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Abstract:Catch Per Unit Effort (CPUE) was commonly used to assess fishery resource abundance. The assessment results can be narrow when using a single special fishing type to assess the whole sea resource density due to complexity and specificity of species. In this study, kg/(kW·d) was used as the standardized unit of CPUE to analyze and compare the catch rates of different fishing types in the South China Sea. Data were collected by the investigations of fishing vessels in 14 major fishing ports of the 3 provinces and autonomous regions of Guangdong, Guangxi and Hainan in 2016. Total of 5256 voyages, 892,109 kW of the fishing vesseles were sampled and investigated. The results showed that nine fishing types’ catching rate (CPUE) were ranked as seine > pair trawl > gillnet > falling-net > stow net > otter trawl > shrimp trawl > pot > fishing tackle. The changing trend of different fishing types’ CPUE were different with the power level of main engine. And the number of CPUE peaks and their corresponding optimal range (the highest rate of capture of the power range) were not the same, specific performances: Variation of CPUE of otter trawl and shrimp trawl showed one peak with the trend of rising first and declining later, corresponding optimal ranges of (200~250) kW (CPUE=8.6 kg∙kW1∙d1) and (150~ 200) kW (CPUE=5.0 kg∙kW1∙d1) for otter trawl and shrimp trawl respectively. Two peaks of variation were showed on CPUE of seine, pair trawl trawler, fishing tackle and gillnet, with the trend of first to decline then rise and last decline, corresponding optimal range: (200~250) kW (CPUE=47.7 kg∙kW1∙d1) for seine, (350~400) kW (CPUE=16.8 kg∙kW1∙d1) for pair trawl, (50~100) (CPUE=2.9 kg∙kW1∙d1) for fishing tackle, (0~50) kW (CPUE=6.9 kg∙kW1∙d1) for gillnet. Three peaks of variation were shown on CPUE of falling-net, corresponding optimal range was (0~50) kW (CPUE=7.0 kg∙kW1∙d1). Seasonal variation of CPUE of different fishing types performed as the mean CPUE of seine was the highest in spring, CPUE of otter trawl, pair trawl, falling-net, fishing tackle and pot were highest in summer, CPUE of stow net were highest in autumn, CPUE of gillnet and shrimp trawl were highest in the winter.

Abstract:Knowledge about the differences or variations in the fish community is important to assess and predict the effects of habitat loss or environment degradation on the river ecosystems. The Bortala River is an important interior river in Xinjiang, China. Although research regarding spring and summer fish communities has been reported, that regarding winter fish communities is lacking. Based on fishery resource surveys in November 2016 at the mainstream of the Bortala River, the fish community structure and diversity of the river were analyzed. The results indicated that a total of 1515 fishes were collected at 4 representative sections, which belonged to 3 orders, 4 families, 14 genera, and 15 species. The dominant species (IRI1000) in the mainstream of the Bortala River were Pseudorasbora parva, Abbottina rivularis, and Triplophysa strauchii. A group-averaged hierarchical cluster based on the Bray-Curtis similarity index identified two spatial patterns of the fish assemblage at the 60% similarity level and four patterns of species composition at the 50% similarity level. The canonical correspondence analysis (CCA) suggested that altitude, temperature, and dissolved oxygen were the major environmental factors affecting the spatial patterns of fish assemblages in winter. The results of this study indicated that the species of native fish have declined, and the species of fish with low economic value have increased significantly. The aquatic ecosystem will be destroyed unless effective measures are taken to protect the native fish. Further studies are needed to investigate the mechanisms by which these factors operate together upon the fish assembles in the Bortala River in winter.

