Fishes

21 pages, 3926 KB

Open AccessArticle

Preliminary Study Finds LEDs, UV Lights, and C-Type Hooks May Reduce Sustainability in Aegean Small-Scale Fisheries

by Yakup Kaska, Doğan Sözbilen, Melissa Ana Vezard, Paolo Casale, Muharrem Hakan Kaykaç, Zafer Tosunoğlu and Earl Possardt

Fishes 2026, 11(5), 299; https://doi.org/10.3390/fishes11050299 - 18 May 2026

Abstract

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 [...] Read more.

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 article belongs to the Special Issue Sustainable Management of Small-Scale and Data-Limited Fisheries: Diagnosis and Strategies)

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29 pages, 9040 KB

Open AccessArticle

Integrated Laser Imaging for Fusiform Fish Measurement in Aquaculture

by Shuxian Wang, Shengmao Zhang, Yongchuang Shi, Zuli Wu and Tianfei Cheng

Fishes 2026, 11(5), 298; https://doi.org/10.3390/fishes11050298 - 18 May 2026

Abstract

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 [...] Read more.

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 article belongs to the Special Issue Computer Vision Applications for Fisheries and Aquaculture)

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17 pages, 2547 KB

Open AccessReview

Status and Development Potential of Bellamya Aquaculture in Asia: Ecology, Integrated Farming Models, and High-Value Utilization

by Wu Jin, Jianwei Liu, Benhe Ma, Xianhui Pan, Xueyan Ma, Xiaojuan Cao and Haibo Wen

Fishes 2026, 11(5), 297; https://doi.org/10.3390/fishes11050297 - 16 May 2026

Abstract

Freshwater snails, specifically those belonging to the genus Bellamya, are increasingly recognized as important components of sustainable aquaculture and aquatic ecosystem management. This review synthesizes current knowledge on their ecological roles, aquaculture practices, utilization, and associated risks to evaluate their potential as [...] Read more.

Freshwater snails, specifically those belonging to the genus Bellamya, are increasingly recognized as important components of sustainable aquaculture and aquatic ecosystem management. This review synthesizes current knowledge on their ecological roles, aquaculture practices, utilization, and associated risks to evaluate their potential as a multifunctional resource. Available evidence shows that Bellamya species function as bioindicators of environmental change and contribute to water purification through grazing, nutrient cycling, and interactions with aquatic plants. In aquaculture, diverse production systems, including rice–snail co-culture and pond-based farming, have been developed, demonstrating high resource-use efficiency and economic value. In addition to their nutritional importance as a protein source, freshwater snails provide opportunities for value-added products in food, biomaterials, and health-related applications. However, challenges remain, including parasite transmission, the bioaccumulation of environmental pollutants, genetic resource degradation, and ecological carrying capacity constraints under intensive farming. Future development depends on advances in breeding, nutrition, and intelligent farming technologies, as well as improved environmental monitoring and regulatory frameworks. Overall, freshwater snail aquaculture represents a promising pathway for integrating food production with ecosystem restoration, but its sustainable expansion requires coordinated efforts in research, management, and industry development. Full article

(This article belongs to the Special Issue Advances in Shellfish Aquaculture)

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14 pages, 510 KB

Open AccessArticle

Identification of Macrophage Migration Inhibitory Factor in Mytilus coruscus and Its Role in Methylation During Antibacterial Immunity

by Xuechun Wang, Chentenghong Yuan, Xirui Si, Pengzhi Qi and Bin Shen

Fishes 2026, 11(5), 296; https://doi.org/10.3390/fishes11050296 - 15 May 2026

Abstract

Macrophage migration inhibitory factor (MIF) is broadly acknowledged as a central pro-inflammatory regulator, owing to its multifaceted functions including immune cell recruitment, initiation and amplification of pro-inflammatory cytokine cascades, enhancement of macrophage viability, facilitation of macrophage polarization toward a pro-inflammatory state, and attenuation [...] Read more.

