Fishery-specific differences in the size selectivity and catch of diamond- and square-mesh codends in two Australian penaeid seines

The selectivities and catch compositions of conventional 30-mm diamond-mesh codends and a new square-mesh design made from 20-mm mesh hung on the bar for river and lagoon penaeid seines in south-eastern Australia were compared. The square-mesh design significantly improved the selectivities of the river seine for school prawns, Metapenaeus macleayi (Haswell), and the lagoon seine for greasyback prawns, Metapenaeus bennettae (Racek & Dall), by increasing their carapace length at 50% probability of retention (L) and by decreasing between-haul variability in selectivity. The presence of weed reduced the L for greasyback prawns caught in the conventional diamond-mesh codend during the lagoon-seine experiment. The differences among codend performances are discussed in terms of the differing methods of operation and composition of catches between the seines. These differences highlight the need to develop and manage modifications to improve the selectivity of fishing gears on a fishery-specific basis.