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Abstract: The Joseph Bonaparte Gulf (JBG) banana prawn subfishery is an important component of Australia''s Northern Prawn Fishery (NPF). However, the species composition of the large volumes of bycatch caught in this region is poorly known. We sampled the prawn trawl bycatch of the JBG from 53 commercial trawls over two years. These samples contained 195 taxa from 85 families; 117 teleost taxa contributing 90.9% of the total biomass, 68 invertebrate taxa (7.7% of biomass), six species of elasmobranchs (1.3% of biomass) and three species of sea snakes (<1% of biomass). The species composition of this bycatch is distinctly different from that of other tropical regions, including the neighbouring Gulf of Carpentaria in the NPF. The estimated 4934t of bycatch taken annually in the JBG consists mainly of teleosts (4486t), invertebrates (382t) and small elasmobranchs (66t), with around 4000t (81.6% of the total biomass) coming from just six teleost families: Synondontidae (17.7%), Rhinoprenidae (15.9%), Trichiuridae (14.1%), Sciaenidae (12.3%), Engraulidae (10.9%) and Polynemidae (10.7%). Of the other taxa, around 58% occurred in less than 10% of trawls and 28% occurred in only one trawl. Eight species have never been recorded from other bycatch studies in northern Australia. The total bycatch take and its teleost component varied seasonally, while some abundant species also showed seasonal and diel differences in their catch rates and size composition. The data collected in this study will be the basis for a long-term bycatch monitoring program in the region. This will improve the accuracy of quantitative risk assessments used to demonstrate the sustainability of bycatch populations impacted by fishing in northern Australia. [Copyright &y& Elsevier]

Abstract: This study presents results from an experimental 10-day research charter that was designed to quantify the effects of (a) a turtle excluder device (TED), (b) a radial escape section bycatch reduction device (BRD) and (c) both devices together, on bycatch and prawn catch rates in the Queensland shallow water eastern king prawn (Penaeus plebejus) trawl fishery. The bycatch was comprised of 250 taxa, mainly gurnards, whiting, lizard fish, flathead, dragonets, portunid crabs, turretfish and flounders. The observed mean catch rates of bycatch and marketable eastern king prawns from the standard trawl net (i.e., net with no TED or BRD) used during the charter were 11.06kg/hectare (ha−1) (S.E. 0.90) swept by the trawl gear and 0.94kgha−1, respectively. For the range of depths sampled (20.1–90.7m), bycatch rates declined significantly at a rate of 0.14kgha−1 for every 1m increase in depth, while prawn catch rates were unaffected. When both the TED and radial escape section BRD were used together, the bycatch rate declined by 24% compared to a standard net, but at a 20% reduction in marketable prawn catch rate. The largest reductions were achieved for stout whiting Sillago robusta (57% reduction) and yellowtail scad Trachurus novaezelandiae (32% reduction). Multidimensional scaling and analysis of similarities revealed that bycatch assemblages differed significantly between depths and latitude, but not between the different combinations of bycatch reduction devices. Despite the lowered prawn catch rates, the reduced bycatch rates are promising, particularly for S. robusta, which is targeted in another fishery. Prawn trawl operators are not permitted to retain S. robusta and the devices examined herein offer the potential to significantly reduce the incidental fishing mortality that this species experiences. [Copyright &y& Elsevier]

Abstract: This paper quantifies the effects of a square mesh codend bycatch reduction device (BRD) and turtle excluder device (TED) in the deepwater eastern king prawn (Melicertus plebejus) fishery on the southeast Queensland coast, based upon on a 10-day research charter. The bycatch comprised 224 taxa, mainly gurnards, flatheads, sandpaper fish, hermit and charybdid crabs, mantis shrimps, sand dollars (i.e. sea urchins), dragonets, snipefish, carids and lizardfish. The total mean bycatch rate was comparatively low (1114.0gha−1 from the standard diamond mesh codend), mainly because of the relatively deep waters associated with the fishery. When the TED and square mesh codend BRD were used together the total mean bycatch rate was significantly reduced by 29% (796.0gha−1) compared to the standard codend, with no significant effect on the prawn catch rate or size frequency distribution. Several bycatch species experienced very large reductions in mean catch rate, due to the square mesh codend, including Graham's conger Gnathophis grahamii (98.2% reduction), dumpling squid Euprymna tasmanica (95.9%), shortsnout threadsail Aulopus curtirostris (90.6%) and sandpaper fish Aulotrachichthys sp. (90.0%). Multidimensional scaling indicated that bycatch assemblages were more affected by latitude and depth than codend type. Based on the results, we recommend that the 47.6mm square mesh codend be made mandatory in the deepwater eastern king prawn fishery as a highly effective BRD. [Copyright &y& Elsevier]