Effects of an increase in mesh size on the catches of fish trawls off New South Wales, Australia

Abstract

In response to claims that fish trawls off New South Wales, Australia, caught excessive quantities of under-size fish, the catches of finfish by a conventional fish trawl (constructed of 90-mm mesh in the body) were compared with those by a fish trawl constructed of 100-mm mesh in the body. Catches by the 100-mm trawl showed a 27% reduction in all by-catch and a 28% reduction in the numbers of retained tiger flathead, compared with catches by the conventional trawl. The 100-mm trawl also showed a 48% and 47% reduction in the numbers and weights respectively of discarded tiger flathead and a 57% and 63% reduction in the numbers and weights respectively of discarded rubberlip morwong. For john dory, however, at a particular locality where large numbers occurred, the 100-mm trawl caught significantly more fish than did the conventional trawl (a mean increase in weight of 66%). There is a need to determine species-specific mesh selectivities and to study the behaviour of fish in trawls. The importance of the results for the future management and operational efficiency of trawl fisheries is discussed.