Macrophage migration inhibitory factor (MIF) is broadly acknowledged as a central pro-inflammatory regulator, owing to its multifaceted functions including immune cell recruitment, initiation and amplification of pro-inflammatory cytokine cascades, enhancement of macrophage viability, facilitation of macrophage polarization toward a pro-inflammatory state, and attenuation of glucocorticoid-mediated immunosuppression. However, functional investigations of MIF in Mytilus coruscus remain limited. In this study, we identified the MIF gene in M. coruscus, and bioinformatic analyses revealed that the gene encodes a 115-amino-acid polypeptide that exhibits close phylogenetic affinity with MIF homologs from other mollusks. McMIF was predominantly expressed in immune-related tissues, with notably high expression levels in the digestive gland. Upon Vibrio alginolyticus infection, both the mRNA and protein levels of McMIF were significantly upregulated, suggesting that McMIF is involved in the antibacterial immune response of M. coruscus. Meanwhile, the m6A modification level of McMIF was markedly reduced following infection, suggesting a potential relationship between m6A modification and the antibacterial immune function of MIF. Furthermore, knockdown of McMIF followed by LPS stimulation led to an increased level of apoptosis in digestive gland cells, suggesting that McMIF is involved in the inhibition of apoptosis induced by immune stimulation. Collectively, these findings provide insights into the immunological characteristics of McMIF in M. coruscus. Full article

(This article belongs to the Special Issue Advances in the Immunology of Aquatic Animals)

23 pages, 21519 KB

Open AccessArticle

Bioaccumulation of Trace Elements in the Most Commercial Fish in the Southern Black Sea and Risk Estimates Related to Their Consumption

by Levent Bat, Süleyman Özdemir, Zekiye Birinci Özdemir and Ayşah Öztekin

Fishes 2026, 11(5), 295; https://doi.org/10.3390/fishes11050295 - 15 May 2026

Abstract

This study evaluates the accumulation of trace elements (Al, Cr, Mn, Fe, Co, Ni, Cu, Zn, As, Cd, Hg, and Pb) in the muscle tissues of six commercially important fish species (Scophthalmus maximus, Merlangius merlangus, Mullus ponticus, Trachurus mediterraneus [...] Read more.

This study evaluates the accumulation of trace elements (Al, Cr, Mn, Fe, Co, Ni, Cu, Zn, As, Cd, Hg, and Pb) in the muscle tissues of six commercially important fish species (Scophthalmus maximus, Merlangius merlangus, Mullus ponticus, Trachurus mediterraneus, Engraulis encrasicolus, and Sprattus sprattus) harvested from multiple locations across the Sinop and Samsun coasts of the southern Black Sea during the 2023–2025 fishing seasons to assess potential human health risks. Element concentrations were quantified using inductively coupled plasma mass spectrometry (ICP-MS) and compared against national and international food safety standards. Results indicated that essential elements, particularly Fe and Zn, exhibited the highest concentrations, while Co and potentially toxic elements (Cd, Pb, As, and Hg) remained at lower levels. Although significant geographical variations in accumulation were observed between sampling locations, inter-species differences were relatively minor. Human health risk assessments, including Estimated Daily Intake (EDI), Target Hazard Quotient (THQ), and Carcinogenic Risk (CR), revealed that all THQ values were well below 1, indicating no non-carcinogenic concerns. Furthermore, CR values for As, Cr, and Pb fell within the acceptable range (10⁻⁶ to 10⁻⁴) defined by the U.S. EPA. Consequently, fish consumption from these regions poses no unacceptable risk, though localized element elevations suggest a need for enhanced environmental monitoring of pollution sources. Full article

(This article belongs to the Special Issue Stress Ecology of Aquatic Animals)

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18 pages, 3493 KB

Open AccessArticle

Gut Microbiota and Metabolome Differences Between Fast- and Slow-Growing Brass Gudgeon (Coreius heterodon)

by Yafan Dai, Leiming Zhang, Xingyu Ma, Bing Xie, Xueying Pei, Xiaolan Shi, Jie Mei, Tao Wang, Guoqin Zhou and Wei Liu

Fishes 2026, 11(5), 294; https://doi.org/10.3390/fishes11050294 - 15 May 2026

Abstract

The gut microbiota plays a crucial role in regulating fish growth. In this study, we performed 16S rRNA sequencing and metabolomics to compare the gut microbiota and metabolic profiles of fast-growing (FG) and slow-growing (SG) brass gudgeon (Coreius heterodon) from the [...] Read more.

