Abstract:In recent years, the concept of ecosystem-based fisheries management (EBFM) has been widely recognized. The achievement of EBFM goals requires a deep understanding of the structure, function, and mechanisms of the ecosystem, as well as appropriate modeling methods to evaluate and predict the changes in biological resources and ecosystems. Fishery ecosystem dynamic models have developed in this context, aiming to investigate the structure and function of fishery ecosystems, and to evaluate the effects of environmental changes and human intervention. This category of models has gradually become the major tool for information synthesis, integration, and prediction in ecosystem research. The fishery ecosystem dynamic models have developed rapidly in the past 20 years, whereas due to their wide diversity, there are substantial difficulties in the selection, construction, and application of those models. This study traces the development of fishery ecosystem dynamic models, and briefly introduces representative models at the population, community, and ecosystem levels, respectively. The fishery ecosystem dynamic models bridge the gap between microcosmic processes and macroscopic phenomena, and serve as a crucial tool for revealing the regulatory mechanisms of ecosystems. In the future, the fishery ecosystem dynamic models need further development, and should be adjusted and improved based on our understanding of the ecosystem, technical foundations, and data sources, in order to provide supports for the practice of EBFM.

Abstract:The ridgetail white prawn (Exopalaemon carinicauda) is an important small to medium-sized economic species. Due to its strong reproductive capacity, fast growth, and excellent environmental adaptability, it has gradually become the main species for the development of saltwater aquaculture modes in China. However, like many aquaculture industries, robust genetic foundations are essential to ensure the growth and economic performance of breeding stock. It is necessary to continuously monitor the genetic variation in broodstock to maintain long-term sustainability. Eleven polymorphic microsatellite loci were used to analyze the genetic diversity and genetic differentiation of four consecutive generations (GP2–GP5) of an E. carinicauda breeding stock from 2021 to 2023 to reveal the genetic variation of different generations under low-salinity culture conditions. The results were as follows. A total of 11 microsatellite loci were amplified, and 70 alleles were detected, with fragment lengths ranging from 138 to 296 bp, of which 10 loci were moderately to highly polymorphic. The average observed heterozygosity (H_o) of GP2–GP5 breeding stock was 0.504, 0.555, 0.499, and 0.416, respectively; the average expected heterozygosity (H_e) was 0.564, 0.546, 0.554, and 0.550, respectively; and the average polymorphic information content (PIC) was 0.518, 0.483, 0.489, and 0.490, respectively. The genetic diversity of white shrimp slightly declined with successive generations of breeding but remained at a moderate level. Genetic differentiation results indicated that the degree of genetic differentiation between adjacent generations gradually increased from GP2 to GP5, showing weak differentiation. Additionally, the sufficient genetic exchange (N_m=11.32–14.62) between adjacent generations of the breeding stock gradually decreased. Cluster analysis also showed differences in genetic composition between generations, with the optimal K value being 2. The effective population size of E. carinicauda in different generations ranged from 3.1 to 37.1 individuals, and inbreeding within the stock was detected (F_is=0.061–0.212). This study illustrated that although the genetic diversity of the second to fifth generations of E. carinicauda remained relatively rich under low-salilnity culture conditions, it slightly declined over several generations. However, the species still showed good breeding potential. The stock exhibits weaker genetic differentiation and unstable structure, necessitating continuous monitoring and reinforcement. In future breeding efforts, it is crucial to prevent a reduction in effective population size to avoid issues such as inbreeding within the stock. The results of this study provide genetic data essential for the next step in developing a breeding plan for new low-salilnity-tolerant white shrimp varieties.

