Abstract:The swimming crab (Crustacea:Decapoda:Brachyura) is a dominant species of portunid crab fisheries and an important economic species worldwide. The key performance traits of crustaceans and other aquaculture species are often depressed by inbreeding, especially if inbreeding effects accumulate too rapidly. Although previous studies have investigated the effects of inbreeding on the morphology, hatchability, and survival of crustaceans, little evidence is available that demonstrates that inbreeding affects crustacean physiology. Therefore, in order to investigate the effects of inbreeding on the oxidative phosphorylation of , cDNAs of the key subunit genes of the four mitochondrial respiratory chain complexes were cloned, sequenced using rapid amplification of cDNA ends (RACE), and then analyzed using bioinformatics technology. The full-length cDNA sequence of the Complex I core subunit genes was 1005 bp in length and contained a 705-bp open reading frame (ORF) that encoded a 234-amino acid polypeptide (GenBank:KY682717). The full-length cDNA sequence of Complex Ⅱ was 915 bp in length and contained a 540-bp ORF that encoded a 179-amino acid polypeptide (GenBank:KY406169). The full-length cDNA sequence of the Complex Ⅲ subunit (Cytc1) gene was 2371 bp in length and contained a 942-bp ORF that encoded a 313-amino acid polypeptide (GenBank:KY406171), and the full-length cDNA for the key subunit of Complex IV was 1171 bp in length and encoded 105 amino acids (GenBank:KY406170). In addition, homology and phylogenetic analyses revealed that the amino acid sequences of the four complexes were highly similar to those of closely related species and had higher conservation in evolution, and could be used as a reference for other marine organisms. The activities and mRNA expression of the four complexes in the hepatopancreas and heart mitochondria of were investigated. Results show that inbreeding reduced the activity of all four complexes and their respective subunit gene in the hepatopancreas (<0.05). Besides, Complex I, Ⅲ and IV activities and their subunit genes in heart were declined by inbreeding (<0.05). Furthermore, the elevated activity and expression of Complex Ⅱ in the heart may indicate that the ability to oxidize succinic acid and the level of aerobic metabolism in the crabs rose by breeding might because the dominant homozygous genes were accumulated during the family-based selective breeding programs. Therefore, it is clear that inbreeding gradually reduces the oxidative phosphorylation pathway and provides a reference for family-based selective breeding programs for .

Abstract:(abalone, Gastropoda) is an economically important species. However, the rapid development of industrialized and intensive farming, as well as frequent hybridization and inbreeding, are gradually reducing the genetic diversity and parental effective group of hybrid abalone, thereby reducing abalone growth and quality. An effective way to improve abalone quality is to breed a new fast-growing and disease-resistant variety. Cross breeding, which increases the yield and viability of hybrid offspring heterosis, is a traditional breeding method that plays an important role in improving aquatic animals. In the present study, we constructed four self-fertilized and twelve reciprocal hybrid families from four cultured populations (Huangdao, HD; Rongcheng, RC; Japan, JP; and Dalian, DL) using a 4×4 complete diallel cross. Based on paternity testing, which was performed using eight polymorphic microsatellite markers, the growth traits, heterosis rate, growth rate, and survival of the F₁ families were compared at 1, 5, 13, and 17 months, and the hybridization efficiency was estimated. Some hybrid offspring exhibited significant growth advantages, when compared to self-fertilized families. The HDRC, HDDL, and JPDL families exhibited greater growth rates than those of other families, and the HDDL, HDJP, RCDL, JPRC, and RCHD families exhibited greater survival rates. Furthermore, the HDRC, HDDL, and DLHD families exhibited significant heterosis in growth parameters and growth rate, and the HDDL, RCDL, and DLHD families exhibited significant heterosis in survival. The heterosis of body weight, body length, and body width of the same family in the same stage and heterosis of the same trait of one family in different stages were found different in the present study, which indicates that hybrid families possess unbalanced and unstable heterosis. Differences in the gene frequency of populations are the basis of heterosis. The results of the present study suggest that there are significant genetic differences among the HD, DL, and RC populations. The superior hybrid offspring identified in the present study can be used as a germplasm reference and provide a basis for breeding new varieties of .

