Fishes

A survey was conducted to evaluate the effectiveness of adaptive resolution imaging sonar (ARIS), also known as an acoustic camera, for monitoring large jellyfish in the Liaodong Bay area, China. The abundance and vertical distribution of large jellyfish species, such as Nemopilema nomurai, Aurelia coerulea, and Cyanea nozakii, were obtained from acoustic camera observation images, and the effectiveness of the acoustic camera method was determined. The acoustic camera method provided visual information on the number of large jellyfish and their positions in the water column and demonstrated that they were more frequently located in the mid-upper water column of the surveyed area. The results show that it is possible to identify three different types of large jellyfish using acoustic camera sonar images, based on their size, shape, outline, and movement trajectory. The acoustic camera method enables the effective monitoring of jellyfish abundance and enables the observation of their vertical distribution, demonstrating its suitability for monitoring large jellyfish in shallow waters. The results show that observations through an acoustic camera can be used to study the horizontal and vertical spatial distribution characteristics of large jellyfish and to observe their behavior. Full article

Ocimum gratissimum (clove basil) essential oil is known for its anesthetic and stress-reducing effects in aquatic animals. In this study, it was synthesized into a microemulsion form and its anesthetic effects on Hemibagrus wyckioides (Asian redtail catfish) juveniles were evaluated. The clove basil essential oil was formulated into a stable oil-in-water microemulsion with a particle size of approximately 36.3 nm and a polydispersity index (PDI) of 0.17. The microemulsion, with concentrations ranging from 125 mg L⁻¹ to 250 mg L⁻¹, effectively induced sedation and anesthesia in fish. It took approximately 2 to 4 min for the fish to reach a state of sedation or anesthesia, depending on the concentration of the clove basil essential oil microemulsion used. After a 30 min induction period using clove basil essential oil microemulsion at concentrations of 125 mg L⁻¹ and 175 mg L⁻¹, the blood cortisol, glucose, and lactate levels, which are stress indicators in fish, were evaluated. The results indicated that the blood cortisol levels in the treatments (6.97 to 7.4 μg dL⁻¹) were consistently lower than in the control group (17.17 μg dL⁻¹) throughout the induction time. However, the glucose (5.6–6.75 mmol L⁻¹) and lactate levels (3.23–5.41 mmol L⁻¹) in the treatment groups increased acutely during the induction time but returned to normal levels (around 3.5 mmol L⁻¹ and 1.6 mmol L⁻¹, respectively) during recovery. This contrasted with the control group, where the lactate and glucose levels remained slightly elevated during the recovery period. Additionally, the recovery time in fish anesthetized with clove basil essential oil microemulsion was consistently short across all of the treatments. These findings highlight the potential application of clove basil essential oil, particularly in microemulsion form, as an effective anesthetic agent for fish. Full article

Methyl farnesoate (MF), a counterpart of insect juvenile hormones in crustaceans, plays essential roles in molting, metamorphosis, and reproduction. In this paper, we isolated a gene-encoding Krüppel homolog 1 from the mud crab Scylla paramamosain (Sp-Kr-h1) and investigated its involvement in MF-regulated vitellogenesis. RT-PCR showed that Sp-Kr-h1 had a wide expression in various tissues. qRT-PCR showed that its expression level in the ovary peaked at stage III. Both in vitro and in vivo experiments suggested that the expression of Sp-Kr-h1 and Vitellogenin (Vg) in the hepatopancreas was significantly induced by MF administration. Further, the RNA interference technique was employed to illustrate the precise role of Sp-Kr-h1 in ovarian development. This revealed that the in vitro silencing of Sp-Kr-h1 significantly decreased the level of Vg transcripts located in the hepatopancreas. Meanwhile, an in vivo experiment demonstrated that oocyte growth was inhibited after the knockdown of Sp-Kr-h1 in female S. paramamosain. In conclusion, this study identified a Kr-h1 gene in S. paramamosain and demonstrated that it is an essential factor for MF-regulated vitellogenesis. Our results provided a new insight into the mechanism underlying MF inducing ovarian development in mud crabs. Full article

