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Abstract:Pacific saury (Cololabis saira) is an important high-seas fishery resource in the Northwest Pacific Ocean for the Chinese mainland. The species is widely distributed in the international waters of the Northwestern Pacific Ocean ranging from the subarctic to subtropical regions. With a long-distance and large-scale migratory route, sauries experience extremely complicated oceanographic and climatic conditions throughout their entire lifecycle. They are known to pass northwards through the Kuroshio- Oyashio Transition Zone (TZ) and then return southwards to the coastal waters of Japan in winter. The species is harvested primarily by the countries of Japan, Russia, South Korea, Taiwan Province, and mainland China. China began Pacific saury fishing in the high seas in 2003, and it has since become one of the most important fisheries for China. Owing to increasingly commercial, cultural, bioeconomic, and ecological values, saury has been listed among the priority species by North Pacific Fisheries Commission (NPFC). Catch per unit effort (CPUE) is an important relative index and dataset of fish abundance commonly used in fisheries stock assessment. Reliable and accurate CPUE plays a significant role in Pacific saury stock assessment. Many statistical models have been used in the previous CPUE standardization research. Here, we compare the performance of Generalized Linear Models (GLMs) and Generalized Additive Models (GAMs) using CPUE data collected from Chinese saury fisheries in the Northwest Pacific Ocean from 2003 to 2017 (excluding data from Taipei of China) and evaluate the influence of spatial, temporal, environmental variables, and vessel length on CPUE. Optimal GLM/GAM models were selected using the Bayesian information criterion (BIC). Explained deviance and five-fold bootstrap cross-validation results were used to compare the performance of the two model types. Fitted GLMs accounted for 52.47% of the total model-explained deviance, while GAMs accounted for 61.9%. Predictive performance metrics and five-fold cross-validation results showed that the best GAM performed better than the best GLM. Therefore, we recommend a GAM as the preferred model for standardizing CPUE of Pacific saury in the Northwest Pacific Ocean. The goal of this study was to identify the best method for standardizing Pacific saury CPUE data and improve the quality of future stock assessment for Pacific saury.

Abstract:The Bohai Sea, a landlocked body of water in China, provides spawning, feeding, and breeding habitats for many economically important species. The summer fishing moratorium in the Bohai Sea was implemented in 1995, and for more than two decades in place it has played an important role in alleviating the intensive fishing pressure on it as a fishery resource as well as in resource conservation. However, the evaluation of the implementation effect of a summer fishing moratorium system in the Bohai Sea has not yet to be reported. Based on the Chinese Fishery Statistics Yearbook and data from the fishery resource survey, we made a comparative analysis of the implementation effects of the summer fishing moratorium system on fishery resources in the Bohai Sea. The results showed that the capture and fishing efficiency in the Bohai Sea increased rapidly in the short term following the end of the summer fishing moratorium. This was especially true for economically important species such as Larimichthys polyactis and Scomberomorus niphonius, which harvests increased 3.96 times and 1.74 times, respectively, and their proportion of total capture yield increased significantly. After 1999, capture yield declined year to year and stabilized in 2008. According to the results of the fishery resources survey, signs of recovery have shown in recent years following the sharp decline of the fishery resources in the Bohai Sea from 1998 to 2014. The biomass of the economically important species increased during the period of 2014~2015, such as Engraulis japonicus, Pampus argenteus, and Portunus trituberculatus, but it was lower than the same period in 1992. During the period of fishing moratorium, the primary fishery species have time and space to grow and spawn. Giving the populations time to replenish has resulted in the total resources increasing more than three times since the beginning of the moratorium, and the average length and weight of fishery organisms has also increased significantly. However, the general trend of miniaturization and degradation of fishery resources has not improved for a long time. In order to ensure the implementation effect and improve the restoration of fishery resources, it is necessary to further enhance the summer fishing moratorium system.

Abstract:In order to assess the current diversity and status of shrimp resources in the coastal waters east of the Zhoushan Islands, data was collected and shrimp fishery resources were investigated from April and November 2018. We used the relative importance index, biodiversity index, and ABC stock curve to identify prawn class based on species composition, biodiversity, dominant species, the spatial distribution of species, and abundance/biomass. The results showed that a total of 32 shrimp species distributed across one order, ten families, and 21 genera, were captured and identified in coastal waters east of the Zhoushan Islands. In the spring, 22 shrimp species were observed, which belonged to nine families and 16 genera. Twenty-nine shrimp species were observed in the fall season, belonging to nine families and 20 genera. There were 19 shrimp species in common between the spring and fall. The number of shrimp species in fall was higher than that of spring, and the dominant species in fall included Parapenaeopsis hardwickii, and Solenocera crassicornis; however, no dominant species was found in spring. The mean value of the biodiversity index and richness index in fall were higher than those in spring, while the evenness index was lower in fall than in spring. The W value of the ABC curve was negative in the spring and positive in the fall. This indicates that the community structure in the spring was greatly disturbed, while that in the fall was less disturbed. In spring and fall, the end of the ABC curve overlapped, showing that the shrimp communities in the coastal waters east of the Zhoushan Islands were certainly polluted to some extent.

