Fishes

17 pages, 2047 KiB

Open AccessArticle

You Are What You Eat: California Sea Cucumbers Become “Fishier” After Integrated Multi-Trophic Aquaculture with Chinook Salmon

by Emaline M. Montgomery, Barb L. Cannon, Miki Nomura, Rodrigo B. Leme, Ian P. Forster and Christopher M. Pearce

Fishes 2025, 10(4), 154; https://doi.org/10.3390/fishes10040154 (registering DOI) - 1 Apr 2025

Abstract

Recent interest in integrated multi-trophic aquaculture (IMTA) as an ecologically-sustainable and climate-conscious aquaculture system has resulted in testing different species partnerships and configurations in anticipation of industrialization. Deposit feeders like the California sea cucumber (Apostichopus californicus) have been suggested as ideal [...] Read more.

Recent interest in integrated multi-trophic aquaculture (IMTA) as an ecologically-sustainable and climate-conscious aquaculture system has resulted in testing different species partnerships and configurations in anticipation of industrialization. Deposit feeders like the California sea cucumber (Apostichopus californicus) have been suggested as ideal partners for IMTA with finfish, due to their ability to consume fish waste as well as their passive nature. However, the nutritional impacts of feeding on fish waste in IMTA have not yet been established for this species. The present study tested the effect of 3 months of inclusion in IMTA with Chinook salmon (Oncorhynchus tshawytscha) on the fatty-acid and nitrogenous-metabolite profiles of California sea cucumbers. The fatty-acid profiles of IMTA sea cucumbers showed significant changes from wild reference individuals, while few differences were detected in amino acids and other nitrogenous metabolites. Sea cucumbers housed directly in cages with salmon showed distinct shifts in their fatty-acid profiles toward higher levels of MUFAs and lower levels of SFAs, while PUFA concentrations remained the same. Sea cucumbers included in IMTA with finfish may be even more healthful for humans due to the accumulation of certain unsaturated fatty acids in their tissues not seen in wild reference individuals. Full article

(This article belongs to the Special Issue Advances in Integrated Multi-Trophic Aquaculture)

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15 pages, 6773 KiB

Open AccessArticle

Transcriptome Analysis of Immune Response Against Edwardsiella tarda Infection in Spotted Sea Bass (Lateolabrax maculatus)

by Zhaosheng Sun, Xia Li, Qingling Zhang, Wei Wang, Huan Wang, Tingshuang Pan and Qian Gao

Fishes 2025, 10(4), 153; https://doi.org/10.3390/fishes10040153 (registering DOI) - 1 Apr 2025

Abstract

Edwardsiella tarda is a gram-negative bacterium reported to be one of the most harmful pathogens in aquaculture. In this study, we conducted transcriptome profiling of the head kidney, liver, and spleen in spotted sea bass (Lateolabrax maculatus) infected with E. tarda [...] Read more.

Edwardsiella tarda is a gram-negative bacterium reported to be one of the most harmful pathogens in aquaculture. In this study, we conducted transcriptome profiling of the head kidney, liver, and spleen in spotted sea bass (Lateolabrax maculatus) infected with E. tarda. A total of 22,015 unigenes were detected by de novo assembly and annotated by comparison with the major databases (NR, GO, COG, KEGG, Swiss-Prot), with 21,065 (NR:95.68%), 11,320 (GO:51.42%), 20,464 (COG:92.95%), 21,295 (KEGG:96.73%), 18,791 (Swiss-Prot:82%). Subsequently, a substantial number of differentially expressed genes (DEGs) were identified (p-adjust < 0.05). In the head kidney, liver, and spleen, there were 1302 upregulated genes and 503 downregulated genes, 377 upregulated genes and 530 downregulated genes, and 1240 upregulated genes and 736 downregulated genes, respectively. Additionally, the expression levels of eight immune-related DEGs were validated by qRT-PCR, further verifying the reliability of the transcriptome data. To the best of our knowledge, this is the first analysis of the transcriptome profile of L. maculatus in response to E. tarda. These findings not only offer fundamental insights into the antibacterial immune mechanisms of spotted sea bass but also serve as a reference for formulating more effective fish disease management strategies. Full article

(This article belongs to the Special Issue Interactions Between Fish and Pathogens in Aquaculture—2nd Edition)

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5 pages, 156 KiB

Open AccessEditorial

Research Progress and Application Prospects of Dietary Supplements in Growth and Immune Regulation of Aquatic Animals

by Jianhua Ming, Qiyou Xu, Changle Qi, Fei Song and Chuanpeng Zhou

Fishes 2025, 10(4), 152; https://doi.org/10.3390/fishes10040152 (registering DOI) - 1 Apr 2025

Abstract

The global aquaculture industry faces increasing challenges, including the need to improve feed efficiency, reduce reliance on fishmeal, and mitigate disease risks while ensuring sustainable production [...] Full article