With the rapid advancement of intelligent aquaculture, precise individual identification of underwater fish has become a crucial method for achieving smart farming. By accurately recognizing and tracking individuals within the same species, researchers can enable individual-level identification and tracking, significantly enhancing the efficiency of research and management. To address the challenges of complex underwater environments and subtle differences among similar individuals that affect recognition accuracy, this paper proposes a fish individual identification method based on global detail enhancement and keypoint region fusion. This method simultaneously learns global refined features and keypoint region features, dynamically capturing effective keypoint features while mitigating errors caused by noise through weighted fusion. The network first employs a global detail enhancement module to extract global features, such as overall morphology and texture information, followed by the extraction of fine-grained features from keypoint regions. Through the weighted fusion, the network further emphasizes critical areas, thereby enhancing robustness and adaptability in complex underwater scenarios. This design effectively integrates global refined features and local keypoint features, providing comprehensive support for accurate fish individual identification. Experimental results show that the proposed method achieves mAP and Rank-1 scores of 89.7% and 95.3%, respectively, and demonstrates strong generalization capabilities in other fish identification tasks. Full article

A pharyngeal jaw and loose pharyngeal teeth from Prairie Creek, Indiana, and loose pharyngeal teeth and two basioccipital pharyngeal processes from Bell Cave, Alabama, appear to be those of Moxostoma hubbsi (Copper Redhorse). Among suckers, only M. carinatum, M. hubbsi, M. robustum, and M. ugidatli have molariform teeth on their pharyngeal jaws, with M. hubbsi having the teeth of the largest relative size. Measurements of most of the teeth from Prairie Creek overlap with those of M. hubbsi, and the largest tooth from Bell Cave is the largest pharyngeal tooth measured. The more complete pharyngeal process of the basioccipital possesses a small condyle and stout processes along it that are indicative of M. hubbsi as well as a smaller centrum for articulation with the Weberian complex. Moxostoma hubbsi currently occupies an area around Montreal, Canada, that was glaciated at the time the fossils were laid down, and the area was later occupied by the Champlain Sea and Lampsilis Lake before becoming riverine about 6000–5000 years ago, meaning that M. hubbsi had to have arrived at its current distribution relatively recently and been extirpated from elsewhere. Full article

Prior to this study, Myanmar was known to host 15 species of snakehead fishes (genus Channa) distributed across Southeast Asia. The region, characterized by its confluence of diverse river systems and two biodiversity hotspots, is presumed to have notable gaps in its biodiversity assessments. Recently, a new snakehead species, Channa shingon, was discovered in China, with its potential distribution in Myanmar warranting further investigation. This study focused on exploring Channa species in Kachin State and examined collected specimens using an integrated approach. The specimens were identified as C. shingon based on their distinct morphological characters, with a maximum standard length of 99.2 mm. Additionally, mitochondrial COI sequence data were generated, and species confirmation was achieved through nucleotide BLAST searches, genetic distance estimations, and phylogenetic analyses. The DNA sequences of C. shingon showed a mean inter-species genetic distance of 7.97% to 27.41% compared with other Channa species in the dataset, while the intra-species genetic distance between the Burmese and Chinese populations was 0.27%. Both Bayesian and maximum-likelihood phylogenetic analyses distinctly separated C. shingon from other congeners through a monophyletic clustering pattern, revealing its sister relationship with C. rubora. Overall, this study provides the first report of C. shingon from Myanmar and suggests its speciation from a common ancestor with C. rubora, likely driven by geographical barriers such as the Irrawaddy River. Furthermore, the study contributes a robust DNA barcode dataset encompassing 85.7% of the global Channa species diversity, which can serve as a valuable resource for further species identification, discovery, and diversity assessments of snakeheads from South and Southeast Asia. Full article

Sinocyclocheilus grahami (Regan, 1904) is the only known cavefish used both in traditional medicine and aquaculture in the world, and it is also a national protected animal. However, its taxonomy and distribution remain ambiguous, hindering effective conservation and resource utilization. This study clarifies the taxonomy of S. grahami through field surveys, specimen examination, and literature reviews, combined with principal component analysis (PCA) for morphological comparison. The results indicate that S. grahami and S. guanduensis show no significant morphological differences, supporting the recognition of S. guanduensis as a junior synonym of S. grahami. Sinocyclocheilus huanglongdongensis, and S. hei, once synonyms of S. grahami, should be valid. The species faces a significant population decline, and its distribution is now restricted to a few unpolluted streams around Dianchi Lake. While artificial breeding has been successful, further studies are needed to determine the medicinal efficacy of these individuals. To address the conservation and sustainable use of this species, habitat restoration should be prioritized, particularly in protecting cave environments and maintaining groundwater connectivity. Additionally, artificial breeding and release in restored habitats are essential to establish a sustainable ecological governance system that supports biodiversity and regional development. Full article

