Search Results (514)

Underwater fish image segmentation is the key technology to realizing intelligent fisheries and ecological monitoring. However, the problems of light attenuation, blurred boundaries, and low contrast caused by complex underwater environments seriously restrict the segmentation accuracy. In this paper, RetinalConet, an underwater fish segmentation network based on bionic retina dual-channel and multi-module cooperation, is proposed. Firstly, the bionic retina dual-channel module is embedded in the encoder to simulate the separation and processing mechanism of light and dark signals by biological vision systems and enhance the feature extraction ability of fuzzy target contours and translucent tissues. Secondly, the dynamic prompt module is introduced, and the response of key features is enhanced by inputting adaptive prompt templates to suppress the noise interference of water bodies. Finally, the edge prior guidance mechanism is integrated into the decoder, and low-contrast boundary features are dynamically enhanced by conditional normalization. The experimental results show that RetinalCoNet is superior to other mainstream segmentation models in the key indicators of mDice, reaching 82.3%, and mIou, reaching 89.2%, and it is outstanding in boundary segmentation in many different scenes. This study achieves accurate fish segmentation in complex underwater environments and contributes to underwater ecological monitoring. Full article

The South China Sea (SCS) is a critical fishery region facing sustainability challenges due to overexploitation, geopolitical tensions, and inadequate monitoring. Traditional monitoring methods, such as AIS and VMS, have limitations due to data gaps and vessel deactivation. We developed an improved remote sensing algorithm using VIIRS nighttime light observations (2013–2022) to detect and classify lit fishing boats in the SCS. The study introduces a Two-Dimensional Constant False Alarm Rate (2D-CFAR) algorithm integrated with morphological analysis, which enhances boats’ detection accuracy. The classification of fishing boat types was based on light power thresholds derived from spatial entropy analysis, where distinct clustering patterns indicated three operational categories: small interfering lights (<1.2–3.7 kW), small-to-medium-sized lit fishing boats (1.2–3.7 to 28.6–43.2 kW), and large lit fishing boats (>28.6–43.2 kW). Our findings reveal a 4.4-fold dominance of small-to-medium-sized lit fishing boats over large lit fishing boats. China’s summer fishing moratorium effectively reduces large lit fishing boats activity by 85%, yet small-to-medium-sized lit fishing boats, primarily from neighboring countries like Vietnam, persist, exploiting this period illegally. Spatially, small-to-medium-sized lit fishing boats concentrate in the central SCS, southeast Vietnam, and Nansha Islands, while large lit fishing boats target upwelling zones near Hainan and Guangdong. Moreover, a new fishing hotspot emerged in eastern SCS, reflecting intensified resource and geopolitical competition. Light intensity analysis reveals rapid growth in contested areas (10% annually, p < 0.01), underscoring ecological risks. These findings highlight the limitations of unilateral policies and the urgent need for regional cooperation to curb illegal, unreported, and unregulated (IUU) fishing. Our algorithm offers a robust tool for monitoring fishing dynamics, providing quantitative insights into vessel distribution, policy impacts, and resource-driven patterns. This supports evidence-based fisheries management and biodiversity conservation in the SCS, adaptable to other marine regions facing similar challenges. Full article

This study examined the spatial distribution and environmental determinants of hairtail (Trichiurus lepturus) catch volumes in the southern coastal waters of South Korea, employing a Spatial Durbin Model (SDM) based on grid-level data collected from 2020 to 2022. Key explanatory variables included chlorophyll-a concentration, dissolved oxygen, salinity, sea surface temperature, and fishing effort. Spatial autocorrelation was confirmed through Moran’s I test, justifying the application of a spatial econometric framework. Among the environmental factors, salinity exhibited the strongest positive direct effect on catch volumes, whereas dissolved oxygen consistently showed a negative effect. Chlorophyll-a concentration exhibited significant positive effects both within local grids and in neighboring areas. Sea surface temperature also had a modest but significant direct effect on catch volumes. Additionally, higher fishing effort was associated with increased catch volumes, emphasizing the spatial impact of human activities on fishery resources. These findings reveal that hairtail tend to aggregate in high-salinity, low-oxygen environments and respond to seasonal oceanographic variations. Overall, the results highlight the value of spatial econometric models in fisheries research by revealing how environmental and anthropogenic factors influence fish catch through both direct and indirect effects. The spatial framework offers deeper insight into the mechanisms driving hairtail distribution, particularly in ecologically complex regions like the Jeju Strait. Full article

