NOAA TECHNICAL MEMORANDUM

NMFS-NEFSCU.S. ATLANTIC 

MARINE MAMMAL STOCK ASSESSMENTS - 1998

By

Gordon T. Waring, Debra L. Palka, Phillip J. Clapham,

Steve Swartz, Marjorie Rossman, Tim Cole, Kathryn D. Bisack

and Larry J. Hansen

U.S. Department of Commerce

National Oceanic and Atmospheric Administration

National Marine Fisheries Service

Northeast Fisheries Science Center

Woods Hole, Massachusetts 02543-1026

December 1998
ii

TABLE OF CONTENTS

EXECUTIVE SUMMARY ...................................................... v

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

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

TABLE 1. A SUMMARY OF ATLANTIC 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 .................................................... 13

FIN WHALE (Balaenoptera physalus):

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

SEI WHALE (Balaenoptera borealis):

Western North Atlantic Stock ............................................. 30

MINKE WHALE (Balaenoptera acutorostrata):

Canadian East Coast Stock ............................................... 33

BLUE WHALE (Balaenoptera musculus):

Western North Atlantic Stock ............................................. 40

SPERM WHALE (Physeter macrocephalus):

Western North Atlantic Stock ............................................. 43

DWARF SPERM WHALE (Kogia simus): 

Western North Atlantic Stock ............................................. 49

PYGMY SPERM WHALE (Kogia breviceps):

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

KILLER WHALE (Orcinus orca):

Western North Atlantic Stock ............................................. 55

PYGMY KILLER WHALE (Feresa attenuata): 
iii

Western North Atlantic Stock ............................................. 57

NORTHERN BOTTLENOSE WHALE (Hyperoodon ampullatus):

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

CUVIER'S BEAKED WHALE (Ziphius cavirostris):

Western North Atlantic Stock ............................................. 61

MESOPLODON BEAKED WHALES (Mesoplodon spp.):

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

RISSO'S DOLPHIN (Grampus griseus):

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

LONG-FINNED PILOT WHALE (Globicephala melas):

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

SHORT-FINNED PILOT WHALE (Globicephala macrorhynchus): 

Western North Atlantic Stock ............................................. 92

WHITE-BEAKED DOLPHIN (Lagenorhynchus albirostris):

Western North Atlantic Stock ............................................ 100

WHITE-SIDED DOLPHIN (Lagenorhynchus acutus):

Western North Atlantic Stock ............................................ 103

COMMON DOLPHIN (Delphinus delphis):

Western North Atlantic Stock ............................................ 110

ATLANTIC SPOTTED DOLPHIN (Stenella frontalis):

Western North Atlantic Stock ............................................ 118

PANTROPICAL SPOTTED DOLPHIN (Stenella attenuata):

Western North Atlantic Stock ............................................ 123

STRIPED DOLPHIN (Stenella coeruleoalba):

Western North Atlantic Stock ............................................ 129

SPINNER DOLPHIN (Stenella longirostris):

Western North Atlantic Stock ............................................ 134

BOTTLENOSE DOLPHIN (Tursiops truncatus):

Western North Atlantic Offshore Stock ..................................... 137
iv

BOTTLENOSE DOLPHIN (Tursiops truncatus):

Western North Atlantic Coastal Stock ...................................... 145

HARBOR PORPOISE (Phocoena phocoena):

Gulf of Maine/Bay of Fundy Stock ......................................... 151

HARBOR SEAL (Phoca vitulina):

Western North Atlantic Stock ............................................ 160

GRAY SEAL (Halichoerus grypus):

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

HARP SEAL (Phoca groenlandica):

Western North Atlantic Stock ............................................ 170

HOODED SEAL (Cystophora cristata):

Western North Atlantic Stock ............................................ 175

INDEX ................................................................... 180
v

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 current report contains only assessment reports for the Atlantic stocks, and updated

reports are identified by a December 1998 date-stamp. This format was selected to facilitate availability and because

the draft 1999 SARs are expected to be available in February 1999.

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 May 1998 meeting of the Atlantic Scientific Review

Group (ASRG), and subsequent revisions were based on their contributions and constructive criticism. In July 1998,

the revised report was available for a 90-day public comment period. The current version reflects changes made in

response to the public comments.

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 1997 publication. A total of 27 of the 31 Atlantic stock assessment

reports were revised for 1998. Most proposed changes incorporate new information into abundance or mortality

estimates. The revised SARs include 15 of the strategic stocks and 12 of the non-strategic stocks relative to the 1996

assessments. Some of the revisions clarified fisheries mortality information which resulted in changes to the status

of some stocks. Information on human interactions (fishery and ship strikes) between the North Atlantic right whale

and North Atlantic humpback whale stocks were re-reviewed and updated. The 1993 fishery induced mortality of a

North Atlantic right whale has been reassigned from the pelagic driftnet fishery to the lobster fishery based on a reexamination of all information. Abundance estimates for humpback whales, Canadian east coast stock of Minke

whales, Western North Atlantic stocks of common dolphins, and harbor seals have been revised. The Western North

Atlantic stock of Atlantic white-sided dolphins is now considered “strategic” based on incidental mortality in the New

England sink gillnet and North Atlantic bottom trawl fisheries. The Western North Atlantic stock of long-finned pilot

whales will remain “strategic” based on mortality in the Atlantic squid, mackerel, butterfish trawl fishery. The

Western North Atlantic stock of pygmy sperm whale is no longer considered “strategic”. One strategic stock that was

not updated, but extensively reviewed by the ASRG was the Western North Atlantic stock (stock complex) of coastal

bottlenose dolphins. New information on observed mortality in the 1995-1996 mid-Atlantic coastal gillnet fishery was

presented. One mortality was observed in 1996, and the preliminary mortality estimate was 4.1 (CV = 0.88). Fishery

effort data are under review and 1996-1997 mortality estimates will be provided in the draft 1999 assessment report.

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.
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), and

Blair Mase, Keith Mullin, and Jim Tobias (Southeast Fisheries Science Center). Also, we acknowledge advice and

comments provided by NEFSC: Richard Merrick and Fred Serchuk; and the Atlantic Scientific Review Group: Donald

Baltz, Solange Brault, Joseph DeAlteris, James Gilbert, Mike Harris, Robert Kenney, Robert MacKinnon, James Mead,

Daniel Odell, Andrew Read, Randall Wells, and Graham Worthy. We also thank Paul Wade, NMFS, Office of

Protected Species, for his comments and guidance at the SRG review meeting, the Marine Mammal Commission, the

Humane Society of the United States, the Blue Water Fishermen’s Association and Hal Caswell (Woods Hole

Oceanographic Institution) for their constructive comments and advice.
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 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 stocks for which significant new information were available. These are identified by the 1998 date-stamp

at the top right corner at the beginning of each report. Gulf of Mexico SARs were not updated from Waring (et al.

1997), therefore were not included in this document. Except for some minor editorial changes, stocks designated by

the 1995 or 1997 date-stamp are unchanged from the 1997 document (Waring et al. 1997). 

In this document, the status of long-finned pilot whale was changed to non-strategic because the 5-year (1992-

1996) mean annual mortality in fishing operations was 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.
2

December 1998

TABLE 1. A SUMMARY OF ATLANTIC 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 1998

stock assessment reports have been revised relative to the 1996 reports.)

Species Stock Area

SRG

Region

NMFS

Center Nmin Rmax Fr PBR

Total

Annual

Mort.

Annual

Fish.

Mort.

Strategic

Status

SAR

Revised

Harbor seal Western

North

Atlantic

ATL NEC 30,990 0.12 1.0 1,859 898 898 N Y

Gray seal Northwest

North

Atlantic

ATL NEC 2,010 0.12 1.0 121 41 41 N Y

Harp seal Northwest

North

Atlantic

ATL NEC N/A N/A N/A N/A 329 329 N Y

Hooded seal Northwest

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 1,667 1,667 Y Y

Risso's dolphin Western

North

Atlantic

ATL NEC 11,140 0.04 0.5 111 18 18 N Y

Atlantic whitesided dolphinWestern

North

Atlantic

ATL NEC 19,196 0.04 0.5 192 218 218 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 15,470 0.04 0.5 155 24712471 Y Y

Atlantic spotted

dolphin

Western

North

Atlantic

ATL NEC 1,61720.04 0.5 16 163163 Y Y

Pantropical spotted

dolphin

Western

North

Atlantic

ATL NEC 1,61720.04 0.5 16 162163 Y Y

Striped dolphin Western

North

Atlantic

ATL NEC 18,220 0.04 0.5 182 11 11 N Y

Spinner dolphin Western

North

Atlantic

ATL NEC N/A N/A N/A N/A 0.31 0.31 N Y
Species Stock Area

SRG

Region

NMFS

Center Nmin Rmax Fr PBR

Total

Annual

Mort.

Annual

Fish.

Mort.

Strategic

Status

SAR

Revised

3

Bottlenose dolphin Western

North

Atlantic,

offshore

ATL NEC 8,79440.04 0.5 88 58 58 N Y

Bottlenose dolphin Western5

North

Atlantic,

coastal

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

Dwarf sperm

whale

Western

North

Atlantic

ATL NEC N/A 0.04 N/A N/A 0.2 0.2 Y Y

Pygmy sperm

whale

Western

North

Atlantic

ATL NEC N/A 0.04 N/A N/A N/A N/A 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 Y

Cuvier's beaked

whale

Western

North

Atlantic

ATL NEC 89560.04 0.5 8.9 9.7 9.77 Y Y

Mesoplodon 

beaked whale

Western

North

Atlantic

ATL NEC 89560.04 0.5 8.9 9.7 9.77 Y Y

Pilot whale, longfinned

(Globicephala

spp..)

Western

North

Atlantic

ATL NEC 4,96880.04 0.5 50 32 329 N Y

Pilot whale, shortfinnedWestern

North

Atlantic

ATL NEC 457 0.04 0.5 4.6 32 329 Y Y

Sperm whale Western

North

Atlantic

ATL NEC 1,617 0.04 0.1 3.2 0.0 0.0 Y Y

North Atlantic

right whale

Western

North

Atlantic

ATL NEC 295 0.025 0.1 0.4 2.3 1.010 Y Y

Humpback whale Western

North

Atlantic

ATL NEC 10,019 0.065 0.1 32.6 5.7 4.411 Y Y

Fin whale Western

North

Atlantic

ATL NEC 1,704 0.04 0.1 3.4 0.5 0.20 Y Y
Species Stock Area

SRG

Region

NMFS

Center Nmin Rmax Fr PBR

Total

Annual

Mort.

Annual

Fish.

Mort.

Strategic

Status

SAR

Revised

4

1. Effort data for the 1996 Atlantic squid, mackerel, butterfish trawl fisheries are currently under review. The estimated mortalities attributed to

these fisheries will be included in the1999 SAR.

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

Sei whale Western

North

Atlantic

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 0.8 0.8 N Y

Blue whale Western

North

Atlantic

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

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

spotted dolphins.

4. Estimates may include sightings of the coastal form.

5. This stock assessment has not been updated. However, a revised assessment, including bycatch data from the 1995-1997 Atlantic coastal sink gillnet fishery,

will be prepared in 1999.

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

7. 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.

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

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

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

11. This is the average mortality of humpback whales based on 5 years of observer data (0.6) and additional fishery impact records (3.8).
5

December 1998

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 U.S.;

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 (Mate et al. 1992). 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). The acceptable

surface copepod resource is 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 photo-identified and catalogued population (through December of 1995)
6

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 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. 

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 U.S. 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 mid-1600s, with the

greatest population decline occurring in the early 1700s. The authors cautioned, however, that the record of removals

is incomplete, the results 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 current population growth rate reported by Knowlton et al. (1994) of 2.5% (CV = 0.12) suggests that the stock

is showing signs of slow recovery. However, as noted during a recent International Whaling Commission (IWC)

workshop on right whale assessment, conflicting data exist and the status of this population is not known (IWC 1999).

As further noted by the IWC, determination of this status is a high priority, notably in light of the known high levels

of anthropogenic mortality in this population.

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

five 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) (Knowlton et al. 1994). Since that report, total

reported calf production in 92/93 was 6; 93/94, 8; 94/95, 7; and 95/96, 22. (The total calf production was reduced

by reported calf mortalities: 2 in 1993, and 3 in 1996. Of the three calf mortalities in 1996, available data suggested
7

one was not included in the reported 21 mother/calf pairs, resulting in a total of 22 calves born.) Of the 46 adult

females considered to be available for calving in the 95/96 season, only 10 were documented to calve. The remaining

11 mothers were first observed with calves this 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,

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

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

The relatively low population size strongly suggests 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. 

ANNUAL HUMAN-CAUSED SERIOUS INJURY AND MORTALITY

For the period 1991 through 1996, the total estimated human-caused mortality and serious injury to right whales

is estimated as 2.3 per year. This is derived from two components: 1) non-observed fishery impact records, 1.0; and

2) ship strike records, 1.3. 

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
8

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).

For one area of concern, the coastal waters of the southeastern U.S., an awareness and mitigation program,

involving ten agencies and organizations, began in 1992, and has been upgraded and expanded annually. Other areas

may be included in the future. For waters of the northeastern U.S., 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.

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).

 The examination of the large whale entanglement records shows that during 1991-96 7 of 13 records of mortality or

serious injury likely to result in mortality included entanglement or fishery interactions. . The reports often do not

contain the detail necessary to assign the entanglements to a particular fishery or location. On the other hand, 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 U.S. 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, this would likely not have occurred had the lobster gear not have created a deep existing wound. 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 perhaps, 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 U.S. MidAtlantic 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 U.S. fisheries are available from several sources. In 1986, NMFS established

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

Southeast Fisheries Science Center (SEFSC). The Northeast Fisheries Science Center (NEFSC) Sea Sampling

Observer Program was initiated in 1989, and since that year, several fisheries have been covered by the program. In

late 1992 and in 1993, the SEFSC provided observer coverage of pelagic longline vessels fishing off the Grand Banks

(Tail of the Banks) and also 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. 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 U.S. 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 U.S. 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
9

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

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

right whale entanglement in fishing gear are often lacking. When direct or indirect mortality occurs, some carcasses

come ashore and are subsequently examined, or are reported as "floaters" at sea; however, the number of unreported

and unexamined carcasses is unknown, but may be significant in the case of floaters. More information is needed about

fisheries interactions and where they occur. 

Other Mortality

Ship strikes are a major cause of mortality and injury to right whales (Kraus 1990). Records from 1991 through

1996 have been summarized in Table 1, yielding a human-induced, non-fishery-related mortality or serious injury rate

of between 1 and 3 (perhaps 4 in 1996) right whales a year.

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

U.S. 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. 

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

whales, January 1991- December 1996. This listing includes only records related to U.S. commercial

fisheries and/or U.S. 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

3/12/91 mortality,

beached

2 y.o.

female

#1907

Amelia I.

FL

P S fractured skull; net,

line, buoys

7/6/91 mortality,

offshore

calf offshore

NJ

P documented vessel

strike

1/5/93 mortality,

offshore

calf St.

Augustine,

FL

P documented vessel

strike

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

12/12/93 mortality,

offshore

female offshore VA P S photos show gash
Date Report 

Type

Sex, age,

ID

Location Assigned Cause: P=primary, 

 S=secondary

Notes

Ship

strike

 Entang./

Fsh.inter

Unknown

uncertain

10

2/22/94 serious

injury

calf

#2404

offshore

NE FL

P S scars, wounds,

flukes limp

11/16/94 serious

injury

3 y.o. juv.,

#2151

nr. Plum I.,

MA

P entangled head, 3

tail wraps,

unsuccessful

disentanglement

7/17/95 mortality,

beached

2 y.o.

male

#2366

Middletown,

RI

P line through mouth,

embedded deeply

right flipper

8/13/95 serious

injury,

offshore

adult

female,

#1045

S. Georges

Bank

P S large head wound,

bone exposed

10/20/95 mortality,

beached

adult

male,

#2250

Long I., N.S. P S wound in back,

spine damaged,

prob. ship strike

1/30/96a

mortality,

offshore

adult

male,

#1623

offshore

GA

P S trauma event, skull

shattered 

8/5/96 serious

injury

unknown SE of

Gloucester, 

MA

P unknown type of

gear entangled

around head,

judged to be a life

threatening

entanglement

Table notes

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

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

 

a

 Date changed from 2/1/96, as reported in previous SAR; 1/30/96 reflects the date of the first report.

b

 Date changed from 3/10/96, as reported in previous SAR; 3/9/96 reflects the date of the first report.

Several additional factors need to be considered when considering mortality and serious injury to right whales:

1) a ship strike or entanglement may occur at some distance from the report location, 2) the mortality or injury may

involve multiple factors--struck and entangled whales are not uncommon, 3) in entanglements, several types of gear

may be involved, 4) possible human-impacts aside from ship strikes and entanglements have been reported, 5) 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, and, lastly, 6) the actual vessel or gear type/source is often

uncertain.
11

With these caveats, the average reported mortality and serious injury to right whales due to ship strikes was 1.3

whales per year ( 8 ship strike events in 6 years) during 1991-96. The total estimated annual average human-induced

mortality and serious injury (including fishery and non-fishery related causes) was 2.3 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 2.3 estimate must be regarded as a minimum

estimate. Of the mortality and serious injury records for U.S. waters, 57% was attributable to ship strikes, and 43%

to entanglement/fishery interaction. 

While this assessment relates to U.S. fisheries and U.S. waters, there are additional records for Canadian waters.

Three records are noteworthy: 1) the mortality of whale #1223 on 5 September 1992 in the Bay of Fundy was attributed

to a probable ship strike, 2) whale #1247 was sighted 21 September 1994 in the Bay of Fundy entangled with line of

unknown gear type tightly wrapped and has not been sighted since. This is considered a serious injury (A.R. Knowlton,

pers. comm.), and 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. 

STATUS OF STOCK

The size of this stock is considered to be low relative to OSP in the U.S. 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 U.S., were designated by

NMFS (59 FR 28793, June 3, 1994). The NMFS ESA 1996 Northern Right Whale Status Review, now in draft,

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 2.3 right whales per year since 1991. 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 fishery-related 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.

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.
12

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. R., S. Nieukirk, R. Mesecar, and T. Martin. 1992. Application of remote sensing methods for tracking large

cetaceans: North Atlantic right whales (Eubalaena glacialis). Final Report to the Minerals Management Service,

Contract No. 14-12-0001-30411, U.S. Department of the Interior, Reston, Virginia. 167 pp. 

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

December 1998

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 U.S. 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 U.S. (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,
14

unlike previous cycles, where an increase in sand lance corresponded to a decrease in herring, herring remained

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

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

Atlantic).

In early 1992, a major research initiative known as the Years of the North Atlantic Humpback (YONAH) (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 were chosen because the greatest proportion of the population off the northeast U.S.

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).

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
15

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 ocean-wide 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 1991 through 199 6, the total estimated human-caused mortality and serious injury to humpback

whales is estimated as 5.7 per year. This is derived from three components: 1) the 1992-1996 observed fishery, 0. 6;

2) additional fishery interaction records, 3.8; and 3) vessel collision records, 1.3. 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. 

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
16

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 1991 to 199 6 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 were

three mortalities where fishery interaction was possible or probable, and 20 records where serious injury attributable

to fishery interaction was possible or probable—for a total of 23 records in the six-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. If these records were considered in conjunction with Canadian and any mid-Atlantic

entanglement reports, the total number of mortalities and serious injuries to humpbacks would be more than the 0.6

humpbacks per year estimated from observed fisheries alone.

Fishery Information

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

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

Southeast Fisheries Science Center (SEFSC). The Northeast Fisheries Science Center (NEFSC) Sea Sampling

Observer Program was initiated in 1989, and several fisheries have been covered by the program. In late 1992 and in

1993, the SEFSC provided 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. 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-
17

sampling techniques. Estimated annual mortality (CV in parentheses), extrapolated from fishery observer data, was

0.7 (1.00) in 1991, 0.4 (1.00) in 1992, 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 1992-1996

was 0.6 humpback whale (CV = 0.22) (Table 2). The 1992-1996 period was used because it provides better

characterization of this fishery. 

In January 1997 (62 FR 33, Jan. 2, 1997), NMFS changed the classification of the Gulf of Maine and U.S. MidAtlantic 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

92-96

1994=12

1995=11

1996=10

Obs. Data

Logbook

 .40, .42,

.87, .99,

.64

0, 1, 

0, 1, 0

 0.4, 1.5, 0,

1.05, 0

1.00,

0.34, 0, 0,

0

0.6 (.22)

TOTAL

0.6 (.22)

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 is a set.

4 For 1991-1993, pooled bycatch rates were used to estimate bycatch in months that had fishing effort but did not

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

increased substantially, and bycatch rates were not pooled for this period.

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

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

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, 1991- 1996. This listing includes only records related to U.S. commercial fisheries

and/or U.S. waters. Cause of mortality or injury assigned based on records maintained by NMFS/NER.
18

Date Report 

Type

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

 S=secondary

Notes

Ship

strike

Entang./

Fsh.inter

Unknown

uncertain

5/31/91 mortality “Silver”

adult female

length = 13.9m

Long Island,

New York

(40E 39' 

 73E 05')

P line and/or cable from

unknown gear; seen

entangled several days

before beaching, fresh

scars, line through

mouth, scars around

pectorals, marks

around mouth and jaw

with exposed bone

8/1/91 serious

injury

“Stalactite”

sex unknown

length (est.) = 

12 m

4 mi NE of

Plum Island,

Mass. 

(42E 51' 

 70E 45')

P gillnet and assorted

lobster, tuna gear and

grappling hook;

trailing 50' netting, net

around mouth and tail;

emaciated and tired;

disentangled 8/11/91;

in poor condition

8/28/91 serious

injury

“Manta”

adult female

born 1984

20 mi SE of

Cape

Elizabeth,

Mass.

(43E 15'

 70E 03')

P entangled around

flukes with line,

moving slowly, tired,

gasping, hanging flesh

between flukes, appears

life threatening

2/14/92 mortality 8.6 m female Chesapeake

Bay mouth

P floater; propeller

wounds, fractured

mandible and eye

socket,; injuries may

not have been

immediately fatal,

some signs of healing

present; animal very

thin; boat collision

4/17/92 mortality 8.9 m female National

Seashore,

Assateague,

Maryland

P possible boat strike,

blunt trauma to right

side, advanced

decomposition
Date Report 

Type

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

 S=secondary

Notes

Ship

strike

Entang./

Fsh.inter

Unknown

uncertain

19

5/13/92 serious

injury

“Strait”

sex unknown,

juvenile

born 1991

NW part

Stellwagen

Bank

(42E 26'

 70E 21')

P gillnet line through

mouth and around

flipper, mouth lines

anchored to bottom,

animal worn out and in

peril, open wounds on

tail, disentangled

8/3/92 serious

injury

unknown 14 mi NE of

Provincetown Mass

(42E 16'

 70E 05')

P orange mesh netting

and line wrapped over

head and back with

about 15-20' trailing,

animal moving slowly

and not fluking

8/9/92 serious

injury

length (est.) = 

13 m

10 mi SE of

Bar Harbor,

Maine

(44E 16' 

 68E 03)'

P monofilament net and

poly lines across back

and one flipper; gear

may be trailing but not

seen; bleeding,

abrasions, labored

breathing

9/17/92 serious

injury

length (est.) = 

13 m

25 mi E of

Portsmouth,

New

Hampshire

(43E 09'

 70E 09')

P 1⁄2", 3-strand grey poly

line w poly ball; poly

ball removed;

breathing labored

9/26/92 serious

injury

length (est.) = 

8 - 10 m

7 mi E of

Montauk

Point, New

York

(41E 00'

 71E 50')

P monofilament gillnet

w/ 5/8" poly lines;

mesh visible; gear

wrapped around head,

flippers, and bunched

at tail region; labored

breathing and

trumpeting

10/8/92 serious

injury

estimated to be

adult size

Great South

Channel

(41E 08'

 69E 11')

P lobster or longline gear

w/large orange buoy;

whale entangled at

dorsal fin; breathing

labored
Date Report 

Type

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

 S=secondary

Notes

Ship

strike

Entang./

Fsh.inter

Unknown

uncertain

20

10/9/92 mortality 8.7 m female Metompkin

Island,

Acomac,

Virginia

P fresh dead; external

bruising and

hemorrhage; boat

collision

10/22/92 mortality unknown Virginia

Beach,

Virginia 

(36E 46'

 75E 57')

P line entanglement scars

and cuts on leading

edge of fluke and

around caudal

peduncle

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 is

trailing; 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
Date Report 

Type

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

 S=secondary

Notes

Ship

strike

Entang./

Fsh.inter

Unknown

uncertain

21

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

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
Date Report 

Type

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

 S=secondary

Notes

Ship

strike

Entang./

Fsh.inter

Unknown

uncertain

22

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

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

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
23

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. While researchers often tend to attribute strikes to large vessels, the record of 7

October 1993 off Atlantic City, NJ, reports a collision (and subsequent injury) with a 33 ft sport-fishing vessel. 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.

While entangled animals are often released, on the other hand, some dead or injured animals likely go unobserved

and unreported. 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

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

whale stock is considered to be low relative to OSP in the U.S. Atlantic EEZ, and this species is listed as endangered

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

REFERENCES

Allen, J., P. Clapham, P. Hammond, S. Katona, F. Larsen, J. Lien, D. Mattila, N. Øien, P. Palsbøll, J. Sigurjonsson, and

T. Smith. 1993. Years of the North Atlantic Humpback (YONAH): Progress Report. Rep. int. Whal. Commn.

SC/45/NA6.

Balcomb, K.C. and G. Nichols. 1982. Humpback whale censuses in the West Indies. Rep. int. Whal. Commn. 32: 401-

406.

Barlow, J., and P.J. Clapham. 1997. A new birth-interval approach to estimating demographic parameters of humpback

whales. Ecology 78 (2): 535-546.

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. 

Christensen, I., T. Haug, and N. Øien. 1992. Seasonal distribution, exploitation and present abundance of stocks of large

baleen whales (Mysticeti) and sperm whales (Physeter macrocephalus) in Norwegian and adjacent waters. ICES

Journal of Marine Science 49: 341-355.

Clapham, P.J. & Mayo, C.A. 1987. Reproduction and recruitment of individually identified humpback whales, Megaptera

novaeangliae, observed in Massachusetts Bay, 1979-1985. Can.. J. of Zool. 65: 2853-2863.

Clapham, P. J. and C. A. Mayo. 1990. Reproduction of humpback whales (Megaptera novaeangliae) observed in the Gulf

of Maine. Rep. int. Whal. Commn. Special Issue 12: 171-175. 

Clapham, P. J. 1992. Age at attainment of sexual maturity in humpback whales, Megaptera novaeangliae. Can. J. Zool.

70: 1470-1472.

Clapham, P. J., L. S. Baraff, C. A. Carlson, M. A. Christian, D. K. Mattila, C. A. Mayo, M. A. Murphy, and S. Pittman.

1993. Seasonal occurrence and annual return of humpback whales, Megaptera novaeangliae, in the southern Gulf

of Maine. Can. J. Zool. 71: 440-443.

Fogarty, M. J., E. B. Cohen, W. L. Michaels, and W. W. Morse. 1991. Predation and the regulation of sand lance

populations: An exploratory analysis. ICES Mar. Sci. Symp. 193: 120-124.
24

Katona, S. K., and J. A. Beard. 1990. Population size, migrations, and feeding aggregations of the humpback whale

(Megaptera novaeangliae) in the western North Atlantic ocean. Rep. int. Whal. Commn. Special Issue 12: 295-

306.

Katona, S. K., J. M. Allen, and P. Stevick. 1994. Maintaining the North Atlantic humpback whale catalog. Progress

report to the Northeast Fisheries Science Center, Contract No. 50EANF-1-00056, May 1994, 26 pp. 

Larsen, A. H., J. Sigurjónsson, N. Øien, G. Vikingsson, and P. J. Palsbøll. 1996. Population genetic analysis of

mitochondrial and nuclear genetic loci in skin biopsies collected from central and northeastern North Atlantic

humpback whales (Megaptera novaeangliae): population identity and migratory destinations. Proceedings of the

Royal Society of London B 263: 1611-1618.

Levenson, C. and Leapley, W.T. 1978. Distribution of humpback whales (Megaptera novaeangliae) in the Caribbean

determined by a rapid acoustic method. J. Fish. Res. Bd. Can. 35: 1150-1152.

Lien, J., W. Ledwell, and J. Naven. 1988. Incidental entrapment in inshore fishing gear during 1988: A preliminary report

to the Newfoundland and Labrador Department of Fisheries and Oceans, 15 pp.

Mattila, D.K. & Clapham, P.J. 1989. Humpback whales and other cetaceans on Virgin Bank and in the northern Leeward

Islands, 1985 and 1986. Can. J. of Zool. 67: 2201-2211.

