• Volume 45,Issue 8,2021 Table of Contents
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    • >PAPERS
    • Effect of an obstacle on swimming kinematics in juvenile silver carp, Hypophthalmichthys molitrix

      2021, 45(8):1406-1414. DOI: 10.11964/jfc.20200812369

      Abstract (339) HTML (0) PDF 5.51 M (728) Comment (0) Favorites

      Abstract:Weirs and dams affect the hydraulics and geomorphology of natural rivers, greatly modifying fish habitat, in some cases, creating barriers that prevent fish swimming upstream. Typical engineering methods to mitigate dam effects on movements of fish include fishway construction and riverbed reconfiguration. Among these measures, it is common to use obstacles to increase bed roughness and create microhabitat that slows flow velocity and helps fish ascend fishways. Obstacles create a complex flow environment in fishway. Understanding swimming behavior in complex flow environment is critical to improving the effectiveness of fishways. A stationary obstacle within a fish passage can be either beneficial or detrimental to fish depending on the direction and magnitude of flow velocity and the ability of the fish to maintain stability. Flow velocity in relation to energy expenditure is critical when considering the effect of obstacles on locomotory behavior. We also discovered how silver carp (Hypophthalmichthys molitrix) alter their locomotory behavior in response to turbulent flow caused by varying flow velocities around obstacles. Silver carp is an important native commercial species in China. Silver carp tend to inhabit fast-flowing streams with structurally complex flow environments. No quantitative kinematic studies have described the locomotory behavior of silver carp in unsteady flow. In this study, the swimming kinematics of juvenile silver carp holding station and moving forward under obstacle conditions were analyzed at different flow velocities (1, 3 and 5 BL/s) (body length per second). Metrics used to quantify kinematics were tail-beat frequency, tail-beat amplitude, ground swimming speed, swimming acceleration, and ground stride. Compared to free stream swimming at flow velocity of 3 BL/s, silver carp holding station behind the obstacle showed a significant decrease in tail-beat frequency and significant increase in tail-beat amplitude; silver carp moving forward behind the obstacle showed a significant decrease in tail-beat frequency, ground swimming speed, swimming acceleration and ground stride, and significant increase in tail-beat amplitude. This result showed that the obstacle help fish to save energy at 3 BL/s. In the obstacle-placed currents, tail-beat frequency of the holding station behavior increased with flow velocity. Tail-beat frequency, tail-beat amplitude and swim acceleration of moving forward behavior increased with flow velocity, while ground stride decreased with flow velocity. At flow velocity of 3 BL/s, we found that silver carp held a preferential position from 5-30 cm downstream of an obstacle where fish might adopt Karmen gait, and residence time accounted for 92.5%. At flow velocity of 1 BL/s and 5 BL/s, silver carp did not hold an evident preferential position in the flume. Silver carp often swam close to the wall, and there was no obvious position preference. Our results indicate that a certain combination of obstacles and flow velocity will create flow refuge for fish. The results may provide important reference for fishway design.

    • Genetic structure analysis of Megalobrama terminalis, Culter alburnus, Chanodichthys mongolicus and their hybrids based on genotyping by sequencing

