Search Results (341)

Introduction: Microplastic (MP) contamination can endanger marine ecosystems and indirectly affect the well-being of humans through the ingestion of marine species. While most research investigates the digestive system, such as the gills and gastrointestinal tract of fish, it still fails to address a major oversight in understanding MP deposition in edible tissues, which is the primary route of human exposure. The differences in contamination levels among pelagic, demersal, and benthic fish in Malaysian waters remain poorly understood. This preliminary study uses Laser Direct Infrared Imaging (LDIR), a new, high-resolution, automated technique, to examine synthetic MP contamination in the edible portion of fish. Materials and Methods: The MPs were extracted from the edible tissue of three fish species representing pelagic (Fish A), benthic (Fish B), and demersal (Fish C) using KOH and sieved onto a gold mesh filter before analysis using LDIR. Results and Discussion: LDIR identified 162 MP particles, revealing clear differences by polymer type and habitat. Pelagic species mostly contained polyethylene (PE) and rubber (n = 8). Demersal species had mostly polyethylene terephthalate (PET) with small amounts of PE and rubber (n = 57). Benthic species showed the highest load, dominated by PET and polypropylene (PP) (n = 97). The morphological assessment of the MPs indicated that the polymers in pelagic fish were smaller, with an area of 2047.82 µm² and a circularity range of 0.14–0.74, indicating consistent shape. Conversely, MPs are irregular and larger in benthic fish, with areas up to 38,837.50 µm² and circularities ranging from 0.02 to 0.81. This pattern reflects specific accumulation related to habitat and potential environmental degradation processes. Conclusions: This preliminary study demonstrates the effectiveness of LDIR for detecting MPs in edible fish tissues. The findings provide a fundamental dataset on MP contamination in edible tissue and emphasize its distribution across ecological zones. Nevertheless, broader research is required to substantiate these data and assess the implications of MP contamination for the environmental stability of human and marine well-being. Full article

Understanding the life-history strategies of deep-sea fishes is essential for improving ecological knowledge and informing conservation efforts. Using otolith microchemistry, this study reconstructed the ontogenetic movement patterns of four grenadier species (Nezumia aequalis, Hymenocephalus billsam, Coelorinchus marinii, and Malacocephalus occidentalis) caught in the continental slope off southern Brazil (Southwestern Atlantic). Elemental signatures (Ba:Ca, Sr:Ca, Li:Ca, Mg:Ca, Mn:Ca, Ni:Ca, Cu:Ca, and Zn:Ca) were quantified along core-to-edge transects of sagittal otoliths using Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS). Ontogenetic shifts were identified using change-point detection (PELT). A general decline in elemental incorporation with age was observed across species, consistent with ontogenetic physiological regulation. Species-specific multi-elemental patterns suggest distinct ecological strategies. Nezumia aequalis exhibited an abrupt decline in Ba:Ca, indicating an early-life environmental shift. Hymenocephalus billsam showed increasing Ba:Ca and Sr:Ca profiles, consistent with continued use of pelagic-associated water masses. Coelorinchus marinii and Malacocephalus occidentalis displayed more complex patterns, with the latter showing pronounced Ba:Ca and Zn:Ca peaks that may reflect mid-life habitat shifts or physiological events. Mn:Ca ratios differed between pelagic and demersal species. Otolith microchemistry combined with change-point analysis could provide insights into deep-sea fish ontogeny, although interpretations should consider both environmental and physiological influences. Full article

