Abstract:DNA methylation is closely linked to biological events, including chromatin inactivation, transgene silencing, genomic imprinting and control of parasitic DNA elements. Because of its efficiency and competence, the methylation-sensitive amplification polymorphism (MSAP) technique has been used increasingly in genomic DNA and individual functional gene studies to analyze DNA methylation levels. In this research, MSAP technology was used to analyze the methylation levels of mantle tissues from , including the mantle edge (Me), mantle pallium (Mp) and mantle central (Mc). Recycling the methylation of specific fragments to be sequenced, comparative analysis and selection the target gene, then used the Real time PCR to analyze the target gene. Results showed that (1163.25±124.34) DNA bands were clear and repetitive by using 15 pairs of primers. Among them, Me had (401.00±40.37) bands, Mp had (380.63±52.39) bands and Mc had (381.63±53.57) bands, and there was no significant difference (>0.05). The percentages of methylation levels were (17.07±2.19)% in Me, (15.48±2.34)% in Mp and (19.61±2.88)% in Mc (<0.05). The methylation levels from high to low were Mc >Me >Mp. Methylation patterns included fully methylated sites, hemi-methylated sites and non-methylated sites. The experiment results showed that the percentages of fully methylated sites were higher than hemi-methylated sites in all areas of the mantle, indicating that the methylation pattern in the genome was mainly a CpG island. After recovering and sequencing the specific bands, we found eight gene sequences, which were methylated by Blast. Of these, there were three sequences with homologous sequences by Local Blast with genome, which were 40S ribosomal protein SA, interference hedgehog and Zinc finger protein castor by gene annotations. Interference hedgehog ( was expressed in Me, Mp and Mc, with the highest expression level in Me and the lowest expression level in Mc ( in Mc was inhibited by DNA methylation. These results confirm that the mantle tissues Me, Mp and Mc have different methylation levels. DNA methylation could also play a role in the regulation of gene expression. The technique helps us to understand the relationship between methylation and expression regulation, and also provides a theoretical basis to elaborate the mechanisms underlying biomin-eralization and immune response in .

Abstract:Glutamate dehydrogenase (GDH) is found widely in many plants, animals and microorganisms as a mitochondrial enzyme, and it is the key enzyme in amino acid catabolism. It is distributed extensively in animal tissues such as the hepatopancreas, kidney and brain. GDH activity is very strong and it may catalyze the glutamic acid oxidative deamination reaction. To explore the function of the GDH gene during ammonia nitrogen metabolism of black tiger shrimps ( (denoted ) was obtained by rapid amplification of cDNA ends. The full length of the sequence of was 2386 bp containing a 5'UTR of 21 bp and a 3'UTR of 688 bp, and the length of the open reading frame (ORF) was 1677 bp encoding 558 amino acids. The predicted molecular mass of the amino acid (aa) sequence was 61.837 kD with an estimated pI of 6.57, and there was a poly A with 27 bp. In common with the GDH of other animals, the structure of the protein contained two conservative domains, ELFV dehydrog N and NAD bind 1 Glu DH. There were 37 phosphorylation sites and three glycosylation sites in this protein. Through multiple sequence alignment and phylogenetic tree analysis, it was concluded that the homology and similarity between was the highest. Analysis of the tissue expression pattern of mRNA was expressed in all tissues tested, including lymphoid tissue, ovary, eyestalk nerve, brain, stomach, muscle, intestines, thoracic nerve, hemolymph, hepatopancreas and gill. The highest levels were found in muscle, the next highest in the eyestalk and the lowest levels in the hemolymph. To study the functions of under conditions of ammonia nitrogen stress, the hepatopancreas and gill were sampled at 6 h, 12 h, 24 h, 48 h, 72 h and 96 h after exposure to different concentrations of ammonia nitrogen. The expression of in the hepatopancreas and gill was significantly different compared with the control group (<0.05), and the expression levels differed between hepatopancreas and gill. The results showed that may play an important role in shrimp ammonia metabolism and may be involved in responses to acute ammonia stress.

