Abstract:With the rapid development of intensive aquaculture， especially in recirculating aquaculture systems （RAS）， the efficient management of solid waste in aquaculture water has become a critical challenge. In RAS， the removal efficiency of suspended solids not only directly determines system performance but also affects its long-term operational stability. As the primary source of solid waste in aquaculture water， the characteristics of fish faeces are key prerequisites for achieving efficient water recycling. Moreover， excessive accumulation of faeces can directly damage fish gill and epidermal health， while also exacerbating microbial competition， promoting abnormal accumulation of nutrients such as ammonia and reactive phosphorus， and triggering water eutrophication and ecosystem dysfunction. This review systematically showed the latest researches on the characteristics of farmed fish faeces， influencing factors， and nutritional regulation strategies. Studies reveal significant interspecific differences in the physical characteristics of fish faeces， such as water stability， settling velocity， and particle morphology， which are jointly regulated by rearing conditions and feed composition. Although the chemical composition of feces is homologous to feed， there are notable differences in nutrient content， with the high enrichment of nitrogen and phosphorus being the primary contributors to water pollution. Regarding nutritional regulation strategies， feed optimization serves as the core approach for source control. This includes： （1） Improving nutrient digestibility by adjusting feed formulations and supplementing exogenous enzymes such as proteases and phytases； （2） Optimizing fecal physical properties using binders and buoyancy regulators； （3） Modulating gut health with probiotics and functional oligosaccharides to indirectly improve fecal composition. Despite current progress， further research is needed to address the specific requirements of different aquaculture systems and species. This review aims to provide a systematic theoretical foundation for innovative feed technology development and promote the green， sustainable advancement of the aquaculture industry.

Abstract:In order to understand the carbon sequestration of phytoplankton in freshwater aquaculture ponds of Litopenaeus vannamei and to find out the relationship among water quality， phytoplankton and carbon sequestration， the primary productivity of the water of Litopenaeus vannamei aquaculture ponds in Fengxian District， Shanghai was detected by black and white bottle method， and the carbon sequestration of phytoplankton was estimated. The results showed that a total of 45 genera belonging to 7 phylum of phytoplankton were observed in the three ponds， including 19， 8， 11， 3， 2， 1 and 1 genera of Chlorophyta， Cyanophyta， Bacillariophyta， Euglenophyta， Chrysophyta， Dinophyta and Cryptophyta， respectively. The phytoplankton densities in pond Ⅰ， Ⅱ and Ⅲ were （7.99±7.84）×10⁵， （1.86±1.55）×10⁶ and （2.57±1.66）×10⁶ ind/L， respectively. There were four species of common dominance in the three ponds， namely Scenedesmus， Oscillatoria， Navicula and Cyclotella. The variation range of daily carbon sequestration per unit area （D_CS） of phytoplankton was 0.27-4.92 g C/（m²·d）， the average value was （1.62±1.12） g C/（m²·d）， the cumulative carbon sequestration of phytoplankton increased slowly with the extension of the cultivation time during the whole cultivation period， and the cumulative carbon sequestration of the 3 experimental ponds was 0.80， 1.11 and 1.31 t C at the end of aquaculture. The results of multiple stepwise regression analysis showed that Chlorophylla （Chl.a）， Total Nitrogen （TN）， Temperature （T）， pH， phytoplankton Euglenophyta and Cyanophyta were the main environmental factors affecting the D_CS of phytoplankton. Pearson correlation analysis and redundancy analysis showed that Chl.a， TN， T， Euglenophyta and Cyanophyta were the key factors affecting the carbon sequestration of phytoplankton， and these results were helpful for us to understand the effects of water quality and phytoplankton community on the carbon sequestration of phytoplankton in Litopenaeus vannamei fresh water aquaculture ponds.

