Abstract:Aquaculture plays a vital role in global food security and continues to provide a source of high-quality protein for humanity. Probiotics are beneficial microorganisms that can be used in aquaculture. They can not only improve the growth performance and immune capacity of aquatic animals, but also inhibit pathogenic bacteria and improve aquaculture water quality. The application of probiotics in aquaculture helps promote the healthy and sustainable development of aquaculture. Therefore, this article firstly introduces the definition and sources of probiotics in aquaculture, expounds the significance and practical application of probiotics in sustainable aquaculture, and discusses the future research direction in this area, in order to provide reliable technical support for the popularization and application of probiotics in sustainable aquaculture..

Abstract:Regional fisheries management organizations (RFMOs) are currently the main mechanism of international high seas fisheries management and one of the focal points of high seas fisheries management research. The development of distant-water fisheries in the West started earlier, and foreign researchers started theoretical and applied RFMO research earlier than those in China. Due to the long history of foreign research on RFMO, a more mature research system on RFMO theory and practice has been formed, with a wide range of research areas and relatively scientific research methods. This has produced a large number of far-reaching research results, which are of great significance for understanding the mechanism of RFMOs, the formulation and implementation of RFMO conservation and management measures, and the development trend of RFMOs. In this paper, bibliometric and knowledge mapping analyses are conducted to review foreign research on RFMO and present the research progress and focus. The results of quantitative analyses show that the number of foreign RFMO studies has been generally on the rise, research topics have covered natural and social sciences such as fishery, environment, and international relations. The United States, the United Kingdom, and Australia have attached great importance to RFMO research. The results of keyword analysis show that the focus of foreign RFMO research includes fisheries management, the Southern Ocean, climate change, ecosystems, marine protected areas, and the law of the sea; the trend of foreign RFMO research has gradually shifted from biological research on biological resources to scientific management of high seas fisheries resources and ecosystem protection. On this basis, this paper conducts further qualitative analyses and finds that foreign RFMO researchers tend to explore the traditional RFMO research topics from a more innovative perspective, conduct the research in a more scientific method, making the research more dialectic, systematic, comparative, and continuous, and their research consciousness is so raised that they are always sensitive to new RFMO research topics. Through quantitative and qualitative analyses of RFMO foreign studies, this paper summarizes their research development and tries to provide some inspiration for domestic scholars to effectively improve the depth and breadth of RFMO research.

Abstract:The distribution patterns of adipose tissue in different fish species are highly diverse. Turbot (Scophthalmus maximus) has a special lipid storage pattern, storing lipid predominantly in the subcutaneous tissue around the fin. In order to better understand the lipid physiology of fish storing lipid in subcutaneous tissue, this study preliminarily investigated the tissue distribution of 29 lipid metabolism-related genes in S. maximus, which are involved in lipogenesis, fatty acid oxidation, biosynthesis and hydrolysis of glycerides, lipid transport, and relevant transcription regulation. Fifteen tissue samples including eye, gill, brain, skin, muscle, liver, stomach, kidney, spleen, heart, foregut, pyloric caeca, hindgut, caecum and subcutaneous adipose tissue around the fin were collected from 30 fish for qRT-PCR analysis (10 fish as a replicate pool). In the PCR experiment, EF1α and RPL13 were used as the reference genes. The amplification efficiency for all primers, which was estimated by standard curves based on dilution series of target template, was within 95%-105%, and the coefficients of linear regression (R²) were ?0.99. A quantitative thermal cycler (Roche LightCycler 96, Basel, Switzerland) was used for the real-time qPCR, and the reaction system and program followed the formal procedures in our laboratory. Each sample was run in triplicate. The mRNA levels were expressed according to the 2^-ΔΔCT method. For each gene, the mRNA level in the tissue with the lowest expression was standardized to be 1.0, and the gene expression levels of other tissues were expressed as folds of 1.0. The results showed that the intestine and brain had high transcription of lipogenic genes such as ACACβ, FAS and SCD1, whereas the liver and muscle had low expression levels of these genes. The intestine also had the highest transcription levels of most apolipoproteins such as ApoA1, ApoA4, ApoB100, and ApoEα and lipid metabolism-related transcription factors such as PPARα1, PPARγ, SREBP1, LXR-α, and HNF4α. The transcription of fatty acid β oxidation-related genes, ACOX1, ACOX3, and CPT1, was low in the muscle. The intracellular glyceridases, HSL, DAGLα, and MGLL, were highly transcribed in the brain, eye, and heart. In conclusion, in S. maximus, the intestine may not only be the place for lipid uptake, but also an important lipogenic organ in S. maximus. The lipid metabolism in the subcutaneous adipose tissue of S. maximus is not active, which may be due to the fact that the subcutaneous tissue is the main organ for lipid storage in S. maximus. This study will help to further elucidate the regulation of lipid metabolism in fish at the molecular level.

