Abstract:In this study, a total of 821 shrimps from four breeding population generations and a wild population of Fenneropenaeus chinensis (2015, 2016, 2017, and 2019) were sequenced using 2b-RAD technology to analyze the genetic diversity characteristics of artificial breeding and wild populations of F. chinensis, mining the selected single nucleotide polymorphism (SNP) sites in the continuous artificial selection process. A total of 83767 SNP sites were obtained by sequencing; F-statistics showed that the average coefficient of genetic differentiation (FST) between wild population and breeding populations was 0.022. The highest degree of genetic differentiation between the wild and breeding populations in 2019 was 0.0260; the lowest degree in 2015 was 0.0190. The FST between wild and breeding populations is less than 0.05, indicating weak genetic differentiation. The population principal component analysis results showed that the genetic structure between wild and breeding populations did not change significantly. The statistical results of genetic diversity showed that the average expected heterozygosity (He) of the wild population and the breeding populations were 0.1716 and 0.1806, respectively; the average observed heterozygosity (Ho) values were 0.1861 and 0.1943; and the average polymorphism information contents were 0.1428 and 0.1515. The mean values of nucleotide polymorphism (Pi) were 0.1732 and 0.1813. Among them, each genetic diversity index of the selected populations in 2017 and 2019 was significantly different compared to the wild population (P＜0.05). Selection and elimination analysis of different generations of breeding and wild populations yielded 92, 103, 166, and 117 selected SNP loci; the number of common loci was 4. The number of common sites with allele frequencies increasing generation by generation between adjacent generations of selective breeding populations was 7107, of which 3674 sites deviated significantly from the Hardy-Weinberg balance (P＜0.05). The allele frequency between adjacent generations of breeding populations decreased to 8501, of which 4101 loci significantly deviated from the Hardy-Weinberg equilibrium (P＜0.05). Results indicate that the population genetic diversity and genetic structure of F. chinensis have not changed significantly after artificial selection and breeding, and a high genetic selection potential is maintained.

Abstract:Neutrophils are the most abundant non-specific immune cells and are critical in researching pathogen invasion resistance. Providing abundant cellular materials is fundamental for understanding the function and immune defense mechanisms of neutrophils. In the study, neutrophils were isolated from grass carp kidneys using a fish-tissue neutrophils isolation kit. The neutrophils were purified by the differential adherent method, and their morphology was identified by Diff’s staining and electron microscopy. The characteristic enzyme myeloperoxidase (MPO) was identified by potassium iodide and pyrro-red G staining. Using a multifunctional microplate reader, its activity was detected by the ability to express MPO and the ability to release reactive oxygen species (ROS) and nitric oxide (NO), stimulated with Phorbol 12-myristate 13-acetate (PMA). Neutrophils could also form neutrophil extracellular traps (NETs). The expression of MPO and the ability to release ROS, NO, and NETs were detected by a multifunctional enzyme plate analyzer. Survival was detected by the trypan blue staining and CCK-8. Results showed that the isolated cells had the morphological characteristics of neutrophils: they were uniform in size, with round or kidney-shaped nuclei, had type A and B particles in the cytoplasm, and indicated the characteristic sepia enzyme of MPO by staining. Purity reached (99.3±0.53)%, the number of viable cells reached (97.70±0.76)%, and the viability remained at (89.91±3.56)% after they were cultured in vitro for 24 h. By stimulation with PMA, the expression of MPO, ROS, NO, and NETs was significantly increased and positively correlated with time. The method of isolating neutrophils from grass carp was successfully established in this study, as the neutrophils showed increased vitality. Furthermore, this study provides a foundation for further research on the function and immune mechanism of fish neutrophils.

