Abstract:In order to explore the trace element composition characteristics of Sthenoteuthis oualaniensis, the composition and distribution of trace elements in 17 statoliths of S. oualaniensis collected in the Nansha islands waters of the South China Sea during March to May by light falling-net vessels in 2017 were analyzed with laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS). The results showed that the statolith of S. oualaniensis contained 56 elements, and calcium (Ca), strontium (Sr), sodium (Na), phosphorus (P), silicon (Si), potassium (K), magnesium (Mg), iron (Fe), barium (Ba) and boron (B) were the ten most abundant elements. The analysis of variance (ANOVA) showed that there was no significant difference in the distribution of all ten most abundant elements between different sexes and hatching groups. There were significant differences in the contents of Ca, Sr, Na, P, Mg, Ba and B, but no significant difference in the contents of Si, K and Fe between different areas of the statolith. The study showed that the trace element composition of S. oualaniensis varied in different habitats and in different growth stages, but the trace element composition of S. oualaniensis of different sexes was basically the same, which further confirmed the feasibility of using trace element distribution characteristics to identify cephalopod populations and study migratory routes.

Abstract:Gills are the main respiratory organ of aquatic animals. Different gill structures have existed in aquatic animals like fish, shrimp and crab, but they all hold similar functions in gas exchange, osmotic pressure regulation, etc. Currently, there is an increasing number of studies on functional genomics in gills of aquatic animals. The aim of this paper is to summarize the main findings on gill functional genomics in recent years, especially the transcriptome sequencing analysis of aquatic animal gills under the stress of different environmental factors, like pollutants of heavy metals, parasitic bacteria, salinity, nitrite, etc., as well as the proteomics and metabolomics of gills under the stress of different environmental factors. The study reveals the impacts of environmental factors on gill-related gene expression, physiological and biochemical status changes, molecular pathways and physiological functions in aquatic animals, so as to provide potential new ideas and directions for healthy fish farming.

Abstract:Studies have shown in mammals that retinoic acid (RA) is a key molecule mediating the initiation of meiosis, and can directly induce meiosis in cultured spermatogonial stem cells (SSCs) and express meiosis specific molecule Scp3. However, although studies have shown that RA plays an important role in testis differentiation and development and meiosis initiation in fish, its role in SSC proliferation and differentiation and whether it can directly mediate SSC meiosis remain unclear. In this study, the three-fluorescence reported plasmid pGRY, which contains three promoters, i.e., elongation factor 1α (ef1α) promoter driven histone H2B-green fluorescent protein (H2B-GFP), scp3 promoter driven puromycin-red fluorescent protein (puro-RFP), and protamine promoter driven yellow fluorescent protein (YFP), was used to transfect SG3 to obtain stable cell line SG3-pGRY. Then the effect of RA signal on the proliferation and differentiation of SG3-pGRY was investigated. The red fluorescent of SG3-pGRY could indeed reflect the expression of endogenous Scp3. Moreover, the SG3-pGRY retained stem property such as strong alkaline phosphatase activity and differentiation potential, indicating that it can be used to monitor the state of cell differentiation. With the condition of 2D culture, that is to say, the cells are sub-cultured when the cell growth density is about 90% in the cell culture plate, RA could inhibit cell proliferation, while Rar (α, β and γ) pan-antagonist BMS493 could promote cell proliferation. Furthermore, the results of real-time PCR showed that RA could significantly down-regulate the expression of pluripotency related genes pou5f3 and klf4 and had no significant effect on the expression of differentiated related genes including ckit, scp3, spo11, rec8a, rec8b except dazl. With the condition of 3D, obvious red fluorescence was observed in RA, BMS493 and control group after 48 h incubation. Compared with 2D conditions, the expressions of differentiation related genes were up-regulated compared with those in 2D culture for 48 h. In addition, the expressions of differentiation related genes in RA group were higher than the control group, whilst the BMS493 group was lower than control group. Taken together, RA signal could inhibit the proliferation and promote the differentiation of SSCs, but it is not essential to induce cell meiosis. This study not only provides a good research model for the study of fish SSC differentiation, but also promotes our in-depth understanding of the role of RA signal in fish SSC proliferation and differentiation.

