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Marine mammal bycatch and estimated mortality in California commercial fisheries during 2005
  • Published Date:
    2006
Filetype[PDF - 713.44 KB]


Details:
  • Corporate Authors:
    Southwest Fisheries Science Center (U.S.)
  • Series:
    Administrative report LJ ; 06-07
  • Document Type:
  • Description:
    Marine mammal bycatch in 2005 is reviewed for five commercial fisheries that operate in California waters. The fisheries are the 1) swordfish and thresher shark drift gillnet fishery; 2) market squid purse seine fishery; 3) sardine purse seine fishery; 4) anchovy, mackerel and tuna purse seine fishery; and 5) halibut and angel shark set gillnet fishery. Observer coverage was 21% in the drift gillnet fishery and less than 2% in purse seine fisheries. The set gillnet fishery has not been observed since 1994 in southern California, but fisher self-reports indicate mortalities still occur. Mortality estimates do not include 2005 stranding data where a fishery interaction was implicated as the cause of death, as these data are currently unavailable. Observed mortalities in 225 observed drift gillnet fishery sets totaled 12 short-beaked common dolphin (Delphinus delphis), three long-beaked common dolphin (D. capensis), one California sea lion (Zalophus californianus) and one northern elephant seal (Mirounga angustirostris). Additionally, one gray whale (Eschrichtius robustus) was released injured. Estimated drift gillnet mortality is 57 (CV = 0.30) short-beaked common dolphin; 14 (CV = 0.57) long-beaked common dolphin; 5 California sea lions (CV = 0.97); and 5 northern elephant seals (CV = 1.00). Observed mortalities in 29 market squid purse seine trips totaled one short-beaked common dolphin and estimated mortality is 87 animals (CV = 0.98). Additionally, 43 California sea lions and three harbor seals were released alive. No mortalities were observed in the other purse seine fisheries, but 19 California sea lions, one harbor seal, and one sea otter (Enhydra lutris) were released alive in 42 observed trips. Fisher self-reports of mortalities in the set gillnet fishery totaled three California sea lions and one harbor seal. Self-reports represent minimum numbers of animals killed, as they are generally underreported by fishermen. Due to a lack of recent observer coverage, total mortality cannot be estimated for this fishery. Previously estimated levels of mortality in this fishery averaged over 1,000 sea lions, 500 harbor seals, and 30 harbor porpoise annually during 1990- 94, based on 2,000 to 7,000 days of fishing effort and 5-15% observer coverage.

  • Supporting Files:
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