Fishes

19 pages, 5979 KiB

Open AccessArticle

Effects of Feeding Frequency on Turbot (Scophthalmus maximus) Performance, Water Quality and Microbial Community in Recirculating Aquaculture Systems

by Xiaoyang Guo, Jiyuan Li, Shihong Xu, Xin Jiang, Teng Guo, Feng Liu, Guang Gao, Jun Li, Yanfeng Wang and Wei Jiang

Fishes 2025, 10(3), 125; https://doi.org/10.3390/fishes10030125 - 12 Mar 2025

Abstract

Recirculating aquaculture systems (RAS) have promising applications in aquaculture. Feed is recognized as a major source of input to the RAS, and feeding frequency will not only impact the performance of turbot, but will also impact the quality of the cultured water. In [...] Read more.

Recirculating aquaculture systems (RAS) have promising applications in aquaculture. Feed is recognized as a major source of input to the RAS, and feeding frequency will not only impact the performance of turbot, but will also impact the quality of the cultured water. In order to rationally manage feeding and reduce aquaculture pollution, this study investigated the effects of feeding frequency on the performance of turbot (Scophthalmus maximus), nitrogen removal (ammonia and nitrite) characteristics and microbial communities in biofilters. The experiment was designed with three treatment groups, which were categorized into feeding once/day (FF1), feeding twice/day (FF2) and feeding three times/day (FF3) for 30 days. The results indicated that weight gain rate (WGR) and specific growth rate (SGR) significantly increased (p < 0.05) in the FF2 group and FF3 group compared with the FF1 group. The feed conversion ratio (FCR) was significantly lower (p < 0.05) in the FF2 group and FF3 group than in the FF1 group. There was no significant change in condition factor (CF). Ammonia and nitrite concentration decreased and water quality fluctuated less as the feeding frequency increased. FF2 showed the highest ammonia and nitrite removal rates. Feeding frequency did not significantly affect biofilter alpha diversity, but significantly altered beta diversity. PICRUSt functional prediction analysis revealed that the relative abundance of functional genes for nitrogen metabolism (amoA, amoB, amoC, hao, nxrA and nxrB) was highest in FF2. Therefore, feeding frequency of twice/day not only benefits the performance of turbot but also stabilizes the water environment and improves the removal of ammonia nitrogen and nitrite in RAS. These results provide theoretical and practical basis for further water improvement by seawater RAS. Full article

(This article belongs to the Section Sustainable Aquaculture)

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17 pages, 1516 KiB

Open AccessArticle

Glycerol Monolaurate Affects Growth, Amino Acid Profile, Antioxidant Capacity, Nutrient Apparent Digestibility, and Histological Morphology of Hepatopancreas in Juvenile Pacific White Shrimp (Litopenaeus vannamei)

by Sami Ullah, Bingge Liu, Yunyun Zheng, Hongbo Guo, Yarui Yang, Muhammad Ijaz Ahmad, Siyu Lv, Shijie Deng, Minjie Zhao and Fengqin Feng

Fishes 2025, 10(3), 124; https://doi.org/10.3390/fishes10030124 - 11 Mar 2025

Abstract

An eight-week feeding trial was conducted to evaluate the effects of dietary supplementation with glycerol monolaurate (GML) on Pacific white shrimp (Litopenaeus vannamei). A basal diet was formulated containing 100 g fish meal, while four additional GML-supplemented diets were prepared: GML1 [...] Read more.

An eight-week feeding trial was conducted to evaluate the effects of dietary supplementation with glycerol monolaurate (GML) on Pacific white shrimp (Litopenaeus vannamei). A basal diet was formulated containing 100 g fish meal, while four additional GML-supplemented diets were prepared: GML1 (0.25 g), GML2 (0.50 g), GML3 (0.75 g), and GML4 (1.00 g). Each diet was given to triplicate tanks containing 50 shrimp, each weighing 1.67 ± 0.25 g. GML2 supplementation enhanced the final body weight, weight gain, condition factor, specific growth rate, and viscerosomatic index of the shrimp compared to the other diets (p < 0.05). The whole-body amino acid profile was significantly high in the GML3 group. The antioxidant and immune indicators in the serum, like total protein, triglyceride, and aspartate aminotransferase, were significantly high in the GML2-supplemented group. The immune and antioxidant indicators in the hepatopancreas of the shrimp, like total protein, triglyceride, total cholesterol, and complement protein 3, were significantly high in the GML2 group. However, the malondialdehyde in their livers and serum were significantly high in the control group. Digestive enzymes were significantly high in the GML2 group. In conclusion, this study confirms that GML may benefit the health of Pacific white shrimp, offering new insights into aquaculture. Full article

(This article belongs to the Special Issue Impacts of Different Feed Additives and Raising Conditions on Shrimp Growth and Health)

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22 pages, 2242 KiB

Open AccessArticle

Controlled Multi-Stage Evaluation of Growth and Physiochemical Traits Between Low- and Normal-Temperature Strains of Scylla paramamosain

by Jiaai Li, Wenfeng Han, Hai Liu and Dongfa Zhu

Fishes 2025, 10(3), 123; https://doi.org/10.3390/fishes10030123 - 10 Mar 2025

Abstract

The mud crab Scylla paramamosain is a key economic crab species along the southern coastal regions of China. This study systematically compared the physiological and biochemical characteristics of low-temperature (LT) and normal-temperature (NT) strains of S. paramamosain at different life stages (juveniles and [...] Read more.