Abstract:As a class of small non-coding RNA molecules, miRNA plays an important role in the molecular regulatory network of vertebrate bone metabolism. Normally, bone metabolism is referred to the modeling and remodeling processes in regulating calcium homeostasis, and scale tissue of fish is an ideal model for the study of bone metabolism due to its abundant quantity and easy acquisition. Salmon calcitonin (sCT) is a small peptide hormone isolated from the gills of salmonidae, which can inhibit the activity of osteoclasts to regulate calcium homeostasis of fish. In order to explore the regulatory mechanism of teleost bone metabolism, intraperitoneal injection of sCT was performed in Oncorhynchus mykiss juveniles and scales were collected 24 h after the injection. High-throughput sequencing technology and bioinformatics methods were performed to evaluate the effect of sCT on the miRNA expression profiles in scales. The results showed that 14 051 631 and 15 816 147 high quality miRNA sequences (18-26 nt) were obtained from the samples of the injection group (IG) and control group (CG), respectively, and 568 and 592 mature miRNA were identified in IG and CG scales, respectively. A total of 24 differentially expressed miRNAs (DEMs) including nine up regulated and 15 down regulated DEMs were identified. Eight miRNAs were randomly selected for quantitative real-time PCR (qRT-PCR) detection, and results were consistent with the RNA-Seq results. GO annotation and enrichment analysis revealed that the predicted target genes of DEMs were mainly annotated in the functions of metal ion binding, calcium ion binding, G protein coupled receptor signaling pathway, Wnt signaling pathway and classical Wnt signaling pathway; these genes were enriched in the negative regulation of NF-kappaB input into the nucleus, the negative regulation of interleukin-1 β (IL-1β) secretion and the binding of transforming growth factor β (TGF-β). KEGG enrichment analysis showed that the predicted target genes of DEMs were significantly enriched in toll-like receptor and estrogen-related signaling pathways. A total of six miRNA (omy-miR-29a-5p, omy-miR-30d-5p, omy-miR-125b-2-p3, omy-miR-138, omy-miR-199b-5p and omy-miR-200b) were identified, which could provide materials for future studies on the molecular mechanism of bone metabolism in teleosts.

Abstract:To provide effective molecular markers for the improvement of high temperature tolerance of Esox lucius, simplified genome sequencing was conducted based on the heat sensitive group (109) and high temperature tolerant group (103) of E. lucius. For InDel markers in 25 chromosomes, the first two PCA were covariables. The Masked Language Mode (MLM) was used to analyze the correlation between the heat tolerance characteristics of E. Lucius. The results showed that most InDel was distributed in introns (63.69%), while exons had few InDel sites (1.30%). Five loci were found to be significantly associated with heat tolerance traits (FDR P-value<0.05), which were located in the intron of safb gene, unknown gene LOC117593903 and CLSTN2 gene, respectively. The three InDel sites of 9N del, 4N del-1 and 4N del-2 were all located in the 3rd intron of Clstn2 gene, and the genotypes of the three sites were highly linked in 212 individuals. The five InDel mutations found in this study may have a significant effect on the heat tolerance traits of E. lucius, and can be used as candidate molecular markers for the improvement of heat tolerance traits of E. lucius. Further, some loci were verified by KASP technique in validation population. It was found that the 9N del site DD genotype was dominant in the heat sensitive group, and the DI genotype was dominant in the high temperature tolerance group, which was basically consistent with the simplified genome sequencing results. Three InDel sites located in the second intron of CLSTN2 gene may affect the transcription of CLSTN2 gene. This gene may be an important candidate gene related to high temperature tolerance in E. lucius. The results provide theoretical basis for marker assisted breeding and candidate molecular markers for the improvement of E. lucius heat tolerance traits.

