2024 Vol. 20 No. 5
Marine ranching is a key strategy for the transformation and upgrading of China's marine fisheries, aiming at promoting the proliferation of marine fisheries resources and ecological environment restoration through artificial intervention. Artificial reefs and stock enhancement are important ways for the construction of marine ranching. Artificial reefs enhance marine habitats, thereby providing niches conducive to the habitation of fish species, while stock enhancement initiatives serve to directly supplement populations of specific marine species. This paper reviews the developmental trajectory, current construction status and benefit evaluation methodologies of marine ranching. It provides an analysis of the underwater physical conditions, hydrodynamic effects, scale effects, and fisheries propagation effects associated with artificial reefs, emphasizing on the importance of their scientific deployment. The paper also summarizes methods for assessing the efficacy of stock enhancement, encompassing mark-recapture techniques, statistical analyses and model-based assessments. Although China has made significant progress in these areas, challenges persist, such as the unclear relationship between the scale of artificial reef construction and ecological benefits, the necessity for enhanced precision in evaluating the outcomes of stock enhancement, and the absence of sophisticated quantitative assessment models. Thus, the paper proposes future research directions and recommendations, including the enhancement of evaluative indicator systems, the intensification of technological innovation, the development of robust quantitative assessment models, and the strengthening of policy and managerial guidance, so as to promote the progression of marine ranching research and practice, thereby realize the sustainable utilization of marine fishery resources and the achievement of marine ecological balance.
Marine ranching is one of the key measures for the conservation of marine fishery resources and environmental restoration in Guangdong Province. To systematically evaluate the ecological benefits of marine ranching construction in Guangdong Province, we applied Entropy Weight Method (EWM) and Fuzzy Matter Element Method (FMEM) to construct a comprehensive evaluation model to evaluate the ecological benefits of the construction of marine ranching. Based on the survey data of biological resources and environmental factors of marine ranching in ten sea areas of Guangdong Province from 2019 to 2021, we screened out 26 key indicators such as transparency, dissolved oxygen, chlorophyll, primary productivity, planktonic biodiversity, etc., and developed three types of standards as a reference. The results show that the comprehensive evaluation scores of the ecological benefits of marine ranching in Guangdong Province from 2019 to 2021 are 0.588 113, 0.609 307 and 0.521 257, respectively, all of which are higher than the evaluation value of the first-class standard of 0.462 171, revealing that the marine ranching in Guangdong Province have maintained high ecological quality and effectively improved the ecological environment of the sea area. Primary productivity has a high importance in ecological benefit evaluation, and the slight decline in the score in 2021 is mainly due to the rise in inorganic nitrogen content and the decrease in the biodiversity indices of plankton and benthic organisms. It is recommended to further improve the evaluation index system to provide a more scientific method for evaluating the ecological benefits of marine ranching.
Modern marine ranching is a main direction for transformation and upgrading of traditional marine fisheries. It is a hotspot for marine fisheries in China and other countries. The increasing diversification and complexity of proliferation and aquaculture for modern marine ranching led to an urgent innovation in sea use management system. This paper sorts out classification system of proliferation and aquaculture mode, openness degree of sea use, types and mode of sea use for marine ranching based on analysis of modern marine ranching connotation. The modern marine ranching is divided into three Type II (Marine proliferation ranching, marine aquaculture ranching and marine conservation ranching) and thirteen Type III based on their operation mode. The modern marine ranching is divided into three Type II (Open aquaculture, semi-closed aquaculture and closed aquaculture) and nine Type III based on their sea use openness. Based on the classification of sea use and the actual situation of modern marine ranching, this paper proposes sea use new types such as aquaculture sea use, proliferation sea use, conservation sea use, fishing sea use and leisure sea use, etc. And it proposes sea use new modes such as marine cage culture, marine raft culture, bottom sowing culture, marine floating structures, etc. The above marine ranching proliferation and aquaculture modes and sea use classification system can provide references for improving the modern management system of sea use in marine ranching.