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

19 pages, 1068 KiB

Open AccessArticle

Impact of Dietary Glutamate on Growth Performance and Flesh Quality of Largemouth Bass

by Bo Zhao, Ju Zhao, Haifeng Liu, Hailong Zhang, Hongying Shan, Jiali Zong, Quanquan Cao and Jun Jiang

Fishes 2025, 10(4), 151; https://doi.org/10.3390/fishes10040151 - 31 Mar 2025

Abstract

The influence of dietary glutamate (Glu) was evaluated in a 56-day feeding trial on the growth performance and flesh quality of largemouth bass (Micropterus salmoides). A total of 1170 fish (average body weight 24.05 ± 0.22 g) were randomly allocated into [...] Read more.

The influence of dietary glutamate (Glu) was evaluated in a 56-day feeding trial on the growth performance and flesh quality of largemouth bass (Micropterus salmoides). A total of 1170 fish (average body weight 24.05 ± 0.22 g) were randomly allocated into six groups, with three replicates per group. They were fed diets containing Glu in levels of 11.40% (G1), 11.88% (G2), 12.53% (G3), 13.27% (G4), 14.33% (G5), and 15.62% (G6). We found that, over a 56-day feeding period, the final body weight (FBW) of largemouth bass was about 4–5 times the IBW. The FBW, percent weight gain (PWG), specific growth rate (SGR), feed efficiency (FE), and protein efficiency ratio (PER) initially increased and then decreased with elevating dietary Glu levels. Likewise, protein content, lipid content, apparent digestibility coefficient of dry matter (ADC_D), and apparent digestibility coefficient of protein (ADC_P) followed a similar pattern. Supplementation with Glu significantly improved the hepatosomatic index (HSI), viscerosomatic index (VSI), and relative gut length (RGL). Moreover, dietary Glu augmentation noticeably enhanced flesh composition such as muscle protein, ash, lipid, amino acid contents, and polyunsaturated fatty acids (PUFAs). Furthermore, dietary Glu supplementation enhanced muscle physicochemical quality (such as drip loss and pH), textural properties (adhesiveness and cohesiveness), and biochemical indices such as total protein (TP) and salt-soluble protein, while decreasing muscle cathepsin B (CtsB) and lactate dehydrogenase (LD) contents, thereby improving flesh quality. In conclusion, these findings suggest that Glu plays a crucial role in enhancing both growth performance and muscle quality in largemouth bass. The optimal dietary requirement for juvenile largemouth bass was estimated to be approximately 125.1 g/kg of diet based on SGR analysis. Full article

(This article belongs to the Section Nutrition and Feeding)

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21 pages, 4249 KiB

Open AccessArticle

Microplastics Enhance the Toxic Effects of Tetracycline on the Early Development of Zebrafish in a Dose-Dependent Manner

by Yanqing Wu, Ziying Zhu, Riying Zhong, Xilin Fang, Xiaocui Wang, Yuanyin Huang, Han Gong and Muting Yan

Fishes 2025, 10(4), 150; https://doi.org/10.3390/fishes10040150 - 27 Mar 2025

Abstract

Microplastic pollution in the environment has greatly increased due to the widespread use of plastics. Antibiotics and microplastic are common contaminants, especially in aquaculture. Microplastics could act as antibiotic vectors that raise the potential of their ecotoxicological effects. In this work, we conducted [...] Read more.

Microplastic pollution in the environment has greatly increased due to the widespread use of plastics. Antibiotics and microplastic are common contaminants, especially in aquaculture. Microplastics could act as antibiotic vectors that raise the potential of their ecotoxicological effects. In this work, we conducted several analyses of biomarker responses to examine the developmental toxicity and toxicological endpoints that polyethylene microplastics (PE-MPs) and tetracycline antibiotics (TC) induced in zebrafish (Danio rerio) embryos/larvae. The results suggested that TC-PE-MPs induced significant physiological perturbations, including attenuated spontaneous cardiac contractions, cardiotoxicity, a dose-dependent elevation in mortality, and a marked reduction in body length, accompanied by morphological alterations. The mechanistic analysis revealed that ROS accumulation triggered enzymatic activity changes, which further induced aberrant vascular development, robust inflammatory responses, and dysregulated gene expression. These findings demonstrate that PE coexistence potentiates TC’s toxicological effects, with combined exposure inducing developmental toxicity during critical organogenesis stages in zebrafish. Overall, the current research demonstrated the detrimental effects of TC-PE-MPs on early fish development, suggesting potential environmental risks. Full article

(This article belongs to the Special Issue Effects of Nanoplastics and Microplastics on Fish Health)

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19 pages, 941 KiB

Open AccessArticle

Fungal Protein from Non-Food Bioresources in Diets for Rainbow Trout (Oncorhynchus mykiss)

by Ashwath Gaudhaman, Sajjad Karimi, Torbjörn Lundh, Margareth Øverland, Mohammad J. Taherzadeh, Markus Langeland, Kartik Baruah and Aleksandar Vidakovic

Fishes 2025, 10(4), 149; https://doi.org/10.3390/fishes10040149 - 27 Mar 2025

Abstract

The growing aquaculture industry has an increasing demand for novel, sustainably produced protein sources for aquafeed. This study aimed to determine the apparent digestibility (AD%), pellet quality, and protein score of four novel fungal proteins in rainbow trout (Oncorhynchus mykiss), namely, [...] Read more.

