Abstract:This paper reviewed the progress of near-shore habitat satellite remote sensing (RS) monitoring and the studies of near-shore ecology impacted by habitat changes. It summarized near-shore habitat geographical, biological, physical and chemical factors which may critically affect marine living organism at the beginning, and then give the main arithmetic by which the habitat factors might be monitored with the recent on duty satellites sensors. It also reviewed the common methods which were used to detect red tide, green algae blooming, and biodiversity. Finally, this paper provides some case studies, such as the study of habitat geographical changes (determined by sea reclamation) impact on biodiversity, and the monitoring of red tide and giant green algae blooming and the distribution of coral reef and mangrove forest, for relevant scientist references.

Abstract:undergoes several molts in its lifetime. We cloned the chitinase gene from using reverse transcriptase polymerase chain reaction and rapid-amplification of cDNA ends. Primers were designed based on the conserved sequence of chitinase from was 2042 bp, including a 1470 bp ORF (encoded 490 amino acid residues), a 35 bp 5′-UTR, and a 537 bp 3′-UTR. The calculated molecular weight and isoelectric point were 53.44 kD and 4.41, respectively. A homology analysis using BLASTn and BLASTx revealed that the S. serrata. The phylogenetic tree of the chitinase gene generated by the Neighbor Joining method suggested that . The expression of was analyzed by real-time fluorescent quantitative PCR. -mRNA was expressed in all tissues examined and levels were highest in the hepatopancreas, with only low levels of expression in the muscle, stomach, gill, and cuticle, and trace levels of expression in the heart, intestine, thoracic ganglion, and brain ganglion. -mRNA expression in the hepatopancreas peaked during the D stage, and there was a significant difference (<0.05) in expression in the hepatopancreas between stages E, AB, and C. In the cuticle, the level of -mRNA expression increased gradually during the molting cycle, and was significantly higher during D stage than during all other stages (<0.05). Expression levels were relatively low in the stomach throughout the molt cycle. In muscle, -mRNA expression was highest during C stage, but there was no difference in the level of expression between the different molting stages ( is a form of acid chitinase and is expressed abundantly in the hepatopancreas. may play a role in the digestion of chitinous food and the degradation of endogenous chitin during the molting cycle of . Our results lay a foundation for research into the biological function and regulation of chitinase in .

Abstract:and provide basic data for the breeding technology, an experiment was conducted where matured zygotes were harvested by artificial inducing spawn and the morphology of embryo and pelagic larva of was observed and recorded under microscope in this study. The effects of seawater temperature on growth and development of the pelagic larva was studied through experimental ecology methods. esults showed that stimulation time for artificial spawning by air-drying should be 12 h when flowing water stimulation was 4 h. The demersal eggs were shaped ellipse (82.6 μm±3.2 in diameter), while the sperms were the type of flagellum (about 50 μm in total length). The embryonic development from zygote to D-larvae stage (104.0 μm±4.3 μm in shell length), creeping larvae stage (255.8 μm±15.0 μm in shell-length) and early juvenile stage (329.1 μm±5.8 μm in shell length) lasted for 20.5 h, 20 d and 36 d, respectively. The results testified that seawater temperature is one of the crucial factors on the growth and development of the pelagic larva. The suitable temperature was from 15℃ to 20℃. The abnormality rate of the larvae at 15℃ was significantly lower than those at 20℃. The highest growth rate was 5.4 μm/d in group 20℃. In 25℃ and 30℃ groups, the abnormality rates were significantly higher than those at 15℃ and 20℃, and the larvae all dead at the sixth day and the fourth days respectively. The larva showed stronger tolerance to lower temperature than higher temperature.