Abstract:The Chinese mitten crab () is a native and important cultured freshwater that is widely distributed in the Yangtze Estuary, China. Many scholars have focused on crab farming, disease prevention, and diet. However, little is known about the feeding rhythm of Chinese mitten crabs, in regards to feeding mode, which is directly related to the feeding time, feeding method, and frequency of feeding strategies, which may affect feed efficiency, as well as aquaculture water. Accordingly, the present study investigated crab feeding behavior under a 24-h photoperiod and, ultimately, established a theoretical basis for determining optimal feeding time, which could benefit large-scale aquaculture and, therefore, improve feed utilization and reduce both water pollution and breeding costs. Crabs with weight of (68.0 ±2.4) g were randomly distributed among 24 cement pools (0.7 m×0.4 m×0.5 m, L×W×H). Each group had three cement pools replicates, each housing 5 crabs, and fed at different time points (10:00, 13:00, 16:00, 19:00, 22:00, 01:00, 04:00, and 07:00). After 10 d, three crabs from each pool were randomly selected and sampled for intestinal and hepatopancreas. The results showed that juvenile crabs exhibited different feeding patterns at different feeding times, and the peak of feeding was observed at 22:00. Based on the average food intake over 6 d, it was clear that the crabs fed primarily at 19:00-22:00. Meanwhile, amylase activity was higher in the hepatopancreas samples of crabs fed at 22:00 than in those of crabs fed at other times (except 19:00). Lipase, alkaline phosphatase, and Na⁺-K⁺-ATPase activities increased from 13:00 to 22:00 and decreased thereafter. Leptin expression in the hepatopancreas of crabs fed at 22:00 p.m. was significantly lower than that of crabs fed at either 13:00 or 16:00, whereas cholecystokinin (CCK) expression was lowest in the intestines of crabs fed at 22:00. In conclusion, feeding of Chinese mitten crab was with an increasing feed intake at 16:00; there after tend to decrease at 22:00. This could be attributed to the visual underdevelopment of the crabs. According to the observed feeding rhythm, Chinese mitten crabs are nocturnal and feed at night. The activities of digestion and absorption enzymes were lowest in crabs fed at 10:00-13:00 and increased from 16:00 to 22:00, with the highest level attained at 22:00. These results could indicate a strong the ability of nutrients digestion and absorption at 22:00. It was consistent with the trend of total feed intake. Digestive and absorption capacity are important indicators of feed utilization and animal growth, and enzyme activity can be used as an indicator of digestive and absorption capacity. On the contrary, the expression of leptin and CCK were downregulated at 22:00. These results were supported by the fact that leptin and CCK are involved in the regulation of food intake. According to previous studies, decreases in leptin and CCK increase the feed intake of animals, which also explains the why, in the present study, the highest feed intake was observed at 22:00. Overall, feeding Chinese mitten crabs at 22:00 could enhance digestion and absorption. Therefore, feeding at 19:00-22:00 could improve feed intake and efficiency.

Abstract:A 56-d feeding experiment in an indoor flowing-through water system was conducted to evaluate the effects of arachidonic acid (ARA) in diets on the growth performance, antioxidant capacity, and body wall fatty acid composition of sea cucumbers () with initial weights of (10.78 ±0.06) g. Six isonitrogenous and isoenergetic diets with varying levels of dietary ARA[0.02% (control group), 0.17%, 0.36%, 0.51%, 0.59%, and 0.98%] were formulated. The ARA content had no significant effect on survival rate (87.50%-94.17%; >0.05). However, both growth rate (WGR) and feed efficiency (FE) increased with increasing ARA content until reaching peak levels at 0.51% dietary ARA, but decreased thereafter (<0.05). Body wall composition analysis indicated that the whole-body lipid content initially decreased but then increased with increasing dietary ARA, whereas the whole-body protein, ash, and moisture contents were unaffected. Superoxide dismutase (SOD), catalase (CAT), and total antioxidant capacity enzyme (T-AOC) activities in the intestinal tract initially increased with increasing ARA content but then decreased (<0.05), whereas the malondialdehyde (MDA) content of the intestinal tract exhibited a contrasting pattern (<0.05). Fatty acid synthase (FAS) and acetyl-COA carboxylase (ACC) activities in the intestinal tract were unaffected when dietary ARA content decreased from 0.02% to 0.59% but decreased significantly when the dietary ARA content increased from 0.59% to 0.98% (<0.05). The ARA and n-6 PUFA contents of the body wall increased with increasing dietary ARA, whereas the EPA and DHA content of the body wall decreased. Therefore, dietary ARA contents of 0.36%-0.51% could be used to promote the growth performance and intestinal antioxidant capacity of sea cucumbers under experimental conditions. The effects of ARA level in diet on the activities of fatty acid synthase, acetyl-CoA carboxylase, and carnitine palmitoyltransferase-1 in the intestinal tract of sea cucumber were also observed in the study.