Abstract:As an important part of grouper culture, tomato hind (Cephalopholis sonnerati) is a rare fish species in China, which has a huge consumer market and broad prospects. Gonad samples of tomato hind from 30 to 380 days were observed using dissection and histological methods to investigate the early gonadal development, gonadal differentiation, and reproductive characteristics of tomato hind under artificial breeding. The results showed that tomato hind is a typical functional protogynous hermaphrodite species with asynchronous ovarian maturation and multiple spawning events. The oocytes can be divided into six phases, and the development of ovarian can be classified into six periods based on the largest transverse section area occupied by different phases of oocytes. Primitive ovarian cavity appeared at 45 days after hatching. The ovarian cavity was observed at 60 days after hatching, indicating the beginning of morphological differentiation of the ovaria. Oogonial began to proliferate at 150 days after hatching. The ovaries developed to stage II at 270 days after hatching, with phase II oocytes predominant and oogonial being activated to proliferate. The ovaries of tomato hind developed rapidly, reaching stage III at 310 days after hatching, and the volume of oocytes increased significantly. The ovaries reached stage IV at 380 days after hatching, when the volume of oocytes increased further and oocytes were filled with yolk. Ovaries of stage V were sampled during the breeding season. The nuclear membrane disappeared, and the yolk homogenized. After the breeding season, the ovaries reached stage VI, were dominated by phase II and III oocytes, and degeneration of oocyte were observed. In many cases, the occurrence of sex change is under social control, such as the disappearance of the dominant individual. Under artificial breeding conditions, sex reversal could occur before first sexual maturation at 380 days after hatching in tomato hind. The histology showed that most oocytes were in phases II and III in the early intersex traditional phase, while a few atretic oocytes, spermatocytes, and sperm cells could be observed. We speculated that the artificial breeding population of tomato hind was a new social group, which only had females at the beginning. Therefore, when the breeding season comes, some individuals will be induced by social factors to sex reversal. This study showed the gonad development and differentiation characteristics of tomato hind under artificial breeding, providing a reference for large-scale artificial breeding and a theoretical basis for sex control breeding.

Abstract:The cannibalism of fish is closely related to stress responses, and aggressive behavior is also affected by the metabolism of serotonin (5-HT) and dopamine. This study was conducted to study the growth, survival, bite marks on the body surface, stress response, and 5-HT and dopamine metabolism in Takifugu rubripes, aiming to explore the effect of moderate feed restriction on cannibalism. Uninjured juvenile Takifugu rubripes (18.61±0.05) g were selected in this experiment. The high amount of feed group (FH) was designed as fish fed four times a day to apparent satiation. The amount of feed was reduced to 85% (FM) and 70% (FL) of the FH group for the treatment groups. Each experimental diet was assigned to triplicate tanks with 30 fish per tank. The feeding trial lasted for 56 days. Bite marks in surviving and dead fish fed the FH diet were observed, while the number was significantly lower compared to that in fish fed the FL and FM diets. The survival rate was significantly lower in the FL and FM groups with moderate feed restriction compared to that in the FH group, but there were no significant differences in final body weight, weight gain, and specific growth rate. Compared with the FH group, the levels of liver glycogen and serum glucose were significantly increased in the FL and FM groups. For the 5-HT pathway, the level of 5-hydroxyindoleacetic acid (5-HIAA) was significantly reduced in the FL group, and relative expression levels of tat1, maob, and htr7 were significantly higher than that in the FM and FH groups. Additionally, relative expression levels of tph1a, tph2, and vmat2 in the FL group were significantly higher than those in the FM group. Compared to the FH group, the expression of tph2 in the FM group was significantly down-regulated, while the expression of ddc was significantly up-regulated. In conclusion, this study revealed that feed restriction was a key factor leading to the cannibalistic behavior of Takifugu rubripes with intact teeth. However, cannibalism was still observed after feeding four times a day to apparent satiation. Moderate feed restriction may exacerbate cannibalism and reduce survival rate by inhibiting the dopamine pathway in the brain. Additionally, Takifugu rubripes may cope with the stress of cannibalism induced by feed restriction via increasing liver glycogen synthesis and gluconeogenesis and enhancing 5-HT metabolism.

