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Fishes, Volume 10, Issue 2 (February 2025) – 48 articles

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16 pages, 676 KiB  
Review
CRISPR-Based Genetic Improvement of Aquaculture Species
by Abdulkadir Bayır, Selma Saoula, Ammar Almansour, Deshou Wang, Mehtap Bayır, Burcu Naz Uzun, Serpil Turhan, Harun Arslan and Gökhan Arslan
Fishes 2025, 10(2), 84; https://doi.org/10.3390/fishes10020084 - 18 Feb 2025
Abstract
The clustered regularly interspaced short palindromic repeat-associated protein (CRISPR-Cas) system is considered a potential game-changer in the aquaculture sector. The CRISPR-Cas9 system is derived from an adaptive mechanism of the immune system of some prokaryotes. The CRISPR/Cas9 system potentially accelerates the rate of [...] Read more.
The clustered regularly interspaced short palindromic repeat-associated protein (CRISPR-Cas) system is considered a potential game-changer in the aquaculture sector. The CRISPR-Cas9 system is derived from an adaptive mechanism of the immune system of some prokaryotes. The CRISPR/Cas9 system potentially accelerates the rate of sustained genetic gain for the aquaculture and seafood production sectors. Unlike conventional genome-editing techniques, CRISPR/Cas9 is more cost-effective, user-friendly, and extremely precise. It enables overcoming large-scale challenges in aquaculture. Traits such as high fertility, external fertilization, shorter generation time, well-established breeding methods, and the ability to raise larvae offer potential benefits for applying CRISPR/Cas9 genome editing in most aquacultural species. The use of genome editing accelerates precise breeding where desired modifications are made to the target gene. There is a high likelihood that the intended alterations will be achieved, resulting in the transmission of the desired trait to the next generation. In this paper, we review how the CRISPR system evolved, its basic categories and different Cas systems, as well as the molecular mechanism of CRISPR/Cas. We also highlight and discuss the potential applications of CRISPR/Cas in the aquaculture industry. Moreover, the challenges of using CRISPR/Cas technology are briefly discussed. This pathway charts a course to a future in which genome editing has the potential to enable aquaculture to fulfill world food requirements with public and ecological safety. Full article
(This article belongs to the Section Genetics and Biotechnology)
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10 pages, 986 KiB  
Article
Incorrect Identification in the Marketing of Serrasalmid Fishes: A Threat to Native Species and Productivity in the Aquaculture Industry
by Diego G. Martins, Fernanda D. Prado, Ricardo Utsunomia, Diogo Teruo Hashimoto, Caio Augusto Gomes Goes, Fausto Foresti, Carlos Egberto Rodrigues Junior and Fabio Porto-Foresti
Fishes 2025, 10(2), 83; https://doi.org/10.3390/fishes10020083 - 18 Feb 2025
Abstract
Interspecific hybridization can offer advantages in fish aquaculture by enhancing traits like growth rate and disease resistance. However, improper management can result in heterogeneous breeding stocks, which pose risks if hybrids interbreed with native populations. This can lead to loss of genetic diversity [...] Read more.
Interspecific hybridization can offer advantages in fish aquaculture by enhancing traits like growth rate and disease resistance. However, improper management can result in heterogeneous breeding stocks, which pose risks if hybrids interbreed with native populations. This can lead to loss of genetic diversity and alterations in population structure. This study aimed to evaluate the prevalence of hybridization within the Brazilian aquaculture industry, focusing on the economically significant Serrasalmid species, such as Piaractus mesopotamicus (pacu), Piaractus brachypomus (pirapitinga), Colossoma macropomum (tambaqui), and their hybrids. Using molecular markers (TROP and APOC SNP markers), 312 individuals from the Companhia de Entrepostos e Armazéns Gerais de São Paulo (CEAGESP), the largest warehouse in Latin America, were assessed. The results revealed that 80% of the samples were misidentified, with a substantial proportion of hybrids (72.12%). Among these hybrids, 71.6% were classified as F1 hybrids, while 28.4% were post-F1 hybrids. These findings highlight the need for improved genetic monitoring and management practices in Brazil’s fish production industry, emphasizing the importance of sustainable practices to ensure the long-term viability of aquaculture while preserving native genetic resources. Full article
(This article belongs to the Section Sustainable Aquaculture)
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12 pages, 1069 KiB  
Article
Portable Smoking Ovens: What Are the PAH Levels in Grilled and Smoked Rainbow Trout?
by Paul Uiuiu, Daniel Cocan, Călin Lațiu, Radu Constantinescu, Vioara Mireșan, Tudor Papuc, Raul-Lucian Savin, Andrada Ihuț, Camelia Răducu, Anca Becze, Cristina Craioveanu and Bogdan Alin Vlaic
Fishes 2025, 10(2), 82; https://doi.org/10.3390/fishes10020082 - 18 Feb 2025
Viewed by 157
Abstract
Fish smoking is one of the oldest preservation methods and has traditional forms in most parts of the world, each with distinct variables. The presence of PAHs in smoked fish is of great concern for producers and consumers alike, as PAHs have great [...] Read more.
Fish smoking is one of the oldest preservation methods and has traditional forms in most parts of the world, each with distinct variables. The presence of PAHs in smoked fish is of great concern for producers and consumers alike, as PAHs have great negative effects on human health. This study aimed to determine the physicochemical characteristics and polycyclic aromatic hydrocarbons (PAHs) content level in smoked rainbow trout Oncorhynchus mykiss (Walbaum, 1792) processed using a commercial portable grilling and smoking oven. Sawdust of hardwood (beech, cherry, sour cherry, walnut, and plum) and softwood (fir, willow) were used to produce aromatic essences. The principal component analysis (PCA) revealed that different tree species tend to accumulate different PAHs in different concentrations. In the case of the generalized additive model (GAM) analyzing fish meat, fir tree reduced the concentration of PAHs in fish meat. When GAM analyzed fish skin, cherry, sour cherry, and willow trees significantly reduced the concentrations of PAHs in fish skin compared to beech trees. Furthermore, the results regarding the skin of the fish suggest that it acts as a protective barrier, trapping smoke particulates and reducing the penetration of PAHs into the meat. The present method clearly shows that, at least in the case of Benzo[a]pyrene, it is safer than traditional methods of smoking. This highlights the need for further research into the physicochemical properties of fish tissue and their impact on PAH accumulation. Full article
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20 pages, 10297 KiB  
Article
Utilizing an Enhanced YOLOv8 Model for Fishery Detection
by Hanyu Jiang, Jiacheng Zhong, Fuyu Ma, Cheng Wang and Ruiwen Yi
Fishes 2025, 10(2), 81; https://doi.org/10.3390/fishes10020081 - 17 Feb 2025
Viewed by 185
Abstract
Due to the complexity of underwater lighting, image clarity and color are significantly affected. Furthermore, in the underwater environment, marine organisms often blend into the background due to their similar colors, making them difficult to distinguish. These organisms are often obscured by various [...] Read more.