Abstract:To screen local probiotic strains, 66 cultivable bacterial strains were isolated from water and sediment samples from cultured ponds of sea cucumber () in Dongying in May 2014. Bacterial antagonistic experiments were conducted using V. parahaemolyticus and , which are main pathogenic bacteria of ‘skin ulcer syndrome’ for . In addition, selective medium was used to test the amylase production and protease activities of the isolated strains and to isolate a potential probiotic strain, DY-6. Then, its physiological-biochemical experiments and similarity analysis of 16s rDNA sequences as well as the growth characteristics of DY-6 experiments have been conducted. The safety experiment for the sea cucumber was also proceed. The DY-6 strain was successful in inhibiting V. alginolyticus, as indicated by inhibition zone diameters of 24, 22, 27, and 37 mm, respectively. Meanwhile, the hydrolysis zone diameters of amylase and protease were 28 and 20 mm, respectively. A safety experiment was designed to test the safety of DY-6 for sea cucumber. During the experiment, all sea cucumbers were in good conditions without falling ill. Based on physiological and biochemical experiments and 16s rDNA sequence analysis, strain DY-6 was determined to be 99% similar to B. velezensis. When compared to four bacterial strains isolated from commercial probiotic products, DY-6 exhibited superior growth at 20-35℃ and under salinities of 0 to 35. Moreover, DY-6 came into the logarithmic growth phase after 4 h of cultivation and reached growth peak after 10 h. In summary, strain DY-6 exhibited superb inhibition of sea cucumber pathogens, rapid growth, and both euryhalinous and euryhaline features. Therefore, DY-6 could be used to reduce the occurrence of sea cucumber disease and is also suitable for use at high temperatures during summer and in fluctuation salinity levels, as in the Yellow River Estuary. Thus, strain DY-6 has potential for commercial development.

Abstract:, which occurs in the coastal waters of China, including the Yellow, East China, and South China Seas, is a favorite seafood of coastal residents and has great economic value. However, because resources have been rapidly reduced by overfishing and artificial breeding technology is immature, breeding high-quality fish fry and germplasm conservation and utilization are critical. The aim of the present study was to analyze and compare the morphology of 238 individuals that were collected from seven locations, including Lian Yungang, Dafeng, Chongming, Zhoushan, Ningde, Xiamen, and Wenzhou. More specifically, one-way ANOVA, principle components analysis, cluster analysis, and discriminant analysis were used to investigate whether the seven geographic populations differed in regards to 13 morphological traits and 20 truss network characters. Because individual size variation could have affected the results, all data were calibrated using body length (BL). One-way ANOVA revealed significant differences between the seven geographical populations, and the four principal components identified using principal component analysis accounted for 53.131%, 9.328%, 4.249%, and 3.406%, respectively, of the variation among populations and 70% in total. The first principal component reflected trunk characteristics-body depth/BL, D6 (origin of pelvic fin to the front edge of head occipital spine)/BL, D7 (the front edge of head occipital spine to origin of anal fin)/BL, D8 (origin of pelvic fin to origin of dorsal fin)/BL, D9 (the front edge of head occipital spine to end point of anal fin)/BL, D11 (origin of anal fin to origin of dorsal fin)/BL, and D14 (origin of dorsal fin to end point of dorsal fin)/BL, which indicates that trunk characteristics can be used as a basis for judging population differences. Both the cluster and principle components analyses showed that there was no obvious north-south differentiation in the species' morphology. Many studies have reported opposite patterns, possibly owing to different sampling times, locations, quantities, and analyses. Discrimination analysis indicated that the comprehensive discrimination rate of the seven populations was 85.3% and that the discriminant accuracy ratio was 62.5%-96.7% and 78.1%-90.6% for P1 (Correct discriminant number of one group/the actual number of the group) and P2 (Correct discriminant number of one group/discriminant number entering the group) respectively. However, the discrimination accuracy of the Zhoushan population was low, owing to its unique geographical factors, including ocean current and freshwater flow. The present study provides basic C. lucidus populations, protecting germplasm resources, and selecting fine varieties.