Abstract:Light is a key environmental factor that influences the growth, culture and survival of aquatic organisms. In the present study, the eye tissues of Ino were observed under the light microscope, scanning electron microscope and transmission electron microscope to provide an enhanced histological and cytological basis for analysis of the physiological response mechanism of abalone to light from the perspective of molecular biology. Findings show that the eye tissues, from the outside to the inside, are:retinal pigment epithelium, outer nuclear layer, inner segment, inner nuclear layer, melanin granules sediment and optical fiber layer. Connective tissue mainly exists between the epithelium and the outer nuclear layer, and a portion of the connective tissue nucleus is a darker color. The optical fiber layer mainly comprises the light red reticular nerve fibers which gradually become dense from the outside to the inside. The front ends of eye tissues are cylinder-shaped with an obvious circular depression, in which the reticular nerve fibers are mostly found. The surface of the eyestalk comprises a large number of reticular fibers where the cavities of various sizes are densely distributed. The surfaces of eye tissues are covered with papillae and the top of every papilla has one or two clusters of ciliary rings. The existence of desmosomes between adjacent cells can be clearly seen, and these can limit the expansion of cells and closely link them. Nucleiare found in various shapes and the double-layer nucleus is tightly enveloped by the cell membrane, which contains euchromatin and a few heterochromatin. Myofibrils are widely distributed and are composed of a large number of myofilaments closely arranged along the myofibrils; however, no obvious connection is formed between them. Loose connective tissue, smooth muscle fiber and others are main components in the tissues. Collagenous and other types of fibers distributed between the connective tissues play a key role in maintaining the flexibility and toughness of cells. Mitochondria, Golgi apparatus and lysosomes are also widely distributed in supporting cells. Amoebocytes are uniquely shaped and distributed between the loose connective tissues with pseudopodia and a large number of high electron density particles. Many melanin granules are densely distributed in the cytoplasm; these can prevent strong light from damaging the optical cells, and they also stabilize the internal environment of the retina. Findings demonstrate the significant role played by the optical tissues of the abalone in sensing and identifying external light environmental factors. They also provide a morphological basis for the optimization and regulation of light environmental factors in aquaculture production, as well as an in-depth discussion of the abalone's physiological response mechanism to light.

Abstract:The large yellow croaker (), mainly distributed in coastal waters of China and East Asia, is one of the most important economic marine fish in China, and represents the largest yield for a single species in Chinese marine net-cage farming. Nevertheless, because of exhaustive fishing, habitat degradation and high-density aquaculture, the genetic diversity of the species is at a low level, and mariculture of the species is facing serious challenges from germplasm degeneration and susceptibility to infectious disease agents. Studies of the large yellow croaker have focused on the comparison of genetic differences among culture populations, and few of them have reported on comparative analysis among a wide range of wild and cultured stocks. To study the genetic diversity of wild and cultivated populations, we amplified and sequenced the mitochondrial cytochrome oxidase I () gene of 336 samples from eight wild populations and six cultivated populations. The amplified fragment was 621 bp, containing a total of 38 mutation sites which included 23 parsimony-informative sites and 15 singleton mutation sites. The results showed that the wild populations contained 38 mutation sites, accounting for 100% of the total variations, while the cultivated populations contained 8 mutation sites accounting for 21.05%. We also detected 34 haplotypes in all 14 groups, and these were characterized by high haplotype diversity (0.587) and low nucleotide diversity (0.00194). The haplotype diversity index of the wild and cultivated populations ranged from 0.714 to 0.952 and from 0.000 to 0.581, respectively. The coefficient of gene differentiation () between wild and cultured groups was 0.04982, accounting for 4.98% of the total variance. There was an extremely significant difference (>0.05), and accounting for 93.56% within populations (<0.01). Analysis of AMOVA and phylogenetic trees revealed that the genetic diversity of the large yellow croaker was in lower level, and that the genetic diversity in cultivated populations was significantly lower than that in wild populations. In addition, the variation within populations contributed its major genetic variation, and there was extremely high genetic differentiation between wild and cultivated groups but not significant within populations. The large yellow croaker from the East China Sea and Yellow Sea should belong to the same geographic population, but there is still a low level of genetic differentiation among the two groups, the genetic diversity of Yellow Sea groups being higher than that of the East China Sea. This study can provide a theoretical basis for resource conservation and germplasm recovery.

Abstract:We collected different geography groups of mandarin fish () from the provinces of Hunan, Guangdong, and Jiangsu, and multiplied them by artificial propagation. Twenty-one families of mandarin fish were set up in 4 years. Based on the data of growth traits measured in mandarin fish we used derivative free restricted maximum likelihood to compute the genetic parameters of 3 growth traits-body weight (BW), body length (BL), body height (BH), by mixed animal models. The genetic parameters of mandarin fish on 210th day were estimated by Asreml program. The heritabilities of BW, BL, BH for 210 day-age of Siniperca chutasi were 0.4, 0.45, 0.29. The different genetic variance components of BW, BL, BH, computed by 3 mixed animal models were compared. The high and moderate heritability of growth traits suggested that additive genetic effect of these traits in mandarin fish were high and it was expected to have good genetic gain through individual selection and family selection. The genetic correlations between BW and BL, BW and BH, BL and BH, were 0.96, 0.93, 0.92, respectively. The high and positive genetic correlations between growth traits suggested that selection for improvement in body weight of mandarin fish would result improvement in other two traits. After two generations, the average body weight of F₂ was 7.5% more than F₁. The genetic gain in BW of F₂ was 7.5 g. The average BW of F₃ was 9% more than F₂, and 17.2% more than F₁. The genetic gain in BW of F₃ was 9.75 g. The average BH was 9.9% more than F₁. The genetic gains in BH was 0.22 cm. It was the right way to improve the value of mandarin fish in aquaculture.

