Abstract:Salinity is one of the most important factors that influence the physiological status of fish. To adapt to different salinity environments, fish need to consume a lot of energy to maintain osmotic pressure balance. As an intermediate product of lipid metabolism, fatty acids not only play an important role in physiological and biochemical processes, but are also an important energy source for the body. The liver is the main lipid storage organ and the main organ for fatty acid metabolism in fish. is a unique model species to study salinity adaptation because it can live in a wide range of salinities. To investigate the effects of salinity on the metabolism of fatty acids in the liver of , this study compared the changes in fatty acid composition and the mRNA expressions of lipoprotein lipase (LPL), malic enzyme (ME) and peroxisome proliferator-activated receptor-alpha (PPAR-α) in the liver of Nile tilapia in saline water (levels 8 and 16) during a two week salinity stress period. The results showed that the plasma osmolality in the salinity group rose to the highest level in 12 h, and the plasma osmolality in the 16-salinity group was significantly higher than in the 8-salinity group. Meanwhile, the plasma osmolality gradually decreased and tended to be stable in the latter stage of treatments. Before 96 h, the content of saturated fatty acids in the liver of the salinity groups was significantly lower than the freshwater group (<0.05). After 96 h, they gradually recovered to the initial level. The content of monounsaturated fatty acids in the liver of the salinity group was significantly lower than the freshwater group (<0.05). The content of long-chain polyunsaturated fatty acids (mainly docosahexaenoic acid DHA, Eicosapentaenoic Acid EPA, and Arachidonic Acid ARA) in the liver of the salinity groups was significantly higher than the freshwater group (<0.05). The mRNA expressions of LPL, ME, and PPAR-α in the liver of the salinity groups was significantly higher than the freshwater group (<0.05). These results indicate that the composition of fatty acids in the liver and lipid metabolism can be impacted by salinity stress, which provides basic information on lipid energy utilization in fish osmoregulation.

Abstract:Estrogens play a crucial role in the normal function of postnatal ovaries and testes in vertebrates. Estrogens have been reported to induce proliferation of spermatogonium stem cells and spermatogonia in both birds and mammals. Previous studies have showed that estrogens bind either to classical intracellular estrogen receptors (Esr1 and Esr2) or to a membrane estrogen receptor such as G protein-coupled estrogen receptor (Gper) and can therefore trigger both genomic or non-genomic signaling pathways. In comparison with the genomic pathway, non-genomic signaling occurs rapidly (within seconds to minutes) and involves the production of secondary messengers, the activation of protein kinases, and the modulation of ion-channels. Gper is a 7-transmembrane protein that belongs to the G protein-coupled receptor (Gpcr) superfamily, the members of which participate in various endocrine and metabolic processes. Gper is widely found in vertebrates such as mammals, birds, reptiles, and fish and is involved in many signaling pathways regulating cell and nervous system repair and other important physiological functions. Gper is very important in germ cell proliferation, in females in particular. is also expressed in germ cells in males, but little information on the role of in gonadal reproduction is available. The Chinese soft-shelled turtle () is a member of the Reptilia family of Chelonia Trionychidae and is an economically important aquaculture species in China. To improve the economic benefits of , it is important to study the characteristics and the mechanism of gonadal differentiation and reproduction of this species. However, limited studies on the reproduction of the turtle exist. The aims of this study were to identify the sequence information and function of Gper in the male turtle. The full-length cDNA sequence was cloned using rapid amplification of cDNA ends technology. Quantitative real-time PCR (qRT-PCR) was used to analyze the expression level of mRNA in different tissues and different developmental stages of the gonad. Finally, the role of was analyzed by injecting letrozole and G-15 to inhibit aromatizing enzyme and Gper was 2023 bp long, including 705 bp at the 5'-UTR, 241 bp at the 3'-UTR, and a 1077 bp open reading frame (ORF) encoding a peptide of 358 amino acids. One exon of the ORF was the same as other reptiles. The putative peptide contained 7-transmembrane domains and an Asp-Arg-Tyr (DRY) structure, and Gper therefore belongs to the Rhodopsin subfamily. Multiple sequence comparisons of vertebrate Gper proteins indicated that Gper has the highest similarity with the corresponding protein in Chelonia while it has the lowest similarity with the corresponding protein in fish. Quantitative real-time PCR detected , and the maximum level was detected in the brain, followed by the ovary. Moreover, under different incubation temperatures, expression in the critical stage of gonadal differentiation showed the same trend:the highest expression level was found in stage 16 of embryonic development, and significantly decreased with gonadal differentiation. After injection of letrozole and G-15, the expression of was significantly decreased in the letrozole treatment group, but the expression of 2 were significantly increased. After inhibiting Gper protein activity, the expression of 2 obviously increased. More than that, the expression of genes related to spermatogenesis and apoptosis significantly increased after G-15 treatment. From the above, the role of Gper in the testes of is likely to be involved in early gonadal differentiation and regulates the proliferation of male germ cells. This study provides new insights into the role of Gper in the gonads of

