Abstract:To breed a Megalobrama amblycephala “Pujiang No.2” pure strain, M. amblycephala varieties “Pujiang No.2” were selected as breeding parents, using UV-inactivated carp sperm stimulation of M. amblycephala eggs. Cold shock was used to inhibit second polar body eduction for the heterogeneous gynogenesis (Meio-G1) and gynogenesis second- (Meio-G2) generation groups. The genetic characteristics of “Pujiang No.2” normal population, Meio-G1, and Meio-G2 populations of M amblycephala were analyzed using twenty pairs of microsatellite primers. The results showed that 129, 99, and 84 alleles were amplified from the normal population, Meio-G1, and Meio-G2, respectively. The average number of alleles (Na) was 4.30, 3.30, and 2.80, and the average number of effective alleles (Ne) was 3.23, 2.24, and 1.76 for the three groups, respectively. The average observed heterozygosity (Ho) was 0.8067, 0.4067, and 0.1733; the average homozygosity (H) was 0.2035, 0.6000, and 0.8263; and the average polymorphic information content (PIC) was 0.6198, 0.4701, and 0.3628, respectively. The results showed that the genetic diversity of Meio-G1 and Meio-G2 decreased compared to that of the normal population, and the genetic diversity of Meio-G2 was the least. The mean Hardy-Weinberg index of Meio-G2 and Meio-G1 showed a heterozygote deficit, as did the gynogenetic normal population. Using the unweighted pair-group method with arithmetic means method based on their genetic distances, the normal and Meio-G1 populations were grouped into one cluster, while the Meio-G2 population was classified into another cluster, indicating a genetic differentiation between the two clusters. The results showed that Meio-G2 was a good breeding material, with high purity and low genetic diversity, providing an important reference value for breeding of Megalobrama amblycephala.

Abstract:The tyrosinase protein family contains key enzymes for regulating the synthesis of melanin, which plays an irreplaceable role in the formation of melanocytes. However, the underlying mechanism of the Tyr gene family in body-color formation is unclear in Plectropomus leopardus. P. leopardus is an economically important tropical fish in China. The body color of farmed P. leopardus has different degrees of degradation, which seriously affects its quality and market price. In this study, a total of five Tyr genes were identified from the whole genome of P. leopardus, and amino acid sequence alignment showed that Tyr family proteins in P. leopardus were highly conserved in relation to homologous proteins of other species, especially the typical tyrosinase functional domain of this family. The phylogenetic and comparative synteny indicated the gain and loss of Tyr genes after teleost-specific whole-genome duplication (3R-WGD). In addition, the results of qRT-PCR showed that the expression levels of all members of Tyr genes in the skin tissues of black individuals were significantly higher than those of red individuals (P＜0.05). This paper preliminarily identified and analyzed the role of the Tyr gene family in the formation of body color, providing a basis for further analyzing the evolution and functional mechanism of the tyrosine protease gene family in Plectropomus leopardus.

Abstract:miRNAs, a class of non-coding single-stranded small RNAs with regulatory roles, play an important part in the regulation of biological rhythms. In order to explore the spatio-temporal expression characteristics of miR-21, as well as the effects of fasting on its expression, real-time fluorescence quantitative PCR was used to analyze the expression of miR-21 in the embryos of different developmental stages and tissues of the Chinese perch Siniperca chuatsi, as well as the rhythmic expression after 5 d of fasting. The results showed that a high level of miR-21 can be detected in the early stage of embryonic development, expression of miR-21 decreases as the embryo develope, and only a small amount of miR-21 could be detected in the early gastrula stage. The expression of miR-21 increased after the gastrula stage, but there was no significant difference in the expression of miR-21 after the neurula stage, except in the tail-bud and heart-beating stages. miR-21 was expressed in all tested tissues, with high levels of expression in heart, intestine, and red muscle. Under normal feeding, miR-21 expression in Chinese perch muscle showed a circadian rhythm: low in the day and high in the night. After 5 d of fasting, expression of miR-21 was still in a circadian rhythm, but its median value, oscillation amplitude, and peak phase were significantly affected. Target gene prediction analysis showed that the 3′UTR sequence of Arntl2 mRNA had miR-21 binding sites. Taken together, results indicated that the expression of miR-21 in the embryo was maternal and began to rise after the neurula stage, suggesting that miR-21 plays an important role in embryonic organogenesis after this stage. The expression of miR-21 was not tissue-specific, but it may play an important role in the growth and development of heart, intestine, and red muscle. Fasting stress could affect the circadian rhythm of miR-21 in Chinese perch muscle, and miR-21 might be involved in the regulation of the rhythm of the Chinese perch by regulating the circadian gene Arntl2, thus affecting muscle growth and physiological functions.

