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).