Abstract:One of the basic requirements for conducting fishery stock assessment and management research is to obtain effective fishery and biological information for target species. Length frequency distribution (LFD) can provide insight into fishery population dynamics and is easier to collect compared with other data type such as age structure and abundance index. However, it is hard to determine the effective sample size required to describe the length structure for specific fish stock. The quantitative relationship between the precision of LFD and the sample size of fish length data could be regarded as an indicator to optimize the sample size of fishery survey design. In order to quantify and compare the relationship between the precision of LFD and sample size of fish length data for three commercial fish species (Larimichthys polyactis, Pennahia argentata and Harpadon nehereus) on the Wentai fishing ground, a simulation study was conducted to calculate the mean square difference (MSD) of LFD based on actual sample size and various simulated sample sizes based on observed length data collected during spring and summer on the Wentai fishing ground. The simulation study assumed that the observed length data are able to reflect the true length structure for three species. In addition, t-test was used to examine the significant difference of mean length for three species in spring and summer. The results showed that, ① Factors such as biology difference and seasonal variation would affect the relationship between the precision of LFD and sample size. All three species showed significant difference of mean length in spring and summer. The dominate length ranges for three species were different between two seasons. ② The accuracy for estimating the precision of LFD would be impacted by the setting numbers of size bin. The MSD values increased with the number of size bin when sample size was small and this relationship did not have seasonal variation. We recommend setting 10 size bins when the effective sample size was set at 50. ③ The precision of LFD could be considered as an effective indicator to optimize sample size. Given the assumption that 50 fish samples per each station can reflect the true length structure for three species in this study, we recommend setting the sample size at the range of 30-40 individuals for L. polyactis, 42-48 individuals for P. argentata and 34-40 individuals for H. nehereus in spring.

Abstract:Seafood is rich in nutrients and is a source of high-quality healthy diet. The development of a seafood-based food strategy through fisheries has the potential to make a significant contribution to global food and nutrition security. However, due to human overfishing and environmental pollution, the marine ecosystem has been greatly damaged, and the sustainable development of marine fisheries is facing many challenges. China is the largest aquaculture country, and aquaculture accounts for the largest proportion in the seafood industry. However, due to the relatively backward aquaculture technology, farmers lack of professional scientific knowledge and imperfect management in the aquaculture industry, serious water eutrophication, water dissolved oxygen parameters reduction, antibiotic abuse and other issues have caused serious environmental burden to the aquaculture water. Artificial seafood is an inevitable trend in the context of social economy, environmental sustainability, and food nutrition safety. It can solve many problems and overcome disadvantages caused by the current traditional seafood industry, including fishing and freshwater aquaculture, and it is the mainstream direction of food in the future.
Artificial seafood meat is mainly divided into two kinds: one is the plant-based seafood meat which is synthesized by extracting high-quality protein, fat and pigment from plants, and the other is the cultured seafood meat which comes from the proliferation and differentiation of stem cells of marine organisms. The main raw material of vegetable meat is protein. The intake of high-quality and high-content protein products can not only meet people's dietary nutritional needs, but also help to improve blood glucose indicators, protect the heart, reduce body weight and reduce the risk of chronic diseases. Cultured meat has great advantages in energy saving, emission reduction and safety, which give a strong impetus to the research of artificial seafood.
In this paper, the development status of artificial seafood meat was summarized, and the research and development process was analyzed emphatically. It is expected that the development and promotion of artificial seafood meat can be promoted through the integration of traditional ideas and new technologies, and win wide recognition from the public.
In order to realize the large-scale production of artificial seafood and meet the human demand for seafood, it is necessary to make good use of the three major sciences of foodomics, food synthetic biology and food perception biology, strengthen technological improvement and innovation, solve the problems in the process of cell culture, and develop a bioreactor suitable for stable proliferation and differentiation of various cells into muscle tissue. In addition, it is necessary to strictly control from food processing to process control and finished product testing, commit to the three major aspects of green, environmental protection, and health, and introduce artificial seafood meat food safety risk assessment and market supervision and management policies as soon as possible, which is of great significance for ensuring the safety of food supply and improving food biological manufacturing technology.

