In this study, we used stable isotope technology to analyze different species (fish, crustaceans, cephalopods, benthos, etc.) collected in spring, summer and autumn in the coastal waters of Jiangsu Province. We used SIBER model to calculate the trophic niche of consumers, and calculated the quantitative indicators of six metrics in different seasons. The results showed that there were no significant differences in δ¹³C and nitrogen δ¹⁵N values among three seasons (p>0.05). In spring, the δ¹³C values ranged from −24.47‰ to −14.50‰, the δ¹⁵N values ranged from 6.86‰ to (14.98±0.49)‰, and the trophic level ranged from 1.52 to 4.28±0.17. In summer, the δ¹³C values ranged from −19.86‰ to −14.44‰, the δ¹⁵N values ranged from 5.79‰ to (12.54±3.50)‰, and the trophic level ranged from 1.25 to 3.52. In autumn, the δ¹³C values ranged from (−22.17±4.90)‰ to (−14.21±0.36)‰, the δ¹⁵N values ranged from 6.30‰ to (14.60±0.51)‰, and the trophic level ranged from 1.34 to 4.15±0.14. The structure of food web was stable in each season, and the trophic niche of some species overlaps in different degrees. In addition, the food sources are more extensive, and the trophic level and community diversity are higher in spring, the food sources of consumers are more abundant, but the degree of trophic niche differentiation is lower in summer, while in autumn, the structure of food web is relatively simple, but the distribution of trophic niche is wider.

Picasso clownfish is named for its disorderly and abstract distribution of white patches in its skin. At the same time, due to the irregular and scarce formation of white patches, it belongs to a valuable clownfish. Therefore, analyzing the formation mechanism of skin white spots in Picasso clownfish can provide a theoretical basis for the artificial breeding of Picasso clownfish. In this study, we sequences the transcriptome of the skin of three color blocks (black, yellow and white） in the same part of the body between the dorsal fin and hip fin of Picasso clownfish. The results show that there are a large number of differentially expressed genes (DEGs） in white skin compared with yellow and black skin. Among them, the genes in the signal pathways related to melanin production (such as melanin production, hedgehog and Wnt signal pathways） show a downward trend in white skin tissue. The expression of upstream regulatory genes (such as ednrba and mitfa） decrease gradually from black to yellow to white skin tissue, but the expression of downstream core genes involved in melanin synthesis (including Tyr, tyrp1b and dct） decreases significantly in white skin assembly. Finally, the validity of transcriptome data is verified by fluorescence quantitative PCR. The results of this study will provide a theoretical basis for future people to interfere with gene expression to regulate clownfish body color.

This study aims to understand the characteristics and variability in the β diversity of fish community and its influencing environmental factors in the Haizhou Bay, which was rich in fishery resources in history but seriously declined in recent years due to overfishing and environmental pollution. The data were collected from fishery resource surveys conducted in the Haizhou Bay and its adjacent waters from 2013 to 2017 using bottom trawl in autumn. β diversity was measured by Sørensen dissimilarity index using pairwise and multiple-site methods. Additionally, β diversity was divided into turnover and nestedness components and the results were analyzed visually by violin plots. On this basis, the generalized dissimilarity modelling (GDM) was used to analyze the relationship between β diversity and its components with environmental factors. The results of this study showed that the β diversity of fish community and its components fluctuated remarkably among survey years, the fluctuation was larger in the shallow water, less for the deep water, and remained at a relatively stable level regarding the whole sea area. The proportion of the turnover component in β diversity was basically maintained at more than 80%. The component of turnover was significantly larger than that of nestedness, implying the changes of fish community in the Haizhou Bay were dominated by turnover. The salinity and chlorophyll concentration of seawater were the main factors influencing β diversity and its turnover component, and the accumulated deviance explained rate of salinity and chlorophyll were 28.05% and 23.33%, respectively, the influence of water temperature was weak. The environmental factors selected in this study had a low explanatory rate for the nestedness component, which was only 1.52%. Our results implied that the characteristics of fish community have been driven by the environment, and the community development can yield corresponding adaptive to environmental changes. The process of changes in β diversity of fish community may be complex. For instance, salinity and chlorophyll concentration affect the prey density of fish and thus affect β diversity, however, more influencing factors have not been evaluated. Further studies on β diversity and its components are necessary to understand the mechanism of changing characteristics of fish community, and to provide scientific reference for the establishment of marine reserves as well as the optimization of marine conservation strategies.

