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Fishes
Volume 10
Issue 4
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Fishes, Volume 10, Issue 4 (April 2025) – 51 articles

Cover Story (view full-size image): eDNA-based metabarcoding surveys were conducted in high-elevation lotic systems in the Great Smoky Mountains National Park, internationally renowned as a center of biodiversity. Two primer sets targeting different regions of the 12S mitochondrial gene were utilized, yielding a total of 568,000 reads per sample assignable to fish taxa. A total of nine families, 26 genera, and 40 species were detected. The primer set producing a shorter amplicon (97 bp vs. 225 bp) detected a greater number of fish species. These data were compared with an extensive body of electrofishing data (1984–2023); strong correlations were observed between species detected using both methods, although eDNA detected a greater number of species. In addition, significant correlations were observed between fish biomass determined via electrofishing and read abundance. View this paper
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19 pages, 3552 KiB  
Article
Effects of Glutamate on Growth Performance, Gut Digestion and Antioxidant Capacity in Juvenile Little Yellow Croaker
by Ruining Liu, Yu Zhang, Xiao Liang, Bao Lou and Junquan Zhu
Fishes 2025, 10(4), 188; https://doi.org/10.3390/fishes10040188 - 21 Apr 2025
Viewed by 206
Abstract
This study is to explore the alleviating effects of glutamate on intestinal damage in cultured little yellow croaker. A total of 900 juvenile fish at a weight of 30.68 ± 0.12 g were randomly separated into six groups with three replicates each, and [...] Read more.
This study is to explore the alleviating effects of glutamate on intestinal damage in cultured little yellow croaker. A total of 900 juvenile fish at a weight of 30.68 ± 0.12 g were randomly separated into six groups with three replicates each, and were fed a basic diet (protein at 44.42% and lipid at 12.48%) with additional glutamate at 0.00%, 0.40%, 0.80%, 1.2%, 1.60%, and 2.00%. Each replica group consisted of 50 fish in a breeding barrel (radius 1.0 m, height 1.5 m), and the experiment lasted for 54 days. The results showed that supplementation with 0.4–1.2% glutamate significantly improved the survival rate, which increased from 75.56% to 91.11%, reduced the feed conversion rate from 1.75 to 1.57, and increased the protein efficiency ratio from 1.55 to 1.85 (p < 0.05). In the intestines, the addition of 0.40–1.2% glutamate increased muscle thickness and villus height (p < 0.05), as well as the activities of pepsin, trypsin, α-amylase, and lipase (p < 0.05). Enzyme activity analysis indicated that the addition of 0.4–1.2% glutamate in the feed significantly enhanced the activities of serum Total Superoxide Dismutase (T-SOD), catalase (CAT), and glutathione peroxidase (GPx) antioxidant enzymes (p < 0.05). Transcriptome analysis of the 1.2% and 0% groups revealed that differentially expressed genes were enriched in glutathione synthesis, nutrient absorption and metabolism, and viral protein interaction with cytokine and cytokine receptor pathways. qPCR experiments verified that the addition of 1.2% glutamate significantly up-regulated the expression of antioxidant-related genes, including glutathione synthetase and Nrf2. In conclusion, the addition of glutamate can enhance growth performance, increase intestinal digestive capacity, activate intestinal glutathione synthesis to alleviate intestinal damage, and maintain intestinal health. Full article
(This article belongs to the Special Issue Application of Protein and Amino Acid in Aquaculture Feed)
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14 pages, 817 KiB  
Article
Typology of Fishing Grounds for Communal Fisheries Business in Korea: A Statistical Approach
by Ji Eun An and Chang Mo Ma
Fishes 2025, 10(4), 187; https://doi.org/10.3390/fishes10040187 - 19 Apr 2025
Viewed by 151
Abstract
This study statistically classifies Korea’s communal fishing grounds (Maeul-Eojang) to inform tailored fisheries policy. We applied principal component analysis (PCA) to reduce 17 socio-economic and demographic indicators into five core factors, followed by K-means clustering to derive distinct types. The methodology was validated [...] Read more.
This study statistically classifies Korea’s communal fishing grounds (Maeul-Eojang) to inform tailored fisheries policy. We applied principal component analysis (PCA) to reduce 17 socio-economic and demographic indicators into five core factors, followed by K-means clustering to derive distinct types. The methodology was validated using Kaiser–Meyer–Olkin and Bartlett’s tests. Five communal fishery types were identified, ranging from well-managed, high-income communities to those in severe decline. The results show that about half of fishing communities fall into a “post-fishery” type with diminishing membership and income, while a quarter maintain robust fisheries through diversification. The typology is compared with previous fishing village classifications, and we discuss policy recommendations for each type—including co-management, tourism support, and targeted aid for declining communities. This research provides an empirical foundation for improving communal fisheries governance and sustaining coastal livelihoods. Full article
(This article belongs to the Section Fishery Economics, Policy, and Management)
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23 pages, 1585 KiB  
Article
Effects of Climate Change on Korea’s Fisheries Production: An ARDL Approach
by Hoonseok Cho, Pilgyu Jung and Mingyeong Jeong
Fishes 2025, 10(4), 186; https://doi.org/10.3390/fishes10040186 - 18 Apr 2025
Viewed by 139
Abstract
This study investigates the impact of rising sea surface temperature (SST), increasing carbon dioxide (CO2) emissions, and precipitation variability (PREC) on Korea’s coastal and offshore fisheries production (COFP) from 1993 to 2023 using an autoregressive distributed lag (ARDL) model. The results [...] Read more.
This study investigates the impact of rising sea surface temperature (SST), increasing carbon dioxide (CO2) emissions, and precipitation variability (PREC) on Korea’s coastal and offshore fisheries production (COFP) from 1993 to 2023 using an autoregressive distributed lag (ARDL) model. The results confirm a long-run cointegration relationship, where a 1% increase in SST, CO2, and PREC is associated with respective declines of 3.52%, 0.82%, and 0.34% in COFP, respectively, suggesting persistent negative effects of ocean warming, acidification, and hydrological variability on fisheries production. Robustness checks using Fully Modified Ordinary Least Squares (FMOLS) and Canonical Cointegrating Regression (CCR) validate the stability of the ARDL results. The short-run analysis reveals that past production levels significantly influence current COFP, while SST fluctuations exhibit delayed but economically meaningful effects. The error correction term (−0.75, p < 0.01) confirms a rapid adjustment toward equilibrium following short-term deviations. These findings underscore the necessity of climate-resilient fisheries management. Policy recommendations include adaptive harvest regulations, climate-integrated stock assessments, and enhanced international cooperation for transboundary fish stocks. Additionally, expanding Marine Protected Areas, promoting climate-resilient aquaculture, and strengthening stock enhancement programs through selective breeding and seed release of climate-adapted species are essential for sustaining fisheries under climate change. Full article
(This article belongs to the Special Issue Effects of Climate Change on Marine Fisheries)
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13 pages, 667 KiB  
Article
A Comparison of White Muscle Quality in Grass Carp Ctenopharyngodon idellus Fed with Commercial Feeds and Barley Malt
by Chongjiang Hu, Zheng Huang, Hongkang Liu, Dingrui Mo, Peng Fu, Haiyan Guo, Wei Jiang, Yong Xie and Yongjun Chen
Fishes 2025, 10(4), 185; https://doi.org/10.3390/fishes10040185 - 18 Apr 2025
Viewed by 108
Abstract
This study was the first report regarding the application of barley malt (BM) for diets of aquaculture species. Triplicate groups of grass carp Ctenopharyngodon idellus with an initial size of about 1.2 kg were selected and fed with either BM or commercial feed [...] Read more.