The gut microbiota plays a crucial role in regulating fish growth. In this study, we performed 16S rRNA sequencing and metabolomics to compare the gut microbiota and metabolic profiles of fast-growing (FG) and slow-growing (SG) brass gudgeon (Coreius heterodon) from the same family, reared under identical conditions for 12 months. Our results revealed that there was no significant difference in the overall gut microbiota structure between FG and SG groups, but significant differences were observed at specific phylum and genus levels. The FG group harbored a greater abundance of potential probiotics (e.g., Prevotella, Lactobacillus, and Lachnospiraceae NK4A136_group), while opportunistic pathogens such as Klebsiella and Pseudomonas were less abundant. Metabolomics analysis identified 136 differential metabolites, among them, 61 were upregulated and 75 were downregulated in the FG group, with higher levels of phosphatidylcholine, acylcarnitine, and amino acid derivatives in the FG group. KEGG pathway analysis showed enrichment of butanoate metabolism, tryptophan metabolism, and pyrimidine metabolism in the FG group. Spearman correlation analysis indicated that specific gut microbiota was significantly correlated with metabolites involved in energy metabolism, gut homeostasis, and oxidative balance. These findings revealed associations between specific gut microbiota, gut metabolites, and growth performance in brass gudgeon. Although overall community structure did not differ significantly between groups, the compositional and metabolic shifts observed suggest that the gut microbiota–metabolite association might be linked to growth variation. This study provided new insights into the microbiota–metabolite–growth axis of brass gudgeon and offers valuable reference information for the development of specialized probiotic feeds for this species. Full article

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23 pages, 4364 KB

Open AccessArticle

Integrative Transcriptome and GWAS Analyses Reveal Growth-Associated Molecular Architecture in Pacific Abalone (Haliotis discus hannai)

by Hyejung Jung, Eun Soo Noh, Hyejin Kim, Hee-Bok Park, Young-Su Seo, In Jun Hwang, Hee Jeong Kong, Jung-Ha Kang and Jungwook Park

Fishes 2026, 11(5), 293; https://doi.org/10.3390/fishes11050293 - 15 May 2026

Abstract

Pacific abalone (Haliotis discus hannai) is a widely cultured and economically important abalone species in aquaculture yet improving growth performance remains a major challenge for stable production. To clarify the molecular architecture associated with growth performance in Pacific abalone, we integrated [...] Read more.

Pacific abalone (Haliotis discus hannai) is a widely cultured and economically important abalone species in aquaculture yet improving growth performance remains a major challenge for stable production. To clarify the molecular architecture associated with growth performance in Pacific abalone, we integrated transcriptome and genome-wide association study (GWAS) data from high-growth and low-growth groups showing significant growth differences. Transcriptome profiles from hepatopancreas and mantle tissues were used to construct a co-expression network of 43,125 genes, summarized into 22 modules associated with tissue specificity and growth-related variation. In parallel, analysis of a custom 60K SNP array identified 67 significant growth-associated SNPs. Integration of these GWAS signals into the co-expression network revealed a core module most strongly correlated with growth index and enriched for SNP-derived candidate genes. Functional enrichment indicated that the core module was associated with proteostasis and growth-related signaling pathways, including insulin, Ras, and MAPK signaling. Protein–protein interaction analysis further identified 11 hub genes with high intramodular connectivity and direct interactions with SNP-derived genes, most of which participate in receptor-mediated and intracellular growth-regulatory functions. These findings provide an integrated molecular framework for growth performance in Pacific abalone and candidate targets for future molecular breeding strategies. Full article

(This article belongs to the Special Issue Applications of Genome-Based Technologies in Aquaculture)

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11 pages, 743 KB

Open AccessArticle

Preference for Natural Stimuli in Juvenile Guppies

by Chiara Varracchio, Cristiano Bertolucci, Giorgio Bertorelle and Tyrone Lucon-Xiccato

Fishes 2026, 11(5), 292; https://doi.org/10.3390/fishes11050292 - 14 May 2026

Abstract

Drawing on the well-documented preference for natural and highly biodiverse environments in humans, it has been proposed that other animals may also recognise and show interest in natural stimuli. If widespread across animals, such a preference could have important evolutionary and welfare implications. [...] Read more.