Abstract:The present study investigated the monthly variation in species composition and abundance of fish larvae and juveniles from April to July 2015 off the Yangtze River Estuary. A total of 35839 larvae and juveniles were collected, and these included 62 species from 45 genera, 30 families, and 14 orders. Species richness ranged from 22 to 36, depending on month, increased from April to June, and then declined sharply in July. Meanwhile, the total abundance of larvae and juveniles ranged from 11.45 to 114.31 individuals per 100 m³ and increased throughout the study period, with small increases during the first three months and a greater increase in July. The number of dominant species varied by month, ranging from 5 to 13, and the dominant species mainly included Chaeturichthys hexanema, Engraulis japonicus, Odontamblyopus rubicundus, Acanthogobius ommaturus, and sp.. The dominant species showed greater replacement over time. The greatest species richness was observed in the nearshore water (<20 m depth), and the spatial pattern of species richness along the depth gradient varied among months. Surface temperature and species richness were positively correlated (<0.05) from April to June but negatively correlated from June to July, and in every month, abundance and surface salinity were negatively correlated (<0.05) in the nearshore water (<20 m depth). The high-abundance region shifted away from the shore over time.

Abstract:The aim for the present study was to analyze data from four otter trawl surveys (conducted between 2015 and 2016) in order to investigate variation in the composition and diversity of fish species in Daya Bay, South China. The data included 131 species, which belonged to 84 genera, 53 families, and 14 orders. Species of the Perciformes were the most predominant, accounting for 54.20%, followed by those of the Agunilliformes and Pleuronectiformes, each accounting for 9.92%. Seasonal (temporal) variations of species number were obvious, with the greatest number of species observed during summer (=32). The predominant fish species included Clupanodon punctatus, Leiognathus brevirostris and . Diversity analysis revealed significant seasonal and spatial differences in fish species diversity. The diversity index (') ranged from 1.516 to 1.998, with the greatest value observed during winter and the lowest during autumn, whereas the evenness index (') ranged from 0.494 to 0.869, with the greatest value observed during winter and the lowest during summer, and the richness index (') ranged from 2.230 to 3.777, with the greatest observed during summer and the lowest during autumn. Model analysis indicated that temperature, salinity, and water depth are the main environmental factors affecting the structure of the fish community in Daya Bay. In terms of spatial distribution, fish diversity was greater in the middle of the bay than in coastal waters. Compared with historical data, the fish community structure has changed significantly, as a result of disturbance from anthropogenic activities, including obvious changes in the composition of dominant species and reduced diversity, suggesting the simplification of fish species appeared in this bay.

Abstract:The present study investigated the feeding habits of in Haizhou Bay and adjacent waters by analyzing the stomach contents of 531 individuals collected from March to December 2011. More than 60 prey species were investigated, with the dominant species being sp. and the main prey groups being shrimp, crabs, and bivalves. The feeding habits of exhibited significant seasonal variation. Shrimp were a major prey group during all four seasons, but a large number of crabs were consumed during summer, whereas the greatest proportions of Polychaeta and Cephalopoda prey were observed during autumn. Ontogenetic variation in diet composition was also observed. For example, small mainly consumed small crustaceans, whereas larger individuals mainly consumed fish and shrimp. Feeding intensity (i.e., percentage of empty stomachs and mean stomach fullness index) also exhibited seasonal variation. The greatest empty stomach percentages and mean stomach fullness indices were both observed during spring, whereas the lowest empty stomach percentages and mean stomach fullness indices were observed during winter and autumn, respectively. Canonical correspondence analysis (CCA) indicated that body length was the most important factor affecting the diet composition of , followed by sea bottom temperature, local chlorophyll a, and seawater pH.