Palaemon gravieri is an ecologically important shrimp species that plays a vital role in depressing jellyfish blooms in the southern Yellow and East China Seas of China. However, information on its distribution pattern and migration route related to environmental variables is fragmented. We conducted independent trawling surveys of P. gravieri between 2018 and 2019. Its sea surface temperature and sea surface salinity lower limits were 8 °C and 30‰, respectively. It showed the highest abundance at sea bottom temperatures and salinities of 12–14 °C and 32–33‰, respectively, in spring; 11–12 °C and 32.5‰ in autumn; and 10.5–14 °C and 31–33‰ in winter. Mean biomass, abundance, and size were ranked seasonally as follows: autumn > winter > spring > summer; autumn > winter and spring; and summer > spring > autumn > winter, respectively. Under the current climate scenario, P. gravieri is mainly concentrated in the inshore areas of the southern Yellow and northern East China Seas. Under SSP1-2.6, SSP2-4.5, SSP3-7.0, and SSP5-8.5 scenarios in 2100, P. gravieri was mainly concentrated in the southern Yellow and northern East China Seas, and in inshore areas of the East China Sea. This species is therefore expected to benefit from climate warming. The findings of this study can facilitate the development of climate-induced fishery strategies and management schemes. Full article

To ensure sustainable marine resource utilization, advanced monitoring methods are urgently needed to mitigate overfishing and ecological imbalances. Conventional fishing activity detection methods, including speed threshold-based approaches and Gaussian Mixture Models, often fail to accurately handle complex vessel trajectories, resulting in imprecise quantification of fishing effort and hindering effective monitoring of illegal, unreported, and unregulated (IUU) fishing activities. To address these limitations, we propose a spatiotemporal adaptive clustering and segmentation (STACS) framework for recognizing fishing activities. First, ST-DBSCAN clustering distinguishes concentrated fishing operations from transit movements. Second, an adaptive segmentation algorithm that incorporates heading stability and local density dynamically partitions trajectories into coherent segments, using spatiotemporal clusters as the basic units. Third, multiple features capturing temporal dynamics and spatial patterns are extracted to characterize fishing behaviors. Finally, an XGBoost classifier with run-length encoding post-processing converts point-level predictions to continuous fishing episodes. Experiments on fishing vessel trajectory datasets demonstrate that STACS outperforms conventional methods and advanced segmentation approaches, improving both point-level classification and segment-level coherence across diverse fishing scenarios. By enhancing IUU fishing detection and reducing classification inconsistencies, STACS provides valuable insights for marine conservation, policymaking, and fisheries management, bridging local behavioral dynamics with global trajectory analysis. Full article

Sea cucumbers, important members of the phylum Echinodermata, play a crucial role in sediment mixing and nutrient cycling on the seafloor. They also hold significant economic value, particularly in Asian food and pharmaceutical markets. In the Mediterranean Sea, the harvesting of sea cucumbers has recently intensified, often without regulation, threatening both species populations and the health of benthic ecosystems. This study investigated the potential of using fatty acid (FA) profiles as ecological biomarkers to trace the different origin and feeding ecology of two sea cucumber species, Holothuria polii and H. tubulosa, collected from ten coastal sites in Italy. A total of 285 individuals were analyzed through lipid extraction and characterization from their body walls using gas chromatography (GC-FID and GC-MS). Key fatty acids identified included arachidonic acid, eicosapentaenoic acid, eicosenoic acid, palmitic acid, palmitoleic acid, stearic acid, and nervonic acid. Principal Component Analysis (PCA) revealed patterns consistent with geographic origin, suggesting that FA profiles can reflect site-specific trophic conditions. The analysis also indicated that sea cucumbers primarily feed on diatoms, bacteria, and blue-green algae, with notable regional variation. This study is the first to successfully apply FA-based trophic markers to differentiate Italian populations of these species, providing insights for ecological monitoring and fishery management. Full article

