文摘
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 4934 t of bycatch taken annually in the JBG consists mainly of teleosts (4486 t), invertebrates (382 t) and small elasmobranchs (66 t), with around 4000 t (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.
