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Penaeid trawls are among the world’s least selective fishing gears. This characteristic has justified decadal attempts at resolution and most commonly via retroactively fitted ‘bycatch reduction devices’ in the posterior sections to promote fish escape. However, ideally unwanted species would never enter a trawl. This study sought to investigate if fish could be avoided in diurnally deployed estuarine penaeid trawls via light emitting diodes (LEDs) located at the frame lines (headline and footrope). The assumption of few confounding effects of attaching six inactive LEDs (i.e. structures) to the frame lines was validated (experiment 1) before separate experiments were done to assess the effects on catches due to six active blue or green LEDs on the footrope (experiment 2) and then on the headline (experiment 3). Catches of the targeted school prawns, Metapenaeus macleayi and some fish (across all sizes; 4–20 cm total lengths), including mulloway, Argyrosomus japonicus, southern herring, Herklotsichthys castelnaui, and painted stinkfish, Eocallionymus papilio were similarly and significantly lower in trawls with at least one active LED treatment, and with greater consistency when these were on the headline. Some loss of target catches would preclude the commercial use of LEDs on the frame lines of the tested trawls. However, evidence of strong responses among some fish and their known behavioural and swimming differences to penaeids might support testing LEDs at other locations, including inside trawls, to reduce bycatches while maintaining target catches.

Highlights •The spatial distribution of fishery stocks in the Beibu Gulf is jointly influenced by environmental factors and human activities such as fishing pressure.•Climate change is projected to alter the spatial aggregation patterns of fish populations, with noticeable shifts in species distribution centroids.•Under different CO2 emission scenarios (RCP2.6 and RCP8.5), significant differences in habitat suitability and expansion trends were observed among fish species.•Sciaenidae is identified as a potentially vulnerable taxon under the low-emission scenario (RCP2.6), showing a reduction in suitable habitat.•Fish community structure in the Beibu Gulf is expected to undergo further changes in response to future climate-driven habitat shifts.

The Individual Transferable Quota (ITQ) system is widely regarded as an effective policy tool to regulate fishing, to maintain the economic level, and to promote the sustainability of resources. However, its implementation can influence the distribution of quotas, potentially leading to changes in the economic structure of the sector, which raises concerns about the future of small-scale vessels. This study evaluates the impact of ITQs on bluefin tuna (Thunnus thynnus) in the Ports of the Strait of Gibraltar, where ITQs have been applied since 2008. To analyze these effects, we use Lorenz curves and Gini indices to examine the evolution of catches and income. The results reveal that the application of ITQs has reinforced the concentration of economic activity in these ports. Based on these findings, we propose a new ITQ distribution to ensure the economic viability of small-scale vessels and to address the concentration caused by the current ITQ system. Our redistribution proposal focuses on reallocating quotas to vessels that no longer catch bluefin tuna as bycatch and those that currently have low allocations. This paper provides insights into the economic consequences of rigid quota allocation systems that may be relevant to fisheries facing similar challenges worldwide.

No summary available.

Highlights •Two-dimensional CFD simulations are performed for the flow around a near-bed cylinder with various cross-sectional shapes.•A particle model is developed and used to simulate particle paths in the cylinders’ wakes.•The simulations are used to access catchment and sediment suspension potential of the different shapes.

No summary available.