Abstract:Bighead carp （Hypophthalmichthys nobilis） is a common freshwater fish species in China. In order to reveal the genetic status of H. nobilis in the middle and lower reaches of the Yangtze River （YR）, 219 individuals were collected from five locations respectively in Shishou （SS）, Changsha （CS）, Ruichang （RC）, Yangzhou （YZ） and Zhangjiagang （ZJG）. The D-loop sequences were tested and analyzed in comparison with those of H. nobilis from the Pearl River （PR, 213 individuals） and Northern America （NA, 33 individuals） downloaded from the NCBI. As a result, 35, 96, and 11 variable sites were observed and 37, 62, and 3 haplotypes were defined in YR, PR, and NA, respectively. Among the YR H. nobilis, high haplotype diversity （H_d, 0.798-0.897） and moderate nucleotide diversity （π, 0.003 38-0.006 53） were detected, except the pairwise pairs of RC vs. ZJG （F_ST = 0.012, P>0.05） and CS vs. YZ （F_ST = 0.018, P>0.05）, significant genetic differentiations （F_ST ranged from 0.031 to 0.125, P<0.05） were found among all the other pairwise stock pairs, and gene flows （N_m ranged from 3.509 to 39.993） were generally detected within the five stocks. According to the haplotype network analysis, the D-loop haplotypes contained multiple clades which were obviously shared among different stocks in YR. Meanwhile, the central haplotypes of YR and PR populations were generally mutual-shared, whereas the haplotypes specific to PR were peripherally distributed. The haplotypes sharing situation further evidenced the possible multiple introductions of NA. Based on the neutrality test, it was predicted that only PR went through population expansion in history. Overall, the study revealed an abundance of genetic variations in H. nobilis of YR and PR, laying a solid foundation for the further protection and utilization of the relevant genetic resources.

Abstract:In order to investigate the gene structure, expression pattern, and molecular function of Kcna gene in Eriocheir sinensis, this study cloned the full-length Kcna gene of E.sinensis （named Es-Kcna）, and conducted bioinformatics analysis and spatio-temporal expression pattern research； observed the changes in growth phenotype characteristics of E.sinensis after RNA interfering with Es-Kcna gene； and screened the SNP molecular markers of Es-Kcna gene and conducted association analysis with population geographic distribution and growth characteristics. The results showed that Kcna gene was located on chromosome 46 of E.sinensis, with a length of 945,304 bp and nine exons. The full-length cDNA was 2 080 bp, the open reading frame was 1 584 bp, and encoded 527 amino acids, the total number of atoms is 8 433, the molecular structure formula is C₂₇₁₉H₄₂₁₀N₇₀₂O₇₈₇S₁₅, the predicted isoelectric point （pI） is 5.23, and the relative molecular weight is 59.81 KDa. Phylogenetic tree analysis showed that Es-Kcna gene was most closely related to the Kcna gene of Portunus trituberculatus, and the crustaceans clustered into a separate clade. Fluorescence quantitative PCR （qRT-PCR） results showed that Es-Kcna gene was expressed in six tissues, including muscle, heart, intestine, eyestalk, gill and hepatopancreas at pre-molting, inter-molting and post-molting stages, with the highest expression abundance identified in muscle tissue. Compared with the control group, the body weight, molting weight gain rate and second walking leg length of the experimental group crabs were significantly decreased after RNA interfering of the Kcna gene. Muscle tissue slice results showed that the diameter of muscle fibers in the walking legs of the experimental group was smaller than that of the control group. In addition, a SNP （A1 461G） was identified in the exon 8 of Es-Kcna gene. The association analysis of population distribution showed that this SNP was significantly enriched in the GG genotype in the wild population of Liaohe River, while the AA genotype was enriched in the wild population of Yangtze River. The association analysis of growth traits showed that the second walking leg length of individuals with the AA genotype was significantly longer than that of individuals with the GG genotype. The present study provided insight into the molecular function on Kcna gene in regulating growth and potential utilization in genetic breeding of E.sinensis, and provided an important reference for distinguishing wild E. sinensis from the Yangtze and Liaohe rivers.

Abstract:Subfamily has lived in the anoxic environment of Qinghai-Tibet Plateau for a long time, which is a natural biological model to study the adaptation mechanism of hypoxia. Transcriptome analysis was made on the kidneys of three species of Schizothorax curvilabiatus and Schizothorax macropogon at high altitude （> 3 600 m） and Schizothorax prenanti at low altitude （< 700 m）. By comparing and analyzing the renal transcriptome of Schizothorax unicornis, Schizothorax megacephalus and Schizothorax homostoma, 504 and 478 differentially expressing genes were screened out respectively, among which 199 genes were commonly differentially expressed. The enrichment analysis of common differential genes by GO （Gene Ontology） and KEGG （Kyoto encyclopedia of genes and genomes） showed that the two groups of common differential genes were mainly enriched in glycolysis/glycogen production, lipid biosynthesis, and angiogenesis. Among them, the high expression of eno3, fbp1α, prpf19, and ctsz may play an important role in the long-term adaptation of Schizothorax at high altitude to hypoxic environment. This study provides a new idea for revealing the long-term hypoxia adaptation of plateau fish.

Abstract:Wnt/β-catenin signaling plays an important role in regeneration in multiple species such as planaria. The study aimed to investigate the effect of Wnt/β-catenin signaling on the regeneration in the annelid, Capitella teleta. Sustained incubation of samples after amputation in 30 μmol/L XAV-939, an exogenous Wnt/β-catenin signaling small molecular inhibitor, revealed that the regeneration of C. teleta was inhibited, with significantly slower regeneration compared to that in the control group and failure to form a regeneration blastema. Neural and muscle growth during regeneration were also affected by inhibition of Wnt signaling revealed by neural and muscle labeling. Subsequently, EdU labeling indicated that the number of proliferating cells in the XAV 939-treated group was significantly less than that in the control group, suggesting that the suppression of the Wnt/β-catenin signaling may have affected the proliferating cells during the regeneration of C. teleta, which alsofurther demonstrating that the Wnt/β-catenin signaling may be involved in the regeneration of C. teleta, and play an important role in the early stage of regeneration. Comparative studies on the regulation of regeneration by wnt signaling in several typical species have shown that the Wnt signaling is relatively conserved in the whole-body regeneration of Cnidaria and Lophotrochozoa.

