Fishes

14 pages, 6090 KiB

Open AccessArticle

Observations on the Biology and Fishery of the Marbled Spinefoot (Siganus rivulatus Forsskål & Niebuhr, 1775) in the Eastern Red Sea

by Zahra Okba, Eyüp Mümtaz Tıraşın and Mark Dimech

Fishes 2025, 10(5), 219; https://doi.org/10.3390/fishes10050219 - 8 May 2025

Abstract

This study aims to enhance our understanding of the marbled spinefoot (Siganus rivulatus) population along the Red Sea coast of Saudi Arabia. It investigates whether the stock is subject to overfishing and tests the hypothesis that current fishing mortality exceeds sustainable [...] Read more.

This study aims to enhance our understanding of the marbled spinefoot (Siganus rivulatus) population along the Red Sea coast of Saudi Arabia. It investigates whether the stock is subject to overfishing and tests the hypothesis that current fishing mortality exceeds sustainable thresholds. A total of 6192 specimens were sampled during a comprehensive survey conducted from 2022 to 2024, utilizing a range of fishing methods, including handline, trap, gillnet, and demersal trawl fisheries. The sampled fish ranged in total length (TL) from 100 to 335 mm and in total weight (W) from 17 to 470 g. The length–weight relationship was W = 0.0175 × TL^2.92. Growth parameters derived from the von Bertalanffy model were TL_∞ = 43.5 cm, K = 1.12 year⁻¹, and t₀ = −0.18 year. The median size at first maturity was estimated at 14.83 cm TL for both sexes. Virtual Population Analysis revealed fishing mortality rates ranging from 0.01 year⁻¹ to 0.89 year⁻¹ across age classes 1 to 5 years, with exploitation levels of 0.6, 0.55, and 0.5 at ages 3, 4, and 5, respectively, indicating slight overfishing. The annual average catch of marbled spinefoot along the Saudi Arabian Red Sea coast was approximately 211 tonnes, contributing an estimated 1.8 million USD to the national economy. Maintaining the current fishing effort at sustainable levels is essential to ensure the long-term viability of this stock. Full article

(This article belongs to the Section Biology and Ecology)

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16 pages, 4306 KiB

Open AccessArticle

Integration of Biofloc and Ozone Nanobubbles for Enhanced Pathogen Control in Prenursery of Pacific White Shrimp (Penaeus vannamei)

by Qinlang Liang, Yazhi Luan, Zhengwen Wang, Jiangbo Niu, Yasong Li, Hua Tang, Zengting Li and Gang Liu

Fishes 2025, 10(5), 218; https://doi.org/10.3390/fishes10050218 - 8 May 2025

Abstract

This study investigates the synergistic effects of integrating ozone nanobubbles (generated via a pure oxygen-fed reactor with nanobubble-diffusing air stones) and biofloc technology (BFT) on water quality optimization, pathogenic load reduction, and growth performance enhancement in Pacific white shrimp (Penaeus vannamei) [...] Read more.

This study investigates the synergistic effects of integrating ozone nanobubbles (generated via a pure oxygen-fed reactor with nanobubble-diffusing air stones) and biofloc technology (BFT) on water quality optimization, pathogenic load reduction, and growth performance enhancement in Pacific white shrimp (Penaeus vannamei) prenursery aquaculture systems. Four treatments were tested: a clear water control (CW), ozonated clear water (CW + O), biofloc (FLOC), and biofloc with ozone (FLOC + O). The FLOC + O group significantly improved water quality, reducing total ammonia nitrogen (TAN) by 61%, nitrite nitrogen (NO₂⁻-N) by 78% compared to CW, and total suspended solids (TSS) by 21% compared to FLOC (p = 0.0015). Ozone application (maintained above 0.3 mg/L, 15 min/day) demonstrated robust pathogen suppression, achieving a sharp reduction in Muscle Necrosis Virus (MNV), a 99.5% inhibition of Vibrio spp. (from 228,885 to 107 CFU/mL), and the clearance of Epistylis spp., as determined via optical microscope. These enhancements directly translated to superior biological outcomes, with the FLOC + O group exhibiting an 82% survival rate (vs. 40% in CW) and 13% higher final body weight (11.65 mg vs. 10.32 mg in CW). The integration of ozone and BFT also accelerated larval development and improved the Zoea II to Mysis I metamorphosis success rate. By maintaining stable microbial communities and reducing organic waste, the combined system lowered the water exchange frequency by 40% and eliminated the need for prophylactic antibiotics. These results demonstrate that ozone–BFT integration effectively addresses key challenges in shrimp prenursery—enhancing disease resistance, optimizing water conditions, and improving growth efficiency. The technology offers a sustainable strategy for the intensive prenursery of Pacific white shrimp, balancing ecological resilience with production scalability. Full article

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

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17 pages, 4541 KiB

Open AccessArticle

Design and Experiment of a Hard-Shell Clam Harvester

by Haiyun Wu, Xiaomeng Wang, Bing Huang, Shide Li, Jincheng Hu, Shancan Fu, Lei Yang, Mengxiang Cui, Zhenwei Chen, Yanan Zeng, Yongcheng Jiang and Tao Zhang

Fishes 2025, 10(5), 217; https://doi.org/10.3390/fishes10050217 - 7 May 2025

Abstract

Hard-shell clams are highly valued for their nutritional and economic benefits, leading to an increase in their aquaculture scale. Harvesting these clams manually leads to low efficiency and high labor intensity; thus, a new type of hard-shell clam harvester has been designed to [...] Read more.