Abstract:Ten microsatellite loci was used to investigate the genetic variation and differentiation of complete set line breeding populations (parental lines A and B of selective F₄ and their reciprocal crosses AB, BA) and wild population (YZ) sampled from the Yangtze River Estuary. The results indicated that: (1) Genetic diversigenetic diversity of the four breeding populations was lower than that of the wild populations. (2) The results of molecular variance analysis (AMOVA), NJ phylogentic tree based on Nei’s genetic distance, principal components analysis (PCA) and STRUCTURE genetic cluster analysis consistently showed that there were significant differentiation (<0.01) among three clusters, namely, AB and AA clustered one group, BA and BB clustered another group and YZ consisted of separate group. (3) According to selective pressure analysis in the Arlequin software and Bayescan software, three microsatellite loci in the breeding populations and one locus in the wild population were detected with significantly positive selection pressure, indicating the continuous strong artificial selection would have resulted in a high level of genetic differentiation between breeding and wild populations. In general, the artificial selection has decreased the genetic diversity within breeding populations and enlarged genetic differentiation between breeding and wild populations. Fortunately, the complete set line breeding could enrich genetic diversity of breeding populations.

Abstract:is a high-valued flatfish species because of the desirable taste of its flesh and its wide tolerance to salinity and temperature. It has become an economically important farmed marine fish in China in recent years. Insulin-like growth factor (IGF)- plays an important role in the regulation of growth and development in teleosts. Our objective was to evaluate the physiological functions of IGF-. The cDNA sequence encoding the mature peptide domain of the A pair of primers were designed based on the conserved sequences of IGF-from Pleuronectiformes and Perciformes species. A 210 bp fragment was obtained and verified as the mature peptide fragment. A homology comparison revealed that the B-, A-, and D-domains of the IGF- mature peptide were highly conserved among vertebrates, but with changes in the C-domain. The mature peptide fragment was reconstructed by RT-PCR with a pair of primers and the subcloned into the prokaryotic expression vector pET-28a with T4 DNA polymerase to successfully construct an recombinant plasmid. The recombinant IGF-II plasmid was highly expressed in being induced by IPTG with a special fusion polypeptide containing His6 at its N-terminus. The SDS-PAGE analysis showed that the polypeptide was expressed in the form of inclusion bodies with a molecular weight of 11.4 kD and accounted for . Western blotting analysis indicated the fusion polypeptide had antigenicity to His6 antibody with primary antibodies (mouse-anti-His6 monoclonal antibody) and secondary antibodies (goat-anti-mouse IgG labeled with horseradish peroxidases). The inclusion bodies were denaturalized using 6 mol/L guanidine HCl, purified using Ni-NTA affinity chromatography, and annealed by gradient dialysis (8 , 0) in urea, after which the purified protein with a molecular weight of 11.4 kD was obtained. The concentration of the recombinant IGF-II was measured using the BCA method after being subject to ultrafiltration. The proliferation experiment revealed that the recombinant protein significantly promoted the proliferation of human embryonic kidney cells (HEK293T) at a concentration of 1.8 μg/mL and inhibited proliferation at a concentration of 5.4 μg/mL, thus verifying its biological activity at a cellular level. In summary, we successfully constructed an prokaryotic expression system and optimized the expression conditions (induction temperature, time, and IPTG concentration). A biologically active fusion protein was obtained following separation, purification, and renaturation. Our results provide information to better understand the role of .

