California marine mammal-fishery interaction study, 1979-1981

Two years of data were collected on the direct interaction between marine mammals and all California commercial and recreational ocean fisheries. Both at-sea and shore interview samples were valuable, and in several fisheries, a more representative estimate of interaction was derived from interview data. Marine mammal mortality is infrequent and usually clustered, and for most fisheries, it was not possible to obtain sufficient at-sea trips to estimate mortality. Possible marine mammal mortality caused by fishing activities per year for all fisheries was about 1,900 California sea lions, 117 harbor seals, 25 elephant seals,15 harbor porpoises, 60 pilot whales, 3 gray whales, and 1 Balaenoptera sp. The fisheries most adversely affected by marine mammal depredation were the commercial salmon troll fishery, the California halibut gill net fishery, the Native American gill net fishery in the Klamath River, and the partyboat fishery near San Diego. A total of about $380,000 annual loss in fish and gear was estimated in the salmon fisheries. The gill net fisheries sustained about a $120,000 annual loss in fish and gear. Nearly all the loss in the gill net and salmon troll fisheries was by California sea lions, but only harbor seals were observed depredating the salmon gill nets in the Klamath River. Other fisheries sustaining losses were the Pacific herring, partyboat and skiff salmon fisheries, and the round haul net fisheries for anchovy and mackerel. No interaction was reported or observed in the pier, shore hook-and-line, skindiving, and bottomfish skiff recreational fisheries. In all the fisheries where depredation occurred, only a small portion of the mammals present were involved in the interaction. 1983 Contract no. 79-ABC-00149 NMFS (National Marine Fisheries Service) SWFSC (Southwest Fisheries Science Center) Library Public Domain 1930