This study examined long-term trends (1991–2019) in landings and fish community structure in the four Egyptian Nile Delta lakes. Using fisheries data, we explored trends in the catch per unit effort (CPUE) and temporal dynamics of landings and fishing effort. Non-metric Multidimensional Scaling (nMDS) and Similarity Percentage Analysis (SIMPER) were employed to assess long-term changes in fish community structure. The results revealed variable productivity across the lakes. Lake Manzala often exhibited higher yields between 1991 and 2004, and notably in 2013 (e.g., 62,372 tons), while Lake Burullus peaked at 81,399 tons in 2019. A reciprocal trend was often observed in their total yields. Lake Burullus catches were dominated by Tilapia and Mullets, while Edku and Mariout showed lower productivity. CPUE patterns varied, with Lake Manzala showing a notable increase, peaking at approximately 52 tons per boat per year in 2013, and Lake Burullus experienced a sharp increase to about 29 tons per boat per year in 2019. A shift towards amateur fishing was observed predominantly in Lake Manzala, alongside a decline in traditional licensing. An increase in fishers operating without boats was also noted across all the Northern Lakes, with contributions from Lake Edko and Lake Manzala. nMDS and SIMPER analyses revealed distinct temporal groupings of years within each lake, indicating significant shifts in fish community structure, likely in response to invasive species, pollution, and habitat degradation. These findings underscore the need for lake-specific management and long-term monitoring to address unsustainable fishing and ecological changes, ensuring biodiversity conservation and fisheries sustainability in the region. Full article

The blue shark (Prionace glauca) is a pelagic species widely distributed in the northwestern Pacific Ocean. The trophic roles of blue sharks across different developmental stages and between sexes remain poorly understood. Fifty-four sharks were sampled (October 2022–March 2024) for precaudal length (PCL) and stable isotope levels (δ¹³C, δ¹⁵N) in the muscle tissue (n = 52). Mean PCL varied based on the month of sampling (p = 0.034), with the smallest individuals occurring in July (143.0 ± 4.3 cm) and the largest in October (178.0 ± 2.6 cm). Stable isotope analysis (δ¹³C and δ¹⁵N) indicated consistent offshore habitat use (δ¹³C: from −20.70 to −18.82‰) and significant nitrogen isotopic differences among life history (δ¹⁵N: from 10.23 to 15.72‰; Kruskal–Wallis test, p = 0.037). The elevated δ¹⁵N values observed in the subadult group (relative to juvenile individuals) are likely due to trophic enrichment associated with morphological development. Females exhibited markedly larger isotopic niches (SEAc = 2.42‰²) than did males (0.57‰²), and niche overlap was greater within each sex (40–52%) than between sexes (<21%). These results revealed sex-specific ecological roles and trophic strategies throughout the life history of P. glauca. Understanding these foraging differences can help with catch reduction and habitat-protection measures in the transboundary pelagic fisheries of the northwestern Pacific. Full article

Arabian Gulf oyster reefs, dominated by the pearl oyster Pinctada radiata, function simultaneously as ecological keystones and cultural touchstones. Rapid coastal urbanization and escalating pollution now threaten reef integrity. This systematic review of 1400 publications distilled 42 rigorously screened studies (3%) that document reef distribution, ecological roles, contaminant burdens, and socio-historical context. The results show that reef structures stabilize sediments, enhance water clarity through exceptional filtration rates, and furnish nursery habitats for commercially important fisheries, while heavy metal bioaccumulation in oyster tissues indicates widespread coastal contamination. The Gulf’s economy and identity were historically anchored in pearling; contemporary restoration initiatives already deploying dozens of sustainable reef modules across hundreds of traditional dive sites seek to revive this heritage and bolster ecological resilience. Persistent knowledge gaps include comprehensive spatial mapping, the effects of climate change and pollutant interactions, and long-term restoration success in hypersaline conditions. An integrated management framework that couples stringent monitoring, pollution mitigation, adaptive restoration, and heritage-centered community engagement is essential to safeguard Gulf oyster ecosystems and the cultural narratives entwined with them. Full article

