Abstract:In this study, we conducted association analysis between microsatellite markers and growth traits such as body weight, total length, body length, body height, body thickness, head length, snout length, caudal stalk height and caudal length in the F₃ population of pikeperch (Sander lucioperca), the fast-growing strain, to identify markers for genetic breeding. The average allele number for each marker was 4.5. The average observed heterozygosity at 0.746 (ranging from 0.520 to 0.954), with expected heterozygosity recorded at 0.691 (with a range of 0.441 to 0.851). The average polymorphism information content was 0.641. The results showed that 38 microsatellite markers had significant association with at least one trait (P<0.05), among which 21 markers, such as HLJSL018, HLJSL021 and HLJSL022, had extremely significant association with the corresponding trait (P<0.01). Specifically, we detected several 2-21 significant microsatellite markers for 9 traits, ranging from 2 to 21, of which only two markers (HLJSL039 and HLJSL042) were identified for body length (P<0.05)； but there are 21 markers significantly associated with the height of the tail stalk, among which 11 markers such as HLJSL018, HLJSL021, and HLJSL022 are highly significant (P<0.01). There are 8 markers significantly associated with body mass, of which HLJSL018 and HLJSL067 are highly significant (P<0.01). A total of 195 dominant genotypes, with a proportion of over 5% higher than the overall mean, were obtained in 38 markers. Each marker obtained 1-10 dominant genotypes, among which HLJSL073 obtained the least dominant genotypes and HLJSL079 obtained the most dominant genotypes. In summary, we assessed the genetic structure of the pikeperch breeding population and identified markers closely associated with growth traits, which can inform the genetic selection of pikeperch.

Abstract:To investigate the effects of water flow on fish body color, the number of melanophore and gene expression in zebrafish skin were investigated under water flow culture with two different flow rates 0.010 m/s (low flow rate) and 0.022 m/s (high flow rate). The results showed that compared with low flow rate, the number of skin melanophore increased significantly after 3 months of culturing zebrafish under higher flow rate, especially in the caudal region of the body of the fish, the expression levels of the skin melanophore marker genes kita, mitfa and tyrp1a were significantly increased as well. Meanwhile, the relative expression level of the xanthophore marker gene csf1ra was significantly decreased, and there was no significant change in the iridophore marker gene pnp4a, indicating that the high flow rate water induced the formation of melanophore and inhibited the formation of xanthophore. The RT-qPCR results showed that the expression of melanophore formation inhibitor gene asip1 was significantly decreased in the skin of zebrafish in the high-flow group compared with that in the low-flow group； the melanocortin receptor gene mc1r and the amelanocortinogen gene pomca, which are related to melanophore formation, were not significantly changed； and the retinoid dehydrogenase genes raldh2 and raldh3, which are related to retinoic acid synthesis, were significantly down-regulated； water flow stimulation upregulated the transient receptor channel protein gene trpv4 and the piezoelectric mechanosensitive channel protein gene piezo2, whereas there was no significant change in piezo1. The above results indicate that the high flow rate water flow induces melanophore formation in zebrafish, possibly as a result of reduced asip1 expression mediated by water flow stimulation through the skin mechanosensitive proteins Trpv4 and Piezo2. Asip1 regulates fat accumulation in addition to melanophore formation, and indeed zebrafish body fullness reduces significantly in the high water flow group compared with low flow rate group. GO enrichment analysiss showed differentially expressed genes was mainly enriched to entries for triglyceride catabolism, HDL particles, lipid binding, etc and differentially expressed genes was significantly enriched in the following KEGG pathways： aminoglycan and nucleotide sugar metabolism, PPAR signaling pathway, linoleic acid metabolism, and arachidonic acid metabolism, etc. RT-qPCR showed the fatty acid peroxidase 2 gene fads2, which is associated with lipid metabolism, was significantly up-regulated, and there was no significant difference in the leptin gene lep, indicating that water flow may affect fat degradation through Asip1 affecting Fads2. In conclusion, this study for the first time reported the effect of water flow on fish body color and proposed a preliminary signaling regulatory pathway, which provides a preliminary theoretical basis for understanding the effect of water flow culture on fish body color and fullness.