      2021, 45(8):1307-1316. DOI: 10.11964/jfc.20200712319

      Abstract (491) HTML (0) PDF 5.45 M (730) Comment (0) Favorites

      Abstract:Distant hybridization is an essential means of breeding among aquatic animal species, genera, subfamilies, and even families, combining parents’ dominant traits to obtain excellent new hybrid varieties. Previous studies on Megalobrama and Culter’s distant hybridization show that Megalobrama and Culter’s hybrid offspring have significant heterosis. However, the analysis of the genetic structure of the fish hybridized from Megalobrama and Culter is still relatively limited, and there is little research on single nucleotide polymorphism markers (SNPs). This study aims to analyze the genetic structure of Megalobrama terminalis, Culter alburnus, Chanodichthys mongolicus, and their hybrids by high-quality SNPs obtained by genotyping by sequencing (GBS) technology. In the study, the total DNA extracted from the fin strips of 6 individuals that included M. terminalis, C. alburnus, C. mongolicus, and their hybrids (F1), was double digested. Simplified genome sequencing was performed using Stacks software to construct a reference genome for SNP comparison. As a result, six individuals produced 7.01 GB of clean data, with an average of 1.17 GB per sample. All samples were used as a group to detect SNP mutations. A total of 399 145 SNP sites were detected. After quality control filtering, 97 911 SNP sites were obtained. SNP analysis indicated that, of parents and their hybrids, the average observed heterozygosity was 0.339 4. The average expected heterozygosity was 0.285 3. The average polymorphic information content was 0.273 7, average nucleotide diversity was 0.372 7, the average minimum allele frequency was 0.247 2, and the average genotyping rate was 93.94%. The principal component analysis (PCA) showed that M. terminalis, C. alburnus, C. mongolicus, and their hybrids clustered at different points, but the clustering points of the two hybrids of M. terminalis and C. alburnus were close. The PCA’s result indicated apparent genetic differentiation among M. terminalis, C. alburnus, C. mongolicus, and their hybrids. Based on the genetic differentiation index and genetic distance between different populations, the results show that the differentiation indexes between M. terminalis, C. alburnus, C. mongolicus, and their hybrids are 0.309 6-0.894 0, and the genetic distance is 0.370 5-2.244 3. The phylogenetic tree constructed using the maximum likelihood (ML) method shows that M. terminalis, C. alburnus, C. mongolicus, and their hybrids are distinguished. C. mongolicus firstly formed a new branch. M. terminalis (♀)×C. mongolicus (♂) was separated as a single branch. However, M. terminalis, C. alburnus, and their hybrids formed a broad branch. In this big branch, M. terminalis first differentiated and formed a separate branch. M. terminalis (♀)×C. alburnus (♂) differentiated again. Finally, M. terminalis (♂)×C. alburnus (♀) differentiated. The genetic structure diagram further supports the analysis results of the phylogenetic tree. The three parents are divided into three subgroups. The hybrids of M. terminalis and C. alburnus are obtained by crossing M. terminalis and C. alburnus. In comparison, the hybrids of M. terminalis (♀)×C. mongolicus (♂) are obtained by crossing M. terminalis (♀) and C. mongolicus (♂). This study will provide more genetic data for the hybrid breeding of M. terminalis, C. alburnus, and C. mongolicus, such as providing SNPs for constructing a high-density genetic map and screening SNP s associated with traits.

    • Evaluation of on competitiveness of China’s provincial recreational fisheries and our suggestions

      2021, 45(8):1415-1429. DOI: 10.11964/jfc.20200712339

      Abstract (336) HTML (0) PDF 17.65 M (693) Comment (0) Favorites

      Abstract:The development of leisure fisheries is an important part of promoting the construction of modern fisheries, and also an important measure to implement the strategy of rural revitalization and to build a strong marine economy. Considering the blank of the current research on the evaluation of the competitiveness of Chinese provincial recreational fisheries, the existing evaluation methods cannot take into account both the ambiguity and randomness of indicators. This study introduced the concept of competitiveness and the normal cloud model method, and evaluated the competitiveness of 30 provinces (except Tibet) of China's provincial-level administrative units for leisure fishery competitiveness by constructing a Chinese provincial leisure fishery competitiveness evaluation index system. The results showed: (1) The overall level of competitiveness of China’s provincial recreational fisheries is not high and the development is uneven. Two thirds of the provincial competitiveness results is in the level Ⅰ (weak) state, lacking the competitiveness of level Ⅳ (relatively strong) provinces; (2) Water resources area per capita, market distance index of source area and market size are common shortcomings of the competitiveness in most provincial units, and the total retail sales of social consumer goods and transportation accessibility indicators are generally highly competitive; (3) Level Ⅰ and Ⅲ provincial competitiveness results have less volatility, level Ⅱ provincial competitiveness results have greater volatility, and level Ⅴ provincial competitiveness results have the most stable results. This study can provide reference for enriching leisure fishery evaluation methods and making industrial development decisions.

    • Comparative analysis of skin and eye transcriptome in the Gobiopterus lacustris

      2021, 45(8):1317-1326. DOI: 10.11964/jfc.20200912401

      Abstract (386) HTML (0) PDF 6.25 M (734) Comment (0) Favorites

      Abstract:Gobiopterus lacustris is a kind of small fish with strong adaptability to salinity and easy to raise in laboratory. It is an ideal model organism and environmental indicator species, whose body is transparent and its organs can be seen through naked eyes. In order to explore the cause of the transparent body color of G. lacustris, the transcriptome analysis of skin and eye of G. lacustris was carried out. A total of 103 686 unigenes were obtained by de novo splicing. The N50 and average length were 1 456 and 2 490 bp, respectively. In Nr, Nt, KO, SwissProt, PFAM, GO and KOG databases, 57 380, 37 343, 31 700, 51 277, 47 020, 47 555 and 25 604 unigenes were annotated respectively. KEGG enrichment showed that tyr, tyrp1 and tyrp2 were significantly down regulated in melanin production pathway. In addition, the results showed that there were 8 113 differentially expressed genes (DEGs) in the skin and eyes of G. lacustris, of which 3 174 were up-regulated in the skin and 4 939 in the eyes. The verification of 10 DEGs by qPCR confirmed that the RNA-Seq analysis was correct. This study enriches the body color research of G. lacustris, provides data for the utilization of G. lacustris genetic resources, and also provides a reference for further study on the formation mechanism of gorgeous body color of fish.

