Effects of catch size and codend type on the escapement of walleye pollock (Theragra chalcogramma) from pelagic trawls

The effectiveness of codend meshes in permitting the escapement of undersized walleye pollock (Theragra chalcogramma) in the Bering Sea pelagic trawl fishery was tested during 13 July-1 August 1994. The alternate-haul method was used to compare catches made with treatment codends (i.e. large mesh codends) and a standard codend (i.e. small mesh codend). Four catcher vessels towed test codends that were fitted directly to their trawl gear. Codends were detachable, and catches were delivered to a factory trawler where sampling took place. Catch weights using treatment codends ranged from 0.3 to 79 t. Escapement of undersized pollock (less than 36 cm) decreased as catch size increased for all treatment codends, until the retention of small pollock in the treatment codends was not significantly different from that in the standard codend (i.e. when catches of treatment codends exceeded 40 t). Potential benefits of codend mesh size regulations for this large-volume fishery are therefore debatable unless catch sizes are somehow restricted.