Due to the complexity of underwater lighting, image clarity and color are significantly affected. Furthermore, in the underwater environment, marine organisms often blend into the background due to their similar colors, making them difficult to distinguish. These organisms are often obscured by various obstacles, and there are varying degrees of overlap between them, posing substantial challenges for underwater object detection using deep learning methods. To address these challenges, we developed an improved object detection model based on YOLOv8, which is robust and less sensitive to noise. We designed the Global Context 3D Perception Module (GC3DPM) to enable global context feature modeling and 3D perception. Additionally, we introduced the Channel Aggregation Efficient Downsampling Block (CAEDB) for more efficient upsampling and to improve the network’s expressive power and information flow through channel aggregation functionality. We further optimized the detection head for more effective use of the top-layer network’s rich semantic information, and addressed the class imbalance that was present in the data. Our proposed method achieves 82.1% precision, 76.5% recall, 79.2% F1-score, 83.3% mAP50, and 48.6% mAP50-95, while reducing the parameter count by 8.3%. The results demonstrate that our method provides an efficient and reliable automatic detection technology for precision underwater fishing. Full article
(This article belongs to the Special Issue Technology for Fish and Fishery Monitoring)
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18 pages, 3322 KiB  
Article
Seasonal Fluctuations in Geosmin and Terpenes in Rainbow Trout (Oncorhynchus mykiss) in an Outdoor Commercial Recirculated Aquaculture System Facility
by Raju Podduturi, Mikael Agerlin Petersen, Peter Stougaard and Niels O. G. Jørgensen
Fishes 2025, 10(2), 80; https://doi.org/10.3390/fishes10020080 - 17 Feb 2025
Viewed by 202
Abstract
Seasonal changes in geosmin and selected terpenes in rainbow trout (Oncorhynchus mykiss) in an outdoor recirculated aquaculture system (RAS) in Denmark were followed over three months. In the water, geosmin varied from 4.1 to 25.7 ng/L, but no seasonal trends were [...] Read more.
Seasonal changes in geosmin and selected terpenes in rainbow trout (Oncorhynchus mykiss) in an outdoor recirculated aquaculture system (RAS) in Denmark were followed over three months. In the water, geosmin varied from 4.1 to 25.7 ng/L, but no seasonal trends were obvious. Variable trends occurred for geosmin relative to concentrations of inorganic N (ammonium, nitrite, and nitrate) and phosphate, and did not indicate a general relationship. The geosmin content of the fish ranged from 669 to 2264 ng/kg and covaried with geosmin in the water. The average number of the geoA gene (encoding geosmin synthase) was 2.41 × 105 copies/L in the water and 3.29 × 107 copies on each bio-element in the biofilter. In only one of the three examined RAS units, geosmin in the water and on the bio-elements covaried with the number of geoA copies. Among the identified four terpenes in the fish flesh, α-pinene was dominant and made up 55.9–62.8% of the terpenes. The presence of aroma-active terpenes in the fish suggests that not only geosmin concentrations should be considered when characterizing taste profiles of farmed rainbow trout. Full article
(This article belongs to the Section Sustainable Aquaculture)
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19 pages, 1472 KiB  
Article
Accounting for Carbon Emissions from Fisheries in China and Analyzing the Decoupling Effect
by Zhiyao Xia and Dameng Hu
Fishes 2025, 10(2), 79; https://doi.org/10.3390/fishes10020079 - 16 Feb 2025
Viewed by 198
Abstract
This study evaluated the carbon emissions as one of the environmental impacts of fishing activities in China during the period of 2010–2022. The decoupling effect of fishery carbon emissions and fishery economic growth was analyzed using a decoupling model. The findings reveal that [...] Read more.
This study evaluated the carbon emissions as one of the environmental impacts of fishing activities in China during the period of 2010–2022. The decoupling effect of fishery carbon emissions and fishery economic growth was analyzed using a decoupling model. The findings reveal that China’s fishery carbon emissions are substantial and exhibit multi-stage variations. Inland areas mainly emit carbon from aquatic feed decomposition and aquaculture equipment electricity consumption, with differing structures between high- and low-emission regions. Coastal areas primarily emit carbon from fishing, supplemented by aquatic feed. From 2010 to 2011, decoupling was poorly idealized as strong negative decoupling, but post-2011 featured mainly weak decoupling with strong decoupling as a complement. After excluding economic factors, carbon intensity and population size positively influenced decoupling, with intensity initially leading and scale later expanding. Structural factors mainly hindered decoupling. Full article
(This article belongs to the Special Issue Fishing Gear Technology and Conservation of Fishery Resources)
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24 pages, 6158 KiB  
Article
Effects of Fish Meal Replacement with Poultry By-Product Meal on Growth Performance, Lipid Metabolism, Hepatic–Intestinal Health and Ammonia Nitrogen Stress in Siniperca chuatsi
by Shulin Tang, Huanchao Ma, Xueming Hua, Lei Wang, Biao Yun, Xuan Zhu and Xueqiao Qian
Fishes 2025, 10(2), 78; https://doi.org/10.3390/fishes10020078 - 15 Feb 2025
Viewed by 188
Abstract
Fish meal (FM) replacement is essential for sustainable aquaculture development. This study investigated the effects of FM replacement with poultry by-product meal (PBM) on growth performance, hepatic and intestinal health and ammonia nitrogen stress resistance in mandarin fish (Siniperca chuatsi). A [...] Read more.
Fish meal (FM) replacement is essential for sustainable aquaculture development. This study investigated the effects of FM replacement with poultry by-product meal (PBM) on growth performance, hepatic and intestinal health and ammonia nitrogen stress resistance in mandarin fish (Siniperca chuatsi). A 52-day feeding trial was conducted using PBM to replace fish meal at levels of 0%, 17.5%, 35.0%, 52.5% and 70.0%. The results showed that FM replacement with PBM did not influence growth performance in mandarin fish. Moderate PBM replacement (≤35.0%) did not harm liver health and enhanced the intestinal structure. However, excessive replacement (≥52.5%) caused hepatocyte damage, reduced antioxidant capacity and decreased survival under ammonia nitrogen stress. Notably, 70% PBM replacement led to severe hepatic lipid accumulation, inhibiting fatty acid β-oxidation and triglyceride hydrolysis pathways. Furthermore, high PBM levels (≥52.5%) also reduced intestinal muscularis thickness, downregulated tight junction proteins and induced inflammation. In conclusion, while PBM replacement does not hinder growth, maintaining levels below 35.0% (PBM ≤ 28.5%) is essential for preserving hepatic lipid metabolism, intestinal health and antioxidant defense in mandarin fish. Full article
(This article belongs to the Section Nutrition and Feeding)
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12 pages, 3546 KiB  
Article
Antiviral Effect and Metabolic Regularity of a Phenylpropanoid- Based Compound as Potential Immunopotentiator
by Dawei Song, Xue Cai, Qianhao Shao, Xinhui Tong, Zhe Zhao, Lei Liu and Guanglu Liu
Fishes 2025, 10(2), 77; https://doi.org/10.3390/fishes10020077 - 15 Feb 2025
Viewed by 186
Abstract
Spring viremia of carp virus (SVCV) is a significant pathogen that has notably hindered the advancement of cyprinid aquaculture in recent years. Infections caused by SVCV are often associated with substantial economic losses due to the absence of effective treatment options. Previous reports [...] Read more.
Spring viremia of carp virus (SVCV) is a significant pathogen that has notably hindered the advancement of cyprinid aquaculture in recent years. Infections caused by SVCV are often associated with substantial economic losses due to the absence of effective treatment options. Previous reports indicated that N-(4-methyl-2-oxo-2H-chromen-7-yl) benzenesulfonamide (N6) exhibits inhibitory effects on SVCV proliferation. This study aims to comprehensively evaluate the anti-SVCV effects of N6 using healthy young carp as the experimental model. The research investigates the antiviral activity of this compound in vivo, the immune response of interferon (IFN)-related genes, its impact on the horizontal transmission of SVCV, and histopathological changes. The results indicate that N6 significantly inhibits SVCV infectivity and apoptosis in EPC cells in vitro. Furthermore, while N6 reduced horizontal transmission of SVCV in a static cohabitation challenge model, the N6-treated SVCV-infected group showed a nearly 3-fold decrease in viral load compared to the control group, it did not completely prevent transmission at established antiviral dosages. Histopathological analysis of the affected fish revealed that N6 effectively mitigated tissue damage induced by SVCV. Additionally, the up-regulation of six IFN-related genes suggests that N6 may indirectly activate IFNs to facilitate the clearance of SVCV in the kidney and spleen, as demonstrated by quantitative reverse transcription polymerase chain reaction (qRT-PCR). These findings provide a foundation for further investigations into the mechanisms by which N6 acts against SVCV and may aid in the development of novel anti-SVCV therapeutics. Full article
(This article belongs to the Section Nutrition and Feeding)
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20 pages, 302 KiB  
Article
Effects of Chicken By-Product Meal as a Fish Meal Replacer in Diets With or Without Jack Mackerel Meal Inclusion: Growth and Feed Availability for Rockfish (Sebastes schlegeli)
by June Kim, Yu Jin Sim and Sung Hwoan Cho
Fishes 2025, 10(2), 76; https://doi.org/10.3390/fishes10020076 - 14 Feb 2025
Viewed by 242
Abstract
The current experiment is conducted to determine the effects of chicken by-product meal (CBM) as a fish meal (FM) replacer in diets, with or without the inclusion of jack mackerel (Trachurus japonicus) meal (JMM), on the growth and feed availability of [...] Read more.