Abstract:Drug residues from aquaculture have been associated with negative effects on human and environmental health. The metabolism of a drug is carried out by a number of enzymes and can influence the formation of drug residues or the drug effect. However, few studies have evaluated the effects of drugs used in aquaculture on drug metabolism enzymes in marine crustaceans. Glutathione S-transferases play an important role in drug metabolism. We isolated and characterized glutathione S-transferase gene in , a species that is widely cultured in the offshore waters of China. The cDNA encoding was first cloned using RT-PCR and Smart-Race. Analysis of the nucleotide sequence revealed that the full-length cDNA clone was 1 010 bp and encoded a protein of 216 amino acids, which had a predicted molecular weight of 24.59 kD with an estimated PI of 5.294. The protein was expected to possess the GST-N structure domain and GST-C structural domain, suggesting that it belonged to the GST subgroup. Comparison of amino acid sequences showed a similarity of more than 78% between . The phylogenetic analysis revealed that the E. sinensis. The level of gene expression in different tissues was analyzed by quantitative real-time PCR. , including the hepatopancreas, gills, muscle, hemolymph, and eyestalk. Expression was highest in the hepatopancreas (expression was up-regulated in the hepatopancreas after intramuscular injection of sulfadiazine (expression was induced by the exogenous drug and increased the capacity for detoxification of the organism. <0.05) lower than controls between 12 and 18 h post injection. This suggests that the function of hepatopancreas cells was disrupted. However, expression of the gene increased significantly between 24 h and 48 h, suggesting that detoxification of hepatopancreas cells was restored. Our results suggest that P. trituberculatus.

Abstract:is distributed in the coastal waters and estuaries of the northwest Pacific Ocean, including the Yellow Sea and East China Sea. This species is rapidly becoming one of the most important marine fishery species in China. Extensive studies have shown that the abundance of C. lucidus has recently declined significantly because of overfishing and environmental degradation. To develop conservation measures there is a need to better understand the genetic population structure of C. lucidus. Fish (n=209) were collected from seven sampling locations in the south Yellow Sea and East China Sea, including Lianyungang, Dafeng, Chongming, Zhoushan, Wenzhou, Ningde, and Xiamen. A 611 bp mitochondrial CO I sequence was amplified by PCR then used for genetic structure analysis. We detected 44 haplotypes, the haplotype diversity index ranged from (0.416±0.112) to (0.720±0.076), and then ucleotide diversity index ranged from (0.00110±0.00035) to (0.00444±0.00164). The results of an AMOVA revealed there were two groups (north and south). The shallow topology of the haplotype neighbor-joining (NJ) tree and the UPGMA tree based on genetic distance suggests there is distinct structure across the seven populations. We define south Wenzhou as part of the southern group, and north Wenzhou as part of the northern group. The estimate of gene flow between the southern and northern groups was <1, which indicates that gene exchanges between these two groups are rare. Based on the expansion parameter τ, we speculate that the separation occurred during the Pleistocene, and the migratory behaviorof C. lucidus likely explains the current lack of differentiation within the southern or northern groups. Our results can be used to inform the sustainable exploitation and conservation of wild C. lucidus populations.

Abstract:Fish insulin-like growth factor-II (IGF-II) plays a key role in the development of IGF-II. Primers were designed based on the salmon IGF-II gene sequence. An RNA extract of liver was used as a template, and the IGF-II gene open reading frame was amplified by one step RT-PCR. The IGF-II gene was inserted into a pSUMO vector to construct an expression vector. The recombinant vector was transformed into SDS-PAGE analysis revealed a 40 kD, and the recombinant protein was mainly in the form of an inclusion body. Pure target fusion protein was obtained by denaturation and renaturation of the inclusion. Purified IGF-II was obtained from the fusion protein following digestion by SUMO protease and separation on a Ni²⁺-NTA column. ELISA and MTT assays were used to quantify the immunological and biological activity of the target protein. The target protein can specifically react with commercial rabbit anti-salmon trout IGF-II antibodies in an antigen conce­ntration-dependent manner. The isolated IGF-II protein has excellent immunogenicity. The MTT assay was used to measure the effect of IGF-II protein on the proliferation of cells (EPC) and rainbow trout gonad (RTG-2) cells. IGF-II protein can effectively stimulate EPC and RTG-2 cell proliferation. The IGF-II protein expressed by the prokaryotic system had good bioactivity. In summary, we successfully cloned the cDNA of IGF-II from liver tissue and constructed the plasmid pSUMO-IGF used for prokaryotic expression. The plasmid was suitable for IPTG induction and expression of IGF-II in bacteria. Additionally, the plasmid contains a SUMO tag, which can improve the level of expression and the stability of the target protein. A 6-NTA, so the purified IGF-II can be obtained from the fusion protein following digestion using SUMO protease and separation on a Ni²⁺-NTA column. Using this method, we obtained a high concentration of IGF-II that had high purity and exhibited the desired bioactivity. growth and reproduction.

