Search Results (43)

Accurate prediction of the potential habitat distribution of Scomber japonicus, an important target species in China’s distant-water fisheries, is essential for fishing ground forecasting. Using catch data for S. japonicus collected from Chinese large-scale purse-seine and trawl fisheries in the Northwest Pacific Ocean from May to November during 2015–2024, this study applied the maximum entropy model (MaxEnt) and the genetic algorithm for rule-set production (GARP) model to predict the potential habitat distribution of S. japonicus in the Northwest Pacific Ocean. The area under the receiver operating characteristic curve (AUC) and the true skill statistic (TSS) were used to evaluate model performance. The MaxEnt model predicted a relatively concentrated highly suitable habitat, whereas the GARP model identified a broader highly suitable area. To reduce the bias and uncertainty associated with single-model predictions, the outputs of the MaxEnt and GARP models were integrated using a weighted ensemble approach, with the optimal weights for MaxEnt and GARP determined as 0.7:0.3. The ensemble model achieved higher predictive performance, with an AUC of 0.983 and a TSS of 0.840. The highly suitable habitat of S. japonicus was mainly concentrated within 147° E–156° E and 40° N–44° N. Chlorophyll concentration, sea surface temperature (SST), and temperatures at depths of 150 m and 200 m were the main environmental variables affecting the potential habitat distribution of S. japonicus in the MaxEnt model. These findings provide useful information for resource utilization, fishing ground forecasting, and sustainable management of S. japonicus in the high seas of the Northwest Pacific Ocean. Full article

Using a balanced panel of ten major fishing and trading nations (China, Chile, Indonesia, Peru, Thailand, Vietnam, Norway, India, Denmark, and Canada) over the years 2000–2020, this study investigated the relationship between international fishery trade and the fishing footprint, a consumption-based ecological indicator measuring the bioproductive marine area required to sustain seafood consumption. Cross-sectional dependence tests, second-generation panel unit root tests (PANICCA), LM bootstrap cointegration analysis, and long-run coefficient estimation using fully modified OLS (FMOLS), dynamic OLS (DOLS), fixed effects, and method of moments quantile regression (MMQR) are all part of the sequential econometric framework used in this analysis. Findings consistently show that the domestic fishing footprint is positively correlated with imports, domestic production, real GDP, and per capita food consumption, but adversely correlated with fishery exports. Additionally, MMQR estimates show that the negative export link becomes stronger at higher quantiles of the distribution of fishing footprint, indicating that the moderating influence of exports is strongest in nations that are already under a lot of ecological strain. Although the panel data do not allow for direct dissection of these channels, these findings are interpreted considering three potential mechanisms: certification-linked catch limits, aquaculture substitution in export volumes, and distant-water fleet displacement. It is recommended that policymakers include sustainability criteria into import laws, broaden the scope of eco-certification, and make investments in aquaculture to supplement the management of wild-capture fisheries. The findings of this study contribute significantly to the monitoring of global sustainability agendas, particularly aligning with United Nations Sustainable Development Goal (SDG) 12 (Responsible Consumption and Production) and SDG 14 (Life Below Water) by providing empirical evidence on how trade dynamics influence the fishing footprint. Full article

This study presents a comprehensive data-limited stock assessment of bonga shad (Ethmalosa fimbriata) and lesser African threadfin (Galeoides decadactylus) in the Central Gulf of Guinea using complementary catch- and abundance-based approaches, including Abundance-based Maximum Sustainable Yield (AMSY), Catch-based Maximum Sustainable Yield ++ (CMSY++), and the Bayesian State-space Schaefer Model (BSM). These models were applied because they are suitable for evaluating stock status in data-limited fisheries using catch and abundance information. While AMSY primarily uses abundance information, CMSY++ integrates catch and productivity priors, whereas BSM incorporates state-space error structures to account for observation uncertainty. Catch time series (1990–2021) were extracted from Food and Agricultural Organization (FAO) FishstatJ accessed in 2023, with catch values for 2022–2023 cautiously extrapolated from recent trends due to the temporary absence of updated official statistics. Standardized and scaled relative abundance indices from Cameroonian and Nigerian EEZ were used to support model estimation and assess the stock status. For Ethmalosa fimbriata, the results from CMSY++ and BSM yielded an MSY estimate of 126 × 10³ t and 95.5 × 10³ t, respectively, while for G. decadactylus, MSY from CMSY++ and BSM were 9.1 × 10³ and 13.4 × 10³, respectively. Stock status indicators suggested the stock was fully exploited based on both AMSY (F/F_MSY = 0.83) and CMSY++ (F/F_MSY = 1.03) and overfished based on BSM (F/F_MSY = 1.77). For G. decadactylus, the analysis based on AMSY suggested an overfished stock state (F/F_MSY = 1.2), while under CMSY++ and BSM, the stock is fully exploited. The log scale CPUE was symmetrical within the expected bounds, and the posterior parameter distributions were constrained, indicating that the model passed the convergence test and had robust parameter estimates. The study recommends maintaining catches within MSY-based reference points as the total allowable catch (TAC) and emphasizes the need for improved data continuity, regional collaboration, and precautionary management for long-term sustainability of fisheries resources in the Central Gulf of Guinea. Full article