Abstract:Compared with the traditional aquaculture system, three-dimensional cultivation is a potential sustainable cultural pattern that integrates aquaculture with hydroponics in which nitrogen-rich effluent from the fish production is utilized for plant growth. Environmental microbiota plays an important role in the intestinal microbiota of aquatic animals. The association among water, sediment and obscure pufferfish (Takifugu obscurus) intestine under two cultivation patterns should be investigated to reveal the microbiota differences. The aim of the study was to understand the bacterial community structure in different cultural patterns of Takifugu obscurus. Here we compared the microbial community structure with composition variation of water, sediment and the intestine of T. obscures in different cultural patterns to explore the relationship among them. The aim of this study is to provide a reference for the further study of microbiota in the three-dimensional cultivation pattern. Illumina MiSeq high-throughput sequencing method was used to sequence and analyze the two high-variation regions (V3-V4) of 16S rRNA gene of microbia of the water, sediment and intestine of T. obscurus in two cultural patterns (the traditional aquaculture and three-dimensional cultivation). The interactions between water microbia and water environment were analyzed by redundancy analysis (RDA). The interactions between intestine microbial and water environment were analyzed by canonical correlation analysis (CCA). The richness and diversity of the bacterial community of water, sediment and intestine of T. obscurus under three-dimensional cultivation patterns were higher than that in the traditional cultural pattern. The bacterial community structure of water and sediment under three-dimensional cultivation patterns was similar to that in the traditional cultural pattern. Actinomycetes (36.19%), Proteobacteria (26.38%), Cyanobacteria (12.23%), and Bacteroidetes (12.06%) were the dominant phyla in water. Proteobacteria (50.73%) and Bacteroidetes (12.48%) were the dominant phyla in sediment. The dominant genus was Rhodococcu (88.23%) in the intestine in the traditional cultural pattern. However, Staphylococcus (28.93%), Arcobacter(25.36%), norank_f_norank_o_Chloroplast(13.31%), Elizabethkingia (8.56%) and Mycoplasma (5.32%) were the dominant genera in the intestine in three-dimensional cultivation pattern. The results of correlation analysis of environmental factors showed that pH had a significant effect on the water bacterial community. The dominant genus Rhodococcus in water were positively correlated with total suspended solid (TSS), total phosphorus (TP), total nitrogen (TN), pH and nitrate. Total ammonia nitrogen (TAN) had a great influence on the intestine bacterial community of T. obscurus. Rhodococcus and Arcobacter as the dominant bacteria in the intestine were in positive correlation with TSS and TP. Acinetobacter and Mycoplasma were in positive correlation with TAN, nitrite and nitrate. Weissella and Staphylococcus were in negative correlation with TSS, COD, TP, TN, nitrate, nitrite and TAN. The research showed that the use of three-dimensional cultivation pattern could improve the diversity of bacteria in the aquacultural ecosystem, reduce the risk of disease outbreak, inhibit the growth of Cyanobacteria, and reduce the oxidative stress damage to aquaculture objects. Furthermore, the cultural patterns could have a certain effect on water and T. obscurus intestine bacterial community by changing nitrogen and phosphorus concentration in the water．

Abstract:To explore the differences of intestinal microbiota for Litopenaeus vannamei in different culture patterns, bacterial diversity and bacterial community composition of L. vannamei from different culture patterns including freshwater pond (FWP), seawater pond (SP), high-intensive pond (HP) and biofloc technology pond (BFP) were studied by using the 16S rRNA gene amplicon sequencing technology in this study. The results showed that the α-diversity indexes of FWP and HP were significantly higher than those of SP and BFP. The relative abundances of intestinal microbiota compositions were significantly different among the four culture patterns. Proteobacteria had the maximal abundance in SP, BFP and HP culture patterns and contributed to the biggest differences for the four culture patterns. The abundance of Cyanobacteria in FWP culture pattern was far higher than that in other culture patterns. Vibrionaceae (Proteobacteria) and Mycoplasmataceae (Tenericutes) were the top two abundant families of core microbiota among the four culture patterns. In addition, the indicators of different culture patterns were different. The indicator group of intestinal bacteria in FWP culture pattern was Propionibacteriaceae, and it was Flavobacteriaceae in BFP culture pattern. Co-occurrence network analysis found that the interactions of intestinal microbiota in the HP culture pattern were higher than that in other three culture patterns, and the co-occurrence network of FWP was the most stable.