Abstract:Steroid acute regulatory protein (StAR) is an important enzyme in the early stage of steroid hormone synthesis. Recent studies have found that aquatic hypoxia can influence synthesis pathway of steroid hormones in fish as an endocrine disruptor, however, little information was observed in crustaceans. In order to investigate the roles of StAR in the oriental river prawn Macrobrachium nipponense under hypoxia, StAR gene has been cloned and characterized. A full-length cDNA sequence of StAR from M. nipponense was cloned by RACE (rapid amplification of cDNA ends) PCR. We examined the expression levels of StAR gene in different tissues by semi-quantitative RT-PCR, at the same time, the expression profile of StAR gene transcription level and protein expression abundance in testis of M. nipponense under hypoxia were also examined by quantitative real-time PCR (qRT-PCR) and Western blot, respectively. The results showed that the cDNA of StAR gene was 3 361 bp in length (NCBI: MW263908), including 323 bp 5'-untranslated regions (UTR), 2 129 bp 3'-UTR, 909 bp open reading frame (ORF), which encodes 302 amino acids. Based on bioinformatics analysis, phylogenetic tree analysis showed that the StAR gene of M. nipponense was closely related to the StAR gene of Portunus trituberculatus. The semi-quantitative RT-PCR results showed that StAR was highly expressed in testis tissues, but the lowest expressed in hepatopancreas and heart tissues. qRT-PCR results showed that the mRNA expression of StAR in the testis from hypoxia 1- 48 h was significantly higher than those in control group, but there was a significant lower mRNA expression of StAR in hypoxia 96 h group than those in control group. In addition, the recombinant plasmid was constructed and the StAR polyclonal antibody was obtained by immunizing rabbit. The expression abundance of StAR protein was detected by Western blot, which was basically similar to the gene expression pattern. In addition, immunohistochemical results showed that StAR protein was expressed in sperm cells and Leydig cell in testis tissue. Acute hypoxic stress significantly inhibited expression level of StAR, which may play an important role in spermatogenesis. The results of this study lay a foundation for further analysis of the molecular mechanism of steroid hormone synthesis in M. nipponense.

Abstract:Sinibrama taeniatus is a small economic fish endemic to the upper reaches of the Yangtze River. In order to figure out the component types of hematocytes and the hematopoiesis process, and thus to further provide valuable information on the fundamental construction of the immune system of S. taeniatus, smears of peripheral blood and imprints including pronephros, body kidney, liver and spleen were stained with Wright-Giemsa staining. After that, the morphological characteristics and distribution of hematocytes in peripheral blood and hematopoietic organs were observed, and the sizes and proportion of different types of hematocytes in the detected four organ prints were statistically analyzed as well. The results showed that the hematocytes of S. taeniatus was mainly comprised of erythrocytes and leukocytes. Leukocytes can be divided into several types including lymphocytes, granulocytes, monocytes, thrombocytes and so on. In the peripheral blood smears, as the main group, lymphocytes accounted for the largest proportion of total leukocytes (65.79%±0.10%), followed by thrombocytes and neutrophils, accounting for 16.76%±0.07% and 13.92%±0.09% respectively. The number of monocytes was the least, only 3.33%±0.01%. The hematopoiesis of S. taeniatus was mainly divided into four lineages: erythroid, lymphoid, monocytoid and granuloid, and each lineage can be further divided into three stages called primitive, immature and mature ones. The second stages of all three kinds varied depending on types. Immature erythrocytes can just be divided into early and late periods, while that of granulocytes consisted early, middle and late periods. Among these four hematopoietic organs, the pronephros and body kidney were the central place, while the spleen maintained the ability of hematopoiesis of various blood cells, and the liver can only host the development of lymphocytes. Blood cells in the immature stage can migrate to peripheral organs to develop and further mature. These results of the present study provided a basis for further research on the immune system of this endemic fish. It may function as a reference for the study of blood cell development and immune system of fish represented by S. taeniatus.