Abstract:The effect of seawater acidification on the energy budget of the mussel Mytilus galloprovincialis was studied using a combined in situ mesocosm and flow-through chambers approach in Sanggou Bay from May to June, 2016. The experimental groups of mussels were acclimated to different experimental pH values obtained by elevating seawater CO2 concentrations. Clearance rates, absorption efficiency, respiration rates, ammonia excretion rates, and O/N ratios of M. galloprovincialis were measured after 10 and 30 days of treatment. The results showed that the clearance rates, O/N ratios, and absorption efficiency of M. galloprovincialis were reduced significantly after 10 days of exposure to acidified seawater (pH 7.7) (P<0.05), whereas the rates of ammonia excretion were increased significantly (P<0.01). The respiration rates in acidified and ambient seawater did not show significant difference (P>0.05). However, after 30 days of exposure to acidified seawater, significantly increased absorption efficiency, respiration rates, and ammonia excretion rates (P<0.05), and significantly reduced clearance rates and O/N ratios were observed (P<0.05). Energy budget analysis showed that a 10-day exposure to acidified seawater resulted in significantly reduced ingestion energy, absorbed energy, and scope for growth (P<0.05), but a significant increase in excreted energy (P<0.05), whereas a 30-day exposure to acidified seawater resulted in significant reduction in ingestion energy (P<0.05), but a significant increment in absorbed energy, respiration energy, excreted energy, and scope for growth (P<0.05). The average values of O/N ratios ranged from 14.28 to 20.46 in all the experiments, suggesting that the energy source changed gradually from fats and carbohydrates to proteins under low pH conditions. These data provide theoretical insights into the possible mechanisms underlying the impact of seawater acidification on the physiological responses of mussels.

Abstract:Saccharina japonica is a major economically important brown macroalgae. It is an important primary producer in the marine ecosystem and is also cultured under long-line in coastal northern China. The aim of this work was to develop an individual growth model capable of simulating the growth of the large-scale raft-cultured kelp in the north of China. The model can provide data support, to some extent, to northern kelp farming. The key processes for kelp growth and its relationship with environmental parameters were analyzed, using the Sanggou Bay aquaculture zone as the study area. We used the visualization model software STELLA, which simulated and predicted the growth of the length and dry weight of kelp. The individual growth model basic framework was Ngrowth = Ggrowth–resp–Ekelp, where, net growth was defined as gross growth minus respiration and erosion consumption. The gross growth of kelp was defined as a function of light, temperature, salinity, and internal nutrient (N and P) content in kelp, whereas the light parameters were obtained from the Sanggou Bay meteorological records, and salinity, temperature, and nutrient (N and P) measurements were observed at the site in Sanggou Bay. According to the model simulated results, model predictions are well within the observed results. The individual growth model simulated the length results and measured values of the kelp, with the fitting degree R2 in the high, medium, and low zones as 0.936, whereas dry weight simulated results and measured values of the kelp had fitting degree R2 in the high, medium, and low zones as 0.963. According to the results, the model can accurately reflect the true growth process of kelp. A reliable individual growth model is the basis for the assessment of aquaculture carrying capacity. In addition, the individual growth model may provide a scientific foundation for aquaculture spatial planning and management.

Abstract:At present, domestic research on anaerobic denitrification is mostly at the laboratory stage. In order to develop highly efficient and suitable denitrification equipment for production, this study uses a self-designed anaerobic reactor with clinoptilolite as the filler, and naturally cultivated biofilm. By connecting the reactor to the primary biofilter of RAS, we aim to preliminarily investigate the reactor’s nitrogen removal effect under different hydraulic retention times (HRT), with a view to direct subsequent research. The results show that during the experiment, the reactor has a good removal effect on inorganic nitrogen (IN) and total nitrogen (TN). When the HRT is short (HRT<7.43 h), ammonium (NH4+-N) is the main form of nitrogen removed from the reactor, whereas with longer HRT (HRT≥7.43 h), nitrogen is removed as nitrate (NO3–-N). When the HRT is 17.52 h, the reactor’s nitrogen removal efficiency is the best, and the removal rate of NO3–-N reaches 77.48%. As HRT continues to extend, the nitrogen removal efficiency decreases. The better the nitrogen removal effect, the greater the accumulation of nitrite (NO2–) and ammonium, with the former accumulating first. Thus, this study can provide reference for the development of anaerobic denitrification equipment.

Abstract:With the development of marine resources in coastal areas, marine engineering affects the growth and development of marine animals. Acute toxicity of suspended solids with different concentrations on Fenneropenaeus chinensis larvae was evaluated by the semi-static method. The results showed that high concentrations of suspended solids inhibited the swimming ability of Fenneropenaeus chinensis larvae. The 48 h-LC50 and 96 h-LC50 values of suspended solids to suspension was 452.21 mg/L and 183.7 mg/L, respectively, and the safe concentration was 18.37 mg/L. The microscopic examination showed that the Fenneropenaeus chinensis larvae body surface sediment had a large quantity of suspended particulate matter in the gills. This study provides a theoretical foundation for an understanding of the toxic effects of suspended solids on marine animals.