Mattila, D.K., Clapham, P.J., Katona, S.K. and Stone, G.S. 1989. Population composition of humpback whales on Silver

Bank. Can. J. of Zool. 67: 281-285.

NMFS. 1991. Recovery plan for the humpback whale (Megaptera novaeangliae). Prepared by the Humpback Whale

Recovery Team for the National Marine Fisheries Service, Silver Spring, Maryland, 105 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.

Øien, N. 1990. Sighting surveys in the northeast Atlantic in July 1988: distribution and abundance of cetaceans. Rep. int.

Whal. Commn. 40: 499-511.

Paquet, D., C. Haycock and H. Whitehead. 1997. Numbers and seasonal occurrence of humpback whales (Megaptera

novaeangliae) off Brier Island, Nova Scotia. Can. Field Nat. 111: 548-552.

Palsbøll, P.J., Allen, J., Bérubé, M., Clapham, P.J., Feddersen, T.P., Hammond, P., Jørgensen, H., Katona, S., Larsen, A.H.,

Larsen, F., Lien, J., Mattila, D.K., Sigurjónsson, J., Sears, R., Smith, T., Sponer, R., Stevick, P. & Øien, N. 1997.

Genetic tagging of humpback whales. Nature 388: 767-769.

Palsbøll, P.J., Clapham, P.J., Mattila, D.K., Larsen, F., Sears, R., Siegismund, H.R., Sigurjónsson, J., Vásquez, O. and

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

behavior on population structure. Marine Ecology Progress Series 116: 1-10.

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

novaeangliae, on Georges Bank and in the Gulf of Maine in relation to densities of the sand eel, Ammodytes

americanus. Fish. Bull., U.S. 84: 271-277. 

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(4): 687-696. 

Price, W.S. 1985. Whaling in the Caribbean: historical perspective and update. Rep. int. Whal. Commn. 35: 413-420.

Reiner, F., M. E. Dos Santos, and F. W. Wenzel. 1996. Cetaceans of the Cape Verde archipelago. Mar. Mamm. Sci. 12:

434-443.

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

Sigurjónsson, P.T. Stevick and N. Øien. 1999. An ocean-basin-wide mark-recapture study of the North Atlantic

humpback whale (Megaptera novaeangliae). Mar. Mamm. Sci. 15 (1):1-32.

Stevick, P., N. Øien and D.K. Mattila. 1998. Migration of a humpback whale between Norway and the West Indies. Mar.

Mamm. Sci. 14: 162-166.

Swingle, W. M., S. G. Barco, T. D. Pitchford, W.A. McLellan and D.A. Pabst. 1993. Appearance of juvenile humpback

whales feeding in the nearshore waters of Virginia. Mar. Mamm. Sci. 9: 309-315.

Volgenau, L., S.D. Kraus, and J. Lien. 1995. The impact of entanglements on two substocks of the western North Atlantic

humpback whale, Megaptera novaeangliae. Can. J. Zool. 73: 1689-1698.

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

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

Washington, D.C. 93 pp. 

Whitehead, H. and M.J. Moore. 1982. Distribution and movements of West Indian humpback whales in winter. Can. J.

of Zool. 60: 2203-2211.
25

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.
26

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. 

December 1998

FIN WHALE (Balaenoptera physalus):

Western North Atlantic Stock

STOCK DEFINITION AND GEOGRAPHIC RANGE

The Scientific Committee of the International

Whaling Commission (IWC) has proposed stock

boundaries for North Atlantic fin whales. Fin whales

off the eastern U.S., 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 U.S. 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. 

Hain et 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 U.S. mid-Atlantic region; however, it is unknown
27

where calving, mating, and wintering for most of the population occurs. Preliminary results from the Navy's IUSS

program (Clark 1995) indicate a substantial deep-ocean component to fin whale distribution. It is likely that fin whales

occurring in the U.S. Atlantic EEZ undergo migrations into Canadian waters, open-ocean areas, and perhaps even

subtropical or tropical regions. 

POPULATION SIZE

Four seasonal abundance estimates for fin whales are available for portions of the northeastern U.S. Atlantic

during spring and summer of 1978-82, June-July 1991, August-September 1991, and August-September 1991 and 1992

(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 were chosen because the greatest proportion of the population off the northeast U.S. 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 interplatform 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, an

estimate of g(0), probability of detecting a group on the track line, but no correction for dive-time. Variability was

estimated using bootstrap resampling techniques.

The best available current abundance estimate for the western North Atlantic fin whale is 2,700 (CV=0.59) from

the 1991-92 northern Gulf of Maine-lower Bay of Fundy line transect surveys because it is relatively recent and covers

the largest portion of the known habitat.
28

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).

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

* 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 2,700 (CV=0.59). The minimum

population estimate for the western North Atlantic fin whale is 1,704 (CV=0.59).

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 1,704 (CV=0.59). 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 3.4. 

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 1991- 96. In a recent review of NER/NMFS fin whale mortality records

from 1991-96, only one had sufficient evidence to confirm that the cause of death involved a fishery entanglement, and
29

two records clearly involved vessel collisions. This translates into an estimated annual human-caused mortality and

serious injury to fin whales of 0.5 per year. As noted in other species accounts, these anecdotal records can provide

only the minimum level of human-caused mortality; and it is highly likely that additional serious injuries and

mortalities go unreported.

Fishery-Related Serious Injury and Mortality 

No 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 26 records of stranded or floating (dead or injured) fin whales for the period 1992-1996 on file at

NER/NMFS showed that three had fishery interactions. Two had net or rope marks, but the evidence on hand was not

sufficient to confirm entanglement as the cause of death. The one confirmable 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 entanglement mortality record 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 cuadal area. The animal's stomach was full. 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 U.S. 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-OPR6. 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. (In press).

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.
30

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. 1992. The fin whale, Balaenoptera physalus, in

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

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

467-494.

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

(editor), 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. 1992. Cetaceans associated with Gulf Stream features off the

northeastern USA shelf. ICES Marine Mammals Comm. CM 1992/N: 12. 29 pp.
31

December 1998

SEI WHALE (Balaenoptera borealis):

Western North Atlantic 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 U.S. 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. 1992). 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 U.S., 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. 

POPULATION SIZE

The total number of sei whales in the U.S. 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 U.S. 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 U.S. coast appeared in the study area. This estimate does not include a correction for divetime 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.
32

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

covered during each abundance survey, and resulting abundance estimate (Nbest) and coefficient of

variation (CV). Unk=Unknown.

Month/Year Area Nbest CV

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 western North Atlantic 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 1991-1997. 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 U.S. 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 it is believed to be insignificant and approaching
33

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-OPR6. 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. 

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. 1992. 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.
34

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. 

December 1998

MINKE WHALE (Balaenoptera acutorostrata):

Canadian East Coast Stock

STOCK DEFINITION AND GEOGRAPHIC RANGE

Minke whales have a cosmopolitan distribution in

polar, temperate and tropical waters. In the North

Atlantic there are four recognized populations —

Canadian east coast, west Greenland, central North

Atlantic, and northeastern North Atlantic (Donovan

1991). These four population divisions were defined by

examining segregation by sex and length, catch

distributions, sightings, marking data and pre-existing

ICES boundaries; however, there are very few data from

the Canadian east coast population. 

Minke whales off the eastern coast of the United

States are considered to be part of the Canadian east

coast 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 U.S. 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 U.S. coast appeared in the study area during this season. This estimate does not include a correction for divetime 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
35

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 nonclosing 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 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 re-sampling 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 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 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 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, so this was the area included in this abundance estimate.

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
36

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

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

Fishery Information

Recent minke whale takes have been observed in U.S. waters in the New England multispecies sink gillnet, Atlantic

pelagic drift gillnet, bluefin tuna purse seine fisheries, and in fish weirs; though all takes have not resulted in a

mortality. The annual mortality estimate from these fisheries during 1992 to 1996 is 0.8 (CV=0) minke whales per year.

USA

 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 U.S. 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 U.S. east coast. This was the first year that the Northeast Regional Observer

Program assumed responsibility for observer coverage of the longline vessels. Between 1983 and 1988, the number of

Japanese longline vessels operating within the EEZ each year were 3, 5, 7, 6, 8, and 8, respectively. Observer coverage

was 100%.

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

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

Southeast Fisheries Science Center (SEFSC). The Northeast Fisheries Science Center (NEFSC) Sea Sampling Observer

Program was initiated in 1989, and since that year several fisheries have been covered by the program. In late 1992,

the SEFSC started observer coverage of pelagic longline vessels fishing off the Grand Banks (Tail of the Banks) south

of Cape Hatteras.

New England Multispecies Sink Gillnet 
37

Two minke whales were taken in the New England multispecies sink gillnet fishery. 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 (Table 3). 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% for years 1990 to 1996. Because no mortalities have been observed within the most

recent five years (1992 to 1996), the annual estimated average New England multispecies sink gillnet fishery-related

mortality for minke whales is zero (Table 2).

Pelagic Drift Gillnet

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 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 (Table 2). Observer

coverage dropped during 1996 because some vessels were deemed too small or unsafe by the contractor that provided

observer coverage. 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, 1995, and 1996 were estimated

separately for each year by summing the observed caught and 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. Estimated average annual mortality and serious injury related to this fishery during 1992-1996

was 0.8 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. 

Other Fisheries 

A minke whale was trapped and released alive in a herring weir off northern Maine in 1990. In U.S. and Canadian

waters the herring weir fishery occurs 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, and 56 active weirs in Maine (Read 1994). It is unknown how many herring weirs currently

exist in U.S. and Canadian waters. 

For U.S. waters, an entanglement database maintained by NE Regional Office for 1975-1992 included 36 records

of minke whales. The gear includes unspecified fishing net, unspecified cable or line, fish trap, weirs, seines, gillnets,

and lobster gear. A review of these records is not complete, however, it was reported that an immature female minke

whale, entangled with line around the tail stock, came ashore on the Jacksonville, Florida, jetty on 31 January 1990 (R.

Bonde, USFWS, Gainesville, FL, pers. comm.). The 1997 List of Fisheries (62FR33, January 2, 1997) reported seven

minke whale mortalities and serious injuries which have been attributed to the lobster fishery during 1990 to 1994.

The NE Regional Office entanglement/stranding database also contains records of minke whales entangled during

1993 to 1997. The records are currently be audited and summaries should be available in the next assessment report.
38

Total annual estimated average U.S. fishery-related mortality and serious injury to this minke whale stock in

fisheries observed by NMFS during 1992-1996 was 0.8 minke whales (CV = 0), though the total from all fisheries is

unknown. After U.S. stranding and entanglement records are audited an updated mortality and serious injury estimate

will be made.

CANADA

 In Canadian waters, information about minke whale interactions with fishing gear is not well quantified or recorded

in most parts of Canada, 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 to 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. More recent records of

interactions are currently being audited and will be reported in the next assessment. In U.S. and Canadian waters the

herring weir fishery occurs 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, and 56 active weirs in Maine (Read 1994). It is unknown how many herring weirs currently exist in U.S. and

Canadian waters. Due to the formation of a cooperative program between Canadian fishermen and biologists it is

expected that in the future more minke whales will be able to be released alive (A. Westgate, pers. comm.). 

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).

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

New England3

Multispecies

Sink Gillnet

92-96 1993=349 Obs. Data

Weighout

Trip logbook 

.07, .05,

.07, .05,

.04

0, 0, 

0, 0, 

0

0, 0, 

0, 0,

 0

0 0 (0)

Pelagic Drift

Gillnet

92-96 1994=124

1995=11

1996=10

Obs. Data

Logbook

.40, .42,

.87, .99,

.64

0

5

, 05, 

0

5

, 45, 

0

5

0

5

, 05,

0

5

,4.55,6,

0

5

0 0.8

(0)

TOTAL 0.8

(0)

1

 Observer data (Obs. Data) are used to estimate by-catch rates, and the data are collected by the Northeast Fisheries

Science Center (NEFSC) Sea Sampling Program. NEFSC collects Weighout (Weighout) landings data, which are

used as a measure of total effort for the sink 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).

2 The observer coverage for the New England multispecies sink gillnet fishery is expressed as percentage of trips,

and for the pelagic drift gillnet fishery, the unit of effort is expressed as percentage of sets.
39

3 By-catch and fishery related information for this fishery remain in this table, despite no observed mortalities during

1992 to 1996 because there was one uninjured minke whale released from this fishery in 1992 (see Table 3).

4

1994-1996 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). In 1994, 1995, and 1996, observer coverage increased substantially,

and by-catch rates were not pooled (Bisack 1997). 

6 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.

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

New England

multispecies

sink gillnet

 92-96 0/0, 0, 0, 0, 0 0, 0, 0, 0, 0 11, 0, 0, 0, 0

Tuna purse

seine

96 0/0 0 1

2

1 The whale was wrapped up in the float rope where the rope was wrapped in front of and behind the dorsal fin and

around the tail. The rope was cut by a crew member while the whale was in the water. It was believed that the

whale was released without any rope around it, because all the rope was hauled in. There was no visible bleeding

or tears in the skin.

2 The minke whale escaped by diving beneath the net. 

Other Mortality

Minke whales have been and are still being hunted in the North Atlantic. From the Canadian East Coast

population, documented whaling occurred from 1948 to 1972 with a total kill of 1,103 animals (IWC 1992). Animals

from other North Atlantic populations are presently still being harvested at low levels.

 Minke whales inhabit coastal waters during much of the year and are subject to collision with vessels. According

to the NE Regional Office marine mammal entanglement and stranding database, on 7 July 1974, a necropsy suggested

a vessel collision; 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. Other reported minke whales that had injuries suggestive

of a vessel collision are currently being audited and will be summarized in the next stock assessment report.

STATUS OF STOCK

The status of minke whales, relative to OSP, in the U.S. Atlantic EEZ is unknown. The minke whale is not listed

as endangered under the Endangered Species Act (ESA). The total fishery-related mortality and serious injury for this

stock is less than 10% of the calculated PBR and, therefore, can be considered to be insignificant and approaching zero

mortality and serious injury rate. This is not a strategic stock because estimated fishery-related mortality and serious

injury does not exceed PBR and the minke whale is not listed as a threatened or endangered species under the ESA.

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.
40

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. Draft 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. 

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.
41

December 1998

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 U.S. 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 U.S. 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
42

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 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 U.S. 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 U.S. 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 U.S. EEZ.

Fishery Information

 With one exception, no fishery information is presented because there are no observed fishery-related mortalities

or serious injury. The exception concerns a blue whale observed in October 1986 on Stellwagen Bank, Massachusetts

(Wenzel et al.. 1988) which had gear (possibly lobster line and a float)around its flipper. The gear type could not be

confirmed, and its origin was unknown.

STATUS OF STOCK

The status of this stock relative to OSP in the U.S. 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 fishery-related 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-OPR6. 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

(editor), 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.
43

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. 
44

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. 

December 1998

SPERM WHALE (Physeter macrocephalus):

Western North Atlantic Stock

STOCK DEFINITION AND GEOGRAPHIC RANGE

The distribution of the sperm whale in the U.S. 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 U.S. EEZ likely

represent only a fraction of the total stock. The nature

of linkages of the U.S. 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 U.S., 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. There exists one tag return of

a male tagged off Browns Bank (Nova Scotia) in 1966

and returned from Spain in 1973. In the U.S. 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 midAtlantic 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 wideranging and occurring in higher latitudes. However, CETAP and NMFS/NEFSC sightings in shelf-edge and off-shelf

waters included many social groups with calves/juveniles (CETAP 1981; Waring et al.. 1992, 1993). The basic social

unit of the sperm whale appears to be the mixed school of adult females plus their calves and some juveniles of both

sexes, normally numbering 20-40 animals in all. There is evidence that some social bonds persist for many years.

POPULATION SIZE

Total number of sperm whales off the U.S. 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,
45

June-July 1991, August-September 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 U.S. 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
46

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

techniques.

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 U.S. 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

U.S. 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
47

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

CURRENT AND MAXIMUM NET PRODUCTIVITY RATES

Current and maximum net productivity rates are unknown for this stock. While more is probably known about

sperm whale life history in other areas, some life history and vital rates information is available for the northwest

Atlantic. These include: calving interval is 3-4 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 405 cm, length at sexual maturity 11.0-12.0 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). 

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 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 1992-1996 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 self-reported fishery information system for large pelagic fisheries. Data files are maintained at the

Southeast Fisheries Science Center (SEFSC). The Northeast Fisheries Science Center (NEFSC) Sea Sampling

Observer Program was initiated in 1989, and since that year several fisheries have been covered by the program. In

late 1992 and in 1993, the SEFSC provided observer coverage of pelagic longline vessels fishing off the Grand Banks

(Tail of the Banks) and 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, midAtlantic coastal sink gillnet, or North Atlantic bottom trawl observed fisheries.

Pelagic Drift Gillnet
48

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. 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, and 0 in 1996.

Estimated average annual mortality and serious injury related to this fishery during 1992-1996 was zero, assuming the

1995 injured sperm whale was not a serious injury. The 1992-1996 time period provides a better characterization of

the current fishery. 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 92-96 0, 0, 0, 0, 0 0, 0, 0, 11,0 0, 0, 0, 0, 0

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.

Other mortality

 Six sperm whale strandings have been documented along the U.S. Atlantic coast between Maine and Miami,

Florida, during 1994-1996 (NMFS unpublished data). 

STATUS OF STOCK

The status of this stock relative to OSP in U.S. 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.
49

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.

Best, P. B. 1974. Biology of the sperm whale. Pages 53-81. In: W. E. Schevill (editor), 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. 

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. 40ENNF500160.

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.

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(2): 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.
50

December 1998

DWARF SPERM WHALE (Kogia simus): 

Western North Atlantic Stock

STOCK DEFINITION AND GEOGRAPHIC RANGE

The dwarf sperm whale (Kogia simus) and the pygmy sperm whale (K. breviceps) appear 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; NMFS unpublished data). Recent analyses of hemoglobin, morphometric and dietary data from

Florida strandings of both species (Barros et al. 1998) suggests that habitat partitioning may exist between the two

species, K. simus occupies more offshore and oceanic waters, whereas K. breviceps inhabits more mid-shelf waters.

Interestingly, a recent analysis of South Africa stranding data indicates that in that region K. simus is the nearshore

species (Plön et al. 1998). 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. 

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. 

CURRENT AND MAXIMUM NET PRODUCTIVITY RATES

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

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

cetacean populations may not grow at rates much greater than 4% given the constraints of their reproductive life history

(Barlow et al. 1995). 

POTENTIAL BIOLOGICAL REMOVAL

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

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

population size is unknown. The maximum productivity rate is 0.04, the default value for cetaceans. The “recovery”

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

sustainable population (OSP) is assumed to be 0.5 because this stock is of unknown status. PBR for the western North

Atlantic dwarf sperm whale is unknown because the minimum population size cannot be estimated. 

ANNUAL HUMAN-CAUSED MORTALITY AND SERIOUS INJURY

Total annual estimated average fishery-related mortality or serious injury to this stock during 1992-1996 was 0.2

dwarf sperm whales (CV = 0; Table 1).
51

Fishery Information

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. 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. 

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

a mandatory logbook system for large pelagic fisheries. The Northeast Fisheries Science Center (NEFSC) Sea Sampling

Observer Program initiated in 1989, and since that year several fisheries have been covered by the program. In late

1992 and in 1993 the SEFSC provided observer coverage of pelagic longline vessels fishing off the Grand 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, midAtlantic coastal sink gillnet, and North Atlantic bottom trawl fisheries. 

Pelagic Drift Gillnet

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

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

1993, 1994, 1995, and 1996 were 233, 243, 232, 197, 164, and 149 respectively. Fifty-nine vessels participated in this

fishery between 1989 and 1993. Since 1994, between 10 to12 vessels have participated in the fishery (Table 2).

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 0 dwarf

sperm whales from 1991-1994, 1.0 in 1995 (CV = 0), and 0 in 1996. Estimated average annual mortality and serious

injury related to this fishery during 1992-1996 was 0.2 dwarf sperm whales (CV = 0) (Table 1). The 1992-1996 time

period provides a better characterization of the current fishery. 
52

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

92-96 1994=12

1995=11

1996=10

Obs. Data

Logbook

.40, .42,

.87, .99,

.64

0, 0, 0, 1,

0

0, 0, 0, 

1

5

, 0

0 0.2 (0)

TOTAL 0.2 (0)

1

1994 to 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. Logbook (Logbook) data are used to measure total

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

3 The observer coverage and unit of effort for the Pelagic Drift Gillnet is a set.

4 For 1991-1993, pooled bycatch rates were used to estimate bycatch in months that had fishing effort but did not

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

increased substantially, and bycatch rates were not pooled for this period. 

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

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

animals. However, the SEFSC mandatory logbook data were taken at face value, and therefore it was assumed that

one set was fished within this trip, and the point estimate would then increase by 0.01 animals.

Other Mortality

 At least 23 dwarf sperm whale strandings have been documented along the U.S. Atlantic coast between Cape

Hatteras, North Carolina, and Miami, Florida, during 1987-1996). Three of the stranded animals had plastic, or a

plastic bag or bags in their stomachs, and one of these three had possible propeller cuts on or near the flukes. 

STATUS OF STOCK

The status of this stock relative to OSP in the U.S. 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. Upon the advice of the Atlantic Scientific Review Group this stock has been

designated a strategic stock because PBR cannot been determined and there is an unknown amount of possible humancaused mortality from the ingestion of marine debris such as plastic bags and from possible boat strikes. 

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. Near-shore vs. off-shore ecotype

differentiation of Kogia breviceps and K. simus based on hemoglobin, morphometric and dietary analyses. The

World Marine Mammal Conference, 20-24 January 1998, Monaco (Abstract).
53

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 235-26. 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. 

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. Southeast Fisheries Science Center, Miami Laboratory, Contribution No. MIA-93/94-

58.

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

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

Mullin, K., 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. 18p.

Plön, S.E.E., R.W. Harris, P.M. Illgner and V.G.C. Cockcroft. 1998. Analysis of pygmy Kogia breviceps and dwarf Kogia

simus sperm whale strandings along the South African coastline using a geographic information system. The

World Marine Mammal Conference, 20-24 January 1998, Monaco (Abstract).

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

December 1998

PYGMY SPERM WHALE (Kogia breviceps):

Western North Atlantic Stock

STOCK DEFINITION AND GEOGRAPHIC RANGE

The dwarf sperm whale (Kogia breviceps) and the pygmy sperm whale (K. simus) appear 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 unpublished data). Recent analyses of hemoglobin,

morphometric and dietary data from Florida strandings of both species (Barros et al. 1998) suggests that habitat

partitioning may exist between the two species, K. simus occupies more offshore and oceanic waters, whereas K.

breviceps inhabits more mid-shelf waters. Interestingly, a recent analysis of South Africa stranding data indicates that

in that region K. simus is the nearshore species (Plön et al. 1998). 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. 

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). 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. 

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 (MMPA Sec. 3. 16 U.S.C. 1362; Wade and Angliss 1997). The minimum

population size is unknown. The maximum productivity rate is 0.04, the default value for cetaceans. The “recovery”

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

sustainable population (OSP) is assumed to be 0.5 because this stock is of unknown status. PBR for the western North

Atlantic pygmy sperm whale was unknown because the minimum population estimate cannot be estimated. 

ANNUAL HUMAN-CAUSED MORTALITY AND SERIOUS INJURY

Fishery Information
55

The level of past or current, direct, human-caused mortality of pygmy sperm whales in the U.S. Atlantic EEZ is

unknown. Available information indicates there is likely little, if any, fisheries interaction with pygmy sperm whales

in the U.S. Atlantic EEZ. 

There were no documented strandings of pygmy sperm whales along the U.S. 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 fisheryinteraction. Finally, the level of technical expertise among stranding network personnel varies widely as does the

ability to recognize signs of fishery interaction.

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

a mandatory self-reporting fishery 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 currently 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

At least 174 (includes one unidentified in 1996 that was assigned by the SAR author to this species, because the

pygmy sperm whales account for the majority of identified Kogia stranding) pygmy sperm whale strandings were

documented along the U.S. Atlantic coast between Cape Hatteras, North Carolina, and Miami, Florida, during 1987-

1996 (NMFS, unpubl. data). Two of the stranded animals had plastic, or a plastic bag or bags in their stomachs, and

one additional animal had possible propeller cuts on it's flukes. 

STATUS OF STOCK

The status of this stock relative to OSP in the U.S. 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. Because there are no observed mortalities or serious injuries between 1992 and 1996, total fisheryrelated mortality and serious injury for this stock is considered insignificant and approaching zero mortality and serious

injury rate

REFERENCES

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

Preparation, Background, and a Summary of the 1995 Assessments. U.S. Dep. Commer., NOAA Tech. Memo.

NMFS-OPR-6, 73 pp.

Barros, N.B., D.A. Duffield, P.H. Ostrom, D.K. Odell and V.R. Cornish. 1998. Near-shore vs. off-shore ecotype

differentiation of Kogia breviceps and K. simus based on hemoglobin, morphometric and dietary analyses. The

World Marine Mammal Conference, 20-24 January 1998, Monaco (Abstract).

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. 

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. Southeast Fisheries Science Center, Miami Laboratory, Contribution No. MIA-93/94-

58.

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

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

Mullin, K., 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. 
56

Plön, S.E.E., R.W. Harris, P.M. Illgner and V.G.C. Cockcroft. 1998. Analysis of pygmy Kogia breviceps and dwarf Kogia

simus sperm whale strandings along the South African coastline using a geographic information system. The

World Marine Mammal Conference, 20-24 January 1998, Monaco (Abstract).

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.
57

July 1995

KILLER WHALE (Orcinus orca):

Western North Atlantic Stock

STOCK DEFINITION AND GEOGRAPHIC RANGE

Killer whales are characterized as uncommon or rare in waters of the U.S. Atlantic Exclusive Economic Zone

(EEZ) (Katona et al. 1988). The 12 killer whale sightings constituted 0.1% of the 11,156 cetacean sightings in the

1978-81 CETAP surveys (CETAP 1982). The same is true for eastern Canadian waters, where the species has been

described as relatively uncommon and numerically few (Mitchell and Reeves 1988). Their distribution, however,

extends from the Arctic ice-edge to the West Indies. They are normally found in small groups, although 40 animals

were reported from the southern Gulf of Maine in September 1979, and 29 animals in Massachusetts Bay in August

1986 (Katona et al. 1988). In the U.S. Atlantic EEZ, while their occurrence is unpredictable, they do occur in fishing

areas, perhaps coincident with tuna, in warm seasons (Katona et al. 1988; NMFS unpublished data). In an extensive

analysis of historical whaling records, Reeves and Mitchell (1988) plotted the distribution of killer whales in offshore

and mid-ocean areas. Their results suggest that the offshore areas need to be considered in present-day distribution,

movements, and stock relationships. 

Stock definition is unknown. Results from other areas (e.g., the Pacific Northwest and Norway) suggest that social

structure and territoriality may be important. 

POPULATION SIZE

The total number of killer whales off the eastern U.S. coast is unknown. 

Minimum Population Estimate

Present data are insufficient to calculate a minimum population estimate. 

Current Population Trend

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

CURRENT AND MAXIMUM NET PRODUCTIVITY RATES

Current and maximum net productivity rates are not known for this stock. The maximum net productivity rate

was assumed to be 0.04 for purposes of this assessment. This value is based on theoretical calculations showing that

cetacean populations may not generally grow at rates much greater than 4% given the constraints of their reproductive

life history (Barlow et al. 1995). 

POTENTIAL BIOLOGICAL REMOVAL

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

productivity rate, and a “recovery” factor (Wade and Angliss 1997). The minimum population size is unknown. The

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

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

is assumed to be 0.5 because this stock is of unknown. PBR for the western North Atlantic killer whale is unknown

because the minimum population size cannot be determined. 

ANNUAL HUMAN-CAUSED MORTALITY

In 1994, one killer whale was caught in the New England multispecies sink gillnet fishery but released alive. No

takes were documented in a review of Canadian gillnet and trap fisheries (Read 1994). 

Fishery Information

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

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

Southeast Fisheries Science Center (SEFSC). The Northeast Fisheries Science Center (NEFSC) Sea Sampling
58

Observer Program was initiated in 1989, and since that year several fisheries have been covered by the program. In

late 1992 and in 1993, the SEFSC provided observer coverage of pelagic longline vessels fishing off the Grand Banks

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

There have been no observed mortalities or serious injuries by NMFS Sea Samplers in the pelagic drift gillnet,

pelagic longline, pelagic pair trawl, New England multispecies sink gillnet, mid-Atlantic coastal sink gillnet, and

North Atlantic bottom trawl fisheries. 

STATUS OF STOCK

The status of killer whales relative to OSP in U.S. Atlantic EEZ is unknown. Because there are no observed

mortalities or serious injury between 1990 and 1995, the total fishery-related mortality and serious injury for this stock

is considered insignificant and approaching zero mortality and serious injury rate. The species is not listed as

threatened or endangered under the Endangered Species Act. In Canada, the Cetacean Protection Regulations of 1982,

promulgated under the standing Fisheries Act, prohibit the catching or harassment of all cetacean species. There are

insufficient data to determine the population trends for this species. This is not a strategic stock because, although PBR

could not be calculated, there is no evidence of human-induced mortality. 

