Abstract:Antarctic krill (Euphausia superba) is a rich resource of polyunsaturated fatty acids and proteins. Therefore the contents of the two nutritional components are the determining factors of the economic value of Antarctic krill. To help improve the efficiency of utilization of Antarctic krill, we employed the Soxhlet extraction method and selected the optimal solvent for lipid extraction from anhydrous ethanol, acetone, petroleum ether, hexane, ethyl acetate and cyclohexane. We also analyzed the seasonal variation in the levels of lipids and proteins, and investigated the effect of the body length on the nutritional contents of Antarctic krill. Samples were collected from the water nearby the South Georgia Islands between June and August 2013 and from the water nearby the South Shetland Islands between December 2013 and May 2014. It shows that anhydrous ethanol was the best extraction solvent examined for determining the lipid content of Antarctic krill. The contents of lipids and proteins of samples from the South Georgia Islands were (22.03±0.51)% and (64.52±0.16)% (in dry matter) respectively. The levels of both lipids and proteins of smaller individuals (<40 mm in total length) were higher than those of the larger ones (>40 mm, P<0.05). The lipid content of samples from the South Shetland Islands showed an increasing trend from early summer to late fall, the level raised from (19.83±0.04)% in December to the peak value (30.58±0.02)% in April, followed by a decline to (28.66±0.03)% in May. In contrast, the protein content was the highest in December (66.75±0.14)% and the lowest in April (58.02±0.23)%. There was a significant and negative correlation between the lipid content and the protein content (P=0.005). These results can be used directly to guide the arrangement of actual fishing operation of the krill fishery.

Abstract:Fouling organisms have caused great damages to offshore platforms in the sea. Some reports have discussed the impacts of fouling organisms on offshore platforms, however, little is known about the situation in the Bohai Sea. In this study, we investigated the species composition, structural characteristics, evolving rules, and factors of fouling organism attachment on offshore platforms in the Bohai Sea, by means of a series of artificial test panel experiments and multiple statistical analyses. The artificial test panel experiments in the Bohai Sea were conducted from September 2013 to September 2014, and we identified a total of 24 species the majority of which were temperate and eurythermal species. The dominant species were Caprella acanthogaster, Grandidierella japonica, Jassa marmorata and Gammaropsis sp. etc. The seasonal panel tests showed that the average biomass on the surface panels and the middle panels were 1764.23 g/m2 and 2322.31 g/m2 respectively. Settlements of fouling organisms occurred throughout the year particularly in summer and autumn，indicating an obvious seasonal variation in species and biomass. The Shannon-Wiener Diversity Index and the Margalef Richness Index were at the highest level in autumn. The multivariate analysis showed that there were three types of fouling organism communities in chronological order, which implied an apparent seasonal variation of fouling organisms in the Bohai Sea. There was significant correlation between the water temperature and the biomass of fouling organisms on the surface and middle panels, and the correlation coefficient was 0.959 and 0.986 respectively (P<0.01). These results provided valuable information on anti-fouling designs for both the restoration of overly used offshore platforms and the construction of new platforms in the Bohai Sea. Moreover, our study could serve as important reference on the prevention and elimination of fouling organisms, and therefore could help reduce security risks of offshore platforms.

Abstract:Human activities have aggravated the offshore ecologic environment in the Liaodong Bay and endangered aquatic bioresources in these areas. The Liaodong Bay used to be an important fishing ground and the habitat of a variety of fish species such as Larimichthys polyactis, Trichiurus lepturus, and Fenneropenaeus chinensis. However, in recent years the fish resources have been diminishing because of water pollution, over-fishing and other human activities. Sustainable development is the key to healthy marine economy, which depends on good marine ecological environment. In this study we evaluated the offshore surface water quality of the Liaodong Bay by analyzing 18 samples collected in three consecutive seasons in 2013 including May (spring), August (summer), and October (autumn). We monitored the concentrations of six typical metallic pollutants (Cu, Pb, Zn, Cd, Hg, As) and employed the Nemerow Pollution Index and the Comprehensive Quality Index to evaluate the degree of heavy metal pollution. The concentrations of these heavy metals were highest in summer. The concentration of Pb did not meet the first-class seawater standard, which was 66.67% higher than the limit, however, all others complied with the first-class seawater standard. Concentrations of all heavy metals were below chronic safe concentration of organisms recommended by National Oceanic and Atmospheric Administration (NOAA) except for Cu. The Nemerow Pollution Index of the offshore surface seawater of the Liaodong Bay was in the range of 0.43-2.37, which was lower than 2.6, thus the pollution degree in 2013 was determined to be clean to slightly polluted. The Comprehensive Quality Index was between 0.39-0.97, which was lower than 1.0, therefore the water environment was acceptable and ranked as clean to slight clean. There were three areas that were relatively heavily polluted, including the Suizhong offshore area, north of the Liaodong Bay estuary area, and the Fuzhou Bay and Jinzhou Bay offshore areas.