Senegalese and Mauritanian fisheries exploit the same species of white grouper but have different exploitation histories. In Senegal, white grouper has been fished for a very long time (since the 1970s), whereas it is relatively recent in Mauritania. In addition, Senegalese small-scale fishermen exploit this species in the Gambia. Nevertheless, mainly for practical reasons, all attempts to assess the status of the stock have, until recently, been conducted at a national level except by the FAO CECAF North working group who assumed it to be a single stock for the three countries. However, their analysis gives very little attention to length frequency data, even though the fisheries have different selectivity that are likely to affect exploitation rates. In addition, management is mainly focused on length, with no TACs or quotas established at national or sub-regional levels. This work is based on a large compilation of available data from the databases of three countries complemented by the collection of length frequencies data within the framework of the European Union Demerstem/PESCAO project. Two approaches were combined (catch and length-based model) to establish a reliable diagnosis of the state of this resource, along with a spatial analysis to identify the areas most affected by fishing. The results obtained for the sub-region show a severe overexploitation of biomass revealed by the Bayesian biomass production surplus model (JABBA). Stock status indicators show overfishing with low biomass (B/Bmsy = 0.34) and high fishing mortality (F/Fmsy = 5.79). Overall, the trajectory of the state of the stock illustrated by the Kobe figure indicates that the white grouper stock has been overexploited since the 1990s. Fishing pressure reached its highest levels during the recent period of 2016–2018 and these results are consistent when considering stock assessment at the national level. However, the length-based model (LBB) indicates a deterioration in average length, particularly in Senegal and the Gambia, especially since 2014. Adults, who migrate, are more abundant in Mauritania. Therefore, due to its high market value, white grouper is increasingly targeted, resulting in an unprecedented rise in fishing mortality over the past decade, particularly among larger individuals, with the most significant pressure observed in Senegal and the Gambia. Given that the stock spans three countries, a coordinated management approach at the stock level is essential. However, management measures must also be adapted to the specific status of the population within each country. Without such a concerted effort, this trend is likely to persist, further endangering the resource. Full article

Water environments contaminated with arsenic (As) have become a significant environmental concern. Previous research has highlighted the detrimental effects of As on fish, but limited knowledge exists regarding its impacts on endocrine systems. To address this gap, zebrafish embryos were exposed to various concentrations (0, 25, 50, 75, and 150 μg/L) of arsenate (AsV) for 120 h post-fertilization (hpf). Our findings indicate that exposure to AsV significantly increases cortisol- and thyroid-stimulating hormone (TSH) levels while decreasing estradiol (E2) and testosterone (T) levels. Additionally, it initially decreases and then increases thyroxine (T4) contents. Furthermore, several key genes relevant to these endocrine systems also show significant influences. The results from principal component analysis demonstrate that TRH, TSH, TRHRb, and TRβ primarily affect the level of T4 while Cyp11b, StAR, hmgrb MC2R, and GR mainly influence cortisol levels. On the other hand, Cyp19a, Cyp17, 17βhsd, ERβ, LHR, hmgrb, and AR predominantly impact E2 and T levels. Transcriptomics and enrichment analysis reveal that these pathways are primarily associated with steroid hormone synthesis and transport. Furthermore, it was found that AsV stimulates the cAMP signaling pathway through a compensation mechanism. These results suggest that AsV may potentially act as environmental endocrine-disrupting chemicals with non-negligible interference effects on the endocrine system in zebrafish. This study holds theoretical value in assessing the environmental risk posed by As overall as well as providing an important basis for addressing human health issues and implementing preventive measures. Full article