Abstract:The aim of the present study was to assess the Indian Ocean yellowfin tuna () using a Bayesian biomass dynamic model and to analyze the impacts of two standardized longline CPUE (catch per unit effort) series from Japan and Taiwan and the prior distributions of intrinsic rate of increase () on the results of the assessments. (1) The models fit the standardized CPUE from Japan better than that from Taiwan, and the results indicated that the stock was overfished and subject to overfishing when the standardized CPUE from Japan was singly used in the models. The opposite might be achieved using the standardized CPUE from Taiwan. Furthermore, when both standardized CPUEs were used, the weighting of the model-estimated Japan standardized CPUE was greater than that of the Taiwan standardized CPUE, and the results were similar for models where only the Japan standardized CPUE was used. (2) If uninformative prior was assigned to was likely to be underestimated, and the carrying capacity (, the estimates of seemed more reasonable. Because there is often a strong negative correlation between in biomass dynamics models, it is difficult to correctly estimate simultaneously, especially under data-poor situations. However, by using informative priors, estimates of parameters of biomass dynamics models can be improved. (3) Deviance information criterion (DIC) and mean square error (MSE) were used to evaluate model fitness, and model S8 was selected as the best model for assessing stock status. According to model S8, Indian ocean yellowfin tuna are overfished and subject to overfishing, which was identical to the results based on Stock Synthesis.

Abstract:The indicator-based approach to fish stock assessment uses many indicators that characterize different attributes of a fish stock in order to assess its status. We considered 19 biological indicators to characterize location, dispersion, traits, fishing and abundance for the small yellow croaker, the indicators were derived from the 16-years (2000-2015) series of bottom trawl surveys over the East China Sea. The one-lag variogram for each indicator was computed, scaled to the indicator variance and ranked, the indicators with highest continuity at lag-one were selected. Min/max autocorrelation factors (MAFs) were calculated for the period 2000-2015 to summarize the multiple time series, detect changes and identity which indicators were responsible for the detected change. According to the variogram results, seven of the 19 indicators exhibited a marked time correlation at the first lag of the variogram below one, including four biological traits (sex ratio, allometric growth coefficient, condition factor, and third quartile of fish length), two spatial indicators (gravity in latitude and spreading area), and one abundance indicator (biomass index). Then the seven selected indicators were used to calculate MAFs during 2000-2015. The first two MAFs had low one-lag variogram values, 0.16 and 0.19, respectively, which represented lower time continuity. The continuity index was also calculated for each of the seven indicators on the first two MAFs, and the four indicators (YCG, BS, SexratioS, and SA) with the highest continuity index were selected to represent the history of the stock. The observed trends of the multivariate time series are described through the MAFs scores. MAF1 divided 16 years into three regimes (2000-2002, 2003-2012, and 2013-2015), and two trends were observed. MAF1 increased from 2000 until 2007 and then decreased until 2015. Whereas MAF2, which was not monotonic and had very small discontinuities, was detailed in two regimes (2000-2012 and 2010-2014) with four trends. From 2000 to 2003, it was close to being flat. From 2003 to 2006, it decreased, and it increased from 2006 to 2012, after which it decreased until 2015. The indicators that contributed the most to MAF1 were YCG (-0.756) and BS (-0.609), and the indicators that contributed the most to MAF2 were SexratioS (0.590), BS (0.539), and SA (-0.606). MAF1 was negatively correlated to YCG and BS, whereas MAF2 was positively correlated to SexratioS and BS but negatively correlated to SA. Due to the different inter-annual variation of biological traits and spatial indicators, the MAFs also exhibited different temporal change patterns at the different time scales.

