Fishes

23 pages, 5105 KiB

Open AccessArticle

Behavioral, Hematological, Histological, Physiological Regulation and Gene Expression in Response to Heat Stress in Amur Minnow (Phoxinus lagowskii)

by Weijie Mu, Jing Wang, Yanyan Zhou, Shibo Feng, Ye Huang and Qianyu Li

Fishes 2025, 10(7), 335; https://doi.org/10.3390/fishes10070335 - 8 Jul 2025

Abstract

Rising water temperatures due to climate change pose a significant threat to Phoxinus lagowskii, a cold-water fish that is ecologically vital to the high-latitude regions of China. This study assessed heat stress effects on behavioral, hematological, histological, physiological, and molecular responses in [...] Read more.

Rising water temperatures due to climate change pose a significant threat to Phoxinus lagowskii, a cold-water fish that is ecologically vital to the high-latitude regions of China. This study assessed heat stress effects on behavioral, hematological, histological, physiological, and molecular responses in P. lagowskii. The critical maximum temperature (CT_max) was determined using the loss of equilibrium (LOE) method, with the CT_max reaching 29 °C. Elevated temperatures lead to an increase in the OBR. Fish were subjected to acute heat stress at 28 °C (below CT_max) for 48 h, with samples collected during the 48 h period. RBC, WBC, HGB, and HCT significantly increased during heat stress but decreased 12 h after heat stress. The levels of serum cortisol and blood glucose after heat stress were significantly higher than those in the control group. After heat stress, the height of the ILCM in the gills increased significantly, and the liver exhibited vacuolar degeneration and hypopigmentation. The activities of Na⁺-K⁺-ATPase and Ca²⁺-Mg²⁺-ATPase in the gills initially increased and then decreased over the duration of heat stress. Most enzyme activities (PK, LDH, PFK, and HK) decreased during heat stress, while LPL and HL levels increased, indicating that lipid metabolism was the primary utilization process under heat stress. There was an increase in SOD activity at 12 h, followed by a decrease at 24 h, and an increase in CAT activity under heat stress. Integrated biomarker response (IBR) and principal component analysis (PCA) were employed to synthesize multi-level responses. The IBR values reached their peak at 3 h and 48 h of heat stress. We observed an upregulation of heat shock proteins (Hsp70, Hsp90, and Hsc70) as well as interleukin-10 (IL-10) in response to heat stress. Our findings offer novel insights into the mechanisms underlying the heat stress response in P. lagowskii, thereby enhancing our understanding of the effects of heat stress on cold-water fish. Full article

(This article belongs to the Special Issue Environmental Physiology of Aquatic Animals)

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14 pages, 665 KiB

Open AccessArticle

Evaluation of Three Atlantic Salmon Strains for Resistance to Copepodid Sea Lice Attachment

by Michael R. Pietrak, Thomas A. Delomas, Demitri Lifgren and Mark P. Polinski

Fishes 2025, 10(7), 334; https://doi.org/10.3390/fishes10070334 - 8 Jul 2025

Abstract

Sea lice have been a persistent pest of the salmon farming industry for more than 50 years. In this study, we aimed to identify if different strains of Atlantic salmon with discrete long-term lice exposure histories had variable resistance to copepodid attachment and/or [...] Read more.

Sea lice have been a persistent pest of the salmon farming industry for more than 50 years. In this study, we aimed to identify if different strains of Atlantic salmon with discrete long-term lice exposure histories had variable resistance to copepodid attachment and/or different attachment-specific transcriptome patterns. We additionally sought to characterize lice distributions on fins, head, and skin and identify if attachment location influenced transcriptomic profiles of lice. Lice counts were correlated with body size and highest on St. John River (SJR; open ocean-run) relative to Grand Lakes Stream (GLS; 200-year restricted ocean-run) or Sebago Lake (CAS; ~11,000 years landlocked) Atlantic salmon. However, lice density was similar between strains. Skin and fins had expectedly different transcriptomic profiles; however, notable differences were not observed between salmon strains. Variance in lice transcriptomes was minimally affected by attachment location even though lice strongly preferred fins relative to head or body. Attached lice did have different transcriptomic profiles on GLS relative to CAS or SJR. This study cumulatively identified a minimal host evolutionary component for sea lice attachment resistance, although lice behavior post-attachment appeared somewhat affected by strain. Non-uniform settlement distributions and tank-specific variability in lice attachment were observed across populations. Full article

(This article belongs to the Section Fish Pathology and Parasitology)

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18 pages, 2761 KiB

Open AccessArticle

Transcriptomic Profiling of Misgurnus anguillicaudatus Reveals the Anti-Inflammatory Action of Lonicera japonica Extract in Response to Lipopolysaccharide Challenge

by Yue Zhao, Chen Wang and Qiuning Liu

Fishes 2025, 10(7), 333; https://doi.org/10.3390/fishes10070333 - 7 Jul 2025

Abstract

Honeysuckle, derived from the dried flower buds or blossoms of Lonicera japonica Thunb, is a traditional Chinese medicine known for its properties in eliminating heat and toxins, reducing inflammation, and alleviating swelling. In this study, we investigated the potential therapeutic and preventive benefits [...] Read more.