Snow crabs (Chionoecetes opilio), a commercially valuable species in Korean waters, have been managed under the Total Allowable Catch (TAC) system since 2002. However, stock assessment has been limited due to difficulties in estimating key ecological traits such as growth, maturity, and mortality. In this study, the Bayesian Schaefer Model (BSM), implemented within CMSY++ framework, was applied to assess the stock status of snow crabs in Korean waters. BSM requires catch and abundance index data, such as catch per unit effort (CPUE) or biomass, as well as prior information on species resilience and relative biomass (B/k). To improve the reliability of B/k priors, we developed a method to calculate them quantitatively using fishery data, sales amounts, and biological information, unlike the qualitative assumptions on stock and fishing conditions proposed in previous research. Two standardized CPUE indices with differing temporal trends in recent years were used as abundance indices. To address the structural uncertainty associated with these divergent trends, we applied a grid-based approach by treating each CPUE index as an independent model scenario and integrating the posterior distributions. A total of 12,000 posterior estimates (6000 per index) were generated through the BSM and used to construct a Kobe plot. Results indicate that the current biomass is slightly above the level supporting maximum sustainable yield, and fishing mortality slightly below the optimal level, suggesting that the stock is healthy and sustainably exploited. Future research should aim to establish a systematic framework for developing quantitative B/k priors to enhance stock assessment accuracy. Full article

As a semi-pelagic fish with commercial value, Mediterranean horse mackerel, Trachurus mediterraneus (Steindachner, 1868), is highly important both for the ecosystem, as a link between trophic levels, and for fisheries and local livelihoods. This study investigates the T. mediterraneus stock along the Romanian coast for more than 10 years (2014–2024), reporting the following data on its bio-ecological characteristics and stock status: size, age, sex ratio, and estimated biomass. Horse mackerel at the Romanian coast revealed an initially slower growth rate followed by acceleration in later years, which may reflect local ecological influences such as resource availability, environmental conditions, or selective pressure. The spatial distribution of the species along the Romanian shelf indicates a clear pattern of coastal aggregation, highlighting the need for targeted and precautionary fisheries management measures, aiming to ensure a sustainable stock. Full article

Skipjack tuna constitutes a crucial fishery resource in the Western and Central Pacific Ocean (WCPO) purse seine fishery, with high economic value and exploitation potential. It also serves as an essential subject for studying the interaction between fishery resource dynamics and marine ecosystems, as its resource abundance is significantly influenced by marine environmental factors. Skipjack tuna can be categorized into unassociated schools and associated schools, with the latter being predominant. Overfishing of the associated schools can adversely affect population health and the ecological environment. In-depth exploration of the spatial distribution responses of these two fish schools to environmental variables is significant for the rational development and utilization of tuna resources and for enhancing the sustainability of fishery resources. In sparsely sampled and complex marine environments, geographic similarity methods effectively predict tuna resources by quantifying local fishing ground environmental similarities. This study introduces geographical similarity theory. This study focused on 1° × 1° fishery data (2004–2021) released by the Western and Central Pacific Fisheries Commission (WCPFC) combined with relevant marine environmental data. We employed Geographical Convergent Cross Mapping (GCCM) to explore significant environmental factors influencing catch and variations in causal intensity and employed a Geographically Optimal Similarity (GOS) model to predict the spatial distribution of catch for the two types of tuna schools. The research findings indicate that the following: (1) Sea surface temperature (SST), sea surface salinity (SSS), and net primary productivity (NPP) are key factors in GCCM model analysis, significantly influencing the catch of two fish schools. (2) The GOS model exhibits higher prediction accuracy and stability compared to the Generalized Additive Model (GAM) and the Basic Configuration Similarity (BCS) model. R² values reaching 0.656 and 0.649 for the two types of schools, respectively, suggest that the geographical similarity method has certain applicability and application potential in the spatial prediction of fishery resources. (3) Uncertainty analysis revealed more stable predictions for unassociated schools, with 72.65% of the results falling within the low-uncertainty range (0.00–0.25), compared to 52.65% for associated schools. This study, based on geographical similarity theory, elucidates differential spatial responses of distinct schools to environmental factors and provides a novel approach for fishing ground prediction. It also provides a scientific basis for the dynamic assessment and rational exploitation and utilization of skipjack tuna resources in the Pacific Ocean. Full article

