A trouser-trawl experiment to assess codends that exclude juvenile mulloway (Argyrosomus hololepidotus) in the Hawkesbury River prawn-trawl fishery

Abstract

A trouser trawl was used to assess two codends designed to reduce the by-catch of juvenile mulloway in the Hawkesbury River prawn-trawl fishery. Simultaneous comparisons were made between the catches and by-catches from each codend with those from a conventional codend. The new design incorporated a panel of netting (40-mm mesh or 85-mm mesh) sewn such that the meshes were square-shaped. The panel was placed into the top of the anterior section of the codend to allow water and swimming fish to escape through these larger openings while allowing prawns to tumble along the conventional diamond-shaped netting (40-mm mesh) on the bottom of the codend (and be retained in the posterior section). Comparisons with a conventional codend (in which all meshes were diamond-shaped) showed that the codend with the 40-mm square-mesh panel reduced the by-catch of small mulloway by a mean of 44% without significantly reducing the catch of prawns. The 85-mm square-mesh panel was excluded from analysis, owing to problems associated with its construction.