Estimates of marine mammal, turtle, and seabird mortality for two California gillnet fisheries: 1990-1995

lncidental kills of marine mammals, turtles, and seabirds are estimated for the California drift gillnet fishery for broadbill swordfish, Xiphias gladius, common thresher shark, Alopias vulpinus, and shortfin mako shark, Isurus oxyrinchus, and the set gillnet fishery for California halibut, Paralichthys californicus, and Pacific angel shark, Squatina californica. for the period July 1990 through December 1995. Estimates were based on observations made by National Marine Fisheries Service observers placed aboard commercial fishing vessels. Yearly observer coverage varied between 4% and 18% of estimated total effort. 'Ibtal fishing effort-days per California Department of Fish and Game fishing block was used as the measure of effort for the drift and set gillnet fisheries. Incidental kill was estimated from observed data and estimates of total effort by using mean-per-unit and ratio estimators. Additional bycatch data collected by NMFS observers were used to derive kill estimates of marine turtles and seabirds.