Chub mackerel (Scomber japonicus) is a key pelagic commercial fish species in the North Pacific Ocean and is one of the priority species managed by the North Pacific Fisheries Commission (NPFC). This study assessed the stock status and maximum sustainable yield (MSY) of S. japonicus using the Length-based Bayesian Biomass (LBB) estimator and the Catch-MSY model. The assessment was based on length-frequency data collected from the light purse seine fishery on the high seas of the North Pacific (6061 individuals sampled during April–December, 2019–2024) combined with historical catch data spanning 1995 to 2024. Management implications were further analyzed using the Kobe plot and the Kobe II Strategy Matrix (K2SM). The results showed that: (1) The LBB model revealed significant interannual variability in stock status of S. japonicus. Although the stock was within sustainable limits (B/B_MSY ≥ 1.0) in 2019, 2021, and 2022, it suffered from overfishing or was heavily overfished in 2020, 2023, and 2024. Notably, integrated data analysis indicated that during 2023–2024, the B/B_MSY ratio dropped to 0.51, reflecting a marked deterioration in the stock condition. (2) The Catch-MSY model estimated the maximum sustainable yield (MSY) at 278,000 t, with a 95% confidence interval (CI) ranging from 162,000 t to 475,000 t. (3) Based on catch data, the Kobe plot indicated that in the final assessment year, the probability of the stock being in a sustainable state was only 23.2% at the 95% confidence level. The probabilities of being recruitment-overfished, fishing-overfished, and severely overfished were 37.6%, 14.9%, and 24.3%, respectively. With relative biomass B/B_MSY < 1 and relative fishing mortality F/F_MSY < 1, the stock status in the final assessment year was diagnosed as recruitment overfishing. (4) Integrating the outputs of the two models, the Kobe plot, and the probabilistic projections of future stock status from the Kobe II Strategy Matrix (K2SM), it is recommended that the total allowable catch (TAC) be set within 60–80% of the baseline TAC during the medium-term management phase (5–10 years), corresponding to a range of 211,300 t to 281,700 t. In the long term, if the stock exhibits positive recovery trends, the TAC could be gradually increased to the MSY level to achieve the maximum sustainable utilization of this fishery resource. Full article

The use of bait in Vietnamese gillnet fisheries to improve fishing efficiency has recently increased, yet its influence on both target species and protected bycatch species is unknown. This study compared the catching performance of baited versus non-baited drift gillnets in a pelagic fishery off central Vietnam to evaluate whether bait can increase catch rates of commercially important species and protected species. Sea trials were conducted during the stewardship fishery using identical gillnets, differing only in the presence of bait bags containing round scad (Decapterus macrosoma). The results showed that baited gillnets significantly increased CPUE of most target species, including skipjack tuna (Katsuwonus pelamis) at 68.2%, frigate tuna (Auxis thazard thazard) at 55%, and bullet tuna (Auxis rochei) at 62.4%, compared to conventional gillnets. Wahoo (Acanthocybium solandri) and mahi mahi (Coryphaena hippurus) also increased by 50.6% and 51.6%, respectively; however, these increases were not statistically significant. Length-based analyses indicated that baited and non-baited gillnets differed in size-dependent catch efficiency, with certain length classes showing significantly higher or lower capture probabilities depending on the species. Notably, baited gillnets also showed a higher likelihood of capturing hammerhead sharks (Sphyrna spp.). These results show that baiting can improve the fishing efficiency in pelagic gillnet fisheries, potentially gaining economic performance. However, the increased interaction with protected species highlights a critical trade-off, underscoring the need for bycatch mitigation measures and management strategies to ensure that improvements in fishing efficiency remain aligned with the principles of sustainable fisheries and long-term ecosystem conservation. Full article

Although Quintero-Puchuncaví Bay, Chile, is a coastal area historically known to be subject to multiple industrial pressures, few studies have focused on the associated risks to marine ecosystems and, through edible species, to human health. We studied concentrations of Cd, Cr, Cu, Mn, Pb, V, Zn, and Hg in marine species and sediments from Quintero-Puchuncaví Bay and a reference site. Results were compared with seafood safety guidelines, and target hazard quotients (THQs) were evaluated. Sediments and biota from the impacted area generally exhibited higher metal concentrations. Zinc (Zn) and copper (Cu) levels were the highest across all species, particularly in crustaceans, reflecting both physiological requirements and anthropogenic inputs. Cadmium (Cd) concentrations were higher in pelagic species from the impacted bay, but no differences were found in sediments or benthic species, suggesting the influence of upwelling conditions. Comparison with seafood safety guidelines revealed that Cd and Pb concentrations exceeded permissible limits in crabs, fish, and mussel species, and THQ ≥ 1 values were found for Cd concentrations in benthic species from the impacted bay, highlighting potential risks to consumers. The absence of permissible thresholds for certain environmentally relevant metals in Chilean regulations underscores the need to align with international standards, certainly to protect coastal ecosystems and human health. Full article