Abstract:This study examined the effect of low-pH stress on physiological metabolism and the histological structure of gill and hepatopancreas in with the body weight of (25.88±4.40) g, using paraffin section technology and the measurement of biological enzyme activity. Based on the 96 h median lethal concentration (LC₅₀), water for 96 h. A control group of the species was also exposed to water of pH 7.6. Each pH level was sampled to measure the activity of metabolic enzymes in the gill and antioxidant properties in the hepatopancreas, and the histological structure of gill and hepatopancreas was observed at 0 h, 2 h, 8 h, 24 h and 96 h. The results showed that the value of pH LC₅₀ was 3.675 at 96 h. The activity of Na⁺-K⁺-ATPase and lactate dehydrogenase (LDH) in gills of the experimental group gradually increased, while activity of cytochrome oxidase (COO) in the gill showed the opposite trend after low-pH stress. As pH stress time was prolonged, the activity of hepatopancreas superoxide dismutase (SOD) and catalase (CAT) in the experimental group increased at first, then declined. The MDA content in the experimental group increased consistently during the exposure time (P. clarkii exposed to low-pH water (pH 3.6) showed impairment of cuticle and exfoliation of respiratory epithelium cells. Observation of hepatopancreas microstructure sampled from exposed to low-pH water (pH 3.6) indicated the appearance of more B cells and inter-transferred vacuoles in the hepatopancreas tubules, which were enlarged. I am not sure I have understood your intention correctly, so please check carefully. It also showed that the number of granular materials in the transferred vacuoles hadincreased and that the structure of the hepatopancreas tubules was impaired. The study indicated that low-pH stress will affect the physiological metabolism and lead to hypoxia. Antioxidant activities by will be induced by short-term pH stress but inhibited when exposure time is prolonged. Low-pH stress will damage the structure of both gill and hepatopancreas.

Abstract:We investigated the ammonia metabolism pathway of after acute carbonate alkalinity gradient stresses, and studied several ammonia metabolism-related genes:glutamine synthetase (), carbamyl phosphate synthetase 1(); serum ammonia concentration; gene expression; and enzyme activity. The serum ammonia concentration increased as the carbonate alkalinity gradient rose, and showed a trend to increase and then decrease, with the greatest at 12 h. Ammonia metabolism-related genes in different tissues were up regulated to various degrees after different alkalinity stresses. The expression change trends showed an increase and then a decrease over time; their expression increased significantly at 12-24 h, then recovered gradually to stable levels. were mainly expressed in the liver; and was mainly expressed in the kidney and gill. Enzyme activity results showed that CA and GS activities increased along with increased alkalinity, and that CA acted most significantly in the gill and GS in the liver. Overall, the results showed that carbonate alkalinity stress can result in the raising of serum ammonia concentrations, and that ammonia metabolism-related genes in the gill, liver and kidney played different roles in adjusting to ammonia metabolism:excreting the ammonia directly in the gill, producing glutamine and urea in the liver, and decreasing the serum ammonia concentration.

Abstract:We investigated how conjugated linoleic acids (CLA) can affect the growth, body composition and me-tabolism-related hepatic enzyme activities of juvenile hybrid grouper (♀ ). Fishes with initial body weight of (63.57±0.56) g were examined after 8 weeks of feeding with isonitrogenous and isolipidic diets in which 0 (CLA0), 0.8% (CLA0.8), 1.6% (CLA1.6), 2.4% (CLA2.4) and 3.2% (CLA3.2) of conjugated linoleic acid were supplemented. The results showed that:(1) there were no significant differences in weight gain ratio (WGR), survival rate (SR), specific growth rate (SGR), condition factor (CF), hepatosomatic index (HIS) and viscerosomatic index (VSI). The protein efficiency ratio (PER) increased as levels of dietary CLA rose, and was significantly higher in all experimental groups than in CLA0 groups (<0.05). Feed intake (FI) was reduced with increasing dietary CLA; FI in group CLA0 was significantly higher than that in other groups (<0.05). Feed conversion ratio (FCR) was decreased, and achieved in the group CLA2.4, which was significantly lower than CLA0 (<0.05); (2) muscle fat content increased as amounts of dietary CLA rose, and the achieved in the group CLA0.8, which was significantly lower than that in group CLA0 (>0.05). The content of saturated fatty acid (SFA) and C_18:0 in the muscle of group CLA1.6 was significantly higher than in group CLA0 (<0.05), and monounsaturated fatty acid (MUFA) content in CLA3.2 achieved minimum as well as C_18:1n-9, which was significantly lower than that of control group ( in groups CLA2.4 and CLA3.2 were significantly higher than in the control group (18:1n-7 content were significantly lower than in group CLA0 ( content of muscle and liver in groups CLA2.4 and CLA3.2 were significantly lower than in group CLA0 ( content in muscle and liver were highly related with dietary CLA supplement, and in all experimental groups were significantly higher than in CLA0 groups (<0.05); (3) dietary conjugated linoleic acid levels among glucose-6-phosphatedehydrogenase (G6PD) activity in the experimental groups were significantly higher than those in the control group (<0.05); acyl-coenzyme aoxidase activity has the highest CLA3.2 activity, which was higher than in the other groups (<0.05); general esterase and fatty acids ynthetase activity in the experimental groups was significantly higher than in the control group (<0.05).The results indicate that dietary CLA can significantly improve the utilization of aquafeed by juvenile hybrid grouper, improve the composition of fatty acids in liver and muscle, and increase metabolism-related hepatic enzyme activities.