Abstract:In shellfish culturing and breeding practice, the width of shell growth lines is an important index to measure the growth rate of shellfish,and anal angle radial rib is the part with the widest growth lines. In order to explore the feasibility of taking anal angle radial rib length as a typical growth trait, this research analyzed the correlation between anal angle radial rib length （X₁） and other growth traits, such as shell length （X₂）, shell height （X₃）, total height （X₄）, shell width （X₅）, live body weight （Y₁）, soft tissue weight （Y₂） and shell weight （Y₃） of Hyriopsis cumingii at different ages and conducted the path analysis of body size traits to body weight traits （live body weight, soft tissue weight and shell weight）.The results of correlation analysis showed that there was a significant positive correlation between anal angle radial rib length and body weight in the first to third instars of H. cumingii. The correlation coefficient between shell length and live body weight was the highest in the first and second instars of mussel, while the correlation coefficient between anal angle radiating rib length and live body weight was the highest in the third instar of mussel. In addition, the correlation coefficient between anal angle radiating rib length and live body weight, soft tissue weight and shell weight showed an increasing trend with the increase of age. The data of path analysis and multiple regression analysis displayed that the main factors affecting the live body weight of 1 to 3 year old were anal angle radial rib length, shell length and shell width, the main factors affecting the soft tissue weight of 3 year old were shell length and shell width, the main factors affecting the shell quality of 1 and 2 year old mussel were shell length and shell width, and the main factors affecting the shell quality of the third instar mussel were anal angle radiating rib length, shell length and shell width. In conclusion, anal angle radial rib length, together with shell length and shell width, can be used as a new typical growth trait to represent the growth rate of H. cumingii.

Abstract:Studies on the biological effects of microplastics pollution on aquatic animals mostly focused on the ocean, but the potential effects on freshwater organisms are less known. In this study, the effects of polystyrene （PS） particles with different particle sizes （5 μm, 1 μm, 100 nm） on juvenile Chinese mitten crab （Eriocheir sinensis） were investigated. Hepatopancreas injury index： alanine aminotransferase （ALT）, aspartate aminotransferase （AST）； serum immune index： alkaline phosphatase （AKP）, acid phosphatase （ACP）； Oxidative stress index： malondialdehyde （MDA）, catalase （CAT）； and neurotoxicity index： acetylcholinesterase （AchE） were analyzed. The pathological changes of gills and hepatopancreas were analyzed by hematoxylin-eosin （H.E） staining. The results showed that exposure to microplastics after 7 d, 100 nm group had significantly higher MDA content, CAT activity decreased significantly, the AKP activity of three treatment group were significantly lower, and 1 μm and 100 nm group of ACP activity was significantly reduced. The activities of AST, ALT and AchE gradually decreased with the decrease of particle size and the extension of exposure time. In conclusion, microplastics with different particle sizes caused varying degrees of hepatopancreas injury, oxidative stress and reduced immune capacity in crabs. The toxicity level was ranked as follows： 100 nm > 1 μm > 5 μm, indicating that the particle size was one of the most important factors affecting the health of Chinese mitten crabs. This study provides basic data and theoretical basis for further understanding the toxic effects of microplastics on freshwater crustaceans.

Abstract:To compare and analyze the nutritional value and quality changes of the meat of M. rosenbergii produced by the Eriocheir sinensis and M. rosenbergii mixed culture mode and the traditional M. rosenbergii exclusive culture mode, the body mass, length and meat yield were measured to compare the the differences in body size of M. rosenbergii under two culture modes； moisture, protein, ash, fat, minerals, fatty acids and amino acids were measured to compare the nutritional value； and texture feature and tasty nucleotides were measured to compare the changes of shrimp meat quality. Compared with the exclusively cultured M. rosenbergii, the specification of M. rosenbergii in the mixed culture mode increased significantly, but its meat yield decreased. The fat content of shrimp meat in mixed culture decreased from （0.91±0.07）% to （0.59±0.05）%, with a significant difference； The contents of calcium, magnesium phosphorous and cuprum in shrimp meat increased； the EPA content in fatty acids decreased from （15.59±0.66）% to （13.64±0.71）%； the EAAI score of amino acids increased slightly； the nutritional value of M. rosenbergii changed slightly； the hardness of shrimp meat in mixed culture increased significantly； and the content of AMP and IMP in tasty nucleotides increased from （78.15±1.23） g/100 g and （162.90±2.67） g/100 g to （86.96±1.87） g/100 g and （175.12±3.01） g/100 g. The quality of shrimp meat in mixed culture was significantly improved. The specification of M. rosenbergii produced by the Eriocheir sinensis and M. rosenbergii mixed culture mode significantly increased, with little change in nutritional composition, and the quality of shrimp meat significantly improved, which is in line with consumer taste and has excellent market prospects.