Abstract:is one of the most important endemic fish species in the Zhegu Lake of Tibet. The age structure and growth characteristics of were investigated by examining 432 samples collected in Zhegu Lake from 2017 to 2019. The body length (), otolith radius, and age were measured to describe the relationships between body length, body weight, and age. The results showed that the body length of ranged 3.1-35.6 cm and that body weight ranged from 0.4 to 645.9 g. Estimated age was between 1 and 11 years, and most individuals were 6 to 8 years of age (accounting for about 35% of the total samples). The relationship between body weight and body length was described by the linear equation, =432), which is consistent with uniform growth characteristics. There was no significant difference in the relationship between body length, body weight, and age between males and females ( was described by the von Bertalanffy equation as t=1114.233[1-e^{-0.149(. The inflection age of the growth curve occurred at 8.263 years at a body length of 27.826 cm and weight of 333.811 g. The apparent growth index was 4.399. The age structure of in Zhegu Lake is simplified and the population is in the growing period, which may be affected by the special geographical location and ecological habitat of Zhegu Lake. The purpose of this study was to provide basic data for the protection of this species in Tibet's fragile ecosystem. This study proposes to suggest measures to control water management in the river entering the lake and limit human activities such as fishing and tourism, so as to improve the ecological environment of Zhegu Lake and protect the population of .}

Abstract:is widely distributed in the southwest of the Yangtze River in China. To determine the morphological variations and distribution of five populations in the Yuanjiang River and Xijiang River basin, 147 samples were collected from main streams and tributaries and nine traditional morphological parameters and 21 truss network features were analyzed by three multivariate analysis methods. There were significant differences in the body area of each part of the lateral surface among the five populations, according to Friedman non-parametric tests. Cluster analysis divided the five populations into three groups:one in the main stream and tributary of the Xijiang River, one in the main stream of the Yuanjiang River and the Jinjiang River tributary, and the other in the Qingshuijiang River. Six principal components were extracted by principal component analysis, and the cumulative contribution to the total variance was 81.93%. The characters of higher contribution rate were concentrated in the caudal peduncle, the head, and the anterior part of trunk. Discriminant analysis screened 10 characters of the head and caudal peduncle and established discriminant functions for the five populations, with a range of individual discrimination accuracy between 92% and 100%. Our results suggest that there are significant morphological differences among in the five populations of the Yuanjiang River and the Xijiang River basin, which provide basic data for population identification and resource evaluation for the species.

Abstract:As the foundation of material circulation and energy flow, microbes play an important role in an aquaculture environment. Consequently, to understand and predict the response of ecosystems to environmental changes, it is necessary to explore the structure and constructive mechanism of microbial communities in aquaculture ponds. Since their introduction from the US in 1984, both the cultivation areas and the production of channel catfish have increased dramatically in China. Along with the US, China has become a major producer and consumer of channel catfish. This study characterized the structure of microbial communities in sediment samples from a channel catfish pond. High-throughput sequencing (Illumina MiSeq) of the V3-V4 hypervariable region in the 16S rRNA gene was used to investigate microbiome structural characteristics. The results showed that the bacterial community structure presented a seasonal change. Samples in winter and spring were more similar than others. The dominant phyla in sediment samples were Proteobacteria, Chloroflexi, Bacteroidetes, Firmicutes and Acidobacteria, which were apparently different from that in the water body of the channel catfish pond. No significant difference of α-diversity was detected between the four seasons. Among the measured environmental variables, water transparency (SD) and total dissolved solids (TDS) were observed as the primary drivers for bacterial communities, which had a significant correlation with the bacterial community structure (<0.05). These results might provide basic references for understanding and managing the bacterial community composition in channel catfish ponds.