Honeysuckle, derived from the dried flower buds or blossoms of Lonicera japonica Thunb, is a traditional Chinese medicine known for its properties in eliminating heat and toxins, reducing inflammation, and alleviating swelling. In this study, we investigated the potential therapeutic and preventive benefits of L. japonica extract on inflammatory diseases induced by lipopolysaccharide (LPS) using Misgurnus anguillicaudatus as a model organism. The fish were fed a diet supplemented with L. japonica extract, followed by LPS injection to induce inflammation. We then analyzed the transcriptional profile to identify differentially expressed genes (DEGs). A total of 6611 DEGs were identified through comprehensive analysis, including Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analyses. Our results revealed significant enrichment of DEGs in pathways associated with proteasome function, immune system regulation, and infectious disease response. These findings suggest a strong correlation between L. japonica and immune defense mechanisms, providing valuable insights into the potential anti-inflammatory effects of this plant, particularly in the context of LPS-induced inflammation. This study highlights the potential use of L. japonica in treating inflammatory diseases and underscores its role in immune regulation. Full article

(This article belongs to the Special Issue Molecular Mechanism of Fish Immune Response to Pathogens)

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15 pages, 1974 KiB

Open AccessArticle

Comparing Year-Class Strength Indices from Longitudinal Analysis of Catch-at-Age Data with Those from Catch-Curve Regression: Application to Lake Huron Lake Trout

by Ji X. He and Charles P. Madenjian

Fishes 2025, 10(7), 332; https://doi.org/10.3390/fishes10070332 - 7 Jul 2025

Abstract

Fish year-class strength (YCS) has been estimated via longitudinal analysis of catch-at-age data and via catch-curve regression, but no study has compared the two approaches. The objective of this study was to compare YCS estimates between the two approaches with application to the [...] Read more.

Fish year-class strength (YCS) has been estimated via longitudinal analysis of catch-at-age data and via catch-curve regression, but no study has compared the two approaches. The objective of this study was to compare YCS estimates between the two approaches with application to the lake trout (Salvelinus namaycush) population in the main basin of Lake Huron, one of the Laurentian Great Lakes of North America. YCSs were reconstructed for both hatchery-stocked and wild lake trout. Akaike information criterion (AIC) and Bayesian information criterion (BIC) were used to compare 14 linear mixed-effects models for longitudinal analysis of catch-at-age data, and three linear mixed-effects models for catch-curve regression. From the best models based on AIC or BIC comparisons, YCS estimates with year-class as a fixed effect were consistent with those estimated with year-class as a random effect. Estimated YCS patterns and trends were the same or similar between the longitudinal analysis and the catch-curve regression, indicating that both approaches provide robust estimates of YCS. Potential bias in using the approach of catch-curve regression could be caused by abrupt changes in adult mortality. It is also critical to recognize multiple recruitment origins for using the approach of longitudinal analysis of catch-at-age data. Full article

(This article belongs to the Section Biology and Ecology)

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14 pages, 239 KiB

Open AccessArticle

Effects of Powdered Salmon Roe Processing Liquid on Enhancing the Palatability of Tuna By-Product Meal-Based Diets in Greater Amberjack (Seriola dumerili)

by Amal Biswas, Ryoma Maruyama, Satoshi Okimura, Hiroshi Fushimi, Hiroya Sato, Yoshihiro Kakinuma, Tomoki Honryo and Hideki Tanaka

Fishes 2025, 10(7), 331; https://doi.org/10.3390/fishes10070331 - 4 Jul 2025

Abstract

A two-factorial experiment was conducted to evaluate the potential for improving the palatability and utilization of tuna by-product meal (TBM) as a replacement for fish meal (FM) via supplementing the diet of juvenile greater amberjack (Seriola dumerili) with powdered salmon roe [...] Read more.

A two-factorial experiment was conducted to evaluate the potential for improving the palatability and utilization of tuna by-product meal (TBM) as a replacement for fish meal (FM) via supplementing the diet of juvenile greater amberjack (Seriola dumerili) with powdered salmon roe liquid (PSRL). FM protein in the control diet (C) was partially replaced with TBM at levels of 25% (T25R0) and 40% (T40R0). PSRL was then added at 5% and 10% to both the T25R0 and T40R0 diets, resulting in the formulations T25R5, T25R10, T40R5, and T40R10. After a 6-week rearing period, during which groups of 30 juveniles (mean initial weight of approximately 1.7 g) were stocked in 500 L tanks, there were no significant differences in the final mean weight, weight gain, or specific growth rate among fish fed diets C, T25R0, and T25R5. However, the other experimental diets showed significantly lower values compared to the C diet (p < 0.05). PSRL supplementation did not significantly enhance either palatability or feeding rate in TBM-based diets (p > 0.05). Two-way ANOVA indicated that only FM replacement with TBM had a significant effect on the growth parameters mentioned above (p < 0.05). A significantly lower whole-body crude lipid content was observed in all test diets compared to that in the C diet, resulting in significantly lower lipid retention efficiency in all test groups except T25R5 and T25R10 (p < 0.05). These results suggest that 25% of FM protein can be replaced with TBM protein in the diet of juvenile greater amberjack, but PSRL does not effectively address the palatability issues associated with TBM-based diets. Full article