Abstract:Here we studied the seasonal, temporal and spatial distribution of petroleum hydrocarbon in the Liaoning Bay based on the all-year-around environmental monitoring data in 2013 and 2014. The source and degree of pollution were also analyzed and discussed. The range of petroleum hydrocarbon concentration in seawater was 0.003-0.239 mg/L with an average of 0.027 mg/L. The concentration tended to decrease over time and exhibited seasonal fluctuation. Petroleum hydrocarbon concentrations in spring, autumn and winter exceeded the limit of the national benchmark with varying degrees. There was a significant correlation between concentrations in the surface and bottom seawater. The petroleum hydrocarbon concentration varied in seasons (autumn > winter > spring > summer), and gradually decreased from inshore to offshore, and from open areas to protected areas. It could be concluded that regions with petroleum hydrocarbon concentrations of 0.030-0.032 mg/L, < 0.024 mg/L, and > 0.032 mg/L accounted for 27%, 10.9%, 4.5% of the total investigated sea area respectively. The region with a concentration of 0.030-0.032 mg/L had an region of 6960 km2 and was mostly within the northern and western coastal region of the Liaodong Bay. The area with petroleum hydrocarbon concentration below 0.024 mg/L was 2806 km2 and was mainly located in the Dalian harbor seal nature reserve. The smallest area was about 1170 km2 in the western harbor area of the Liaodong Bay. Analysis also showed that seasonal variation in petroleum hydrocarbon concentration was affected by the pollution from fishing vessel operations, and that the major sources of petroleum hydrocarbon were the terrestrial inputs and marine anthropogenic activities.

Abstract:In this study we investigated the effect of incubation temperatures (16℃, 18℃, 20℃, 22℃, 24℃, 28℃, and 30℃) on the embryonic development and larval activity of the Epinephelus moara. The stage of embryonic development after 12 hours of hatching, the hatching rate and the deformity rate of newly-hatched larvae were also measured and analyzed. We performed the starvation test on the newly-hatched larvae and evaluated their daily survival rate and the survival activity index (SAI) at different temperatures. It showed that the embryos could be hatched at 18−28℃. The hatching time was negatively correlated to the temperature as shown in the equation y=12139x−1.869 (R2=0.993, P<0.01), in which y was the hatching time and x was the temperature. The highest hatching rate (71.01%) and the lowest deformity rate (9.7%) were observed at 22℃. A lower hatching rate (65.37%) and higher deformity rate (13.07%) appeared at 20℃. The hatching rate decreased gradually when the temperature was below 22℃, and reached 24.39% at 18℃. The hatching rate also decreased significantly when the temperature was above 22℃, and the lowest hatching rate (16.11%) appeared at 28℃. The effect of temperature on the deformity rate of newly-hatched larvae showed an opposite pattern. The embryonic development stopped at the stage of blastula at 16℃. At 30℃, the cell dividing ceased at the embryo body stage. The SAI first increased and then decreased along with the rise in the temperature. At 20℃, SAI of the larva was the highest (25.97) with the longest half-death time of 7 d. Therefore, the optimal hatching temperature for the fertilized eggs of E. moara could be 22–24℃, and the most suitable temperature for the survival of newly-hatched larvae could be 20–22℃.

Abstract:Reciprocal hybrids of Platichthys stellatus and Kareius bicoloratus have been reported, however, little is known about the nutritional facts of their muscles. In this study we analyzed the nutritional components in muscles of P. stellatus, K. bicoloratus and the reciprocal hybrids (initial body weight 338.32–445.98 g) using the current national standard methods. We found that the obverse hybrid (P. stellatus♀×K. bicoloratus♂) had significantly higher crude protein content than the inverse (K. bicoloratus♀×P. stellatus♂, P<0.05), but not significantly different from that of P. stellatus and K. bicoloratus (P>0.05). The crude lipid content of the obverse hybrid (1.44%) was significantly higher than that of the other three species (P<0.05). The inverse hybrid had the lowest level of crude lipid (0.43%) and significantly higher moisture level than the other three species. There was no significant difference in the muscle ash content among the four species (P>0.05). The obverse hybrid had significantly lower juice loss yield, water loss yield and fat loss yield than P. stellatus and K. bicoloratus (P<0.05), and its cooked meat yield was obviously higher than that of the inverse hybrid (P<0.05). The obverse hybrid possessed the highest contents of essential amino acid, delicious amino acid and total amino acid, and its ratio of branched-chain amino acid amount to aromatic amino acid amount was close to the normal value in humans. The contents of essential amino acids in the four species were higher than the Food and Agriculture Organization of the United Nations/World Health Organization (FAO/WHO) standard, moreover, it was the highest in the obverse hybrid of which the level was even higher than egg protein standard. The obverse hybrid had remarkably higher amino acids score (AAS), chemical score (CS) and essential amino acid index (EAAI) than the other three species, whereas the inverse hybrid had the lowest scores. These findings indicated that the obverse hybrid showed apparent hybrid advantages and exhibited higher nutritional values and muscle qualities than P. stellatus and K. bicoloratus. However these advantages were not present in the inverse hybrid. Our study provided valuable information for the selection of traits in the breeding between P. stellatus and K. bicoloratus.