This study was the first report regarding the application of barley malt (BM) for diets of aquaculture species. Triplicate groups of grass carp Ctenopharyngodon idellus with an initial size of about 1.2 kg were selected and fed with either BM or commercial feed (CF) to apparent satiation for 8 weeks in outdoor ponds connected with a flow-through aquaculture system. The results showed that the final body weight (1651 g) was lower in the BM fish than in the CF fish (1791 g). The edible part was lower in the BM fish than in the CF fish as indicated by the viscerosomatic index. Except for ash levels, which were lower in the fillet of the BM fish than for that of the CF fish, moisture, protein, and lipid levels were not impacted by the application of BM. Water-holding capacity indicators (drop loss, frozen exudation rate, and cooking loss) of grass carp muscle were not relevant to dietary modifications. Hematoxylin-eosin (HE) staining showed that the diameter of the myofibers was decreased while density was increased in response to the application of BM, which contributed to the improvement in textural properties (hardness, gumminess, and chewiness) in the muscle of the BM fish as compared to the CF fish. Glutamic acid level was highest, followed by aspartic acid, lysine, leucine, alanine, and arginine in grass carp muscle. Except three amino acids (proline, phenylalanine, and histidine), the amounts of the other 15 amino acids, essential amino acids, semi-essential amino acids, nonessential amino acids, and delicious amino acids were not impacted by different treatments, suggesting that the application of BM had a minor effect on the amino acid composition of grass carp muscle. Oleic acid (C18:1n-9), linoleic acid (C18:2n-6), and palmitic acid (C16:0) were the most abundant fatty acids in grass carp muscle. The amounts of poly-unsaturated fatty acid (PUFA) in the muscle decreased in response to the application of BM as the diet of grass carp, and n-6 PUFAs (C18:2n-6 and C20:2n-6) rather than n-3 PUFAs accounted for this change, which is beneficial for human health. In conclusion, the application of BM had minor impacts on the proximate composition and amino acid composition but improved textural properties and decreased n-6 PUFAs in the fillet of grass carp. Full article
(This article belongs to the Special Issue Growth, Metabolism, and Flesh Quality in Aquaculture Nutrition)
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14 pages, 2569 KiB  
Article
The Effect of the Marine Environment on the Distribution of Sthenoteuthis oualaniensis in the East Equatorial Indian Ocean
by Shigang Liu, Liyan Zhang, Peng Lian, Jianhua Kang, Puqing Song, Xing Miao, Longshan Lin, Rui Wang and Yuan Li
Fishes 2025, 10(4), 184; https://doi.org/10.3390/fishes10040184 - 17 Apr 2025
Viewed by 115
Abstract
Sthenoteuthis oualaniensis is one of the most commercially important marine cephalopod species distributed throughout tropical and subtropical waters of the Indo-Pacific Seas. The Indian Ocean is a main fishing ground for S. oualaniensis with a high population density. To explore the distribution of [...] Read more.
Sthenoteuthis oualaniensis is one of the most commercially important marine cephalopod species distributed throughout tropical and subtropical waters of the Indo-Pacific Seas. The Indian Ocean is a main fishing ground for S. oualaniensis with a high population density. To explore the distribution of S. oualaniensis in the east equatorial Indian Ocean, four surveys were carried out using light-lift-net fishing vessels. Meanwhile, marine environmental data were also collected, including the sea surface temperature, sea temperature at 100 m depth, mixed layer depth, sea surface chlorophyll-a concentration, sea surface height, and eddy kinetic energy. Generalized Additive Models were used to analyze the relationship between the catch per unit effort (CPUE) for S. oualaniensis and environmental factors. The results showed that the average CPUE of S. oualaniensis was 14.55 kg/h in the four surveys, which was considerably lower than in the South China Sea and Northwest Indian Ocean. In terms of seasonal distribution, the high-CPUE stations were closer to the continental shelf in spring, while they shifted towards the deeper and offshore water in autumn, demonstrating a seasonal migration trend. Pearson correlation analysis showed that CPUE reflected a significant negative correlation with both sea temperature at 100 m depth and eddy kinetic energy (p < 0.001). The Generalized Additive Models revealed that sea surface height was the most significant factor affecting CPUE with a variance explanation of 30.1%. Furthermore, the optimal CPUE prediction model was established by stepwise regression, which contains two factors, sea surface height and eddy kinetic energy, with a variance explanation of 34.9%. This study provides insights into the environmental factors influencing the distribution of S. oualaniensis, which is essential for the sustainable utilization and management of this species. Full article
(This article belongs to the Special Issue Assessment and Management of Fishery Resources)
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11 pages, 475 KiB  
Article
Optimizing Cryopreservation of Pseudoplatystoma magdaleniatum Semen: Evaluation of Two Permeable and Two Non-Permeable Cryoprotectants
by César Montes-Petro, Betty Rodríguez-Peroza, Diana Madariaga-Mendoza, Carlos Tapia-Pacheco, José Espinosa-Araujo and Víctor Atencio-García
Fishes 2025, 10(4), 183; https://doi.org/10.3390/fishes10040183 - 17 Apr 2025
Viewed by 172
Abstract
The study aimed to evaluate the effectiveness of the cryopreservation protocols for Pseudoplatystoma magdaleniatum semen using dimethyl sulfoxide (DMSO) or methanol (MET) as permeable cryoprotectants at two concentrations (5% and 10%) combined with 12% egg yolk (Y12%) or 5% skimmed milk powder (SMP5%) [...] Read more.
The study aimed to evaluate the effectiveness of the cryopreservation protocols for Pseudoplatystoma magdaleniatum semen using dimethyl sulfoxide (DMSO) or methanol (MET) as permeable cryoprotectants at two concentrations (5% and 10%) combined with 12% egg yolk (Y12%) or 5% skimmed milk powder (SMP5%) and glucose (6%), resulting in eight treatments. A semen pool (n = 8) was diluted in a 1:4 ratio, packed in 2.5 mL straws, and frozen in nitrogen vapors. It was thawed at 35 °C for 90 s. Sperm kinetics and motility duration of fresh, prefrozen, and thawed semen were analyzed using a CASA system. The osmolarity of seminal plasma and cryosolutions was estimated. Fertilization (F) and embryo viability (E) rates of thawed semen were evaluated. The osmolarity of seminal plasma was 251.1 ± 3.3 mOsmol/kg and, in the cryosolutions, ranged between 1248.3 ± 19.9 mOsmol/kg (DMSO5% + Y12%) and 3488.2 ± 1.5 mOsmol/kg (MET10% + Y12%). After thawing, total motility ranged from 38.2% to 60.5%, representing a significant reduction compared to fresh semen (95.4 ± 2.1%) (p < 0.05). The best fertilization and embryo viability rates of thawed semen were obtained with DMSO5% + SMP 5% (F = 20.7%, E = 11.7%) and MET10% + SMP5% (F = 20.1%, E = 11.5%) (p < 0.05). A cryopreservation protocol for P. magdaleniatum semen with 5%DMSO or 10%MET combined with SMP5% is possible, but further study is necessary to optimize its fertilizing capacity. Full article
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18 pages, 2312 KiB  
Article
Feeding Habits of Mene maculata (Teleostei: Menidae) in the Southwestern Waters of Taiwan, Western Pacific Ocean
by Yi-Chen Wang, Ming-An Lee and Jia-Sin He
Fishes 2025, 10(4), 182; https://doi.org/10.3390/fishes10040182 - 16 Apr 2025
Viewed by 239
Abstract
This study investigated the feeding habits of moonfish (Mene maculata) in the waters of southwestern Taiwan in the Western Pacific Ocean using commercial trawling nets and Taiwanese purse seines. For this, we analyzed the body size and stomach content of moonfish [...] Read more.
This study investigated the feeding habits of moonfish (Mene maculata) in the waters of southwestern Taiwan in the Western Pacific Ocean using commercial trawling nets and Taiwanese purse seines. For this, we analyzed the body size and stomach content of moonfish specimens collected from the study area between January and December 2023. The length–weight relationship revealed hypoallometric growth patterns in both male and female specimens, with allometric coefficients of 2.6574 and 2.7219, respectively. Stomach content analysis indicated that the specimens primarily fed on Calanoida (zooplankton; %PSIRI = 36.79) and Benthosema pterotum (fish; %PSIRI = 19.23). Dietary composition varied with body size and sampling time. Larger individuals consumed higher proportions of fish. The percentage of empty stomachs was high, likely attributable to the fishing gear used and sampling time. Based on the results of this study, it is speculated that moonfish feed mainly before early morning or at other times during the day. Full article
(This article belongs to the Special Issue Fish Trophic Ecology: Revealing the Responses to Global Change from Individuals to Ecosystems)
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16 pages, 2158 KiB  
Article
The Impact of Feeding Rates on the Growth, Stress Response, Antioxidant Capacity, and Immune Defense of Koi (Cyprinus carpio var. koi)
by Saixing Duan, Shengyu Gao, Xiaolong Xu, Qi Wei, Ze Tao, Gaoxiao Xu, Quanzhou Liu, Bing Wei and Chaofan He
Fishes 2025, 10(4), 181; https://doi.org/10.3390/fishes10040181 - 16 Apr 2025
Viewed by 242
Abstract
The feeding rate is critical for fish growth and the feed conversion ratio (FCR). Prior research has primarily evaluated the optimal feeding rate by examining growth performance and the FCR. Given the high cost of koi as an ornamental fish, it is essential [...] Read more.
