Abstract:Seaweed-bivalve polyculture and Integrated Multi-Trophic Aquaculture (IMTA) of seaweed, bivalves, fishes, and sea cucumbers have been conducted in Sanggou Bay for decades, leading the development of eco-farming globally. To understand the dynamic changes of macrobenthos and the health status of benthic habitats in the Sanggou Bay, five surveys of macrobenthos were conducted in different mariculture areas of to understand the impact of aquaculture on the benthic ecosystem from May to September 2019. The community characteristics of macrobenthos, such as species abundance, composition, distribution, and biodiversity were analyzed in different mariculture areas in five surveys, and the health status of the benthic ecosystem in Sanggou Bay was assessed using the AZTI Marine Index (AMBI) and multivariate-AMBI(M-AMBI). A total of 56 species were identified, including 31 Polychaetes, 10 Crustacea, 9 Mollusca, 3 Echinodermata, and 2 species of other taxa. The dominant species were Lumbrinereis sp., Tharyx multifilis, Notomastus latericeus, Mediomastus californiensis, Amaeana occidentalis, Paranthura japonica, Scoloplos sp., Potamocorbula laevis, Glycinde gurjanovae, and Cirolana japonensis. During the breeding period, the community diversity index H' of the shellfish and cage culture areas showed a downward trend, indicating that shellfish and cage culture activities have caused excessive organic particle accumulation in the sediments. The abundance/biomass curves showed that the macrobenthos community structure in the Sanggou Bay breeding area began to be disturbed in July, and was moderately disturbed in August and September. The AMBI and M-AMBI Index analyses showed that the macrobenthic community was not disturbed or slightly disturbed and the benthic habitat health tended to relatively good.

Abstract:Interleukin-17 (IL-17) plays an important role in inflammation and host defense in mammals. To investigate the biological function of CcIL-17N, two CcIL-17N genes were identified from the common carp (Cyprinus carpio) whole-genome using BLAST and gene cloning performed by genomics, named as CcIL-17Na and CcIL-17Nb, respectively. They were encoded by the complementary sequence of intron 2 of the TOP3B gene. Synteny analysis indicated that SDF2L and PPM1F were present on both sides of IL-17N, except for Takifugu rubripes. These two IL-17N isoforms encoded 136 amino acids, including 3 exons, and exhibited 97.1% similarity in sequence. The similarity between CcIL-17Na and CcIL-17Nb of common carp with other teleosts were estimated to be 65.3%-97.1%, 64.7%-96.3%, and of 32.9%-51.4%, 31.4%-50.7% in comparison with other IL-17 family members in common carp. The phylogenetic tree of teleost IL-17 family members showed that 7 members constitute 6 credible branches, of which IL-17A/F1 and IL-17A/F3 constitute a branch, and the remaining six members form a branch separately. IL-17N of common carp was clustered with zebrafish and grass carp with a bootstrap of 95%, with medaka, T. rubripes, tilapia, etc. clustered with a bootstrap of 84%, with Lepisosteus osseus IL-17N with a bootstrap of 70%, and finally coelacanth IL-17N with a bootstrap of 97%. CcIL-17Ns expression level at 0.5 and 12 h after fertilization was significantly higher than that at 25, 35, 60, 120 h, and larval fish stage (P<0.01). CcIL-17Ns expression in the brain of summerlings and adult fish was the highest, which was significantly higher than other tissues (P<0.05 or P<0.01). CcIL-17Ns expression in all tissues was up-regulated under Aeromonas hydrophilis infection. CcIL-17Ns expression in the brain was significantly up-regulated for 6 h after infection (P<0.05). At 1 d, CcIL-17Ns expression in other tissues was significantly up-regulated, and the expression was decreased for 3 d and 7 d after infection, with no significant difference from the control group (P>0.05). Recombinant prokaryotic expression plasmid pMAL-c2X-17N was constructed and transformed into Escherichia coli Transetta (DE3) for prokaryotic expression. Soluble recombinant common carp IL-17N protein (rccIL-17N, MBP-17N) was obtained by Ni-NTA. Under the induction of different concentrations of MBP-17N protein (0.1, 1, 10, and 100 ng/mL), kidney tissue was incubated for 8 h. qPCR indicated that IL-1β and NF-κB was significantly up-regulated at 0.1, 1, 10, and 100 ng/mL of MBP-17N. IFN-γ was significantly up-regulated under 1 and 10 ng/mL MBP-17N, whereas IL-6 was significantly up-regulated at 0.1 and 1 ng/mL. CCL20 was significantly up-regulated at 1, 10, and 100 ng/mL. Furthermore, TRAF6 gene significantly upregulated at 1 ng/ml than that of the control group. In conclusion, this study revealed that ccIL-17N was highly conserved in evolution. Meanwhile, ccIL-17N is involved in inflammatory response based on its role in A. hydrophila infection and rccIL-17N function.

