The use of a three level net in determining the effect of current on height in the water column of three species of penaeid prawn

A beam trawl divided into three separate nets, one on top of each other was used to collect data on the distribution in the water column of three species of penaeid prawns. 114 Penaeus plebejus Hesse, 263 Metapenaeus bennettae Racek and Dall, and 2,705 M. macleayi (Haswell) were caught, a total of 610 in the top net, 933 in the middle net, and 1,539 in the bottom net. The distribution at two sites, one influenced by tidal current and the other not, was similar for P. plebejus and M. bennettae with no significant difference between the catches in the three nets. M. macleayi of 1.1–9 mm carapace length were caught in significantly larger numbers in the bottom net at both sites. M. macleayi of 9.1 + mm carapace length were more likely to be caught in the bottom net at the site not influenced by tidal current, but were evenly distributed between nets when tidal currents were present. The results are used to evaluate the performance of the beam trawl in estimating the distribution of prawns in the water column and to further investigate the explanation given by Coles (1979) concerning similarity in catches regardless of trawl alignment.