The six6 and vgll3 genes play evolutionarily conserved roles in developmental processes and life history traits across species, including teleosts. Notable differences in genotype and allele frequencies of these genes have been observed between farmed and wild populations of European seabass and gilthead seabream, suggesting potential roles in traits associated with domestication. Here, we hypothesized that genetic variations in the six6 and vgll3 are associated with distinct expression profiles that underlie domestication-related traits in the two species. Using quantitative PCR (qPCR), we examined the expression profiles of these genes in early developmental stages across genotypes linked to domestication. Our results confirmed that vgll3 and six6 genotypes significantly influenced their expression in gilthead seabream, with statistically significant differences between genotypes. In European seabass, six6 expression did not significantly differ among genotypes, although heterozygous larvae showed higher variability that decreased at the juvenile stage. Meanwhile, no genetic variation was observed in vgll3, precluding genotype-specific expression analysis. Altogether, our findings provide the first evidence confirming that prior DNA-based associations of these genes with domestication traits are reflected at the mRNA level, particularly in vgll3 in gilthead seabream. This highlights the potential functional relevance of these genetic variations in shaping expression profiles linked to domestication in the species. Full article

Aquatic organisms face substantial challenges from climate change, particularly due to rising water temperatures, which significantly impact their growth and survival. This investigation utilized 960 Koi carp (Cyprinus carpio koi) (Initial Body Weight, 0.304 ± 0.005 g). After a 10-day acclimatization period, the fish were distributed equally across 12 glass aquaria (80 × 40 × 45 cm), with three replicates per treatment. This study encompassed two phases. The first phase (10–60 Days Post-Hatching, dph) involved four temperature regimes: T1 (26 °C), T2 (28 °C), T3 (30 °C), and T4 (26/30 °C daily fluctuation). The second phase (60–120 dph) maintained all groups at 30 °C. Initially, T1 exhibited the best growth performance, indicated by the highest Final Body Weight, Weight Gain, Specific Growth Rate (SGR), and Thermal Growth Coefficient (TGC), along with the highest survival rate. Gene expression analysis revealed that HSP70, HSP90, SOD, BCL-2, and FASN were upregulated in T3 and T4, indicative of stress, while MYOD was highest in T1. During the second phase, T4 displayed superior growth and a healthier body composition with elevated moisture and protein, and reduced fat content compared to T1 and T2. HSP70, HSP90, and BCL-2 expression increased significantly in T1, suggesting thermal stress, whereas MYOD levels rose across all treatments, peaking in T4, which correlated with its growth. Further, there were strong relationships among growth parameters, gene expression, and body composition, with T4 exhibiting the highest essential and non-essential amino acids and a unique fatty acid profile. Overall, the results suggest that manipulated temperature significantly influences Koi carp’s characteristics, making it more adaptable to future environmental stress. Full article

The tropical gar (Atractosteus tropicus) is a primitive freshwater fish of significant commercial importance in southeastern Mexico. However, its population is in danger due to habitat loss and overexploitation. Cultivation emerges as a viable reproductive management strategy; yet further studies are crucial to understanding molecular markers guiding reproductive management, differentiation, and sexual maturation in this species. We analyzed the expression of five sex-related genes (foxl2, sox9, cyp17a1, dmrt1, and cyp19a1) in the brain, liver, and gonads of adult A. tropicus (four females and five males). Methodologically, we collected samples and conducted RNA extraction, cDNA synthesis, and gene expression analysis using qPCR. The gonadal histology provided morphological context that reveals that the differential expression of genes establishes differences between sexes. The sexual phenotype of females is observed with the high expression of dmrt1, while in males, there is a reduction in the expression of dmrt1 and high levels of sox9, foxl2, and cyp17a1. Our findings establish dmrt1 and cyp19a1 as potential sex biomarkers and provide a molecular basis for developing sexing protocols in A. tropicus. Full article

Serum amyloid A (SAA) is one of the most abundant acute-phase response proteins and has been extensively studied in vertebrates for its role in modulation of the inflammatory response and as a marker of disease diagnosis. By comparison, SAA is rarely identified in aquatic species and its physical functions are also not well studied. The present study identified the only one gene encoding SAA protein in oyster Crassostrea gigas. The open reading frame (ORF) of CgSAA was of 417 bp, encoding a putative polypeptide of 138 amino acid residues with a predicted molecular weight of 15.66 kDa. CgSAA was composed of a signal peptide (residues 1–22) and a conserved SAA domain (residues 36–138). The mRNA expression of CgSAA in normal individuals was detectable but at a low level, with the lowest expression level in the tissue of labial palp and a slightly higher expression level in hemocytes. The mRNA expression level of CgSAA was significantly up-regulated at 6 h (2.76-fold of that in control group, p < 0.01) post V. splendidus stimulation. It was also significantly induced under environmental stress at high temperature (34 °C) or low salinity (15‰ salinity). The recombinant protein rCgSAA was expressed in Escherichia coli and purified by affinity chromatography. After rCgSAA was injected into oysters or incubated with culture primary hemocytes, the mRNA expressions of the cytokines CgIL17-1, CgIL17-5, and CgTNF were all significantly up-regulated. The results collectively suggested that CgSAA, as a conserved acute-phase response protein in oyster, was quickly induced under environmental stress and promoted the expressions of cytokines, which provide fresh ideas for understanding the roles of SAA proteins in aquatic invertebrates. Full article