Abstract:L-amino acid oxidase (LAAO) is a kind of immune protease widely found in nature. In order to explore the gene sequence characteristics of LAAO (PmLAAO) and its expression changes after stimulation by Vibrio parahaemolyticus, the full-length cDNA of PmLAAO was cloned in this study. The length of its open reading frame (ORF) is 1767 bp, encoding a total of 588 amino acids, and has the structure domain of FAD-binding domain and amino acid oxidase (Amino_oxidase), which is a member of the amino acid oxidase family. The results of multiple sequence comparisons and phylogenetic trees showed that PmLAAO was closely related to bicrustacea, among which LAAO was the most similar to the Mytilus californianus. qRT-PCR results showed that PmLAAO was expressed in gill, mantle, adductor muscle, gonadal gland and digestive gland, with the highest expression level in gill tissue. After stimulation by Vp, the expression level of PmLAAO in gill tissue was significantly increased, and the expression level was the highest 48 h after stimulation. These results provide a reference for the functional activity of the novel immune protease LAAO in bivalve shellfish.

Abstract:In order to explore the effects of NaHCO₃ stress on antioxidant enzymes and tissue structure of gill and hepatopancreas of grass carp, three NaHCO₃ concentration groups (10, 20, 30 mmol/L) were used to stress grass carp with NaHCO₃, and the antioxidant enzymes (SOD, CAT) activity and histopathological observation of gill and hepatopancreas were carried out. The results showed that under NaHCO₃ stress, the activities of SOD and CAT in gill and CAT in hepatopancreas of grass carp increased first and then decreased within 72 h, and only the activity of SOD in hepatopancreas increased within 72 h. In each experimental group, the activities of antioxidant enzymes in the two tissues were significantly different from those in the blank group. Compared with the blank group, in the gill tissue of grass carp in the experimental group, the gill filaments were seriously folded and wrinkled, the PVC of the flat epithelial cells was seriously exfoliated, and the MRC of the mitochondria-enriched cells was swollen ； in the hepatopancreas, the swelling of the pancreatic cells, the increase of the intercellular space, the deviation of the hepatocyte nucleus and the decrease of the vacuolization were observed. Studies have shown that NaHCO₃ stress can affect the antioxidant level of grass carp and cause tissue damage to the gills and hepatopancreas of grass carp, and the degree of damage increases with the increase of concentration. This study could provide reference for the breeding and application of grass carp in saline-alkali waters.

Abstract:In order to study the effects of calcium lactate to water on the growth, molt, and calcium deposition of juvenile Chinese mitten crab (Eriocheir sinensis), this study conducted a 90-day (two complete molting cycles) rearing experiment on female juvenile crabs with an initial body mass of (4.78±0.51) g. Calcium lactate was added to freshwater at concentrations of 0 mg/L, 218 mg/L, 436 mg/L and 654 mg/L and the calcium ion content in water is 45.6 mg/L, 84.4 mg/L, 123.2 mg/L and 163.6 mg/L.(recorded as Treatment 1# to 4#). The results showed： (1) The addition of calcium lactate improved survival rates of juvenile E. sinensis significantly. (2) With the increase in calcium lactate content, there was an upward trend of body mass, weight gain rate, specific growth rate, and hepatopancreas index of juvenile E. sinensis during the first molting cycle, but the differences were not significant. However, during the second molting cycle, the body weight, carapace length and carapace width growth rates of juvenile E. sinensis significantly increased with the calcium lactate addition, and among them, treatment 3# and 4# were significantly higher than treatment 1#. (3) The addition of calcium lactate had no significant effect on the intermolt duration but significantly reduced the rate of limb loss after each molting. (4) In terms of calcium deposition, the addition of calcium lactate significantly increased the calcium content in hemolymph during the first and second molting cycles, as well as calcium content in the muscle during the first molting cycle. (5) Increasing calcium lactate content significantly elevated the expression of es EcR2- mRNA and es RXR- mRNA. (6) Calcium lactate had no significant effect on water pH, ammonia nitrogen and nitrite, but water hardness and alkalinity significantly rose with increasing calcium lactate content. In summary, the addition of 654 mg/L calcium lactate to the water improved the survival, growth performance, calcium deposition in tissues, and expression of molting-related genes in juvenile E. sinensis, as well as reduced the limb loss rate after each molting.