The current experiment is conducted to determine the effects of chicken by-product meal (CBM) as a fish meal (FM) replacer in diets, with or without the inclusion of jack mackerel (Trachurus japonicus) meal (JMM), on the growth and feed availability of rockfish (Sebastes schlegeli). A two-way ANOVA experimental design [FM replacement level (FMRL, 25% and 50%) × JMM inclusion (without and with)] was adopted. The control (Con) diet contained 55% FM. In the Con diet, 25% and 50% of FM were substituted with CBM, either without or with the inclusion of 22% JMM, referred to as the CBM25, CBM50, CBM25J, and CBM50J diets, respectively. A total of 375 juvenile fish were distributed into 15 tanks with triplicates. The 25% FM replacement diets led to significantly (p < 0.003 and p < 0.004, respectively) greater weight gain and specific growth rate (SGR) of rockfish than the 50% FM replacement diets. Furthermore, the CBM-replaced diets with JMM inclusion led to significantly (p < 0.003 and p < 0.002, respectively) greater weight gain and SGR of fish compared with those without JMM inclusion. Weight gain and SGR of rockfish fed the Con and CBM25J diets were significantly (p < 0.001 for both) greater than those of fish fed the CBM25, CBM50, and CBM50J diets. However, neither dietary FMRL nor JMM inclusion had significant (p > 0.05) effects on feed consumption, blood chemistry, or the biochemical composition of rockfish. In conclusion, 25% of FM could be replaced with CBM in the 55% FM-based diet, including JMM, without adverse effects on the growth, feed availability, blood chemistry, or biochemical composition (proximate composition and amino and fatty acid profiles) of rockfish. Full article
(This article belongs to the Section Nutrition and Feeding)
24 pages, 5201 KiB  
Article
A Deep Learning Approach to Automated Treatment Classification in Tuna Processing: Enhancing Quality Control in Indonesian Fisheries
by Johan Marcus Tupan, Fredrik Rieuwpassa, Beni Setha, Wilma Latuny and Samuel Goesniady
Fishes 2025, 10(2), 75; https://doi.org/10.3390/fishes10020075 - 13 Feb 2025
Viewed by 383
Abstract
The Indonesian maritime territory harbors a rich diversity of marine resources, making up approximately 37% of global fish species diversity. Tuna, particularly in Maluku Province, stands out as a vital economic asset with growing production and export numbers. Current practices for processing and [...] Read more.
The Indonesian maritime territory harbors a rich diversity of marine resources, making up approximately 37% of global fish species diversity. Tuna, particularly in Maluku Province, stands out as a vital economic asset with growing production and export numbers. Current practices for processing and evaluating tuna meat, however, face significant limitations due to basic infrastructure and reliance on manual inspection methods, leading to potential contamination risks and treatment identification errors. This research addresses these challenges by implementing an advanced deep learning solution based on convolutional neural networks (CNNs) to automatically identify three distinct treatment categories for tuna loin: No-Treatment, CO-Treatment, and CS-Treatment. Trained on a comprehensive image dataset, the model demonstrated exceptional performance with 95% accuracy. While field testing confirmed the model’s strong performance in correctly identifying treatment categories, occasional classification errors highlighted areas for improvement in data preprocessing. This study provides a significant step forward in automated fish processing assessment technology, offering a promising solution to longstanding challenges in the marine processing industry. Full article
(This article belongs to the Special Issue Management and Technology for Tuna Fisheries)
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23 pages, 3009 KiB  
Review
Advancing Fisheries Research and Management with Computer Vision: A Survey of Recent Developments and Pending Challenges
by Jesse Eickholt, Jonathan Gregory and Kavya Vemuri
Fishes 2025, 10(2), 74; https://doi.org/10.3390/fishes10020074 - 12 Feb 2025
Viewed by 400
Abstract
The field of computer vision has progressed rapidly over the past ten years, with noticeable improvements in techniques to detect, locate, and classify objects. Concurrent with these advances, improved accessibility through machine learning software libraries has sparked investigations of applications across multiple domains. [...] Read more.
The field of computer vision has progressed rapidly over the past ten years, with noticeable improvements in techniques to detect, locate, and classify objects. Concurrent with these advances, improved accessibility through machine learning software libraries has sparked investigations of applications across multiple domains. In the areas of fisheries research and management, efforts have centered on the localization of fish and classification by species, as such tools can estimate the health, size, and movement of fish populations. To aid in the interpretation of computer vision for fisheries research management tasks, a survey of the recent literature was conducted. In contrast to prior reviews, this survey focuses on employed evaluation metrics and datasets as well as the challenges associated with applying machine learning to a fisheries research and management context. Misalignment between applications and commonly used evaluation metrics and datasets mischaracterizes the efficacy of emerging computer vision techniques for fisheries research and management tasks. Aqueous, turbid, and variable lighted deployment settings further complicate the use of computer vision and generalizability of the reported results. Informed by these inherent challenges, culling surveillance data, exploratory data collection in remote settings, and selective passage and traps are presented as opportunities for future research. Full article
(This article belongs to the Section Fishery Economics, Policy, and Management)
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23 pages, 5624 KiB  
Article
Heat Shock Factors in the European Eel: Gene Characterization and Expression Response to Different Environmental Conditions and to Induced Sexual Maturation
by Leonor Ferrão, Luz Pérez, Juan F. Asturiano and Marina Morini
Fishes 2025, 10(2), 73; https://doi.org/10.3390/fishes10020073 - 12 Feb 2025
Viewed by 320
Abstract
Heat shock factors (HSFs) are transcription factors that regulate responses to environmental changes and play roles in physiological mechanisms like spermatogenesis. This study analyzed the HSF gene family and their expression profiles in the European eel under different environmental conditions and during testis [...] Read more.
Heat shock factors (HSFs) are transcription factors that regulate responses to environmental changes and play roles in physiological mechanisms like spermatogenesis. This study analyzed the HSF gene family and their expression profiles in the European eel under different environmental conditions and during testis maturation. Six HSF genes were identified in the studied vertebrates, in which the eel presents two HSF1 paralogs (HSF1a and HSF1b), likely resulting from the teleost whole-genome duplication event, while only one paralog is present for the other HSF (HSF2, HSF4, and HSF5). All five HSF genes were highly expressed in the testis, but some were also detected in the brain, intestine, and gills. Our findings showed that HSF1 changed their expression in response to different temperature and salinity conditions, suggesting that these may support males in perceiving the temperature and salinity changes possibly found during reproductive migration. During hCGrec-induced spermatogenesis, HSF genes presented a decreasing expression profile throughout testis maturation (with significant differences in HSF1a and HSF4), except HSF5, which showed the highest levels after 4 weeks of hormonal treatment. Our study indicates that HSF genes are potentially implicated in the response to environmental changes perception and during gonadal maturation. Full article
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25 pages, 2423 KiB  
Article
Molecular Immune Responses of Ruditapes decussatus to Vibrio Infection at Different Temperatures: Expression of Key Genes and Resilience-Associated Single Nucleotide Polymorphisms
by Dimitrios K. Papadopoulos, Ioannis A. Giantsis, Athanasios Lattos, Konstantina Bitchava and Basile Michaelidis
Fishes 2025, 10(2), 72; https://doi.org/10.3390/fishes10020072 - 11 Feb 2025
Viewed by 316
Abstract
The impact of pathogenic Vibrio on bivalves is expected to be aggravated by global warming, posing a growing threat to aquaculture. Clam production has been particularly vulnerable, with significant losses attributed to the lack of pathogen-resistant strains. In this study, the mantle cavity [...] Read more.