Abstract:Benthic macroalgae are highly productive and increase biodiversity through the provision of a habitat for marine organisms and act as spawning, nursery, and feeding grounds for an extensive range of marine fauna. As a dominant habitat-former on temperate rocky coastlines, benthic macroalgae are important fundamental species in the temperate marine climate owing to their high productivity and extensive distribution. However, the loss of benthic macroalgal habitats has been widespread along the rocky coastlines owing to various perturbations, including climate change, species invasion, sedimentation increase, and anthropogenic stress. The establishment of artificial reefs have been proven an efficient approach for the recovery of the benthic macroalgae ecosystem. For the past three decades, the habitats of benthic macroalgae in Laoshan Bay of Qingdao have been destroyed by anthropogenic activities such as mariculture and fisheries. To mitigate the habitat losses of benthic macroalgae and restore the spawning grounds, artificial rocky reefs were deployed in two coastal areas, Huangshankou, which has high levels of wave motion and Sanmuqian, which has low levels of wave motion, between 2009 and 2010. After the deployment of artificial reefs, the marine habitats underwent a long-term and dynamic process prior to the formation of stable ecosystems. The inter-month variation and distributional pattern of benthic macroalgal communities were a reflection of the self-adaption of the ecosystem to the changing conditions. To study the community characteristics, inter-monthly variation, and response to the environmental factors of benthic macroalgae in the artificial reef zones, the horizontal and vertical distribution of the benthic macroalgae in two artificial reef zones were investigated between May and September 2015. Wave motion indexes between the two artificial reef zones showed extremely significant differences, whereas similar conditions were found among different wave depths in the same artificial reef zones. The temperature range between May and November showed significant variation, whereas no significant difference was found between artificial reef zones at same the time. A total of 26 species of 21 genera, belonging to three phyla were found; among these, 15 species belonged to Rhodophyta, 7 species belonged to Phaeophyta, and 4 species belonged to Chlorophyta, which accounted for 57.69%, 26.92%, and 15.38% of the total, respectively. The replacement of benthic macroalgal species in different months displayed significant differences: were the predominant species during spring, summer, and autumn, respectively. The species diversity indices of benthic macroalgae increased at first and decreased subsequently, whereas the indices in Sanmuqian reef zone were generally higher than those in Huangshankou Reef zone. Differences in the species diversity indices and the dominant species in different months were mainly caused by temperature variations and different temperature adaptability of macroalgal species. Redundancy analysis further proved that temperature was the key influential factor in the monthly replacement of benthic macroalgae and contributed to 37.64% of the variation, whereas wave motion and depth were the key influencing factors in the horizontal and vertical distribution of benthic macroalgae and accounted for 26.54% and 19.13% of the variation, respectively. The results indicated that the artificial reefs provided efficient substrates for benthic macroalgae in Laoshan Bay. The benthic macroalgal communities showed relative stable seasonal perturbation in the artificial reefs, which reach maturity and have the ability to withstand the external disturbances 5 years after deployment of the artificial reefs.

Abstract:In order to restore the resources in northern coastal water of Zhejiang Province, the large-scale release had been carried out from 2013 to 2016. A total of 7835×10⁴ ind. fertilized eggs were released, and at the same time, the follow-up monitoring survey were carried out. Considering the certain point information and supplementary sample data, we estimated several indicators including growth equation and death coefficient, built the model of fishery stock assessment, finished the simulation analysis of the variation trend of fishery production and residual rate. Meanwhile, we introduced the supplementary abilities of breeding population to quantitatively evaluate the enhancement effect. The results indicate that, the released in northern area of Zhejiang Province between year 2013 to 2016, its limited body length is 138 mm, the growth parameters is -0.05237 a., the total mortality coefficient () is 1.74, the fishing mortality coefficient ( ind. fertilized eggs could receive 137.3 kg production, when still supplement 502 ind. sexually mature individuals into study area. Generally speaking, stock enhancement serves the purpose of population restoration and increases both production and income in certain degree. The model estimation analysis shows:if people could postpone the capture two month, the capture production may add 10.0%, and the growth of the sexually mature individuals will also increase 27.5%. On the other hand, if the fishing mortality coefficient could reduce to 0.76, the production may increase to 155.6 kg/a, and the proportion of sexually mature individuals may add 29.4%. Finally, we hope could put forward the suggestions about improving the effect of releasing and using the resources reasonably according to the research.