Abstract:Potassium deficiency often occurs in inland low-salinity saline waters, which is a major challenge to fishery utilization of such resources. In order to explore the effects of potassium deficiency in low-salinity water on the growth, survival, body composition, gill and hepatopancreas tissue structure of Litopenaeus vannamei, a 60-day growth experiment was set up using diluted artificial seawater at salinity of 2. Juvenile shrimps with body weight of (1.04±0.23) g were cultured under the conditions of Na⁺/K⁺ (mg/mg) ratio of 27, 47, 67, 87 and 107 (group A, B, C, D and E, respectively). The results showed that the survival rate of group E was 44.64%±20.95%, which was significantly lower than that of groups A, B and D; body weight of group E was (4.86±0.66) g, which was significantly lower than that of the other four groups. There were no significant differences in wet weight, weight gain and specific growth rate between groups A and D, but they were all higher than those in group E. The feed coefficient in group E was the highest and significantly different from that in groups A and D. In terms of body composition, there were no significant differences in potassium and ash content of whole body between all groups, and water content in group E was higher than that in other groups, and significantly different from that in groups A and B. The crude protein content in group E was the lowest, and was significantly different from that in group B. In group E, the shrimp gill cuticle was significantly damaged, the number of red blood cells decreased, vacuoles increased, the volume of hepatopancreas B cells and their internal transport vesicles increased, and the structure of hepatic tubules was damaged. The results indicated that severe potassium deficiency under low salinity conditions causes damage to the gills and hepatopancreas of the shrimp, which also reduces its survival and growth. Potassium deficiency in water body has a significant effect on the growth of L. vannamei even in the early stage, while its influence on the survival increasesh along the culture period, which means supplementation of potassium is necessarily at the beginning of farming. These findings would help to provide theoretical and practical support for the aquaculture exploitation of inland low salinity waters.

Abstract:Triploid technology is widely used in aquatic animal breeding and has produced huge economic benefits. It is possible to increase the size of pearl by using the fast growth of triploid. In this study, the hypotonic shock was used to induce triploid of Pinctada martensii for the first time to explore the comprehensive effect of hatching rate, growth rate, survival rate and triploid rate. We used the controlled variable method to find the optimal conditions for inducing triploid P. martensii from 7 different salinity, 3 different initial induction times and 3 different induction time. Meanwhile, the cleavage rate, hatching rate, the changes in survival rate, shell length and triploid rate of P. martensii were explored. Results showed that the highest triploid rates of D-shaped larvae were 64.16%±6.92%, 65.87%±6.51%, and 65.14%±1.93%. The optimal conditions for highest triploid rates were at a salinity of 14, when 50% of first polar body (PB I) was released from fertilized eggs, and 15 min after induction, respectively. The results showed that triploid larvae did not show obvious advantages. The effect of hypotonicity shock on embryos caused a decrease in larval survival rate and triploid rate. Through principal component analysis of cleavage rate, hatching rate, 15-day-old survival rate, shell length and triploid rate, the first two principal components were retained in the three induction conditions. The cumulative variance contribution rate of the retained principal components exceeds 85%. The comprehensive evaluation scores of 50% PB I released from fertilized eggs, salinity of 14, and 15 minutes of induction were 6th, 1st, and 1st respectively in their respective experiments. The study showed that there was no obvious advantage in the growth of the triploid of P. martensii larvae, and the two conditions of 50% PB I released from fertilized eggs and 15 minutes of induction were suitable for the triploid induction of P. martensii. This study can provide a new idea for the P. martensii triploid breeding, which may improve production efficiency.

Abstract:The morphological characteristics of some species of the genus Cynoglossus are highly similar, making it difficult to identify and distinguish between species. For example, in the case of tongue soles with three complete lateral lines on the eye side, C. abbreviatus (Gray, 1834), C. trigrammus (Günther, 1862) and C. purpureomaculatus (Regan). There are three opinions on the validity and interspecies relationship of the three species: only C. abbreviatus as a valid species; C. abbreviatus and C. trigrammus as a valid species, and C. purpureomaculatus is a synonym of of C. trigrammus; all three species are valid species. In order to resolve this classification confusion, the 28 morphological characteristics of the specimens from the original descriptions of three tongue soles, type specimens measured in this study, and the specimens from the coast of mainland China were compared and the COⅠ Barcoding were amplified. The results show that values of eight meristic, 16 proportional characters and two descriptive features among the three species were consistent, containing and largely overlapping; only other two descriptive features showed difference. One is the relative size of the snout length to the length of the upper margin of the upper eye from the base of the dorsal fin, which in C. abbreviatus and C. purpureomaculatus is the continuous values (slightly longer, equal or slightly shorter), while significantly longer in C. trigrammus.The other difference is the coloration of the ocular-side body. For C. purpureomaculatus, the standard length is usually less than 200 mm, and there are irregular dark-brown speckles spread over the entire body; the standard length of C. abbreviatus is usually more than 250 mm, and the speckles disappear gradually with increasing of body length . But the cloud-shaped dark-brown blotches sparsely over the area between posterior head to anterior 3/4 of the body in C. trigrammus. The COⅠ genetic distances between C. abbreviatus and C. purpureomaculatus was 0.000-0.002, suggesting the differences are intra-specific, while that between these former two species and C. trigrammus were 0.141-0.145, suggesting inter-specific differences. Based on the above morphological and molecular results, the conclusion of this study is C. abbreviatus and C. trigrammus were affirmed as a valid species, and C. purpureomaculatus is a junior synonym of C. abbreviatus. The results of this study provide a scientific basis for the correct classification of Pleuronectiformes.