Abstract:To explore the optimal breeding density of exclusive crabseed for out-season crab at lunar June （Eriocheir sinensis）， this study took juvenile crab as the test object， and set 4 density groups： D1 10 ind./m²， D2 20 ind./m²， D3 30 ind./m² and D4 40 ind./m². The growth performance and culture benefit of each density group were compared and analyzed by pond culture experiment. Results indicated： （1） With the increase of culture density， the average body mass of crabs in group D1 was significantly higher than that in the other three groups during culture. In terms of weight gain rate and specific growth rate， group D1 always had an advantage over the other groups from July to October， but was significantly lower than the other groups from October to November. （2） D3 group achieved the best breeding effect， which was reflected in relatively impressive size and yield， and achieved the highest survival rate， the lowest early maturing rate and feed coefficient. （3） In terms of size distribution， the final size of buckled crabs in groups D1 and D2 was mainly concentrated in the range of 35-45 g， and the weight of buckled crabs in groups D3 and D4 was mainly concentrated in the range of 25-35 g. With the increase of stocking density， the proportion of juvenile crabs in each density group less than 35 g gradually increased， while the proportion of juvenile crabs greater than 35 g gradually decreased. （4） In terms of economic benefits， D4 group achieved the highest income and profit， while D3 group achieved the highest return-on-investment. According to the comprehensive evaluation， the breeding density model of 30 ind./m² can obtain relatively considerable yield and feed coefficient， and its harvest size is also larger， which is the optimal breeding density of June yellow large size crab species.

Abstract:This experiment was conducted to study the effects of dietary methionine levels on the growth performance， digestion and absorption related indexes and antioxidant capacity of juvenile Micropterus salmoides. 1 440 largemouth bass with an initial body weight of （0.18 ± 0） g were selected and randomly divided into 6 groups （each group had 4 replicates， with 60 replicates each）. They were raised in nylon cages with a water volume of 50 L in an outdoor aquaculture system， and fed with equal nitrogen and fat feed ranging from T1 to T6（methionine additions of 0， 0.5%， 1.0%， 1.5%， 2.0% and 2.5%， with measured values of 0.67%，1.08%，1.43%，1.78%，2.22% and 2.61%，respectively）. The experimental period is 30 days. The results showed that as the feed methionine level increased， the weight gain rate， specific growth rate， and protein deposition of the experimental fish first increased and then decreased， and the feed coefficient first decreased and then increased. The weight gain rate and specific growth rate of the 1.08%， 1.43%， 1.78%， 2.22% and 2.61% groups were significantly higher than the 0.67% group （P<0.05）， and the feed coefficient was significantly lower than the 0.67% group （P<0.05）； With the increase of feed methionine levels， the activity of trypsin in the intestinal tract of experimental fish showed a trend of first increasing and then decreasing， with the highest in the 1.78% group， and had no significant effect on other intestinal enzyme activities； With the increase of feed methionine levels， the activities of GSH-Px， CAT， T-SOD， and LZM in the liver of experimental fish first increased and then decreased. CAT， T-SOD， and LZM activities were highest at 1.78%， significantly higher than those in the 0.67% group（P<0.05）. Using specific growth rate as an evaluation indicator，the demand for methionine in juvenile largemouth bass is 1.72%， accounting for 3.23% of the feed protein.

Abstract:In order to investigate the change and evolution of fish community structure in Jinze Reservoir from 2017 to 2022， Margalef richness index， Shannon diversity index， Pielou evenness index， abundance biomass curvilinear method， completeness index， and clustering analysis were used to investigate and analyze the fish community.The results showed：A total of 5 119 fish were collected in the survey， belonging to 7 orders， 12 families， 34 genera， and 46 species. The dominant species in Jinze Reservoir in the 2017 survey were Coilia nasus， Pseudorasbora parva， Hypophthalmichthys molitrix， Aristichys nobilis， Carassius auratus，and the dominant species in Jinze Reservoir in 2018-2022 were Coilia nasus， Hypophthalmichthys molitrix， Aristichys nobilis and Carassius auratus.After clustering analysis： at the level of 70% similarity， 2017， 2018， and 2019 were separate groups， and 2020， 2021， and 2022 were groups， and the fish communities were similar in the last three years. The fish Margalef richness index and Shannon diversity index in Jinze Reservoir from 2017 to 2022 were overall high and showed an upward trend in fluctuation； the Pielou evenness index declined and then stabilized， and the competitive advantages of the dominant species gradually appeared. The fish integrity index evaluated the Jinze Reservoir as "fair" in 2017 and "good" in the remaining years. The biomass of population abundance method showed that the biomass of abundance curves of Jinze Reservoir from 2017 to 2022 did not cross and the statistic W was greater than 0， which indicated that the structure of the fish community was stable. The study showed that the fish diversity in Jinze Reservoir was getting higher from 2017 to 2022， the community structure was not negatively affected， and the ecosystem remained stable.This study can provide a reference for the management of fish resources in the reservoir and the construction of an ecological reservoir.