    • Expression analysis of CYP2J3-like gene at different growth rates of Litopenaeus vannamei

      2021, 45(8):1327-1339. DOI: 10.11964/jfc.20200912407

      Abstract (711) HTML (0) PDF 12.36 M (780) Comment (0) Favorites

      Abstract:As the most important cultured shrimp in China, Litopenaeus vannamei constitutes about 70% of the world's cultured shrimp production, and has high commercial value. With the development of culturing technology, high-density farming has become a trend. In order to obtain a commercial size in a short time, it is necessary to cultivate some varieties that grow fast. Single nucleotide polymorphisms (SNPs) brought genetic diversity research into a new stage. SNPs widely existed in genome, and they serve as suitable markers for linkage map, genome wide association studies (GWAS), and marker assisted selection (MAS) of target traits. There were few researches to discover SNPs of important phenotype in L. vannamei, and therefore there was still insufficient information of SNPs available for genetic diversity studies of L. vannamei. Especially, the discovery of growth-related SNPs by transcriptome sequencing was rarely reported in L. vannamei. With the development of next generation sequencing (NGS), the cost of sequencing has greatly fallen, which makes SNPs identification feasible in non-model species. RNA-seq based on NGS has been used widely, and it can identify SNP markers efficiently, because it focuses on the functional information in the genome with expression level of functional gene. In this study, SNPs of a P450 gene and its potential transcriptional factors were detected in different growth rate individuals by RNA-seq. We hope to give an example for the effective use of transcriptome data and a way for the accumulation of genetic and breeding data of shrimp. The inbreeding and crossbreeding offspring of four L. vannamei strains with diverse genetic backgrounds were cultured in net cages of ponds. The top five fastest growing individuals or top five slowest growing individuals in each net cage were put into a pool, respectively. The two kinds of RNA pools (rapid-growing group, RG; slow-growing group, SG), which were sequenced by RNA-seq, were used to find different expression genes and SNPs. The target DNA fragments, which were amplified from two kinds of DNA pools (RG and SG) by PCR, were sequenced by NGS to find SNPs. A different expression P450 gene, which was selected by comparing transcriptomes of two RNA pools of L. vannamei, was named LvCYP2J3-like with a 1 488 bp open reading frame encoding a protein of 495 aa and an integral P450 domain, which might be involved in the inactivation of ecdysones. Six transcription factors of LvCYP2J3-like were predicted by bioinformatics. They are TATA-box-binding protein (TBP), TBP1, TATA element modulatory factor (TMF), pancreas transcription factor (PTF), PTF1A and PTF1A1. The variance analysis of the 7 gene by q-PCR showed there was significant difference of expression levels in tissues, development stages and molting cycle. LvCYP2J3-like was detected in all tissues samples. The expression levels from high to low were eyestalk, gill, intestinal tract, muscle, hepatopancreas and haemocytes. Multiple comparisons showed that there were significant differences between the two groups (P < 0.05). The expression pattern of PTF1A was similar to that of LvCYP2J3-like, with the highest expression in eyestalk and the second in gill (P < 0.05), but no expression was detected in other tissues. LvCYP2J3-like had significantly different expressions in five development stages, with the highest in mysis larva stage (P < 0.05). The expression pattern of PTF and PTF1A was similar to LvCYP2J3-like in development stages. LvCYP2J3-like had a similar pattern with TBP in molting cycle, and there was the highest expression level in premolt stage D1 (P < 0.05). The expression level of LvCYP2J3-like, PTF and TBP in SG were higher than that in RG (P < 0.05), but PTF1A1, TBP1 and TMF had higher expression levels in RG (P < 0.05). There were 4 and 11 SNPs with significant difference of allele frequency (P < 0.05), in sequences of LvCYP2J3-like and its predictive transcription factors, respectively. The expression pattern of LvCYP2J3-like implied that it played a role in development and molting cycle. Its expression level was closely related to environmental stress. The results suggested that genetic diversity of these genes was related to their activities and expressions, which affects the growth rate of shrimp. This study will provide useful data for the genetic and breeding research of L. vannamei.

