Abstract:There has been extensive research into the role of nucleotides and their related metabolic products in aquatic feeds. Nucleotides and metabolites play key roles in many biological processes and are considered conditionally essential nutrients. During periods of rapid growth or certain disease states, dietary nucleotides may spare the cost of de novo nucleotides synthesis and optimize the function of rapidly dividing tissues, such as those in the gastrointestinal and immune systems. Research on dietary nucleotides in aquatic animals has illustrated that they may improve diet palatability, enhance growth in early stages of development, and maintain intestinal and liver health, as well as increase immunity and disease resistance. Despite their apparent importance, little is known about the benefits of supplementary nucleotides in . We evaluated the effects of dietary nucleotides on growth, body composition, midgut morphology, and anti-oxidant activity in the hepatopancreas and serum in juvenile . We randomly assigned 960 shrimp (mean body weight: 1.01 g±0.02 g) into 8 triplicate groups. Group G0 (control) was fed a base diet and the remaining seven groups (G0.1, G0.2, G0.4, G0.6, G0.8, G1.0, and G1.2) were fed the base diet supplemented with 0.1, 0.2, 0.4, 0.6, 0.8, 1.0, or 1.2 g/kg, respectively, of a nucleotide mixture containing adenosine-5′-monophosphate (AMP), cytidine-5′-monophosphate (CMP), uridine-5′- monophosphate disodium salt (UMP), inosine-5′-monophosphate disodium salt (IMP), and guanosine-5′-monophosphate disodium salt (GMP) (1 : 1 : 1 : 1 : 1 , mix-NT). All groups were fed their respective diets three times a day (8:00, 15:00, and 20:00) at the same fixed rate, which ranged from 4% to 6% of body weight, for 7 weeks. Specific growth rate (SGR) and survival (SR) tended to increase as the concentration of the dietary mix-NT increased, peaking in the group supplemented with 0.6 g/kg, though the differences among the groups were not significant (>0.05). The feed conversion rate (FCR) was lower in the treatment groups than in the control group, but not significantly (>0.05). The whole body moisture content was significantly affected by the level of dietary mix-NT supplementation (<0.05), but there were no significant differences in the content of crude protein, ether extract, or ash (>0.05). The dietary mix-NT had a significant effect on the hepatosomatic index (HSI) in the group supplemented with 0.6 g/kg (<0.05). Glutamic-oxaloacetic transaminease (GOT), glutamic-pyruvic transaminase (GPT), and uric acid (UA) content were significantly lower in shrimp fed 0.4 g/kg mix-NT (>0.05). There was a significant increase in the midgut jejunum wall thickness in shrimp fed 0.1–0.8 g/kg mix-NT, but there no significant difference in villus height of all groups. Alkaline phosphatase (AKP) activity and total antioxidant capacity (T-AOC) in the hepatopancreas tended to increase as the level of supplementation with dietary mix-NT increased, and were significantly higher in groups G0.2 and G0.4, respectively, than in the control (<0.05). Adding mix-NT had no significant effect on serum alkaline phosphatase (AKP) and superoxide dismutase (SOD) activity (>0.05). In conclusion, supplementing the diet with a mixture of 5 nucleotides improves hepatopancreas function, maintains intestinal morphology, and enhances anti-oxidant activity in the hepatopancreas of juvenile . It would be interesting to determine the effects of nucleotide supplementation on immune function, particularly with respect to white spot syndrome virus (WSSV).

Abstract:PAE) family, is thought to have an endocrine disrupting effect on vertebrates and humans and has been identified as priority controlled hazardous substance in the United States and China. In order to evaluate the effect of DPB, we examined liver and gill levels of superoxide dismutase (SOD) and malondialdehyde (MDA), and brain levels of crimson snapper (DBP for respectively. The safe concentration (SC) of DBP was 2.04Gill superoxide dismutase (SOD) activity increased significantly as the concentration of DBP increased. In contrast, there was no clear pattern of induction or inhibition for liver SOD activity, though levels in the groups exposed to 0.5 were significantly different from the control ( was significantly higher after 6 h, but decreased thereafter. Similarly, increased then decreased, and. Brain levels of were 32.07%, 62.07%, and 61.60% higher in fish exposed to 0.125, , activity was lower in the treatment groups than in the control group after 96 h exposure (DBP on . It could be concluded that DBP causes oxidative stress and neurotoxicity in aquatic organisms. Thus, attention should be given to the potential ecological risk posed by this contaminant.

Abstract:a benthic dwelling fish distributing throughout the Indian Ocean and Western Pacific,plays an important role in marine ecosystems. Despite its abundance and importance to fisheries, little is known about the biology of this species. We evaluated ontogenetic and diet variation in the feeding ecology of in the areas adjacent to the Changjiang River Estuary. We collected a total of 450 individuals ranging in size from 64 standard length (SL) during monthly surveys in the south Yellow Sea and the north East China Sea between September 2009 and August 2010. Based on stomach content analysis, was a generalist. We identified 39 prey species, of which other fish were the most abundant, accounting for 84.13% of the total food by weight. At the species level, the primary prey were Apogonichthys lineatus,The feeding intensity, as indicated by the percentage of empty stomachs and the mean stomach fullness index, varied significantly among seasons. Feeding activity was the highest in autumn and lowest in winter. There were significant seasonal differences in the diet of Decapods were more important in spring, whereas fish were more important during other seasons. Both the feeding intensity and diet composition varied significantly among different size classes. There were two abrupt changes in diet composition at about 100 and 250 mm SL, the latter characterized by a switch from euryphagy to stenophagy. The trophic level of was 3.80, suggesting that this species was a high level predator within the food web in the Yellow Sea and East China Sea.