Abstract:A cost-efficient formula of feed in fish farming usually contains a large amount of low-cost energy sources supplemented with sufficient level of high-cost essential nutrients such as protein. Carbohydrate is the least costly dietary energy for animals. However, the utilization of carbohydrate varies a lot between different fish species, and the mechanisms underlying distinctive carbohydrate-consuming abilities have been obscure. In this study we aimed to explore the effects of different carbohydrate sources on daily weight growth (DWG), feed utilization and digestive enzyme activities of Trachinotus ovatus. Fish (initial weight 31.24±0.58 g) were fed with 5 groups of isonitrogenous and isolipidic diets each of which contained 1 type of carbohydrate at 20% including glucose, sucrose, dextrin, corn starch or gelatinized corn starch. Each group was fed for 8 weeks. The results showed that different carbohydrate sources significantly affected the DWG, feed efficiency (FE) and the protein efficiency ratio (PER) (P<0.05). The gelatinized corn starch group had significantly higher DWG (2.19 g/d), FE (0.82%) and PER (1.88) than other groups (P<0.05), and there was no significant difference between the two starch groups (P>0.05). The glucose group had the lowest DWG, FE and PER (P<0.05). Dietary carbohydrate sources also had great effects on activities of digestive enzymes (P<0.05). The protease activity of the two starch groups was significantly lower than that of the other three groups (P<0.05). The sucrose group displayed the highest amylase activity (P<0.05). The lipase activity was boosted along with the increase in the molecular weight of the dietary carbohydrate, and was the highest in the gelatinized corn starch group. In conclusion, large-molecule carbohydrates may have better effects on the growth of T. ovatus than glucose, sucrose and dextrin. Gelatinized corn starch was the optimal carbohydrate source in this study.

Abstract:This experiment was conducted to investigate the effects of small molecule weight fish protein hydrolysate on the growth performance and the expression of insulin-like growth factor I receptor (IGF-IR) mRNA in the liver of juvenile turbot (Scophthalmus maximus L.). Four isonitrogenous and isoenergetic diets were formulated and fed to fish with initial weight of (4.16±0.01) g. In the experimental diets, fish meal was replaced with fish protein hydrolysate by 0% (UF-0), 5% (UF-5), 10% (UF-10), and 20% (UF-20) of total dietary protein, respectively. The experiment lasted 12 weeks. The results showed that there were no significant differences in the weight gain rate and specific growth rate among groups UF-0, UF-5 and UF-10 (P>0.05), but these groups showed higher values than group UF-20 (P<0.05). UF-0 and UF-5 showed similar feeding rate (P>0.05), which was significantly lower than that of UF-10 and UF-20 (P<0.05). The feed efficiency, protein efficiency, and protein retention effiency of UF-0 and UF-5 were significantly higher than those of UF-10 and UF-20 (P<0.05), and the parameter values of UF-10 were significantly higher than those of UF-20 (P<0.05). There were no differences in the contents of crude protein and crude lipid among groups UF-0, UF-5 and UF-10 (P>0.05), but the values in these groups were higher than those of UF-20 (P<0.05). The content of essential amino acids in the muscle and the ratio of essential amino acids to non-essential amino acids in group UF-5 was higher than those of other groups (P<0.05). It was also found that the expression of insulin-like growth factor I receptor (IGF-IR) mRNA in the liver increased with increasing levels of dietary fish protein hydrolysate, and it was higher in UF-20 compared to other three groups (P<0.05). These results indicated that low level of small molecule weight fish protein hydrolysate could improve the growth and feed utilization of juvenile turbot. However, higher level may restrain the growth. Furthermore, dietary fish protein hydrolysate could improve the expression of IGF-IR mRNA in the liver of juvenile turbot.