Abstract:The geoduck clam Panopea japonica is of high commercial potential. Currently, its sales in China account for over 90% of its global sales and all the geoduck clams sold in the Chinese market are imported from Sea of Japan. However, artificial breeding of P. japonica on a large scale is rarely reported. This study for the first time tried artificial breeding of the geoduck clam P. japonica in an indoor hatchery in spring and autumn. Growth and development of the artificially bred P. japonica in the two different seasons were compared as well. The results showed that for the parental P. japonica, the reproduction peak period was observed in May and October, with a single spawning amount of (3×10⁶) - (5×10⁶) eggs/female and an egg diameter of 75-85 µm. In spring, when the water temperature was raised to 18.6-19.0℃, the lowest growth rate was observed in 6-9 days old and 15-18 days old individuals, with a daily growth rate of shell length at 1-3 μm/day. For the larvae at other growth stages, average growth rate of shell length was 9-15 μm/day. After 30-40 days’ cultivation, P. japonica developed into the juvenile stage and the average shell length reached (4.94±0.93) mm. For juveniles, the average growth rate of shell length was 50-167 μm/day. In spring, average production was 2 695 spat/m³. Fertilization rate, hatching rate, larval survival rate, metamorphosis rate and juvenile survival rate of P. japonica artificially cultivated in spring were 89.60%±3.21%, 38.60%±3.77%, 13.40%±1.52%, 29.80%±4.82% and 40.60%±1.74%, respectively. In autumn, the water temperature was from 17.4 ℃ to 13.2 ℃. Growth and development of larval P. japonica were relatively slow and after 148 days’ cultivation, average shell length of the juveniles reached (2.88±0.47) mm and average production was 6 666 spats/m³. Fertilization rate, hatching rate, larval survival rate, metamorphosis rate and juvenile survival rate of P. japonica artificially cultivated in autumn were 95.20%±1.92%, 14.60%±2.41%, 70.60%±5.46%, 59.20%±3.35% and 70.40%±2.30%, respectively. Then the spat was transferred to outside pool for further cultivation, which could eventually reach (13.22±2.39) mm. In comparing the growth and development of the artificially bred P. japonica in spring and autumn in Northern China, large size seeds suitable for bottom sowing could be produced in autumn at a relatively low cost. This study has provided a scientific basis for larval breeding, high-efficient cultivation and resource restoration of P. japonica in China.

Abstract:This trial was conducted to evaluate the effects of dietary Enteromorpha prolifera ( EP ) with different fishmeal inclusion on growth and flesh quality of Pacific white shrimp (Litopenaeus vannamei). This trial was designed with 2×3 factors, and two basal diets were designed to contain 18% (A) and 15% (B) fishmeal. Then the EP was added in both basal diets at the levels of 0, 3%, 6% to form six isonitrogenous and isoenergetic diets with crude protein content of 38.5%, referred to as A0, A3, A6, and B0, B3, B6, respectively. A total of 6 treatments was conducted with 4 replicates per treatment and 50 L. vannamei per replicate. After 8 weeks of feeding, the growth performance, body composition, nutrient utilization, flesh water-holding capacity and texture property of the L. vannamei were measured. The results showed that both fishmeal and EP levels in diets significantly affected the final body weight, weight gain rate (WGR) and feed conversion ratio (FCR) of shrimp. The A0 group had a final weight of 22.6 g with the highest WGR (654.2%) and the lowest FCR (1.61)，while the B6 group had a final weight of 20.8 g with the lowest WGR (595.7%) and the highest FCR (1.81) among the six groups. The supplementation of 3% EP in both basal diets did not significantly affect the growth performance, while the supplementation of 6% EP significantly decreased the WGR, increased the FCR. At the same supplementation level of EP, the WGR of 15% fishmeal groups (B groups) was numerically lower than that of 18% fishmeal groups (A groups). The EP level significantly affected the crude protein and crude lipid content of whole shrimp. The crude protein content of A6, B0, B3 and B6 groups was significantly lower than that of A0 group, and the crude fat content of A6 and B6 groups was significantly lower than that of A0 and B0 groups. The fishmeal and EP levels in diets significantly affected the protein efficiency ratio (PER) and protein retention efficiency (PRE), and the EP level also significantly affected the lipid retention efficiency (LRE) and apparent digestibility coefficient of crude protein (ADCCP). The PER, PRE, LRE and ADDCP of A3, A6 and B3, B6 groups were significantly lower than those of A0 and B0 groups respectively. In terms of flesh quality, the supplementation of 6% EP significantly reduced the cooking loss and thawing loss, and increased the flesh collagen content. The flesh hardness and chewiness of A3, A6 and B6 groups were also significantly higher than those of A0 and B0 groups, respectively. In conclusion, the supplementation of 3% EP in diet did not significantly affect the growth of L. vannamei, and 6% EP supplementation improved the flesh quality, although this supplementation reduced the weight gain and feed utilization.