    • >ROUNDUPS
    • Advances of immune-related microRNA research in teleost fish

      2021, 45(8):1430-1437. DOI: 10.11964/jfc.20200312202

      Abstract (360) HTML (0) PDF 5.33 M (653) Comment (0) Favorites

      Abstract:MicroRNAs, which are small non-coding RNAs with 18-25 nt, play important roles in immune response of teleost fish. Recently, more and more differentially expressed miRNAs (DE miRNAs) associated with immune response have been identified through high-throughput sequencing and RT-PCR technology. It is assumed that if the same miRNAs are detected as DE miRNAs in several species of teleost fish challenged with different viruses/bacteria, they are likely to be evolutionarily conserved miRNAs involved in the regulation of immune gene networks in the hosts. Based on the above assumption, ten miRNAs were discovered as responding to viral challenge, and eight miRNAs were described in response to bacterial challenge. In addition, the functional study of miRNA has also attracted attention with marked progress. It has been identified that miRNAs are involved in many immune response processes, such as in preventing the virus replication, in regulating interferon response, inflammation and cell apoptosis.

    • Lipid metabolism and its physiological and ecological effects of sharks

      2021, 45(8):1438-1450. DOI: 10.11964/jfc.20200912397

      Abstract (442) HTML (0) PDF 6.04 M (705) Comment (0) Favorites

      Abstract:As the key species, sharks play an important role in regulating the structure and function of the food web of marine ecosystems. In recent decades, due to the continuous increase of global shark catches, the resource status is not optimistic. Eighty percent of marine species are assessed as near endangered by International Union for Conservation of Nature. However, the lack of knowledge on the basic biology, physiology, ecology and other important life history processes of sharks hinders the effective regulation and protection of shark resources. In this paper, we summarized the lipid metabolism pathways of sharks and its effects and the differences of lipid metabolism between sharks and teleosts, in order to further understand the life history of sharks. Shark’s liver is the primary organ where the lipid storage and synthesis, fatty acid oxidation and ketone body formation occur. Digestion and absorption of lipids from diet is the exogenous pathway and lipid synthesis in liver is the endogenous pathway of lipid accumulation of sharks. The lipid metabolism pathways in shark are unique compared with those of the teleost fish. The free fatty acids in shark’s blood are transported by binding with lipoproteins, while those in teleost are carried by albumin and usually have adipose tissues. The oxidation of fatty acids in extrahepatic tissues is limited, which is more dependent on the metabolic capacity of the ketone body which plays a limited role and is only used as alternative sources in the teleost fish. Triacylglycerol and free fatty acid in shark’s liver are the main energy sources, and squalene can provide additional buoyancy. During reproduction, female sharks provide nutrients for their offspring with yolk sac. The fatty acid profiles in the liver and muscles can be used to investigate the trophic ecology on ecological roles, resource partitioning and nutritional physiology of the shark species. Understanding the lipid metabolism pathways of sharks is of great significance for revealing their evolutionary process, understanding their mysterious life history and making effective management strategies for shark conservation.

    • >PAPERS
    • Redescription and phylogenetic analysis of Myxobolus tricostatus (Myxozoa: Myxobolidae)

      2021, 45(8):1340-1349. DOI: 10.11964/jfc.20200712343

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      Abstract:Myxobolus tricostatus was found initially to infect the gills of grass carp in the late 1970s with simple and insufficient taxonomic data, so the taxonomic validity was problematic. In order to supplement description and verify the validity of M. tricostatus, we redescribed M. tricostatus collected from Lake Tangxun in Wuhan city, Hubei Province, using the integrative taxonomic approach of combining myxospore morphology, molecular data and ecological information of host and infection site, which has been widely accepted for the taxonomy of Myxozoa. Here, the plasmodia, tissue tropism and molecular data of M. tricostatus are first provided. The morphological features of the concerned species are as follows: whitish plasmodia infecting the gills measured (2.4±0.3) (2.1-2.7) mm in length and (0.8±0.1) (0.6-0.9) mm in width; mature spores encapsulated by a transparent mucous envelope were ovoid in frontal view and fusiform in sutural view, measuring (10.3±0.4) (9.4-11.0) μm long, (9.5±0.5) (8.7-10.9) μm wide, and (7.4±0.5) (6.4-8.0) μm thick; no "V"-shaped folds were observed on the posterior end of the spore; three parallel ridges could be observed in sutural view; two equal polar capsules were pyriform and coiled with 7-8 turns of polar filament. Histological observation showed that the plasmodia dwelled between the gill filaments, and no serious inflammation was found in the surrounding tissues. BLAST search indicated that M. tricostatus was most similar to M. elegans with the similarity of 89.58%, which was definitely below the intraspecies similarity range. Phylogenetic analysis revealed that M. tricostatus branched with M. elegans from the gills of Leuciscus idus and Rutilus rutilus with high support values within the clade of Cyprinidae gill-infecting Myxobolus spp. including M. enoblei, M. minutus and M. bibullatus from the gills of Catostomidae fish. The present phylogenetic results further confirmed that host affinity and tissue tropism provide strong evolutionary signal for tissue-infecting Myxobolidae. In conclusion, we provided here supplemeemtary morphological, histological and molecular data of M. tricostatus, and verified the validity of its classification.