Abstract:As a new type of marine environmental pollutant, microplastics are chemically stable and difficult to degrade, and can accumulate in the marine environment for a long time and be deposited in marine organisms, which may eventually pose a threat to human health, and therefore, are of concern to scholars from all areas. To investigate the microplastics uptake characteristics in stomach tissues of Todarodes pacificus (T. pacificus) and its relationship with individual size (mantle length and body weight), stomach tissue weight and feeding grade. In this study, a total of 30 samples of T. pacificus were collected in the East China Sea from January to March 2018 with Chinese production survey vessels. The accumulation characteristics of microplastics in their stomach tissues were investigated using statistical and correlation analysis. The study results showed that the mantle length of T. pacificus ranged from 87-208 mm, with an average mantle length of 159.6 mm; body weight ranged from 16-188 g, with an average weight of 91.6 g; stomach weight ranged from 0.1-7.3 g, with an average stomach weight of 0.71 g. The presence of microplastics was found in the stomach tissues of 16 samples of T. pacific, with a detection rate of 53.3%. In this study, 18 microplastic particles were found, and the abundance of microplastic ranged from 0 to 3 items/individual, with an average abundance of 0.6 items/individual; the size of particles ranged from 0.332 to 4.337 mm, with an average particle size of 1.252 mm, with 72% of the microplastic particles smaller than 1 mm. The colors of microplastics were mainly black (38.9%), white (33.3%), blue (22.2%) and gray (5.6%), and they consisted of cotton, polyester and rayon, accounting for 44.5%, 33.3% and 22.3% of the total, respectively. The correlation analysis showed that the content of microplastics in the stomach tissues of T. pacificus was not significantly correlated with its stomach tissues weight and feeding grade, but was significantly and positively correlated with mantle length, body weight and age. [Conclusion] The content of microplastics in the stomach tissues of T. pacificus increased gradually with the increase of mantle length, body weight and age. The deposition of microplastics in the stomach tissues of T. pacificus gradually increased with their individual growth, which indicated that their intake of microplastics was greater than its excretion. Whether this accumulation phenomenon continus unceasingly or the dynamic balance of intake and excretion is maintained when a certain amount is reached requires further study.

Abstract:TheMuraenesox cinereus and other eels of Anguilliformes are common near-bottom ferocious carnivorous fish in the waters of the Zhoushan Islands. Studying the trophic niches of eels can provide an understanding of the trophic levels they occupy in the marine ecosystem of Zhoushan Islands. TheMuraenesox cinereus, Dysomma anguillare, Conger myriaster, Pisodonophis cancrivorus and Rhynchocongerbrevirostris caught from the waters of the Zhoushan Islands were selected as the research objects in this study. The carbon and nitrogen stable isotope technology was used to analyze the trophic niche and interspecies diet relationship of five eels. A total of 143 samples of 5 kinds of eels’ carbon and nitrogen stable isotopes were determined in this study. We found that the total anal length of the five eels varies from 43.00 to 383.00 mm, with an average of 157.14 mm. And the weight varies from 15.60 to 1184.50 g, with an average of 150.07 g. The δ¹³C range of the overall sample is ?21.91‰ to ?14.97‰, with an average value of ?17.03‰±1.14‰, while the δ ¹⁵N range is 9.56‰ to 15.13‰, with an average value of 11.50‰±1.36‰. The results of Non-Parametric test showed that there were extremely significant differences in the stable isotope ratios of carbon and nitrogen among different species. Pearson correlation analysis showed that, the δ¹³C and δ¹⁵N values of the 5 species of eels were not significantly correlated with anal length. Except for the D. anguillare, the δ¹³C value of the remaining four types of eels were not significantly correlated with the anal length, and the δ¹⁵N value were extremely significantly positively correlated with the anal length. The overall trophic levels of the five eels range from 3.16 to 4.79, with an average value of 3.73. The SIAR showed thatM. cinereus mainly feed on fishes, shrimps and stomatopoda, while D. anguillare mainly feed on shrimps and stomatopoda. Fishes were the main food of C. myriaster, and cephalopods were secondary.P. cancrivorus mainly fed on fishes, shrimps and Cephalopods, while R. brevirostris fed on fishes, shrimps and stomatopoda on average. The nutritional niche of M. cinereus overlaped with the other 4 species of eels. It indicated that the diet sources ofM. cinereus and other species have a certain degree of homogeneity, and there was food competition. The corrected version of the Standard Ellipse Area (SEAc) of P. cancrivorus and R. brevirostris were the two largest values, indicating that the eating habits of the two are generalized, and the feeding groups mainly depend on the availability of food organisms. There was no niche overlap between the D. anguillare, C. myriaster, and R. brevirostris. It showed that there are differences in their feeding source, which reflected the differences in the feeding habits of related species in sympatric distribution. This study described the interspecies diet relationship and evolutionary coexistence mechanism of the five species of eels in the waters of the Zhoushan Islands, which can provide a basic reference for the research on the characteristics of the food web structure and the resource effects in the waters of the Zhoushan Islands.

