We analyzed the nutrient composition (moisture, crude protein, crude fat, crude ash), amino acids and fatty acid contents in muscles of Pacific white shrimps (Litopenaeus vannamei) cultured in floating cages and ponds. The crude protein content of the cage group was significantly higher than that of the pond group (P < 0.05), but the contents of the moisture, crude fat and crude ash of the two groups were not significantly different (P > 0.05). Eighteen kinds of common amino acids were detected in two groups, and the contents of total amino acids (TAA), aspartic acid (Asp), isoleucine (Ile), arginine (Arg) and proline (Pro) of the cage group were significantly higher than those of the pond group (P < 0.05), but the contents of the essential amino acids (EAA), half-essential amino acids (HEAA), delicious amino acids (DAA) and prawn flavor amino acids (PFAA) of the two groups were not significantly different (P > 0.05). Thirty kinds of common fatty acids were detected in two groups, and the contents of saturated fatty acids (SFA), mono-unsaturated fatty acids (MUFA), poly-unsaturated fatty acid (PUFA) and n-3 PUFA (EPA and DHA) of the cage group were significantly higher than those of the pond group (P < 0.05). The contents of palmitic acid (C_16:0) of two groups were both the highest, and the content of EPA+DHA of the cage group was 1.90-fold of the pond group (P < 0.05). The results indicate that the nutrient composition of shrimps cultured in floating cages is superior to those cultured in ponds, having higher nutritional value.

To evaluate the primary productivity in the Pearl River Delta, the spatio-temporal distribution of primary productivity and its relationship with environmental factors were investigated by multivariate statistical methods during March, June, September and December in 2015. The concentration of primary productivity (C) ranged from 98.81 mg·(m²·d)^-1 to 927.21 mg·(m²·d)^-1 with an annual average of 346.51 mg·(m²·d)^-1. The primary productivity varied in different seasons (spring> winter> summer> autumn).The annual average of primary productivity ranged from 232.60 mg·(m²·d)^-1 at Shiqiao to 600.61 mg·(m²·d)^-1 at Zhujiangqiao. Positive relationship was found between primary productivity and transparency, nitrogen and phosphorus as well as chlorophyll a(P < 0.01, n=52), whereas the primary productivity showed negative correlation with silicate(P < 0.01, n=52). The primary productivity and eutrophication composite index (EI) showed linear relationship. Compared with other watersheds, the Pearl River Delta was at medium or high eutrophication status with relative low primary productivity, so it is needed to prevent pollutions with a tendency towards heavy eutrophication.

To investigate the spatio-temporal relationship among the main fishery resources in the Bohai Sea, we carried out a bottom trawl survey there from August 2014 to May 2015, and then made a preliminary analysis of the horizontal spatial distribution, spatial distance and the seasonal characteristics of three groups of fishery resources. The results show that the concentration areas of the three groups of fishery resources demonstrated spatial differentiation. The trend of spatial differentiation became more and more significant, as the concentration areas of the three groups aggregated. The distance among three groups was longer in summer and autumn than in winter and spring. Among the three groups of fishery resources, the distance between cephalopoda and crustacean was relatively short, while the distances between cephalopoda and fish, and fish and crustacean were relatively longer, which was associated with difference of the locomotivity of the three groups of organisms.

According to the fisheries resources data collected from the Nansha waters of Pearl River Estuary in November 2015, we investigated the community structure, dominant species and diversity of fishery resources in this area, and 40 fishery species, mainly fishes and crustaceans, were found, including 21 demersal fishes, 3 pelagic fishes and 16 crustaceans. The index of relative importance (IRI) was used to measure ecological dominance of species to decide the role each species played in the community. The dominant species were Charybdis acuta and Parapenaeopsis hungerfordii in autumn, whose IRIs were higher than 1 000. The range of catch rates in weight was 0.63~11.15 kg·h^-1 (average:4.23 kg·h^-1). The range of catch rates in individual number was 84~885 ind·h^-1 (average:433 ind·h^-1). The average Shanon-Wiener diversity index (H′), Pielou evenness index (J′) value and Margalef richness index (D) of fishery resources in autumn were 2.07, 1.64 and 0.59, respectively. The analysis shows that sizes of the catch were generally small, and the catch mainly consisted of small commercial crustaceans and juveniles of commercial fishes. The spatial distribution of diversity of catches had little variation of in all stations. Compared with the fisheries catches in autumn 2002, the species diversity declines and the community structure is relatively simple at present.

