Abstract:Half-smooth tongue sole (Cynoglossus semilaevis) is a unique marine aquaculture fish species known for its high nutritional value and commercial potential. However, half-smooth tongue sole exhibits typical sexual dimorphism, characterized by substantially faster growth rates in females than in males, resulting in female adults being two to four times heavier than male adults. Previous studies have successfully obtained dmrt1^–/– ZZ from male half-smooth tongue sole using TALEN genome editing technology targeting dmrt1 gene. The growth rate of dmrt1^–/– ZZ males exceeds twice that of normal male fish, with weights comparable to normal female fish. This successfully addresses the issue of stunted growth in the male half-smooth tongue sole and lays the foundation for the establishment of gene editing breeding techniques for this species. Reports on the impact of transgenic organisms on the surrounding environment have raised marked concerns regarding the environmental safety of genetically-modified organisms. A pressing question is whether the edited genes could affect the environment through gut microbiota or other behavior during the rearing process. Compared to transgenic technology, gene editing has the advantage of not involving exogenous genes. Several studies on the gut microbiota of gene-edited animals have shown that no marked changes in gut microbiota composition were observed in animals after gene editing. To assess the health status and environmental safety of the gene-edited half-smooth tongue sole, this study investigated the changes in gut microbiota of the dmrt1 homozygous mutant male fish. High-throughput sequencing technology was used to compare the gut microbiota between dmrt1^–/– ZZ males and normal male and female fish kept under the same aquaculture conditions. Environmental safety risks were assessed by testing the genotypes of normal fish cohabiting with dmrt1^–/– ZZ males, as well as the eDNA from the water environment where they were raised. There were no marked differences in alpha diversity and composition of the gut microbiota between dmrt1^–/– ZZ male and normal male and female fish, and no differences were observed in the predicted functions of the gut microbiota. The differences in gut microbiota may influence growth variations. The gut microbiota composition of dmrt1 homozygous mutant male fish was similar to that of female fish, suggesting that certain microbial populations may be involved in regulating growth rates, which could play a role in enhancing the growth rate of dmrt1^–/– ZZ males. No edited genes were detected in the normal individuals cohabiting with the dmrt1^–/– Z males. Water samples taken from five sampling points along the drainage path of the aquaculture environment of the dmrt1^–/– ZZ males were amplified and sequenced indicating no presence of the edited target gene. In conclusion, dmrt1 gene editing does not lead to marked changes in the gut microbiota of dmrt1^–/– ZZ male half-smooth tongue sole and does not affect other individuals reared in the same environment, indicating no environmental risks. This study provides a reference for safety assessment methods of gene-edited aquatic animals.

Abstract:Polymeric immurnoglobulin receptor (pIgR) is an important fish mucosal immune factor, which plays a key role in mediating the secretion and transport of polyimmunoglobulin into the mucus of mucosal immune tissue. In this study, the full-length cDNA sequence of Aristichthys nobilis pIgR gene was cloned using PCR and RACE technology. The full-length cDNA sequence of Aristichthys nobilis pIgR gene was 1885 bp, and its open reading frame (ORF) was 1008 bp, encoding 336 amino acids. Aristichthys nobilis pIgR had a signal peptide sequence, followed by the extracellular region, transmembrane region, and intracellular region. The extracellular region included two immunoglobulin-like domains (ILD), and its tertiary structure was twisted “L”. The phylogenetic tree was constructed using the NJ method. The results showed that the pIgR gene of Aristichthys nobilis was clustered with the pIgR of cypriniformes. The expression level of the pIgR gene in different tissues of Aristichthys nobilis was detected using quantitative real-time PCR (qRT-PCR). The highest expression level of pIgR gene was found in the liver, followed by the spleen, intestine, head kidney, gill, and skin. A low expression level was found in the middle kidney, heart, and brain, and the lowest expression level was found in the muscle. Aristichthys nobilis was infected with Aeromonas hydrophila at 5 d. The pathological changes in immune-related tissues with a high expression level of the pIgR gene were observed using tissue sections and HE staining. It was found that the intestinal villus mucous cells increased, the width of the intestinal villi widened, and the intestinal wall thickened, showing prominent symptoms of intestinal inflammation. Many inflammatory cells appeared in the head kidney and spleen, and many vacuolar cells were observed in the spleen. The width of the hepatic sinuses increased. The gill filament was deformed and shortened, and the gill cell withered. The expression level of Aristichthys nobilis pIgR gene in the gill, intestine, spleen, liver, and head kidney increased first and then decreased within 28 d after being infected with Aeromonas hydrophila. The relative expression of pIgR gene reached the peak at 5 d in the intestine and gill, and reached the maximum at 7 d in the head kidney and 14 d in the spleen and liver after infection, respectively. The relative expression level of the pIgR gene at the peak in the intestine (18.63 fold) and gill (16.53 fold) of Aristichthys nobilis was higher than that in the head kidney (9.38 fold), spleen (15.98 fold), and liver (12.28 fold). The experimental results showed that Aeromonas hydrophila infection not only caused immune-related tissue lesions and triggered the inflammation responses but also affected the respiratory system and digestive system of Aristichthys nobilis. pIgR may play a key role in the mucosal immune system of Aristichthys nobilis against bacterial infection.