Abstract:Microsatellite markers have been widely used in parentage identification, genetic linkage mapping, and diversity study of aquatic animals, due to the advantages including mendelian inheritance pattern, wide distribution, high polymorphism, high repeatability and stability, and co-dominant inheritance. This technique efficiently helps with analysis of genetic background of different populations, as well as selective breeding. Multiplex PCR could amplify many microsatellite loci simultaneously, therefore is an efficient, rapid, and economic method, and could be a powerful tool of parentage identification, pedigree management, and population genetic analysis of aquatic animals. In order to improve the efficiency and reduce the cost of genetic studies of Litopenaeus vannamei, previously reported microsatellite loci with high polymorphism were selected in developing multiplex PCR systems in this study. Four multiplex PCR systems were successfully established and optimized based on the allelic lengths and annealing temperatures of the microsatellite loci. We used these systems to perform pedigree analysis of 11 families of selected L. vannamei, and found that the average number of alleles (Na) was 6, the average polymorphism information content (PIC) was 0.5813, and the average observed heterozygosity (Ho) and expected heterozygosity (He) were 0.513 and 0.636 respectively. Together with Cervus 3.0 software, the four multiplex PCR systems were also used to verify the capacity of parentage assignment in the 11 families of L. vannamei of which the pedigree relationships were already known. The combined exclusion probability of the first parent (CE-1P), the second parent (CE-2P), and a parent pair (CE-PP) were shown to be 0.99525487, 0.99990862, and 0.99999986 respectively. Further analysis suggested that if all the multiplex PCR systems were used for pedigree analysis, the accuracy rates of both simulated assignment rate and parentage identification could reach 100%. It also indicated that the full-sib and half-sib families had great capability for precise identification. In conclusion, the four multiplex PCR systems for microsatellite markers could serve as an efficient and accurate approach in further genetic diversity and pedigree analysis of L. vannamei.

Abstract:Yellow head virus (YHV) is a highly lethal pathogen that causes majority of shrimp diseases. In this study we conducted the epidemiology study and revealed the existence of YHV and the current infectious situation in China. We collected 299 samples in 2012-2014 and detected YHV using the nested RT-PCR method that was recommended in the World Organization for Animal Health (OIE) manual. Genes of some YHV-positive samples were sequenced and underwent the phylogenetic tree analysis. The epidemiology survey showed that the YHV infection rate was 11% and this virus was found in cultured Litopenaeus vannamei, Fenneropenaeus chinensis, Marsupenaeus japonicus and Macrobrachium rosenbergii in China. F. chinensis showed the highest infection rate. F. chinensis and M. rosenbergii were newly reported as natural hosts of YHV. We then amplified a 1002 bp fragment located in the ORF1b region. The alignment results suggested that YHVs from the six infected samples shared 81.0%-90.5% sequence identity with the six YHV genotypes archived in NCBI. The phylogenetic tree analysis showed that YHVs from the six samples clustered in one branch, but they did not share the same branch with the six already known YHV strains. YHVs in the 6 samples were relatively closely related to YHV Type 1 (YHV-1) and had higher similarity with YHV-1b than with YHV-1a. We also amplified a 509 bp sequence located in the ORF3 region. It encoded gp116 and was different from the 545 bp of YHV Type 1a (YHV-1a), the 383 bp of YHV-1b and the 476 bp of YHV-2 (GAV). We next compared the ORF2 sequence of two samples and found that they were 99.8% identical in gene sequence and had the same protein sequence. Their sequence similarities with YHV-1 and YHV-2 (GAV) were 85.9% and 80.9% respectively. Results of gene sequence alignment suggested that the YHV found in China was a new pathogenic strain.

Abstract:Three bacterial strains, 20131023A00, 20131023A01, and 20131023A05, were isolated from shrimp guts and the farming ponds using inorganic selecting medium. When cultured in the liquid selecting medium (pH=7.2) containing 0.12% ammonia nitrogen at 28℃ for 24 h, the ammonia conversion rates of the three strains were (38.9±0.1)%, (43.1±0.4)%, and (49.9±0.5)% respectively. Using the paper disk method, we identified that 20131023A05 was the only strain that antagonized Vibrio parahaemolyticus. We measured the diameters of inhibition zones produced by Strain 20131023A05 on the plates coated with V. parahaemolyticus at the densities of 1.57×105 CFU/cm2, 1.57×104 CFU/cm2, and 1.57×103 CFU/cm2, and the diameters were (9.14±0.05) mm, (11.57±0.03) mm, and (13.59±0.02) mm respectively. It was identified that the strain had the closest genetic relationship with Pseudoalteromonas piscicida according to 16S rDNA sequencing. Marsupenaeus japonicus immersed with Strain 20131023A05 at 2.5×105 CFU/ml showed resistance to intramuscular-injected V. parahaemolyticus and the relative survival rate (RPS) was 35%. We applied strain 20131023A05 at 3.13×104 CFU/ml once every three days as well as brown sugar (70% of diet) every day in the culture water of Litopenaeus vannamei for 60 days. Subsequently the concentration of ammonia nitrogen in the water became significantly lower than the control and other groups. Our results suggested that Strain 20131023A05 could function in both ammonia removal and V. parahaemolyticus inhibition, therefore may have great potentials in shrimp farming industry.