Abstract:Species of the Carangidae family are important warm water and temperature marine economic fish. They are also a primary product of future deep-sea fishing and aquaculture development in China. However, as there are many species of Carangidae, and their related species are similar in morphology, traditional morphological identification methods have significant limitations. The accurate classification and identification of Carangidae species is a focus area of resource conservation and sustainable development and utilization. Therefore, research on the DNA barcoding of Trachinidae fish is scientifically significant and has economic value. To verify the applicability of DNA barcodes in the identification and classification of Carangidae, 17 sequences were collected from 7 species and 6 genera, and other valid sequences in Barcode of Life Data (BOLD) were screened. A total of 273 DNA barcode sequences of 95 species in 25 genera were obtained. Then the DNA barcode classification system for Carangidae was constructed by BLAST comparison, genetic distance calculation, and phylogenetic relationship analysis. Results indicated that: (1) The average genetic distance levels of three taxa, intergeneric, interspecific within genera, interspecific, and intraspecific of Carangidae were 0.186, 0.169, 0.090, and 0.008, respectively. The average genetic distance of the interspecific was 21 times that of the intraspecific. DNA barcoding is suitable for the classification and identification of Carangidae. (2) DNA barcode technology could identify species with incorrect morphological identifications, indicating that DNA barcodes can make up for the limitations of traditional morphological identification and accurately correct the morphological classification results of Carangidae. (3) DNA barcode analysis of Carangidae shows that there are still certain “homologous” and “heterologous” phenomena in BOLD. It is suggested that the information accuracy should be strictly evaluated when using the database information. (4) The phylogenetic analysis results of 95 species of Carangidae support the classification of Parona signata as Trachinotinae and provide new insights into the taxonomic status of this species. This study has enriched the DNA barcode database of Carangidae and provided molecular biological evidence for the species identification and systematic classification of Carangidae.

Abstract:Based on quarterly bottom trawl survey data from 2018 to 2019, we analyzed the dynamic changes in fish community structure and their relationship with environmental factors in the survey area using ecological indicators, such as resource density, relative importance index, and diversity index. Results showed that there are 84 fish species in the survey area, belonging to two classes, 14 orders, 39 families, and 69 genera. There were seven dominant species, including Harpadon nehereus, Trichiurus japonicas, Pennahia argentata, Setipinna tenuifilis, Benthosema pterotum, Stolephorus commersonnii, and Amblychaeturichthys hexanema, whose composition has changed dramatically. The highest biomass index value was in summer, at 3.25×10³ kg/km² . The highest abundance index value was in autumn, which was 6.64×10⁵ ind/km² . The highest diversity index values of H′ and J′ were in winter, at 1.92 and 0.71. The distribution of T. japonicus and B. pterotum is positively correlated with depth and salinity. The distribution of P. argentata is strongly positively correlated with temperature and negatively correlated with pH. S. commersonnii, S. tenuifilis, and H. nehereus have a low preference for environmental factors. By exploring the spatial and temporal changes of fish community structure in the Oujiang River Estuary, the results of this study provide scientific evidence for protecting fishery resources and improving the quality and function of fishery environments in the estuary area.

Abstract:Macrobrachium nipponense is a freshwater prawn with high economic value. It is widely distributed in most freshwater water bodies and in all river systems of Henan Province. With the development of aquaculture, the change of ecological environment in the water area, and the influence of contrived factors, the germplasm resources of M. nipponense have also been gradually affected in recent years. To provide a reference for M. nipponense in Henan Province, we assess the germplasm resources and genetic diversity of M. nipponense in Henan Province. The mitochondrial COI gene was used as a marker to investigate population genetics of 135 M. nipponense samples from 18 populations in Henan Province. The samples covered four main water systems in Henan Province, including the Yangtze, Yellow, Huaihe, and Haihe Rivers. Results showed that the 18 populations of M. nipponense in Henan Province contained 27 haplotypes. The average haplotype diversity (H_d) and average nucleotide diversity (π) were 0.78574 and 0.01059, respectively. The Huaihe population had the lowest genetic diversity, and the Yangtze River population showed the highest genetic diversity. High Hd and low π were observed for the four rivers. AMOVA showed that major genetic variation (66.03%) occurred within the population, and 40.22% of the genetic variation existed among populations. There was no significant genetic differentiation for M. nipponense from the four water systems based on phylogenetic and haplotype network analyses. The demographic history analysis showed that M. nipponense of Henan province did not experience recent population expansion, maintaining a relatively stable population size. This study can provide basic guidance for protecting and reasonably utilizing the germplasm resource of M. nipponense in Henan Province, providing reference material for the whole of China.