(This article belongs to the Section Nutrition and Feeding)

22 pages, 2652 KiB

Open AccessReview

Content of Short-Lived Radionuclides (⁹⁵Zr, ⁹⁵Nb, ¹⁰³Ru, and ¹⁰⁶Ru) in Fish

by Nataliia E. Zarubina, Vladislav Semak and Liliia P. Ponomarenko

Fishes 2025, 10(7), 330; https://doi.org/10.3390/fishes10070330 - 4 Jul 2025

Abstract

This review addresses the intake, distribution, and bioaccumulation of the short-lived radionuclides ⁹⁵Zr, ⁹⁵Nb, ¹⁰³Ru, and ¹⁰⁶Ru in aquatic ecosystems before and after the 1986 accident at the Chornobyl Nuclear Power Plant. Particular attention is given to a detailed [...] Read more.

This review addresses the intake, distribution, and bioaccumulation of the short-lived radionuclides ⁹⁵Zr, ⁹⁵Nb, ¹⁰³Ru, and ¹⁰⁶Ru in aquatic ecosystems before and after the 1986 accident at the Chornobyl Nuclear Power Plant. Particular attention is given to a detailed analysis of these processes in fish belonging to different ecological groups, as well as in their various organs and tissues. Observational data indicate that ⁹⁵Zr and ⁹⁵Nb predominantly accumulate in external organs, with comparatively lower concentrations observed in internal organs. In contrast, ¹⁰³Ru and ¹⁰⁶Ru exhibit higher bioavailability and a marked tendency to accumulate in internal tissues. A notable feature of ¹⁰⁶Ru is its gradual increase in muscle tissue over time following the accident. These findings are critical for advancing our understanding and assessment of the ecological status of contaminated aquatic environments, for predicting the long-term impacts of accidental radionuclide release, and for informing strategies related to environmental monitoring and the safe exploitation of aquatic biological resources. Full article

(This article belongs to the Section Biology and Ecology)

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17 pages, 8305 KiB

Open AccessArticle

Characterization and Analysis of the Role of Corazonin in Regulating Ovarian Development in the Mud Crab Scylla paramamosain

by Shiying Yang, Liangjie Liu, Yiwei Tang, An Liu and Haihui Ye

Fishes 2025, 10(7), 329; https://doi.org/10.3390/fishes10070329 - 4 Jul 2025

Abstract

Corazonin (Crz) is widely found in insects and crustaceans. In insects, Crz participates in the regulation of various physiological activities, including heartbeat, body color change, molting, and reproduction. However, the physiological effects of Crz in crustaceans remain largely unclear. In this study, the [...] Read more.

Corazonin (Crz) is widely found in insects and crustaceans. In insects, Crz participates in the regulation of various physiological activities, including heartbeat, body color change, molting, and reproduction. However, the physiological effects of Crz in crustaceans remain largely unclear. In this study, the cDNAs encoding Crz and its putative receptor were isolated from the mud crab Scylla paramamosain. Tissue distribution analysis revealed that Sp-Crz was predominantly expressed in neural tissues, while its receptor (Sp-CrzR) was widely expressed in S. paramamosain, with a high expression level in the Y-organ. During ovarian development, Sp-Crz expression in the eyestalk ganglion was upregulated at the early and late vitellogenic stages, whereas its expression level in the cerebral ganglion displayed an initial downregulation at the early stage, followed by a remarkable upregulation at the late vitellogenic stage. The expression level of Sp-CrzR mRNA in the ovary increased significantly at the late vitellogenic stage. However, an opposite expression pattern was observed in the hepatopancreas and Y-organ. The immunohistochemistry result showed that Sp-Crz was distributed in the cells of the lamina ganglionaris, the medulla interna, and the X-organ of the eyestalk ganglion. It was revealed that the level of Sp-Vg in the hepatopancreas was not affected by the addition of Sp-Crz in vitro. However, the expression of Sp-VgR in ovarian explants was significantly induced by 6 h treatment with Sp-Crz at a concentration of 1 nM. In addition, the level of Sp-VgR in the ovary was significantly upregulated by 12 h injection of Sp-Crz. After long-term administration of Sp-Crz, the expression of Sp-VgR in the ovary, the E₂ content in hemolymph, the oocyte diameter, and the gonadosomatic index of S. paramamosain were significantly increased. In summary, these findings collectively indicate that the Sp-Crz signaling system participates in regulating the ovarian development of the mud crab. This study provides a new insight into the biological function of Crz during the ovarian development of the mud crab, which is of great significance for the sustainable development and utilization of mud crab resources. Full article

(This article belongs to the Section Aquatic Invertebrates)

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26 pages, 1724 KiB

Open AccessArticle

Phosphorus Pools Associated with Fish in the Archipelago Sea

by Harri Helminen

Fishes 2025, 10(7), 328; https://doi.org/10.3390/fishes10070328 - 3 Jul 2025

Abstract

This study compiles and updates data to construct the phosphorus budget of the Archipelago Sea (northern Baltic Sea, Europe), with a particular focus on estimating phosphorus pools associated with fish populations. Biomass data and species-specific phosphorus content were utilized, and a bioenergetic modeling [...] Read more.

