Deterring Harbor seal predation on chum salmon at Whatcom Creek
Salmon runs in Washington have declined statewide, with several species such as coho, Chinook, and sockeye listed as threatened under the Endangered Species Act. Predation by pinnipeds on out-migrating juvenile salmon and returning adult salmon, especially at bottlenecks (e.g. dams and fish ladders), represents a significant obstacle in salmon recovery efforts. Some studies suggest harbor seals may consume nearly 6% of their body weight (4-5 kg) in fish each day, with some variability around seal size and season (Aarts et al., 2019). Per capita fish consumption for harbor seals has been estimated at 2.1 kg/day/seal (Howard et al., 2013). In the San Juan Islands, harbor seal diets switch from a primarily non-salmonid diet in the winter and spring to greater than 50% adult salmonid in the summer and fall, coinciding with
increases in salmonid abundance during seasonal runs (Lance et al., 2012).
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