Hard-shell clams are highly valued for their nutritional and economic benefits, leading to an increase in their aquaculture scale. Harvesting these clams manually leads to low efficiency and high labor intensity; thus, a new type of hard-shell clam harvester has been designed to overcome this challenge. Based on biological characteristics and sediment properties of hard-shell clams, a 3D model of the harvester has been created utilizing SolidWorks software (version 2022), which has a working length of 980 mm, an excavation depth range from 0~12 mm, and an angle of entry of 22 degrees. To optimize the efficiency of the machine, a Discrete Element Method (DEM) simulation trial was conducted through a three-factor three-level experiment using EDEM software. Results indicated an optimal harvest efficiency of 91.17% with the machine achieving a running speed of 0.526 m/s, roller speed of 4.772 r/min, and excavation depth of 73.067 mm. Field experiments verified the feasibility of the harvester, demonstrating high accuracy when compared to simulation results. Full article

(This article belongs to the Section Fishery Facilities, Equipment, and Information Technology)

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11 pages, 1991 KiB

Open AccessArticle

The Combined Effects of Multiple Invasive Species on Persistence of Imperiled Pahrump Poolfish

by Brandon L. Paulson, Kevin D. Guadalupe, Shawn C. Goodchild and Craig A. Stockwell

Fishes 2025, 10(5), 216; https://doi.org/10.3390/fishes10050216 - 7 May 2025

Abstract

Many ecosystems have been invaded by more than one non-native species, but research evaluating the combined effects of multiple invasive species has been limited. In the southwest USA, many aquatic systems have been invaded by multiple species such as non-native crayfish and non-native [...] Read more.

Many ecosystems have been invaded by more than one non-native species, but research evaluating the combined effects of multiple invasive species has been limited. In the southwest USA, many aquatic systems have been invaded by multiple species such as non-native crayfish and non-native fishes. We document the rapid decline of a population of the endangered Pahrump Poolfish, Empetrichthys latos, which occurred following the sequential introduction of Red Swamp Crayfish, Procambarus clarkii, and Western Mosquitofish, Gambusia affinis. We also report the results of mesocosm experiment where we tested individual and combined effects of invasive Red Swamp Crayfish and Western Mosquitofish on experimental populations of Pahrump Poolfish. Survival rates were near 100% for adult poolfish in allopatry but were significantly lower for the other two treatments; when poolfish were sympatric with crayfish (~53%), and when poolfish were sympatric with both crayfish and mosquitofish (~55%). In allopatry, poolfish produced over 90 juveniles per mesocosm, while approximately 65 juveniles per mesocosm when poolfish were sympatric with crayfish, but this difference was not significant. However, juvenile production plummeted to near zero when poolfish were sympatric with both crayfish and mosquitofish. This study demonstrates that Pahrump Poolfish must be actively managed to detect and control invasive species, otherwise extinction will likely occur. This study also provides an example of the compounding effects of multiple invasive species. Full article

(This article belongs to the Section Biology and Ecology)

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10 pages, 447 KiB

Open AccessArticle

Kinetic Analysis of the Thermal Inactivation Behavior of AMP Deaminase and IMPase in Each Muscle Type of Yellowtail Seriola quinqueradiata

by Ayumi Furuta, Renri Okura, Chinatsu Kobayashi and Shota Tanimoto

Fishes 2025, 10(5), 215; https://doi.org/10.3390/fishes10050215 - 7 May 2025

Abstract

In this study, a kinetic analysis was conducted to clarify the thermal inactivation behavior of AMP deaminase and IMPase, enzymes involved in the generation and degradation of inosine 5′-monophosphate (IMP) in the dorsal ordinary muscle (OM) and dark muscle (DM) of yellowtail Seriola [...] Read more.

In this study, a kinetic analysis was conducted to clarify the thermal inactivation behavior of AMP deaminase and IMPase, enzymes involved in the generation and degradation of inosine 5′-monophosphate (IMP) in the dorsal ordinary muscle (OM) and dark muscle (DM) of yellowtail Seriola quinqueradiata. Both enzymes were extracted from each part of the fish muscle, heated in the range of 50–60 °C, and then measured for residual enzyme activity. Based on these data, kinetic analysis was performed. When comparing fish muscle types, the thermal stability at 50 °C and 55 °C and the temperature dependence of both AMP deaminase and IMPase tended to be higher in the DM. When comparing the two enzymes, the thermal stability of IMPase was higher than that of AMP deaminase at 50 °C in both muscle types. These results suggest that to prepare heated yellowtail muscle with a high IMP content, it is important to consider the thermal inactivation behavior of enzymes and use slow heating to maintain AMP deaminase activity and produce sufficient IMP in OM. For DM, rapidly increasing the product temperature to ≥60 °C to inactivate IMPase is required to preserve the IMP content. Full article

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

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24 pages, 2560 KiB

Open AccessArticle

Comparison of Bioinformatic Pipelines for eDNA Metabarcoding Data Analysis of Fish Populations

by Romulo A. dos Santos and Petr Blabolil

Fishes 2025, 10(5), 214; https://doi.org/10.3390/fishes10050214 - 6 May 2025

Abstract

Environmental DNA (eDNA) metabarcoding has gained popularity as a biomonitoring tool, leading to the emergence of various bioinformatic pipelines. However, comparisons are essential to assessing the reliability and similarity of results. In this study, we compared five bioinformatic pipelines (Anacapa, Barque, metaBEAT, MiFish, [...] Read more.