Based on the date collected by quarterly otter trawl surveys in Zhelin Bay from 2011 to 2012, we analyzed the fish species composition, resources structure and trophic level. A total of 99 fishes were collected during the surveys. The proportions of demersal fish, tropical fish, and carnivorous fish were 49.49%, 78.78% and 79.79%, respectively. The composition of the dominant species of biomass and abundance percentages was similar, including Parachaeturichthys polynema, Harpodon nehereus and Johnius belengeri. The maximal biomass and abundance of fish were in summer in Zhelin Bay. The average body weight of fish in four seasons was less than 15 g. The composition of fish was more abundant in spring and autumn. The dominance of biomass of fish was the highest in winter. The feeding habit of fish in Zhelin Bay was mainly intermediate carnivorous and advanced carnivorous. The change of trophic level of four seasons was inconspicuously. The annual average trophic level index was 3.478 of intermediate level. It was in summer that the average body weight of high trophic level fish peaked.

A survey of fish resources in Qingshitan Reservoir was conducted from April 2015 to January 2016.And 3 750 fish(153.28 kg)were collected, and 32 species belonging to 5 orders, 12 families and 27 genera had been identified. Cypriniformes, which accounted for 53.13% of all species and 61.92% of all individuals, was the dominant fish fauna. According to the analysis of relative importance index (IRI), the most dominant species were Carassius auratus, Cyprinus carpio and Hemiculter leucisculus. The analysis of species diversity shows that Margalef index (D) was 2.58~3.52;the Shannon-Wiener species diversity index (H′) was 1.62~1.92;the Pielou evenness index (J′) was 0.53~0.63, which was the highest in summer but relatively lower in winter. The diversity of fish decreased from the mouths of streams, and from islands to the center of the reservoir. The result of species diversity analysis indicates that there was no significant difference in the fish communities among seasons and sampling sites.

We explored the distribution of PAHs in pond waters in the Changsha Bay and assessed their ecological risk to the cultured oyster. It is indicated that the range of the 16 USEPA priority PAHs in water, suspended solids, oysters and surficial sediment from the oyster ponds were 6.62~21.2 ng·L^-1 (average:9.87 ng·L^-1), 92.9~355 μg·kg^-1(average:198μg·kg^-1), 12.7~17.4 μg·kg^-1(average:15.5 μg·kg^-1)and 247~615 μg·kg^-1(average:322 μg·kg^-1), respectively. Compositional analysis of the PAHs reveals that 3-ring PAHs were dominated in the sediments, followed by 4-ring compounds. The isomeric ratios of the PAHs in sediment show that the source of the PAHs in the oyster ponds were originated predominantly from high temperature pyrolytic inputs, which may be related with the thermal power plants around the culture zone. The Effects Range Low (ERL) and Effects Range Median (ERM) were applied to assess the ecological risk. It is indicated that the PAHs in the sediment were lower than the ERL values, which was rarely associated with adverse effects on oysters cultured in the ponds. However, attention must be paid to the compounds such as fluorine and anthracene due to their contents between ERL and ERM, which will cause adverse effects on the oyster.

Gold grass carp is a kind of grass carp (Ctenopharyngodon idellus) that was introduced from abroad in the 1990s. We used 15 microsatellite markers to analyze the genetic structure and genetic diversity of gold grass carp population and four grass carp populations [Yuanjiang (YJ), Ningxiang (NX), Honghu (HH) and Xijiang (XJ)] from the Yangtze River and the Pearl River of China. The results show that all the 15 microsatellite loci were highly polymorphic, with polymorphism information content (PIC) of 0.763~0.939. The expected heterozygosity (H_E) of gold grass carp population was 0.662, lower than those of the four Chinese grass carp populations (H_E=0.852~0.885). The analysis of genetic differentiation index (F_ST) indicates that the F_ST between gold grass carp population and YJ, NX, HH, XJ populations were 0.157 2, 0.129 5, 0.147 5 and 0.114 4, respectively. Genetic distance analysis shows that the genetic distance between gold grass carp population and XJ population was the shortest (0.476 3), and was the longest with YJ population (0.810 7). The NJ phylogenetic tree based on genetic distance shows that the four Chinese grass carp populations clustered together as one branch, and gold grass carp population as another. The result shows that the genetic diversity of gold grass carp population is lower than that of Chinese grass carp population, with relative distant genetic relationship.