Abstract:This study investigated the annual changes in ovary development in hooksnout carp and methods to improve artificial breeding and promote its rapid commercialization. The annual range in the gonadosomatic index (GSI) in female hooksnout carp in Hubei Province was 1.16%–11.65%. The spawning period was from mid-April to mid-July, and the average absolute fecundity of the female before spawning was 6165.4 eggs. In autumn, when the water temperature gradually decreased (September to October), the GSI of the ovaries gradually decreased, and the ovaries degenerated to phase III and entered hibernation. In February of the following year, GSI of the carp was relatively low (1.16%–1.65%), and the proportion of phase III oocytes in the ovary increased after a further decrease in water temperature to ＜8.0 ℃ in February. In the scaled-up artificial breeding experiment, the combination of luteinizing releasing hormone (LRH-A2; 5 μg/kg) and human chorionic gonadotropin hCG (1000 IU/kg) had the best induction effect of 87.0%. A 0.3% NaCl solution was the best fertilization medium, with an optimal sperm-to-egg ratio of 5.0×104 –1.0×105 : 1, which produced average fertilization and hatching rates of 66.6% and 80.1%, respectively. The induction time was 20.0–26.0 h before May 15, 16.0–17.0 h after May 15, with accumulated temperature of 400.00–430.00 ℃·h. The hatching time was 69.0–90.0 h in water of 20.0– 25.0 ℃, and 42.5–48.0 h in water ＞26.0 ℃, with a hatching accumulated temperature of 1200.00–1300.00 ℃·h. This study also successfully conducted second-induced spawning of hooksnout carp broodstock in the same year and found that the spawning effect of the second breeding was not substantially different from that of the first. This study achieved scaled-up artificial breeding of hooksnout carp, laying an important foundation for the genetic improvement and commercialization of hooksnout carp.

Abstract:To evaluate the advantages of nucleus implantation in spring and autumn and their relationship with key environmental factors, production indicators and marine environmental factors across four production cycles from April 2020 to July 2022 were analyzed. Spring (S) and autumn (F) nucleus implantation groups were established, with implantation conducted in April 2020 (S20), April 2021 (S21), October 2020 (F20), and October 2021 (F21). The monthly survival rates of the cultured pearl oysters were monitored, and key environmental factors such as water temperature, dissolved oxygen, and salinity were measured. Pearls were harvested after 9 m of cultivation, and production indicators, including the retention rate, high-quality pearl rate, and pearl layer thickness, were recorded. Water temperature fluctuated seasonally from 17.23–33.23 ℃. The S groups (S20 and S21) and F groups (F20 and F21) experienced temperatures above or near 30 ℃ for five and two months, respectively. Dissolved oxygen levels varied from 4.44–8.08 mg/L with seasonal changes. Except for October, when salinity was relatively low, salinity remained stable between 30‰–35‰ in other months. The pH was stable and fluctuated between 8.05 and 8.28. The water transparency was 80–200 cm and was generally lower in summer and autumn and higher in winter and spring. At the end of the cultivation period, the survival rates were the highest in F21, followed by F20, S21, and S20, with the group F being better than the group S (P＜0.05). In the group S, water temperature showed a strong negative correlation with stage-specific survival rates (P＜0.05), whereas no correlations were found between survival rates and other environmental factors (P＞0.05). In group F, no correlation was observed between the environmental factors and survival rates (P＞0.05). The retention, commercial pearl, and high-quality pearl rates among the groups were similar (P＞0.05), but the pearl layer thickness in the group S was greater than that in the group F (P＜0.05), with an increase of approximately 20%. Nucleus implantation in autumn substantially improved the survival rate of the transplanted pearl oysters and increased pearl production, whereas the pearls produced by nucleus implantation in spring were of a better quality. In group S, the elevated mortality rate during summer was primarily attributed to high temperatures. This study provides valuable data and theoretical insights for healthy cultivation of seawater pearls.