The impact of pathogenic Vibrio on bivalves is expected to be aggravated by global warming, posing a growing threat to aquaculture. Clam production has been particularly vulnerable, with significant losses attributed to the lack of pathogen-resistant strains. In this study, the mantle cavity of the grooved carpet shell clam Ruditapes decussatus (Linnaeus, 1758) was injected with Vibrio splendidus at 18 °C, 22 °C, and 24 °C and the transcription of the phagelysozyme, Cu-Zn superoxide dismutase (Cu-Zn sod), tumor necrosis factor receptor associated factor 6 (traf6), inhibitor of NF-κB (IκB), and Fas-associated protein with death domain (fadd) genes were assessed during a 20-day period. Additionally, the coding sequences of lysozyme, fadd, and IκB in Ruditapes decussatus were characterized for the first time, and SNPs were identified. Some SNPs showed significantly different distributions between infection-resistant and infection-susceptible individuals. Infected clams experienced increased mortality at elevated temperatures. Lysozyme mRNA was upregulated in infected groups across all temperatures. The sustained increase on day 20, coinciding with elevated traf6 mRNA, suggests a prolonged activation of the immune response. Cu-Zn sod transcription at 18 °C and 22 °C peaked on day 7 and returned to control levels by day 20, indicating an effective immune response, while at 24 °C, infected animals showed a continuously increased transcription. IκΒ and traf6 transcription, reflecting NF-κB pathway activity, varied with temperature and showed transient stimulation at higher temperatures. The pattern of fadd expression indicated a late induction of apoptosis, particularly at 18 °C and 24 °C. Overall, this study illustrates the involvement of five key genes in host–pathogen interactions and identifies potential markers for selection for Vibrio resistance in Ruditapes decussatus. However, given the weak correlation observed, further research is needed on the link between these polymorphisms and pathogen resilience. Full article
(This article belongs to the Special Issue Prevention and Control of Aquatic Animal Diseases)
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22 pages, 37493 KiB  
Article
Morphology and Histology of the Digestive System of Japanese Mantis Shrimp (Oratosquilla oratoria)
by Ran Wang, Fangrui Lou, Pei Yang, Shengyao Qiu and Lei Wang
Fishes 2025, 10(2), 71; https://doi.org/10.3390/fishes10020071 - 10 Feb 2025
Viewed by 393
Abstract
This study investigated the characteristics of the digestive system in adult Japanese mantis shrimp (Oratosquilla oratoria), which is a species of carnivorous crustacean, with a focus on morphological and histological analysis. The digestive system of O. oratoria includes the mouthparts, the [...] Read more.
This study investigated the characteristics of the digestive system in adult Japanese mantis shrimp (Oratosquilla oratoria), which is a species of carnivorous crustacean, with a focus on morphological and histological analysis. The digestive system of O. oratoria includes the mouthparts, the esophagus, cardiac stomach, pyloric stomach, midgut, hindgut, anus and hepatopancreas. The histological structure of each organ is composed of the mucosal epithelial layer, submucous layer, muscularis, and outer membrane. Besides, the foregut is covered with a diverse chitinous layer. The labrum is densely populated with minor salivary glands. The mandibular-gastric mill apparatus and evenly arranged bifurcated setae are observed in the cardiac stomach. The secondary filter of the pyloric stomach is subtly intricate, with fine spicules and seta plate. The midgut, being the longest segment of the digestive tract and accounting for 59.39% of body length, has villi covered with dense microvilli. The hindgut also forms villi, but the height of the villi (695.96 μm) is 3.20 times that of the midgut (217.41 μm). The hepatopancreas encircles the entire pyloric stomach, midgut, and hindgut. The hepatosomatic index is approximately 3.83%. Full article
(This article belongs to the Section Sustainable Aquaculture)
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13 pages, 3481 KiB  
Article
Citrobacter freundii Caused Head Ulcer Disease and Immune Response in Juvenile Procambarus clarkii
by Yong He, Xiudan Yuan, Jinlong Li, Xing Tian, Zhigang He, Chunfang Zeng, Yukun Xie, Li Liu, Shiming Deng and Dongwu Wang
Fishes 2025, 10(2), 70; https://doi.org/10.3390/fishes10020070 - 9 Feb 2025
Viewed by 336
Abstract
Red swamp crayfish (Procambarus clarkii) is one of the most important aquaculture species in China. Frequent outbreaks of diseases seriously threatened the sustainable development of the industry. It is necessary to understand the causes of disease and study the mechanism of [...] Read more.
Red swamp crayfish (Procambarus clarkii) is one of the most important aquaculture species in China. Frequent outbreaks of diseases seriously threatened the sustainable development of the industry. It is necessary to understand the causes of disease and study the mechanism of disease resistance in P. clarkii. In this paper, the pathogenic bacteria causing head ulcers in juvenile P. clarkii were found and identified as Citrobacter freundii, which can cause severe pathological changes in the hepatopancreas and intestines of juvenile P. clarkii. Detection of humoral immune factors revealed that PO activity and lysozyme activity of infected P. clarkii were significantly enhanced at 15 and 20 dpi, respectively. Transcriptome analysis was conducted of hepatopancreas from normal and diseased P. clarkii after C. freundii injection, as well as bacteria-free control of P. clarkii. It was found that DEGs are rich in NF-κB, oxidative phosphorylation, JAK/STAT, Leukocyte transendothelial migration, MAPK, and PPAR signaling pathway. These pathways are related to immune modulation, metabolism, and pathogen clearance. Meanwhile, immune-related genes such as Gip, nfyA, psmD13, and FGFR were significantly highly expressed in the normal group, which was verified by qRT-PCR results, suggesting that they may be the key regulatory genes for juvenile P. clarkii resistance to C. freundii. This study will help to elucidate the molecular mechanism of the immune response of P. clarkii to C. freundii. The results are instructive for the prevention and treatment of P. clarkii diseases and for further understanding of the invertebrate immune system. Full article
(This article belongs to the Section Aquatic Invertebrates)
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17 pages, 5659 KiB  
Article
Thyroid-Active Agents Triiodothyronine, Thyroxine and Propylthiouracil Differentially Affect Growth, Intestinal Short Chain Fatty Acids and Microbiota in Little Yellow Croaker Larimichthys polyactis
by Xiao Liang, Yu Zhang, Ting Ye, Feng Liu and Bao Lou
Fishes 2025, 10(2), 69; https://doi.org/10.3390/fishes10020069 - 7 Feb 2025
Viewed by 397
Abstract
Thyroid dysfunction may affect the intestinal microbiota through short-chain fatty acids (SCFAs) in marine fish. This study investigated the effects of triiodothyronine (T3, 20 ng/g) and thyroxine (T4, 20 ng/g), and propylthiouracil (PTU, 5000 ng/g) on growth performance, intestinal SCFA profiles, and microbiota [...] Read more.