The feeding rate is critical for fish growth and the feed conversion ratio (FCR). Prior research has primarily evaluated the optimal feeding rate by examining growth performance and the FCR. Given the high cost of koi as an ornamental fish, it is essential to consider the effects of feeding rates on its welfare and health. This study aimed to examine the impact of the feeding rate on the growth, stress response, antioxidant capacity, and immune defense of koi. A total of 240 fish, with an initial body weight of 10.02 ± 0.18 g, were randomly assigned to six groups and fed expanded diets at 1%, 2%, 3%, 4%, 5%, and 6% of body weight per day (BW/day) for a duration of eight weeks. The study results indicated that the daily weight gain of fish at 3–4% BW/day was significantly greater than that of the other groups. Fish in both high and low feeding rate groups exhibited reduced antioxidant capacity and heightened inflammatory response, as indicated by a notable decrease in catalase (CAT) and superoxide dismutase (SOD) activity, along with diminished expression of cat and sod, as well as a significant increase in the expression of tnf-α, il1, and il10. The elevated feeding rate did not enhance immune defense mechanisms. Furthermore, a low feeding rate resulted in heightened stress and reduced immunity in koi, as indicated by a significant reduction in plasma cortisol (COR), complement C3, complement C4, total protein (TP), albumin (ALB), and globulin (GLO) levels, along with decreased activities of lysozyme (LZM) and myeloperoxidase (MPO). The optimal feeding rate for enhancing non-specific immunity in koi is a daily intake of 3–4% of body weight on extruded feed. Our findings reveal that underfeeding led to diminished antioxidants and immune defenses in koi, while overfeeding also proved detrimental. An optimal feeding rate of 3–4% body weight per day is necessary to enhance growth and health in this species. Full article
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17 pages, 2037 KiB  
Article
Effects of Fermented Soybean Meal Replacing Fishmeal and Adding Lentinus edodes Fermentation Supplementation on Japanese Eel (Anguilla japonica) Cultivated in Pond Cage
by Jie Yu, Fei Xiao, Qian Xiao, Dongming Chen, Guoyong Zhou, Huanbin Jiang, Xiaoya Fan, Herong Shi and Huihong Zhao
Fishes 2025, 10(4), 180; https://doi.org/10.3390/fishes10040180 - 16 Apr 2025
Viewed by 227
Abstract
Replacing fishmeal (FM) with plant-based protein sources remains a significant challenge, particularly for carnivorous fish. This study investigates the effect of dietary Lentinus edodes fermentation (LEF) supplementation on Japanese eel (Anguilla japonica) fed with fermented soybean meal (FSM) as a partial [...] Read more.
Replacing fishmeal (FM) with plant-based protein sources remains a significant challenge, particularly for carnivorous fish. This study investigates the effect of dietary Lentinus edodes fermentation (LEF) supplementation on Japanese eel (Anguilla japonica) fed with fermented soybean meal (FSM) as a partial FM replacement. The positive control consisted of 64% FM (Con), and the negative control (FSM group) included 52% FM plus 12% FSM. Two experimental diets were formulated by adding 2% LEF (LEF2 group) and 3% LEF (LEF3 group) to the negative control diet. The experimental diet was administered to Japanese eels weighing 62.50 ± 2.14 g for 12 weeks. The experimental fish were randomly assigned to four groups, with three replicates of 100 fish per group. The results indicated that growth performance and feed efficiency were significantly reduced in the FSM group, but were significantly improved by LEF supplementation (p < 0.05). LEF supplementation did not significantly affect muscle crude fat and protein content compared to the FSM group (p > 0.05), but significantly increased muscle amino acid content and levels of certain fatty acids (linoleic acid, γ-linolenic acid, eicosatrienoic acid, DHA) (p < 0.05). LEF supplementation reduced serum TC and LDL-C levels, increased HDL-C levels, significantly increased CAT and T-SOD activities, and reduced MDA levels in both serum and liver (p < 0.05). ALT and AST activities were significantly elevated in the FSM group, accompanied by liver histological abnormalities, which were improved by LEF supplementation. LEF supplementation increased the thickness of the muscularis, villus height, and goblet cell count in the intestine (p < 0.05). Compared to the control, the FSM group significantly upregulated spleen tnf-α gene expression and downregulated the expression of anti-inflammatory factors (ifn-α, ifn-γ, socs1, mavs). LEF supplementation ameliorated the reduced immunocompetence induced by FM replacement with FSM by enhancing the expression of immune-related genes (irak4, ifn-α, ifn-γ, irf3, irf11, socs1, mavs, traf3) in the spleen. These results suggest that the beneficial effects of LEF supplementation on growth performance and feed efficiency may be attributed to its improvement of liver damage and intestinal histology, as well as its enhancement of antioxidant capacity and immunity. Full article
(This article belongs to the Special Issue Pivotal Roles of Feed Additives for Fish)
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26 pages, 4364 KiB  
Article
Purification of Intensive Shrimp Farming Effluent by Gracilaria Coupled with Oysters
by Junjing Li, Yu Xu, Yunlong Deng, Xiaojuan Hu, Haochang Su, Guoliang Wen and Yucheng Cao
Fishes 2025, 10(4), 179; https://doi.org/10.3390/fishes10040179 - 15 Apr 2025
Viewed by 169
Abstract
In this study, we explored the ability of Gracilaria vermiculophylla coupled with Crassostrea hongkongensis to purify aquaculture effluent by analysing the purification of intensive shrimp farming effluent using G. vermiculophylla under different environmental conditions. After determining the optimal conditions, we further investigated the [...] Read more.
In this study, we explored the ability of Gracilaria vermiculophylla coupled with Crassostrea hongkongensis to purify aquaculture effluent by analysing the purification of intensive shrimp farming effluent using G. vermiculophylla under different environmental conditions. After determining the optimal conditions, we further investigated the capability of the G. vermiculophylla and oyster coupling in intensive shrimp farming effluent purification. The shrimp farming density was 200 individuals per cubic metre (equivalent to 0.2 individuals per litre). The optimal environmental parameters were as follows: oyster biomass of 4.5 kg·m−3, G. vermiculophylla biomass of 2 kg·m−3, water temperature of 25–30 °C, and salinity of 15–30‰; the total inorganic nitrogen, PO43−-P, total nitrogen, and total phosphorus removal rates were 59.56%, 97.43%, 63.67%, and 76.25%, respectively, with G. vermiculophylla increasing in weight by 31.01%. For every 1 kg increase in the dry weight of G. vermiculophylla, 36.89 g of N and 12.40 g of P could be absorbed from the effluent. Our findings indicate that the coupling of G. vermiculophylla with oysters greatly contributed to the purification of effluent from intensive shrimp farming and can, thus, be used for treating intensive shrimp farming effluent. Full article
(This article belongs to the Special Issue Advances in Shrimp Aquaculture: Management and Sustainability)
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20 pages, 3616 KiB  
Article
Long-Term Heavy Metal Bioaccumulation in Sprat (Sprattus sprattus) from the Romanian Black Sea: Ecological and Human Health Risks in the Context of Sustainable Fisheries
by Andra Oros and Madalina Galatchi
Fishes 2025, 10(4), 178; https://doi.org/10.3390/fishes10040178 - 15 Apr 2025
Viewed by 307
Abstract
This study evaluates the heavy metals concentrations in sprat (Sprattus sprattus, Linnaeus, 1758) from the Romanian Black Sea, assessing both ecological implications and human health risks associated with consumption. Using long-term data spanning 1994–2019, levels of copper (Cu), cadmium (Cd), lead [...] Read more.
