality (Estimated CVs) and the mean annual

mortality (CV in parentheses).

Fishery Years Vessels Data Type 1 Observer

Coverage 2 

Observed

Mortality3

Estimated

Mortality3

Estimated

CVs 

Mean

Annual

Mortality

New England

Multispecies

Sink Gillnet

 93-97 349 Obs. Data

Weighout,

Logbooks

 .05, .07,

.05, .04, .06

 2, 3, 7, 3,

16

 18, 19, 117,

49, 131

 1.00,

.95, .42,

.49, .50

 67

 (.27)

 TOTAL 67

(.27)

1 Observer data (Obs. Data) are used to measure by-catch rates, and the data are collected within the Northeast Fisheries Science

Center (NEFSC) Sea Sampling Program. NEFSC collects Weighout (Weighout) landings data, and total landings are used as a

measure of total effort for the sink gillnet fishery. Mandatory logbook (Logbook) data are used to determine the spatial

distribution of some fishing effort in the New England multispecies sink gillnet fishery.

 2 The observer coverage for the New England multispecies sink gillnet fishery is measured in trips.

3

In 1994 and 1995, respectively, observed mortality on “marine mammal trips” was 2 and 6 animals. Only these mortalities were

used to estimate total gray seal by-catch. In 1994 and 1995, one mortality in each year was recorded on a “fish trip.” See Bisack

(1997) for “trip” type definitions. In 1997 all observed takes were on marine mammal trips, including 12 taken on pingered trips.

Other Mortality

 The 1992-1996 gray seal strandings data are currently under review. Forty-two stranding were recorded in 1997, extending from

Maine (11) to Maryland (1). Most of the strandings were in Maine (11) and Massachusetts (12). Two animals showed signs of

human interactions, including one that was shot. 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 necessarily show signs of entanglement or other fishery 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
156

Act. Recent data indicate that this population is increasing. The total fishery-related mortality and serious injury for this stock is

believed to be very low relative to the population size in Canadian waters and can be considered insignificant and approaching zero

mortality and serious injury rate. The level of human-caused mortality and serious injury in the USA Atlantic EEZ is unknown, but

believed to be very low relative to the total stock size; therefore, this is not a strategic stock. 

REFERENCES

Anon. 1986. Seals and sealing in Canada. Rep. of the Royal Commission on Seals and Sealing, Vol. 1, 65 pp. Available from

Canadian Government Publishing Centre, Ottawa, Canada.

Bonner, W. N. 1981. Grey seal, Halicoerus grypus. In: S. H. Ridgway and R. J. Harrison, Eds., Handbook of Marine Mammals,

Vol. 2. Pp. 111-144. London: Academic Press.

Barlow, J., S.L. Swartz, T.C. Eagle, and P.R. Wade. 1995. U.S. Marine Mammal Stock Assessments: Guidelines for Preparation,

Background, and a Summary of the 1995 Assessments. U.S. Dep. Commer., NOAA Tech. Memo. NMFS-OPR-6, 73 pp.

Bisack, K.D. 1997. Harbor porpoise bycatch estimates in the New England multispecies sink gillnet fishery: 1994 and 1995. Rep.

int Whal. Comm. 47:705-14.

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. Bonner, W. N. 1981. Grey seal Halichoerus grypus Fabricus, 1791. Pages 111-144

in S. H. Ridgway and R. J. Harrison (eds), Handbook of Marine Mammals, Vol. 2: Seals. Academic Press, London, 359 pp.

Davies, J. L. 1957. The geography of the gray seal. J. Mamm. 38: 297-310.

Katona, S. K., V. Rough, and D. T. Richardson. 1993. A field guide to whales, porpoises, and seals from Cape Cod to

Newfoundland. Smithsonian Institution Press, Washington, DC. 316 pp. 

Lens, S. 1997. Interactions between marine mammals and deep water trawlers in the NAFO regulatory area. ICES C.M. 8/Q. 10

pp.

Mohn, R. and W. D. Bowen. 1994. A model of grey seal predation on 4VsW cod and its effects on the dynamics and potential yield

of cod. DFO Atlantic Fisheries Res. Doc. 94/64.

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

Special Issue 15: 133-147. 

Rough, V. 1995. Gray seals in Nantucket Sound, Massachusetts, winter and spring, 1994. Final report to Marine Mammal

Commission, Contract T10155615, 28 pp. NTIS Pub. PB95-191391.

Stobo, W. T. and K. C. T. Zwanenburg. 1990. Grey seal (Halichoerus grypus) pup production on Sable Island and estimates of

recent production in the northwest Atlantic. Pages 171-184 in W. D. Bowen (ed), Population biology of sealworm

(Pseudoterranova decipiens) in relation to its intermediate and seal hosts. Can. Bull. Fish. and Aq. Sci. 222. 

Wade, P.R., and R.P. Angliss. 1997. Guidelines for assessing marine mammal stocks: Report of the GAMMS Workshop April 3-5,

1996, Seattle, Washington. U.S. Dep. Commer., NOAA Tech. Memo. NMFS-OPR-12, 93 pp.

Walden, J. 1996. The New England gillnet effort survey. NOAA, NMFS, NEFSC, Woods Hole, Massachusetts. NEFSC [Northeast

Fisheries Science Center] Ref. Doc. 99-10. 38p. 
157

October 1999

HARP SEAL (Phoca groenlandica):

Western North Atlantic Stock

STOCK DEFINITION AND GEOGRAPHIC RANGE

The harp seal occurs throughout much of the North Atlantic and Arctic Oceans (Ronald and Healey 1981; Lavigne and Kovacs

1988); however, in recent years, numbers of sightings and strandings have been increasing off the east coast of the United States from

Maine to New Jersey (Katona et al. 1993; Stevick and Fernald 1998; B. Rubinstein pers. comm., New England Aquarium). These

appearances usually occur in January-May, when the western North Atlantic stock of harp seals is at its southern most 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 Kovacs 1988). The largest stock is located in the western North Atlantic off eastern Canada and is divided into

two breeding herds which breed on the pack ice. The Front herd breeds off the coast of Newfoundland and Labrador, and the Gulf

herd breeds near the Magdalen Islands in the middle of the Gulf of St. Lawrence (Sergeant 1965; Lavigne and Kovacs 1988). The

second stock breeds in the White Sea off the coast of the Soviet Union, and the third stock breeds on the West Ice off of eastern

Greenland (Lavigne and Kovacs 1988; Anon 1998). 

Harp seals are highly migratory (Sergeant 1965; Stenson and Sjare 1997). Breeding occurs at different times between midFebruary and April for each stock. Adults then assemble north of their whelping patches to undergo the annual molt. The migration

then continues north to Arctic summer feeding grounds. In late September, after a summer of feeding, nearly all adults and some of

the immature animals migrate southward along the Labrador coast, usually reaching the entrance to the Gulf of St. Lawrence by early

winter. There they split into two groups, one moving into the Gulf and the other remaining off the coast of Newfoundland.

Following mating, the seals disperse to feed, and in late April they again concentrate in large numbers on the ice to molt.

The extreme southern limit of the harp seal's habitat extends into the USA Atlantic Exclusive Economic Zone (EEZ) during winter

and spring. The influx of harp seals and geographic distribution in New England to mid-Atlantic waters is based primarily on

strandings, and secondarily on fishery bycatch (McAlpine and Walker 1990; Rubinstein 1994).

POPULATION SIZE

The total population size of harp seals is unknown; however, three seasonal abundance estimates are available which used a

variety of methods including aerial surveys and mark-recapture (Table 1). Generally, these methods include surveying the whelping

concentrations and modeling pup production. Harp seal pup production in the 1950s was estimated at 645,000 (Sergeant 1975),

decreasing to 225,000 by 1970 (Sergeant 1975). Estimates began to increase at this time and have continued to rise, reaching 478,000

in 1979 (Bowen and Sergeant 1983; Bowen and Sergeant 1985) and 577,900 in 1990 (Stenson et al. 1993).

Roff and Bowen (1983) developed an estimation model to provide a more precise estimate of total population. This technique

incorporates recent pregnancy rates and estimates of age-specific hunting mortality (CAFSAC 1992). Total population can be

determined by multiplying pup production by a factor between 5.35 and 5.38, giving a total of approximately three million harp seals

in 1990 (Table 1).

 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) (Table 1). 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 were 4.5-4.8 million harp seals (Table1).
158

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

1990 Eastern Atlantic Canada-Labrador 577,900 pups none reported

1994 Eastern Atlantic Canada-Labrador 702,900 pups 0.09

1990 Eastern Atlantic Canada-Labrador 3 million none reported

1990 Eastern Atlantic Canada-Labrador 3.1 million none reported

1994 Eastern Atlantic Canada-Labrador 4.5-4.8 million none reported

Minimum population estimate

Present data are insufficient to calculate the minimum population estimate for USA waters. It is estimated there are at least 4.8

million harp seals in Canada (Shelton et al. 1996). 

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 1990 the average annual growth rate has been estimated to be about

5% (Shelton et al. 1996). 

CURRENT AND MAXIMUM NET PRODUCTIVITY RATES

Current and maximum net productivity rates are unknown for this stock. The best data are based on Canadian studies. Recent

studies indicate that pup production has increased, but the rate of population increase cannot be quantified at this time (Stenson et

al. 1996). The mean age of sexual maturity was 5.8 yrs in the mid-1950's, declining to 4.6 yrs in the early 1980's and then increasing

to 5.4 yrs in the early 1990's (Sjare et al. 1996).

For purposes of this assessment, the maximum net productivity rate was assumed to be 0.12. This value is based on theoretical

modeling showing that pinniped populations may not grow at rates much greater than 12% given the constraints of their reproductive

life history (Barlow et al. 1995). 

POTENTIAL BIOLOGICAL REMOVAL

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

a “recovery” factor (MMPA Sec. 3. 16 U.S.C. 1362; Wade and Angliss 1997). The minimum population size is unknown. The

maximum productivity rate is 0.12, the default value for pinnipeds. The “recovery” factor, which accounts for endangered, depleted,

threatened stocks, or stocks of unknown status relative to optimum sustainable population (OSP) was set at 1.0 because it was

believed that harp seals are within OSP. PBR for the western North Atlantic harp seal in USA waters is unknown. Applying the

formula to the minimum population estimate for Canadian waters results in a "PBR" of 288,000 harp seals. 

ANNUAL HUMAN-CAUSED MORTALITY AND SERIOUS INJURY

 Harp seals have been commercially hunted since the mid-1800's in the Canadian Atlantic (Stenson 1993). A total allowable catch

(TAC) of 200,000 harp seals was set for the large vessel hunt in 1971. The TAC varied until 1982 when it was set at 186,000 seals,

and remained at this level through 1995 (Stenson 1993; Anon 1998). The TAC was increased to 250,000 and 275,000, respectively

in 1996 and 1997 (Anon 1998). 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 (1997) (Stenson 1993; Anon 1998). The commercial

catches do not account for subsistence takes.

 Total annual estimated average fishery-related mortality or serious injury to this stock during 1993-1997 was 383 harp seals

(CV = 0.29; Table 2). 

Fishery Information
159

USA

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

self-reported fisheries information system for large pelagic fisheries. Data files are maintained at the Southeast Fisheries Science

Center (SEFSC). The Northeast Fisheries Science Center (NEFSC) Sea Sampling Observer Program was initiated in 1989, and since

that year several fisheries have been covered by the program. In late 1992 and in 1993, the SEFSC provided observer coverage of

pelagic longline vessels fishing off the Grand Banks (Tail of the Banks) and provides observer coverage of vessels fishing south of

Cape Hatteras. 

Recent by-catch has been observed by NMFS Sea Samplers in the New England multispecies sink gillnet fisheries, but no

mortalities have been documented in the Mid-Atlantic coastal gillnet, Atlantic drift gillnet, pelagic pair trawl or pelagic longline

fisheries. 

In 1993, there were approximately 349 full and part-time vessels in the New England multispecies sink gillnet fishery, which

covered the Gulf of Maine and southern New England (Table 2). An additional 187 vessels were reported to occasionally fish in the

Gulf of Maine with gillnets for bait or personal use; however, these vessels were not covered by the observer program (Walden 1996)

and their fishing effort was not used in estimating mortality. Observer coverage in terms of trips has been 1%, 6%, 7%, 5%, 7%,

5%,4%, and 6% for 1990 to 1997, respectively. The fishery has been observed in the Gulf of Maine and in Southern New England.

There were 69 harp seal mortalities observed in the New England multispecies sink gillnet fishery between 1990 and 1996. Annual

estimates of harp 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 (1990-1993), 861

in 1994 (0.58), 694 in 1995 (0.27), 89 in 1996 (0.55), and 269 in 1997 (0.50). The 1994 and 1995 by-catches, respectively, include

16 and 153 animals from the estimated number of unknown seals (based on observed mortalities of seals that could not be identified

to species). The unknown seals were prorated, based on spatial/temporal patterns of by-catch of harbor seals, gray seals, harp seals,

and hooded seals. Average annual estimated fishery-related mortality and serious injury to this stock attributable to this fishery during

1993-1997 was 383 harp seals (CV = 0.29). The stratification design used is the same as that for harbor porpoise (Bravington and

Bisack 1996). The by-catch 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.

CANADA

An unknown number of harp seals have been taken in Newfoundland and Labrador groundfish gillnets (Read 1994). Harp seals

are being taken in Canadian lumpfish and groundfish gillnets, and trawls, but estimates of total removals have not been calculated to

date (Anon. 1994). 

There were 3,121 cod traps operating in Newfoundland and Labrador during 1979, and about 7,500 in 1980 (Read 1994). This

fishery was closed at the end of 1993 due to collapse of Canadian groundfish resources.

In 1996, observers recorded 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 by-catches occurred year-round, but interactions were highest during April-June.

Many of the seals that died during fishing activities were unidentified. The proportion of sets with mortality (all seals) was 2.7 per

1,000 hauls (0.003).
160

Table 2. Summary of the incidental mortality of harp seal (Phoca groenlandica) by commercial fishery including the years

sampled (Years), the number of vessels active within the fishery (Vessels), the type of data used (Data Type), the annual

observer coverage (Observer Coverage), the mortalities recorded by on-board observers (Observed Mortality), the estimated

annual mortality (Estimated Mortality), the estimated CV of the annual mortality (Estimated CVs) and the mean annual

mortality (CV in parentheses).