Abstract:is the main fish species obtained from falling-net fishery in the South China Sea. The development and utilization of its resources has a positive significance for safeguarding China's marine rights in the South China Sea and alleviating the pressure of near-shore fishing. To have a better understanding of the fishing grounds and seasons and catch per unit effort (CPUE) characteristics of S. oualaniensis in the central-southern part of the South China Sea were studied based on a generalized additive model and data acquired in the sea. The results showed that (1) the explained variance of optimization model was 63.7%, the determination coefficient was 0.576, and the influencing factors included latitude and longitude (explained variance was 18%), moon phase (16.8%), sea surface temperature (SST) (14.8%), month (3.8%), operation time (5.7%) and vertical temperature gradient of 0-50 m (Δ50) (4.6%). (2) During the investigation, 336 operations were conducted, the catch weight was 93.259 t, and the average CPUE was 277.557 kg/net. The CPUE of in the sea area near 10°-12° N, 112°-114° E was the highest, and the CPUE of September was obviously higher than that of April. This might be related to the Vietnam offshore flow that exists along the eastern coast of Vietnam. (3) The influence curve of moon phase on the CPUE was V-shaped, which decreased first and then increased. There was a significant difference in the CPUE of between bright moonlight nights and no-moonlight nights. The CPUE on no-moonlight nights (348.970 kg/net) was significantly higher than that on bright moonlight nights (181.176 kg/net). The reason for the significant difference might be that the effect of the fish lamp for attracting fish was diminished in bright moonlight. (4) The confidence coefficient of the influence curve of SST on the CPUE was higher when SST was 28℃ to 30℃. In this range, the influence curve showed a trend of first decreasing, then increasing, and then decreasing, and the peak was located near 29.5℃. The optimal SST of fishing grounds ranged from 29.00℃ to 29.49℃, at which the CPUE (348.724 kg/net) and catch weight (30.688 t) were both the highest. When SST was 28.50℃ to 29.99℃, the catch weight (69.619 t) accounted for 74.65% of the total weight, the CPUE (309.419 kg/net) was 1.11 times the average CPUE, and this SST range was suitable for catching . (5) The impact of month on CPUE increased from March to May, and it decreased from August to November. There were significant differences in the CPUE of in different months, and the CPUE of August and September was higher than that of March and April. The production of was mainly concentrated in April (28.380 t), August (28.932 t), and September (27.960 t), with little difference in weight. Falling-net fishing operations were mainly concentrated in spring, and the falling-net fishing vessels tended to fish in coastal waters after the closed fishing season. In response to this phenomenon, falling-net fishing vessels might be encouraged to go to open sea for catching after the closed fishing season, which had a positive effect on alleviating the pressure of near-shore fishing. (6) One-way analysis of variance showed no significant difference in CPUE among the different operation times. The CPUE of increased initially, then reduced with operation time. The maximum value appeared at 1 hours (410.932 kg/net). The highest catch weight appeared at 21 hours, but the CPUE was low at this time, at only 180.043 kg/net. (7) One-way analysis of variance showed no significant difference in CPUE among different Δ50. The CPUE was highest when Δ50 was in the range of 0.100-0.149℃/m, and the maximum catch weight appeared when Δ50 was in the range of 0.000-0.049℃/m. The research results could provide reference and technical support for the development of fishing in the South China Sea.