Abstract:To assess the impact of cascade hydropower stations on the health of aquatic ecosystem in the middle reaches of Jinsha River and to explore and establish relevant evaluation systems， surveys of fish resources and water environmental elements were conducted in December 2021， April 2022， and July 2022 in both the reservoir and tailwater parts of each station and its primary tributaries. Historical survey data from April to May 2007， March to April 2008， and June to July 2008 were utilized as reference conditions. The distribution range， discriminant capacity， and redundancy of the selected indicators were sequentially performed. Evaluation criteria were established through the implementation of the ratio method. Consequently， specific fish-index of biotic integrity （F-IBI） assessment frameworks tailored to both the main stem and tributaries of the Jinsha River were formulated. Additionally， an investigation into the correlation between F-IBI scores and various water environmental factors was undertaken. The results suggested that： Evenness index （M3）， percentage of cyprinid species （M4）， percentage of mid-lower layer fish species （M11）， percentage of individuals of fish producing floating eggs （M18）， and total number of fish individuals （M22） were screened out and analyzed as main stem core indicators. While percentage of loach species（M5）， M11， percentage of carnivorous fish individuals （M13）， M18， percentage of individuals with special spawning methods （M21） and M22 were filtered as tributaries core indicators. 32 monitoring points have been set up in the middle reaches of the Jinsha River. F-IBI scores range from 6.54 to 63.11 points， with evaluation grades of “sub-healthy”， “normal”， “medium risk”， “high risk” and “fishless” accounting for 3.70%， 29.6%， 48.1%， 11.1%， and 7.4% of monitoring points， respectively. In terms of correlations， the F-IBI values demonstrated a significant negative association with water temperature （WT， r=-0.404 9， P=0.044 7） and a significant positive correlation with secchidepth（SD， r=0.569 1， P=0.003 0） and flow velocity （v， r=0.450 9， P=0.046）. In conclusion， the research results indicated that the cascade hydropower stations in the middle reaches of the Jinsha River exerted a significant impact on the overall health of its aquatic ecosystem， with a notably higher level of impact observed in the tributaries compared to the main stem.

Abstract:To investigate the current structural status of the Feiyun River Estuary ecosystem under the influence of factors such as fish stock decline and eutrophication， and to evaluate the proliferation capacity of the water-purifying fish species Konosirus punctatus in this area， this study analyzed ecosystem characteristics using the Ecopath model based on biological resource survey data collected from four voyages in the Feiyun River Estuary between 2022 and 2023. The study also estimated the proliferation capacity of Konosirus punctatus by considering food web structure and energy flow. The model's functional groups encompassed 26 categories， essentially covering the entire process of energy flow within the ecosystem. The results revealed： （1） The trophic levels in the Feiyun River Estuary ranged from 1.00 to 3.84， with a total conversion efficiency of 8.623%. （2） The ratio of total primary production （TPP） to total respiration （TR） in the ecosystem was 1.629， which is greater than 1； the connectance index （CI） was 0.413， which is less than 1； and the system omnivory index （SOI） was 0.234， also less than 1. （3） The existing biomass of Konosirus punctatus was 0.040 5 t/km²， with a proliferation ecological capacity of 0.081 0 t/km². After proliferation， the TPP/TR， CI， and SOI values of the ecosystem all approached 1 more closely. The research indicated that： （1） The energy flow in the Feiyun River Estuary ecosystem generally adhered to the laws of the energy pyramid， with a food web structure dominated by grazing food chains. （2） The ecosystem's maturity was relatively low， its food web structure was simple， its resistance to external disturbances was weak， and its energy utilization efficiency was insufficient. （3） Scientific stock enhancement and release of Konosirus punctatus could promote the maturity and stability of the Feiyun River Estuary ecosystem. This study provides valuable insights for the conservation of fishery resources and ecological environment protection in the Feiyun River Estuary.