Abstract:The lenok (Pallas) is one of the most important salmonid fish in northeast China. To date, no information on the optimal dietary protein and lipid levels of this species has been reported. A 10-week feeding trial with four dietary protein levels (40%, 45%, 50% and 55% crude protein) and two dietary lipid levels (8% and 16% crude lipid) was conducted to assess the dietary protein and lipid levels for the growth and of amino acids of juvenile lenok. The results showed that weight gain (WG), specific growth rate (SGR), condition factor (CF) and hepatosomatic index (HSI) were significantly affected by dietary protein and lipid levels (<0.05), and there were also significant interactions between these two factors (<0.05). WG, SGR, CF and HIS rose with increasing dietary protein levels at each lipid level, and decreased after that. The growth of fish fed the high-lipid level diet was significantly higher (<0.05) than that of fish fed the low-lipid level diet at 40% and 45% protein diet, whereas these values showed an opposite trend at 50% and 55% protein diet. Fish fed diets with low protein levels had the lowest survival levels of all groups. The lipid content of muscle increased significantly with increasing lipid levels (<0.05), while moisture, crude protein and ash content were not affected by dietary lipid level. The protein content of muscle increased significantly with increasing protein levels (<0.05), while lipid and ash content were not affected by dietary protein level. The lipid content of fish fed high-lipid level diets was significantly higher than that of fish fed lower-lipid level diets at each protein level. The protein content of fish fed diets 55P/8L and 55P/16L was significantly higher than that of fish fed in other groups. Seventeen amino acids were found in the muscle of fish. The percentages of total amino acids and the ratios of essential amino acids:total amino acids showed no significant difference among the treatments (>0.05). The content of the different amino acids was stable and the constitutional rate of the EAAs met Food and Agriculture Organization and World Health Organization standards. The results indicated that the optimum protein and lipid levels for the lenok were 50% and 8%, respectively; and the optimum protein:energy ratio for this species was 29.36 g/MJ.

Abstract:This study evaluates the effects of substituting fishmeal with earthworm meal on the growth, muscle composition, and biochemistry index in serum and immunity performance in the loach with an average initial body weight of (3.86±0.23) g. Five experimental diets with the same nitrogen and energy content were formulated to replace fishmeal using 0 (as the control group), 25%, 50%, 75% and 100% of earthworm meal. The experimental fish were fed the alternative diets in net cages for 10 weeks. Results showed that dietary fishmeal replacement with earthworm meal had no significant effect on the survival rate of loach. The feed conversion ration (FCR) and weight gain rate (WGR) increased (<0.05), and the condition factor (CF) and hepatosomatic index (HSI) decreased (<0.05), as levels of substitution rose to the maximum. There was no significant difference in splenic index (SI) or specific growth rate (SGR) in any of the groups. The content of fat in the flesh at levels of 75% and 100% replacement was significantly higher compared with the control group (<0.05); and the content of flesh crude protein and moisture in the 100% replacement diet was significantly lower than in the control group (<0.05). As the content of earthworm meal rose, the content of Arg, Cys and Asp in flesh protein also increased (>0.05), but that of Pro, His, Met, Thr and Phe in flesh protein decreased significantly (>0.05) in the vitality of alanine aminotransferase (ALT), lipase (LPS) and amylase (AMS), or in the content of high density lipoprotein cholesterol (HDL-C)in the serum of treatment groups. As the fishmeal content dropped, triglyceride (TG) and total cholesterol (TCHO) increased (<0.05), but aspartate aminotransferase (AST) decreased significantly (<0.05). As levels of substitution increased up to the maximum, the vitality of catalase, glutathion peroxidase (GSH-Px) and lysozyme (LZM) in the hepatopancreas decreased; the content of malonaldehyde (MDA) and the vitality of alkaline phosphatase (AKP) in the hepatopancreas increased; and morbidity and death rate after bacterium Aeromonas hydrophila challenge also increased. There was no significant difference in the vitality of total superoxide dismutase (TSOD) and total antioxidant capacity in the hepatopancreas of treatment groups (>0.05). This study demonstrated that replacing 22% of the fishmeal in the diet by earthworm meal had no significant effect on growth and survival, and could promote muscle composition. It could also effectively protect the hepatopancreas from damage and peroxidation by reactive oxygen; however, it would significantly inhibit loach immunity performance.

