Search Results (2,539)

Turbot (Scophthalmus maximus) is a globally important species in both capture fisheries and aquaculture. With the development of the turbot farming industry in China and several European countries, enhancing its aquaculture eco-economic performance has become a key concern among stakeholders. Turbot is a major species in marine fish aquaculture in China. As the world’s leading producer of farmed turbot, the bioeconomic dynamics of this species under recirculating aquaculture systems (RASs) remain poorly understood, which hinders optimal resource allocation, green development, and industrial upgrading of the turbot farming sector. In this study, a bioeconomic model for turbot cultured in industrial RASs was developed based on empirical production data and published literature. The optimal harvesting strategies under the industrial RAS production mode were analyzed. The results indicated the following: (1) for a two-year grow-out cycle commencing with stocking at the beginning of the year, at a farm-gate price of 7.56 USD/kg, the maximum cumulative profit of 41,846.08 USD occurred at t = 22.69 months, while the maximum monthly average profit of 1937.65 USD/month occurred at t = 20.49 months. The optimal harvesting time for single-batch culture was t = 22.69 months, whereas for continuous culture, it was t = 20.49 months. (2) Extended analysis incorporating fish price variation revealed that higher market prices corresponded to later optimal harvesting times. (3) February to April was identified as the optimal stocking window. Based on the bioeconomic dynamics elucidated herein, this study provides a theoretical foundation for related research and proposes producer-oriented strategy recommendations for reference by relevant stakeholders. Full article

Plastic pollution has emerged as one of the most pervasive environmental challenges, with microplastics (MPs) widely distributed across marine ecosystems worldwide. This study aimed to assess the uptake of MPs by key fish and invertebrate species from different locations in the coastal zone of the Bulgarian Black Sea. Fish were collected during routine monitoring surveys in September–November 2024, while invertebrates were obtained via scuba diving. The presence of MPs in fish stomachs and invertebrate soft tissues, and their polymer composition, shape and size were analyzed using an Agilent 8700 LDIR Chemical Imaging System. Potential biological effects of ingested MPs were evaluated by an integrated Specific Oxidative Stress (SOS) index. The results revealed MP uptake levels comparable to those reported globally. Small-sized particles (<50 µm) with rounded shapes were most abundant across studied taxa. Polymer composition varied considerably depending on species and sampling region, indicating differences in exposure sources and environmental conditions. Oxidative stress levels in both fish and invertebrates showed substantial interspecific variation, and clear differences between the northern and southern region of the Bulgarian Black Sea. Overall, elevated uptake of MPs appears to contribute to oxidative stress in marine organisms, potentially affecting their health status, resilience, and adaptive capacity, as reflected by increased SOS index values. Full article

The goal of this Special Issue was to collect the latest research results on the topics of (1) the physiological response of fish to various stressful situations and nutritional changes, (2) the replacement of fish meal and fish oil with sustainable, alternative protein and lipid sources in fish feeds, and (3) supplementing fish feeds with various additives in order to enhance the immune response and increase the stress and disease resistance of fish reared in intensive systems. These topics are very important for the development of a more effective and sustainable intensive aquaculture, as fish farming systems are becoming more intensive and industrialized, which results in a more stressful environment for farmed fish. Another important challenge is providing enough high-quality fish feed to fulfill the increasing demand of intensive aquaculture. There are 14 original research articles published in this Special Issue. The authors come from a wide array of countries, and they worked with a wide variety of freshwater and marine fish species, which are important for intensive aquaculture. These articles represent only a modest contribution to the overall literature of stress and nutritional physiology of farmed fish. However, each of these papers contain interesting new information regarding the solution of the two major problems of intensifying aquaculture: environmental stresses and nutrition management. Full article

Marine fisheries provide a nutrient source for humans, and Indonesian marine fisheries have the second-highest production rate globally. Reliable evidence of the volume of captured fish is crucial for the sustainable management of Indonesian fisheries. The Labuan Fishing Port in Banten Province, Sunda Strait, was surveyed between September 2022 and March 2023. Based on personal inspections and an anonymous questionnaire, fishermen used various methods to catch fish. The captures by fisheries showed that the gear types, including purse seines and a mix of several types of gear, were the largest contributors to officially registered (auctioned) production, with 85.85% and 83.91% of their captures being auctioned, while bottom otter trawls auctioned 7.91% of their capture only. The reported reasons for unrecorded catch varied, with time pressure and lack of supervision being the leading factors. Most unrecorded captured fish were sold directly to buyers or taken home for consumption. Thus, the reports are considered inaccurate. Implementation of real-time data capture techniques and enhancements to marketing and auction systems was recommended. Full article