This study evaluates the heavy metals concentrations in sprat (Sprattus sprattus, Linnaeus, 1758) from the Romanian Black Sea, assessing both ecological implications and human health risks associated with consumption. Using long-term data spanning 1994–2019, levels of copper (Cu), cadmium (Cd), lead (Pb), nickel (Ni), and chromium (Cr) in dorsal muscle tissues were analyzed to identify contamination trends and episodic pollution events. Although most concentrations remained below regulatory thresholds, occasional exceedances of Cd and Pb suggest intermittent pollution inputs. Health risks were assessed using dietary indices including estimated daily intake (EDI), target hazard quotient (THQ), total hazard quotient (TTHQ), and carcinogenic risk index (CRI). Findings indicate that, under current exposure levels, regular sprat consumption poses minimal risk. However, prolonged intake during peak contamination periods may contribute to cumulative toxic effects, with implications for ecosystem stability and food safety. Given the persistence of heavy metals and their interactions with co-occurring pollutants, such as persistent organic pollutants (POPs) and polycyclic aromatic hydrocarbons (PAHs), ongoing monitoring remains essential. This study supports the development of sustainable environmental policies aimed at protecting marine biodiversity and consumer health in the Black Sea region. Full article
(This article belongs to the Section Environment and Climate Change)
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16 pages, 2458 KiB  
Article
Mitogenomic and Phylogenetic Analyses of Lysmata lipkei (Crustacea: Decapoda: Lysmatidae)
by Xixi Zhang, Zhihuang Zhu, Jianxin Wang, Ge Shi and Qi Lin
Fishes 2025, 10(4), 177; https://doi.org/10.3390/fishes10040177 - 14 Apr 2025
Viewed by 196
Abstract
This study aims to elucidate the characteristics of the mitogenome of Lysmata lipkei and investigate its phylogenetic relationships. Using both the Illumina NovaSeq 6000 (Illumina, Inc., San Diego, CA, USA) and PacBio Sequel II (Pacific Biosciences of California, Inc., Menlo Park, CA, USA) [...] Read more.
This study aims to elucidate the characteristics of the mitogenome of Lysmata lipkei and investigate its phylogenetic relationships. Using both the Illumina NovaSeq 6000 (Illumina, Inc., San Diego, CA, USA) and PacBio Sequel II (Pacific Biosciences of California, Inc., Menlo Park, CA, USA) platforms, the complete mitogenome sequence of L. lipkei was determined. The mitogenome of L. lipkei was annotated, measuring 17,497 bp in length and comprising 13 protein-coding genes (PCGs), 2 ribosomal RNA genes (rRNAs), and 22 transfer RNA genes (tRNAs). The nucleotide composition of the genome exhibited an AT bias of 63.4%. Among the PCGs, the most frequently used codon was UUA. All tRNAs, except for trnD, which lacks the TψC loop, were capable of forming the typical cloverleaf structure. Phylogenetic trees for Caridea were constructed using Bayesian Inference (BI) and Maximum Likelihood (ML) methods based on the nucleotide sequences of the 13 PCGs. Both methods yielded consistent topological structures, with L. lipkei showing the closest phylogenetic relationship to L. kuekenthali. Additionally, Lysmatidae, Thoridae, and Hippolytidae formed a monophyletic clade. This research not only filled the gap in mitogenome data for Lysmatidae but also provided novel molecular insights into Caridean phylogenetics. Full article
(This article belongs to the Section Genetics and Biotechnology)
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14 pages, 2821 KiB  
Article
Spatial–Temporal Variations in Fish Larvae and Juveniles in the Surf Zone Along the Coast of Jiangsu Province, China
by Xiaodong Wang, Yuying Chen, Boran Qin, Tianyu Zhang, Junsheng Zhong, Jinjin Shi and Chuqing Wang
Fishes 2025, 10(4), 176; https://doi.org/10.3390/fishes10040176 - 13 Apr 2025
Viewed by 237
Abstract
Surf zones are important nursery grounds for fish larvae and juveniles. However, little is known about fish larvae and juveniles in the surf zone along the coast of Jiangsu Province. To describe the species composition of fish larvae and juveniles, monthly collections were [...] Read more.
Surf zones are important nursery grounds for fish larvae and juveniles. However, little is known about fish larvae and juveniles in the surf zone along the coast of Jiangsu Province. To describe the species composition of fish larvae and juveniles, monthly collections were conducted at eight stations during the spring tide from February 2024 to January 2025. The fish larvae and juveniles were sampled using a seine net (1m × 4m; 1 mm mesh aperture), with sampling repeated three times at each station per month. A total of 1435 fish larvae and juveniles were collected, belonging to 42 species and 37 genera in 21 families. Almost half of them were postflexion larvae. Gobiidae, with 14 species, was the most diverse family. Based on the index of relative importance (IRI) result, the dominant species was Amoya pflaumi, accounting for 35.33% of the total number of individuals collected. Common species were Mugil cephalus, Amblychaeturichthys hexanema, Tridentiger trigonocephalus, Acanthogobius ommaturus, Mugilogobius abei, Thryssa mystax, Periophthalmus modestus, Sillago sihama, and Mugilogobius myxodermus. All other species were classified as rare. No fish larvae or juveniles were collected in February 2024 and January 2025. The species number, catch per unit effort (CPUE), Margalef’s richness index, Pielou’s evenness index, and Shannon–Wiener diversity index showed similar trends, and significant differences could be found for each parameter among sampling months. The cluster analysis from the ten months (excluding February 2024 and January 2025) indicated a significant seasonal change in the community structure of fish larvae and juveniles. Fish larvae and juveniles were abundant and diverse at one station near an aquaculture tidal flat for seaweed. This study provides essential basic data to support the management and conservation of fishery resources in the surf zone along the coast of Jiangsu Province. Full article
(This article belongs to the Special Issue Biodiversity and Spatial Distribution of Fishes, Second Edition)
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13 pages, 2796 KiB  
Article
Revealing the Structure and Biodiversity Patterns of Fish Communities in River Networks Based on Environmental DNA
by Ziyu Liu, Yongsheng Wu, Wenhui You, Shuxin Li, Ge Shi and Chen Zhang
Fishes 2025, 10(4), 175; https://doi.org/10.3390/fishes10040175 - 13 Apr 2025
Viewed by 234
Abstract
Revealing taxonomic, functional, and phylogenetic dimensions of biodiversity is critical for the effective conservation and management of aquatic organisms in freshwater ecosystems subjected to multiple threats. Fish biodiversity patterns in river ecosystems exhibit complex spatiotemporal variation influenced by hydrological connectivity and the dispersal [...] Read more.
Revealing taxonomic, functional, and phylogenetic dimensions of biodiversity is critical for the effective conservation and management of aquatic organisms in freshwater ecosystems subjected to multiple threats. Fish biodiversity patterns in river ecosystems exhibit complex spatiotemporal variation influenced by hydrological connectivity and the dispersal ability of species within the river network. This study utilized eDNA metabarcoding to investigate fish communities in three subtropical mountain rivers, aiming to uncover the community structure and spatiotemporal dynamics of the multidimensional biodiversity of fish communities across varying positions within the river network. The three biodiversity indices of the fish communities at the confluence were significantly greater than those of the mainstream community in the dry season, whereas the phylogenetic diversity of the fish community at the tributaries during the wet season was significantly greater than that in the mainstream. This likely reflected the unique spatial configuration of confluences and the seasonal dispersal of fish in the river network. The results of this study highlighted the important role of confluences and tributaries in river networks and the fact that they need to be prioritized to conserve riverine fish diversity. Full article
(This article belongs to the Special Issue Mapping and Monitoring Aquatic Biodiversity in Hotspot Habitat Areas Using Environmental DNA (eDNA))
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18 pages, 4255 KiB  
Article
Sub-Lethal Effects of Predators in Aquaculture: Assessment of Chronic Exposure to Conspecific Alarm Substance on Feeding and Growth Performances of Nile Tilapia
by Rafaela Torres Pereira, Alexandre Luiz Arvigo, Caio Akira Miyai, Augusto Rysevas Silveira, Percília Cardoso Giaquinto, Helton Carlos Delicio, Leonardo José Gil Barcellos and Rodrigo Egydio Barreto
Fishes 2025, 10(4), 174; https://doi.org/10.3390/fishes10040174 - 12 Apr 2025
Viewed by 266
Abstract
In aquaculture practices, fish are mostly protected from lethal actions of predators. However, sub-lethal effects can be challenging to prevent, as they may be associated with chemical cues signaling predation risk that easily dissolve and spread in water, serving as potential stressors. These [...] Read more.