Abstract:Xinzhou section is a typical stream-sandbank habitat in the lower reaches of the Yangtze river. In order to understand the larvae and juvenile fish assemblage feature in this section, Structure, dominant species, abundance and spatial-temporal distribution were investigated, from April 15 to August 4, 2018, and the relationships with environmental factors were probed at the same time. 121246 larvae and juvenile fish were identified, belonging to 6 orders, 8 families and 34 species. 79338 larvae and juvenile fish were captured in the south branch, accounting for 65.44% of the whole species; and 41908 in the north branch, accounting for 34.56%. Among the spawning types, fish species with pelagic eggs (16) were dominant; whereas, fish with floatability eggs taken the largest number, which were 92623 individuals. was the first dominant species and other dominant species are Rhinogobius giurinus. The diurnal variation trend of abundance in north and south branch were consistent. The larval and juvenile fish abundance reached its peak level (2001.28 ind/100 m³) on July 13, which showed a high correlation with water level. The abundance of inshore sampling points was higher than that of mid-channel, and the abundance of south branch was higher than that of north branch. Redundancy analysis found that water level, water temperature, turbidity and transparency are the main environmental factors affecting the assemblage structure of larval and juvenile fish. Water level is the main positive correlation factor. The cluster analysis divided the 6 sampling points into 3 groups, showing significant differences in assemblage structure of larval and juvenile fish (=0.017). The results showed that there was a significant influence on the distribution of larvae and juvenile fish in Xinzhou section, and the breeding conditions of fish in the south branch were better. The results provided the scientific data of the early fish resource in Xinzhou section and the protection strategy of fish resource in the lower reaches of the Yangtze River.

Abstract:The Gibel carp, (Bloch), is an important freshwater farming species that grows rapidly, has a high meat yield, and wide adaptability. However, in the past decade, diseases have been a severe challenge to successful culture systems. The parasitic disease caused by causes massive deaths of the larval and adult Gibel carp every year. Establishing an efficient, sensitive, and specific detection method is of great significance for the early diagnosis and prevention of the disease. In this study, a single-tube, semi-nested polymerase chain reaction assay to detect and monitor the infection of was developed with two newly designed primer pairs, which were designed based on 18S rDNA. The specificity, sensitivity, repeatability, and applicability of the assay were evaluated. The results indicated that amplification was positive only in the Carassius auratus gibelio Bloch were all negative; the lowest detection was 4.2 copy/μL of the target gene. The clinical detection samples showed that was present in the ovaries, kidneys, and spleen of asymptomatic Gibel carp from the epizootic zone, with a positive incidence of 40%, 32%, and 8%, respectively. In conclusion, the method developed in this study is of high specificity and sensitivity, which provides a new and reliable technical means for the early diagnosis and control of .

Abstract:Dibutyl phthalate (DBP), a kind of plasticizer, had been included in the priority control pollutants list in China. The impact on marine organisms has caused widespread concern. At present, the research on the impact of DBP on marine organisms focuses on the growth, reproduction, and development of plankton, crustaceans, and fish. There are limited studies on the effects of antioxidant indicators in shellfish. Biochemical indicators such as antioxidants and disease resistance of organisms are important indicators of the degree of stress in response to pollutants and are widely used in ecotoxicology research. As one of the main varieties of seawater shellfish cultured in China, has a strong bioaccumulation in the marine environment and can be used as a biomonitoring species for environmental pollution. To study the changes of the antioxidant defense system, superoxide dismutase (SOD) and catalase (CAT) activity, and malondialdehyde (MDA) content in the gills and visceral mass of at five concentrations of DBP (0 mg/L, 100 mg/L, 200 mg/L, 280 mg/L, and 360 mg/L), with two stages of clear water flushes, were measured. This was to explore the effect of DBP stress on the biological indicators of and to determine whether the function of the body could be restored by the flushes of clear water. The experimental results show that the activities of SOD, CAT, and MDA content in gills and visceral mass of were not identical. Under DBP stress, SOD activity in gills and visceral mass was basically increased, then decreased, and then increased; CAT activity was decreased first and then increased; MDA content generally increased. When they were transferred to clean seawater, the activity of SOD in the gills and visceral mass of showed a trend of decreasing first and then increasing, and CAT activity was increased first. After CAT activity in the visceral mass decreased, and the MDA content in the gills increased, the visceral mass showed a trend of increasing CAT activity first and then decreasing, and the concentration-effect and time-effect were more obvious. This indicated that, under DBP stress, the body was induced to produce reactive oxygen free radicals to reduce the damage of free radicals to cells. With the prolongation of stress time and the increase in concentration, the activity of SOD and CAT in most concentration groups showed a trend of decreasing first and then increasing, which may be because of the inability of the antioxidant system in to remove excess oxygen free radicals in time. When the DBP stress exceeds the capacity of the body (which causes a certain amount of oxidative damage to the cells), SOD and CAT activity is inhibited, and the tendency to increase may be related to the metabolic consumption of DBP and the self-repairing regulation of . It can induce the body to perform lipid peroxidation, which will cause the increase in MDA content. This damage is difficult to return to normal with a release of clean seawater. Although SOD and CAT activity did not show complete synchronization, this phenomenon is consistent with the organism's antioxidant enzyme response mechanism. In short, the change of antioxidant enzyme activity in marine organisms is a dynamic process, which may be affected by many factors such as environment, concentration, biological individual, and tissue differences. Therefore, it is necessary to comprehensively consider the response mechanism. The results of this paper evaluated the effect of DBP on from the perspective of oxidative damage, and provided reference data for the comprehensive understanding of the mechanism of DBP on marine organisms in the future, and provides a scientific basis for aquaculture health and risk assessment of marine shellfish.

