Beidou vessel monitoring system (VMS), which monitors fishing operations of vessels by vessel position characteristics, can provide scientific references for the development and management of fishery. We explored the large-size light falling-net fishery in the South China Sea based on VMS data in 2018. Beidou VMS obtained a total of 8 821 681 records of 121 vessels from Guangdong, Guangxi and Hainan Provinces, with an average of 406 records per vessel per day. There is a difference in the frequency of Beidou VMS transmission among the vessels from different provinces, and VMS signals were more frequently transmitted when a vessel was operating in the open South China Sea than when it was fishing along the coast. The vessels mainly operated fishing in the Nansha Islands in spring, off the Pearl River Estuary in summer, and in the Beibu Gulf and Zhongsha and Xisha Islands waters in autumn and winter. In 2018, the vessels operated 19 986 fishing days in the South China Sea, decreasing from 7 768 d (38.87%) in spring, 4 738 d (23.71%) in autumn, 4 406 d (22.05%) in winter to 3 074 d (15.38%) in summer. Moreover, we discussed the advantages and disadvantages of Beidou VMS in monitoring the large-size light falling-net vessels. It is showed that using Beidou VMS to study the large-scale light falling-net vessel in the South China Sea can monitor their spatial distribution and dynamic changes quickly and comprehensively.
Jiangmen is located in the southwest of the Pearl River Estuary. It is the spawning ground and nursery ground for various small fish. We identified the species of fish eggs from Jiangmen coastal waters of the Pearl River Estuary in sping based on DNA barcoding analysis, then described and preliminarily classified the morphological characteristics of fish eggs. We acquired a total of 13 taxa, which belonged to three orders and ten families. Four and eight taxa were identified to species and genus levels, respectively (Ambassis gymnocephalus, Gerres limbatus, Sillago sihama, Cynoglossus puncticeps, Sardinella sp., Stolephorus sp., Acanthopagrus sp., Alepes sp., Johnius sp., Sillago sp. and Cynoglossus sp.). One taxon was identified in family (Leiognathidae sp.). The results demonstrate that most fish eggs collected in the survey area can be classified by morphological characteristics such as shape, fish eggs size, perivitelline space, number and pigment distribution of oil globules. In addition, the colour, amount and distribution of pigments of the embryo are also important in species identification when the embryo is well developed. However, it is difficult to distinguish the closely related species only by the morphological characteristics of a single developmental stage. Further morphological studies should be conducted in the future.
To protect the genetic diversity of a critically endangered species Ochetobius elongatus, taking seven individuals of O. elongatus collected from the field investigation in the Yangtze River as samples, we sequenced two mitochondrial genes (Cytb and ND2) and two nuclear genes (mhy6 and RAG2) for the seven samples by Sanger sequencing technique. Combining with the published four gene sequences of 52 O. elongatus samples in the Pearl River, we explored the genetic structure of O. elongatus between the Pearl River and the Yangtze River, so as to provide scientific support for its conservation. We applied phylogenetic analyses, haplotype networks and divergence time estimation. Phylogenetic analyses and haplotype networks reveal that O. elongatus populations in the two rivers generated two deep and independent lineages, and formed private alleles at the nuclear gene level. The results suggest that O. elongatus populations in the two rivers evolved independently without agene flow. The rapid lifting of the Qinghai-Xizang Plateau during the middle Pleistocene might be an important factor that triggered the split of O. elongatus populations in the two rivers 0.38~0.76 million years ago (Ma). In view of the strictly geographical division of O. elongatus populations between the two rivers at both mitochondrial and nuclear gene levels, we suggest that these two populations should be regarded as two evolutionary significant units, and targeted strategies should be urgently put forward to manage and protect its resources.
