AN OCEAN-BASIN-WIDE MARK-RECAPTURE STUDY OF THE NORTH ATLANTIC HUMPBACK WHALE (MEGAPTERA NOVAEANGLIAE)

Although much is known about the humpback whale, Megaptera novaeangliae, regional studies have been unable to answer several questions that are central to the conservation and management of this endangered species. To resolve uncertainties about population size, as well as the spatial and genetic structure of the humpback whale population in the North Atlantic, we conducted a two-year ocean-basin-wide photographic and biopsy study in 1992-1993. Photographic and skin-biopsy sampling was conducted of animals in feeding and breeding areas throughout most of the range of this species in the North Atlantic, from the West Indies breeding grounds through all known feeding areas as far north as arctic Norway. A standardized sampling protocol was designed to maximize sample sizes while attempting to ensure equal probability of sampling, so that estimates of abundance would be as accurate and as precise as possible. During 666 d at sea aboard 28 vessels, 4,207 tail fluke photographs and 2,326 skin biopsies were collected. Molecular analyses of all biopsies included determination of sex, genotype using six microsatellite loci, and mitochondrial control region sequence. The photographs and microsatellite loci were used to identify 2,998 and 2,015 individual whales, respectively. Previously published results from this study have addressed spatial distribution, migration, and genetic relationships. Here, we present new estimates of total abundance in this ocean using photographic data, as well as overall and sex-specific estimates using biopsy data. We identify several potential sampling biases using only breeding-area samples and report a consistent mark-recapture estimate of oceanwide abundance derived from photographic identification, using both breeding and feeding-area data, of 10,600 (95% confidence interval 9,300-12,100). We also report a comparable, but less precise, biopsy-based estimate of 10,400 (95% confidence interval of 8,000-13,600). These estimates are significantly larger and more precise than estimates made for the 1980s, potentially reflecting population growth. In contrast, significantly lower and less consistent estimates were obtained using between-feeding-area or between-breeding-area sampling. Reasons for the lower estimates using the results of sampling in the same areas in subsequent years are discussed. Overall, the results of this ocean-basin-wide study demonstrate that an oceanwide approach to population assessment of baleen whales is practicable and results in a more comprehensive understanding of population abundance and biology than can be gained from smaller-scale efforts.

[1]  H. E. Winn,et al.  The song of the humpback whale Megaptera novaeangliae in the West Indies , 1978 .

[2]  M. Bérubé,et al.  Identification of sex in Cetaceans by multiplexing with three ZFX and ZFY specific primers , 1996 .

[3]  P. Palsbøll,et al.  Determination of gender in cetaceans by the polymerase chain reaction , 1992 .

[4]  R. Bowman,et al.  Occurrence, population composition, and habitat use of humpback whales in Samana Bay, Dominican Republic , 1994 .

[5]  Peter L. Tyack,et al.  MALE COMPETITION IN LARGE GROUPS OF WINTERING HUMPBACK WHALES , 1983 .

[6]  H. Whitehead,et al.  Distribution and movements of West Indian humpback whales in winter , 1982 .

[7]  K. Mullis,et al.  Primer-directed enzymatic amplification of DNA with a thermostable DNA polymerase. , 1988, Science.

[8]  W. M. Swingle,et al.  APPEARANCE OF JUVENILE HUMPBACK WHALES FEEDING IN THE NEARSHORE WATERS OF VIRGINIA , 1993 .

[9]  R. Hudson,et al.  Genetic tagging of humpback whales , 1997, Nature.

[10]  J. Barlow,et al.  A NEW BIRTH-INTERVAL APPROACH TO ESTIMATING DEMOGRAPHIC PARAMETERS OF HUMPBACK WHALES , 1997 .

[11]  N. Øien,et al.  Populations genetic analysis of nuclear and mitochondrial loci in skin biopsies collected from central and northeastern North Atlantic humpback whales (Megaptera novaeangliae): population identity and migratory destinations , 1996, Proceedings of the Royal Society of London. Series B: Biological Sciences.

[12]  M. Bérubé,et al.  SEX RATIO OF THE GULF OF MAINE HUMPBACK WHALE POPULATION , 1995 .

[13]  S. Katona,et al.  Population composition of humpback whales, Megaptera novaeangliae, on Silver Bank, 1984 , 1989 .

[14]  P. Arctander,et al.  Distribution of mtDNA haplotypes in North-Atlantic humpback whales: The influence of behavior on population structure , 1995 .

[15]  K. Balcomb,et al.  Abundance and Distribution of Humpback Whales (Megaptera novaeangliae) in West Greenland Waters , 1984 .

[16]  M. Bérubé,et al.  Identification of sex in cetaceans by multiplexing with three ZFX and ZFY specific primers. , 1996, Molecular ecology.

[17]  E. J. Wick,et al.  Population Status of the Razorback Sucker in the Middle Green River (U.S.A.) , 1996 .

[18]  N. Øien,et al.  MIGRATION OF A HUMPBACK WHALE (MEGAPTERA NOVAEANGLIAE) BETWEEN NORWAY AND THE WEST INDIES , 1998 .

[19]  H. E. Winn,et al.  Population Estimate of the Humpback Whale (Megaptera novaeangliae) in the West Indies by Visual and Acoustic Techniques , 1975 .

[20]  P. Clapham,et al.  Humpback whales, Megaptera novaeangliae, and other cetaceans on Virgin Bank and in the northern Leeward Islands, 1985 and 1986 , 1989 .

[21]  Phillip J. Clapham,et al.  Seasonal occurrence and annual return of humpback whales, Megaptera novaeangliae, in the southern Gulf of Maine , 1993 .

[22]  F. Wenzel,et al.  Cetaceans of the Cape Verde archipelago , 1996 .

[23]  Hal Whitehead,et al.  Identification of Humpback Whales by Fluke Photographs , 1979 .

[24]  P. Palsbøll,et al.  Composition and Dynamics of Humpback Whale Competitive Groups in the West Indies , 1992 .

[25]  P. Corkeron,et al.  Evidence for a sex-segregated migration in the humpback whale (Megaptera novaeangliae) , 1995, Proceedings of the Royal Society of London. Series B: Biological Sciences.

[26]  I. Christensen,et al.  Seasonal distribution, exploitation and present abundance of stocks of large baleen whales (Mysticeti) and sperm whales (Physeter macrocephalus) in Norwegian and adjacent waters , 1992 .