Abstract:Nowadays, in aquaculture, the popularity of antibiotics and the increase in the use of other drugs have made it easier for residual antibiotics and drugs to invade natural water bodies. The environmental effects of antibiotics in the ecosystem have caused more and more pollution to the water environment and threatened the survival of aquatic organisms. After strict regulation and control of the use of antibiotics, the use of genetically modified vaccines that can replace antibiotics has become more and more common. Cyanobacteria is a natural bait for shrimp seedlings. Directly feeding Litopenaeus vannamei with Synechococcus-expressedvp28 to control WSSV can play a role of “medicinal and food homology”. However, the problem facing the current application of transgenic cyanobacteria as a subunit vaccine is the safety of its environmental release. Danio rerio is one of the most commonly used model creatures. In the previous Synechococcus-expressedvp28 oral vaccine efficacy experiment, the feasibility of the oral vaccine was verified, showing that its efficacy and safety can be trusted. This environmental release experiment was built on this basis. In this study, Synechococcus-expressedvp28 were administered to L. vannamei to verify the effect of its dose gradient against WSSV and to determine its half effective dose (ED₅₀). After feeding D. rerio on the basis of this ED₅₀, the effects of the Synechococcus-expressed vp28 on aquatic organisms and water environment were explored by measuring the enzymatic indicators in D. rerio, observing the tissue sections, and the changes in nitrogen and phosphorus in the aquaculture water. The results of the study showed that with the increase of the dose of Synechococcus-expressedvp28 oral vaccine, the anti-WSSV efficacy of L. vannamei also increased and the measured ED₅₀ was 0.027 g. Feeding D. rerio by freeze-dried wild-type and transgenic Synechococcus with the shelled-out Artemia for 15 days, the body length and color of D. rerio were not significantly different. The CAT in the transgenic group was significantly lower than that blank and wild-type groups. There was no significant difference in SOD and POD between wild-type and transgenic groups. There was no significant difference in the liver and heart of D. rerio through the tissue section. The ammonia nitrogen in wild-type and transgenic groups was lower than that in the blank group, and there was no significant difference between total nitrogen and total phosphorus. The results of this study further showed that the Synechococcus-expressed vp28 can effectively enhance the anti-WSSV ability of L.vannamei, and as its dose increases, the disease resistance has a more significant expression. In the current experimental results, there is no obvious toxicological effect on D. rerio, and after feeding with Synechococcus-expressed vp28, it does not show a significant effect on the quality of aquaculture water. This shows that this subunit vaccine has less impact on aquatic organisms, and can provide a basis and more possibilities for subsequent industrial-scale applications and development.