Fishery Years Vessels Data Type 1 Observer

Coverage 2 

Observed

Mortality3

Estimated

Mortality 

Estimated

CVs 

Mean

Annual

Mortality

New England

Multispecies

Sink Gillnet

 93-97 349 Obs. Data

Weighout,

Logbooks

 .05, .07,

.05, .04, .06

 0, 33, 27,

9, 40

 0, 861, 694,

89, 269

 0, .58, .27,

.55, .50

 383

(.29)

TOTAL 383

(.29)

1 Observer data (Obs. Data) are used to measure by-catch rates, and the data are collected within the Northeast Fisheries Science

Center (NEFSC) Sea Sampling Program. NEFSC collects Weighout (Weighout) landings data, and total landings are used as a

measure of total effort for the sink gillnet fishery. Mandatory logbook (Logbook) data are used to determine the spatial

distribution of some fishing effort in the New England multispecies sink gillnet fishery.

 2 The observer coverage for the New England multispecies sink gillnet fishery is measured in trips.

3

In 1997 thirty-one harp seals were taken on pingered trips, all observed mortality was on "mammal trips." See Bisack (1997)

for “trip” type definitions.

Other Mortality

From 1988-1993 strandings each year were under 50, approaching 100 animals in 1994, and exceeding 100 animals in 1995-1996

(Rubinstein 1994; B. Rubinstein, New England Aquarium, pers. comm.). In addition, in 1996 there was a stranding in North Carolina.

In 1997, 119 strandings were recorded, including one in North Carolina. The majority of the stranding occurred in Maine (17),

Massachusetts (28), and New York (48). The increased number of strandings may indicate a possible shift in distribution or

expansion southward into USA waters; if so, fishery interactions may increase. 

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

increasing in Canadian waters. The species is not listed as threatened or endangered under the Endangered Species Act. The total

fishery-related mortality and serious injury for this stock is believed to be very low relative to the population size in Canadian waters

and can be considered insignificant and approaching zero mortality and serious injury rate. The level of human-caused mortality and

serious injury in the USA Atlantic EEZ is unknown, but believed to be very low relative to the total stock size; therefore, this is not

a strategic stock. 

REFERENCES

Anon. 1998. Report of the Joint ICES/NAFO Working Group on Harp and Hooded Seals. 28 August-3 September 1997,

Copenhagen, Denmark. ICES CM 1998/Assess:3. 35 pp.

Barlow, J., S.L. Swartz, T.C. Eagle, and P.R. Wade. 1995. U.S. Marine Mammal Stock Assessments: Guidelines for Preparation,

Background, and a Summary of the 1995 Assessments. U.S. Dep. Commer., NOAA Tech. Memo. NMFS-OPR-6, 73 pp. 

Bravington, M. V. and K. D. Bisack. 1996. Estimates of harbor porpoise by-catch in the Gulf of Maine sink gillnet fishery, 1990-93.

Rep. int Whal. Commn. 46:567-574.

Bisack, K.D. 1997. Harbor porpoise bycatch estimates in the New England multispecies sink gillnet fishery: 1994 and 1995. Rep.

int Whal. Comm. 47:705-14.

Bonner, W. N. 1990. The natural history of seals. Fact on File, New York, 196 pp. 

Bowen, W.D. and D.E. Sergeant. 1983. Mark-recapture estimates of harp seal pup (Phoca groenlandica) production in the

northwest Atlantic. Can. J. Fish. Aquat. Sci. 40: 728-742.
161

Bowen, W. D. and D. E. Sergeant. 1985. A Mark-recapture estimate of 1983 Harp seal Pup Production in the Northwest Atlantic.

NAFO SCR. Doc. 85/I/1. 

CAFSAC. 1992. Update on population estimates of Harp seal in the Northwest Atlantic. Canadian Atlantic Fisheries Scientific

Advisory Committee, CAFSAC Adv. Doc. 92/8.

Katona, S. K., V. Rough, and D. T. Richardson. 1993. A field guide to whales, porpoises, and seals from Cape Cod to

Newfoundland. Smithsonian Institution Press, Washington, DC. 316 pp. 

Lavigne, D. M. and K. M. Kovacs. 1988. Harps and Hoods Ice Breeding Seals of the Northwest Atlantic. University of Waterloo

Press, Waterloo, Ontario, Canada, 174 pp. 

Lens, S. 1997. Interactions between marine mammals and deep water trawlers in the NAFO regulatory area. ICES C.M. 8/Q. 10

pp.

McAlpine , D. F. and R. H. Walker. 1990. Extralimital records of the harp seal, Phoca groenlandica, from the western North Atlantic:

a review. Mar. Mamm. Sci. 6:243-247.

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

Special Issue 15: 133-147. 

Roff, D. A. and W. D. Bowen. 1983. Population dynamics and management of the Northwest Atlantic harp seal. Can. J. Fish.

Aquat. Sci. 40: 919-932. 

Ronald, K. and P. J. Healey. 1981. Harp Seal. Pages 55-87 in S. H. Ridgway and R. J. Harrison (eds), Handbook of marine

mammals, Vol. 2: Seals. Academic Press, New York, 359 pp. 

Rubinstein, B. 1994. An apparent shift in distribution of ice seals, Phoca groenlandica, Cystophora cristata, and Phoca

hispida, toward the east coast of the United States. M.A. Thesis, Boston University, Boston, MA, 45 pp. 

Sergeant, D.E. 1965. Migrations of harp seal Pagophilus groenlandicus (Erxleben) in the Northwest Atlantic. J. Fish. Res. Bd.

Can. 22:433-464.

Sergeant, D. E. 1975. Estimating numbers of Harp seals. Rapp. P. -v. Reun. Cons. int Explor. Mer. 169: 274-280.

Shelton, P. A., N. G. Caddigan and G. B. Stenson. 1992. Model estimates of harp seal population trajectories in the Northwest

Atlantic. CAFSAC Res. Doc. 92/89, 23 pp. 

Shelton, P.A., G.B. Stenson, B. Sjare and W.G. Warren. 1996. Model estimates of harp seal numbers-at-age for the Northwest

Atlantic NAFO Sci. Coun. Studies 26:1-14.

Sjare, B., G.B. Stenson and W.G. Warren. 1996. Summary of female harp seal reproductive parameters in the Northwest Atlantic.

NAFO Sci. Coun. Studies 26:41-46.

Stenson, G. B. 1993. The status of pinnipeds in the Newfoundland region. NAFO SCR Doc. 93/34.

Stenson, G. B., R. A. Myers, M. O. Hammill, I-H Ni, W. G. Warren, and M. S. Kingsley. 1993. Pup Production of Harp Seals,

Phoca groenlandica, in the Northwest Atlantic. Can. J. Fish. Aquat. Sci. 50: 2429-2439.

Stenson, G.B., M.O. Hammill, M.C.S. Kingsley, B. Sjare, W.G. Warren, and R.A. Myers. 1996. 1994 pup production of Northwest

Atlantic harp seals, Phoca groenlandica. NAFO Sci. Coun. Studies 26: 47-62.

Stenson, G.B. and B. Sjare. 1997. Seasonal distribution of harp seals, Phoca groenlandica, in the Northwest Atlantic. ICES C.M.

1997/CC:10 (Biology and Behavior II). 23 pp.

Stevick, P.T. and T.W. Fernald. 1998. Increase in extralimital records of harp seals in Maine. Northeastern Naturalist 5(1)75-

82.

Wade, P.R., and R.P. Angliss. 1997. Guidelines for assessing marine mammal stocks: Report of the GAMMS Workshop April 3-5,

1996, Seattle, Washington. U.S. Dep. Commer., NOAA Tech. Memo. NMFS-OPR-12, 93 pp.

Walden, J. 1996. The New England gillnet effort survey. NOAA, NMFS, NEFSC, Woods Hole, Massachusetts. NEFSC [Northeast

Fisheries Science Center] Ref. Doc. 99-10. 38p.
162

October 1999

HOODED SEAL (Cystophora cristata):

Western North Atlantic Stock

STOCK DEFINITION AND GEOGRAPHIC RANGE

The hooded seal occurs throughout much of the North Atlantic and Arctic Oceans (King 1983) preferring deeper water and

occurring farther offshore than harp seals (Lavigne and Kovacs 1988; Stenson et al. 1996). Hooded seals tend to wander far out of

their range and have been seen as far south as Puerto Rico, with increased occurrences from Maine to Florida. These appearances

usually occur between January and May. Although it is not known which stock these seals come from, it is known that during this

time frame, the Northwest Atlantic stock of hooded seals are at their southern most point of migration in the Gulf of St. Lawrence.

The worlds' hooded seal population is divided into three separate stocks, each identified with a specific breeding site (Lavigne and

Kovacs 1988). In the northwest Atlantic, whelping occurs in the Davis Strait, off Newfoundland and in Gulf of St. Lawrence

(Stenson et al. 1996). One stock, which whelps off the coast of eastern Canada, is divided into two breeding herds (Front and Gulf)

which breed on the pack ice. The Front herd (largest) breeds off the coast of Newfoundland and Labrador and the Gulf herd breeds

in the Gulf of St. Lawrence. The second stock breeds in the Davis Strait, and the third stock occurs on the West Ice off eastern

Greenland.

Hooded seals are a highly migratory species. Hooded seals remain on the Newfoundland continental shelf during winter/spring

(Stensonet al. 1996). Breeding occurs at about the same time in March for each stock. Adults from all stocks then assemble in the

Denmark Strait to molt between late June and August (King 1983; Anon 1995), and following this, the seals disperse widely. Some

move south and west around the southern tip of Greenland, and then north along the west coast of Greenland. Others move to the

east and north between Greenland and Svalbard during late summer and early fall (Lavigne and Kovacs 1988). Little else is known

about the activities of hooded seals during the rest of the year until they assemble again in February for breeding. 

Hooded seals are rarely found in the USA Atlantic Exclusive Economic Zone. Small numbers of hooded seals at the extreme

southern limit of their range occur in the winter and spring seasons. The influx of harp seals and geographic distribution in New

England to mid-Atlantic waters is based on stranding data.

POPULATION SIZE

The number of hooded seals in the western North Atlantic is unknown. Seasonal abundance estimates are available based on a

variety of analytical methods based on commercial catch data, and including aerial surveys. These methods often include surveying

the whelping concentrations and modeling the pup production. Several estimates of pup production at the Front are available.

Hooded seal pup production between 1966 and 1977 was estimated between 25,000 - 32,000 annually (Benjaminsen and Oritsland

1975; Sergeant 1976; Lett 1977; Winters and Bergflodt 1978; Stenson et al. 1996). Estimated pup production dropped to 26,000

hooded seal pups in 1978 (Winters and Bergflodt 1978). Pup production estimates began to increase after 1978, reaching 62,000

(95% CI. 43,700 - 89,400) by 1984 (Bowen et al. 1987). Bowen et al. (1987) also estimated pup production in the Davis Strait

at 18,600 (95% C.I. 14,000 - 23,000). A 1985 survey at the Front (Hay et al. 1985) produced a estimate of 61,400 (95% C.I. 16,500

- 119,450). Hammill et al. (1992) estimated pup production to be 82,000 (SE=12,636) in 1990. No recent population estimate is

available, but assuming a ratio of pups to total population of 1:5, pup production in the Gulf and Front herds would represent a total

population of approximately 400,000-450,000 hooded seals (Stenson 1993). Based on the 1990 survey, Stenson et al. (1995)

suggests that pup production may have increased at about 5% per year since 1984. However, because of exchange between the Front

and the Davis Strait stocks, the possibility of a stable or slightly declining level of pup production are also likely (Stenson 1993;

Stenson et al. 1996). It appears that the number of hooded seals is increasing.
163

Table 1. Summary of pup production estimates for western North Atlantic hooded seals. Year and area covered during each

abundance survey, and resulting abundance estimate (Nmin) and coefficient of variation (CV). 

Month/Year Area Nmin CV

1978 Front herd: Newfoundland/ Labrador 26,000 none reported

1984 Front herd: Newfoundland/Labrador 62,000 none reported

1984 Davis Strait 18,600 none reported

1985 Front herd: Newfoundland/Labrador 61,400 none reported

1990 Front herd: Newfoundland/Labrador 82,100 none reported

Minimum population estimate

Present data are insufficient to calculate the minimum population estimate for USA 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 USA Atlantic EEZ, judging from stranding records, although the actual magnitude of

this increase is unknown. The Canadian population appears to be increasing but, because different methods have been used over time

to estimate population size, the magnitude of this increase has not been quantified. 

CURRENT AND MAXIMUM NET PRODUCTIVITY RATES

Current and maximum net productivity rates are unknown for this stock. The most appropriate data are based on Canadian

studies. Pup production in Canada may be increasing slowly (5% per annum), but due to the wide confidence intervals and lack of

understanding regarding stock dynamics, it is possible that pup production is stable or declining (Stenson 1993). 

For purposes of this assessment, the maximum net productivity rate was assumed to be 0.12. This value is based on theoretical

modeling showing that pinniped populations may not grow at rates much greater than 12% given the constraints of their reproductive

life history (Barlow et al. 1995). 

POTENTIAL BIOLOGICAL REMOVAL

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

a “recovery” factor (MMPA Sec. 3. 16 U.S.C. 1362; Wade and Angliss 1997). The minimum population size is unknown. The

maximum productivity rate is 0.12, the default value for pinnipeds. The “recovery” factor, which accounts for endangered, depleted,

threatened stocks, or stocks of unknown status relative to optimum sustainable population (OSP) was set at 1.0 because it was

believed that harp seals are within OSP. PBR for the western North Atlantic hooded seal in USA waters is unknown. Applying

the formula to abundance estimates (400,000) in Canadian waters results in a PBR= 24,000 hooded seals. 