Abstract:To monitor the long-time-series urbanization process of the Lingang Special Area of China （Shanghai） Pilot Free Trade Zone and analyze its spatiotemporal continuous change characteristics and driving forces， this study utilized Landsat long-time-series remote sensing images from 1984 to 2020. Annual average and pixel-level time-series curves of the Normalized difference built-up index （NDBI）， Normalized difference vegetation index （NDVI）， and Normalized difference water index （NDWI） were constructed. Linear regression fitting was employed for abrupt change detection to determine the start and end years of urbanization. Based on this， 1984 and 2020 were selected as benchmark years， and a random forest classifier was used to classify the land use/cover types of Shanghai Lingang Special Area. The results showed that from 1984 to 2020， the additional urban land mainly originated from water bodies and vegetation. The urban land area increased by 346.73 km²， with an average annual growth rate of 12.85%. Taking 2001 and 2010 as turning points， the process was divided into three stages： slow development stage （1984-2000）， with an average annual growth rate of 8.83%， medium-speed development stage （2001-2010）， with an average annual growth rate of 12.49%， and rapid development stage （2011-2020）， with an average annual growth rate of 15.39%. The study revealed that economic and population growth were the primary driving forces of urban land expansion. Spatially， the urbanization development of Shanghai Lingang Special Area exhibited characteristics of coastal and patchy distribution. The speed and sources of urban land expansion varied across different periods， and economic development and urbanization process promoted each other. This research holds extremely important practical significance for the future refined urban construction of the Yangtze River Economic Belt and the rational and effective utilization of estuarine and coastal resources.

Abstract:Affected by natural factors such as human activities and climate change， some ecosystems in the coastal zone of Shanghai are facing problems such as habitat degradation and damage to ecosystem structure and function， and ecological restoration is urgently needed. In the context of the dual carbon goals， how to guide the ecological protection and restoration of the coastal zone has become a major issue. Based on the physicochemical and location characteristics of the coastal zone， this study extracted the main characteristics of the coastal zone of Shanghai， and sorted out the difficulties of ecological restoration and management caused by natural and human factors such as the contradiction between economic development and ecological protection， the change of water and sediment conditions， and the spread of invasive alien species. It is suggested that the ecological restoration of the coastal zone of Shanghai should explore the green and diversified development model from the perspective of management， carry out the construction of the coastal zone with ecosystem integration from the perspective of restoration technology application， and form a long-term and multi-dimensional ecological restoration effect evaluation system from the perspective of ecological restoration effect tracking， so as to provide reference for the ecological restoration and high-quality development of the coastal zone of Shanghai.

Abstract:In order to study the carbon sequestration capabilities of coastal blue carbon ecosystems represented by mangroves， salt marshes， etc.， this paper uses multi-source and multi-temporal Landsat images， Random Forest algorithms， and InVEST model blue carbon module to evaluate the spatiotemporal distribution characteristics and carbon storage of typical coastal blue carbon ecosystems in the East China Sea during 1992-2022. The results show that： during 1992-2022， in the East China Sea coastal zone， the aquaculture area>tidal flats area>salt marshs area>mangroves area； aquaculture are distributed along the coast of the East China Sea， mangroves mainly distributed in Quanzhou Bay and other areas； salt marshes and tidal flats are mainly distributed in the Yangtze River Estuary-Hangzhou Bay； aquaculture are mainly transformed into water and cultivated land， and tidal flats are mainly transformed into aquaculture and water， salt marshes and mangroves are mainly transformed into aquaculture； during 1992-2022， the typical coastal blue carbon storage in the East China Sea showed an overall upward trend， with an average annual growth rate of 1.26 Tg C/a； the total net carbon sequestration value is 41.61 Tg C. The study results can provide decision-making support and scientific services for the East China Sea coastal zone to formulate measures to reduce emissions and increase sinks， improve carbon sequestration capabilities， and respond to global climate change.