Abstract:Todarodes pacificus is one of the most abundant cephalopod resources in the Northwest Pacific Ocean. Understanding of its fishery ecology is the basis for sufficient exploitation of this resource. Statolith are a vital material for studying the age and growth, population structure and life history of cephalopods. The morphological growth patterns of statoliths of T. pacificus was studied for the first time using samples collected in the Sea of Japan by Chinese squid jigging fishery fleets in December 2018 (an El-Nino period). The results indicated that the dorsal dome, lateral dome and wing dome of the statoliths were relatively large and the rostrum dome was relatively small. The result of principal component analysis indicated that the total statolith length (TSL), lateral dome length (LDL), wing length (WL) and maximum width (MW) could be used as morphological parameters to study the morphological growth of statolith. The analysis of covariance (ANCOVA) indicated that there was no significant difference in the relationships between these morphological parameters versus mantle length (ML) and body weight (BW) in different genders. Based on the result of the Akaike’s information criterion (AIC), the relationships between ML, BW and TSL, LDL, MW were best described by power functions growth models, but linear function growth models were more effective for WL. The absolute morphological growth of statolith was gradually decreased, while the relative morphological growth of statolith was maintained steadily with increasing individual growth. This research not only provides reference for study of life history of T. pacificus thorough statolith, but also provides scientific basis for growth pattern of hard tissues of cephalopods under the effect of extreme weather patterns.

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Abstract:This study aims to explore the damage mechanism of hemoglobin on Ctenopharyngodon idella kidney (CIK) cells. Firstly, the growth of CIK cells stimulated by hemoglobin and heme was observed, and the results showed that hemoglobin and heme significantly inhibited the growth of CIK cells. Secondly, the expression of iron metabolism-related genes in CIK cells was detected after stimulated by hemoglobin and hem. The results showed that the stimulation of hemoglobin and heme up-regulated the expression of iron metabolism-related genes to different degrees. The expression of inflammation and antioxidant-related enzymes in CIK cells after stimulated by hemoglobin and heme was also examined. The results suggested that hemoglobin and heme could activate the expression of inflammatory factors through NF-κB pathway, such as pro-inflammatory cytokines TNF-α, IL-1β and IL-6, the anti-inflammatory factor IL-10 and chemokines IL-4 and IL-8, and also activate the expression levels of three antioxidant enzymes, including Superoxide dismutase (SOD), Catalase (CAT) and Glutathione peroxidase (GSH-Px). In order to further detect the toxic effect of hemoglobin on CIK cells, this study also detected the intracellular iron and ROS in CIK cells after hemoglobin stimulation. The results showed that hemoglobin stimulation significantly increased intracellular iron and ROS. Finally, we also examined the expression of apoptosis-related genes in CIK cells after stimulated by hemoglobin and heme, and the results showed that both hemoglobin and heme significantly activated the expression levels of apoptosis-related genes in CIK cells. In conclusion, the results of this study suggest that the high oxidative activity of hemoglobin can activate the expression of iron metabolism- and inflammation-related genes, as well as increasing intracellular iron and ROS levels, leading to up-regulated expression of apoptosis genes in CIK cells.