In order to assess the environmental and ecological effects of oyster culture in typical semi-enclosed bays, as well as to elucidate the role and significance of oysters in the management and restoration of marine environments. Based on high-throughput sequencing technology, we explored the characteristics of the changes in the structure and function of water body colonies in the oyster culture area within a typical urban semi-enclosed bay (Dapeng Cove) in four seasons, and compared the characteristics of the differences in environmental factors in the water body and sediment between the culture area and the control area in the four seasons. The results indicate that oyster culture caused relatively little disturbance to environmental factors such as nutrients in the water of Dapeng Cove, but its biological sedimentation enhanced the enrichment of total organic carbon (TOC), sulfides (Sul), and some heavy metals in the sea area. The high-throughput sequencing results show that the relative abundance of colonies such as Chloroflexi, Desulfobacteraceae and Actinobacteria in the winter oyster culture area was significantly higher than that in the control area (p<0.05). The redundancy analysis (RDA) reveals that the main environmental factors affecting bacterioplankton structure between the oyster culture area and the control area in winter were ${\mathrm{SiO}}_3^{2-} $, sea surface temperature (SST) and salinity. The results of biogeochemical function of water colonies predicted based on the FAPROTAX model show that the biogeochemical effects of nitrogen (N) and sulfur (S) mediated by bacteria in the oyster culture area in winter were significantly higher than those in the control area (p<0.05). In conclusion, oyster culture causes certain disturbances to the bacterial structure and composition of seawater in Dapeng Cove, but its degree and scope of influence are constrained by a combination of factors such as seasonal changes in physical and chemical factors and hydrological conditions. Furthermore, oysters culture facilitates the biogeochemical cycling of elements such as nitrogen and sulfur.
The construction of artificial reefs is crucial for maintaining marine ecology and protecting fishery resources. The pore shape and size are the key elements for the structural design with a significant impact on the aggregation of fish. We designed and made the artificial reef models with different pore shapes (Round, square, diamond) and different sizes (1.0, 2.0, 3.0, 4.0 cm) for Lutjanus erythropterus, a common reef-dwelling fish in the artificial reef area. Then we observed the attractive effect on the juveniles and observed their behavioral changes in an indoor experimental pool. The results show that without the artificial reef model, the juveniles mainly concentrated in the peripheral area of experimental pool. But when the reef model was placed, the average distribution ratio of the juveniles in the reef area increased significantly (p<0.05). For the pore shape study, there was no significant difference in the average distribution rate of the juveniles in the artificial reef placement area (VI area) among the three treatment groups (p>0.05), with the proportion of the diamond treatment group being the highest [(19.84±6.08)%]. However, for the pore size study, there were significant differences among the three treatment groups (p<0.05), 4.0 cm size group (About 2.0 times the body height of juvenile) being the highest [(25.36±5.04)%], while 1.0 cm size group (About 0.5 times the body height of juvenile) being the lowest [(14.54±3.09)%]. In terms of activity ability, there were obvious differences between the artificial reef model experimental group and the blank control group. The average speed of juveniles decreased from (13.36±5.21) cm·s−1 in the control group to (4.29±1.59) cm·s−1 in the reef group, the average acceleration decreased from (106.93±69.17) cm·s−2 to (54.45±21.47) cm·s−2, and the percentage of activity time decreased from (68.01±8.61)% to (40.29±11.85)%, and all were the lowest in the circular 4.0 cm group, the square 4.0 cm group and the diamond 4.0 cm group. It is showed that at this stage, L. erythropterus juvenile has the strongest tropism to the artificial reef model with a circular pore shape and the size group of 4.0 cm, but the activity level is relatively low, showing the most significant attractive effect.
In order to understand the status of fish resources in the Beihai Yintan Marine Ranching sea area of Guangxi Province, we conducted two acoustic surveys with a split-beam scientific echosounder (Simrad EK80) in March 2022 and January 2023. We evaluated the fish density, fish biomass density and spatial distribution in the survey sea area by using echo integration method combined with trawl sampling (Mesh size: 4.0 cm×2.5 cm). The results show that both in the artificial reef area and control area, the catches were mainly composed of small individuals (Average masses of individuals in 2022 and 2023 were 8.64 and 29.8 g, respectively). In March 2022, the average fish densities of acoustic evaluation species in the artificial reef area and control area were 66 003 and 41 903 inds·km−2, respectively. The average fish biomass densities in the artificial reef area and control area were 726.66 and 469.90 kg·km−2, respectively. In January 2023, the average fish densities of acoustic evaluation species in the artificial reef area and control area were 17 194 and 11 110 inds·km−2, respectively. The average fish biomass densities in the artificial reef area and control area were 665.94 and 406.85 kg·km−2, respectively. The artificial reef area showed a significant fish catching effect. The fishery resources were distributed mainly in water layers below 5 m, and those in reef areas had a wider vertical distribution range than those of the control area. The average target strength (TS) of the two survey voyages in the artificial fish reef area were greater than that in the control area, and more single targets were detected in the artificial fish reef area with a more concentrated distribution than in the control area. The results reveal the impact of artificial reefs on the redistribution of fish resources.