Abstract:In order to study the optimal low salt acclimation method of Sinonovacula contricta, the low salt semi-lethal salinity was set by 5 gradients of salinity 0, 1, 2, 3 and 5, and the low salt semi-lethal salinity was 2.005 at 96 h. With this salinity as the target salinity, three different domestication methods A, B and C were set (Group A： equal-velocity domestication； Group B： alternate domestication； Group C： gradient acclimation). The S. constricta were acclimated with low salinity from 16 to 2, and then acclimated to the target salinity for 4 days. The survival rate and submerged sludge rate of three acclimation methods were recorded. Oxygen consumption rate and ammonia emission rate of each group were detected. Superoxide dismutase (SOD) activity and Malondialdehyde (MDA) content were determined. The results showed that the survival rate (88%) and submerged mud rate (90%) of S. constricta in group C were significantly higher than those in groups A and B when acclimated to salinity 2. The oxygen consumption rate and ammonia emission rate of group C were significantly higher than those of groups A and B. Superoxide dismutase (SOD) activity reached its peak at salinity 4, and group C was significantly higher than groups A and B. Malondialdehyde (MDA) content reached its peak when acclimated to salinity 2, and was significantly lower in group C than in groups A and B. In conclusion, the low salt acclimation method of gradient acclimation (C) group is more beneficial to low salt culture of S. constricta. The results of this study provide an important reference for the development of Marine shellfish aquaculture species in China's inland low-salt waters.

Abstract:Intestinal microbiota plays a crucial role in the nutritional metabolism and immune functions of animals. In order to investigate the impact of two cultivation modes, namely grass-based shrimp farming and paddy field shrimp farming, on the intestinal microbiota and muscle flavor of Macrobrachium rosenbergii, this experiment focused on specimens raised in different cultivation areas with the same breeding cycle. The specimens were categorized into a grass-based cultivation group (Grass Group) and a paddy field cultivation group (Paddy Group). The study conducted analyses on the structure of intestinal microbiota, muscle amino acids, and trace elements in the muscle content. Firstly, at the phylum level classification of shrimp intestinal microbiota, Firmicutes, Proteobacteria, and Tenericutes were identified as dominant phyla under both cultivation modes (with a relative abundance > 5%). Additionally, Cyanobacteria and Bacteroidetes were identified as specific dominant phyla in the Grass Group. At the genus level classification, Lactococcus, Enterobacter, and Candidatus_Hepatoplasma were identified as dominant genera in both groups. Secondly, in terms of microbiota diversity analysis, the number of operational taxonomic units (OTUs) in the Paddy Group was significantly higher than that in the Grass Group, indicating a higher species diversity of intestinal microbiota in Macrobrachium rosenbergii under paddy field cultivation. The functional prediction of the intestinal microbiota revealed that the functions in both cultivation modes were mainly concentrated in metabolic regulation pathways. Finally, in the analysis of nutritional components and the evaluation of muscle flavor, it was proved that there was no significant difference in the total contents of umami amino acids and sweet amino acids between them. However, the Paddy Group exhibited significantly higher levels of serine, glycine, and arginine in the muscle compared to the Grass Group. The iron content in the muscle of Macrobrachium rosenbergii under paddy field cultivation was significantly higher, while copper and zinc content were significantly lower compared to the Grass Group. There were no significant differences in the content of other mineral elements. In conclusion, Macrobrachium rosenbergii under paddy field cultivation exhibited superior muscle flavor and a more diverse intestinal microbiota. The results of this study can provide technical references and guidance for different health cultivation modes of Macrobrachium rosenbergii.