    • Effects of sexual maturity and body size on statolith shape of Sthenoteuthis oualaniensis in the Northwest Indian Ocean

      2021, 45(8):1350-1360. DOI: 10.11964/jfc.20200712348

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      Abstract:In this paper, the effects of sexual maturity and body size on the statolith shape of Sthenoteuthis oualaniensis in the northwest Indian Ocean were studied, the growth inflection points of statolith shape were evaluated, which would provide a basis for the subsequent studies on the population identification and life history of S. oualaniensis. Statolith, which is mainly composed of dorsal dome, lateral dome, rostrum dome and wing region, is one of the most important hard tissues of Cephalopods to study the age, growth, population structure and life history. According to the samples of S. oualaniensis totaled 1 009 in number collected in the northwest Indian Ocean from February to May of 2019 by the Chinese light falling-net fishery fleets, the total statolith length (TSL), lateral dome length (LDL), wing length (WL) and maximum width (MW) are considered as the indicators of external form growth, and the ratio of MW to TSL is considered as the indicator of changes in statolith shape. The external form growth and statolith shape changes affected by sex, gonad maturity and individual size are analyzed by the analysis of variance (ANOVA) and Least-significant difference (LSD). The results indicated that the changes of TSL, LDL, WL and MW between different sexes were statistically significant. For both female and male samples, the changes of TSL, LDL, WL and MW between different gonad maturity and different mantle length ranges were also statistically significant. However, changes of ratio of MW to TSL in different sexes showed no significant differences but changes in different gonad maturity and different mantle length ranges showed very significant differences. The study showed that sexual maturation and size of S. oualaniensis had an obvious effect on its statolith growth in both males and females. Stage III gonadal maturity and 300-500 mm mantle length are the growth inflection points of statolith shape of female individuals, while there is no distinct inflection point in male individuals. The characteristic parameters of statolith increased rapidly with the growth of gonad and mantle length before the inflection point, while increased slowly after the inflection point.

    • Spatial autocorrelation of Priacanthus spp. resources in the northern South China Sea

      2021, 45(8):1361-1373. DOI: 10.11964/jfc.20200512256

      Abstract (443) HTML (0) PDF 10.75 M (796) Comment (0) Favorites

      Abstract:Understanding the spatial autocorrelation characteristics of the distribution of economic fish is helpful to reveal the distribution pattern of its habitat and the formation mechanism of fishing grounds, which provides a basis for the evaluation and rational exploitation of the resources. Due to long-term overfishing, the fishery resources in the northern South China Sea have declined seriously, especially in the shallow area of 100-m isobath. As an important fishing target of bottom trawling in the South China Sea, the resources of Priacanthus spp. are under great pressure, so exploring the pattern characteristics of the spatial distribution of the resources can provide a certain reference basis for the sustainable utilization and scientific management of the resources. However, some studies denied that the spatial autocorrelation was affected by the spatial scope of the study area, and the spatial autocorrelation varied greatly under different analysis scales, thus weakening the actual effect of fishery resources assessment and scientific management. Therefore, based on the data of bottom trawl fishery in the northern South China Sea by a fishery information network from 2009 to 2014, this study used the methods of global spatial autocorrelation and local spatial autocorrelation to analyze the dynamic changes of spatial autocorrelation of Priacanthus spp. resources. And the incremental spatial autocorrelation analysis was added to improve the accuracy of the research results. The results were as follows: ① the results of global spatial autocorrelation analysis showed that in the whole study area, the interannual resources of Priacanthus spp. were mainly in low-density area and less in high-density area. ② according to the incremental spatial autocorrelation analysis, the resources of Priacanthus spp. showed a strong spatial autocorrelation within the scale of 76-87 km, and showed a significant aggregation distribution pattern. ③ the local spatial autocorrelation analysis showed that the distribution of hot and cold spots of Priacanthus spp. resources varied greatly from year to year, and the hot spot fishing areas were mainly concentrated between the 50-m and 100-m isobath in the middle part of the study area. The cold spot fishing areas were concentrated in the sea area near the 50-m isobath. In this paper, the incremental spatial autocorrelation method was introduced to explore the spatial autocorrelation of Priacanthus spp. resources, which provided a new idea for mining the temporal and spatial distribution characteristics of fishery resources.