To thoroughly evaluate the effectiveness of artificial reefs in marine ranching, and to promote the sustainable use and effective management of marine resources, we conducted the fixed-point acoustic monitoring of fish resources by using a split-beam scientific echosounder (Simrad EK80) in two research areas: the artificial reef area of Zhuhai Dazhizhou Marine Ranch in July 2023 and the artificial reef area of the southern Beihai Yintan Marine Ranch in December 2023. The study systematically analyzed the distribution of target strength (TS), diurnal variations in the nautical area scattering coefficient (NASC), and current conditions within the monitored marine areas. The results show that in the Beihai artificial reef area, the TS of fish resources ranged from −51.9 to −31.0 dB, with an average of −44.8 dB. In the Zhuhai Dazhizhou Marine Ranch, the TS of fish resources ranged from −51.7 to −25.5 dB, with an average of −45.4 dB. Diurnal monitoring data indicate that the TS variation range and average values of fish resources in the artificial reef areas were generally better than those in the control areas, with fish resources primarily distributed at depths greater than 5 meters, more abundant in the artificial reef areas. In the Beihai artificial reef area, the correlation coefficient between the bottom NASC and current speed was 0.416 74, indicating a significant positive correlation between them (p<0.05). The results demonstrate the diurnal and nocturnal variation patterns in the fishery resources of marine ranching, further enrich the research methodology for monitoring the fishery resources of marine ranching, and provide a reference basis for the dynamic management of the fishery resources of marine ranching.
Marine ranching is an important component of carbon sink fisheries. In order to assess the biological carbon storage of fishery resources in different functional areas of marine ranching, based on the trawl survey data from the Zhuhai Wailingding marine ranching in spring, we analyzed the current status of fishery resources, measured the biological carbon content of fishery resources, and estimated the biological carbon storage of fishery resources in the marine ranching. The results show that the biomass of fishery resources in spring was 4 505.48 kg; the resource density was 458.34 kg·km−2, which was 23.34% higher than that in the contrast area; the carbon content of wet biological samples in fishery resources was 6.53%−17.02% for Osteichthya, 8.55%−10.19% for Chondroichthya, 6.70%−11.84% for Crustacea, 6.48%−9.89% for Cephalopoda, and 27.04%−27.39% for Bivalva; the biological carbon storage of fishery resources of the marine ranching was 495.63 kg; the carbon density was 50.42 kg·km−2, which was 46.40% higher than that in the contrast area; the carbon density followed a descending trend of stock enhancement area>new artificial reef area>original artificial reef area>contrast area. It is preliminarily suggest that according to the differences in biological carbon content among different fishery resources, the carbon storage capacity of marine ranching could be improved by adjusting the structure of fishery resources through artificial reefs, stock enhancement and other means.
Timely assessment of fish resources in state-level marine ranching demonstration zone is important in promoting the construction of marine ranching. Based on the fishery resources survey data in the southern area of Guangxi Yintan in April 2022, we analyzed the characteristics of fish resources, community stability, fish community structure and their correlation with environmental factors to provide references for research on the ecological effects of marine ranching in Beibu Gulf. The results show that the fish individual density, biomass density and number of species in the demonstration zone were higher than those in the control zone. The fish species composition in the demonstration and control zones was moderately dissimilar at species level. In addition, fish communities in both zones were somewhat disturbed. The fish community in the survey area was divided into four significantly different clusters (p<0.05), which were located in the southern station of the demonstration zone B and the control zone (Cluster I), the northern station of the control zone (Cluster II), the junction of the demonstration zone A and B (Cluster III), and the demonstration zone A (Cluster IV). The average dissimilarity index of Cluster I and III was 53.88%, and the divergent species that ranked in the top three in terms of their contribution were Alepes djedaba, Decapterus marauds and Trachurus japonicus, while the average dissimilarity index of Cluster III and IV was 48.85%, with the top three divergent species (T. japonicus, Leiognathus brevirostri and Saurida undosquamis) contributing to the dissimilarity index. Water temperature and chemical oxygen demand were the main environmental factors significantly influencing the structure of the fish community in the survey area, while dissolved oxygen and phytoplankton density had a slightly weaker effect.