Drawing on the well-documented preference for natural and highly biodiverse environments in humans, it has been proposed that other animals may also recognise and show interest in natural stimuli. If widespread across animals, such a preference could have important evolutionary and welfare implications. However, we currently lack investigations of this preference outside humans. To begin filling this gap, we examined whether juvenile guppies (Poecilia reticulata) exhibit a spontaneous preference for natural stimuli. In a dichotomous choice test, guppies were given the opportunity to choose between an environment containing live aquatic plants and one with structurally similar, in shape and size, artificial plants. After habituation to the testing apparatus, guppies spent significantly more time in the environment with live plants, suggesting a preference for natural stimuli. This supports the idea that, beyond humans, other animals may also be capable of recognizing and responding to natural stimuli. Full article

(This article belongs to the Section Physiology and Biochemistry)

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28 pages, 10868 KB

Open AccessArticle

Habitat Use, Residency, and Connectivity of Bull Sharks (Carcharhinus leucas) in the Bazaruto Seascape, Mozambique

by Stephanie K. Venables, Lukas Müller, Christoph A. Rohner, Andrea D. Marshall, Jimmy van Rijn, Nilza de Catarina, John D. Filmalter and Ryan Daly

Fishes 2026, 11(5), 291; https://doi.org/10.3390/fishes11050291 - 14 May 2026

Abstract

Bull sharks (Carcharhinus leucas) are highly mobile coastal predators, whose broad movements complicate conservation planning, particularly in the Western Indian Ocean, where key habitats remain poorly understood. Using passive acoustic telemetry, this study assessed the habitat use, residency, and regional connectivity [...] Read more.

Bull sharks (Carcharhinus leucas) are highly mobile coastal predators, whose broad movements complicate conservation planning, particularly in the Western Indian Ocean, where key habitats remain poorly understood. Using passive acoustic telemetry, this study assessed the habitat use, residency, and regional connectivity of adult bull sharks within the Bazaruto Seascape, Mozambique, evaluating the area’s ecological role within a wider movement network. Sharks tagged around Bazaruto exhibited high residency (mean R_max = 0.45) and year-round presence, with core habitat concentrated along seaward reef systems and inshore areas off the San Sebastian Peninsula. Although most core habitat areas (82%) overlapped with existing marine protected areas, important habitats extended beyond protected area boundaries. In addition to supporting resident individuals, the seascape functioned as a seasonal waypoint within a regional movement corridor, with transient sharks exhibiting short periods (<5 days) of seasonal residency (primarily between May and November). Movement patterns revealed strong connectivity with other aggregation sites along the southeast African coast and occasional long-distance movements across the Mozambique Channel to Madagascar and beyond. These findings demonstrate that the Bazaruto Seascape provides both critical habitat and acts as a connectivity node for resident and transient bull sharks, highlighting the need for conservation strategies that combine local spatial protection with broader regional and transboundary management frameworks. Full article

(This article belongs to the Special Issue Habitat as a Template for Life Histories of Fish)

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20 pages, 2315 KB

Open AccessArticle

Age and Growth of Pacific Sardine (Sardinops sagax) off the U.S. Pacific Coast, 2012–2021

by Kelsey C. James, Jonathan M. Walker, Brittany D. Schwartzkopf, Emmanis Dorval and Brad E. Erisman

Fishes 2026, 11(5), 290; https://doi.org/10.3390/fishes11050290 - 14 May 2026

Abstract

Pacific sardine (Sardinops sagax) are an economically important forage fish in the Northeast Pacific Ocean that undergo large changes in abundance over decadal scales and exhibit high individual variation in somatic growth. Past studies have suggested that somatic growth in Pacific [...] Read more.

Pacific sardine (Sardinops sagax) are an economically important forage fish in the Northeast Pacific Ocean that undergo large changes in abundance over decadal scales and exhibit high individual variation in somatic growth. Past studies have suggested that somatic growth in Pacific sardine may be density-dependent and vary regionally in response to environmental conditions. We analyzed somatic growth in Pacific sardine off the U.S. Pacific Coast during the recent period of low abundance (2012–2021) and compared the results to those of previous studies to evaluate evidence of spatial or temporal variation in growth. Sampled fish (n = 3228) ranged in length from 30 to 291 mm SL and in age from 0 to 9 years and displayed high individual variation in length-at-age and age-at-length. Length-at-age data were best explained by the von Bertalanffy growth model, and sample distribution simulations showed the dataset to be robust and unbiased. Estimated growth parameters (L_∞ = 243, K = 0.795, t₀ = −0.638) were consistent with an opportunistic life history strategy characterized by rapid growth, early maturation, and a short lifespan. While the estimated growth rate (K) was higher than in a previous study conducted during a period of high abundance and indicated that growth may be density-dependent, the parameter estimates from the previous study were influenced by sample distribution bias. Similarly, differences in study region, season, collection method, aging methods, and other factors precluded any definitive conclusions on the source of reported differences in growth patterns among studies. Full article

