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Red seabream (Pagrus major) is an important fisheries species in Japan, where it has been managed since 2025. Accurate stock assessment is necessary for rational fisheries management, and catch per unit effort (CPUE) is one of the key indexes used for this purpose. In the present study, the CPUE of red seabream in the East China Sea and Sea of Japan was standardized by incorporating seawater temperature and salinity based on fishing data obtained from bottom trawlers operating in key fishing grounds in these regions. We used data from operation reports available from 1982 to 2022, including fishing positions and efforts during each cruise and incorporated temperature and salinity data into the model from 1993. We applied a delta log-normal model for CPUE standardization and revealed an increase in this index since the early 1990s. We examined the horizontal distribution patterns of red seabream in each fishery grid that is 30 × 30 min latitude and longitude, and observed that the high-CPUE area extended northeastward from Taiwan to Japan along the shelf edge, which corresponds to the main fishing grounds covered by Japanese fleets after 2000. The probability of presence of red seabream increased drastically when water temperature at a depth of 50 m exceeded 15 °C. The reasons for the observed stock fluctuations may be a reduction in fishing pressure and warming seawater temperature.

Fisheries targeting sole (Solea solea) are primarily conducted using demersal beam and otter trawls. Despite the economic importance of sole across its wide distribution range, there is limited knowledge regarding its size selectivity in trawl codends. Understanding how codend mesh size and shape influence the size selection of sole is critical for defining technical measures and assessing the implications of regulatory changes for both the stock and the fisheries targeting this species. We developed a morphology-based model to predict size selectivity for sole across a range of sizes and mesh openings in both diamond and square mesh configurations, following the FISHSELECT methodology. This methodology has been successfully applied to several fish and crustacean species. The predicted size selectivity for sole codends aligns well with the relatively limited number of experimental estimates available, providing a morphologically based explanation for sole size selectivity. We predict size selectivity for diamond mesh codends ranging from 50 mm to 120 mm and estimate the number and weight of sole retained above and below the minimum conservation reference size (MCRS), using an experimentally derived population. Our results demonstrate that the various technical regulations implemented across the broad distribution area result in markedly different catch efficiencies and potential discard ratios for sole.

The connecting channels of the Laurentian Great Lakes provide socially and economically important fisheries. The St. Clair – Detroit River System, which connects the upper and lower Great Lakes, provides world-class recreational fishing opportunities for several popular sport fishes. These fisheries have been shaped by a wide range of anthropogenic modification and use of the Great Lakes as well as the introduction and subsequent ecological effects of invasive species such as dreissenid mussels (Dreissena spp.) and round goby (Neogobius melanostomus). Smallmouth bass (Micropterus dolomieu) are among the most popular sportfish species in Lake St. Clair. The Michigan Department of Natural Resources has been monitoring smallmouth bass populations since 1972 over two intensive sampling periods, 1972–1985 and 2002–2023. During the later period, improvements in population size structure have been observed, transforming the fishery into one comprising many larger individuals. Our objective was to analyze trends in smallmouth bass population relative abundance, growth rates, and mortality during two intensive sampling periods to better understand the changes in population size structure. Linear regression was performed for fishery metrics separately for the early (1972–1985) and late (2002–2023) sample periods, and the slopes of those regressions were compared to evaluate changes in population trajectory. Significantly different slopes for proportional size distribution of larger individuals existed between the early and late periods. Catch-per-unit effort did not differ between the early and late periods, though biomass caught per unit effort did. Growth rates changed at a similar rate between the early and late period. Mortality decreased at a steady rate across the study, with no change between the early and late time periods. We concluded that a long-term decreasing trend in mortality is likely the largest driver in improved size structure shaping the trophy smallmouth bass fishery that exists today.

Spanish mackerel species are migratory species, also are highly commercially valuable in Taiwan. However, in recent years, climate change and variability have influenced oceanographic conditions, substantially impacting the population dynamics of pelagic species. This study developed weighted habitat suitability index models for three crucial Scomberomorus species—Scomberomorus commerson, Scomberomorus niphonius, and Scomberomorus guttatus—in the waters off Taiwan. Remote sensing data including sea surface temperature, sea surface chlorophyll-a, sea surface salinity, and sea surface height, along with voyage data records that included detailed catch data from Taiwanese drift gillnet fisheries were collected during 2011–2019. The primary fishing grounds for S. commerson are located in the central to southwestern Taiwan Strait, while S. niphonius and S. guttatus are mainly found in the coastal waters off western Taiwan. In autumn, the oceanographic factor preferences are relatively similar among Scomberomorus species, with sea surface temperature being the primary influencing factor. Sea surface height turns to the main influencing factor in winter. Based on the results of the weighted habitat suitability model, we found seasonal differences in habitat preferences and ranges. There is more pronounced overlap in potential habitat in autumn and partial separate condition in potential habitat in winter among Scomberomorus species. Further exploration of the spatiotemporal distribution dynamics of Scomberomorus species under different ENSO periods revealed that during La Niña periods, the potential habitat ranges are broader and extend further south. In contrast, during El Niño periods, and the potential habitat ranges contract northward. Habitat suitable index model may be a useful approach for evaluating possible changes in habitat suitability resulting from climate change or other oceanographic phenomena and in offering suggestions for fishery scientific management.

Abandoned, lost or discarded fishing gear (ALDFG) has profound adverse effects on the marine environment and ecosystem through plastic pollution and continuous capture of target and non-target species, so-called “ghost fishing”. A trap fishery is usually conducted in a large area of fishing grounds, increasing the risk of interaction with other fisheries and resulting in high fishing gear loss and ghost fishing. This study evaluated the catch efficiency and catch-at-length of derelict traps targeting bigfin reef squid (Sepioteuthis lessoniana), herein called squid, in Khanh Hoa province, Vietnam. Here, two experimental treatments were investigated 1) trap with an egg cluster and soaked for 30 days (EXP1) and 2) trap without an egg cluster (empty trap) and soaked for 30 days (EXP2). Those experimental treatments were considered as derelict traps and were compared to the conventional daily soaked traps (CTR). Results showed that although derelict traps captured squid significantly less than conventional traps at all size classes, the capture was substantial. The mean catch-per-unit-efforts (CPUEs; number of squid per trap) of EXP1 and EXP2 were 0.42 and 0.17, respectively, compared to 0.59 for CTR, demonstrating that lost fishing gear can continuously capture animals for long periods after it is abandoned. A majority of captured target species were pregnant females, which has significant negative ecological impacts. In addition to the impacts on living resources, the derelict traps could contribute tonnes of plastic waste into the waters annually. Taken together, the study showed that derelict fishing gear is a serious threat to fisheries sustainability, ecosystem health, and marine debris pollution. In order to mitigate the problems caused by derelict fishing gear, an effective collaboration among fishermen, scientists, management, agencies, and other stakeholders is needed.