Abstract:Land-based aquaculture systems play an important role in the era of facility-based fisheries. Whether it is a full-cycle land-based recirculating aquaculture model or a land-based nursery model in deep-sea aquaculture， or land-based aquaculture in land-sea relay aquaculture models， the performance of land-based systems is critical. However， land-based aquaculture systems still face challenges in solid waste management， especially the efficient collection and removal of settleable particles like uneaten feed and feces. Accumulation of these wastes adversely impacts the stability of water quality， biological safety of cultured organisms， and production operations. To accurately and comprehensively describe the factors influencing the movement of settleable particles in aquaculture tanks， this paper focuses on reviewing the effects of hydrodynamic characteristics of aquaculture tanks， structural characteristics of the tanks， and the inherent properties of settleable particles on the movement of settleable particles. Aiming at the difficulties of removing settable particles in land-based systems， this paper proposes valuable research directions to improve the aquaculture environment， enhance fish health， and improve the water quality of the aquaculture system， thus providing theoretical support and practical guidance for production.

Abstract:To accelerate the development of solar photovoltaic systems from land to sea， it is very important to master the hydrodynamic response characteristics of floating photovoltaic （FPV） under wave loads. In this research， the hydrodynamic response characteristics of a FPV under regular waves are studied based on computational fluid dynamics method（CFD）， and verified by physical model experiment. The results show that the surge and heave motion increase with the increase of wavelength when the wave height is constant and the wavelength range is 3-5 m. The maximum mooring force response of the floating photovoltaic platform also shows an increasing trend with the increase of wavelength under the condition of wavelet height， but the growth trend is gentle. The mooring force response of the platform increases significantly when the wave height is 0.2 m and the wavelength exceeds 4.5 m. The research shows the incident wave and the floating platform have obvious attack phenomenon when the wave steepness is large， and the action position is mainly concentrated on the buoy position of the floating platform. This study provides theoretical reference and data support for the design and optimization of offshore floating photovoltaic， which has very important scientific significance and application value.

Abstract:Waterweed is one of the key elements in Eriocheir sinensis （Chinese mitten crab） pond aquaculture. In order to investigate the mutual influence and mechanism of waterweed clump planting offset and pond flow field in aquaculture ponds， this paper conducts a numerical simulation study on the flow field characteristics of waterweed clump offset based on porous media. Using the solid volume fraction of waterweed clump as a clue， a set of porous media experimental devices are established to quantify the resistance of waterweed. A numerical model of waterweed clump is established based on field measurement samples， and the influence of waterweed clump offset on the pond flow field is studied through 5 sets of incremental offset experiments in Fluent. The study shows that increasing the offset can significantly change the flow velocity distribution from strip-like to patchy， promoting lateral mixing of water. The index of flow uniformity fluctuates around 0.6， and the medium offset has the highest uniformity of water flow. The velocity and uniformity inside the waterweed clump increase with the increase of offset， mainly depending on the area where the secondary waterweed clump leaves the shear zone of the first row of waterweed clumps. The energy utilization rate of the highest offset condition can reach 0.49， 4.6 times the lowest value. The vertical vortex behind the waterweed clump is opposite to the change trend of the boundary layer separation vortex. A high offset will weaken the range of action of the vertical vortex and enhance the range and intensity of the boundary layer separation vortex. The research results help to understand the energy circulation and material distribution in crab ponds， and scientifically guide the planning of waterweed planting in crab ponds.