Abstract:In order to study the tolerance and physiological response of Neocaridina denticulata to hypoxia at different temperatures, N. denticulata was placed in a closed breathing bottle at different temperatures (20, 25 and 30 ℃) to induce acute hypoxia stress. The oxygen consumption rate, lethal dissolved oxygen level, and enzyme activities related to antioxidant and respiratory metabolism of the shrimp were detected. The results showed that the oxygen consumption rate of shrimp increased significantly with increasing temperature and dissolved oxygen in water. The lethal dissolved oxygen level of shrimp was less than 0.1 mgO₂/L when the shrimp live in water with temperatures from 20 ℃ to 30 ℃. In the oxygen-enriched control, the activities of shrimp succinate dehydrogenase (SDH), cytochrome c oxidase (COX), and lactate dehydrogenase (LDH) all increased with increasing water temperature, while the activity of superoxide dismutase (SOD) first increased and then decreased. Under hypoxic stress conditions, COX and LDH activities increased with increasing water temperature, while SDH activity remained relatively constant, and SOD activity decreased. Compared with shrimp in oxygen-rich water, the shrimp under hypoxia stress displayed significantly decreased SDH activity and significantly increased LDH activity, as well as relatively constant COX activity. At 30 ℃, the SOD activity of shrimp treated with hypoxia stress was significantly lower than in the oxygen-enriched group. However, at 20 ℃ and 25 ℃, there was no significant difference in SOD activity between the oxygen-enriched and hypoxia stress groups. It is therefore suggested that N. denticulata has strong tolerance to hypoxia and a physiological mechanism of rapidly increasing anaerobic respiratory enzyme activity, as well as decreasing aerobic respiratory enzyme activities to cope with hypoxia stress.

Abstract:To study the response mechanism of Macrobrachium nipponense to high-temperature stress, we set up a control (20±0.5) ℃ and high-temperature (30±0.5) ℃ groups. The dissolved oxygen concentration was (6.5±0.5) mg/L. The expression profiles of heat shock proteins 21 (MnHSP21), 60 (MnHSP60), 70-3 (MnHSC70-3), and 90 (MnHSP90) in M. nipponense hepatopancreas and gill tissues were measured at 0, 12, 24, 36, and 48 h under high-temperature stress. Then we measured the activities of superoxide dismutase (SOD), glutathione S-transferase (GST), glutathione peroxidase (GPX), and catalase (CAT), as well as tissue structure of M. nipponense under high-temperature stress. The results showed that four heat shock protein genes were induced in hepatopancreas and gill tissues. The expression of MnHSC70-3 gene was the most significant among the four heat shock protein genes, indicating that this gene is an important molecule for high-temperature stress response in M. nipponense. At the same time, expression trends of the four genes were more obvious in the hepatopancreas than in gill tissue, indicating that hepatopancreas is a more important organ for M. nipponense in terms of high-temperature stress response. Under high-temperature stress, the activity of all related antioxidant enzymes changed to varying degrees. The activity of SOD, GST, and CAT in the hepatopancreas increased significantly, while the activity of GPX changed only slightly. The SOD enzyme activity in gill tissue was significantly lower than in the control group (P＜0.05), and the enzyme activity levels of GST, GPX, and CAT were significantly higher than in the control group (P＜0.05). The structure of hepatopancreas and gill tissue changes under high-temperature stress. The secretory cells and internal transport vesicles in hepatopancreas increase in volume, while the layered epithelium of the gill tissue structure was slightly curved, and the arrangement of blood cells was disordered. Compared with 36 h, there was no obvious change in tissue structure after 48 h of stress. In summary, high-temperature stress activated the antioxidant system of M. nipponense and induced the expression of heat shock protein genes. The MnHSC70-3 gene may play an important role in the heat tolerance of M. nipponense. Changes in the activity of antioxidant enzymes under high-temperature stress may be essential to avoid oxidative damage. This study aimed to provide a reference for healthy farming by clarifying the response mechanism of M. nipponense to hightemperature stress.