Abstract:Vibrios were common microbe in marine aquaculture. Most of them such as Vibrio anguillarum, V. harveyi and V. parahaemolyticus etc. were opportunistic pathogen to aquaculture animals. In the latest years, shrimp culture worldwide was subjected to heavy economic loss which was caused by V. parahaemolyticus infection. In order to find a high effective and safety method to control the serious shrimp vibrio disease, instead of using antibiotics, screening and using probiotics is a promising way. In this study, a strain was isolated from a shrimp pond and designated as 2013082515 (Strain 15). The antibacterial effect and minimum antibacterial concentrations of Strain 15 were analyzed using V. anguillarum, V. harveyi and V. parahaemolyticus as indicator bacteria. At the same time, the antibacterial effect of Strain 15 against other seven marine vibrios including V. vulnificus, V. alginolyticus, V. diabolicus, V. campbellii, V. natriegens, V. brasiliensis and V. rotiferianus was analyzed. Biological safety evaluation test on Strain 15 used as probiotic was conducted by injection and immersion challenge. The results showed that Strain 15 had obvious antibacterial effect against three indicator bacteria. Furthermore, the strongest antibacterial effect presented on V. anguillarum with an inhibition zone around (34.90±0.36) mm, the second largest inhibition zone presented on V. harveyi around (25.74±0.17) mm; The minimal inhibitory concentration of Strain 15 on V. anguillarum, V. harveyi and V. parahaemolyticus was 2.50×104 CFU/ml, 2.50×105 CFU/ml, and 2.50×105 CFU/ml respectively, and the antibacterial effect of Strain 15 against other 7 vibrios were obtained in different degree. Data also showed that Strain 15 at high concentrations (injection challenge 1.84×107 CFU/ml, immersion challenge 4.17×107 CFU/ml) had potential toxicity to shrimp. In order the identify Strain 15, both gas chromatographic analysis of bacterial whole cell fatty acids and 16S rDNA sequencing were employed. The results showed that Strain 15 was a Pseudoalteromonas sp. Results from this study could provide technical support for developing biological agents used for preventing vibriosis in aquatic animals.

Abstract:DNA methylation was one of key epigenetic modifications in eukaryotes genomes, and has been extensively studied in the field of fishery in recent years. Here we applied MSAP (Methylation-sensitive amplified polymorphism) and analyzed the level and pattern of methylation of genomic DNA in the body wall, the respiratory tree, and the digestive tract of Apostichopus japonicus and white A. japonicus. We also compared the effects of DNA methylation in specific gene expression in different tissues of A. japonicus and white A. japonicus. In this study, a combination of 9 pairs of primers was used for the amplification of stable and clear fragments of the two populations. A total of 5932 and 5208 sites were detected in normal A. japonicus and white A. japonicus respectively, and they were mainly located at the unmethylated CCGG sites. There were 4317 and 3944 unmethylated sites in normal A. japonicus andwhite A. japonicus populations, accounting for 72.78% and 75.73% respectively. The methylation rates in the body wall, respiratory tree, and digestive tract of normal A. japonicus were about 31.07%, 23.36%, and 26.34% respectively, and those in A. japonicus were 29.88%, 23.25%, and 19.45%. These results suggested that the methylation rate in the body wall was the highest in both populations. It was inferred that the degree and pattern in DNA methylation could be different at both tissues and populations. DNA methylation may play an important role in the process of tissue differentiation and development in normal A. japonicus and white A. japonicus. Fully-methylated sites outnumbered hemi-methylated sites in the three tissues of both populations. This study provided better understanding of distinct levels and patterns of genome DNA methylation in different tissues and populations. Our findings also shed light on the relationship between the DNA methylation and the albino body wall of white A. japonicus

Abstract:In this study we compared the nutrient compositions of the body walls of green and white sea cucumbers that were cultured in the same environment. It was found that there were significant differences in the contents of moisture, polysaccharides and ash, as well as the production rate of the body wall between the green and white sea cucumbers (P<0.05). However, there was no difference in the content of crude proteins and crude fat (P>0.05). Twenty major types of fatty acids were detected in the body wall, and there were no significant differences in the contents of the total fatty acids and polyunsaturated fatty acids (P>0.05). The content of saturated fatty acids was higher in green sea cucumber than in white sea cucumber, whereas the content of monounsaturated fatty acids was lower in green sea cucumber (P<0.05). Contents of AA and DHA were also lower in green sea cucumber (P<0.05). Seventeen types of major amino acids were detected in body walls, and the contents of EAA, FAA and DAA were not significantly different between white and green sea cucumbers (P>0.05). Green sea cucumbers had lower levels of aspartic acid, arginine, Mn, and Cr in the body wall than white sea cucumber (P<0.05). The contents of heavy metals such as Pb, Cd, Hg and As in the body wall of both green and white sea cucumbers met the food safety standard. In conclusion, under the same culture conditions, white sea cucumber exhibited higher quality than green sea cucumber in terms of the production rate of the body wall, the contents of polysaccharide and unsaturated fatty acid, the relative percentage of AA and DHA, and the levels of arginine, aspartic acid and trace elements (Mn and Cr).

