Gulf of Alaska | Mammals
Diverse diet of resident killer whales in southern Alaska revealed by two distinct sampling methods Presenter: Dan Olsen , waterdogdan@gmail.com, North Gulf Oceanic Society Amy Van Cise , avancise@gmail.com, University of Washington Kim Parsons , Kim.Parsons@noaa.gov, Northwest Fisheries Science Center, NOAA Craig Matkin , comatkin@gmail.com, North Gulf Oceanic Society Brianna Wright , brianna.wright@dfo-mpo.gc.ca, Department of Fisheries Oceans Canada The assessment of diet for resident (salmon specialist) killer whales is important in understanding predator impact throughout the ecosystem. Diet composition in other studies across the North Pacific appears to vary, but include Chinook, chum, coho, and sockeye salmon. We collected and analyzed 257 samples of fish scales or flesh from feeding events during 1991-2021, and 86 fecal samples during 2016-2021 from Southern Alaska resident killer whales. Between both data sets, samples primarily contained chum, Chinook, and coho salmon, as well as Pacific Halibut, Arrowtooth Flounder, and Sablefish. In early season Prince William Sound, both datasets were dominated by chum salmon (66.67% for scales/flesh, n= 30, 72.30% for fecal, n=12). In early season Kenai Fjords, both datasets were dominated by Chinook salmon (80.6% for scale/flesh, n=139; 70.11% for fecal, n=70). In late season, Coho dominated the scale/flesh dataset (69.05%, n=84). The late season fecal dataset had insufficient samples for significant results, but no single species appeared dominant. Fecal sample proportional composition varied significantly between the two regions in the study (PERMANOVA R2 = 0.17, p-value = 0.001), as well as between early and late seasons (PERMANOVA R2 = 0.06, p-value = 0.01). Within PWS, fecal sample proportional composition varied significantly between early and late seasons (PERMANOVA R2 = 0.25, p-value = 0.02). These results show that the diet composition is more diverse than previously thought, and is dominated by different salmon species depending on season and region. Winter and offseason sampling will be critical for accurate ecosystem modeling, as it is likely that distinct feeding events are currently missed in season or locations that are difficult to survey.
Alaska Marine Science Symposium 2023 26
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