Abstract:To explore the differences in circadian behavioral rhythms and the changing regularity of different fish species, and improve artificial culture technology, we analyzed and compared the circadian behavioral rhythms of Hippocampus kuda and Oryzias melastigma under the artificial culture conditions detailed in this paper. The results showed that under the conditions of light intensity of 2000 lx, temperature of 25±1 ℃, salinity of 25±0.5, and photoperiod of 14L : 10D, the behavioral rhythms of H. kuda and O. melastigma during the daytime are stronger than in the nighttime. H. kuda showed the strongest rhythm and the most abundant behavioral component between 08:00 and 10:00. The macroscopic behavior components included active behaviors (swimming 47.40±1.1%, crawling 3.0±0.6%, moving 4.80±0.7%), and inactive behaviors (swing 32.50±2.1%, resting 12.30±0.8%). The microcosmic behavior components included gill operculum movement 38.77±1.14 times/min, jaws movement 38.77±1.14 times/min, and eyeball rotation 108.50±5.52 r/min, dorsal fin movement 116.87±0.64 times/min and pectoral fin movement 67.81±2.27 times/min. The sub-strongest rhythmic period was 12:00–14:00, and the rhythmic behaviors were dominated by swinging with a percentage of 59.20±5.1%. O. melastigma also had the strongest activity between 08:00 and 10:00, in which the percentage of swimming amounted to 88.0±1.1%; the frequency of gill operculum movement was 407.88±3.8 times/min, jaw movement 407.88±3.8 times/min, eyeball rotation 7.38±0.9 r/min, dorsal fin movement 373.17±2.5 times/min, pectoral fin movement 400.83±6.8 times/min, and tail movement 416.58±7.7 times/min. Therefore, both H. kuda and O. melastigma have strong circadian behavioral rhythms, and the period of 8:00–10:00 is their peak period of behavioral activity, which is the strongest rhythm and the most abundant behavioral components. Therefore, the period of 08:00–10:00 can be selected as a suitable observation time for related behavioral studies.

Abstract:The recruitment of dormant Microcystis aeruginosa (DMCs) is an important phase in the formation of Microcystis aeruginosa blooms in aquaculture ponds. When subjected to external environmental stress, such as low temperature, low light, exogenous allelopathic substances, nutrient deficiency, Microcystis aeruginosa cells form DMCs due to damage to the photosynthetic system, phycobilisomes, ribosomes, and other organelles. These DMCs sink to the surface of the sediment to avoid environmental stress. The DMCs are used as seed sources to restart and recruit (repair damaged organelles) once conditions improve. They enter the overlying water, waiting for another outbreak of algal blooms. A higher recruitment rate of DMCs can significantly enhance the interspecific competitiveness of Microcystis aeruginosa, making it prone to population outbreaks and the formation of algal blooms, and vice versa. Therefore, inhibiting the recruitment of DMCs is an effective method for proactively preventing and controlling the outbreak of Microcystis aeruginosa blooms in aquaculture ponds. In order to investigate the effect and mechanism of Pseudomonas lactis BJ-1, an intestinal bacterial strain of Aristichthys nobilis, on the recruitment of resting DMCs in vitro, BJ-1 bacteria were mixed with DMCs and embedded into pond sediment to construct low-concentration bacterial groups (G1), higher-concentration bacterial groups (G2), and high-concentration bacterial groups (G3). The sterile group was used as a control. The recruitment experiment was conducted for 21 days at a water temperature of 25 ℃, light intensity of 15 μmol·m^–2s ^–1, and light-dark cycle ratio of 12 h∶12 h. Mechanism and field verification experiments were performed based on the experimental results. The experimental results showed that the strain BJ-1 continued to proliferate from the beginning of the experiment to the 6th day. After the 6th day, the bacterial concentrations of the low-concentration bacterial group G1, the higher-concentration bacterial group G2, and the high-concentration bacterial group G3 were maintained at (0.99±0.23)×10⁷ cfu·g^–1, (3.40±0.27)×10⁷ cfu·g^–1, and (5.21±0.39)×10⁷ cfu·g^–1, respectively. DMCs began to recruit from the 6th day, and compared with the control group, the content of capsular extracellular polysaccharides (CPSs) in DMCs in G2 and G3 groups decreased significantly, and the photosynthetic efficiency and recruitment rate of DMCs significantly decreased (P＜0.05). In contrast, there was no significant difference between the G1 group and the control group (P＞0.05). At the same time, the experiment found that strain BJ-1 can secrete the metabolite 3-benzylpiperazin-2,5-dione, and its concentration shows a positive linear relationship with BJ-1 bacterial concentration (R² =0.997). The minimum effective concentration of metabolite 3-benzylpiperazin2,5-dione to inhibit the recruitment of DMCs was 0.8 μg·L^–1. The concentrations of 3-benzyl piperazine-2,5-dione in group G2 and group G3 were (0.95±0.24) and (1.41±0.19) μg·L^–1, respectively. At these concentrations, the intracellular reactive oxygen species (ROS) level of DMCs increased significantly (P＜0.05), and the photosynthetic efficiency and recruitment rate of DMCs decreased significantly (P＜0.05). An analysis of differentially expressed genes (DEGs) showed that DMCs encoding photosynthetic genes (psbD1), DNA repair genes (recA), and carbon fixation (ntcA and rbcL) functional genes were significantly down-regulated under higher bacterial concentrations (G2 group), confirming at the molecular level that bacteria BJ-1 can inhibit the photosynthetic efficiency of DMCs. Validation experiments showed that strain BJ-1 can effectively reduce the recruitment rate of DMCs in outdoor pond environments. The experimental results showed that BJ-1 bacteria in the gut of Aristichthys nobilis at higher concentrations (≥3.40×10⁷ cfu·g^–1) can inhibit the photosynthetic efficiency of DMCs in vitro by reducing the CPSs content of DMCs and secreting the metabolite 3-benzylpiperazin-2,5-dione, ultimately hindering the recruitment of DMCs. The experimental results provide new evidence for “controlling algae with Aristichthys nobilis” and also provide new ideas for preventing and controlling Microcystis aeruginosa blooms in aquaculture ponds.

Abstract:Species coexistence is one of the core issues in community ecology, and exploring the coexistence patterns of community species can help with better understanding the ecological processes that affect community assembly. In the context of frequent El Niño-Southern Oscillation (ENSO) events, the changes in species coexistence patterns of fish communities and their responses to ENSO events in the bay remain largely unknown. Changes in species co-occurrence patterns within fish communities over the past decade and their relationships with the Oceanic Niño Index (ONI) were examined using null model analysis based on the data collected from the fish resources survey in the spring and autumn in the Haizhou Bay and its adjacent waters from 2013 to 2022. The results showed that the fish communities in the Haizhou Bay generally showed a nonrandom species co-occurrence pattern from 2013 to 2022, and exhibited an aggregation co-occurrence pattern in most years, with the aggregation pattern more pronounced in autumn than in spring. The species co-occurrence pattern of fish communities was influenced by important species pairs, and the important species pairs varied in different years. In most cases, dominant species such as Enedrias fangi and Hexagrammos otakii formed an aggregated coexistence pattern with other fish species, while fish species such as flatfish and Callionymus formed a segregated coexistence pattern with other fish species in most cases. The species co-occurrence pattern of fish communities was influenced by the selection of C-score and V-ratio indicators in the null model analysis. The fish communities were almost always in an aggregated co-occurrence pattern at ENSO neutral conditions. However, the species co-occurrence pattern mostly shifted from an aggregated pattern to a random pattern when ENSO events occurred, and there was a certain correlation between the fluctuation trend of ONI and species co-occurrence pattern of the fish communities.