Abstract:In order to understand the nutritional quality of Chinese mitten crabs cultured with compound feed and chilled fish during hoarding, Chinese mitten crab cultured with compound feed and Chinese mitten crab cultured with fresh fish were stockpiled for three months to compare their edible rate, conventional nutrients, fatty acids and free amino acid composition. The results showed that： during the hoarding period, the gonadal index of the two bait Chinese mitten crab showed an upward trend, the hepatopancreatic index and total edible rate showed a downward trend, and there was no significant change in the meat yield； during the hoarding period, the water and protein content of liver and pancreas of the two bait Chinese mitten crab showed an upward trend, the fat content showed a downward trend, the gonadal fat showed a downward trend, and there was no obvious change in nutrients in the muscle； the content of C18:2n6 （LA） in the edible tissue （except for the fine nest） of Chinese Mitten Crab cultured with compound feed was significantly higher than that in Chinese mitten crab cultured with chilled fish, while the contents of EPA and DHA in hepatopancreas and ovaries were significantly lower than those in Chinese mitten crab cultured with chilled fish. After stockpiling, the contents of edible tissues C18:2n6（LA）, C20:4n6 （ARA） and ∑n-6PUFA in Chinese mitten crab cultured with compound feed increased and were significantly higher than those in Chinese mitten crab cultured with fresh fish, and the contents of EPA, DHA and ∑n-3PUFA in Chinese mitten crab cultured with fresh fish were increased and significantly higher than those in Chinese mitten crab cultured with compound feed； after hoarding the two bait Chinese mitten crab, the content of sweet amino acids （Gly） in the muscles increased, while the content of bitter amino acids （His, Ary, Pro） decreased, and the content of umami amino acids and sweet amino acids in the gonads decreased. In summary, there was no obvious “ointment” phenomenon during the hoarding of Chinese mitten crab cultured by two kinds of bait, but there was a significant loss of edible tissue nutrients, especially the liver and pancreas. From the perspective of fatty acids and amino acids, the content of LA and ARA of compound feed cultured Chinese mitten crab increased during the hoarding period, and the EPA and DHA content of chilled fish cultured Chinese mitten crab increased. On the whole, hoarding had a certain optimization effect on Chinese mitten crab fatty acids, the content of sweet amino acids in muscles increased, while the content of umami amino acids and sweet amino acids in the gonads decreased, and the overall quality deteriorated.

Abstract:The Chinese mitten crab （Eriocheir sinensis） is an important economic crab in China. It occupies an important position in the fishery economy, with an annual output value of more than 100 billion yuan. Although there are five E. sinensis varieties approved by China National Committee for Original and Improved Aquatic Species, they cannot fully meet the diversified needs of E. sinensis breeding industry. The breeding of super-sized E. sinensis broodstock has been a revolution in the crab industry since 2019. The use of offspring of super-sized broodstock for adult crab culture has indeed effectively improved the crab cultivation specifications. Super-sized broodstocks can produce a large number of eggs, and the offspring of super-sized broodstocks have obvious growth advantages at the juvenile crab stage and the adult crab culturing stage, and the price of megalopa bred by super-sized broodstocks is also relatively high. Therefore, nursery workers tend to use super-sized crabs as broodstocks for breeding work. However, in the artificial breeding process, the selection of broodstock weight of E. sinensis varies greatly. Now, it is popular to use super-sized broodstock to breed offspring, but the reproductive performance and breeding effect of super-sized broodstock are not clear. In this study, the broodstock of super-sized strains （Size Ⅰ： dam weight ≥300 g, sire weight ≥400 g） were used as the experimental object, and the broodstock with smaller size （Size Ⅱ： dam weight ≥150 g, sire weight ≥ 250 g） were used as the control group. The effects of broodstock sizes on reproductive performance and egg quality were compared, and the ecological breeding effects of these two strains were further discussed. The results showed that： （1） In terms of reproductive performance, the survival rate, fecundity and reproductive effort of Size Ⅰ broodstock were significantly lower than those of Size Ⅱ, and the egg production was significantly higher than that of Size Ⅱ； There were no significant differences in egg diameter, egg weight, moisture, crude protein, total lipid and ash contents. （2） In terms of breeding effect, the feeding amount for larvae showed a “low-high-low” trend during the breeding period, and the highest feeding amount was observed between Zoea Ⅴ and the megalopa stage. Although the seedling yield of single crab in Size Ⅰ was significantly higher than that of Size Ⅱ, the per unit area yield was significantly lower in Size Ⅱ broodstock, and the dilution ratio was also relatively lower in Size Ⅱ broodstock. In conclusion, although the super-sized broodstock exhibited significantly higher broodstock quantity and individual seedling yield compared to the small-sized parental stock, the super-sized parental stock demonstrated lower broodstock incubation rate, survival rate, and dilution rate compared to the small-sized broodstock. Further research is needed to explore how nutritional regulation can be utilized to enhance the reproductive performance of super-sized broodstock.

Abstract:In order to study the egg hatching time and the effects of lettuce leaves, aquatic periphyton, artificial pellets, as well as their partial combinations on growth performance to the juvenile snails Radix plicatula, a subset of 10 newly laid egg masses were collected and their hatching time were record under indoor conditions. In addition, the shell length, shell width, body weight and survival rate for the juvenile snails feeding with different diets were analyzed. The results showed that the egg hatching time was 6.0-7.5 days with a 96.37% hatching rate when the water temperature ranged from 25.0 ℃ to 32.5 ℃. There was no significant difference in the survival rate for the 0-5 week old snails feeding with different diets, however, significant difference in the growth performance was found among the snail in different diet groups. The growth rate for 0-2 weeks old snails feeding with lettuce + aquatic periphyton was the fastest, followed by the snails feeding with aquatic periphyton. The growth rate for 3-5 weeks old snails with an initial body mass of 0.005 g feeding with lettuce + artificial pellets was greater than that feeding with lettuce or artificial pellets. Furthermore, no significant differences were found between the 3-5 weeks old snails with an initial body mass of 0.026 g fed by lettuce or lettuce + artificial pellets for their shell height, shell width and body mass. The results indicated that the R. plicatula egg hatching time is 6.0-7.5 days with a mean hatching rate of 96.37% with the water temperature ranging from 25.0 ℃ to 32.5 ℃. Aquatic periphyton and the leaves of lettuce are ideal food sources for 0-2 weeks old and 3-5 weeks old R. plicatula, respectively, and artificial pellets have a promoting effect on the growth of juvenile snails. The results of this study will provide a basis for large-scale production of R. plicatula.