This study compiles and updates data to construct the phosphorus budget of the Archipelago Sea (northern Baltic Sea, Europe), with a particular focus on estimating phosphorus pools associated with fish populations. Biomass data and species-specific phosphorus content were utilized, and a bioenergetic modeling approach was applied to Baltic herring (Clupea harengus membras) and European perch (Perca fluviatilis) to estimate species-specific food consumption and nutrient excretion. Between 2001 and 2024, average total phosphorus concentrations were 28% higher than during the baseline period of 1983–1989. From 1998 to 2023, the annual average fish catch in the Archipelago Sea was 15,516.5 tons (16.3 kg/ha), with 73.1% consisting of commercially harvested herring. Other abundant catch species included, for example, pikeperch (Sander lucioperca), northern pike (Esox lucius), and European smelt (Osmerus eperlanus). On average, the annual catch contained 83.4 tons of phosphorus. Fishing may have annually removed an amount of phosphorus equivalent to approximately 0.6% of the total phosphorus pool in the water column and surface sediment, or 1.4% of the estimated total phosphorus load to the Archipelago Sea. The contribution of fish to phosphorus turnover is minor, as nutrient recycling is dominated by plankton. Planktivorous fish and their prey recycle nutrients already present in the water column and are therefore not the primary drivers of eutrophication. Full article

(This article belongs to the Section Biology and Ecology)

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18 pages, 6861 KiB

Open AccessArticle

Evolutionary Dynamics and Functional Conservation of amh Signaling in Teleost Lineages

by Lingqun Zhang, Qingke Zhang, Kai Hu, Wei Lu, Weigang Li, Fengchi Wang and Jie Cheng

Fishes 2025, 10(7), 327; https://doi.org/10.3390/fishes10070327 - 3 Jul 2025

Abstract

The anti-Müllerian hormone (amh) and its receptor, amhr2, along with the downstream bone morphogenetic protein receptors (bmprs), have been recognized as the central regulators in teleost sex determination (SD) and differentiation. However, their evolution and function in reproduction [...] Read more.

The anti-Müllerian hormone (amh) and its receptor, amhr2, along with the downstream bone morphogenetic protein receptors (bmprs), have been recognized as the central regulators in teleost sex determination (SD) and differentiation. However, their evolution and function in reproduction among diverse teleost lineages may represent species-specific patterns and still need more explanation. In this study, systematic investigations of amh signaling genes, including amh, amhy (Y-linked paralog of amh), amhr2, bmpr1, and bmpr2, were conducted among teleost species. The results revealed generally conserved gene copy number, phylogeny, structure, and synteny, among teleost amh signaling genes. Notably, significantly accelerated evolutionary rates (dN/dS) were found in teleost amhy compared to amh, and amh exhibited faster molecular evolution in amhy-SD teleosts than in non-amhy-SD teleosts, suggesting their enhanced evolutionary plasticity in teleosts. Expression profiling identified testis-biased expression of the most amh signaling genes in fish species with different SD genes and mechanisms, including Lateolabrax maculatus and Dicentrarchus labrax from Order Perciformes, Cynoglossus semilaevis and Paralichthys olivaceus from Order Pleuronectiformes, and Salmo salar and Oncorhynchus mykiss from Order Salmoniformes, with ovary-biased expression also found in Salmoniformes. A weighted gene co-expression network analysis further uncovered strong species-specific functional interactions between amh signaling components and genes of germ-cell development, the meiotic process, etc. Collectively, the integrated evidence from this study supports the hypothesis that amh signaling provides the key molecules governing sex differentiation in a species-specific manner in diverse teleost lineages, independent of its SD role, and interacts with functions of both testis and ovary development. Full article

(This article belongs to the Special Issue Sex and Reproductive Regulation in Marine Animals)

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13 pages, 1652 KiB

Open AccessArticle

Effect of Stocking Density on Water Quality, Harmful Nitrogen Control, and Production Performance of Penaeus vannamei in Biofloc-Based Systems with Limited Water Exchange

by Wujie Xu, Bin Zhang, Yongzhen Zhao and Yucheng Cao

Fishes 2025, 10(7), 326; https://doi.org/10.3390/fishes10070326 - 3 Jul 2025

Abstract

Biofloc technology (BFT) represents a promising approach among sustainable options for the sustainable intensification of shrimp aquaculture, helping to mitigate environmental impacts while maintaining production yields. This study evaluated the effects of stocking density (200, 400, 600, and 800 ind/m³) on [...] Read more.