Abstract:an economically important wild fish species in China, has declined significantly in recent years. Bisphenol A (BPA) is an endocrine disrupting contaminant (EDC) that is ubiquitous in aquatic environments. It interferes with the growth, development, and reproduction of aquatic animals. Under normal conditions, sexual differentiation and reproductive development are controlled by sex hormones (estrogens and androgens) in fish. When present, EDCs upset the balance of hormones in the body and disrupt sexual differentiation. The effects of EDCs vary depending on the timing of exposure. Exposure during the embryo or juvenile stages can affect sexual differentiation and sex organ development. Conversely, exposure during the adult stages interferes with the organs or organ structure. We evaluated the effect of exposure to BPA (0, 50 μg/L, 200 μg/L, or 1 000 μg/L) in larvae (25 days post hatching; dph) and juveniles (95 dph) for 3 weeks and 2 weeks, respectively. We used fluorescent quantitative PCR (QRT-PCR) to quantify the level of gene expression in the gonads. BPA exposure significantly up-regulated the expression of expression, and down-regulated CYP17a, and mRNA was first down-regulated and then up-regulated, relative to the control, following a change in expression. The effects in the ovary were more complex; BPA initially inhibited the expression of , but expression later increased significantly. BPA inhibited the expression of in the ovary. These data suggest that BPA exposure interfered with steroid synthesis in the early stages of sexual differentiation in was up-regulated, thereby increasing steroid synthesis and altering the balance of estrogens and androgens. This change has an effect on sexual differentiation by interfering with the expression of T. obscurus by inhibiting steroidgenic gene expression, but there is a compensatory effect over time. Gene expression fluctuates in females, but the mechanism is currently poorly understood.

Abstract:Selenium yeast (SY) and tea polyphenols (TP) belong to high-quality natural antioxidants. As an organic selenium source, SP has the effects of both antioxidant and immune-enhancer. Tea polyphenols (TP) is a term for polyphenols in tea, which is helpful to free radicals scavenging, anti-bacterial and anti-inflammatory actions, immunomodulatory effects and so on. In the present study, a two-factorial and three-level experiment was designed to evaluate the effects of dietary SP and TP on selenium deposition in the muscle and liver, the activities and mRNA levels of antioxidant enzymes in the liver of juvenile Wuchang bream, (mean weight 1.75 g±0.01 g). Totally nine semi-purified diets were formulated to provide graded levels of Se (0, 0.25 mg/kg, 0.50 mg/kg) and TP (0, 50 mg/kg, 100 mg/kg). After 8 weeks of feeding trial, the results showed that: (1) Both dietary SY and TP significantly enhanced the weight gain rate (WGR) and specific gain rate (SGR) in juvenile Wuchang bream (>0.05) are there significant interaction effects of dietary SY and TP on WGR and SGR. (2) Dietary SY significantly enhanced selenium contents in the muscle and liver (significant effect of dietary TP on selenium deposition (>0.05), and the interaction effect of dietary SY and TP on selenium deposition was significant in liver (. (3) Both dietary SY and TP significantly enhanced the activities of glutathione peroxidase (GPX), superoxide dismutase (SOD), catalase (CAT) by upregulating the expression of these antioxidant enzyme genes. The difference is that SY upregulated mRNA expression of <0.05), whereas TP raised the transcription of of SP and TP has synergistic gene expression significantly and promoting the transcription of . As a result, fish fed the combination diets with SY and TP had higher hepatic total antioxidant capacity (T-AOC) and lower content of malondialdehyde (MDA) than fish in the other dietary groups (<0.05). In light of the above results, it could be concluded that a basal diet supplemented with 0.50 mg/kg SY and 50 mg/kg TP could help keep better antioxidant status by improving the antioxidant enzymes activities and reduced hepatic MDA in the liver of juvenile Wuchang bream.