In aquaculture practices, fish are mostly protected from lethal actions of predators. However, sub-lethal effects can be challenging to prevent, as they may be associated with chemical cues signaling predation risk that easily dissolve and spread in water, serving as potential stressors. These cues originate from predators, stressed or injured prey releasing blood, a conspecific alarm substance (CAS), and/or other bodily fluids. In this study, we simulated a small-scale net cage system and assessed the feeding and growth of Nile tilapia exposed chronically to a CAS. Nile tilapia, an invasive species in many aquatic systems, frequently coexist freely alongside those cultivated in cages. Consequently, caged tilapia may regularly be exposed to a CAS, potentially leading to chronic stress and impacting growth and development. Fish were exposed daily to either a CAS or a control vehicle (distilled water) for 45 days (one fish per cage). Fish in both conditions exhibited similar increases in body mass, weight gain, and length over time and displayed an allometric negative growth profile, indicating that the CAS did not affect the length–weight relationship as well. Specific and relative growth rates, condition factor, body axes, food intake, and feeding conversion efficiency were also unaffected by the CAS over time. This body of evidence suggests that the CAS did not act as a chronic stressor for caged Nile tilapia and a possible explanation is habituation. Full article
(This article belongs to the Special Issue Stress Physiology in Aquatic Animals)
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17 pages, 8464 KiB  
Article
UM-YOLOv10: Underwater Object Detection Algorithm for Marine Environment Based on YOLOv10 Model
by Rengui Mai and Ji Wang
Fishes 2025, 10(4), 173; https://doi.org/10.3390/fishes10040173 - 11 Apr 2025
Viewed by 279
Abstract
In order to address the challenges of a low detection accuracy, missed detections, and false detections in marine precious biological target detection within complex marine environments, this paper presents a novel residual attention module called R-AM. This module is integrated into the backbone [...] Read more.
In order to address the challenges of a low detection accuracy, missed detections, and false detections in marine precious biological target detection within complex marine environments, this paper presents a novel residual attention module called R-AM. This module is integrated into the backbone network of the YOLOv10 model to improve the model’s focus on the detailed features of biological targets during feature extraction. Additionally, the introduction of a bidirectional feature pyramid with adaptive feature fusion in the neck network enhances the integration of semantic information from deep layers, and localization cues from shallow layers improve the model’s ability to distinguish targets from their environments. The experimental data showed that the improved YOLOv10 model achieved 92.89% at mAP@0.5, increasing by 1.31% compared to the original YOLOv10 model. Additionally, the mAP@0.5:0.95 was 77.13%, indicating a 3.71% improvement over the original YOLOv10 model. When compared to the Faster R-CNN, SSD, RetinaNet, YOLOv6, and YOLOv7 models, the enhanced model exhibited increases of 1.5%, 1.7%, 4.06%, 4.7%, and 1.42% in mAP@0.5, respectively. This demonstrates a high detection accuracy and robust stability in complex seabed environments, providing valuable technical support for the scientific management of marine resources in underwater ranches. Full article
(This article belongs to the Section Fishery Facilities, Equipment, and Information Technology)
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11 pages, 2807 KiB  
Article
Study on the Flow Velocity Preference of the Four Major Chinese Carps Using Convolutional Neural Networks
by Ning Qiu, Wenjing Li, Yi Yu, Jianna Jia, Guoqiang Ma and Shitao Peng
Fishes 2025, 10(4), 172; https://doi.org/10.3390/fishes10040172 - 11 Apr 2025
Viewed by 203
Abstract
Flow velocity is a critical factor in determining the suitability of fish habitats. Understanding the preference patterns of the four major Chinese carps (FMCCs) for different flow velocities is crucial for their habitat conservation and restoration. In this study, the preference of individual [...] Read more.
Flow velocity is a critical factor in determining the suitability of fish habitats. Understanding the preference patterns of the four major Chinese carps (FMCCs) for different flow velocities is crucial for their habitat conservation and restoration. In this study, the preference of individual fish species, approximately 15 cm in length, for flow velocity was investigated at flow velocity gradients of 0.0, 0.4, 0.8, 1.2, 1.6, and 2.0 times their body length. Additionally, a deep learning algorithm based on convolutional neural networks (CNNs) was employed for fish target detection. The results showed that, at this length, black carp (Mylopharyngodon piceus) preferred fast currents when the inlet flow velocity was between 0.4 and 1.6 times their body length, while grass carp (Ctenopharyngodon idella), silver carp (Hypophthalmichthys molitrix), and bighead carp (Hypophthalmichthys nobilis) preferred fast currents when the inlet flow velocity of the test flume was between 0.4 and 2.0 times their body length. However, this preference for fast currents decreased as the overall flow velocity increased to a specific threshold, eventually leading to their avoidance. The highest preference for fast currents among the four species was observed at inlet flow velocities of 1.2, 0.4, 0.8, and 0.8 times their body length, respectively. The findings of this study provide important insights into habitat conservation and restoration for the FMCCs in projects focused on the construction of navigation channels and water conservancy. Full article
(This article belongs to the Topic The Importance of Fish Phenotype in Aquaculture, Fisheries and Conservation)
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15 pages, 2429 KiB  
Article
Effects of Stocking Densities on the Growth Performance and Physiology of Juvenile Piaractus brachypomus in Recirculating Aquaculture System
by Imaculada de Morais Carvalho Ananias, Sidney dos Santos Silva, André de Sena Souza, Fábio Aremil Costa dos Santos, Thamara Bentivole Magalhães, Wagner Junio de Freitas Martins, Gisele Cristina Favero and Ronald Kennedy Luz
Fishes 2025, 10(4), 171; https://doi.org/10.3390/fishes10040171 - 11 Apr 2025
Viewed by 287
Abstract
The effects of different stocking densities on the growth and physiology of juvenile Piaractus brachypomus were evaluated in two experiments. Experiment I used juveniles weighing 1.5 ± 0.4 g at the following densities for 20 days: D0.68—0.68 kg/m3; D [...] Read more.
The effects of different stocking densities on the growth and physiology of juvenile Piaractus brachypomus were evaluated in two experiments. Experiment I used juveniles weighing 1.5 ± 0.4 g at the following densities for 20 days: D0.68—0.68 kg/m3; D1.45—1.45 kg/m3; D4.41—4.41 kg/m3; and D7.17—7.17 kg/m3. Experiment II used juveniles weighing 6.66 ± 1.3 g at the following densities for 20 days: D1.0—1.00 kg/m3; D1.95—1.95 kg/m3; D5.63—5.63 kg/m3, and D7.90—7.90 kg/m3. Both experiments showed a reduction in dissolved oxygen levels in the water, with Experiment II showing a plateau effect from 2.34 kg/m3 (p < 0.05). Final weight, final length, weight gain, daily weight gain, and specific growth rate were inversely proportional to density (p < 0.05), while final biomass, feed intake, and feed conversion were directly related to density in both experiments (p < 0.05). At the end of Experiment II, plasma triglycerides decreased as stocking density increased (p < 0.05), and hemoglobin and mean corpuscular volume were higher at the lowest density (D1.0) (p < 0.05). High stocking densities reduced dissolved oxygen, characterizing a hypoxic state in both experiments, affecting growth and some physiological parameters. Therefore, studies testing stocking densities for P. brachypomus in normoxic situations are still needed. Full article
(This article belongs to the Section Fishery Economics, Policy, and Management)
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19 pages, 12747 KiB  
Article
Impact of Faba Bean (Vicia faba L.) Diet and Subsequent Withdrawal on GIFT Tilapia (Oreochromis niloticus) Muscle Quality
by Guanling Xu, Wei Xing, Tieliang Li, Shibo Wei, Ying Zhang, Tingting Song, Huanhuan Yu and Lin Luo
Fishes 2025, 10(4), 170; https://doi.org/10.3390/fishes10040170 - 11 Apr 2025
Viewed by 264
Abstract
To systematically evaluate FB’s effects on tilapia muscle quality, two distinct experimental phases are designed, the crispy texture development phase (0–16 weeks) and the crispy texture retention phase (17–24 weeks), which can determine the minimum faba bean (FB) feeding duration required to achieve [...] Read more.