Abstract:Ovary development and oogenesis are important in fish reproductive biology. It is fundamental to understand the ovary developmental characteristics for the investigation of resources, population structure, artificial breeding, and germplasm conservation. In this study, to understand Eleutheronema tetradactylum ovary development and oogenesis, changes of tissue structure in ovary development and oocyte structure in different phases during oogenesis were observed via tissue section with an H-E staining technique. The results showed that the ovary of E. tetradactylum is a membrane-type one, and is close to the abdominal surface of the middle kidney, and the two ovaries were separated at the front end and fused at the back end, presenting a "Y" shape. Oogenesis was divided into five phases, fewer follicular cells began to appear around the oocytes in medium phase II, monolayer follicular cells were formed in later phase II, monolayer thecal cells were formed in medium phase III. The yolk nucleus began to appear in middle phase II and disappeared in early phase III. The yolk vesicle appeared near the nucleus and cytoplasmic margin in early phase III. The yolk granules began to appear between the yolk vesicles in late phase III, and filled the yolk vesicles in early phase IV, the yolk lamellae was formed in late phase IV. During ovary development, each stage had different oocyte phases. In stage V, the oocyte diameter showed a bimodal distribution, with peaks in the range of 50.00 to 100.00 μm and 300.00 to 350.00 μm, respectively. This indicated that the ovary showed asynchronous development and batch spawning. This research elaborated the reproduction rules and strategies, and enriched E. tetradactylum reproductive biology information, providing necessary theoretical reference for the protection, development, utilization, and improvement of E. tetradactylum artificial breeding techniques.

Abstract:Japanese scad (Decapterus maruadsi), a warm water pelagic fish, is an important economic species in China. Based on a quarterly bottom trawl survey in offshore waters of southern Zhejiang from 2015 to 2018, this study explored the length-weight relationships, growth heterogeneity, and natural mortality of Japanese scad. A total of 1,134 individuals were measured, with fork length (L) ranging from 45.0 to 247.0 mm and body weight (W) ranging from 0.7 to 206.6 g. The length-weight relationship was revealed to be W=5.01×10^-6L^3.17 for Japanese scad in the inshore waters of southern Zhejiang. A linear mixed effect model considering the random effects from season, gender, and year performed the best, with the lowest AIC and RMSE values. Results from the best model indicated that 1) individuals collected in the autumn tended to gain more weight than those collected in spring and summer at the same length; 2) individuals collected in 2018 grew with better condition, whereas those in 2017 and 2018 gained less weight at the same length; 3) there was no substantial differences between female and male Japanese scad. Therefore, year and season significantly influenced Japanese scad growth in the inshore waters of southern Zhejiang with the best growth condition in autumn 2018. Based on several empirical equations including Pauly, Pauly update, Jensen, Hoenig and Lorenzen methods, this study estimated the natural mortality for Japanese scad, which ranged from 0.36 to 1.41. This study exhibited that season and year significantly influenced the length-weight relationships of Japanese scad and the results could provide important information and knowledge for further study and fishery management for this important species in the coast waters of China.

