Test out our new Bento Search

Pacific bluefin tuna (Thunnus orientalis, PBF), a highly migratory and commercially important species, faces intense fishing pressure. Taiwanese PBF catches, which reached a nadir in 2012, gradually increased from 2014 onwards, culminating in a dramatic fivefold surge after 2019. This study analyzed the adult population from PBF landings in Taiwan from 2010 to 2023 to inform fisheries management. We found a strong correlation between declining juvenile catches in Japanese troll or purse seine fishery and increasing adult catches in Taiwanese and Japanese longline fishery, with a 7–9 year lag. Age estimation, using otolith annuli and age-length keys, revealed a temporal shift in age composition. Despite the substantial increase in Taiwanese catch size, the average age of landed PBF decreased. The spawning stock, previously dominated by older individuals (14–18 years), now primarily consisted of younger fish (8–12 years). Prior to 2014, most PBF measured between 220 and 240 cm in fork length; after 2017, this range generally decreased to 200–220 cm. Permutation test using fish size and otolith direct ageing data suggested a lower mean fork length at age for the PBF landed in the recent years compared to earlier years. Furthermore, a linear mixed model showed a relationship between fork length and fishing year, indicating a consistent decrease in fork length across all age groups. These results suggest that reduced fishing pressure on juvenile PBF (0–1 years old) has allowed more individuals to reach adulthood, contributing to the observed recovery of the spawning population. These findings provide valuable insights into the effective fishery management and PBF stock rebuilding in Taiwan and other regions.

The widespread use of drifting fish aggregation devices (FADs) in tuna purse seine fisheries since the mid-1990s has raised sustainability concerns due to increased fishing mortality of unwanted species, such as small-sized tunas and silky sharks (Carcharhinus falciformis, FAL). A better understanding of ways to mitigate the catch unwanted species while increasing the catch of target species is critical for developing ecosystem-based management approaches. Here, we analyzed fisheries logbook data and scientific observer records of 345 FAD-associated fishing sets collected in the Western and Central Pacific Ocean to assess the influence of spatial-temporal strategies and fishing practices on the catch composition. Results demonstrate that technical adjustments can enhance the potential sustainability of tuna purse seine fisheries. Especially, small-sized tuna catches were concentrated in northern and eastern regions (2°N–6°N, 170°E–175°E), while FAL bycatch exhibited a more widespread distribution. Fishing practices factors, such as the duration of the purse seine gear set (∼9 min) and the time of the set relative to sunrise (∼30 min); substantially increased tuna catches while minimizing small-sized tuna catches. Seasonal analysis revealed that the pre-closure period (January to June) positively impacted tuna catches and reduced small-sized tuna catches. Moreover, FADs submerged structure at depths of 80 m stabilized tunas and FAL, while small-sized tunas tended to associate with deeper structures (90 m).

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.