Abstract:In order to improve the ecological compatibility and data acquisition efficiency of aquaculture underwater observation， a bionic underwater observation device with low disturbance and high stability was designed. In this experiment， the morphological design of bionic manta rays was adopted， the outline of biological specimens was extracted based on computer vision，the external morphological model of the NACA0013 airfoil was constructed， and the radial kinematic model was established by combining the Lighthill theory. The hydrodynamic performance was verified by the moving tank test， and the actual water area test was carried out to evaluate the degree of disturbance to the fish population and the image transmission ability. The results show that the goodness of fit between the biomimetic body contour and the NACA0013 airfoil is 0.944， which has excellent hydrodynamic characteristics， and the thrust， lift and pitch moment values reach the maximum when θ=50° and f=0.830 Hz in the moving tank test， and the oscillation is regular， indicating the stability of the motion. After testing， the average tracking rate of fish schools is as high as 36.5%， which proves that the device has minimal interference with fish schools and excellent environmental compatibility， and can transmit high-definition images of the integration of bionic manta rays and natural fish in real time， which fully meets the needs of ecological observation. The results show that NACA0013 airfoil has a significant streamlined fitting advantage. The thrust， lift and pitching moments of the bionic manta rays increased with the increase of motion amplitude and frequency， but were significantly affected by the environmental flow velocity. When the movement speed of the bionic manta ray was 0.3 m/s， the fish follow-up rate reached the peak. The device can realize non-disturbance detection in aquaculture and provide effective data support for aquaculture management. This study provides a new eco-friendly underwater observation equipment for aquaculture， and its bionic design and intelligent control methods can be extended to the fields of marine ecological monitoring and underwater robots， so as to promote the development of low-interference underwater technology.

Abstract:To explore the exposure situation of organochlorine pesticides （OCPs） in the coral reef area of Weizhou Island， Guangxi， gas chromatography-tandem triple quadrupole mass spectrometry （GC-MS/MS） was used to study the pollution levels， sources， and bioaccumulation characteristics of seven kinds of OCPs in seawater， sediments， coral host （i.e.， coral polyp hosts） tissues， and Symbiodinium in the coral reef areas in the northwest， southwest， and east directions around Weizhou Island. The results showed that OCPs were commonly present in the seawater of the coral reef area of Weizhou Island. DDTs were the main components among OCPs. The concentration of ∑₇OCPs in seawater was（119±118） pg/L， and the concentration of ∑₆DDTs was（84.1±82.3） pg/L. The concentrations of ∑₇OCPs in sediments， coral host tissues， and zooxanthellae were（0.27±0.22） ng/g dry weight， （1.90 ± 2.04） ng/g dry weight， and（17.7±7.29） ng/g dry weight， respectively. The average values of lg BAFs of the seven target OCPs in coral host tissues and Symbiodinium were 2.04-3.44 and 2.25-4.06， indicating that Symbiodinium had a stronger enrichment ability for OCPs than coral hosts. Whether this higher enrichment ability will bring higher ecological risks is worthy of in-depth study. The results of ecological risk assessment showed that the ecological risks of the seven target OCPs in the sediments and seawater of the coral reef area of Weizhou Island were currently at a relatively low level. The results of source apportionment showed that historical residues were the main sources of DDTs in the coral reef area of Weizhou Island， mainly dominated by dicofol products.

Abstract:By combining literature review and actual investigation， a preliminary evaluation system for the low-carbon and green development of rural complexes with 16 specific indicators across four levels has been established. Based on the weights of the indicators determined by the Analytic Hierarchy Process （AHP）， the fuzzy comprehensive evaluation method is used to assess the carbon sequestration of the ecological environment， the efficient use of resources， and the greening of economic development of rural complexes. After applying the aforementioned evaluation system to the rural complex in the rural villages of Jinshan District， Shanghai， the results show that the overall low-carbon and green development of this rural complex is good （89.23/100）， with highlights in the three dimensions of ecological environment， social resources， and economic development， reflecting the significant effectiveness of the rural complex in promoting the transformation and upgrading of the agricultural industry and driving farmers' income and wealth. However， there is still room for improvement in terms of carbon sequestration per unit area and visitor experience and satisfaction. It is recommended to further introduce low-carbon agricultural technologies to enhance the soil carbon pool， combine local cultural resources to create distinctive agricultural tourism projects， and strengthen the construction of tourist feedback mechanisms to further improve service quality.