Sediment is the geological material that carries information of the evolution history of the earth and the changes of human activities. In order to understand the current situation and ecological risk of sediments, based on the survey data of 2020 and 2021 in adjacent waters of Wailingding marine ranching, we investigated the contents of particle size, characteristics indexes and six heavy metals. By using Nemero comprehensive pollution index, potential ecological risk index and geo-accumulation index, we evaluated the potential ecological risk of heavy metals. Furthermore, we discussed the possibility of heavy metal sources. The results indicate that the main type of sediments in the survey sea area was silty clay, with significant spatial differences in the content of various elements, showing a gradually decreasing trend with the increase of offshore distance. All the six heavy metals had a high positive correlation with total organic carbon. The assessment results obtained by three ecological risk assessment methods are basically consistent: the high pollution area was mainly located in the artificial reef construction area, northeast of Wailingding. The results of the nemero comprehensive pollution index show that the sediment was at Level 1 of cleanliness. The potential ecological risk index shows that Hg had the highest proportion in the evaluation, and its potential risk coefficient and ground accumulation index were significantly higher than those of other heavy metals. The results reveal that the ecological risk of heavy metals in the sediments is generally at low level, but heavy metals, especially Hg, still needs to be highly concerned.
The numerical model of gravity deepwater cage, which is the foundation for the numerical simulation analysis of mechanical characteristics of cage, undertakes the majority of the work in the cage simulation process. In order to solve the problems of tedious modeling and low efficiency in this process, we proposed a parameterized rapid modeling method for gravity deepwater cage. Firstly, each component of the cage was parameterized according to its structural characteristics. Then, the modeling program was compiled and the corresponding operation interface was developed. Finally, the rapid creation of gravity deepwater cage model was achieved in OrcaFlex. Engineering test shows that the program can improve the efficiency of cage modeling greatly and facilitate the engineering calculation of gravity deepwater cages. The study provides references for the model rapid creation and numerical analysis of gravity deepwater cages of various specifications.
To estimate the quantity of Trachinotus ovatus in marine cages accurately, a method for estimating the quantity of fish is proposed by using high-frequency horizontal mechanical scanning sonar and deep learning technology. Differentiating water layers and clustering layer by layer to realize counting is the main way of this method, which mainly involves three parts: fish identification, fish cluster and fish quantity fitting. Firstly, high-frequency horizontal mechanical scanning sonar is used to conduct spiral detection on marine cages to obtain fish image information, which is labeled to build training data set of improved CS-YOLOv8s. After training, the CS-YOLOv8s model is used to recognize fish location information in the images. Secondly, the cages are divided into water layers with a water depth spacing of 40 cm, and the identification coordinate data of each water layer are clustered through DBSCAN method to generate fish quantity data of each water layer. Finally, the quantity data of each water layer is fitted with the given quantity of fish in the cage, and the fitting model of fish quantity is established. The results show that in the quantitative experiment of marine cages, the accuracy of this method is 87.14%, and it can achieve a good estimation of the quantity of T. ovatus.
In order to solve the problem of holding pike crabs after fishing, the crab claw of pike crabs need to be tied up individually, and crab claw gathering is important for crab claw binding. In this study, a bionics-based crab claw gathering device for pike crabs was designed, which is inspired by the natural movement of Portunus crab claws. After a careful analysis of the physiological structure of crab claw, we understood the characteristics of their activities well, and then designed this bionics-based crab claw closing device. The device tested the pincer closing for 10 Portunus crabs of different body masses, and 8 individuals were successfully closed. For the crabs with size of 133 mm3 and body mass over 130 g, the effect is better. Thus, the device provides a preliminary and effective solution to effectively solve the problem of Portunus crab claw closing.