Abstract:The quantitative evaluation of the heavy metal waste output from marine fish farming can provide scientific data for improving industrial planning and farming management of aquaculture. In this study, we analyzed contents of iron (Fe), copper (Cu), manganese (Mn), chromium (Cr), cadmium (Cd), and lead (Pb) in 48 samples of formulated feed and 144 samples large yellow croaker (Larimichthys crocea) whole-fish collected from six net-pen feeding trials, and determined the retention efficiency and waste outputs of the heavy-metals for the first time using a modified nutritional model that has been widely used for assessing nitrogen (N) and phosphorus (P) waste outputs of fish farming. The results showed that, the sequences were Mn (709.284 mg/kg)＞Fe (175.154 mg/kg)＞ Cu (34.215 mg/kg)＞Pb (7.339 mg/kg)＞Cr (0.688 mg/kg)＞Cd (0.413 mg/kg) for the content of the heavy-metals in the feed, Fe (10.187 mg/kg)＞Mn (2.392 mg/kg)＞Cu (0.581 mg/kg)＞Cr (0.464 mg/kg)＞Cd (0.014 mg/kg)＞Pb (0.013 mg/kg) for the content of the heavy-metals in the whole-fish body, Fe (6.36%)＞Cr (5.71%)＞Cd (4.58%)＞Pb (2.90%)＞Cu (1.75%)＞Mn (0.35%) for the retention efficiency of the heavy-metals, and Mn [0.9764 g/kg fish gain]＞Fe [0.1990 g/kg fish gain]＞Cu [0.0422 g/kg fish gain]＞Cr [0.0081 g/kg fish gain]＞Pb [0.0007 g/kg fish gain]＞Cd [0.0004 g/kg fish gain] for the waste outputs of fish farming. The heavy-metal contents depended on either the heavy-metal content in the feed or the retention efficiency of the heavy metals. Fe and Cr in whole-fish bodies were mainly affected by retention efficiency of these elements, while contents of Mn, Cu, Pb, and Cd in whole-fish were mainly affected by the feed content of these elements. The waste outputs of Fe, Cu, and Mn significantly positively correlated to wastes of N and P, respectively, suggesting that the wastes of Fe, Cu, and Mn increased with the increase of wastes of N and P. Considering the critical roles of N, P, and Fe as the nutrients limiting growth of phytoplankton and primary productivity in ocean, the results indicated that waste outputs of offshore aquaculture of large yellow croaker could remarkably elevate biomass of phytoplankton and primary productivity in ocean.

Abstract:Environmental DNA (eDNA) technology was applied to monitor six Apostichopus japonicus cultivation ponds during the summer and autumn of 2023 to investigate the phytoplankton community structure and its impact on the environment in sea cucumber (Apostichopus japonicus) cultivation ponds. The survey results showed that 8 phyla, 103 genera, and 162 species of phytoplankton were detected in the summer, while 8 phyla, 248 genera, and 465 species were recorded in the autumn. The phytoplankton species composition and relative abundance were dominated by Dinoflagellata, Chlorophyta, and Bacillariophyta. A seasonal succession was observed in dominant species, with 41 dominant species identified, mainly belonging to Dinoflagellata, Chlorophyta, and Bacillario phyta. The biodiversity and evenness indices of phytoplankton were lower in summer than in autumn, whereas the richness index was higher in summer. According to biodiversity indices, the A. japonicus cultivation ponds were classified as lightly to moderately polluted during the study period. Redundancy analysis (RDA) of the phytoplan kton community structure and environmental factors revealed that the relative abundances of Bacillariophyta, Dinoflagellata, and Chlorophyta were positively correlated with nitrate concentration, phosphate concentration, and total phosphorus, nitrate, and ammonia nitrogen, respectively. These findings provided a scientific basis for environmental regulation in A. japonicus cultivation.