Abstract:To evaluate the effects of dietary pancreatin on growth performance, biochemical indexes, and enterohepatic structure of juvenile largemouth bass (Micropterus salmoides), specimens with of the initial body quality of (8.00±0.50) g, 630 were randomly divided into 6 groups, each group of three repetition, 35 fishes each repetition. The control group was fed with a basic diet, and 5 experimental groups were fed with pancreatin-added diet of different concentrations of pancreatin (P250, P500, P750, P1000, P1250). The experimental period was 70 days. The results show that： The growth performance of fish first increased and then decreased with the increase of pancreatin dosage. The final average weight, weight gain rate and specific growth rate of fish in P750 group were the highest, and the feed ratio was the lowest, which were significantly different from the control group. Compared with the control group, the contents of serum total protein and albumin increased, which were the highest in P500 group and P750 group, respectively. The contents of serum triglyceride and total cholesterol in the P500 and P750 groups decreased significantly. The activities of aspartate aminotransferase (AST) and alanine aminotransferase (ALT) first decreased and then increased with the increasing amount of trypsin added. In the P750 group, the activity of AST was the lowest, and the activity of alkaline phosphatase was the highest. Compared with the control group, the P500 and P750 groups had a significant reduction in lipid vacuolization area and a significant increase in villus width； Fluff number increased significantly in the P500 group. In conclusion, dietary pancreatin could significantly improve the growth performance, biochemical indexes, liver antioxidant and enterohepatic structure of largemouth bass, and there was a dose effect of pancreatin. Based on the comprehensive analysis and the index of weight gain rate, it is suggested that the appropriate amount of pancreatin in the diet of largemouth bass is 679 mg/kg.

Abstract:In order to understand the species composition and diversity characteristics of the main fish communities in Dianshan Lake, environmental DNA technology was used to analyze the species diversity of fish in Dianshan Lake. The results showed that a total of 7 orders, 12 families, 36 genera and 43 species of fish were detected in the environmental DNA samples from 10 stations in Dianshan Lake, of which 24 species were detected in June (summer) and 32 species were detected in November (autumn). Most of the species were found in the traditional fishery resources investigation of Dianshan Lake. Among them, Coilia nasus, Carassius auratus, Acheilognathus macropterus, Culter alburnus and Mugil cephalus were the main species. The α diversity analysis showed that the average values of Chao 1 index, Observed species index, Shannon diversity index, Simpson index and Pielou evenness index in Dianshan Lake in autumn were higher than those in summer. The analysis of fish species difference among sites showed that the sites with higher diversity and richness were S1, S2, S3 and S5, which were all sites with higher primary productivity and less human disturbance. The results show that the environmental DNA technique is highly sensitive and can be used as an effective supplementary method for the survey of fish species diversity in Dianshan Lake.

Abstract:The intermuscular bones of fish are closely related to their locomotion； the more athletic the fish is, the greater the number of intermuscular bones and the relatively higher the muscle fat content. In order to investigate whether C. brachygnathus exists migratory ecological taxa in Poyang Lake, samples of C. brachygnathus were collected from different sampling sites of Poyang Lake, such as Qianyanqiao. In addition, samples of C. nasus from Zhoushan Shengsi and Qingcaosha Reservoir at the mouth of the Yangtze River were collected in order to investigate the effect of migration on the formation of intermuscular bones of C. nasus. The morphology, number and muscle protein and fat content of medullary arch ossicles and pulse arch ossicles were compared by anatomical method and conventional measurement method. The results showed that： (1) The number of intermuscular bones of C. brachygnathus was the least in the Poyang Lake which was 100.67±6.34； The number of intermuscular bones in Qianyanqiao was the largest which was 127.67±6.18. (2)The intermuscular bone number of C.nasus in Poyang Lake was 129.60±0.98 which was significantly higher than C. brachygnathus of 110.60±2.97. (3) The number of Poyanghu intermuscular bones of the same species was significantly higher than that of 113.67±3.29 intermuscular bones of the Qingcaosha but lower than that of 147.67±3.09 intermuscular bones of Shengsi ； (4) The protein content of muscle in the C.nasus in Poyang Lake was lower than that of the C. brachygnathus, and the fat content was higher than that of the C.brachygnathus. Suggesting that the C.nasus need to oscillate more in order to fulfil the needs of long-distance migration and to stimulate more intermuscular spine formation. These results are important for the understanding of the difference in the origin of the migratory populations of C. nasus and C. brachygnathus in Poyang Lake, and lay the foundation for the further research on the biology of the migratory populations in Poyang Lake.