The mud crab Scylla paramamosain is a key economic crab species along the southern coastal regions of China. This study systematically compared the physiological and biochemical characteristics of low-temperature (LT) and normal-temperature (NT) strains of S. paramamosain at different life stages (juveniles and adults), integrating temperature gradient experiments with conventional aquaculture evaluations. The experimental results revealed the following: (1) Growth superiority: LT-strain crabs exhibited significantly greater final weight, survival rate, hepatopancreatic index, and gonadal index than their NT counterparts (p < 0.05). Moreover, LT individuals displayed an enhanced nutritional profile, with 16.56% higher muscle crude fat and a 23.80% increase in ovarian ash content. (2) Immune competence: Juvenile LT crabs exhibited greater antioxidant capacity at 18–21 °C, with significantly higher total antioxidant capacity (T-AOC) and superoxide dismutase (SOD) activity than NT crabs (p < 0.05). In adults, immune enzyme activity remained superior, particularly in serum acid phosphatase (ACP). (3) Nutritional advantage: LT mature females exhibited higher accumulation of essential amino acids (e.g., lysine, threonine) and polyunsaturated fatty acids (C18:2n-6, C20:2n-6) in the hepatopancreas and gonads (p < 0.05). These findings confirm the LT strain’s superior cold resilience and aquaculture potential, offering practical insights for S. paramamosain selective breeding programs and sustainable aquaculture development. Full article

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16 pages, 3344 KiB

Open AccessArticle

Effects of Water Temperature, Light Intensities and Photoperiod on the Survival and Growth of Juvenile Schizothorax irregularis and Diptychus maculates

by Zhulan Nie, Huimin Hao, He Zhao, Nianhua Zhao, Li Li, Zhuang Qiang, Syeda Maira Hamid and Jie Wei

Fishes 2025, 10(3), 122; https://doi.org/10.3390/fishes10030122 - 10 Mar 2025

Abstract

An experimental ecological method was used to study the effects of water temperature, photoperiod, and light intensity on the survival, feeding, and growth of juvenile Schizothorax irregularis and Diptychus maculates. The Box–Benhnken experiment was designed to predict the optimal environmental conditions for [...] Read more.

An experimental ecological method was used to study the effects of water temperature, photoperiod, and light intensity on the survival, feeding, and growth of juvenile Schizothorax irregularis and Diptychus maculates. The Box–Benhnken experiment was designed to predict the optimal environmental conditions for juvenile growth. With the maximum specific growth rate at 15 °C and a photoperiod of LD16:8, the results demonstrated that the juvenile S. irregularis had a survival rate of over 85% in water temperatures ranging from 5 to 25 °C. A daily light duration of 15.86 h and a light intensity of 1166.28 lx, with the water temperature maintained at 10.45 °C, allowed the juvenile S. irregularis fish to attain the optimal circumstances for growth and survival. At water temperatures below 25 °C, the juvenile D. maculates exhibited maximum specific growth rates at 10 °C and LD16:8 light period. Additionally, as the light intensity reached 1000 lx, the juvenile fish grew better. Furthermore, the juvenile D. maculates fish achieved theoretically optimal survival and growth circumstances when the water temperature was maintained at 10.87 °C with a light period of 15.0.5 h per day and a light intensity of 1474.68x. The results showed that both fish species may be raised in captivity in highland regions, but precise control over water temperature is required. Full article

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14 pages, 2283 KiB

Open AccessArticle

Molecular Phylogeny and Evolutionary History of the Genus Cyprinus (Teleostei: Cypriniformes)

by Yanyan Chen, Heng Xiao, Zhaoping Yue, Xiaoyun Wu, Ruiguang Zan and Shanyuan Chen

Fishes 2025, 10(3), 121; https://doi.org/10.3390/fishes10030121 - 10 Mar 2025

Abstract

The genus Cyprinus encompasses economically vital freshwater fish species; yet the phylogenetic relationships and evolutionary history of many taxa within this genus remain unresolved. To address this knowledge gap, we reconstructed the molecular phylogenetic and estimated divergence times using complete mitochondrial cytochrome b [...] Read more.

The genus Cyprinus encompasses economically vital freshwater fish species; yet the phylogenetic relationships and evolutionary history of many taxa within this genus remain unresolved. To address this knowledge gap, we reconstructed the molecular phylogenetic and estimated divergence times using complete mitochondrial cytochrome b (CYTB) sequences of 76 Cyprinidae specimens, within Cyprinidae, including 4 outgroup species. Phylogenetic trees were reconstructed using maximum likelihood (ML) and Bayesian inference (BI) methods, while divergence times were estimated using a Bayesian relaxed molecular clock approach. The results confirmed the monophyly of the genus Cyprinus. The relationships among C. (Cyprinus) multitaeniata, C. (C.) pellegrini, C. (C.) acutidorsalis, and three Erhai Lake species (C. (C.) longipectoralis, C. (C.) barbatus, and C. (C.) chilia) were resolved with strong support. Cyprinus (C.) multitaeniata is basal. The species in Erhai Lake form a monophyletic group, and C. (C.) acutidorsalis is at the top of the phylogenetic tree. The taxonomic delineation within the genus Cyprinus remains controversial, particularly regarding the proposed division into two subgenera (Cyprinus and Mesocyprinus), which has been historically constrained by limited specimen availability for Mesocyprinus. Our comprehensive phylogenetic analysis reveals significant evolutionary divergence patterns: The genus Cyprinus diverged from Carassius during the 56.9 Mya. Notably, the Erhai Lake radiation species (C. (C.) longipectoralis, C. (C.) barbatus, and C. (C.) chilia) originated during 2.03 Mya, while the Lake Biwa endemic C. (C.) haematopterus demonstrates 8.7 Mya. We identified a late Pleistocene speciation event (0.75 Mya) in C. (C.) acutidorsalis, coinciding with its adaptation to brackish water ecosystems. The native C. (C.) pellegrini of Xingyun Lake and Chilu Lake may have originated 4.8 Mya, when the ancient lake that its ancestral population inhabited became isolated. These findings provide robust molecular evidence supporting the recognition of two evolutionary distinct subgenera within Cyprinus. Full article