REFERENCES

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

Preparation, Background, and a Summary of the 1995 Assessments. U.S. Dep. Commer., NOAA Tech. Memo.

NMFS-OPR-6, 73 pp.

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

continental shelf. Cetacean and Turtle Assessment Program, University of Rhode Island. Final Report #AA551-

CT8-48 to the Bureau of Land Management, Washington, DC, 538 pp. 

Katona, S. K., J. A. Beard, P. E. Girton, and F. Wenzel. 1988. Killer whales (Orcinus orca) from the Bay of Fundy to the

Equator, including the Gulf of Mexico. Rit. Fiskideild. 9: 205-224. 

Mitchell, E. and R. R. Reeves. 1988. Records of killer whales in the western North Atlantic, with emphasis on eastern

Canadian waters. Rit. Fiskideild. 9: 161-193. 

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

Commn. Special Issue 15: 133-147.

Reeves, R. R. and E. Mitchell. 1988. Killer whale sightings and takes by American pelagic whalers in the North Atlantic.

Rit. Fiskideild. 9: 7-23

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

April 3-5, 1996, Seattle, Washington. U.S. Dep. Commer., NOAA Tech. Memo. NMFS-OPR-12, 93 pp.
59

July 1995

PYGMY KILLER WHALE (Feresa attenuata): 

Western North Atlantic Stock

STOCK DEFINITION AND GEOGRAPHIC RANGE

The pygmy killer whale is distributed worldwide in tropical and subtropical waters (Ross and Leatherwood 1994).

Sightings of these animals in the northern Gulf of Mexico occur primarily over the deeper waters off the continental

shelf (NMFS unpublished data). There is no information on stock differentiation for the Atlantic population. 

POPULATION SIZE

A single sighting of this species was made during a 1992 winter, visual sampling, line-transect vessel survey of

the U.S. Atlantic Exclusive Economic Zone (EEZ) from Miami, Florida, to Cape Hatteras, North Carolina (Hansen

et al. 1994). This sighting, of a herd of six animals, was not made during visual sampling effort; therefore, the sighting

could not be used to estimate abundance of pygmy killer whales, but it does confirm the presence of this species in the

U.S. Atlantic EEZ. 

Minimum Population Estimate

The minimum population estimate based on the count of animals in the single sighting, was six pygmy killer

whales (Hansen et al. 1994). 

Current Population Trend

No information was available to evaluate trends in population size. 

CURRENT AND MAXIMUM NET PRODUCTIVITY RATES

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

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

cetacean populations may not grow at rates much greater than 4% given the constraints of their reproductive life history

(Barlow et al. 1995). 

POTENTIAL BIOLOGICAL REMOVAL

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

productivity rate, and a “recovery” factor (Wade and Angliss 1997). The minimum population size is six (6). The

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

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

is assumed to be 0.5 because this stock is of unknown status. PBR for the western North Atlantic pygmy killer whale

is 0.1.

ANNUAL HUMAN-CAUSED MORTALITY AND SERIOUS INJURY

The level of past or current, direct, human-caused mortality of pygmy killer whales in the U.S. Atlantic EEZ is

unknown; however, there has historically been some take of this species in small cetacean fisheries in the Caribbean

(Caldwell and Caldwell 1971). Available information indicates there likely is little, if any, fisheries interaction with

pygmy killer whales in the U.S. Atlantic EEZ. There have been no logbook reports of fishery-related mortality or

serious injury and no observed fishery-related mortality or serious injury has been observed.

There have been no documented strandings of pygmy killer whales in the along the U.S. Atlantic coast during

1987-present which have been classified as likely caused by fishery interactions or other human-related causes.

Stranding data probably underestimate the extent of fishery-related mortality and serious injury because not all of the

dolphins which die or are seriously injured in fishery interactions wash ashore, nor will all of those that do wash ashore

necessarily show signs of entanglement or other fishery-interaction. Finally, the level of technical expertise among

stranding network personnel varies widely as does the ability to recognize signs of fishery interaction. 
60

Fishery Information

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

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

Southeast Fisheries Science Center (SEFSC). The Northeast Fisheries Science Center (NEFSC) Sea Sampling

Observer Program was initiated in 1989, and since that year several fisheries have been covered by the program. In

late 1992 and in 1993, the SEFSC provided observer coverage of pelagic longline vessels fishing off the Grand Banks

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

There have been no observed mortalities or serious injuries by NMFS Sea Samplers in the pelagic drift gillnet,

pelagic longline, pelagic pair trawl, New England multispecies sink gillnet, mid-Atlantic coastal sink gillnet, and

North Atlantic bottom trawl fisheries. 

Other Mortality

 This stock may be subjected to human-induced mortality caused by habitat degradation (e.g., industrial and

agricultural pollution) and indirect effects of fisheries on prey. There have been, however, no studies to date which

have determined the amount, if any, of indirect human-induced mortality resulting from habitat degradation or

competition for prey. 

STATUS OF STOCK

The status of pygmy killer whales relative to OSP in U.S. Atlantic EEZ is unknown. The species is not listed as

threatened or endangered under the Endangered Species Act. There are insufficient data to determine the population

trends for this species. The total known fishery-related mortality and serious injury for this stock is less than 10% of

the calculated PBR and, therefore, can be considered insignificant and approaching zero mortality and serious injury

rate. The western North Atlantic pygmy killer whale is considered a non-strategic stock.

REFERENCES

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

Preparation, Background, and a Summary of the 1995 Assessments. U.S. Dep. Commer., NOAA Tech. Memo.

NMFS-OPR-6, 73 pp.

Caldwell, D. K. and M. C. Caldwell. 1971. The pygmy killer whale, Feresa attenuata, in the western Atlantic, with a

summary of world records. J. Mamm. 52:206-209. 

Hansen, L. J., K. D. Mullin and C. L. Roden. 1994. Preliminary estimates of cetacean abundance in the northern Gulf of

Mexico from vessel surveys, and of selected cetacean species in the U.S. Atlantic Exclusive Economic Zone from

vessel surveys from vessel surveys. Southeast Fisheries Science Center, Miami Laboratory, Contribution No. MIA93/94-58 

Ross, G. J. B. and S. Leatherwood. 1994. Pygmy killer whale Feresa attenuata (Gray 1874). Pages 387-404 in S. H.

Ridgway and R. Harrison (eds), Handbook of marine mammals, Vol. 5: The first book of dolphins. Academic

Press, San Diego, 418 pp. 

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

April 3-5, 1996, Seattle, Washington. U.S. Dep. Commer., NOAA Tech. Memo. NMFS-OPR-12, 93 pp.
61

December 1998

NORTHERN BOTTLENOSE WHALE (Hyperoodon ampullatus):

Western North Atlantic Stock

STOCK DEFINITION AND GEOGRAPHIC RANGE

Northern bottlenose whales are characterized as extremely uncommon or rare in waters of the U.S. Atlantic

Exclusive Economic Zone. The two sightings of three individuals constituted less than 0.1% of the 11,156 cetacean

sightings in the 1978-82 CETAP surveys. Both sightings were in the spring, along the 2,000 m isobath (CETAP

1982). In 1993 and 1996, two sightings of single animals, and in 1996, a single sighting of six animals (one juvenile),

were made during summer shipboard surveys conducted along the southern edge of Georges Bank (Anon. 1993; Anon.

1996).

Northern bottlenose whales are distributed in the North Atlantic from Nova Scotia to about 70E in the Davis Strait,

along the east coast of Greenland to 77E and from England to the west coast of Spitzbergen. It is largely a deep-water

species and is very seldom found in waters less than 2,000 m deep (Mead 1989). 

There are two main centers of bottlenose whale distribution in the western north Atlantic, one in the area called

"The Gully" just north of Sable Island, Nova Scotia, and the other in Davis Strait off northern Labrador (Reeves et al.

1993). Studies at the entrance to the Gully from 1988-1995 identified 237 individuals and estimated the local

population size at about 230 animals (95% C.I. 160-360) (Whitehead et al. 1997). These individuals are believed to

be year-round residents and all age and sex classes are present (Gowans and Whitehead 1998). Mitchell and Kozicki

(1975) documented stranding records in the Bay of Fundy and as far south as Rhode Island. Stock definition is

unknown. 

POPULATION SIZE

The total number of northern bottlenose whales off the eastern U.S. coast is unknown. 

Minimum Population Estimate

Present data are insufficient to calculate a minimum population estimate. 

Current Population Trend

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

CURRENT AND MAXIMUM NET PRODUCTIVITY RATES

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

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

cetacean populations may not grow at rates much greater than 4% given the constraints of their reproductive life history

(Barlow et al. 1995). 

POTENTIAL BIOLOGICAL REMOVAL

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

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

population size is unknown. The maximum productivity rate is 0.04, the default value for cetaceans. The “recovery”

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

sustainable population (OSP) is assumed to be 0.5 because this stock is of unknown status. PBR for the western North

Atlantic northern bottlenose whale is unknown because the minimum population size cannot be determined. 

ANNUAL HUMAN-CAUSED MORTALITY

No mortalities have been reported in U.S. waters. A fishery for northern bottlenose whales existed in Canadian

waters during both the 1800s and 1900s. Its development was due to the discovery that bottlenose whales contained

spermaceti. A Norwegian fishery expanded from east to west (Labrador and Newfoundland) in several episodes. The
62

fishery peaked in 1965. Decreasing catches led to the cessation of the fishery in the 1970s, and provided evidence that

the population was depleted. A small fishery operated by Canadian whalers from Nova Scotia operated in the Gully,

and took 87 animals from 1962 to 1967 (Mead 1989; Mitchell 1977). 

Fishery Information

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

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

Southeast Fisheries Science Center (SEFSC). The Northeast Fisheries Science Center (NEFSC) Sea Sampling

Observer Program was initiated in 1989, and since that year several fisheries have been covered by the program. In

late 1992 and in 1993, the SEFSC provided observer coverage of pelagic longline vessels fishing off the Grand Banks

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

There have been no observed mortalities or serious injuries by NMFS Sea Samplers in the pelagic drift gillnet,

pelagic longline, pelagic pair trawl, New England multispecies sink gillnet, mid-Atlantic coastal sink gillnet, and

North Atlantic bottom trawl fisheries. 

STATUS OF STOCK

The status of northern bottlenose whales relative to OSP in U.S. Atlantic EEZ is unknown; however, a depletion

in Canadian waters in the 1970's may have impacted U.S. distribution and may be relevant to current status in U.S.

waters. The species is not listed as threatened or endangered under the Endangered Species Act. There are insufficient

data to determine the population trends for this species. Because there are no observed mortalities or serious injury,

the total fishery-related mortality and serious injury for this stock is considered to be approaching zero mortality and

serious injury rate. This is not a strategic stock because there are no recent records of fishery-related mortality or

serious injury. 

REFERENCES

Anon. 1993. Cruise results, NOAA ship DELAWARE II, Cruise No. DEL 93-06, Marine Mammal Survey. NOAA NMFS

NEFSC, Woods Hole Laboratory, Woods Hole, MA 5 pp.

Anon. 1996. Cruise results, R/V ABEL-J, Cruise No. AJ-9601, Part III, Marine Mammal Survey. NOAA NMFS NEFSC,

Woods Hole Laboratory, Woods Hole, MA 7 pp.

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

Preparation, Background, and a Summary of the 1995 Assessments. U.S. Dep. Commer., NOAA Tech. Memo.

NMFS-OPR-6, 73 pp.

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

continental shelf. Cetacean and Turtle Assessment Program, University of Rhode Island. Final Report #AA551-

CT8-48 to the Bureau of Land Management, Washington, DC, 538 pp. 

Gowans, S. and H. Whitehead. 1998. Social organization of northern bottlenose whales. The World Marine Mammal

Science Conference, Monaco, January 1998 (Abstract).

Mead, J. G. 1989. Bottlenose whales. Pages 321-348. In: S. H. Ridgway and R. Harrison (eds), Handbook of marine

mammals, Volume 4: River dolphins and the larger toothed whales. Academic Press, New York. 

Mitchell, E. D. 1977. Evidence that the northern bottlenose whale is depleted. Rep. int. Whal. Commn. 27: 195-203.

Mitchell, E. D. and V. M. Kozicki. 1975. Autumn stranding of a northern bottlenose whale (Hyperoodon ampullatus) in

the Bay of Fundy. J. Fish. Res. Bd. Can. 32: 1019-1040.

Reeves, R.R., E. Mitchell and H. Whitehead. 1993. Status of the northern bottlenose whale, Hyperoodon ampullatus. Can.

Fld. Nat. 107:490-508.

Whitehead, H., S. Gowans, A. Faucher, and S.W. McCarrey. 1997. Population analysis of northern bottlenose whales in

the Gully, Nova Scotia. Mar. Mamm. Sci. 13(2): 173-185.

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

April 3-5, 1996, Seattle, Washington. U.S. Dep. Commer., NOAA Tech. Memo. NMFS-OPR-12, 93 pp.
63

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. 

December 1998

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 U.S. 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 midAtlantic region off the northeast U.S. 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 U.S. coast (CETAP 1982). 

POPULATION SIZE

The total number of Cuvier's beaked whales off the

eastern U.S. coast is unknown. However, seven

estimates of the undifferentiated complex of beaked

whales (Ziphius and Mesoplodon spp.) are 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 U.S. 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; 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
64

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 2,000 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.
65

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
66

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 Cuvier’s beaked whales.

ANNUAL HUMAN-CAUSED MORTALITY AND SERIOUS INJURY

 The 1992-1996 total average estimated annual fishery-related mortality of beaked whales in the U.S. EEZ was

9.7 (CV = 0.07).

Fishery Information

There is no historical information available that documents incidental mortality in either U.S. or Canadian Atlantic

coast fisheries (Read 1994). 

Current data on incidental takes in U.S. fisheries are available from several sources. In 1986, NMFS established

a mandatory self-reported fishery information system for large pelagic fisheries. Data files are maintained at 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 fishery 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 U.S. 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, midAtlantic coastal sink gillnet, or North Atlantic bottom trawl observed fisheries. 

Pelagic Drift Gillnet

The estimated total number of hauls in the pelagic drift gillnet fishery increased from 714 in 1989 to 1,144 in

1990; thereafter, with the introduction of quotas, effort was severely reduced. The estimated number of hauls in 1991,

1992, 1993, 1994, 1995, and 1996 were 233, 243, 232, 197, 164, and 143, respectively. Fifty-nine different vessels

participated in this fishery at one time or another between 1989 and 1993. Since 1994, between 10-12 vessels have

participated in the fishery (Table 2). Observer coverage, expressed as percent of sets observed, was 8% in 1989, 6%

in 1990, 20% in 1991, 40% in 1992, 42% in 1993, 87% in 1994, 99% in 1995, and 64% in 1996. Effort was

concentrated along the southern edge of Georges Bank and off Cape Hatteras. Examination of the species composition

of the catch and locations of the fishery throughout the year, suggested that the pelagic drift gillnet fishery be stratified

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

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 fishery-related beaked whale mortalities were observed between 1989 and 1995. 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 1992-1996 total average

estimated annual fishery-related mortality of beaked whales in the U.S. EEZ was 9.7 (CV = 0.07) (Table 2). The 1992-

1996 period provides a better characterization of the current pelagic drift gillnet fishery. 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.
67

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

 92-

96

1994=12

1995=11

1996=10

Obs. Data

Logbook

.40, .42,

.87, .99,

.64

1, 5, 4, 9,

8

9.7, 12,

4.8, 9.15

 13

.24, .16,

.08, 0, .12

9.7

 (.07)

TOTAL 9.7

 (.07)

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.

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 92-96 1/9.7, 5/12, 4/4.8, 9/9.1, 8/13 0, 0, 0, 12

0

0, 0, 0, 0, 0

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”.

Other Mortality

From 1992-1996, 21 beaked whales (11(includes one tentative identification) -Gervais's beaked whales;2 -True's

beaked whale; 1- Blainville’s beaked whale; 6 -Cuvier's beaked whale- one 1996 animal showed signs of human

interactions propeller marks ) stranded along the U.S. Atlantic coast between Florida and Massachusetts (NMFS

unpublished data). 

STATUS OF STOCK

The status of Cuvier's beaked whale relative to OSP in U.S. 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
68

trends and the level of human-caused 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. (editor). 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.
69

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.
70

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. 

December 1998

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). Off the northeast U.S. 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 U.S. 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 U.S. coast is unknown. However, seven

estimates of the undifferentiated complex of beaked whales (Ziphius and Mesoplodon spp.) are 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
71

the population off the northeast U.S. 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; 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 U.S. coast. The

collective 1990-95 data suggest that, seasonally, at least several hundred beaked whales are occupying these waters,
72

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. 

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
73

5.5 m for males, maximum age for females were 30 growth layer groups (GLG's) and for males was 36 GLG's, which

may be annual layers (Mead 1984). 

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

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

constraints of their reproductive life history (Barlow et al. 1995). 

POTENTIAL BIOLOGICAL REMOVAL

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

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

population size for the undifferentiated complex of beaked whales is 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 1992-1996 total average estimated annual fishery-related mortality of beaked whales in the U.S. EEZ was 9.7

(CV = 0.07).

Fishery Information

There is no historical information available that documents incidental mortality in either U.S. or Canadian Atlantic

coast fisheries (Read 1994). 

Current data on incidental takes in U.S. fisheries are available from several sources. In 1986, NMFS established

a mandatory self-reported fishery information system for large pelagic fisheries. Data files are maintained at 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 U.S. 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, midAtlantic coastal sink gillnet, or North Atlantic bottom trawl observed fisheries. 

Pelagic Drift Gillnet

The estimated total number of hauls in the pelagic drift gillnet fishery increased from 714 in 1989 to 1,144 in

1990; thereafter, with the introduction of quotas, effort was severely reduced. The estimated number of hauls in 1991,

1992, 1993, 1994, 1995, and 1996 were 233, 243, 232, 197, 164, and 143, respectively. Fifty-nine different vessels

participated in this fishery at one time or another between 1989 and 1993. Since 1994, between 10-12 vessels have

participated in the fishery (Table 2). Observer coverage, expressed as percent of sets observed, was 8% in 1989, 6%

in 1990, 20% in 1991, 40% in 1992, 42% in 1993, 87% in 1994, 99% in 1995, and 64% in 1996. Effort was

concentrated along the southern edge of Georges Bank and off Cape Hatteras. Examination of the species composition

of the catch and locations of the fishery throughout the year, suggested that the pelagic drift gillnet fishery be stratified

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

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 fishery-related beaked whale mortalities were observed between 1989 and 1995. The
74

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 1992-1996 total average

estimated annual fishery-related mortality of beaked whales in the U.S. EEZ was 9.7 (CV = 0.07) (Table 2). The 1992-

1996 period provides a better characterization of the current pelagic drift gillnet fishery. 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), 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

92-96 1994=12

1995=11

1996=10

Obs. Data

Logbook

.40, .42,

.87, .99,

.64

1, 5, 4, 9,

8

9.7, 12,

4.8, 9.15

 13

.24, .16,

.08, 0, .12

9.7

 (.07)

TOTAL 9.7

 (.07)

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.

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 92-96 1/9.7, 5/12, 4/4.8, 9/9.1, 8/13 0, 0, 0, 12

0

0, 0, 0, 0, 0

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”.

Other Mortality
75

From 1992-1996, 21 beaked whales (11(includes one tentative identification) -Gervais's beaked whales;2 -True's

beaked whale; 1- Blainville’s beaked whale; 6 -Cuvier's beaked whale- one 1996 animal showed signs of human

interactions propeller marks ) stranded along the U.S. Atlantic coast between Florida and Massachusetts (NMFS

unpublished data).

STATUS OF STOCK

The status of Mesoplodont beaked whales relative to OSP in U.S. 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. 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.
76

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.

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.
77

Figure 2. Distribution of Risso's dolphin sightings from

NEFSC shipboard and aerial surveys during the summer

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

December 1998

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 U.S. 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 mid-Atlantic bight and extends further into oceanic waters (Payne et

al. 1984). In general, the population occupies the mid-Atlantic continental shelf edge year round, and is rarely seen

in the Gulf of Maine (Payne et al. 1984). During 1990, 1991 and 1993, spring/summer surveys conducted in

continental shelf edge and deeper oceanic waters had sightings of Risso's dolphins associated with strong bathymetric

features, Gulf Stream warm-core rings, and the Gulf Stream north wall (Waring et al. 1992; Waring 1993). There is

no information on stock differentiation of Risso's dolphin in the western North Atlantic. 

POPULATION SIZE

The total number of Risso's dolphins off the eastern

U.S. and Canadian Atlantic coast is unknown, although

four estimates are available from selected regions during

spring and summer 1978-82, June-July 1991, AugustSeptember 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 U.S. 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
78

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 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 U.S. 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
79

* 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. 

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 0.5 because this stock is of unknown status.

PBR for the western North Atlantic Risso’s dolphin is 111.

ANNUAL HUMAN-CAUSED MORTALITY

 Total annual estimated average fishery-related mortality to this stock during 1992-1996 was 18 Risso's dolphins

(CV = 0.17; 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 U.S. 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 U.S. 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 U.S. Atlantic EEZ. In 1982, there were 112

different foreign vessels; 16%, or 18, were Japanese tuna longline vessels operating along the U.S. 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 U.S. 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 U.S. fisheries are available from several sources. In 1986, NMFS established

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

Southeast Fisheries Science Center (SEFSC). The Northeast Fisheries Science Center (NEFSC) Sea Sampling

Observer Program was initiated in 1989, and since that year several fisheries have been covered by the program. In
80

late 1992 and in 1993, the SEFSC provided observer coverage of pelagic longline vessels fishing off the Grand Banks

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

By-catch has been observed by NMFS Sea Samplers in the pelagic drift gillnet fishery, pelagic pair trawl fishery,

and pelagic longline fishery, but no mortalities or serious injuries have been documented in the New England

multispecies sink gillnet, mid-Atlantic coastal sink gillnet, or North Atlantic bottom trawl observed fisheries.

Pelagic Drift Gillnet

The estimated total number of hauls in the pelagic drift gillnet fishery increased from 714 in 1989 to 1,144 in

1990; thereafter, with the introduction of quotas, effort was severely reduced. The estimated number of hauls in 1991,

1992, 1993, 1994, 1995, and 1996 were 233, 243, 232, 197, 164, and 149 respectively. Fifty-nine different vessels

participated in this fishery at one time or another between 1989 and 1993. Since 1994, between 10 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 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 fishery

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 1992-1996 total average estimated annual fishery-related mortality of Risso’s dolphins in the U.S. EEZ was 10.5

(CV = 0.20) (Table 2). The 1992-1996 period provides a better characterization of the current pelagic drift gillnet

fishery. 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

 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% (212) and 55% (238),

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).

The 1992-1995 estimated mean annual Risso’s dolphin mortality attributable to this fishery is 2.8 (CV= 0.44) (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. 

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

(Goudy 1995, 1996). Results of these studies were inconclusive in identifying factors responsible for marine mammal

bycatch.

Pelagic Longline
81

Total effort for the pelagic longline fishery, based on mandatory self-reported fishery information, was 11,279 sets

in 1991, 10,605 sets in 1992, 11,538 sets in 1993 11,231 sets in 1994, and 12,713 in 1995 (Cramer 1994; Scott and

Brown 1997). 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. From 1992-1995 two mortalities were

observed, one each in 1993 and 1994 (Cramer 1994; Scott and Brown 1997) (Table 2). Estimated annual fisheryrelated mortality (CV in parentheses) was 0 in 1992 (0), 13 in 1993 (0.19), 7 in 1994 (1.0) and 0 in 1995 (0). The

1992-1995 estimated mean annual Risso’s dolphin mortality attributable to this fishery is 5.0 (CV= 0.37) (Table 2).

Injured and released alive animals are not included in the Table 2 mortality estimates. Total average annual total

fishery-related mortality is 18.3 Risso’s dolphins (CV = 0.17).

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

Pelagic Drift

Gillnet

 92-96 1994=123

1995=11

1996=10

Obs. Data

Logbook

 .40, .42,

.87, .99,

.64

15, 1, 1,

6, 0

31, 14, 1.5

6

4

, 0

.27, .42,

.16, 0, 0

10.5 

(.20)

Pelagic Pair

Trawl

92-95 12 Obs. Data

Logbook

.10, .18,

.52, .54

1, 0, 0, 2 4.3, 3.2, 0,

3.7

.76, 1.0, 0,

.45

2.8

(.44)

Longline 92-95 Obs. Data

Logbook

.05 0, 1, 1, 0 0, 13, 7, 0 0, .19, 1.0,

0

5.0

(.37)

TOTAL 18.3

(.17)

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

Fisheries Science Center (NEFSC) Sea Sampling Program. NEFSC collects 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.
82

5

Injured and released alive animals are not included in the Table 2 mortality estimates.
83

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 Longline 92-95 0, 1/13, 1/7, 0 0, 0, 6 1 , 210, 0, 0, 21

1 Summary of observer comments for each animal as reported in Scott and Brown (1997): 1994 Trip A44004 (2

animals)- released alive, hooked in dorsal fin; mainline wrapped around body immediately adjacent to flukes; #2

released alive, hooked in tail fluke and mainline; gear cut to release animal, swam away with mainline and leader

around tail; TripA53037 - released alive; gear wrapped around animal, cut loose by crew, swam away quickly;

Trip A62002 (3 animals)- a good amount of mainline was tangled around animal, released with a fair amount

of mainline around fluke, some blood noticed around caudal peduncle; #2 hooked in mouth, animal released with

hook in mouth and approximately 7 fathoms of 400 lb test line trailing from mouth; #3 apparently hooked in

mouth, appeared to be wound up the midsection of the body with line, animal swam off quite sluggishly. 1995

Trip A411031 - hooked in mouth, gangion cut to free animal, alive; Trip #A44040 - alive, mainline and gangion

wrapped around tail, all gear cut before animal released; Trip 62058 - gear cut from animal, alive; Trip A41032 -

mouth hooked, line snapped and animal swam off; Trip A44043 - #1 mainline cut from around tail flukes and

pulled from mouth, animal swam sway quickly; #2 mainline cut from around tail flukes, animal swam off slowly

after blowing.

2

Injured and released alive animals are not included in the Table 2 mortality estimates.

Other mortality

From 1995-1996, three Risso’s dolphins stranding were recorded along the Atlantic coast (NMFS unpublished

data).

STATUS OF STOCK

The status of Risso's dolphins relative to OSP in the U.S. Atlantic EEZ is unknown. The species is not listed as

threatened or endangered under the Endangered Species Act. There are insufficient data to determine the population

trends for this species. 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 1992-1996 average annual fishery-related mortality did 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. 
84

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.

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.

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.
85

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. 

December 1998

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 U.S. 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 unpubl. 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 U.S. 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 U.S. waters

during spring, summer and autumn 1978-82, August

1990, June-July 1991, August-September 1991, JuneJuly 1993, and July-September 1995. Because longfinned 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 long-finned 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 U.S. 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
86

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 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 2,000 m 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 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 2,000 m isobaths from the southern edge of

Georges Bank, across the Northeast Channel to the southeastern edge of the Scotian Shelf (Table 1; Anon. 1993b).

Data were collected by two alternating teams that searched with 25x150 binoculars and were analyzed using

DISTANCE (Buckland et al. 1993; Laake et al. 1993). Estimates include school size-bias, if applicable, but do not

include corrections for g(0) or dive-time. Variability was estimated using bootstrap resampling techniques.

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 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.

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 U.S. 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 unpubl. data.) because this survey is recent and provided the most

complete coverage of the known habitat.
87

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). Unk=unknown.

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). 
88

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 0.50 because this stock is of unknown status (Wade and

Angliss 1997). PBR for the western North Atlantic Globicephala sp. is 50.

ANNUAL HUMAN-CAUSED MORTALITY

 Total annual estimated average fishery-related mortality to this stock during 1992-1996 was 32 pilot whales (CV

= 0.09; 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 U.S. 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 U.S. 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 U.S. 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 U.S. vessels involved

in joint venture fishing operations in which U.S. 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 U.S. fisheries are available from several sources. In 1986, NMFS established

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

Southeast Fisheries Science Center (SEFSC). The Northeast Fisheries Science Center (NEFSC) Sea Sampling

Observer Program was initiated in 1989, and since that year several fisheries have been covered by the program. In

late 1992 and in 1993, the SEFSC provided observer coverage of pelagic longline vessels fishing off the Grand Banks

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

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.
89

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. Fifty-nine different vessels

participated in this fishery at one time or another between 1989 and 1993. Since 1994, between 10-12 vessels have

participated in the fishery (Table 2). Observer coverage, expressed as percent of sets observed, was 8% in 1989, 6%

in 1990, 20% in 1991, 40% in 1992, 42% in 1993, 87% in 1994, 99% in 1995, and 64% in 1996. Effort was

concentrated along the southern edge of Georges Bank and off Cape Hatteras. Examination of the species composition

of the catch and locations of the fishery throughout the year, suggested that the pelagic drift gillnet fishery be stratified

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

1989 to 1993, were obtained using the aggregated (pooled 1989-1993) catch rates, by strata (Northridge 1996).