Abstract:In order to study the change rule of nutrient substance in ovaries of female Alosa sapidissima at the late stage of development and improve the fertilization rate of eggs, the contents of amino acids, fatty acids, vitellogenin （VTG）and cathepsin D （CTSD）and their mRNA expression in the ovaries of female Alosa sapidissima at the stages Ⅳ and Ⅴ of gonadal development were compared and analyzed by biochemical analysis, enzyme-linked immunosorbent assay and fluorescence quantitative PCR. The results showed that the water content （75.73%） in stage Ⅳ ovary was significantly lower than that （90.64%） in stage V ovary, while the crude protein content （16.07%）, crude fat content （2.86%） and crude ash content （1.28%） were significantly greater than those （5.83%, 1.25%, 0.81%） in stage Ⅴ ovary. Among the 18 amino acids detected in the ovaries of stages Ⅳ and Ⅴ, the content of glutamic acid was the highest （8.64% and 8.13%）. Among the 8 essential amino acids, the contents of threonine, phenylalanine, lysine and tryptophan in stage Ⅳ were significantly higher than those in stage Ⅴ, and the first limiting amino acid of both was tryptophan. The total amino acid （TAA）, semi-essential amino acid （HEAA） and total non-essential amino acid （NEAA） in stage Ⅳ were significantly higher than those in stage Ⅴ. A total of 19 fatty acids were detected in the ovaries of the two stages, and the contents of C17:0, C20:1n9, C20:4n6 and C20:5n3 in stage Ⅳ were significantly higher than those in stage Ⅴ； the contents of ∑ MUFA, ∑ PUFA, ∑ UFA, ∑ n3PUFA and EPA + DHA in stage Ⅳ were greater than those in stage Ⅴ, and ∑ UFA （70.54%） reached significant differences. The content of VTG in stage Ⅳ ovary was higher than that in stage Ⅴ ovary, but it was not significant, while the content of CTSD in stage Ⅳ ovary was significantly lower than that in stage Ⅴ ovary. The expression of VTG gene in stage Ⅴ ovary was significantly higher than that in stage Ⅳ, 13.88 times of that in stage Ⅳ, while the expression of VTG gene in liver was significantly lower than that in stage Ⅳ, accounting for 25% higher than that in stage Ⅳ. From stage Ⅳ to stage Ⅴ, CTSD mRNA expression showed down-regulation in the ovary and up-regulation in the liver, but none of them was significant. Therefore, under the current aquaculture conditions, the accumulation of nutrients in the ovary is uneven during the late development of the Alosa sapidissima, and it is recommended to appropriately adjust the feed formula, increase the ratio of limiting amino acids tryptophan, methionine, L-Phenylalanine and lysine and threonine with lower content, increase the ratio of polyunsaturated fatty acids C20:3n6, C20:4n6 （AA）, C22:6n3 （DHA） and C20:5n3 （EPA）, and decrease the ratio of C18:2n6c in order to ensure the balance of nutrients required for the late development of the ovary.

Abstract:The anatomical and histological characteristics of spleen, head kidney and trunk kidney of Hemibarbus labeo were studied by dissection, paraffin sections and H. E staining. The results showed that the spleen is single with dark red. It is applanate and oval, and is separated into many lobes by the connective tissue diaphragm from the capsule. The boundary between red pulp and white pulp in the lobes is not obvious. The spleen contains many of the red blood cells, lymphocytes and melano-macrophages, and the blood vessels are rich. The kidney can be obviously divided into the head kidney and the trunk kidney. The head kidney is located above the diaphragm of the back of the heart at the front end of the body cavity, divided into left and right lobes, and distributed symmetrically. The parenchyma of the head kidney has no nephron, and is mainly composed of lymphoid tissue, including red blood cell centers and white blood cell canters. The head kidney also contains many of red blood cells, lymphocytes, granulocytes, and a certain number of melano-macrophages, which are similar to the spleen. The trunk kidney is located in the thoracic and abdominal segments of the fish body, and close to the two sides of the spine on the back of the body cavity. Its parenchymal part is mainly composed of nephron, collecting segment and lymphoid tissue. Many of red blood cells, lymphocytes, granulocytes, and melano-macrophages can be observed in the lymphatic tissue. These results indicated that the spleen and head kidney are important immune and hematopoietic organs, and the trunk kidney also plays an important role in immunity and hematopoiesis in addition to urinary function in H. labeo.

Abstract:To investigate the threshold of purification efficiency of Ulva meridionalis for aquaculture wastewater，in addition to identifying the optimal algal density and treatment duration for the purification of such wastewater，U. meridionalis was cultured in simulated aquaculture wastewater using a bluepard biochemical incubator. Six density gradients of 0.5，1.0，1.5，2.0，2.5g/L（treatment groups）and 0 g/L （control group）were established. The concentration of NH⁺₄-N、NO^-₂-N、NO^-₃-N and PO^3-₄-P in the simulated aquaculture wastewater was respectively measured at 0，12，24，36，48，60，and 72 hours. U. meridionalis demonstrated a significant purification effect on aquaculture wastewater （P＜0. 05）. The optimal U. meridionalis density for effective purification of the culture wastewater was determined to be 2. 5 g/L. The optimal treatment times for achieving effective purification of NH⁺₄-N、NO^-₂-N、NO^-₃-N and PO^-₄-P in aquaculture wastewater，at the optimum algal density，were found to be 24，60，48，and 72 hours， respectively. Additionally，the removal efficiency of U. meridionalis for different forms of inorganic nitrogen was influenced by the composition of nitrogen sources present in the aquaculture wastewater. It was observed that NH⁺₄-N was preferentially absorbed，followed by NO^-₃-N，and finally NO^-₂-N. The treatment of aquaculture wastewater with U. meridionalis s at an algal density of 2. 5 g/L for a duration of 72 hours yielded the most effective purification of nitrogen and phosphorus in the wastewater. This study provided data support for biological purification of aquaculture wastewater.