(This article belongs to the Section Taxonomy, Evolution, and Biogeography)

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17 pages, 5231 KiB

Open AccessArticle

Environmentally Relevant Sulfamethoxazole Induces Developmental Toxicity in Embryo-Larva of Marine Medaka (Oryzias melastigma)

by Jianxuan Huang, Lei Ye, Siyi Huang, Zuchun Chen, Jiahao Gao, Yangmei Li, Yusong Guo, Zhongduo Wang, Jian Liao, Zhongdian Dong and Ning Zhang

Fishes 2025, 10(3), 120; https://doi.org/10.3390/fishes10030120 - 8 Mar 2025

Abstract

Sulfamethoxazole (SMX), a commonly used sulfonamide antibiotic, poses a threat to aquatic life due to its widespread presence in the environment. This study aims to investigate the specific effects of SMX on the development of marine medaka (Oryzias melastigma) embryos and [...] Read more.

Sulfamethoxazole (SMX), a commonly used sulfonamide antibiotic, poses a threat to aquatic life due to its widespread presence in the environment. This study aims to investigate the specific effects of SMX on the development of marine medaka (Oryzias melastigma) embryos and larvae. Marine medaka embryos were exposed to SMX at concentrations of 0 (solvent control group, SC group), 1 μg/L (low concentration group, L group), 60 μg/L (middle concentration group, M group), and 1000 μg/L (high concentration group, H group). The results indicated that SMX exposure significantly accelerated the heart rate of embryos (p < 0.0001) and shortened the hatching time while also causing anomalies such as reduced pigmentation, smaller eye size, spinal curvature, and yolk sac edema. SMX also led to a decrease in the total length of the larvae. The M group and the H group exhibited a significant increase (p < 0.05) in lipid accumulation in the visceral mass of the larvae. In the L group and the M group, there was a significant increase (p < 0.0001) in the swimming distance of the larvae. At the molecular level, SMX exposure affected the transcript levels of the genes involved in the cardiovascular system (ahrra, arnt2, atp2a1, and cacan1da), antioxidant and inflammatory systems (cat, cox-1, gpx, pparα, pparβ, and pparγ), nervous system (gap43, gfap, α-tubulin), intestinal barrier function (claudin-1), detoxification enzymes (ugt2c1-like), and lipid metabolism (rxraa) in the embryos to larval stage. The microbiome analysis showed that at the phylum level, exposure to SMX resulted in an increase in the abundance of Proteobacteria. Additionally, the abundance of Actinobacteriota significantly increased in the L group (p < 0.05). At the genus level, the abundance of Bifidobacterium significantly increased in the L group (p < 0.05), while the abundance of Vibrio significantly increased in the H group (p < 0.05). The alpha diversity analysis revealed a significant decrease in the Chao1 index in the L and H groups, indicating a reduction in microbial richness. The beta diversity analysis showed differences in the microbial communities of marine medaka larvae among different SMX exposure groups. This study elucidates the negative impacts of SMX on the development of marine medaka embryos and larvae and their microbial composition, providing a scientific basis for assessing the risks of SMX in marine ecosystems. Full article

(This article belongs to the Special Issue Toxicology of Anthropogenic Pollutants on Fish)

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26 pages, 4940 KiB

Open AccessArticle

Integration of Gill and Intestinal Osmoregulatory Functions to Assess the Smoltification Window in Atlantic Salmon

by Jonás I. Silva-Marrero, Floriana Lai, Sigurd O. Handeland, Cindy Pedrosa, Virginie Gelebart, Pablo Balseiro, Juan Fuentes, Ivar Rønnestad and Ana S. Gomes

Fishes 2025, 10(3), 119; https://doi.org/10.3390/fishes10030119 - 8 Mar 2025

Abstract

The transfer time of Atlantic salmon smolts from freshwater to seawater remains a challenge in aquaculture, with the “smolt window” referring to the optimal timeframe for seawater readiness. Our study monitored Atlantic salmon osmoregulatory adaptations during smoltification under continuous light (LL) and winter [...] Read more.