Abstract:studing the effect and mechanism of variability of habitat factors on important biological resources in the Yangtze River estuary (YRE), we evaluated the relationship between fish community structure and environmental factors in the YRE. We collected fish by bottom trawling and obtained environmental data from 30 stations in the YRE in May and June 2010. In addition, we used historical data to analyze the effect of large hydraulic projects on fish community dynamics in the YRE. We collected a total of 40 fish species belonging to 23 families and 12 formers. The Engraulidae and Gobiidae families were the most abundant (5 species each), followed by Sciaenidae (4 species), and Cynoglossidae (3 species). The trawl catches were dominated by young-of- year juveniles. The most abundant species (94.11% of the total catch) by life history type were (marine migrant), (anadromous). Cluster and non-metric multidimension scaling analysis revealed significant spatial variation in the fish community. Of the nine environmental variables we measured, water depth, bottom salinity, and surface salinity were the most significant factors influencing fish species richness and density in the inner zone. Conversely, the fish community in the outer zone was primarily influenced by the bottom pH, surface salinity, and bottom temperature. The number of fish species declined compared to historical catches in May (69 species, 1.72×10⁴ ind/km²)and June (62 species, 2.29×10⁴ ind/km²) in 1985, though fish density (5.2×10⁴ ind/km²) increased. Our results indicate the YRE has still been the spawming and nursery ground for commercial species, but fish community structure has varied.

Abstract:We evaluated the community structure and diversity of invertebrates in the northern region of China Sea using data collected from bottom trawl surveys in May and August 2010. We collected a total of 32 invertebrate species, including 15 species of shrimp, 10 species of crab, and 7 species of squid. Shrimps were dominant in Bohai Sea, accounting for 86.57% of the biomass and 96.55% of individuals in May and 46.16% of the biomass and 80.85% of individuals in August. In contrast, the north region of the Yellow Sea was dominated by crabs in May (s). We quantified the ecological dominance of a species using an index of relative importance (IRI). The dominant species changed between seasons and regions. We calculated three diversity indexes to analyze the diversity of invertebrates: the species abundance index (), and the species evenness index (Bohai Sea than in the northern region of the Yellow sea. The Bray-Curtis , a measure of the similarity of the invertebrate community in the two regions, was 0.315 in May and 0.297 in August. The season transformation index (AI) and the transfer index (MI) suggested that some species migrated from Bohai Sea.

Abstract:sinking depth and sinking speed of tuna purse seines. We attached a micro-temperature and depth recorder (10 TDR-2050) to a purse seine on the “JINHUI NO.6” vessel (Shanghai Pelagic Fishing Company) and collected data from 23 sets in the Western and Central Pacific Ocean (WCPO) between October and December 2006. The sinking depth did not achieve the theoretical maximum sinking depth, instead accounting for 51.4% of the maximum stretched height (311.1m) of the netting. The relationship between ) for the mid section of leadline can be described using the formula:+ =0.998 3). The sinking speed differed among the sections of the lead line. The fastest sinking speed was recorded at the back wing end, followed by the mid section and the bulk. The sinking speed decreased with depth, the deeper the sinking depth of leadline, the lower the sinking speed. Fluctuations in the confidence interval of the average sinking speed of leadline followed a pattern of large-small-large as the depth increased. The relationship between the sinking speed () at the mid part of leadline can be described using the formula: −4 = 0.986 7). Our observations provide insight into ways to improve sinking performance in tuna purse seines and a reference for fishing operations.

Abstract:Fishing parameters (such as the shooting speed of mainline, vessel speed, time interval between two hooks, numbers of hooks between two floats) can be adjusted to deploy the hooks to water layers that are preferred by target species, such as tuna. As a result, the catch rate of the target species can be increased and the catch of bycatch species (e.g., loggerhead turtles, Carcharhinus falciformis) can be reduced. Together, these actions improve fishing efficiency and help maintain biological diversity. To better understand the relationship between these factors and the fishing depth of longline gear, we developed a numeric model of the behavior of a pelagic longline. We conducted surveys on board Chinese large scale tuna longliners in the Indian Ocean between September 2008 and January 2009. During the surveys, the vessels targeted bigeye tuna (), swordfish () and billfishes (Istiophoridae). The hook depths (188 hooks) were measured using temperature depth recorders (TDRs) and the three dimensional current was measured at a range of depth at 24 sites using an acoustic doppler current profiler (ADCP). We developed a three-dimensional numerical longline model (3DNLM) using finite element analysis and the minimum potential energy principle method. We used Matrix Laboratory (MATLAB) software to program and conduct the numerical calculations. The three dimensional current data were assigned to seven, 50 m depth intervals (e.g., 0100, or 300). The coordinates of all the nodes of the longline (including the float lines, mainline, and branch lines) were calculated by inputting three-dimensional current profile data, fishing gear parameters (the diameter of the mainline and branch line, the total weight of the branch line and the bait in the water, the elastic modulus of the mainline,the length of the branch line, and the length of the float rope), operating parameters (vessel speed, line shooter speed, and the time interval between two hooks) model. The model then outputs the shape of the longline under water and the depth of each hook. model was able to accurately depict the three-dimensional here was no significant difference between the hook depth=0.22>0.05). The average difference between two methods was 12.03 m (range: 0.02–40.36 m, =188)The shape was related to the force of the branch line. This load was concentrated at the respective node of the main line and made the depth of this node deeper. The main line between two nodes may have floated somewhat because of lift generated by sea currents, especially upwelling currents. shape and the hook depthsC_N90 was defined as the drag coefficient associated with water flow plumb to the cylinder. The value of the drag coefficient () of the study object.