Abstract:The Japanese flounder (Paralichthys olivaceus) is one of the most important marine culture species in China. However, the outbreak of diseases has seriously affected the industrial culture of this particular fish. Among these diseases, the one caused by the lymphocystis disease virus has been spreading widely and has resulted in severe economic losses every year. In order to select new varieties of Japanese flounder that are resistant to lymphocystis disease in China, and to elucidate the mechanism of disease resistance at the molecular level, we used a high-throughput sequencing technique to analyze the transcriptome of kidney tissues of the Japanese flounder, and screened out a number of functional genes closely related to resistance, including efhd2 and tbc1d25. In this study, we cloned the full-length cDNA sequences of efhd2 and tbc1d25 by using RACE (rapid-amplification of cDNA ends). The efhd2 gene was 5231 bp in length, of which the length of the 5' untranslated region (5' UTR) was 142 bp and the length of the 3' UTR was 4390 bp. The open reading frame (ORF) was 699 bp in length, and encoded 232 amino acids with a molecular weight of 26.4 kDa and an isoelectric point of about 5.08. The full length of the tbc1d25 gene was 3173 bp, of which the 5' UTR length was 108 bp, and the 3' UTR length was 464 bp. The ORF was 2601 bp in length and encoded 866 amino acids with a molecular weight of 96.4 kDa and an isoelectric point of about 5.47. Multiple sequence alignment revealed that the amino acid sequences of EFHD2 have 83%, 88%, 73%, and 72% homology with Danio rerio, Oryzias latipes, Mus musculus, and Homo sapiens respectively; and those of TBC1D25 have 71%, 74%, 72% and 74% homology with these four species, respectively. The expression profiles of efhd2 and tbc1d25 were analyzed by quantitative real-time PCR (qRT-PCR). Both efhd2 and tbc1d25 were expressed at the fertilized egg, 4-cell, 32-cell, 128-cell, high blastocyst, low blastocyst, early gastrula, late gastrula, sarcomere, heartbeat, and hatched larva stages. The expression level of efhd2 in the 4-cell, low blastocyst and early gastrula stage was lower than that in other stages (P<0.05); the expression level of efhd2 began to increase from the sarcomere stage and reached the highest level at the hatched larva stage, and was significantly higher than that in other groups (P<0.05). The expression level of the tbc1d25 gene in the fertilized egg was significantly higher than that in other stages (P<0.05); during development, the expression level of tbc1d25 decreased to the lowest level in late gastrula (P<0.05); there was no significant difference in the expression level of tbc1d25 in late gastrula, sarcomere, and heartbeat stages (P<0.05). In the lymphocystis disease-resistant and -sensitive individuals, the expression of efhd2 and tbc1d25 was detected in head, kidneys, liver, blood, gills, heart, gonads, muscle, intestine and spleen. The expression of efhd2 and tbc1d25 was significantly higher in the blood of lymphocystis disease-resistant individuals than in the lymphocystis disease-sensitive individuals. This study provides a basis for further studying the gene function of efhd2 and tbc1d25, as well as the mechanism of disease resistance of the Japanese flounder to lymphocystis disease.

Abstract:To elaborate the mechanism of corticotropin-releasing hormone (crh) on feeding in gibel carp (Carassius auratus gibelio), we cloned and identified the full-length cDNA sequence of crh for the first time. We also employed real-time quantitative PCR (RT-PCR) to explored crh mRNAon distribution in different tissues and investigated the expression of crh mRNA during postprandial and fasting. Here, a 920 bp full-length of crh gene cDNA was obtained, including a 53 bp of 5-UTR, a 378 bp of 3-UTR, and a 489 bp of an open reading frame (ORF). The ORF of the gibel carp crh gene contains 162 bp nucleotides, including an 11-amino acid conserved region, a 24-amino acid signal peptide, and a 41-amino acid mature peptide. The amino acid sequence of crh shares a high level of similarity with teleost CRH (99% with Carassius auratus and 96% with Cyprinus carpio). The expression of gibel carp crh was observed in almost all tissues, with the highest expression detected in the hypothalamus, followed by the myelencephalon and heart. There was no significant change in crh gene expression in the fed group compared with the fasted group in gibel carp hypothalamus after a meal (P>0.05). However, the expression level of the crh gene showed a significant decrease after fasting on day 5 and day 7 (P<0.01), a significant increase of the crh gene was observed after refeeding on day 9 and day 11. The results suggest that the crh gene may play a critical role in feeding regulation in gibel carp.