Abstract:NO₂^--N in secondary saline-alkali water in Northwest China has been at a relatively high concentration for a long time, which has seriously restricted the sustainable development of the saline-alkali aquaculture industry. Based on regular fixed-point monitoring of the Caowotan Fisheries and Agriculture Demonstration Area (104°7'40″E, 37°19'6″N) in Jingtai, Gansu, inorganic nitrogen conversion in different types of secondary saline-alkali water and its correlation with environmental factors were studied by paired sample t test, Duncan multiple comparison, and Pearson's correlation analysis. The results showed that:(1) inorganic tri-state nitrogen (NO₂^--N, NH₄⁺-N, NO₃^--N) and total nitrogen (TN) in the secondary saline-alkali water were at high concentrations and fluctuated seasonally[NO₂^--N (0.3±0.2) mg/L, NH₄⁺-N (1.93±1.25) mg/L, NO₃^--N (2.92±1.5) mg/L, TN (13.91±5.85) mg/L]. The proportion of inorganic nitrogen in TN was below 50%, indicating that the proportion of organic nitrogen in secondary saline-alkali water was higher; (2) pH was positively correlated with NO₂^--N, negatively correlated with NO₃^--N, and salinity was negatively correlated with NO₃^--N, pH and salinity aggravated the accumulation of NO₂-N; (3) aquaculture significantly reduced NO₃^--N and carbonate alkalinity in secondary saline-alkali water, showing ecological improvement of saline-alkali aquaculture to secondary saline-alkali water.

Abstract:To assess the sediment environmental quality synthetically from Shanghai aquaculture ponds, 360 sediment samples collected from 36 farms from 2016 to 2019 were investigated and the distribution characteristics of total nitrogen (TN), total phosphorus (TP), total organic carbon (TOC), and heavy metals (Cu, Zn, Pb, Cd, Cr, Hg, As) were analyzed. The results showed there was no significant difference between the average concentrations of TN, TP, TOC, and those heavy metals in the 0-10 cm and 10-20 cm layers. The mean values of TN, TP, and TOC (dry weight) in the surface 20 cm pond sediment were (873.37±352.45) mg/kg, (685.66±199.66) mg/kg, and (6.62±3.05) mg/g respectively, and in pond sediments there was a significant positive correlation among them. Methods of comprehensive index and the organic index were used to evaluate the accumulation of nitrogen, phosphorus and organic matter, and the results indicated that the nitrogen and organic matter accumulation in pond sediments was relatively low and phosphorus accumulation was high, but was still lower than the high-yielding ponds in other areas. The over-limit ratio of Cr, Cd, Cu, and Hg was 6.42%, 3.21%, 4.13%, and 1.38%, respectively and concentrations of Zn, Pb, and As in all samples met the certain criteria. The sediment assessment was conducted using a geo-accumulation index (I_geo), potential ecological risk index (RI), and consensus-based sediment quality guidelines (CBSQGs). Results of the risk assessment indicated that, generally, Shanghai pond sediments were unpolluted, had a low ecological risk, and were nontoxic.

Abstract:The jumbo flying squid Dosidicus gigas is an environmentally sensitive cephalopod. The habitat variation of D. gigas is greatly affected by multi-scale climate variability. In this study, we constructed a habitat suitability index (HSI) model based on two critical environmental variables (sea surface temperature (SST) and sea surface height (SSHA) from 1950 to 2015), and analyzed seasonal habitat distribution for D. gigas off Peru under different climate conditions. The results suggested that habitat suitability during the cold Pacific Decadal Oscillation (PDO) was higher than that during the warm PDO. Compared with the cold PDO, suitable D. gigas habitat during the warm PDO shifted southeastward. The spatial distribution of suitable habitat was consistent with the overlapping areas of both the suitable SST and SSHA ranges, indicating that the two critical environmental variables were significantly related to the spatial distribution of suitable habitats. Moreover, the HSI anomalies on the D. gigas fishing ground were significantly negatively correlated with the PDO index. The habitat suitability on the D. gigas fishing ground in spring was higher than that in winter, and the spatial distribution of suitable habitat in winter was further Southeast than that in spring. The longitudinal and latitudinal distribution of suitable SST and the most suitable SST on the fishing ground of D. gigas showed significant variability between June and November. The distribution of the most suitable SST in spring (September to November) shifted northwestward; however, the distribution of the most suitable SST in winter (June to August) shifted southeastward. The difference in seasonal habitat distribution for D. gigas under different climate conditions may be owing to the monthly difference in distribution of the most suitable SST. Our findings indicated that there were significant differences in the habitat suitability on D. gigas fishing grounds under different PDO periods, and the difference in seasonal distribution could be explained by monthly differences in environmental variables.