Estimates of total annual by-catch for 1994 and 1995 were estimated from the sum of the observed caught and the

product of the average bycatch per haul and the number of unobserved hauls as recorded in self-reported fishery

information. Variances were estimated using bootstrap re-sampling techniques. 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 1992-1996 was 20.8 pilot

whales (0.08) (Table 2). The 1992-1996 period provides a better characterization of this fishery (i.e., fewer vessels and

increased 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. 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 fishery information in 1993. In 1994 and

1995 observers reported one and twelve mortalities, respectively (Table 2). The estimated fishery-related mortality to

pilot whales in the U.S. Atlantic attributable to this fishery in 1994 was 2.0 (CV=0.49) and 22 (CV=0.33) in 1995. The

average mortality between 1992 and 1995 was 6 (CV=0.31) for this fishery. 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.

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

(Goudy 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 U.S. Atlantic ( including Caribbean) and Gulf of Mexico EEZ (SEFSC

unpublished data). Interactions between the pelagic longline fishery and pilot whales have been reported; however,
90

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 for

the pelagic longline fishery (Atlantic, including the Caribbean), based on mandatory self-reported fishery information,

was 11,279 sets in 1991, 10,605 sets in 1992, 11,538 in 1993, 11,231 sets in 1994, and 12,713 in 1995 (Cramer 1994;

Scott and Brown 1997). The fishery has been observed nearly year round within every statistical reporting area within

the EEZ and beyond. Most of the estimated marine mammal by-catch was from EEZ waters between South Carolina

and Cape Cod. Pilot whales are frequently observed to feed on hooked fish, particularly big-eye tuna (NMFS

unpublished data). Between 1990-1995 fifty-four pilot whales (including one identified as a short-fin pilot whale) were

released alive, and one mortality was observed. January-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 April-June. During the JulySeptember 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 Barnegat Bay and Cape Hatteras. The 1990-1993, estimated take was based on a generalized linear model

(Poisson error assumption) fit to the available observed incidental take and self-reported incidental take and effort data

for the fishery (SEFSC unpublished data). The 1994-1995 estimates were based on the Delta-lognormal method

(details in Scott and Brown 1997). The estimated fishery-related mortality to pilot whales in the U.S. Atlantic

attributable to this fishery was: 22 in 1992 (CV = 0.23), and zero in 1993-1995; average annual mortality between

1992-1995 was 5.5 pilot whales (0.23) (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.

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. In 1997 one decomposed pilot whale was taken in the mid-Atlantic region. 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 bycatch for this fishery. 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.

Atlantic Squid, Mackerel, Butterfish Trawl

The mid-Atlantic mackerel and squid trawl fisheries were combined into the Atlantic mid-water trawl fishery in

the revised proposed list of fisheries in 1995. The fishery occurs along the U.S. mid-Atlantic continental shelf region

between New Brunswick, Canada, and Cape Hatteras year around. The mackerel trawl fishery was classified as a
91

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 fishery information from the mackerel trawl fishery between 1990-1992. One mortality was observed

in the 1996 Illex squid fishery. The effort data for this fishery are currently under review. Total fishery-related

mortality and serious injury cannot be estimated separately for the two species of pilot whales in the U.S. 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 estimated annual fishery-related mortality of pilot whales from NMFS-observed

fisheries was the sum of integer-rounded annual mortality estimates across the pelagic longline (1992-1995), pelagic

drift gillnet (1992-1996), pelagic pair trawl (1992-1995), and was 32 pilot whales, Globicephala sp. (CV = 0.32)

(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. 

Between January 1993 and December 1994, 36 Spanish deep water trawlers, covering 74 fishing trips (4,726

fishing days and 14,211sets), were observed in NAFO Fishing Area 3 (off the Grand Bank) (Lens 1997). A total of

47 incidental catches were recorded, which included one long-finned pilot whale. The incidental mortality rate for

pilot whales was (0.007/set).
92

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

Estimated7

Mortality 

Estimated

CVs 

Mean

Annual

Mortality

Pelagic

Drift

Gillnet

92-96 1994=123

1995=11

1996=10

Obs. Data

Logbook

.40, .42,

.87, .99,

.64

14, 114,

17, 9, 7

33, 31, 20,

9.15, 11

.16, .19,

.06, 0, .17

20.8

 (.08)

Pelagic

Pair Trawl

92-95 12 Obs. Data

Logbook

.09, .17,

.52, .54

0, 06 , 1,

12

0, 0, 2, 22 0, 0, .49,

.33

6.0

(.31)

Atlantic

squid,

mackerel,

butterfish

trawl

96 NA Obs. Data

Logbook

.007 1 NA NA NA

Longline 92-95 Obs. Data

Logbook

.05 1, 0, 0, 0 22, 0, 0, 0 .23, 0, 0,

0

5.5

 (.23)

TOTAL 32

 (.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 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.

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 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

In 1993, 5 pilot whales were taken on a tow without an observer. An estimate could not be made based on

unobserved tows.

7 Annual mortality estimates do not include any animals injured and released alive.
93

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 Injured5 Uninjured

Pelagic Drift Gillnet 92-96 14/33, 11/31,

17/20,9/9.1,7/11

1

1

, 12, 0, 0, 0 0

Pelagic Long Line 92-95 1/22, 0, 0, 0 NA, NA, 53, 44 NA, NA,

9

3

,114

North Atlantic Bottom

Trawl

92-96 0, 0, 0, 0, 0 0, 0, 0, 0, 0 0, 0, 1, 0, 0

1 Released alive with moderate injury (observers's comments).

2 Released alive with condition unknown.

3

1994: Trip A02 - alive, cut from gear, condition unknown; Trip A28030 - #1 alive, mainline wrapped around

fluke, one end of line cut and the other pulled free, animal swam away; #2 hooked in pectoral fine, gangion cut

and animal swam away; Trip A32006 - #1-#5 alive, gangion cut, animal swam away; #6 tangled in mainline, cut

free, animal swam away; Trip A44004 - #1 alive, hooked in dorsal fin, mainline cut to release animal with gangion

still attached; #2 animal cut from mainline several wraps of mainline and part of gangion around base of

flukes/tail, animal swam off slowly; #3 hooked in mouth, broke gangion from mainline, swam away strongly

trailing 50 fathoms of mainline from its mouth; Trip A54005 - #1 alive, gear around flipper; #2 alive, gear around

body Trip A44043 - hooked in flipper; gangion broke off as it was hauled.

4

1995: Trip A53034 - animal cut free, swam away quickly; Trip A41031 - cut loose with leader still attached, line

parted as it neared the vessel, ‘mouth hooked’; Trip A25041 - alive, animal hooked or maybe wrapped in mono,

condition unknown; Trip A44040 - alive, hooked in flipper, cut from gangion ;Trip A62058 -#1 animal

extensively wrapped in mainline around caudal peduncle, most of the line cut away, animal released with the

remaining line trailing; #2 alive, gear cut from animal; Trip A41032 - mouth hooked, line snapped and animal

swam off; Trip A44043 - hooked in flipper, gangion broke off as it was hauled; Trip A62071 - hooked imbedded

in caudal peduncle, one or tow wraps of the gangion along with the hook were left in the animal, sluggishly swam

away, (shortfin pilot whale)- hooked in mouth, gangion clipped as close to the mouth as possible, released with

hook in mouth; Trip A41034 - #1 animal swam away after breaking line, condition unknown; #2 hooked in mouth,

leader cut to free animal, condition unknown; #3 leader cut to free animal, condition unknown; #4 same as #3,

but animal swam towards a small pod; Trip A44048 -hooked in mouth, cut from mainline, swam away trailing

gangion and 100 ft of mainline; Trip T12 - alive, entangled in mainline, mono cut away.

5

Injured and released alive animals are not included in the Table 2 mortality estimates.

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 1992-1996, 60 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 U.S. 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
94

1971, and increased abundance of herring, mackerel, and squid stocks. There are insufficient data to determine the

population trends for this species. The species is not listed under the Endangered Species Act. The total fishery-related

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

considered to be insignificant and approaching zero mortality and serious injury rate. This is not a strategic stock

because the 1992-1996 estimated average annual fishery-related mortality to pilot whales, Globicephala sp., does not

exceed PBR. 

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. Status of fishery resources off the northeastern United States for 1993. NOAA Tech. Mem. NMFS-F/NEC101, 140 pp.

Anon. 1993b. 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. 

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. 

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.

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.
95

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.

National Marine Fisheries Service. 1995. Final environmental impact statement for a regulatory amendment for the

western Atlantic bluefin tuna fishery. July 20, 1995. Available from NOAA, NMFS, Office of Protected Species,

Silver Springs, MD.

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. 

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. 
96

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.

December 1998

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 U.S. Atlantic Exclusive Economic Zone

(EEZ) is generally thought to be Cape Hatteras, North Carolina

(Leatherwood and Reeves 1983). Sightings of these animals in

U.S. 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, linetransect vessel survey of the U.S. 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 short-finned

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). 
97

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). The maximum productivity rate is 0.04, the default value for cetaceans. The

“recovery” factor, which accounts for endangered, depleted, threatened stocks, or stocks of unknown status relative to

optimum sustainable population (OSP) is 0.50 because this stock is of unknown status (Wade and Angliss 1997). PBR

for the western North Atlantic short-finned pilot whales is 4.6. 

ANNUAL HUMAN-CAUSED MORTALITY AND SERIOUS INJURY

 Total annual estimated average fishery-related mortality to this stock during 1992-1996 was 32 pilot whales (CV

= 0.09; Table 2). 

Fishery Information

USA

The level of past or current, direct, human-caused mortality of short-finned pilot whales in the U.S. Atlantic EEZ

is unknown. The short-finned pilot whale has been taken in the pelagic longline fishery in Atlantic waters off the

southeastern U.S. (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 U.S. 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 U.S. 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 U.S. 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 U.S. vessels involved

in joint venture fishing operations in which U.S. 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 U.S. fisheries are available from several sources. In 1986, NMFS established

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

Southeast Fisheries Science Center (SEFSC). The Northeast Fisheries Science Center (NEFSC) Sea Sampling

Observer Program was initiated in 1989, and since that year several fisheries have been covered by the program. In

late 1992 and in 1993, the SEFSC provided observer coverage of pelagic longline vessels fishing off the Grand Banks

(Tail of the Banks) and provides observer coverage of vessels fishing south of Cape Hatteras.
98

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 been documented in the New England multispecies sink

gillnet or mid-Atlantic coastal sink gillnet.

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. Fifty-nine different vessels

participated in this fishery at one time or another between 1989 and 1993. Since 1994, between 10-12 vessels have

participated in the fishery (Table 2). Observer coverage, expressed as percent of sets observed, was 8% in 1989, 6%

in 1990, 20% in 1991, 40% in 1992, 42% in 1993, 87% in 1994, 99% in 1995, and 64% in 1996. Effort was

concentrated along the southern edge of Georges Bank and off Cape Hatteras. Examination of the species composition

of the catch and locations of the fishery throughout the year, suggested that the pelagic drift gillnet fishery be stratified

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

1989 to 1993, were obtained using the aggregated (pooled 1989-1993) catch rates, by strata (Northridge 1996).

Estimates of total annual by-catch for 1994 and 1995 were estimated from the sum of the observed caught and the

product of the average bycatch per haul and the number of unobserved hauls as recorded in self-reported fishery

information. Variances were estimated using bootstrap re-sampling techniques. 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 1992-1996 was 20.8 pilot

whales (0.08) (Table 2). The 1992-1996 period provides a better characterization of this fishery (i.e., fewer vessels

and increased 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. 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 fishery information in 1993. In 1994 and

1995 observers reported one and twelve mortalities, respectively (Table 2). The estimated fishery-related mortality to

pilot whales in the U.S. Atlantic attributable to this fishery in 1994 was 2.0 (CV=0.49) and 22 (CV=0.33) in 1995. The

average mortality between 1992 and 1995 was 6 (CV=0.31) for this fishery. 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.

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.
99

Pelagic Longline

The pelagic longline fishery operates in the U.S. 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 for

the pelagic longline fishery (Atlantic, including the Caribbean), based on mandatory self-reported fishery information,

was 11,279 sets in 1991, 10,605 sets in 1992, 11,538 in 1993, 11,231 sets in 1994, and 12,713 in 1995 (Cramer 1994;

Scott and Brown 1997). The fishery has been observed nearly year round within every statistical reporting area within

the EEZ and beyond. Most of the estimated marine mammal by-catch was from EEZ waters between South Carolina

and Cape Cod. Pilot whales are frequently observed to feed on hooked fish, particularly big-eye tuna (NMFS

unpublished data). Between 1990-1995 fifty-four pilot whales (including one identified as a short-fin pilot whale) were

released alive, and one mortality was observed. January-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 April-June. During the JulySeptember 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 Barnegat Bay and Cape Hatteras. The 1990-1993, estimated take was based on a generalized linear model

(Poisson error assumption) fit to the available observed incidental take and self-reported incidental take and effort data

for the fishery (SEFSC unpublished data). The 1994-1995 estimates were based on the Delta-lognormal method

(details in Scott and Brown 1997). The estimated fishery-related mortality to pilot whales in the U.S. Atlantic

attributable to this fishery was: 22 in 1992 (CV = 0.23), and zero in 1993-1995; average annual mortality between

1992-1995 was 5.5 pilot whales (0.23) (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.

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. In 1997 one decomposed pilot whale was taken in the mid-Atlantic region. 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 bycatch for this fishery. 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.
100

Atlantic Squid, Mackerel, Butterfish Trawl

The mid-Atlantic mackerel and squid trawl fisheries were combined into the Atlantic mid-water trawl fishery in

the revised proposed list of fisheries in 1995. The fishery occurs along the U.S. 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 fishery information from the mackerel trawl fishery between 1990-1992. One mortality was observed

in the 1996 Illex squid fishery. The effort data for this fishery are currently under review, therefore the estimated

fishery-related mortality has not been determined. 

Total fishery-related mortality and serious injury cannot be estimated separately for the two species of pilot whales

in the U.S. 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 estimated annual fishery-related mortality

of pilot whales from NMFS-observed fisheries was the sum of integer-rounded annual mortality estimates across the

pelagic longline (1992-1995), pelagic drift gillnet (1992-1996), and pelagic pair trawl (1992-1995), and was 32 pilot

whales, Globicephala sp. (CV = 0.09) (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. 

Between January 1993 and December 1994, 36 Spanish deep water trawlers, covering 74 fishing trips (4,726

fishing days and 14,211sets), were observed in NAFO Fishing Area 3 (off the Grand Bank) (Lens 1997). A total of

47 incidental catches were recorded, which included one long-finned pilot whale. The incidental mortality rate for

long-finned pilot whales was (0.007/set).
101

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

Estimated7

Mortality 

Estimate

d CVs 

Mean

Annual

Mortality

Pelagic

Drift

Gillnet

92-96 1994=123

1995=11

1996=10

Obs. Data

Logbook

.40, .42,

.87, .99,

.64

14, 114,

17, 9, 7

33, 31, 20,

9.15, 11

.16, .19,

.06, 0,

.17

20.8

 (.08)

Pelagic

Pair Trawl

92-95 12 Obs. Data

Logbook

.09, .17,

.52, .54

0, 06 , 1,

12

0, 0, 2, 22 0, 0, .49,

.33

6.0

(.31)

Atlantic

squid,

mackerel,

butterfish

trawl

96 NA Obs. Data

Logbook

0.007 1 NA NA NA

Longline 92-

95

Obs. Data

Logbook

.05 1, 0, 0, 0 22, 0, 0, 0 .23, 0, 0,

0

5.5

 (.23)

TOTAL 32

 (.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 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.

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 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

In 1993, 5 pilot whales were taken on a tow without an observer. An estimate could not be made based on

unobserved tows.

7 Annual mortality estimates do not include any animals injured and released alive.
102

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 Injured5 Uninjured

Pelagic Drift Gillnet 92-96 14/33, 11/31,

17/20,9/9.1,7/11

1

1

, 12, 0, 0, 0 0

Pelagic Long Line 92-95 1/22, 0, 0, 0 NA, NA, 53, 44 NA, NA,

9

3

,114

North Atlantic Bottom

Trawl

92-96 0, 0, 0, 0, 0 0, 0, 0, 0, 0 0, 0, 1, 0, 0

1 Released alive with moderate injury (observer's comments).

2 Released alive with condition unknown.

3

1994: Trip A02 - alive, cut from gear, condition unknown; Trip A28030 - #1 alive, mainline wrapped around

fluke, one end of line cut and the other pulled free, animal swam away; #2 hooked in pectoral fine, gangion cut

and animal swam away; Trip A32006 - #1-#5 alive, gangion cut, animal swam away; #6 tangled in mainline, cut

free, animal swam away; Trip A44004 - #1 alive, hooked in dorsal fin, mainline cut to release animal with gangion

still attached; #2 animal cut from mainline several wraps of mainline and part of gangion around base of

flukes/tail, animal swam off slowly; #3 hooked in mouth, broke gangion from mainline, swam away strongly

trailing 50 fathoms of mainline from its mouth; Trip A54005 - #1 alive, gear around flipper; #2 alive, gear around

body Trip A44043 - hooked in flipper; gangion broke off as it was hauled.

4

1995: Trip A53034 - animal cut free, swam away quickly; Trip A41031 - cut loose with leader still attached, line

parted as it neared the vessel, ‘mouth hooked’; Trip A25041 - alive, animal hooked or maybe wrapped in mono,

condition unknown; Trip A44040 - alive, hooked in flipper, cut from gangion ;Trip A62058 -#1 animal

extensively wrapped in mainline around caudal peduncle, most of the line cut away, animal released with the

remaining line trailing; #2 alive, gear cut from animal; Trip A41032 - mouth hooked, line snapped and animal

swam off; Trip A44043 - hooked in flipper, gangion broke off as it was hauled; Trip A62071 - hooked imbedded

in caudal peduncle, one or tow wraps of the gangion along with the hook were left in the animal, sluggishly swam

away, (shortfin pilot whale)- hooked in mouth, gangion clipped as close to the mouth as possible, released with

hook in mouth; Trip A41034 - #1 animal swam away after breaking line, condition unknown; #2 hooked in mouth,

leader cut to free animal, condition unknown; #3 leader cut to free animal, condition unknown; #4 same as #3,

but animal swam towards a small pod; Trip A44048 -hooked in mouth, cut from mainline, swam away trailing

gangion and 100 ft of mainline; Trip T12 - alive, entangled in mainline, mono cut away.

5

Injured and released alive animals are not included in the Table 2 mortality estimates.

Other Mortality

There were 190 short-finned pilot whale strandings documented during 1987- August 1996 along the U.S. Atlantic

coast between Cape Hatteras, North Carolina, and Miami, Florida; four 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 U.S. 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 1992-96 estimated average annual fishery-related mortality to pilot whales, Globicephala sp., exceeds

PBR.
103

REFERENCES

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

Preparation, Background, and a Summary of the 1995 Assessments. U.S. Dep. Commer., NOAA Tech. Memo.

NMFS-OPR-6, 73 pp. 

Buckland, S. T., D. R. Anderson, K. P. Burnham and J. L. Laake. 1993. Distance Sampling: estimating abundance of

biological populations. Chapman & Hall, London, 446 pp. 

Cramer J. 1994. Large pelagic logbook newsletter - 1993. NOAA Tech. Mem. NMFS-SEFSC-352, 19 pp.

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. MIA93/94-58.

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. 

Leatherwood, S. and R. R. Reeves. 1983. The Sierra Club handbook of whales and dolphins. Sierra Club Books, San

Francisco, 302 pp. 

Lee, D. W., C. J. Brown, A. J. Catalano, J. R. Grubich, T. W. Greig, R. J. Miller and M. T. Judge. 1994. SEFSC pelagic

longline observer program data summary for 1992-1993. NOAA Tech. Mem. NMFS-SEFSC-347. 19 pp. 

Mullin, K., W. Hoggard, C. Roden, R. Lohoefener, C. Rogers and B. Taggart. 1991. Cetaceans on the upper continental

slope in the north-central Gulf of Mexico. OCS Study/MMS 91-0027. U.S. Dept. of the Interior, Minerals

Management Service, Gulf of Mexico OCS Regional Office, New Orleans, Louisiana, 108 pp. 

National Marine Fisheries Service. 1995. Final environmental impact statement for a regulatory amendment for the

western Atlantic bluefin tuna fishery. July 20, 1995. Available from NOAA, NMFS, Office of Protected Species,

Silver Springs, MD.

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. 
104

August 1997

WHITE-BEAKED DOLPHIN (Lagenorhynchus albirostris):

Western North Atlantic Stock

STOCK DEFINITION AND GEOGRAPHIC RANGE

White-beaked dolphins are the more northerly of the two species of Lagenorhynchus in the Northwest Atlantic

(Leatherwood et al. 1976). The species is found in waters from southern New England, north to western and southern

Greenland and Davis Straits (Leatherwood et al. 1976; CETAP 1982), in the Barents Sea and south to at least Portugal

(Reeves et al., in press). Differences in skull features indicate that there are at least two separate stocks, one in the

eastern and one in the western North Atlantic (Mikkelsen and Lund 1994). No genetic analyzes have been conducted

to distinguish the stock structure.

In waters off the northeastern U.S. coast, white-beaked dolphin sightings have been concentrated in the western

Gulf of Maine and around Cape Cod (CETAP 1982). The limited distribution of this species in U.S. waters has been

attributed to opportunistic feeding (CETAP 1982). Prior to the 1970's, white-sided dolphins (L. acutus) in U.S. waters

were found primarily offshore on the continental slope, while white-beaked dolphins were found on the continental

shelf. During the 1970's, there was an apparent switch in habitat use between these two species. This shift may have

been a result of the increase in sand lance in the continental shelf waters (Katona et al. 1993; Kenny et al. 1996). 

POPULATION SIZE

The total number of white-beaked dolphins in U.S. and Canadian waters is unknown, although one abundance

estimate is available for part of the known habitat in U.S. waters, and two estimates are from Canadian waters (Table

1).

A population size of 573 white-beaked dolphins (CV=0.69) was estimated from an aerial survey program

conducted from 1978 to 1982 on the continental shelf and shelf edge waters between Cape Hatteras, North Carolina

and Nova Scotia (Table 1; CETAP 1982). The estimate is based on spring data because the greatest proportion of the

population off the northeast U.S. coast appeared in the study area during this season. This estimate does not include

a correction for dive-time or g(0), the probability of detecting an animal group on the track line. This estimate may

not reflect the current true population size because of its high degree of uncertainty (e.g., large CV), its old age, and

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

A population size of 5,500 white-beaked dolphins was based on an aerial survey off eastern Newfoundland and

southeastern Labrador (Table 1; Alling and Whitehead 1987).

A population size of 3,486 white-beaked dolphins [95% confidence interval (CI) = 2,001-4,971]was estimated

from a ship-based survey of a small segment of the Labrador Shelf in August 1982 (Table 1; Alling and Whitehead

1987). A CV was not given, but, assuming a symmetric CI, it would be 0.22.

 There are no abundance estimates for this species in waters between the Gulf of Maine and the

Newfoundland/Labrador region. 

Table 1. Summary of abundance estimates for western North Atlantic white-beaked dolphins. Month, year, and

area covered during each abundance survey, and resulting abundance estimate (Nbest) and coefficient of

variation (CV). Unk=unknown.

Month/Year Area Nbest CV

spring 1978-82 Cape Hatteras, NC

to Nova Scotia 573 0.69

1980's E. Newfoundland

and SE Labrador 5,500 None reported

August 1982 Labrador shelf 3,486 0.22
105

Minimum Population Estimate

Present data are insufficient to calculate a minimum population estimate in U.S. Exclusive Economic Zone (EEZ)

waters. 

Current Population Trend

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

CURRENT AND MAXIMUM NET PRODUCTIVITY RATES

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

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

cetacean populations may not grow at rates much greater than 4% given the constraints of their reproductive life history

(Barlow et al. 1995).

 

POTENTIAL BIOLOGICAL REMOVAL

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

productivity rate, and a “recovery” factor (Wade and Angliss 1997). The minimum population size of white-beaked

dolphins is unknown. The maximum productivity rate is 0.04, the default value for cetaceans. The “recovery” factor,

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

sustainable population (OSP) is assumed to be 0.5 because this stock is of unknown status. PBR for the western North

Atlantic white-beaked dolphin is unknown.

ANNUAL HUMAN-CAUSED MORTALITY AND SERIOUS INJURY

White-beaked dolphins have been taken in cod traps and the Canadian groundfish gillnet fisheries off

Newfoundland and Labrador and in the Gulf of St. Lawrence (Alling and Whitehead 1987; Read 1994; Hai et al.

1996); however, the total number of animals taken is not known. 

There are no documented reports of fishery-related mortality or serious injury to this stock in the U.S. EEZ. 

Fishery Information

Because of the absence of observed fishery-related mortality and serious injury to this stock in the U.S. EEZ, no

U.S. fishery information is provided. 

The Canadian Atlantic groundfish gillnet fishery is important and widespread. Many fisherman hold groundfish

gillnet licenses but the number of active fishermen is unknown. In 1989, approximately 6,800 licenses were issued

to fishermen along the southern coast of Labrador, and northeast and southern coast of Newfoundland. About 3,900

licenses were issued in 1989 in the Gulf of St. Lawrence and 659 licenses were issued in the Bay of Fundy and

southwestern Nova Scotia. 

Other Mortality

White-beaked dolphins were hunted for food by residents in Newfoundland and Labrador (Alling and Whitehead

1987). These authors, based on interview data, estimated that 366 white-beaked dolphins were taken each year. The

same authors reported that 25-50% of the killed dolphins were lost.

STATUS OF STOCK

The status of white-beaked dolphins, relative to OSP, in U.S. Atlantic coast waters is unknown. They are not listed

as threatened or endangered under the Endangered Species Act. There are insufficient data to determine population

trends for this species. Because there are insufficient data to calculate PBR it is not possible to determine if stock is

strategic and if the total fishery-related mortality and serious injury for this stock is significant and approaching zero

mortality and serious injury rate. However, because this stock has a marginal occurrence in U.S. waters and there are

no documented takes in U.S. waters, this stock has been designated as not strategic. 
106

REFERENCES

Alling, A. K. and H. P. Whitehead. 1987. A preliminary study of the status of white-beaked dolphins, Lagenorhynchus

albirostris, and other small cetaceans off the coast of Labrador. Can. Fld. Nat. 101(2): 131-135.

Barlow, J., S. L. Swartz, T. C. Eagle, and P. R. Wade. 1995. U.S. Marine mammal stock assessments: Guidelines for

preparation, background, and a summary of the 1995 assessments. U.S.Dept. Commer., NOAA Tech. Memo.

NMFS-OPR-6, 73 pp.

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

continental shelf. Cetacean and Turtle Assessment Program, University of Rhode Island. Final Report #AA551-

CT8-48 to the Bureau of Land Management, Washington, DC, 538 pp. 

Hai, D.J., J. Lein, D. Nelson, and K. Curren. 1996. A contribution to the biology of the white-sided dolphin, Lagenorhnchus

albirostris, in waters off Newfoundland. Can..Fld. Nat. 110(1).

Katona, S. K., V. Rough, and D. T. Richardson. 1993. A field guide to whales, porpoises, and seals from Cape Cod to

Newfoundland. Washington, D. C. : Smithsonian Institution Press. 316 pp. 

Kenney, R. D., P. M. Payne, D. W. Heineman and H. E. Winn. 1996. Shifts in Northeast shelf cetacean distributions

relative to trends in Gulf of Maine/Georges Bank finfish abundance. Pp. 169-196. In: K. Sherman, N.A. Jaworski

and T. Smada (eds.) The northeast shelf ecosystem: assessment, sustainability, and management. Blackwell

Science, Cambridge, MA 02142, USA.

Leatherwood, S., D. K. Caldwell, and H. E. Winn. 1976. Whales, dolphins, and porpoises of the western North Atlantic.

A guide to their identification. U.S. Dept. of Commerce, NOAA Tech. Rep. NMFS Circ. 396, 176 pp. 

Mikkelsen, A.M.H. and A. Lund. 1994. Intraspecific variation in the dolphins Lagenorhnchus albirostris and L. acutus

(Mammalia: Cetacea) in metrical and non-metrical skull characters, with remarks on occurrence. J. Zool., Lond.

234:289-299.

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

Commn. Special Issue 15: 133-147. 