The growing aquaculture industry has an increasing demand for novel, sustainably produced protein sources for aquafeed. This study aimed to determine the apparent digestibility (AD%), pellet quality, and protein score of four novel fungal proteins in rainbow trout (Oncorhynchus mykiss), namely, PEKILO^® (PEK) derived from Paecilomyces variotii, Aspergillus oryzae (AO), Rhizopus oligosporus (RO), and Rhizopus delemar (RD). All fungi were grown on various side-streams, such as beet vinasse, thin stillage, and whole stillage. The diets were produced by extrusion technology and consisted of control and test diets with a 30:70 test ingredient/control ratio. Feeding lasted for 39 days. Each tank had 20 fish, with three replicates per dietary treatment. One-way ANOVA was performed to compare the means of the groups with each other. The dry matter (DM) digestibility of PEK was significantly higher than that of AO, RD, and RO, all with similar digestibility. The crude protein AD% for PEK was 86.5%, which is significantly higher than that of the other fungal sources. AO, PEK, RD, and RO had similar crude fat AD% compared to each other, at 83.8%, 87.4%, 90.5%, and 88.5%, respectively. The pellet quality was found to deteriorate with addition of fungal proteins. PEK had high AD% for most of the macronutrients tested and better pellet quality. Full article

(This article belongs to the Section Nutrition and Feeding)

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13 pages, 1015 KiB

Open AccessArticle

Effect of Feeding Frequency and Restriction on the Growth Performance, Physiology, and Intestinal Histomorphometry of Colossoma macropomum in a Recirculating Aquaculture System

by Yhago Patrycky Antunes Souza Assis, Matheus Philip Santos Amorim, Lívia de Assis Porto, Paulo Edson Camilo Mol de Oliveira, Carina Alves Santos, Gean Paulo Andrade Reis, Ronald Kennedy Luz and Gisele Cristina Favero

Fishes 2025, 10(4), 148; https://doi.org/10.3390/fishes10040148 - 26 Mar 2025

Abstract

This study investigated the growth performance and physiological and intestinal histomorphometry of juvenile tambaqui Colossoma macropomum (51.68 ± 3.87 g), fed continuously or subjected to weekly cycles of feed restriction (one day of no feeding followed by six days of feeding) associated with [...] Read more.

This study investigated the growth performance and physiological and intestinal histomorphometry of juvenile tambaqui Colossoma macropomum (51.68 ± 3.87 g), fed continuously or subjected to weekly cycles of feed restriction (one day of no feeding followed by six days of feeding) associated with feeding frequencies of two or three times a day, for 84 days, in a recirculating aquaculture system (RAS). Growth performance and blood parameters were determined after 42 and 84 days. Liver, adipose tissue and intestine were collected after 84 days to determine the somatic indices, liver lipid levels and intestinal histomorphometry. Restricted fish had greater feed intake compared to continuously fed after 42 days, as well as greater specific growth rate (SGR) and better feed conversion between 43 and 84 days. No significant differences were observed for restriction, feeding frequency or the interaction for blood parameters after 42 and 84 days, somatic indices and liver lipid levels after 84 days, with the exception of plasma glucose, which was higher for restricted fish after 84 days. The feed restriction promoted a greater intestinal villi perimeter and height compared to continuously fed fish, as did fish fed twice a day compared to those fed three times a day, with an interaction between factors. We concluded that six days of feeding per week and twice-daily feeding frequency can be used as a feeding protocol for tambaqui juveniles over an 84-day period in RAS and this management protocol can also help reduce feed and labor costs in the production of this species. Full article

(This article belongs to the Special Issue Fish Farming in Recirculating Aquaculture Systems)

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18 pages, 2308 KiB

Open AccessArticle

Effect of Blue Finance and Marine Environmental Quality on the Marine Fishery Economy

by Yiying Jiang, Lei Huang, Xiya Zhu, Weirong Song and Yang Liu

Fishes 2025, 10(4), 147; https://doi.org/10.3390/fishes10040147 - 26 Mar 2025

Abstract

This study investigates the effects of blue finance and marine environmental quality of the marine fishery economy using panel data for marine fisheries in China’s coastal provinces spanning 2011–2023. We use entropy, moderating effects, and threshold effects to calculate the level of blue [...] Read more.