In order to understand the genetic potential of three selective breeding populations of blunt snout bream (Megalobrama amblycephala), the genetic diversity were assessed in four populations [three selective breeding populations and one foundation population (F₀) of "Pujiang No.1" selected strain] of blunt snout bream on 14 polymorphic transcriptomic microsatellite loci. The parameters of genetic variabilities in three selective breeding populations are summarized as follows:the average number of alleles (A) was 7.928 6~8.785 7;the average number of effective alleles (A_E) was 4.409 4~4.878 4;the value of average observed heterozygosity (H_O) was 0.491 1~0.574 4;the value of average expected heterozygosity (H_E) was 0.741 3~0.751 8;the value of average polymorphism information content (PIC) was 0.691 2~0.705 2;the value of average Wright′s inbreeding coefficient (F_IS) was 0.229~0.352. The genetic diversity indices of A_E and H_E in three selective breeding populations were higher than those in foundation population (F₀). The LSD-t test shows that no significant difference (P>0.05) existed between foundation population (F₀) and three selective breeding populations in terms of A_E and H_E. Estimation of effective population size (N_e) for three selective breeding populations was 11.0~29.3. Recent genetic population bottleneck was detected in three selective breeding populations. The genetic distance (D_A, D_SW) among three selective breeding populations were 0.175 4~0.358 8 and 0.804 7~1.054 4, respectively. Relatively high genetic diversity and genetic potential were maintained in three selective breeding populations. Low effective population size and bottleneck effect may lead to loss of heterozygosity and inbreeding depression. Scientific measures should be taken to protect the genetic potential of selective breeding populations in the future.

Taking Microcystis aeruginosa and Scenedesmus obliquus as samples, we investigated the effect of concentration of nitrate and phosphate on algal growth. The results show that the maximum inhibitory rates of nitrate limitation on algal growth rate, biomass and chlorophyll content of M.wesenbergii were 2.25%, 2.75% and 40.01%, respectively, while those of S.obliquus were 38.56%, 58.64% and 72.51%, respectively. The maximum inhibitory rates of phosphate limitation on algal growth rate, biomass and chlorophyll content of M.wesenbergii were 11.79%, 10.94% and 51.94%, respectively, while those of S.obliquus were 22.69%, 49.62% and 26.87%, respectively. The positive correlation was observed among nitrate, phosphorus concentrations and algal growth rate, biomass both in linear or exponential types. Growth of S.obliquus was inhibited seriously compared with that of M.wesenbergii at nitrate or phosphate limitation. Lower sensitivity to nitrate or phosphate limitation of M.wesenbergii might support the priority of algal growth and competition.

The study investigates the tissue expression of transferrin (Tf), tumor necrosis factor alpha (TNFα) and C-type lysozyme (C-Lys) in healthy Trachinotus ovatus after it was infected with Photobacterium damselae subsp. piscicida in kidney. The results show that after infection, the accumulative mortalities of T.ovatus reached the maximum in 48 h (76.4%); and the colony of P.damselae in T.ovatus′ kidney continued to decline in 3~96 h from 1.07×10⁶ CFU·g^-1to 1.29×10³ CFU·g^-1. The Tf and TNFα expressions were the highest in the liver, and the C-Lys expression was the highest in the head kidney in healthy T.ovatus. After TOS1 infected, the Tf expression in 3~12 h in test group was higher than that of control and was the highest in 6 h (17.99 times as high as that of control). The TNFα expression of the test group was higher than that of the control after infection of 3 h, 6 h and 24 h. The TNFα expression was the highest in 24 h (6.05 times higher than that of control). The C-Lys expression in infection group was lower than that in control in 3~96 h. The study indicates that the Tf and TNFα expressions can be promoted while C-Lys will be suppressed after TOS1 infection in T.ovatus′ kidney.

To investigate the swimming performance and swimming behavior during fatigue cycle，we tested the juvenile Aristichthys nobilis′ swimming capability by increasing velocity with mobile Brett-type swim tunnels by LoliTrack，and then assessed the swimming capability of juveniles at different actuating state.Results show that the oxygen consumption rate (M_O2) before swiming fatigue increased with swimming speed significantly. The burst swimming speed M_O2 was higher than the critical swimming speed M_O2.Video analysis displays that there was significant linear correlation between tail beat frequency and swimming speed. Meanwhile，the juveniles showed burst-coast behavior continuously for two tests at the critical swimming speed in the two groups of repeat fatigue. However，during the transition from the test of burst swinmming speed to the test of critical swimming speed，the juveniles did not show that behavior. After the test of the first critical swimming speed，the second critical swimming speed was higher than that of the test of burst swimming speed. Neither of the burst swimming speed in two tests had significant difference. Anaerobic exercise consumption of bighead carp led to significant decrease of aerobic swimming performance，and aerobic exercise had no effect on anaerobic exercise.

