Short vs long penaeid trawls: Effects of side taper on engineering and catching performances

Abstract: As part of efforts to minimise unwanted environmental impacts of penaeid trawling, the importance of side taper (and therefore total length) on the (i) engineering performance and (ii) selectivity of a generic trawl was investigated in an Australian fishery. Four designs (‘1N2B two-seam’, ‘1N2B four-seam’, ‘1N5B two-seam’ and ‘1N5B four-seam trawls’) were tested; all identical (7.35-m headlines and 42-mm mesh) except for their tapers (1N2B—25° to the tow vs 1N5B—35°) and panel number (two vs four). Irrespective of panels, compared to the 1N2B trawls, the shorter 1N5B designs achieved significantly greater predicted mean wing-end spreads (4.7–5.6%), while reducing drag (up to 4.3%) and also the numbers (perha trawled) of one teleost (southern herring, Herklotsichthys castelnaui; by up to 66%). However, catches of the targeted school prawns (Metapenaeus macleayi), were also significantly lower in the 1N5B trawls (by up to 50%; and biased towards smaller individuals escaping). The catch reductions were attributed to the shorter 1N5B bodies increasing the probability of mesh encounters (both species) and/or allowing H. castelnaui to swim forward and escape. [Copyright &y& Elsevier]