Prawns will make noises passively when they eat. Investigating the effects of different particle sizes of pellet feed on the characteristics of feeding sound signals of L. vannamei can provide a theoretical basis for the application of automatic feeding based on feeding sound signals. With passive acoustic method, we recorded the acoustic signals of L. vannamei (Body length of 9−10 cm) feeding pellets of different sizes (0.4, 0.8 and 1.2 mm) in the laboratory. The results of the waveform, spectrogram and spectrum map reveal that the characteristics of feeding acoustic signals by feeding pellets of different sizes were similar, and the frequencies were 5−45 kHz. The spectral frequency peak of acoustic signals of the shrimps fed with pellets of 0.4 and 0.8 mm was about 17 kHz, and that of shrimps fed with pellets of 1.2 mm was about 10 kHz. In addition, there were obvious differences in the acoustic signals between feeding Nereis succinea and pellets. The frequency range of acoustic signals of feeding N. succinea was 5−45 kHz, and the spectral frequency peak was about 7 kHz. Finally, compared with the feeding acoustic signals of L. vannamei in farming pond, it is found that the signal characteristics collected in the pond were similar with those in the laboratory, and the only difference is that there was no secondary peak in the high frequency region of signals in the pond-cultured shrimp.
Symphysodon aequifasciatus has a unique parental rearing behavior. In the previous study, two C-type lectins (CTLs) were found to be highly expressed in the skin of parent fish, but with different expression patterns. In order to investigate the difference in the potential immune functions of the specific CTLs, we cloned two CTL genes (SaCD302 and SaMBL), then simulated and analyzed their immune esponse patterns under pathological infection. The results show that the ORF region ofSaCD302 and SaMBL were 741 and 795 bp in length, encoding 246 and 264 amino acids (aa), respectively. The SaCD302 sequence contained a signal peptide (aa 1–29), a C-type lectin-like domain (CTLD) (aa 32–169) and a transmembrane domain (aa 184–206). Two low complexity regions (aa 32–92 and aa 104–121) and a CTLD (aa 137–263) were expressed in SaMBL sequence. Moreover, SaCD302 and SaMBL shared the highest similarity with that of Archocentrus centrarchus. SaCD302 was highly expressed in the head kidney, followed by the liver and gill. Compared with the intestine, liver, spleen and gonads, the skin had the higher expression of SaMBL. After Aeromonas hydrophila infection, SaCD302 expression was significantly upregulated in the spleen, head kidney, intestine and skin, whileSaMBL was only upregulated in the head kidney, intestine and skin, and these two genes were expressed in different temporal manners, indicating that they might play different roles in the immune defense of S. aequifasciatus.
In order to explore the response of apoptosis related genes in the spleen of Trachinotus ovatus infected by Streptococcus agalactiae, we infected the spleen tissues of T. ovatus by S. agalactiae for a pathological observation. The blood routine indexes of the fish before and after infection, as well as different times (0 h, 6 h,12 h, 24 h, 48 h, 72 h, 96 h, 120 h) after infection, the serum lactate dehydrogenase (LDH), spleen alkaline phosphatase (ALP), and acid phosphatase (ACP) and quantitative analysis of Caspase-3, Caspase-8, and Caspase-9 genes. The results reveal that after artificial infection with S. agalactiae, the body of T. ovatus showed obvious pathological changes, mainly manifested as protruding eyes, turbidity and bleeding. Histopathological observation shows that the spleen tissue had inflammatory lesions. Compared with the control group, the number of red blood cells (RBC), hemoglobin concentration (Hgb) and hematocrit (HCT) in the infected group decreased significantly, while the number of white blood cells (WBC), neutrophils (NE) and lymphocytes (LYM) increased, and the mean red blood cell volume (MCV) increased. The activities of serum LDH, spleen ALP and ACP were up-regulated with time. The expressions of Caspase-3, Caspase-8 and Caspase-9 were significantly up-regulated in spleen. The results show that the body of T. ovatus infected by S. agalactiae had an obvious immune response.