Abstract:The leukocyte enzyme myeloperoxidase (MPO) is widely present in animals, and is involved in various physiological responses in vivo. When the body is stimulated and the stress reaction is produced, MPO content increases rapidly, showing strong oxidation activity and destruction of invading microorganisms, and enhancing immunity. The strong oxidizing property of MPO has an immense influence on the oxidative metabolism of drugs. Praziquantel (PZQ) is a quinoline pyrazine derivative, and widely used in aquaculture as an anti-parasite drug. In this experiment, PZQ was used as a model drug and crucian carp as a model organism. Analysis of the relationship between MPO mRNA expression and concentration of PZQ in the crucian carp was made after single-dose oral administration of PZQ in an attempt to establish a method for the evaluation of fish in vivo drug residues with MPO genetic. In this study, blood samples were collected at 0.25 h, 0.5 h, 1 h, 3 h, 6 h, 12 h, 24 h, 48 h and 96 h after oral administration of 10 mg/kg PZQ, and PZQ concentrations of the samples were simultaneously detected using high-performance liquid chromatography. Pharmacokinetic analysis was performed using the DAS 3.0 program. Pharmacokinetic parameters were based on classical compartmental model analysis. PZQ can be absorbed quickly into the blood and eliminated rapidly. Concentration and time data of PZQ in the blood can best be described by a two-compartmental open pharmacokinetic model; the pharmacokinetics equation was t-21.409e-^{1.206. The peak concentration of PZQ was 2.85 μg/mL in the first hour and it was below the detection limit after 96 h. The relative expression of MPO was explored for the first time, using real-time fluorescent quantitative PCR (RT-PCR) with the reference gene of -actin. The peak value in the relative expression of MPO mRNA also appeared in the first hour. At 0.25, 0.5, 1, 3 and 6 h the relative expression of MPO mRNA showed an extremely significant difference compared with the control group (<0.05), then gradually decreased to a relatively low value (no significant difference) with the control group at 48 h. In addition, the difference between the control group and the blank control group was 0.993, which showed that the full price feed and the mouth irrigation method had no effect on the experimental results. Correlation analysis indicated that the correlation coefficient of the MPO mRNA relative expression amount and PZQ concentration in blood was highly correlated (=0.96). This suggests that MPO may participate in the oxidative metabolism of PZQ. This study provides a new approach to the molecular evaluation of drug residues in aquatic animals, and a theoretical basis for the safe use of drugs in aquaculture.}

Abstract:Myxosporean disease caused by Carassius auratus gibelio in Yancheng City, Jiangsu Province, China, in recent years. The pathogen specifically parasitizes the pharyngeal tissue of C. auratus gibelio, histopathological observations at different stages of the disease, and pathophysiological analyses in the middle stage of the disease, were carried out. Histopathological results showed that, at the trophozoite stage, M. pharynae parasitized the pharyngeal submucosa of fish, resulting in slight hyperemia of the pharynx, and sporocysts were formed by fibroblast packages, but no pathological changes were found in other tissues and organs at this early stage of the disease. The pharynx was greatly enlarged in the middle stage of the disease due to the increasing number of small sporocysts and proliferation of trophozoites, which developed into mature spores that formed a large sporocyst. Serious congestion appeared within the walls of sporocysts, which were mainly composed of the connective tissue of fibrocytes, collagenous fibers and elastic fibers. The nuclei of fibrocytes underwent karyopyknosis and necrosis, and there was atrophy in the connective tissue in the walls, which gradually thinned. Pale staining was seen in epithelial cells and taste buds in the pharyngeal mucosa, which eventually became necrotic. Cell hyperplasia mainly appeared in secondary gill lamellae. Renal glomeruli expanded, hyaline degeneration appeared in renal tubular epithelial cells and necrocytosis occurred in some parts of the kidney. No pathological changes appeared in the liver, spleen, intestine or in the head of the kidney. Further necrotic tissues and cells in the walls of sporocysts, and in the pharyngeal mucosa and submucosa, resulted in holes through which mature spores and necrotic tissues passed into the blood stream during the late stage of the disease. Many necrotic cells and mature spores came from necrotic pharynx regions in the intestine. Histopathological changes in other organs and tissues were similar to those in the middle stage of the disease. Pathophysiological analysis in the middle stage of the disease showed that the number and size of red blood cells, hemoglobin, thrombocytes, total pro-tein, albumin, globin, glucose, alanine aminotransferase, aspartate aminotransferase and alkaline phosphatase in the diseased fish were significantly lower than those in the healthy fish (<0.01). Erythrocyte osmotic brittleness, numbers of white blood cells, neutrophils and monocytes, and total bilirubin, creatinine, urea and lactate dehydrogenase were significantly higher in the diseased fish than those in the healthy fish(<0.01). There were no significant differences in lymphocytes and eosinophils between diseased fish and healthy fish (>0.05). Diseased fish eventually died because of feeding difficulty and respiratory dysfunction caused by the enlarged pharynx, which blocked the oropharyngeal cavity, leading to hyperplasia in secondary gill lamellae, kidney lesion, anemia and other changes and further necrotic pharyngeal tissues forming a bleeding hole.