The present study incorporates age- and length-based methods to estimate the stock status of Nile tilapia (Oreochromis niloticus) in the inland fisheries of Lake Nasser, Egypt. In 2021, a total of 570 specimens were sampled to determine the length–weight relationships, condition factor, maturity schedules, age structure and growth parameters. The age estimations were quite accurate, suggesting a lifespan of 5 years. Females attained 50% maturity at a length of 27.85 cm and age of 2.30 years, while males attained maturity at 29.93 cm and 2.45 years. The von Bertalanffy model best described growth parameters using the Bayesian approach. Length-based reference points produced from aLBI indicate a close association between length at initial maturity (L_mat = 29.3 cm) and optimal harvest length (L_opt = 30.8 cm). The Froese indicators indicate that all the proportions of mature fish (P_mat = 44.8%), fish of optimum size (P_opt = 35.6%), and big spawners (P_mega = 18.1%) were below sustainability targets. The results indicate that non-selective fishing gear is responsible for growth and recruitment overfishing by harvesting fish at, or below, maturity. The integrated Bayesian–aLBI approach offers a rigors and transparent assessment for inland fisheries with limited data and support for size-based management actions to rebuild the Nile tilapia stock in Lake Nasser. Full article

Reliable real-time detection and counting of tuna during distant-water deck operations is critical for automated catch monitoring but remains challenging due to strong illumination variation, background clutter, and frequent occlusion. This study proposes YOLOv10n-EMCNet, an improved lightweight detector based on YOLOv10n, integrating an ESC-based C2f enhancement in the backbone, a Multi-Branch and Scale Modulation-Fusion Feature Pyramid Network (SMFPN) in the neck, and a Convolutional Attention Fusion Module (CAFM) in the head for fine-grained representation and multi-scale feature fusion. An end-to-end detection–tracking–counting pipeline is further constructed by combining the detector with DeepSORT and an ROI-based de-duplication strategy. On the tuna dataset, YOLOv10n-EMCNet achieved 94.84% mAP@0.5, 65.29% mAP@0.5:0.95, and 91.77% recall with 6.5 GFLOPs. In addition, a controlled comparison among DeepSORT, ByteTrack, and OC-SORT on challenging videos showed that DeepSORT provided the best overall balance between counting accuracy, identity stability, and runtime efficiency. In shipboard video validation on four representative videos covering daytime high glare, nighttime low light, dense occlusion, and dense multi-target, the proposed pipeline achieved an average counting accuracy of 91.4%, with an average relative error of 8.62% and an average absolute error of 1.25 fish per video, while operating at approximately 30 FPS on an RTX 4090D platform. These results provide encouraging preliminary evidence that the proposed method can support automated tuna monitoring under representative shipboard conditions. Full article