Abstract:为了对沙带鱼(Lepturacanthus savala)进行有效的分类鉴定, 明确目前黄海海域是否存在沙带鱼的自然分布, 本研究在形态学描述与测量的基础上, 利用 DNA 条形码技术对沙带鱼及其近缘种进行了分析。共采集了来自黄海、东海(台湾海峡)及南海(北部湾)的疑似沙带鱼样品 16 尾及其近缘种样品 1 尾, 测定并获取 DNA 条形码序列 17 条。结合已报道的带鱼科 8 种鱼类的 18 条 DNA 条形码序列对全部样品进行了物种鉴定, 运用 Kimura 2-parameter (K2P)模型构建了其系统进化关系。研究结果显示: 全部疑似沙带鱼样品的 DNA 条形码序列均与 GenBank 中沙带鱼(L. savala)的对应序列具有最高的相似性; 沙带鱼的种内遗传距离远小于其与同属罗氏沙带鱼(Lepturacanthus roelandti)的种间遗传距离; 在系统发育树中, 全部的疑似沙带鱼均与已发表的沙带鱼 DNA 条形码序列聚为一支。 研究结果表明, DNA 条形码技术可弥补形态学方法在沙带鱼及其近缘种鉴定中的不足, 实现沙带鱼的有效鉴定; 与此同时, 本研究进一步证实了沙带鱼在黄海的存在, 结果可为黄海沙带鱼资源的保护和可持续利用提供科学依据。

Abstract:Artificial reefs are a key tool for the restoration of ecological habitat in marine ranches. The construction of artificial reefs has many ecological effects, such as flow field, shelter, and bait effects. The attached community on artificial reefs are an important factor for the formation of bait effect. To explore the effects of reef age on community structure and functional traits of attached organisms, quadrate sampling was conducted on an artificial reef at Furong Island in Laizhou Bay in the spring, summer, and autumn of 2019. A total of 94 species of attached organisms were collected. Arthropoda had the largest number of species (33), followed by Mollusca, which included 21 species. There were 66 species on short-age (1 a) artificial reef (AR-AB), and 79 species on long-age (4–5 a) artificial reef (AR-CD). There were differences in the species composition and dominant species of attached community for different seasons and reef ages. AR-CD were significantly higher than AR-AB in Margalef species richness, Shannon-Wiener diversity, and Pielou evenness indices. Six functional traits (including feeding habits, mobility, habitat, body size, longevity, and flexibility) were selected to compare the relative abundance of functional traits in different seasons and reef ages. The results showed that the artificial reefs in this area are more likely to be attached by those species with filter-feeder, inactivity, sessile, long-lived (＞ 5 a), and extremely small (＜1 cm) characteristics, but no body flexibility (Membranipora grandicella, for example). The differences in functional traits between AR-AB and AR-CD were reflected in feeding habits, mobility, and habitat. The relative abundance of predator, high mobility, burrower, and crawler characteristics in AR-CD were significantly higher than in AR-AB (P＜0.05). However, the relative abundance of filter-feeder, sessile, and inactivity characteristics in AR-CD were significantly lower than in AR-AB (P＜0.05). The functional diversity index and functional redundancy of the attached community of AR-CD were higher than that of AR-AB, though the differences were non-significant. In this study, traditional biodiversity indices and biological traits were used to analyze the differences in community structure and functional traits of attached organisms between short- and long-aged reefs in different seasons, providing a new perspective on the ecological effects of artificial reefs.