Abstract:To study the genetic diversity and genetic differentiation of a Ptychidio jordani population in the Xijiang River Basin, Guangxi Province, China, mitochondrial D-loop sequences from six rivers were subjected to polymer chain reaction and DNA sequencing analysis. The A+T base composition was much higher (65.7%) than the C+G combination (34.3%) in 139 individuals, which have a D-loop sequence length of 725 bp, and a transversion ratio R of 11.5. Twenty-five polymorphic sites were defined. An NJ system tree of haplotypes and network structure diagram revealed two distinct branches among 23 haplotypes but no obvious geographic clusters, because the haplotypes from different geographic groups were mixed in two branches. Individuals from six different geographic populations had superior genetic diversity (Hd=0.71585~0.92063, Pi=0.00173~0.00668) and extremely significant genetic differentiation (Fst=0.36737, P<0.001). Analysis of molecular variance indicated that most of the variation was intragroup (63.26%). The results of a neutrality test (Tajima’s D= –0.50322, P-value=0.34600; Fu’s Fs= –5.05210, P-value=0.08800) and nucleotide mismatch distribution showed that the population of P. jordani in the Xijiang River Basin had not experienced a population expansion in recent years. The genetic diversity of the P. jordani in the Xijiang River Basin exhibited high haplotype and low nucleotide diversity. Various degrees of genetic differentiation intergroups indicate that a dam barrier and fishing factors may be contributing to their occurrence, and a cascade development of water resources may be the primary cause of population genetic differentiation of P. jordani.

Abstract:The contents and storage patterns of soil organic carbon (SOC) and total nitrogen (TN), spatial distribution characteristics of SOC and TN, C/N ratios, and correlation between SOC and TN in Xiandao Park and Shajing (Guangxi) mangrove wetlands were assessed. The average SOC and TN contents of the Xiandao Park mangrove wetlands were 24.5 and 1.06 g/kg, respectively, and those of the Shajing mangrove wetlands were 11.9 and 0.71 g/kg, respectively. SOC storage capacities of the Xiandao Park and Shajing mangrove wetlands were 181.03 and 92.4 t/hm2, respectively, and were significantly different (P<0.05). TN storage capacities of Xiandao Park and Shajing mangrove wetlands were 8.23 and 5.12 t/hm2, respectively. The highest-to-lowest vertical distribution of SOC storage at both sites and TN storage at Xiandao Park was 20~40 cm > 40~60 cm > 0~20 cm, while TN storage at Shajing decreased with increasing soil depth. A significant correlation was observed between SOC and TN contents at Shajing (P<0.01); the correlation coefficient was 0.947. C/N ratio at both sites ranged from 16.77 to 24.39, indicating that the organic matter came primarily from the land. A significant correlation between soil C/N and SOC storage was evident at Xiandao Park (P<0.01), and a significant negative correlation between C/N and TN storage was evident at Shajing (P<0.05). The SOC storage of the Xiandao Park mangrove wetlands was higher than that of Chinese forests, indicating that mangrove soil has a higher carbon sequestration capacity.

Abstract:The Humboldt squid (Dosidicus gigas) is one of the most abundant fisheries resource in the Southeast Pacific Ocean. It has become an important component of China's offshore fisheries due to its high economic value. Accurate abundance index prediction is important to the rational development and utilization of D. gigas. In this study, the correlation analysis and grey system method were used to establish a model (GM) for predicting the abundance of squid in the southeastern Pacific based on fishery data as well as environmental and climatic factors, including Sea Surface Temperature (SST), Pacific Decadal Oscillation (PDO), Oceanic Nino Index (ONI), and Chlorophyll concentration a (Chl a). The results showed that the SST of the spawning ground in February, the Chl a of the spawning ground in March, the PDO in December, and the ONI in October had significant correlations with the abundance of squid. The GM (1, 4) model with SST, PDO, and ONI as independent variables had the highest accuracy (> 85%), which could be used to accurately predict the abundance of D. gigas in the Southeast Pacific.