Abstract:Hexachlorobenzene （HCHs）, dichlorodiphenyltrichloroethane（DDTs） and poly-chlorinated biphenyls （PCBs） were determined in water, soil and mussel samples using GC-MS/MS, in order to investigate the concentrations, composition and distribution characteristics of legacy persistent organic pollutants （POPs） in different medium in the mussel mariculture area of the Huaniao Island, Yangtze estuary. The results showed that legacy POPs were widely detected in the samples, and the concentrations of HCHs, DDTs and PCBs ranged from 10.8 to 49.1, 169 to 900 and 10.4 to 34.4 ng/g（lipid weight） in mussel, 0.22 to 1.76, 0.07 to 0.29 ng/L and 9.45-51.8 pg/L in water, and 0.18 to 10.4, 2.62 to 69.6 and 0.40 to 0.69 ng/g（dry weight） in soil, respectively. DDTs were the main pollution compounds in mussel. The composition of target compounds in water and soil samples from the mariculture area reflected their exposure to residual pollutant emissions, with a dominance of highly chlorinated PCBs and DDT degradation products in mussels, which was associated with bioaccumulation characteristics. There were many significant positive correlations among HCHs, DDTs and PCBs in soils, as well as in mussels, reflecting the possible existence of similar sources of contaminants. The relationship between mussel tissues and non-biological medium can be seen in the principal component analysis. Health risk assessment showed that population ingestion of local mussels posed little risk of exposure and carcinogenic potential. This study can provide a basis for understanding the fate of legacy POPs among the different medium in the mussel mariculture area and the risk of mussel consumption by the population.

Abstract:In order to explore the key marine environmental factors affecting the growth and fattening of triploid Crassostrea angulata and promote the development of triploid oyster culture to the deep waters in the outside bay, a 10-month survey was conducted on the triploid C. angulata culture area in Huangqi Bay from December 2021 to September 2022. The growth indexes of oysters and marine environmental factors of the culture areas both outside and inside the bay were obtained, and the data were analyzed by Redundancy analysis （RDA） and other methods. The results showed that there were significant differences in growth indexes of oysters such as shell length, shell width, total mass, soft tissue mass, and fillet yields between the inner and outside bay groups, with all those indexes being significantly higher in the outside bay than those in the inner bay, while the difference of shell heights inside and outside bay was not significant. The contents of nitrate nitrogen, chlorophyll-a and phytoplankton cell density in the seawater in the outside bay were significantly higher than those in the inner bay, and there was no significant difference between other indexes inside and outside the bay. The results of RDA analysis showed that the main factors affecting the growth indexes of oysters were water temperature, nitrate nitrogen, phytoplankton cell density and chemical oxygen demand. What's more, phytoplankton cell density and chlorophyll-a content had the greatest effect on oyster fillet yield. Comprehensive analysis showed that water temperature, phytoplankton biomass and nutrients were the key marine environmental factors affecting the growth and fattening of triploid oysters. The average chlorophyll-a content in the sea area was above 6 μg/L for at least one month from spring to early summer, which was beneficial to the fattening of oysters. The selection of non-pollution source, good water exchange conditions, abundant food, rich nutrient supply, stable salinity and low wind waves in the outside bay to cultivate triploid oysters may be helpful to improve the yield and quality of oysters.

Abstract:Three carriers （Bumpy clay, Carrageenan and Diatomaceous earth） were selected for the preparation of immobilized microbial particles, and the different particle properties, pollutant removal performance and influencing factors were investigated in the present paper. The particle performance studies showed that the mechanical strength of the immobilized particles was high for Bumpy clay and Diatomaceous earth and low for Carrageenan； with nutrient supplementation, Bumpy clay and Carrageenan could stably release 1.50×10⁶ CFU/mL and 2.60×10⁵ CFU/mL of microorganisms, while the release of Diatomaceous earth was poor. According to fitting results of the Monod equation, it could be obtained that the Diatomaceous earth immobilized microbial particles had the largest specific degradation rate （μ_max） for COD_Mn. Carrageenan was comparable to it, and the lowest μ_max was observed for Bumpy clay. While the Ks of Diatomaceous earth particles was significantly lower than that of the other two particles. Also, the kinetics of ammonia degradation showed a similar pattern to that of COD_Mn. The effect of environmental conditions on the degradation performance of the immobilized microbial particles showed that the highest first-order rate constants （k₁） for COD_Mn were found under neutral （pH=7） condition for the three materials. The k₁ for ammonia degradation were higher for Bumpy clay and US diatomaceous earth under neutral and alkaline conditions, however the highest rate of ammonia degradation was found for Carrageenan under neutral conditions. The k₁ of COD_Mn and ammonia by immobilized microbial particles increased with the increase of temperature, among which the Bumpy clay was more sensitive to the change of temperature. Except for the Diatomaceous earth particles, the k₁ for COD_Mn degradation by the other two immobilized microorganisms increased significantly （P < 0.05） with the increase of the initial concentration of the pollutant. There was no significant difference in the k₁ of COD_Mn at different aeration intensities （P > 0.05）, and higher aeration intensity was beneficial to the degradation of ammonia.

