Size selection of Atlantic cod, haddock and pollock (saithe) by otter trawls with square and diamond mesh codends of 130–155 mm mesh size

Abstract

The size selection of otter trawls equipped with square or diamond mesh codends with mesh sizes of 130–155 mm was examined for Atlantic cod ( Gadus morhua), haddock ( Melanogrammus aeglefinus) and pollock ( Pollachius virens) in 14 cruises with research or commercial fishing vessels conducted off the Canadian Atlantic coast in 1988–1991. Square mesh codends gave a 50% retention length approximately 10% higher for cod and haddock than did diamond mesh codends of the same mesh size. Selection range of cod and haddock was approximately one third narrower for square mesh netting than for diamond mesh netting. Parameter estimates for pollock were too few to allow firm conclusions, but were generally similar to the other species. Present data were found to be consistent with selection data for cod and haddock published since 1980 for mainly smaller mesh sizes. When the present and published data sets were combined, square mesh was found to have 50% retention lengths that were 12% and 5% higher for cod and haddock, respectively, than for diamond mesh sizes, in the 130–155 mm range. Selection range for square mesh netting was 0.60 that of a diamond mesh with the same 50% retention length. For pollock, selection data were relatively few, and less consistent than for the other species, preventing firm conclusions.