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

Published source details Broadhurst M.K., Sterling D.J. & Millar R.B. (2013) Progressing more environmentally benign penaeid-trawling systems by comparing Australian single- and multi-net configurations. Fisheries Research, 146, 7-17.
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This study is summarised as evidence for the following.

	Action	Category
	Modify the design or configuration of trawl gear (mixed measures) Action Link

Modify the design or configuration of trawl gear (mixed measures)

A replicated study in 2012 of sandy mud bottom in an estuary flowing into the Tasman Sea, Australia (Broadhurst et al. 2013) found that changes to the configuration (number of nets, one to four) of prawn trawl gear resulted in lower overall catches of non-target fish species in triple trawls, and fewer of one of six of the main non-target individual fish species in multi-rigged trawls compared to a single trawl net. Average weight, but not number, of all non-target catch (more than 95% of which was just six fish species) differed between trawl configurations and was lower only in triple-rigged trawls (0.5 kg/ha) compared to single-rigged trawls (1.0 kg/ha), but similar for all other comparisons between trawl types (double-rigged: 0.7 kg/ha, quadruple-rigged: 0.7 kg/ha). Individually for the main six fish species caught, the catch rate of only yellowfin bream Acanthopagurus australis differed between trawl designs and was lower in double-rigged, triple-rigged and quadruple-rigged (2 ind/ha) trawls than in single trawls (4 ind/ha). But there were no differences between trawl designs in the catch rates of five other unwanted fish species, fork-tail catfish Arius graeffei, narrow-banded sole Synclidopus macleayanus, bullrout Notesthes robusta, silver biddy Gerres subfasciatus and mulloway Argyrosomus japonicus (see original paper for species individual data by gear type). Catch rates of the target school prawn Metapenaeus macleayi were similar across trawl configurations, (single: 600, double: 750, triple: 900, quadruple: 1,450 ind/ha), although single-rigged trawls retained larger individuals. In March and May 2012, a total of 36 experimental deployments/trawl configuration were made in the Clarence River estuary (3–18 m depth) of four trawl configurations: single, double, triple or quadruple-rigged. All used 45 mm mesh, but each configuration had different technical specifications (see original paper for details).

(Summarised by: Leo Clarke)