Abstract: Hox gene clusters play an important role in the early embryonic development, tissue differentiation and morphogenesis in animals. Megalobrama amblycephala, also known as Wuchang fish, is an economically important freshwater fish and widely distributed in lakes in the middle and lower reaches of the Yangtze River in China.In order to explore the Hox distribution, evolution and expression patterns in M. amblycephala, we conducted a series of analyses based on the whole genome M. amblycephala. In the present study, we identified all the Hox clusters of M. amblycephala from the whole genome data. Combined with the multiple methods, we analyzed chromosome distribution and constructed the Hox phylogenetic tree based on protein sequences. In addition, the expression patterns of Hox in different tissues were further investigated by calculating the number of transcriptional fragments (FPKM).The results showed that 49 Hox genes were identified in the genome of M. amblycephla, and were divided into 7 groups: HoxAa, HoxAb, HoxBa, HoxBb, HoxCa, HoxCb and HoxDa. Transcriptome results indicated that M. amblycephala Hox gene family had different expression patterns. There were significant differences in the expression level of all Hox genes in the muscle of M. amblycephala and Danio rerio, while the expression pattern was similar. In the HoxA cluster, HoxA10b, HoxA3a, HoxA2a and HoxA1a were highly expressed in the muscles of M. amblycephala, and the expression level was higher than that of D. rerio; HoxA13a and HoxA13b are not expressed in the muscle of both of fishes; In the HoxB cluster, HoxB10a, HoxB9a and HoxB7a were highly expressed in muscle tissue of M. amblycephala, while HoxB9a, HoxB8a, HoxB7a and HoxB6a were highly expressed in muscle tissue of D. rerio. In the HoxC cluster, HoxC9a, HoxC2a, HoxC3a and HoxC6b are highly expressed in muscle tissue of M. amblycephala and HoxC8a and HoxC3a are highly expressed in D. rerio, while HoxC13a, HoxC12a, HoxC11a, HoxC4a, HoxC1a, HoxC13b, HoxC12b and HoxC11b are very low or even not expressed in muscle tissue of the two fish species; In the HoxD cluster, HoxD10a, HoxD9a and HoxD3a are highly expressed in muscle tissue of M. amblycephala and HoxD9a is highly expressed in D. rerio, while the expression levels of HoxD13a, HoxD12a and HoxD11a are not expressed in muscle tissue of M. amblycephala and HoxD13a is not expressed in muscle tissue of D. rerio. In addition, comparative transcriptome analysis of three embryonic stages and three tissues of M. amblycephala indicated that HoxA2a, HoxA3a, HoxB9a, HoxB3a, HoxB8a, HoxB1b, HoxB5a, HoxB5b, HoxC3a and HoxC4a were highly expressed at the juvenile fish, while others showed low or even no expression in muscle, intermuscular bone and connective tissues except HoxB7a, HoxB10a and HoxB9a, HoxC3a and HoxC8a. In the HoxD family, HoxD9a, HoxD10a and HoxD11a were expressed in the stage II of embryo. Taken together, these results may lay the foundation for further exploring the function of the Hox gene family of M. amblycephala, and may also provide reference data for other fish Hox studies. In addition, studying the expression patterns of Hox in the formation of intermuscular bone of M. amblycephala also provides reference and theoretical basis for the study of intermuscular bone in other bony fishes.

Abstract:Myxozoa are microscopic parasites that principally infect fish. Some species can cause serious fish disease leading to great economic losses. Thelohanellus kitauei is one of those pathogenic species found in many areas. To clarify the genetic variation and phylogenetic relationships among different geographic strains of T. kitauei. Comparative analyses were conducted on strains of T. kitauei from Chongqing of China, Hubei of China, Shioda of Japan, Jeonbuk of Korea and Seoul of Korea based on their morphology. The comparison and analyses were also conducted for their site variation, similarity, genetic distance, genotype and phylogeny based on 18S rDNA sequences. The morphological characteristics of strains of T. kitauei from different localities were generally consistent. Among different strains, the similarities were 99.5%-100.0%, variation sites were 0-6, genetic distances were 0.000-0.004, based on 18S rDNA sequences. The phylogenetic analysis showed that thelohanellids with membrane sheath clustered as a clade and the remaining thelohanellids without membrane sheath clustered as another clade. The clade without membrane sheath was divided into fin-infection group and gill-infection group. The membrane sheath should not be used as a valid feature for species identification of T. kitauei whose identification should still be according to its morphology and morphometry of the spore excluding membrane sheath. Though the shape and size of membrane sheath was unstable, its presence or absence on thelohanellids might associate with phylogeny of thelohanellids. And the evolution pattern for clade possessing membrane sheath might be different from the clade without membrane sheath. The strains of T. kitauei did not form special differentiation in different parasitic sites and also did not form monophylies in different localities. The reason for this genetic situation might be: the isolation time was not long enough or there was the high frequence of gene flow among different strains which led to limited population differentiation.