Germline stem cells (GSCs) are crucial for gametogenesis, genetic conservation, and molecular breeding. Although GSCs lines have been well studied in mammals and several model teleost species, progress in commercial marine teleosts remains limited. In this study, we report a successful establishment of a long-term stable ovarian cell line derived from the Asian seabass (Lates calcarifer), designated the Seabass Ovarian (SBO) cell line. Ovaries were dissociated using a combined collagenase–trypsin digestion protocol; the cells were propagated and maintained in DMEM supplemented with bFGF, LIF, and fish serum. The SBO cells exhibited strong alkaline phosphatase activity. Furthermore, the cultured cells robustly expressed both germ-cell specific markers (Vasa) and pluripotency associated proteins (Nanog, SSEA-1). These findings indicate the successful isolation and long-term maintenance of an ovarian cell line expressing female germline stem cell markers from Asian seabass ovaries. The established cell line not only provides a valuable in vitro model for elucidating the mechanisms behind germ cell differentiation but also serves as a crucial cellular resource for advancing genetic breeding, germplasm preservation, and surrogate broodstock technologies in marine teleosts. Full article

Japanese flounder (Paralichthys olivaceus) is an economically important species in China’s marine fishery industry. However, due to long-term intensive fishing, its wild population has declined sharply. Artificial stock enhancement has become a core measure for restoring its resources. This study aimed to investigate the effects of different immersion durations and concentrations of SrCl₂ solution (10, 20, 40, 80 mg/L) on strontium (Sr) deposition in the otoliths of P. olivaceus, and to systematically evaluate the impacts of Sr marking on the fish’s antioxidant capacity and digestive enzyme activity. The results showed that the otolith Sr/Ca ratio was positively correlated with marking concentration and duration; the optimal parameters were 40 mg/L for 4 days, with the Sr/Ca ratio returning to baseline after 30 days post-marking, and a 100% marking success rate. There were no significant differences in body length, body weight, or condition factor between the experimental groups and the control group (p > 0.05), but mortality was significantly increased in the 80 mg/L group. Digestive enzymes exhibited a dose-dependent response to Sr exposure, characterized by activation at low concentrations and inhibition at high concentrations; lipase was the most sensitive, with an inhibition threshold of 10 mg/L. Sr marking within the range of 20–40 mg/L for 4–8 days significantly activated the activity of T-AOC, CAT, GPx, and SOD (p < 0.05) and reduced MDA content, indicating that the antioxidant system was activated without causing persistent oxidative damage. In conclusion, Sr marking is a safe and efficient method for otolith marking in Paralichthys olivaceus. The recommended protocol is immersion in a 40 mg/L SrCl₂ solution for 4 days, followed by a 30-day recovery period in clean seawater before being used for stock enhancement evaluation. This study provides a scientific basis and technical support for assessing the effectiveness of stock enhancement in P. olivaceus. Full article

Monitoring marine organisms plays a vital role in biodiversity conservation, marine environmental management, and fisheries resource management. However, the underwater environment is often low-light and turbid, leading to indistinct target boundaries. Moreover, the wide variety of marine organisms—with significant differences in color, scale, texture, and morphology—can easily result in missed detections. To address these challenges, this paper proposes a multi-class marine organism detection method using multi-scale attention-enhanced You Only Look Once 11 nano (YOLO11n). The method incorporates the Convolutional Block Attention Module (CBAM) into the YOLO11n network, enabling the model to better focus on key feature regions while effectively suppressing background noise interference in complex marine environments. In addition, the model is trained using the Complete Intersection over Union (CIoU) loss function, which enhances bounding box regression accuracy, especially in handling targets of varying scales. The effectiveness of the proposed method is validated on the publicly available BrackishMOT dataset. The proposed model achieves an overall mAP@0.5 of 0.481, computed as the average AP across six organism categories. Category-wise results indicate stronger performance on visually distinguishable targets, such as Jellyfish, Starfish, and Small fish, with AP values of 0.808, 0.678, and 0.677, respectively. In contrast, performance remains limited for rare or visually ambiguous categories. These results suggest that the proposed method is effective for multi-class marine organism detection, particularly when discriminative visual features are present. Full article