Environmental DNA (eDNA) metabarcoding has gained popularity as a biomonitoring tool, leading to the emergence of various bioinformatic pipelines. However, comparisons are essential to assessing the reliability and similarity of results. In this study, we compared five bioinformatic pipelines (Anacapa, Barque, metaBEAT, MiFish, and SEQme) using samples collected from three reservoirs in the Czech Republic during the autumn and summer seasons. Negative and positive controls were used to monitor potential contamination during sample processing. eDNA was amplified, targeting the 12S fish rRNA gene, sequenced, and analyzed with the selected bioinformatic pipelines. Statistical analyses were applied to assess result similarity, including the number of detected taxa, read count, alpha and beta diversities, and the Mantel test. Our findings showed consistent taxa detection across pipelines, with increased sensitivity compared to traditional methods. Alpha and beta diversities and the Mantel test also exhibited significant similarities between pipelines. Divergences were observed based on the reservoir, season, and their interaction. In conclusion, the choice of bioinformatic pipeline did not significantly affect metabarcoding outcomes or their ecological interpretation. Full article

(This article belongs to the Special Issue Fish DNA Barcoding)

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9 pages, 660 KiB

Open AccessArticle

Dietary Supplementation of Astragalus Polysaccharides Modulates Growth Physiology, Metabolic Homeostasis, and Innate Immune Responses in Rice Field Eels (Monopterus albus)

by Chengcheng Wu, Hang Yang, Yutong Yang, Quan Yuan, Weiwei Lv, Gelana Urgesa Ayana, Mingyou Li, Di Su, Wenzong Zhou and Qinghua Zhang

Fishes 2025, 10(5), 213; https://doi.org/10.3390/fishes10050213 - 6 May 2025

Abstract

To investigate the dietary effects of Astragalus polysaccharides (APSs) on the growth performance, lipid metabolism, antioxidant activity, and non-specific immunity of Asian swamp eel (Monopterus albus) during the domestication stage, fish were randomly allocated into quadruplicate groups receiving Tenebrio molitor-based [...] Read more.

To investigate the dietary effects of Astragalus polysaccharides (APSs) on the growth performance, lipid metabolism, antioxidant activity, and non-specific immunity of Asian swamp eel (Monopterus albus) during the domestication stage, fish were randomly allocated into quadruplicate groups receiving Tenebrio molitor-based diets supplemented with Astragalus polysaccharides (APSs) at graded concentrations of 0 (CON), 700 (APS1), 1400 (APS2), and 2100 (APS3) mg/kg body weight for 28 days. The results showed that dietary APSs at 700–1400 mg/kg·bw significantly enhanced the weight gain rate (WG) and decreased the feed conversion ratio (FCR) of M. albus (p < 0.05). Concurrently, hematological analysis revealed that hemoglobin levels increased by 19.9% and 23.0% in the 700 and 1400 mg/kg APS groups, respectively (p < 0.05). In terms of lipid metabolism, supplementation with APSs significantly increased the serum high-density lipoprotein (HDL) content in all treatment groups (p < 0.05). Lower serum triglyceride (TG) levels were found in the APS2 group (p < 0.05), and decreased triglyceride (TG), cholesterol (CHO), and low-density lipoprotein (LDL) levels were displayed in the APS3 group (p < 0.05). Among the antioxidant parameters, the supplementation with 700 mg/kg·bw APSs significantly increased the glutathione peroxidase (GSH-Px) and catalase (CAT) activity levels of M. albus (p < 0.05). The APS2 group had a significantly increased total antioxidant capacity (T-AOC) and CAT activity levels (p < 0.05), and the APS3 group had significantly increased CAT activity levels (p < 0.05). In addition, the APS1 and APS3 groups had significantly reduced malondialdehyde (MDA) levels (p < 0.05). In terms of non-specific immunity, the APS1 and APS2 groups showed significantly increased superoxide dismutase (SOD) and lysozyme (LZM) activity levels of M. albus (p < 0.05), and the addition of 700 mg/kg·bw APSs significantly increased the levels of alkaline phosphatase (AKP) activity (p < 0.05). Furthermore, the levels of acid phosphatase (ACP) activity were significantly increased in all experimental groups (p < 0.05). In conclusion, the optimal APS addition for T. molitor as biocarrier bait is 700 mg/kg, corresponding to 352 mg/kg, which elicits improvements in the growth parameters, lipid homeostasis regulation, oxidative stress mitigation, and innate immune potentiation of M. albus during the domestication stage. Full article

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

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21 pages, 9299 KiB

Open AccessArticle

Seasonal Trends in Water Retention of Atlantic Sea Cucumber (Cucumaria frondosa): A Modeling Approach

by Pete Brown, Heather J. Burke, Juran C. Goyali, Wade Murphy and Deepika Dave

Fishes 2025, 10(5), 212; https://doi.org/10.3390/fishes10050212 - 6 May 2025

Abstract

Sea cucumbers are widely consumed as a delicacy or in eastern medicine across many Asian countries. Due to the depletion of traditional stocks, new species are increasingly harvested, including the Atlantic sea cucumber (Cucumaria frondosa), the most abundant, cold-water species found [...] Read more.