Abstract:中华鲟(Acipenser sinensis)为国家一级重点保护野生动物。2004—2014 年在长江口水域标志放流中华鲟 12570 尾, 标志回捕中华鲟 24 尾次, 接收 18 枚落式卫星数据回收标志(PAT)信息。本研究根据标志放流信息, 分析研究长江口标志放流中华鲟降海洄游和分布特征。研究结果表明: (1)长江口标志放流中华鲟分布于经度跨度 7°, 纬度跨度 9°的长江口水域和东海及黄海海域, 主要聚集分布区为长江口水域和舟山群岛海域; (2)标志放流中华鲟具有显著的降海洄游趋势, 放流后短期滞留在长江口淡水环境, 7 d 后具有进入海洋的行为; (3)长江口标志放流中华鲟进入海洋后, 其迁移方向会出现随机性, 在迁移过程中具有折返、转向、停滞的特征。本研究通过对长江口增殖放流的中华鲟标志回捕信息开展研究, 旨在揭示中华鲟降海洄游和分布特征, 为中华鲟资源保护提供科学依据。

Abstract:As a spawning ground for many fish species, Bohai Bay plays a significant role in maintaining sustainable inshore fish stocks in Bohai and the Yellow Sea. In recent decades, the loss or fragmentation of fish habitats has been taking place in Bohai Bay as a result of exogenous interference factors, such as human activity and climate change. An understanding of the distribution pattern of fish eggs is urgently needed to protect fish recruitment. However, a comprehensive insight into how fish eggs are distributed in Bohai Bay is still lacking. To better understand how environmental conditions affect the distribution of fish eggs in Bohai Bay, an integrated habitat suitability index (HSI) model, including three physical and chemical environmental variables, sea surface temperature (SST), sea surface salinity (SSS), and seawater pH, was developed in this study. Meanwhile, three empirical HSI algorithms (geometric mean method; minimum method; continued product method, CPM) were performed to select the best algorithm. The data used for analysis comes from independent trawl surveys, applying standardized sampling protocols from 2014 to 2018. The results showed that (1) the fish eggs in Bohai Bay were mainly distributed in areas where the ranges of SST, SSS, and pH are 21.6?24.8 ℃, 30.07?32.60, and 8.03?8.21, respectively. (2) The SI of each environmental variable varies by month. (3) CPM was the optimal HSI model for fish eggs in Bohai Bay based on the evaluation criteria of Akaike information criterion. (4) In May, the HSI model shows an acceptable performance. In June and July, there may be potential unconsidered factors that dominate the distribution of fish eggs under suitable SST, SSS, and pH conditions. This study enhances our understanding of the relationships between fish eggs and different environmental factors. Moreover, the models built can be used to detect potential spawning grounds for fish in Bohai Bay. These findings may increase awareness among researchers and policymakers. A more comprehensive survey and scientific site layout will be helpful to gain a deeper understanding in the future.

Abstract:Different fishing strategies have different effects on adaptive changes in the morphological characteristics of fish species. To evaluate the impact of different fishing strategies on the growth characteristics of fish, the marine medaka (Oryzias melastigma) was used as the model organism. Seven fishing strategies were used: 90% large individual fishing (high-intensity large individual fishing, H-B), 90% random fishing (high-intensity random fishing, M-R), 75% large individual fishing (middle-intensity large individual fishing, H-B), 75% random fishing (middle-intensity random fishing, M-R), 50% large individual fishing (low-intensity large individual fishing, L-B), 50% random fishing (low-intensity random fishing, L-R), and 75% small individual fishing (middle-intensity small individual fishing, M-S). The growth characteristics of O. melastigma in the F1–F3 generations were determined. The egg diameter and larval length of O. melastigma were significantly different under the different fishing strategies in the same generation (P＜0.01). Among different generations, the egg diameter increased in the high- intensity fishing treatment group (90% fishing strategy condition) and decreased in the low intensity fishing treatment group (50% fishing strategy condition). However, different generations had little effect on the hatchability and survival rate of the next generation of eggs. The growth rate of the low-intensity fishing treatment group was higher than that of the other treatment groups in the juvenile stage among different generations. During the intergenerational larval development stage, the growth rate of the high-intensity fishing treatment group increased rapidly. This growth rate was significantly higher in the early stage than in the late stage. However, the growth rate of the high-intensity fishing treatment group was lower in the larval and juvenile stages. With the increase in external fishing pressure, the instantaneous growth rate of the high-intensity fishing treatment group was the lowest among the same generation. The instantaneous growth rates of the low-intensity and large individual fishing strategy groups were stable among generations. Similar to the current fishing strategy, high intensity and large individual fishing will lead to great differences in the biological characteristics of fish in three generations. Therefore, for the sustainable utilization of fishery resources and to predict the development trend of fish evolution, it is imperative to study the changes in biological traits of fish caused by fish-induced evolution by simulating the different fishing strategies.