Reeves, R.R., R. L. Brownell Jr., C. C. Kinze, C. Smeenk and J. Lein. (in press). White-beaked dolphin (Lagenorhnchus

albirostris (Gray 1846). In: S.H. Ridgway and R. Harrison (eds.) Handbook of marine mammals, Vol 6.

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

April 3-5, 1996, Seattle, Washington. U.S. Dep. Commer., NOAA Tech. Memo. NMFS-OPR-12, 93 pp.
107

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. 

December 1998

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 very 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 U.S. 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 U.S. 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,

June-July 1993, 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
108

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 U.S. 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 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). This survey included the area covered by the above 1991 and

1992 surveys. For the 1995 survey, the 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 U.S. 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
109

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

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 0.5 because this stock is of unknown status. PBR for the

western North Atlantic white-sided dolphin is 192.

ANNUAL HUMAN-CAUSED MORTALITY AND SERIOUS INJURY

Fishery Information

USA

Recently, within U.S. waters, white-sided dolphins have been caught in the New England multispecies sink gillnet

fisheries, pelagic drift gillnet fishery, and the North Atlantic bottom trawl fishery (Table 2). Estimated average

annual fishery-related mortality and serious injury to the western North Atlantic white-sided dolphin stock from these

U.S. fisheries during 1992-1996 was 218 dolphins per year (CV = 0.23).

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 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 U.S. vessels involved in jointventure fishing operations in which U.S. 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 U.S. 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 U.S. 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 U.S. east coast. This was the first year that the
110

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.

New England Multispecies Sink Gillnet

Between 1990 and 1996 there were 35 mortalities observed in the New England multispecies sink gillnet fishery.

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%, and 4% for years 1990 to 1996, respectively.

The fishery has been observed in the Gulf of Maine and in Southern New England. In January to March, the by-catch

occurred in Massachusetts Bay, south of Cape Ann and west of Stellwagen Bank. From April to June, by-catch

locations became more dispersed, from Casco Bay to Cape Ann, along the 30 fathom contour out to Jeffreys Ledge,

with one take location near Cultivator Shoal and one in southern New England near Block Island. In July through

September, incidental takes occurred from Frenchman's Bay to Massachusetts Bay. In inshore waters, the takes were

aggregated while offshore takes were more dispersed. In October through December, takes were confined from Cape

Elizabeth out to Jeffreys Ledge and south to Nantucket Sound. 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),

and 114 in 1996 (0.61) (Table 2; Bisack 1997). Average annual estimated fishery-related mortality during 1992-1996

was 159 white-sided dolphins (0.24) (Table 2).

Pelagic Drift Gillnet 

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 fishery 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. 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 and the product of the average by-catch per haul and the number of unobserved hauls as recorded

in logbooks. Variances were estimated using bootstrap re-sampling techniques (Bisack 1997). 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. Estimated average annual mortality and serious

injury related to this fishery during 1992-1996 was 0.7 white-sided dolphins (0.21) (Table 2).

North Atlantic Bottom Trawl 

Three mortalities were documented between 1991 and 1996 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. Vessels in the North Atlantic bottom trawl fishery, a Category

III fishery under the MMPA, were observed in order to meet fishery management needs, rather than marine mammal

management needs. An average of 970 (CV = 0.04) vessels (full and part time) participated annually in the fishery

during 1989-1993. The fishery is active in New England waters in all seasons. The one white-sided dolphin taken

in 1992 was in a haul that was composed of 43% cod, 20% silver hake, and 17% pollock. One of the 1994 takes was
111

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 1997). The average annual estimate

fishery-related mortality during 1992-1996 was 58.4 white-sided dolphins (CV = 0.57) (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). 

Between January 1993 and December 1994, 36 Spanish deep water trawlers, covering 74 fishing trips (4,726

fishing days and 14,211sets), were observed in NAFO Fishing Area 3 (off the Grand Bank) (Lens 1997). A total of

47 incidental catches were recorded, which included six white-sided dolphins. The incidental mortality rate for whitesided dolphins was (0.042/set). More recent information on Canadian white-sided dolphin takes were not available.

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

92-96 1993=349 Obs. Data

Weighout

Trip Logbook

 .07, .05,

.07, .05,

.04

9, 7,

103, 23,

2

3

154, 205,

2403, 803,

1143

.35, .31,

.51, 1.16,

.61

158.6

(.24)

Pelagic Drift

Gillnet

92-96 1994=114

1995=12

1996=10

Obs. Data

Logbook

.40, .42,

.87, .99,.64

0

5

, 25,

 05, 

0

5

, 05

0.85, 2.75,

0

5

, 

0

5

, 05

.71, 0.17,

0, 

0, 0

0.7

(.21)

North Atlantic

Bottom Trawl

92-96 1993=970 Obs. Data

Weighout

.006, .004,

.004,.0116,

NA6

1, 0, 

2, 0,

 0

110, 0,

182, 0,

 0

.97, 0,

 .71, 0,

 0

58.4 

(.57)

Total 217.7

(.23)

1 Observer data (Obs. Data) are used to estimate by-catch rates, and the data are collected by the Northeast Fisheries

Science Center (NEFSC) Sea Sampling Program. NEFSC collects Weighout (Weighout) landings data, which are

used as a measure of total effort for the sink gillnet fishery. 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 by

the Southeast Fisheries Science Center (SEFSC).

2 The observer coverage for the sink gillnet fishery is expressed as a percentage of trips, the pelagic drift gillnet

fishery is expressed as a percentage of sets, and the Atlantic bottom trawl fishery is expressed as a percentage of

days fished.

3 White-sided dolphins taken on observed pinger trips were added directly to the estimated total by-catch for that

year. There was one observed white-sided dolphin take on a pinger trip in 1994, which was not included in the

observed mortality column above. No takes were observed on pinger trips during 1995 and 1996.

4 1994 to 1996 are shown, other years were not available on an annual basis.
112

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). In 1994 to 1996, observer coverage increased substantially, so by-catch

rates were not pooled (Bisack 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). Observer coverage is currently not available for 1996.

Other Mortality

Mass strandings involving up to a hundred or more animals at one time are common for this species. From 1968

to 1995, 349 Atlantic white-sided dolphins were known to have stranded on the New England coast (Hain and Waring

1994; Smithsonian stranding records 1996). The causes of these strandings are not known. Because such strandings

have been known since antiquity, it could be presumed that recent strandings are a normal condition (Gaskin 1992).

It is unknown whether human causes, such as fishery interactions and pollution, have increased the number of

strandings. Stranding data probably underestimate the extent of fishery-related mortality and serious injury because

not all of the marine mammals which die or are seriously injured may wash ashore, nor will all of those that do wash

ashore necessarily show signs of entanglement or other fishery-interaction. Finally, the level of technical expertise

among stranding network personnel varies widely as does the ability to recognize signs of fishery interaction.

STATUS OF STOCK

The status of white-sided dolphins, relative to OSP, in the U.S. Atlantic EEZ is unknown. The species is not listed

as threatened or endangered under the Endangered Species Act. There are insufficient data to determine 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. 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. NOAA,

NMFS, NEFSC. Woods Hole, MA. 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. 

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, N.M.F.S., Northeast Fisheries Science Center, Woods Hole, Massachusetts, 12

pp. 

Hain, J. H. W. and G. T. Waring. 1994. Statuses 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. NMFSNE-106, Northeast Fisheries Science Center, Woods Hole, Massachusetts. 
113

Katona, S. K., V. Rough, and D. T. Richardson. 1993. A field guide to whales, porpoises, and seals from Cape Cod to

Newfoundland. Smithsonian Institution Press, Washington, DC, 316 pp. 

Kenney, R.D., 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. 

Lens, S. 1997. Interactions between marine mammals and deep water trawlers in the NAFO regulatory area. ICES C.M.

8/Q. 10 pp.

Northridge, S. 1996. Estimation of cetacean mortality in the U.S. Atlantic swordfish and tuna driftnet and pair trawl

fisheries. Draft final report to the Northeast Fisheries Science Center, Contract No. 40ENNF500045, 18 pp. 

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.

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.

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 whitesided 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.
114

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. 

December 1998

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 U.S. coast (CETAP 1982; Selzer and Payne

1988; Waring et al. 1992). They are widespread from Cape Hatteras northeast to Georges Bank (35o to 42o North

latitude) in outer continental shelf waters from mid-January to May (Hain et al. 1981; CETAP 1982; Payne et al.

1984). Common dolphins move northward onto Georges Bank and the Scotian Shelf from mid-summer to autumn.

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 U.S. 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

U.S. 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
115

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 2,000 m 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 1,645 (CV=0.47) common dolphins was estimated from a June and July 1993 shipboard line

transect sighting survey conducted principally between the 200 and 2,000 m isobaths from the southern edge of

Georges Bank, across the Northeast Channel to the southeastern edge of the Scotian Shelf (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 highuse habitats off the northeastern U.S. 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
116

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. 

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 0.5 because this stock is of unknown status. PBR for the

western North Atlantic common dolphin is 161.

ANNUAL HUMAN-CAUSED MORTALITY AND SERIOUS INJURY

 Total annual estimated average fishery-related mortality to this stock during 1992-1996 was 247 common

dolphins (CV = 0.14; 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 U.S. With implementation of the Magnuson Fisheries Conservation and Management Act

(MFCMA), an observer program was established which has recorded fishery data and information of incidental bycatch of marine mammals. DWF effort in the Atlantic coast Exclusive Economic Zone (EEZ) under MFCMA has been

directed primarily towards Atlantic mackerel and squid. From 1977 through 1982, an average of 120 different foreign

vessels per year (range 102-161) operated within the Atlantic coast EEZ. In 1982, there were 112 different foreign

vessels; 16%, or 18, were Japanese tuna longline vessels operating along the U.S. 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 U.S. vessel involved in joint-venture fishing

operations in which U.S. captains transfer their catches to foreign processing vessels. The by-catch occurred during

winter/spring (December to May). 
117

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

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

Southeast Fisheries Science Center (SEFSC). The Northeast Fisheries Science Center (NEFSC) Sea Sampling

Observer Program was initiated in 1989, and since that year several fisheries have been covered by the program. In

late 1992 and in 1993, the SEFSC provided observer coverage of pelagic longline vessels fishing off the Grand Banks

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

By-catch has been observed by NMFS Sea Samplers in the pelagic drift gillnet, pelagic pair trawl, mid-Atlantic

coastal sink gillnet, North Atlantic bottom trawl, New England multispecies sink gillnet, and Atlantic squid, mackerel,

butterfish trawl fisheries, but no mortalities or serious injuries have documented in pelagic longline fishery. 

Pelagic Drift Gillnet

The estimated total number of hauls in the pelagic drift gillnet fishery increased from 714 in 1989 to 1,144 in

1990; thereafter, with the introduction of quotas, effort was severely reduced. The estimated number of hauls in 1991,

1992, 1993, 1994, 1995, and 1996 were 233, 243, 232, 197, 164, and 149 respectively. Fifty-nine different vessels

participated in this fishery at one time or another between 1989 and 1993. Since 1994, between 10-12 vessels have

participated in the fishery (Table 2). Observer coverage, expressed as percent of sets observed, was 8% in 1989, 6%

in 1990, 20% in 1991, 40% in 1992, 42% in 1993, 87% in 1994, 99% in 1995, and 64% in 1996. Effort was

concentrated along the southern edge of Georges Bank and off Cape Hatteras. Examination of the species composition

of the catch and locations of the fishery throughout the year, suggested that the pelagic drift gillnet fishery be stratified

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

1989 to 1993, were obtained using the aggregated (pooled 1989-1993) catch rates, by strata (Northridge 1996).

Estimates of total annual by-catch for 1994 and 1995 were estimated from the sum of the observed caught and the

product of the average bycatch per haul and the number of unobserved hauls as recorded in self-reported fishery

information. Variances were estimated using bootstrap re-sampling techniques. 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 fisheryrelated mortality during 1992-1996 attributable to this fishery was 164 common dolphins (CV = 0.04) (Table 2).

Injured and released alive animals are not included in the Table 2 mortality estimates. The 1992-1996 period provides

a better characterization of this fishery (i.e., fewer vessels and increased 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.

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

by-catch, 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 fisheryrelated 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). Average annual estimate fishery-related mortality

attributable to this fishery during 1992-1993 was 18.2 common dolphins (CV = 0.30) (Table 2). 

During the 1994 and 1995 experimental pelagic pair trawl fishing seasons, fishing gear experiments were

conducted to collect data on environmental parameters, gear behavior, and gear handling practices to evaluate factors
118

affecting catch and bycatch (Goudey 1995, 1996). Results of these studies have been presented at Offshore Cetacean

Take Reduction Team Meetings. 

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%, and 4% for 1990 to 1996, 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 (1992-1996) 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.

Atlantic Coastal Gillnet

Observer coverage of the U.S. 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% and 4% for 1995

and 1996 (Table 2). 

No common dolphins were taken in observed trips during 1993 and 1994. Two common dolphin were observed

taken in 1995 and 1996 (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) and 43 in 1996

(0.79). Average annual estimated fishery-related mortality attributable to this fishery during 1995-1996 was 25

common dolphins (CV = 0.68)

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. Three mortalities were observed between 1991-1995. 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),

and 142 in 1995 (0.77). Average annual estimated fishery-related mortality attributable to this fishery during 1992-

1996 was 28.4 common dolphins (CV = 0.77) (Table 2). 

Atlantic Squid, Mackerel, Butterfish Trawl

The mid-Atlantic mackerel and squid trawl fisheries were combined into the Atlantic mid-water trawl fishery in

the revised proposed list of fisheries in 1995. The fishery occurs along the U.S. 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

(Table 2). The estimate of the annual mortality is underway.

Estimated average annual mortality and serious injury during 1992-1996 for all of the NMFS-observed fisheries

is 247 common dolphins per year (CV = 0.14) (Table 2). 

CANADA

Between January 1993 and December 1994, 36 Spanish deep water trawlers, covering 74 fishing trips (4,726

fishing days and 14,211sets), were observed in NAFO Fishing Area 3 (off the Grand Bank) (Lens 1997). A total of
119

47 incidental catches were recorded, which included one common dolphin. The incidental mortality rate for common

dolphins was (0.007/set).
120

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

Estimated

6

Mortality 

Estimated

CVs 

Mean

Annual

Mortality

Pelagic Drift

Gillnet 

92-96 1994=11

1995=12

1996=103

Obs. Data 

Logbook

.40, .42, .87,

.99, .64

97, 113,

142, 82,

74

223, 227,

238, 163,

834,106

.12, .09,

.08, .02, 0,

.07

163.6

(.04)

Pelagic Pair

Trawl

92-95 12 Obs. Data

Logbook

.10, .18, .52,

.54

3, 6, 0, 3 32, 35, 0,

5.6

.48, .43, 0,

.35

18.2

(.30)

New England

Multispecies

Sink Gillnet

92-96 349 Obs. Data

Weighout,

Logbooks

 .07, .05,

.07, .05, .04

0, 0, 0, 0,

1

0, 0, 0, 0,

63

0, 0, 0, 0,

1.39

12.6

(1.39)

Mid-Atlantic

Coastal Sink

Gillnet 

95-96 NA7 Obs. Data

Weighout

 .05, .04 2, 2 7.4, 43 .69, .79 25.0

(.68)

 

Atlantic squid,

mackerel,

butterfish trawl

96 NA7 Obs. Data

Logbook

0.007 3 NA7 NA7 NA7

North Atlantic

Bottom Trawl

92-96 970 Obs. Data

Weighout

.006, .004,

.004, .0115,

NA7

0, 0, 0, 3,

0

0, 0, 0,

142, 0

0, 0, 0,

.77, 0

28.4

(.77)

TOTAL 247

(.14)

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 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.

7 Data not available.
121

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 Injured5 Uninjured

Pelagic Drift

Gillnet

 92-96 97/227, 113/238, 142/163, 82/83, 74/106 1

1

, 32, 13, 0, 341, 0, 0, 0, 0

1 Released alive and severely injured.

2 Released alive, 2 were moderately injured and 1 common dolphin was severely injured.

3 Released alive and gear was “in/around several body parts”.

4 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.

5

Injured and released alive animals are not included in the Table 2 mortality estimates.

Other Mortality

From 1992-1996, 42 common dolphins were stranded between North Carolina and Massachusetts, predominantly

along beaches in the latter state (NMFS unpublished data).

STATUS OF STOCK

The status of common dolphins, relative to OSP, in the U.S. Atlantic EEZ is unknown. The species is not listed

as threatened or endangered under the Endangered Species Act. There are insufficient data to determine the population

trends for this species. 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.

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. 

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. 

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

Gaskin, D. E. 1992. Status of common dolphin, . Delphinus delphis, in Canada. Can. Fld. Nat. 106: 55-63.

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.

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.

Hain, J. H.W., R. K. Edel, H. E. Hays, S. K. Katona, and J. D. Roanowicz. 1981. General distribution of cetaceans in the

continental shelf waters of the northeastern U.S. Pages II1-II277 in CETAP (Cetacean and Turtle Assessment
122

program), A characterization 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. 

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.). 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. 

Reilly, S. B. and J. Barlow. 1986. Rates of increase in dolphin population size. Fish. Bull., U.S. 84(3): 527-533.

Selzer, L. A. and P. M. Payne. 1988. The distribution of white-sided (Lagenorhynchus acutus) and common dolphins

(Delphinus delphis) vs. environmental features of the continental shelf of the northeastern United States. Mar.

Mamm. Sci. 4(2): 141-153.

Sergeant, D. E., A. W. Mansfield and B. Beck. 1970. Inshore records of cetacea for eastern Canada, 1949-68. J. Fish. Res.

Bd. Can. 27: 1903-1915.

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.

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.
123

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. 

December 1998

ATLANTIC SPOTTED DOLPHIN (Stenella frontalis):

Western North Atlantic Stock

STOCK DEFINITION AND GEOGRAPHIC RANGE

There are two species of spotted dolphin in the Western Atlantic — the Atlantic spotted dolphin, Stenella frontalis,

formerly S. plagiodon (Perrin et al. 1987), and the pantropical spotted dolphin, S. attenuata. These species are difficult

to differentiate at sea. 

Atlantic spotted dolphins are distributed in tropical and warm temperate waters of the western North Atlantic

(Leatherwood et al. 1976). Their distribution is from southern New England, south through the Gulf of Mexico and

the Caribbean to Venezuela (Leatherwood et al. 1976; Perrin et al. 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 U.S. 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 U.S. 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 U.S. 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.

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
124

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.

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 to this stock during 1992-1996 was 16 spotted dolphins

(Stenella sp.) (CV = 0.08; Table 2). 
125

Fishery Information

No spotted dolphin mortalities were observed in 1977-1991 foreign fishing activities. 

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

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

Southeast Fisheries Science Center (SEFSC). The Northeast Fisheries Science Center (NEFSC) Sea Sampling

Observer Program was initiated in 1989 and since that year several fisheries have been covered by the program. In

late 1992 and in 1993, the SEFSC provided observer coverage of pelagic longline vessels fishing off the Grand Banks

(Tail of the Banks) and provides observer coverage of vessels fishing south of Cape Hatteras. Total fishery-related

mortality and serious injury cannot be estimated separately for the two species of spotted dolphins in the U.S. 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. Fifty-nine different vessels

participated in this fishery at one time or another between 1989 and 1993. Since 1994, between 10-12 vessels have

participated in the fishery (Table 2). Observer coverage, expressed as percent of sets observed, was 8% in 1989, 6%

in 1990, 20% in 1991, 40% in 1992, 42% in 1993, 87% in 1994, 99% in 1995, and 64% in 1996. Effort was

concentrated along the southern edge of Georges Bank and off Cape Hatteras. Examination of the species composition

of the catch and locations of the fishery throughout the year, suggested that the pelagic drift gillnet fishery be stratified

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

1989 to 1993, were obtained using the aggregated (pooled 1989-1993) catch rates, by strata (Northridge 1996).

Estimates of total annual by-catch for 1994 and 1995 were estimated from the sum of the observed caught and the

product of the average bycatch per haul and the number of unobserved hauls as recorded in self-reported fishery

information. Variances were estimated using bootstrap re-sampling techniques. 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 1992-1996 was 11.9 (0.08) (Table 2). The

1992-1996 period provides a better characterization of the pelagic drift gillnet fishery (i.e., fewer vessels and increased

observer coverage).

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 for the pelagic longline

fishery (Atlantic, including the Caribbean), based on mandatory self-reported fishery information, was 11,279 sets in

1991, 10,605 sets in 1992, 11,538 in 1993, 11,231 sets in 1994, and 12,713 in 1995 (Cramer 1994; Scott and Brown

1997). The fishery has been observed nearly year round within every statistical reporting area within the EEZ and

beyond. Most of the estimated marine mammal by-catch was from EEZ waters between South Carolina and Cape Cod.

The 1992-1993, estimated take was based on a generalized linear model (Poisson error assumption) fit to the available

observed incidental take and self-reported incidental take and effort data for the fishery (SEFSC unpublished data).

The 1994-1995 estimates were based on the Delta-lognormal method (details in Scott and Brown 1997). Annual

estimates of mortality and serious injury were based on observed takes across the entire pelagic longline fishery
126

(including the Gulf of Mexico). All observed takes were used because the species occurs throughout the area of the

fishery, but observed takes were infrequent in any given region of the fishery. Estimated annual mortality and serious

injury attributable to this fishery (CV in parentheses) was 0 in 1992, 16 in 1993 (CV = 0.19), 0 in 1994 and 1995;

average annual mortality and serious injury attributable to this fishery in 1992-1995 was 4.0 spotted dolphins (CV

=0.19) (Table 2). Annual mortality estimates do not include any animals injured and released alive.

 The 1992-1996 total average estimated annual fishery-related mortality of spotted dolphins in the U.S. EEZ was

15.9 (CV = 0.08) (Table 2). 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.

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 

Estimate

d CVs 

Mean

Annual

Mortality

Pelagic

Drift

Gillnet

92-96 1994=113

1995=12

1996=10

Obs. Data

Logbook

.40, .42,

.87, .99,

.64

12, 0, 29,

0, 2

 204, 8.4,

29, 0, 2

.18, .40,

.01, 0, 05

11.9

(.08)

Pelagic

Longline

92-95 Obs. Data

Logbook

.05 0, 1, 0, 0, 0, 16, 0, 0 0, .19, 0,

0

4

 (.19)

TOTAL 15.9

(.08)

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

Fisheries Science Center (NEFSC) Sea Sampling Program. Mandatory logbook (Logbook) data are used to measure

total effort for the pelagic drift gillnet 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.

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

 92-95 0, 1/16, 0, 0 0, 0,11, 0 0, 0, 11, 0
127

1

1994: Trip F15- Pantropical spotted dolphin released alive, tail wrapped in dropline and all was removed; Trip F16-

Atlantic spotted dolphin, released alive, hook in corner of mouth, gangion line wrapped around mouth, line was

removed but hook remained.

2 Annual mortality estimates do not include any animals injured and released alive.

Other Mortality

From 1995-1996, six 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 U.S. Atlantic EEZ is unknown. The species is not

listed as threatened or endangered under the Endangered Species Act. There are insufficient data to determine the

population trends for this species. 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 average annual fishery-related mortality and serious injury of

spotted dolphins would exceed PBR for this stock (if it could be calculated) even if the minimum population estimate

for spotted dolphins were exclusively S. frontalis.

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.

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.
128

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. 

December 1998

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 U.S. 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 U.S. coast is unknown; however, two

abundance estimates are available for the combination of

both spotted dolphin species within portions of the

northeastern U.S. Atlantic during spring and summer of

1978-82, and July-September 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 U.S. 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, AugustSeptember 1991 and June-July 1993 sighting surveys spotted dolphin abundance was not estimated.
129

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 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.
130

ANNUAL HUMAN-CAUSED MORTALITY AND SERIOUS INJURY

 Total annual estimated average fishery-related mortality or to this stock during 1992-1996 was 16 spotted dolphins

(Stenella sp.) (CV = 0.08; Table 2). 

Fishery Information

No spotted dolphin mortalities were observed in 1977-1991 foreign fishing activities. 

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

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

Southeast Fisheries Science Center (SEFSC). The Northeast Fisheries Science Center (NEFSC) Sea Sampling Observer

Program was initiated in 1989 and since that year several fisheries have been covered by the program. In late 1992 and

in 1993, the SEFSC provided observer coverage of pelagic longline vessels fishing off the Grand Banks (Tail of the

Banks) and provides observer coverage of vessels fishing south of Cape Hatteras. Total fishery-related mortality and

serious injury cannot be estimated separately for the two species of spotted dolphins in the U.S. 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. Fifty-nine different vessels participated

in this fishery at one time or another between 1989 and 1993. Since 1994, between 10-12 vessels have participated in

the fishery (Table 2). Observer coverage, expressed as percent of sets observed, was 8% in 1989, 6% in 1990, 20% in

1991, 40% in 1992, 42% in 1993, 87% in 1994, 99% in 1995, and 64% in 1996. Effort was concentrated along the

southern edge of Georges Bank and off Cape Hatteras. Examination of the species composition of the catch and

locations of the fishery throughout the year, suggested that the pelagic drift gillnet fishery be stratified into two strata,

a southern or winter stratum, and a northern or summer stratum. Estimates of the total by-catch, from 1989 to 1993,

were obtained using the aggregated (pooled 1989-1993) catch rates, by strata (Northridge 1996). Estimates of total

annual by-catch for 1994 and 1995 were estimated from the sum of the observed caught and the product of the average

bycatch per haul and the number of unobserved hauls as recorded in self-reported fishery information. Variances were

estimated using bootstrap re-sampling techniques. 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 FebruaryApril, 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 1992-1996 was 11.9 (0.08) (Table 2). The 1992-1996 period

provides a better characterization of the pelagic drift gillnet fishery (i.e., fewer vessels and increased observer coverage).

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 for the pelagic longline

fishery (Atlantic, including the Caribbean), based on mandatory self-reported fishery information, was 11,279 sets in

1991, 10,605 sets in 1992, 11,538 in 1993, 11,231 sets in 1994, and 12,713 in 1995 (Cramer 1994; Scott and Brown

1997). The fishery has been observed nearly year round within every statistical reporting area within the EEZ and

beyond. Most of the estimated marine mammal by-catch was from EEZ waters between South Carolina and Cape Cod.

The 1992-1993, estimated take was based on a generalized linear model (Poisson error assumption) fit to the available
131

observed incidental take and self-reported incidental take and effort data for the fishery (SEFSC unpublished data). The

1994-1995 estimates were based on the Delta-lognormal method (details in Scott and Brown 1997). Annual estimates

of mortality and serious injury were based on observed takes across the entire pelagic longline fishery (including the

Gulf of Mexico). All observed takes were used because the species occurs throughout the area of the fishery, but

observed takes were infrequent in any given region of the fishery. Estimated annual mortality and serious injury

attributable to this fishery (CV in parentheses) was 0 in 1992, 16 in 1993 (CV = 0.19), 0 in 1994 and 1995; average

annual mortality and serious injury attributable to this fishery in 1992-1995 was 4.0 spotted dolphins (CV =0.19) (Table

2). Annual mortality estimates do not include any animals injured and released alive.

 The 1992-1996 total average estimated annual fishery-related mortality of spotted dolphins in the U.S. EEZ was

15.9 (CV = 0.08) (Table 2). 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.

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 

Estimate

d CVs 

Mean

Annual

Mortality

Pelagic

Drift

Gillnet

92-96 1994=113

1995=12

1996=10

Obs. Data

Logbook

.40, .42,

.87, .99,

.64

12, 0, 29,

0, 2

 204, 8.4,

29, 0, 2

.18, .40,

.01, 0, 05

 11.9

(.08)

Pelagic

Longline

92-95 Obs. Data

Logbook

.05 0, 1, 0, 0, 0, 16, 0, 0 0, .19, 0,

0

4

 (.19)

TOTAL 15.9

(.08)

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

Fisheries Science Center (NEFSC) Sea Sampling Program. Mandatory logbook (Logbook) data are used to measure

total effort for the pelagic drift gillnet 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.
132

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

 92-95 0, 1/16, 0, 0 0, 0,11, 0 0, 0, 11, 0

1

1994: Trip F15- Pantropical spotted dolphin released alive, tail wrapped in dropline and all was removed; Trip F16-

Atlantic spotted dolphin, released alive, hook in corner of mouth, gangion line wrapped around mouth, line was

removed but hook remained.

2 Annual mortality estimates do not include any animals injured and released alive.

Other Mortality

From 1995-1996, 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, five animals were

successfully lured with food back to sea (NMFS unpubl. data).

STATUS OF STOCK

The status of pantropical spotted dolphins, relative to OSP in the U.S. Atlantic EEZ is unknown. The species is

not listed as threatened or endangered under the Endangered Species Act. There are insufficient data to determine the

population trends for this species. 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 average annual fishery-related mortality and serious injury of

spotted dolphins would exceed PBR for this stock (if it could be calculated) even if the minimum population estimate

for spotted dolphins were exclusively S. attenuata.