Marine coastal ecosystems provide a variety of habitats for biodiversity. However, they are affected by bycatch, the unintentional capture of non-target species during fishing operations such as gillnets, trammel nets, and longlines. To mitigate bycatch, modifications such as LED and UV lights in gillnets and trammel nets and C-type (circle) hooks in longlines have been studied worldwide. Yet, studies remain limited in Türkiye. This study aimed to evaluate the effectiveness of these gear modifications in small-scale fisheries along the Aegean coast of Türkiye. Paired trials were conducted to compare standard (control) and modified (LED, UV, or C-type hook) fishing gears. Trials resulted in four sea turtles caught in LED and UV nets with no significance. Other vulnerable species caught in UV trammel nets showed significance. Overall, modified gears showed a significant reduction in commercial species catch, while increasing non-target species captures. These preliminary findings contradict much of the literature, which generally reports these modifications as effective bycatch reduction tools. The results emphasize the necessity of developing regionally adapted gear modifications and conducting more extensive experiments to validate their performance. The implementation of locally optimized bycatch mitigation tools may help achieve a balance between marine conservation and the socioeconomic sustainability of small-scale fisheries. Full article

This paper details the implementation of an integrated engineering framework for the real-time assessment of pose and size in fusiform fish, utilizing laser-camera technology. The design, comprising a camera and laser emitter, leverages laser triangulation for accurately measuring distances between key points, providing a reliable baseline for data comparison. Enhanced with the yolov7 model backbone, it includes detection and segmentation features, enabling precise image instance segmentation of fish and laser lines. The system’s dual-network structure, which combines fully connected regression and DSNT-MobileFaceNet networks, efficiently identifies six crucial landmarks on fish—an essential step for detailed pose analysis. This method facilitates the accurate determination of two-dimensional fish posture by analyzing the relative positions of these landmarks. A notable capability of this system is its ability to infer depth information from laser lines on the fish’s body, aiding in the accurate measurement of dimensions such as body length and depth. Empirical results demonstrate the system’s effectiveness, with high mean Average Precision (mAP) values for both object detection (0.9560 for fish, 0.8550 for laser lines) and segmentation (0.9740 for fish, 0.8420 for laser lines). The DSNT-MobileFaceNet network, in particular, shows excellent fitting accuracy with an $R^2$ value of 0.9170. The deep learning model achieves an average error rate of 7.75% in detecting fish data, markedly improving upon the baseline error rate of 14.70%. Overall, this study confirms the proposed system’s capability in accurately assessing fish pose and size. As a rigorous proof of concept validated in a controlled laboratory environment, this work establishes a foundational framework for non-invasive morphological monitoring, suggesting its future applicability in marine biology and aquaculture. Full article

This study considers ocean–atmosphere influences on marine productivity over the shelf of Peru. Annual fish catch since 1961 and monthly satellite phytoplankton fluorescence (FLH) since 1997 in the area 7–14 S, 80–76 W provide a basis for statistical evaluation of environmental indicators from reanalysis fields. Monthly FLH is correlated with the year-on-year change in (anchovy) fish catch, wherein the autumn season (Mar–Aug) shows optimal association. The temporal record of FLH is regressed onto various fields, and the upper and lower 10 years are identified for composite analysis. Statistical results link the Southern Oscillation to wind patterns and oceanic response, wherein greater anchovy catch tends to follow La Niña. A case study is made of the change from El Niño in 2023 to La Niña in 2024. Composites indicate that cyclonic wind vorticity spreads phytoplankton across the Peruvian shelf under La Niña, resulting in a 33% increase in fluorescence from 0.26 to 0.39. Full article

Reliable species-level information on elasmobranchs (sharks, rays, and skates) in the Arabian Gulf remains limited, despite these fish being among the most threatened marine vertebrates. Taxonomic uncertainty, driven by morphological similarities and incomplete reference datasets, continues to hinder accurate biodiversity assessments in the region. In this study, NADH dehydrogenase subunit 2 (NADH2) gene sequences were analyzed to assess the taxonomic status of elasmobranchs in United Arab Emirates waters, based on 182 specimens representing 31 species (15 sharks and 16 batoids) across 12 families. Shark lineages were consistently recovered and matched closely with published references, indicating a stable taxonomy. Batoids (rays), however, showed greater complexity, including misidentification among morphologically similar taxa, gaps in available reference sequences, and signs of possible cryptic diversity, reflecting persistent challenges in species identification and the need for more comprehensive molecular resources. Our findings highlight the value of genetic approaches in improving taxonomic resolution and establishing robust biodiversity baselines. Expanding reference databases, applying multi-locus genomic approaches, and broadening regional sampling will be essential to refining taxonomic frameworks and informing conservation management for elasmobranchs in the Arabian Gulf. Full article