Abstract:The dynamic changes of phytoplankton community and its relationship with major environmental factors are important for understanding the changes of lake and reservoir water environment and carrying out water environmental quality assessment. In this study, a monthly survey of phytoplankton and water environmental factors in Qiandao Lake was conducted from 2021 to 2022, and the characteristics of phytoplankton community structure, spatial and temporal distribution pattern and main environmental driving factors were analyzed, in order to provide important basic data for understanding the latest water environment changes and ecosystem evolution in Qiandao Lake. The results showed that a total of 240 species belonging to 8 phyla were identified, with Chlorophyta (51.67%), Bacillariophyta (21.67%) and Cyanophyta (17.84%) as the main species, and Cyanophyta and Bacillariophyta as the main dominant species. The average annual biological density from 2021 to 2022 was (404.21±116.59)×10⁴ cells/L, and the average annual biomass was (0.84±0.22) mg/L, showing significant spatio-temporal differences in both biological density and biomass. Cyanophyta had the highest biological density and biomass of phytoplankton. Shannon diversity index showed significant seasonal differences, but no significant spatial differences, and there was no spatio-temporal difference in other indices. Spearman correlation analysis showed that phytoplankton density and biomass were significantly positively correlated with water temperature, ammonia nitrogen and permanganate index, and negatively correlated with transparency. RDA analysis showed that water temperature, ammonia nitrogen and nitrite were the main environmental factors affecting the distribution of phytoplankton dominant species in Qiandao Lake.

Abstract:The Shennongjia Forestry District (Shennongjia) located in the northwestern region of Hubei Province, serves as the watershed between the upper and middle Chang-Jiang basin. Due to the unique natural environment and well-developed river networks, Shennongjia harbors a relatively high species diversity of freshwater fish, thus making it one of the hotspots areas of biodiversity research in China. However, there is still a lack of essential understanding of the fish diversity in this region. An updated checklist of fishes in the Shennongjia is provided, based on the results of the field survey conducted from 2021 to 2022 and combined with historical records of fish diversity in this district and the latest taxonomic progress of relevant taxa in the known literature.This updated checklist includes a total of 52 species, 44 of which are native and eight alien. The Cypriniformes dominates the fish fauna of Shennongjia. Two families of Cyprinidae and Xenocyprididae have the highest number of species. There are six newly recorded species, three previously undescribed species, and 12 species undergoing nomenclatural changes. Eight historically recorded species are excluded from this list, but 27 historically recorded species uncollected during this field survey are remained.The updated checklist presented here can serve as a fundamental reference for future biodiversity analyses and the biodiversity conservation of Shennongjia.

Abstract:Zooplankton are important food organism in the marine ecosystem, and its community structure and population distribution reflect the productivity of the waters. In order to understand the interspecific relationship of the zooplankton community and the impact of changes in environmental factors on the niche differentiation of dominant species in the Bailanzi waters, basing on the zooplankton survey data in March and December of 2022 and June of 2023, we obtained the dominance index of zooplankton in this sea area through calculating the Levins niche width value and Pianka niche overlap value of the dominant species, and divided the niche types of the dominant species into broad niche species, medium niche species and narrow niche species. The redundancy analysis method was used to explore the main environmental factors affecting the niche differentiation of dominant species of zooplankton in Bailanzi waters. The results showed that there were 9 dominant species and all of them were wide ecological niche species in March 2022, 5 dominant species and all of them were wide ecological niche species in December 2022, and 6 dominant species, including 3 wide ecological niche species and 3 narrow ecological niche species, in June 2023. The niche overlap indexes of the dominant zooplankton species in March 2022 ranged from 0.54 to 1.00, and those in December 2022 ranged from 0.60-0.98 in March 2022, 0.62-0.99 in December 2022, and 0.62-0.99 in June 2023. Redundancy analysis showed that the main environmental factors affecting zooplankton distribution are temperature and salinity, followed by pH, dissolved oxygen (DO), ammonia nitrogen (NH₃-N), dissolved inorganic phosphorus (DIP), dissolved inorganic nitrogen (DIN), chemical oxygen demand (COD). The research results are expected to provide basic information for an in-depth understanding of the interspecific relationships of zooplankton communities in Bailanzi waters and the adaptation mechanism of zooplankton to environmental changes, and provide a theoretical reference for high-quality marine ranch construction in this waters.