(This article belongs to the Special Issue Ecology of Fish: Age, Growth, Reproduction and Feeding Habits)

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21 pages, 1017 KB

Open AccessReview

Monoterpenes as Natural Anesthetics to Mitigate Stress in Fish: Advances Using the Zebrafish Larvae Model

by Raquel S. F. Vieira, Cláudia A. Rocha, Carlos A. S. Venâncio and Luís M. Félix

Fishes 2026, 11(5), 289; https://doi.org/10.3390/fishes11050289 - 13 May 2026

Abstract

During production, fish are exposed to multiple environmental, physiological, and physical stressors, which compromise development, productivity, and welfare and urge the implementation of effective and safe stress-mitigating strategies, particularly during early developmental stages. Larval zebrafish (Danio rerio) constitute a powerful model [...] Read more.

During production, fish are exposed to multiple environmental, physiological, and physical stressors, which compromise development, productivity, and welfare and urge the implementation of effective and safe stress-mitigating strategies, particularly during early developmental stages. Larval zebrafish (Danio rerio) constitute a powerful model for studying acute stress responses due to the numerous advantages they offer, such as developmental transparency, a conserved hypothalamic–pituitary–interrenal (HPI) axis, and suitability for high-throughput screening. This review examines the potential of natural monoterpenes as stress-reducing compounds and compares their performance with conventional synthetic anesthetics. Evidence from vortex-flow stress paradigms, behavioral profiling and biochemical assays shows that acute stress in zebrafish larvae triggers metabolic disruption, behavioral hyperactivity and enzyme imbalance, with cortisol responses depending on stimulus intensity. Monoterpenes such as thymol and menthol consistently reduce stress-induced hyperactivity, support redox homeostasis and display favorable safety profiles at low doses and short exposures. Nevertheless, as research into these substances is still recent, evidence of any potential adverse effects is still limited. Although individual monoterpenes may act on different subsets of molecular targets, their multimodal mechanisms, including gamma-aminobutyric acid (GABA)ergic enhancement, voltage-gated ion channel and transient receptor potential (TRP) modulation, suggest broader and potentially safer actions compared to single-target anesthetics as tricaine methane sulfonate (MS-222). Collectively, these findings suggest that monoterpenes offer promising natural alternatives for stress mitigation in aquaculture and the refinement of research procedures involving early life stages. Full article

(This article belongs to the Special Issue Fish Health and Welfare in Aquaculture and Research Settings)

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25 pages, 3387 KB

Open AccessArticle

Revealing Ontogenetic Vertical Migration in Deep-Sea Grenadiers (Macrouridae) from the Southwestern Atlantic Through Otolith Microchemistry

by César Santificetur, Rodolfo Miguel Silva, Ana Méndez, Jorge Pisonero and Alberto Teodorico Correia

Fishes 2026, 11(5), 288; https://doi.org/10.3390/fishes11050288 - 12 May 2026

Abstract

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 [...] Read more.

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

(This article belongs to the Special Issue Application of Otoliths in Fish Ecology and Fisheries)

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13 pages, 913 KB

Open AccessArticle

Biochemical Properties of Collagen from Four Flatfish Species in Cold Area: In Relation to Physiological Temperature and Amino Acid Composition

by Tetsuro Sugai, Katsuji Morioka and Kohsuke Adachi

Fishes 2026, 11(5), 287; https://doi.org/10.3390/fishes11050287 - 12 May 2026

Abstract

Collagen (ASC) was purified from four flatfish species (Greenland halibut, blackfin flounder, stone flounder, and slime flounder) collected from a cold area in Japan to investigate their biochemical properties. Sodium dodecyl sulfate–polyacrylamide gel electrophoresis pattern, Fourier transform infrared spectroscopy, and circular dichroism analysis [...] Read more.