Biofloc technology (BFT) represents a promising approach among sustainable options for the sustainable intensification of shrimp aquaculture, helping to mitigate environmental impacts while maintaining production yields. This study evaluated the effects of stocking density (200, 400, 600, and 800 ind/m³) on the water quality, nitrogen dynamics, and production performance of Penaeus vannamei in BFT systems with limited water exchange (<10%). During an eight-week production-scale trial, water quality exhibited density-dependent deterioration, with TAN and NO₂⁻-N peaks increasing from 0.4 to 2.3 mg/L and 1.0 to 4.2 mg/L, respectively, as density rose from 200 to 800 ind/m³. Concurrently, DO and pH declined significantly from 6.7 to 5.1 mg/L and 7.6 to 7.3, respectively. Production performance revealed critical trade-offs: while yield rose from 3.62 to 9.09 kg/m³, individual growth metrics declined, including harvest body weight (19.14 to 14.12 g), size variation (14.03% to 23.90%), and survival rate (94.6% to 79.8%). Quadratic regression analysis and response surface analysis identified 400~600 ind/m³ as the optimal density range, achieving balanced outcomes: yield (6.74~8.43 kg/m³), harvest body weight (16.72~18.03 g), survival rate (84.0%~93.5%), and feed conversion ratio (1.14~1.22). These findings provide actionable guidelines for optimizing stocking density in commercial BFT systems, highlighting the importance of balancing productivity with environmental sustainability under limited water exchange. Full article

(This article belongs to the Special Issue Advances in Shrimp Aquaculture: Management and Sustainability)

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15 pages, 2319 KiB

Open AccessArticle

Visual Characterization of Male and Female Greenshell™ Mussels (Perna canaliculus) from New Zealand Using Image-Based Shape and Color Analysis

by Murat O. Balaban, Graham C. Fletcher and Meng Zhou

Fishes 2025, 10(7), 325; https://doi.org/10.3390/fishes10070325 - 3 Jul 2025

Abstract

Machine vision/image analysis is used in the sorting and handling of many aquatic species. Pictures of 474 New Zealand Greenshell™ (Perna canaliculus, Gmelin, 1791) whole unopened mussels (215 females and 259 males) from the top and from the side were analyzed [...] Read more.

Machine vision/image analysis is used in the sorting and handling of many aquatic species. Pictures of 474 New Zealand Greenshell™ (Perna canaliculus, Gmelin, 1791) whole unopened mussels (215 females and 259 males) from the top and from the side were analyzed to evaluate if visual attributes (size, shape, and color) can be used to differentiate gender. Size (length, width, height, and view area), color, and shape (by elliptic Fourier analysis and by ray length-ray angle analysis) were analyzed and differences by gender tested. Application of Artificial Neural Networks (ANN), Principal Component Analysis (PCA), Canonical Discriminant Analysis (CDA), and Random Forest (RF) to the shape parameters failed to reliably predict gender. Comprehensive morphometric and color characterization of males and females, as well as shape parameters, are presented as a reference for future image-based research. The parasitic crustacean pea crab can change the shape of mussel shells, and elliptic Fourier analysis can quantify this difference. Full article

(This article belongs to the Section Aquatic Invertebrates)

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18 pages, 2731 KiB

Open AccessArticle

Effects of Co-Feeding Dry and Live Feed from the Onset of Exogenous Feeding on Red Seabream Pagrus major Larviculture and Pre-Growing

by Sofia Brinkmann Bougali, Nafsika Karakatsouli, Kostas Ntomalis, Anemos Kastelis, Vasiliki-Anna Alexopoulou, Alkisti Batzina and Isidoros Markakis

Fishes 2025, 10(7), 324; https://doi.org/10.3390/fishes10070324 - 3 Jul 2025

Abstract

Current feeding protocols used in commercial hatcheries of Mediterranean fish species are, for a species-dependent period after hatching, based on live feeds which have often raised issues of biosecurity, stability, availability, price and nutrients content. Instead, dry feeds can offer stability in nutritional [...] Read more.

Current feeding protocols used in commercial hatcheries of Mediterranean fish species are, for a species-dependent period after hatching, based on live feeds which have often raised issues of biosecurity, stability, availability, price and nutrients content. Instead, dry feeds can offer stability in nutritional value, price and supply. The aim of the present study was to evaluate an alternative feeding protocol by co-feeding live and dry feed at first feeding red seabream larvae (on 3 days post-hatching—3 dph, DF3) and to compare it to a standard feeding protocol (i.e., dry feed introduced on 22 dph, DF22). Larvae productivity and functional development of the digestive system were evaluated under actual production conditions in a commercial hatchery. Additionally, post-larvae efficiency during pre-growing was evaluated under controlled laboratory conditions. The results obtained showed that the experimental protocol (DF3) promoted larval growth without affecting larval survival and the efficiency of the digestion processes. After pre-growing, DF3-produced juveniles showed a decreased incidence of spinal cord malformations, while the initially gained growth advantage was maintained. The present study shows the feasibility of an alternative feeding protocol for red seabream intensive larviculture and points out the critical role that larval rearing may have for later production stages. Full article

(This article belongs to the Section Nutrition and Feeding)

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15 pages, 2654 KiB

Open AccessArticle

Presence and Potential Effect of Microplastics Associated with Anthropic Activity in Two Benthic Fishes Serranus scriba and Lithognathus mormyrus

by Amanda Cohen-Sánchez, Juan Alejandro Sanz, Montserrat Compa, Maria Magdalena Quetglas-Llabrés, Maria del Mar Ribas-Taberner, Lorenzo Gil, Silvia Tejada, Samuel Pinya and Antoni Sureda

Fishes 2025, 10(7), 323; https://doi.org/10.3390/fishes10070323 - 3 Jul 2025

Abstract

Plastic pollution poses a massive problem to the environment, particularly seas and oceans. Microplastics (MPs) ingestion by marine species can generate many adverse effects, including causing oxidative stress. This study evaluated the effects of anthropic activity-related MP presence in two coastal fish species— [...] Read more.