Abstract:Neosalanx taihuensis is an icefish endemic to China and mainly distributed in the middle and lower reaches of the Yangtze and Huaihe rivers and affiliated lakes. In recent years, the natural resources of this species have declined markedly. To assess the genetic diversity and genetic structure of wild populations of N. taihuensis, we amplified and sequenced mitochondrial cyt b gene sequences from 144 individuals from four lakes [Tai Lake (TH), Gaoyou Lake (GY), Hongze Lake (HZ) and Luoma Lake (LM)] in Jiangsu Province. The results detected 29 polymorphic nucleotide sites and 25 haplotypes among the cyt b sequences of the 144 individuals. Haplotype diversity was 0.682±0.037, and nucleotide diversity was 0.00231±0.00021. The GY population showed the highest genetic diversity among the four populations and the TH population the lowest. Analysis of molecular variance showed that 71.53% of the molecular variation was among populations and 28.47% was within populations, with the molecular variation originating mainly from interpopulation differences. A pairwise fixation index (Fst) revealed significant differences between the LM population and the TH, GY, and HZ populations, and no significant differences among the TH, GY, and HZ populations. A phylogenetic tree and a minimum spanning network showed that the 25 haplotypes form two distinct geographical clades: one consisting of the TH, GY, and HZ populations, and the other consisting of the LM population. The results of a neutrality test showed that the values of Tajima’s D and Fu’s Fs were negative, and had significant differences. The mismatch distribution was unimodal, which indicated that the four N. taihuensis populations had experienced population expansion. As the genetic diversity of the N. taihuensis populations is low, measures to protect its wild resources are warranted. The TH, GY, and HZ populations should be protected and managed as a whole population and the LM population as a distinct population.

Abstract:The aim of this project was to investigate the characteristics of the microbiota structure and the activity of digestive and nonspecific immune enzymes in the gastrointestinal tract of large yellow croaker (Larimichthys crocea). We systematically analyzed the composition and distribution of microbiota in the stomach, pyloric caecum, and gut of large yellow croaker using high-throughput sequencing. Moreover, we conducted comparative analysis of the gastrointestinal tract microbiota in large yellow croakers cultured via the industrialized or net cage culture pattern. Under these two aquaculture patterns, we analyzed the activity of digestive and nonspecific immune enzymes in the gastrointestinal tract through biochemical methods. The microbiota diversity in the gastrointestinal tract declined under both aquaculture patterns. The genera including Lactobacillaceae(f), Fructobacillus and Flavobacterium, and etc, were the shared and dominant microbiota. The abundances of Bacteroides and Anaerostipes declined from the beginning of the gastrointestinal tract to the end, while those of Flavobacterium and genera represented by Lactobacillaceae (f) and the E01_9C_26_marine_group increased under both aquaculture patterns. Genera belonging to Prevotella_9 and Lactobacillaceae(f) were the main different species between these two aquaculture patterns. Under the industrialized pattern, the composition of microbiota and number of genes involved in metabolic pathways associated with nutrition and immunity were not significantly different between the pyloric caecum and gut (P>0.05), while these values obviously different from those in the stomach. In contrast, under net cage culture, differences between the stomach and pyloric caecum or gut decreased. The microbiota composition of the gastrointestinal tract of large yellow croakers cultured with these two patterns was similar to that of the feed. Additionally, the stomach and pyloric caecum exhibited nonspecific immune enzyme activities, indicating that the entire gastrointestinal tract functions as a chemical immune barrier. These results can serve as a basis for healthy large yellow croaker cultures and provide a theoretical foundation for studying the physiological functions of the gastrointestinal tract microbiota.

Abstract:Tuna is rich in nutrients and one of three major fish recommended by the International Nutrition Society. Large tuna such as Thunnus albacares, T. maccoyii, T. obesus, and T. thynnus are used as top-grade aquatic products, mainly in the form of sushi or other fresh fish products. Small tuna such as T. alalunga and Katsuwonus pelamis are mainly used in canned tuna and processed katsuobushi. The price of different species of tuna varies greatly, especially because selling tuna without the head or skin can lead to mislabeling and substandard products, which harms the interests of consumers and undermines market functions. This study was aimed at the identification T. albacares, T. maccoyii, T. obesus, T. thynnus, T. alalonga, and K. pelamis. Using tuna DNA as a template, three pairs of universal primers were used to amplify and sequence the DNA fragments of three genes (16S rRNA, Cyt b, and COⅠ) from six species of tuna. The sequencing results were manually corrected to remove the primer regions, which were compared with reference sequences in GenBank by BLAST analysis on the National Center for Biotechnology Information website. The COⅠ gene was analyzed by the Barcode of Life Data System (www.boldsystems.org). As a result, DNA sequences of 16S rRNA (576 bp), Cyt b (652 bp) and COⅠ (307 bp) were obtained from 63 samples of six species of tuna. Genetic diversity parameters such as Number of Haplotypes (h), Haplotype diversity (Hd), Average number of nucleoside difference (k), and Nucleotide diversity (π) were calculated by DnaSP 5.10 software. C-conserved sites, PI-parsimony-informative sites, and V-variable sites were calculated using Mega 7.0 software, which performed 1000 bootstrap tests with neighbor joining. The Kimura 2-parameter model was used to construct a phylogenetic evolutionary tree. The experimental results showed that 16S rRNA was relatively conservative and could not distinguish among the six tuna species. Cyt b and COⅠ could be used to identify the species. However, it is possible that COⅠ and Cyt b sequences can be used together as a DNA barcode for tuna research. A multi-gene DNA-barcode species-identification method that provides technical support for the identification of tuna and its fish products would be of great significance in promoting the accurate identification and healthy development of aquatic products.