    • Fish community structure and biodiversity in the offshore waters of Zhoushan Islands in spring and autumn

      2021, 45(8):1374-1383. DOI: 10.11964/jfc.20200612287

      Abstract (345) HTML (0) PDF 7.62 M (744) Comment (0) Favorites

      Abstract:In order to understand the species composition, spatial distribution, biodiversity, and community structure characteristics of fish resources in the waters off the Zhoushan Islands, a trawl survey was conducted in the waters off the Zhoushan Islands in April (spring) and October (autumn) 2018. Studies have shown that: (1) there are 106 species of fish in the waters off Zhoushan Islands, belonging to 12 orders, 47 families and 80 genera, including 63 species in spring, belonging to 12 orders, 34 families and 49 genera, and 85 species in autumn, belonging to 12 orders, 45 families. (2) the number of fish species in this survey is 63 in spring and 85 in autumn. Compared with the historical survey results, the total number of fish species significantly reduced in spring, but slightly increased in autumn. This may be due to the previous use of beam drag shrimp nets, and bottom trawl nets were used in this investigation. The difference in nets may cause differences in the main fishing targets, or it may be due to the different layout of survey stations; (3) the dominant fish species in the two seasons changed. Obviously, the dominant species in spring are Lophius litulon, Lepidotrigla japonica and Apogon lineatus, while in autumn the dominant species are L. litulon and A. japonicum; (4) The value of fish biodiversity index is greater in autumn than that in spring, and the evenness index (J') of spring and autumn is relatively small compared to diversity index (H') and richness index (D), and the value of biodiversity index in spring and autumn basically increases with the increase of water depth, and the water depth interval is higher than 80 m. In spring and autumn, the horizontal distribution of D, H', and J' values is lower in the western part of the survey sea area and lower in the sea area near the island. The open sea area far from the islands in the south is greater. However, since there are only 1 and 3 stations with a water depth greater than 80 m and less than 50 m, and it is also related to factors such as seasonal fish activities, and the water depth in the outer waters The degree of impact on biodiversity and the specific reasons need to be further explored; (5) through cluster analysis and non-metric multi-dimensional scaling analysis, it can be obtained that 3 communities are divided into 3 communities at a similarity level of 35% in spring and 45% similarity in autumn. It is divided into two communities at 45% level. The species similarity in autumn is higher than that in spring, and the biomass and species level in spring are lower than those in autumn. The composition of fish communities in waters where the depth gradient does not change greatly depends on temperature. The changes in water temperature caused changes in the dominant species and dominance of fish in the sea, and the migration of migratory fishes caused changes in the concentration of fish populations, which may be one of the main reasons affecting the stability and changes of fish communities in the waters off Zhoushan Islands. (6) the ABC curve shows that the spring fish community structure outside the Zhoushan Islands is undisturbed, which may be caused by the small temperature difference between different stations in the sea area in spring and the relatively stable environment. The biomass dominance curve in autumn has always been below the abundance dominance curve, which indicates that fish individuals are generally small, mainly small fishes, and some large individuals with obvious biomass dominance are almost non-existent. They are perennial and large in size. There are very few fishes, and the fish communities off the Zhoushan Islands are seriously disturbed. There is a large number of supplementary groups in autumn, which has a certain impact on the size of fish communities. Therefore, the ABC curve to determine the stable state of the community needs further discussion.

    • Molecular cloning and functional study of mannose receptor gene in Epinephelus coioides