This study investigates the effects of blue finance and marine environmental quality of the marine fishery economy using panel data for marine fisheries in China’s coastal provinces spanning 2011–2023. We use entropy, moderating effects, and threshold effects to calculate the level of blue finance and marine environmental quality, the moderating role of marine environmental quality in blue finance’s effect on the marine fishery economy, and the threshold effect of blue finance and marine environmental quality on the marine fishery economy. We find that (1) blue finance can improve the marine fishery economy, with an influence coefficient of 0.245. (2) The quality of marine environment plays a transmission mechanism role in the impact of blue finance on the development of marine fishery economy quality. (3) Blue finance and marine environmental quality both have a first-order threshold effect on the marine fishery economy, showing a U-shaped curve relationship. Full article

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

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11 pages, 889 KiB

Open AccessReview

Residues of 6PPD-Q in the Aquatic Environment and Toxicity to Aquatic Organisms: A Review

by Chaoju Li, Yuanqiang Yang, Zikun Tian, Zhiqiu Huang, Yi Huang and Yuhang Hong

Fishes 2025, 10(4), 146; https://doi.org/10.3390/fishes10040146 - 25 Mar 2025

Abstract

N-(1,3-dimethylbutyl)-N’-phenyl-p-benzoquinone (6PPD-Q) is an emerging environmental contaminant that is widely distributed in aquatic environments and presents significant toxicological risks to aquatic organisms. As 6PPD-Q is primarily derived from oxidative transformation of the tire antioxidant N-(1,3-dimethylbutyl)-N’-phenyl-p-phenylenediamine (6PPD), its persistence and potential for bioaccumulation in [...] Read more.

N-(1,3-dimethylbutyl)-N’-phenyl-p-benzoquinone (6PPD-Q) is an emerging environmental contaminant that is widely distributed in aquatic environments and presents significant toxicological risks to aquatic organisms. As 6PPD-Q is primarily derived from oxidative transformation of the tire antioxidant N-(1,3-dimethylbutyl)-N’-phenyl-p-phenylenediamine (6PPD), its persistence and potential for bioaccumulation in aquatic organisms have raised widespread concerns. This study reviews the environmental sources, spatial distribution, migration, and transformation behaviors of 6PPD-Q, as well as its degradation mechanisms in different environmental media. Additionally, this review systematically explores the toxicological effects of 6PPD-Q on aquatic organisms, including its physiological, biochemical, and molecular impacts on fish, crustaceans, mollusks, and algae, with a focus on potential toxicological mechanisms. Finally, we discuss the limitations of current research on 6PPD-Q and propose key directions for future studies, including long-term ecological risk assessments, mechanisms of bioaccumulation, metabolic pathway analysis, and optimization of pollution control strategies, aiming to provide a scientific basis for the ecological risk assessment and pollution management of 6PPD-Q. Full article

(This article belongs to the Special Issue Aquatic Ecotoxicology: Field and Laboratory Approaches)

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33 pages, 2651 KiB

Open AccessArticle

Ichthyofaunal Metabarcoding in the Southern Appalachians: Use of eDNA Metabarcoding in Fish Surveys in Lotic Systems of the Great Smoky Mountains National Park with Comparisons to Historic Electrofishing Data

by Ben F. Brammell, Sara A. Brewer, Karsner S. Fetter, Lauren E. Slone, Matt A. Kulp and Ben R. S. McLaughlin

Fishes 2025, 10(4), 145; https://doi.org/10.3390/fishes10040145 - 22 Mar 2025

Abstract

eDNA appears well positioned to play a significant role in the future of biomonitoring, and the need to assess the efficacy of eDNA-based surveys in a variety of habitats is increasing. We conducted an eDNA metabarcoding-based survey of fish communities in the Great [...] Read more.

eDNA appears well positioned to play a significant role in the future of biomonitoring, and the need to assess the efficacy of eDNA-based surveys in a variety of habitats is increasing. We conducted an eDNA metabarcoding-based survey of fish communities in the Great Smoky Mountains National Park (GSMNP), located in eastern Tennessee and western North Carolina. The GSMNP, widely recognized as a biodiversity hotspot, encompasses 211,419 hectares of the Southern Appalachian Mountains with elevations up to 2205 meters and is home to approximately 73 species of fish, including 12 families and three species classified as endangered or threatened. We collected 50 water samples in first to sixth order streams at elevations of 336 to 1462 meters, including all major watersheds found in the park. eDNA was amplified utilizing two primer sets which each target differing regions of the 12S mitochondrial gene and generate amplicons of varying size (97 and 225 bp, respectively), and sequencing was conducted to an expected read depth of 400,000 reads per sample per marker. We detected a total of 40 fish species; of these, 36 were detected with the primer set which produces a 97 bp amplicon, and 12 of these 36 were detected only by this primer set. Species assemblages varied between stream orders, and species richness decreased with increasing elevation and increased with increasing stream order. Significant correlations were observed between biomass data from electrofishing monitoring (1984–2023) and eDNA metabarcoding read counts in five of seven species examined, including all salmonids. eDNA metabarcoding was demonstrated to be effective in assessing fish communities in high-elevation lotic systems in the Southern Appalachians, and our results suggest that primers targeting shorter amplicons may exhibit greater efficacy in these ecosystems. 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, 568 KiB