Abstract:With the development of shrimp culture industry, bacterial diseases are becoming very serious. To explore the new methods of controlling bacterial diseases in shrimps through quorum quenching (QQ), potential probiotics with QQ activity from the culture system of Litopenaeus vannamei were screened and identified in the present study. The safety of QQ strains was evaluated and fermentation conditions were optimized. The Agrobacterium tumefaciens A136 liquid X-gal method was used to screen QQ strains. Two bacterial fermentation broths showed significant degradation of hexanoyl homoserine lactone (C6-HSL), while the degradation activities were both lost after boiling water bath treatment. The strains were subjected to 16S rDNA gene sequencing analysis, and BDZ5 and W1B were identified as Bacillus sp. and Cobetia sp., respectively. The safety evaluation results showed that strains BDZ5 and W1B were not hemolyzed and were not sensitive to most antibiotics. After injection of the two strains, the cumulative mortality of shrimp did not increase, and the serum immune and antioxidase enzyme activities in shrimp did not change significantly, indicating that the two strains are safe for shrimp. Single factor condition optimization results showed the optimal growth conditions of BDZ5 as follows: initial pH 7.0, salinity 20, and 0.0005% MnCl2 for 48 h culture time. Moreover, the optimal growth conditions of W1B were as follows: initial pH 6.0, salinity 40, and 0.05% CaCl2 for 48 h. Except for the culture time, the optimal C6-HSL degradation conditions of two strains were different from their growth conditions. Under the culture condition of initial pH 7.5, salinity 30, and 0.0005% MnCl2 for 48 h, the degradation rate of the signal molecule C6-HSL by the action of the two active bacteria reached the maximum. The results of the study can provide excellent strains for controlling bacterial diseases in shrimp based on QQ and provide reference materials for large-scale fermentation and subsequent application of the strains.

Abstract:The c-Jun N-terminal kinase (JNK) is a member of the mitogen-activated protein kinase superfamily, which plays an important role in cell proliferation, apoptosis, and immune stress. To further explore the immune defense mechanism of JNK in Portunus trituberculatus, the EST sequence of PtJNK was isolated from the transcriptome database of P. trituberculatus. In this study, the JNK gene of P. trituberculatus (PtJNK) was successfully cloned by RACE; measurements showed a cDNA length of 3240 bp and an open reading frame of 1380 bp. PtJNK consists of 459 amino acids, including a serine/threonine protein kinase (S-TKc) domain with a conserved Thr-Pro-Tyr (TPY) motif, which is a typical feature of the JNK gene family. The results of tissue expression and distribution show that the PtJNK gene is expressed in all tissues. Real-time PCR was used to detect the expression of PtJNK under different pathogenic stimuli. The results show that expression of the gene is significantly down-regulated after injection of Vibrio parahaemolyticus (P<0.05), while expression is significantly up-regulated when white spot syndrome virus is injected (P<0.05). To sum up, PtJNK gene is a widely expressed gene, and expression of the gene differs according to pathogen.