To investigate the function of the nanos1 gene in the reproductive development of Macrobrachium rosenbergii, we cloned its nanos1 gene. The cDNA sequence was 2 811 bp, encoding 243 amino acids. Phylogenetic analysis shows that it had the highest homology with Eriocheir sinensis, higher homology with nanos1 in fish but lower homology with mammals. We detected the expression level of the gene at different embryonic developmental stages and in larvae by real-time fluorescence quantitative PCR. The results show that the expression level of nanso1 mRNA was the highest at unfertilized stage, significantly higher than that at fertilized stage and the other embryonic developmental stages (P<0.05). During the embryonic development, the expression was the highest at fertilization stage, significantly higher than that at cleavage stage and very significantly higher than that at late embryonic development (P<0.01). The expression level of this gene at cleavage stage was significantly higher than that from blastocyst stage to larval stage. The expression level from blastocyst stage to larval stage was low and there was no difference.In situ hybridization shows that nanos1 mRNA was expressed in the cytoplasm of oocytes and primary oocytes (Oc1, Oc2, Oc3 and Oc4). The results show that nanos1 is closely related to the development of female germ cells of M. rosenbergii.
To explore the regulatory mechanism of fish response to hypoxia stress, we stressed 1-month-old wild zebrafish (Danio rerio) by hypoxia to 1.5 mg·L−1 for 2 months, and then investigated the liver tissues by transcriptome sequencing and comparative analysis. According to the KEGG analysis performed on 3 270 differential genes in normoxia and hypoxia groups, the genes mainly enriched in pathways such as cell proliferation, lipid metabolism, carbohydrate metabolism and amino acid metabolism. Among them, the up-regulated 1 864 genes were mainly related to cell proliferation, while the down-regulated 1 406 genes were mainly involved in lipid metabolism. We performed a GO enrichment analysis on the differential genes, and found that the function of iron ion banding was significantly different. Based on the analysis of expression of iron metabolism-related genes, the iron ion storage related genes fthl28 and fthl31 changed significantly, which suggests that the iron ion content in zebrafish liver (ZFL) tissue changes significantly under hypoxic stress. Moreover, we conducted the in vitro validation experiments by using ZFL cells which were subjected to 0.1% (Volume fraction) O2 hypoxia stress. The results show that with the prolongation of hypoxia stress time, the survival rate of ZFL cells decreased, and the expression of iron metabolism-related genes and ferritin in the cells decreased significantly. In conclusion, iron metabolism regulation is an important response process under hypoxia stress. Hypoxia may lead to disturbance of intracellular iron metabolism, and prolonging hypoxia time will form a new iron homeostasis. The study provides a theoretical basis and references for exploring the hypoxia adaptation mechanism of fish.
In order to improve the growth rate of the cultured population of Cyprinus carpio var. Quanzhounensis in Quanzhou, two generations of breeding were carried out by family breeding method. The body mass and body length indexes of 3 699 individuals in 121 families of G0, G1 and G2 generations of C. carpio were measured. The heritability, phenotypic correlation and genetic correlation of body mass and body length traits were estimated by mixed linear model. The selection progress of G0−G2 generations was evaluated by the method of breeding value and least square value estimation based on target traits. The results show that the coefficient of variation of body mass and body length was 0.50−0.72 and 0.18−0.22 respectively. The heritability estimates were 0.132 (P<0.01) and 0.122, respectively (P<0.01). The genetic correlation and phenotypic correlation were 0.921 (P<0.01) and 0.995 (P<0.01), respectively. The value of selective reaction in body mass estimated by breeding value based on target traits and least square estimation was 12.82% and 15.45%, respectively, while 2.76% and 6.60% in body length, respectively, which indicates that the evenness of body mass was low, not conductive to breeding production, but had high breeding and improvement potential. In general, this population ofC. carpio var. Quanzhounensis obtained effective genetic progress after two successive generations by the family breeding, but with a modest progress. In is suggested that molecular-assisted selection (MAS) and marker-assisted large-scale mixed families' selection should be adopted in the future breeding so as to improve the breeding efficiency.