ANNUAL HUMAN-CAUSED MORTALITY AND SERIOUS INJURY

In Atlantic Canada, hooded seals have been commercially hunted at the Front since the late 1800's. In 1974 total allowable catch

(TAC) was set at 15,000, and reduced to 12,000 in 1983 and to 2,340 in 1984 (Stenson 1993; Anon 1998). From 1991- 1992 the

TAC was increased to 15,000. A TAC of 8,000 was set for 1993, and held at that level through 1997. From 1974 through 1982,

the average catch was 12,800 animals, mainly pups. Since 1983 catches ranged from 33 in 1986 to 6,425 in 1991, with a mean catch

of 1,001 between 1983 and 1995. In 1996 catches (25,754) were more than three times the allowable quota (Anon 1998). The high

catch was attributable to good ice conditions and strong market demand. Catches in 1997 were 7,058, slightly below the TAC.

Hunting in the Gulf of St. Lawrence (below 500N) has been prohibited since 1964. No commercial hunting of hooded seals is

permitted in the Davis Strait. 

 Total annual estimated average fishery-related mortality or serious injury to this stock in USA waters during 1993-1997 was

5.6 hooded seals (CV = 0.96; Table 2). 

Fishery Information
164

USA

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

self-reported fisheries information system for large pelagic fisheries. Data files are maintained at the Southeast Fisheries Science

Center (SEFSC). The Northeast Fisheries Science Center (NEFSC) Sea Sampling Observer Program was initiated in 1989, and since

that year several fisheries have been covered by the program. In late 1992 and in 1993, the SEFSC provided observer coverage of

pelagic longline vessels fishing off the Grand Banks (Tail of the Banks) and provides observer coverage of vessels fishing south of

Cape Hatteras. 

Recent by-catch has been observed by NMFS Sea Samplers in the New England multispecies sink gillnet fisheries, but no

mortalities have been documented in the Mid-Atlantic coastal gillnet, Atlantic drift gillnet, pelagic pair trawl or pelagic longline

fisheries. 

In 1993, there were approximately 349 full and part-time vessels in the New England multispecies sink gillnet fishery, which

covered the Gulf of Maine and southern New England (Table 2). An additional 187 vessels were reported to occasionally fish in the

Gulf of Maine with gillnets for bait or personal use; however, these vessels were not covered by the observer program (Walden 1996)

and their fishing effort was not used in estimating mortality. Observer coverage in terms of trips has been 1%, 6%, 7%, 5%, 7%,

5%,4%, and 6% for 1990 to 1997, 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 1996-1997. The 1995 by-catch includes five animals from the estimated number of unknown seals

(based on observed mortalities of seals that could not be identified to species). The unknown seals were prorated, based on

spatial/temporal patterns of by-catch of harbor seals, gray seals, harp seals, and hooded seals. Average annual estimated fisheryrelated mortality and serious injury to this stock attributable to this fishery during 1993-1997 was 5.6 hooded seals (CV = 0.96).

The stratification design used is the same as that for harbor porpoise (Bravington and Bisack 1996). The by-catch occurred only in

winter (January-May) and was in waters between Cape Ann and New Hampshire.

CANADA

An unknown number of hooded seals have been taken in Newfoundland and Labrador groundfish gillnets (Read 1994).

There were 3,121 cod traps operating in Newfoundland and Labrador during 1979, and about 7,500 in 1980 (Read 1994). This

fishery was closed at the end of 1993 due to collapse of Canadian groundfish resources. 

Hooded seals are being taken in Canadian lumpfish and groundfish gillnets and trawls; however, estimates of total removals have

not been calculated to date. 
165

Table 2. Summary of the incidental mortality of hooded seal (Cystophora cristata) by commercial fishery including the years

sampled (Years), the number of vessels active within the fishery (Vessels), the type of data used (Data Type), the annual

observer coverage (Observer Coverage), the mortalities recorded by on-board observers (Observed Mortality), the estimated

annual mortality (Estimated Mortality), the estimated CV of the annual mortality (Estimated CVs) and the mean annual

mortality (CV in parentheses).

Fishery Years Vessels Data Type 1 Observer

Coverage 2 

Observed

Mortality

Estimated

Mortality 

Estimated

CVs 

Mean

Annual

Mortality

New England

Multispecies

Sink Gillnet

 93-97 349 Obs. Data

Weighout,

Logbooks

 .05, .07,

.05, .04, .06

 0, 0, 1, 0,

0

 0, 0, 28, 0, 0 0, 0, .96,

0, 0

 5.6

 (.96)

TOTAL 5.6

(.96)

1 Observer data (Obs. Data) are used to measure by-catch rates, and the data are collected within the Northeast Fisheries Science

Center (NEFSC) Sea Sampling Program. NEFSC collects Weighout (Weighout) landings data, and total landings are used as a

measure of total effort for the sink gillnet fishery. Mandatory logbook (Logbook) data are used to determine the spatial

distribution of some fishing effort in the New England multispecies sink gillnet fishery.

 2 The observer coverage for the New England multispecies sink gillnet fishery is measured in trips.

Other Mortality

 In 1988-93, strandings were less than 20 per year, and from 1994- 1997 they increased to about 50 per annum (Rubinstein 1994;

B. Rubinstein, New England Aquarium, pers. comm; NMFS unpublished data). Carcasses were recovered from Massachusetts,

Connecticut, and New York (Rubinstein 1994), North Carolina and U.S. Virgin Islands (NMFS, unpublished data). The increased

number of strandings may indicate a possible shift in distribution or range expansion southward into USA waters and, if so, fishery

interactions may increase. 

STATUS OF STOCK

The status of hooded seals relative to OSP in USA Atlantic EEZ is unknown. They are not listed as threatened or endangered

under the Endangered Species Act. The total fishery-related mortality and serious injury for this stock is believed to be very low

relative to the population size in Canadian waters and can be considered insignificant and approaching zero mortality and serious

injury rate. This is not a strategic stock because the level of human-caused mortality and serious injury is believed to be very low

relative to overall stock size.

REFERENCES

Anon. 1995. Report of the Joint ICES/NAFO Working Group on Harp and Hooded Seals. 5-9 June 1995, Dartmouth, Nova Scotia

Canada. NAFO SCS Doc. 95/16. Serial No. N2569. 40 pp.

Anon. 1998. Report of the Joint ICES/NAFO Working Group on Harp and Hooded Seals. 28 August - 3 September 1997,

Copenhagen, Denmark. ICES CM 1998/Assess:3. 35 pp.

Barlow, J., S.L. Swartz, T.C. Eagle, and P.R. Wade. 1995. U.S. Marine Mammal Stock Assessments: Guidelines for Preparation,

Background, and a Summary of the 1995 Assessments. U.S. Dep. Commer., NOAA Tech. Memo. NMFS-OPR-6, 73 pp. 

Benjaminsen, T., and T. Oritsland. 1975. The survival of year-classes and estimates of production and sustainable yield of northwest

Atlantic harp seals. int Comm. Northwest Atl. Fish. Res. Doc. 75/121. 

Bowen, W.D., R.A. Myers and K. Hay. 1987. Abundance estimation of a dispersed, dynamic population: Hooded seals

(Cystophora cristata) in the Northwest Atlantic. Can. J. Fish. Aquat. Sci. 44: 282-295.

Bravington, M. V. and K. D. Bisack. 1996. Estimates of harbor porpoise by-catch in the Gulf of Maine sink gillnet fishery, 1990-93.

Rep. int Whal. Commn. 46:567-574. 
166

Hammill, M. O., G. B. Stenson, and R. A. Myers. 1992. Hooded seal (Cystophora cristata) pup production in the Gulf of St.

Lawrence. Can. J. Fish. Aquat. Sci. 49: 2546-2550.

Hay, K., G. B. Stenson, D. Wakeham, and R. A. Myers. 1985. Estimation of pup production of hooded seals (Cystophora

cristata) at Newfoundland during March 1985. Con. Atl. Fish. Sci. Adv. Comm. 85/96. 

King, J. E. 1983. Seals of the World. Cornell University Press, Ithaca, NY, 240 pp. 

Lavigne, D. M. and K. M. Kovacs. 1988. Harps and Hoods Ice Breeding Seals of the Northwest Atlantic. University of Waterloo

Press, Waterloo, Ontario, Canada, 174 pp. 

Lett, P.F. 1977. A model to determine stock size and management options for the Newfoundland hooded seal stock. Can. Atl.

Fish. Sci. Adv. Comm. Res. Doc. 77/25.

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

Special Issue 15: 133-147.

Rubinstein, B. 1994. An apparent shift in distribution of ice seals, Phoca groenlandica, Cystophora cristata, and Phoca

hispida, toward the east coast of the United States. M.A. Thesis, Boston University, Boston, MA, 45 pp. 

Sergeant, D.E. 1976. Research on hooded seals Cystophora cristata Erxleben in 1976. International Commission for the

Northwest Atlantic Fisheries Research Document 76/X/126.

Stenson, G. B. 1993. The status of pinnipeds in the Newfoundland region. NAFO SCR Doc. 93/34.

Stenson, G.B., R.A. Myers, I-H Ni and W.G. Warren. 1996. Pup production of hooded seals (Cystophora cristata) in the

northwest Atlantic. NAFO Sci. Coun. Studies 26: 105-114.

Wade, P.R., and R.P. Angliss. 1997. Guidelines for assessing marine mammal stocks: Report of the GAMMS Workshop April 3-5,

1996, Seattle, Washington. U.S. Dep. Commer., NOAA Tech. Memo. NMFS-OPR-12, 93 pp.

Walden, J. 1996. The New England gillnet effort survey. NOAA, NMFS, NEFSC, Woods Hole, Massachusetts. NEFSC [Northeast

Fisheries Science Center] Ref. Doc. 99-10. 38p.

Winters, G. H. And B. Bergflodt. 1978. Mortality and productivity of the Newfoundland hooded seal stock. 

International Commission for the Northwest Atlantic Fisheries Res. Doc. 78/XI/91.
167

October 1999

BOTTLENOSE DOLPHIN (Tursiops truncatus):

Gulf of Mexico Bay, Sound, and Estuarine Stocks

STOCK DEFINITION AND GEOGRAPHIC RANGE

Bottlenose dolphins are distributed throughout the bays, sounds, and estuaries of the Gulf of Mexico (Mullin 1988). The

identification of biologically-meaningful “stocks” of bottlenose dolphins in these waters is complicated by the high degree of

behavioral variability exhibited by this species (Shane et al. 1986; Wells and Scott 1999), and by the lack of requisite information

for much of the region. 

Previous stock assessment reports have provisionally identified distinct stocks in each of 33 areas of contiguous, enclosed, or

semi-enclosed bodies of water adjacent to the Gulf of Mexico (Table 1, Waring et al. 1997), based on descriptions of relatively

discrete dolphin “communities” in some of these areas. A “community” includes resident dolphins that regularly share large portions

of their ranges, exhibit similar distinct genetic profiles, and interact with each other to a much greater extent than with dolphins in

adjacent waters. The term, as adapted from Wells et al. (1987), emphasizes geographic, genetic, and social relationships of dolphins.

Bottlenose dolphin communities do not constitute closed demographic populations, as individuals from adjacent communities are

known to interbreed. Nevertheless, the geographic nature of these areas and long-term stability of residency patterns suggest that

many of these communities exist as functioning units of their ecosystems and, under the Marine Mammal Protection Act, must be

maintained as such. Also, the stable patterns of residency observed within communities suggest that long periods would be required

to repopulate the home range of a community were it eradicated or severely depleted. Thus, in the absence of information supporting

management on a larger scale, it is appropriate to adopt a risk-averse approach and focus management efforts at the level of the

community rather than at some larger demographic scale. Support for this risk-averse approach derives from several sources. 

Long-term (year-round, multi-year) residency by at least some individuals has been reported from nearly every site where

photographic identification or tagging studies have been conducted in the Gulf of Mexico. In Texas, some of the dolphins in the

Matagorda-Espiritu Santo Bay area (Gruber 1981; Lynn 1995; Würsig and Lynn 1996), Aransas Pass (Shane 1977; Weller 1998),

San Luis Pass (Maze 1997), and Galveston Bay (Bräger 1993; Bräger et al. 1994; Fertl 1994) have been reported as long-term

residents. Hubard (1998) reported sightings of dolphins tagged 12-15 years previously in Mississippi Sound. In Florida, long-term

residency has been reported from Choctawhatchee Bay (1989-1993, F. Townsend, unpublished data), Tampa Bay (Wells 1986; Wells

et al. 1996a), Sarasota Bay (Irvine and Wells 1972; Irvine et al. 1981; Wells 1986, 1991; Scott et al. 1990; Wells et al. 1987),

Lemon Bay (Wells et al. 1996b), and Charlotte Harbor/Pine Island Sound (Shane 1990; Wells et al. 1996b, 1997). In many cases,

residents emphasize use of the bay, sound, or estuary waters, with limited movements through passes to the Gulf of Mexico (Shane

1977, 1990; Gruber 1981; Irvine et al. 1981; Lynn 1995, Maze 1997). These habitat use patterns are reflected in the ecology of the

dolphins in some areas; for example, residents of Sarasota Bay, Florida lacked squid in their diet, unlike non-resident dolphins

stranded on nearby Gulf beaches (Barros and Wells 1998). 

Genetic data also support the concept of relatively discrete bay, sound, and estuary stocks. Analyses of mitochondrial DNA

haplotype distributions indicate the existence of clinal variations along the Gulf of Mexico coastline (Duffield and Wells, in press).

 Differences in reproductive seasonality from site to site also suggest genetic-based distinctions between communities (Urian et al.

1996). Mitochondrial DNA analyses suggest 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 between adjacent

communities in Tampa Bay, Sarasota Bay, and Charlotte Harbor/Pine Island Sound, along the central west coast of Florida (Duffield

and Wells 1991, in press). Examination of protein electrophoretic data resulted in similar conclusions for the Florida dolphins

(Duffield and Wells 1986).

The long-term structure and stability of at least some of these communities is exemplified by the residents of Sarasota Bay,

Florida. This community has been observed since 1970 (Irvine and Wells 1972; Scott et al. 1990; Wells 1991). The number of

dolphins regularly occupying the Sarasota Bay area has remained consistently at about 100. At least four generations of identifiable

residents currently inhabit the region, including half of those first identified in 1970. Maximum immigration and emigration rates of

about 2-3% have been estimated (Wells and Scott 1990).