Abstract:To clarify the genetic diversity characteristics of domestic commercial brand seedlings of Litopenaeus vannamei, six domestic commercial brands of L. vannamei, namely, Huanghua R, Dongying M, Guangzhou P, Guangzhou Z, Hainan S, and Hainan Z, were collected from Hebei, Shandong, Guangdong, and Hainan Province. Their genetic diversity was detected using eight microsatellite markers. The results showed that the average allele number (Na), expected heterozygosity (He), observed heterozygosity (Ho), and polymorphic information content (PIC) were 4.5~9.5, 0.516~0.733, 0.346~0.550, and 0.472~0.700, respectively. The genetic diversity of the six brands ranged from high to low: Huanghua R > Guangzhou Z > Guangzhou P > Hainan Z >Dongying M > Hainan S, and 48 Hardy-Weinberg equilibrium tests were conducted on the 6 brands of L. vannamei using 8 microsatellite loci. It was observed that, 4.17% (2/48) showed significant deviation (0.01

Abstract:Six key parameters for the dynamic energy budget (DEB) model of the disk abalone (Haliotis discus hannai) were obtained through physiological experiments. The goal was to determine the influence of starvation on energy consumption and the influence of temperature on oxygen consumption. The value of four parameters, i.e., Volume-specific maintenance costs , Volume- specific costs for structure , Maximum storage density , and Energy content of reserve , was calculated through measuring energy consumption when oxygen consumption rate and dry flesh weight had ceased to decrease and remained steady during the starvation period. The value of Arrhenius temperature ( ) was determined by measuring oxygen consumption rate of abalone per unit dry weight under different mperature gradients. The value of shape coefficient (δm) was calculated with a regression equation based on length and body mass data. The results showed: After the starvation experiment, dry flesh weight and oxygen consumption rate decreased by 26.3% and 70%, respectively. Meanwhile, the oxygen consumption rate increased from 2.69 mg/(ind.∙h) to 0.8 mg/(ind.∙h), and remained constant. The dry flesh weight decreased from (5.21±0.89) g to (3.84±0.22) g. Calculated according to the standard formulas, the values of and were 20.18 J/(cm3∙d) and 8120 J/cm3, respectively. The content of organic matter before and after starvation was 80% and 58%, respectively. Through conversion of the organic content, the values of and were 2726 J/cm3 and 32583 J/g, respectively. For abalone of different sizes, temperature was proportional to the oxygen consumption rate at water temperatures of 5℃~20℃, and the temperature was inversely proportional to the oxygen consumption rate over 20℃. Before the turning point of 20℃, the ln value of the oxygen consumption rate was linearly correlated to the reciprocal of the thermodynamic temperature. The absolute value of the slope of the linear regression equation was the Arrhenius temperature value ( =7196 K) before the turning point (20℃). Through biological statistical analysis, there was a cubic function relationship between abalone shell length (L) and volume (V): V=0.0639L3.1621 (R²=0.9852). The slope was shown as the Shape coefficient value (δm=0.43), which was calculated by linear regression of volume of the cube root of the soft tissue and shell length. This study provides scientific data support for the construction of an individual-based model following the DEB theory for H. discus hannai.

Abstract:Hybridization between the ‘Bohai Red’ and Argopecten irradians concentricus was conducted. The hybrids exhibited heterosis in terms of survival rate, growth rate, and heat tolerance, demonstrating substantial potential to replace A. irradians concentricus. To ensure the efficient use of these hybrids, we need to understand the genetic structure of the hybrids and their parents. Microsatellites are widely used to assess the genetic diversity of aquaculture species and to construct a quantitative trait locus due to their characteristics such as abundant polymorphism, rich information, and high codominance and conservation. In this research, the genetic diversity of 90 individuals in 3 populations of A. irradians concentricus, ‘Bohai Red’, and their hybrids was analyzed using 8 pairs of microsatellite primers. A total of 67 alleles were amplified, and 4~14 alleles at each locus were generated, with a mean allele number of 8.5. Effective allele number, expected heterozygosity, and polymorphic content were the highest in ‘Bohai Red’ (2.3947, 0.504, and 0.462, respectively). The genetic differentiation index, gene flow, and fixed coefficient were 0.1398, 1.5387, and 0.3698, respectively. Between the hybrids and ‘Bohai Red’, the genetic distance was the smallest (0.1188) and the genetic similarity was the highest (0.888), suggesting their similar genetic structures. These findings provide a reference for the genetic analyses of ‘Bohai Red’ and A. irradians concentricus as well as for the breeding of new varieties.