The transfer time of Atlantic salmon smolts from freshwater to seawater remains a challenge in aquaculture, with the “smolt window” referring to the optimal timeframe for seawater readiness. Our study monitored Atlantic salmon osmoregulatory adaptations during smoltification under continuous light (LL) and winter signal regime (6 weeks LD 12:12) followed by 6 or 8 weeks of constant light. Fish were subsequently reared in seawater for 8 weeks and subjected to a stress event of cyclic hypoxia at the conclusion of the trial. Significant differences in growth trajectories were observed between the LL and LD groups, with fish receiving the winter signal showing compensatory growth after seawater transfer. Gill Na⁺/K⁺-ATPase (NKA) activity, plasma ions, glucose, and cortisol levels confirmed the importance of the winter signal for seawater adaptation. Molecular markers, including nka isoforms, Na⁺-K⁺-2Cl⁻ cotransporter (nkcc), cystic fibrosis transmembrane conductance regulator (cftr), and Na⁺/HCO₃⁻ cotransporter (nbc), showed distinct temporal expression patterns, particularly in gills and midgut. Notably, the LD group with delayed seawater transfer exhibited enhanced growth and improved hypo-osmoregulatory capacity. These findings underscore the advantages of a winter signal in smoltification and suggest that delaying seawater transfer for up to 8 weeks could be beneficial. Full article

(This article belongs to the Special Issue Rhythms in Marine Fish and Invertebrates)

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14 pages, 1913 KiB

Open AccessArticle

Assessment of 18 Years of Genetic Marker-Assisted Selection and Augmentation of Native Walleye in the Upper New River, Virginia, USA

by Sheila Harris, George Palmer, John Copeland, Joe Williams and Eric Hallerman

Fishes 2025, 10(3), 118; https://doi.org/10.3390/fishes10030118 - 6 Mar 2025

Abstract

Walleye Sander vitreus is a valued sportfish in eastern North America, including the upper New River of Virginia, where individuals can grow to a large size (>7 kg). After construction of dams, especially Claytor Dam in 1939, the population declined and non-native walleye [...] Read more.

Walleye Sander vitreus is a valued sportfish in eastern North America, including the upper New River of Virginia, where individuals can grow to a large size (>7 kg). After construction of dams, especially Claytor Dam in 1939, the population declined and non-native walleye were stocked. Stocking of non-native walleye was stopped in 1997, and molecular marker data showed that the presumptive native population had persisted. To restore the native stock, selection of broodstock candidates bearing native marker alleles and hatchery-based augmentation have been practiced over a 20-year period. We evaluated the success of the marker-assisted selection and hatchery-based augmentation program. Marker-assisted selection of native New River walleye began with mean frequencies of marker alleles at microsatellite loci Svi17 and Svi33 of ~30%, and continuing selection has driven marker allele frequencies to ~65–70%. Numbers of walleye collected in fall gillnet and spring electrofishing surveys were responsive to augmentations with hatchery fish 2–3 years earlier. Stocking was not practiced in 2012–2013, and a decrease in walleye catch rates was noted in 2016, suggesting that the native New River walleye population still depends upon hatchery-based augmentation. We recommend the development of a small panel of single nucleotide polymorphism markers for more rigorous selection of broodstock representative of the native walleye population. Full article

(This article belongs to the Section Genetics and Biotechnology)

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15 pages, 5402 KiB

Open AccessArticle

Comparative Transcriptomic Analysis of Male and Female Gonads in the Zig-Zag Eel (Mastacembelus armatus)

by Fangyu Cui, Yuanyuan Wang, Haiyan Liang, Yexin Yang, Zhiyong Jiang, Jiahuan Song, Chao Liu, Yuli Wu, Xidong Mu and Yi Liu

Fishes 2025, 10(3), 117; https://doi.org/10.3390/fishes10030117 - 6 Mar 2025

Abstract

The zig-zag eel (Mastacembelus armatus) is a unique economic fish species in China and exhibits significant dimorphism of male and female phenotypes. Cultivating all-male seedlings can significantly improve production efficiency. To investigate sex differentiation and gonadal development in M. armatus, [...] Read more.

The zig-zag eel (Mastacembelus armatus) is a unique economic fish species in China and exhibits significant dimorphism of male and female phenotypes. Cultivating all-male seedlings can significantly improve production efficiency. To investigate sex differentiation and gonadal development in M. armatus, high-throughput sequencing technology was used to analyze the transcriptomes of male and female gonads at different developmental stages, both before and after sex differentiation. We identified key genes involved in sex differentiation, male-specific differentially expressed genes (DEGs), including dmrt1, amh, sox9, gsdf, and dmrt2b, and female-biased DEGs, including foxl2, rspo1, gdf9, bmp15, and wnt4. GO and KEGG enrichment analyses revealed that signaling pathways such as MAPK, Wnt, and TGF-β play significant roles in sex differentiation in M. armatus. The expression levels of 13 sex-related genes, including dmrt1, sox9, amh, foxl2, rspo1, and wnt4, were determined by RT–qPCR in addition to RNA sequencing. RT-qPCR validation results were consistent with the transcriptomic data, confirming the reliability of our findings. This research provides valuable insights into the mechanisms of sex differentiation in M. armatus and lays a foundation for developing all-male populations in aquaculture. Full article

(This article belongs to the Special Issue Genetics and Breeding in Aquaculture)

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17 pages, 4014 KiB

Open AccessArticle

Photoelectrocatalytic Coupling of Chlorine Radicals Enhances Sulfonamide Antibiotic Degradation in Saline-Alkaline Waters in Cold-Water Fish Aquaculture

by Qikai Liu, Yang Liu, Yaqi Mao, Ru Li, Yujie Jiao, Jiali Lei and Fenzhen Zhang

Fishes 2025, 10(3), 116; https://doi.org/10.3390/fishes10030116 - 6 Mar 2025

Abstract

The degradation of organic matter using TiO₂ nanotube photocatalytic technology is limited by the short lifetime and diffusion radius of the generated hydroxyl radicals, decreasing the removal efficiency. This study developed a chlorine radical-coupled photoelectrocatalytic system, significantly enhancing the performance of TiO [...] Read more.