Abstract:In order to construct genotype II grass carp reovirus (GCRV) virus-like particulars (VLPs) based vaccines, the immunogenic GCRV-VP3/VP4/VP35 protein was assembled into GCRV-VLPs using baculovirus expression system (BEVS). The structural protein VP35 encoded by the segment S11 of GCRV-II was inserted into baculovirus vector pFastBacHTA^TM using BEVS, and the identified recombinant vector was transformed into DH10Bac competent cells to screen recombinant plasmid Bacmid-VP35. Recombinant baculovirus pFHB-VP35 was obtained by transfecting recombinant plasmid Bacmid-VP35, recombinant baculovirus pFHB-VP3 and pFHB-VP4 was obtained by transfecting recombinant plasmid Bacmid-VP3 and Bacmid-VP4 which have been successfully constructed in our laboratory. Then the titers of recombinant baculovirus were determined by Bac-PAK rapid titer kit and the expression of proteins was identified by IFA and Western blot. The results showed that high titers of pFHB-VP35, pFHB-VP3, and pFHB-VP4 were obtained, and the corresponding proteins were successfully expressed in infected Sf9 cells. GCRV-VLPs were assembled co-infection of Sf9 cells with pFBH-VP35, pFBH-VP3, and pFBH-VP4, and the GCRV-VLPs were identified by electron microscopy (EM). The results showed that the three proteins could self-assemble in Sf9 cells and formed VLPs with diameter of 65-72 nm similar with natural viruses. This study lays a foundation for development of novel vaccines for preventing the disease caused by GCRV genotype II.

Abstract:This paper aims to explore the changes in plasma membrane, vitality, ultrastructure and enzyme activity of giant grouper sperm in cryopreservation, and provides a theoretical basis for elucidating the relevant mechanisms affecting the cryopreservation quality of sperm. The semen of giant grouper was collected and stored for 0, 23, 49 and 61 months. Plasma membrane integrity was assessed in fresh sperm and cryopreserved sperm by Y-aniline black staining. The motion parameters of giant grouper sperm before and after cryopreservation were analyzed using computer assisted sperm analysis system. Changes in the activity of six enzymes (SDH, CAT, GR, T-SOD, GSH-Px and CK) ATP content were measured for seminal plasma and sperm. The ultrastructure of fresh and cryopreserved sperm was observed by scanning electron microscope and transmission electron microscope. Fresh sperm had the highest plasma membrane integrity of 83.43%±2.73%, and sperm plasma membrane integrity was significantly reduced after cryopreservation (P<0.05). CASA results showed that the highest mobility was 90.47%±3.34%. Sperm motility was significantly reduced after cryopreservation (P<0.05), but its value stayed within the range of 63.95%±3.66%-68.58%±2.73% after 23-61 months of storage. The VSL VCL and VAP value of cryopreserved sperm had no significant difference compared to fresh sperm (P>0.05). The ultrastructure of fresh sperm showed that the sperm morphology and structure were normal, the mitochondria were arranged regularly, with normal morphology and size. After cryopreservation, the sperm morphology and structural damage was obvious. The damage is manifested as sperm head plasma membrane damage, cytoplasmic leakage, cell nuclear membrane damage, flagella fracture or shedding of the tail. The results of changes in the activities of six enzymes and ATP contents of seminal plasma and spermatozoa before and after cryopreservation freezing of giant grouper sperm showed that after cryopreservation, three enzymes, SOD, GSH-Px and CAT, and ATP contents in spermatozoa were significantly reduced. The enzyme activities in seminal plasma were increased, and all the enzyme activities were significantly different except for GR and CAT. Cryopreservation had a great effect on the enzyme’s activities, ultrastructure and spermatozoa energy of fish. The results have accumulated rich data for the mechanism of frozen fish sperm damage, and provided a technical reference and evaluation index for the long-term cryopreservation of fish sperm.