Thyroid dysfunction may affect the intestinal microbiota through short-chain fatty acids (SCFAs) in marine fish. This study investigated the effects of triiodothyronine (T3, 20 ng/g) and thyroxine (T4, 20 ng/g), and propylthiouracil (PTU, 5000 ng/g) on growth performance, intestinal SCFA profiles, and microbiota composition in little yellow croakers Larimichthys polyactis. The results showed that dietary thyroid-active agent supplementation significantly decreased weight gain, and specific growth ratio. Moreover, dietary T3, T4, and PTU induced the states of hyperthyroidism, hyperthyroidism, and hypothyroidism, respectively, leading to differential alterations in intestinal SCFA profiles. Specifically, only dietary T4 supplementation significantly increased the diversity of intestinal microbiota. Our findings suggest that the genera Vibrio and Sediminibacterium play key roles in multiple metabolic pathways within the host intestine. Correlation analyses further indicated that intestinal acetic acid and isobutyric acid were characteristic metabolites involved in the alteration of the genus Vibrio abundance. These results provide a foundation for further investigation into the effects of thyroid-disrupting activities on growth, intestinal SCFA profiles, and microbiota composition in marine fish. Full article
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12 pages, 1311 KiB  
Article
Relationship Between the Feeding Habits of Chlamys farreri and the Community Structure and Abundance of Phytoplankton in the Yellow Sea
by Lei Li, Jiaying Cai, Dagui Liao, Yinjie Zheng, Wei Kang, Qian Gao, Xinya Chen, Yebing Yu, Yanming Sui and Mei Jiang
Fishes 2025, 10(2), 68; https://doi.org/10.3390/fishes10020068 - 6 Feb 2025
Viewed by 529
Abstract
Filter-feeding shellfish primarily rely on suspended particles in the surrounding waters for nourishment. This study aims to understand the potential food sources for Chlamys farreri in the Yellow Sea off Long Island, Shandong Province, China, by comparing the phytoplankton composition in the aquaculture [...] Read more.
Filter-feeding shellfish primarily rely on suspended particles in the surrounding waters for nourishment. This study aims to understand the potential food sources for Chlamys farreri in the Yellow Sea off Long Island, Shandong Province, China, by comparing the phytoplankton composition in the aquaculture waters with the stomach contents of the scallops. The abundance of dominant species in the aquaculture waters exhibited significant shifts between summer and autumn. Key environmental factors influencing phytoplankton abundance included salinity and nutrient levels. Notably, there were differences in the types of phytoplankton that C. farreri could filter and consume, displaying a marked preference for 17 distinct phytoplankton species during foraging. The proportional similarity observed in summer suggested that C. farreri feeding behavior was selective and not influenced by the surrounding phytoplankton community. Diatom phytoplankton dominated both the aquaculture waters and the stomach contents of the scallops, while only minimal amounts of Dinoflagellates, Cyanophyceae, Chlorophyceae, and Chrysophyceae were found in the stomach contents. This relationship between marine phytoplankton and the stomach contents of the scallops provides foundational data for enhancing aquaculture yields of C. farreri. Full article
(This article belongs to the Section Biology and Ecology)
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21 pages, 5015 KiB  
Article
The Variation in a Fish Egg Community and Its Relationship with Environmental Factors in Daya Bay, South China Sea
by Sifan Wang, Fengxia Wu, Yiyong Rao, Huaxue Liu, Shufei Zhang, Ming Dai, Yangguang Gu, Gang Hou and Honghui Huang
Fishes 2025, 10(2), 67; https://doi.org/10.3390/fishes10020067 - 5 Feb 2025
Viewed by 356
Abstract
To assess the impact of the marine environment on the community of fish eggs in Daya Bay, we collected fish egg samples across four seasons during 2022. A total of 51 species of fish eggs were gathered. The fish egg community exhibited significant [...] Read more.
To assess the impact of the marine environment on the community of fish eggs in Daya Bay, we collected fish egg samples across four seasons during 2022. A total of 51 species of fish eggs were gathered. The fish egg community exhibited significant seasonal and spatial variations. The number of fish egg species was highest in spring and lowest in winter, while overall abundance peaked during summer. The abundance of eggs from large economic fish (Sparidae) showed a declining trend; however small pelagic fish (Leiognathidae, Engraulidae) have become dominant over time. Spatially, higher abundance is observed in the inner bay compared to the outer bay, particularly around coastal bank waters, near islands and reefs. Additionally, environmental factors and geographical location significantly influenced the fish egg community. For instance, Stolephorus continentalis and Photopectoralis bindus demonstrated a significant positive correlation with both temperature and water depth; conversely, Acanthopagrus schlegelii exhibited a negative correlation with water temperature. Full article
(This article belongs to the Section Environment and Climate Change)
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21 pages, 9645 KiB  
Article
Staying Close to Home: Horizontal Movements of Satellite-Tracked Reef Manta Rays Mobula alfredi (Krefft, 1868) in the World’s Largest Manta Sanctuary
by Edy Setyawan, Abraham B. Sianipar, Ronald Mambrasar, Muhamad Izuan, Abdy W. Hasan, Fahmi, Mujiyanto, Orgenes Ambafen, Imanuel Mofu, Mochamad Iqbal Herwata Putra and Mark V. Erdmann
Fishes 2025, 10(2), 66; https://doi.org/10.3390/fishes10020066 - 5 Feb 2025
Viewed by 642
Abstract
Indonesia is home to significant populations of globally vulnerable reef manta rays (Mobula alfredi) in at least four key regions: Berau, Nusa Penida, Komodo, and Raja Ampat. Despite detailed population studies in each of these regions, little is known about their [...] Read more.
Indonesia is home to significant populations of globally vulnerable reef manta rays (Mobula alfredi) in at least four key regions: Berau, Nusa Penida, Komodo, and Raja Ampat. Despite detailed population studies in each of these regions, little is known about their horizontal movement patterns. Our study used satellite telemetry to investigate reef manta rays’ habitat use and home ranges. A total of 33 manta rays were tagged with SPLASH10F-321A satellite tags across the four regions: Berau (n = 5), Nusa Penida (n = 8), Komodo (n = 6), and Raja Ampat (n = 14), yielding usable data from 25 tags. The rays were tracked for 7 to 118 days (mean ± SD = 50 ± 30) from July 2014 to July 2022. The results showed localized movements, strong residency near tagging sites, and high site fidelity as evidenced by area-restricted search (ARS) behaviors and frequent revisitations. Most manta rays showed restricted home ranges in each region, with no connectivity between regions. Across 25 individuals, the home range (95% utilization distributions) varied significantly, ranging from 19 to 48,294 km2 (mean ± SD = 4667 ± 10,354). These findings offer important insights into the spatial movement patterns of reef manta rays in Indonesia, allowing the formulation of more effective management strategies. Full article
(This article belongs to the Special Issue Movement and Conservation of Large Marine Fauna)
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18 pages, 3121 KiB  
Article
Glycosylation on the Antifreeze and Antioxidant Capacities of Tilapia Gelatin Hydrolysates
by Ying Liu, Zongcai Tu, Qiuyu Lu, Shengnan Zhan, Ru Jia, Zhaohui Qiao, Huamao Wei and Tao Huang
Fishes 2025, 10(2), 65; https://doi.org/10.3390/fishes10020065 - 5 Feb 2025
Viewed by 375
Abstract
The antifreeze and antioxidant capacities of tilapia (Oreochromis mossambicus) gelatin hydrolysates were investigated, after glycosylation with saccharides of varying molecular weights, to enhance their functional properties to widen its commercial application in frozen aquatic products. Glycosylation was conducted by mixing gelatin [...] Read more.