Traditional otter board controls working depth by changing length of the warp and towing speed, and adjusts working posture by changing fixed joint positions between otter board, warp and sweep line, which involves complex operation. To provide scientific references for the design and research of controllable variable-water-depth otter boards, we designed a multi-blade controllable otter board and employed computational fluid dynamics (CFD) simulation to investigate the effects of the rotation direction and angle (−40°~40°) of blades at different positions (Upper and lower ends) on its hydrodynamic performance. The results reveal that: 1) when the blades were closed, the lift coefficient of the multi-leaf controllable otter board reached its maximum value of 0.88 at an attack angle of 20°; its lift-to-drag ratio peaked at 8.85 at an attack angle of 5°. 2) At an attack angle of 0°, when the blades at both ends of the otter board rotated in a negative direction, the lift gradually decreased to zero and reversed its direction at a rotation angle of −20°; when the blades rotated in a positive direction, the lift coefficient first increased and then decreased, reaching its maximum value of 0.32 at a rotation angle of 20°; the lift-to-drag ratio decreased as the rotation angle increased. 3) At an attack angle of 20°, when the blades at both ends of the otter board rotated in a positive direction, the lift coefficient continuously decreased; when the blades rotated in a negative direction, the lift coefficient first increased and then decreased, reaching its maximum value of 1.05 at a rotation angle of −10°; the lift-to-drag ratio peaked at 5.25 at a rotation angle of −20°. 4) Under the two angles of attack, when the blades at both ends rotated individually in a positive direction, the Z-axis force coefficient increased first and then decreased.
To characterize the diet and biology of juvenile Mystus guttatus, and to provide a scientific basis for its resource conservation and population restoration, we applied DNA macro barcode technology to analyze the species characteristics of stomach contents of M. guttatus juvenile and water body in the river channel of M. guttatus conservation farm in Luodian County, Guizhou Province. The results show that: 1) A total of 109 species of organisms were identified in the stomach contents of M. guttatus juvenile, belonging to 15 phyla and 12 major categories. On phylum level, the relative abundance of Arthropods was the highest, followed by Rotifera, Chlorophyta and Chordata. On genus level, the relative abundance of Sinodiaptomus was the highest, followed by Brachionus, Barbus and Paralamyctes. 2) A total of 193 species belonging to 18 phylum were obtained in the river channel where M. guttatus juvenile fish lived. On phylum level, the relative abundance of Arthropods was the highest, followed by Chlorophyta. On genus level, the relative abundance of Sinodiaptomus was the highest, followed by Chlamydomonas. Other genus with higher relative abundance were Brachionus, Tintinnidium and Monoraphidium. Arthropoda, Rotifera and Chlorophyta were relatively abundant groups in the stomach contents of M. guttatus juvenile and water body. The relative abundance of Chordate was low, ranking 15th in the water body, and 4th in the stomach contents. The results indicate that the dietary selection of M. guttatus juvenile is influenced by both the availability of food in water environment and the preference of juvenile. From the perspective of energy balance benefits, the feeding process of M. guttatus juvenile follows the principle of obtaining maximum benefits with minimal energy input, which is beneficial for its survival and growth.
Subfatin plays an important role in lipid metabolism, inflammation and energy consumption in mammals, but its functions in fish are rarely reported. To investigate the physiological function of subfatin in glucolipid metabolism of grass carp, we took Ctenopharyngodon idella as the research object and cloned the subfatin gene by RT-PCR. The oral glucose tolerance test (OGTT), fast and refeeding, inducing lipid accumulation and primary hepatocyte culture were proceeded. The results show that the grass carp subfatin was 861 bp, encoding 286 amino acids, and three O-linked glycosylation sites were located in the subfatin. The results of OGTT experiment show that after glucose treatment of grass carp for 1 and 3 h, the expression of subfatin mRNA was significantly up-regulated in liver and intestinal tissues, and it was also significantly up-regulated in the brain and kidney tissues after 3 h of glucose treatment. In fast and refeeding experiment, the results show that the expression of subfatin mRNA in brain, fat, intestinal and liver tissues was significantly down-regulated after 14-day starvation treatment, and was significantly up-regulated after re-feeding. In induced lipid accumulation experiment, the results show that subfatin expression in brain, fat, intestinal and liver tissues was significantly up-regulated in the induced group. In primary hepatocytes, subfatin expression level increased significantly by treatment with glucose, oleic acid and glucagon. However, subfatin level decreased significantly by treatment with insulin. In conclusion, this study demonstrates that Subfatin is involved in the process of glucose and lipid metabolism in grass carp and plays a regulatory role, which provides a theoretical basis for elucidating the physiological functions of Subfatin in fish.