Abstract:A total of 69 sites were deployed in the main and tributary streams of the Yangtze River Basin to evaluate and analyze the spatial autocorrelation of main water quality parameters and to explore the influence of multiple environmental elements on the water quality of the Yangtze River at different spatial scales. The results showed that nearly half of the sampling sites had water quality of category 3 or above， with obvious differences between the main streams and tributaries. DO， TP and TN had obvious aggregation trends on the whole， but had specific distribution characteristics in the local space. In addition， the relationship between water quality parameters and influencing factors at different spatial scales is complex， and the application of Geographically Weighted Regression model is always better than Ordinary Least Squares model. At the global scale， precipitation and water body area positively contributed to water quality and were the main factors influencing DO and NH₃-N， while temperature and nighttime lighting had negative effects and were the key correlates of TP， TN， permanganate index， and WQI （composite pollution status index）， with temperature also significantly influencing water body pH. At the local scale， there were complex correlations between multiple influencing factors and water quality parameters， with differences in their roles at different spatial scales， mainly in the effects of NDVI （Normalized difference vegetation index）， population density and built-up land. In summary， this study thoroughly explored the main driving mechanisms of water quality changes at multiple spatial scales， providing an important basis for the protection and regulation of water quality in the Yangtze River.

Abstract:This study systematically analyzes the species composition， abundance， and spatial distribution of bycatch in purse seine fisheries using tuna fishery and bycatch data provided by the Western and Central Pacific Fisheries Commission （WCPFC） from 2013 to 2022. Additionally， the correlation between bycatch rates and the catch rates of three major target species：skipjack tuna （Katsuwonus pelamis）， yellowfin tuna （Thunnus albacares）， and bigeye tuna （Thunnus obesus） was examined to identify distinct bycatch patterns and their relationship with target species composition.The results indicate that 48 bycatch species were recorded， totaling 439 623 individuals， primarily comprising cetaceans， sharks， and sea turtles. Among these， the silky shark （Carcharhinus falciformis） was the most frequently bycaught species， with 418 387 individuals， accounting for 95% of the total bycatch. Bycatch was predominantly concentrated in waters between 10°S-10°N latitude and 140° E-150° W longitude. Furthermore， bycatch rates were generally higher in eastern longitudes than in western longitudes， with cetacean bycatch exhibiting the most pronounced east-west variation.Correlation analysis revealed no significant relationship between the bycatch rates of cetaceans and sharks and the catch rates of target tuna species. However， the bycatch rate of sea turtles showed a positive correlation with the catch rates of skipjack and bigeye tuna. These findings highlight the high bycatch risk associated with purse seine fisheries， particularly for silky sharks， which dominate the bycatch composition. The overall higher bycatch rates in eastern longitudes further underscore the need for region-specific mitigation strategies.This study provides valuable scientific insights to support bycatch reduction measures， contributing to the conservation and sustainable management of marine ecosystems.

Abstract:Under the background of the 10-year fishing ban policy on the Yangtze River， how the recreational fishing industry can achieve high-quality development without affecting the recovery of fishery resources has increasingly drawn widespread social attention. Based on the current development status of the recreational fishing industry in China and the survey data from fishery administration officers in the Yangtze River Basin， this study explores the challenges and opportunities faced by the recreational fishing industry. Through a comparison of recreational fishing management systems at home and abroad， it proposes suggestions for the high-quality development path of the recreational fishing industry in the Yangtze River Basin. The study shows that recreational fishing in the Yangtze River Basin plays a dominant role in freshwater recreational fishing in China. The fishery administration officers believe that the management of recreational fishing should be strengthened in terms of management objects， restrictive measures， legal responsibilities and other aspects. They have a good understanding and willingness to implement recreational fishing management， and the implementation of recreational fishing licensing management policies has a good practical foundation. It is suggested that measures such as implementing a registration and filing system， exploring licensing management pilots， compiling recreational fishing guidelines， strengthening the publicity of civilized fishing， strengthening fishery law enforcement， and improving recreational fishing laws and regulations be taken to standardize the management of recreational fishing and promote the high-quality development of the industry. This study can provide a reference for the high-quality development of the recreational fishing industry in the Yangtze River Basin in the future.