Abstract:This study used microsatellite molecular markers and mitochondrial COI gene sequence information to investigate the effects of stock enhancement on Fenneropenaeus chinensis in the southern waters of the Shandong Peninsula, assessing the ecological contribution of the released F. chinensis. This species is an important economic shrimp species in China's Bohai and Yellow Sea regions, playing a key role in fishing and marine aquaculture. However, due to issues such as overfishing, disease, and environmental pollution, there has been a substantial decline in resources since the 1980s. To restore the dwindling resources of F. chinensis, China took the lead in conducting stock enhancement activities in the Bohai Sea. After nearly 40 years of continuous release, F. chinensis resources in the Bohai and Yellow Seas have been restored to some extent. The purpose of this study was to evaluate the effectiveness of stock enhancement of F. chinensis in the southern waters of the Shandong Peninsula using SSR (simple sequence repeats) and mitochondrial COI molecular marker technology. The experimental sample collection was divided into three stages. In the first stage, in May 2023, 404 parental F. chinensis were collected from Haiyang Yellow Sea Aquatic Products Co., Ltd. in the southern part of the Shandong Peninsula after the completion of production of released seedings. In the second stage, during the autumn fishing season of F. chinensis in September 2023, a total of 461 individual F. chinensis were recaptured in the sea areas of Huangdao, Haiyang, and Laoshan. In the third stage, from March to April 2024, 110 and 399 migrating individuals of P. chinensis were collected in the Laoshan and Rizhao sea areas, respectively. All the samples were frozen and transported to the laboratory for storage. Genomic DNA was extracted using the conventional phenol-chloroform isoamyl alcohol method, and DNA quality was detected by agarose gel electrophoresis and spectrophotometer. The experiment used parent–offspring tracing methods based on microsatellite molecular markers and mitochondrial COI gene sequence information to evaluate the effectiveness of stock enhancement of F. chinensis in the southern waters of the Shandong Peninsula. Eight polymorphism-rich microsatellite loci were used for PCR amplification and genotyping, combined with mitochondrial COI gene sequence analysis. Gene Mapper software was used to read allele data, and Cervus software was used for statistical analysis to determine potential parent-offspring pairs. The parentage relationship between released individuals and recaptured individuals was further verified using partial mtDNA sequence haplotypes. The results showed that 350 alleles were detected at eight SSR loci, with the number of alleles detected per locus ranging from 7 to 80, and the average number of alleles was 31.8. The observed heterozygosity (Ho) ranged from 0.606 to 0.896, the expected heterozygosity (He) ranged from 0.619 to 0.972, and the average polymorphism information content (PIC) value was 0.856. A total of five SNP polymorphic sites and seven haplotypes were detected in the COI sequence, with Hap01 accounting for 80% as the main type. The haplotype diversity was 0.065, and the nucleotide diversity value was 0.00033. A total of 121 individuals from stock enhancement were monitored in the recaptured samples from the autumn fishing season of 2023 and the migratory recapture samples of 2024. Further verification with mitochondrial COI gene sequences excluded nine unfit individuals. Among 970 recaptured individuals, 112 individuals from stock enhancement were detected, including 56 individuals from stock enhancement out of 461 individuals recaptured during the autumn fishing season of 2023, accounting for 12.4% of the total recaptured individuals. 56 individuals from stock enhancement were detected in the migratory recapture samples of 2024, accounting for 9.2% of the total recaptured individuals. Microsatellite markers showed high levels of genetic diversity, while mitochondrial DNA detected lower haplotype diversity. This is mainly because nuclear genes have higher levels of genetic variation. In the traceability analysis of stock-enhanced F. chinensis, SSR markers provided sufficient individual identification capabilities. However, the lower the number of bases in the repeat unit, the higher the level of simple sequence repeat variation. But dinucleotide repeats can produce rich variability while often causing deviations in allele reading results due to base mismatches and slippages during PCR, which affects the accuracy of parent–offspring tracing results. Therefore, it is necessary to combine it with mitochondrial COI gene sequences that strictly follow maternal inheritance for re-verification to ensure the accuracy of allele reading and correction. This study provides a detailed assessment of the effectiveness of stock enhancement of F. chinensis in the Yellow Sea located on the southern coast of the Shandong Peninsula. This indicates that the enhancement of F. chinensis in the southern waters of the Shandong Peninsula had a significant contribution to the biomass of autumn in the current year and the resources of reproductive migration in the following year. Evaluating the effectiveness of stock enhancement of F. chinensis in the Yellow Sea and the Bohai Sea is not only of considerable importance for the conservation of F. chinensis resources but also makes an important contribution to the local marine ecosystem. This study can provide a scientific reference for the stock enhancement of F. chinensis in the Yellow Sea and the Bohai Sea.

