Preliminary report of a squid subsurface driftnet experiment in the north Pacific during 1991

An experiment utilizing six Japanese commercial squid driftnet vessels was conducted in the North Pacific during June-August 1991 to test for differences in catch and bycatch rates (CPUEs) of surface and sub-surface driftnets (set 2m below the sea surface). The ratio of subsurface CPUE to surface CPUE by vessel indicated that the sub-surface net substantially reduced CPUEs for flying squid, Pacific pomfret and seabirds; but the ratio varied considerably among vessels for northern fur seal, small cetaceans and sea turtles. Result of the Wilcox two-sided signed rank tests indicated that (1) the sub-surface driftnet reduced CPUEs for flying squid Pacific pomfret and seabirds (dark shearwaters) significantly (P 0.01), but (2) no differences in CPUE for northern fur seal, small cetaceans and sea turtles (P >0.05).