Genetic exchange occurs between resident communities; hence the application of the demographically and behaviorally-based term

“community” rather than “population” (Wells 1986). Up to about 30% of calves in Sarasota Bay apparently have been sired by

non-residents (Duffield and Wells in press). A variety of potential exchange mechanisms occur in the Gulf. Small numbers of inshore

dolphins traveling between regions have been reported, with patterns ranging from traveling through adjacent communities (Wells
168

1986; Wells et al. 1996a,b) to movements over distances of several hundred km in Texas waters (Gruber 1981; Würsig and Lynn

1996; Würsig unpublished data). In many areas year-round residents co-occur with non-resident dolphins, providing potential

opportunities for genetic exchange. About 17% of group sightings involving resident Sarasota Bay dolphins include at least one nonresident as well (Wells et al. 1987). Similar mixing of inshore residents and non-residents is seen off San Luis Pass, Texas (Maze

1997). Non-residents exhibit a variety of patterns, ranging from apparent nomadism recorded as transience in a given area, to apparent

seasonal or non-seasonal migrations. Passes, especially the mouths of the larger estuaries, serve as mixing areas. For example, several

communities mix at the mouth of Tampa Bay, Florida (Wells 1986), and most of the dolphins identified in the mouths of Galveston

Bay and Aransas Pass, Texas were considered transients (Henningsen 1991; Bräger 1993; Weller 1998). 

Seasonal movements of dolphins into and out of some of the bays, sounds, and estuaries provide additional opportunities for

genetic exchange with residents, and complicate the identification of stocks in coastal and inshore waters. In small bay systems such

as Sarasota Bay, Florida and San Luis Pass, Texas residents move into Gulf coastal waters in fall/winter, and return inshore in

spring/summer (Irvine et al. 1981; Maze 1997). In larger bay systems, seasonal changes in abundance suggest possible migrations,

with increases in more northerly bay systems in summer, and in more southerly systems in winter. Fall/winter increases in abundance

have been noted for Matagorda Bay (Gruber 1981; Lynn 1995; Würsig and Lynn 1996), Aransas Pass (Shane 1977; Weller 1998),

Tampa Bay (Scott et al. 1989), and Charlotte Harbor/Pine Island Sound (Thompson 1981; Scott et al. 1989). Spring/summer

increases in abundance have been reported for Galveston Bay (Henningsen 1991; Bräger 1993; Fertl 1994) and Mississippi Sound

(Hubard 1998). 

Much uncertainty remains regarding the structure of bottlenose dolphin stocks in many of the Gulf of Mexico bays, sounds, and

estuaries. Given the apparent co-occurrence of resident and non-resident dolphins in these areas, and the demonstrated variations

in abundance, it appears that consideration should be given to the existence of a complex of stocks, and to the roles of bays, sounds,

and estuaries for stocks emphasizing Gulf of Mexico coastal waters. A starting point for management strategy should be the

protection of the long-term resident communities, with their multi-generational geographic, genetic, demographic, and social stability.

These localized units would be at greatest risk from geographically-localized impacts. Complete characterization of many of these

basic units would benefit from additional photo-identification, telemetry, and genetic research (Wells 1994). 

The current provisional stocks follow the designations in Table 1, with a few revisions. Available information suggests that Block

B35, Little Sarasota Bay, can be subsumed under Sarasota Bay, and B36, Caloosahatchee River, can be considered a part of Pine

Island Sound. As more information becomes available, additional combination or division may be warranted. For example, a number

of geographically and socially distinct subgroupings of dolphins in regions such as Tampa Bay, Charlotte Harbor, Pine Island Sound,

Aransas Pass, and Matagorda Bay have been identified, but the importance of these distinctions to stock designations remain

undetermined (Shane 1977; Gruber 1981; Wells et al. 1996a,b, 1997; Würsig and Lynn 1996).

Understanding the full complement of the stock complex using the bay, sound, and estuarine waters of the Gulf of Mexico will

require much additional information. The development of biologically-based criteria to better define and manage stocks in this region

should integrate multiple approaches, including studies of ranging patterns, genetics, morphology, social patterns, distribution, life

history, stomach contents, isozyme analyses, and contaminant concentrations. Spatially-explicit population modeling could aid in

evaluating the implications of community-based stock definition. As these studies provide new information on what constitutes a

bottlenose dolphin "biological stock," 

current provisional definitions will likely need to be revised. As stocks are more clearly identified, it will be possible to conduct

abundance estimates using standardized methodology across sites (thereby avoiding some of the previous problems of mixing results

of aerial and boat-based surveys), identify fisheries and other human impacts relative to specific stocks, and perform individual stock

assessments. As recommended by the Atlantic Scientific Review Group (November 1998, Portland, Maine), a workshop will be

held during 1999 to review current information pertaining to bottlenose dolphin stock structure in Gulf of Mexico bays, sounds, and

estuaries, conduct simulations of alternative stock structure and, if warranted, propose a new stock structure.
169

Table 1. Bottlenose dolphin abundance (NBEST), coefficient of variation (CV), minimum population estimate (NMIN), and

Potential Biological Removal (PBR) in U.S. Gulf of Mexico bays, sounds, and other estuaries. Blocks refer to aerial

survey blocks illustrated in Fig. 1. Blocks with an abundance of zero were surveyed but not considered stocks at this

time (but see Note 1 below).

Blocks Gulf of Mexico Estuary NBEST CV NMIN PBR Year Reference

B51 Laguna Madre 80 1.57 31 0.3 1992 A

B52 Nueces Bay, Corpus Christi Bay 58 0.61 36 0.4 1992 A

B50 Compano Bay, Aransas Bay, San Antonio Bay,

Redfish Bay, Espiritu Santo Bay

55 0.82 30 0.3 1992 A

B54 Matagorda Bay, Tres Palacios Bay, Lavaca Bay 61 0.45 42 0.4 1992 A

B55 West Bay 29 1.10 14 0.1 1992 A

B56 Galveston Bay, East Bay, Trinity Bay 152 0.43 107 1.1 1992 A

B57 Sabine Lake 0

1

- 1992 A

B58 Calcasieu Lake 0

1

- 1992 A

B59 Vermillion Bay, West 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 Mississippi River Delta 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. Vincent Sound, Apalachicola Bay, St. Georges

Sound

387 0.34 293 2.9 1993 A

B14-15 Apalachee Bay 491 0.39 358 3.6 1993 A

B16 Waccasassa Bay, Withlacoochee Bay, Crystal Bay 100 0.85 54 0.5 1994 A

B17 St. John’s Sound, Clearwater Harbor 37 1.06 18 0.2 1994 A

B32-34 Tampa Bay 559 0.24 458 4.6 1994 A

B20 Sarasota Bay 97 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 Sound, Charlotte Harbor, 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 Thousand Islands, Gullivan

Bay

208 0.46 144 1.4 1994 A

B27 Whitewater Bay 242 0.37 179 1.8 1994 A

B28 Florida Keys (Bahia Honda to Key West) 29 1.00 14 0.1 1994 A

References: A- Blaylock and Hoggard 1994; B- Wells 1992; C- Scott et al. 1989

Notes:

1 During earlier surveys (Scott et al. 1989), the range of seasonal abundances was as follows: B57, 0-2 (CV= 0.38); B58, 0-6 (0.34);

B59, 0-0; B30, 0-182(0.14); B07, 0-0; B21, 0-15(0.43); and B36, 0-0.

2 Block not surveyed during surveys reported in Blaylock and Hoggard 1994.

3 No CV because NBEST was a direct count of known individuals.
170

Figure 1. U.S. Gulf of Mexico bays and sounds. Each of the alpha-numerically designated blocks corresponds

to one of the NMFS Southeast Fisheries Science Center logistical aerial survey areas listed in Table 1. The

bottlenose dolphins inhabiting each bay and sound are considered to comprise a unique stock for purposes of

this assessment. 

POPULATION SIZE

Population size (Table 1) for all of the stocks except Sarasota Bay, Florida, was estimated from preliminary analyses of linetransect data collected during aerial surveys conducted in September-October 1992 in Texas and Louisiana; in September-October

1993 in Louisiana, Mississippi, Alabama, and the Florida panhandle (Blaylock and Hoggard 1994); and in September-November 1994

along the west coast of Florida (NMFS unpublished data). Standard line-transect perpendicular sighting distance analytical methods

(Buckland et al. 1993) and the computer program DISTANCE (Laake et al. 1993) were used. Stock size in Sarasota Bay, Florida,

was obtained through direct count of known individuals (Wells 1992). 

Minimum Population Estimate

The minimum population estimate (Table 1) is the lower limit of the two-tailed 60% confidence interval of the log-normally

distributed abundance estimate. This is equivalent to the 20th percentile of the log-normal distribution as specified by Wade and

Angliss (1997). The minimum population estimate was calculated for each block from the estimated population size and its associated

coefficient of variation. Where the population size resulted from a direct count of known individuals, the minimum population size

was identical to the estimated population size. 

Current Population Trend

The data are insufficient to determine population trends for all of the Gulf of Mexico bay, sound, and estuary bottlenose dolphin

communities. The Sarasota Bay community, however, has been monitored since 1970 and has remained relatively constant over the

last 20+ years at approximately 105 animals (Wells 1998). Three anomalous mortality events have occurred among portions of these

dolphin communities between 1990 and 1994; however, it is not possible to accurately partition the mortalities between bay and

coastal stocks, thus the impact of these mortality events on communities is not known. 

CURRENT AND MAXIMUM NET PRODUCTIVITY RATES

Current and maximum net productivity rates are not known for the dolphin communities that comprise these stocks. While

productivity rates may be estimated for individual females within communities, such estimates are confounded at the stock level due

to the influx of dolphins from adjacent areas which balance losses, and the unexplained loss of some individuals which offset births

and recruitment (Wells 1998). Continued monitoring and expanded survey coverage will be required to address and develop estimates

of productivity for these dolphin communities. The maximum net productivity rate was assumed to be 0.04. This value is based
171

on theoretical modeling showing that cetacean populations may not grow at rates much greater than 4% given the constraints of their

reproductive life history (Barlow et al. 1995).

POTENTIAL BIOLOGICAL REMOVAL

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

a “recovery” factor (Wade and Angliss 1997). The “recovery” factor, which accounts for endangered, depleted, and threatened

stocks, or stocks of unknown status relative to optimum sustainable population (OSP), is assumed to be 0.5 because these stocks

are of unknown status. PBR for each stock is given in Table 1. 

ANNUAL HUMAN-CAUSED MORTALITY AND SERIOUS INJURY

There are a number of difficulties associated with the interpretation of stranding data. It is possible that some or all of the

stranded dolphins may have been from a nearby coastal stock; however, the proportion of stranded dolphins belonging to another

stock cannot be determined because of the difficulty of determining from where the stranded carcass originated. Stranding data

probably underestimate the extent of fishery-related mortality and serious injury because not all of the dolphins which die or are

seriously injured in fishery interactions wash ashore, nor will all of those that do wash ashore necessarily show signs of entanglement

or other fishery-interaction. Finally, the level of technical expertise among stranding network personnel varies widely as does the

ability to recognize signs of fishery interaction, and the condition of the carcass if badly decomposed can inhibit the interpretation

of cause of death.

A total of 1,881 bottlenose dolphins were found stranded in the USA Southeast Gulf of Mexico from 1993 to 1997 (Table 2)

(NMFS unpublished data). Of these, 57 or 3% showed evidence of human interactions as the cause of death (e.g., gear entanglement,

mutilation, gunshot wounds). Bottlenose dolphin are known to become entangled in recreational and commercial fishing gear (Wells

et al. 1998; Gorzelany 1998; Wells and Scott 1994) and some are struck by recreational and commercial vessels (Wells and Scott

1997). In 1998 alone, two resident bottlenose dolphins and an associated calf were killed by vessel strikes and a resident young-ofthe-year died from entanglement in a crab-pot float line (R.S. Wells personal communication).

The Gulf of Mexico menhaden fishery was observed to take 9 bottlenose dolphins (three fatally) between 1992 and 1995 (NMFS

unpublished data). There were 1,366 sets observed out of 26,097 total sets, which if extrapolated for all years suggests that as many

as 172 bottlenose dolphins could have been taken in this fishery with up to 57 animals killed. An observer program is urgently needed

to obtain statistically reliable information for this fishery on the number of sets annually, the incidental take and mortality rates, and

the communities from which bottlenose dolphins are being taken.

Some of the bay, sound and estuarine communities were the focus of a live-capture fishery for bottlenose dolphins which supplied

dolphins to the U.S. Navy and to oceanaria for research and public display for almost two decades (NMFS unpublished data).

During the period between 1972-89, 490 bottlenose dolphins, an average of 29 dolphins annually, were removed from a few locations

in the Gulf of Mexico, including the Florida Keys. Mississippi Sound sustained the highest level of removals with 202 dolphins taken

from this stock during this period, representing 41% of the total and an annual average of 12 dolphins (compared to a current PBR

of 13). The annual average number of removals never exceeded current PBR levels, but it may be biologically significant that 73%

of the dolphins removed during 1982-88 were females. The impact of those removals on the stocks is unknown. 

Fishery Information

Annual fishing effort for the shrimp trawl fishery in the USA Gulf of Mexico bays, sounds, and estuaries during 1988-1993

averaged approximately 2.20 million hours of tows (CV = 0.11) (NMFS unpublished data). There have been no reports of incidental

mortality or injury in any of these stocks associated with the shrimp trawl fishery. 

A fishery for blue crabs operates in estuarine areas throughout the Gulf of Mexico coast employing traps attached to a buoy with

rope. Bottlenose dolphins have been reported stranded with polypropylene rope around their flukes (NMFS 1991; McFee and

Brooks, Jr. 1998; NMFS unpublished data), indicating the possibility of entanglement with crab pot lines. This fishery has not been

monitored by observers and there are no estimates of bottlenose dolphin mortality or serious injury for this fishery. 