The present study examined fish biodiversity, livelihood dependence, cultural importance, and genetic connectivity in two ecologically linked habitats of the Sylhet region, Bangladesh: Hakaluki Haor and the Surma River. Surveys documented 60 fish species with distinct assemblage patterns between sites. Hakaluki Haor was dominated by floodplain spawners and small indigenous species that contribute to year-round subsistence harvests, whereas the Surma River supported a greater proportion of migratory and pelagic species, most notably Tenualosa ilisha. These ecological contrasts reflected differences in hydrology, habitat diversity, and fishing intensity. Household surveys confirmed the central role of fisheries in sustaining income and food security, while cultural practices surrounding hilsa consumption reinforced local stewardship norms. Mitochondrial cytochrome b sequence analysis of T. ilisha revealed low genetic differentiation between sites, indicating a single, well-connected stock maintained by seasonal flooding and the absence of major migration barriers. This convergence of ecological and genetic evidence supports treating the two sites as an integrated management unit. Effective conservation will require protecting hydrological connectivity, safeguarding dry season refugia, coordinating seasonal fishing restrictions across habitats, and incorporating cultural values into policy frameworks. The findings strengthen the scientific basis for national and regional conservation strategies and demonstrate the value of combining biological, socio-economic, and cultural dimensions in managing connected wetland–river systems. This approach can serve as a transferable model for other tropical floodplain–river complexes facing similar ecological and livelihood challenges. Full article

Polychlorinated biphenyls (PCBs) remain a major concern in marine ecosystems, where bioaccumulation in fish occurs as complex congener mixtures whose dynamics challenge conventional indicator approaches. This study develops and evaluates a data-driven framework for refining mixture-based indicators of PCB contamination by integrating ensemble machine learning with explainable artificial intelligence. Focusing on PCB-138 as a target indicator of cumulative PCB burden, we analyse concentrations of 24 organochlorines together with biological covariates in four Mediterranean edible pelagic fish species (sardine, anchovy, horse mackerel, and chub mackerel). Comparative evaluation of indicator performance shows that alternative congener combinations, including i4 PCBs (-138, -153, -170, -180), i6 PCBs (-138, -153, -170, -180, -118, -123), and mixtures incorporating DDD and DDE, more effectively represent total PCB burden than traditional indicator groups. Clustering identifies two distinct bioaccumulation settings, characterized by high-concentration coherent congener effects and low-concentration heterogeneous responses, demonstrating that indicator performance depends on concentration range and mixture context. The study illustrates how interpretable machine learning approaches can serve as formal tools for indicator evaluation and optimisation, strengthening long-term monitoring and management of legacy contaminants in marine ecosystems, particularly under conditions of persistent exposure and renewed inputs from sediment remobilization and riverine transport. Full article

The complex ocean dynamics in the Northwest Pacific high-seas fishing grounds shape phytoplankton communities, which serve as the foundation for commercially pelagic species. This study investigates how mesoscale eddies modulate phytoplankton groups’ structures by analyzing the spatiotemporal evolution of eight phytoplankton functional types (PFTs) from 2014 to 2023. Utilizing high-resolution AI-driven model data (AIGD-PFT) and a normalized radial distance grid (0–2 R), we quantified PFTs concentrations within cyclonic (CE) and anticyclonic (AE) eddies, validated by Biogeochemical Argo (BGC-Argo) and in situ measurements. Results reveal that diatoms and dinoflagellates dominate the region, accounting for 88.7% of phytoplankton with distinct seasonal peaks in spring and autumn, respectively. CE significantly enhance diatom and dinoflagellate concentration, particularly within the 0.4 R–1.2 R dynamic ring, while AE favor the aggregation of picophytoplankton, such as Prochlorococcus, in mid-to-low latitudes. Correlation analysis indicates that diatom abundance is strongly linked to dissolved oxygen and negatively correlated with sea surface height. We conclude that mesoscale eddies drive the spatial remodeling of phytoplankton communities by altering local physical and nutrient conditions. These findings provide a critical ecological context for assessing the habitat distribution and sustainable management of North Pacific fisheries across different trophic levels. Full article

Silver pomfret (Pampus argenteus, family Stromateidae) is a highly valuable marine fish species with significant commercial demand; however, its aquaculture remains undeveloped due to limited knowledge of captive breeding and seed production. To our knowledge, this is the first successful report on the induction of maturation, natural spawning, and larval rearing of silver pomfret under captive conditions in Korea. Wild broodstock (33 individuals in 2020; 250 individuals in 2021) were collected from the southern coastal waters of Korea using set nets. In the first year, water temperature management alone successfully induced gonadal maturation, as evidenced by a significant increase in the gonadosomatic index (GSI) and the presence of vitellogenic oocytes (400–500 μm) in April. In the second year, natural spawning was observed on fifteen occasions from May to September 2022, yielding a total number of 157,050 eggs. Fertilized eggs were spherical, transparent, and pelagic, with diameters ranging from 1.29 to 1.37 mm. Hatched larvae (total length: 4.85 ± 0.22 mm) exhibited poor feeding responses to rotifers and high early mortality within two weeks post-hatching, with the maximum rearing period reaching 24 days post-hatching. These findings demonstrate that water temperature management alone is sufficient to induce maturation and natural spawning of silver pomfret, and highlight the critical need for optimizing larval feeds, improving broodstock nutritional management, and conducting endocrine profiling during reproduction to establish a complete aquaculture protocol for this species. Full article

