Summary

This report documents the results of the FRDC funded study into the mesh selectivity of fish traps used in NSW.

The selectivity of standard 50 mm hexagonal wire mesh used in the fishery was found to be inappropriate for all species with minimum legal lengths, (snapper, rubberlip morwong, bream and tarwhine) in addition to pearl perch, because large numbers of undersized fish were captured and subsequently discarded with unknown mortality rates. The selectivity of 50 mm hexagonal mesh appeared to be suitable for all other important species without minimum legal lengths in the fishery.

The study investigated the use of escape panels of 50 x 75 mm welded mesh in traps to reduce the catch of undersized fish. Trials using these escape panels showed that they retained fewer undersized fish per trap lift, but they still retained large numbers of undersized snapper and rubberlip morwong. Catches of marketable snapper, rubberlip morwong, bream, silver trevally, sweep, tuskfish, pearl perch, carpet shark and conger eels were virtually unaffected when using 50 x 75 mm welded mesh. Estimated catches of some other important species in the fishery suggest substantial losses of marketable fish may occur when using these mesh panels (i.e. ocean jackets, tarwhine, pigfish and goatfish). Many fishers have adopted the use of 50 x 75 mm welded mesh as escape panels in fish traps.

Trials of 4 larger, novel mesh types showed the difficulty of designing trap meshes with appropriate selectivities for all important species in such a multi-species fishery. Results showed that some of the new meshes trialed as escape panels may be appropriate for snapper, but potential losses of species either with minimum legal lengths smaller than snapper or with no minimum legal lengths may be large, and that uptake of these larger meshes should therefore be on a voluntary basis.