      2021, 45(8):1279-1295. DOI: 10.11964/jfc.20200812385

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      Abstract:Mannose receptor (MR), also known as CD206, is an endocytosis receptor involved in pathogen recognition and antigen presentation. As a link between innate immunity and adaptive immunity, MR plays an important role in immune response. Viral nerve necrosis (VNN) caused by nerve necrosis virus (NNV) is a highly contagious neuropathological disease, which has caused the death of more than 50 important farmed juvenile fishes worldwide. At the same time, NNV is also one of the main viral pathogens causing huge economic losses to the Epinephelus coioides culture industry. Innate immunity can recognize pathogens by combining pattern recognition receptor (PRR) with pathogen-associated molecular pattern (PAMP). C-type lectins belong to PRR. MR as a member of C-type lectins family, is of great significance to study whether MR has immune function in NNV. Most of the studies on MR in fish are focused on the antibacterial activity of MR, but the relationship between MR and antivirus in fish is unknown. In order to study the immune function of EcMR gene against red grouper nerve necrosis virus (Red-spotted grouper nervous necrosis virus, RGNNV), EcMR gene was cloned and expressed. The results showed that the EcMR cDNA full length sequence was 4 877 bp, and its open reading frame encoded 1446 amino acids. The protein domain of EcMR was composed of a signal peptide, an extracellular ricin-like β-type clover domain (RICIN), a fibronectin type Ⅱ domain (FN Ⅱ), eight tandem C-type lectin-like domains (CLECTs) and a transmembrane domain. The results of real-time quantitative PCR (qRT-PCR) showed that EcMR gene widely existed in 8 examined tissues and the relative expression of mRNA was in the following order of gill > head kidney > brain > spleen > liver > peripheral blood > heart > muscle. The results showed that RGNNV could proliferate rapidly in GF-1 cells and significantly activate the expression of EcMR gene at 6 h and 24 h after infection. In order to further explore the effect of RGNNV on GF-1 cells, the apoptosis of GF-1 cells infected by RGNNV was detected by the Alexa Fluor® 488 annexin V/Dead Cell Apoptosis Kit. The results showed that RGNNV infection could promote the apoptosis of GF-1 cells, and the apoptosis rate increased with the prolongation of infection time. At the same time, the results of qRT-PCR and enzyme activity assay showed that RGNNV infection could significantly promote the transcription level of apoptosis-related genes, and the expression of inflammatory cytokines and the enzyme activity levels of Caspase-3, Caspase-8 and Caspase-9. To sum up, this study successfully cloned the EcMR gene and revealed its correlation in the process of RGNNV invasion. The results of this study will provide some basic theoretical reference for the prevention and control of grouper viral diseases.

    • Niches of four large crustacean species in Laizhou Bay

      2021, 45(8):1384-1394. DOI: 10.11964/jfc.20200812378

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      Abstract:Niche theory explains mechanisms of interspecific coexistence and competition in communities. Chinese shrimp (Fenneropenaeus chinensis), swimming crab (Portunus trituberculatus), Japanese stone crab (Charybdis japonica), and Japanese mantis shrimp (Oratosquilla oratoria) are all large-bodied commercially exploited crustacean species in Laizhou Bay, China, with similar food habits. Populations of two of these species, F. chinensis and P. trituberculatus, are also regionally enhanced. Study of the community status, interspecific associations, and spatial niche characteristics of these four crustacean species is warranted to guide stock enhancement and fishing quota management. Data for analysis of community status and spatial niche were collected by bottom-trawl surveys at 20 stations in summer from 2010 to 2019. Representative samples of these four crustacean species, and their potential food sources were collected in 2010, 2011, 2018 and 2019. Using stable carbon and nitrogen isotopes we analyze trophic levels, nutritional niches, and diets of these crustaceans. Average F. chinensis biomass (51.0 g/h) was lowest, followed by P. trituberculatus (107.0 g/h). In most years, O. oratoria and C. japonica were most dominant, and F. chinensis and P. trituberculatus were typically important species in the community. Associations between these four species are not strong, with a significant positive association occurring mainly between F. chinensis and the other three species. The niche width of C. japonica is greatest (2.45), followed by O. oratoria (2.13), F. chinensis (1.92), and P. trituberculatus (1.93). A high niche overlap is apparent between F. chinensis and the other three species; trophic levels of each are similar, ranging 3.02-3.28. The total niche area of F. chinensis is the greatest, while that of P. trituberculatus is similar to those of C. japonica and O. oratoria. Nutritional niche overlaps between P. trituberculatus and C. japonica are relatively high. Proportionally more bivalves are ingested by F. chinensis than any of the other species, for which diets are more homogeneous. Although populations of P. trituberculatus and F. chinensis have expanded through enhancement, the crustacean community structure in Laizhou Bay has not changed greatly. On the basis of community status, inter-species connectivity, spatial niche width and overlap, trophic level and nutritional niche, and the diets of these four crustaceans, F. chinensis is least competitive with other taxa, and P. trituberculatus is more competitive with C. japonica and O. oratoria. To maximize benefits of regional crustacean enhancement, we suggest consideration be given to competition between species, and niche similarities, to determine appropriate release sites and quantities.