Abstract:This work aimed to investigate the histological structure and mucous cell distributing features in the digestive system of Bahaba flavolabiata. Conventional paraffin sections were used, with H&E and AB-PAS (Alcian blue and periodic acid Schiff reagent (AB, pH 2.5)) staining. The esophagus was crude and short, and the Bu-type stomach was divided into three portions: the cardiac stomach, fundic stomach, and pyloric stomach. There were eight pyloric caeca, and the intestine had two inflections in the body cavity. The histological analysis revealed that the digestive tract wall was composed of serosa, muscularis, submucosa, and mucosa, from the outer wall inwards. The muscularis of the esophagus was thick, but the mucosa was thin, and the epithelium did not have mucous. Muscularis and mucosa of the stomach were thick and composed of simple columnar epithelium, with a gastric gland found in the lamina propria. The pyloric caeca were characterized as having large cavity diameters, and numerous mucosa folds, with very thin muscularis layers. The muscularis in the intestine was thicker than that in the pyloric caeca, with numerous mucosa folds. Here, mucous cells were found in the epithelium. AB-PAS staining revealed that only type Ⅰ and type Ⅱ mucous cells were present in the entire digestive tract of B. flavolabiata, except in the esophagus. Numerous type Ⅰ mucous cells were found in the gastric gland and epithelium of the stomach. Only type Ⅱ mucous cells were found distributed in the epithelium of pyloric caeca mucosa. A large number of type Ⅱ and a smaller number of type Ⅰ mucous cells were found in the intestine. The former were distributed mostly on the surface of the epithelium and the latter in the basal layer of the epithelium. Characteristics of the histological structure and mucous cell distribution in digestive systems are in accordance with the habits and predacity of B. flavolabiata.

Abstract:Astronotus ocellatus is a tropical, benthic freshwater fish that originated in South America and is a great favorite for a vast number of aquariums. With the development and extension of the “Belt and Road Initiative” Economic Zone, as an inland area of Xinjiang, the development of ornamental fish is particularly fast, but the rapid development is accompanied by a series of disease problems, such as common parasitic diseases, which are a common factor restricting the development of fisheries. The aim was to investigate the XinJiang common ornamental fish parasite epidemic and classification situation. This study combines the traditional morphological identification methods of parasites with modern molecular biology methods, researching the parasitic monogenean species of A. ocellatus, at the gill site. The subjects were common A. ocellatus selected from the Urumqi Ornamental fish market. From 2016 May to 2017 June, 18 fish samples were collected. The results of the experimental analysis showed that parasites on the gills of A. ocellatus were Gussevia asota, belonging to Dactylogyridae, Ancyrocephalinae, Gussevia. The morphological parameters of the parasite were measured and compared with all the morphological data previously reported on the parasite It was found that there were certain differences between the data measured by different countries. By data retrieval, there is no sequence information of Gussevia Asota molecules in the GenBank database. Therefore, the G. asota 28S rDNA gene sequence was determined and submitted, obtaining GenBank sequence number: MG596661. Phylogenetic tree species from different genera of Ancyrocephalinae were analyzed. Phylogenetic analysis indicated that G. asota was at the top of the phylogenetic tree, with Ligophorus having the closest relationship, and together forming a sister group. And then get together with the parasites of the Cichlidogyrus, as a large branch, the kinship with Ancyrocephalus and Cleidodiscus is the furthest.

Abstract:The distribution frequency and characteristic of base repeats of EST-SSR (expressed sequence tag - simple sequence repeats) were induced and analyzed in 21 kinds of decapod crustaceans by applying bioinformatics methods. The results showed that EST-SSR abundances were different between various crustacean species. Exopalaemon carinicauda had the most abundant EST-SSR (868.02/Mb), whereas Scylla paramamosain had the least (286.48/Mb) in pleocyemata. Penaeus monodon had the most abundant EST-SSR (641.19/Mb), whereas Litopenaeus setiferus had the least (166.96/Mb) in dendrobranchiata. The abundance of EST-SSR with di-, tri-, and tetra-nucleotide motifs was more than that of those with penta- and hex- nucleotide motifs, which accounts for 41.11% in pleocyemata and 28.00% in dendrobranchiata. EST-SSR of compound (Ⅰ) type occupied a large proportion in the pleocyemata (51.38%) and dendrobranchiata (65.13%). The frequency of the AC/GT repeat motif distribution was highest in dinucleotides, and ACC/GGT and AAT/ATT repeat motifs were the most abundant in the trinucleotide repeats in the pleocyemata. The frequency of AG/CT repeat motif distribution was highest in dinucleotides, and the distribution frequency of AAT/ATT motifs was significantly higher than other motifs of dinucleotide repeats in the dendrobranchiata. A total of 12,155 sequences containing SSRs were predicted; moreover, Gene Ontology (GO) Classification with the blast2go application was performed based on sequences containing SSRs of Exopalaemon carinicauda. The results demonstrated that ‘cellular process’ comprised the largest proportion in the biological process category, whereas ‘binding’ comprised the largest proportion in the molecular function category. Additionally, the cellular component category showed that many sequences likely possessed ‘cell parts’ and ‘cell’ by GO annotation. This study compared the characteristics of EST-SSR in different species of crustaceans and the diverse regions of the species genome. The consequences deepened our understanding of the distribution of SSRs and provided a reference for the development and practical applications of EST-SSR markers. The results also provided powerful information for future conservation and breeding research.