Abstract:Phytoplankton samples were collected both inside and outside a large scale raft mussel culture area of Gouqi island in September 2023. The diurnal variation characteristics of phytoplankton community inside and outside the culture area were analyzed by using abundance and diversity index and multivariate statistical methods. A total of 7 phyla and 158 species of phytoplankton were collected(103 species inside and 98 species outside the area), including 104 species of diatom(accounting for 65.82%), 30 species of Pyrrophyta(accounting for 18.99%), and 15.19% for the rest species. During the daytime, 94 species were collected in the inner area, while 103 species were collected at night. In the outer area, 93 species were collected during the daytime, and 98 species were collected at night. The dominant species of phytoplankton in the aquaculture area were 9 species, while in the outer area, there were 12 dominant species. Among them, Skeletonema costatum and Noctiluca scintillans were dominant species throughout the day in both areas. The average abundance of phytoplankton in the inner area was (1.77×10⁷±2.5×10⁶) cells/L during the daytime and (1.64×10⁷±2.31×10⁶) cells/L at night, while in the outer area, it was (1.87×10⁷±3.36×10⁶) cells/L during the daytime and (1.75×10⁷±2.72×10⁶) cells/L at night. The abundance variation in the inner area showed a multi-peak pattern, with peak values occurring during the rising and falling tides and the high tide. In contrast, the abundance variation in the outer area showed a single-peak pattern, closely related to tidal changes, with the peak value only occurring during the high tide.Non-metric multidimensional scaling (nMDS) analysis showed that there was no significant difference in phytoplankton community between day and night in the aquaculture area (P>0.05), but there was significant difference in phytoplankton community outside the area (P<0.05), which was significantly correlated with tidal changes (P<0.01). Temperature, dissolved oxygen and salinity were significantly correlated with the number and abundance of phytoplankton (P<0.05), the number of phytoplankton species was significantly negatively correlated with phosphate and nitrate (P<0.05), and the abundance was significantly positively correlated with ammonia nitrogen and silicate (P<0.05). The results showed that the impact of large-scale raft culture on phytoplankton community in local waters could present a more positive result at the stage of red tide organism aggregation.

Abstract:In order to understand the community structure and distribution characteristics of macrobenthic shellfish in the coastal waters of Zhejiang, the fixed-point bottom trawl fishery resources survey was conducted from August 2020 to April 2021. The surveyed sea was divided into two areas, the northern and the southern part in Zhejiang, with 29°N as the boundary. A total of 41 species of shellfish belonging to 25 genera, 25 families and 6 orders were collected and identified. The absolute dominant species in all seasons were Bursa rana and Turritella terebra bacillum. There were obvious regional differences in number of species and shellfish biomass distribution in the north and the south areas during different seasons. The shellfish biomass for spring and autumn was higher than that for summer and winter, and it decreased from the north to south area in other seasons except summer. In summer, differences in the average biomass of shellfish were not found in the north region and the south areas. In terms of diversity analysis, The richness index (D) and the diversity index (H') were the highest in spring and the lowest in summer, and the evenness index (J') was the highest in winter and the lowest in spring. Hierarchical Cluster analysis (Cluster) results showed that the shellfish communities were divided into 3 groups at 60% similarity level in Zhejiang coastal waters. Group Ⅰ was in the southern area in spring, summer and autumn, Group Ⅱ was in the northern area in spring, summer and autumn, and Group Ⅲ was the whole area in the winter, and there were differences in the north and the south areas in spring, summer and autumn. The stress value of non-metric multidimensional analysis was 0.08, which had explanatory significance. CCA analysis showed that depth and bottom sea temperature had significant effects on benthic shellfish distribution. This study can provide some reference for shellfish biodiversity conservation and sustainable use for shellfish resources in the coastal waters of Zhejiang.

Abstract:As an important part of the marine ecosystem, the oceanic waters have unique biodiversity and rich fishery resources. Therefore, efficient and accurate detection of the oceanic fish diversity is an important prerequisite for the utilization and management of fishery resources. However, traditional capture-based survey methods have certain limitations. eDNA technology can be used as an important supplement to traditional survey methods due to its characteristics and advantages such as wider application scenarios, more prominent cost effectiveness, higher detection sensitivity, finer species resolution, and lower taxonomic order bias. It has a broad application prospect in the far-reaching oceanic fish diversity monitoring and fishery resource survey. This paper summarizes the current status of eDNA in the study of fish diversity and its application advantages and challenges in the study of oceanic marine fish diversity. Meanwhile, combined with the environmental characteristics of oceanic waters, we further discuss the application potential of eDNA in the study of fish diversity in the oceanic waters and possible challenges.The relevant content can provide a systematic scientific reference for further research in the future.