Taking ovate pompano (Trachinotus ovatus) meat as raw material and taking enzymatic hydrolysate and bile salts in vitro binding rate as index, we screened the optimal protease from five kinds of food protease. Then we used orthogonal design to optimize hydrolysis conditions in order to improve the binding rate of bile acid salts and used GPC method to analyze the molecular weight distribution of peptides. The results show that the tryptic hydrolysates had higher binding rate than that of the other protease hydrolysates, and the in vitro binding rate of sodium cholate, sodium glycocholate and sodium taurocholate by enzymatic protein (100 mg·mL^-1) was 42.1%, 33.5% and 30.1%, respectively, which was 78.3%, 74.4% and 76.8% equivalent to the positive control cholestyramine (20 mg·mL^-1). The maximum percentage of sodium glycocholate hydrate binding rate was obtained under the conditions:hydrolytic time of 2 h, enzyme additives of 2 000 U·g^-1, meal-to-water ratio of 1:4 (g·mL^-1, at pH 8, 37 ℃). Under the optimal condition, the in vitro binding rate of sodium glycocholate hydrate by enzymatic hydrolysate (20 mg·mL^-1) was corresponding to 48.3% of positive control cholestyramine at the same concentration. The relative molecular weight of peptides below 3 kD in enzymolysis products accounted for 77.30%.

To develop light-pickled bass products, we study the processing technology of light pickled semi-dry bass (Micropterus salmoides) by investigating the effects of different hurdles on the sensory quality, flavor and microbial of products during processing via hurdle technology. We optimized several pretreatment and curing factors (salt, sugar, wine, citric acid, curing temperature and time), drying process [drying way, temperature and water activity (A_w)] and package process (package treatment, sterilization way and package way) so as to determine the best processing technology. The optimal conditions are listed as follows:4 g·L^-1 citric acid to clean the material; 60 g·L^-1 salt, 20 g·L^-1 sugar and 1.5% wine to cure bass for 4 h at 4 ℃; drying for 12 h at (30±2)℃; controlling the best A_w 0.883 of product; vacuum packaging; 24 h of 0~4 ℃ treatment before pasteurization at 85 ℃ for 30 min. Thus, the light-salted bass products were improved so that they can still hold good quality and special flavor, reduce microbial and be stored for a long time. The products under 4 ℃ can be preserved for more than two months.

Flow cytometry, which is widely used in fish breeding, can detect cell cycle and DNA content of living organisms rapidly. However, the current studies mainly focus on experiments based on fish blood and germ cells, which have limitation in periodicity and operation. We used different tissues of Ctenopharyngodon idellus by flow cytometry to obtain a desired and stable histogram showing DNA content of the fin tissues from four different fishes. All fin tissues exhibited cell cycle phenomenon, and low ratio appeared at time phase of G₀/G₁. Besides, Danio rerio was used as internal calibration to detect the DNA content (C value) of Megalobrama amblycephala (1.25±0.07) pg, and the result has no significant difference with the results of other studies. Therefore, it is concluded that use of fin as alternative for blood and germ cells for flow cytometry research is scientific and feasible.

Crisp grass carp (Ctenopharyngodon idellus) is one of the characteristic fishery products in Guangdong Province, but its "no crispness" and "semi crispness" have seriously restricted the industry′s development. In order to explore the evaluation method of crispness, we combined a production process (120 d faba bean + 30 d artificial feed). The muscle samples were collected once every 30 d, and the changes of sensory crispness, texture characteristics and muscle fiber structure were detected. The results demonstrate that sensory crispness of grass carp increased continuously with the increase of production time (before 120 d) in faba bean group, while the diameter of muscle fiber decreased and the density increased gradually (P < 0.05);after 60 d, the texture characteristics (hardness, springiness, chewiness, cohesiveness and gumminess) in faba bean group were significantly better than those of the control (P < 0.05). Feeding artificial diet of 30 d did not affect the sensory crispness, texture characteristics and muscle fiber structure (P>0.05). The correlation analysis shows that the correlation among hardness, springiness, chewiness, gumminess and sensory crispness was much higher (R²>0.90, P < 0.05). It is concluded that the hardness, springiness, chewiness and gumminess can be used to evaluate the crispness, and 30-day feed did not affect the crispness.