Sea cucumbers are widely consumed as a delicacy or in eastern medicine across many Asian countries. Due to the depletion of traditional stocks, new species are increasingly harvested, including the Atlantic sea cucumber (Cucumaria frondosa), the most abundant, cold-water species found in the North Atlantic. This species is harvested in NAFO subdivision 3Ps off the south coast of Newfoundland and Labrador, Canada. As part of their respiration, stress response, and locomotion, sea cucumbers draw and retain oxygenated water within their body cavity, resulting in significant water content at landing. Historically, Fisheries and Oceans Canada (DFO) have applied a 23% deduction to the landed weight to account for this water retention. To validate this deduction, the authors conducted experiments across thirteen sampling events in 2019 and 2020. Randomized samples were collected during offloading and were categorized into three sizes of bin—small (x ≤ 150 g), medium (150 g < x ≤ 250 g), and large (x > 250 g)—and water loss was measured. Water loss was analyzed in relation to multiple factors, including processor, unloading method, year, license, month, fishing area, hold location, size, and processing method. Key findings included the following: (a) sea cucumbers typically contained more than 23% free water; (b) large and medium-sized specimens, which dominated landings, retained more free water; (c) water loss was highest for the samples collected from the top of the hold; (d) the unloading method influenced free water retention, as did the processing method used to cut the sea cucumbers; (e) license, processor, and fishing area had strong collinearity with other factors or were not found to be statistically significant; and (f) water loss appeared higher in 2020 than 2019, largely due to the increased use of vacuum transfer methods. Based on these findings, DFO revised the water retention allowance to 34%. Full article

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

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12 pages, 1676 KiB

Open AccessArticle

Diet Composition and Feeding Intensity of Four-Spotted Megrim, Lepidorhombus boscii (Risso, 1810), in the Eastern Adriatic Sea

by Nika Ugrin, Mate Šantić, Željka Trumbić and Svjetlana Krstulović Šifner

Fishes 2025, 10(5), 211; https://doi.org/10.3390/fishes10050211 - 5 May 2025

Abstract

Feeding habits of the four-spotted megrim, Lepidorhombus boscii, from the eastern Adriatic Sea were examined. A total of 1070 individuals collected using a bottom trawl net between July 2020 and June 2021 were analyzed. A high percentage of empty stomachs (63.27%) was [...] Read more.

Feeding habits of the four-spotted megrim, Lepidorhombus boscii, from the eastern Adriatic Sea were examined. A total of 1070 individuals collected using a bottom trawl net between July 2020 and June 2021 were analyzed. A high percentage of empty stomachs (63.27%) was recorded. The food composition proved that L. boscii is a carnivorous species. The identified prey of L. boscii was divided into seven groups: Teleostei, Bivalvia, Gastropoda, Cephalopoda, Isopoda, Mysida, and Decapoda. Decapods were the most important prey (%IRI = 58.18), followed by cephalopods (%IRI = 10.93). At the species level, the most important prey were the decapods Parapeneus longirostris (%IRI = 11.48) and Goneplax rhomboides (%IRI = 5.92). Statistically significant seasonal variations in diet were recorded; decapods dominated in spring, summer, and winter, whereas cephalopods prevailed in autumn. There were no statistically significant differences in the food composition between the three size categories. Decapods were the most important prey in all size categories (%IRI > 50). The lowest feeding intensity, as well as the highest percentage of empty stomachs, was recorded in winter, which is also the main spawning season of this species in the Adriatic Sea. 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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18 pages, 3017 KiB

Open AccessArticle

Climate Risk in Intermediate Goods Trade: Impacts on China’s Fisheries Production

by Shunxiang Yang, Zefang Liao, Yingli Zhang, Yuqing Ren and Hang Qu

Fishes 2025, 10(5), 210; https://doi.org/10.3390/fishes10050210 - 3 May 2025

Abstract

Climate change, especially extreme weather events, has significantly heightened the vulnerability of fisheries production supply chains. This study firstly investigates the input-driven climate risks through intermediate goods trade and their indirect impacts on China’s fisheries sector and constructs the Climate Risk-Trade-Production Model (CRTPM). [...] Read more.

