A preliminary assessment of the effects of introducing a grid in the trawl fishery for the North-East Arctic cod

Abstract

A number of studies have dealt with the testing of alternations of existing gears meant to reduce by-catch of non-target species or sizes. Such alternations can for example be changes in mesh size, mesh shape or introduction of sorting devices (grids, outlets, etc.). Some of the these gear alternations have also been implemented in the fishery. In the fishery for North East Arctid cod, e.g., the use of an approved sorting grid became mandatory in 1997. However, an assessment of what one should expect to gain concerning stock size, stock composition and thus yield by introducing a new gear has usually not been done, probably because it is difficult to do such assessments with age-structured stock models. Lately, however, there has been an increasing demand for studies dealing with these aspects. The aim of the present work is to stimulate the effects on fishing mortality, stock size and yield by introducing a sorting grid in the trawl fishery for North East Arctic cod. Results from selectivity studies with ordinary commercial trawls withmesh size 135 mm in the codend, both with and without a sorting grid (Sort-X, single grid) mounted in the extention, are used in an age-length structured stock model Fleksibest, to stimulate these effects.