Abstract:This study determined the particle release area based on the abundance data of largehead hairtail eggs obtained from the ichthyoplankton surveys in the coastal waters of the southern Yellow Sea (119°E-124°E, 33°N-37°N) conducted from 2018 to 2022. Subsequently, the Finite-volume Coastal Ocean Model (FVCOM) coupled with the Lagrangian particle tracking algorithm was employed to simulate the transport process of largehead hairtail larvae. The primary objectives were to investigate the spawning periods, spawning grounds, and nursery habitats of largehead hairtail in the southern Yellow Sea, and to assess the influence of oceanic conditions on the egg distribution and larval dispersion. The results indicated that largehead hairtail spawned in spring and summer in the southern Yellow Sea with the eggs appeared in May, July and August, and August was the peak spawning month. Largehead hairtail eggs were mainly distributed in 19-30 m waters in May, and 11-70 m waters in August. The sea surface temperature and sea bottom temperature for the presence of largehead hairtail eggs was 13.9-29.7 and 8.4-28.3 ℃ respectively. The Random Forest model analysis revealed that water temperature and depth were the main environmental factors affecting the abundance of largehead hairtail eggs. Particle tracking simulation experiments showed that the particles released in May mainly spread towards the northwest coastal area of the particle release area after 1-15 days (when the swim bladder has not formed and the larvae have no vertical migration behavior), and after 16-40 days(when the swim bladder has formed and the larvae have vertical migration behavior), the particles left the coastal area and spread eastward to the waters near a 50 m water depth. In July and August, before the occurrence of vertical migration behavior, larvae stayed in the near-bottom layer and most of them were transported from the release area to the nearshore waters； After that, larvae moved slightly from the near-shore aggregation area to the off-shore direction. Some of the individuals released in the offshore deep-water areas spread to the north and northeast in a short-distance, and the dispersal pattern did not change significantly in their whole larval stages. Aggregation areas of largehead hairtail larvae derived from field surveys in August were consistent with the results of particle transport simulation experiments. We thought that the season and spatial location of spawning, the diel vertical migration characteristics of larval fish, and the regional upwelling and frontal structure were the dominant factors that shape the transport pattern of largehead hairtail larvae. The results of the study provide a scientific basis for understanding the habitat selection mechanism of egg and larvae stages and early replenishment dynamics of this fish in the southern Yellow Sea, and help for the management and protection of largehead hairtail resources.

Abstract:By adopting FVCOM-simulated 3-D physical field and based on the biological processes of chub mackerel (Scomber japonicus) in its early life history from the individual-based biological model,the individual-based ecological model for chub mackerel at its early transport dynamics in the Yellow Sea was constructed through coupling the physical field from April to August with the biological model by the method of Lagrange particle tracking.The results showed that the model can accurately simulate the transport path、density and retention distribution of eggs and larvae of chub mackerel in the spawning ground in Qingdao Shidao offshore in the Yellow Sea.The study found that under average climate conditions, chub mackerelin the spawning ground in Qingdao Shidao offshore was overall transported to the southern part of Shandong Peninsula after spawning, eggs and larvae of chub mackerel were finally distributed in the range of 32°N-37°N and 121°E-124°E,and had a large distribution in the waters of the provisional measures of the China-Korea Fisheries Agreement(hereinafter referred to as the waters of the Agreement). Since spawning in April, some eggs and larvae of chub mackerel have begun to enter the waters of the Agreement, and from July to August, 50% of the super-individuals have entered the 40-80 m isobath in the waters of the Agreement and have been stranded for more than 300 hours, illustrating the spawning ground in Qingdao Shidao offshore contributes significantly to the replenishment of chub mackerel resources in the waters of the Agreement.The biopatch density and retention area of eggs and larvae of chub mackerel were mainly concentrated in the sea area of 33.5°N-37.5°N and 121°E-124.5°E, and this sea area was determined to be the main fattening ground for larvae of chub mackerel in the Yellow Sea, and 3/5 of the fattening ground was in the waters of the Agreement, indicating that the physical environment of the waters of the Agreement had a great impact on the replenishment of chub mackerel resources in the spawning ground in Qingdao Shidao offshore. There were obvious differences in the transport distribution of eggs and larvae of chub mackerel in different years, and the main dynamic reason for the interannual difference in the transport distribution of chub mackerel in the Yellow Sea is the location of the cold center of the Yellow Sea Cold Water Mass.