The degradation of organic matter using TiO₂ nanotube photocatalytic technology is limited by the short lifetime and diffusion radius of the generated hydroxyl radicals, decreasing the removal efficiency. This study developed a chlorine radical-coupled photoelectrocatalytic system, significantly enhancing the performance of TiO₂ nanotube arrays in removing sulfonamide antibiotics (SAs) from cold-water aquaculture systems. The highest degradation rates were observed at 5 mM NaCl and 15 mM NaNO₃. When SA concentrations were 0.1–10 mg/L, degradation efficiency decreased with higher initial concentrations. The best degradation was achieved at an initial pH of 3 for SA. Humic acid and sodium acetate, natural organic matter in the water column, served as low-concentration promoters and high-concentration inhibitors. In our study, three degradation intermediates were identified, and hydrolysis and nitration reactions are proposed as the primary pathways for SA degradation. We confirmed that oxygen radicals play a major role in this system. Furthermore, toxicology experiments revealed the weakening of the toxicity of the degraded products. This study provides an efficient method for treating organic matter in cold-water fish culture water in chloride-containing saline and alkaline waters. Full article

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23 pages, 2887 KiB

Open AccessArticle

Red Mullet (Mullus barbatus) Collected from North and South Euboean Gulf, Greece: Fishing Location Effect on Nutritive Quality

by Roxana-Georgiana Nita, Vassilis Athanasiadis, Dimitrios Kalompatsios, Martha Mantiniotou, Aggeliki Alibade, Chrysanthi Salakidou and Stavros I. Lalas

Fishes 2025, 10(3), 115; https://doi.org/10.3390/fishes10030115 - 5 Mar 2025

Abstract

Red mullet (Mullus barbatus), a prominent fish species in the Mediterranean Sea, is a fish with a particular abundance of unsaturated fatty acids and other nutrients, including a substantial quantity of minerals. The nutritive quality parameters (lipid quality indices, fatty acid [...] Read more.

Red mullet (Mullus barbatus), a prominent fish species in the Mediterranean Sea, is a fish with a particular abundance of unsaturated fatty acids and other nutrients, including a substantial quantity of minerals. The nutritive quality parameters (lipid quality indices, fatty acid profiles, and mineral content, along with proximate composition) of 75 red mullet samples collected from five distinct locations (L1–L5) in the North and South Euboean Gulf, Euboea Island (Evia), Greece, were examined. It was hypothesized that the different habitats may have an impact on each fish’s chemical composition. Proximate composition (protein, ash, moisture, fat, and minerals) and bioactive compound determination (total carotenoids, and vitamins A, E, and C) were conducted on the lyophilized fish samples. The protein and lipid content of the wet fillet varied substantially from 10.8 to 14.3 and 13.2 to 16.8% w/w, respectively. The samples exhibited statistically non-significant variation in the total SFAs and MUFAs (p > 0.05). The level of total PUFAs was above 30% in all the samples and no significant differences were observed between them. However, arachidonic acid (20:4 ω-6) was only detected in fish samples from two locations (i.e., L1 and L3). The concentrations of Fe, Na, Mg, K, Ca, Ag, Sr, Li, and Zn varied significantly (p < 0.05) in relation to the size of the fish samples. The highest concentrations of heavy metals were detected at the northern location (L5), indicating a possible negative correlation between size and arsenic concentration. The varied mineral composition and fatty acid content of the samples can be attributed to their distinctive biological characteristics (i.e., length and weight) and dietary environments. Full article

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20 pages, 2236 KiB

Open AccessArticle

Effects of Melatonin on the Growth and Diurnal Variation of Non-Specific Immunity, Antioxidant Capacity, Digestive Enzyme Activity, and Circadian Clock-Related Gene Expression in Crayfish (Procambarus clarkii)

by Jinglong Chen, Youhai Du, Mengyue Zhang, Jiahui Wang, Jianhua Ming, Xianping Shao, Aimin Wang, Hongyan Tian, Wuxiao Zhang, Silei Xia, Weigen Cheng, Jinlan Xu, Xiaochuan Zheng and Bo Liu

Fishes 2025, 10(3), 114; https://doi.org/10.3390/fishes10030114 - 5 Mar 2025

Abstract

This study aimed to investigate the effects of dietary melatonin supplementation on growth and diurnal non-specific immunity, antioxidant capacity, digestive enzyme activities, and circadian clock-related gene expression in crayfish (Procambarus clarkii). A total of 500 healthy juvenile crayfish (6.68 ± 0.31 [...] Read more.