Open AccessReview

Using BioFloc Technology to Improve Aquaculture Efficiency

by Gennady Matishov, Besarion Meskhi, Dmitry Rudoy, Anastasiya Olshevskaya, Victoria Shevchenko, Liliya Golovko, Tatyana Maltseva, Mary Odabashyan and Svetlana Teplyakova

Fishes 2025, 10(4), 144; https://doi.org/10.3390/fishes10040144 - 22 Mar 2025

Abstract

In the present study, literature information on the functioning of the biofloc technology (BFT) system, its components, the state of the organism of hydrobionts, and water quality is analyzed. It is shown that this technology allows reducing financial costs for water treatment by [...] Read more.

In the present study, literature information on the functioning of the biofloc technology (BFT) system, its components, the state of the organism of hydrobionts, and water quality is analyzed. It is shown that this technology allows reducing financial costs for water treatment by 30%, increasing the efficiency of protein assimilation in the feed composition by two times, and creating a high-protein substrate, which can be further used as a component of feed for aquaculture. The BFT contains a large number of microorganisms, including photoautotrophic microorganisms (algae), chemoautotrophic microorganisms (nitrifying bacteria), and heterotrophic microorganisms (fungi, infusoria, protozoa, and zooplankton). This technology contributes to the improvement in water quality, aquaculture productivity, and hydrobionts. Despite the higher initial costs, BFT can yield higher economic profits. In this paper, the authors summarize data from many recent studies devoted to BFT. Based on the analysis of a number of studies, it can be concluded that this technology has a high potential for scaling up in industrial aquaculture. Full article

(This article belongs to the Special Issue Biofloc Technology in Aquaculture)

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24 pages, 6376 KiB

Open AccessArticle

Fish Ecology and Hydrological Responses to a Run-of-River Hydroelectric Project in Ecuador

by Ibon Tobes, Emily Conrad, Jordi Rivera-Albuja, Blanca Ríos-Touma and Rafael Miranda

Fishes 2025, 10(4), 143; https://doi.org/10.3390/fishes10040143 - 21 Mar 2025

Abstract

Hydropower development is rapidly expanding in biodiversity-rich regions like the Ecuadorian Andes, raising major concerns about its ecological impacts. This study evaluates fish species composition and habitat characteristics in the Cristal and Dulcepamba Rivers, with a particular focus on the effects of the [...] Read more.

Hydropower development is rapidly expanding in biodiversity-rich regions like the Ecuadorian Andes, raising major concerns about its ecological impacts. This study evaluates fish species composition and habitat characteristics in the Cristal and Dulcepamba Rivers, with a particular focus on the effects of the San José del Tambo Hydroelectric Project on the Dulcepamba River. Sampling conducted during the dry season (November–December 2023) at 15 sites incorporated fish surveys, habitat analyses, and environmental quality evaluation. The results showed marked declines in fish abundance, richness, and diversity in sections of the Dulcepamba River directly affected by water diversions, with species richness reduced to only three species at a site most impacted by discharge reduction. Conversely, the Cristal River, with its unaltered hydrology, supported considerably greater diversity, including 12 species at one site. Environmental integrity indices (Andean–Amazon Biotic Index, Biological Monitoring Working Party Index, Andean Riparian Quality Index, and Fluvial Habitat Index) further underscored the Cristal River’s superior conservation status. In the Dulcepamba River, reduced discharge in the environmental flow of the Hydroelectric Project—below mandated environmental discharge levels—led to river drying, disrupted connectivity, and impaired fish migration. This study provides essential insights into these highly biodiverse yet poorly studied ecosystems, which are increasingly threatened by anthropogenic pressures. The findings highlight the critical need to reconcile energy development with conservation efforts in these vulnerable Andean environments. Full article

(This article belongs to the Section Biology and Ecology)

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17 pages, 3432 KiB

Open AccessArticle

Stock Status of Two Commercially Important Catfishes, Mystus gulio (Hamilton 1822) and Mystus cavasius (Hamilton 1822), in Relation to Environmental Variables Along the Lower Stretches of the River Ganga, India

by Basanta Kumar Das, Susmita Jana, Archisman Ray, Dibakar Bhakta, Canciyal Johnson, Thangjam Nirupada Chanu, Subhadeep Das Gupta and Mitesh H. Ramteke

Fishes 2025, 10(4), 142; https://doi.org/10.3390/fishes10040142 - 21 Mar 2025

Abstract

Mystus gulio and Mystus cavasius are small indigenous fish species (SIFs) found throughout the year at the various stretches of the river Ganga and contribute significantly to the commercial fishery. The current study was conducted with a total of 609 specimens of M. [...] Read more.