Plastic pollution poses a massive problem to the environment, particularly seas and oceans. Microplastics (MPs) ingestion by marine species can generate many adverse effects, including causing oxidative stress. This study evaluated the effects of anthropic activity-related MP presence in two coastal fish species—Serranus scriba (more related to rocky bottoms) and Lithognathus mormyrus (more related to sandy bottoms)—in two areas of Mallorca Island (Western Mediterranean) with varying anthropic pressures with similar mixed rocky/sandy bottoms. A total of eight fish samples per species and per area (total n = 32), as well as three water samples (500 mL each) and three sediment samples per area, were collected and analyzed. The results showed that despite plastic presence in both areas, the area with higher tourism affluence was also the most polluted. Fourier transform infrared spectroscopy analysis confirmed that the majority of recovered polymers were polyethylene and polypropylene. The pattern of MPs presence was reflected in the biomarker analysis, which showed higher values of antioxidants, namely catalase (CAT) and superoxide dismutase (SOD); detoxification, namely glutathione s-transferase (GST); and inflammation, namely myeloperoxidase (MPO)—enzymes in the gastrointestinal tract of fish from the more polluted area. However, no statistical differences were found for malondialdehyde (MDA) as a marker of lipid peroxidation. As for differences between species, S. scriba presented a higher presence of MPs and measured biomarkers than in L. Mormyrus, suggesting higher exposure. In conclusion, these results showed that increased anthropic activity is associated with a higher presence of MPs which, in turn, induces an adaptative response in exposed fish. Moreover, species living in the same area could be differentially affected by MPs, which is probably associated with different behavioural and feeding habits. Full article

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

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14 pages, 1561 KiB

Open AccessArticle

Estimates on Age, Growth, Sex Composition, and Mortality of Silurus lanzhouensis (Chen, 1977) in the Upper Yellow River, China

by Peilun Li, Jiacheng Liu, Shuhan Xiong, Tai Wang, Yongjie Wang and Jilong Wang

Fishes 2025, 10(7), 322; https://doi.org/10.3390/fishes10070322 - 3 Jul 2025

Abstract

Silurus lanzhouensis is a large-sized commercial fish species endemic to the mid-upper reaches of the Yellow River, serving as a “Card of Aquatic Biological Species in the Yellow River”. However, due to factors such as overfishing and habitat changes, it has been listed [...] Read more.

Silurus lanzhouensis is a large-sized commercial fish species endemic to the mid-upper reaches of the Yellow River, serving as a “Card of Aquatic Biological Species in the Yellow River”. However, due to factors such as overfishing and habitat changes, it has been listed as an endangered species. In order to protect and restore its wild resources, we conducted a detailed study for the first time from 2022 to 2024 on the age composition, growth characteristics, mortality rate, and current status of resource exploitation of the S. lanzhouensis population in the upper Yellow River. A total of 489 individuals underwent measurements for their total length (L) and body weight (W), with age determination conducted using lapillus otoliths. The collected samples exhibited a spectrum of total lengths spanning from 2.5 to 63.7 cm, body weights ranging from 0.11 to 1974.15 g, and ages ranging from 1 to 6 years. Further analysis of the length–weight relationships unveiled an allometric growth index (b) of 2.9562 for the overall samples, indicating an isometric growth pattern. Additionally, insights into the growth characteristics of S. lanzhouensis were provided by the von Bertalanffy growth function, revealing an asymptotic total length (L_∞) of 119.30 cm and a growth coefficient (K) of 0.1278 yr⁻¹. The growth characteristic index (φ) totaled 3.2598, suggesting a moderate growth rate in comparison to other Silurus species. The total mortality rate (Z) recorded for the population of S. lanzhouensis was found to be 0.5296 yr⁻¹. Through the application of three distinct methodologies on exhaustive samples, the average natural mortality rate (M) was calculated to be 0.3105 yr⁻¹. Consequently, the fishing mortality rate (F) for the entire sample set was determined to be 0.2191 yr⁻¹, leading to an exploitation rate (E) of 0.4137. Based on the survey findings, it is evident that the population of S. lanzhouensis has not been subjected to over-exploitation, attributable to ongoing stock enhancement. These results also provide foundational data for the protection and restoration of S. lanzhouensis in the upper Yellow River. Full article

(This article belongs to the Section Biology and Ecology)

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23 pages, 2732 KiB

Open AccessArticle

Impacts of Low-Order Stream Connectivity Restoration Projects on Aquatic Habitat and Fish Diversity

by Xinfeng Li, Xuan Che, Xiaolong Chen, Changfeng Tian and Jiahua Zhang

Fishes 2025, 10(7), 321; https://doi.org/10.3390/fishes10070321 - 2 Jul 2025

Abstract

River barriers constitute a key factor that is degrading river connectivity and represent a critical research focus in riverine ecosystem conservation. Management authorities and river restoration agencies globally have increasingly employed barrier removal or modification for connectivity restoration projects in recent years, practices [...] Read more.