This study aimed to investigate the effects of dietary melatonin supplementation on growth and diurnal non-specific immunity, antioxidant capacity, digestive enzyme activities, and circadian clock-related gene expression in crayfish (Procambarus clarkii). A total of 500 healthy juvenile crayfish (6.68 ± 0.31 g) were randomly distributed into five groups with four replicates each and fed five different diets supplemented with melatonin at 0, 25, 50, 75, and 100 mg/kg for 60 days. The results indicated that dietary supplementation of 50 mg/kg melatonin significantly increased the weight gain rate (WGR), specific growth rate (SGR), and survival rate (SR) of juvenile Procambarus clarkii. However, no significant differences were observed in the hepatosomatic index (HSI), meat yield, and condition factor (p > 0.05). When the dietary melatonin level was 50 mg/kg, the activities of LZM and ALP in the hemolymph of Procambarus clarkii were higher than the levels at both 15:00 and 03:00, while the activities of AST and ALT remained at lower levels during these two time points. It also significantly upregulated the mRNA expression levels of Clock, Per1, Cry1, Tim1, and Tim2 in the hepatopancreas (p < 0.05). Furthermore, dietary melatonin at 50 mg/kg significantly reduced the activities of alanine aminotransferase (ALT) and aspartate aminotransferase (AST), as well as the malondialdehyde (MDA) content across day and night (p < 0.05). No significant differences were found in acid phosphatase (ACP) at 15:00, alkaline phosphatase (ALP), and amylase (AMS) activities in the hepatopancreas and intestine at 3:00 among the groups (p > 0.05). At 15:00, supplementation with 50 mg/kg significantly upregulated Bmal1 mRNA expression (p < 0.05). Melatonin supplementation at 50–75 mg/kg resulted in significantly higher levels of TP, LZM, ALP, and CAT activities, as well as significantly higher mRNA expression of Clock, Bmal1, Cry1, Per1, Tim1, and Tim2 in the hepatopancreas at 3:00 compared to 15:00 (p < 0.05), with the opposite trend observed for MDA content (p < 0.05). No significant differences were found in ACP, ALT, and AST activities between 3:00 and 15:00 among the groups (p > 0.05). Thus, dietary supplementation of 50 mg/kg melatonin could promote the growth of juvenile Procambarus clarkii, enhance their non-specific immunity and antioxidant capacity during both day and night, increase the activities of digestive enzymes in the hepatopancreas and intestine, and regulate the expression of circadian clock-related genes. Full article

(This article belongs to the Special Issue Effect of Dietary Supplementation on the Growth and Immunity of Fish and Shellfish—2nd Edition)

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12 pages, 1513 KiB

Open AccessArticle

Identification of Different Ecomorphotypes of Coilia nasus in the Dawanzhou Section of the Yangtze River

by Jiahao Liu, Tao Jiang, Junren Xue, Xiubao Chen, Hongbo Liu and Jian Yang

Fishes 2025, 10(3), 113; https://doi.org/10.3390/fishes10030113 - 5 Mar 2025

Abstract

X-ray electron probe microanalyzer technology was used to study the microchemistry and habitat history of Coilia nasus collected from the Dawanzhou section of the Yangtze River between May and June 2023. The Sr/Ca ratio from the otolith core to the otolith diameter was [...] Read more.

X-ray electron probe microanalyzer technology was used to study the microchemistry and habitat history of Coilia nasus collected from the Dawanzhou section of the Yangtze River between May and June 2023. The Sr/Ca ratio from the otolith core to the otolith diameter was low (640–1100 µm), representing the first stage of development. In the second stage, C. nasus exhibited two distinct types. The first type, which included individuals 5HK05 and 6HK03, exclusively inhabited brackish estuarine waters. The second type, comprising 13 individuals, resided in higher-salinity seawater environments (Sr/Ca > 7). Furthermore, individuals 5HK01, 5HK03, 5HK07, and 6HK05 displayed a phase with a high Sr/Ca ratio compared to other fish. Freshwater coefficient analysis indicated that C. nasus in the Dawanzhou water area was unlikely to continue upstream to Dongting Lake in the middle reaches of the Yangtze River but may have entered Poyang Lake through its mouth or reproduced in its upper reaches. Analysis of sexual maturity and migration history suggested that the Dawanzhou section primarily serves as a migration channel for C. nasus, with a potential spawning ground for this high-value fish located nearby. Full article

(This article belongs to the Section Biology and Ecology)

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17 pages, 3866 KiB

Open AccessArticle

Size-Selective Harvesting Effects on Reproductive Investment in Marine Medaka (Oryzias melastigma)

by Guochen Gan, Guankui Liu, Xinyao Sun, Wenbo Deng, Fengming Lv, Yongjun Tian and Peng Sun

Fishes 2025, 10(3), 112; https://doi.org/10.3390/fishes10030112 - 4 Mar 2025

Abstract

Long-term selective fishing pressure often leads to miniaturization, smaller size, and early sexual maturity in many commercial fish species. To adapt, these species increase energy allocations toward maturation and reproduction, which can reduce population productivity and recruitment. However, how different fishing pressures affect [...] Read more.

Long-term selective fishing pressure often leads to miniaturization, smaller size, and early sexual maturity in many commercial fish species. To adapt, these species increase energy allocations toward maturation and reproduction, which can reduce population productivity and recruitment. However, how different fishing pressures affect reproductive investment and energy allocation between growth and reproduction remains unclear. In this study, we designed three size-selective harvesting strategies—large, random, and small harvests—to examine their effects on the growth and reproductive investment of marine medaka (Oryzias melastigma). We analyzed changes in length, weight, and gonad weight across different harvest times. Results showed that the “large harvest” group allocated more energy to reproduction, leading to miniaturization and earlier maturation, while the “small harvest” group focused more on growth, resulting in larger fish at the same age. This study provides experimental evidence on how size-selective harvesting alters reproductive investment in fish populations, offering valuable insights for the sustainable exploitation of fishery resources. Full article

(This article belongs to the Section Biology and Ecology)

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14 pages, 2351 KiB

Open AccessArticle

Human Trophic Level and Trade Openness: Insights from Global Seafood Consumption Patterns

by Kyu Sung Lee, Dae Eui Kim and Song Soo Lim

Fishes 2025, 10(3), 111; https://doi.org/10.3390/fishes10030111 - 4 Mar 2025

Abstract

This study investigates the relationship between Human Trophic Level (HTL) and trade openness within the context of seafood consumption patterns. Utilizing a comprehensive panel dataset spanning from 1990 to 2019 and covering 168 countries, this study applied fixed effects and random effects models [...] Read more.