Climate change, especially extreme weather events, has significantly heightened the vulnerability of fisheries production supply chains. This study firstly investigates the input-driven climate risks through intermediate goods trade and their indirect impacts on China’s fisheries sector and constructs the Climate Risk-Trade-Production Model (CRTPM). Key findings include: (1) The input-driven climate risk indicator for China’s fisheries sector has increased over the period 1995–2020, with Brazil, Canada, the United States, Japan, South Korea, and Russia as major contributors. (2) From 1995 to 2020, rising climate risk index in Brazil and Canada negatively affected China’s fisheries output, with a 1% increase in climate risk index resulting in production declines of 0.173% and 0.367%, respectively. (3) In contrast, a reduction in the climate risk index in the United States and Japan lowered intermediate goods prices, boosting China’s output by 0.934% and 0.172%, respectively, for every 1% decrease in the climate risk index. (4) Climate risk index in South Korea and Russia, while initially increasing, eventually stabilized, having minimal impact on China’s fisheries production. It is the importance of monitoring extreme weather events to mitigate the economic vulnerabilities of China’s fisheries. Full article

(This article belongs to the Special Issue Effects of Climate Change on Marine Fisheries)

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22 pages, 4857 KiB

Open AccessArticle

eDNA Metabarcoding Reveals the Depth-Structured Variation of Coral Reef Fish

by Jinfa Zhao, Lin Lin, Yong Liu, Teng Wang, Yu Liu, Yayuan Xiao, Jianzhong Shen, Hongyu Xie, Hai Huang and Qiuying Han

Fishes 2025, 10(5), 209; https://doi.org/10.3390/fishes10050209 - 2 May 2025

Abstract

Global coral reef ecosystems face various levels of disturbance pressure. Understanding the depth-structured variation in coral reef fish communities can help us to better grasp and predict the adaptive changes of the ecosystem under different stressors. This study applied eDNA metabarcoding technology to [...] Read more.

Global coral reef ecosystems face various levels of disturbance pressure. Understanding the depth-structured variation in coral reef fish communities can help us to better grasp and predict the adaptive changes of the ecosystem under different stressors. This study applied eDNA metabarcoding technology to analyze the spatial distribution of the coral reef fish at various depths (0 m, 5 m, 10 m, 15 m, 20 m, 30 m, 40 m, 50 m, and 60 m) within the Xisha Islands of China. The results indicated that the eDNA technology detected a total of 213 amplicon sequence variants (ASVs), including 33 species that were not identified using traditional methods. Herbivorous fish generally dominated in relative abundance across different depths. Moreover, the similarity among depth groups was largely absent, and significant differences existed in fish assemblages across depth gradients, consistent with the unique depth preferences of fish microhabitats. Importantly, our findings revealed distinct depth-structured variation among different functional groups of coral reef fish. Large carnivorous fish initially increased and then decreased along the depth gradient from 0 to 60 m, with a turning point around 20 m, while large herbivorous fish displayed the opposite trend. Small carnivorous and small herbivorous fish consistently declined along the same depth gradient. Additionally, the Margalef index (D) and Function richness (FRic) both displayed a consistent downward trend with increasing depth, while the Shannon–Wiener index (H′), Pielou index (J′), Quadratic entropy (RaoQ), Functional dispersion (FDis), and Functional evenness (FEve) initially increased and then decreased, peaking around 20 m. This study revealed that eDNA metabarcoding is an effective tool for evaluating coral reef fish biodiversity, community composition, and spatial distribution. It enhances our understanding of distribution dynamics and offers valuable insights for coral reef conservation and restoration efforts. Full article

(This article belongs to the Special Issue Conservation and Population Genetics of Fishes)

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16 pages, 2753 KiB

Open AccessArticle

Effects of Astragalus–Ginseng Dietary Supplementation on the Growth and Stress Resistance of Yellow Catfish (Pelteobagrus fulvidraco)

by Wenkai Lin, Haijing Xu, Xinlan Ma, Zifeng Yin, Aimin Wang, Junqiang Qiu and Mingyou Li

Fishes 2025, 10(5), 208; https://doi.org/10.3390/fishes10050208 - 2 May 2025

Abstract

Astragalus and ginseng, esteemed as traditional Chinese herbal medicines, have demonstrated the ability to bolster physical health and enhance the immune function of organisms. In this study, the effects of a dietary astragalus–ginseng mixture on the growth performance, intestinal health, and nonspecific immunity [...] Read more.

Astragalus and ginseng, esteemed as traditional Chinese herbal medicines, have demonstrated the ability to bolster physical health and enhance the immune function of organisms. In this study, the effects of a dietary astragalus–ginseng mixture on the growth performance, intestinal health, and nonspecific immunity of yellow catfish (Pelteobagrus fulvidraco) were evaluated, by measuring growth performance indices, intestinal villus morphology, enzyme activities, and expression levels of immune-related genes. Yellow catfish (n = 120, initial weight: 5.07 ± 0.18 g) were randomly assigned to four dietary groups: a control group (CT, 0 mg/kg) and three astragalus–ginseng treatment groups (AG1, 500 mg/kg; AG2, 1000 mg/kg; AG3, 2000 mg/kg). Each group had three replicates and was fed for six weeks. The results demonstrate that the treatment significantly enhanced the growth performance, as evidenced by increases in FBW, WG, WGR, SGR, and HSI. These improvements may be related to an increase in intestinal villi length and increased LPS activity, both of which are associated with enhanced digestive function. Meanwhile, the activity of antioxidant enzymes in the liver, including CAT, SOD, and GSH, was increased, whereas the level of MDA was decreased. In the serum, GSH was up-regulated, while SOD activity was decreased. Immune-related enzyme activities, such as ALT and LZM, were up-regulated, while AST showed no significant difference. Moreover, the treatment also promoted the expression of the anti-inflammatory factor IL-10. The pro-inflammatory factors, such as IL-1β, IL-6, and TNF-α, were decreased with the addition of low concentrations but increased with high concentrations. In conclusion, supplementation with an astragalus–ginseng mixture could promote growth performance by increasing digestive enzyme activity and intestinal villi length, and improve disease and stress resistance traits by modulating immune genes and antioxidant enzyme activity. A dosage of 1000 mg/kg was found to be optimal. Full article