Abstract:Aquaculture is one of the world’s fastest growing food production sectors. The outbreak of infectious bacterial diseases in aquaculture is a major concern in the industry. Among the pathogens causing these diseases, species are responsible for several diseases in cultured animals. Models describing the growth and survival of pathogenic spp. populations represent a promising tool for improving predictions of a outbreak. Traditionally, the control of vibriosis involved the indiscriminant use of antibiotics at high concentrations, resulting in negative effects on aquaculture ecosystems and development of antibiotic-resistant pathogens. Thus, there is an urgent need to develop alternative techniques to prevent a and conduct a risk assessment, the concentration of and a range of microbial, physical, and chemical indices were monitored every week for 12 months in a recirculating aquaculture system (RAS) containing Atlantic salmon Monte Carlo simulation was used to model the effects of environmental factorsVibrioThis allowed characterization of the likelihood of harm resulting from the pathogen. In this simulation, uncertainty about the concentration of spp. was modelled with a PERT distribution. Tornado sensitivity analysis, used to compare the relative importance of variables, was conducted in ModelRisk 4.0. (COD), and salinity, and yielded a good fit to the observed data (=0.694). A stepwise multiple regression yielded the following formula: lg( spp. abundance at the sampling site. The predicted The predicted time of peak abundance was also consistent with the observed values. model failed to estimate the concentration of model deviated significantly from the observed values. These observations suggest that the occurrence of in seawater. The Monte Carlo simulation revealed that COD was strongly correlated with the concentration of spp..suggesting that spp. in In contrast, the rank correlation output was much lower for , which indicates that the probability of pathogen outbreaks and growth was less sensitive to those variables. reachlead to an outbreak of a disease. offers an easily applied tool that can be used by aquaculture farms to identify the risk factors associated withIn the RAS used in the current study, the majority of excess nutrients are derived from feed or runoff, some of which are converted into fish and feces. The levels of COD generally undergo a dramatic change after every feeding, spp. populations. The use of multiple regression analysis made it possible to calculate the threshold value for COD and other variables on the incidence of associated pathogen events. Because of the range of requirements for cultured animals, the risk factors may vary and include factors. tion for researchers and managers of the aquaculture farm to predict the abundance of species in the system.

Abstract:We used stomach content analysis to evaluate the feeding habits of the dominant fish species in Laizhou Bay. The species were classified into one of five feeding habits, including zooplanktivores, benthivores, piscivores, omnivores, and generalist predators. , and is omnivorous; , Chaeturichthys stigmatias are benthivorous; Synechogobius hasta and are generalist predators. Of the species that are harvested commercially, fish were the dominant taxa in the food web from 1959 to 1993. However, the biomass of invertebrates, including , has gradually increased and constituted 42.8% of the total biomass in 2008 and 72.1% in 2011. Thus, invertebrates are now the dominant taxa among harvested species. The food web in 1959 included benthivores, piscivores, and generalist predators, among which piscivores accounted for 78.7% of the biomass. More recently, piscivores have been absent from the food web in Laizhou Bay, except in 2008. Zooplanktivores were the dominant species in 1982 and 1993, accounting for 71.1% and 72.2% of the biomass, respectively. From 1998 to 2008, the biomass of zooplanktivores declined and the biomass of benthivores increased dramatically. In 2011, the food web in Laizhou Bay included only benthivores and generalist predators, among which benthivores accounted for 82.6% of the biomass. Using cluster analysis and a simplified version of the food web from 1959 to 2011, we showed that the food web in Laizhou Bay has experienced five stages of evolution, changing from a piscivore-dominated system to a zooplanktivore-dominated system, to a zooplanktivore and benthivore system (with a higher proportion of zooplanktivores), to a benthivore and zooplanktivore system (with a higher proportion of benthivores) to a benthivore-dominated system. The species at low and medium trophic levels have replaced the species at higher trophic levels and have become the top predators in the Laizhou Bay ecosystem. The food chain is now considerably shorter and energy transfer occurs primarily through the detritus food chain. The mean trophic level declined from 4.4 to 3.4 between 1959 and 2011, which is more rapid than in the Bohai Sea. Variation in dominant species composition, individual miniaturization, and intraspecific changes in feeding are the primary factors explaining the decline in the trophic level in Laizhou Bay.