Abstract:Hengsha Shoal is located in the Yangtze River estuary, which is rich in biological resources. However, in recent years, owing to construction in the estuary, the community structure of aquatic species in this area has changed. To understand the community structure of swimming species in the Hengsha Shoal and adjacent waters of the Yangtze River Estuary to determine the construction effect, this study carried out a bottom trawl data survey in the summer of 2019. The community structure was analyzed by studying the dominant species, species diversity, and community structure characteristics. The results showed that there were 68 swimming species in summer, including 29 fish species, including 8 orders and 16 families; 30 arthropod species, including 2 orders and 15 families; and 9 mollusks species including 4 orders and 7 families. The species composition mainly comprised arthropods and fishes. The dominant species were Exopalaemon annandalei, Palaemon gravieri, and Chaeturichthys stigmatias, which are mainly small, low nutrition, and short life cycle species. The population characteristics showed a trend of miniaturization and low nutrition. The survey showed that the biodiversity index in this area is low, the community structure of swimming species is generally unstable, greatly disturbed by the environment, and there are obvious spatial differences. The results of cluster and ordination analyses showed that the investigated area can be roughly divided into two groups, and the differences of species community structure between the two groups were very significant (R=0.825, P<0.01). The main contributing species of the differences between the groups were E. annandalei, P. gravieri, C. stigmatias, and Larimichthys polyactis, and salinity and water temperature were the main factors that contributed to differences of community structure. Generally, recent beach reclamation and construction of a deep-water channel may have impacted the community structure of swimming species in Hengsha waters.

Abstract:Setipinna taty plays an important role in the dynamics of marine ecosystems that often support valuable fisheries. To explore the temporal-spatial distribution of S. taty suitable habitats in the South inshore area of Zhejiang Province, ae Habitat Suitability Index (HSI) was used to analyze habitat characteristics of this species based on fishery independent survey data collected in four seasons from 2016 to 2018. HSI models with two different algorithms, Arithmetic Mean Model (AMM-HSI) and Geometric Mean Model (GMM-HSI), were constructed using S. taty abundance and environmental variables, including water temperature, depth, and salinity. Cross validation was used to evaluate the predictive performance of AMM-HSI and GMM-HSI and the model with the best predictive performance was used to predict the most suitable S. taty habitat distribution. The results showed that the suitability index (SI) of each environmental variable showed considerable differences in each season. The optimal water temperature for S. taty is 11.2-33.6℃, water depth is 19-46.6 m, and salinity is 27.8-33.2. GMM-HSI accuracy was higher than that of AMM-HSI, and GMM-HSI values predicted in spring, summer, and autumn were more evenly distributed at each interval than that of the AMM-HSI values. HSI model results showed that S. taty habitats with high suitability in spring are concentrated South of 28°N and West of 121.5°E. In summer, 27.5°N-28.5°N and east of 122°E are considerably more suitable for S. taty. The areas 27.5°N-29°N, west of 122.5°E and south of 27.5°N, west of 121.33°E in autumn, and west of 122.5°E in winter were found to be suitable habitats, which suggested that the optimum habitat distribution of S. taty changes seasonally. This was mainly related to S. taty migratory activities and ocean currents in the South inshore area of Zhejiang Province. Generally, the most suitable S. taty habitat is concentrated West of 122.5°E in winter, whereas South of 28.5°N and West of 122.5°E in spring, summer, and autumn. Therefore, the area South of 28.5°N could be recognized as the main suitable habitat for S. taty in the South inshore area of Zhejiang Province. This study showed that the HSI model can effectively explain the habitat distribution and changes of S. taty in this area, which has important significance for S. taty sustainable utilization. Small fishes, such as S. taty, are presently an import fishery focus because of overfishing and habitat degeneration in marine environments; therefore, the analysis of S. taty distribution is valuable for fishery resource management and conservation.