Mystus gulio and Mystus cavasius are small indigenous fish species (SIFs) found throughout the year at the various stretches of the river Ganga and contribute significantly to the commercial fishery. The current study was conducted with a total of 609 specimens of M. gulio with a total length ranging from 84 to 190 mm and 377 specimens of M. cavasius with a total length ranging from 51 to 232 mm, collected from eight selected sites of lower stretches of the river Ganga between July 2018 and October 2019 to analyse their growth, mortality, and exploitation status. The sample specimens’ length-frequency distribution, primarily taken from bag nets and set barrier nets used in artisanal fisheries, was assessed using the FiSAT II programme. For M. gulio, the estimated asymptotic length (L_∞), growth coefficient (K), and initial condition factor (t₀) were 183.23 mm, 0.31 yr⁻¹, and −0.486 years, and for M. cavasius, these values were 246.23 mm, 0.19 yr⁻¹, and −0.302 years, respectively. The estimates for the total (Z), natural (M), and fishing (F) mortality rates were 1.78, 0.49, and 1.29 yr⁻¹ for M. gulio and 0.68, 0.33, and 0.35 yr⁻¹ for M. cavasius, respectively. Both M. gulio (May to July) and M. cavasius (June to August) experienced a single spawning peak. The estimated exploitation ratio (E) for M. gulio was 0.72, which is higher than the optimal level of exploitation (E_opt) and the maximum level of exploitation (E_max). On the other hand, the E value for M. cavasius was 0.52, which means that it was exploited at the right level. The fishing pressure was found to be slightly excessive for the current stocks of M. gulio, which should be considered for proper management of the fishery in the river Ganga. The present study, the first of its kind, highlights the stock status of these two commercially important species and the management measures taken to revive the stock along the lower stretches of the Ganga in India. The environmental parameters of the lower stretches of the river Ganga show favourable conditions for the optimum growth of M. gulio and M. cavasius. Full article

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

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12 pages, 12897 KiB

Open AccessArticle

Effects of CO₂ and O₂ in Modified Atmosphere Packaging on Water Retention, Protein Stability, and Microbial Growth in Atlantic Salmon Fillets

by Yun-Fang Qian, Cheng-Jian Shi, Cheng-Cheng Liu, Jing-Jing Zhang and Sheng-Ping Yang

Fishes 2025, 10(4), 141; https://doi.org/10.3390/fishes10040141 - 21 Mar 2025

Abstract

Modified atmosphere packaging (MAP) is commonly used to prolong the shelf life and maintain the quality of perishable food. However, it may contribute to more severe juice loss and texture changes in salmon. To explore the reasons why, this study designed different ratios [...] Read more.

Modified atmosphere packaging (MAP) is commonly used to prolong the shelf life and maintain the quality of perishable food. However, it may contribute to more severe juice loss and texture changes in salmon. To explore the reasons why, this study designed different ratios of O₂ (to inhibit anaerobic bacteria), CO₂ (to inhibit Gram-negative bacteria), and N₂ (to maintain the packaging shape) in order to investigate the effects of MAP on the properties, structure, and oxidation of salmon proteins. The experiments’ results showed that MAP with about 60% CO₂ could slow bacterial growth effectively, as well as the accumulation of total volatile basic nitrogen and cooking loss. The carbonyl content decreased with increasing CO₂ contents but increased with high contents of O₂. A low concentration of O₂ (10%) was also beneficial for the inhibition of oxidation and degradation of proteins, and the lowest carbonyl content was found in 60%CO₂/10%O₂/30%N₂ conditions, with 2.01 μmol/g protein on day 12. Overall, we report that MAP with 60%CO₂ and 10%O₂ is properly able to limit structure changes in the myofibrils of salmon fillets during cold storage. Full article

(This article belongs to the Special Issue Advances in Comprehensive Exploration and Utilization of Aquatic Products)

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19 pages, 1745 KiB

Open AccessArticle

Enhancing Management Strategy Evaluation: Implementation of a TOPSIS-Based Multi-Criteria Decision-Making Framework for Harvest Control Rules

by Jikun Liu, Zhenlei Song, Yuhang Xie and Zhe Zhang

Fishes 2025, 10(4), 140; https://doi.org/10.3390/fishes10040140 - 21 Mar 2025

Abstract

Management Strategy Evaluation (MSE) tools are inspired by the need for transparency, efficiency, and collaboration in harvest control rule (HCR) management. MSEs provide quantified metrics of the HCR performances and indicate the goodness in multiple dimensions, but providing HCR rankings based on such [...] Read more.