Abstract:Mischief Reef has unique landforms and rich biological resources, and its marine microorganisms and fishery resources are being developed and utilized. To understand the bacterial diversity in the aquaculture area of Mischief Lagoon in summer, as well as its correlation with environmental factors, the community structure of seawater bacteria were analyzed through high-throughput sequencing technology, the main environmental impact factors were explored, and its functions were predicted by PICRUSt. The results showed that the bacteria of Mischief Reef lagoon had rich community composition. A total of 29 phyla, 57 classes, 152 orders, 256 families, and 439 genera were detected. The dominant bacteria include Proteobacteria, Cyanobacteria, Bacteroidetes, and Actinobacteria. There were differences in the alpha diversity index between the three water layers of each site, but none of them reach a significant level. Using redundancy analysis, it was found that the main environmental impact factors are salinity, COD, COD/NO₃-N, and active silicate. The main functions, determined by PICRUSt functional prediction, included metabolism (amino acid metabolism, carbohydrate metabolism, energy production and conversion), genetic information processing (protein translation and modification, DNA replication, recombination and repair), and information processing (signal transduction mechanism, coenzyme transport, inorganic ion transport). This study analyzes the marine community structure of the Mischief Reef Lagoon aquaculture area in summer and its relationship with factors, providing a scientific basis for understanding the microbial diversity and rational development and utilization of the South China Sea, marine fisheries development and protection, and ecosystem protection.

Abstract:Composition and species diversity of catches caught by pelagic longline fishing in the tropical Western and Central Pacific Ocean (WCPO, 2°03′─11°17′S 163°14′─173°35′E) during May 2018 and Mar 2019 were analyzed. The generalized linear mixed model (GLMM) and circle statistics methods were used to assess the effects of temporal and spatial factors, such as water depth and lunar phase, on the catch composition and species diversity. The results showed that: (1) the total number of catches was 3673, and catches consist of 35 species, in 30 genera, 21 families, and 9 orders. According to index of relative importance (IRI), bigeye tuna (Thunnus obesus) and yellowfin tuna (Thunnus albacores) are dominant species, while blue marlin (Makaira nigricans), albacore (Thunnus alalunga), silky shark (Carcharhinus falciformis), long-snouted lancetfish (Alepisaurus ferox), and pelagic stingray (Pteroplatytrygon violacea) are important species. (2) The CPUEs of bigeye tuna, yellowfin tuna, and bycatch species were (1.66±0.89), (1.39±1.45), and (2.52±1.27) ind/1000 hooks, respectively. The ShannonWiener (H'), Margalef (D) and Pielou (J) indices were (1.78±0.28), (2.53±0.60), and (0.79±0.09), respectively. (3) The GLMM model fit indicated that the lunar phase (cosine) had an extremely significant effect on the CPUE of bigeye tuna (P=0.001, higher CPUE in full moon and lower in new moon), and the lunar phase (sine) had a marginal effect on the CPUE of yellowfin tuna (higher CPUE in the first quarter and lower in the last quarter lunar phase). As for bycatch species, no significant effect of lunar phase on CPUE was detected. Water depth had a highly significant effect on CPUEs (P＜0.001). (4) No significant effect of lunar phase on species diversity indices was detected. However, water depth significantly influences the Shannon-Weiner index (H′) and Margalef index (D) (P＜0.001). The results revealed that the high richness of species and complexity of community in the tropical WCPO would provide good community tolerance to environmental changes and fishing activities.