Abstract:“Helong grouper” is the hybrid progeny produced by female longtooth grouper (Epinephelus bruneus) and male giant grouper (E. lanceolatus). As a new breed of hybrid grouper, there is no report on the diseases of the Helong grouper, at home or abroad. In July 2017, the Helong grouper on a fish farm in Shandong Province suddenly died, and the cumulative mortality was as high as 80% within 10 d. A field survey found that the water temperature was 28℃ and the salinity was 31 during epidemics. The appearance of diseased fish was normal. However, they were unresponsive, and died at the bottom of the tank. Clinical examination and necropsies revealed that the spleen and kidney of diseased fish were severely swollen and crispy. Histopathology studies indicated that tissues of diseased fish were severely damaged. A large number of basophilic, homogeneous cytoplasmic, swollen cells, with a diameter of 10~15 μm were observed in these tissues. In ultra-thin tissue sections of the spleen and head kidney, there are a large number of iridovirus-like particles, with a diameter of 130~150 nm in the cytoplasm of the swollen cells. Using specific PCR primers, severe infections of red sea bream iridovirus (RSIV) were detected in the spleen, head kidney, kidney, and liver tissues of diseased fish, which was consistent with electron microscopy observations. The complete coding sequence (CDS) of the major capsid protein (MCP) gene of the virus was 1362 bp in length. Based on the CDS of the MCP gene, a phylogenetic tree of 19 species (isolates) of the iridovirus was constructed. The tree showed that the iridovirus infecting the Helong grouper belongs to the RSIV cluster of the genus Megalocytivirus, family Iridovirus. This article describes for the first time the histopathological features of the iridoviral disease of the Helong grouper and confirmed that RSIV can naturally infect the hybrid grouper. This study not only revealed that the Helong grouper is a new susceptible host of RSIV, but also provided an important reference for the diagnosis and control of hybrid grouper viral disease.

Abstract:Bacillus subtilis, B. licheniformis, and B. pumilus, were isolated from healthy Litopenaeus vannamei, and were added to the base feed surface in single and mixed treatments. Probiotic feed was fed to the shrimp daily, and the shrimp were infected by white spot syndrome virus (WSSV) three weeks later. During the virus infection, the cumulative mortality and the number of WSSV copies in the gill tissue were statistically analyzed for each group. The relative expression of cysteinyl aspartate specific proteinase gene (Caspase) and Thioredoxin gene (Trx) in the intestinal tissue of the shrimp was measured by real-time PCR during feeding of probiotic feed and virus infection. The results showed that the cumulative mortality of B. subtilis (Group A), B. licheniformis (Group B), B. pumilus (Group C) and B. subtilis+B. licheniformis+B. pumilus (Group D), were (73.3±7.0)%, (63.3±5.5)%, (75.0±7.9)% and (50.0±5.3)% respectively, significantly lower than that of the control group (Group PBS), where the cumulative mortality of shrimp was 100%. The number of WSSV copies in each experimental group firstly increased, and then declined in the whole infection stage, but the number of WSSV copies of Bacillus groups was significantly higher than that of the control group every time (P<0.05 or P<0.01). The number of WSSV copies in the gill tissue of the mixed Bacillus group was extremely significantly lower than that of the control group, in the 8 d after virus infection. The relative expression of the Caspase gene was not significant in the 21 d of feeding with probiotic feed. After WSSV infection, the relative expression of Caspase in the intestinal tissue of each group firstly increased and then decreased, with time, reaching the maximum at the 18th h. The relative expression of Caspase in the intestinal tissue of the mixed Bacillus group was the highest, with the expression level at the 96th h still significantly higher than that of the control group. Feeding with Bacillus spp. and infection of WSSV, both could stimulate expression of the Trx gene, and the stimulation of feeding with Bacillus spp. was relatively gentle. After WSSV infection, relative expression of the Trx gene in the intestinal tissue of each Bacillus group grew quickly to its maximum at the 18th h, which was extremely significantly higher than that of the control group, and the activation on Trx gene expression from the mixed Bacillus group was the strongest. It can be surmised that the enhancement of the anti WSSV infection ability of shrimp may be related to the reduction of the speed of virus amplification in the target tissue, and the increase of the expression level of the anti-infection genes, such as Caspase and Trx, that were brought by feeding Bacillus spp.