Abstract:, belonging to the family , are important economic fish species in the Lyusi fishing ground. With the rapid improvement of fishing power and production efficiency, coastal fisheries generally suffer from different degrees of overfishing, and the resources of also suffer from a continuous decline. The purpose of this paper is to provide a reference for the rational development and utilization of resources by analyzing their fatty acid composition, nutritional value, feeding habits, and dietary changes. The fatty acid composition of 46 individuals, collected from the Lyusi fishing ground during autumn 2018, was measured, and a dietary analysis was performed, based on the fatty acid labeling method. The results showed that fatty acid content of (21.77 mg/g); their SFA contents were similar (36.00%); the MUFA content of (15.92%), and the PUFA content of C. lucidus (47.91%). PUFA/SFA and n-3/n-6 of were higher than those found in common aquatic fish. The n-3/n-6 of P<0.05), whereas the PUFA/SFA of P<0.01). The characteristic fatty acids C18:2n6c and C20:5n3 (EPA) of P<0.05) and DHA/EPA had a significantly positive correlation with body length ( had a significantly negative correlation with body length ( had a higher herbivorous diet when the body length was less than 70 mm (<0.05), and a significant decrease in herbivorous diet when the body length was greater than or equal to 120 mm ( had a higher herbivorous diet when the body length was less than 70 mm (<0.05), and a significant decrease in herbivorous diet when the body length was greater than or equal to 100 mm ( (2.6-5.9) partially overlapped with (2.6-3.3). The research indicated that the nutritional values of were very high; the larger individuals' fish oil of had a higher nutritional value, and the smaller individuals of were more beneficial to cardiovascular health. Their trophic levels were partially overlapping, and their feeding habits were similar. As the body length increased, the herbivorous diet decreased and carnivorous diet increased, and the body length was similar when the diet changed. Therefore, they may have a certain niche overlap and food competition.

Abstract:is an important economic fish species from coastal China. It is also one of the few large-scale catch species that maintain a high yield in China. Studies have shown that the relationship between fork length and body weight differs between seasons and areas. To better understand the seasonal and sexual variations in relationships between the fork length and weight (, we used the trawl survey data at the East China Sea fishing grounds from October 2018 to March 2019 and constructed a generalized linear model and nine linear mixed models. Based on the collected 367 samples, the relationship between fork length and body weight () is obtained, in which the estimated mean value of condition factor a is 3.022×10^-5, and the estimated mean value of allometric growth parameter b is 2.794. Both the Bayesian Information Criterion (BIC) value and the root mean square error (RMSE) value indicated that the most complex linear mixed model (i.e. month and gender have random effects on both parameters ) had the best performance. According to the results of the difference analysis between the best model and the generalized linear model, the relationship between the fork length and weight of <0.01). In the best model, was higher in October and November (feeding period) and lower in December and January (overwintering period), while was higher in males and lower in females. It can be concluded that the relationship between the fork length and weight of was significantly affected by season and sex. The linear mixed model allows the easier combination of season and sex, which would be of great value in the heterogeneity studies of fish life history traits.