River barriers constitute a key factor that is degrading river connectivity and represent a critical research focus in riverine ecosystem conservation. Management authorities and river restoration agencies globally have increasingly employed barrier removal or modification for connectivity restoration projects in recent years, practices that are widely discussed and empirically supported in academia. However, existing research predominantly focuses on large dams in primary rivers, overlooking the more severe fragmentation caused by low-head barriers within low-order streams. This study targets the Yanjing River (total length: 70 km), a third-order tributary of the Yangtze River basin, implementing culvert modification and complete removal measures, respectively, for two river barriers distributed within its terminal 9 km reach. Using differential analysis, principal component analysis (PCA), cluster analysis, Mantel tests, and structural equation modeling (SEM), we systematically examined the mechanisms by which connectivity restoration projects influences aquatic habitat and fish diversity, the evolution of reach heterogeneity, and intrinsic relationships between aquatic environmental factors and diversity metrics. Results indicate that (1) the post-restoration aquatic habitat significantly improved with marked increases in fish diversity metrics, where hydrochemical factors and species diversity exhibited the highest sensitivity to connectivity changes; (2) following restoration, the initially barrier-fragmented river segments (upstream, middle, downstream) exhibited significantly decreased differences in aquatic habitat and fish diversity, demonstrating progressive homogenization across reaches; (3) hydrological factors exerted stronger positive effects on fish diversity than hydrochemical factors did, particularly enhancing species diversity, with a significant positive synergistic effect observed between species diversity and functional diversity. These studies demonstrate that “culvert modification and barrier removal” represent effective project measures for promoting connectivity restoration in low-order streams and eliciting positive ecological effects, though they may reduce the spatial heterogeneity of short-reach rivers in the short term. It is noteworthy that connectivity restoration projects should prioritize the appropriate improvement of hydrological factors such as flow velocity, water depth, and water surface width. Full article

(This article belongs to the Special Issue Biodiversity and Spatial Distribution of Fishes, Second Edition)

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17 pages, 8160 KiB

Open AccessArticle

Modeling the Hydrolysis of Soybean Flour Proteins Digested with Gastric Proteases of the Marine Fish Sparus aurata and Commercial Non-Starch Polysaccharidases

by Óscar Martínez, Lorenzo Márquez, Francisco J. Moyano and Manuel Díaz

Fishes 2025, 10(7), 320; https://doi.org/10.3390/fishes10070320 - 2 Jul 2025

Abstract

Soybean flours are widely used as a protein-rich ingredient in fish aquafeeds, and to obtain value-added compounds after a previous treatment with proteases. Additionally, non-starch polysaccharidases (NSPases) enhance dietary protein bioaccessibility and have been used as feed additives. In this study, defatted soybean [...] Read more.

Soybean flours are widely used as a protein-rich ingredient in fish aquafeeds, and to obtain value-added compounds after a previous treatment with proteases. Additionally, non-starch polysaccharidases (NSPases) enhance dietary protein bioaccessibility and have been used as feed additives. In this study, defatted soybean flour was hydrolyzed using Sparus aurata gastric proteases and varying doses of a commercial blend of acidic NSPases. Reactions occurred at 25 °C for 3 h under typical fish stomach pH conditions (3.5–5.6). We modeled the hydrolytic process using response surface methodology, focusing on the released peptides and carbohydrates. The main finding was the efficient control of the degree of protein hydrolysis. We achieved 6–25% hydrolysis for peptides below 10 kDa by adjusting the carbohydrase dose and reaction pH. This work confirms that acidic commercial NSPases improve soybean flour protein hydrolysis when combined with S. aurata gastric proteases. Full article

(This article belongs to the Section Nutrition and Feeding)

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10 pages, 1499 KiB

Open AccessArticle

Habitat Matters: Behavior and Activity of Round Goby (Neogobius melanostomus) at Different Substrates

by Anna Dziubińska, Mariusz Sapota and Emilia Socha

Fishes 2025, 10(7), 319; https://doi.org/10.3390/fishes10070319 - 2 Jul 2025

Abstract

This study focuses on the behavior of the Round Goby in relation to various types of hard substrates, which may be crucial in the context of the emergence of hydrotechnical structures in their habitat. The aim of this study was to determine the [...] Read more.

This study focuses on the behavior of the Round Goby in relation to various types of hard substrates, which may be crucial in the context of the emergence of hydrotechnical structures in their habitat. The aim of this study was to determine the behavior and habitat preferences of the Round Goby in relation to specific types of hard substrates. Three types of substrates were used in the experiments: bare, colonized by benthic organisms, and rocky. Laboratory observations were conducted and divided into three variants, each with two cycles—daytime and nighttime. Each variant involved different combinations of two substrates. It was found that during the day, fish spent more time on vegetated substrates than on bare or rocky ones. At night, the opposite trend was observed. The lowest activity was recorded when the fish had a choice between bare and rocky substrates. The largest fish in the experiments changed their habitat most frequently, indicating that body size influences the activity level. However, no significant differences were found in either the time spent on specific substrates or the number of substrate changes. In addition, it was observed that the total length of Round Gobies did not affect their activity level. Full article