Abstract:Three experiments were conducted in this study to explore proper on-land culture conditions for Gloiopeltis furcata thalli. In the first experiment vegetable fragments with different sizes (0.5cm, 1cm, and 1.5cm) and cut parts (cut from base, top, and fork) were incubated in lab for 60 days. In the second experiment G. furcata thalli were incubated in different containers (square tank, acrylic cylinder, and plastic membrane cylinder), and with different densities (0.5 g/L, 1 g/L, 2 g/L, and 4 g/L). In the third experiment G. furcata thalli dried in different ways (indoor wind, artificial climate incubation chambers, air-conditioning and fan) were stored at different temperatures (4℃ and –18℃). We found that with a certain size there was no significant difference in the growth between vegetable fragments from various cut parts. Vegetable fragments with a length of 0.5 cm grew slower than those with other lengths (1.0 cm and 1.5 cm, P<0.05). The SGR (specific growth rate) of G. furcata thalli was the lowest in the square tank (P<0.05), and was decreased along with the increase in culture density (P<0.05). The survival rate was higher in G. furcata thalli dried with air-conditioning and fan (P<0.05) and was 93.8% after preserved at –18℃ for 6 months. However, the survival rate of all groups decreased to 0 in 1 month after stored at 4℃. The results indicated that appropriate on-land culture conditions included reasonable size of vegetable fragments (> 0.5 cm), density between 0.5 g/L and 1 g/L, and plastic membrane cylinder as the container. Vegetable fragments for culture can be readily obtained if preserved at –18℃

Abstract:In order to find out an effective method to identify Pyropia yezoensis germplasm, we tested the efficacy of four common DNA barcodings—RUBISCO Spacer, UPA, Cox2-3, and ITS-5.8S—in determining the genetic relationships between six strains of P. yezoensis from China and Japan. The four DNA barcodings showed high sequence homologies varying from 97.8% to 100%, and the homology of RUBISCO Spacer was 100%. Four Chinese strains (LS, B4, HT, and TM18) shared the same UPA sequence. However, the barcoding was different from that of the Japanese strains GT and ROS-2 and the homology was 99.2%. The homologies of Cox2-3 and ITS-5.8S sequences were 97.8%-99.2% and 98.4%-99.8% respectively, which were lower than those of RUBISCO Spacer and UPA. Phylogenesis of UPA, Cox2-3 and ITS-5.8S sequences revealed that the four Chinese strains clustered into one branch according to their UPA and ITS-5.8S sequences, whereas the two Japanese strains belonged to another branch. These results were consistent with their actual relationships. Moreover, the four Chinese strains could be further distinguished according to their ITS-5.8S sequences, but were identified as in the same branch with the Cox2-3 barcoding. The results confirmed that ITS-5.8S was the most effective barcoding for identifying P. yezoensis strains in this study

Abstract:The aim of this study was to identify the effects of high temperature (25℃) on the activity of antioxidant enzymes, the chlorophyll content, and the chlorophyll fluorescence parameter of Saccharina japonica young sporophytes. Samples were taken every 4 h over a 48 h period. The major results included: (1) after 12 h culture the content of soluble proteins of the 25℃ group reached the maximum value that was 37.9% higher than initial level (P<0.05). (2) MDA content of the 25℃ group increased over the time and reached the highest value after 48 h, which was significantly different from the control group (P<0.05). (3) The chlorophyll content of the 25℃ group decreased during prolonged culture, the lowest value appeared after 48 h and was 38.5% lower than the initial level (P<0.05). (4) At high temperature the POD activity decreased over the time, the minimum appeared after 48 h and was 47.2% lower than initial (P<0.05); The SOD activity fluctuated, reached the minimum after 8 h, and the maximum activity was observed after 40 h which was 36% higher than the initial level (P<0.05); The CAT activity declined to the lowest level after 48 h and was 75.8% lower than initial (P<0.05). (5) The value of Fv/Fm of the 25℃ group dropped to the lowest after 48 h and was 56.8% lower than initial (P<0.05). Our results provide important information for the selection of heat-resistant S. japonica.