Lutjanus gibbus, a kind of coral reef fish with delicious meat and high economic value, whose spawning aggregation can easily lead to overfishing. Based on 67 individuals of L. gibbus collected by diving fishing in the waters of Meiji Reef in July 2020, we investigated its basic biological characteristics, including sex ratio, sexual maturity body length, egg diameter characteristics, fecundity and feeding habits, in order to provide basic biological data for the protection and management of L. gibbus. The results show that the ratio of female to male of L. gibbus was 2:1; the 50% sexually mature body lengths of males and females were 204.757 and 201.623 mm, respectively; the egg diameter of Stage IV gonadal was 0.176–0.419 mm with an average of 0.296 mm; the frequency distribution of egg diameter was unimodal. The fecundity of L. gibbus was 51 858–276 205 eggs with an average of 139 145 eggs. Its fecundity had a significant power function relationship with body length and body mass. The preys of L. gibbus from Meiji Reef were crabs, fish, snails, shellfish and shrimps. The stable isotope study shows that the average trophic level of L. gibbus was 3.33, and its feeding habits changed significantly with individual development (The niche width was narrower and the trophic level was higher).
In order to explore the feasibility of removing and controlling the spread of antibiotic resistant genes (ARGs) by the fishing oxidant trichloroisocyanuric acid (C3Cl3N3O3) in the aquaculture water environment, we applied the real-time quantitative PCR to monitor and determine the ARGs concentrations in the offshore source water, storage water of sedimentation tank and reserved water after oxidation and disinfection for 29 d. The final concentration of trichloroisocyanuric acid used for oxidation and disinfection was 40 mg·L−1. The target ARGs were commonly found in the aquaculture environments, including sul1, sul2, tetX, tetM, floR, cmlA and qnrA. The results show thatsul1, sul2, floR and tetX were the dominant ARGs among the above mentioned water samples. The number of types and total concentration of ARGs were the highest in offshore source water. The total concentrations of ARGs in the storage water of sedimentation tank were lower than those in the offshore source water, especially that the concentrations of sul2 andfloR were 0.86 and 0.34 lg lower than those in the offshore source water, respectively. After the oxidation and disinfection by trichloroisocyanuric acid, the total concentrations of ARGs in the reserved water decreased, and compared with the offshore source water, the concentrations of sul2 and floR decreased by 1.58 and 1.30 lg, respectively. The results indicate that offshore source water is the main source of ARGs in the aquaculture environment. Oxidation and disinfection treatment on offshore source water with trichloroisocyanuric acid can reduce the concentrations of common ARGs in the aquaculture water significantly, which is helpful to prevent and control the spread of ARGs in aquaculture environments.
Understanding the developmental time sequence characteristics of the spine and appendage skeletal system of Platax teiracan provide a theoretical basis for its seedling breeding, environmental adaptation and classification. We stained and analyzed the spine, pectoral fin, pelvic fin, anal fin and caudal fin ofP. teira larvae (0–30 dah) by the method of cartilaginous and bony staining. The results show that there were 24 vertebrae, and the tail bone was composed of five subcaudal bones and two upper caudal bones. The development sequence of appendage branch fin bones was pectoral fin, abdominal fin, caudal fin, anal fin and dorsal fin. The first hatched fish already had pectoral branch fin bone primordium and notochord. At 4 dah, the pectoral fin and pelvic fin developed first; at 7 dah, medullary arch and vein arch appeared; at 13 dah, the morphology and number of larval bones were basically stable; at about 26 dah, ossification began in juvenile fish, and the spine and spine were the first to complete ossification; at 30 dah, the larvae entered the juvenile stage, and their appearance has been fixed. The typical characteristics were three black bands on the head, trunk and tail, and the body was white silver. When being stimulated or stressed by external stimulation, the body color changed to black instantly, and the shape had no difference from that of the juvenile. The developmental sequence of the spine and appendage bones was basically the same with that of other sea fish, but the time nodes and number of the development of bone were different.
