U.S. ATLANTIC MARINE MAMMAL STOCK ASSESSMENTS - 1998

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  • NOAA TECHNICAL MEMORANDUMNMFS-NEFSC-

    U.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 CommerceNational Oceanic and Atmospheric AdministrationNational Marine Fisheries ServiceNortheast Fisheries Science CenterWoods Hole, Massachusetts 02543-1026December 1998

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    TABLE OF CONTENTS

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

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

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

    TABLE 1. A SUMMARY OF ATLANTIC MARINE MAMMAL STOCK ASSESSMENTREPORTS FOR STOCKS OF MARINE MAMMALS UNDER NMFSAUTHORITY 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):

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    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

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    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

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    EXECUTIVE SUMMARY

    Under the 1994 amendments of the Marine Mammal Protection Act (MMPA), the National Marine FisheriesService (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 forthe Atlantic (includes the Gulf of Mexico) were published in July 1995 (Blaylock et al. 1995). The MMPA requiresNMFS and USFWS to review these reports annually for strategic stocks of marine mammals and at least every 3 yearsfor stocks determined to be non-strategic. The second edition of the SARs (1996 assessments) was published inOctober 1997 and contained all the previous reports, but major revisions and updating were only completed for strategicstocks (Waring et al. 1997). Updated reports were identified by a 1997 date-stamp at the top right corner at thebeginning of each report. The current report contains only assessment reports for the Atlantic stocks, and updatedreports are identified by a December 1998 date-stamp. This format was selected to facilitate availability and becausethe 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 FisheriesScience Center (SEFSC). NMFS staff presented the reports at the May 1998 meeting of the Atlantic Scientific ReviewGroup (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 inresponse to the public comments.

    Table 1 contains a summary, by species, of the information included in the stock assessments, and alsoindicates those that have been revised since the 1997 publication. A total of 27 of the 31 Atlantic stock assessmentreports were revised for 1998. Most proposed changes incorporate new information into abundance or mortalityestimates. The revised SARs include 15 of the strategic stocks and 12 of the non-strategic stocks relative to the 1996assessments. Some of the revisions clarified fisheries mortality information which resulted in changes to the statusof some stocks. Information on human interactions (fishery and ship strikes) between the North Atlantic right whaleand North Atlantic humpback whale stocks were re-reviewed and updated. The 1993 fishery induced mortality of aNorth Atlantic right whale has been reassigned from the pelagic driftnet fishery to the lobster fishery based on a re-examination of all information. Abundance estimates for humpback whales, Canadian east coast stock of Minkewhales, Western North Atlantic stocks of common dolphins, and harbor seals have been revised. The Western NorthAtlantic stock of Atlantic white-sided dolphins is now considered strategic based on incidental mortality in the NewEngland sink gillnet and North Atlantic bottom trawl fisheries. The Western North Atlantic stock of long-finned pilotwhales will remain strategic based on mortality in the Atlantic squid, mackerel, butterfish trawl fishery. TheWestern North Atlantic stock of pygmy sperm whale is no longer considered strategic. One strategic stock that wasnot updated, but extensively reviewed by the ASRG was the Western North Atlantic stock (stock complex) of coastalbottlenose dolphins. New information on observed mortality in the 1995-1996 mid-Atlantic coastal gillne