Abstract:Environmental DNA (eDNA) is the general term of DNA released by organisms in ice, soil, air, water, sediment and other environments, which has been widely used in field investigation of aquatic biological resources in recent years. Platyrhina sinensis is mainly distributed in the western area of the North Pacific Ocean, and the coastal area of Zhoushan may be the northern limit of its distribution. In order to explore the feasibility of eDNA technology in the detection of P. sinensis, the qualitative and quantitative detection of P. sinensis in Zhoushan offshore was carried out based on eDNA technology at the same time. In this study, the COI gene sequences of P. sinensis and Platyrhina tangi were compared and analyzed. Primer Express 3.0 software was used to design specific primers and TaqMan probe of P. sinensis. Three fixed net survey stations A, B and C were designed in Zhujiajian offshore, Zhoushan, and samples of P. sinensis were collected regularly. Water samples (stations A, B1, B2, C1, C2 and D) were collected on December 19, 2017, April 14, 2018 and July 14, 2018, respectively, and eDNA droplet digital PCR detection was carried out. Significant difference analysis was conducted between eDNA detection results and water temperature and sampling sites. The results showed that: the concentrations of eDNA of P. sinensis were different at different stations and at different times. The effects of water sampling sites on eDNA concentration of P. sinensis were significant, and there were significant differences in eDNA at different sampling sites in different seasons. This study showed that eDNA detection was sensitive. Water temperature, water depth and substrate quality all affected the distribution of P. sinensis. The results of this study lay a foundation for eDNA tracking and monitoring of P. sinensis in other sea areas.

Abstract:The skeleton, swim bladder, muscle and so on are the basic structure of fish body, which is also the basis of studies on the classification and internal structure of fish. In recent years, many scholars at home and abroad studied the fish body internal skeleton structure for a variety of fish, but there was few exploration to the skeleton of tunas. X-ray computed tomography (CT) uses the characteristics of X ray that can penetrate the organism and the internal structure imaging of the organism can be built. X-ray CT has the higher resolution for the density of the organ. X-ray CT can display the large density difference between the soft tissue and skeleton structure clearly, it can also display the small density difference between soft tissue structures and organs. Because CT imaging is a kind of digital imaging, the image data of CT can be processed in different methods by using computer software, including three-dimensional display, etc., and can be used for further in-depth study. In this paper, the body of yellowfin tuna (Thunnus albacares) was scanned by X-ray CT, the layer thickness is 1 mm, and the study method and results can be used to provide the reference for the further studies on ichthyology, fish pathology and fish acoustic target strength. The T. albacares was provided by the Chinese pelagic fishery enterprise and was caught from the Kiribati waters in the western and central Pacific Ocean. The fork length, body wide, body height, and body weight of this fish were 66.0 cm, 13.6 cm, 16.5 cm, and 5.75 kg, respectively. Before the measurement, the fish was taken out from the cold storage 24 hs ahead of time. The fish was put into a CT scan system in the hospital. The model of the CT scan system was TOSHIBA Aquilion. The CT data were input into the medical imaging software Mimics (MIS_Research_21.0). The software can be used to identify the CT value (unit: HU) of skeleton, swim bladder, and muscles. The CT threshold value of the skeleton, swim bladder, and muscles were set to 126-1 500, –1015- –985, and 50-110 HU, respectively. The software automatically extracted CT values within the threshold range of skeleton, swim bladder, and muscles. The 3D images of skeleton, swim bladder, muscles, the body internal structure and the relative position of the swim bladder in the body internal structure of T. albacares were reconstructed and their corresponding volumes and surface areas etc. were measured. The results showed that: ① the clear images of T. albacares skeleton, muscles and swim bladder etc. can be obtained by X-ray CT scan; ② mimics, a medical imaging software, can be used to calculate the volumes and surface areas of skeleton, swim bladder and muscle of T. albacares. The volume of skeleton, swim bladder and muscle of T. albacares was accounting for 7.76%, 0.88% and 91.36% of the fish body volume, respectively and the surface area of skeleton, swim bladder and muscle of T. albacares was accounting for 29.52%, 0.74% and 69.74% of body surface area, respectively. This study suggested that: ① X-ray CT scanning is the low injury, most convenient and intuitive method for imaging fish skeleton, swim bladder and muscle; ② mimics, a medical imaging software, can be used to reconstruct the fish body and calculate the volumes and surface areas of fish skeleton, swim bladder and muscle; ③ X-ray CT scanning can be used for the in-depth study of ichthyology, fish pathology and fish acoustic target strength.