Abstract:In order to explore the differences of biochemical and physical properties of Aristichthys nobilis muscle in different operation and management modes and different reservoirs, the biochemical characteristics such as fat, protein, amino acid, fatty acid and physical properties such as texture of two-year-old bighead carp muscle in Qingcaosha Reservoir, Chenhang Reservoir and Jinze Reservoir were analyzed by conventional biochemical analysis and histological characteristics analysis. The results showed that the crude protein content of bighead carp muscle was between 18.11% and 19.38%, and the crude ash content was between 1.27% and 1.34%, without significant difference among the three reservoirs. The pH value （6.45%） and moisture content （80.69%） of bighead carp muscle in Qingcaosha Reservoir were significantly higher than those in Chenhang Reservoir （6.27%, 78.43%） and Jinze Reservoir （6.24%,79.28%）. The crude fat content of bighead carp in Jinze Reservoir （1.31%） was significantly higher than that in Qingcaosha Reservoir （0.93%） and Chenhang Reservoir （0.91%）. There were 17 kinds of amino acids and fatty acids detected in the muscle of bighead carp in the three reservoirs. The contents of total SFA （14.15%） and MUFA （40.87%） in the muscle of bighead carp in Jinze Reservoir were significantly higher than those in Qingcaosha Reservoir （12.93%,30.29%） and Chenhang Reservoir （11.18%,29.64%）. The contents of total PUFA in Qingcaosha Reservoir（56.79%） and Chenhang Reservoir （59.24%） were significantly higher than those in Jinze Reservoir （44.88%）. The texture indexes such as hardness, elasticity and cohesiveness were significantly different, except for adhesion. The number and length of muscle cells of bighead carp in Jinze Reservoir were significantly lower than those in Qingcaosha Reservoir and Chenhang Reservoir. The results showed that different reservoir environments had no significant difference in crude protein and crude ash content of bighead carp muscle, but had significant difference in fat content and histological characteristics of muscle fiber. The muscle of bighead carp in the three reservoirs was a high-quality protein source, and the nutritional value of bighead carp muscle in Chenhang Reservoir was higher.

Abstract:This study is based on synchronous data collection in the intertidal zone of the raft culture area on Shengsi Gouqi Island from February to July 2022 （the rapid growth period of large seaweed from March to April, the mature period in May, and the decline period from June to July）. Relative importance index, Shannon-Weaver diversity, and Margalef richness index were used in combination with multivariate statistical methods such as clustering and sorting to analyze the species composition, abundance density changes, and clustering characteristics of amphipods attached to different structures on rafts and large seaweed.A total of 24 amphipod species were collected, belonging to 16 genera in 7 families within 2 suborders. Among these, 24 amphipod species were collected in the aquaculture habitat, while only 4 species were collected in the intertidal zone. The dominant species on the aquaculture rafts were Ampithoevalida, Sunampithoeplumosa, Hyaleschmidti, Caprellakroyeri, Caprelladecipiens, and Caprellaequilibra. In the intertidal zone, no dominant species were observed, and the IRI values for all species were less than 5.The overall abundance density of amphipods showed a monthly increasing trend, rising from （580±90）ind./m² during the rapid growth period of large seaweed from February to April to （3 800±400）ind./m² during the decline period from June and July. The highest average abundance density among different sites was found on the floaters, with （9 700±400）ind./m² while the lowest was observed on the mussel strings with （4 800±100） ind./m². Amphipods had the highest abundance and diversity during the rapid growth period of large seaweed, followed by the mature period, and the lowest values were observed during the decline period. Yibei strings had the highest abundance and diversity indices.In terms of clustering characteristics, amphipod communities not only exhibited significant temporal variations but also significant differences among different sites （P<0.01）. In terms of amphipods' selection and utilization of different large seaweeds, six amphipod species, including Ampithoe valida, exhibited a significant positive correlation with the biomass of brown and green algae （P<0.01）.The study found that large-scale raft-based aquaculture areas support a diverse, structurally varied, and highly abundant amphipod resource. This conclusion can provide an important basis for the construction of artificial habitats in marine ranching and the optimization of ecosystem structure.

Abstract:Sepia esculenta as an important cephalopod resource in China，has high economic and nutritional value. This paper was based on a trawl survey of Sepia esculenta samples collected in the central part of the East China Sea（123. 0°E-127. 5°E，27. 5°N-31. 5°N）from September of the same year to March of the following year from 2017 to 2021，and analyzed their mantle length and body mass composition，gonadal development，and the first sexual maturity mantle length L₅₀. The results showed that the dominant mantle length groups of both female and male individuals in the Sepia esculenta are 81-120 mm and 81-140 mm， respectively；the dominant body mass groups are 41-280 g and 41-200 g，respectively. Individuals with low gonadal development in the Sepia esculenta grow faster than individuals with high gonadal development；and females grow faster than males. During the investigation period，the gonads developed over time；no I stage individuals were found in the group with a mantle length of over 161 mm. The results using the logistic equation and polynomial mantle length and body mass model to estimate L₅₀ are：124. 30 mm and 127. 98 mm for females，129. 18 mm and 142. 44 mm for males，respectively. The L₅₀ estimated based on the polynomial mantle length and body mass equation has a better fitting effect. The Sepia esculenta has obvious seasonal reproductive characteristics，with a breeding period of 1-3 months during the sampling period；during maturity，females transit more energy from body growth to gonadal development，and their change in growth mode is significantly earlier than males；to facilitate fishing by fishermen and ensure that all individuals have reached maturity，it is recommended that the minimum opening length of the Sepia esculenta in the central waters of the East China Sea should be greater than 142 mm.