Collagen (ASC) was purified from four flatfish species (Greenland halibut, blackfin flounder, stone flounder, and slime flounder) collected from a cold area in Japan to investigate their biochemical properties. Sodium dodecyl sulfate–polyacrylamide gel electrophoresis pattern, Fourier transform infrared spectroscopy, and circular dichroism analysis revealed the typical structure of type I collagen. The denaturation temperature (Td) of ASC positively correlated with the physiological temperature (Tp) using previously reported data, which were obtained from fish (a total of 32 species). In this study, the lowest hydroxyproline (Hyp)/Pro/imino acid (Pro + Hyp) content was observed in Greenland halibut ASC (Tp is lowest), whereas the highest Ser content was observed in slime flounder ASC (Tp is highest). Using the data obtained from a previous study, a positive/negative correlation could be found between Td and Hyp/Ser, which is consistent with our previous reports. The Pro content in the present data followed the pattern of Hyp but exceeded the value predicted from Td by approximately 30 residues. These results may suggest that the collagen extracted from four flatfish in the cold area adopted decreasing imino acid content and increasing serine content for their adaptation. Full article

(This article belongs to the Section Processing and Comprehensive Utilization of Fishery Products)

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12 pages, 245 KB

Open AccessEditorial

Challenges of Fishery Biology and Fish Population Dynamics in Fisheries Management

by María de Lourdes Jiménez-Badillo

Fishes 2026, 11(5), 286; https://doi.org/10.3390/fishes11050286 - 11 May 2026

Abstract

More than 30,000 species of bony fishes, sharks and rays have been identified worldwide [...] Full article

(This article belongs to the Special Issue The Roles of Fishery Biology and Fish Population Dynamics in Fisheries Management)

13 pages, 2268 KB

Open AccessArticle

Dietary Lysophospholipids Enhance the Function of Lutein Rather than Lycopene in Pacific White Shrimp

by Chaojie Zhu, Ziling Song, Zhengwei Ye, Yanjiao Zhang, Jiahao Liu, Lindong Xiao, Chenchen Bian, Qiang Ma, Yuliang Wei, Mengqing Liang and Houguo Xu

Fishes 2026, 11(5), 285; https://doi.org/10.3390/fishes11050285 - 11 May 2026

Abstract

Our previous studies found that lipid emulsifiers can promote the absorption and deposition of liposoluble pigments in shrimp. The present study aimed to further investigate the effects of liposoluble pigments lutein (LUT) and lycopene (LYC), and their combination with lysophospholipids (LPL), on the [...] Read more.

Our previous studies found that lipid emulsifiers can promote the absorption and deposition of liposoluble pigments in shrimp. The present study aimed to further investigate the effects of liposoluble pigments lutein (LUT) and lycopene (LYC), and their combination with lysophospholipids (LPL), on the growth performance, body coloration, and lipid composition of Pacific white shrimp Penaeusvannamei. Five diets were formulated: a control diet (Control), Control + 0.02% lutein (LUT), Control + 0.02% lycopene (LYC), LUT + 0.1% LPL (LUT + LPL), and LYC + 0.1% LPL (LYC + LPL). The feeding trial lasted for 8 weeks. There were no significant differences in shrimp growth and body composition among all groups. Both LUT and LYC increased the redness (a*) and yellowness (b*) of cooked shrimp. LPL synergistically enhanced the pigmentation-improving effects of LUT but weakened those of LYC. Additionally, LYC decreased the redness and yellowness of raw shrimp. Both LUT and LYC reduced the contents of saturated fatty acids and EPA while increasing the DHA content; LPL further enhanced this modulatory effect. In conclusion, LPL acts synergistically with LUT to improve the body coloration and modify the fatty acid composition of Pacific white shrimp, but its effect with LYC is limited. Full article

(This article belongs to the Special Issue Effect of Dietary Supplementation on the Growth and Immunity of Fish and Shellfish—3rd Edition)

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14 pages, 596 KB

Open AccessArticle

Dietary Glycerides of Short- and Medium-Chain Fatty Acids Modulate Intestinal Barrier and Protect Against Vibrio anguillarum in Juvenile Gilthead Sea Bream (Sparus aurata)

by Daniel Montero, Samira Sarih, Marta Carvalho, Félix Acosta, Luís Monzón-Atienza, Alvaro Gordillo, Ehab Aboelsaadat and Silvia Torrecillas

Fishes 2026, 11(5), 284; https://doi.org/10.3390/fishes11050284 - 10 May 2026

Abstract

As aquaculture adopts more sustainable feed formulations, interest in functional feed additives has grown to help mitigate the health and performance challenges associated with low-marine-ingredient diets. This study evaluated the effects of dietary supplementation with a commercial blend of mono-, di-, and triglycerides [...] Read more.