Abstract:Ocean acidification is one of the major changes in marine ecosystem in this century. This has a negative effect on the fertilization, development, growth, and survival of marine mollusks. Presently, physiological effects of ocean acidification on some economic shellfish are not clear. To study the effects of ocean acidification on the physiological ecology of economic shellfish is of great significance for environmental science, ecology, and aquaculture. The feeding, respiratory metabolism, and energy budget of Scapharca broughtonii at different pH levels (pH 8.2~7.6) were studied in the laboratory. The results showed that the feeding and defecation rates of S. broughtonii were significantly (P<0.05) affected by pH, and there was a declining trend on the feeding and defecation rates with a decrease in pH value. The oxygen consumption rate was also significantly (P<0.05) affected by pH, showing an obvious downward trend with decreasing pH value. There was an initial decrease in ammonia excretion rate, which then increased with a decrease in pH value. O : N ratio at low pH value was lower than that of normal seawater, indicating that low pH value could inhibit the respiratory metabolism of S. broughtonii to some extent. The energy budget at different pH values indicated that energy ingestion, respiratory consumption, fecal energy loss, and energy absorbed in the growth process all decreased with a decrease in pH value. Interestingly, energy loss during excretion decreased first and then increased. According to energy budget equation, we found that pH had a significant effect on energy distribution of S. broughtonii (P<0.05). As the pH value decreases, the proportion of energy consumed during respiration and excretion increases, while the proportion involved in excrement and growth decreases. Under low pH conditions, S. broughtonii will make appropriate physiological adjustments to reduce the feeding rate and increase the metabolic rate, resulting in a decrease in energy, which leads to a decrease in energy deposition in the growth process. This study suggested that the feeding and metabolism of S. broughtonii decreased significantly under short-term acidification, which may be a synergistic effect of increased cell energy demand and nitrogen loss.

Abstract:In the 1990s, kelp (Laminaria japonica) aquaculture was over capacity in Sanggou Bay; however, the area used for kelp aquaculture has almost doubled since then. Consequently, the levels and proportion of nutrients has changed since the end of last century. In order to address this problem, we previously established standard long line culture to reduce kelp density. After two years, profit had increased significantly; however, the reasons why kelp growth improved in the standard long line culture area compared to the traditional area remained unknown. This study was carried out to elucidate the advantages of standard kelp long line culture in Sanggou Bay. There were two 40 hm2 experimental areas: a standard kelp long line culture area and a traditional long line culture area. The distance between the two areas was approximately 50 m. The growth and composition of kelp, light density, and current in both areas were measured throughout the experiment. The length, width, average thickness, wet weight, projected area, and specific growth rate of kelp were higher in the standard long line culture area than in the traditional long line culture area, with kelp weight significantly higher in the standard area. The carbon, nitrogen, and protein content of the kelp in the standard long line culture area was significantly higher than that in the traditional culture area, and the quality of the kelp product was greatly improved. During the later stages of cultivation, the ratio of the sum of the projection area of cultured kelp in the standard culture area to the corresponding cultured sea area was 6.33, while that of the traditional area was 9.15. The light density of the water layer beneath the kelp in the standard area was significantly higher than that in the traditional area, and the current speed was also higher in the standard area than in the traditional culture area. Our results showed that kelp overlap decreased in the standard area and that total light density was higher in the standard area than in the traditional area. Moreover, the increased current in the standard area carried more nutrients to the kelp. These may be the factors resulting in differences between the two methods of kelp culture.

Abstract:The effect of salinity and Na3VO4 on photosynthesis of Bangia fuscopurpurea and Bangia atropurpurea was investigated, respectively, to investigate the photosynthetic physiology of Bangia, using chorophyll Ⅱ fluorescence and photosynthetic oxygen evolution measurements. The main results were as follows: The conversion efficiency of primary light energy of PSⅡ (Fv/Fm) of B. fuscopurpurea declined rapidly in salinity conditions lower than natural seawater while that of B. atropurpurea declined in salinity higher than freshwater, and the decrease was positively related to the level of stress. The Fv/Fm of B. fuscopurpurea was significantly inhibited under salinity 0 and 8 after 3 days of hyposaline treatment. No significant difference was seen among the different hyposalinity-stressed groups of B. fuscopurpurea. The Fv/Fm of B. atropurpurea under hypersaline stress was significantly lower than that of the control from the first day, and recovered to control levels after 6 or 7 days of hypersaline treatment. Saline stress had significant effects on net photosynthetic rate (Pn) in both Bangia species. Respiratory oxygen consumption rate (Rd) decreased at the early stage and then rapidly recovered to the level of the control on the first day. After 1 day, Rd of the hyposalinity-stressed B. fuscopurpurea groups was significantly lower than the control. As the hypersalinity continued, Rd of the stressed B. atropurpurea increased and became significantly higher than the control. After 3 days, the Fv/Fm of B. fuscopurpurea decreased significantly under treatment with 200~500 μmol/L Na3VO4. The decrease of Fv/Fm in B. atropurpurea with Na3VO4 treatment was positively correlated with Na3VO4 concentration. In general, with an increase in Na3VO4 concentration, the salinity stress had significant inhibitory effect on the Fv/Fm and Pn of Bangia. Rd of both B. fuscopurpurea and B. atropurpurea increased with stress, an effect that was more obvious in B. atropurpurea. The present results reveal that both marine and freshwater Bangia respond quickly to saline stress. The enhancement of Rd and regulation of plasma membrane-H+-ATPase may play an important role in response to saline stress. Long-term saline stress had irreversible harmful effects on photosynthesis in Bangia.