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

Coastal waters of eastern Guangdong are important fishing grounds and ecologically sensitive areas in the northern South China Sea, where nekton communities are increasingly affected by environmental heterogeneity and human activities. However, systematic studies on the spatial differentiation and driving mechanisms of nekton communities in this region remain insufficient. This study aimed to clarify the community structure, diversity distribution characteristics, and key driving environmental factors of nekton in the coastal waters of eastern Guangdong, and thereby provide scientific support for an ecological health assessment and sustainable utilization of fishery resources in this region. Based on bottom-trawl survey data from 19 stations in the coastal waters of eastern Guangdong, northern South China Sea, this study systematically analyzed the species composition, dominant species, and diversity distribution pattern of nekton and their correlations with environmental factors using methods including the Index of Relative Importance, Alpha diversity indices, Beta diversity indices, and redundancy analysis. A total of 119 nekton species belonging to three phyla, four classes, 14 orders, and 56 families were collected. Among them, there were 79 fish species (accounting for 66.39%), 36 crustacean species (30.25%), and four cephalopod species (3.36%). The dominant species were Trachypenaeus curvirostris and Portunus sanguinolentus (IRI ≥ 1000). Wilcoxon’s test showed that there were significant differences in the Shannon–Wiener index, Gini–Simpson index, and Pielou’s evenness between the nearshore and offshore groups, while no significant regional difference was observed in the richness index. Cluster analysis, based on the Bray–Curtis distance, divided the 19 stations into five clusters, with significant differentiation in species composition and functional structure within the nearshore group. RDA results indicated that environmental factors collectively explained 99.66% of the variation in community structure. Particulate Inorganic Carbon (PIC), Phosphate (PO₄³⁻), Distance to Port, Summer Maximum Chlorophyll-a (Chl-a), and Total Suspended Matter (TSM) were identified as the key driving factors. The coastal waters of eastern Guangdong boast rich nekton species, with significant differences in community structure between nearshore and offshore areas. The heterogeneity of the natural environment and human activity disturbances jointly shape the nekton diversity pattern in this region. The research results can provide a theoretical basis for regional marine ecological protection and fishery resource management. Full article

Background: Studies of fish supply chain efficiency often rely on price spreads or frontier-based measures, which do not fully capture actor-level coordination performance in heterogeneous, informal supply chains. This study addresses this gap by developing a composite Market Efficiency Index (MEI) that integrates financial performance, operational quality, service equity, and relational governance. Methods: The MEI, a multidimensional alternative to frontier-based measures, was developed and applied to data collected from 250 supply chain actors in Sri Lanka. Results: The results show a clear efficiency gradient along the supply chain, with fishers scoring the lowest (MEI = 0.44), intermediaries moderate (MEI = 0.54), and retailers the highest (MEI = 0.67), yielding an overall system efficiency of 0.55 and relational governance emerging as the weakest system-level dimension. These results indicate persistent structural differences in value distribution and in how well the fish supply chain functions as a cohesive network, driven by liquidity constraints, information asymmetry, and weak cold-chain infrastructure. Conclusions: A multidimensional supply chain assessment provides a more effective basis for diagnosing coordination constraints and enables targeted digital interventions that offer feasible pathways to improve transparency, liquidity, and inclusiveness in smallholder-dominated fish supply chains. Full article

The present study evaluated the efficacy of moderate electric fields (MEFs) treatments against surimi, an intermediate seafood protein product, to enhance microbial safety and food quality at mild temperatures and electric field strength. The pathogens that have been associated with seafood, such as Listeria monocytogenes and Vibrio parahaemolyticus, were selected and investigated under varying conditions of applied MEF duty cycle (DC, 50 or 100% square-wave form with 20 kHz at 34 V/cm), temperature (20–60 °C), and treatment time (up to 10 min) against different surimi concentrations (10–20%). Microbial reductions in both L. monocytogenes and V. parahaemolyticus significantly increased with elevated temperature at higher duty cycle, and a maximum log reduction of 7.2 and 5.9 was achieved at 60 °C under both DC50% and 100% after 10 min, respectively. The potential MEF-induced inactivation of quality-deteriorating enzymes in fish products, including trimethylamine-N-oxide (TMAO) reductase, serine- and cysteine- proteases, was numerically evaluated based on enzyme-specific electrophoretic temperature rise. Overall, these findings highlight MEF as a promising hurdle technology for enhancing both microbial safety and enzyme control in marine-based protein products. Full article