Gillnets are not used in Texas, and gillnets over 46 m3 in area were not allowed in Florida past July 1995, but fixed and runaround

gillnets are currently in use in Louisiana, Mississippi, and Alabama. These fisheries, for the most part, operate year around. They

are state-controlled and licensed, and vary widely in intensity and target species. No marine mammal mortalities associated with

gillnet fisheries have been reported in these states, but stranding data suggest that gillnet and marine mammal interaction does occur,

causing mortality and serious injury.
172

Table 2. Bottlenose dolphin strandings in the USA Gulf of Mexico (West Florida to Texas) from 1993 to 1997. Data are from the

Southeast Marine Mammal Stranding Database (SESUS).

State 1993 1994 1995 1996 1997 Total

Florida

No. Stranded 134 51 101 133 63 482

No. Human Interactions 4 2 3 2 0 11

% With Human Interactions 3% 4% 3% 2% 0% 2%

Alabama

No. Stranded 48 16 15 17 14 110

No. Human Interactions 1 0 1 0 1 3

% With Human Interactions 2% 0% 7% 0% 7% 3%

Mississippi

No. Stranded 64 25 32 59 42 222

No. Human Interactions 4 0 4 2 2 12

% With Human Interactions 6% 0% 12% 3% 5% 5%

Louisiana

No. Stranded 14 74 31 92 42 253

No. Human Interactions 0 0 1 3 1 5

% With Human Interactions 0% 0% 3% 3% 2% 2%

Texas

No. Stranded 133 227 110 208 136 814

No. Human Interactions 4 6 7 7 2 26

% With Human Interactions 0% 3% 6% 3% 0% 3%

Totals

No. Stranded 393 393 289 509 297 1881

No. Human Interactions 13 8 16 14 6 57

% With Human Interactions 3% 2% 6% 3% 2% 3%

Other Mortality

The near shore habitat occupied by many of these stocks is adjacent to areas of high human population, and in some bays, such

as Mobile Bay in Alabama and Galveston Bay in Texas, is highly industrialized. The area surrounding Galveston Bay, for example,

has a coastal population of over 3 million people. More than 50% of all chemical products manufactured in the USA are produced

there and 17% of the oil produced in the Gulf of Mexico is refined there (Henningsen and Würsig 1991). Many of the enclosed bays

in Texas are surrounded by agricultural lands which receive periodic pesticide applications. 

Concentrations of chlorinated hydrocarbons and metals were examined in conjunction with an anomalous mortality event of

bottlenose dolphins in Texas bays in 1990 and found to be relatively low in most; however, some had concentrations at levels of

possible toxicological concern (Varanasi et al. 1992). No studies to date have determined the amount, if any, of indirect humaninduced mortality resulting from pollution or habitat degradation. However, a recent health assessment of 35 bottlenose dolphins

from Matagorda Bay, Texas associated high levels of chlorinated hydrocarbons with low health assessment scores (Reif et al., in

review). Morbillivirus has also been implicated in the deaths of bottlenose dolphins in some of these communities (Duignan et al.

1996).
173

STATUS OF STOCK

The status of these stocks relative to OSP is unknown and this species is not listed as threatened or endangered under the

Endangered Species Act. The occurrence of three anomalous mortality events among bottlenose dolphins along the USA Gulf of

Mexico coast since 1990 (NMFS unpublished data) is cause for concern; however, the effects of the mortality events on stock

abundance have not yet been determined. The available evidence suggests that bottlenose dolphin stocks in the northern and western

coastal portion of the USA Gulf of Mexico may have experienced a morbillivirus epidemic in 1993 (Lipscomb 1993; Lipscomb et

al. 1994). Seven of 35 live-captured bottlenose dolphins (20%) from Matagorda Bay, Texas, in 1992, tested positive for previous

exposure to cetacean morbillivirus (Reif et al., in review), and it is possible that other estuarine resident stocks have been exposed

to the morbillivirus (Duignan et al. 1996). 

The relatively high number of bottlenose dolphin deaths which occurred during the mortality events in the last decade suggests

that some of these stocks may be stressed. Fishery-related mortality and serious injury for each of these stocks is not known, but

considering the evidence from stranding data, the total fishery-related mortality and serious injury exceeds 10% of the total PBR, and,

therefore, it is not insignificant and approaching the zero mortality and serious injury rate. For these reasons, and because the PBR

for most of these stocks would be exceeded with the incidental capture of a single dolphin, each of these stocks is a strategic stock.

REFERENCES

Barlow, J., S.L. Swartz, T.C. Eagle and P.R. Wade. 1995. U.S. Marine Mammal Stock Assessments: Guidelines for Preparation,

Background and a Summary of the 1995 Assessments. NOAA Technical Memorandum. NMFS-OPR-6, 73 pp.

Barros, N.B. and R.S. Wells. 1998. Prey and feeding patterns of resident bottlenose dolphins (Tursiops truncatus) in Sarasota

Bay, Florida. J. Mamm. 79(3):1045-1059.

Blaylock, R.A. and W. Hoggard. 1994. Preliminary estimates of bottlenose dolphin abundance in southern U.S. Atlantic and Gulf

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440.

Bräger, S., B. Würsig, A. Acevedo, and T. Henningsen. 1994. Association patterns of bottlenose dolphins (Tursiops truncatus)

in Galveston Bay, Texas. J. Mamm. 75(2): 431-437. 

Buckland, S.T., D.R. Anderson, K.P. Burnham, and J.L. Laake. 1993. Distance sampling: Estimating abundance of biological

populations. Chapman & Hall, London. 446 pp. 

Duffield, D.A. and R.S. Wells. 1986. Population structure of bottlenose dolphins: Genetic studies of bottlenose dolphins along the

central west coast of Florida. Contract Report to National Marine Fisheries Service, Southeast Fisheries Center, Contract No.

45-WCNF-5-00366, 16 pp. 

Duffield, D.A. and R.S. Wells. 1991. The combined application of chromosome, protein and molecular data for the investigation of

social unit structure and dynamics in Tursiops truncatus. Pages 155-169 in A.R. Hoelzel (ed), Genetic Ecology of Whales and

Dolphins. Rep. int. Whal. Commn., Special Issue 13, Cambridge, U.K. 

Duffield, D.A. and R.S. Wells. In press. The molecular profile of a resident community of bottlenose dolphins, Tursiops

truncatus. In C.J. Pfeiffer (ed), Cell and Molecular Biology of Marine Mammals. 

Duignan, P.J., C. House, D.K. Odell, R.S. Wells, L. Hansen, M.T. Walsh, D.J. St. Aubin, B.K. Rima and J.R. Geraci. 1996.

Morbillivirus infection in bottlenose dolphin: evidence for recurrent epizootics in the Western Atlantic and Gulf of Mexico. Mar.

Mamm. Sci. 12(4):499-515.

Fertl, D.C. 1994. Occurrence, movements, and behavior of bottlenose dolphins (Tursiops truncatus) in association with the

shrimp fishery in Galveston Bay, Texas. M. Sc. thesis, Texas A&M University, College Station. 117 pp.

Gruber, J.A. 1981. Ecology of the Atlantic bottlenosed dolphin (Tursiops truncatus) in the Pass Cavallo area of Matagorda Bay,

Texas. M. Sc. thesis, Texas A&M University, College Station. 182 pp. 

Henningsen, T. 1991. Zur Verbreitung und Ökologie des Großen Tümmlers (Tursiops truncatus) in Galveston, Texas. Diploma

thesis, Christian-Albrechts-Universität, Kiel, Germany. 80 pp. 

Henningsen, T. and B. Würsig. 1991. Bottle-nosed dolphins in Galveston Bay, Texas: Numbers and activities. Pages 36-38 in P.

G. H. Evans (ed), European research on cetaceans - 5. Proceedings of the Fifth Annual Conference of the European Cetacean

Society, Sandefjord, Norway, 21-23 February, 1991. Cambridge, UK. 

Hubard, C.W. 1998. Abundance, distribution, and site fidelity of bottlenose dolphins in Mississippi Sound, Mississippi. M. Sc.

thesis, University of Alabama, Tuscaloosa. 101 pp.

Irvine, B. and R.S. Wells. 1972. Results of attempts to tag Atlantic bottlenose dolphins (Tursiops truncatus). Cetology 13:1-5.
174

Irvine, A.B., M.D. Scott, R.S. Wells and J.H. Kaufmann. 1981. Movements and activities of the Atlantic bottlenose dolphin,

Tursiops truncatus, near Sarasota, Florida. Fish. Bull. U.S. 79:671-688.

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. 72 pp. 

Lipscomb, T.P. 1993. Some answers to questions about morbillivirus. Pages 4-5 in R.A. Blaylock, B. Mase, and D. K. Odell (eds),

Strandings, Vol. 2, No. 3, SEFSC Miami Laboratory, Miami, Florida, 7 pp. 

Lipscomb, T.P. 1994. Morbilliviral disease in an Atlantic bottlenose dolphin (Tursiops truncatus) from the Gulf of Mexico.

Journal of Wildlife Diseases 30(4): 572-576.

Lynn, S.K. 1995. Movements, site fidelity, and surfacing patterns of bottlenose dolphins on the central Texas coast. M. Sc. thesis,

Texas A&M University, College Station. 92 pp. 

Maze, K.S. 1997. Bottlenose dolphins of San Luis Pass, Texas: Occurrence patterns, site fidelity, and habitat use. M. Sc. thesis,

Texas A&M University, College Station. 79 pp.

McFee, W.E. and W. Brooks, Jr. 1998. Fact finding meeting of marine mammal entanglement in the crab pot fishery: A summary.

U.S. Fish and Wildlife Service unpublished report.

Mullin, K.D. 1988. Comparative seasonal abundance and ecology of bottlenose dolphins (Tursiops truncatus) in three habitats

of the north-central Gulf of Mexico. Ph. D. dissertation, Mississippi State University, Starkville. 135 pp.

NMFS. 1991. Proposed regime to govern the interactions between marine mammals and commercial fishing operations after October

1, 1993. Draft Environmental Impact Statement, June 1991. 

Reif, J.S., L.J. Hansen, S. Galloway, G. Mitchum and T. L. Schmitt. In review. The relationship between chlorinated hydrocarbon

contaminants and selected health parameters in bottlenose dolphins (Tursiops truncatus) from Matagorda Bay, Texas, 1992.

Colorado State University, Fort Collins, and NMFS, Southeast Fisheries Science Center, Miami, Florida. 

Scott, G.P., D.M. Burn, L.J. Hansen and R.E. Owen. 1989. Estimates of bottlenose dolphin abundance in the Gulf of Mexico from

regional aerial surveys. CRD88/89-07.

Scott, G.P. 1990. Management-oriented research on bottlenose dolphins by the Southeast Fisheries Center. Pages 623-639 in S.

Leatherwood and R. R. Reeves (eds), The bottlenose dolphin. Academic Press, San Diego. 653 pp. 

Scott, M.D., R.S. Wells, and A.B. Irvine. 1990. A long-term study of bottlenose dolphins on the west coast of Florida. Pages 235-

244 in S. Leatherwood and R. R. Reeves (eds), The bottlenose dolphin. Academic Press, San Diego. 653 pp. 

Shane, S.H. 1977. The population biology of the Atlantic bottlenose dolphin, Tursiops truncatus, in the Aransas Pass area of

Texas. M. Sc. thesis, Texas A&M University, College Station. 238 pp. 

Shane, S.H. 1990. Behavior and ecology of the bottlenose dolphin at Sanibel Island, Florida. Pages 245-265 in S. Leatherwood and

R.R. Reeves (eds), The bottlenose dolphin. Academic Press, San Diego. 653 pp.

Shane, S.H., R.S. Wells and B. Würsig. 1986. Ecology, behavior, and social organization of the bottlenose dolphin: A review. Mar.

Mamm. Sci. 2(1):34-63.

Thompson, N.B. 1981. Estimates of abundance of Tursiops truncatus in Charlotte Harbor, Florida. NOAA/NMFS/SEFSC/Miami

Laboratory, Fishery Data Analysis Technical Report.

Urian, K.W., D.A. Duffield, A.J. Read, R.S. Wells and D.D. Shell. 1996. Seasonality of reproduction in bottlenose dolphins,

Tursiops truncatus. J. Mamm. 77:394-403.

Varanasi, U., K.L. Tilbury, D.W. Brown, M.M. Krahn, C.A. Wigren, R.C. Clark, and S.L. Chan. 1992. Pages 56-86 in L. J. Hansen

(ed), Report on Investigation of 1990 Gulf of Mexico Bottlenose Dolphin Strandings, Southeast Fisheries Science Center

Contribution MIA-92/93-21, 219 pp. 

Wade, P.R. and R.P. Angliss. 1997. Guidelines for assessing marine mammal stocks: Report of the GAMMS Workshop April 3-5,

Seattle, Washington. NOAA Technical Memorandum. NMFS-OPR-12, 93 pp.

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

Mammal Stock Assessments -- 1996. NOAA Technical Memorandum. NMFS-NE-114.

Weller, D.W. 1998. Global and regional variation in the biology and behavior of bottlenose dolphins. Ph. D. dissertation, Texas

A&M University, College Station. 142 pp.

Wells, R.S. 1986a. Population structure of bottlenose dolphins: behavioral studies along the central west coast of Florida. Contract

report to NMFS, SEFSC. Contract No. 45-WCNF-5-00366, 58 pp. 

Wells, R.S. 1986b. Structural aspects of dolphin societies. Ph. D. dissertation, University of California, Santa Cruz. 234 pp. 
175

Wells, R.S. 1991. The role of long-term study in understanding the social structure of a bottlenose dolphin community. Pages 199-

225 in K. Pryor and K.S. Norris (eds), Dolphin Societies: Discoveries and Puzzles. University of California Press, Berkeley.

397 pp.

Wells, R.S. 1992. The marine mammals of Sarasota Bay. Pages 9.1-9.23 in Sarasota Bay: Framework for action. Sarasota Bay

National Estuary Program, Sarasota, Florida. 