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. 

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. 
133

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.
134

Figure 1. Distribution of striped dolphin sightings from

NEFSC shipboard and aerial surveys during the summer in

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

December 1998

STRIPED DOLPHIN (Stenella coeruleoalba):

Western North Atlantic Stock

STOCK DEFINITION AND GEOGRAPHIC RANGE

The striped dolphin, Stenella coeruleoalba, is distributed worldwide in temperate and tropical seas of the world.

Striped dolphins are found in the western North Atlantic from Nova Scotia south to at least Jamaica and in the Gulf of

Mexico. In general, striped dolphins appear to prefer continental slope waters offshore to the Gulf Stream (Leatherwood

et al. 1976; Perrin et al. 1994; Schmidly 1981). There is no information concerning striped dolphin stock structure in

the western North Atlantic. 

In waters off the northeastern U.S. coast, striped dolphins are distributed along the continental shelf edge from Cape

Hatteras to the southern margin of Georges Bank, and also occur offshore over the continental slope and rise in the midAtlantic region (CETAP 1982). Continental shelf edge sightings in this program were generally centered along the

1,000 m depth contour in all seasons (CETAP 1982). During 1990 and 1991 cetacean habitat-use surveys, striped

dolphins were associated with the Gulf Stream north wall and warm-core ring features (Waring et al. 1992). Striped

dolphins seen in a survey of the New England Sea Mounts (Palka 1997) were in waters that were between 200 to 270C

and deeper than 900 m. Sightings of striped dolphins between Cape Hatteras, NC and the Atlantic side of Florida have

not been documented in dedicated sighting surveys (Palka 1997), though there are records of strandings on beaches from

North Carolina to Florida (Smithsonian database). 

Although striped dolphins are considered to be uncommon in Canadian Atlantic waters (Baird et al. 1993), recent

summer sightings (2-125 individuals) in the deeper and warmer waters of the Gully (submarine canyon off eastern Nova

Scotia shelf) suggest that this region may be an important part of their range (Gowans and Whitehead 1995; Baird et

al. 1997). 

POPULATION SIZE

The total number of striped dolphins in the U.S.

Exclusive Economic Zone (EEZ) is unknown; however,

three abundance estimates are available for portions of

the northeastern U.S. Atlantic during spring and summer

1978-82, August to September 1991, and July to

September 1995 (Table 1; Figure 1).

A population size of 36,780 striped dolphins

(CV=0.27) was estimated from an aerial survey program

conducted from 1978 to 1982 on the continental shelf

and shelf edge waters between Cape Hatteras, North

Carolina and Nova Scotia (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 sighting

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 U.S. 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 (e.g., large CV), its old age, and it
135

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

A population size of 25,939 (CV=0.36) and 13,157 (CV=0.45) striped dolphins was estimated from line transect

aerial surveys conducted from August to September 1991 using the Twin Otter and AT-11, respectively (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 interplatform calibration analysis has not been conducted.

Due to insufficient numbers of striped dolphin sightings collected during the August 1990, June-July 1991 (Waring,

1998), and June-July 1993 shipboard sighting surveys, striped dolphin abundances for these surveys were not estimated.

A population size of 31,669 (CV=0.73) striped dolphins was estimated from a July to September 1995 sighting

survey conducted by two ships and an airplane that covered waters from Virginia to the mouth of the Gulf of St.

Lawrence (Table 1; 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.

The best available current abundance estimate for striped dolphins is 31,669 (CV=0.73) 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 western North Atlantic striped dolphins. Month, year, and area

covered during each abundance survey, and resulting abundance estimate (Nbest) and coefficient of

variation (CV).

Month/Year Area Nbest CV

spring & summer

1978-82 Cape Hatteras, NC to Nova Scotia 37,780 0.27

Aug-Sep 1991 Cape Hatteras, NC to Nova Scotia 25,939 and

13,157*

0.36 and

0.45*

Jul-Sep 1995 Virginia to Gulf of St. Lawrence 31,669 0.73

* 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 striped dolphins is 31,669 (CV=0.73). The minimum

population estimate for the western North Atlantic striped dolphin is 18,220 (CV=0.73).

Current Population Trend

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

CURRENT AND MAXIMUM NET PRODUCTIVITY RATES
136

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

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

cetacean populations may not grow at rates much greater than 4% given the constraints of their reproductive life history

(Barlow 1995). 

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 18,220 (CV=0.73). The maximum productivity rate is 0.04, the default value for cetaceans. The “recovery” factor,

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

population (OSP) is 0.5 because this stock is of unknown status. PBR for the western North Atlantic striped dolphin

is 182.

ANNUAL HUMAN-CAUSED MORTALITY AND SERIOUS INJURY

 Total annual estimated average fishery-related mortality to this stock during 1992-1996 was 10.7 striped dolphins

(CV = 0.08; Table 2). 

Fishery Information

USA

No mortalities were observed in 1977-1991 foreign fishing activities off the northeast U.S. coast. Nineteen

mortalities were documented between 1989 and 1993 (see below) in the pelagic drift gillnet fishery, and two mortalities

were documented in 1991 in the North Atlantic bottom trawl fishery.

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

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

Southeast Fisheries Science Center (SEFSC). The Northeast Fisheries Science Center (NEFSC) Sea Sampling Observer

Program was initiated in 1989 and since that year several fisheries have been covered by the program. In late 1992 and

in 1993, the SEFSC provided observer coverage of pelagic longline vessels fishing off the Grand Banks (Tail of the

Banks) and provides observer coverage of vessels fishing south of Cape Hatteras.

By-catch has been observed by NMFS Sea Samplers in the pelagic drift gillnet and North Atlantic bottom trawl

fisheries but no mortalities or serious injuries have been documented in the pelagic longline fisheries, pelagic pair trawl,

New England multispecies sink gillnet, and mid-Atlantic coastal sink gillnet fisheries.

Pelagic Drift Gillnet

The estimated total number of hauls in the pelagic drift gillnet fishery increased from 714 in 1989 to 1,144 in 1990;

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

1993, 1994, 1995, and 1996 were 233, 243, 232, 197, 164, and 149 respectively. Fifty-nine different vessels participated

in this fishery at one time or another between 1989 and 1993. Since 1994, between 10-12 vessels have participated in

the fishery (Table 2). Observer coverage, expressed as percent of sets observed, was 8% in 1989, 6% in 1990, 20% in

1991, 40% in 1992, 42% in 1993, 87% in 1994, 99% in 1995, and 64% in 1996. Effort was concentrated along the

southern edge of Georges Bank and off Cape Hatteras. Examination of the species composition of the catch and

locations of the fishery throughout the year, suggested that the pelagic drift gillnet fishery be stratified into two strata,

a southern or winter stratum, and a northern or summer stratum. Estimates of the total by-catch, from 1989 to 1993,

were obtained using the aggregated (pooled 1989-1993) catch rates, by strata (Northridge 1996). Estimates of total

annual by-catch for 1994 and 1995 were estimated from the sum of the observed caught and the product of the average

bycatch per haul and the number of unobserved hauls as recorded in self-reported Fishery information. Variances were

estimated using bootstrap re-sampling techniques. Forty striped dolphin mortalities were observed in this fishery

between 1989 and 1996 and occurred east of Cape Hatteras in January and February, and along the southern margin

of Georges Bank in summer and autumn. Estimated annual mortality and serious injury (CV in parentheses) attributable

to this fishery was 39 striped dolphins in 1989 (0.31), 57 in 1990 (0.33), 11 in 1991 (0.28), 7.7 in 1992 (0.31), 21 in

1993 (0.11), 13 in 1994 (0.06), 2 in 1995 (0), and 7 in 1996 (CV = 0.22). The 1992-1996 average annual mortality and

serious injury to striped dolphins in the pelagic drift gillnet fishery was 10.7 (0.08) (Table 2). The 1992-1996 period

provides a better characterization of this fishery (i.e., fewer vessels and increased observer coverage).
137

North Atlantic Bottom Trawl

Vessels in the North Atlantic bottom trawl fishery, a Category III fishery under the MMPA, were observed in order

to meet fishery management needs, rather than marine mammal management needs. An average of 970 vessels (full

and part time) participated annually in the fishery during 1989-1995. The fishery is active in New England waters in

all seasons. The only reported fishery-related mortalities (two) occurred in 1991. Total estimated mortality and serious

injury attributable to this fishery in 1991 was 181 (CV = 0.97); average annual mortality and serious injury during 1992-

1996 was zero (Table 2). 

 Total estimated average annual fishery-related mortality and serious injury to this stock in the Atlantic during

1992-1996 was 10.7 (CV = 0.08) (Table 2). 

CANADA

No mortalities were documented in review of Canadian gillnet and trap fisheries (Read 1994). However, in a recent

review of striped dolphins in Atlantic Canada two records of incidental mortality have been reported (Baird et al. 1997)

In the late 1960's and early 1970's two mortalities each, were reported in trawl and salmon net fisheries. 

Between January 1993 and December 1994, 36 Spanish deep water trawlers, covering 74 fishing trips (4,726 fishing

days and 14,211sets), were observed in NAFO Fishing Area 3 (off the Grand Bank) (Lens 1997). A total of 47

incidental catches were recorded, which included two striped dolphins. The incidental mortality rate for common

dolphins was (0.014/set)

Table 2. Summary of incidental mortality of striped dolphins (Stenella coeruleoalba) due to commercial fisheries

from 1990 through 1996 and calculation of the mean annual mortality rate (CV in parentheses).

Fishery Years Number

Vessel

Data

Type1

Range of

Observer

Coverage2

Observed

Mortality

Estimated

Mortality

CVs Mean

Annual

Mortalit

y

Pelagic

Drift

Gillnet

92-96 1994=123

1995=11

1996=10

Obs Data

Logbook

.40, .42,

.87, .99,

.64

0, 13, 12,

2, 7

7.74, 21,

13, 2.05,

10

.31,

.11,

.06, 0,

.22

 10.7

 (.08)

TOTAL 10.7

 (.08)

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

Fisheries Science Center (NEFSC) Sea Sampling Program. Mandatory logbook (Logbook) data are used to measure

total effort for the pelagic drift gillnet and longline fishery, and these data are collected at the Southeast Fisheries

Science Center (SEFSC).

2 Observer coverage for the pelagic drift gillnet and bottom trawl fishery are in terms of sets.

3

1994 - 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 logbook). If you assume 1 set, the point

estimate would increase by 0.01 animals.

Other Mortality

From 1995-1996, five striped dolphins were stranded between Massachusetts and Florida (NMFS unpublished data).

STATUS OF STOCK

The status of striped dolphins, relative to OSP, in the U.S. Atlantic EEZ is unknown. The species is not listed as

threatened or endangered under the Endangered Species Act. There are insufficient data to determine the population
138

trends for this species. The total fishery-related mortality and serious injury for this stock is less than 10% of the

calculated PBR, therefore can be considered to be insignificant and approaching zero mortality and serious injury rate.

Average annual fishery-related mortality and serious injury does not exceed the PBR; therefore, this is not a strategic

stock. 

REFERENCES

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

from NEFSC, Woods Hole Laboratory, Woods Hole, MA.

Baird, R.W., S. K. Hooker, H. Whitehead, and R. Etcheberry. 1997. A Review of records of striped dolphins (Stenella

coeruleoalba) from Canadian waters. IWC Doc. SC/49/SM4, 10 pp. 

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

Preparation, Background, and a Summary of the 1995 Assessments. U.S. Dep. Commer., NOAA Tech. Memo.

NMFS-OPR-6, 73 pp.

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

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

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

continental shelf. Cetacean and Turtle Assessment Program, University of Rhode Island. Final Report, Contract

AA51-C78-48, Bureau of Land Management, Washington, DC, 538 pp. 

Cramer, J. Large pelagic logbook newsletter - 1993. NOAA Tech. Mem. NMFS-SEFSC-352, 19 pp.

Gowans, S. and H. Whitehead. 1995. Distribution and habitat partitioning by small odontocetes in the Gully, a submarine

canyon on the Scotian Shelf. Can. J. Zool. 73:1599-1608.

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

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

Leatherwood, S., D. K. Caldwell and H. E. Winn. 1976. Whales, dolphins, and porpoises of the western North Atlantic.

A guide to their identification. U.S. Dept. of Commerce, NOAA Tech. Rep. NMFS Circ. 396, 176 pp. 

Lens, S. 1997. Interactions between marine mammals and deep water trawlers in the NAFO regulatory area. ICES CM

1997/Q:8. 10 pp.

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.

Palka, D.L. 1997. A review of striped dolphins (Stenella coeruleoalba) in US Atlantic waters. IWC Doc. SC/49/SM26, 13

pp.

Perrin, W. F., C. E. Wilson, and F. I. Archer II. 1994. Pages 129-159 in: S. H. Ridgway and R. Harrison (eds.), Handbook

of marine mammals, Volume 5: The first book of dolphins, Academic Press, San Diego. 

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

Commn. Special Issue 15: 133-147. 

Schmidly, D. J. 1981. Marine mammals of the southeastern United States coast and the Gulf of Mexico. Pub. No.

FWS/OBS-80/41, U.S. Fish and Wildlife Service, Office of Biological Services, Washington, DC, 163 pp. 

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

3-5, 1996, Seattle, Washington. U.S. Dep. Commer., NOAA Tech. Memo. NMFS-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 Marine Mammals Comm. CM 1992/N:12, 29 pp.
139

December 1998

SPINNER DOLPHIN (Stenella longirostris):

Western North Atlantic Stock

STOCK DEFINITION AND GEOGRAPHIC RANGE

Spinner dolphins are distributed in oceanic and coastal tropical waters (Leatherwood et al. 1976). This is presumably

an offshore, deep-water species (Schmidly 1981; Perrin and Gilpatrick 1994), and its distribution in the Atlantic is very

poorly known. In the western North Atlantic, these dolphins occur in deep water along most of the U.S. coast south to

the West Indies and Venezuela, including the Gulf of Mexico. Spinner dolphin sightings have occurred exclusively in

deeper (>2,000 m) oceanic waters (CETAP 1982; Waring et al. 1992) off the northeast U.S. coast. Stranding records

exist from North Carolina, South Carolina, and Florida in the Atlantic and in Texas and Florida in the Gulf of Mexico.

The North Carolina strandings represent the northernmost documented distribution of this species in the Atlantic. Stock

structure in the western North Atlantic is unknown. 

POPULATION SIZE

The number of spinner dolphins inhabiting the U.S. Atlantic Exclusive Economic Zone (EEZ) is unknown and

seasonal abundance estimates are not available for this species since it was rarely seen in any of the surveys. 

Minimum Population Estimate

Present data are insufficient to calculate a minimum population estimate. 

Current Population Trend

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

CURRENT AND MAXIMUM NET PRODUCTIVITY RATES

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

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

cetacean populations may not grow at rates much greater than 4% given the constraints of their reproductive life history

(Barlow et al. 1995). 

POTENTIAL BIOLOGICAL REMOVAL

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

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

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

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

population (OSP) is assumed to be 0.5 because this stock is of unknown status. PBR for the western North Atlantic

spinner dolphin is unknown because the minimum population size is unknown.

ANNUAL HUMAN-CAUSED MORTALITY AND SERIOUS INJURY

Total average annual estimated average fishery-related mortality and serious injury to this stock in the Atlantic

during 1992-1996 was 0.38 spinner dolphin (CV = 0.35).

Fishery Information

 There was no documentation of spinner dolphin mortality or serious injury in distant-water fleet (DWF) activities

off the northeast U.S. coast (Waring et al.. 1990). No takes were documented in a review of Canadian gillnet and trap

fisheries (Read 1994). 

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

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

Fisheries Science Center (SEFSC). The Northeast Fisheries Science Center (NEFSC) Sea Sampling Observer Program

was initiated in 1989 and since that year several fisheries have been covered by the program. In late 1992 and in 1993,
140

the SEFSC provided observer coverage of pelagic longline vessels fishing off the Grand Banks (Tail of the Banks) and

provides observer coverage of vessels fishing south of Cape Hatteras.

By-catch has been observed by NMFS Sea Samplers in the pelagic drift gillnet fishery, but no mortalities or serious

injuries have been documented in the pelagic longline, pelagic pair trawl, Northeast multispecies sink gillnet, midAtlantic coastal gillnet, and North Atlantic bottom trawl fisheries.

The estimated total number of hauls in the pelagic drift gillnet fishery increased from 714 in 1989 to 1,144 in 1990;

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

1993, 1994, 1995, and 1996 were 233, 243, 232, 197, 164, and 149 respectively. Fifty-nine different vessels participated

in this fishery at one time or another between 1989 and 1993. Since 1994, between 10-12 vessels have participated in

the fishery (Table 2). Observer coverage, expressed as percent of sets observed, was 8% in 1989, 6% in 1990, 20% in

1991, 40% in 1992, 42% in 1993, 87% in 1994, 99% in 1995, and 64% in 1996. Effort was concentrated along the

southern edge of Georges Bank and off Cape Hatteras. Examination of the species composition of the catch and locations

of the fishery throughout the year, suggested that the pelagic drift gillnet fishery be stratified into two strata, a southern

or winter stratum, and a northern or summer stratum. Estimates of the total by-catch, from 1989 to 1993, were obtained

using the aggregated (pooled 1989-1993) catch rates, by strata (Northridge 1996). Estimates of total annual by-catch

for 1994 and 1995 were estimated from the sum of the observed caught and the product of the average bycatch per haul

and the number of unobserved hauls as recorded in self-reported Fishery information. Variances were estimated using

bootstrap re-sampling techniques. One spinner dolphin mortality was observed between 1989 and 1993 and occurred

east of Cape Hatteras in March 1993. Estimated annual fishery-related mortality and serious injury attributable to this

fishery (CV in parentheses) was 0.7 in 1989 (1. 00), 1.7 in 1990 (1.00), 0.7 in 1991 (1.00), 1.4 in 1992 (0.31), 0.5 in

1993 (1.00), and zero from 1994-1996. Total average annual estimated average fishery-related mortality and serious

injury to this stock in the Atlantic during 1992-1996 was 0.38 spinner dolphin (CV = 0.35) (Table 1). The 1992-1996

period provides a better characterization of this fishery (i.e., fewer vessels and increased observer coverage).

Table 1. Summary of the incidental mortality of spinner dolphins (Stenella longirostris) by commercial fishery

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

data used (Data Type), the annual observer coverage (Observer Coverage), the mortalities recorded by onboard observers (Observed Mortality), the estimated annual mortality (Estimated Mortality), the estimated

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

Fishery Years Vessels 1 Data Type 2 Observer

Coverage 3 

Observed

Mortality

Estimated

Mortality 4

Estimated

CVs 4

Mean

Annual

Mortality

Pelagic

Drift

Gillnet

 92-

96

1994=12

1995=11

1996=10

Obs. Data

Logbook

.40, .42,

.87, .99,

.64

1, 0, 0, 0,

0

1.4, 0.5, 0,

0

5

, 0

 

.31, 1.0, 0,

0, 0

0.31

 (.35)

TOTAL 0.31

(.35)

1

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

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

Fisheries Science Center (NEFSC) Sea Sampling Program. Mandatory logbook (Logbook) data are used to measure

total effort, and the data are collected at the Southeast Fisheries Science Center (SEFSC).

3 The observer coverage and unit of effort for the Pelagic Drift Gillnet is a set.

4 For 1991-1993, pooled bycatch rates were used to estimate bycatch in months that had fishing effort but did not have

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

substantially, and bycatch rates were not pooled for this period. 

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

vessel fished 1.4 sets per day as estimated from the 1995 SS data, the point estimate may increase by 0.8 animals.

However, the SEFSC mandatory logbook data was taken at face value, and therefore it was assumed that 1 set was

fished within this trip, and the point estimate would then increase by 0.1 animals.
141

STATUS OF STOCK

The status of spinner dolphins relative to OSP in the U.S. Atlantic EEZ is unknown. The species is not listed as

threatened or endangered under the Endangered Species Act. There are insufficient data to determine the population

trends for this species. PBR cannot be calculated for this stock, but no fishery-related mortality and serious injury has

been observed since 1992; therefore, total fishery-related mortality and serious injury can be considered insignificant and

approaching zero mortality and serious injury rate. Population size and PBR cannot be estimated, but fishery-related

mortality is very low; therefore, this stock is not a strategic stock. 

REFERENCES

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

Preparation, Background, and a Summary of the 1995 Assessments. U.S. Dep. Commer., NOAA Tech. Memo.

NMFS-OPR-6, 73 pp.

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

continental shelf. Cetacean and Turtle Assessment Program, University of Rhode Island. Final Report, Contract

AA51-C78-48, Bureau of Land Management, Washington, DC, 538 pp. 

Leatherwood, S., D.K. Caldwell, and H.E. Winn. 1976. Whales, dolphins, and porpoises of the western North Atlantic. A

guide to their identification. U.S. Dept. of Commerce, NOAA Tech. Rep. NMFS Circ. 396, 176 pp.

Northridge, S. 1996. Estimation of cetacean mortality in the U.S. Atlantic swordfish and tuna drift gillnet and pair trawl

fisheries. Final report to the Northeast Fisheries Science Center, Contract No. 40ENNF500045, 18 pp. 

Perrin, W. F. and J. W. Gilpatrick, Jr. 1994. Spinner dolphin. Pages 99-128 in: S. H. Ridgway and R. Harrison (eds),

Handbook of marine mammals, Volume 5: The first book of dolphins. Academic Press, San Diego, 418 pp. 

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

Commn. Special Issue 15: 133-147. 

Reilly, S. B. and J. Barlow. 1986. Rates of increase in dolphin population size. Fish. Bull., U.S. 84(3): 527-533.

Schmidly, D. J. 1981. Marine mammals of the southeastern United States coast and the Gulf of Mexico. Pub. No.

FWS/OBS-80/41, U.S. Fish and Wildlife Service, Office of Biological Services, Washington, DC, 163 pp. 

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

3-5, 1996, Seattle, Washington. U.S. Dep. Commer., NOAA Tech. Memo. NMFS-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. 
142

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. 

December 1998

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 unpubl 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 U.S. Exclusive Economic Zone (EEZ) waters south of Cape Hatteras. 

POPULATION SIZE

The total number of bottlenose dolphins off the Atlantic U.S. coast is unknown; however, six abundance estimates

are available for portions of the northeastern U.S. Atlantic during fall of 1978-82, August 1990, June - July 1991, AugustSeptember 1991, June-July 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 U.S. 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
143

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 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 2,000 m 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 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 2,000 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 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 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.

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 U.S. 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 unpubl. data) because this survey is recent and provided the most complete coverage of the known habitat.
144

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 1992-1996 was 58

bottlenose dolphins (CV = 0.22). 

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 U.S. prior to 1977. A fisheries observer program which recorded fishery data and
145

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 U.S. 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 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 U.S. east coast.

Between 1983 and 1991, the number of foreign fishing vessels operating within the U.S. 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 U.S. fisheries are available from several sources. In 1986, NMFS established a

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

Fisheries Science Center (SEFSC). The Northeast Fisheries Science Center (NEFSC) Sea Sampling Observer Program

was initiated in 1989, and since that year several fisheries have been covered by the program. In late 1992 and in 1993,

the SEFSC provided observer coverage of pelagic longline vessels fishing off the Grand Banks (Tail of the Banks) and

provides observer coverage of vessels fishing south of Cape Hatteras. 

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

Although there have been no reported mortalities of this stock by the pelagic longline fishery, one bottlenose dolphin

was taken and released alive during 1993 in offshore waters outside of the U.S. EEZ (NMFS unpublished data). Vessels

in this fishery 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 for the

pelagic longline fishery (Atlantic, including the Caribbean), based on mandatory self-reported fishery information, was

11,279 sets in 1991, 10,605 sets in 1992, and 11,538 in 1993 (Cramer 1994). The fishery has been observed nearly year

round within every statistical reporting area within the EEZ and beyond.

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. Fifty-nine different vessels participated

in this fishery at one time or another between 1989 and 1993. Since 1994, between 10-12 vessels have participated in

the fishery (Table 2). Observer coverage, expressed as percent of sets observed, was 8% in 1989, 6% in 1990, 20% in

1991, 40% in 1992, 42% in 1993, 87% in 1994, 99% in 1995, and 64% in 1996. Effort was concentrated along the

southern edge of Georges Bank and off Cape Hatteras. Examination of the species composition of the catch and locations

of the fishery throughout the year, suggested that the pelagic drift gillnet fishery be stratified into two strata, a southern

or winter stratum, and a northern or summer stratum. Estimates of the total by-catch, from 1989 to 1993, were obtained

using the aggregated (pooled 1989-1993) catch rates, by strata (Northridge 1996). Estimates of total annual by-catch

for 1994 and 1995 were estimated from the sum of the observed caught and the product of the average bycatch per haul

and the number of unobserved hauls as recorded in self-reported fishery information. Variances were estimated using

bootstrap re-sampling techniques. 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), 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 1991-1996 was 13.6 bottlenose dolphins (CV=0.06) (Table

2). 
146

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 JuneNovember in 1992, from June-October in 1993 (Northridge 1996), and from mid-summer to November in 1994 and 1995.

Sea sampling began in October 1992 (Gerrior et al. 1994), and 48 sets (9% of the total) were sampled in that season, 102

hauls (17% of the total) were sampled in 1993. In 1994 and 1995, 52% (212) and 55% (238), 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). The 1992-1995 estimated mean annual bottlenose dolphin mortality attributable to this fishery is 45 (CV=0.28)

(Table 2). Annual mortality estimates do not include any animals injured and released alive. 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. 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.

Atlantic Squid, Mackerel and Butterfish Trawl

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 U.S. 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 fishery

information from the mackerel trawl fishery between 1990-1992.

 Total annual estimated average fishery-related mortality or serious injury to this stock during 1992-1996 was 58

bottlenose dolphins (CV = 0.22; Table 2). 
147

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 onboard observers (Observed Mortality), the estimated annual mortality (Estimated Mortality), the estimated

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

Fishery Years Vessels Data Type 1 Observer

Coverage 2 

Observed

Mortality

Estimated

Mortality 

Estimated

CVs 

Mean

Annual

Mortality

Pelagic Drift

Gillnet

92-96 1994=123

1995=11

1996=10

Obs. Data

Logbook

.40, .42,

.87, .99,

.64

12, 6, 12,

5, 0

 28, 22, 13,

5.04, 0

 .10, .13,

.05, 0, 0

13.6

(.06)

Pelagic Pair

Trawl

92-95512 Obs. Data

Logbook

.10, .18,

.52, .54

4, 17, 2,

9

73, 85, 4.0,

17

.49, .41,

.40, .26

44.8

(.28)

TOTAL 58.4

(0.22)

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 Annual mortality estimates do not include any animals injured and released alive.

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 Pair Trawl 92-95 4/73, 17/85, 2/4, 9/17 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
148

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. 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 is below PBR.

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 Midand 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.

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.

Kenney, R. D. 1990. Bottlenose dolphins off the northeastern United States. Pages 369-386 in: S. Leatherwood and R. R.

Reeves (eds), The bottlenose dolphin. Academic Press, San Diego, 653 pp. 

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

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

Mead, J.G. and C.W. Potter. 1995. Recognizing two populations for the bottlenose dolphin (Tursiops truncatus) off the

Atlantic coast of North America: morphologic and ecologic considerations. International Biological Research

Institute Reports 5:31-43. 

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.
149

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.

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.
150

Figure 1. Sightings of bottlenose dolphins during

aerial surveys to the 25 m isobath north of Cape

Hatteras during summer 1994, 9 km past the eastern

Gulf Stream wall south of Cape Hatteras during winter

1991, and three coastal surveys within one km of shore

from New Jersey to mid-Florida during the summer in

1994.

August 1997

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) 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;

Walker et al.. in press). 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 U.S. 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. There are currently insufficient

data to allow separation of locally resident bottlenose

dolphins (such as those from the Indian/Banana River) from

the coastal stock in the western North Atlantic.

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. A 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 disjunct

distribution of bottlenose dolphins centered on the 25 m

isobath which was observed during surveys of the region

(CETAP 1980). The lowest density of bottlenose dolphins

was observed over the continental shelf, with higher

densities along the coast and near the continental shelf

edge. The coastal stock is believed to reside south of Cape

Hatteras in the late winter (Mead 1975; Kenney 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 U.S. Atlantic coast. Figure 1 illustrates the distribution of 584 bottlenose dolphin

herd sightings during aerial surveys from shore to approximately 9 km past the Gulf Stream edge south of Cape Hatteras
151

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), and within one km of the shore from New Jersey to mid-Florida during three

coastal surveys conducted during the summer in 1994 (Blaylock 1995). 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. 

A working hypothesis for the coastal bottlenose dolphin stock structure postulates that there are local, resident stocks

in certain embayments and that transient stocks migrate seasonally into and out of these embayments (Scott et al.. 1988).