This study investigates the spatiotemporal dynamics of zooplankton communities in the tropical low-latitude Northwestern Pacific Ocean based on field surveys conducted in August 2021 and November 2022. Redundancy analysis identified nitrate, silicate, temperature, and salinity as the primary factors influencing community structure. The distribution of dominant zooplankton groups exhibited close correlations with key environmental gradients, showing distinct habitat preferences corresponding to different hydrographic conditions. Zooplankton abundance in August 2021 was significantly higher than that in November 2022, which is presumably attributed to eddy-induced nutrient upwelling and enhanced primary productivity. Comparisons with adjacent marine regions reveal general consistency in overall zooplankton abundance and community species composition, while the observed seasonal discrepancies are closely associated with local unique hydrographic characteristics. These results highlight the role of nutrient–temperature–salinity interactions in structuring zooplankton communities and underscore their sensitivity to environmental variability. The findings provide a scientific basis for understanding pelagic ecosystem dynamics in oligotrophic waters and for developing management strategies under changing climate and oceanographic conditions. Full article

Understanding the reproductive physiology of marine fish is critical for sustainable fisheries management, particularly under environmental variability. This study evaluated seasonal changes in body parameters (condition factor, Kn, and gonadosomatic index, GSI, as proxies for body condition and reproductive status, respectively) and biochemical composition (P, proteins; G, glucose; L, lipids; fatty acids; and bioenergetic ratios L/P, LG, all as proxy of integrated biochemical condition) of female gonads in Strangomera bentincki, a key pelagic species in the Humboldt Current System (HCS) off south-central Chile. Moreover, environmental factors (sea surface temperature and chlorophyll-a) were also analyzed to explore their influence on the FA profile of gonads. Female body parameters showed significant seasonal variations, with high values of Kn and GSI in autumn and spring, respectively. The biochemical composition also revealed significant seasonal variation in protein and glucose content, with the highest protein levels in winter and elevated glucose in autumn. While total lipid and energy content remained relatively stable across seasons, the L/P and L/G ratios presented seasonal variations. Similarly, the fatty acid composition showed pronounced seasonal differences, particularly with increased polyunsaturated fatty acids (e.g., DHA) in winter. The SST was the environmental factor with the greatest influence on the seasonal variations in the gonadal FA profile. Altogether, these findings suggest a partial capital breeding strategy in S. bentincki, where reproductive investment depends on both accumulated reserves and environmental conditions during reproduction. This study underscores the importance of incorporating reproductive biochemical indicators into ecosystem-based fisheries management models to improve assessments of stock health and reproductive potential. Full article

Reconciling hydropower development with aquatic biodiversity conservation is a central challenge for sustainable river management worldwide. Cascade dam configurations, in which multiple impoundments are arranged in series along a single channel, impose longitudinal environmental gradients that restructure biological communities across trophic levels. Whether the resulting multi-trophic responses are independently driven by shared abiotic gradients (environmental filtering) or mechanistically coupled through direct food-web interactions (trophic cascading) remains unresolved. We surveyed phytoplankton, zooplankton, and benthic macroinvertebrates simultaneously at seven stations along a 430 km gradient downstream of Danjiangkou Dam in the Hanjiang River, the largest tributary of the Yangtze River and the source of China’s South-to-North Water Diversion Middle Route, over eight seasonal campaigns (2015–2017). Variance partitioning, piecewise structural equation modeling, Mantel tests, and co-occurrence network analysis were applied to partition environmental and trophic pathways. Environmental filtering dominated community restructuring at all three trophic levels, while the biotic proxy for direct trophic interactions explained less than 0.4% of community variation, consistent with weak detectable trophic coupling at seasonal resolution. Distance from Danjiangkou Dam shaped downstream transparency and turbidity gradients that mediated trophic-level-specific responses along distinct environmental axes (pH and water temperature for phytoplankton, conductivity for zooplankton, and transparency for benthic macroinvertebrates). Benthic macroinvertebrates were systematically decoupled from the pelagic analytical framework, absent from the cross-trophic co-occurrence network and structured more by spatial configuration than by water-column variables. Hub species in the network were associated with downstream mineralized conditions, confirming that network architecture reflects shared environmental preferences rather than biotic interactions. These findings support a management shift from single-dam mitigation toward cascade-scale coordination of environmental flow regimes, sediment connectivity, and substrate restoration as integrated strategies for sustaining multi-trophic biodiversity in regulated rivers. Full article