Wells, R.S. 1994. Determination of bottlenose dolphin stock discreteness: Application of a combined behavioral and genetic

approach. Pages 16-20 in K.R. Wang, P.M. Payne, and V.G. Thayer (compilers), Coastal Stock(s) of Atlantic Bottlenose

Dolphin: Status Review and Management. Proceedings and Recommendations from a Workshop held in Beaufort, NC, 13-14

September 1993. NOAA Technical Memorandum. NMFS-OPR-4. 120 pp.

Wells, R.S. 1998. Progress report: Sarasota long-term bottlenose dolphin research. Unpublished contract report to the U.S.

Department of Commerce, NOAA Fisheries, Southeast Fisheries Science Center, Miami. 5 pp.

Wells, R.S. and M.D. Scott. 1990. Estimating bottlenose dolphin population parameters from individual identification and capturerelease techniques. Pages 407-415 in P.S. Hammond, S.A. Mizroch and G.P. Donovan (eds), Individual Recognition of Cetaceans:

Use of Photo-Identification and Other Techniques to Estimate Population Parameters. 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. Academic Press, San Diego. 

Wells, R.S., M.D. Scott and A.B. Irvine. 1987. The social structure of free-ranging bottlenose dolphins. Pages 247-305 in

Genoways, H. (ed), Current Mammalogy, Vol. 1. New York, Plenum Press.

Wells, R.S., K.W. Urian, A.J. Read, M.K. Bassos, W.J. Carr and M.D. Scott. 1996a. Low-level monitoring of bottlenose dolphins,

Tursiops truncatus, in Tampa Bay, Florida: 1988-1993. NOAA Technical Memorandum. NMFS-SEFSC-385, 25 pp. + 6

Tables, 8 Figures, and 4 Appendices.

Wells, R.S., M.K. Bassos, K.W. Urian, W.J. Carr and M.D. Scott. 1996b. Low-level monitoring of bottlenose dolphins, Tursiops

truncatus, in Charlotte Harbor, Florida: 1990-1994. NOAA Technical Memorandum. NMFS-SEFSC-384, 36 pp. + 8 Tables,

10 Figures, and 5 Appendices. 

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. 1997. Low-level

monitoring of bottlenose 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. 1996. Movements, 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 Appendices. 
176

October 1999 

DWARF SPERM WHALE (Kogia simus):

Northern Gulf of Mexico Stock

STOCK DEFINITION AND GEOGRAPHIC RANGE

The dwarf sperm whale appears to be distributed worldwide in temperate to tropical waters (Caldwell and Caldwell 1989).

Sightings of these animals in the northern Gulf of Mexico occur primarily along the continental shelf edge and over the deeper waters

off the continental shelf (Mullin et al. 1991; Southeast Fisheries Science Center, SEFSC, unpublished data). Dwarf sperm whales

and pygmy sperm whales (Kogia breviceps) are difficult to distinguish and sightings of either species are often categorized as

Kogia sp. Sightings of this category were documented in all seasons during seasonal GulfCet aerial surveys of the northern Gulf

of Mexico during 1993-1995 (Hansen et al. 1996). The few reliable sightings of dwarf sperm whales during those surveys were more

numerous in spring, probably a result of greater survey efforts in that season (Jefferson and Shapiro 1997). Pygmy and dwarf sperm

whales have been sighted in the northwestern Gulf of Mexico in waters 1000 m deep, on average (Davis et al. 1998). However, these

authors cautioned that inferences on preferred bottom depths should await surveys for the entire Gulf of Mexico. The difficulty in

sighting pygmy and dwarf sperm whales may be exacerbated by their avoidance reaction towards ships, and change in behavior

towards approaching survey aircraft (Würsig et al. 1998). In a recent study using hematological and stable-isotope data, Barros et

al. (1998) speculated that dwarf sperm whales may have a more pelagic distribution than pygmy sperm whales, and/or dive deeper

during feeding bouts. There is no information on stock differentiation. 

POPULATION SIZE

Estimates of abundance of Kogia sp. were derived through the application of distance sampling analysis (Buckland et al. 1993)

and the computer program DISTANCE (Laake et al. 1993) to sighting data collected during 1991-1994 spring-summer, visual

sampling, line-transect vessel surveys of the northern Gulf of Mexico (Hansen et al. 1995), which includes data collected as part

of the GulfCet program (Hansen et al. 1996). These surveys were conducted throughout the area from approximately the 200 m

isobath along the USA coast to the seaward extent of the USA Exclusive Economic Zone. The seasonal GulfCet aerial surveys

included only a small portion of the species’ range and therefore, these data were not used to estimate population size. Estimated

abundance of Kogia sp. by survey year [coefficient of variation (CV) in parentheses] was 109 in 1991 (0.68), 1,010 in 1992 (0.40),

580 in 1993 (0.45), and 162 in 1994 (0.61) (Hansen et al. 1995). Survey effort-weighted estimated average abundance of Kogia sp.

for all surveys combined was 547 (CV = 0.28) (Hansen et al. 1995). Estimates of dwarf sperm whale abundance cannot be provided

due to uncertainty of species identification at sea. 

Minimum Population Estimate

A minimum population estimate was not calculated because of uncertainty of species identification at sea. 

Current Population Trend

There is insufficient information to describe any population trend of this species in the Gulf of Mexico.

CURRENT AND MAXIMUM NET PRODUCTIVITY RATES

Current and maximum net productivity rates are not known for this stock. The maximum net productivity rate was assumed to

be 0.04. This value is based on theoretical modeling showing that cetacean populations may not grow at rates much greater than 4%

given the constraints of their reproductive life history (Barlow et al. 1995).

POTENTIAL BIOLOGICAL REMOVAL

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

and a “recovery” factor (Wade and Angliss 1997). The “recovery “ factor, which accounts for endangered, depleted, and threatened

stocks, or stocks of unknown status relative to optimum sustainable population (OSP) is assumed to be 0.5 because this stock is of

unknown status. PBR for the dwarf sperm whale is unknown because the minimum population estimate cannot be estimated.

ANNUAL HUMAN-CAUSED MORTALITY AND SERIOUS INJURY
177

The level of past or current, direct, human-caused mortality of dwarf sperm whales in the northern Gulf of Mexico is unknown.

Available information indicates there likely is little, if any, fisheries interaction with dwarf sperm whales in the northern Gulf of

Mexico. There have been no logbook reports of fishery-related mortality or serious injury and no fishery-related mortality or serious

injury has been observed.

There were no documented strandings of dwarf sperm whales in the northern Gulf of Mexico during 1987-October 1998 which

were classified as likely caused by fishery interactions, but there have been stranding investigation reports of dwarf sperm whales

which may have died as a result of other human-related causes. Stranding data probably underestimate the extent of fishery-related

mortality and serious injury because not all of the marine mammals which die or are seriously injured may wash ashore, nor will all

of those that do wash ashore necessarily show signs of entanglement or other fishery-interaction. Finally, the level of technical

expertise among stranding network personnel varies widely as does the ability to recognize signs of fishery interaction. 

Fisheries Information

Pelagic swordfish, tunas, and billfish are the targets of the longline fishery operating in the USA Gulf of Mexico. Total longline

effort for the Gulf of Mexico pelagic fishery, including OCS edge, continental slope, and Mexican territorial waters, based on

mandatory logbook reporting, was 4,400 sets in 1991, 4,850 sets in 1992, and 3,260 sets in 1993 (Cramer 1994). This fishery has

been monitored with about 5% observer coverage, in terms of trips observed, since 1992. There were no reports of mortality or

serious injury of dwarf sperm whales by this fishery. 

Pair trawl fishing gear has the potential to capture marine mammals, but there have been no reports of mortality or serious injury

to marine mammals in the Gulf of Mexico. This fishery has not been observed by NMFS observers, and there are no other data

available as to the extent of this fishery in the Gulf of Mexico. It is assumed that it is very limited in scope and duration. 

Other Mortality

A total of at least 16 dwarf sperm whale strandings were documented in the northern Gulf of Mexico from 1990 through October

1998. 

STATUS OF STOCK

The status of this stock relative to OSP is unknown and there are insufficient data to determine population trends. This species

is not listed under the Endangered Species Act. Although the PBR cannot be calculated, there is no known fishery-related mortality

or serious injury to this stock and, therefore, total fishery-related mortality and serious injury can be considered insignificant and

approaching zero mortality and serious injury rate. The total level of fishery-related mortality and serious injury is unknown, but

it is believed to be insignificant.

REFERENCES

Barlow, J., S.L. Swartz, T.C. Eagle, and P.R. Wade. 1995. U.S. Marine Mammal Stock Assessments: Guidelines for Preparation,

Background and a Summary of the 1995 Assessments. U.S. Dep. Commer., NOAA Tech. Memo. NMFS-OPR-6, 73 pp.

Barros, N.B., D.A. Duffield, P.H. Ostrom, D.K. Odell, and V.R. Cornish. 1998. Nearshore vs. offshore ecotype differentiation of

Kogia breviceps and K. simus based on hemoglobin, morphometric and dietary analyses. Abstracts. World Marine Mammal

Science Conference. Monaco. 20-24 January. 

Buckland, S. T., D. R. Anderson, K. P. Burnham and J. L. Laake. 1993. Distance Sampling: estimating abundance of biological

populations. Chapman & Hall, London, 446 pp. 

Caldwell, D. K. and M. C. Caldwell 1989. Pygmy sperm whale Kogia breviceps (de Blainville, 1838): dwarf sperm whale Kogia

simus Owen, 1866. Pages 235-260 in S. H. Ridgway and R. Harrison (eds), Handbook of marine mammals, Vol. 4: River

dolphins and the larger toothed whales. Academic Press, San Diego. 

Cramer, J. 1994. Large pelagic logbook newsletter - 1993. NOAA Tech. Mem. NMFS-SEFSC-352, 19 pp. 

Davis, R.W., G.S. Fargion, N. may, T.D. Leming, M. Baumgartner, W.E. Evans, L.J. Hansen, and K. Mullin. 1998. Physical habitats

of cetaceans along the continental slope of the north-central and western Gulf of Mexico. Mar. Mamm. Sci., 14:490-507.

Hansen, L.J., K.D. Mullin, T.A. Jefferson and G.P. Scott. 1996. Visual surveys aboard ships and aircraft. Pages 55-132. In: R.W.

Davis and G.S. Fargion (eds). Distribution and abundance of marine mammals in the north-central and western Gulf of Mexico:

Final Report. Volume II: Technical Report. OCS Study MMS 96-0027. Prepared by the Texas Institute of Oceanography and

the National Marine Fisheries Service. U.S. Dept. of the Interior, Minerals Mgmt. Service, Gulf of Mexico OCS Region, New

Orleans, LA. 357pp.
178

Hansen, L. J., K. D. Mullin and C. L. Roden. 1995. Estimates of cetacean abundance in the northern Gulf of Mexico from vessel

surveys. Southeast Fisheries Science Center, Miami Laboratory, Contribution No. MIA-94/95-25, 9 pp. + tables and figures.

Jefferson, T.J. and A. Schiro. 1997. Distribution of cetaceans in the northern Gulf of Mexico. Mammal Rev., 27:27-50. 

Laake, J. L., S. T. Buckland, D. R. Anderson, and K. P. Burnham. DISTANCE user’s guide, V2.0. Colorado Cooperative Fish &

Wildlife Research Unit, Colorado State University, Ft. Collins, Colorado, 72 pp. 

Mullin, K., W. Hoggard, C. Roden, R. Lohoefener, C. Rogers and B. Taggart. 1991. Cetaceans on the upper continental slope in the

north-central Gulf of Mexico. OCS Study/MMS 91-0027. U.S. Dept. of the Interior, Minerals Management Service, Gulf of

Mexico OCS Regional Office, New Orleans, Louisiana 108 pp. 

Wade, P.R., and R.P. Angliss. 1997. Guidelines for assessing marine mammal stocks: Report of the GAMMS Workshop April 3-5,

Seattle, Washington. U.S. Dep. Commer., NOAA Tech. Memo. NMFS-OPR-12, 93 pp.

Würsig, B., S.K. Lynn, T.A. Jefferson, and K.D. Mullin. 1998. Behavior of cetaceans in the northern Gulf of Mexico relative to

survey ships and aircraft. Aquat. Mammals, 24:41-50.
179

October 1999 

PYGMY SPERM WHALE (Kogia breviceps):

Northern Gulf of Mexico Stock

STOCK DEFINITION AND GEOGRAPHIC RANGE

The pygmy sperm whale appears to be distributed worldwide in temperate to tropical waters (Caldwell and Caldwell 1989).

Sightings of these animals in the northern Gulf of Mexico occur primarily along the continental shelf edge and over the deeper waters

off the continental shelf (Mullin et al. 1991; Southeast Fisheries Science Center, SEFSC, unpublished data). Pygmy sperm whales

and dwarf sperm whales (Kogia simus) are difficult to distinguish and sightings of either species are often categorized as Kogia

sp. Sightings of this category were documented in all seasons during seasonal GulfCet aerial surveys of the northern Gulf of Mexico

during 1993-1995 (Hansen et al. 1996). The difficulty in sighting pygmy and dwarf sperm whales may be exacerbated by their

avoidance reaction towards ships, and change in behavior towards approaching survey aircraft (Würsig et al. 1998) In a recent study

using hematological and stable-isotope data, Barros et al. (1998) speculated that dwarf sperm whales may have a more pelagic

distribution than pygmy sperm whales, and/or dive deeper during feeding bouts. There is no information on stock differentiation.

POPULATION SIZE

Estimates of abundance of Kogia sp. were derived through the application of distance sampling analysis (Buckland et al. 1993)

and the computer program DISTANCE (Laake et al. 1993) to sighting data collected during 1991-1994 spring-summer, visual

sampling, line-transect vessel surveys of the northern Gulf of Mexico (Hansen et al. 1995) (Fig. 1), which includes data collected

as part of the GulfCet program (Hansen et al. 1996). These surveys were conducted throughout the area from approximately the

200 m isobath along the USA coast to the seaward extent of the USA Exclusive Economic Zone. The seasonal GulfCet aerial surveys

included only a small portion of the species’ range and therefore, these data were not used to estimate population size. Estimated

abundance of Kogia sp. by survey year [coefficient of variation (CV) in parentheses] was 109 in 1991 (0.68), 1,010 in 1992 (0.40),

580 in 1993 (0.45), and 162 in 1994 (0.61) (Hansen et al. 1995). Survey effort-weighted estimated abundance of Kogia sp. for all

surveys combined was 547 (CV = 0.28) (Hansen et al. 1995). Estimates of pygmy sperm whale abundance cannot be provided due

to uncertainty of species identification at sea. 