To systematically evaluate FB’s effects on tilapia muscle quality, two distinct experimental phases are designed, the crispy texture development phase (0–16 weeks) and the crispy texture retention phase (17–24 weeks), which can determine the minimum faba bean (FB) feeding duration required to achieve optimal textural modification and can assess the persistence of improved textural properties following FB withdrawal, respectively. The results demonstrated that a 60% FB inclusion diet administered for 16 weeks did not adversely affect tilapia growth performance. Significant improvements in textural parameters, including hardness, springiness, chewiness, and shear force, were observed in FB-fed tilapia as early as 8 weeks, with these enhancements being maintained throughout the 16-week feeding period. These superior textural characteristics persisted during the subsequent retention phase following FB withdrawal. Microstructural analysis revealed that the 60% FB diet significantly enhanced muscle-fiber density while reducing fiber diameter in tilapia during the 8–16 week feeding period. These microstructural modifications persisted throughout the texture retention phase, maintaining significant differences compared to the control group. Serological analysis demonstrated the FB group elevated Superoxide dismutase (SOD) activity and reduced malondialdehyde (MDA) levels at 4 weeks, though these differences normalized thereafter. qRT-PCR showed the 60% FB clearly increased the expression of mstn at 8 weeks, while col1a-2 and myog expressions also obviously improved at 12 weeks. In summary, dietary 60% FB improved tilapia muscle crispiness by altering texture and microstructure via gene-expression regulation. The minimum duration was 8 weeks to achieve crispiness in tilapia by the 60% FB diet without adverse effects on growth, immunity, and hepatopancreas function. Furthermore, the crispy texture of tilapia fillets was maintained for at least 2 months following withdrawal of the 60% FB diet after 16 weeks of continuous feeding. Full article
(This article belongs to the Special Issue Growth, Metabolism, and Flesh Quality in Aquaculture Nutrition)
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24 pages, 6012 KiB  
Article
Using Baited Remote Underwater Video Surveys (BRUVs) to Analyze the Structure of Predators in Guanahacabibes National Park, Cuba
by Dorka Cobián-Rojas, Jorge Angulo-Valdés, Pedro Pablo Chevalier-Monteagudo, Lázaro Valentín García-López, Susana Perera-Valderrama, Joán Irán Hernández-Albernas and Hansel Caballero-Aragón
Fishes 2025, 10(4), 169; https://doi.org/10.3390/fishes10040169 - 10 Apr 2025
Viewed by 693
Abstract
The reef fish communities of the Guanahacabibes National Park have been studied for 20 years using various methodologies that have allowed us to understand aspects of their diversity and structure. However, due to gaps in information about the abundance and distribution of mesopredators [...] Read more.
The reef fish communities of the Guanahacabibes National Park have been studied for 20 years using various methodologies that have allowed us to understand aspects of their diversity and structure. However, due to gaps in information about the abundance and distribution of mesopredators (big fish and sharks), a new study was conducted in 2017 to determine their structure, explore the influence of different factors on their spatial variability, and evaluate their behavior. To achieve this, the Baited Remote Underwater Video Surveys (BRUVs) methodology was successfully applied, locating a single set of BRUVs at 90 sites distributed across 9 sectors of the park’s functional zoning. Variability in mesopredator metrics and their potential prey was assessed through a PERMANOVA analysis; a distance-based linear model (DISTLM) was used to explore the relationship between mesopredator abundance and biological, abiotic, and condition variables; and animal behavior was classified as incidental, cautious, or aggressive. A total of 64 fish species were identified, 7 of which were mesopredators, and 3 were sharks. An uneven distribution and abundance were observed among sectors, with the most abundant mesopredators being Carcharhinus perezi, Sphyraena barracuda, and Mycteroperca bonaci. Mesopredator abundance was more closely related to the condition of zone use and its regulations than to biological and abiotic variables. Sharks were more abundant in strictly protected areas, which coincided with relatively murky waters and stronger currents. More than 50% of the observed sharks displayed exploratory and aggressive behavior towards the bait basket. The analyzed metrics validate the effectiveness of the management of the protected area and suggest the presence of healthy and resilient mesopredator fish communities. Full article
(This article belongs to the Special Issue Movement Ecology and Conservation of Large Marine Fishes (and Sharks))
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15 pages, 1646 KiB  
Article
Comparing Ecosystem Structure and Function of the Geheyan Reservoir Based on the Ecopath Model After a Fishing Ban
by Miao Xiang, Haoran Liu, Nian Wei, Zihao Meng, Feifei Hu and Xuemei Li
Fishes 2025, 10(4), 168; https://doi.org/10.3390/fishes10040168 - 9 Apr 2025
Viewed by 260
Abstract
The Geheyan Reservoir, located on the Qingjiang River, a tributary of the Yangtze River, is important for regional water supplies and ecological conservation. Understanding changes in ecosystem structure and function has become critical for assessing efficacy after the implementation of a fishing ban. [...] Read more.
The Geheyan Reservoir, located on the Qingjiang River, a tributary of the Yangtze River, is important for regional water supplies and ecological conservation. Understanding changes in ecosystem structure and function has become critical for assessing efficacy after the implementation of a fishing ban. This study employs the Ecopath model to examine the ecosystem characteristics of the Geheyan Reservoir before (2017) and after (2022) the fishing ban. The results show significant differences in trophic levels, energy transfer efficiency, and ecosystem maturity between the two periods. The trophic levels increased from 3.36 pre-fishing ban to 3.89 post-ban, indicating an enhanced complexity in the food web structure. The highest eco-trophic efficiency for major commercial fish species increased after the ban, indicating improved energy utilization efficiency. However, energy transfer bottlenecks were still observed between trophic levels II and IV, suggesting ongoing challenges in nutrient cycling. The total primary production-to-total respiration ratio (6.93) and the connectivity index (0.25) indicate that the ecosystem’s maturity and stability have improved after the fishing ban. These findings underscore the ban’s effectiveness and provide a scientific foundation for sustainable management of Geheyan Reservoir and similar ecosystems in the Yangtze River Basin. Full article
(This article belongs to the Special Issue Adaptation and Response of Fish to Environmental Changes)
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16 pages, 5727 KiB  
Article
Immune Response Analysis of Head Kidney in Large Yellow Croaker (Larimichthys crocea) Following Nocardia seriolae Infection
by Lu Yuan, Ziqi Ban, Kejing Huang, Rongrong Ma, Suming Zhou, Jianhu Jiang, Chenjie Fei and Jiasong Xie
Fishes 2025, 10(4), 167; https://doi.org/10.3390/fishes10040167 - 8 Apr 2025
Viewed by 261
Abstract
The large yellow croaker (Larimichthys crocea), one of the most economically valuable marine fish species in China, suffers significant economic losses in aquaculture due to infectious diseases caused by marine pathogens, such as Nocardia seriolae. The pathogenic mechanisms underlying N. [...] Read more.
