Using dive behavior and active acoustics to assess prey use and partitioning by fin and humpback whales near Kodiak Island,Alaska |
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| Authors: | Briana H Witteveen Alex De Robertis Lei Guo Kate M Wynne |
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| Affiliation: | 1. School of Fisheries and Ocean Sciences, Alaska Sea Grant Marine Advisory Program, University of Alaska Fairbanks, Kodiak, Alaska 99615, U.S.A;2. Resource Assessment & Conservation Engineering Division, Alaska Fisheries Science Center, National Marine Fisheries Service, NOAA, Seattle, Washington 98115, U.S.A |
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| Abstract: | Near the Kodiak Archipelago, fin (Balaenoptera physalus) and humpback (Megaptera novaeangliae) whales frequently overlap spatially and temporally. The Gulf Apex Predator‐prey study (GAP) investigated the prey use and potential prey partitioning between these sympatric species by combining concurrent analysis of vertical whale distribution with acoustic assessment of pelagic prey. Acoustic backscatter was classified as consistent with either fish or zooplankton. Whale dive depths were determined through suction cup tags. Tagged humpback whales (n = 10) were most often associated with distribution of fish, except when zooplankton density was very high. Associations between the dive depths of tagged fin whales (n = 4) and the vertical distribution of either prey type were less conclusive. However, prey assessment methods did not adequately describe the distribution of copepods, a potentially significant resource for fin whales. Mean dive parameters showed no significant difference between species when compared across all surveys. However, fin whales spent a greater proportion of dive time in the foraging phase than humpbacks, suggesting a possible difference in foraging efficiency between the two. These results suggest that humpback and fin whales may target different prey, with the greatest potential for diet overlap occurring when the density of zooplankton is very high. |
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| Keywords: | pelagic backscatter
Balaenoptera physalus
Megaptera novaeangliae
suction‐cup tag multi‐frequency differencing prey partitioning humpback whale fin whale Gulf of Alaska |
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