Impact of codend mesh sizes on selectivity and retention of Acadian redfish Sebastes fasciatus in the Gulf of Maine trawl fishery

Abstract

A trouser trawl was used to determine the size selectivity of three sizes of mesh opening (114, 140 and 165mm double 5mm twine diamond) on a commercial fishing vessel fishing off Provincetown, Massachusetts, USA. Fifty-six tows were completed in March and April 2013, catching over 42,000kg of Acadian redfish (Sebastes fasciatus) and about 6000kg of other species. Robust models for the mean L50s and selection ranges, and confidence intervals, were developed for all three tested codends, incorporating both within and between haul variability. L50 and selection ranges were determined for the nominal 114mm (L50:22.3cm; SR:3.3cm), 139mm (L50:29.2cm; SR:4.4cm), and 165mm (L50:33.6cm; SR:5.0cm) codends. All measures of model validity were positive. These models are fully adequate to provide guidance to managers and fishermen on size retention of redfish and appropriate codend mesh size. Additionally, simulation of fishing of the three tested codends on the observed population indicated that substantial escape of redfish through codend meshes occurs (51–96%), suggesting that investigation of escape of redfish is warranted to support a sustainable fishery. The observed population also indicates that inadequate numbers of larger redfish may be available to support a higher-priced market.