This study investigates the relationship between Human Trophic Level (HTL) and trade openness within the context of seafood consumption patterns. Utilizing a comprehensive panel dataset spanning from 1990 to 2019 and covering 168 countries, this study applied fixed effects and random effects models to uncover the dynamics between trade openness, seafood diversity, and socioeconomic factors. The findings reveal a significant positive correlation between trade openness and HTL, demonstrating that increased access to diverse and high-trophic-level seafood products fosters improvements in national HTL. Additionally, economic development exhibits a non-linear relationship with HTL, where higher income initially drives a preference for high-trophic-level species, but dietary patterns diversify at advanced income levels. This study also highlights geographic disparities, with landlocked countries benefiting most from trade openness, whereas island and peninsula nations are influenced more by geographic and economic factors. These insights underscore the pivotal role of trade in shaping sustainable seafood consumption and provide actionable guidance for policymakers aiming to align economic growth with ecological sustainability. Full article

(This article belongs to the Section Fishery Economics, Policy, and Management)

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16 pages, 2425 KiB

Open AccessArticle

Impact of Plant-Based Diets on Hepatosomatic Index, Circulating Globulins and Growth in Rainbow Trout (Oncorhynchus mykiss)

by Alejandro Villasante, Elías Figueroa, Karina Godoy, Patricio Dantagnan, Johana López-Polo, Rafael Opazo and Jaime Romero

Fishes 2025, 10(3), 110; https://doi.org/10.3390/fishes10030110 - 4 Mar 2025

Abstract

Serum proteins are essential for maintaining osmotic pressure, regulating pH, transporting metabolites, and supporting immune responses. Studying the effects of plant-based diets on these proteins is crucial to understanding their impact on fish health and immune function. Methods: This study was conducted in [...] Read more.

Serum proteins are essential for maintaining osmotic pressure, regulating pH, transporting metabolites, and supporting immune responses. Studying the effects of plant-based diets on these proteins is crucial to understanding their impact on fish health and immune function. Methods: This study was conducted in a recirculation system, with rainbow trout distributed across nine tanks and fed three diets: fishmeal (control), medium plant meal (MPM; 40% of fishmeal replacement), and high plant meal (HPM; 80% of fishmeal replacement). Plasma protein and plasma glucose levels were measured at the initial and final stages, under both fasting (24 h after fast) and postprandial (6 h after fed) conditions, to assess dietary impacts. Additionally, the hepatosomatic index (HSI) was calculated at the end of the experiment to evaluate potential liver adaptations to the diets. Results: The initial protein and glucose levels were similar across all groups. However, by the end of the treatment, the fishmeal-fed group showed significantly higher total protein and globulin levels, while the albumin levels remained consistent across diet types. A significant interaction between sampling time and dietary treatment in fish reduced the clarity of dietary effects on postprandial plasma glucose levels. Furthermore, the HSI was significantly lower in fish fed the high plant meal (HPM) diet compared to the fishmeal and medium plant meal (MPM) groups, suggesting potential metabolic adaptation in response to plant-based diets. Conclusions: Replacing fishmeal with plant-based proteins in rainbow trout diets reduces total globulin and protein concentrations but leaves albumin unaffected, alongside reductions in fasting and postprandial glucose levels. The low growth and different HSI in fish fed plant-based diets highlights potential liver stress, emphasizing the need for further research to optimize sustainable aquaculture feeds while maintaining fish health and performance. Full article

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19 pages, 7556 KiB

Open AccessArticle

A Hypothetical Protein Fragment from Large Yellow Croaker (Larimichthys crocea) Demonstrates Significant Activity Against Both Bacterial and Parasite

by Chunmei Yan, Meiling Chen, Hao Xu, Jian Jin, Xiande Liu, Zhiyong Wang and Dongling Zhang

Fishes 2025, 10(3), 109; https://doi.org/10.3390/fishes10030109 - 4 Mar 2025

Abstract

Antimicrobial peptides (AMPs) are biocompatible and biodegradable, making them an attractive alternative to traditional antimicrobial agents and chemical preservatives. Here, a novel α-helix amphiphilic anionic AMP Lc149 was screened from a large yellow croaker (Larimichthys crocea) using a Bacillus subtilis expression [...] Read more.