The large yellow croaker (Larimichthys crocea), one of the most economically valuable marine fish species in China, suffers significant economic losses in aquaculture due to infectious diseases caused by marine pathogens, such as Nocardia seriolae. The pathogenic mechanisms underlying N. seriolae infection in L. crocea and the host immune responses remain inadequately characterized. To investigate the molecular mechanisms of this infection, we conducted transcriptome sequencing on the head kidney tissues of L. crocea at 1, 3, 7, and 14 days post-infection with N. seriolae. In total, 421, 1052, 3215, and 2459 upregulated genes, along with 1853, 1777, 3718, and 3134 downregulated genes were identified, respectively. KEGG enrichment analysis revealed that differentially expressed genes were predominantly associated with immune and metabolic pathways. Notably, pathways involved in Toll-like receptor signaling, ECM–receptor interaction, cytokine–cytokine receptor interaction, and focal adhesion were significantly enriched, highlighting an immune response to N. seriolae infection in L. crocea. In addition, significant enrichment of the citrate cycle (TCA cycle) and oxidative phosphorylation pathways in metabolic processes suggests an upregulated ATP synthesis to meet the heightened energy demand associated with the immune response to infection. These findings contribute to a deeper understanding of the immune defense mechanisms in the head kidney of L. crocea against N. seriolae infection and elucidate aspects of N. seriolae pathogenicity. Full article
(This article belongs to the Section Fish Pathology and Parasitology)
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18 pages, 2154 KiB  
Article
Reconstruction of Recreational Catch and Multi-Fisheries Stock Assessment of Hairtail (Trichiurus lepturus) in Korean Waters Under a Data-Limited Situation
by Sang Chul Yoon, Moo-Jin Kim, Heejoong Kang and Min-Je Choi
Fishes 2025, 10(4), 166; https://doi.org/10.3390/fishes10040166 - 8 Apr 2025
Viewed by 161
Abstract
Accurate catch data are essential for effective fisheries management. This study reconstructs the historical recreational catch of hairtail (Trichiurus lepturus) in Korean waters by incorporating unreported catches to improve stock assessment accuracy. Using a Bayesian state-space surplus production model, we conducted [...] Read more.
Accurate catch data are essential for effective fisheries management. This study reconstructs the historical recreational catch of hairtail (Trichiurus lepturus) in Korean waters by incorporating unreported catches to improve stock assessment accuracy. Using a Bayesian state-space surplus production model, we conducted a multi-fishery stock assessment by integrating abundance indices from eight major fisheries. The multigear mean standardization (MGMS) method was applied to derive standardized CPUE indices for each fishery, providing a more comprehensive evaluation of stock trends. The results indicate that excluding recreational catches and multiple CPUE indices may lead to biased stock assessments of hairtail in Korean waters. Models using an integrated CPUE index (SMSC) yielded higher MSY and biomass estimates, suggesting a more optimistic stock condition, whereas fishery-specific CPUE models (MSC) provided more precautionary estimates. The Kobe plot analysis indicates recent stock recovery, but continued monitoring and adaptive management are required to ensure long-term sustainability. This study highlights the importance of integrating recreational catch data and multi-fishery approaches in stock assessments, particularly under data-limited conditions, to enhance resource management and policy decision-making. Full article
(This article belongs to the Special Issue The Roles of Fishery Biology and Fish Population Dynamics in Fisheries Management)
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14 pages, 2579 KiB  
Article
Environmental DNA Was Utilized to Assess Fish Diversity and Community Structure in the Qingshui River
by Fujiang Huang, Ruiyuan Zhang, Zhengyu Lv, Yan Xiang, Wenwu Min, Xue Wang, Wei Liu, Wei Wang and Sheng Zeng
Fishes 2025, 10(4), 165; https://doi.org/10.3390/fishes10040165 - 8 Apr 2025
Viewed by 267
Abstract
An accurate assessment of fish stocks is crucial for maintaining the health and stability of aquatic ecosystems. To understand the characteristics of fish diversity in the Qingshui River, this study utilized high-throughput sequencing data obtained through environmental DNA macrobarcoding technology (eDNA). The research [...] Read more.
An accurate assessment of fish stocks is crucial for maintaining the health and stability of aquatic ecosystems. To understand the characteristics of fish diversity in the Qingshui River, this study utilized high-throughput sequencing data obtained through environmental DNA macrobarcoding technology (eDNA). The research explored differences in fish diversity and community characteristics in the Qingshui River by analyzing fish community structure, α diversity, β diversity, and the redundancy of environmental factors. This analysis aims to provide data support for water ecological monitoring and management. The results were as follows: (1) A total of 91 species of fishes from 18 families and seven orders were detected in the eDNA survey, and the dominant species was Cypriniformes, accounting for 72.5%. (2) There were significant differences in α diversity analysis in the Qingshui River (p < 0.05). (3) The fish community structure was similar in β diversity analysis. (4) In the redundancy analysis of environmental factors, pH, DO, TN, TP, NO2− and MnO4− have the greatest impact on the Qingshui River Basin. eDNA technology has the advantages of high efficiency and low harm and can be used for water ecological monitoring and management. It provides a scientific basis for fish protection and a valuable reference for fish monitoring in the future. Full article
(This article belongs to the Special Issue Mapping and Monitoring Aquatic Biodiversity in Hotspot Habitat Areas Using Environmental DNA (eDNA))
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16 pages, 2851 KiB  
Article
A Catch Community Diversity Analysis of Purse Seine in the Tropical Western and Central Pacific Ocean
by Jiaojiao Fei, Jian Zhang, Xiao Wang, Yuntao Wu and Yuxiu Teng
Fishes 2025, 10(4), 164; https://doi.org/10.3390/fishes10040164 - 7 Apr 2025
Viewed by 204
Abstract
Epipelagic fish communities dominate fish assemblages and are an important part of marine ecosystems due to their high abundance, vertical migration behavior, and global distribution. Purse seine fisheries are key components of marine fisheries in the tropical Western and Central Pacific Ocean (WCPO), [...] Read more.
Epipelagic fish communities dominate fish assemblages and are an important part of marine ecosystems due to their high abundance, vertical migration behavior, and global distribution. Purse seine fisheries are key components of marine fisheries in the tropical Western and Central Pacific Ocean (WCPO), primarily targeting skipjack tuna (Katsuwonus pelamis, SKJ), yellowfin tuna (Thunnus albacares, YFT), and bigeye tuna (Thunnus obesus, BET). In this study, WCPO purse seine fishery data from 2014 to 2022, combined with environmental factor data, were used, and Mantel tests and correlation analysis were employed to analyze the diversity, fish coexistence mechanisms, and environmental responses of catch communities under the following two different fishing strategies: free–swimming schools (FSCs) and drifting fish aggregating devices (DFADs). Mantel tests indicated that nitrate (NO3−), the Oceanic Niño Index (ONI), and pH significantly impact the diversity of the FSCs community, whereas NO3− significantly affects the diversity of the DFADs community. Based on the correlation analysis results, in the FSCs community, yellowfin tuna was positively correlated with bigeye tuna, and yellowfin tuna was negatively correlated with skipjack tuna and black marlin (Istiompax indica, BLM). In the DFADs community, yellowfin tuna was only positively correlated with skipjack tuna and bigeye tuna. In addition, species with high correlations were also positively correlated. The results of this study provide a theoretical basis for the biodiversity conservation of catch communities under two different purse seine fishing strategies in the WCPO. Full article
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12 pages, 2564 KiB  
Article
Nitrogen Budget and the Effects of Sea Grape (Caulerpa lentillifera) Density on the Water Quality and Growth Performance of Asian Seabass (Lates calcarifer) in a Polyculture System
by Roongparit Jongjaraunsuk, Kanokwan Khaodon, Saroj Rermdumri, Alongot Intarachart and Wara Taparhudee
Fishes 2025, 10(4), 163; https://doi.org/10.3390/fishes10040163 - 7 Apr 2025
Viewed by 311
Abstract
The nitrogen budget and the effects of varying densities of sea grape (Caulerpa lentillifera) on water quality and the growth performance of Asian seabass (Lates calcarifer) in a polyculture system were evaluated. Four treatments were tested, each stocked with [...] Read more.