In the Indian-Banana River, 28 of 36 marked bottlenose dolphins either resided in or returned to the river system for a

period of at least ten years (Odell and Asper 1990). Eight of the marked dolphins were never positively resighted. None

of the marked dolphins were reported from outside the river system; however, search outside of the river system was

limited. If the working hypothesis is correct, exchange between resident and transient components of the coastal stock

could be sufficient to mask any genetic indicators of stock distinction, even though the stock components might be

sufficiently distinct to respond differently to population pressures. Additional, recent information, suggests that more than

one stock does exist along the mid-Atlantic coast (summarized in Hohn 1997).

POPULATION SIZE

 Mitchell (1975) estimated that the coastal bottlenose dolphin population which was exploited by a shore-based net

fishery until 1925 (Mead 1975) was at least 13,748 bottlenose dolphins in the 1800s. Recent estimates of bottlenose

dolphin abundance in the U.S. 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 1991 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 approximately 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 Januaryearly March 1995, following nearly the same design as the 1991 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.

Either of the aerial line transect surveys and the resulting abundance estimates may have included dolphins from

the offshore stock. It is not currently possible to distinguish the two bottlenose dolphin ecotypes during visual aerial

surveys and the distribution of the two ecotypes in U.S. Atlantic EEZ waters is uncertain. Additional research is needed

to interpret the significance of the line transect survey results.

 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
152

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 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. 

Minimum Population Estimate

Reasonable assurance of a minimum population estimate was not provided by line transect surveys because the

proportion of dolphins from the offshore stock which might have been observed is unknown. The minimum population

size was therefore taken as 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 U.S. 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 1991 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. PBR for

the U.S. Atlantic coastal bottlenose dolphin stock is 25 dolphins. 

ANNUAL HUMAN-CAUSED MORTALITY AND SERIOUS INJURY

From 1992-1995, one hundred and eighty-nine bottlenose dolphins stranded in waters north of Cape Hatteras

(Virginia to Massachusetts) (NMFS, unpublished data). The majority of the strandings within this northern area occurred

in Virginia (n = 116, 61%). An unknown number (analysis underway) of these animals have shown signs of

entanglement with fishing gear or interactions with fishing activities. 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). Signs of interaction with fisheries (entanglement, net marks, missing appendages) were present in 22% of the

bottlenose dolphin strandings investigated in North Carolina in 1993 (NMFS unpublished data). In 1994, 1995, and 1

January-August 31, 1996, one hundred and ninety-two, 196, and 154, respectively, strandings were reported in the NMFS

southeast region (Florida to North Carolina) (NMFS, unpublished data). In 1994, 24 (12%) showed signs of human

interaction, 14 (7% of total strandings) had evidence of entanglement with fishing gear. In 1995, 23 (12%) showed signs

of human interaction, 12 (6%) cases had evidence of entanglement with fishing gear. Southeast U.S. Marine mammal

stranding records indicated that from 1988-1995 an average of 22 bottlenose dolphins showed signs of human interaction

(net marks, entanglement, mutilations, boat strikes, gunshot wounds) annually. 
153

Gear Type Effort

Haul seines 222

Purse seines 11,962

Otter trawls, bottom 22,550

Otter trawls, midwater 70

Table I. 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). 

North Carolina stranding records show the highest incidence of fishery interactions from the SE Atlantic Region.

North Carolina data from 1993 through 1996 have been examined to better determine the annual percentages of human

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. Of the 230 bottlenose dolphin

strandings reported in North Carolina from 1993 to 1996, evidence of fisheries interactions was documented in 67 cases

(42% of those cases for which a human interaction determination could be made). In addition, other types of human

interaction (i.e.: prop cuts, gun shots, etc.) were documented in 17 instances (11% of the total number of cases in which

a determination was made) (NMFS, unpublished data).

Stranding data probably underestimate the extent of fishery-related mortality and serious injury because not all of

the dolphins which die or are seriously injured may wash ashore, nor will all of those that do wash ashore necessarily

show signs of entanglement or other fishery-interaction. In addition, the level of technical expertise among stranding

network personnel varies widely as does the ability to recognize signs of fishery interaction.

Fishery Information

Menhaden purse seiners have reported an annual incidental take of one to five bottlenose dolphins (NMFS 1991,

pp. 5-73). Observer data are not available. 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). 

Coastal gillnets operate in different seasons targeting different species in different states throughout the range of this

stock. Most nets are 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 I.

Observer coverage of the U.S. 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 observer, 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. Hence, this observer program

is not covering those components of the coastal gillnet complex

responsible for most of the interactions with coastal bottlenose

dolphins.

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 I. One bottlenose dolphin was recovered dead

from a shrimp trawl in Georgia in 1995 (Southeast U.S. Marine

Mammal Stranding Network unpublished data), but no

bottlenose dolphin mortality or serious injury has been

previously reported to NMFS. 
154

A haul seine fishery operates along northern North Carolina beaches during the spring and fall targeting mullet, spot,

sea trout, and bluefish. There has been no by-catch of marine mammals reported to NMFS. 

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. 

There are limited observer data directly linking serious injury and mortality to fisheries (e.g., in the stop net fishery

in North Carolina), but the total number of bottlenose dolphins assumed from this stock which stranded showing signs

of fishery or human-related mortality exceeded PBR in 1993 and again by mid-1997. In North Carolina alone, humanrelated mortality approached PBR in each of the intervening years. The total fishery-related mortality and serious injury

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

approaching zero mortality and serious injury rate.

The species is not listed as threatened or endangered under the Endangered Species Act, but because this stock is

listed as depleted under the MMPA it is a strategic stock. 

REFERENCES

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

Preparation, Background and a Summary of the 1995 Assessments. U.S. Dep. Commer., NOAA Tech. Memo.

NMFS-OPR-6, 73 pp.

Blaylock, R. A. 1995. A pilot study to estimate abundance of the U.S. Atlantic coastal migratory bottlenose dolphin stock.

NOAA Tech. Mem. NMFS-SEFSC-362, 9 pp.

Blaylock, R. A. and W. Hoggard. 1994. Preliminary estimates of bottlenose dolphin abundance in southern U.S. Atlantic

and Gulf of Mexico continental shelf waters. NOAA Tech. Mem. NMFS-SEFSC-356, 10 pp. 

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

biological populations. Chapman & Hall, London, 446 pp. 

CETAP (Cetacean and Turtle Assessment Program). 1982. "A Characterization of Marine Mammals and Turtles in the Midand 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. 

Duffield, D. A. 1986. Investigation of genetic variability in stocks of the bottlenose dolphin (Tursiops truncatus). Final

report to the NMFS/SEFC, 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.

Geraci, J. R. 1989. Clinical investigation of the 1987-88 mass mortality of bottlenose dolphins along the U.S. central and

south Atlantic coast. Final Report to National Marine Fisheries Service, U.S. Navy, Office of Naval Research, and

Marine Mammal Commission, 63 pp. 

Hersh, S. L. and D. A. Duffield. 1990. Distinction between northwest Atlantic offshore and coastal bottlenose dolphins based

on hemoglobin profile and morphometry. Pg. 129-139 in: S. Leatherwood and R. R. Reeves (eds), The bottlenose

dolphin. Academic Press, San Diego, 653 pp. 
155

Hohn, A.A. 1997. Design for a multiple-method approach to determine stock structure of bottlenose dolphins in the midAtlantic. 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. 

Kenney, R. D. 1990. Bottlenose dolphins off the northeastern United States. Pg. 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.

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.

Mead, J. G. 1975. Preliminary report on the former net fisheries for Tursiops truncatus in the western North Atlantic. J.

Fish. Res. Bd. Can. 32(7): 1155-1162.

Mead, J.G. and C.W. Potter. 1995. Recognizing two populations of the bottlenose dolphin (Tursiops truncatus) off the

Atlantic coast of North America: morphologic and ecologic considerations. International Biological Research

Institute Reports 5:31-43.

Mitchell, E. 1975. Porpoise, dolphin and small whale fisheries of the world. Status and problems. Int. Union Conserv.

Natur. Resour. Monogr. 3: 1-129.

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. 

Odell, D. K. and E. D. Asper. 1990. Distribution and movements of freeze-branded bottlenose dolphins in the Indian and

Banana Rivers, Florida. Pg. 515-540 in: S. Leatherwood and R. R. Reeves (eds), The bottlenose dolphin. Academic

Press, San Diego, 653 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. 

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. 

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. 

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. In press. The diets of modern and historic bottlenose dolphin populations

reflected through stable isotopes. Mar. Mamm. Sci.
156

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. 

December 1998

HARBOR PORPOISE (Phocoena phocoena):

Gulf of Maine/Bay of Fundy Stock

STOCK DEFINITION AND GEOGRAPHIC RANGE

This stock is found in U.S. 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 (OctoberDecember) 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 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). 
157

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 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 re-scaled human life table, estimated the upper bound of the annual potential growth rate to be 9.4%.

Woodley and Read (1991) used a re-scaled Himalayan tahr life table to estimate a likely annual growth rate of 4%. In

an attempt to estimate the potential population growth rate which incorporated many of the uncertainties in survivorship

and reproduction, Caswell et al. (1998) used a Monte Carlo method to calculate a probability distribution of growth rates,

which indicated that the median estimate for the potential annual rate of increase is approximately 10%. This analysis

underscored the considerable uncertainty that exists regarding the potential rate of increase in this population. For the

purposes of this assessment, the maximum net productivity rate, Rmax 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
158

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). Given the three available estimates for the potential

productivity rate, the value for Rmax is currently being re-evaluated.

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, 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 U.S. New England multispecies sink

gillnet, Mid-Atlantic coastal gillnet, and Atlantic pelagic drift gillnet fisheries, and in the Canadian Bay of Fundy sink

gillnet fishery and herring weir fishery. The average annual mortality estimate of harbor porpoises for 1992 to 1996

from the above U.S. fisheries is 1,667 (CV=0.09). 

USA

Recent data on incidental takes in U.S. fisheries are available from several sources. In 1986, NMFS established a

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

Fisheries Science Center (SEFSC). The Northeast Fisheries Science Center (NEFSC) Sea Sampling Observer Program

was initiated in 1989, and since that year several fisheries have been covered. From late 1992, the SEFSC provided

observer coverage of pelagic longline 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 U.S. 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 362 harbor porpoise mortalities related to this fishery observed between

1990 and 1996 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%, and 4% for years 1990

to 1996, 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 include 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 1990-1996 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), and 1200
159

(0.25) in 1996. Average estimated harbor porpoise mortality and serious injury in the New England multispecies sink

gillnet fishery during 1992-1996 was 1,460 (0.10).

There appeared to be no evidence of differential mortality in U.S. 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.

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 with pingers that were not in the experiment (Table 2). During 1995 to 1996, experimental fisheries were

conducted where all nets in a designated area 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 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. All takes from pingered nets were added directly to the estimated total bycatch for the rest of that year in the rest

of the fishery. 

U.S. Atlantic Coastal Gillnet

Before an observer program was in place, Polacheck et al. (1995) reported one incidental take in shad nets in the

York River, Virginia. Then in July 1993, an observer program was initiated in the U.S. 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% and 4% for

1995 and 1996 (Table 2). No harbor porpoises were taken in observed trips during 1993 and 1994. During 1995 and

1996, respectively, 6 and 19 harbor porpoises were observed taken (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. All documented bycatches during 1995 and 1996 were from January to April. 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, the estimated annual mortality (CV in parentheses) attributed to this fishery was 103

(0.57) and 311 (0.31) for 1995 and 1996, respectively. 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 harbor porpoise mortality and serious injury from the

Mid-Atlantic coastal gillnet fishery during 1995 and 1996 was 207 (CV=0.27) (Table 2). 

Pelagic Drift Gillnet

One harbor porpoise was observed taken during 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 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 (size/condition) for observers. 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
160

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, 1995, and 1996 were estimated separately for each year by summing 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 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 for 1994 to1996. Average estimated harbor

porpoise mortality and serious injury in the Atlantic pelagic drift gillnet fishery during 1992-1996 was 0.4 (CV=0.34)

(Table 2).

North Atlantic Bottom Trawl

One harbor porpoise mortality was observed in the North Atlantic bottom trawl fishery between 1989 and 1996.

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 total harbor porpoise by-catch in the Bay of Fundy sink gillnet fishery was thought to

be low, based on casual observations and discussions with fishermen. 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 estimates of 424

harbor porpoises. No measure of variability was estimated. The observer program was expanded in 1994 and the bycatch was estimated to be between 80-120 harbor porpoises 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 August 20 to September 30, 1996. Preliminary estimates

of by-catch from 1996 were in the range of 20-50 harbor porpoises.

Herring Fishing Weirs

Harbor porpoises takes have been observed in Canadian fishing weirs, though not in U.S. fishing weirs. However,

no program has been set up to observer U.S. fishing weirs. In the Bay of Fundy, weirs are presently 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). It is unknown how many herring weirs currently exist in U.S. and Canadian waters.

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). Records from more

current interactions are presently being audited and will be presented in the next report.
161

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 onboard observers (Observed Mortality), the estimated annual mortality (Estimated Mortality), the estimated

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

Fishery Years Vessels Data Type 1 Observer

Coverage 2 

Observed

Mortality

Estimated

Mortality 

Estimated

CVs 

Mean

Annual

Mortality

New England

Multispecies

Sink Gillnet

92-96 1993=349 Obs. Data

Weighout,

Trip Logbook

 .07, .05,

.07, .05,

.04

 513, 533,

993,433,

523

12003,14003,

21003,14003,

12003

 .21, .18,

.18, .27,

.25

1460

(.10)

Pelagic Drift

Gillnet

92-96 1994=114

1995=12 

1996=10 

Obs. Data

Logbook

.40, .42,

.87, .99,

.64

0, 1, 

0, 0,

0

 0.45, 1.55, 

0, 0,

0

1.00, .34,

0, 0,

0

0.4

(.34)

Mid-Atlantic

Coastal Sink

Gillnet

95-966 NA7 Obs. Data

Weighout

.05, .04 6, 19 103, 311 .57, .31 207

(0.27)

TOTAL 1667

(.09)

1

 Observer data (Obs. Data) are used to estimate by-catch rates, and are collected by the Northeast Fisheries Science

Center (NEFSC) Sea Sampling Program. NEFSC collects Weighout (Weighout) landings data. Total landings are

used as a measure of total effort for the sink gillnet fisheries. 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 estimate total effort for the pelagic drift gillnet fishery, and are

collected at the Southeast Fisheries Science Center (SEFSC).

2 The observer coverage for the sink gillnet fishery is expressed as a percentage of trips; for the pelagic drift gillnet

fishery it is expressed as a percentage of sets, the unit of effort for this fishery; and for the Mid-Atlantic coastal sink

gillnet fishery it is expressed as a percentage of fish landed, the unit of effort for this fishery.

3 Harbor porpoise taken on observed pinger trips were added directly to the estimated total by-catch for that year.

There were 10, 33, 44, 0, and 11 observed harbor porpoise takes on pinger trips from 1992 to 1996, respectively.

In addition, there were nine observed harbor porpoise takes in 1995 on trips dedicated to fish sampling versus marine

mammals (Bisack 1997a).

4

1994 to 1996 are shown, other years were 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). In 1994 to 1996, observer coverage increased substantially, and so bycatch rates were not pooled (Bisack 1997b). 

6 Only 1995 and 1996 data are reported because the observed coverages in 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 not available.

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. Although, in recent years it was believed to have nearly stopped (Polacheck 1989) until recent public media
162

reports 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 U.S. 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).

Stranding data probably underestimate the extent of fishery-related mortality and serious injury because not all of

the marine mammals which die or are seriously injured may wash ashore, nor will all of those that do wash ashore

necessarily show signs of entanglement or other fishery-interaction. Finally, the level of technical expertise among

stranding network personnel varies widely as does the ability to recognize signs of fishery interaction.

STATUS OF STOCK

The status of harbor porpoises, relative to OSP, in the U.S. Atlantic EEZ is unknown. The National Marine Fisheries

Service has proposed listing the Gulf of Maine harbor porpoise as threatened under the Endangered Species Act (NMFS

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 zero mortality and serious injury rate. This is a

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

REFERENCES

Barlow, J. and P. Boveng. 1991. Modeling age-specific mortality for marine mammal populations. Mar. Mamm. Sci. 7:50-

65. 

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. NMFSOPR-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. 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. 

Caswell, H., S. Brault, A. Read, and T. Smith. (1998). Harbor porpoise and fisheries: an uncertainty analysis of incidental

mortality. Ecological Applications, 8(4):1226-1238.

Cox, T.M., A.J. Read, S. Barco, J. Evans, D. Gannon, H.N. Koopman, W.A. McLellan, K. Murray, J. Nicolas, D.A. Pabst,

C. Potter, M. Swingle, V.G. Thayer, K.M. Touhey, and A.J. Westgate. 1998. Documenting the bycatch of harbor

porpoises, Phocoena phocoena, in coastal gill net fisheries from stranded carcasses. Fish. Bull. 96(4):727-734.

CUD [Conservation and Utilization Division]. 1994. Estimating harbor porpoise by-catch in the Gulf of Maine sink gillnet

fishery, NOAA, NMFS, NEFSC Ref. Doc. 94-24, Woods Hole, Massachusetts. 

Gaskin, D. E. 1977. Harbour porpoise, Phocoena phocoena (L.), in the western approaches to the Bay of Fundy 1969-75.

Rep. int. Whal. Comm 27: 487-492. 
163

Gaskin, D. E. 1984. The harbor porpoise Phocoena phocoena (L.): Regional populations, status, and information on direct

and indirect catches. Rep. int. Whal. Comm 34: 569-586. 

Gaskin, D. E. 1992. The status of the harbour porpoise. Can. Fld. Nat. 106: 36-54.

Gilbert, J. R. and K. M. Wynne. 1985. Harbor seal populations and fisheries interactions with marine mammals in New

England, 1984. Fourth Annual Report, Contract NA-80-FA-C-00029, Northeast Fisheries Center, Woods Hole,

MA, 15 pp. 

Gilbert, J. R. and K. M. Wynne. 1987. Harbor seal populations and fisheries interactions with marine mammals in New

England. Final Report Contract NA-EA-C-0070, Northeast Fisheries Center, Woods Hole, Massachusetts. 15 pp.

Haley, N. J. and A. J. Read. 1993. Summary of the workshop on harbor porpoise mortalities and human interaction. NOAA

Tech. Mem. NMFS-F/NER 5. 

Johnston, D.W. 1995. Spatial and temporal differences in heavy metal concentrations in the tissues of harbour porpoises

(Phocoena phocoena L.) from the western North Atlantic. M.S. Thesis, University of Guelph, Guelph, Ontario,

Canada. 152pp.

Kraus, S.D., A. Read, E. Anderson, K. Baldwin, A. Solow, T. Sprawling and J. Williamson. 1997. Acoustic alarms reduce

porpoise mortality. Nature 388: 525.

Kraus, S. D., J. H. Prescott, and G. S. Stone. 1983. Harbour porpoise, Phocoena phocoena, in the U.S. coastal waters of the

Gulf of Maine: A survey to determine seasonal distribution and abundance. Report to the Director, National Marine

Fisheries Service, Northeast Region, Woods Hole, Massachusetts, 15 pp. 

NEFSC [Northeast Fisheries Science Center]. 1992. Harbor porpoise in eastern North America: Status and research needs.

Results of a scientific workshop held May 5-8, 1992 at the Northeast Fisheries Science Center, Woods Hole, MA.

NOAA, NMFS, NEFSC Ref. Doc. 92-06, Woods Hole, Massachusetts. 

NMFS [National Marine Fisheries Service]. 1993. Proposed listing of Gulf of Maine population of harbor porpoises as

threatened under the Endangered Species Act. Federal Register 58: 3108-3120, January 07, 1993. 

Northridge, S. 1996. Estimation of cetacean mortality in the U.S. Atlantic swordfish and tuna driftnet and pair trawl

fisheries. Draft final report to the Northeast Fisheries Science Center, Contract No. 40ENNF500045, 18 pp. 

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.L., Read, A.J., Westgate, A.J. and Johnston, D.W. 1996. Summary of current knowledge of harbour porpoises in

U.S. and Canadian Atlantic waters. Rep. int. Whal. Commn 46:559-565.

Palka, D. 1995a. 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. 1995b. Influences on spatial patterns of Gulf of Maine harbor porpoises. pp. 69-75 In: A.S. Blix, L. Walløe and

Ø. Ulltang (eds.) Whales, seals, fish and man. Elsevier Science B.V. The Netherlands.

Palka, D. (editor). 1994. Results of a scientific workshop to evaluate the status of harbor porpoises (Phocoena phocoena)

in the western North Atlantic. NOAA, NMFS, NEFSC [Northeast Fisheries Science Center] Ref. Doc. 94-09, Woods

Hole, Massachusetts. 

Polacheck, T. 1989. Harbor porpoises and the gillnet fishery. Oceanus 32(1): 63-70.

Polacheck, T., F. W. Wenzel, and G. Early. 1995. pp 169-180 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. 

Read, A.J. and A.J. Westgate. 1997. Monitoring the movements of harbour porpoises (Phocoena phocoena) with satellite

telemetry. Marine Biology 130:315-22.

Read, A.J., J.R. Nicolas and J.E. Craddock. 1996. Winter capture of a harbor porpoise in a pelagic drift net off North

Carolina. Fish. Bull. US 94: 381-83.

Read, A. J. and A. A. Hohn. 1995. Life in the fast lane: The life history of harbour porpoises from the Gulf of Maine. Mar.

Mamm. Sci. 11(4)423-440.

Smith, G. J. D., A. J. Read, and D. E. Gaskin. 1983. Incidental catch of harbor porpoises, Phocoena phocoena (L.), in

herring weirs in Charlotte County, New Brunswick, Canada. Fish. Bull., U.S. 81(3): 660-2.
164

Smith, T., D. Palka, and K. Bisack. 1993. Biological significance of by-catch of harbor porpoise in the Gulf of Maine

demersal gillnet fishery. NOAA, NMFS, NEFSC [Northeast Fisheries Science Center] Ref. Doc. 93-23, Woods Hole,

Massachusetts. 

Trippel, E.A., J. Y. Wang, M. B. Strong, L. S. Carter and J. D. Conway. 1996. Incidental mortality of harbour porpoise

(Phocoena phocoena) by the gillnet fishery in the lower Bay of Fundy. Can. J. Fish. Aquat. Sci. 53:1294-1300.

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.

Wang, J.Y., D.E. Gaskin and B.N. White. 1996. Mitochondrial DNA analysis of harbour porpoise, Phocoena phocoena,

subpopulations in North American waters. Can. J. Fish. Aquat. Sci. 53: 1632-45.

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. 

Westgate, A.J., D.C.G. Muir, D.E. Gaskin, M.C.S. and Kingsley. 1997. Concentrations and accumulation patterns of

organochlorine contaminants in the blubber of harbour porpoises, Phocoena phocoena, from the coast of

Newfoundland, the Gulf of St. Lawrence and the Bay of Fundy/Gulf of Maine. Envir. Pollut 95: 105-119.

Woodley, T. H. and A. J. Read. 1991. Potential rates of increase of a harbor porpoise (Phocoena phocoena) population

subjected to incidental mortality in commercial fisheries. Can. J. Fish. Aquat. Sci. 48:2429-35. 
165

December 1998

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 U.S. 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 fivefold. Coast-wide aerial surveys along the Maine coast have been conducted in May/June during pupping in 1981, 1982,

1986, 1993, and 1997 (Table 1; Gilbert and Stein 1981; Gilbert and Wynne 1983, 1984; Kenney 1994; and Gilbert and

Guldager 1998). 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
166

Minimum Population Estimate

A minimum population estimate is 30,990 seals, based on uncorrected total counts along the Maine coast in 1997.

Current Population Trend

 The 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 recover factor (FR ) for this stock

is 1.0, the value for stocks with unknown population status, but know to be increasing. PBR for counts in U.S. waters

is 1,859.

ANNUAL HUMAN-CAUSED MORTALITY

Total annual estimated average fishery-related mortality or serious injury to this stock during 1992-1996 was 898

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 U.S. 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

aquaculture industry (i.e., salmon farming), and by deliberate shooting (NMFS unpublished data). 

Fishery Information

USA

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

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

Fisheries Science Center (SEFSC). The Northeast Fisheries Science Center (NEFSC) Sea Sampling Observer Program

was initiated in 1989, and since that year several fisheries have been covered by the program. In late 1992 and in 1993,

the SEFSC provided observer coverage of pelagic longline vessels fishing off the Grand Banks (Tail of the Banks) and

provides observer coverage of vessels fishing south of Cape Hatteras. 

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
167

and released alive, indicating they were snagged as they followed baited hooks. Infrequent reports suggest seals may rob

bait off longlines, although this loss is considered negligible (Gilbert and Wynne 1985). 

Incidental takes in lobster traps in inshore waters off Maine are reportedly rare. Captures of approximately two seal

pups per port per year were recorded by mid-coastal lobstermen off Maine (Gilbert and Wynne 1985). Seals have been

reported to rob bait from inshore lobster traps, especially in the spring, when fresh bait is used. These incidents may

involve only a few individual animals. Lobstermen claim that seals consume shedding lobsters. 

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%, and 4% for 1990 to 1996, respectively. The fishery has been

observed in the Gulf of Maine and in Southern New England. There were 224 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 1996. 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 1990-1996 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), and 911 in 1996 (0.27). The 1994 and 1995 by-catches,

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 1992-1996 was 898 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). 
168

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

92-96 349 Obs. Data

Weighout,

Logbooks

 .07, .05,

.07, .05,

.04

 24, 22,

86, 56, 36

 373, 698,

1330, 1179,

911

 .23, .19,

.25, .21,

.27

898

(.11)

TOTAL 898

(.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 and 1996, respectively, observed mortality on “marine mammal trips” was 59, 41 and 37 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”. 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).

However, the 1992-1997 harbor seal strandings data are currently under review and will be provided in the 1999 report.

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).

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 U.S. 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 humanrelated mortality and serious injury does not exceed PBR.
169

REFERENCES

Anon. 1996. Report of the Gulf of Maine Aquaculture-Pinniped Interaction Task Force. Available from NMFS, Office of

Protected Resources. Silver Springs, MD. 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, NOAANMFS 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.
170

Temte, J.L., M.A. Bigg and O. Wiig. 1991. Clines revisited: the timing of pupping in the harbour seal (Phoca vitulina). J.

Zool. Lond. 224: 617-632.

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

3-5, 1996, Seattle, Washington. U.S. Dep. Commer., NOAA Tech. Memo. NMFS-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. 
171

December 1998

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 Sabel

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).

Unk=unknown.

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

The minimum population estimate for U.S. waters, based on uncorrected total counts (see above), is 2,010 gray seals.

Current Population Trend

Gray seal abundance is likely increasing in the U.S. Atlantic Exclusive Economic Zone (EEZ), but the percent

increase is unknown. The population has been increasing for several decades in Canadian waters. 
172

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 2,010 (CV=unk). The maximum productivity rate is 0.12, the default value for pinnipeds. The recover factor (FR ) for

this stock is 1.0, the value for stocks with unknown population status, but know to be increasing. PBR for the western

North Atlantic gray seal is 121.

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 U.S. waters (Rough 1995).

 Total annual estimated average fishery-related mortality or serious injury to this stock during 1992-1996 was 41 gray

seals (CV = 0.30; Table 2). 

Fishery Information

USA

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

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

Fisheries Science Center (SEFSC). The Northeast Fisheries Science Center (NEFSC) Sea Sampling Observer Program

was initiated in 1989, and since that year several fisheries have been covered by the program. In late 1992 and in 1993,

the SEFSC provided observer coverage of pelagic longline vessels fishing off the Grand Banks (Tail of the Banks) and

provides observer coverage of vessels fishing south of Cape Hatteras. 

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%, and 4% for 1990 to 1996, respectively. The fishery has been observed

in the Gulf of Maine and in Southern New England. There were 15 gray seal mortalities observed in the New England

multispecies sink gillnet fishery between 1992 and 1996 (Table 2). Eight 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), and 49 in 1996 (0.49). The
173

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 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 1992-1996 was 41 gray seals (CV = 0.30 ). 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

92-96 349 Obs. Data

Weighout,

Logbooks

 .07, .05,

.07, .05,

.04

 0, 2, 3, 7,

3

 0, 18, 19,

117, 49

 0, 1.00,

.95, .42,

.49

41

(.30)

TOTAL 41

(.30)

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.

Other Mortality

 The 1992-1997 gray seal strandings data are currently under review and will be provided in the 1999 report.