Antimicrobial peptides (AMPs) are biocompatible and biodegradable, making them an attractive alternative to traditional antimicrobial agents and chemical preservatives. Here, a novel α-helix amphiphilic anionic AMP Lc149 was screened from a large yellow croaker (Larimichthys crocea) using a Bacillus subtilis expression system. Lc149 is a hypothesized protein fragment not annotated in the genome of a large yellow croaker. Both extracellular protein and recombinant Lc149 (rLc149) exhibited significant killing effects against Gram-negative Escherichia coli and Vibrio harveyi. Scanning and transmission electron microscopy revealed that rLc149 had the ability to disrupt bacterial cell membranes, causing irregular cell morphology, severe cell membrane damage, cytoplasm agglutination, and intracellular content leakage. Confocal laser scanning microscopy and flow cytometry further confirmed bacterial cell destruction and mortality rates of over 80%. Gel retardation assays and SDS-PAGE electrophoresis showed that rLc149 was unable to bind to bacterial DNA, but did reduce bacterial protein contents. Additionally, rLc149 maintained antibacterial activity against E. coli and V. harveyi upon exposure to temperatures of 25–100 °C, UV radiation time of 0–60 min, pH levels of 3–12, and different proteases. Biosafety assays revealed low hemolytic toxicity to erythrocytes of large yellow croaker, rabbit, and shrimp, and low cytotoxicity to large yellow croaker kidney cells and HEK 293T cells. More deeply, rLc149 also possessed significant killing activity against parasites. Therefore, rLc149 can be considered an antibacterial and antiparasitic drug in fisheries. Full article

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

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21 pages, 2975 KiB

Open AccessArticle

Environmental Sustainability in the Culture of Macroalgae, Oysters, and Low-Trophic Fish

by Suellen Araujo Alves, Michelle Roberta Santos, Patricia Moraes-Valenti, Dioniso Souza Sampaio and Wagner C. Valenti

Fishes 2025, 10(3), 108; https://doi.org/10.3390/fishes10030108 - 3 Mar 2025

Abstract

Aquaculture plays a crucial role in meeting the needs of a growing human population and achieving the sustainable development goals outlined in Agenda 2030. However, it is essential that this sector grows sustainably. In this study, we hypothesized that environmental sustainability decreases as [...] Read more.

Aquaculture plays a crucial role in meeting the needs of a growing human population and achieving the sustainable development goals outlined in Agenda 2030. However, it is essential that this sector grows sustainably. In this study, we hypothesized that environmental sustainability decreases as the trophic level of farmed species increases and that it is higher in integrated systems compared to monocultures. To test these hypotheses, we conducted a comparative analysis of the environmental sustainability indicators of some aquaculture systems, including the farming of primary producers, filter feeders, and low-trophic phagotrophs. We compiled secondary data on eighteen environmental sustainability indicators from seven aquaculture systems. Five are monocultures, including the farming of macroalgae (Hypnea pseudomusciformis), oysters (Crassostrea gazar) in a tropical environment, oysters in a subtropical environment, as well as tambatinga (hybrid Colossoma macropomum × Piaractus brachypomus) and tambaqui (Colossoma macropomum). Additionally, two are integrated systems: tambaqui raised in hapa nets (small cage-like enclosures) within Amazon river prawn (Macrobrachium amazonicum) ponds, and tambaqui and prawns cohabitating freely in the same ponds. A benchmark tool was utilized to establish reference values for comparing indicators between the systems, and a method was developed to create environmental sustainability indices that integrate all indicators. Environmental sustainability tends to decrease as trophic levels rise, supporting the initial hypothesis. However, the data revealed that Integrated Multi-Trophic Aquaculture (IMTA) systems ultimately have lower environmental sustainability than monocultures, which was contrary to our expectations. Algae and oyster farming were found to be more environmentally sustainable than low-trophic fish farming systems. Among these, the integrated systems did not demonstrate significantly greater sustainability than the monocultures, as initially anticipated. To gain a comprehensive understanding of sustainability, further research on the social and economic sustainability of these systems is necessary. Full article

(This article belongs to the Section Sustainable Aquaculture)

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11 pages, 4183 KiB

Open AccessArticle

Cyprinid herpesvirus 2 ORF41 Protein Degrades Pyruvate Dehydrogenase (PDH)-E1β to Promote Viral Replication in Gibel Carp Brain (GiCB) Cells

by Mingyang Xue, Chen Xu, Zhenyu Huang, Yan Meng, Nan Jiang, Yuding Fan and Yong Zhou

Fishes 2025, 10(3), 107; https://doi.org/10.3390/fishes10030107 - 3 Mar 2025

Abstract

Cyprinid herpesvirus 2 (CyHV-2) is a major pathogen posing a serious threat to crucian carp farming and has led to major economic losses in China’s aquaculture industry. This research aimed to explore how the CyHV-2-ORF41 protein influences viral replication. Firstly, we found that [...] Read more.

Cyprinid herpesvirus 2 (CyHV-2) is a major pathogen posing a serious threat to crucian carp farming and has led to major economic losses in China’s aquaculture industry. This research aimed to explore how the CyHV-2-ORF41 protein influences viral replication. Firstly, we found that ORF41 overexpression in Gibel carp brain (GiCB) cells significantly enhanced CyHV-2 replication. Subsequently, GST pull-down and LC-MS/MS analyses were conducted to identify ORF41’s protein interactions. The results showed that ORF41 might interact with pyruvate dehydrogenase (PDH)-E1β, an enzyme connecting glycolysis to the tricarboxylic acid (TCA) cycle. Furthermore, ORF41 expression decreased the PDH-E1β levels, leading to pyruvate and lactic acid accumulation. Molecular docking and dynamics simulations confirmed a stable interaction between ORF41 and PDH-E1β. This research not only deepens our understanding of CyHV-2’s mechanisms of infection but also suggests potential targets for therapeutic strategies in aquaculture. Full article

(This article belongs to the Special Issue Prevention and Control of Aquatic Animal Diseases)

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