Hypoxia stress will weaken the immune function and antioxidant capacity of Eriocheir sinensis. In order to reveal the immune protection and anti-oxidation regulation mechanism of nanometer selenium (nano-Se) on E. sinensis under hypoxia stress, we had fed E. sinensis with different doses of nano-Se (0, 0.1, 0.2, 0.4, 0.8 and 1.6 mg·kg−1) in basic diets for 90 d. After the feeding, we conducted a hypoxia stress test and injected Aeromonas hydrophila under hypoxia stress. The results show that: 1) The mortality of E. sinensis under hypoxia stress for 24 h and that infected with A. hydrophila under hypoxia stress reached 62.45% and 100%, respectively. The levels of hemocyanin and the hemocyte count in crab hemolymph, and the activities of superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GSH-Px) in crab tissues increased significantly under hypoxia stress for 12 h (P<0.05), as well as there was a decreasing trend under stress to 24 h. The contents of lactic acid (LD) and malondialdehyde (MDA) continued to rise from 12 to 24 h under hypoxia stress. 2) Appropriate addition amount (0.1−0.4 mg·kg−1) of nano-Se reduced the mortality of E. sinensis significantly and the lethality of A. hydrophila under hypoxia stress (P<0.05), increasing the levels of hemocyanin, the hemocyte count and the activities of antioxidant enzymes (SOD, CAT, GSH-Px) under hypoxia stress significantly, but decreasing the contents of LD and MDA (P<0.05). The addition of 0.8−1.6 mg·kg−1 nano-Se had aggravated hypoxia stress injury. These results indicate that appropriate addition of nano-Se to the diets can improve the decrease of immune response and antioxidant ability of E. sinensis under hypoxia stress, and the optimal dose of nano-Se in basal diets is 0.2 mg·kg−1.
Rich in proteins and other active substances, seafoods have been widely used in the food and cosmetic industries. How to remove fishy substances such as trimethylamine from seafoods with high selectivity is a challenge for the current seafood processing. In this paper, zeolite imidazole framework-8 (ZIF-8), zeolites socony mobil-5 (ZSM-5) and activated alumina were characterized by powder X-ray diffraction and scanning electron microscopy, and their adsorption performance for the typical fishy substance (Trimethylamine) was also investigated. Adsorption kinetics tests show that the adsorption saturation of the three adsorbents reached at about 600 min in a 200 mg·L−1 trimethylamine solution. The adsorption isotherms of the three adsorbents at 25 ℃ were tested and their adsorption capacities for trimethylamine followed a descending order of ZIF-8 (517.1 mg·g−1) > activated alumina (401.8 mg·g −1) > ZSM-5 (390.3 mg·g −1). Under the same conditions, the adsorption uptake of trimethylamine on ZIF-8 was 3.2 times higher than that on activated carbon, exceeding those of most materials in the same period. Fourier transform infrared spectroscopy tests and Zeta potential tests show that the adsorption interactions between ZIF-8 and trimethylamine were dominated by C-H···π interaction, C-H···N interaction and electrostati force.
Investigating the best acclimation temperature conditions for Epinephelus fuscoguttatus ♀×E. lanceolatus ♂ can provide a theoretical basis for its survival and circulation. We decreased the water temperature to 24, 20, 18 and 16 ℃ at the rate of 0.5−1.0 ℃·h−1, then recorded the physiological responses and survival time, as well as the changes of water quality, non-specific immune index and antioxidant indicator. The results show that the survival time of the grouper increased with the decrease of temperature within the range of 24−16 ℃. When the water temperature was maintained at 16 ℃, the concentration of total ammonia nitrogen (TAN) increased slowly, and the survival time was the longest, up to 109 h. The non-specific immune and antioxidant parameters changed after the grouper being cultured at different temperatures for 48 h. Compared with the control group, the contents of complement protein 3 (C3), globulin (GLB) and total protein (TP) increased in 16 ℃ group significantly, while the other indexes had no significant changes. The activities of superoxide dismutase (SOD) and catalase (CAT) in the liver tissue in 16 ℃ group increased significantly. However, the activity of glutathione peroxidase (GPx) decreased significantly, but higher than those of the other temperature groups. Compared with the other temperature treated groups, the content of malondialdehyde (MDA) decreased significantly. Thus, 16 ℃ temporary culture can not only maintain good water quality, but also reduce the metabolic level of fish and maintain the homeostasis of internal environment, so as to reduce the damage caused by oxidative stress reaction. It is suitable for temporary culture and transportation of Epinephelus fuscoguttatus ♀×E. lanceolatus ♂.
