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Marine mammal and seabird bycatch in observed California commercial fisheries in 2007
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  • Description:
    Marine mammal and seabird bycatch is reported for two California commercial gillnet fisheries, based on fishery observer data collected in 2007. Estimates of bycatch in the gillnet fisheries are generated using ratio estimation methods. Observations from two California purse seine fisheries are also reported, but no protected species bycatch was observed. A deep-set longline fishery was also observed in 2007 (at 100% observer coverage), but data confidentiality regulations prevent the reporting of observer information from this fishery because only one vessel was active. In the California/Oregon large mesh drift gillnet fishery for thresher sharks and swordfish, 204 sets were observed out of an estimated 1,241 sets fished by all vessels (16.4% observer coverage). Observed bycatch totals were nine short-beaked common dolphins (Delphinus delphis), one Pacific white-sided dolphin (Lagenorhynchus obliquidens), one northern right whale dolphin (Lissodelphis borealis), eight California sea lions (Zalophus californianus), and one northern elephant seal (Mirounga angustirostris). All marine mammals were dead upon retrieval. Estimated bycatch is 54 (CV = 0.41) short-beaked common dolphins; 6 (CV = 1.00) Pacific white-sided dolphins; 6 (CV = 1.01) northern right whale dolphins; 48 (CV = 0.65) California sea lions; and 6 (CV = 0.94) northern elephant seals. In the halibut and white seabass set gillnet fishery, 248 sets were observed out of an estimated 1,387 sets fished by all vessels (17.8% observer coverage). Observed bycatch totals were 34 California sea lions, two harbor seals (Phoca vitulina), one unidentified pinniped, four Brandt's Cormorants (Phalacrocorax penicillatus), and one unidentified cormorant. All animals were dead upon retrieval. Estimated bycatch is 190 (CV = 0.68) California sea lions, 11 (CV = 0.73) harbor seals, 5 (CV = 1.20) unidentified pinnipeds, 22 (CV = 0.56) Brandt's cormorants, and 1 (CV = 1.16) unidentified cormorant. In the California squid purse seine fishery, 83 sets were observed during 32 fishing trips, with approximately 1.3% observer coverage. In the California anchovy, mackerel, sardine purse seine fishery, 142 sets were observed during 76 fishing trips, with approximately 5% observer coverage. No marine mammal or seabird mortality was observed in either fishery. Photographic evidence from the squid purse seine fishery indicates that vessels in this fishery interact with Ashy Storm Petrels (Oceanodroma homochroa), which land on deck after getting disorientated by lights used to attract squid. These storm petrels are occasionally preyed upon by Western Gulls (Larus occidentalis) after becoming disoriented. There is currently a petition before the US Fish and Wildlife Service to list the Ashy Storm Petrel as endangered under the Endangered Species Act (ESA).
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