(This article belongs to the Section Nutrition and Feeding)

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18 pages, 633 KiB

Open AccessArticle

Can We Turn Harmful Invasive Non-Native Fish Species into a Valuable Food Resource?

by Milica Jaćimović, Marko Stanković, Dejana Trbović, Dušan Nikolić, Marija Smederevac-Lalić and Zoran Marković

Fishes 2025, 10(5), 207; https://doi.org/10.3390/fishes10050207 - 1 May 2025

Abstract

This study explores the potential of utilizing black bullhead (Ameiurus melas Rafinesque, 1820), an invasive freshwater species, as a stocking fish for aquaculture. Fish were mass-removed from Ponjavica Nature Park during two periods (2018–2019 and 2020–2021), with selected individuals reared to evaluate [...] Read more.

This study explores the potential of utilizing black bullhead (Ameiurus melas Rafinesque, 1820), an invasive freshwater species, as a stocking fish for aquaculture. Fish were mass-removed from Ponjavica Nature Park during two periods (2018–2019 and 2020–2021), with selected individuals reared to evaluate growth, survival, and meat quality. A total of 20,145 individuals were removed in the first period (168 reared), and 15,921 in the second (120 reared). Two rearing systems—cages and recirculating aquaculture systems (RAS)—and four feed types were tested. Results demonstrated the species’ adaptability to intensive aquaculture, with good growth, resilience to high-protein diets, and tolerance to high stocking densities. Cage systems generally showed superior growth performance, while RAS produced higher survival rates. Both systems achieved favorable feed conversion ratios. Meat analysis revealed optimal levels of polyunsaturated fatty acids (PUFAs) in RAS and cage-reared fish, enhancing the species’ nutritional value for human consumption. These findings demonstrate the feasibility of repurposing black bullhead as a sustainable aquaculture resource. This dual-purpose approach addresses ecological concerns while offering economic benefits through increased fish production and affordable, nutritious food availability. Further technological development is needed to optimize production systems for broader implementation. Full article

(This article belongs to the Section Sustainable Aquaculture)

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25 pages, 1484 KiB

Open AccessReview

Sustainable Aquaculture Systems and Their Impact on Fish Nutritional Quality

by Nafuza Turlybek, Zhadyrassyn Nurbekova, Akmaral Mukhamejanova, Bayan Baimurzina, Maral Kulatayeva, Karlygash M. Aubakirova and Zerekbay Alikulov

Fishes 2025, 10(5), 206; https://doi.org/10.3390/fishes10050206 - 1 May 2025

Abstract

The growing global demand for fish necessitates the exploration of sustainable aquaculture practices. This has led to a focus on the quality and sustainable production of fish products with minimal environmental impact. Thus, the objective of this review is to study and evaluate [...] Read more.

The growing global demand for fish necessitates the exploration of sustainable aquaculture practices. This has led to a focus on the quality and sustainable production of fish products with minimal environmental impact. Thus, the objective of this review is to study and evaluate how different aquaculture systems impact the quality and nutritional profile of fish. Fish are rich sources of protein, containing almost 20% protein and essential amino acids and vitamins. The nutritional value and quality of fish products are directly related to the conditions under which they are produced through aquaculture. This article considers various aquaculture systems, including closed-loop systems, pond farming, marine aquaculture, and aquaponic systems. The operating principles, advantages, and inherent limitations of each fish-rearing system are subjected to rigorous critical analysis in this review. Such practices are necessary to meet the growing demand for fish and to maintain the integrity of aquatic ecosystems for future generations. Full article

(This article belongs to the Special Issue Ensuring Safe and Sustainable Aquaculture: A One Health Perspective)

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22 pages, 9500 KiB

Open AccessArticle

Increased CO₂ Concentration Mitigates the Impact of Nitrite on Zebrafish (Danio rerio) Liver and Gills

by Xinyu Wang, Yao Tang, Hui Yang, Ya He, Kang Ou-Yang, Liangmou Wang, Qian Zhang, Dapeng Li and Li Li

Fishes 2025, 10(5), 205; https://doi.org/10.3390/fishes10050205 - 1 May 2025

Abstract

Nitrite and carbon dioxide (CO₂) are common environmental substances in intensive aquaculture ponds. However, the effects and mechanisms of their combined exposure on aquatic animals remain unclear. In this study, we investigated the toxic effects of 2.5, 5, and 10 mg/L [...] Read more.