Abstract:Enzyme-catalyzed synthesis of oligo-methionine (OMet) has been available, however, little is known on the application of OMet in aquatic feed. In this study, an 8 week feeding trial was conducted to investigate the effects of dietary crystalline methionine (CMet) and OMet on the growth performance, feed utilization and protein metabolism responses of juvenile large yellow croaker (Larimichthys crocea) with initial body weight of (26.0±1.6) g. A practical diet with low fish meal content (31.8%) was used as the control diet (LF). Six other experimental diets (CMet 0.35, CMet 0.65, CMet 0.95, OMet 0.35, OMet 0.65, and OMet 0.95) were formulated with 0.35%, 0.65% and 0.95% CMet or OMet respectively. The weight gain rate (WGR) of fish treated with OMet or CMet was significantly higher than control and increased significantly along with the elevated level of supplement (P<0.05). The WGR was the highest in fish treated with OMet 0.95. The WGR and protein efficiency ratio (PER) of fish in OMet treatment were significantly higher than those treated with CMet (P<0.05). In all treatments there was no significant difference in survival rate, feed conversion ratio or body composition (crude protein, crude lipid, ash, and moisture, P>0.05). Compared to CMet treatment, OMet caused lower hepatosomatic index (HSI) and higher activities of glutamic-oxaloacetic transaminase (GOT) and glutamic-pyruvic transaminase (GPT) in the liver (P<0.05). Meanwhile, the methionine level greatly affected activities of GOT. The fish in OMet 0.95 treatment showed the lowest HSI and the highest GPT and GOT activities. However, in all groups no significant difference was detected in the concentrations of ammonia and urea nitrogen in the serum (P>0.05). This study indicated that compared to CMet, OMet might be more effective in improving the growth performance and feed utilization of large yellow croakers, therefore could replace the former as the external methionine source to balance the amino acids in the soybean protein feed.

Abstract:The oyster Crassostrea hongkongensis is the main aquaculture species along south China coast and has an important economic value. The Maowei Bay adjacent to Qinzhou of Guangxi Province has been the largest natural oyster seed field, and oysters originating from this area are named after the place (Qinzhou oyster). The estuary of the Dafeng River is a major aquaculture site for Qinzhou oyster in Guangxi Province. Due to the promotion of the deepwater-raft-hanging-culture mode, massive death of oysters has occurred frequently in spring since 2008 and resulted in the rapid drop in the amount of oyster seeds in the Maowei Bay. In this study we explored the reproductive cycle of oyster gonad development and investigated the causes of the massive death, using one-year old oysters from the estuary of Dafeng River (HH, whose larva came from the Maowei Bay). We developed a method for rapid identifying the developmental stage of oyster gonad with the combination of naked-eye observation, biopsy and histological analysis. We also compared the gonad development of two-year old oysters from inside (HH) and outside (XF) of the estuary of the Dafeng River and from the Maowei Bay (MS). We found that Qinzhou oysters had only one breeding cycle each year which can be divided into 4 gonad developmental stages: the undifferentiated stage from January to March, the differentiation stage in April when the gender became distinguishable, the mature and discharging stage from May to October when the oysters spawned repeatedly, and the resting stage from November to December during which the gonads atrophied and disappeared. Gonad development of XF oysters started half a month earlier than HH oysters and one month earlier than MS oysters. In 2014 it was observed that the gonad of XF oysters developed into mature stage in April. The variation might be caused by differences in temperature, salinity and food abundance. Moreover, in overly hot and dry weather the gonad discharge was inhibited probably by high salinity, which may explain the massive death in the high salinity area. Therefore, we recommend close monitoring on the gonad development and seawater salinity in spring. The oysters should be harvested or transported to the inner estuary immediately after they mature, so as to avoid the massive death caused by scarce rainfall

Abstract:Ozone (O3) is a strong oxidizing agent that has been widely used in factory recirculating aquaculture systems. The proper concentration is a key to the utilization of ozone. Ozone at inappropriately high concentration could impair the growth, behavior, and health of farmed fish. Furthermore, ozone at high concentration also affects the biofilm in the biofilter, which could reduce the efficiency of water treatment in the recirculating aquaculture systems (RAS). In this study, ozone was added in RAS at different concentrations, and the subsequent effects on the activity and purification effectiveness of biofilm were tested. It was shown that when the Oxidation-Reduction Potential (ORP) was lower than 450 mV, the efficiency of ammonia nitrogen treatment was increased along with the elevation in ozone concentration. Under this condition the highest removal rates of ammonia nitrogen and nitrite nitrogen reached 39.9% and 28.2% respectively, and the survival rate of bacteria in the biofilm was 88.1%. This suggested that ozone did not affect the efficiency of the biofilter as ORP was below 450 mV. When ORP was 500 mV, after 24-hour treatment with ozone the removal efficiency was decreased from 36.5% to 12.2% for ammonia nitrogen, and from 28.1% to 8.4% for nitrite nitrogen. When ORP was 550 mV, 4-hour ozone treatment reduced the efficiency from 47.5% to 5.0% for ammonia nitrogen, and from 32.1% to 3.3% for nitrite nitrogen. This implied that higher ORP significantly reduced the efficiency of water treatment. The survival rate of bacteria in the biofilm dropped from 88.1% to 31.5%. Our study indicated that the effectiveness of water treatment and the survival rate of bacteria could be greatly affected by ozone. To ensure the safety and cost efficiency of RAS, we recommended that the concentration of ozone added in RAS should be controlled to keep ORP in the biofilter under 400 mV.