Corals are one of the carriers for recording information about changes in the marine environment. For example, determining U/Ca to reconstruction of sea water temperature or measure the Th/U isotopic ratio for dating to reconstruction sea level etc. However, measuring the U and Th contents and isotopic ratio of corals is a prerequisite for extracting the recorded marine environmental change information, the difficulty lies in the separation of Ca matrix and enrichment and purification of trace U and Th. Based on this, this study modified the pretreatment method of separation and purification U and Th with single column stage of UTEVA resin, and then combined with high resolution inductively coupled plasma mass spectrometry to determine U and Th contents of corals. The results demonstrate that the HNO₃ medium concentration decrease from 3 mol/L to 2 mol/L will not affect the absorption efficiency of U and Th; 2 mL Milli-Q water can completely elute U, which significantly reduces the procedure blank value of the entire process of U; the improved method is used to determine the U and Th contents of three Hainan littoral corals (n=6, 1σ): U are (3.46±0.02)μg/g, (2.67±0.05)μg/g, (2.15±0.07)μg/g, respectively, Th are (10.12±0.24)ng/g, (4.82±0.10)ng/g, (5.65±0.12)ng/g, respectively; and the determination accuracy is below 3.3%, recovery rate of standard addition of U, Th are 97.9%–100.9%, 97.3%–99.7%, respectively. The method has high accuracy and good precision. This study provides a more accurate, convenient and rapid experimental method for the analysis of U and Th content and isotopic ratio in corals and other carbonate samples.

Based on the investigations of surface sediments at six sampling stations of nine cruises carried out in the sea around the Yongxing Island of Xisha from 2009 to 2017, the background values of seven heavy metals are determined through the process of mathematical statistics, the contents and inter-annual variations of heavy metals are analyzed, and the contents of the heavy metals are evaluated by means of single factor standard index and potential ecological risk index. The results show that the background values of heavy metals in the sediments of the study area are low, the average level of them meet the first class of marine sediment quality, and the quality of sediment is excellent. The inter-annual variations of seven heavy metals in the sediments of the study area are slightly different and generally significant and affected obviously by the development activities on the Yongxing Island. From 2009 to 2017, the contents of Zn, Cd, Cu, Cr, As and Hg are to increase first and then decrease, while the content of Pb is to increase. The assessment by means of potential ecological risk index shows that the multi year average of potential ecological risk indexes are in the order of Cd, Hg, As, Cu, Pb, Cr, Zn, and Cd and Hg are the main potential ecological risk factors of the study area.

Chub mackerel (Scomber japonicus) is a major target species in the Northwest Pacific fishery. Understanding changes in its fishing grounds is of great significance for assessing population size, resource, utilization, and management of the fishery. Based on catch data of high sea light purse seine fishery of China from 2014 to 2019, the spatial and temporal patterns of chub mackerel fishing grounds in the Northwest Pacific using the global Moran index, the local hot spot analysis, center of gravity migration trajectory model, and standard deviation ellipse are analyzed in this study. The results show that: (1) catches of chub mackerel mainly concentrates in the area between 39°−44°N and 147°−155°E, the annual catches show a trend of first increase and then decrease, the annual CPUE decrease year by year, the monthly catches show a trend of first increase and then decrease, which maintaines at a high level from June to October, and the monthly CPUE increases with month. (2) The spatial autocorrelations of annually and monthly chub mackerel catches are significant, and the monthly autocorrelations are stronger than annually ones, indicated highly aggregated distribution of the fishing grounds. (3) The distributions of chub mackerel hot spots and cold spots show a certain spatial agglomeration, but their distribution patterns and the areas cover varied apparently with years and months. (4) The gravity center of fishing ground generally show northwest shift from year to year, and in term of seasonal changes, moves northwest from April to August, and then turnes back to the southwest. (5) The annual and monthly shifts in directions of fishing grounds are consistent, showing an southwest-northeast pattern with strong directivity and aggregation. The spatial correlation models used in this analysis present a new look at spatial and temporal patterns of the chub mackerel fishing grounds, which may provide useful information for the rational development and utilization of the chub mackerel resource.