Lanternfishes (Myctophidae) dominate mesopelagic ecosystems and play a central role in pelagic food webs through their high biomass and diel vertical migration, yet detailed information on their age structure and growth dynamics remains limited in the Northwest Pacific Ocean. This study reconstructs age, growth patterns, and life-history strategies of D. gigas and D. perspicillatus using sagittal otolith microstructure analysis. Specimens were collected during oceanographic surveys conducted in 2023 and 2024, and individual ages were estimated by counting daily otolith growth increments. Somatic growth trajectories were evaluated using multiple nonlinear growth models, including the von Bertalanffy, Gompertz, and Logistic functions, and growth dynamics were further assessed through derivative-based growth speed analyses. The results reveal pronounced interspecific differences in growth strategy and longevity. D. perspicillatus exhibited rapid early somatic growth, a compressed age structure, and an early approach to asymptotic length, indicating a short-lived life-history strategy characterized by early growth deceleration and high population turnover. In contrast, D. gigas showed faster early growth, prolonged somatic development, greater inter-individual variability, and substantially larger maximum body size, reflecting delayed maturation and extended lifespan. Otolith microstructural zonation clearly corresponded to larval, juvenile, and adult growth phases in both species. The predominance of younger age classes in the catch and interannual differences in size structure were primarily attributed to ontogenetic habitat shifts, cohort composition, and sampling availability rather than intrinsic changes in growth dynamics. Full article

Mercury (Hg) contamination in deep-sea ecosystems is of increasing concern due to its strong bioaccumulation potential and implications for seafood safety. However, depth-resolved information on Hg speciation and tissue-specific accumulation in deep-sea fish remains limited, particularly in semi-enclosed marginal seas such as the East Sea of Korea. In this study, total mercury (THg) and methylmercury (MeHg) concentrations were quantified in multiple tissues (muscle, liver, gill, bone, and skin) of deep-sea fish collected across a pronounced depth gradient (100–1300 m). Hg concentrations increased significantly with sampling depth (p < 0.05), indicating depth-driven enrichment processes. MeHg accounted for 61.8–87.4% of THg and predominated in muscle and liver, highlighting its toxicological relevance. Human health risk assessment based on Estimated Daily Intake (EDI) and Target Hazard Quotient (THQ) suggested that average exposure levels remained below international safety thresholds. Nevertheless, several deep-sea taxa (e.g., Lycodes tanakae and Malacocottus gibber) approached cautionary levels under high-consumption scenarios. These findings demonstrate that habitat depth is a key ecological driver of Hg accumulation in deep-sea fish and underscore the importance of depth-resolved, species-specific monitoring for effective seafood safety management as deep-sea fisheries expand. Full article

Coastal zones are critical areas of marine ecosystems, where biodiversity is a key ecological element for maintaining ecosystem stability and ensuring the sustainability of fishery resources. The Shengsi Ma’an Archipelago Marine Special Reserve features heterogeneous habitats such as rocky reefs, seaweed beds, and artificial aquaculture areas, which are significantly affected by human activities. This study focused on the nearshore waters of Lvhua Island within the reserve. Based on the degree of human disturbance, the study area was divided into five typical habitat types: cage culture area (A), intertidal seaweed bed (B), marine platform area (C), open waters (D), and mussel culture area (E). Environmental DNA (eDNA) technology was employed to analyze the characteristics of eukaryotic community structures across these habitats and their coupling mechanisms with environmental factors. The results showed that a total of 767,360 valid sequences were obtained from 15 seawater samples. Clustering into operational taxonomic units (OTUs) yielded 811 OTUs, taxonomically covering 50 phyla, 104 classes, 220 orders, 334 families, 435 genera, and 530 species. The number of OTUs shared across all habitats was 387. The intertidal seaweed bed (B) had the highest proportion of unique OTUs (4.8%) and showed significant differences (0.01 < p < 0.05) in OTU composition compared to the marine platform area (C) and the mussel culture area (E). Among the major dominant phyla, the abundance of Dinoflagellata across sites was A (74.56%) > E (68.32%) > B (62.15%) > C (58.74%) > D (55.21%). The abundance of Arthropoda across sites was D (27.34%) > C (19.98%) > B (17.89%) > E (9.17%) > A (8.25%). Each of the other sites had 1-2 dominant phyla. Among the major dominant genera, the abundance of an unclassified genus of Dinophyceae was B (41.39%) > C (23.31%) > D (22.03%) > E (19.27%) > A (18.56%). The genus Noctiluca was endemic to Site A, with an abundance of 39.98%. The genus Calanus was dominant in site D (26.17%). The genus Meganyctiphanes was unique to sites C (12.12%) and D (8.76%). The genus Ectopleura was unique to site A. The genus Botrylloides was unique to site E. The remaining genera were evenly distributed across sites without significant habitat specificity. Alpha diversity analysis revealed that the marine platform area (C) had the highest Shannon index (3.32 ± 0.22) and Pielou index (0.54 ± 0.04), while the mussel culture area (E) had the highest Chao1 index (578.96 ± 10.25). All diversity indices were lowest in the cage culture area (A). Principal coordinate analysis (PCoA) and ANOSIM tests indicated significant differences (p < 0.05) in eukaryotic community structures among different habitats. Samples from the seaweed bed clustered separately and were distant from other habitats. Redundancy analysis (RDA) showed that pH was the key environmental factor driving the differentiation of eukaryotic community structure. Temperature was negatively correlated with dissolved oxygen, while salinity was positively correlated with pH. The combined differences in environmental factors were the main drivers of eukaryotic community structure differentiation. In conclusion, this study clarifies the regulatory role of habitat type on the eukaryotic community structure in the nearshore waters of Ma’an Archipelago, confirming a negative correlation between human activity intensity and biodiversity, and a positive correlation between natural habitat complexity and biodiversity. The research findings provide scientific support for assessing the health of the marine ecosystem and formulating ecological conservation and management strategies in this region. Full article