The nitrogen budget and the effects of varying densities of sea grape (Caulerpa lentillifera) on water quality and the growth performance of Asian seabass (Lates calcarifer) in a polyculture system were evaluated. Four treatments were tested, each stocked with 20 fish (average weight: ~20 g; density: 2.66 kg/m3). Treatment 1 (control) contained no sea grapes, while treatments 2, 3, and 4 included 100, 200, and 400 g of sea grapes, corresponding to 0, 667 g/m3, 1333 g/m3, and 2666 g/m3, respectively. Significant (p < 0.05) reductions in total ammonia nitrogen (TAN), total suspended solids (TSS), and turbidity were observed with increasing sea grape density; however, no significant differences (p > 0.05) were found among the three sea grape treatments. Higher sea grape densities increased nitrite (NO2–N) and nitrate (NO3–N) concentrations due to enhanced nitrification. Approximately 65% of the nitrogen input originated from feed, but only 47.78–48.96% was assimilated into fish biomass. Nitrogen losses included 1.17–1.46% via water exchange and final drainage, while 45.27–50.76% was likely retained in sediments, volatilized, or lost through denitrification. Sea grapes effectively absorbed total nitrogen (TN), demonstrating their potential as biofilters for improving water quality without compromising fish growth performance. The optimal density was 100 g of sea grapes per 2.66 kg/m3 of seabass biomass, offering a sustainable strategy to enhance productivity while mitigating environmental impacts. Full article
(This article belongs to the Section Sustainable Aquaculture)
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18 pages, 4689 KiB  
Article
Development and Evaluation of an Escape Vent for Undersized Swimming Crab (Portunus trituberculatus) Bycatch Reduction in Pots
by Su-Bong Park, Hyun-Young Kim, Joon-Yong Yang and Gun-Ho Lee
Fishes 2025, 10(4), 162; https://doi.org/10.3390/fishes10040162 - 5 Apr 2025
Viewed by 211
Abstract
We sought to develop and evaluate an escape vent designed for undersized swimming crabs (Portunus trituberculatus) to reduce bycatch, contributing to the preservation of marine resources. To this end, we conducted aquarium experiments and selectivity analysis to determine the appropriate size [...] Read more.
We sought to develop and evaluate an escape vent designed for undersized swimming crabs (Portunus trituberculatus) to reduce bycatch, contributing to the preservation of marine resources. To this end, we conducted aquarium experiments and selectivity analysis to determine the appropriate size of the escape vent that would allow only undersized crabs with a carapace length of 64 mm or less to escape. The optimal dimensions for the escape vent were approximately 34.1 mm in height and 69.1 mm in width. During the sea trial, the average bycatch rates for undersized crabs per pot were 57.2%, 15.0%, and 22.3% for the control, basic, and door types, respectively. Regarding legal-sized crab catch per pot, averages of 1.40, 1.72, and 1.62 individuals were obtained for the three pot types. To our knowledge, this study is the first to assess the optimal size for an escape vent capable of reducing the bycatch of undersized crabs while maintaining legal-sized swimming crabs capture. Full article
(This article belongs to the Special Issue Fishing Gear Technology and Conservation of Fishery Resources)
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26 pages, 1610 KiB  
Article
Inter- and Intra-Estuarine Comparison of the Feeding Ecology of Keystone Fish Species in the Elbe and Odra Estuaries
by Jesse Theilen, Sarah Storz, Sofía Amieva-Mau, Jessica Dohr, Elena Hauten, Raphael Koll, Christian Möllmann, Andrej Fabrizius and Ralf Thiel
Fishes 2025, 10(4), 161; https://doi.org/10.3390/fishes10040161 - 4 Apr 2025
Viewed by 255
Abstract
Food webs in estuarine ecosystems serve as important biological indicators. The feeding ecology of four keystone fish species, pikeperch (Sander lucioperca L.), smelt (Osmerus eperlanus L.), ruffe (Gymnocephalus cernua L.) and flounder (Platichthys flesus L.), in the Elbe and [...] Read more.
Food webs in estuarine ecosystems serve as important biological indicators. The feeding ecology of four keystone fish species, pikeperch (Sander lucioperca L.), smelt (Osmerus eperlanus L.), ruffe (Gymnocephalus cernua L.) and flounder (Platichthys flesus L.), in the Elbe and Odra estuaries was analyzed using stomach content analyses. Important prey of pikeperch were fishes and mysids in both estuaries. Amphipods were especially important as prey for smelt in the Elbe estuary, whereas smelt caught in the Odra estuary mainly consumed mysids. Ruffe fed mainly on amphipods in the Elbe estuary, while annelids (lower section) and insect larvae (upper section) were the most important prey in the Odra estuary. Flounder favored copepods as prey in the Elbe estuary, while bivalves were preferred in the Odra estuary. Higher dietary overlaps were found in the Elbe estuary between smelt vs. ruffe, pikeperch vs. ruffe, and pikeperch vs. smelt. In the Elbe estuary, a shift in the diet composition of pikeperch, smelt, and ruffe was observed from 2021 to 2022 compared to food analyses from the 1990s. These shifts included an increased consumption of amphipods, while mysids and copepods had recently decreased in their diets. These changes indicate a restructuring of the food web, potentially linked to environmental changes, which highlights the sensitivity of estuarine ecosystems. Full article
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20 pages, 2383 KiB  
Article
Age, Growth, and Mortality of the Common Pandora (Pagellus erythrinus, L. 1758) in the Central Aegean Sea: Insights into Population Dynamics
by Alexandros Theocharis, Sofia Vardali and Dimitris Klaoudatos
Fishes 2025, 10(4), 160; https://doi.org/10.3390/fishes10040160 - 4 Apr 2025
Viewed by 293
Abstract
This study investigates the age, growth, and mortality of the common pandora (Pagellus erythrinus) in the Central Aegean Sea, providing critical insights into its population dynamics and sustainability. A total of 589 specimens were analyzed, identifying nine age cohorts with mean [...] Read more.
This study investigates the age, growth, and mortality of the common pandora (Pagellus erythrinus) in the Central Aegean Sea, providing critical insights into its population dynamics and sustainability. A total of 589 specimens were analyzed, identifying nine age cohorts with mean total lengths ranging from 13.18 cm to 32.94 cm. Growth parameters, estimated using the von Bertalanffy growth model, yielded an asymptotic length (L∞) of 39.53 cm and a growth coefficient (k) of 0.16 year−1, indicating moderate growth rates. The population exhibited non-isomorphic growth (b = 2.49, R2 = 98.4), suggesting slower weight gain relative to length. Mortality estimates indicated natural mortality (M) at 0.321 year−1, total mortality (Z) at 0.52 year−1, and fishing mortality (F) at 0.2 year−1, resulting in an exploitation rate (E) of 0.38. The fishing mortality at maximum sustainable yield (FMSY) was estimated at 0.33, with an exploitation rate at MSY (EMSY) of 0.51, suggesting that the population is currently harvested sustainably but close to the threshold of overexploitation. These findings provide essential reference points for fisheries management and highlight the need for continuous monitoring to ensure the long-term sustainability of P. erythrinus in Greek waters. Full article
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19 pages, 835 KiB  
Review
Current Challenges and Issues in the Application of Astaxanthin
by Limin Peng, Zhiqiang Zhang, Qing Li and Hui Yang
Fishes 2025, 10(4), 159; https://doi.org/10.3390/fishes10040159 - 4 Apr 2025
Viewed by 433
Abstract
Astaxanthin, a xanthophyll carotenoid, exhibits potent biological functions, including antioxidant, immune regulation, growth promotion, improved reproductive capacity, and enhancement of the body color of aquatic animals. In recent years, with the rapid development of the aquaculture industry, the application of astaxanthin in aquaculture [...] Read more.
Astaxanthin, a xanthophyll carotenoid, exhibits potent biological functions, including antioxidant, immune regulation, growth promotion, improved reproductive capacity, and enhancement of the body color of aquatic animals. In recent years, with the rapid development of the aquaculture industry, the application of astaxanthin in aquaculture has garnered increasing attention. Studies have demonstrated that astaxanthin significantly enhances the antioxidant capacity of aquatic animals, reduces oxidative damage, and regulates the expression of immune-related genes, thereby improving immunity and disease resistance. Moreover, astaxanthin promotes growth and reproductive performance, particularly in high-value aquaculture species, where it also serves as a natural pigment to increase market competitiveness. However, the low bioavailability and high production costs of astaxanthin remain major constraints to its widespread use in aquaculture. To address these limitations, various strategies—such as microencapsulation, liposomal delivery, and nanotechnology—have been explored to improve its stability and water solubility. Additionally, expanding astaxanthin sources and optimizing production processes are effective approaches to reducing costs. This review summarizes recent advances in astaxanthin research within aquaculture, highlights its multifunctional roles in promoting the health and production efficiency of aquatic animals, and discusses the current challenges and future research directions. Full article
(This article belongs to the Section Welfare, Health and Disease)
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