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

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21 pages, 1520 KiB

Open AccessArticle

Pharmacokinetics, Pharmacodynamics and Depletion of Florfenicol Applied in White Leg Shrimp (Litopenaeus vannamei) Aquaculture and Impact on Shrimp Hepatopancreas Histology

by Thi Kim Duyen Huynh, Quoc Thinh Nguyen, Marie-Louise Scippo, Thi Hoang Oanh Dang, Mathias Devreese, Caroline Douny, Siska Croubels, Quoc Viet Le and Minh Phu Tran

Fishes 2025, 10(7), 318; https://doi.org/10.3390/fishes10070318 - 2 Jul 2025

Abstract

Florfenicol (FF) is one of the common antimicrobials used to control bacterial disease in shrimp aquaculture. This study aimed to determine the pharmacokinetics (PK) parameters of FF in white leg shrimp plasma, hepatopancreas and muscle as well as its residue depletion in shrimp [...] Read more.

Florfenicol (FF) is one of the common antimicrobials used to control bacterial disease in shrimp aquaculture. This study aimed to determine the pharmacokinetics (PK) parameters of FF in white leg shrimp plasma, hepatopancreas and muscle as well as its residue depletion in shrimp muscle and the impact on shrimp hepatopancreas histology during and after FF medication. In the PK experiment, shrimp were fed once at 10 mg FF/kg body weight (bw) via oral in-feed administration to determine PK parameters in plasma, hepatopancreas and muscle. The maximum concentration (C_max) of 60.56 μg/L in plasma was observed after 1.77 h (T_max). In muscle, a C_max of 11.76 μg/kg was attained after 0.20 h, while in hepatopancreas, the C_max was higher (386.92 μg/kg) and was rapidly obtained (T_max = 0.19 h). The C_max values in shrimp plasma were below the minimum inhibitory concentration (MIC) against Vibrio parahaemolyticus, known to cause acute hepatopancreatic necrosis disease (AHPND) in shrimp. Therefore, it can be concluded that to ensure the effectiveness of this treatment, the dose should be higher than 10 mg FF/kg bw. FF depletion in white leg shrimp muscle and its histological impact on hepatopancreas were determined after feeding FF-medicated feed once-a-day or twice-a-day for 3 consecutive days with a dose of 10 mg FF/kg bw. The residues in shrimp muscle were rapidly eliminated and fell below the limit of quantification at 24 h after stopping medication. The withdrawal time of FF in shrimp muscle was 27.9 degree-days (2 days at 26.5 °C) according to the maximum residue limit (MRL) of 100 µg/kg set by the European Commission and Korean Ministry and when feeding FF twice-a-day for 3 days. The results from histological analysis showed that there was no negative effect on shrimp hepatopancreas after stopping medication in both once- and twice-a-day treatments. Full article

(This article belongs to the Section Welfare, Health and Disease)

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20 pages, 723 KiB

Open AccessArticle

Changes in Subcellular Responses in the Digestive Gland of the Freshwater Mussel Unio crassus from a Historically Contaminated Environment

by Zoran Kiralj, Zrinka Dragun, Jasna Lajtner, Krešimira Trgovčić, Tatjana Mijošek Pavin, Bruno Bušić and Dušica Ivanković

Fishes 2025, 10(7), 317; https://doi.org/10.3390/fishes10070317 - 2 Jul 2025

Abstract

Utilizing a multi-biomarker approach, we assessed the potential adverse effects of pollutants on subcellular responses in the digestive gland of the freshwater mussel Unio crassus from a historically contaminated lowland section (KIZ) of the river Mrežnica compared to its less impacted upstream karstic [...] Read more.

Utilizing a multi-biomarker approach, we assessed the potential adverse effects of pollutants on subcellular responses in the digestive gland of the freshwater mussel Unio crassus from a historically contaminated lowland section (KIZ) of the river Mrežnica compared to its less impacted upstream karstic section (REF) and their seasonality (spring vs. autumn). This approach accounted for the diverse modes of action of pollutants by including biomarkers of metal exposure (metallothioneins, MT), general stress (total cytosolic proteins, TP), antioxidative capacity (catalase, CAT; glutathione, GSH; glutathione-S-transferase, GST), oxidative damage (malondialdehyde, MDA), and neurotoxicity (acetylcholinesterase, AChE). Only in spring, MT concentrations were 15% higher at the REF site (4.38 ± 1.06 µg mg proteins⁻¹) compared to the KIZ site (3.69 ± 0.63 µg mg proteins⁻¹), likely related to elevated Cd bioaccumulation due to the karstic substrate. Regardless of the season, mussels from KIZ showed consistently lower TP and GSH, with significantly higher CAT, GST, and MDA levels, indicating elevated stress, activation of antioxidant defenses, and oxidative damage from chronic exposure to pro-oxidant pollutants, including metal(loid)s and organic contaminants (e.g., ibuprofen, nicotine). Compared to the REF site, AChE activity at the KIZ site was higher in late spring and lower in early autumn, indicating seasonal variability in AChE activity at the contamination-impacted location driven by fluctuating exposure to neurotoxicants, such as drugs and insecticides. Overall, biomarker responses indicated that mild historical pollution, reinforced by current low-capacity sources, has an observable impact on mussel health, posing long-term risks to sediment-dwelling aquatic organisms. Full article

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

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