The antifreeze and antioxidant capacities of tilapia (Oreochromis mossambicus) gelatin hydrolysates were investigated, after glycosylation with saccharides of varying molecular weights, to enhance their functional properties to widen its commercial application in frozen aquatic products. Glycosylation was conducted by mixing gelatin hydrolysates with ribose, glucose, maltose, and dextran (20 kDa) at a 1:1 mass ratio; the glycosylation products had a pH of 10 and were incubated at 80 °C for 1 h. The results showed that the glycosylation degree ranked as: ribose > glucose > maltose > dextran. The mass spectrometry analysis showed that 17, 32, and 5 glycosylation sites were identified for ribose, glucose, and maltose, respectively, suggesting a molecular weight-dependent effect. Spectroscopic analyses, including ultraviolet and infrared spectroscopy, revealed that the gelatin hydrolysate structure was expanded, with chromophores in hydrophilic environments; a blue shift in the amide A and II bands confirmed that the amino group was involved. Fluorescence spectroscopy showed conformational changes with a red shift at 303.4 nm and a reduction in intensity. Antifreeze activity, such as catalase freezing protection and shrimp surimi protein stability, and antioxidant activity, including radical scavenging and metal ion chelation, were significantly improved. Ribose exhibited the strongest effects, followed by maltose and glucose. These results demonstrate the potential of glycosylation to improve gelatin hydrolysates for functional applications. Full article
(This article belongs to the Section Processing and Comprehensive Utilization of Fishery Products)
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13 pages, 5211 KiB  
Article
Preferred and Optimal Swimming Speeds in Rainbow Trout (Oncorhynchus mykiss) at Three Temperatures
by Ólavur av Fløtum Mittún, Morten Bo Søndergaard Svendsen, Lars Emil Juel Andersen, Heiðrikur Bergsson and John Fleng Steffensen
Fishes 2025, 10(2), 64; https://doi.org/10.3390/fishes10020064 - 4 Feb 2025
Viewed by 692
Abstract
Sustained exercise in aquaculture is known to improve the health and growth of finfish. Implementing exercise regimes has become an increasing focus in aquaculture practice. This study examined the relationship between the preferred swimming speed (Upref) and the optimal swimming speed [...] Read more.
Sustained exercise in aquaculture is known to improve the health and growth of finfish. Implementing exercise regimes has become an increasing focus in aquaculture practice. This study examined the relationship between the preferred swimming speed (Upref) and the optimal swimming speed (Uopt) in rainbow trout (Oncorhynchus mykiss) under non-migratory conditions typical of aquaculture environments. Using a circular raceway, rainbow trout were allowed to swim voluntarily to determine Upref. Uopt was measured using a forced-swimming test in a swim tunnel respirometer. Experiments were conducted at three temperatures (10 °C, 15 °C, and 20 °C). The results revealed a significant difference between Upref (1.18 ± 0.14, 1.17 ± 0.19, and 1.24 ± 0.15 BL s−1, respectively) and Uopt (1.4 ± 0.19, 1.5 ± 0.15, and 1.6 ± 0.24 BL s−1, respectively) across all temperatures. Aerobic scope was greatest at 15 °C (3.8), consistent with the species’ thermal range. Notably, swimming at Upref required 18–22% less energy than Uopt, suggesting that Upref is more suitable for aquaculture systems. This study introduces a minimally invasive and stress-free method for determining Upref and provides insights that can optimize flow regimes in aquaculture tanks, improving both energy efficiency and fish welfare. Full article
(This article belongs to the Special Issue Technology for Fish and Fishery Monitoring)
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16 pages, 1240 KiB  
Article
Stock Structure of the Gulf Hake Urophycis cirrata (Teleostei: Phycidae) in South-Western Atlantic Using Otolith Shape and Elemental Analyses
by César Santificetur, Carmen Lúcia Del Bianco Rossi-Wongtschowski, André Ruperti, Agostinho Almeida, Edgar Pinto and Alberto Teodorico Correia
Fishes 2025, 10(2), 63; https://doi.org/10.3390/fishes10020063 - 4 Feb 2025
Viewed by 485
Abstract
Urophycis cirrata is an important demersal fish species targeted by Brazilian industrial fisheries. With high exploitation rates, its stock(s) is(are) currently deemed fully exploited or overexploited. While basic ecological information, such as length at first maturity, exists, knowledge of its population structure is limited. [...] Read more.
Urophycis cirrata is an important demersal fish species targeted by Brazilian industrial fisheries. With high exploitation rates, its stock(s) is(are) currently deemed fully exploited or overexploited. While basic ecological information, such as length at first maturity, exists, knowledge of its population structure is limited. A sub-sample of 90 sagittal otoliths of U. cirrata juveniles (300–411 mm total length) collected during the Program for Assessment of the Sustainable Potential of Living Resources in the Exclusive Economic Zone (REVIZEE) in 2001/2002 was analyzed. Samples came from the outer continental shelf and upper slope of the southeast-south Brazilian coast, divided into three regions: northern (Cabo São Tomé to São Sebastião), central (São Sebastião to Cabo Santa Marta Grande), and southern (Cabo Santa Marta Grande to Chuí). Otolith shape (elliptic Fourier descriptors) and elemental (element:Ca) signatures were examined using univariate (ANOVA, Tukey) and multivariate (MANOVA, LDFA) statistical methods. An overall reclassification success rate of 86% was achieved using both signatures. However, individuals from the three regions were not fully separable, indicating a single, albeit not homogeneous, population unit for fisheries management. As fish stocks are dynamic, contemporary studies should be conducted to verify whether this population structure persists. Full article
(This article belongs to the Section Biology and Ecology)
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13 pages, 1617 KiB  
Article
Body Shape Variation in Atlantic Salmon (Salmo salar, L.) Fed Fishmeal and Fish Oil-Free Diets
by Jorge G. Chollet-Villalpando, Frederic T. Barrows and Ewen McLean
Fishes 2025, 10(2), 62; https://doi.org/10.3390/fishes10020062 - 2 Feb 2025
Viewed by 971
Abstract
Post-smolt Atlantic salmon were fed control (C), plant protein- (PP), and animal protein (AP)-based diets over a 90-day period. At trial start, the outline shape variation in the salmon body was recorded using two-dimensional Cartesian coordinates of a combination of 12 landmarks (LM) [...] Read more.
Post-smolt Atlantic salmon were fed control (C), plant protein- (PP), and animal protein (AP)-based diets over a 90-day period. At trial start, the outline shape variation in the salmon body was recorded using two-dimensional Cartesian coordinates of a combination of 12 landmarks (LM) and three semi-landmarks from each of the 48 fish. The identical landmarks were then assessed at trial end for the differing dietary treatments. These datasets were used to determine whether diet exerted a measurable effect on body shape to enable authentication of fishmeal/fish oil-free status. Most differences in shape at trial end were visualized at the base of the dorsal and pelvic fins and caudal peduncle. The greatest shape variation between PP and AP groups was found at the base of the pectoral and pelvic fins. While PP and AP groups were more similar in shape than control fish, the recorded differences were not significant enough to verify dietary origins. The number of animals employed and the length of the trial period were likely insufficient to distinguish alterations in body shape with any certainty. Future trials should employ larger numbers of animals and be of longer length to verify whether PP-based feeds cause changes in body shape. Full article
(This article belongs to the Section Nutrition and Feeding)
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13 pages, 5424 KiB  
Article
Identification and Characterization of Myxobolus pronini (Cnidaria: Myxozoa) from Gibel Carp Carassius auratus gibelio and Goldfish C. auratus: New Fish Host, Infection Site, and Geographic Distribution in China
by Fan Zhou, Xiaoyi Zhang, Peng Ding, Ronghua Sun, Zhe Wang and Yang Liu
Fishes 2025, 10(2), 61; https://doi.org/10.3390/fishes10020061 - 2 Feb 2025
Viewed by 301
Abstract
Myxozoans represent a significant group of parasitic pathogens affecting both wild and farmed fish. For accurate and comprehensive early detection, the composition of myxozoan pathogens in fish has consistently been a primary focus for parasitologists. In China, we undertook an investigation into myxozoan [...] Read more.