Abstract:Skipjack tuna (Katsuwonus pelamis) is an important resource for purse seine fishing in the Western and Central Pacific Ocean. In order to explore the spatial and temporal differences in the impact of environmental factors on the fishing rate of skipjack tuna, this paper evaluates the fishing logbook data of tuna purse seine fishing vessels in the Western and Central Pacific Ocean from 2009 to 2018 in mainland China, as well as the corresponding marine environmental data. Exploratory regression analysis, spatial autocorrelation analysis, and the geographically weighted regression (GWR) model are used to explore the spatial and temporal heterogeneity of standardized environmental factors and the fishing rate of skipjack tuna. The results show that: (1) The fishing rate of skipjack tuna has spatial aggregation. In terms of space, there are 2–3 main aggregation areas, which are concentrated in 152°–164°E, 3°N–7°S sea area on the west side, 164°–175°E, 5°N–4°S sea area on the east side, and 175°–180°E sea area in the second quarter. In terms of time, the degree of aggregation had values of fourth quarter＞first quarter＞second quarter. (2) The spatial heterogeneity degree of the effects of environmental factors on the fishing rate of skipjack tuna had values of sea level anomaly (SLA)＞mixed layer depth (MLD)＞net primary production (NPP)＞sea surface temperature gradient (SSTG). (3) SLA and MLD had significant negative effects on the fishing rate of skipjack tuna because the corresponding values of SLA and MLD were smaller in the surface nutrient-rich areas. NPP and SSTG were mainly positively affected because the frontal where the cold and warm water intersects is greatly affected by these two factors. (4) The GWR model was tested, and it was found that its residuals showed smaller spatial autocorrelation, indicating that the GWR model has a better fitting effect and is better than the ordinary least squares (OLS) method.

Abstract:The V-type otter board is an important part of the single-ship bottom-trawl system. In order to explore the hydrodynamic variations of V-shaped otter boards in various working postures, we applied a numerical simulation method (computational fluid dynamics, CFD) to compare the hydrodynamic characteristics of the otter board with different aspect ratios (0.4, 0.5, 0.6, 0.7) and dihedral angles (16°, 19°, 22°, 25°), then selected one V-shaped otter board with superior hydrodynamic characteristics. Next, the hydrodynamic coefficient, surrounding flow field distribution, and surface pressure variation of this otter board were each analyzed in different positions of forward, backward, inward, and outward inclinations of 5°, 10°, 15° and 20°. The results show that: 1) the V-shaped otter board (No.13 otter board) with aspect ratio λ=0.7 and dihedral angle Γ=16° has the best hydrodynamic performance. The lift coefficient reaches its maximum value of 1.482 at 37.5°. The expansion efficiency reaches the maximum when the angle of attack is 10°. 2) With an increasing angle of attack, the pressure on the headstream surface of the No.13 otter board gradually increases, and the velocity difference between the headstream surface and the back flow surface of the otter board also increases. 3) When the No.13 otter board has different degrees of forward and backward inclination or inward and outward inclination, the lift coefficient decreases, and the drag coefficient decreases with increasing inclination angle. 4) With the increasing inclination angle, the pressure center of the headstream surface moves to the front of the otter board, and the change of the back vortices on the center of the otter board surface is not obvious. When the otter board is tilted back and forth, the pressure distribution of its flow face clearly changes; that is, with increasing inclination, the pressure center gradually moves up and down the front end, and the vortex of the otter board's center surface gradually decreases. The results of this study provide a scientific reference for predicting the variation of hydrodynamic characteristics of an otter board with different working positions and adjusting its stability.

Abstract:金枪鱼属(Thunnus)鱼类是我国远洋渔业极为重要的渔获资源, 其表型纹理信息不仅具有鱼种的特异性, 而且可作为分类的科学依据。传统鱼类纹理特征分析主要是定性描述分析, 而计算机视觉技术可为鱼类纹理特征提供定量分析数据。因此, 本研究通过计算机视觉对 3 种金枪鱼图像进行预先定位基准点, 通过移动基准点确定纹理特征区域并自动截取。对纹理图像进行灰度转换和灰度量化处理, 量化的灰度图像进行灰度共生矩阵计算, 并对灰度共生矩阵进行归一化处理。通过归一化的灰度共生矩阵计算出 6 个纹理指标, 并分析纹理指标的距离和方向的变化趋势, 通过因子分析研究金枪鱼纹理指标。研究结果表明, 通过计算机视觉的纹理分析, 3 种金枪鱼纹理指标提取效果较好, 其纹理指标在距离值为 4 时, 变化趋势趋于稳定, 而 3 种金枪鱼的纹理指标方向变化, 其均值方向具有代表性。3 种金枪鱼的因子分析, 第 1 主成分贡献率为 81.10%, 表明提取的 6 个纹理指标意义较大且效果较好。 以期为金枪鱼智能识别奠定前期基础, 也为其他鱼类表型纹理研究提供借鉴和参考。