Abstract:Two populations of Litopenaeus vannamei from Haiyang and Weifang in Shandong Province were sampled. TaqMan qPCR was used to measure Enterocytozoon hepatopenaei (EHP) in the shrimp hepatopancreas one by one, and then the extracted DNA samples were pooled by 5-pool (5∶1), 25-pool (25∶1), 50-pool (50∶1), 100-pool (100∶1), and 150-pool (150∶1) to test the EHP in the pooled samples. The amplification used a special threshold cycle value (Ct) of samples lower/higher than an assumed critical cycle value (Ca), differentiated as an analyzed positive/negative ratio in the single sample test and pooled sample test. The relationship between different pooling modes and the analyzed positive rate, diagnostic sensitivity, diagnostic specificity, and quantitative accuracy were compared. The results showed that the detection for high pooling rate samples could be reduced in very low analytic sensitivity. When the positive rate of individuals in the pooled samples was above 30%, the detection results of the high pooling rate were consistent with that of the single sample detection. If the positive rate of individuals with heavy infections in the pooled sample were not less than 6.7%, satisfying results could be obtained in the sample with a pooling rate below 50∶1; while the positive rate of individuals with light infections in the pooled sample were not less than 16%, the satisfying result could be obtained in the sample with a pooling rate below 25∶1. The pooled samples with a positive rate below 1.3% of individuals with heavy infection, or a positive rate below 8% of individuals with light infection, might lead to false negative results in all pooling rates. All of the pooling modes have good diagnostic specificity. The sample with a 50∶1 pooling rate had a similar diagnostic sensitivity to the sample with a 5∶1 pooling rate, which is the highest pooling rate recommended by the OIE standard. It had a very significant correlation between the mean of the detected EHP load of pooled sample, and the mean of the known EHP load calculated according to the single sample, with a ratio of 0.27~2.83. The quantitative test results of the pooled samples could roughly reflect the average EHP load of the single sample at the order of magnitude. This study provides a reference for sample detection in aquatic animal disease diagnosis, and epidemiological investigations.

Abstract:Three viable counting methods, including MTT assay, ATP bioluminescence assay, and high-throughput growth curve assay, for live Vibrio parahaemolyticus were compared in a high-throughput manner on a 96-well culture plate. The standard curves and linear ranges of these three methods were determined. The results showed that the directly detected index of MTT assay is OD555 nm, which is the absorption at 555 nm of DMSO-dissolved formazan produced from MTT. The liner standard curve for viable V. parahaemolyticus between logarithmic viable counts (LgC) and the logarithmic OD555 nm (LgOD555 nm) was LgC=(1.0439±0.0200)LgOD555 nm+(8.0565±0.0125), with a correlation index R²= 0.9965, and the linear detection range is 7.8×106~2.5×108 CFU/ml. The directly detected index of ATP bioluminescence assay is the relative luminescence unit (RLU), which is produced by ATP of viable cells. The liner standard curve between LgC and LgRUL was LgC=(0.9590±0.0065)LgRLU+(0.9949±0.0366), with a correlation index R²=0.9994, and the linear detection range is 1.0×104~3.0×108 CFU/ml. The directly detected index of the high-throughput growth curve method is the spinodal time (Ts), which is the time reaching the reflection point on the growth curve. The liner standard curve between LgC and Ts was LgC=–(0.8727±0.0230)Ts+(9.0128±0.1572), with a correlation index R²=0.9924, and a linear detection range of 1.0×100~1.0×107 CFU/ml. These three methods were used to measure 10 broths of V. parahaemolyticus and comparison with the plate counting method, respectively. The results showed both the ATP bioluminescence assay and the high-throughput growth curve method had satisfying accuracy, but the MTT assay had lower accuracy. The high-throughput growth curve has the widest linear range and is the most suitable for high throughput measurement.

