Estimates of marine mammal, sea turtle, and seabird bycatch in the California large-mesh drift gillnet fishery: 1990-2021

Bycatch of marine mammals, sea turtles, and seabirds in the California thresher shark / swordfish drift gillnet fishery from 1990 to 2021 is estimated with random forest classification and regression trees. Tree estimates are compared with annual ratio estimates using the same observer data. Biases associated with ratio estimators (systematic under- and overestimation of bycatch) are notable when observed bycatch is rare, when each annual bycatch estimate is informed only by data from the same year, and observer coverage is low. 2022 Southwest Fisheries Science Center, Marine Mammal and Turtle Division, bycatch, marine mammal bycatch, sea turtle bycatch, seabird bycatch, California, large-mesh drift gillnet NMFS (National Marine Fisheries Service) SWFSC (Southwest Fisheries Science Center) Submitted https://doi.org/10.25923/kh19-sk22 Public Domain 2279