Abstract:Cryptochrome (Cry) is a kind of blue violet light receptor, which widely exists in animals, plants, bacteria and human body. At present, the research on cry mainlmainly focuses on its biological function, but rarely reported in crustacean biological rhythm. Exopalaemon carinicauda is a unique marine economic shrimp in China. Studying and understanding the circadian clock genes will help deepen the understanding of the biological clock regulation mechanism of crustaceans represented by E. carinicauda. The results showed that the full length of cry1 in E. carinicauda was 2 190 bp, the open reading frame was 1 845 bp, the 5 'noncoding region was 241 bp, and the 3' noncoding region was 104 bp. A total of 614 amino acids were translated. The predicted molecular weight of the protein was 70.5 ku and the theoretical isoelectric point was 5.09. After analyzing the amino acid sequence of Cry1, it was found that the Cry1 contains a structure homologous to DNA photolyase at 117-246 aa of N-terminal and a FAD binding domain at C-terminal. Homology analysis showed that the cry1 of E. carinicauda shared the highest homology with Litopenaeus vannamei and Euphausia superba (71.6% and 68.3%, respectively). Results of qRT-PCR analysis showed that cry1 of E. carinicauda was expressed in eyestalk, gill, heart, stomach, hepatopancreas, gonad, muscle, intestine and ventral cord nerve, and the expression level of eyestalk was the highest. The expression results at different time periods showed that the expression level of the cry1 in the eyestalks of E. carinicauda firstly decreased with the increase of the light time within 0-24 h, then began to increase after the lowest value at 9 h, and then decreased at 18 h. To the second trough, and finally re-entering the dark period, there is a significant increase again, and it was consistent with the more active rhythm of the E. carinicauda in the dark phase. After performing RNA interference under different light color conditions, the expression of cry1 in RNA interference group was significantly lower than that in control group under two light color conditions, which indicated that the expression of cry1 gene was successfully interfered in this study. The expression of cry1 in blue light was significantly higher than that in white light at 3-6 h after injection, but decreased at 9-24 h. The difference indicates that the cry1 is involved in the light signal transduction process under both blue and white light conditions, particularly involved in responding to the blue light periodic rhythm. This study provides a theoretical basis for in-depth exploration into the regulatory mechanism of crustacean circadian clock in the current situation where there is little research on crustacean circadian clock genes.

Abstract:High performance liquid chromatography-tandem mass spectrometry of thiamphenicol in various tissues of Ictalurus punctatus was established in this study. This method has a linear correlation in the concentration range of 5-100 ng/mL, with a correlation coefficient of 0.998. The average recovery was 79.05%-95.58%, and the relative standard deviation was between 2.01% and 9.36%. The quantitative limits of thiamphenicol were 5.0 μg/L in plasma, and 5.0 μg /kg in muscle, skin, kidney, and liver. The pharmacokinetics of thiamphenicol in I. punctatus was investigated after oral administration with a single dose of 17.5 mg/kg body weight at the water temperature of 28 ℃. The concentration of thiamphenicol in each tissue was determined by high performance liquid chromatography-tandem mass spectrometry, and the data were processed by 3p97 pharmacokinetic software. The results showed that concentration-time data in plasma was described by a first-order absorption with two-compartment model. The T_peak was 8.00 h, the C_max was 933.75 μg/L, the AUC was 12.10 mg/L, the T_1/2β was 69.32 h and the T_1/2ka was 4.97 h. Pharmacokinetic results showed that thiamphenicol was distributed in a two-compartment model in the channel catfish, which was eliminated by first-order pharmacokinetics. The absorption, distribution and elimination of thiamphenicol in channel catfish were relatively fast. The study manifested that the mode of administration and precise administration dosing were also important in the control of channel catfish disease. The method is simple and reliable, and meets the requirements for the determination and pharmacokinetic study of thiamphenicol. The data are of great benefit for practical applications of thiamphenicol in channel catfish.

Abstract:By establishing a viable and efficient technique for culturing hypothalamic neurons in vitro, in order to lay the foundation for studying the feeding mechanism and energy metabolism of mandarin fish, the hypothalamus of mandarin fish was isolated and digested into single cell suspension by type I collagenase. The cell morphology was observed on the 3rd, 4th, 5th and 6th day of culture and the results showed that on the third day of culture, the number of cells was small, the cell body was small and single distribution; on the 4th day of culture, the number of cells increased significantly, with typical neuron morphology and full cell body; on the 5th day, the fusion degree of the cell body increased, the bulge increased, and many branches connected with each other to form a dense network of nerve fibers; on the 6th day, the activity of cells decreased and apoptosis began. CCK-8 method was used to detect the cell activity. The results showed that the cell activity was the highest on the 5th day of culture. Two methods were used to identify neurons, the RT - PCR showed that cultured hypothalamic cells could express noggin, and the purity of neurons in hypothalamus was 95.9% by immunofluorescence. These results show that the neurons in the hypothalamus of mandarin fish with high purity can be obtained by this culture method, which lays a foundation for further study on the feeding mechanism and energy metabolism mechanism of mandarin fish at the cell level.

