Abstract
Various plastic strips and sheets (termed ‘simple anterior fish excluders’−SAFEs) were positioned across the openings of penaeid trawls in attempts at reducing the unwanted bycatches of small teleosts. Initially, three SAFEs (a single wire without, and with small and large plastic panels) were compared against a control (no SAFE) on paired beam trawls. All SAFEs maintained targeted Metapenaeus macleayi catches, while the largest plastic SAFE significantly reduced total bycatch by 51% and the numbers of Pomatomus saltatrix, Mugil cephalus and Herklotsichthys castelnaui by up to 58%. A redesigned SAFE (‘continuous plastic’) was subsequently tested (against a control) on paired otter trawls, significantly reducing total bycatch by 28% and P. saltatrix and H. castelnaui by up to 42%. The continuous-plastic SAFE also significantly reduced M. macleayi catches by ~7%, but this was explained by ~5% less wing-end spread, and could be simply negated through otter-board refinement. Further work is required to refine the tested SAFEs, and to quantify species-specific escape mechanisms. Nevertheless, the SAFE concept might represent an effective approach for improving penaeid-trawl selectivity.
Highlights
The capture and mortality of unwanted organisms by mobile demersal fishing gears is a global issue affecting many fisheries [1]
The four beam-trawl configurations were towed at similar speed over the ground (SOG) and STWs covering predicted mean ± SE areas between 1.90 ± 0.02 and 1.95 ± 0.02 ha per 40-min deployment, which were not significantly different (LMM, p>0.05; Table 2)
This study validates the concept of locating simple bycatch reduction devices’ (BRDs) anterior to penaeid trawls for improving their species selectivity [13, 14]
Summary
The capture and mortality of unwanted organisms (termed ‘bycatch’) by mobile demersal fishing gears is a global issue affecting many fisheries [1]. This is especially the case for penaeid trawling, which despite contributing only ~1.5% towards the total global marine wild harvest (estimated at a plateau of ~80 m t since 1985 [2]), accounts for >25% of all discarded bycatch (~7.3 m t per annum [1]); typically comprising small teleosts (
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