Abstract:Based on the economic and ecological value of macroalgae, the recruitment of new cultivated species with potential is necessary for the healthy development of the seaweed cultivation industry. Costaria costata is a brown alga with high nutritional and economic value. This natural seaweed resource is not found in China. In this study, the MaxEnt model and ArcGIS were used to predict the suitability and potential invasion risk of C. costata in China and explore the influence of different factors on the growth of sporophyte, to support the cultivation of C. costata. The prediction model of C. costata distribution was constructed based on correlation analysis between environmental factors, a selection of the global natural distribution points of C. costata, screening of the regulation parameter, and the ratio of the training set to test set on the prediction performance of the model. Results showed that the model performed the best when the regularization parameter was 1 and the ratio of training set to testing set was 70 : 30. The prediction model for C. costata distribution was constructed by eight environmental factors based on the correlation of environmental factors and model contribution rate. Among them, the temperature and light intensity had the most significant influence on the natural distribution. When the light intensity was not less than 4 μmol/(m2 ·s), the annual variation was 52 μmol/(m2 ·s), the monthly mean temperature was not less than 7 ℃, and the annual variation was 27 ℃, indicating the high suitable distribution probability of C. costata. The model showed that the suitable areas of C. costata in China were primarily distributed in the Yellow Sea and Bohai Sea, accounting for 11.32% of the total sea area; among which the marginal biogenic areas of C. costata in Yellow and Bohai Sea are primarily distributed in the coastal areas of Liaodong Bay, the northern coastal areas of Bohai Bay, and the coastal areas from Qingdao to Lianyungang, accounting for 2.99% of the total sea area. The low adaptable areas are primarily distributed in the coastal area of Liaodong Bay, the coastal area of Dalian, and the coastal area of Shandong Peninsula, accounting for 5.09% of the total sea area. The middle adaptable areas are primarily distributed in the southwest coastal area of Liaodong Bay, accounting for 1.33% of the total sea area. The high suitability areas are primarily distributed in the northern and southern coastal area of Liaodong Bay, accounting for 1.91% of the total sea area. The single-factor growth experiment results showed that, when the temperature was 10 ℃, the light intensity was 60 μmol/(m2 ·s), the salinity was 36, the nitrate was 1 mg/L, and the phosphate was 0.1 mg/L, indicating the highly relative growth rate of C. costata sporophyte. Combined with the field investigation, C. costata was found on the floating shelf in Changdao Island in Yantai and Longwangtong Bay in Dalian, consistent with the predicted results. This study showed that the coastal areas of Liaodong Bay, Dalian, and Shandong Peninsula are suitable areas for the introduction and cultivation of C. costata. However, attention should be paid to the risk of high invasion in the northern and southern coastal areas of Liaodong Bay. If artificial cultivation is performed, ecological safety assessment should be strengthened.