Abstract:In this study we aimed to explore the influence of feeding rate on the growth of the Chinese giant salamander Andrias davidianus under certain conditions in industrial aquaculture such as water temperature 18–19℃, pH 8.0 and dissolved oxygen 6.0 mg/L. Chinese giant salamander aged 2, 3, 4 and 5-year-old were fed with fresh dead carp at five different rates, and the corresponding growth rates were recorded during 60 days. We compared a variety of growth traits between different groups including the weight gain, the total length increment, the feed coefficient, the weight gain rate, the specific growth rate and the food conversion rate. Two-year-old Chinese giant salamander with feeding rate 2.0% had a significantly lower feed coefficient but higher weight gain rate and food conversion rate than those fed at 1.7%, 2.3%, 2.6%, and 2.9%. Moreover, its specific growth rate was also higher than that of groups fed at 1.7% and 2.6% (P<0.05). Three-year-old Chinese giant salamander with feeding rate 2.2% had a significantly lower feed coefficient than those fed at 1.9%, 2.5%, 2.8%, but higher weight gain rate and specific growth rate than those fed at 1.6%, 1.9%, 2.5% and 2.8%. Their food conversion rate was significantly higher than those fed at 2.5% and 2.8% (P<0.05). Four-year-old Chinese giant salamander with feeding rate 2.3% had a significantly lower feed coefficient but higher weight gain rate and specific growth rate compared to those fed at 1.7%, 2.0% and 2.9%, and its the food conversion rate were significantly higher than those fed at 1.7% and 2.9% (P<0.05). Five-year-old Chinese giant salamander fed at 2.5% had a significantly lower feed coefficient than those fed at 1.9%, higher weight gain rate and specific growth rate than those fed at 1.9%, 2.2%, 2.8% and 3.1%, and higher food conversion rate than those fed at 2.2%, 2.8% and 3.1% (P<0.05). In order to reduce the feed coefficient and to raise the weight gain rate, specific growth rate and food conversion rate, we recommended that the appropriate feeding rates should be 2.0%, 2.2%, 2.3% and 2.5% for 2, 3, 4 and 5-year-old Chinese giant salamander respectively. The optimal feeding rate appeared to increase along with growing age, which conformed to equation y=0.000212x+2.07 (r2=0.8797).

Abstract:In this study we applied one-single factor and response surface method to optimize the culture medium and other conditions for strain YS1069, which would improve the yield of xylanase. First, the single factor method was used to screen eight factors including the nitrogen source, the carbon source, the inorganic salts, the inoculation volume, the liquid volume, Na2CO3, fermentation temperature and fermentation time. The optimal results corresponding to each single factor was as follows: bean cake powder 25 g/L, wheat bran 40 g/L, NaNO3 0.9 g/L, K2HPO4 3 g/L, MgSO4·7H2O 0.6 g/L, inoculums at 4%, 30 ml/250 ml (v/v) liquid volume, Na2CO3 18 g/L, cultured at 30℃ for 96 h. Secondly, these main variables were evaluated with the Plackett-Burman test. The results suggested that Na2CO3, wheat bran and MgSO4·7H2O were the most impactful factors. Finally, the optimal levels of the three factors were determined with central composite design and Design-Expert 8.05 software. The results were shown as follows: Na2CO3 21.86 g/L, wheat bran 51.41 g/L, and MgSO4·7H2O 0.59 g/L. Under the optimized conditions, the production of xylanase was increased by 5 folds.

Abstract:In this study we compared the ratios of mannuronic acid to guluronic acid (M/G) in different brown algae species of Costaria costata, Scytosiphon lomentarius, Sargassum pallidum, Undaria pinnatifida, Saccharina japonica, and monitored the change of M/G during the growth of S. japonica. The M/G ratio was determined with a high performance liquid chromatography (HPLC) with pre-column derivatization technique. The results showed that C. costata had the highest M/G ratio (2.22), which was followed by S. japonica (2.10), and S. lomentarius had the lowest value (0.60). These demonstrated that algin of C. costata and S. japonica had small intensity but excellent water-holding capacity, and that algin of S. lomentarius had the opposite properties. The M content showed the order as C. costata (18.84%) > S. japonica (14.83%) > S. lomentarius (8.77%). The algin of S. lomentarius had the lowest level of M (14.58%) and the highest G content. The characteristics including fast growth rate, high yield, and commercial cultivation would make S. japonica as suitable material in food industry that requires excellent elasticity and water-holding capacity, such as food coating and thickener. They could also be largely applied in medicine that demands high M content. The algin of S. lomentarius, owning to its high G content and combination with Ca2+ and other metal cations to form compact structures, can be applied to the removal of toxic metal ions as well as calcium in foods. Algin with high G content could also be used as gelatinizers, additives in the food industry, textile and rubber industries. M/G ratios of different species of S. japonica were similar, and they declined over time and reached the minimum at maturity, which was caused by the transformation from M to G during the growth. Our study provided more information for both industrial production and scientific research.