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. 
174

 STATUS OF STOCK

The status of the gray seal population, relative to OSP, in U.S. Atlantic EEZ waters is unknown. The species is

not listed as threatened or endangered under the Endangered Species Act. Recent data indicate that this population

is increasing. In New England waters, both the number of pupping sites and pup production is increasing. The total

fishery-related mortality and serious injury for this stock is less than 10% of the calculated PBR and, therefore, can

be considered to be approaching zero mortality and serious injury rate. The estimated annual level of human-caused

mortality and serious injury in the U.S. Atlantic EEZ does not exceed PBR and 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.

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.

Bonner, W.N. 1981. Grey seal, Halichoerus grypus. In: S.H. Ridgway and R. J. Harrison, eds., Handbook of Marine

Mammals, vol. 2, pp. 111-144. London: Academic Press.

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. Ridgeway 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 (editor), 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. 
175

December 1998

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 mid-February and April for each stock. Adults then assemble north of their whelping patches to undergo the

annual molt. The migration then continues north to Arctic summer feeding grounds. In late September, after a

summer of feeding, nearly all adults and some of the immature animals migrate southward along the Labrador coast,

usually reaching the entrance to the Gulf of St. Lawrence by early winter. There they split into two groups, one moving

into the Gulf and the other remaining off the coast of Newfoundland. Following mating, the seals disperse to feed, and

in late April they again concentrate in large numbers on the ice to molt.

The extreme southern limit of the harp seal's habitat extends into the U.S. 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 on stranding data. 

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 (Table

1). 
176

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 U.S. waters. It is estimated there

are at least 4.5-4.8 million harp seals in Canada (Shelton et al.. 1996). 

Current population trend

The population appears to be increasing in U.S. waters, judging from the increased number of stranded harp seals,

but the magnitude of the suspected increase is unknown. However, most of these strandings represent juveniles and

pups, and there is no evidence of a resident stock in U.S. waters (Rubinstein 1994; Rubinstein pers. com.). 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 recover

factor (FR ) for this stock is 1.0, the value for stocks with unknown population status, but know to be increasing. PBR

for the western North Atlantic harp seal in U.S. 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.
177

 Total annual estimated average fishery-related mortality or serious injury to this stock during 1992-1996 was

329 harp seals (CV = 0.33; Table 2). 

Fishery Information

USA

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

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

Southeast Fisheries Science Center (SEFSC). The Northeast Fisheries Science Center (NEFSC) Sea Sampling

Observer Program was initiated in 1989, and since that year several fisheries have been covered by the program. In

late 1992 and in 1993, the SEFSC provided observer coverage of pelagic longline vessels fishing off the Grand Banks

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

Recent by-catch has been observed by NMFS Sea Samplers in the New England multispecies sink gillnet fisheries,

but no mortalities have been documented in the Mid-Atlantic coastal gillnet, Atlantic drift gillnet, pelagic pair trawl

or pelagic longline fisheries. 

In 1993, there were approximately 349 full and part-time vessels in the New England multispecies sink gillnet

fishery, which covered the Gulf of Maine and southern New England (Table 2). An additional 187 vessels were

reported to occasionally fish in the Gulf of Maine with gillnets for bait or personal use; however, these vessels were

not covered by the observer program (Walden 1996) and their fishing effort was not used in estimating mortality.

Observer coverage in terms of trips has been 1%, 6%, 7%, 5%, 7%, 5%, and 4% for 1990 to 1996, respectively. The

fishery has been observed in the Gulf of Maine and in Southern New England. There 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), and 89 in 1996 (0.55). 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 1992-1996 was 329 harp seals (CV = 0.33). 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 mainly in waters between Cape Ann and New Hampshire. One observed 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).
178

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

Mortality

Estimated

Mortality 

Estimated

CVs 

Mean

Annual

Mortality

New England

Multispecies

Sink Gillnet

92-96 349 Obs. Data

Weighout,

Logbooks

 .07, .05,

.07, .05,

.04

 0, 0, 33,

27, 9

 0, 0, 861,

694, 89

 0, 0, .58,

.27, .55

329

(.33)

TOTAL 329

(.33)

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

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, pers. comm.). In addition, in 1996 there was a stranding in

North Carolina. The increased number of strandings may indicate a possible shift in distribution or expansion

southward into U.S. waters; if so, fishery interactions may increase. 

STATUS OF STOCK

The status of the harp seal stock, relative to OSP, in the U.S. 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 U.S. 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.

Bonner, W. N. 1990. The natural history of seals. Fact on File, New York, 196 pp. 

Bowen, W.D. and D.E. Sergeant. 1983. Mark-recapture estimates of harp seal pup (Phoca groenlandica) production in

the northwest Atlantic. Can. J. Fish. Aquat. Sci. 40: 728-742.

Bowen, W. D. and D. E. Sergeant. 1985. A Mark-recapture estimate of 1983 Harp seal Pup Production in the Northwest

Atlantic. NAFO SCR. Doc. 85/I/1. 

CAFSAC. 1992. Update on population estimates of Harp seal in the Northwest Atlantic. Canadian Atlantic Fisheries

Scientific Advisory Committee, CAFSAC Adv. Doc. 92/8.
179

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.

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.
180

December 1998

HOODED SEAL (Cystophora cristata):

Western North Atlantic Stock

STOCK DEFINITION AND GEOGRAPHIC RANGE

The hooded seal occurs throughout much of the North Atlantic and Arctic Oceans (King 1983) preferring deeper

water and occurring farther offshore than harp seals (Lavigne and Kovacs 1988; Stenson et al.. 1996). Hooded seals

tend to wander far out of their range and have been seen as far south as Puerto Rico, with increased occurrences from

Maine to Florida. These appearances usually occur between January and May. Although it is not known which stock

these seals come from, it is known that during this time frame, the Northwest Atlantic stock of hooded seals are at their

southern most point of migration in the Gulf of St. Lawrence. The worlds' hooded seal population is divided into three

separate stocks, each identified with a specific breeding site (Lavigne and Kovacs 1988). In the northwest Atlantic,

whelping occurs in the Davis Strait, off Newfoundland and in Gulf of St. Lawrence (Stenson et al.. 1996). One stock,

which whelps off the coast of eastern Canada, is divided into two breeding herds (Front and Gulf) which breed on the

pack ice. The Front herd (largest) breeds off the coast of Newfoundland and Labrador and the Gulf herd breeds in

the Gulf of St. Lawrence. The second stock breeds in the Davis Strait, and the third stock occurs on the West Ice off

eastern Greenland.

Hooded seals are a highly migratory species. Hooded seals remain on the Newfoundland continental shelf during

winter/spring (Stenson et al.. 1996). Breeding occurs at about the same time in March for each stock. Adults from

all stocks then assemble in the Denmark Strait to molt between late June and August (King 1983; Anon 1995), and

following this, the seals disperse widely. Some move south and west around the southern tip of Greenland, and then

north along the west coast of Greenland. Others move to the east and north between Greenland and Svalbard during

late summer and early fall (Lavigne and Kovacs 1988). Little else is known about the activities of hooded seals during

the rest of the year until they assemble again in February for breeding. 

Hooded seals are rarely found in the U.S. Atlantic Exclusive Economic Zone. Small numbers of hooded seals at

the extreme southern limit of their range occur in the winter and spring seasons. The influx of harp seals and

geographic distribution in New England to mid-Atlantic waters is based on stranding data. 

POPULATION SIZE

The number of hooded seals in the western North Atlantic is unknown. Seasonal abundance estimates are

available based on a variety of analytical methods based on commercial catch data, and including aerial surveys. These

methods often include surveying the whelping concentrations and modeling the pup production. Several estimates of

pup production at the Front are available. Hooded seal pup production between 1966 and 1977 was estimated between

25,000 - 32,000 annually (Benjaminsen and Oritsland 1975; Sergeant 1976; Lett 1977; Winters and Bergflodt 1978;

Stenson et al.. 1996). Estimated pup production dropped to 26,000 hooded seal pups in 1978 (Winters and Bergflodt

1978). Pup production estimates began to increase after 1978, reaching 62,000 (95% CI. 43,700 - 89,400) by 1984

(Bowen et al.. 1987). Bowen et al.. (1987) also estimated pup production in the Davis Strait at 18,600 (95% C.I.

14,000 - 23,000). A 1985 survey at the Front (Hay et al. 1985) produced a estimate of 61,400 (95% C.I. 16,500 -

119,450). Hammill et al. (1992) estimated pup production to be 82,000 (SE=12,636) in 1990. No recent population

estimate is available, but assuming a ratio of pups to total population of 1:5, pup production in the Gulf and Front herds

would represent a total population of approximately 400,000-450,000 hooded seals (Stenson 1993). Based on the 1990

survey, Stenson et al.. (1996) suggests that pup production may have increased at about 5% per year since 1984.

However, because of exchange between the Front and the Davis Strait stocks, the possibility of a stable or slightly

declining level of pup production are also likely (Stenson 1993; Stenson et al.. 1996). It appears that the number of

hooded seals is increasing.
181

Table 1. Summary of pup production estimates for western North Atlantic hooded seals. Year and area covered

during each abundance survey, and resulting abundance estimate (Nmin) and coefficient of variation (CV).

Month/Year Area Nmin CV

1978 Front herd: Newfoundland/ Labrador 26,000 None reported

1984 Front herd: Newfoundland/Labrador 62,000 None reported

1984 Davis Strait 18,600 None reported

1985 Front herd: Newfoundland/Labrador 61,400 None reported

1990 Front herd: Newfound/Labrador 82,100 None reported

Minimum population estimate

Present data are insufficient to calculate the minimum population estimate for U.S. waters. It is estimated that

there are approximately 400,000 hooded seals (5:1 ratio of adults to pups) in Canadian waters (Stenson et al.. 1993).

Current population trend

The population appears to be increasing in U.S. Atlantic EEZ, judging from stranding records, although the actual

magnitude of this increase is unknown. The Canadian population appears to be increasing but, because different

methods have been used over time to estimate population size, the magnitude of this increase has not been quantified.

CURRENT AND MAXIMUM NET PRODUCTIVITY RATES

Current and maximum net productivity rates are unknown for this stock. The most appropriate data are based on

Canadian studies. Pup production in Canada may be increasing slowly (5% per annum), but due to the wide confidence

intervals and lack of understanding regarding stock dynamics, it is possible that pup production is stable or declining

(Stenson 1993). 

For purposes of this assessment, the maximum net productivity rate was assumed to be 0.12. This value is based

on theoretical modeling showing that pinniped populations may not grow at rates much greater than 12% given the

constraints of their reproductive life history (Barlow et al. 1995). 

POTENTIAL BIOLOGICAL REMOVAL

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

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

population size is unknown. The maximum productivity rate is 0.12, the default value for pinnipeds. The recover

factor (FR ) for this stock is 1.0, the value for stocks with unknown population status, but know to be increasing. PBR

for the western North Atlantic hooded seal in U.S. waters is unknown. Applying the formula to abundance estimates

(400,000) in Canadian waters results in a PBR= 24,000 hooded seals. 

ANNUAL HUMAN-CAUSED MORTALITY AND SERIOUS INJURY

In Atlantic Canada, hooded seals have been commercially hunted at the Front since the late 1800's. In 1974 total

allowable catch (TAC) was set at 15,000, and reduced to 12,000 in 1983 and to 2,340 in 1984 (Stenson 1993; Anon

1998). From 1991- 1992 the TAC was increased to 15,000. A TAC of 8,000 was set for 1993, and held at that level

through 1997. From 1974 through 1982, the average catch was 12,800 animals, mainly pups. Since 1983 catches

ranged from 33 in 1986 to 6,425 in 1991, with a mean catch of 1,001 between 1983 and 1995. In 1996 catches

(25,754) were more than three times the allowable quota (Anon 1998). The high catch was attributable to good ice

conditions and strong market demand. Catches in 1997 were 7,058, slightly below the TAC.

Hunting in the Gulf of St. Lawrence (below 500N) has been prohibited since 1964. No commercial hunting of

hooded seals is permitted in the Davis Strait. 
182

 Total annual estimated average fishery-related mortality or serious injury to this stock in U.S. waters during

1992-1996 was 5.6 hooded seals (CV = 0.96; Table 2). 

Fishery Information

USA

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

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

Southeast Fisheries Science Center (SEFSC). The Northeast Fisheries Science Center (NEFSC) Sea Sampling

Observer Program was initiated in 1989, and since that year several fisheries have been covered by the program. In

late 1992 and in 1993, the SEFSC provided observer coverage of pelagic longline vessels fishing off the Grand Banks

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

Recent by-catch has been observed by NMFS Sea Samplers in the New England multispecies sink gillnet fisheries,

but no mortalities have been documented in the Mid-Atlantic coastal gillnet, Atlantic drift gillnet, pelagic pair trawl

or pelagic longline fisheries. 

In 1993, there were approximately 349 full and part-time vessels in the New England multispecies sink gillnet

fishery, which covered the Gulf of Maine and southern New England (Table 2). An additional 187 vessels were

reported to occasionally fish in the Gulf of Maine with gillnets for bait or personal use; however, these vessels were

not covered by the observer program (Walden 1996) and their fishing effort was not used in estimating mortality.

Observer coverage in terms of trips has been 1%, 6%, 7%, 5%, 7%, 5%, and 4% for 1990 to 1996, respectively. The

fishery has been observed in the Gulf of Maine and in Southern New England. There was one hooded seal mortality

observed in the New England multispecies sink gillnet fishery between 1990 and 1996. Annual estimates of hooded

seal by-catch in the New England multispecies sink gillnet fishery reflect seasonal distribution of the species and of

fishing effort. Estimated annual mortalities (CV in parentheses) from this fishery during 1990-1996 was zero (1990-

1994), and 28 in 1995 (0.96), and zero in 1996. The 1995 by-catch includes five animals from the estimated number

of unknown seals (based on observed mortalities of seals that could not be identified to species). The unknown seals

were prorated, based on spatial/temporal patterns of by-catch of harbor seals, gray seals, harp seals, and hooded seals.

Average annual estimated fishery-related mortality and serious injury to this stock attributable to this fishery during

1992-1996 was 5.6 hooded seals (CV = 0.96). The stratification design used is the same as that for harbor porpoise

(Bravington and Bisack 1996). The by-catch occurred only in winter (January-May) and was in waters between Cape

Ann and New Hampshire.

CANADA

An unknown number of hooded seals have been taken in Newfoundland and Labrador groundfish gillnets (Read

1994).

There were 3,121 cod traps operating in Newfoundland and Labrador during 1979, and about 7,500 in 1980 (Read

1994). This fishery was closed at the end of 1993 due to collapse of Canadian groundfish resources. 

Hooded seals are being taken in Canadian lumpfish and groundfish gillnets and trawls; however, estimates of total

removals have not been calculated to date. 
183

 Table 2. Summary of the incidental mortality of hooded seal (Cystophora cristata) by commercial fishery

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

of data used (Data Type), the annual observer coverage (Observer Coverage), the mortalities recorded by

on-board observers (Observed Mortality), the estimated annual mortality (Estimated Mortality), the

estimated CV of the annual mortality (Estimated CVs) and the mean annual mortality (CV in

parentheses).

Fishery Years Vessels Data Type 1 Observer

Coverage 2

Observed

Mortality

Estimated

Mortality 

Estimated

CVs 

Mean

Annual

Mortality

New England

Multispecies

Sink Gillnet

92-96 349 Obs. Data

Weighout,

Logbooks

 .07, .05,

.07, .05,

.04

 0, 0, 0, 1,

0

 0, 0, 0, 28, 0 0, 0, 0,

.96, 0

5.6

(.96)

TOTAL 5.6

(.96)

1 Observer data (Obs. Data) are used to measure by-catch rates, and the data are collected within the Northeast

Fisheries Science Center (NEFSC) Sea Sampling Program. NEFSC collects Weighout (Weighout) landings data,

and total landings are used as a measure of total effort for the sink gillnet fishery. Mandatory logbook (Logbook)

data are used to determine the spatial distribution of some fishing effort in the New England multispecies sink

gillnet fishery.

 2 The observer coverage for the New England multispecies sink gillnet fishery is measured in trips.

Other Mortality

 In 1988-93, strandings were less than 20 per year, and from 1994-1996 they increased to about 50 per annum

(Rubinstein 1994; Rubinstein, pers. comm). Carcasses were recovered from Massachusetts, Connecticut, and New

York (Rubinstein 1994), North Carolina and U.S. Virgin Islands (NMFS, unpubl. data). The increased number of

strandings may indicate a possible shift in distribution or range expansion southward into U.S. waters; if so, fishery

interactions may increase. 

STATUS OF STOCK

The status of hooded seals relative to OSP in U.S. Atlantic EEZ is unknown, but the population appears to be

increasing in Canada. They are not listed as threatened or endangered under the Endangered Species Act. The total

fishery-related mortality and serious injury for this stock is believed to be very low relative to the population size in

Canadian waters and can be considered insignificant and approaching zero mortality and serious injury rate. This is

not a strategic stock because the level of human-caused mortality and serious injury is believed to be very low relative

to overall stock size.

REFERENCES

Anon. 1995. Report of the Joint ICES/NAFO Working Group on Harp and Hooded Seals. 5-9 June 1995, Dartmouth,

Nova Scotia Canada. NAFO SCS Doc. 95/16. Serial No. N2569. 40 pp.

Anon. 1998. Report of the Joint ICES/NAFO Working Group on Harp and Hooded Seals. 28 August - 3 September 1997,

Copenhagen, Denmark. ICES CM 1998/Assess:3. 35 pp.

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

Preparation, Background, and a Summary of the 1995 Assessments. U.S. Dep. Commer., NOAA Tech. Memo.

NMFS-OPR-6, 73 pp. 

Benjaminsen, T., and T. Oritsland. 1975. The survival of year-classes and estimates of production and sustainable yield

of northwest Atlantic harp seals. Int. Comm. Northwest Atl. Fish. Res. Doc. 75/121.

Bowen, W.D., R.A. Myers and K. Hay. 1987. Abundance estimation of a dispersed, dynamic population: Hooded seals

(Cystophora cristata) in the Northwest Atlantic. Can. J. Fish. Aquat. Sci. 44: 282-295.
184

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.

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.
185

INDEX

Arctic, 14, 40, 55, 160, 170, 175

Atlantic spotted dolphin, 2, 118, 119, 121-123, 127

Balaenoptera acutorostrata, 33, 37-39

Balaenoptera borealis, 30, 32

Balaenoptera musculus, 40-42

Basque whalers, 6

Bay of Fundy, 2, 5, 6, 8, 10, 11, 26, 27, 33, 34, 36, 37,

39, 44, 56, 59, 60, 62, 68, 75, 82, 87,

96, 101, 103-105, 107, 109, 111, 119,

124, 130, 138, 151-153, 155, 157-160,

162, 164, 168

Blainville’s beaked whale, 65, 71, 72

blue whale, 4, 40-42

bottlenose dolphin, 3, 137-143, 145-150

Brevortia tyrannus, 148

Canada, 8, 27, 30, 31, 36, 37, 40, 41, 48, 56, 66, 72, 79,

86, 87, 91, 96, 107, 108, 114, 116, 117,

132, 151, 155, 156, 158, 160, 162, 164,

167-172, 174-179

Canadian East Coast, v, 4, 33-35, 38

Cape Cod Bay, 5, 6, 8, 11, 22

Cape Hatteras, 8, 14, 16, 21, 25-27, 30, 31, 33-36, 43-47,

49-51, 53, 54, 56-58, 60, 61, 63, 64,

67-70, 74-77, 81-86, 92-96, 98, 100,

104, 106, 110, 111, 113, 114, 118-120,

123-125, 129-131, 135, 137-140,

145-147, 149, 153-155, 161, 167, 172,

177

Chesapeake Bay, 18, 118, 157

chlorinated hydrocarbons, 91, 149

coastal gillnet, 78, 114, 115, 120, 125, 142, 148, 153,

154, 157, 172, 177

cod traps, 8, 16, 36, 37, 87, 96, 101, 162, 168, 172, 177

common dolphin, 2, 110-114, 116

Connecticut, 148, 178

contaminants, 89, 91, 149-151, 159

Cystophora cristata, 174, 175, 178, 179

DDT, 89

Delaware, 13, 21, 38, 43, 47, 60, 66, 72, 79, 84, 90, 93,

108, 116, 143

Delphinus delphis, 110, 115-117

drift gillnet, 8, 9, 16, 17, 24, 35-38, 46-48, 50-52, 54, 56,

58, 60, 64-66, 70, 71, 73, 77, 78, 80,

84, 85, 87-89, 91, 94, 96-99, 105-108,

113, 115-117, 120-122, 125-127,

131-133, 135, 136, 140, 142, 143,

153-157, 172, 177

dwarf sperm whale, 3, 49, 51-54

ecotype, 51, 54, 137, 145

entanglement, 7-11, 15, 16, 19, 22, 27, 28, 31, 36, 38, 50,

54, 57, 85, 94, 108, 147, 148, 150, 157,

161, 163, 168

Eubalaena glacialis, 5, 11, 12

Feresa attenuata, 57, 58

fin whale, 3, 25-29, 41

foreign fishing, 14, 26, 30, 33, 44, 61, 68, 74, 76, 82, 84,

89, 93, 100, 104, 106, 110, 112, 118,

119, 123, 125, 129, 131, 138, 140

Georges Bank, 5, 8, 10, 13, 16, 21, 24, 26, 27, 30, 34-36,

43-47, 50, 59, 61-64, 67-70, 74, 75, 77,

81-83, 85, 86, 94, 95, 102-104, 106,

108, 110, 111, 113, 120, 125, 129-131,

135, 137-140, 154

Georgia, 5, 8, 28, 148

gillnet, 4, 7-9, 11, 16-20, 24, 35-39, 46-48, 50-52, 54-56,

58, 60, 64-66, 70, 71, 73, 77, 78, 80,

84, 85, 87-89, 91, 94, 96-99, 101, 102,

105-109, 113-117, 120-122, 125-128,

131-136, 140, 142, 143, 148, 150,

153-159, 161-165, 167-169, 172-174,

177-179

Globicephala macrorhynchus, 92

Globicephala melas, 81, 84, 90, 92, 93

Grampus griseus, 74, 78, 79

gray seal, 2, 164, 166-169

Great South Channel, 5, 7, 11, 19, 21, 22, 30, 85, 86, 94,

95

Greenland, 5, 13, 15, 33, 40, 46, 59, 87, 96, 100, 103,

107, 151, 160, 162, 168, 170, 175

groundfish, 8, 15, 37, 87, 96, 101, 107, 155, 161, 162,

168, 172, 177

Gulf of Maine, 2, 5, 8, 13-16, 23-30, 32-34, 39, 42, 44,

48, 55, 62, 66, 68, 72, 74, 75, 80-82,

91, 100, 102-104, 106, 108-111, 113,

114, 117, 119, 122, 124, 127, 130, 133,

138, 143, 151-154, 157-159, 161, 162,

164, 167, 169, 172, 173, 177, 179

Gulf of Mexico, 1, 5, 11, 33, 40, 48, 49, 52-54, 56-58, 61,

67, 85, 86, 92, 95, 99, 110, 118, 120,

123, 125-127, 129, 133, 134, 136, 140,

149

Gulf Stream, 29, 34, 43-45, 48, 61-63, 66-69, 73-75,

80-83, 91, 92, 104, 110, 111, 117, 118,

122, 124, 129, 130, 133, 136, 138, 139,

144-146

gunshot wounds, 147
186

Halichoerus grypus, 166, 168, 169

harbor porpoise, 2, 29, 39, 48, 66, 72, 80, 91, 109, 117,

122, 127, 133, 143, 151-159, 162, 164,

168, 169, 172, 173, 177, 179

harbor seal, 2, 158, 160-164

harp seal, 2, 170-174

haul seine, 149

health assessment, 149

herring weirs, 8, 36, 37, 155, 158, 162, 168

hooded seal, 2, 175-179

humpback whale, 3, 13, 15-17, 23, 24

Hyperoodon ampullatus, 59, 60

Indian/Banana River, 137, 145

Key West, 148

killer whale, 3, 55-58

Kogia breviceps, 51-54

Kogia simus, 49, 51, 52, 54

Lagenorhynchus acutus, 103, 107-109, 117

Long Island, 17, 48, 145, 160

longline fishery, 35, 77, 85, 86, 88, 93, 95, 97, 113, 120,

121, 125, 126, 132, 140

long-finned pilot whale, 1, 81, 84, 87, 89, 90, 92, 93, 96

mackerel, 2, 13, 22, 76, 84, 86-90, 93, 96, 97, 105, 106,

112-115, 140, 141, 161

Maine, 2, 5, 8, 13-16, 19, 20, 22-30, 32-37, 39, 42, 44,

46-48, 55, 62, 66, 68, 72, 74, 75, 80-82,

89, 91, 100, 102-106, 108-111, 113,

114, 117, 119, 122, 124, 127, 130, 133,

138, 143, 151-167, 169, 170, 172-175,

177, 179

mark-recapture, 14, 24, 170, 173

Maryland, 11, 18, 24, 147, 157

Massachusetts, 1, 5, 8, 9, 11, 13, 23, 25, 29, 39, 41, 47,

48, 55, 65, 66, 71, 73, 80, 89-91, 99,

106, 108, 109, 116, 117, 132, 133, 143,

147, 153, 154, 157-159, 162, 164-166,

169, 174, 178, 179

matrilines, 5

Megaptera novaeangliae, 13, 17, 23, 24, 41

menhaden, 148

Mesoplodon bidens, 72

Mesoplodon densirostris, 72

Mesoplodon mirus, 67

metals, 151

minke whale, 4, 33-39

mutilation, 142, 157

net entanglement, 8, 22

New England, 5, 8, 13, 25, 31, 33, 35, 37-39, 43, 46, 50,

54-56, 58, 60, 64, 67, 70, 77, 84, 86,

94, 95, 100, 105-109, 113-115, 118,

120, 125, 129, 131, 132, 141, 148,

153-170, 172-175, 177-179

New Jersey, 20, 22, 81, 92, 98, 145, 146, 148, 151, 157,

170

New York, 17, 19, 28, 38, 42, 48, 60, 66, 67, 72, 79, 90,

108, 114, 116, 122, 127, 133, 143, 148,

151, 154, 155, 157, 160, 173, 174, 178

North Carolina, 13, 14, 21, 22, 26, 30, 33, 44, 49, 51, 53,

54, 57, 61, 67, 81, 92, 98, 100, 103,

104, 110, 114, 116, 118, 122, 123, 127,

129, 134, 137, 145, 147-149, 151, 154,

157, 158, 173, 178

Orcinus orca, 55, 56

pair trawl, 8, 16, 24, 38, 39, 46, 48, 50, 52, 54, 56, 58,

60, 64, 66, 73, 77-80, 84, 85, 87, 88,

90, 91, 94, 96, 97, 99, 108, 109, 113,

115-117, 120-122, 125-127, 131, 133,

135, 136, 140-143, 157, 158, 172, 177

pantropical spotted dolphin, 2, 118, 119, 121, 123, 124,

127

PCBs, 89

Phoca groenlandica, 170, 173, 174, 179

Phoca vitulina, 160, 163-165

Phocoena phocoena, 151, 156-159

photo-identification, 6, 7, 41

Physeter macrocephalus, 23, 43, 47, 48

Plymouth, 6

polychlorinated biphenyls, 89

population growth rate, 6, 7, 152

pygmy killer whale, 3, 57, 58

pygmy sperm whale, 3, 49, 52-54

right whale, 3, 5-8, 11, 12, 30

Risso’s dolphin, 75-79

salmon gillnets, 37, 87, 96, 162, 168

Scotian Shelf, 5, 30, 34, 43-45, 48, 62, 63, 68, 69, 75, 82,

83, 104, 110, 111, 116, 133, 137-139

sei whale, 4, 30-32

ship collisions, 7

ship strikes, 7, 9, 10, 15, 22

short-finned pilot whale, 81, 84, 90, 92, 93, 98

sink gillnet, 4, 35, 37, 38, 46, 50, 54-56, 58, 60, 64, 70,

77, 84, 94, 105-108, 113-115, 120, 125,

131, 135, 140, 148, 153, 155-157,

162-164, 167-169, 172, 173, 177-179

South Carolina, 78, 86, 89, 95, 120, 125, 134, 148

sperm whale, 3, 43, 45-49, 51-54

spinner dolphin, 2, 134-136

squid, 2, 76, 84, 86-90, 93, 96, 97, 105, 106, 112-115,

140, 141

Stellwagen Bank, 13, 18, 20, 22, 30, 36, 41, 106, 162
187

Stenella attenuata, 2, 123, 127

Stenella clymene, 110

Stenella frontalis, 2, 118, 123

Stenella longirostris, 134, 135

Strait of Belle Isle, 6, 40

striped dolphin, 2, 129-131

swordfish, 24, 39, 48, 52, 66, 73, 80, 91, 99, 109, 117,

122, 127, 133, 136, 143, 158

tunas, 77, 85, 94, 113, 141

white-beaked dolphin, 2, 100-102

white-sided dolphin, 2, 102, 103, 105-109

Ziphius cavirostris, 61, 65, 66, 71