Management Strategy Evaluation (MSE) tools are inspired by the need for transparency, efficiency, and collaboration in harvest control rule (HCR) management. MSEs provide quantified metrics of the HCR performances and indicate the goodness in multiple dimensions, but providing HCR rankings based on such criteria is uncommon or use a simple Weight Sum Method (WSM). Acknowledging some theoretical limitations of the WSM, we propose using Technique for Order Preference by Similarity to Ideal Solution Method (TOPSIS) as an efficient alternative algorithm for recommending HCRs and conduct a sensitivity analysis of management objectives under the two frameworks, one based on simulated history and the other on the history of North Pacific Albacore (NPALB). Two conclusions are drawn based on the computation of the HCR ranking differences generated with the WSM and TOPSIS: (1) The alteration in the overall ranking of HCRs is visible, and its influence could vary substantially with user preference with theoretical merits. (2) It is common to notice shifts in the ranking for top HCRs, which potentially contributes valuable insights for practical decision making. Full article

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

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11 pages, 1641 KiB

Open AccessArticle

An Inexpensive 3D Camera System Based on a Completely Synchronized Stereo Camera, Open-Source Software, and a Raspberry Pi for Accurate Fish Size, Position, and Swimming Speed

by Ólavur av Fløtum Mittún, Lars Emil Juel Andersen, Morten Bo Søndergaard Svendsen and John Fleng Steffensen

Fishes 2025, 10(4), 139; https://doi.org/10.3390/fishes10040139 - 21 Mar 2025

Abstract

The visual underwater monitoring of fish size, position, and swimming speed is experiencing increasing interest in aquaculture and marine research. Despite the long-standing use of video monitoring, there is no methodological consensus, but numerous researchers and developers advocate for 3D video capture techniques [...] Read more.

The visual underwater monitoring of fish size, position, and swimming speed is experiencing increasing interest in aquaculture and marine research. Despite the long-standing use of video monitoring, there is no methodological consensus, but numerous researchers and developers advocate for 3D video capture techniques to facilitate biometric estimations. Most of the previous systems, however, use partially synchronized cameras (within one frame), which causes an inherent error if observing moving fish in relation to the camera. This study proposes the use of a completely synchronized 3D camera system for underwater video capture, which can be calibrated, and which allows analyses to be performed using open-source software(s). We present data on the maximum theoretical error in the size estimation of swimming fish. This article presents a guide on how to build and set up the camera hardware and run the system, including a formal study investigating pre-measured lengths, and an informal study investigating the lengths of Atlantic cod (Gadus morhua). Full article

(This article belongs to the Special Issue Technology for Fish and Fishery Monitoring)

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15 pages, 649 KiB

Open AccessArticle

Exploring Nationwide Oyster Aquaculture Data: An Index to Compare Regulatory, Production, and Economic Attributes of Oyster Aquaculture Among U.S. States and Regions

by Anthony R. Lima

Fishes 2025, 10(4), 138; https://doi.org/10.3390/fishes10040138 - 21 Mar 2025

Abstract

Wild oyster reefs have been harvested for centuries and continue to face anthropogenic pressures, including climate change, pollution, and habitat reduction. Oyster aquaculture has grown to supplement depleted wild stocks and strengthen local economies, but development has not occurred at the same rate [...] Read more.

Wild oyster reefs have been harvested for centuries and continue to face anthropogenic pressures, including climate change, pollution, and habitat reduction. Oyster aquaculture has grown to supplement depleted wild stocks and strengthen local economies, but development has not occurred at the same rate across all regions. Across the United States, states have a variety of political and cultural influences that impact oyster aquaculture policy, constraining the ability to make direct comparisons among locations that could enhance aquaculture expansion in slower-to-develop states and regions. This research developed a four-part index to compare regulatory, production, and economic attributes of oyster aquaculture among 23 coastal states. The final index score—a summation of the four individual index components—provides a broad integrated view of oyster aquaculture across the U.S. The results indicate that coastal states in the U.S. Mid-Atlantic and New England regions have the greatest number of resource and policy attributes in place to support oyster aquaculture, whereas coastal states in the Gulf of Mexico and Western Pacific region have relatively less in the way of aquaculture-supporting structures. As the oyster aquaculture industry continues to grow in the U.S., results from this study can help organizations involved in oyster aquaculture to make informed decisions to expand permitting, leasing, and production systems, following the model from states who have been active in oyster aquaculture for decades. Mindful and cautious improvements can facilitate sustainable sources of seafood and stable income generation for coastal communities while reducing pressures on wild stocks. Full article

(This article belongs to the Special Issue Fisheries Monitoring and Management)

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14 pages, 6326 KiB

Open AccessArticle

Transcriptomic Responses of Gonadal Development to Photoperiod Regulation in Amur Minnow (Phoxinus lagowskii)

by Mingchao Zhang and Yingdong Li

Fishes 2025, 10(3), 137; https://doi.org/10.3390/fishes10030137 - 20 Mar 2025

Abstract

Photoperiod regulates reproductive physiology in many fishes, but its sex-specific molecular effects under artificial manipulation remain unclear, especially in cold-water species. In this study, we investigated whether photoperiod manipulation during the reproductive season could modulate the rate and efficiency of gonadal development in [...] Read more.