In order to develop the algaolytic bacterial agent for chloride type saline-alkali water, we selected the algaolytic bacterial strain Bacillus cereus CZBC1, and investigated the algaolytic effects of the filtrate group (FG), the bacterium group (BG), and the bacterial solution group (BSG) in the chloride type saline-alkali water with the initial density of Microcystis aeruginosa of 105 and 106 cell·mL−1, respectively. The results show that the strain CZBC1 had both direct and indirect ways of dissolving microalgae. When strain CZBC1 in FG, BG and BSG acted on M. aeruginosa, their microalgal cells could deform, fade or rupture, playing a good role in dissolving algae in chloride type saline-alkali water. When the initial microalgal density was 105 cell·mL−1, the microalgal density could be reduced to 2.30×10 cell·mL−1 in BSG and 1.27×102 cell·mL−1 in BG on the 6th day, which were extremely significantly lower than that in the control group (CG) (3.65×105 cell·mL−1, p<0.01), and the highest algicidal rates in both groups could reach over 99%. When the initial microalgal density was 106 cell·mL−1, the microalgal density could be reduced to 8.30×105 cell·mL−1 in BSG on the 6th day, which was significantly lower than that in CG (3.17×106 cell·mL−1, p<0.05), and its highest algicidal rate could reach over 78.8%. The algicidal effect of BSG was better than that of BG and FG. The results indicate that in order to prevent and control microcystis blooms in chloride type saline alkali ponds, it is recommended to prioritize prevention and regularly apply algicidal bacteria CZBC1 to prevent and control the formation of harmful algal blooms.
In order to investigate the potential role of immunoglobulin of egg yolk (IgY) in the prevention and control of Vibrio parahaemolyticus in Litopenaeus vannamei culture, we prepared three V. parahaemolyticus strains from serotypes (O1: KUT and OUT: KUT) as inactivated vaccines and immunized against laying hens to prepare IgY, respectively. Then we evaluated the titer, inhibitory effect and cross reaction of anti-V. parahaemolyticus IgY by ELISA and tube agglutination tests. The results show that all the three strains induced high specific level of IgY. The trends of antibody agglutination titer and ELISA titer were similar, both reaching the plateau of antibody titer from 10 to 60 d after the fourth immunization, with agglutination titer above 1∶8 and ELISA titer above 1∶6 400. The prepared IgY showed strong cross-ELISA and cross-agglutination reaction with other V. parahaemolyticus for the same serotype, but had lower cross-ELISA reaction and no cross-agglutination reaction with other serotype strains. This study clarifies that V. parahaemolyticus can stimulate the production of high specific level of IgY in laying hens, but does not have cross-protective potency against different serotypes of strains, which provides references for the development and application of anti-V. parahaemolyticus IgY products.
Mosaic disease is a novel disease that has emerged during the culture of Chinese sturgeon (Acipenser sinensis) in recent years. In order to study the flora markers for monitoring the health status of A. sinensis, we analyzed the microbial community structure of the skin mucosa of healthy and diseased juveniles by using high-throughput sequencing technology. The results show that compared with healthy fish, the diversity and richness of diseased fish reduced significantly (p<0.001). On genus level, the skin mucosa of healthy fish was composed of Lactobacillus, Acinetobacter, norank_f-Muribaculaceae, Leuconostoc and Pseudomonas, while the skin mucosa of diseased fish was composed of Flavobacterium and Acinetobacter, and the proportion of Flavobacterium was 78.38%. The significant difference analysis shows that five sensntive taxa were screened, reflecting the health status of Chinese sturgeon. This study indicates that compared with healthy fish, mosaic disease destroyed the normal homeostasis of microbiota in skin mucosa. The dominant bacterial community changed from Lactobacillus and Acinetobacter to Flavobacterium. Therefore, Flavobacterium have been identified as a marker to monitor the pathogen of mosaic disease in A. sinensis. Its relative abundance can be utilized to evaluate the risk of disease in A. sinensis.