As aquaculture adopts more sustainable feed formulations, interest in functional feed additives has grown to help mitigate the health and performance challenges associated with low-marine-ingredient diets. This study evaluated the effects of dietary supplementation with a commercial blend of mono-, di-, and triglycerides of short- and medium-chain fatty acids (SCFAs and MCFAs; BalanGUT™ AQ P, BASF) on growth, health, and disease resistance to Vibrio anguillarum in juvenile gilthead sea bream (Sparus aurata) fed practical low fishmeal and fish oil diets. Over an 8-week trial, fish were fed diets containing 0.3%, 0.5%, or 1% of a glyceride blend of SCFAs and MCFAs (BalanGUT™ AQ P) or a Control diet without functional additive supplementation. Growth performance and feed utilization were not affected by the supplementation of SCFAs/MCFAs glycerides, although non-significant trends (p > 0.05) toward improved specific growth rate (up to 12%) and reduced feed conversion ratio (up to 17%) were observed in sea bream fed supplemented diets, particularly during the 4 initial weeks and at the highest inclusion level (1%). Moderate (0.5%) and high (1%) supplementation levels of SCFAs and MCFAs significantly improved survival following Vibrio anguillarum challenge, despite no significant changes being observed in general systemic innate immune markers, such as serum lysozyme or ACH50 activities. SCFAs/MCFAs supplementation, particularly at 0.3% or 0.5%, also modulated intestinal morphology, including thinner submucosa and smaller goblet cell area in the posterior intestine, suggestive of a more homeostatic mucosa and reduced basal inflammation when feeding a low-FM/FO-based diet. These results suggest that the protective effects of this SCFAs/MCFAs glyceride blend are mediated primarily through local rather than systemic immune modulation. Overall, this study supports the use of functional SCFAs and MCFAs glyceride blends as a functional strategy to promote resilience and health in fish fed sustainable, low-marine-ingredient diets. Full article

(This article belongs to the Special Issue Advancing Aquatic Animals Nutrition: Functional Additives and Physiological Regulation)

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25 pages, 4230 KB

Open AccessArticle

Optimization of Aeration Tube Configuration Considering the Efficiency of Waste Collection and Water Mixing in Aquaculture Tanks

by Can Cui, Dezhen Li, Fuzhi Zu, Dejun Feng, Xiaoyu Qu and Yi Tao

Fishes 2026, 11(5), 283; https://doi.org/10.3390/fishes11050283 - 9 May 2026

Abstract

Proper configuration of aeration tubes is crucial for improving water quality and promoting the welfare and growth of cultured organisms in Recirculating Aquaculture Systems (RASs). To investigate the effects of aeration tube shapes (arc-shaped, disc-shaped, and linear-shaped) and positions (d = r [...] Read more.

Proper configuration of aeration tubes is crucial for improving water quality and promoting the welfare and growth of cultured organisms in Recirculating Aquaculture Systems (RASs). To investigate the effects of aeration tube shapes (arc-shaped, disc-shaped, and linear-shaped) and positions (d = r, 1/2r) on performance, this study conducted experiments in a circular RAS tank. Methodologically, feed pellets were used to simulate solid waste, while ink was added to visualize the flow field, and mixing performance was quantitatively assessed using the spatial distribution uniformity. The results indicated that without aeration, the physical presence of the tubes affected waste collection but had minimal impact on water mixing. Under aeration conditions, placing tubes at d = 1/2r instead of d = r resulted in more efficient waste collection and improved water mixing. Waste collection performance was ranked as arc-shaped > disc-shaped > linear-shaped, whereas water mixing performance ranked linear-shaped > arc-shaped > disc-shaped. It is therefore recommended to place arc-shaped aeration tubes at d = 1/2r to achieve optimal overall performance. These findings provide valuable baseline insights into the selection and placement of aeration devices, offering preliminary practical guidance for aquaculture engineering. Full article

(This article belongs to the Section Sustainable Aquaculture)

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22 pages, 4992 KB

Open AccessArticle

Impact of Exposure Routes of Copper Oxide Nanoparticles in the Clam Ruditapes decussatus

by Maria J. Bebianno, Mustafa Tuncsoy, Thiago L. Rocha, Tania Gomes and Taina Garcia

Fishes 2026, 11(5), 282; https://doi.org/10.3390/fishes11050282 - 9 May 2026

Abstract

The increasing production of diverse applications of engineered nanoparticles along with their potential release into the marine environment from both point and diffuse sources have become a significant concern for ocean health. Due to their unique physical properties, particularly their high surface-to-volume ratio, [...] Read more.