Abstract:In order to explore the growth pattern and characteristics of phenotypic traits of Konosirus punctatus at different ages, as well as the relationship between traits and month of ages at the best growing season, phenotypic traits data of total length, body length, head length, trunk length, caudal peduncle length, eye diameter, body height, caudal peduncle height, body width, interorbital distance and body mass collected from K. punctatus at two, four, six, eight months old were analyzed by principal component and discriminant analysis in this study. The results showed that there were different degrees of positive correlation among all the phenotypic traits at different ages. The correlation coefficients between body mass and total body length, body height, body width at each month were large. The correlation coefficients between eye diameter and eye spacing and other traits were small, and the correlation coefficients between body weight and other traits at eight months old were less than those at two, four and six months old. The principal components of K. punctatus at different months of age were different. The first principal component was mainly based on the growth of body mass and length increase. The second principal component showed the growth state of body width at two months old, which also showed the growth state of eye diameter at four, six, eight months old. The third principal component showed the growth state of head at two and four months old, as well as the growth state of eye diameter at six months old and that of body width at eight months old. By stepwise discriminant analysis, the discriminant function of each month was established after eliminating three traits. The overall discriminant accuracy was 99.3%, especially the discriminant accuracy of two, four and eight month of age of K. punctatus reached to 100%. The relation equation between body length and body mass of 2-8 months of age was W=0.017L^2.929 (R²=0.981) of K. punctatus. This study proved that total length and body length and body height and body width are the most important morphological traits in the growth stage of K. punctatus. The study established the discriminant function in the different growth stage of K. punctatus, which demonstrated that the growth pattern of K. punctatus is isokinetic growth at two to eight months old. This study provides a theoretical evidence and suggested measure indices for the selection and breeding of K. punctatus.

Abstract:A 8-week feeding trial was conducted to study the effect of dietary guanidinoacetic acid (GAA) on the growth performance, hepatic anti-oxidative capacity and muscle energy metabolism of channel catfish (Ictalurus punctatus). Four isonitrogenous and isocaloric experimental diets with 0 (control diet), 300, 600, and 900 mg/kg GAA (GAA0, GAA300, GAA600, and GAA900) were formulated. The results showed that appropriate dietary GAA could improve the average final body weight (FBW) and weight gain rate (WGR), but not significantly. While the viscerosomatic index (VSI) and intraperitoneal fat ratio (IPF) of experiemental I. punctatus were significantly affected by dietary GAA levels, with the lowest values in GAA300 group. Based on the quadratic regression analysis of IFP and VSI, the optimal dietary GAA level for I. punctatus was 275 mg/kg and 150 mg/kg, respectively. The addition of GAA in diet had no significant effect on moisture content, crude protein, crude fat and ash content of whole fish, as well as the free amino acids and fatty acids in muscle. While the hydroxyproline (HYP) in muscle was significantly increased with the increase of dietary GAA for better muscle quality. Additionally, dietary GAA can improve hepatic anti-oxidative capacity. The total antioxidative capacity (T-AOC) and superoxide dismutases (SOD) activities of fish in GAA300 group were significantly higher than those of the control group. GAA can also improve muscle energy metabolism, and the succinate dehydrogenase (SDH) and pyruvate kinase (PK) activities of fish in GAA300 group were significantly higher than those of the control group. Conclusively, dietary GAA has no significant effect on growth performance and feed utilization of I. punctatus. While 150-300 mg/kg GAA in diet can reduce intraperitoneal fat content and viscerosomatic index, and improve hepatic anti-oxidative capacity and muscle energy metabolism of I. punctatus.