Nitrite and carbon dioxide (CO₂) are common environmental substances in intensive aquaculture ponds. However, the effects and mechanisms of their combined exposure on aquatic animals remain unclear. In this study, we investigated the toxic effects of 2.5, 5, and 10 mg/L CO₂ in the presence of 2 mg/L nitrite on hematological, blood gas parameters, and liver physiological and pathological changes in zebrafish (Danio rerio) over 14 days and 28 days. Our results demonstrated a reduced nitrite uptake and accumulation in the gills and liver of zebrafish exposed to nitrite and varying levels of CO₂. Increased CO₂ levels also led to a decrease in the expression of gill ae1, whereas the transcriptional levels of nhe1 and nhe3b, nkcc and nbc1 were notably upregulated. Moreover, there was a decrease in Cl⁻ and Na⁺ concentrations, along with an increase in K⁺ concentrations. These changes suggested that zebrafish responded to increased CO₂ stress by reducing their absorption of chloride-dependent nitrite, excreting H⁺ and maintaining their internal pH. Exposure to higher CO₂ levels in the presence of nitrite resulted in lower blood MetHb levels and liver oxidative stress compared to the nitrite single-exposure treatment. Furthermore, co-treatment with CO₂ and nitrite attenuated the nitrite-induced damage to genes related to mitochondrial respiratory chain function (ndufs1, mtnd5, mtycb, atp5f1b, mtatp8), leading to elevated ATP levels. Exposure to nitrite alone increased the expression of lipolytic genes (hsla, cpt1aa, atgl) and decreased the expression of lipid synthesis genes (fasn, acaca), resulting in a decrease in TG and TC content in zebrafish liver. However, co-treatment with CO₂ and nitrite prevented the nitrite-induced disruption of lipid metabolism, as evidenced by the improvement in TG and TC levels, as well as transcriptional levels of lipid metabolism-related genes. In conclusion, our study suggests that in the presence of 2 mg/L nitrite, increased CO₂ (2.5–10 mg/L) may modulate ion transporter genes to reduce the chloride-dependent nitrite uptake and maintain pH homeostasis, concurrently alleviating oxidative stress, restoring mitochondrial respiratory function, and improving lipid metabolism in a dose-dependent manner. These changes may be related to the increase in the concentration of bicarbonate ions in the water as the CO₂ level rises. These findings shed light on the potential protective effects of CO₂ in mitigating the harmful effects of nitrite exposure in aquatic animals. Full article

(This article belongs to the Section Physiology and Biochemistry)

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20 pages, 5084 KiB

Open AccessArticle

Bacterial Community Composition and Prevalence of Aeromonas dhakensis in Four Tilapia Freshwater Aquaculture Systems in Malaysia

by Sook Ling Lim, Suat Moi Puah, Siti Nursyuhada Baharudin, Nur Insyirah Mohd Razalan, Kieng Soon Hii, Wei Ching Khor, Yen Ching Lim, Kyaw Thu Aung, Kek Heng Chua, Po Teen Lim and Chui Pin Leaw

Fishes 2025, 10(5), 204; https://doi.org/10.3390/fishes10050204 - 1 May 2025

Abstract

The tilapia (Oreochromis) aquaculture industry in Malaysia has expanded rapidly to meet the increasing demand for animal protein. However, this growth is challenged by microbial infections, particularly those caused by the emerging pathogen Aeromonas dhakensis. This study aimed to investigate [...] Read more.

The tilapia (Oreochromis) aquaculture industry in Malaysia has expanded rapidly to meet the increasing demand for animal protein. However, this growth is challenged by microbial infections, particularly those caused by the emerging pathogen Aeromonas dhakensis. This study aimed to investigate the microbial community composition across four distinct tilapia farming systems and assess associated water physicochemical parameters, with a focus on detecting the presence of A. dhakensis and elucidating its environmental associations. Water physicochemical parameters were measured to evaluate environmental conditions, microbial communities were characterized through 16S rDNA metabarcoding, and A. dhakensis was detected using both microbiological and molecular approaches. Principal component analysis (PCA) and canonical correspondence analysis (CCA) were employed to explore the influence of environmental variables and microbial community dynamics on pathogen occurrence. Our results indicated that floating cages exhibited higher levels of temperature, ammonium, and fecal coliform, while cement tanks showed signs of nutrient accumulation. PCA revealed that both systems were associated with degraded water quality. A total of 45 A. dhakensis strains with distinct fingerprints were isolated. The 16S metabarcoding revealed Proteobacteria, Actinobacteria, and Planctomycetota as the dominant phyla. Alpha diversity did not differ significantly among pond systems, while beta diversity revealed variations in microbial assemblages across aquaculture systems. CCA identified dissolved oxygen, temperature, macronutrients (phosphate, ammonium, nitrate, and nitrite), and turbidity as significant environmental drivers shaping the microbial community structure across the pond systems. In conclusion, this study highlights the importance of environmental factors, particularly dissolved oxygen, temperature, and nutrient levels, in shaping microbial community composition and potentially influencing the presence of pathogenic bacteria such as A. dhakensis. These findings underscore the need for improved environmental management in tilapia aquaculture to mitigate disease risks and support fish health. Full article

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

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14 pages, 2563 KiB

Open AccessArticle

Integrative Metabolomic and Transcriptomic Analyses Reveal the Impact of Methionine Supplementation to Gibel Carp (Carassius auratus gibelio)

by Yujie Liu, Rendong Qian, Qiyou Xu and Jianhua Zhao

Fishes 2025, 10(5), 203; https://doi.org/10.3390/fishes10050203 - 1 May 2025

Abstract

The experiment was conducted to evaluate the molecular mechanism of methionine supplementation on the growth of gibel carp. In the study, the following five groups were included: the control group (FM) was fed with a high-plant protein diet as basal diet, and four [...] Read more.