Abstract:Modern high-intensity aquaculture has seen a rapid increase in annual cultured production over recent decades, and it is essential to deal with the amount of waste produced. Aquaculture effluent is typically characterized by increased nitrogen species (ammonia, nitrites and nitrates), organic carbon, phosphates, suspended solids, and high biological oxygen demand and chemical oxygen demand. Probiotics are defined as live microbial or cultured product feed supplements that beneficially affect water quality or the host. For example, some strains can degrade ammonia, nitrites or nitrates and are important for water manipulation in intensive aquaculture. As a result, the use of probiotics in aquaculture is gaining increasing scientific and commercial interest worldwide. A strain with high protease activity, which can degrade protein or nitrogen, is key to its commercial application in probiotics production. To breed a B. subtilis BC2) was mutated using different doses of ultraviolet (UV) radiation, and a preliminary study determined the optimal UV radiation conditions. The value of flat transparent circle to colony diameter (. The results showed that the value of mutated strain B38 increased from 3.01 to 6.42. A spectrophotometry method with Forint phenol (Lowry) was used to measure the protease activity of the mutated strain. The protease activity of B38 was 86.82 U/mL, which was increased by 3.14 times compared with the original strain. After ten successive generations, the protease activity of B38 was 77.01 U/mL and did not change significantly, showing its good genetic stability. Cellulase activity analysis was used to determine whether the UV mutagenesis also affected other enzyme activity. The result showed that the cellulase activity of B38 was not significantly different from BC2. Subsequently, we evaluated the ability of mutated strain B38 to degrade feed protein. Protein content in the feed medium was assayed by the Kjeldahl method. The liquid protein degradation ability of B38 was an increase of 2.57 times compared with original strain BC2. However, the ability of B38 to degrade solid protein did not increase significantly. The UV-mutated high protease-producing B38 strain provides an important foundation for the development and application of aquatic probiotics.

Abstract:The Pacific oyster () is one of the most important cultured bivalve species in the world. Given that oysters with golden shell coloration are rarely seen in the market and are sold at much higher prices than others, developing the golden shell line of to have enhanced growth traits and survival rates is of great consequence. A series of 3×3 diallel crosses of three full-sib inbreeding families in the golden shell color strain of ) with better growth and survival performance was conducted, including three inbreeding groups (AA, BB, CC) and six hybrid groups (AB, AC, BA, BC, CA, CB). Growth performance, survival rate and heterosis were evaluated and compared at larval and juvenile stages between different groups. The results showed that most of the hybrid groups presented better growth performance and survival rate than their inbreeding groups at different stages. At the larval stage of day 5, the larval shell height and shell length of all the hybrid groups were significantly greater than the inbreeding groups (<0.05). At days 10, 15 and 20, the shell height and shell length of the CB and BC groups were outstanding:the differences between them and their correspond-ing inbreeding groups were significant (<0.05), and the heterosis was obvious. At day 10, the larval survival rate of CB was significantly greater than AA and CA(<0.05). The heterosis of larval shell height, shell length and survival rate among all hybrid groups were between 1.88% and 14.24%, 0.28% and 14.67% and 10.72% and 23.22%, respectively. At the juvenile stage, each group also showed differences in growth and survival characteristics, and the three growth traits and survival rate of hybrid groups showed different heterosis. At days 85 and 130, the shell height of hybrid group CB was greater than the other experimental groups. The heterosis of the survival rate of AC, CA and CB groups showed a clear trend to increase with age. At day 190, the juvenile survival rate of AC and BC was significantly greater than AA and CC (<0.05). The heterosis of the juvenile shell height, shell length, total weight and survival rate was between 11.04% and 9.42%, 11.59% and 13.98%, 3.85% and 27.99% and 3.60% and 12.63%, respectively. All results were consistent with those of the larval stage, showing bad constancy and balance. This result provides an important basis for genetic improvement and better utilization of heterosis of the golden shell color strain of .

Abstract:Marine coastal ecosystems are commonly used for the aquaculture of suspension-feeding bivalves, such as oyster, scallops and mussels. The food sources for these bivalves often depend on particulate organic matter and benthic microalgae. Recent studies have suggested that attached microalgae and bacteria also become important food sources for suspension-feeding bivalves. Knowledge of the dietary regime of bivalves is crucial for understanding the coastal food web and cultured bivalve management. The ark shell, , is one of the most important commercial bivalve species in China. They are usually cultured both in raft mariculture and bottom sowing proliferation. However, information on the food sources for cultured 13C and N) and stomach content analysis, this study analyzed the dietary regime of under two different proliferation and culturing modes in May and September 2014, aimed to approach the potential food sources of in this area. Results showed that there was a clear seasonal variation in C value in the raft mariculture area (RMA) in May was significantly lower than that in September, but there was an opposite trend in the bottom sowing proliferation area (BSPA). There were no significant differences in under two proliferation and culturing modes in May, but the in the RMA were clearly higher than those in the BSPA in September. The POMs, mainly including phytoplankton, were the greatest sources of food in the RMA, with a contribution rate of 61.0%-62.9%, followed by attached microalgae (37.2%-39.0%). Comparatively, benthic microalgae was the most important food source in the BSPA, with a contribution rate of 51.7% in May and 72.5% in September. Stomach content analysis showed that Coscinodiscus, Pleurosigma, Nitzschia and . The similarity analysis results indicated the proportional similarity (PS) values between stomach content in the BSPA and the benthic microalgae community were 85.30% in May and 77.20% in September, which may suggest that show a certain selectivity for diatoms of weaker planktonic habit, which sink easily, and for benthic diatoms. Overall, the results can improve our understanding of the biology of , and provide theoretical evidence for scientific aquaculture management of suspension-feeding bivalves under these two proliferation and culturing modes.