Abstract:To clarify the role of Ctenopharyngodon idella allograft inflammatory factor-1 (AIF-1) in host immune response, AIF-1 expression profile in peripheral blood leukocytes was investigated with lipopolysaccharide exposure using western blot. Then, the effect of AIF-1 on cell viability was assayed with a CCK-8 kit, cell apoptosis was detected by flow cytometer, ATP production, mitochondrial membrane potential, reactive oxygen species and nitric oxide were determined with the corresponding kit. Finally, the levels of inflammatory cytokine tumor necrosis factor-alpha (TNF-α), interleukin 1β (IL1β), interleukin 6 (IL6) were measured using ELISA kits. The results shown that lipopolysaccharide stimulated AIF-1 secretion from leukocytes. Furthermore, C. idella AIF-1 induced leukocyte proliferation, and increased mitochondrial membrane potential, subsequently promoted ATP production, prevented leukocyte apoptosis. In addition, it provoked inflammatory mediator reactive oxygen species, nitric oxide, inflammatory cytokine TNF-α, IL1β, IL6 released from leukocytes. These results indicated AIF-1 was a potential stimulator for leukocyte viability and associated with C. idella immune response.

Abstract:Properties of myofibrillar proteins (MPs) in Larimichthys crocea remain to be further studied to meet the high-value development and utilization of MPs. The purpose of this study is to investigate the effect of different pH on the structural and emulsifying properties of myofibrillar protein in L. crocea. MP from L. crocea was treated with low-salt phosphate buffer at pH 2, 4, 6, 8, 10 and 12, and MP degradation was analyzed by SDS-PAGE. Moreover, the hydrophilicity of MP was investigated by contact angle and fluorescence spectrophotometry. Emulsions were prepared with MP solution at different pH and soybean oil at ratio of 1∶1 (V/V) by high-speed homogenization. The stability of emulsions was determined by analyzing the droplet potential, particle size and the emulsion index of emulsions. At pH 4, the band color of MP in SDS-PAGE was light. At pH 6-12, the myosin heavy chain band largely disappeared; however, the actin band gradually deepened in color and macromolecular aggregates appeared at the top of band. The comprehensive analysis of contact angle and fluorescence spectrum showed that the hydrophobicity of MP increased with pH. Meanwhile, the MP emulsions were negatively charged with the Zeta potential absolute value of (49.63±1.52) mV and small emulsion droplets at pH 8, exhibiting better stability than MP emulsions at other pH values. However, the MP emulsions showed poor emulsion stability and even demulsification occurred at pH 12. The change of MP structure was beneficial to improve the stability of MP emulsions at pH 8. These results can provide a theoretical basis for the development and application of MP from L. crocea in the food industry.

Abstract:In the process of industrial circular recirculating aquaculture, solid wastes will greatly harm the farmed fish. Improving the self-cleaning ability of the recirculating aquaculture tank is an effective way to remove the solid wastes in the recirculating aquaculture tank. The self-cleaning ability of recirculating aquaculture tank refers to the process of automatically collecting solid wastes to the center of the tank by adjusting the water flow in the tank. A series of indoor experiments have been conducted to study the effect of water inlet angle on the self-cleaning ability of the recirculating aquaculture tank, and the particle imaging velocimetry (PIV) is used to measure the flow field. In the test, a total of 9 cases of different setting angles of the inlet pipe were designed for the circular tank with a symmetrical dual water inlet mode. A camera set directly above the tank is used to record the collection process of the solid wastes under different cases. By analyzing the movement process of the solid wastes and the amount of residual solid wastes in the tank, the effect of the setting angle of the inlet pipe on the solid waste collection process and self-cleaning ability in recirculating aquaculture tank have been quantified. The PIV system was used to measure the flow field in the water layer of 1, 2, 10, 19 cm from the bottom of the tank. By analyzing the flow pattern, resistance coefficient, velocity uniformity coefficient and other hydrodynamic parameters of the recirculating aquaculture tank, the mechanism of the setting angle of the inlet pipe on the solid waste collection process and self-cleaning ability in the recirculating aquaculture tank is clarified. The results show that: the setting angle of the inlet pipe obviously affects the self-cleaning ability of the recirculating aquaculture tank, and the self-cleaning ability firstly increases and then decreases with the increase of the setting angle. The self-cleaning ability of the recirculating aquaculture tank shows good performance under the cases of 45° and 50°; the setting angle of the water inlet pipe affects the self-cleaning ability of the recirculating aquaculture tank by affecting the velocity magnitude and flow pattern in the bottom water layer. The velocity magnitude rate determines whether the solid waste can be picked up, and the flow pattern determines whether the solid waste can be collected to the water outlet. Therefore, in aquaculture practice, it is recommended to set the angle of the inlet pipe of the tank similar to the research in this article to 45° to 50° working condition to improve the self-cleaning ability of the recirculating aquaculture tank and improve the comprehensive performance of circulating aquaculture.