Abstract:Heat shock protein 90 (Hsp90) plays important roles in correct protein folding, intracellular material transport, cell proliferation regulation, and gametogenesis. In this study, the full-length cDNA of Hsp90 (SnHsp90) of Sipunculus nudus was cloned using RACE technology. The results showed that SnHsp90 is 3110 bp in length, including a 3´ UTR of 582 bp and a 5´ UTR of 72 bp. The open reading frame is 2456 bp in length and it encodes 818 amino acids. Sequence analysis showed that SnHsp90 has a signal peptide, with three tag sequences FLREL, IGQFGVGFYS, and LPLNVSRE and a conserved module, GxGxG, of type B Hsp90, thereby indicating that SnHsp90 belongs to the Hsp90B subgroup. Compared with other species, SnHsp90 showed the highest similarity (77.72%) with the Hsp90 of duck-billed bean sprouts. Three-dimensional structural modeling showed that the spatial conformation of Hsp90 among different species is highly conserved. Phylogenetic tree analysis showed that SnHsp90 was clustered into one branch of Hsp90 of annelids such as Capitella teleta and Helobdella robusta. The Hsp90 of all invertebrates was clustered into one branch, whereas that of the vertebrates was clustered into another branch, thus suggesting that SnHsp90 is closely related to the Hsp90 of Capitella teleta. RT-PCR results showed that SnHsp90 was expressed in different tissues of S. nudus, such as those of the body wall, muscles, and kidney tubes. SnHsp90 can also be expressed at different developmental stages of oocytes, and it is significantly expressed in Egg2 (oocyte in early stage of vigorous yolk synthesis) and Egg6 (excretive oocyte) (P<0.05). This result suggests the involvement of SnHsp90 in correct protein folding, yolk synthesis, and environmental stress resistance of S. nudus. The above results provide a basis for further exploration of the developmental mechanism of Sipunculus nudus oocytes.

Abstract:The phenotypic characteristics of Vibrio anguillarum are related to the pathogenicity of the bacteria, such as swimming motion, ability of membrane formation, and extracellular protease production. To identify the genes affecting phenotypic changes in V. anguillarum, this study used transposon mini-Tn10 (pLOF/Kana) to construct a library of V. anguillarum M3 mutant strains and to screen the strains and related genes that affect phenotypic changes. It is proved that there is a certain correlation between mutants causing these phenotypic changes and the virulence. Mutations of 1152 strains of M3 mutant library were screened, and mutant strains with significant changes in swimming ability (strain 6G_1), casein enzyme activity (strains 5A_11, 7B_12, and 7E_12), gelatin enzyme activity (strain 7H_1), and biofilm formation ability (strains 5E_2, 6A_2, and 6E_12) were noted. Further analysis revealed that a phosphodiesterase-related gene mutation caused increased swimming capacity (P<0.05), leuD, rseB, and thiQ mutations caused a significant decrease in caseinase activity (P<0.05), and potD mutations caused a significant decrease in gelatinase activity (P<0.05). Moreover, mutations in leuO, ilvH and grpB resulted in a significant decrease in the ability to form bacterial membranes (P<0.05). Moreover, we observed a virulent infection in these mutant strains, which showed that LD50 of wild type M3 was 2.04 times higher than that of 6G_1 and the virulence was relatively increased. Additionally, 5A_11, 7B_12, and 7E_12 LD50 were 2.96 times, 3.25 times, and 3.36 times higher than that of wild-type M3, respectively. The LD50 with the strain 7H_1 was 1.25 times higher than that of wild M3, and the LD50 with the strains 5E_2, 6A_2, and 6E_12 were 3.34, 4.08, and 1.84 times higher than that of wild M3, respectively. These results lay a foundation for further study on the pathogenic mechanism of V. anguillarum.