Background: Fish escape events from aquaculture facilities are increasing and pose significant ecological, economic, and traceability concerns. Accurate methods to differentiate between wild, cultured, and escaped fish are essential for fishery management and seafood authentication. Methods: This study analyzed muscle tissue from Sparus aurata, Dicentrarchus labrax, and Argyrosomus regius using a multiomics approach. Heavy metals were quantified by ICP-MS, fatty acid profiles were assessed via GC-MS, and metabolomic and lipidomic signatures were identified using 1H NMR spectroscopy. Multivariate statistical models (MDS and PLS-LDA) were applied to classify fish origins. Results: Wild seabream showed significantly higher levels of arsenic (9.5-fold), selenium (3.5-fold), and DHA and ARA fatty acids (3.2-fold), while cultured fish exhibited increased linoleic and linolenic acids (6.5-fold). TMAO concentrations were up to 5.3-fold higher in wild fish, serving as a robust metabolic biomarker. Escaped fish displayed intermediate biochemical profiles. Multivariate models achieved a 100% classification accuracy across species and analytical techniques. Conclusions: The integration of heavy metal analysis, fatty acid profiling, and NMR-based metabolomics enables the accurate differentiation of fish origin. While muscle tissue provides reliable biomarkers relevant to human exposure, future studies should explore additional tissues such as liver and gills to improve the resolution of traceability. These methods support seafood authentication, enhance aquaculture traceability, and aid in managing the ecological impacts of escape events. Full article

The sustainability of coastal ecosystems, associated fisheries, and environmental quality is increasingly threatened by anthropogenic activities and rapidly expanding urbanization. This study investigated the ecological impacts of increased coastal urbanization on intertidal sediment quality and the biological parameters of the wedge clam Donax trunculus along the central Moroccan Atlantic coast. Between 2018 and 2022, a period characterized by intensified urban activity, total organic matter (TOM) in sediment significantly increased, whereas temperature and pH remained stable. Concurrently, D. trunculus populations experienced notable declines in abundance and biomass, along with marked disruptions in reproductive dynamics. The proportion of sexually mature individuals decreased, while spent individuals and male-biased sex ratios became more prominent. These findings suggest that urbanization-related pressures such as sediment enrichment, pollution, and physical disturbance are exerting measurable stress on this key bioindicator species. The results highlight the need for improved coastal management to mitigate the ecological consequences of rapid urban expansion on coastal sustainability. Full article

Elasmobranch species are considered a global conservation priority due to their susceptibility to fishing pressure. In the Madeira Archipelago, Northeastern Atlantic, most elasmobranch species are caught as bycatch in artisanal drifting longline fishery targeting scabbardfishes. All commercial elasmobranch landings carried out in this archipelago over three decades (1990–2020) were analysed, aiming to provide a reliable overview of Madeira’s elasmobranch fisheries and their evolution. A total of 2316 tonnes of elasmobranchs were landed during the study period, corresponding to approximately EUR 2.1 million in first-sale value. The most representative period occurred from 2003 to 2013, corresponding to 75.21% of the total elasmobranch landings. A general pattern of supply and demand was evident, with mean price values typically showing an inverse trend to landed tonnage. At the species level, Centrophorus squamosus appears as the dominant species, representing about 89% of the total elasmobranch species landed, followed by Prionace glauca, with approximately 3%. The high dominance of C. squamosus in the scabbardfish fishery raises significant ecological and management concerns, as this deep-water shark species is known for its vulnerability to overexploitation. Management measures currently in place need to be updated and ought to be based on studies on the type and size of hooks for each fishery, to ultimately infer about species-specific survival rates, as well as the fishing gears’ soak time. Moreover, studies on the enhancement of food supply through fisheries discards are still missing, even though it is highly likely that this input may alter the dynamics of marine food webs. Full article