Abstract:The Yalong River is the biggest tributary of the Jinsha River. Periphytic algae are an important component of the aquatic ecosystem, playing an important role in the energy flow and matter cycling of river food chains. To understand the community structure of periphytic algae and its relation to the environmental conditions, surveys were conducted in the lower Yalong River and its tributaries between June and August 2018 (102°6′6″E, 28°46′21″N–101°49′22″E, 26°38′38″N). A total of 95 species of periphytic algae belonging to 49 genera of five phyla were identified, among which Bacillariophyta (57 species) were the dominant taxa, followed by Chlorophyta (20 species) and Cyanophyta (14 species). The species richness was highest in the Yalong River, followed by the Anning River, and lowest in the Anning River tributaries. The dominant species in the lower Yalong River were Achnanthes sp., Gomphonema sp., Leptolyngbya gelatinosa, Synedra sp., Navicula sp., Oocystis naegelii, and Cymbella sp.; the dominant species in the Anning River were Achnanthes sp. and Aphanocapsa elachista; and the dominant species in the tributaries of the Anning River were Achnanthes sp., L. gelatinosa, Gomphonema sp., Navicula sp., and Cocconeis placentula. The algal density in the Yalong River was significantly lower than that in the Anning River and its tributaries. The algal density in the Anning River was higher than that in the tributaries. Upstream to downstream, the species richness in the Anning River increased under a longitudinal gradient, the proportion of Bacillariophyta in the Anning River decreased gradually, while the proportion of Chlorophyta and Cyanophyta increased gradually. Redundancy analysis indicated that the periphytic algae structure in the lower Yalong River was relative to the ecological factors, such as water temperature, turbidity, and substrate type. Current velocity and altitude were the main environmental factors affecting the distribution of periphytic algae in the Anning River under a longitudinal gradient. This study provides a scientific basis for the research on and conservation of biodiversity in high-altitude areas.

Abstract:Myxobolus honghuensis is a parasitic pathogen that causes pharyngeal myxosporidiosis. The infection often results in massive mortality in cultured gibel carp Carassius auratus gibelio (Bloch). Currently, there is no effective drug for treating pharyngeal myxosporidiosis. Most myxosporeans have a complex life history involving two alternative hosts. Myxosporean infection in fish hosts occurs primarily through the horizontal transmission of actinosporean released by invertebrate hosts. Domestic researchers have performed many studies on the life history of myxosporea parasitized by C. auratus gibelio. Approximately 20 species of actinosporean have been discovered and reported. However, no invertebrate host and actinosporean have been found in M. honghuensis. In this study, gibel carp larvae were obtained by artificial insemination, hatched, and nursed in an indoor water circulation system with tap water at a temperature of (23±1) ℃. Single tube semi-nested PCR, fluorescence quantitative PCR, and oligonucleotide fluorescence in situ hybridization (FISH) were used to detect M. honghuensis infection in brood stock tissues, eggs, and larvae. The covet infection rate of M. honghuensis in the 34 gibel carp females used in this study (A1–A22, B1–B12) was 50% to 75%. The positive infection rate in eggs and pseudobranch was higher than that in ovarian tissue samples. The pre-sporogenic stage of M. honghuensis was detected in the ovary, pseudobranch, kidney, and spleen of gibel carp. The 15 and 30 days post-hatch samples of gibel carp larvae (A1, A8, B8, and B9) obtained from infected females and completely cultured indoors were positive for M. honghuensis infection. The presence of M. honghuensis in the pseudobranch, gill, and kidney tissues of 15 days post-hatch larva was confirmed via FISH. The collective results reveal transovarian transmission of M. honghuensis in gibel carp.

Abstract:Estuary is an essential habitat for fish, occupying an important position in the sustainable development of fishery resources. Carrying out evaluation research on estuary habitat quality is of great significance for understanding the status of estuary habitat functions and providing management bases. In this paper, the research methods and application progress of estuarine fish habitat quality assessment are reviewed, mainly focusing on three aspects: (1) based on the quantity distribution characteristics of fish, through the correlation between the quantity distribution characteristics of fish and environmental factors, exploring the suitable habitat distribution pattern of fish species; (2) based on the survival performance characteristics of fish, screening the survival performance characteristics indicators of each stage of fish life history and evaluating the quality of different types of habitats; and (3) based on the community structure characteristics of fish, comprehensive evaluating estuary fish habitat quality by constructing a fish community evaluation index. The evaluation of habitat quality of estuarine fish is helpful for understanding the change mechanism of estuarine fishery ecological function, providing a theoretical basis for the rational control of human activities along estuaries, the development of monitoring and early warning techniques for estuarine habitat quality, and the scientific implementation of estuarine habitat protection and restoration.