The influence on catch of monofilament and multifilament netting in otter prawn trawls

Abstract

In Moreton Bay, Queensland, the catch obtained using monofilament polyamide (PA) otter trawl-nets with multifilament polyethylene (PE) cod ends was compared with that obtained using multifilament PE trawl-nets of identical mesh opening (38 mm). Monofilament PA otter trawl-nets retained fewer small prawns ( < 24 mm carapace length) than conventional multifilament PE nets, but both nets caught similar quantities of larger prawns ( > 24 mm carapace length). The higher retention rate of small prawns by multifilament PE gear was reflected in the greater catch weights of Peraeus plebejus, Metapenaeus bennettae and Metapenaeopsis novaeguineae in those nets. Catch weights of larger prawn species such as Penaeus esculentus and Metapenaeus endeavouri did not differ between nets. Winter whiting ( Sillago maculata) and squid ( Loligo spp.) were trawled in similar abundance in both nets, although the monofilament retained fewer squid < 50 mm mantle length. More marketable ( > 15 cm carapace width) sand crabs ( Portunus pelagicus) were caught in the monofilament net. There was not significant difference in the trash (noncommercial component) weight caught in both nets. Over the range of towing speeds tested (1.7–2.3 kn), use of monofilament nets significantly reduced total gear drag.