Background: The Tibetan Plateau, which is known for its high elevation and low oxygen levels, presents a challenging environment for its inhabitants. To adapt to these hypoxic conditions, species of Schizothoracine, a subfamily of Cyprinidae, have developed unique physiological mechanisms and functions. Transforming growth factor-β (TGF-β) is a multifunctional cytokine involved in the regulation of cell growth, differentiation, apoptosis, and the cellular immune response. However, its specific role in adaptation to hypoxia remains poorly understood. Methods: In this study, we aimed to characterize the TGF-β1 gene in Gymnocypris dobula (Gd) and Schizothorax prenanti (Sp) and to test whether TGF-β1 contributes to hypoxia adaptation in plateau Schizothoracine fish. The predicted protein for Gd-TGF-β1 contains several primary domains, including cwf21 (cdc5 protein 21), GYF (Glycine-Tyrosine-Phenylalanine), FN1 (Fibronectin 1), a conservative domain, and a signal peptide. Results: The results of tissue distribution revealed that the mRNA level of TGF-β1 in brain, heart, muscle, skin, gills, and spleen—which are key tissues involved in oxygen sensing, transport, and physiological adaptation to hypoxic environments—was significantly lower in G. dobula than that in S. prenanti. Western blotting analysis revealed that the expression of activated TGF-β1 in G. dobula was significantly higher than that in S. prenanti. To investigate whether TGF-β1 in G. dobula possesses hypoxic adaptive features, Gd-TGF-β1 and Sp-TGF-β1 were cloned into an expression vector and transfected into 293-T cells, which are widely used due to their ease of culture, high transfectability, and well-characterized properties. We found that the survival rate of cells transfected with Gd-TGF-β1 was significantly higher than that of cells transfected with Sp-TGF-β1 after hypoxia treatment. Conclusions: These findings suggest that G. dobula may promote hypoxic adaptation through the activation and increased expression of TGF-β1. Changes in TGF-β1 expression may play a role in the adaptation of G. dobula to hypoxic conditions. 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

This study estimated the density distribution of Antarctic krill inhabiting an area near the South Shetland Islands using two acoustic analysis methods recommended by the Commission for the Conservation of Antarctic Marine Living Resources, based on data collected using an echosounder installed on commercial fishing vessels. Mean Antarctic krill density for the entire survey area was estimated with two methods recommended by the Commission for the Conservation of Antarctic Marine Living Resources. The mean body length of krill collected using trawl gear was 49.06 ± 4.15 mm (range: 22.0–67.0 mm), with mode of krill observed at 50 mm body length. Using the swarm-based method and the frequency differences according to krill size, the mean densities of krill for stations and transects were 14.86 g/m² (CV = 47.09%) and 13.10 g/m² (CV = 41.16%), respectively. Furthermore, using the dB-difference method for the entire survey area, the average densities were 10.76 g/m² (CV = 43.83%) and 10.14 g/m² (CV = 53.48%), respectively, using the frequency difference based on krill size determined at all stations and per transect. Full article

