Population spatial structuring on the feeding grounds in North Atlantic humpback whales (Megaptera novaeangliae) |
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Authors: | P T Stevick J Allen P J Clapham S K Katona F Larsen J Lien D K Mattila P J Palsbøll R Sears J Sigurjónsson T D Smith G Vikingsson N Øien & P S Hammond |
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Institution: | Sea Mammal Research Unit, University of St Andrews, Fife, UK; Hebridean Whale and Dolphin Trust, Tobermory, Isle of Mull, UK; College of the Atlantic, Bar Harbor, ME, USA; Alaska Fisheries Science Center, National Marine Mammal Laboratory, Seattle, WA, USA; Greenland Institute for Natural Resources, Nuuk, Greenland; Biopsychology Programme and Ocean Sciences Centre, Memorial University of Newfoundland, St Johns, NF, Canada; Center for Coastal Studies, Provincetown, MA, USA; Department of Population Biology, University of Copenhagen, Copenhagen Ø, Denmark; Mingan Island Cetacean Study, Saint-Lambert, QC, Canada; Marine Research Institute, Skulagata, Reykjavik, Iceland; Northeast Fisheries Science Center, Woods Hole, MA, USA; Institute of Marine Research, Nordnes, Bergen, Norway |
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Abstract: | Population spatial structuring among North Atlantic humpback whales Megaptera novaeangliae on the summer feeding grounds was investigated using movement patterns of identified individuals. We analysed the results from an intensive 2-year ocean-basin-scale investigation resulting in 1658 individuals identified by natural markings and 751 individuals by genetic markers supplemented with data from a long-term collaborative study with 3063 individuals identified by natural markings. Re-sighting distances ranged from <1 km to >2200 km. The frequencies ( F ) of re-sighting distances ( D ) observed in consecutive years were best modelled by an inverse allometric function ( F =6631 D −1.24, r 2=0.984), reflecting high levels of site fidelity (median re-sighting distance <40 km) with occasional long-distance movement (5% of re-sightings >550 km). The distribution of re-sighting distances differed east and west of 45°W, with more long-distance movement in the east. This difference is consistent with regional patterns of prey distribution and predictability. Four feeding aggregations were identified: the Gulf of Maine, eastern Canada, West Greenland and the eastern North Atlantic. There was an exchange rate of 0.98% between the western feeding aggregations. The prevalence of long-distance movement in the east made delineation of possible additional feeding aggregations less clear. Limited exchange between sites separated by as little as tens of kilometres produced lower-level structuring within all feeding aggregations. Regional and temporal differences in movement patterns reflected similar foraging responses to varying patterns of prey availability and predictability. A negative relationship was shown between relative abundance of herring and sand lance in the Gulf of Maine and humpback whale movement from the Gulf of Maine to eastern Canada. |
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Keywords: | site fidelity movement foraging |
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