Abstract:Sea bass (Lateolabrax japonicus) is an economically important marine species widely cultured in Asia. Due to the high content of water and protein in fish, it is susceptible to the influence of microorganisms, fat oxidation and endogenous enzymes during circulation, resulting in quality deterioration. Freezing was a common storage method, but the increase of ice crystals can easily cause quality loss such as low water holding capacity, protein denaturation, and microstructure damage. Iced storage, which can effectively inhibit the growth of microorganisms, has gradually become one of the primary methods for prolonging the shelf life of L. japonicus. In recent years, there have been many studies on quality change in fish fillets during frozen storage, while there were few studies on the correlation between changes in freshness and protein biochemical properties of L. japonicus. Therefore, the quality change mechanism of L. japonicus during iced storage needs to be further explored. In this study, the effects of storage time on the freshness and protein biochemical properties of L. japonicus fillets during iced storage were investigated. The value of sensory characteristics, pH, texture, color, thiobarbituric acid (TBA), total volatile based nitrogen (TVB-N), total viable count (TVC) and protein content, SDS-PAGE, sulfhydryl and carbonyl contents of L. japonicus fillets were measured periodically to analyze changes of L. japonicus fillets during iced storage. And correlation analysis between the main freshness indicators and biochemical characteristics of myofibrillar protein were conducted. During the storage, the brightness of L. japonicus fillets values decreased from 57.92±0.66 to 46.62±1.54, the redness values decreased from −(4.34±0.39) to −(5.21±0.08), the hardness values decreased (174.92±16.80 to 122.25±15.73) significantly, the pH increased in the early stage and then decreased. Moreover, the value of TBA and TVB-N value increased from (0.35±0.01) mg/kg and (9.41±1.03) mg/100 g to (0.97±0.04) mg/kg and (33.18±0.83) mg/100 g, respectively. After 16 d of storage, the TVC was increased to (6.35±0.41) lg (CFU/g), which exceeded the secondary freshness standard, and the sensory score was unacceptable. The content of myofibrillar protein and sulfhydryl decreased from (104.21±3.42) mg/g and (145.81±1.02) mmol/g prot to (72.03±5.25) mg/g and (137.28±1.29) mmol/g prot, respectively. While the carbonyl content increased from (0.63±0.03) nmol/mg to (1.45±0.06) nmol/mg. The SDS-PAGE pattern of myofibrillar protein showed a new protein band around 30 ku, which may be the degradation product of troponin T. Troponin T, which was involved in the contraction of striated muscle bound by myosin, may be phosphorylated, improving the activity of endogenous protease and promoting the degradation of troponin in the late storage period. Moreover, the 90 ku protein band I almost completely disappeared, and the protein may be completely degraded by endogenous proteases. Correlation analysis showed that the correlation coefficients remain high between TBA value, TVC, protein content and carbonyl content. TBA were significantly negatively correlated with protein content, which may be related to the large amount of non-heme iron, which was released after the denaturation of myoglobin and hemoglobin, promoted fat oxidation. The content of myofibrillar protein was significantly decreased on the 16^th day, and the protein appeared significantly degraded in the pattern of SDS-PAGE. This result was consistent with the significant negative correlation between the TVB-N value and the protein content. The structure of myofibrillar protein of fish was easily destroyed during the long-time storage, and the hydrophobic residues were cross-linked to form insoluble aggregates, which reduced the solubility of the protein. In addition, the content of myofibrillar protein was significantly negatively correlated with the content of carbonyl groups. Active oxygen could cause the oxidation of amino acid side chains and protein backbones, leading to protein breaks or protein cross-linking aggregation. These modifications would also reduce the solubility of protein, which was not conducive for the freshness of fish. The results of this study showed that the L. japonicus fillets reached the inedible level after 16 days of iced storage. The freshness indexes of L. japonicus fillets all had a good correlation with storage time apart from pH value. These indexes can be used to characterize the freshness quality of L. japonicus fillets during iced storage. Mass reproductive microorganisms and the interaction between lipids oxidation and protein oxidation in the late ice storage may be the main reason for the quality deterioration. Studies also found that there was a good correlation between the freshness index, protein degradation, protein oxidation and fat oxidation of fillets during iced storage. In the future, metabolomics, proteomics and other omics can be used to further identify different characteristic biomarkers related to metabolites and oxidized proteins. Mass spectrometry and bioinformatics could also be used to further analyze the new bands appearing in the electrophoresis pattern, and the protein of fish muscle myofibril during storage can be further identified. In future, the molecular mechanism of proteins degradation and oxidation could be investigated in depth. And the mechanism of fish softening still needs further exploring, including the interaction relationship between activity of proteases and microorganisms. In addition, it can be seen that the seabass fillets exceeded the acceptable range when they were frozen to 16 days from the sensory score and some other indexes of freshness, while the TVB-N value was still within the edible limit. Accordingly, although the traditional quality detection methods are rigorous and scientific, there is a significant lag in the detection of aquatic products, and a single indicator could not be a reliable indicator for the freshness identifying of fish samples. Therefore, electronic noses and hyperspectral imaging, nuclear magnetic resonance and other new technologies, combined with different modeling methods, are promising ways to be used to evaluate and predict the shelf life of different aquatic products.