Addressing the illegal, unreported, and unregulated (IUU) fishing in the water beyond its jurisdiction poses a significant challenge for China as it aims to establish itself as a responsible participant in global fishing governance. Inadequate regulation and enforcement largely contribute to the increase in the suspected illegal fishing by Chinese vessels, fishing enterprises, and crew members. In 2020, China revised the RDWF (2020) to address the growing issues of IUU fishing. This study aims to evaluate the effectiveness of the RDWF (2020) in addressing China’s IUU fishing in distant water. This paper concludes that RDWF (2020) represents an incremental advancement in China’s initiatives to eliminate IUU fishing. RDWF (2020) emphasizes the government’s responsibilities in regulating vessel quantities and ensuring accurate reporting. Furthermore, RDWF (2020) adopts measures to fulfill China’s responsibilities under RFMOs. Additionally, RDWF (2020) expands the roster of operators liable for penalties and delineates IUU fishing activities that necessitate sanctions. Ultimately, RDWF (2020) develops an evaluation system to monitor compliance with anti-IUU fishing obligations as stipulated by international treaties and Chinese laws and regulations. However, RDWF (2020) encounters limitations that may impede its effectiveness in addressing IUU fishing, such as the lack of responsibilities assigned to administrative bodies, insufficient penalties for serious IUU fishing activities, and inadequate compliance with international standards for sustainable fishing. This paper provides policymakers specific recommendations for improving the identified areas of RDWF (2020) and offers insights for distant-water fishing nations that are grappling with significant IUU fishing issues to make gradual improvements in combating IUU fishing. Full article

The large pelagic species play an important role in transferring energy in vast distant marine ecoregions. Results obtained report on extraordinary findings of important commercial species in southeast–south Brazilian waters, including the Southern bluefin tuna Thunnus maccoyii and the Pacific bluefin tuna Thunnus orientalis, an endemic species from the Pacific Ocean. These specimens were identified within the genomic description of 10 individuals randomly selected from the catch to evaluate the catch composition of pelagic longline fisheries off Brazilian waters. Most of the records were from T. maccoyii (6), followed by the Bigeye tuna T. obesus (2), Yellowfin tuna T. albacares (1), and T. orientalis (1). Yellowfin and Bigeye tuna are expected to be captured in the vicinity of the longline fishing areas. However, the unlikely presence of the cold-water T. maccoyii and the warm-water T. orientalis suggests a long migration from common species ranges that could be influenced by climate change. These results imply a readjustment of spatial management structures for these species. Full article

This study estimated the economic value of international fisheries observer programs for Korean distant water fisheries using the contingent valuation method (CVM). The model included economic factors, socio-demographic variables, and proxy variables that reflected participants’ familiarity with seafood consumption. An online survey was conducted with 16,924 participants, of whom 1000 provided usable responses (resulting in a final response rate of 5.9%). The survey results indicated that 74.2% of households were willing to pay to support international fisheries observer programs. The weighted average willingness to pay (WTP), adjusted for the participation rate, was estimated at USD 7.01 per household, leading to an annual aggregated WTP of USD 153,097,825. These findings highlight the significance of international fisheries observer programs in promoting the sustainability and effective management of Korean distant water fisheries. Full article

Accurate estimation of fish stock abundance and exploitability is critical for effective fishery management; however, fishery-dependent data are often affected by temporal and spatial heterogeneities due to the seasonal migration of fish, posing challenges for refined stock management. Previous studies have largely ignored these spatio-temporal dynamics, assuming static populations. This study develops a seasonal spatio-temporal model for Japanese sardine (Sardinops melanostictus) in the Northwest Pacific Ocean (NPO), using fishery-dependent data from 2014 to 2022. Seasonal standardized abundance indices (spring, summer, autumn, and an overall average) were generated and integrated with the abundance maximum sustainable yield (AMSY) method for stock assessment. The performance of the AMSY method using a spatio-temporal index was compared with the conventional model-based index, showing the superiority of the spatio-temporal approach. Results indicate a gradual increase in sardine abundance, with a significant shift in the center of gravity toward the northeast. The stock is in a sustainable state with a 94.8–99% probability of recovery. Although the stock is recovering, careful management is advised to prevent future declines. This framework offers a novel approach for assessing distant water and coastal fishery resources. Full article