The study of spatial patterns of fish populations provides reference for reasonable utilization and management of fishery resources, which depends greatly on the quality of data collected from well-designed surveys. So appropriate sampling designs are essential in fishery-independent surveys, which can greatly affect the accuracy and applicability of the survey results. Computer simulation study is conducted to investigate the effects of sampling design on the spatial pattern of fish populations based on the data collected from bottom trawl surveys in the southern waters off Shandong Peninsula in four seasons from 2016 to 2017 in this study. Four sampling methods, including simple random sampling (SRS), systematic sampling (SYS), stratified random sampling (StRS) and stratified systematic sampling (StSS) with four levels of sample sizes are considered as potential sampling designs in this simulation study. The effects of different sampling designs on the estimation of mean crowding index and poly block index (PBI) for Conger myriaster and Enedrias fangi are examined. Relative estimation error (REE) and relative bias (RB) are used to measure the performances of different sampling designs. The results show that the simulated values of spatial pattern indices from SYS and StSS are closer to the “true” values, and the performances of SRS and StRS are relatively poor. The REE of estimation of spatial pattern indices for target fish populations decreased significantly with sample size. The original spatial pattern of fish populations has a certain effect on the estimation of spatial pattern indices. The precision of estimation of PBI decreased with the increase of the “true” values of spatial pattern indices, with PBI being overestimated when it is high. Different sampling designs have a certain effect on the estimation of spatial pattern indices of fish populations, and the degree of population aggregation also affected the analysis results. Therefore, the spatial pattern indices of target fish populations could be incorporated into the survey goals in sampling designs to improve the fishery-independent surveys with multiple objectives.

In order to study the relationship between daily increment of statolith and environment of neon flying squid (Ommastrephes bartramii) for different cohorts in the North Pacific during feeding ground, we explore the relationship between daily increment of statolith microstructure and environmental variables by gradient forest method (GFM) and generalized additive model (GAM) based on the samples collected in the North Pacific from 2010 to 2016. The results show that the life cycle of O. bartramii is about one year. The age of the autumn cohort ranges from 165 d to 345 d, and the age of winter-spring cohort ranges from 95 d to 271 d, respectively. Sea water temperature at the depth of 100 m (Temp_100), sea surface temperature (SST), sea surface salinity (SSS) and mixed layer depth (MLD) are the key environmental variables for the daily growth of autumn cohort. Temp_100, MLD, sea surface height (SSH) and chlorophyll a concentration (CHL) are the key environment variables for the daily growth of winter-spring cohort. GAM analysis shows that the daily increment width of statolith is significantly correlated with the key environmental variables selected by GFM (p<0.01). Key environmental variables of different cohorts suggest that the growth of O.bartrarnii is significantly affected by water temperature and prey abundance.

In order to further interpret the community structure of nekton and explore the ecological process of community structure changes, community structure of nekton in the Minnan sea area are analyzed based on the niche preemption model (NPM), broken stick model (BSM), overlapping niche model (ONM), dominance pre-emption model (DPM) and random assignment model (RAM) a total of 5 species abundance pattern models. The results show that there are 192 species of nekton in the Minnan sea area, including 132 species of fish, 31 species of crab, 13 species of shrimp, 10 species of cephalopod, 6 species of stomatopod. The fitting effect of NPM in the abundance distribution of nekton is better than that of ONM, the dominant species have dominant position and species niche do not overlap in Minnan sea area. From the open sea to the coastal area, the distribution pattern of nekton abundance changes from DPM to NPM, the simulation result of NPM is worse, and the simulation result of BSM is better, the status of dominant species decreased, the number of species increased, and species abundance distribution tendes to uniform.The fitting effect of DPM on the abundance distribution of nekton is better than that in the deep fishing area. With the increase of latitude, the fitting effect of the abundance distribution of nekton is better gradually, the dominant position of dominant species gradually increased, the number of species become less, and species abundance distribution tendes to unevenness, however, the fitting effect of DPM on the species abundance distribution of nekton in shallow fishing areas is poor, and the dominant position of dominant species gradually declines, the number of species becomes more, and species abundance distribution tendes to uniform. Therefore, niche preemption model is suitable to study the abundance distribution patterns of nekton in the Minnan sea area.

Trichiurus haumela is one of the major commercial fish populations in the Beibu Gulf of the northwestern South China Sea. It is of great significance to estimate population parameters and assess the stock status of T. haumela for the fishery management in the Beibu Gulf. Based on the biological data of T. haumela collected in the Beibu Gulf from 2006 to 2016, the asymptotic length (L_inf), the optimal length-at-first-capture (L_{c_opt}), relative mortality (M/k and F/k), exploitation rate (E), and relative biomass (B/B₀) are estimated using the length-based Bayesian biomass estimation method (LBB). The results show that the L_inf is 44.4 cm, the mean of L_{c_opt} is 28.5 cm, the mean of M/k and F/k are 1.32 and 2.76, the F/M is 2.20 and the E and B/B₀ are 0.67 and 0.16, respectively. The anal length of the first gonadal maturation (L_50%) is 28.63 cm fitted by Logistic models. The results show that the current stock of T. haumela in the Beibu Gulf is over-exploited, the extant biomass is relatively low, the length-frequency tendes to simplification and miniaturization.