Abstract:Based on acoustic and bottom trawl survey data in the Guishan wind farm area in autumn 2019, we analyzed the species composition, species dynamics, and spatial distribution of fisheries resources in that area. A total of 72 species of swimming organisms and benthic invertebrates were caught, of which 34 species were assessed in this survey. The number and biomass estimated by the acoustic method were 5.97×10⁵ ind/km² and 15.13 t/km², respectively. Fish aggregation distribution characteristics were obvious in this area, and the density was higher in the northwest and southeast regions. The distribution range of fish single TS was -68--41dB, of which -68--58dB was dominant (79.12%), corresponding to a fish body length of 3-8 cm. With increasing water depth, the mean fish TS first decreased and then increased. This study was the first acoustic survey of fisheries resources in this area. The assessment results could provide accurate information on the quantity and distribution of various fish species, and provide basic data for monitoring long-term changes in fisheries resources after the wind farm has been completed.

Abstract:Fish eggs could significantly impact fish population recruitment. The distribution and variation in the number of fish eggs impacts the dynamics of the spawning ground, which is fundamental for maintaining marine ecosystem balance. Haizhou Bay is an important fishing ground in China, and it is also an important spawning and nursery ground for various fishes. Recently, owing to the impact of overfishing and other factors, the fish community structure in Haizhou Bay changed considerably. Presently, Cynoglossus joyneri is a dominant and important economic species in Haizhou Bay and adjacent waters. Based on survey data in the spawning grounds of this area from May to August in 2014 and 2016-2018, a habitat suitability index (HSI) model of C. joyneri eggs was constructed to analyze its spawning habitat characteristics. A boosted regression tree (BRT) model was used to evaluate the weight of each environmental variable in each month, including sea surface temperature, sea bottom temperature, sea surface salinity, depth, and velocity data. The arithmetic mean model (AMM) and geometric mean model (GMM) were used to build the HSI model, and the model fitness was evaluated by cross-validations. Results showed that the range of environmental factors of C. joyneri suitable spawning habitat was similar in different months, but the weights of environmental factors changed considerably. Cross-validation showed that the GMM performed better in May and July, whereas the AMM produced a better estimation in June and August. Cynoglossus joyneri spawning ground distribution varied in different months, and was mainly distributed in the south of the research area in May, and moved northward from June to August. The scope of distribution also expanded gradually. The results showed that the HSI model could be used to reflect the distribution and variations of C. joyneri spawning grounds in Haizhou Bay and adjacent waters. Therefore, different protective measures could be formulated for reproductive parents and juveniles of C. joyneri according to the conditions of suitable habitats in different months, and consequently could be valuable for understanding supplementary mechanisms and determining effective management measures for C. joyneri.

Abstract:Recently, Oratosquilla oratoria (Crustacea) abundance and economic status have significantly increased in marine ecosystems, but the relationship between spatial distribution and environment factors is still unclear. To understand O. oratoria habitat distribution and the influence of the main environmental factors, the present study was carried out in 2016-2017 in the coastal waters of Shandong. Four surveys of the fishery resources and environmental factors were carried out, and the results were analyzed comparatively using generalized linear, generalized additive, and back propagation neural network models to determine the relationships between O. oratoria spatial distribution and environmental factors. The results indicated significant seasonal differences in O. oratoria density, with the highest density in summer, followed by spring and autumn, and the lowest in winter. O. oratoria density in the near shore was higher than that in the far shore, and it gradually increased from south to north. The model analysis showed that latitude, bottom-layer temperature, and bottom-layer salinity significantly affected O. oratoria density distribution. Among the three models, the generalized additive model was the best fit, and the back propagation neural network model had the best prediction accuracy. By comparing the results of the different models, this study revealed O. oratoria spatial distribution characteristics and key environmental factors affecting distribution, and provided theoretical support for rational O. oratoria fisheries development and utilization.