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Evidence of two subaggregations of humpback whales on the Kodiak, Alaska, feeding ground revealed from stable isotope analysis
Author(s) -
Wright Dana L.,
Witteveen Briana,
Wynne Kate,
HorstmannDehn Larissa
Publication year - 2015
Publication title -
marine mammal science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.723
H-Index - 78
eISSN - 1748-7692
pISSN - 0824-0469
DOI - 10.1111/mms.12227
Subject(s) - humpback whale , foraging , fishery , predation , forage fish , trophic level , whale , whaling , population , capelin , zooplankton , biology , isotope analysis , food web , cetacea , geography , ecology , demography , sociology
Knowledge of humpback whale ( Megaptera novaeangliae ) foraging on feeding grounds is becoming increasingly important as the growing North Pacific population recovers from commercial whaling and consumes more prey, including economically important fishes. We explored spatial and temporal (interannual, within‐season) variability in summer foraging by humpback whales along the eastern side of the Kodiak Archipelago as described by stable carbon (δ 13 C) and nitrogen (δ 15 N) isotope ratios of humpback whale skin ( n = 118; 2004–2013). The trophic level ( TL ) of individual whales was calculated using basal food web δ 15 N values collected within the study area. We found evidence for the existence of two subaggregations of humpback whales (“North,” “South”) on the feeding ground that fed at different TL s throughout the study period. Linear mixed models suggest that within an average year, Kodiak humpback whales forage at a consistent TL during the feeding season. TL estimates support mixed consumption of fish and zooplankton species in the “North” (mean ± SE ; 3.3 ± 0.1) and predominant foraging on zooplankton in the “South” (3.0 ± 0.1). This trend appears to reflect spatial differences in prey availability, and thus, our results suggest North Pacific humpback whales may segregate on feeding aggregations and target discrete prey species.