Abstract:The spatio-temporal distribution of phytoplankton is influenced by physical and chemical factors such as water temperature, salinity, dissolved oxygen, pH, and nutrients. Nitrogen (N) and phosphoros (P) are essential for the growth of phytoplankton which play a key role in determining the abundance of phytoplankton. The species composition, community similarity, and diversity of phytoplankton affect the structure and function of ocean ecosystems. Marine phytoplankton can be used as a rapid and sensitive indicator of environmental changes. The coastal region of Qinhuangdao is used by fish, shrimp, and crabs for spawning and feeding. However, this region has experienced an increase in the frequency of red tides as a result of pollution and marine development.We evaluated the species composition, spatio-temporal distribution, community structure of phytoplankton and the relationship between phytoplankton abundance and environmental factors based on data collected during five surveys conducted from May to September, 2010. We identified 96 species belonging to 46 genera of phytoplankton. The phytoplankton community was primarily composed of Bacillariophyta and Pyrrophyta. The majority were neritic species or cosmopolitan species which were eurythermal and euryhaline, while the remainder was oceanic warm water or oceanic species. The dominant species include Chaetoceros A total of 48 red tide causative species were observed (~50% of total species). The mean phytoplankton abundance ranged from 6.20×10⁴ cells/m³ to 4129.53×10⁴ cells/m³. Abundance peaked in September 2010 and was lowest in July 2010. The and community structure was healthy. The highest indices of community structure and biodiversity were observed in September, and biodiversity was lowest in June. The community similarity of phytoplankton was relatively high and the range in similarity was from 40% to 70% from May to September. The community similarity was ranked in order: September>July>August>May>June. The average abundance of phytoplankton was significantly negatively correlated with salinity(=37) and significantly positively correlated with inorganic nitrogen nutrients (=37). We conclude that inorganic nitrogen is the primary factor explaining the increase in phytoplankton abundance during the study period. A canonical correspondence analysis of the relationship between phytoplankton species and environmental factors indicated that N/P, salinity, nitrate, silicate, nitrite, and water temperature were the main environmental factors which influenced the community structure of phytoplankton in the coastal areas of Qinhuangdao.

Abstract:The Pearl River Delta (PRD) in Guangdong province is one of the most economically prosperous areas in China. Economic development in this region has resulted in an estimated 10% increase in the volume of domestic and industrial wastes in the past few years. The complex river web of the delta, characterized by multiple river channels, forms the entrance for the Pearl River into the South China Sea. A number of studies have focused on measuring the physical and chemical factors in this region, but there has been little attention paid to aquatic organisms. Our objective was to document the ecological characteristics of copepods in the river network of the Pearl River Delta. The species composition, biomass, and biodiversity of copepods were measured in samples collected from the water in March, May, August, and December of 2012. A total of 31 copepod species representing 24 genera and 9 families were identified, including copepodids and nauplii. The dominant copepod species exhibited seasonal and spatial changes in abundance, with being the most common species. The biomass of copepods and nauplii exhibited seasonal changes in abundance, and both were more abundant during the wet season than in the dry season. The copepod biomass was characterized by even horizontal distribution, whereas the nauplii biomass generally decreased along a gradient from southwest to northeast. In general, the average biodiversity and evenness indices were higher in the wet season than in dry season, and decreased from the southwest to northeast. The results of principal component analysis revealed that the community structure of copepods in the Pearl River Delta river network was significantly positively correlated with temperature, total phosphorus, total nitrogen, ammonia nitrogen, and permanganate contents, positively correlated with chlorophyll acontent, and significantly negatively correlated with water transparency and pH.