Abstract:Light is one of the primary environmental factor which has an important impact on the growth, development, metabolism and morphology of fish. In order to analyze the effect of light intensity on the growth and physiological performance of Pelteobagrus fulvidraco, this study recorded the growth and physiological performance of P. fulvidraco within a range o light intensity (1-8 W/m²) by light control experiments. According to the results, P. fulvidraco in the groups (light intensity of 3-6 W/m²) had highest weight gain rate (8.33%-11.78%), specific growth rate (0.53-0.74 %/d), and lowest feed coefficient (6.42-9.17). Pepsin and lipase activities in P. fulvidraco increased, indicating improved the digestive performance. While the activities of superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GSH-Px), alkaline phosphatase (AKP) and acid phosphatase (ACP) decreased, showing that antioxidation and immune performance were inhibited. Affected by fish metabolism, there were differences in water quality factors such as ammonia nitrogen and dissolved oxygen in aquaculture water under different light intensities. This study showed that light intensity within 3-6 W/m² could promote the growth and digestive performance of P. fulvidraco, and provides a theoretical basis for efficient culture of P. fulvidraco.

Abstract:Large yellow croaker (Larimichthys crocea) is the most important warm-water marine commercial fish, which is widely distributed in the southeast coastal regions in China, such as Zhejiang, Fujian and Guangdong provinces. It is highly sensitive to cold and starvation, and massive death of this species can be observed during winters, leading to significant economic losses for farmers. This study aims to explore the response mechanism of L. crocea to oxidative damage caused by low temperature and starvation. Fish with an average weight of (21.38±2.46) g were exposed to low temperature (8 °C) or/and under starvation stress. The fish were divided into four groups: control group (C group), cold group (CC group), fasting group (F group) and cold+fasting group (CF group), each with three replicates. The experiment lasted 30 d, survival rate was calculated, liver samples were obtained for histological observation, chemical fluorescence and LC-MS technology were used to analyze the difference of reactive oxygen species (ROS) and metabolites in different treatment groups. The results showed that compared with C group, the survival rate of CC group, F group and CF group was significantly decreased, while the ROS content was significantly increased (P<0.05), and demonstrated vacuolation and nuclear atrophy, indicating cold and starvation stresses induced oxidative damage. A total of 184 and 50 differential metabolites were obtained from CCvs. C and CF vs. F, respectively. There were five important co-metabolic pathways: glycerophospholipid metabolism, glycosylphosphatidylinositol (GPI) - anchor biosynthesis, arginine biosynthesis, sphingolipids metabolism and autophagy, indicating cell membrane fluidity and autophagy played an important role in cold adaptation. A total of 184 and 50 different metabolites were obtained from F vs. C and CF vs. CC, respectively. There were four important overlapping metabolic pathways: glycerophospholipid metabolism, glycosylphosphatidylinositol (GPI) - anchor biosynthesis, ABC transporters and autophagy, indicating energy and material transport function, as well as autophagy played an important role in starvation stress of L. crocea. 126 differential metabolites were obtained from CF vs. C, which were significantly enriched in glycosylphosphatidylinositol (GPI) - anchor biosynthesis, glycerophospholipid metabolism, oxidative phosphorylation, starch and sucrose metabolism, FoxO signal pathway, autophagy and glutathione metabolism, indicating cell membrane fluidity, energy metabolism, autophagy and antioxidant systems played an important role in cold and starvation adaptation. The results provide scientific basis for further study about the effects of low temperature and fasting on the physiological functions of L. crocea.