Minimum Population Estimate

A minimum population estimate could not be calculated because of uncertainty of species identification at sea. 

Current Population Trend

There is insufficient information to describe any population trend for this species in the Gulf of Mexico.

CURRENT AND MAXIMUM NET PRODUCTIVITY RATES

Current and maximum net productivity rates are not known for this stock. The maximum net productivity rate was assumed to

be 0.04. This value is based on theoretical modeling showing that cetacean populations may not grow at rates much greater than 4%

given the constraints of their reproductive life history (Barlow et al. 1995).

POTENTIAL BIOLOGICAL REMOVAL

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

and a “recovery” factor (Wade and Angliss 1997). The “recovery “ factor, which accounts for endangered, depleted, and threatened

stocks, or stocks of unknown status relative to optimum sustainable population (OSP) is assumed to be 0.5 because this stock is of

unknown status. PBR for the pygmy sperm whale is unknown because the minimum population estimate cannot be estimated.

ANNUAL HUMAN-CAUSED MORTALITY AND SERIOUS INJURY

The level of past or current, direct, human-caused mortality of pygmy sperm whales in the northern Gulf of Mexico is unknown.

Available information indicates there likely is little, if any, fisheries interaction with pygmy sperm whales in the northern Gulf of

Mexico. There have been no logbook reports of fishery-related mortality or serious injury and no fishery-related mortality or serious

injury has been observed.
180

There have been no documented strandings of pygmy sperm whales in the northern Gulf of Mexico during 1987-October 1998

which have been classified as likely caused by fishery interactions, but there have been stranding investigation reports of pygmy

sperm whales which may have died as a result of other human-related causes. Stranding data probably underestimate the extent of

fishery-related mortality and serious injury because not all of the marine mammals which die or are seriously injured may wash

ashore, nor will all of those that do wash ashore necessarily show signs of entanglement or other fishery-interaction. Finally, the level

of technical expertise among stranding network personnel varies widely as does the ability to recognize signs of fishery interaction.

Fisheries Information

Pelagic swordfish, tunas, and billfish are the targets of the longline fishery operating in the USA Gulf of Mexico. Total longline

effort for the Gulf of Mexico pelagic fishery, including OCS edge, continental slope, and Mexican territorial waters, based on

mandatory logbook reporting, was 4,400 sets in 1991, 4,850 sets in 1992, and 3,260 sets in 1993 (Cramer 1994). This fishery has

been monitored with about 5% observer coverage, in terms of trips observed, since 1992. There were no reports of mortality or

serious injury of pygmy sperm whales by this fishery. 

Pair trawl fishing gear has the potential to capture marine mammals, but there have been no reports of mortality or serious injury

to marine mammals in the Gulf of Mexico. This fishery has not been observed by NMFS observers, and there are no other data

available as to the extent of this fishery in the Gulf of Mexico. It is assumed that it is very limited in scope and duration. 

Other Mortality

At least 20 pygmy sperm whale strandings were documented in the northern Gulf of Mexico from 1990 through October 1998.

Two of these animals had a plastic bag or pieces thereof in their its stomachs (Tarpley and Marwitz 1993, Barros, unpublished data).

Another animal stranded apparently due to injuries inflicted by impact, possibly with a vessel. 

STATUS OF STOCK

The status of this stock relative to OSP is unknown and there are insufficient data to determine population trends. This species

is not listed under the Endangered Species Act. Although the PBR cannot be calculated, the total known fishery-related mortality

and serious injury for this stock is zero and, therefore, can be considered insignificant and approaching zero mortality and serious

injury rate. The total level of fishery-related mortality and serious injury is unknown, but it is believed to be insignificant.

REFERENCES

Barlow, J., S.L. Swartz, T.C. Eagle, and P.R. Wade. 1995. U.S. Marine Mammal Stock Assessments: Guidelines for Preparation,

Background and a Summary of the 1995 Assessments. U.S. Dep. Commer., NOAA Tech. Memo. NMFS-OPR-6, 73 pp.

Barros, N.B., D.A. Duffield, P.H. Ostrom, D.K. Odell, and V.R. Cornish. 1998. Nearshore vs. offshore ecotype differentiation of

Kogia breviceps andK. simus based on hemoglobin, morphometric and dietary analyses. Abstracts. World Marine Mammal

Science Conference. Monaco. 20-24 January.

Buckland, S. T., D. R. Anderson, K. P. Burnham and J. L. Laake. 1993. Distance Sampling: estimating abundance of biological

populations. Chapman & Hall, London, 446 pp. 

Caldwell, D. K. and M. C. Caldwell 1989. Pygmy sperm whale Kogia breviceps (de Blainville, 1838): dwarf sperm whale Kogia

simus Owen, 1866. Pages 235-260 in S. H. Ridgway and R. Harrison (eds), Handbook of marine mammals, Vol. 4: River

dolphins and the larger toothed whales. Academic Press, San Diego. 

Cramer, J. 1994. Large pelagic logbook newsletter - 1993. NOAA Tech. Mem. NMFS-SEFSC-352, 19 pp. 

Davis, R.W., G.S. Fargion, N. may, T.D. Leming, M. Baumgartner, W.E. Evans, L.J. Hansen, and K. Mullin. 1998. Physical habitats

of cetaceans along the continental slope of the north-central and western Gulf of Mexico. Mar. Mamm. Sci., 14:490-507.

Hansen, L.J., K.D. Mullin, T.A. Jefferson and G.P. Scott. 1996. Visual surveys aboard ships and aircraft. Pages 55-132. In: R.W.

Davis and G.S. Fargion (eds). Distribution and abundance of marine mammals in the north-central and western Gulf of Mexico:

Final Report. Volume II: Technical Report. OCS Study MMS 96-0027. Prepared by the Texas Institute of Oceanography and

the National Marine Fisheries Service. U.S. Dept. of the Interior, Minerals Mgmt. Service, Gulf of Mexico OCS Region, New

Orleans, LA. 357pp.

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. 
181

Laake, J. L., S. T. Buckland, D. R. Anderson, and K. P. Burnham. DISTANCE user’s guide, V2.0. Colorado Cooperative Fish &

Wildlife Research Unit, Colorado State University, Ft. Collins, Colorado, 72 pp. 

Mullin, K., W. Hoggard, C. Roden, R. Lohoefener, C. Rogers and B. Taggart. 1991. Cetaceans on the upper continental slope in the

north-central Gulf of Mexico. OCS Study/MMS 91-0027. U.S. Dept. of the Interior, Minerals Management Service, Gulf of

Mexico OCS Regional Office, New Orleans, Louisiana 108 pp. 

Tarpley, R.J., and S. Marwitz. 1993. Plastic debris ingestion by cetaceans along the Texas coast: two case studies. Aquat.

Mammals, 14:93-98.

Wade, P.R., and R.P. Angliss. 1997. Guidelines for assessing marine mammal stocks: Report of the GAMMS Workshop April 3-5,

Seattle, Washington. U.S. Dep. Commer., NOAA Tech. Memo. NMFS-OPR-12, 93 pp.

Würsig, B., S.K. Lynn, T.A. Jefferson, and K.D. Mullin. 1998. Behavior of cetaceans in the northern Gulf of Mexico relative to

survey ships and aircraft. Aquat. Mammals, 24:41-50.
182

 Appendix I1. Observer comments relating to condition of marine mammals observed caught in 1994-1997 by US pelagic longline vessels operating in the Atlantic. Listing

includes unique trip identifier (TRIP #), date of capture, species taken, latitude (Lat), longitude (Lon), and comments. Information provided by M. Tork

(NEFSC) and D. Lee (SEFSC). 

Trip # Date Species Lat Lon Comments

A02 1/8/94 Pilot whale 37 15 74 20 alive; cut from gear; condition unknown

A28030 8/9/94 Pilot whale 39 01 72 41 alive; mainline wrapped around fluke; one end of linecut and the other pulled to free animal; animal swam away

8/16/94 Pilot whale 38 55 72 51 hooked in pectoral fin; gangion cut and animal swam away

A32006 8/11/94 Pilot whale 37 15 74 29 alive; gangion cut; animal swam away

8/11/94 Pilot whale 37 15 74 29 same as previous entry

8/11/94 Pilot whale 37 15 74 29 same as previous entry

8/11/94 Pilot whale 37 15 74 29 same as previous entry

8/11/94 Pilot whale 37 15 74 29 same as previous entry

8/12/94 Pilot whale 37 20 74 20 tangled in mainline; cut free; swam away

A32008 8/26/94 Risso’s dolphin 38 45 72 54 dead; animal wrapped in gear; mainline wrapped around body immediately adjacent to flukes

A44004 9/16/94 Pilot whale 38 24 73 24 alive; hooked in dorsal fin; mainline cut to release animal with gangion still attached

9/17/94 Pilot whale 38 16 73 30 animal cut from mainline several wraps of mainline and part of gangion around base of flukes/tail; animal swam off

slowly

9/18/94 Risso’s dolphin 38 02 73 17 hooked in mouth; broke gangion from mainline; released alive

9/19/94 Pilot whale 37 50 73 19 hooked in mouth; broke gangion from mainline; swam away strongly trailing 50 fathoms of mainline from its mouth

9/21/94 Risso’s dolphin 39 52 70 02 hooked in tail fluke and mainline; gear cut to release animal; swam away with mainline and leader around tail

A53037 9/21/94 Risso’s dolphin 39 55 69 20 alive; gear wrapped around animal; cut loose by crew; swam away quickly

A54003 9/21/94 Killer whale 47 24 40 48 alive

A62002 10/21/94 Risso’s dolphin 39 48 69 59 a good amount of mainline was tangled around animal; released with a fair amount of mainline around fluke; some blood

noticed around caudal peduncle

10/25/94 Risso’s dolphin 39 44 70 54 hooked in mouth; animal released with hook in mouth and approximately 7 fathoms of 4001 b test line trailing from

mouth

10/27/94 Risso’s dolphin 39 46 70 56 apparently hooked in mouth; appeared to be wound up the midsection of the body with line; animal swam off quite

sluggishly
183

Appendix I (continued).

Trip # Date Species Lat Lon Comments

A54005 12/9/94 Pilot whale 35 42 74 42 alive; gear around flipper

12/9/94 Pilot whale 35 42 74 42 alive; gear around body

F15 6/18/94 Pantropical Spotted dolphin 27 37 88 25 alive; tail wrapped in dropline; all line removed

F16 7/14/94 Atlantic spotted dolphin 29 07 87 20 alive; hook in corner of mouth, gangion line wrapped around mouth; line was removed but hook remained

A53034 8/30/95 Pilot whale 46 13 40 07 animal cut free; swam away quickly

A41031 8/9/95 Pilot whale 40 20 67 55 cut loose with leader still attached- line parted as it neared the vessel; "mouth hooked" 

8/12/95 Risso’s dolphin 40 25 67 30 hooked in mouth; gangion cut to free animal; alive

A25041 8/10/95 Pilot whale 40 15 67 53 alive; animal hooked or maybe wrapped in mono; condition unknown

A44040 8/4/95 Pilot whale 37 33 74 10 hooked in flipper; cut from gangion; alive

8/13/95 Risso’s dolphin 39 25 72 02 alive; mainline and gangion wrapped around tail; all gear cut before animal released

A62058 8/11/95 Pilot whale 37 01 74 31 animal extensively wrapped in mainline around caudal peduncle; most of the line cut away; animal released with the

remaining line trailing

A62058 8/14/95 Pilot whale 37 09 74 24 gear cut from animal; alive

A41032 8/30/95 Pilot whale 38 04 73 46 mouth hooked; line snapped and animal swam off

A44043 8/31/95 Risso’s dolphin 39 43 71 49 mainline cut from around tail flukes and pulled from mouth; animal swam away quickly

9/3/95 Pilot whale 39 05 72 30 hooked in flipper; gangion broke off as it was hauled 

9/7/95 Risso’s dolphin 39 05 72 32 mainline cut from around tail flukes; animal swam off slowly after blowing

9/28/95 Shortfin Pilot whale 38 21 73 31 hooked in mouth; gangion clipped as close to the mouth as possible; released with hook in mouth
184

Appendix I (continued).

Trip # Date Species Lat Lon Comments

A41034 10/4/95 Pilot whale 37 00 74 36 animal swam away after breaking line; condition unknown

10/10/95 Pilot whale 35 43 74 37 hooked in mouth; leader cut to free animal; condition unknown

10/11/95 Pilot whale 35 46 74 42 Leader cut to free animal; condition unknown

10/11/95 Pilot whale 35 46 74 42 same as previous entry except animal swam towards 3 other "waiting" whales and swam away with them

A44048 10/16/95 Pilot whale 37 45 73 25 hooked in mouth; cut from mainline; swam away trailing gangion and 100 feet of mainline

T12 10/23/95 Pilot whale 26 42 79 40 alive; entangled in mainline, mono cut away

F29 8/4/95 Unid MM 39 24 72 17 animal not seen by observer; crew was pulling in gangion when they noticed it was a mm; line broke and animal swan

away; crew called out whale; other large dolphin (unknown) in area.F38

F38 7/28/96 Rissos’s dolphin 29 01 87 47 Muscle tissue sample taken from the head, and the lower jaw was also saved. The animal was entangled in the main

line and brought aboard dead 

F39 8/30/96 Risso’s dolphin 39 24 72 17 Mainline wrapped around flukes, unwrapped flukes, swam away

Risso’s dolphin 39 24 72 17 Mainline wrapped around flukes, unwrapped flukes, swam away

Risso’s dolphin 38 15 73 18 Hooked in mouth, line cut, 914 cm of line left attached (animal pulling very lively) swam away uninjured

K17 12/14/96 Unidentified mammal 30 26 76 55 Was tangled in line, black tail section seen just before dive, animal was free with no line attached

F45 2/25/97 Clymene dolphin Tail wrapped in mainline; mainline cut free. Animal swam away healthy

F38 7/28/96 Risso’s dolphin 27 40 87 31 Samples (mandible, skin, blubber, and muscle) taken.