Myxozoans represent a significant group of parasitic pathogens affecting both wild and farmed fish. For accurate and comprehensive early detection, the composition of myxozoan pathogens in fish has consistently been a primary focus for parasitologists. In China, we undertook an investigation into myxozoan infection in fish from Shandong Province, China, successfully isolating a myxozoan species from gibel carp Carassius auratus gibelio Bloch, 1782 and goldfish C. auratus Linnaeus, 1758. In the present study, this myxozoan species was identified by detailed morphological and molecular analysis. This parasite is characterized by the presence of visible plasmodia in various organs (intestine, liver, gallbladder, and abdominal cavity) of gibel carp as well as the abdominal cavities of goldfish. In comparison to all documented myxozoan species, this myxozoan species exhibits morphological identity with Myxobolus pronini Liu, Batueva, Zhao, Zhang, Zhang, Li, Li, 2016, in terms of spore morphology. Molecular sequence analysis, including sequence similarity, variable site, and the secondary structure of SSU rRNA, indicates that the present myxozoan species closely resembles M. pronini. Furthermore, phylogenetic analyses revealed that all isolates collected from different organs and hosts in this study clustered with M. pronini, forming a distinct branch within the Carassius-infecting clade. Consequently, the present myxozoan species can be confidently identified as M. pronini. Compared with the previous reports on M. pronini, this study documents, for the first time, goldfish as a host, intestines and gallbladders as the sites of infection, and Shandong Province as the geographic distribution of this myxozoan species. Full article
(This article belongs to the Special Issue Fish Diseases Diagnostics and Prevention in Aquaculture)
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14 pages, 567 KiB  
Article
Effects of Dietary Protein Levels on Growth Performance, Plasma Parameters, and Digestive Enzyme Activities in Different Intestinal Segments of Megalobrama amblycephala at Two Growth Stages
by Wuxiao Zhang, Silei Xia, Bo Liu, Hongyan Tian, Fei Liu, Wenping Yang, Yebing Yu, Caiyuan Zhao, Naresh Kumar Dewangan, Aimin Wang and Tao Teng
Fishes 2025, 10(2), 60; https://doi.org/10.3390/fishes10020060 - 31 Jan 2025
Viewed by 455
Abstract
An 8-week rearing trial was designed to estimate the dietary protein requirement and evaluate the effects of dietary protein on growth performance, plasma parameters, and digestive enzyme activities of blunt snout bream at two growth stages. Six practical diets were prepared to feed [...] Read more.
An 8-week rearing trial was designed to estimate the dietary protein requirement and evaluate the effects of dietary protein on growth performance, plasma parameters, and digestive enzyme activities of blunt snout bream at two growth stages. Six practical diets were prepared to feed two sizes of fish (larger fish: initial weight of 153.69 ± 0.85 g; smaller fish: initial weight of 40.89 ± 0.28 g) with graded protein levels (26%, 28%, 30%, 32%, 34%, and 36%). Our results show that the final weight, weight gain (WG), and specific growth rate (SGR) of the fish initially rose to peak values and then declined as the dietary protein levels increased. The higher WG and SGR were recorded in the larger fish fed diets containing 30%, 32%, and 34% protein, and in the smaller fish fed a 30% protein diet, all significantly higher than those in the control group (p < 0.05). No significant differences were observed in the feed conversion ratio (FCR), viscerosomatic ratio (VR), hepatosomatic index (HSI), condition factor (CF), or survival rate among the treatments at both growth stages (p > 0.05). The plasma total protein (TP) content was highest at both growth stages in fish fed a 30% protein diet (p < 0.05). As the dietary protein level increased, the plasma urea content of the larger fish increased, peaked in the 34% protein group (p < 0.05), and then remained stable. In contrast, no significant difference in the plasma urea content was seen among the treatment groups of the smaller fish (p > 0.05). Protease activity in the fish foregut at both growth stages peaked in the 32% protein group (p < 0.05). In the midgut of the larger fish, protease activity was higher in the control group, while in the smaller fish, it was higher in the 36% protein group (p < 0.05). In the larger fish, hindgut protease activity was higher in the 34% protein group (p < 0.05), while in the smaller fish, there was no significant difference in the hindgut protease activity among all groups (p > 0.05). The dietary protein levels had no significant effect on lipase activity in the foregut, midgut, or hindgut, or on amylase activity in the foregut or midgut of the fish at the two growth stages (p > 0.05). However, hindgut amylase activity was highest in the control group of the smaller fish (p < 0.05). Based on regression analysis, the optimal dietary protein levels for the larger and smaller fish were 30.45% and 29.95%, respectively. Overall, appropriate dietary protein levels (30%) could improve the growth performance, immune function, and health status of fish at two growth stages and promote the adaptive response of their digestive system, especially the spatial regulation of protease activity in different gastrointestinal regions. Full article
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24 pages, 11534 KiB  
Article
Genetics of Physiological Variation Within and Between Larval Wild-Type AB and Backcrossed NHGRI-1 Zebrafish (Danio rerio)
by Gil Martinez-Bautista, Moira Ryann Cartee, Dyuksha Kunder, Crystelle Lee, Karol Tang, Neha Nagarajan, Pamela Padilla and Warren Burggren
Fishes 2025, 10(2), 59; https://doi.org/10.3390/fishes10020059 - 31 Jan 2025
Viewed by 466
Abstract
Changes in the environment promote variations in fish physiological responses. Genetic variation also plays a role in physiological variation. To explore the role of genetics in physiological variation, we assessed variation of cardiac function (heart rate, stroke volume, and cardiac output), oxygen consumption, [...] Read more.
Changes in the environment promote variations in fish physiological responses. Genetic variation also plays a role in physiological variation. To explore the role of genetics in physiological variation, we assessed variation of cardiac function (heart rate, stroke volume, and cardiac output), oxygen consumption, yolk conversion efficiency, and cost of development in embryonic and larval AB wild-type and NHGRI-1 zebrafish (low heterozygosity line backcrossed from AB wild-type) exposed to different temperature and oxygen regimes. Fish were exposed from fertilization to 7 days post-fertilization (dpf) to control conditions (28 °C, 21% O2) or to low temperature (23 °C, 21% O2), high temperature (33 °C, 21% O2), moderate hypoxia (28 °C, 13% O2), or severe hypoxia (28 °C, 10% O2). We hypothesized that (1) assessed physiological variables will respond similarly in both fish lines and (2) data variability in the low heterozygosity NHGRI-1 zebrafish will be lower than in AB zebrafish. Cardiac function decreased at lower temperature and in hypoxia in both AB and NHGRI-1 zebrafish. Oxygen consumption was increased by higher temperature and hypoxia in AB fish and by severe hypoxia in NHGRI-1 fish. Yolk conversion efficiency was decreased by lower temperature and hypoxia in AB fish and increased by higher temperature and decreased by hypoxia in NHGRI-1 fish. Cost of development was higher mainly in hypoxia-treated fish. Supporting our hypothesis that genetics contributes to physiological variation, NHGRI-1 zebrafish data showed significantly lower coefficients of variation in 84% of assessed endpoints. We conclude that (1) there is a strong genetic component to physiological variation in fishes and (2) low heterozygosity NHGRI-1 zebrafish are useful models for reducing the ‘noise’ from genetic backgrounds in physiological research in fish, which may aid interpretation of experimental results and facilitate reproducibility. Full article
(This article belongs to the Section Physiology and Biochemistry)
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14 pages, 1365 KiB  
Article
Age and Feeding Habits of Trematomus bernacchii in the Ross Sea
by Zhenlin Li, Peng Sun, Siqing Xu, Yehui Wang and Yongjun Tian
Fishes 2025, 10(2), 58; https://doi.org/10.3390/fishes10020058 - 30 Jan 2025
Viewed by 562
Abstract
Trematomus bernacchii is a widely distributed, commercially valuable species that plays a significant role in the Benthic ecosystem of the Southern Ocean. Current research mainly explores its molecular responses to cold adaptation and environmental stress, while questions regarding its biological characteristics, such as [...] Read more.