Abstract:The Pacific oyster (Crassostrea gigas) which originated from East Asia, has been a dominant commercial species in northern China. However, frequent mass mortality during summer in farming areas has severely restricted the development of oyster aquaculture. In order to develop a new strain of C. gigas with the traits of fast growth and high survival rate, intra-specific hybridization was carried out using the “Haida No. 1” strain (H) and orange shell strain (O), which were successively mass selected for 11 and 8 generations, respectively. The heterosis for growth and survival as well as general combining ability (GCA) and specific combining ability (SCA) were assessed for two purebred groups HH [H(♀)×H(♂)] and OO [O(♀)×O(♂)] and two reciprocal hybrids HO [H(♀)×O(♂)] and OH [O(♀)×H(♂)]. On day 20, the mid-parent heterosis (M_F1) for survival of hybrid groups was 58.03%. Compared to HH groups, the survival rate of HO and OH increased by 31.48% and 35.80%, respectively. On day 360, the growth among four groups followed the order OH>HO>HH>OO, theM_F1 for shell height and living weight of reciprocal hybrids were 24.65% and 46.02%, respectively. Compared to HH groups, the shell height and living weight of OH group on day 360 increased by 23.51% and 39.60%, respectively. Two hybrid groups also exhibited high heterosis in survival, with mid-parent heterosis M_F1 and high-parent heterosis H_HO, H_OH at 68.31%, 40.29% and 53.96%, respectively. As male parent, the “Haida No.1” strain exhibited negative value for general combining ability in survival on day 180. However, the general combining ability was positive when the “Haida No.1” strain was employed as parent at other stages, which indicated the “Haida No.1” strain can be chosen as an excellent parental strain for crossbreeding with other strains of C. gigas. The values of special combining ability for growth and survival of OH group were higher than those of HO group. This suggested the progeny with higher heterosis could be obtained by using the “Haida No.1” strain as male parent and orange shell strain as female parent.

Abstract:Mannan oligosaccharide is a new kind of feed additive whose effects on fish flesh quality has not been well studied. In this study, 315 healthy juvenile Oreochromis niloticus with an average body weight of (2.2±0.2) g were randomly divided into three treatment groups: control group (C, 35% carbohydrate), high carbohydrate diet group (HC, 45% carbohydrate) and high carbohydrate diet supplemented with mannan-oligosaccharide (HM, 45% carbohydrate, 0.5% mannan oligosaccharide). Three tanks for each group, and 35 fish reared in each tank. After feeding trial for 10 weeks, the growth indicator, muscle nutritional composition and flesh texture of all groups were determined. Compared with the control group, the hepatosomatic index, muscle cohesiveness, myofiber number, content of inosinic acid and triglyceride, proportion of delicious amino acids, and elative expression of CAST gene, which could improve muscle growth, were significantly increased in the fish of HC group; the muscle hardness, gumminess and chewiness, myofiber diameter, cooking loss, proportion of essential amino acids, contents of fatty acids, diglyceride and phosphatidylinositol, and relative expression of MyoG gene, which functions in the differentiation of muscle fibers, were significantly decreased in the fish of HC group. Compared with the HC group, the muscle springiness, proportion of essential amino acids, contents of fatty acids and diglyceride, and CAST gene relative expression were significantly increased in O. niloticus of HM group; the muscle adhesion, number of myofiber, contents of inosinic acid, phosphatidylethanolamine and phosphatidyl choline, and MyoG gene relative expression in O. niloticus of HM group were significantly decreased. Compared with the control group, the weight gain rate, muscle cohesion and contents of triglyceride and fatty acids were significantly increased in fish of the HM group; the hepatosomatic index, muscle hardness and chewiness, content of phospholipid in the fish of HM group were significantly decreased. The above results indicated that with the addition of manna oligosaccharides in high carbohydrate diet, the meat yield of O. niloticus was greatly improved, the flesh quality was improved due to elevated water holding capacity, texture and nutritional value of amino acids, but the decreased phospholipid content should not be neglected. In this study, the effects of mannan oligosaccharides on the growth and muscle quality of O. niloticus were comprehensively evaluated, with a view to broadening its application as a feed additive.