The experiment was conducted to evaluate the molecular mechanism of methionine supplementation on the growth of gibel carp. In the study, the following five groups were included: the control group (FM) was fed with a high-plant protein diet as basal diet, and four treatment groups were supplemented with 0.25% crystalline methionine (CM₅₀), 0.50% crystalline methionine (CM₁₀₀), 0.25% coated methionine (HM₅₀) or 0.50% coated methionine (HM₁₀₀), respectively. Each group consisted of four replicates of 25 fish each. The weight gain rate and specific growth rate of gibel carp in the HM₁₀₀ group were significantly higher than the FM group. The hepatopancreas transcriptomic (n = 4) and metabolomic (n = 6) analysis for the FM group and HM₁₀₀ group showed that the significantly differential metabolites mainly related to amino acid metabolism, protein digestion and absorption, and aminoacyl-tRNA biosynthesis. Additionally, some genes that were significantly different in these two groups were involved in energy metabolism and transmembrane transporter activity. Therefore, the improvement of fish growth by 0.50% coated methionine supplementation might be achieved through altering amino acid and energy-related metabolism in hepatopancreas, which provides new insights for understanding the impact of methionine on the growth of fish. Full article

(This article belongs to the Section Nutrition and Feeding)

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17 pages, 32026 KiB

Open AccessArticle

Histological, Immunohistochemical, and Ultrastructural Characterization of Cartilage in Molly Fish (Poecilia sphenops): Insights into Skeletal Adaptations in Teleosts

by Doaa M. Mokhtar, Mohammed A. Abdel-Ghani, Enas A. Abdelhafez, Marco Albano, Khalid M. Alkhodair and Giacomo Zaccone

Fishes 2025, 10(5), 202; https://doi.org/10.3390/fishes10050202 - 30 Apr 2025

Abstract

Cartilage is a crucial component of the vertebrate skeletal system, providing structural integrity, flexibility, and adaptive functions across species. In teleost fish, cartilage exhibits significant morphological and functional diversity, providing specialized biomechanical properties essential for aquatic life. This study presents a detailed histological, [...] Read more.

Cartilage is a crucial component of the vertebrate skeletal system, providing structural integrity, flexibility, and adaptive functions across species. In teleost fish, cartilage exhibits significant morphological and functional diversity, providing specialized biomechanical properties essential for aquatic life. This study presents a detailed histological, immunohistochemical, and ultrastructural investigation of cartilage in molly fish (Poecilia sphenops), identifying five distinct types of cartilage: hyaline-cell, scleral, cell-rich hyaline, elastic cell-rich, and matrix-rich hyaline cartilage. Histological staining techniques revealed notable differences in cellular architecture and composition of the extracellular matrix among the cartilage types. Immunohistochemical analysis demonstrated the expression of S100 protein and acetylcholinesterase (Ach), suggesting their involvement in cartilage regulation and maintenance. Endochondral ossification was observed in the head and gill arches. Electron microscopy provided detailed insights into chondrocyte morphology, interactions between cartilage and the perichondrium, and interactions between telocytes and fibroblasts. The findings enhance our understanding of skeletal adaptations in teleost fish, emphasizing the functional diversity of cartilage in aquatic environments. This study contributes to evolutionary biology and may have implications for regenerative medicine and biomaterials research. Full article

(This article belongs to the Special Issue Skeletal Development of Fishes: Using New Technologies to Study Bone Biology)

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19 pages, 1719 KiB

Open AccessArticle

Insights into the Movements and Habitat Use of Blue Marlins (Makaira nigricans) in the Southwestern Atlantic Ocean

by Osman Crespo-Neto, Bruno C. L. Macena, Bruno Mourato, Eduardo G. Pimenta, Eduardo W. Wanick, José C. Pacheco and Alberto F. Amorim

Fishes 2025, 10(5), 201; https://doi.org/10.3390/fishes10050201 - 28 Apr 2025

Abstract

Understanding the ecology of large pelagic fishes is important for species conservation and maintaining ecosystem dynamics. The Atlantic blue marlin (Makaira nigricans) is usually targeted in recreational fisheries and occasionally captured as bycatch in pelagic longline fisheries, yet it is considered [...] Read more.

Understanding the ecology of large pelagic fishes is important for species conservation and maintaining ecosystem dynamics. The Atlantic blue marlin (Makaira nigricans) is usually targeted in recreational fisheries and occasionally captured as bycatch in pelagic longline fisheries, yet it is considered an overexploited stock in the Atlantic. In this study, pop-up archival satellite tags were deployed on twenty-one blue marlins in the Southwest Atlantic Ocean between February 2006 and August 2021. Results show that blue marlin spent an average of 57% of their time in shallow waters (<10 m) and mostly at temperatures between 26 °C and 28 °C during both day and night. Minimum linear distances observed ranged from 124 to 1995 km, with tracking periods lasting 5 to 215 days. Overall, tagged blue marlins remained around the tagging region during the tracking period, except for six individuals that exhibited more directional movements offshore. The results provided in this study are relevant for better understanding the habitat use of blue marlins in the Southwest Atlantic Ocean and to support analysis for stock assessment purposes, which are often affected by uncertainties and large misreporting rates in the region. Full article

(This article belongs to the Special Issue Movement and Conservation of Large Marine Fauna)

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