Trematomus bernacchii is a widely distributed, commercially valuable species that plays a significant role in the Benthic ecosystem of the Southern Ocean. Current research mainly explores its molecular responses to cold adaptation and environmental stress, while questions regarding its biological characteristics, such as length-related and sex-related differences in diet, remain to be addressed. This study assessed the age and feeding habits of T. bernacchii in the Ross Sea through stomach content morphological analysis and DNA metabarcoding analysis, examining dietary shifts by growth and sex. The research revealed that T. bernacchii primarily feeds on fish eggs, polychaetes, echinoderms, and mollusks. Other dietary components include algae, cnidarians, and crustaceans. Minor dietary differences were found between sexes. Polychaetes dominated all size classes, with Crustacea and Cnidaria declining as body length increased, while Echinoderms and Mollusca were more abundant in larger specimens. Evidence of egg cannibalism was also noted. These findings enhance our understanding of the trophic ecology of T. bernacchii and contribute to the construction of the Benthic food web of the Ross Sea. Full article
(This article belongs to the Section Biology and Ecology)
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19 pages, 15335 KiB  
Article
Optimal Dietary Carbohydrates to Lipids Ratio for Fast and Coordinated Test Growth of Juvenile Sea Urchin (Strongylocentrotus intermedius)
by Panke Gong, Haijing Liu, Dan Gou, Weixiao Di, Jiahao Cao, Jun Ding, Yaqing Chang and Rantao Zuo
Fishes 2025, 10(2), 57; https://doi.org/10.3390/fishes10020057 - 30 Jan 2025
Viewed by 386
Abstract
Rapid and coordinated test growth is crucial for maintaining the normal body shape of Strongylocentrotus intermedius juveniles. In total, 270 S. intermedius (1.19 ± 0.01 g) were randomly assigned to 18 floating cages. Three cages of sea urchins were fed kelp (Saccharina [...] Read more.
Rapid and coordinated test growth is crucial for maintaining the normal body shape of Strongylocentrotus intermedius juveniles. In total, 270 S. intermedius (1.19 ± 0.01 g) were randomly assigned to 18 floating cages. Three cages of sea urchins were fed kelp (Saccharina japonica) (control diet) or one of five formulated feeds with different carbohydrate-to-lipid ratios (C/L) (1, 2, 4, 8, and 16) for 90 days. The results suggested that the weight gain rate of S. intermedius fed C/L4 was markedly greater than that fed C/L1 and C/L16 except for kelp, C/L2, and C/L8. The test diameter (TD) and test height (TH) gain rates of S. intermedius fed C/L4 were markedly greater than those fed other dry feeds except for C/L2. The TH/TD of S. intermedius fed kelp was markedly greater than that fed dry feeds, except for C/L1 and C/L2. Juvenile S. intermedius fed C/L2 showed higher test magnesium content, larger holes, and longer and thinner trabeculae than those fed other dry feeds. Overall, juvenile S. intermedius fed C/L4 had the highest body weight gain rate and test growth rate among the formulated feed groups. Juveniles fed C/L2 had the most coordinated test growth reflected by TD/TH, which is comparable to those fed kelp. Therefore, the optimal C/L for rapid and coordinated test growth of juvenile S. intermedius should be higher than 2 but lower than 4. Full article
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16 pages, 3515 KiB  
Article
Variations of Length–Weight Relationships for Six Fish Species from the Lower Yarlung Zangbo River Catchment, Tibet, China
by Huiping Ding, Mantang Xiong, Yang Yang, Tian Zhong, Feng Chen, Yutian Gong, Dongya Zhang, Sijin Jiang and Zhiming Zhang
Fishes 2025, 10(2), 56; https://doi.org/10.3390/fishes10020056 - 29 Jan 2025
Viewed by 493
Abstract
The lower reaches of the Yarlung Zangbo River are one of the most important biodiversity hotspots worldwide. With the rapid economic development in the area coupled with global climate change, the fish resources and diversity of this region are experiencing serious threats. Basic [...] Read more.
The lower reaches of the Yarlung Zangbo River are one of the most important biodiversity hotspots worldwide. With the rapid economic development in the area coupled with global climate change, the fish resources and diversity of this region are experiencing serious threats. Basic biological information on most fishes in the river is limited, restricting the conservation of local fish resources. This study aimed to provide estimates of length–weight relationships (LWRs) for six fish species from the lower Yarlung Zangbo River catchment, Tibet, China. From 2023 to 2024, 4034 specimens belonging to two families, five genera, and six species were collected using various types of fishing techniques. The LWRs of five species, namely Schizothorax curvilabiatus, Schizothorax molesworthi, Pseudecheneis sulcata, Parachiloglanis hodgarti, and Exostoma labiatum were reported for the first time to FishBase, except Garra tibetana. The b values calculated from the LWRs ranged between 2.738 and 3.172, and the r2 values for all LWRs estimates ranged from 0.931 to 0.989. Sexual variations of LWRs were observed in S. molesworthi and P. sulcata; seasonal variations were detected in S. curvilabiatus, S. molesworthi, G. tibetana, P. sulcata, and P. hodgarti; and geographical differences were discovered in S. molesworthi, G. tibetana, P. sulcate, P. hodgarti, and E. labiatum. Additionally, this study updated information for FishBase by providing a new record of maximum standard length for S. curvilabiatus, S. molesworthi, G. tibetana, and P. hodgarti and a new record of total length for P. sulcata. The findings of this study are essential for the management and conservation of locally indigenous fish and fisheries. Full article
(This article belongs to the Special Issue Conservation and Population Genetics of Fishes)
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17 pages, 3447 KiB  
Article
Using Nearshore Fish Communities to Evaluate Eutrophication Impact in Temperate Estuaries
by Mark D. Saunders, Nathanael Bergbusch, Kyle M. Knysh, Leah P. MacIntyre, Christina C. Pater, Michael R. S. Coffin, Monica Boudreau, Michael R. van den Heuvel and Simon C. Courtenay
Fishes 2025, 10(2), 55; https://doi.org/10.3390/fishes10020055 - 29 Jan 2025
Viewed by 746
Abstract
Using fishes as indicators of estuarine degradation is informative in long-term monitoring programs. Beach seine hauls were used in four estuaries that differed in their trophic and tidal status. The study found that inner, middle, and outer estuarine nearshore fish communities differed significantly [...] Read more.
Using fishes as indicators of estuarine degradation is informative in long-term monitoring programs. Beach seine hauls were used in four estuaries that differed in their trophic and tidal status. The study found that inner, middle, and outer estuarine nearshore fish communities differed significantly at from all estuaries, for all sampling times. To reduce the effects of within-estuary variability, between-estuary differences were examined separately for inner, middle, and outer estuarine areas. These analyses revealed differences in north-south and trophic status in communities between estuaries. The north-south differences were characterized by more benthic fishes, such as mummichogs and fourspine stickleback in the microtidal northern estuaries and proportionally more pelagic fishes, such as Atlantic silversides and river herring in the mesotidal estuaries. In both multivariate and univariate analyses, mummichogs were also featured as being most abundant in the more eutrophic estuaries. The distance-based redundancy analysis showed that bare sediment coverage was the strongest correlate of the north-south differences, while the Ulva to Zostera plant gradient was more influential in predicting eutrophication impacts on communities in the inner and middle estuary. Full article
(This article belongs to the Section Environment and Climate Change)
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