The increasing production of diverse applications of engineered nanoparticles along with their potential release into the marine environment from both point and diffuse sources have become a significant concern for ocean health. Due to their unique physical properties, particularly their high surface-to-volume ratio, these nanoparticles can exhibit enhanced bioavailability and toxicity to marine biota. Copper oxide nanoparticles (CuO NPs) are especially prevalent due to their wide range of commercial applications. In the aquatic environment, these nanoparticles typically become part of colloidal fraction and are subjected to physicochemical transformations, leading to the formation of aggregates that eventually sink and deposit onto the bottom substrate. Therefore, sediments, in addition to the water column, act as the primary route of exposure to benthic organisms. The clam Rudipates decussatus is a marine suspension-feeder of great ecological and economic importance in Europe. Ruditapes decussatus were exposed to CuO NPs (10 μg L⁻¹) or an equivalent concentration of ionic copper (Cu²⁺) in both water and water/sediments matrices for 15 days to compare the toxicological impact of different exposure routes. Copper accumulation was monitored in both gills and digestive gland, alongside various biomarkers of susceptibility, exposure, and damage. The results revealed distinct uptake patterns that were dependent on the exposure routes, the chemical form of the metal and the specific tissue responses. Highlighting the complex impact of these contaminants on marine biodiversity. Full article

(This article belongs to the Section Environment and Climate Change)

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23 pages, 17215 KB

Open AccessArticle

Comparative In Vitro Bioactivity of Traditional Aqueous and Alcoholic Preparations of Arnica (Chiliadenus glutinosus): Effects on Marine Fish Pathogens, PLHC1 Cells and Gilthead Seabream (Sparus aurata) Leucocytes

by Jose Carlos Campos-Sánchez, Francisco A. Guardiola and María Ángeles Esteban

Fishes 2026, 11(5), 281; https://doi.org/10.3390/fishes11050281 - 9 May 2026

Abstract

Arnica (Chiliadenus glutinosus (L.) Fourr.) is an endemic plant widely used in Spanish traditional medicine as infusions and alcoholic macerates for different ailments. Despite this use, information about the biological activity of these preparations in fish-related models is scarce. In the present [...] Read more.

Arnica (Chiliadenus glutinosus (L.) Fourr.) is an endemic plant widely used in Spanish traditional medicine as infusions and alcoholic macerates for different ailments. Despite this use, information about the biological activity of these preparations in fish-related models is scarce. In the present study, the arnica extract bioactivity assay evaluated aqueous, ethanolic, and methanolic extracts at different doses (0, 0.001, 0.01, 0.125, 0.25, 0.5, and 1 mg mL⁻¹) to compare their antioxidant activity, effects on four marine fish pathogens (Vibrio harveyi, Vibrio anguillarum, Photobacterium damselae and Tenacibaculum maritimum), cytotoxicity on the PLHC1 tumour cell line, and their impact on immunological parameters in head-kidney leucocytes (HKLs) of gilthead seabream (Sparus aurata). All extracts showed dose-dependent antioxidant activity, while bactericidal effects depended on the solvent and were mainly observed at the highest concentrations. Ethanolic and methanolic extracts displayed clear cytotoxicity, whereas the aqueous extract showed lower toxicity and was selected for further evaluation. In the carrageenan stimulation assay, selected concentrations (0, 0.25, and 0.5 mg mL⁻¹) of the aqueous extract were tested in leucocytes stimulated with λ-carrageenan (0 and 1000 µg mL⁻¹), and respiratory burst and phagocytic activity, cell morphology, and gene expression were analysed. The aqueous extract reduced respiratory burst and phagocytic capacity in activated leucocytes and was associated with morphological signs of cell activation. It also downregulated crel and casp9 expression. These results provide a comparative view of the in vitro bioactivity of different traditional preparations of arnica and show that their biological effects strongly depend on the solvent used and the concentration tested, providing initial experimental information on their cellular effects in fish. Full article

(This article belongs to the Section Physiology and Biochemistry)

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