    • Analytical research of spatial distribution of fish larvae and juveniles in summer and autumn in the eastern Chongming, Yangtze River Estuary

      2021, 45(8):1395-1405. DOI: 10.11964/jfc.20200412230

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      Abstract:The CEB (Chongming Eastern Beach) is located on the crestal plane of the diluted water at the mouth of the Yangtze River. Under the action of strong currents and tides, it forms a wealth of food and provides a unique place for growth and development of fish larvae. To investigate the distribution and diversity of fish larvae, using big larval net (mesh size of 0.5 mm) to conduct 10 min horizontal trawl, while collecting real-time data of environmental parameters of the water column including temperature (SST), salinity (SSS), depth (DEP), turbidity (TUR), and chlorophyll a (Chl). A total of 10 925 fish larvae and juveniles, belonging to 52 species, 14 families, were collected. Among them, the most abundant were freshwater fish of 22 species (42%), followed by estuarine fish of 19 species, accounting 37% of total, coastal fish of 7 species (13%) and 4 species of offshore fish (8%). Whereas the most common species were Cyprinidae family, consisting of 14 species (27%); Gobiidae family had 12 species (23%); the families of Engraulidae and Osmeridae had both 5 species (10%). The dominant species were (Coilia mystus, 21.51%),(Colia nastus, 18.11%),(Hemiculter bleekeri, 16.34%),(Pseudolaubuca sinensis, 10.82%)and (Acanthogobius ommaturus, 9.38%), respectively. In all, the fish larvae of pre-flexion comprised 76.49% of the total catch, 11.94% of the flexion stage, 8.01% of the post-flexion stage, 3.43% of the juvenile stage. However, the density of fish larvae in the stages of pre-flexion and flexion had a declining tendency, while the density of fish larvae in the stage of post-flexion rose, as the season changed. The number of species, bio-diversity and the density of fish larvae were higher in the summer season than those in the autumn season. The Non-metric Multi-dimensional Scaling and the Cluster Analysis demonstrated that the fishes can be classified as two groups, rich in the freshwater type, followed by the estuary type. Based on the results of this research and other surveys of Coilia family larvae, it shows that there is a significant difference in the spatial distribution of Coilia nasus and Coilia mystus at the larval stage of the Yangtze River. This research showed that the Gobiidae was distributed in a scattered manner, and traces of the larvae and juveniles were found in the southern branch, northern branch of the Yangtze River Estuary and Dongtan water area. Like many estuaries in the world, the Gobiidae have special living habits, which enable them to adapt to the huge runoff and sedimentation of the estuary. At present, many nets and fyke nets for eel fishing have been set up along the Yangtze River Estuary. There is no effective method to assess the damage to larvae and juveniles. In addition, the feeding of larvae and juveniles and the protection of nurseries are the key to the protection and restoration of fishery resources. The CEB of the Yangtze River estuary is a buffer water area for Chinese sturgeon juveniles to descend and migrate to the sea. The density of larvae and juveniles in this water area will significantly affect the species preservation and continuation of Chinese sturgeon. Therefore, it is urgent to develop effective and systematic long-term tracking.

    • Cloning and expression of ASDIGIRR and ASTRAF6 genes of Acipenser sinensis

      2021, 45(8):1296-1306. DOI: 10.11964/jfc.20200812383

      Abstract (500) HTML (0) PDF 5.90 M (814) Comment (0) Favorites

      Abstract:Acipenser sinensis is one of the ancient and rare fishes in China between teleost fish and cartilaginous fish, but it is vulnerable to different diseases in the process of artificial reproduction and culture, so it is necessary to deeply study the immune regulation of A. sinensis to provide theoretical basis for its prevention of diseases. A single Ig-IL-1R-related molecule (SIGIRR) and tumor necrosis factor receptor-associated factor 6 (TRAF6) are two important signal transduction elements in the signal transduction pathway of toll-like receptors. In this study, homologues of SIGIRR and TRAF6 of A. sinensis, named ASDIGIRR and ASTRAF6, were identified, and their expression levels in normal tissues and Poly (I:C) induced expression were investigated. Results show that ASDIGIRR and ASTRAF6 were expressed in 10 tissues of healthy sturgeon, and the highest expression was found in intestinal tract and head kidney, respectively. After incubating A. sinensis spleen cells with Poly(I:C), the expression of ASDIGIRR was significantly down-regulated at 3 h, and returned to the normal level at 6 h, then increased to the highest level at 24 h and then decreased, and at 48 h still higher than the control group. While the expression of ASTRAF6 reached the highest level at 6 h, and maintained till 24 h, then decreased to the lowest level at 48 h. The results show that ASDIGIRR and ASTRAF6 play an important role in the immune defense of A. sinensis against pathogen invasion.

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