Abstract:Due to the constraints of land resources and environment and the continuous progress of science and technology, human beings have entered an era of deep exploitation of marine resources and utilization of marine space. With the depletion of offshore fishery resources and the aggravation of marine pollution, the construction of marine ranching has become an important measure to improve marine ecological environment and repair fishery resources. Among them, artificial reefs are the infrastructure of modern marine ranching, and ensuring the normal utility of artificial reefs is the key link of marine ranching construction. In order to study the influence of the upstream inflow angle on artificial reefs at different velocities, in this paper, based on Ansys-Fluent, the RNG k-ε turbulence model is used to conduct numerical flume simulation. The hydrodynamic characteristics of a 3 m cube-diagonal open-hole fish reef under three incoming velocities (0.5, 1.0 and 1.5 m/s) and four attack of angles (0°, 15°, 30° and 45°) were compared and analyzed, including upwelling volume, back eddy volume, resistance and overturning moment. Studies have shown that there are upwelling and back eddy areas with significant characteristics in and around the artificial reef. The scale of the flow field is basically not affected by the flow velocity, while flow velocity is the main factor affecting the stability of cube-diagonal hole-opening reef. The greater the flow velocity, the greater the resistance and overturning moment acting on the reef, and the worse the stability of the reef. The flow field effect of artificial reefs is mainly influenced by the inflow angle. The flow field effect scale of the artificial reefs reaches the optimum when the inflow angle is 30°-45°, and the upwelling volume and back eddy volume reach the maximum when the reef is 45°. The weight assignment method is used to introduce a comprehensive evaluation model for the construction effect of artificial reefs. Through comprehensive evaluation and analysis, the sea area with the maximum flow velocity not exceeding 1 m/s should be selected when placing artificial reefs without considering the conditions of seabed sedimentation, wind and waves, etc. Moreover, the construction effect of the reef is the best when the inflow angle is within the range of 30° to 45°, which can provide a certain theoretical basis for the artificial reef deployments in practical engineering.

Abstract:Reducing trawl bycatch rates on non-target species is a hot topic in fisheries science. The sorting grid is widely used in trawl fisheries to reduce bycatch and improve trawl selectivity. The change in hydrodynamic force of the bycatch reduction device influences the behavioral response of fish after contact, determining the device's separation efficiency and selectivity. Therefore, understanding the hydrodynamic performance of the bycatch reduction device is critical for improving the selectivity of trawl gear. This study investigated the effects of grid sizes (Grid-0.3, Grid-0.4 and Grid-0.5) on the mesh opening degree, spatial geometry, and drag of codend under three different grid angles (A-30°, A-45° and A-60°) using flume tank experiment. The results showed that: (1) The average mesh opening angle of codend without grid was 22°±5°. The average mesh opening angle of the codend with Grid-0.4 and Grid-0.5 was 3.3% and 18.8% respectively, greater than that of the codend without grid, while the mesh opening angle of the codend with Grid-0.3 was 9.2% lower than that of the codend without grid. (2) Grid-0.4 has the least influence on the codend shape and was streamlined to accommodate it, while Grid-0.3 and Grid-0.5 distorted the codend. (3) The differences in the drag of the codend with Grid-0.3 at different grid angles were small with an average similar to that of the codend without grid. The average drag of codend with Grid-0.4 and Grid-0.5 at different grid angles was 12.7% and 24.4% greater than that of the codend without grid, respectively. Except for the codend with Grid-0.3 at A-30°, the codend drag increased with increasing grid angle and size. The findings could have a significant impact on the research on bottom trawl selectivity and the protection of demersal fishery resources in China, particularly research on devices that can effectively release bycatch and juvenile fish.