Abstract:e evaluated the effects of aeration rate (0, 50 mL/min, 100 mL/min, 200 mL/min, 400 mL/min, 800 mL/min) on the growth and nutrient uptake rates of the thalli of the brown alga . The thalli were incubated in the laboratory for 15 d and were measured every 5 d. additionally, the pigment content and concentration of soluble proteins and soluble sugar in thalli were measured at the end of the experiment. Both aeration rate and culture time significantly influenced the relative growth rate (RGR) and PO₄³⁻-P uptake rate of , but only culture time had a significant effect on the rate of NO₃⁻-N uptake. On the first day, aeration rate had a significant effect on the nutrient uptake rate. At the highest aeration rate we tested (800 mL/min), NO₃⁻-N and PO₄³⁻-P uptake rates were 133.77% and 89.51% higher, respectively, than in the control (0), and RGR was also 95.04% higher than in the control. However, the positive impact of aeration rate on thalli growth rate and nutrient uptake rate decreased as culture time increased. At the highest aeration rate, the NO₃⁻-N uptake rate was 24.87% lower than in the control at the end of the experiment and the PO₄³⁻-P uptake rate was 46.03% higher than in the control. Conversely, the RGR of thalli was 75.16% higher than in the control at this time. High aeration rates appeared to inhibit the synthesis of chlorophyll a, carotenoids, and soluble sugars, but significantly promote soluble proteins synthesis. Our results suggest that water movement does not exert a direct effect on thalli growth and biomass, but rather an indirect effect induced by changes in nutrient uptake and other physiological processes.

Abstract:(15.24 g±2.9 g) to three kinds of artificial shelters under different . Additionally, we evaluated the effect of rearing),and feeding frequency (1, 2, 3, or 4 mealsper day)(0.50 g±0.02 g) in a 7-week net cage culture experiment. were attracted to all 3 artificial shelters types, but particularly to the shelters constructed of scallop cages (S1). The association of fish with the artificial shelters increased under dark conditions, . As density increased, the final weight, specific growth rate (SGR) all increased. For fish reared in the no shelter group, the DWGR and SGR of the low density group was significant lower than for the medium and high density groups the final weight was significant lower than in the high density group .The availability of artificial shelters was associated with a significant increase in the final weight in the low and medium density groups coefficient of variation for body weight (CV _{increased with stocking density. The presence of shelters was associated with a lower than in the absence of shelters. The difference was very significant between low and medium density groups (among the groups when the satiation feeding frequency was more than twice per day (, significantly and better growth could be achieved by using artificial shelters in the cultivation environment with a feeding frequency of twice per day.}

Abstract:Abstract: We evaluated the effects of trawl wing length (Lw) on the performance of trawl gear with large-size mesh. Trawl model tests were carried out in a towing tank at East China Sea Fisheries Research Institute. We measured the effect of Lw/L on the resistance, height of net mouth, and hydrodynamic performance of the trawl by testing six wings of differing lengths attached to trawls of equal longitudinal length (L). Trawl resistance increased with increasing Lw/L, but was relatively constant when Lw/L exceeded 36.45%. As Lw/L increased, trawl resistance increased at higher speeds. The height of the net mouth increased as Lw/L increased, reaching a maximum when Lw/L was 36.45%–38.69%, then declining. The effect of Lw/L on the height of the trawl mouth was not influenced by trawling velocity. There was little change in the height at lower speeds but a significant change at high speeds. The hydrodynamic performance of the trawl was highest when Lw/L was>36.45%, and decreased as Lw/L increased further. We conclude that an Lw/L of 36.45% is optimal when designing wing length. However, in practice it may be necessary to lengthen the wing of a trawl based on actual operating conditions.