Abstract:Neritic tuna and mackerels catch in the Indian Ocean have increased rapidly in recent years, whereas these species currently lack comprehensive assessment due to their predominant capture in artisanal or small-scale fisheries, where fishery statistics are insufficient and the necessary data required for routine stock assessment are lacking. In order to better understand the resource status and develop appropriate management measures, this study applied three data-limited methods （Monte carlo catch-msy,Depletion-based stock reduction analysis, Optimized catch-only assessment method） to assess Bullet tuna, Frigate tuna, Kawakawa, Longtail tuna, Indo-Pacific King Mackerel, and narrow-barred Spanish mackerel in the Indian Ocean. Stock status were evaluated based on relative biomass （B/B_MSY） and relative fishing mortality （F/F_MSY）. Results showed that Frigate tuna and Indo-Pacific King Mackerel had a healthy status [P（B/B_MSY>1）=78%,P（F/F_MSY<1）=67%； P（B/B_MSY>1）=78%, P（F/F_MSY<1）=55%], Bullet tuna and Kawakawa were at higher risk of overfishing [P（B/B_MSY>1）=78%,P（F/F_MSY<1）=33%；P（B/B_MSY>1）=78%,P（F/F_MSY<1）=45%]. Longtail tuna and narrow-barred Spanish mackerel were at higher risk of being overfished and were subject to overfishing [P（B/B_MSY>1）=33%,P（F/F_MSY<1）=44%；P（B/B_MSY>1）=55%,P（F/F_MSY<1）=33%]. Of the three models, CMSY and DB-SRA resulted in close MSYestimates, with CMSY giving the most cautious assessment results （overfishing in all six species） and OCOM giving the most optimistic results, with some differences in the judgement of the current resource status of the species among the three models. Sensitivity analyses showed that both the priori setting of r and B_end/K had a large impact on the CMSY results； DB-SRA was sensitive to B_t/K and more robust to K. All three models were applicable for neritic tunas and mackerels stock assessment； however, relying on a single approach may lead to bias results. It is recommended that when using data-limited methods, multiple models should be used to reduce bias. The findings of this study can provide a reference for the management of neritic fisheries in the Indian Ocean.

Abstract:Jumbo flying squid Dosidicus gigas is widely distributed in the Eastern Pacific Ocean. It has a short-lived life cycle and tends to extremely respond to environmental and climate variability. In order to investigate the difference of the effects of environmental factors on habitat distribution of Dosidicus gigas in different regions in the Eastern Pacific Ocean, the present study developed a habitat distribution model for this squid in summer and autumn in the equator, off Peru and Chile.The fisheries data in the equatorial waters of the Pacific Ocean, the waters off Peru from 2016-2018, and the waters off Chile from 2015-2017 were used and obtained from National distant-water fisheries data center of China.Seven marine environmental factors including Sea surface temperature （SST）, Eddy kinetic energy （EKE）, Sea surface salinity （SSS）, Sea surface height （SSH）, Chlorophyll concentration （Chl.a）, Mixed layer depth （MLD）, and Dissolved oxygen concentration （DO） were considered in this study.The maximum entropy model（MaxEnt）was applied to investigate the distribution of suitable habitat for Dosidicus gigas and the differences in the effects of the environmental factors on it were examined in different seasons in different waters.The results showed that the AUC values of the maximum entropy model were higher than 0.8 in different seasons in different areas, and the actual fishing locations coincided with the range of suitable habitats fitted by the model.The distribution of optimal habitats in the three regions was as follows： in the equatorial waters in summer, the optimal habitats were mainly distributed within the ranges of 110°W-120°W, 1°N-3°S； in autumn, the optimal habitats for Dosidicus gigas were mainly distributed within the ranges of 97°W-117°W, 1.5°N-1.5°S, and the distribution of suitable habitats was extended to the east from summer to autumn.In summer, the optimal habitats of Dosidicus gigas off Peru were mainly located in the range of 75°W-86°W, 15°S-20°S； in autumn, the optimal habitats of Dosidicus gigas were mainly located in the range of 75°W-84°W, 15°S-20°S, with the optimal habitats moving southeastward from summer to autumn. The optimal habitats of Dosidicus gigas in summer off Chile were mainly distributed in the range of 73°W-85°W, 20°S-30°S； in autumn, the optimal habitatswere mainly distributed in the range of 75°W-85°W, 20°S-28°S, and the overall suitable habitats moved to the northeast from summer to autumn. Based on the contribution rate of each environmental factor in the habitat model,SSH, Chl.a, SSS and SST were the important environmental factors affecting jumbo flying squid habitat in the equatorial waters； SSH, MLD, DO and SST were the important environmental factors affecting jumbo flying squid habitat in the offshore Peru, and SSH, SST, Chl.a and MLD were the important environmental factors affecting jumbo flying squid habitat in the offshore Chile. Our findings suggested that significant geographical difference was shown in the environmental factors affecting Dosidicus gigas distribution in different regions.

Abstract:In order to ascertain the fish community in the coastal waters of Fujian, this study carried out four surveys in the coastal waters of Fujian in May （spring） and November （autumn） in 2022,February（winter）and July （summer） in 2023. Quarterly bottom trawl sampling surveys analyzed the species composition, floristic characteristics, dominant species, diversity, and degree of community disturbance of fish in the sea area, and elaborated on the group structure of fish communities. A total of 200 species of fish were collected in this study, belonging to 22 orders, 80 families, and 149 genera. The suitable temperature type is mainly warm water （accounting for 75%）, and the fauna type is mainly bottom fish （accounting for 47.50%）. The average mass density of fish is 687.16 kg/km², which is highest in summer and lowest in winter； the average abundance is 42 909.10 ind./km², which is highest in autumn and lowest in winter. There are 14 dominant species in each quarter, among which Trichiurus japonicus is the dominant species throughout the year. The Margalef index （D） of fish is the highest in autumn, while the Shannon-Wiener index （H'） is the lowest. The Pielou index （J'） does not change much throughout the year, and the peak value appears in winter. Cluster analysis showed that the fish community in the coastal waters of Fujian can be clearly divided into two types of fish communities： northern coastal and southern coastal fish communities, and there are significant differences in community species composition among different regions in each season. Quantitative biomass curves showed that fish communities are moderately disturbed in spring and severely disturbed in summer, autumn, and winter.