Abstract:Hangzhou Bay, which is located in northeastern Zhejiang Province, is a typical subtropical estuary. Because of the bay's rich food resources, many fish, shrimp, and crab species migrate from deep sea waters to Hangzhou Bay for spawning and feeding. However, recent coastal pollution and overfishing have seriously damaged the bay's marine environment and fishery resources. Some commercial species, such as , have declined or disappeared, which may contribute to the collapse of the marine ecosystem. Macroinvertebrates are one of the most important groups of marine organisms in estuaries and play an important role in estuary food chains. Therefore, the current macroinvertebrate community structure and condition of the marine environment in Hangzhou Bay must be studied in order to provide scientific information for the ecological remediation efforts in Hangzhou Bay. The macroinvertebrate community structure of northern Hangzhou Bay was characterized, based on a field investigation of fishery resources in February, May, August, and November of 2016. The investigation focused on species composition, seasonal variation in macroinvertebrate community structure, and the relationship between the community and environmental factors. Macroinvertebrates were captured at 12 sampling stations using a beam trawl of 20 m in length and 4 m in width. The beam length was 6 m, and the opening height of the net was 2 m, with the smallest net mesh of 25 mm. Trawling was performed at 1.5-4.4 knots for 15-63 min at each station, and water temperature, salinity, and depth were recorded at the same time. Index of relative importance, cluster analysis, and multivariate statistics were used to analyze species composition, dominant species, and community structure characteristics. A total of 22 species (18 genera, 15 families, 5 orders, and 4 classes) were captured during the study. Decapoda dominated, accounting for 77.3% of the total species number, followed by Stenoglossa, which only accounted for 9.1%. Five dominant species were identified (Potamocorbula amurensis, and was a dominant species during all seasons, whereas was a dominant species during winter, spring, and autumn. CLUSTER analysis and non-metric multidimensional scaling (NMDS) indicated that the macroinvertebrate community of northern Hangzhou Bay could be clustered into two groups at 44% Bray-Curtis similarity level. Group I was classified as the winter/spring assemblage, whereas group Ⅱ was classified as the summer/autumn assemblage. Group I consisted of 19 stations in February and May, and Group Ⅱ consisted of 21 stations in August and November. The dissimilarity between Group I and Ⅱ was as high as 57.76%, and analysis of similarity (ANOSIM) indicated that community structure of the two groups was significantly different (<0.01). BIOENV indicated that the macroinvertebrate community structure of northern Hangzhou Bay was closely related to water temperature and salinity (correlation coefficient:0.39). The present research indicated that the macroinvertebrate community structure of northern Hangzhou Bay is simple and that the main dominant species were small shrimps. There was a significant difference in the seasonal variation of the macroinvertebrate community structure of northern Hangzhou Bay, and the dominant species varied each season. Water temperature, salinity, and the ecological migration of dominant species probably impact the replacement of macroinvertebrate community structure in northern Hangzhou Bay, and the macroinvertebrate community structure of northern Hangzhou Bay is seriously disturbed.

Abstract:Beijiang River, the second largest river of the Pearl River Basin, is an important species gene pool which has 143 species fish in datum. Shijiao reservoir is the first cascade river-type reservoir between Qingyuan hydro-junction and Feilaixia hydro-junction. Because of the blocking effect and other human activities, fishery resources had a declined tendency. Up to now, no relative research was reported in this area since the hydro-junction was built, so the actualities of fishery resource is unknown. To understand the current situation of fish resource, a split beam echosounder EY60 (120 kHz, 200 W) was used to survey the fish resource and behavior feature from 2015 to 2016 in different seasons. All the surveys were divided into a certain elementary distance sampling unit EDSU, so that for every survey, 200-250 EDSU with independent estimates of biomass, density and behavior were available. Echoview 4.9 was used to process acoustic data. The results show that there was significant difference in fish density, behavior feature in different survey periods and different survey areas. The average fish density in the survey area was (0.008±0.0125) ind/m³ in December 2015, (0.1601±0.1123) ind/m³ in March 2016 and (0.0405±0.0449) ind/m³ in June 2016 respectively. Fish individuals had evident seasonal variation tendency, characterized that fish mainly resided in dam area in winter and spring and migrated to upstream area in summer. According to the vertical distribution data, fish mainly distributed in 4-12 m layers and the distribution had significantly difference in different area (<0.01). Fish's behaviors such as swimming speed, swimming direction and depth preference were significantly different in different season. Take migration direction as examples, fish mainly migrated horizontally from dam area to upstream area and swimming down in vertical direction in summer, winter has opposite situation. As a whole, this study reveals a clear pattern of fish distribution, migration and behavior feature in different season, and shows the applicability of acoustic method to study fish behaviors in large scale area. The results can provide reference for fishery resources sustainable development and fishery engineering design of Beijiang River.

