Progressing more environmentally benign penaeid-trawling systems by comparing Australian single- and multi-net configurations

摘要

The engineering and catching efficiencies of single-, double-, triple- and quad-rigged penaeid trawls (all with the same cumulative headline - 14.63 m and sweep lengths - 9.76 m) were compared across the same spatio-temporal scales in an attempt to identify the more environmentally benign configurations (in terms of species selectivity, fuel intensity and habitat contact). The relative system efficiencies reflected a complex array of interacting factors, but broadly environmental performance improved with an increasing number of nets in the configuration. The single rig had the least fishing capability due to having the lowest wing-end spread (a 'spread ratio' - SR to headline length of 63.50%), but the greatest drag, and required the most fuel (predicted mean of 2.88 L per ha trawled). Further, this system caught significantly more yellowfin bream, Acanthopagrus australis and fewer (but larger) of the targeted school prawns, Metapenaeus macleayi than the multi-trawl rigs. Compared to single rig, the double rig had an improved SR (68.76%) and was easier to tow (2.44 L per ha trawled). However, triple and quad rigs similarly achieved the greatest SRs (75.46 and 74.37%) and at lower drag and fuel consumptions (2.13 and 2.21 L per ha trawled, respectively). Providing effort is regulated, the latter two configurations, but especially triple rig (which had relatively less total benthic contact), could be the most suitable base from which to progress modifications to further reduce the environmental impacts of penaeid trawling