Photoperiod regulates reproductive physiology in many fishes, but its sex-specific molecular effects under artificial manipulation remain unclear, especially in cold-water species. In this study, we investigated whether photoperiod manipulation during the reproductive season could modulate the rate and efficiency of gonadal development in the Amur minnow (Phoxinus lagowskii). High-throughput RNA sequencing was used to analyze transcriptomic responses of gonadal tissues under three photoperiod regimes: natural light (12L:12D), continuous light (24L:0D), and continuous darkness (0L:24D) over a 9-week experimental period. Our results revealed distinct sex-specific gonadal responses to photoperiodic changes. In males, continuous light significantly promoted spermatogenesis by upregulating meiosis-related genes (REC114 and syp3) and steroid biosynthesis. In females, prolonged light exposure induced ovarian stress, evidenced by vitellogenin (Vtg3) upregulation and retinoic acid suppression, whereas continuous darkness promoted lipid storage via downregulation of gluconeogenesis (PC and Fbp2) and fatty acid oxidation (ACSL1a). Additionally, immune activation, marked by IL1RAPL1-A upregulation, was observed in all groups except continuous-light males, with females exhibiting broader immune pathway engagement. These findings provide novel insights into the regulatory mechanisms of photoperiod-induced gonadal development and highlight potential strategies for optimising photoperiod management in cold-water fish aquaculture. Full article

(This article belongs to the Special Issue Rhythms and Clocks in Aquatic Animals)

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17 pages, 5381 KiB

Open AccessArticle

In Situ Study on the Influence of a Dark Environment on the Upstream Behaviors of Plateau Fishes in Fishways: A Pilot Study

by Biao Wang, Fei Yao, Jianzhang Lv, Hongze Li, Zhe Wang, Yongzeng Huang, Kaixiao Chen, Wei He, Xiaogang Wang and Jingjuan Li

Fishes 2025, 10(3), 136; https://doi.org/10.3390/fishes10030136 - 20 Mar 2025

Abstract

To help fish to bypass dams and other human-made barriers, some fishways have ingeniously incorporated extended tunnel sections. This innovative design not only optimizes the overall structure of the fishway but also significantly reduces disturbances to the surrounding ecosystem. However, the potential challenges [...] Read more.

To help fish to bypass dams and other human-made barriers, some fishways have ingeniously incorporated extended tunnel sections. This innovative design not only optimizes the overall structure of the fishway but also significantly reduces disturbances to the surrounding ecosystem. However, the potential challenges posed by long tunnel sections to fish upstream migration remain insufficiently studied and poorly understood. This study conducted in situ experiments utilizing a passive-integrated-transponder (PIT) system to quantitatively assess the effects of dark and natural light environments on the upstream migration behavior of plateau-endemic fishes (Schizothorax macropogon, Schizothorax waltoni, and Schizothorax oconnori) in a vertical-slot fishway. A 655 m section of the fishway was selected for the experiment, with shading cloth used to simulate the dark environment (DE) of tunnel sections, and its removal serving as the natural light environment (NE). The results showed that in the DE, the upstream behaviors of S. macropogon, S. waltoni, and S. oconnori were not hindered. The entry efficiency at the experimental segment (Ee) of all three species exceeded 65% in the DE, which was higher than that in the NE. The passage efficiency (Ep) of S. macropogon and S. waltoni showed no significant difference between the DE and NE, whereas S. oconnori exhibited a significant difference, with an overall Ep of 0% in the NE and 75.0% in the DE. Additionally, the DE caused a temporary disruption to the diel migration rhythms of the three species. The transit speeds (St) of S. macropogon and S. waltoni were both elevated in the DE, with S. waltoni showing a particularly significant increase; its average St in the DE (0.080 m/s) was much higher than in the NE (0.021 m/s). Ridge regression analysis further indicated that the DE was the primary factor influencing the St and had a positive effect on upstream behavior. Moreover, differences in the upstream migration performances of different species under varying light conditions highlighted species-specific sensitivity to light. This study offers key insights for fish passage design in canyon hydropower projects and highlights the potential of tunnel-type fishways in restoring river connectivity. Full article

(This article belongs to the Special Issue Habitat Assessment and Conservation of Fishes)

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