Abstract:The present study sampled every month from June to November in 2016, aimed to assess the effect of oxidoreductase activity on the removal rate of pollutants from constructed wetlands and to determine whether matrix enzyme activity can be used to assess the effectiveness of overall removal rate. Integrated vertical-flow constructed wetlands that incorporated two substrates (bio-ceramics and pebbles) and three plant species () were constructed to investigate the activity of four oxidoreductases (dehydrogenase, polyphenol oxidase, peroxidase, and nitrate reductase) and to explore the relationship between enzyme activity and removal rates of total nitrogen (TN), nitrate nitrogen (NO₃^--N), total phosphorus (TP), orthophosphate (PO₄^3--P), and COD_Mnfrom aquaculture wastewater. Oxidoreductase activities were significantly different in the experimental operation cycle. Dehydrogenase and peroxidase activities initially increased and then decreased, and the enzyme activities reached maximum levels during the peak of plant growth. Polyphenol oxidase and nitrate reductase activities were not significantly different from June to August and reached maximum levels when the plants stopped growing. Dehydrogenase, polyphenol oxidase, and peroxide activities exhibited similar vertical distributions (i.e., surface > middle > lowest), whereas nitrate reductase activity exhibited the opposite trend. There were significant positive correlations between nitrate reductase activity and the removal rate of NO₃^--N (=0.0444) and between dehydrogenase activity and the removal rate of COD_Mn (=0.0439). The activities of polyphenol oxidase and peroxidase were not significantly correlated with the removal rates of TN, NO₃^--N, TP, PO₄³-P, and COD_Mn. Accordingly, dehydrogenase can be used as an indicator of the effectiveness of COD_Mn removal in constructed wetlands, and nitrate reductase activity can be used as an indicator of the effectiveness of NO₃^--N removal.

Abstract:Natural mortality coefficient () is a key parameter in fisheries stock assessment. Its accuracy directly determines the reliability of assessment results and also influences the establishment of fisheries management. Most mathematical models of fish stock dynamics incorporate , either directly or indirectly. Fishery scientists have explored accurate estimates of for a long time, in order to develop a more precise understanding of fish populations and to establish a more scientific basis for managing fisheries resources and sustainable development. The present study introduces and evaluates the most common models for estimating natural mortality coefficients for fish populations from three aspects, namely life-history parameters, tag-return, and age-structure. The first approach to estimate the instantaneous rate of natural mortality in fish stocks is based on the observation that is strongly correlated with life history parameters, such as maximum observed age, age at reproductive maturity, asymptotic fish length, and growth rate. The Pauly empirical equation, Gislason empirical equation, and Tanaka's maximum observed age's method are among the most commonly used methods for assessing inshore fisheries in China. By classifying tagging data, based on catch per unit effort, size at release, and the probability of tag loss, Chapman, Hampton, and Treble have each constructed their own models, and some scholars have combined these methods to develop a model that is superior to any of the individual models. The assessment results of using tag-return methods would have a high reliability, but the huge costs of investigation, lower credibility of recapture, and prior model assumptions contribute to poor generality. Considering that age is the potentially most important factor affecting estimates of , virtual population analysis (VPA) and cohort analysis (CA) are established using catch-at-age data. These methods could be used to reliably estimate fish stocks with long-term catch data. However, considering the incomplete and inaccurate statues of historical catch data in Chinese coastal fishes, the practicality of the VPA or CA models is relatively low. Meanwhile, taking and some coastal fish stocks as examples, this study compared estimation results through different methods and found that Pauly empirical equation is more reasonable to calculate . Then, this paper introduced the misapplications of Pauly empirical equation in inshore fisheries of China. The main misapplications were equation error, unit error and calculation mistake. According to the limited data and fishery exploitation status, we suggest that Pauly empirical equation has a positive meaning to assess the for major economic fish stocks in China.