Abstract:This study used a generalized additive model (GAM) and habitat suitability indices to study the relationship between the Indian Ocean albacore tuna (Thunnus alalunga) habitat and the deep scattering layer based on the fishing yield data, acoustic survey data, sea surface temperature and chlorophyll-a concentration from 2011 to 2020 in the south Indian Ocean. A comparative analysis was conducted on the effects of different environmental factors on the habitat suitability index of albacore tuna. The GAM results showed that the deviance explanations of the combination of deep scattering layer, sea surface temperature, and chlorophyll concentration were the highest at 42.60%. The highly suitable areas (HSI＞0.6) for the habitat of albacore tuna were generally distributed between 20°S and 35°S. The highest correlation between the high HSI level (HSI＞0.6) of the combination of deep scattering layer and sea surface temperature and the yield of albacore tuna in 2021 was 0.542. The results suggested that the deep scattering layer improved the variance explained by environmental factors on the yield of albacore tuna and had a high correlation with high catch areas. This study provided a new reference for the distribution of Indian Ocean albacore tuna resources.

Abstract:Biofouling refers to the phenomenon where fouling organisms attach to and accumulate on artificial surfaces, adversely impacting human production activities. In recent years, the economic losses caused by biofouling have accounted for a substantial portion of the production costs in China’s mariculture industry. However, current control technologies remain inadequate, highlighting the urgent need to develop green and sustainable control strategies tailored to marine aquaculture environment. Using trophic cascade effects to control fouling organisms has become a focal point of recent research. This approach enables the selection of different biological agents based on the specific environmental characteristics of a given marine area, achieving effective control of fouling organisms while also providing certain economic benefits. This study focused on the selection of representative fish species including Siganus canaliculatus, Sparus latus, Rhabdosargus sarba, and Triacanthus biaculeatus, from the Dongshan Bay region of the Fujian Province, to evaluate their potential as ecological controllers of biofouling in Dongshan Bay. High-throughput sequencing technology was used to analyze the 18S rDNA gene sequences within the digestive tracts of these four fish species to elucidate their dietary composition and assess the differences in their consumption of fouling organisms. The results indicated significant differences in the dietary composition of the four fish species. Triacanthus biaculeatus predominantly consumed osteichthyes, displaying a strong carnivorous preference, while Siganus canaliculatus, Sparus latus, and Rhabdosargus sarba exhibited omnivorous feeding habits. Notably, Sparus latus showed a preference for herbivorous diet, while Rhabdosargus sarba tended towards carnivorous prey. Of particular interest is the finding that Siganus canaliculatus demonstrated an obvious preference for consuming fouling organisms, particularly ascidians, as a major component of its diet. Furthermore, the study revealed that larger individuals of Siganus canaliculatus [(180±2) mm] consumed a greater quantity and variety of ascidians than smaller individuals [(120±2) mm]. This study highlights the potential application of Siganus canaliculatus in the ecological control of biofouling, providing new scientific insights and theoretical support for the development of ecological biofouling control strategies and methods.