Abstract:This study investigated the effects of dietary fish meal replacement by seaweeds or residues on growth performance and related biochemical indices of juvenile tiger puffer (Takifugu rubripes), with 2 fishmeal diets containing 60% and 45% fishmeal as the control 1, and the control 2, and other four diets with 30% fishmeal replaced by 10% four kinds of seaweeds or residues (Gracilaria verrucosa, Enteromorpha prolifera, Algae residue, Fungi residue) and vegetables protein(wheat gluten, corn gluten meal, and soybean meal), and they were named as C1, C2, JL, HT, ZZ, and JZ. Each diet was fed to three replicates of 25 tiger puffers with initial body weight of (17.33±0.55) g for 56 d. The results showed as follows: The special growth ratio (SGR) of HT group were significantly higher than that of other groups (P<0.05). The SGR of ZZ group was significantly higher than C2 and JL groups (P<0.05). The feed efficiency ratio (FER) of C1 and HT groups were significantly higher than C2 and JZ groups (P<0.05). The protein productive value (PPV) and protein efficiency ratio (PER) of C1 were significantly higher than C2 and JZ groups (P<0.05). No significant differences were found in activities of serum glutamic pyruvic transaminase (GPT), serum glutamic oxalacetic transaminase (GOT), liver GPT and liver GOT (P>0.05). No significant differences were found in activity of serum superoxide dismutase (SOD) and content of malondialdehyde (MDA). Crude protein content of whole body in JZ group was significantly higher than ZZ group (P<0.05). And crude lipid contents in whole body in HT and ZZ groups were significantly higher than C2 group (P<0.05). Above results showed that replaced 30% fish meal with 10% G. verrucosa, E. prolifera, algae residue or fungi residue and vegetable proteins have no adverse effect on the growth performance of juvenile tiger puffer, and E. prolifera can significantly improve the growth performance.

Abstract:Centropristis striata is an economically important marine fish worldwide. In this study, the nutritional content in the muscle of C. striata was compared and evaluated by routine biochemical analysis methods between males and females. The results showed that the female C. striata contained significantly lower moisture than the males (P<0.01). However, the crude fat content in the fresh muscle of females was significantly higher (P<0.01) than that in the muscle of males. There was no significant difference in the crude protein and crude ash content in fresh muscle between females and males (P>0.05). Sixteen common amino acids were detected in the muscles of both males and females. Except for methionine, lysine, and glycine content, there were no significant differences between the other 13 amino acids, total amino acids (TAA), essential amino acids (EAA), and delicious amino acids (DAA) (P>0.05). According to the amino acid score (AAS) and chemical score (CS), the first limiting amino acid for both male and female C. striata was methionine, and the second was valine. The essential amino acids index (EAAI) of the male C. striata was 85.28, a little higher than that of female C. striata (84.84). The composition proportions of the essential amino acids in the muscles of C. striata are all in accordance with the FAO/WHO Standard. The ratios of branched chain amino acids to aromatic amino acids (F values) in the flesh of male and female C. striata were 2.28 and 2.24, respectively. The monounsaturated fatty acid (MUFA) concentration in the male C. striata was higher than that in females, the difference was highly significant (P<0.01), but the polyunsaturated fatty acid (PUFA) and EPA+DHA (Eicosapentenoic acid+docosahexoenoic acid) content were not significantly different between the males and females. The ratio of ∑n-3 PUFA to ∑n-6 PUFA in the flesh of the male C. striata was 6.43, which was higher than that of the females (5.51). In addition, the ratio of K to Na in the muscles of the males (14.27) was higher than that of the females (8.27). In conclusion, it can be suggested that male C. striata has a higher edible value than females.