Abstract:The Scotia Sea is the most densely distributed area of Antarctic krill (Euphausia superba) resources, and is also the traditional fishing ground for krill fishery, but population structure of krill is complex and varies widely in this region. It plays the key role of females in the population for stabling structure and maintaining size of population. In order to understand the population dynamics of krill in this region, the temporal and spatial variability in female stock of krill resource in this region was analyzed using samples randomly collected by fishery surveys from January to September, 2016 to 2022.The results showed that there were significant differences in the development stages of krill annually. During 2016-2022, female krill stock was mainly dominated by subadults, followed by adults, and the proportion of juveniles was low. For the perspective of the annual variation of sexual maturity, the proportions of subadults(stages 2FC and 2FD) were generally higher than that of stage 2FB individuals.In terms of seasons, the female stock structure was relatively simple in winter and spring, while that was very complex in summer and autumn, the subadults was predominant in the stock. In addition, the structure of female krill stock was different between regions, the proportion of adults in the South Orkney Islands was the highest (65.4%), while the subadults was predominant in the stock (89.9%) and no juveniles occurred at South Georgia.

Abstract:Tuna is rich in protein and polyunsaturated fatty acids and is a major deep-sea commercial food fish. It is frozen and preserved immediately after catching to reduce its nutrient loss and quality degradation. Therefore, to improve the edible quality of tuna, the thawing process of frozen tuna has become a key technology affecting the development of the tuna industry. To investigate the effects of different thawing methods on the quality of tuna, a comparative study of three thawing methods (salt-water thawing, ST； refrigerated thawing, RT； and low-voltage electrostatic field thawing, LV) in terms of water-holding, color, texture, antioxidant properties, freshness, and microstructure was carried out in this paper. The results showed that the thawing method significantly affected the quality of tuna. The ST group could better maintain the water holding capacity (79.878%±3.913%) and freshness [(8.750±0.495) mg/100 g] of tuna meat and effectively reduce the thawing time. However, the ST group had higher levels of oxidation and microstructural damage. The RT group was significantly better than the ST group regarding color, texture, and oxidation inhibition； however, the RT group had a high thawing loss rate and poor freshness. Compared with the other two thawing methods, the LV group can better maintain the color, texture, freshness [(8.367±0.404) mg/100 g], and water-holding capacity (77.827%±0.215%) of the tuna meat, and it can effectively inhibit the oxidation of lipids and proteins during the thawing process of tuna. At the same time, the LV group showed the smallest damage to the microstructure. In conclusion, low-voltage electrostatic field thawing can maintain tuna meat quality better. This paper provides the theoretical basis and practical exploration for improving the thawing quality of frozen fish products.

Abstract:Graphene oxide (GO) membranes have good separation performance, but their low water flux and poor stability need further improvement.For this reason, this paper employs a hydrothermal method to prepare reduced graphene oxide (RGO), and utilizes silicon dioxide (SiO₂) to intercalate RGO, and then prepares RGO/SiO₂ composite membranes by vacuum filtration.The results show that SiO₂ intercalation further improves the water flux without loss of rejection and stability.When SiO2 (0.05 mg/mL) is 3 mL, the pure water flux of the RGO/SiO₂ composite membrane is as high as 21.1 L/(m²·h·bar) which is about 6 times of that of the pure GO membrane, and the retention rate of Na₂SO₄ is about 83.7%.The order of rejection for different salts was R(Na₂SO₄) > R(MgSO₄) > R(NaCl) > R(MgCl₂). Therefore, the RGO/SiO₂ composite membrane has a certain potential for application in desalination.