Abstract:The fish's testis, commonly known as fish white, is often discarded as waste owing to its specific odor and is one of the by-products of fish processing. A basic protein, protamine, can be extracted from the testis of fish. Protamine has the advantages of high safety, good antibacterial performance, and high thermal stability. It can be used as an antibacterial ingredient in some foods in the field of food preservation. It has obvious antibacterial activity under alkaline conditions and is a promising antibacterial agent. Here, the testis of Takifugu obscurus was used as the raw material, and the protamine was extracted by acid extraction. The extraction coefficient was used to determine the optimal extraction parameters. According to the results of orthogonal test, the importance factors of the extraction of protamine are as follows: extraction times > sulfuric acid dosage > sulfuric acid concentration>95% ethanol; optimal extraction conditions are: sulfuric acid concentration 0.2 mol/L, sulfuric acid dosage is 2.5 times, the number of extractions was 2, and the amount of 95% ethanol was 2.5 times. Under this condition, the extraction rate of protamine from T. obscurus was 3.82%, and the protein content was 89.01%. According to the tricine-SDS-PAGE, the extracted crude protamine has two bands with molecular weights of 25 kDa and 20 kDa, respectively. Analysis of its lytic acid composition found that arginine and alanine content were relatively higher, accounting for 31.40% and 17.39%, respectively. This study is of great significance for the efficient use of testes of puffer-fish (dark-spotted oriental carp), and also lays a theoretical foundation for the application of stag beetle (dark-spotted oriental carp) protamine in the food and pharmaceutical fields.

Abstract:To analyze and conduct a scientific evaluation of nutritional value of Datnioides pulcher, the common nutrient components, amino acid composition, and acid composition in muscle of D. pulcher were determined on the basis of conventional nutritional components analysis. Then comparison was made between the fish and some economic fishes from the same family and other freshwater fishes with common quality. The results showed that the content of moisture, crude protein, crude fat, and crude ash in the fresh muscle of D. pulcher was 65.6%, 19.6%, 7.6%, and 1.3%, respectively. Sixteen kinds of amino acids of D. pulcher were found in dry muscle, of which seven were essential amino acids (EAA). In dry muscle, the total amino acid (TAA) content was 18.72%, the content was 6.81%, and the ratio of EAA to TAA was 36.09%. The essential amino acid index (EAAI) was 79.46%, which met the high-quality protein standard established by the Food and Agriculture Organization and Word Health Organization (FAO/WHO). According to the amino acids score (AAS) and chemical score (CS), the first and second limiting amino acids were Val and Met, respectively, and the EAAI of D. pulcher was 79.46. The flavor amino acid (FAA) content was 42.15%. There were 16 kinds of unsaturated fatty acids (UFA), which accounted for 68.41% of muscle, among which oleic acid and linoleic acid, with richness in docosahexaenoic acid (DHA) and docosapentaenoic acid (DPA), were 23.99% and 10.56%, respectively; meanwhile, DHA and DPA (relatively lacking in fish oil) contents were 8.5% and 5.1%, respectively. Results of the comprehensive analysis showed that the contents of amino acids and UFA in muscle of D. pulcher are higher, and the composition of amino acids is reasonable. Thus, D. pulcher is a high-quality fish with high ornamental value as well as edible value, and offers good prospects for exploitation and utilization.

Abstract:With the development of fishery technology and people's improving living standards, the demand for aquatic organisms has gradually increased. Whether in terms of economic value, ornamental value and educational significance, aquatic organisms have gradually become an indispensable part of our lives. However, aquatic organisms especially fish still have a low level of welfare in the process of the breeding, transportation and display. Finding a suitable method to solve the problems of low welfare of aquatic organism has become an important issue for improving aquatic organism welfare. As one of the technical means to improve the welfare of captive animals, environmental enrichment can increase the living conditions and welfare of captive animals by adding some stimulating factors to the captive environment, so as to make the captive animals have normal psychological and physiological health and show their natural behaviors. At present, compared with foreign countries, domestic researches on environment enrichment of aquatic organisms is still in its infancy. Using environmental enrichment technology to improve the living conditions, ensure and enhance the level of welfare of aquatic organisms has become a research hotspot. Therefore, based on the review of the research progress and application of environmental enrichment technology in aquatic organisms at home and abroad, this paper divided the environmental enrichment technology of the aquatic organisms into four categories, discussed the existing problems of environmental enrichment technology and put forward some suggestions, in order to provide more scheme reference and theoretical basis for environmental enrichment technology of aquatic organisms.

Abstract:In this review, we have provided an overview of the current knowledge on the different molecular mechanisms of sex differentiation in major economic bivalves. The representative species of bivalves were introduced to understand the different mechanisms of sex differentiation or sex determination. The review provides a brief summary of the recent discoveries on sex differentiation in oysters, scallops, pearl oysters, and other common economically important bivalve species. The review highlights the various sex differentiation-associated molecular mechanisms by focusing on the involvement of nucleic acids, proteins, hormones, and so on. The current research trends on sex differentiation in bivalves have been discussed, which may help to advance our understanding of the sex differentiation and gonadal development of the Yesso scallop and other bivalves.