Abstract:With the continuous development and utilization of saline-alkali land, increasing quantities of saline-alkali water are being used for fisheries. However, the high pH value of the saline-alkali water environment is always a major factor restricting such aquaculture. Previous studies have revealed that the water environment pH value is mainly a result of the impact of CO₂ balance system (CO₃^2--HCO₃^--CO₂); the CO₂ balance system and activities of algae are also closely related. , two dominant microalgae species in saline-alkali aquaculture ponds, are of great importance in feed, nutrition and the aquaculture industry. Most studies have focused on the growth and reproduction of , and only a few have reported on their relationship to the pH value of the water environment. In this study, anorthogonal experiment was designed to study the effects of temperature (20℃, 25℃ and 30℃) and light intensity (2000 lx, 4000 lx and 6000 lx) on the regulation of environmental pH by the growth of . The results showed that temperature, light intensity and their interactions had a significant effects on the pH value of the algal medium, and there was a clear increase in pH during the exponential growth phase of these species. The water environment pH value of the medium generally increased by more than 9.50 as that alga grew under various temperature and light intensity conditions. The highest pH value of this medium was observed at 2000 lx and 25℃. Under these conditions, the water environment pH value of the medium reached its maximum value of 10.83 on the 9th day and the maximum algal density of 1.1×10⁷ cells/mL on the10th day. The highest pH value of the medium was observed at 6000 lx and 30℃. With the temperature and light intensity increasing, the maximum pH value and algal density were 7.73 and 8.0×10⁶ cells/mL, respectively, on the10th day. ANCOVA analysis showed a positive correlation between pH value and density of algae in the water environment. The correlation coefficient was 0.904; M. aeruginosa is much more likely to result in a higher pH water value than that of <0.01). Results also shows that a high pH value in the water environment can promote growth, which can promote a further increase in pH value. This is one of the main reasons for the high pH in aquaculture ponds, which always affects the healthy development of aquaculture. The results of this research can help in the regulation of water quality in aqua-culture ponds, avoiding higher water pH by algae control. Controlling the density of cells/mL can help to reduce the pH value of the water environment, and this is important for ensuring that water is suitable for the growth of culture organisms. These results can provide data to support the subsequent research and provide a reference for the future studies.

Abstract:We analyzed data from the investigation of fishery resources in Dafeng, off the north coastal waters of Jiangsu Province, east of China, to examine the community structure and influences upon it. Cluster analysis was used to divide the community structure based on the spatial distribution of species composition, diversity and dominant species. We found that during the spring (May) and autumn (November) the coastal water fishes in the northern Jiangsu shoal could be classified into three communities:the coastal waters to the west of the sand ridge; the sea of the central sand ridge; and the tidal creek. The difference in fish community structure was also demonstrated by the total number of fish species in spring[tidal creek (15)>sand ridge (11)>coastal (3)]; and autumn[(tidal creek (18)>coastal (12)>sand ridge (11)]. There was a similar diversity index in spring[tidal creek (1.57,1.89), sand ridge (1.19,1.57)>coastal (0.51,0.69)]; and autumn[tidal creek (1.54,1.54)>coastal (1.02,0.96)> sand ridge (0.92,0.83)]. The tidal creek and open sea are adjacent, so the sand ridge obstructs the sea fish in moving offshore when encountering the end of the tidal creek and makes the benthic fishes stay at the bottom of the ditch which render the accumulation of species, diversity increasing. The spatial distribution of dominant species shows that tidal creek species are mostly and other spawning fishes; the sand ridge mostly consists of and other filter-feeding fishes. We conclude that the community structure of fishes in the sandy ridge and tidal creek in the northern Jiangsu shoal varies, and that topographic changes and environmental change caused by the terrain are the main reasons for this. Using the topography of the tidal creek and sand ridge is an advance that not only focuses on the environmental factors influencing fish community structure changes, but also provides a reliable basis for the management and conservation of fisheries in Subei shoal.