A number of viral diseases have significantly impeded the growth of the aquaculture industry. Antiviral drugs represent an effective means of controlling infection. However, the efficacy of the entire therapeutic process is contingent upon the availability of an efficient delivery system. This study selected three common antiviral drugs and constructed corresponding drug delivery systems utilising single-walled carbon nanotubes (SWCNTs) as carriers. The reliability of carbon nanotubes as delivery carriers was evaluated by detecting the therapeutic effect on infectious splenic and renal necrosis virus (ISKNV). The findings demonstrated that SWCNTs can effectively enhance the absorption of the three drugs into the body, prolong their metabolic half-life, and improve the survival rate of fish infected with ISKNV. The Ribavirin-SWCNTs (RBV-SWCNTs) group exhibited the most pronounced protective effect, with a mortality rate of less than 25%. It was observed that SWCNTs facilitated the rapid transportation of ribavirin, with the drug content in the RBV-SWCNTs group being approximately double that of the free ribavirin group. Furthermore, this system markedly diminished the viral load, augmented enzyme activities, and elevated antiviral gene expression. This study indicated that carbon nanotubes are optimal carriers for antiviral drugs, which have considerable potential as a delivery vehicle for antiviral drugs to prevent viral infections in aquaculture. Full article

Elasmobranch species are susceptible to anthropogenic stressors such as fishing activities, particularly the bycatch in bottom-trawl fisheries. Understanding the diversity, segregation, and population structure of species at risk of capture is critical for enhancing their conservation. This study evaluated the species composition and population structure dynamics of susceptible elasmobranch species caught as bycatch in the Mexican shrimp trawl fishery in the southern Gulf of Mexico. Data were collected by examining bycatch from 55 fishing trips conducted between 2013 and 2017 during closed and commercial fishing seasons. We analyzed the species composition, length, sex ratio, and maturity stages of susceptible species across zones, sampling seasons, and depth. Six dominant species (Rostroraja texana, Gymnura lessae, Narcine bancroftii, Pseudobatos lentiginosus, Squatina dumeril, Hypanus americanus) accounted for >98% of all captures and were found in all fishing zones, seasons, and depths. These species were caught in a range of sizes, from newborns to mature individuals, and showed both inter- and intraspecific segregation patterns across fishing zones, seasons, and depths. The elasmobranch composition and population structure in bycatch are influenced by ontogenetic segregation and bathymetric distribution of the species. Current Mexican shrimp trawl fishery regulations benefit the majority of elasmobranchs by providing comprehensive spatiotemporal protection and selective exclusion mechanisms. However, small-sized ray species and juveniles of larger species continue to face fishing pressure. The preset study highlights the southern Gulf of Mexico as an important reproductive area for demersal elasmobranchs and unravels their complex segregation behavior, leading to the identification of potential risk zones and seasons. The impacts of bycatch on the most susceptible elasmobranchs may be mitigated through improvements in trawl fishing technology and the implementation of additional temporal bans in specific trawling areas, enhancing species-specific conservation efforts. Full article

This review summarizes data on the accumulation of three short-lived biogenic radionuclides—⁵⁴Mn, ⁶⁰Co, and ⁶⁵Zn—in various fish species in the cooling pond of the Chornobyl Nuclear Power Plant in Ukraine, along with an analysis of the available literature. Significant differences exist in ⁵⁴Mn, ⁶⁰Co, and ⁶⁵Zn accumulation levels among the different fish species. Food intake is the primary pathway for these radionuclides to enter the fish organisms. These radionuclides accumulate differently in various organs and tissues. There is no consensus on the specific organ that primarily accumulates each radionuclide. In most studies, the highest concentrations of ⁵⁴Mn have been recorded in internal organs. The kidneys are identified as the main organ accumulating ⁶⁰Co. The highest concentrations of ⁶⁵Zn are typically found in the liver and kidneys; however, significant accumulation is also noted in external organs and tissues (gills, fins). In most cases, the lowest concentrations of ⁵⁴Mn, ⁶⁰Co, and ⁶⁵Zn are observed in the muscle tissues of fish. Full article