0045 8/3/97 Pilot whale Pilot whale brought up; animal sluggish but swimming at side of vessel. Gear was tangled and wrapped around flukes

only. Main line and gangions were cut and all gear removed. Animal then swam slowly away. Only injury suffered

were lacerations around flukes from gear, no knives used to free animal.

1

 This is Table 17 taken from: Johnson, D.R., C.A. Brown, and C. Yeung. 1999. Estimates of marine mammal and marine turtle catch by the US Atlantic pelagic longline fleet in 1992-1997. NOAA

Tech. Mem. NOAA-SEFSC-418, 70p.
185

INDEX

Arctic ............................. 15, 33, 156, 166, 171

Atlantic spotted dolphin ........... 1, 2, 116, 117, 119, 120,

122, 126, 192

Balaenoptera acutorostrata ...................... 36, 42-44

Balaenoptera borealis ............................. 30, 32

Balaenoptera musculus............................ 33-35

Barataria Bay ..................................... 178

Basque whalers...................................... 6

Bay Boudreau ..................................... 178

Bay of Fundy ......... 2, 5, 6, 9, 11, 26, 27, 36, 37, 39, 41, 45,

47, 60, 67, 74, 81, 86, 95, 99-101, 103, 106, 108,

117, 123, 129, 145-147, 149, 150, 152, 154-156,

158, 161, 164

billfish ....................................... 186, 189

Blainville’s beaked whale ............................. 71

blue whale .................................... 4, 33-35

Bonsecour Bay .................................... 178

bottlenose dolphin .......... 2-4, 128-134, 136-144, 176-184

Brevortia tyrannus ................................. 141

Calcasieu Lake .................................... 178

Canada ........ 9, 28, 30, 31, 33, 34, 41, 46, 50-52, 55, 57, 64,

71, 78, 86, 89, 94, 95, 103, 105, 112, 114, 115,

145, 149, 151, 152, 154-156, 158, 160, 162-168,

170-175

Canadian East Coast ......................... 3, 36-38, 44

Canadian fisheries .................................. 147

Cape Cod Bay ............................ 5, 6, 8, 11, 21

Cape Hatteras ....... 8, 15-18, 20, 25-27, 30, 31, 36-40, 46-50,

53, 54, 56, 57, 59, 61, 62, 66-69, 73-76, 80-86,

91, 93, 94, 97, 100, 102, 107, 108, 110-112, 116-

119, 122-125, 128-131, 136-140, 142, 147, 149,

157, 163, 168, 173

Chesapeake Bay ............................... 116, 152

chlorinated hydrocarbons ..................... 90, 142, 182

Clearwater Harbor ................................. 178

clymene dolphin ................................... 193

coastal gillnet .......... 77, 101, 102, 111, 113, 118, 124, 133,

141, 142, 147, 148, 152, 168, 173

cod traps............... 9, 17, 41, 86, 95, 158, 164, 168, 173

common dolphin ......................... 2, 107-112, 114

Compano Bay .................................... 178

Connecticut .............................. 141, 153, 174

contaminants ........... 88, 89, 137, 142, 143, 145, 155, 183

Crystal Bay ...................................... 178

Cystophora cristata .................... 170, 171, 174, 175

DDT ............................................. 88

Delaware ......... 14, 20, 44, 46, 51, 57, 64, 71, 78, 83, 88, 92,

105, 114, 134, 139, 153

Delphinus delphis ......................... 107, 113-115

drift gillnet ........ 8-10, 17, 18, 23, 38, 39, 42, 44, 49-51, 54,

55, 57, 62-64, 69, 70, 72, 76, 77, 79, 83, 84, 87-

89, 93, 96-98, 101-105, 110, 113-115, 118-120,

124-126, 131-134, 147, 149, 151-153, 168, 173

dwarf sperm whale .......... 1, 3, 4, 53-55, 57, 185, 186, 189

East Bay ......................................... 178

ecotype .................... 55, 57, 128, 136, 139, 186, 189

entanglement ........ 8, 9, 11, 17, 18, 21, 22, 28, 31, 38, 40, 43,

44, 57, 84, 93, 105, 140, 143, 152, 157, 159, 165,

180, 183, 186, 189

epidemic ......................................... 182

estuaries ......................... 136, 137, 176-178, 180

Eubalaena glacialis ............................. 5, 12, 13

fin whale .................................. 3, 25-29, 34

foreign fishing ........ 15, 26, 30, 36, 47, 59, 67, 73, 75, 81, 83,

88, 92, 100, 102, 108, 109, 116, 118, 122, 124,

129, 131

Georges Bank ....... 5, 9, 10, 14, 17, 18, 20, 23, 26, 27, 30, 37,

39, 40, 46-48, 50, 54, 59-62, 66-69, 73, 74, 76,

80-82, 84, 85, 93, 99, 100, 102, 106-108, 110,

118, 124, 128-131, 149

Georgia ....................... 5, 8, 28, 138, 140, 141, 159

gillnet ....... 8-10, 12, 17-19, 23, 38, 39, 41, 42, 44, 45, 49-51,

54, 55, 57, 62-64, 69, 70, 72, 76, 77, 79, 83, 84,

86-89, 93, 95-98, 101-106, 110, 111, 113-115,

118-120, 124-127, 131-134, 141-143, 147-155,

157-161, 163-165, 168-170, 173-175, 181

Globicephala macrorhynchus .......................... 91

Globicephala melas ...................... 80, 83, 89, 91, 92

Grampus griseus .............................. 73, 77, 78

gray seal ............................... 2, 160, 162-165

Great South Channel ....... 5, 7, 11, 12, 20, 21, 30, 84, 85, 93

Greenland .......... 5, 14, 16, 33, 36, 49, 86, 95, 99, 103, 145,

156, 158, 164, 166, 171

groundfish .......... 9, 17, 41, 86, 95, 103, 147-151, 157, 158,

164, 168, 173

Gulf of Maine ....... 2, 5, 8, 9, 14-18, 22, 23, 25-30, 32, 35-38,

40, 45, 47, 48, 51, 60, 64, 67, 72-74, 79-81, 89,

99, 100, 102, 103, 105-108, 111, 115, 117, 120,

123, 126, 129, 134, 145-148, 153-155, 157, 158,

160, 163, 165, 168, 169, 173, 175

Gulf of Mexico .............. 1, 2, 4, 5, 12, 33, 36, 51, 59, 66,

76-78, 84, 85, 87, 91, 94, 96-98, 107, 111, 116,

118, 119, 122, 124-126, 131, 136, 138, 142, 176-

190

Gulf Stream ....... 26, 29, 37, 46-48, 52, 59-61, 65-68, 72-74,

79-82, 90, 91, 100, 107, 108, 115-117, 121, 123,

129, 130, 135-138

Gullivan Bay ..................................... 178
186

gunshot wounds ............................... 140, 180

Halichoerus grypus ........................ 162, 164, 165

harbor porpoise ........ 2, 29, 45, 51, 64, 72, 79, 89, 105, 106,

115, 120, 126, 134, 145-155, 158, 160, 164, 165,

168, 169, 173, 175

harbor seal ............................. 2, 154, 156-160

harp seal ................................... 2, 166-170

haul seine ........................................ 141

health assessment .......................... 142, 143, 182

herring weirs ............. 9, 41, 150-152, 154, 155, 158, 164

hooded seal ............................... 1, 2, 171-175

humpback whale ....................... 3, 14, 16-18, 22-24

Indian/Banana River ............................ 128, 136

Key West .................................... 141, 178

killer whale ..................................... 3, 191

Kogia breviceps ................. 55-58, 185, 186, 188, 189

Kogia simus .............. 53-55, 57, 58, 185, 186, 188, 189

Lagenorhynchus acutus .................. 99, 104-106, 115

Long Island .......................... 11, 40, 51, 137, 156

longline fishery ........ 39, 76, 84, 85, 87, 92, 94, 96, 110, 111,

118, 119, 124, 125, 131, 186, 189

long-finned pilot whale .......... 80, 83, 86, 88, 89, 91, 92, 95

mackerel .......... 14, 21, 75, 83, 86-89, 92, 94, 96, 101-104,

109, 110, 112, 113, 131, 132, 157

Maine ....... 2, 5, 8, 9, 14-19, 21-23, 25-30, 32, 35-41, 45, 47-

51, 60, 64, 67, 72-74, 79-81, 88, 89, 99-103, 105-

108, 111, 115, 117, 120, 123, 126, 129, 134, 145-

148, 150, 152-163, 165, 166, 168-171, 173, 175,

177

mark-recapture ....................... 15, 16, 23, 166, 170

Maryland ................... 12, 23, 55, 140, 152, 153, 165

Massachusetts ........ 1, 5, 8, 9, 11, 12, 14, 22, 25, 29, 34, 45,

51, 55, 63, 65, 71, 72, 79, 88-90, 98, 105, 106,

114, 115, 135, 140, 147, 148, 152-155, 158-162,

165, 169, 170, 174, 175

matrilines .......................................... 5

Megaptera novaeangliae .................. 14, 18, 22-24, 34

menhaden .................................... 141, 180

Mesoplodon bidens ................................. 71

Mesoplodon densirostris .......................... 71, 72

Mesoplodon mirus .................................. 66

metals ....................................... 145, 182

minke whale ............................ 3, 36, 38-42, 44

morbillivirus .................................. 182, 183

mutilation ................................ 133, 152, 180

net entanglement .................................. 8, 22

New England ....... 5, 8, 14, 22, 25, 31, 36, 39, 40, 43-46, 50,

54, 57, 62, 66, 69, 76, 83, 85, 93, 94, 101-106,

110, 111, 113, 116, 118, 124, 132, 141, 147-149,

151, 153-166, 168-171, 173-175

New Jersey ......... 19, 22, 57, 80, 91, 97, 136, 137, 139, 141,

145, 152, 153, 159, 166

New York .......... 29, 35, 44, 51, 57, 64, 66, 71, 78, 89, 102,

103, 105, 111, 114, 120, 126, 134, 141, 145, 148,

149, 152, 153, 156, 159, 169, 170, 174, 184

North Carolina ....... 14, 15, 20-22, 26, 30, 36, 47, 53, 55-57,

59, 66, 73, 80, 91, 97, 99, 100, 102, 107, 111,

114, 116, 120, 122, 126, 128, 136, 140-145, 148,

152, 153, 155, 169, 174

pair trawl ......... 9, 18, 23, 44, 50, 51, 54, 55, 57, 62, 64, 72,

76-79, 83, 84, 87, 89, 93, 96-98, 105, 106, 110,

111, 113-115, 118-120, 124-126, 131-134, 153,

154, 168, 173, 186, 189

pantropical spotted dolphin .......... 1, 2, 116, 117, 122, 123,

125, 126, 192

PCBs ............................................ 88

Perdido Bay ...................................... 178

Phoca groenlandica ..................... 166, 169, 170, 175

Phoca vitulina ............................. 156, 159-161

Phocoena phocoena .................... 145, 151, 154, 155

photo-identification ......... 6, 7, 34, 137, 138, 143, 177, 184

Physeter macrocephalus ..................... 22, 46, 50, 51

Pine Sound ....................................... 178

Plymouth .......................................... 6

polychlorinated biphenyls ............................ 88

population growth rate .......................... 6, 7, 146

pygmy killer whale ................................... 3

pygmy sperm whale .............. 3, 4, 55-57, 186, 188, 189

Redfish Bay ...................................... 178

right whale ............................. 3, 5-9, 11-13, 30

Risso’s dolphin .................... 73-75, 77, 78, 191-193

Sabine Lake ....................................... 178

salmon gillnets ....................... 41, 86, 95, 158, 164

Scotian Shelf ....... 5, 30, 37, 46-48, 52, 60, 61, 67, 68, 74, 81,

82, 100, 107, 108, 114, 128-130, 134

sei whale ................................ vii, 1, 3, 30-32

ship collisions ....................................... 8

ship strikes ........................... 1-9, 11, 17, 22, 50

short-finned pilot whale ............... 80, 83, 89, 91, 92, 97

sink gillnet ......... 39, 44, 50, 54, 57, 62, 69, 76, 83, 93, 101,

102, 104, 105, 110, 111, 113, 118, 124, 131, 141,

147-154, 158-160, 163-165, 168, 169, 173-175

South Carolina ........ 77, 85, 88, 94, 111, 119, 125, 131, 140,

141, 143, 144, 159

sperm whale .............. 1, 3, 4, 46-57, 185, 186, 188, 189

spinner dolphin ..................................... 2

squid ....... 75, 83, 86-89, 92, 94, 96, 101-104, 109, 110, 112,

113, 131, 132, 176

St. Andrew Bay ................................... 178

St. Joseph Bay .................................... 178

Stellwagen Bank .................... 15, 19, 21, 30, 40, 158

Stenella attenuata ............................ 4, 122, 126

Stenella clymene ................................... 107

Stenella frontalis ............................. 4, 116, 122
187

Strait of Belle Isle ................................. 6, 33

striped dolphin ...................................... 2

swordfish ........ 18, 23, 39, 44, 50, 51, 54, 55, 62, 64, 69, 72,

76, 79, 84, 89, 93, 98, 102, 106, 110, 115, 118,

120, 124, 126, 131, 134, 149, 154, 186, 189

Ten Thousand Islands .............................. 178

TerreBonne Bay ................................... 178

Trinity Bay ...................................... 178

tunas ....................... 76, 84, 93, 110, 132, 186, 189

Vermillion Bay .................................... 178

West Bay ........................................ 178

West Cote Blanche Bay ............................. 178

Whitewater Bay ................................... 178

white-beaked dolphin ................................. 2

white-sided dolphin ....................... 2, 99, 101-106

Ziphius cavirostris ......................... 59, 63, 64, 70