Mortality of Chionoecetes crabs incidentally caught in Alaska's weathervane scallop fishery

Mortality of Chionoecetes crabs incidentally caught in Alaska's weathervane scallop fishery

G.E. Rosenkranz

Mortality of Chionoecetes crabs incidentally caught in Alaska's weathervane scallop fisheryThis is part of Crabs in Cold Water Regions: Biology, Management, and Economics
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Description

Catcher-processor vessels fishing for weathervane scallops (Patinopecten caurinus) off Alaska have been required to carry onboard observers on all trips since 1993. Besides collecting biological data on scallops, these observers examined over 100,000 Tanner crabs (Chionoecetes bairdi) and snow crabs (C. opilio) incidentally caught by dredges in the Bering Sea scallop fishery and classified each as dead or alive. I used graphical methods and generalized linear modeling (GLM) to explore relationships between mortality rates (proportion classified dead) and variables such as species, sex, shell condition, and injuries. Mortality rates were high for crabs with injury to the carapace and there was a strong positive relationship between mortality rate and number of new injuries. Mortality rates were consistently higher for snow crabs than for Tanner crabs, and mortality rates tended to decline with shell size for new-shell crabs of both species. Due in part to large sample sizes, all variables analyzed except weight of the scallop catch were significant in the GLM. Between-year and between-vessel differences in mortality rates were also important to GLM fit. Overall, 24% of the crabs inspected by observers were recorded as dead.

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