Relative selectivity of four sampling methods using traps and trawls for male snow crabs (Chionoecetes opilio)

Catch rate and catch composition of male snow crabs were compared for four sampling methods. These methods were: (1) large-meshed commercial traps, (2) small-meshed traps, (3) bottom trawl deployed during the day. and (4) bottom trawl deployed at night. Catches were characterized in terms of crab body sizes, shell conditions, and claw allometry. We concluded that: 1) mean and modal size of crabs captured in large-meshed traps was larger than those captured in small-meshed traps which, in turn, were larger than those caught in the trawl; the size of crabs caught in the trawl at night was larger than those caught during the day; 2) large-clawed crabs predominated in the catches from traps whereas small-clawed animals predominated in the trawl catches; 3) soft-shell crabs were more common in trawl than in trap catches whereas old-shell crabs were more common in trap than in trawl catches; 4) mean size of the crabs caught increased with depth for all sampling methods, but especially so for traps; and 5) catch per unit effort for both large- and small-clawed crabs increased with depth for all sampling methods.