Abstract:The aim of this study is to study the effects of palygorskite, a new antibacterial substance, on the growth performance, digestibility, antioxidant capacity and intestinal microbiota of Litopenaeus vannamei. The juvenile shrimp with an initial weight of (0.17±0.01) g were selected and fed with diets with 0% (control), 0.1% (S1), 0.2% (S2), 0.4% (S3), and 0.8% (S4) palygorskite, respectively, as well as the antibiotic control group diet (E) containing 0.2% enrofloxacin and were cultured for 8 weeks. The weight gain of shrimp in the palygorskite treatment groups did not increase significantly, but the survival rate of shrimp in the S1 and S2 groups was significantly higher than that in the control group, and there was no significant difference from the E group. Compared with the control group, the palygorskite supplementation groups showed increases in the activities of intestinal amylase, lipase and trypsin, as well as the lipase activity in the hepatopancreas of juvenile shrimp. The serum acid phosphatase and alkaline phosphatase activities in the S2 group were significantly higher than those in the control and E groups. The hepatopancreas superoxide dismutase activity of the S3 or S4 groups was significantly higher than that of the other groups. The α diversity analysis of intestinal microbiota showed that the Chao1 index of intestinal microbial richness decreased in the S2 group, but the coverage increased significantly. Compared with the control group, the abundance regulation of some genera in the S2 group was similar to that of enrofloxacin compared with the E group. According to the difference analysis of metabolic pathways and the mapping of interspecific relationships, palygorskite can upregulate 4 pathways of taurine, glutathione, galactose and fatty acid metabolism and increase the cooperation ability among intestinal microbes. Adding 0.1%-0.2% palygorskite to the diet can significantly improve the survival rate, digestibility and hepatopancreas antioxidant capacity of L. vannamei and play a role similar to that of enrofloxacin in regulating the abundance of intestinal microbiota in shrimp.

Abstract:Echo-sounder buoys can provide accurate geographic positioning of drifting fish aggregating devices (DFADs) and estimates of tuna stock biomass for tuna purse seine fisheries remotely and on a continuous basis, effectively reducing the "carbon footprint" of the purse seine fleet in searching for fish and fleet operating costs, thereby increasing the success of the fleet currently, DFADs-based tuna purse seine catches account for 54% of the total tuna purse seine fishery catch. In addition to its commercial application, the echosounder buoy has the potential to serve as a scientific platform for observing pelagic biodiversity, providing data to describe pelagic fish activity patterns for scientific research, helping to improve understanding of the accompanying behavior of DFADs, as well as the potential to develop an abundance index for tuna stock assessment independent of fisheries data. This paper firstly introduces the definition, types and structures, ecological impact and related management measures of DFADs, as well as the evolution, categories and data structure of echo-sounder buoys. The application of echo-sounder buoys in tuna purse seine fishery was reviewed from the aspects of: biomass assessment, fish association behavior and ecological impact posed by DFADs. Among them, tuna floating objects associated schools are analyzed and discussed in terms of the rapidity and persistence of tuna aggregation of DFADs, while the colonization time is the main indicator of the rapidity of tuna aggregation, and the continuous residence time and colonization rate are the key indicators of the persistence of tuna aggregation. The ecological impact assessment of DFADs mainly discusses the impact of DFADs stranding events, the number of DFADs deployment and DFADs bycatch on the marine ecological environment. This paper prospects the echo-sounder buoys on technical support in the future to reduce the target species and species, the development trend of the juvenile mortality from fishery resources and the sustainable management and marine biodiversity protection discussed combining fishery resources assessment data buoy observation data and to explore the climate change and human activities on the marine ecological influence the huge potential of the ecological system.