The Chinese soft-shelled turtle (Pelodiscus sinensis) is an aquatic reptile prized for its nutritional and health benefits. Given its adaptability to various culturing modes including the greenhouse, pond and rice culturing modes, we conducted a comparative analysis of the morphology, organ trait and nutritional composition of turtles cultured in three culturing modes. This study investigated the plasticity of morphology and physiology, as well as the variations in nutritional composition across varying culturing modes. The results demonstrated that after approximately 120 days of cultivation, significant changes were observed in the morphology, physiology and nutritional composition of turtles from each culturing mode. In terms of morphology, rice turtles exhibited an arched shell shape, broad plastron, elongated limbs, narrow interocular distance and slender head and neck. Pond turtles displayed similar morphological characteristics to rice turtles, with the additional features of a flattened body shape and narrower plastron. Greenhouse turtles presented a flattened shell shape, narrow plastron, shortened limbs, wider interocular distance and stocky head and neck. Regarding the organ characteristics, the specific weights of liver, viscera, internal fat lumps and condition factors were significantly higher in greenhouse turtles compared to rice turtles and pond turtles (p < 0.05). Conversely, the specific weights of the back carapace, calipash and edible part were significantly lower than those in rice turtles and pond turtles (p < 0.05). Nutritional analysis revealed that crude protein, total amino acid, essential amino acid, flavor amino acid, pharmacodynamic amino acid, collagen and EPA+DHA contents were significantly higher in rice turtles and pond turtles than greenhouse turtles (p < 0.05). However, crude fat and unsaturated fatty acid contents were significantly higher in greenhouse turtles than in rice turtles and pond turtles (p < 0.05). In summary, Chinese soft-shelled turtles exhibited significant morphological and organ plasticity in response to different culturing modes. While the rice and pond culturing modes could enhance the nutritional quality of turtles to some extent, the impact of commercial feed on fatty acid profiles must be carefully considered. Full article

In recent years, safety concerns in aquaculture have become increasingly prominent due to various factors. Concurrently, the emergence of artificial intelligence (AI) has offered novel approaches to addressing these challenges. This paper provides a comprehensive review and synthesis of AI applications in aquaculture safety over the past few decades, while also suggesting future directions. Utilizing bibliometric tools such as Citespace and VOSviewer, we analyzed 513 publications spanning from 1998 to 2025. Our analysis highlighted a growing global research interest in this emerging field. Furthermore, it is forecasted that the integration of remote sensing technology, immune response monitoring, and cross-disciplinary innovations will drive the transformation of aquaculture safety management toward a more intelligent, proactive, and sustainable approach. These advancements are expected to enhance the precision and efficiency of risk assessment and disease prevention in aquaculture systems. Full article

The high-quality development of China’s fishery economy serves as its core objective, with robust financial support playing a pivotal role. This study employs provincial panel data spanning 2005 to 2020 and utilizes the entropy method to evaluate the level of high-quality development in China’s fishery economy across three dimensions: fundamental security, sustainability, and comprehensive efficiency. From the perspectives of formal and informal finance, it compares their support effects on different aspects of high-quality development in China’s fishery economy, while also exploring the mechanisms underlying these effects by considering factors such as industrial uncertainty and economic scale. The findings indicate that, overall, the support provided by both formal and informal finance for high-quality development in the fishery economy is insufficient. Further analysis reveals a significant threshold effect of fishery economic scale, with turning points at 108.44 billion CNY and 232.98 billion CNY for formal and informal finance, respectively. For higher-level indicators, such as sustainability and comprehensive efficiency, formal and informal financial systems demonstrate complementary roles, depending on the scale of the regional fishery economy. Furthermore, industrial uncertainty serves as a significant mediating factor only for formal financial support, with the levels of sustainability and comprehensive efficiency most affected. Full article