The Black Sea is highly vulnerable to environmental degradation, making the evaluation of contaminant transfer within its food webs essential for ecosystem protection, sustainable resource management, and human health risk assessment. Marine organisms accumulate contaminants through three main processes: bioconcentration (direct uptake from the abiotic environment), biomagnification (trophic transfer through consumption of contaminated prey), and bioaccumulation, which integrates contaminants from all exposure pathways. Despite numerous studies reporting contaminant concentrations in Black Sea waters, sediments, and biota, integrated analyses of trophic transfer within both pelagic and benthic food webs in the Romanian coastal sector remain limited. This study assessed the bioamplification of heavy metals—HMs, persistent organic pollutants—POPs (OCPs, PCBs) and polycyclic aromatic hydrocarbons—PAHs along the main pelagic and benthic food webs in the Romanian coastal sector, based on concentrations measured in representative invertebrate and fish species. The results revealed a compartment-driven contamination pattern, with the benthic food web functioning as an important reservoir and transfer pathway. Heavy metals showed variable and context-dependent trophic transfer, with selective amplification for Cu and Ni in some benthic links, trophic dilution or neutral transfer for Cd and Pb, and more consistent retention for Cr. In contrast, several PCB congeners showed clear biomagnification, particularly in benthic predator–prey relationships. PAHs displayed compound-dependent trophic transfer, with more pronounced amplification in benthic pathways. Overall, biomagnification was stronger for organic pollutants, particularly PCBs, than for heavy metals. The study contributes to two United Nations Sustainable Development Goals (SDGs): SDG 14 (Life Below Water) and SDG 12 (Responsible Consumption and Production). Full article

The Black Sea waters and sediments accumulate a wide range of pollutants, which, together with natural factors, can have diverse and combined effects on marine organisms. Cellular oxidative stress (OS) is a common response to environmental stressors and thus an indicator of the physiological resilience of organisms. The present study analyzed OS in fish species from the Bulgarian part of the Black Sea. Samples of 18 fish species were obtained during monitoring trawling in the northern and southern regions of the Bulgarian Black Sea and were analyzed. The OS-specific biomarkers (lipid peroxidation, glutathione, and antioxidant enzymes) were spectrophotometrically measured in the liver and gills. The obtained results revealed pronounced variability in pro- and antioxidant responses, shaped by sampling location, species identity, and tissue type. In fish sampled from the northern part, the liver showed stronger antioxidant activation, while the gills exhibited higher lipid peroxidation. Benthic fish exhibited pronounced hepatic antioxidant responses. Pelagic species had higher gill lipid peroxidation. Generalist feeders displayed variable stress responses associated with a diverse diet and the presence of multiple contaminants in it. In conclusion, OS was most pronounced in benthopelagic and pelagic species, which were more stressed in the northern Bulgarian part of the Black Sea, while benthic or coastal fish species experienced greater environmental pressure in the southern part. Full article

The round sardinella (Sardinella aurita Valenciennes, 1847) is a widely distributed migratory pelagic fish inhabiting the Mediterranean Sea and the eastern Atlantic coasts. The species is heavily exploited and represents a valuable resource for global fisheries. In the Mediterranean area, uptakes of round sardinella are particularly high in the Ionian and Levant regions, where landings have shown fluctuating yet significant peaks in recent decades. Given its migratory nature, understanding the connectivity among populations is crucial for delineating appropriate fishery management units. Previous studies employing morphometric, meristic, and molecular analyses have yielded mixed results regarding population structuring. Here, the genetic differentiation among Eastern Mediterranean S. aurita populations was investigated using a multi-marker approach: the mitochondrial cytochrome c oxidase subunit I (COI), cytochrome b (CytB), control region (CR), and 16S ribosomal RNA (16S rRNA), and seven species-specific nuclear simple sequence repeats (SSRs). Overall, the results indicate high genetic diversity coupled with weak population structuring across the Eastern Mediterranean. These analyses aim at clarifying stock boundaries towards supporting sustainable management strategies at a regional scale for this ecologically and economically important species. Full article