Abstract:Antarctic sea ice vatiation can have direct or indirect effects on the environments and a variety of marine organisms. The Sea Ice Extent was considered as an index to indicate the changes in Antarctic sea ice, and in this study, its impacts on fishing ground of Argentine shortfin squid Illex argentinus in the Southwest Atlantic Ocean were explored. In this study, the catch per unit effort (CPUE) was used to indicate squid abundance, and we evaluated the influences of sea ice extent and sea water temperature at different depths on stock variations of I. argentinus, based on the fishery data from January to June during 2013-2018 obtained from the Chinese squid-jigging Science and Technology Group as well as the sea ice extent data and the sea water temperature data of 5 m, 55 m, 95 m and 195 m depth on the fishing ground. The results indicated that the catch, CPUE, sea ice extent, sea water temperature at different depths exhibited significant annual and monthly variations. The correlation analysis suggested that Antarctic sea ice extent was positively correlated with CPUE on an annual and monthly scale. Sea ice extent was negatively correlated with annual and monthly sea water temperature at the depth of 5 m, but was positively correlated with sea water temperature at the depth of 95 m. Based on the histogram analysis, the monthly suitable and the most preferred sea water temperature for I. argentinus were evaluated at different depths. Positive relationship was found between the monthly percentages of suitable temperature at different depths accounting for the whole fishing ground and the sea ice extent, suggesting that the sea ice extent would affect the proportions of suitable habitats at different depths and further affect the abundance of I. argentinus. Our findings indicated that sea ice extent would have significant impacts on sea water temperature at different depths, and would further affect the fishing ground distribution and also squid abundance.

Abstract:In order to understand the mechanism and influencing factors of high pressure jet cavitation of nozzle in a submerged environment, this study has focused on the evolutionary process of cavitation bubbles and combined finite volume method with mixed multi-phase flow model to analyze the cavitation, velocity distribution, and experimental cavitation intensity of fishing net cleaning equipment. The results show that the cavitation inception, growth, and collapse primarily occurred in the peripheral region of the flow field. The shape of cavitation erosion zone is the shape of ring on the test sample target. Several small dense erosion pits were densely distributed in the ring-shaped erosion zone and erosion marks were observed in the center. The cavitation erosion intensity is greatly affected by the nozzle structure, and compared with inlet diameter D=4-6 mm nozzle, the maximum vapor volume fraction of D=3 mm nozzle increased by 6.4% to 19.5%. The nozzle outlet enlargement angle greatly increased the cavitation intensity. The nozzle with an outlet angle of 30° exhibited an optimal cavitation erosion performance . With the same nozzle necking diameter and the aspect ratio n=3-6, the increase of the aspect ratio increases the cavitation intensity of the nozzle, and compared with aspect ratio n=4-6 nozzles, the maximum volume fraction of nozzle increased by 16.9%; The larger the nozzle outlet diameter d is, the less the influence degree of the aspect ratio on cavitation is; The influence degree order of nozzle structure, nozzle diameter D, outlet angle α and the aspect ratio n for cavitation intensity is α>D>n.