Abstract:There are many coastal islands in Zhejiang Province. Affected by multiple factors such as Zhejiang-Fujian Coastal Current, Taiwan Warm Current, and diluted river water, an ecological environment with abundant nutrients and sufficient food, which provides an ideal habitat and food source for many marine organisms, has been formed. Fish adapt significantly to these environmental factors, such as water temperature, salinity, depth, chlorophyll a concentration, and pH, and usually only grow and reproduce in specific environments. Therefore, it is of positive significance for the sustainable utilization of fishery resources and fishery management to study the selection of suitable areas for fish and its relationship with environmental factors and to predict the distribution of the potentially suitable areas. Setipinna taty is widely distributed in the coastal waters of China. It has attracted much attention due to its rapid growth, early sexual maturity, and strong resource recovery ability. In recent years, the fishing species in Zhejiang coastal waters have gradually shifted to small fish due to the decline of fishery resources. As one of the main fishing species in Zhejiang coastal waters at present, the protection and sustainable utilization of Setipinna taty resources are particularly important. However, there is still a lack of research on the distribution of potential suitable areas of Setipinna taty. Based on 81 distribution points recorded during the bottom trawl survey of the spawning ground in the offshore area of Zhejiang Province, in combination with six marine environmental data such as salinity, chlorophyll a, and primary productivity, we used the maximum entropy model to predict the spatial distribution of the potentially suitable areas of Setipinna taty, explore the relationship between its distribution and the main influencing factors, and comprehend the distribution characteristics of Setipinna taty The research also explored the relationship between its distribution and major influencing factors. The results were as follows: (1) The MaxEnt model demonstrated good prediction accuracy and reliability (AUC=0.812) for simulating potentially suitable areas for Setipinna taty. (2) Salinity, chlorophyll a, and primary productivity were identified as key factors affecting the distribution of potentially suitable areas for Setipinna taty; among them, the percent contribution of salinity was the highest (PC=49.10%), which was an important factor affecting its distribution. (3) The high suitability areas for Setipinna taty were concentrated in the north of Zhoushan fishing ground, the waters around Hangzhou Bay, Xiangshan County, Sanmen County, and the coastal waters of Wenzhou, accounting for approximately 22.88% of the sea area. The remainder of the potential suitability area was centered around the high suitability area. The objective of this study was to offer a theoretical foundation for the protection and sustainable utilization of Setipinna taty resource in the coastal waters of Zhejiang. In addition, the important role of environmental factors in fish distribution was revealed by predicting the potential suitable area of Setipinna taty in the coastal waters of Zhejiang. We should fully consider and monitor the changes in key environmental factors in future protection of fishery resources to ensure the sustainable development of fishery resources.

Abstract:Largemouth bass ranavirus (LMBV) is widely prevalent in China, seriously threatening the safety of largemouth bass (Micropterus salmoides) aquaculture. Chinese herbal medicines have become important for screening LMBV prevention and treatment drugs. Many natural medicine plants have been shown to have direct or indirect antiviral effects. Natural medicine plants can directly impair the virus architecture, hinder the virus invasion, or block the virus entry. In multiple cases, natural medicine plant ingredients have been confirmed to inhibit the virus by stimulating the host’s innate immune responses. Cirsium japonicum has many biological activities such as antivirus and anti-inflammation properties. The anti-LMBV effect of Cirsium japonicum aqueous extract (CJAE) was analyzed in vitro and in vivo to investigate the inhibitory effect on LMBV. CCK-8 tests determined that the safe concentration of CJAE on Siniperca chuatsi brain cells (SCB3) was ≤1000 μg/mL, and CC₅₀ value was 1487.0 μg/mL. The qPCR and indirect immunofluorescence assay showed that CJAE could effectively inhibit the synthesis of viral nucleic acid and MCP protein in SCB3 cells, and the EC50 value was 457.3 μg/mL. Moreover, the inhibition rates of CJAE on LMBV invasion and replication were 98.46% and 99.31%, respectively. CJAE was added to the basal diet at 0.5%, 1.0%, and 1.5% to feed largemouth bass twice daily for 15 days. Then a challenge test (1×10⁶ TCID₅₀ LMBV) was conducted. Feeding CJAE could provide 35%–60% RPS and reduced the viral load of spleen, liver, kidney and intestine of largemouth bass by 87.57%–99.99% through tissue virus copy number determination, which differed significantly from that in the control group (P＜0.01). CJAE increased the phagocytic activity of head kidney leukocytes by 35.88%–60.75% through phagocytosis assay, and activated the expression of phagocytosis-related genes (FcγRIa, CFL and Lyn) through mRNA expression determination; CJAE significantly improved the inflammation of largemouth bass caused by LMBV infection through tissue H&E staining. Further studies showed that CJAE significantly activated the expression of anti-inflammatory factors (IL-10) and inhibited the expression of pro-inflammatory factors (TNF-a and IL-1β). This study explored the anti-LMBV activity and underlying mechanisms of CJAE and supplied new insights for screening anti-LMBV drugs. This study provides a basis for using CJAE to prevent LMBV infection in production and further analysis of anti-LMBV active ingredients in CJAE.