Abstract:In order to evaluate the application of Sargassum thunbergii, Sargassum horneri, Saccharina japonica, degummed kelp, Ulva lactuca L., and their mixture in juvenile sea cucumbers [(10.02±0.03) g], an 8-week-long experiment was conducted in a circulating water system. Growth performance, body composition, intestinal digestive enzyme activities, and nonspecific immune performance were analyzed. Results showed that the weight gain rate (WGR) and specific growth rate (SGR) of sea cucumbers fed S. thunbergii and the seaweed mixture were significantly higher than those of other groups (P<0.01), and were the lowest in sea cucumbers fed degummed kelp. Sea cucumbers fed degummed kelp had significantly lower ratio of intestine weight to body weight (IBR) and ratio of viserosomatic weight to body weight (VBR) than those of the other groups (P<0.05). Different seaweed did not significantly affect survival rate (P>0.05). Body wall moisture, crude ash, crude protein, and the crude fat of sea cucumbers were not significantly affected by the seaweeds (P>0.05). The intestinal trypsin activities in sea cucumbers fed S. thunbergii, and the seaweed mixture were significantly higher than those in the kelp, degummed kelp, and Ulva groups, and were the lowest for degummed kelp (P<0.01). The different seaweeds had no significant effect on alpha amylase and lipase activity (P>0.05), but significant effects were observed in the hydrochloric acid-insoluble ash of fecal matter (P<0.01). Intestinal total-superoxide dismutase (T-SOD), acid phosphatase (ACP), and alkaline phosphatase (AKP) activities in the sea cucumbers fed S. thunbergii and seaweed mixture were significantly higher than those in the other groups (P<0.01). Intestinal malondialdehyde (MDA) content in sea cucumbers fed degummed kelp was significantly higher than that in the other groups (P<0.01). In conclusion, a comprehensive consideration of growth performance and nonspecific immune performance indicated that the four seaweeds individually cannot achieve the feeding effect of replacing dietary S. thunbergii; however, using mixed seaweeds can achieve an effect similar to S. thunbergii under these experimental conditions.

Abstract:In this paper, Sargassum thunbergii, Nitzschia, Ulva lactuca, and Callithamnion corymbosum were used as the experimental species to determine the influence of different light qualities (white, blue, and red light), medical treatments (1% ammonium nitrate, 3% ammonium sulfate, and 1% citric acid), and freshwater immersion on their photosynthetic efficiencies. The effectiveness of various harmful algae removal methods which are harmless to young sporophytes of S. thunbergii, were also discussed. The results showed that: for RGR (relative growth rate), Pn (apparent photosynthetic rate), and Pn/R (the ratio of apparent photosynthetic rate and respiratory oxygen consumption rate), S. thunbergii under blue light were significantly larger than those under white and red light. In comparison, Pn of Nitzschia reached its peak under the red light. The Pn of S. thunbergii and Nitzschia under blue light was significantly higher than that under white and red light, indicating that S. thunbergii outcompetes Nitzschia under blue light. Irreversible injury appeared when young sporophytes of S. thumbergii were exposed to ammonium nitrate, ammonium sulfate, and citric acid. These chemical treatments also inhibited the growth of C. corymbosum, but the effects were not significant on newborn branches of S. thunbergii and U. lactuca. Freshwater treatment caused harm to S. thumbergii young sporophytes and C. corymbosum, but there was little negative effect on U. lactuca, and newborn branches of S. thunbergii. These results suggest that in the early stages of S. thunbergii cultivation, increasing the irradiation of blue light or reducing the irradiation of red light to a certain extent, can promote the growth of S. thunbergii, and inhibit the growth of Nitzschia. The use of ammonium nitrate, ammonium sulfate, and citric acid should be avoided in the removal of unwanted algae from young sporelings of S. thunbergii. While it is not advisable to use fresh water during the early stages, a fresh water soak for half an hour can remove the unwanted algae and causes no harm to the newborn branches of S. thunbergii.

Abstract:Marine plastic pollution has become a major global environmental issue combined with global climate change, ozone depletion, and ocean acidification. Microplastics (less than 5 mm in diameter), as emergent contaminants, are of great concern globally. Available studies show that microplastics are present in marine fisheries waters, and marine fishery organisms, an important source of high-quality protein for humans, have been contaminated by microplastics. Therefore, the study on microplastics pollution in marine fishery waters and their biological effects has attracted increased attention. In the present study, we summarized the main sources of microplastics in marine fishery waters and their pollution status, summed up the main toxic effects of microplastics on the marine fishery organisms and the corresponding toxicity mechanisms, discussed the transfer of microplastics along the marine food chain and their potential impact on the quality and safety of seafood, analyzed the current problems, and finally, provided the outlook for future work. This study provides a scientific basis for better evaluation of the effect of microplastics on the marine fisheries resources as well as seafood quality and safety.