According to the seasonal fishery resource survey data from 2016 to 2017 in the adjacent waters of Changshan Islands, two-stage generalized additive model is used to examine the spatio-temporal distribution of Paralichthys olivaceus abundance and its relationships with relevant factors. The results show that the abundance of P. olivaceus exhibites obvious seasonal variation, and the abundances in spring and autumn is higher than those in winter and summer. In spring and autumn, it mainly distributes in the waters of 120.5°−122.5°E; and in summer and winter, it moves to the waters with suitable water temperature. The occurrence probability of P. olivacvacus is mainly affected by season, bottom salinity and bottom temperature. The probability of occurrence is relatively high at the salinity of 31. The relative abundance of P. olivaceus are mainly affected by bottom salinity and depth, and the relative resources is higher at the depth of 33 m. The spatio-temporal heterogeneity of the abundance distribution of P. olivaceus is affected by multiple factors in the adjacent waters of Changshan Islands.

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.

Cynoglossus semilaevis as a representative species of Pleuronectiformes, is an important marine economic fish in Chinese coastal areas. The abnormal body color of C. semilaevis has been perplexing the practitioners for a long time. There are many reasons leading to abnormal body color, among which the genetic factors are thought to be the most fundamental reasons. The present researches on hypermelanosis of the blind side of C. semilaevis mainly focus on environment, nutrition, physiology, cloning of known pigmental genes and so on, while the digging of new funtional genes is still lacking. In this study, skin samples with different colors of C. semilaevis are selected for transcriptome sequencing. Through GO and KEGG functional enrichment and comparative analysis of different genes, differential expressed genes are screened in six melanogenesis-related KEGG pathways and the top ten genes are verified by qPCR. In this study, we find five functional genes with significant changes in the hypermelanotic skin on the blind side of C. semilaevis, which refer to txndc, alox15b, ptgs2, ptgis, and atp1a2a (p<0.05). The expression levels of txndc, alox15b, ptgs2, and ptgis genes in the melanization group are higher than those in the control group. In terms of function, three of these five genes are related to arachidonic acid (AA) to some extent. This provides theoretical support for the hypothesis that nutritional regulation related to unsaturated fatty acids may be involved in the molecular mechanism of abnormal body color in C. semilaevis.

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.

The Bohai Sea and Yellow Sea are continental shelf areas with high production of dimethyl sulfide (DMS). Field investigation of DMS in this area is helpful to accurately assess its amount released from the ocean and its negative feedback on global climate change. Both model-based and direct measurement methods are based on DMS concentration in surface seawater and lower atmosphere, respectively, so advanced detection technology plays a decisive role in the accurate flux estimation. Gas chromatography, mass spectrometry, chemiluminescence and satellite remote sensing are commonly used observation techniques. At this paper, a method based on benzene-assisted photoionization positive ion mobility spectrometry (BAPI-PIMS) for in-situ observation of DMS in seawater is proposed. Combined with dynamic gas stripping and on-line water removal Nafion tube sampling system, the interference of environmental water vapor is eliminated. Under the optimal conditions, the linear range based on the two DMS product ions is 0.10−120 nmol/L, and the detection limit is as low as 0.065 nmol/L. Then the demonstrated method is applied to field detect DMS in the Bohai Sea and northern Yellow Sea, and the concentration of DMS in surface seawater ranged from 0.08 nmol/L to 0.96 nmol/L, while the air-sea exchange flux ranged from 0.12 μmol/(m²·d) to 17.75 μmol/(m²·d). Lastly, the difference between DMS detected on field and in lab and the main impact factors are discussed via the correlation analysis and canonical correspondence analysis, and results show that nutrients and phytoplankton community are the main factors during the seawater preservation, indicating the important significance of field observation method established currently for accurate evaluation of DMS release from the ocean.

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.

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.

Based on the fish survey data of the offshore waters of southern Zhejiang in August 2016 (summer), November 2016 (Autumn), March 2017 (winter) and May 2017 (spring), the relationship between dominant fish species is determined by niche breadth, niche overlap, cluster analysis, variance ratio (VR) method, chi-square test, association coefficient (AC) and species pair common percentage (PC). The results show that: (1) 169 species of fish are collected, including 26 major species; (2) in the spatial dimension, the niche breadth of Scomber japonicus is the largest (2.83); the niche overlap between Sardinella zunasi and Thryssa chefuensis is the largest (0.97); in the temporal dimension, the niche breadth of Harpadon nehereus is the largest (1.34); the niche overlap of six groups is equal to 1.00; in the spatial and temporal dimension, the niche breadth of Harpadon nehereus is the largest (3.08); the niche overlap between Sardinella zunasi and Thryssa chefuensis is the largest (0.97); (3) the variance ratio analysis showed that the VR deviation is significant, and the overall positive association of the major fish is significant, among which 170 groups of species pair association reached a significant level (χ²≥3.841). The results of the AC and the PC showed that the interspecific connection tended to be positive.

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.