Abstract:Schizothorax macropogon is a second-grade protected animal with high ecological and economic value. Currently, most of the related research has focused on resource investigation, individual biology, and population genetics. However, to date, there have been relatively few studies on gut microorganisms. In this study, we extracted the intestinal contents of S. macropogon with saprolegniasis and healthy states, respectively. We analyzed the number of OTUs, colony composition, abundance, and Alpha diversity of intestinal microorganisms, and predicted their functions by high-throughput sequencing. Alpha diversity analysis showed that the richness and diversity of the gut microbial community in the healthy group was higher than that in the sick group. PCoA analysis showed that there was a significant difference between the gut microbes in the healthy and sick group of S. macropogon. The histogram of species distribution showed that the gut microorganisms in the healthy group and sick group of S. macropogon were similar in the composition of community structure but differed in relative abundance. Bacteria acquired a total of seven dominant phyla, including Cyanobacteria, Proteobacteria, and Fusobacteriota. The endemic genera in the diseased group were Bacteroides, and Proteocatella. Five dominant phyla of fungus were obtained, including Ascomycota, Basidobolomycota, and Rozellomycota. The endemic genus in the healthy group was Cererhiza, and the endemic genera in the sick group were Boeremia and Tausonia The discriminant plot statistics showed that the healthy group had the highest number of fungi in the healthy group. The discriminant plot showed that there were 38 bacterial marker species and 45 fungal marker species between the healthy group and sick group in the gut of S. macropogon. The co-occurrence network of microorganisms in the intestine of S. macropogon had high connectivity and coherence. According to the functional prediction analysis, there was a significant difference in the functional flora of intestinal bacteria between the healthy group and the sick group (P＜0.05). The relative abundance of the healthy group was higher than that of the sick group. The present study revealed the community composition and diversity of the gut microorganisms of S. macropogon, preliminarily analyzed the relationship between the health status of S. macropogon, and its gut microorganisms, and provided a database for the study of the intestinal flora of endemic fishes in the Qinghai–Xizang Plateau.

Abstract:To research the timing of the breeding population and juveniles of Coilia nasus into or out of the Poyang Lake in the early period of the fishing ban, support the conservation of the resources and identification of the habitat of Coilia nasus in Poyang Lake, a fixed station was set up in the Hukou region during its fishing season from April to October in 2023. The resource dynamics of the breeding population in the lake and juveniles out of the lake were tracked and monitored. Both the timing and the environmental impact factors were then analyzed. In terms of the breeding population in the lake, the range of quantity caught per unit from April to July was 19~971 ind./(1000 m² ·h), with an average of (294±201) ind./(1000 m² ·h). Correspondingly, the range of weight caught per unit was 0.83~84.25 kg/(1000 m² ·h), with an average of (25.92±18.10) kg/(1000 m² ·h). The range of body length was 150.6~382.1 mm, with an average of (298.2±29.1) mm. The range of body weight was 10.6~238.1 g, with an average of (89.9±29.8) g. The ratio of male to female was 2.2 : 1, and the proportion of gonadal development from Stage I to V was in the order of 0.09%, 46.01%, 38.00%, 13.84%, and 2.06%. The results showed that May was the peak period for the breeding population moving into the lake. The mean values of quantity and weight caught per unit were (514±168) ind./(1000 m² ·h) and (47.04±16.08) kg/(1000 m² h), respectively. These were significantly higher than those of other months (P＜0.01). The body length and body weight decreased significantly along with the migration during the fishing season (P＜0.01). The maximum of the average body length occurred in May (301.5±26.4) mm, and the minimum was recorded in July (292.2±30.6) mm. For body weight, the maximum and minimum were in April (98.5±34.0) g and July (82.0±25.2) g, respectively. In the same period, the proportion of females continued to increase, and males decreased. For gonadal development, the proportion of individuals for Stage II decreased from 81.14% in April to 22.22% in July and increased from 18.77% in