Abstract:The Taiwan Strait, located between the South China Sea and the East China Sea, is an important channel for migratory fishes between the two waters, and therefore has a unique and high diversity of fish species due to its spatial marine environment. However, the rapid development of coastal aquaculture and excessive exploitation of natural resources has resulted in habitat degradation, and the ecosystem has been reverting to a low stage of development. Understanding the relationships between environmental factors and fish assemblages is thus essential for sustainable exploitation of fish resources. In this paper, fish species composition, dominant species, fauna characteristics, species diversity and spatial distribution in the Taiwan Strait and its adjacent waters were studied using data collected from bottom trawl surveys in summer(July) 2014. We also identified the spatial structures of fish assemblages and their relationships with environmental variables. In total, 84 fish species were captured in the survey, belonging to 69 genera, 48 families and 16 orders; these were mainly composed of warm-water, continental shelf demersal fish and continental shelf reef-associated fishes. The primary dominant species were with an average biomass of 33.84 kg/h and 31.56 kg/h, respectively. Cumulative biomass accounted for 46.92% of total fish biomass, and the regression contribution of the biomass to total biomass was 0.30 and 0.62, respectively. High biomass of the dominant species was mainly distributed in the offshore waters of the northern Taiwan Strait, an obvious overlapping of ecological spatial niche. According to hierarchical cluster analysis,fish assemblages were classified into two groups:a coastal community dominated by coastal species such as ; and a widespread community dominated by species such as Trichiurus japonicas, Tentoriceps cristatus, Benthosema pterotum, Trachurus japonicas, Psenopsis anomala and . Diversity analysis showed that the Shannon-Wiener diversity index ' ranged between 0.22 and 2.31 with a mean of 1.44; the Pielou evenness index ranged from 0.11 to 0.72 with a mean of 0.51; and the Margalef species richness index ranged from 0.36 to 4.04 with a mean of 1.59. Significant linear negative correlation existed between the Margalef species richness index and total biomass. A positive correlation with water depth was also found, which indicated that the Margalef species richness index rose with depth, but decreased as biomass increased. Canonical correspondence analysis suggested that the main environmental factors affecting the spatial patterns of the fish assemblage in summer were bottom water salinity, inorganic nitrogen, temperature and temperature difference between surface layer and bottom layer. However, the main environmental factors affecting the spatial patterns of the dominant fish assemblage were bottom water salinity, temperature and inorganic nitrogen.

Abstract:The Western and Central Pacific Ocean (WCPO) purse seine fishery is an important part of Chinese oceanic fisheries. Forecasting the gravity center of a fishing ground with strong interannual change has become increasingly urgent. This study examined the relationship between a purse seine fishing ground, based on the 2011-2014 purse seine log sheet of the Shanghai Kaichuang Fishery Company, and the synchronous oceanic datasets such as Niño3.4 index, and the Tropical Atmosphere Ocean project (TAO). The latter data set provided sea surface temperature (SST) and sea surface wind (SSW). Data were analyzed using the time-lagged correlation method. We identified fishing ground variation induced by oceanic change, and the fields suitable for forecasting the fishing ground, along with their time-lagged number. A regression model was built and verified in this paper. A clear relationship between the fishing ground with SSW and SST was shown in the monthly maps of oceanic fields and fishing ground gravity centers for 2011-2014. In time-lagged correlation analysis results:(1) the correlation coefficient between the longitude of the gravity center with the mean zonal SSW anomaly of 180°E(UA_180), the UA of 165°E (UA_165), the meridian SSW anomaly of 180°E(VA_180), the VA of 165°E (VA_165), the 29℃ SST isothermal longitude value (SST_29) and Niño3.4 index (Nino) was 0.79, 0.82, -0.54, -0.41, 0.75 and 0.47, respectively; and the lagged time was 1, 0, 2, 0, 0 and 0 months, respectively; (2) the correlation coefficient between the latitude of the gravity center with the UA of 180°E and 165°E was 0.55 and 0.63, respectively, and the lagged time was 2 and 1 months. The correlation coefficient with the VA_180 and VA_165 was negative and less than 0.5, and the lagged time was 2 months and synchronic. There was no significant relationship between Niño and the latitude position of the fishing ground. We found a regression equation of gravity longitude center (GC_Lon) and latitude center (GC_Lat):GC_Lon=137.534+2.36159UA_165_{, GC_Lat=0.236156+0.51587UA_165(; and the model R square was 0.72 and 0.34, respectively. The longitude gravity center was much more reasonable than that of the latitude. The error gap between the reality and the predictive value from the models was more than 2° in longitude and latitude, mainly because there were delays when no fishing was permitted in the fishing ground in the east WCPO in November and December 2014.The difference in the central fishing ground between the model results and the Shanghai Kaichuang Fishery Company log sheets were reasonable:the longitude was less than 0.5° and the latitude was about 1.5°. This paper presents clear evidence that the change in fishing grounds followed variations in SST and SSW, and we believe that the influence of the SSW has not been focused on in this way before. We also discovered that the zonal wind speed anomaly at 165°E and 180°E longitude had the same effective influence on the fishing ground as a 29℃ sea surface isotherm. These findings will advance related research into purse seine fishing grounds, and the forecasting models may assist purse seine companies in budgeting for their permitted fishing days.}