Abstract:In the past three decades, China's aquaculture industry has achieved rapid development, and its production has always been leading the world. In 2018, the ratio of China's aquaculture production to world production was as high as 60%. At the same time, the disadvantages of high-density, intensive farming have gradually emerged. For example, an illogical combination of nutritional elements such as sugars, proteins, fats, vitamins and minerals in aquatic feeds leads to nutritional disease in fish, which has a huge impact on production. The prevalence of nutritional metabolic diseases has severely restricted the sustainable and healthy development of aquaculture, and it is urgent to address this. The etiology and pathogenesis of nutritional metabolic diseases such as excessive body fat accumulation and fatty liver are extremely complicated. Disorders of energy metabolism are caused by a combination of internal genetics and external environment. At present, the prevention and treatment of nutritional metabolic diseases are mainly through moderately reducing fry stocking density and feeding nutritionally balanced feeds as much as possible. However, there are still some restrictions in terms of genetics. Increasingly, studies show that genes play an important role in metabolic diseases. Finding genes related to metabolic diseases, especially those involved in and regulating the glucose and lipid metabolism pathways, and studying their biological functions and mechanisms of action has gradually attracted the attention of the aquaculture scientific community and industry. At present, the gene database related to nutritional metabolic diseases is in the developmental stage. The genes which regulate the physiological activities and metabolic functions of fish can be obtained from the database. However, the establishment of a gene database network platform for disease regulation is still in the preliminary stage of research. Therefore, this paper firstly gives a brief introduction to the definition of fish nutritional metabolic disease and its pathogenesis. Secondly, the NCBI genomic database was interrogated, and we found that the database contains 265 fish species, and the size of their genomes varies widely. The has a genome size of 0.001005 Mb, which is the smallest. The fish with a genome size ranging from 609.39 to 699.33 Mb occur most frequently, with 47 species in total. There are 36 species of fish with a genome size of 701.7-799.42 Mb. The database also shows the number of chromosomes in 64 fish species, with different numbers of chromosomes in different fish species. Among them, the largest number of chromosomes occurs in Chanos chanos has 16 pairs of chromosomes, which is the lowest number of chromosomes. In addition, nearly 40% (23 species) of the 64 species have 24 pairs of chromosomes. By investigating the Ensembl database, the genomic data of 58 fish species in 17 orders were obtained. Among them, Perciformes includes the most species of fish (23). Next, Siluriformes includes 12 species of fish. There is only one fish species in the orders Characiformes, Gadiformes, Gymnotiformes, Myxiniformes, Polypteriformes, Synbgranchiformes, Siluriformes, and Lepidosteiformes. By investigating the KEGG database, we found that it contains a database of 41 fish species. Among them, the number of genes related to glycolipid metabolism in is 2540, which is the highest number, and the number of genes related to glucose and lipid metabolism is lowest in , at 1075. This paper highlights the number of genes that regulate the various pathways of glycolipid metabolism in zebrafish, and briefly introduces other fish databases and metabolic-related databases which provide theoretical support for the development of the gene database network platform related to nutritional metabolic diseases, and lays a solid foundation for the treatment and prevention of fish nutritional metabolic diseases.

Abstract:The recent outbreak of the COVID-19 virus has raised concerns regarding the trade in aquatic wildlife. Species of aquatic wildlife are both valuable natural resources and important ecosystem constituents. Their value is reflected not only in maintaining an ecological balance but also in meeting the diverse needs of human cultivation, development and utilization. Aquatic wildlife plays an irreplaceable role in achieving sustainable socio-economic development, as well as improving and enriching human material and cultural life. However, from the perspective of valuing aquatic wildlife, there exists a certain conflict between protection and utilization. In this paper, we examine the seemingly disparate aims of aquatic wildlife protection and breeding and utilization, and consider future progress with respect to aquatic wildlife resource protection and regulation of the breeding and utilization of aquatic animals. Appeal society actively encourage and promote aquatic wild animal domestication and breeding and processing enterprise, guide the consumer right edible safety of domestic products, and expand and improve the aquatic wild animals living space and environment, realization of aquatic wildlife species gauge touch is growing stronger, finally realize the sustainable use of wildlife resources.