In order to optimize the sterilization process of laver (Porphyra spp.) and develop high-quality instant wet laver products, we measured the heat penetration curves during high-pressure heat treatment (110, 115, 121 ℃) and normal pressure heat treatment (85, 90, 95 ℃) for low-acid and acidified lavers (pH≤4.6). Combined with preservation experiment and microbial analysis, we determined the F-value (Safe sterilization heating time) corresponding to the two sterilization methods, and explored the effects of different temperature-time combinations on the sensory and nutritional quality of laver with the same F-value. Results show that low-acid laver could reach commercial sterility when F0 was 3 min under high-pressure heat sterilization, and acidified laver could also reach the preservation requirements when
To study the comprehensive utilization of by-products from eel processing, the angiotensin-converting enzyme inhibitory peptide was prepared from eel (Anguilla japonica) bone collagen by enzymatic hydrolysis. The ACE inhibitory activity and degree of hydrolysis were used as evaluation indexes, we determined the optimal hydrolysis conditions by single factor and response surface experiments. Furthermore, the amino acid composition and molecular mass distribution of the hydrolysate prepared under the optimized conditions were determined. The results show that alkaline protease was the optimal enzyme, and the optimal hydrolysis conditions were as follows: temperature of 50 ℃, mass concentration of 15 g·L−1, hydrolysis time of 5.25 h, enzyme dosage of 3.1% (Mass fraction) and pH of 9.2. Under these conditions, the ACE inhibitory activity was 70.33%, which was close to the predicted value. The molecular weight of peptides below 1 000 D and 1 000–3 000 D in enzymatic hydrolysate accounted for 57.02% and 36.55%, respectively. Amino acid composition analysis shows that the content of hydrophobic amino acids related to ACE inhibition activities (Such as Pro、Val、Ile、Leu、Phe) increased.
To understand the relationship between the morphological traits and the body mass of coral trout (Plectropomus leopardus) is important for its breeding. In this study, we selected 159 individuals of the same batch of 4-month-old P. leopardus juveniles as the experimental objects to explore the correlation between the eleven morphological traits and body mass. The results show that there were significnat correlation between snout length (x9) and body mass (P<0.05), and extremely significant correlation between the other ten morphological traits and body mass. The results of path analysis reveals that the standard length (x2), body depth (x4), body width (x5), head height (x7), snout length (x9) were the main decisive morphological traits on body mass. The direct effect coefficient of body depth on body mass was 0.444, indicating that body depth mainly affected body mass through direct action. However, the other morphological traits mainly affected body mass indirectly via body depth. The total decision coefficient of five morphological traits on body mass was 0.853, indicating that these morphological traits were the main factors affecting body mass. After eliminating the morphological traits with insignificant coefficient to body mass, we established the multiple regression equation by multiple regression analysis. The morphological traits retained by the multiple regression analysis were consistent with that by path analysis.
Due to the growing demand for instant food and lifestyle change after the COVID-19, aquatic pre-made products become popular. The unique nutritional and functional characteristics and processing suitability of aquatic products make them suitable for the development of ready-to-eat, instant heat, instant cooked and ready-to-use pre-made products. However, due to their unique fishy taste, texture and perishable characteristics, appropriate pretreatment technology, flavor and quality improvement and maintenance technology as well as storage technology in the processing and storage process need to be adopted so as to improve the quality of pre-made products. The main factors affecting the quality and safety of aquatic product pre-made products include biological hazards, chemical hazards and physical hazards. Therefore, quality control technologies of aquatic pre-made products including the raw material collection, processing process and the cold chain transportation process are necessary. In the future, aquatic pre-made products should be more nutritious, high-quality and diversified because of the improvement of nutrition and quality control technology.