Abstract:The offshore waters of southern Zhejiang serve as an important fishing ground in China, where Pennahia argentata is a common economic fish species. This study explores the habitat of P. argentata in the offshore waters of southern Zhejiang in order to reveal the environmental changes during its individual development. The experiment is based on the otolith samples of P. argentata in this area, and ICP-MS technology is used to measure the Sr and Ca elements in the otolith microstructure. By analyzing the Sr/Ca ratio, it is found that the range of environmental changes for P. argentata habitat is between 3.39×10^-3 and 8.12×10^-3, indicating the existence of two habitat types： freshwater and brackish water settlement, and brackish-freshwater and seawater mix. In addition, Sr element has been proven to be an effective tracer of the fish habitat history. This discovery not only enriches our understanding of the ecological habits of P. argentata, but also provides a new, feasible, and accurate method and approach for studying the migration routes of P. argentata.

Abstract:The Eastern Pacific Equatorial region is an important fishing ground for China, and there is a close relationship between mesoscale eddies and the distribution of fishing grounds. In this study, a vector geometry method based on flow field was used to identify mesoscale eddies in the Eastern Pacific Equatorial region （85°W-125°W, 5°S-5°N） using 2012-2018 meteorological satellite remote sensing data and filtering out vortices with a lifespan longer than one week. The spatial distribution, radius range, lifecycle, migration path, and velocity of mesoscale eddies in this region were analyzed. The relationship between the eddy and the fishing ground distribution was also discussed. The results showed that the number of anticyclonic eddies in the Eastern Pacific Equatorial region was greater than that of cyclonic eddies. The eddy lifecycle was relatively short, with the majority lasting no more than one week. The eddy radius was mainly concentrated in the range of 250-310 km, and the migration velocity was mainly concentrated at 6-18 m/s, with a migration distance of 25-50 km. There were two regions, called as "tropical regions," near the 5°N and 5°S, which exhibited more frequent eddy activity, while near the equator, there were almost no eddies present. Additionally, some characteristics of the eddies （period and radius） showed obvious interannual variations. These findings provide a basis for analysis of fishing ground formation, temporal and spatial distribution, and the development of fishing forecasts in the Eastern Pacific Equatorial region.

Abstract:This paper outlines the principal challenges confronting fisheries resources and their management in the South China Sea through summarizing resource characteristics in each fisheries zone.It is evident that the South China Sea stands as China's most productive sea in terms of fisheries resources. Nevertheless, economically significant species in the northern fisheries zone are currently facing a critical issue of resource over-exploitation. Conversely, there is substantial development potential in the outer sea. In the South China Sea's current fisheries management, the fishing moratorium system has restored major economic species before reopening. Yet, its impact is limited, necessitating additional research and survey data to conclusively assess its effectiveness. Future studies are imperative for a comprehensive evaluation of the moratorium system's ability to sustain fisheries resource rehabilitation.The management and conservation of fishery resources face substantial challenges due to human activities, climate warming, ocean acidification, reliance on outdated stock assessment methods, etc. Achieving sustainable use of fishery resources in the South China Sea is of great significance, and this can be accomplished through developing reasonable measures for the conservation and management of fishery resources, conducting comprehensive resource surveys, and employing appropriate methods for stock assessment.

Abstract:Marine fish culture industry in China, as the pillar industry of aquaculture, has contributed to the optimization of China's aquaculture. However, the development of this industry is limited by a wide range of environmental concerns, resulting from the ecological impacts of aquaculture inputs and resources. In order to achieve sustainable social-economic-environmental development under the Greater Food Approach, marine fish culture industry is promoting green development and industrial transformation and upgrading. Green development efficiency （GDE） is an important criterion for measuring the level of green development. It considers not only economic development efficiency but also environmental costs. Therefore, this study focused on the key scientific issue of the key factors affecting the GDE of marine fish culture industry. This paper established an evaluation index system and used the super-slack-based measure model （Super-SBM） to evaluate the GDE of marine fish culture industry. Tobit model was constructed to analyze the factors affecting the GDE of marine fish culture industry. The results showed that the GDE of marine fish culture industry was in an inefficient state with the GDE of 0.8868, 0.9687, 0.7344 from 2017 to 2019. Trachinotusovatus and Rachycentroncanadum were the two culture species in an efficient state from 2017 to 2019, Larimichthyscrocea was in an efficient state in 2018, and Scophthalmus maximus was in an efficient state in 2019. Other marine fish culture species were in an inefficient state from 2017 to 2019. With the Tobit model, the influence factors of the green technology level, the scale proportions of green modes and the market price had significant positive effects on the GDE, while the influence factor of the policy support had insignificant positive effects on the GDE. The results of this paper present suggestions to improve the GDE of marine fish culture industry in China and provide valuable insights for improving the GDE of marine fish culture industry.

Abstract:Estimating the potential productivity of aquaculture is of great significance for ensuring food safety, but the traditional fishery statistics cannot reflect the dynamic change of the productivity of China's aquaculture. Based on the two measurement programs of agricultural production capacity, the paper put forward an innovative comprehensive measurement scheme, measuring the achievable capacity of aquaculture by production modes, by provinces and by regions.As shown in the research, the calculation scheme proposed in this paper can be popularized nationwide and applied to the calculation of aquaculture capacity in different provinces, prefectures and counties. Large-scale investigation is an important work in the next step. The achievable capacity of Chinese aquaculture is 73 million tons. The decrease of aquaculture area has brought great negative impact on the productivity of aquaculture, and the increase of yield per unit makes great contribution to the productivity. Guizhou and Yunnan provinces in the southwest, Jilin and Heilongjiang provinces in the northeast have the greatest potential to expand production capacity in the future. Stabilizing the aquaculture area and improving the unit yield level are two ways to improve fishery production capacity. Improving the unit yield level of marine water aquaculture would have a more important role in improving the production capacity of large water aquaculture.