April to 77.78% in July for Stage III. In terms of the population moving out of the lake, the range of quantity caught per unit was 11~8571 ind./(1000 m2 ·h) from July to October, with an average of (1316± 1908) ind./(1000 m² ·h). Timing showed that the peak period was in July and September, and the mean value of quantity caught per unit in July was (2845±2940) ind./(1000 m² ·h), followed by September (1769± 1862) ind./(1000 m² ·h)). Meanwhile, the minimum of the average quantity caught per unit was (285±327) ind./(1000 m² ·h) in October. Environmental factors analysis showed that the quantity caught per unit for the juvenile population out of Poyang Lake was consistent with the trend of water level difference. The results show that the fishing season of Coilia nasus in Poyang Lake was advanced, and the duration was prolonged. Furthermore, the miniaturization of the population improved, and the resource recovery was substantial.

Abstract:In this study, a composite cage that integrates many modules, such as a steel frame structure, dive system, energy, and monitoring system, is proposed. It is necessary to conduct hydrodynamic numerical simulation tests to understand the capability to resist waves and currents and ensure the long-term safe and coordinated operation of each system. First, the wave force acting on the cage is calculated based on the potential flow theory. Then, using the motion equation to solve the dynamic response of the cage, a numerical model is constructed to study the potential of the cage under extreme sea conditions. The results indicate that: The dynamic response of the cage in the floating and submerged states is significantly correlated with the wave parameters. The tension of the anchor rope on the upstream side is always greater than that on the downstream side, and the anchor rope tension is positively correlated with the wave height and period in both states. The heave, surge, and pitch are all positively correlated with wave height in both states; it is positively correlated with the period when floating, but has no obvious correlation with the period when sinking. Surge is positively correlated with the period in both states, whereas the pitch is negatively correlated with the period when floating and positively correlated with it period when sinking. The dynamic responses of the cage in the floating and submerged states were significantly correlated with the current velocity. The tension of the anchor rope increases with the increase in flow speed in both states. When the cage is in the floating state, the pitch is positively correlated with the flow speed, the heave is negatively correlated with the flow speed, and there is no obvious correlation between the pitch and the flow speed. The overall variation amplitude of the surge and pitch is between −13% and 20%, and the average variation amplitude does not exceed 7%. When the cage is in the floating state, the maximum heave, surge, and pitch values were 0.549 m, 1.055 m, and 7.116°, respectively. After the cage was submerged, the anchor rope tension, heave, surge, and pitch decreased. The amplitudes were 59%, 70%, 57%, and 49%, respectively, indicating that the cage has a good capability to resist waves and currents. These results have practical significance for improving the safety and efficiency of submersible cage work.

Abstract:To address the issues of low efficiency and insufficient accuracy in monitoring fish populations in aquaculture, this study proposes a real-time fish monitoring method based on an omnidirectional scanning sonar and the You Only Look Once (YOLO) model using tilapia (Oreochromis sp.) as the research object. The proposed method used an omnidirectional scanning sonar to collect underwater fish shoal image data. By using the YOLOv8 algorithm combined with real-time monitoring, the proposed method achieved target recognition and analysis. Euclidean distance-based spatial analysis algorithms were used to merge and exclude anomalous data points to obtain the number and spatial distribution of fish schools. Experiments were conducted to evaluate fish schools of varying sizes (50, 100, 150, and 200 individuals) and achieved monitoring accuracies of 93.5, 94.5, 89.6, and 85.8%, respectively, with an average accuracy of 90.9%. This method substantially enhanced the real-time monitoring and accuracy of fish school population assessments. This provides an efficient solution for monitoring fish schools in aquaculture towards optimizing aquaculture management, improving production efficiency, and promoting the sustainable development of ecological aquaculture.