长江中下游浅水湖泊团氿东氿禁渔前后鱼类群落变动OA

The Tuanjiu-Dongjiu Culter alburnus National Aquatic Germplasm Resource Reserve is a shallow lake located in the middle and lower reaches of the Yangtze River,with natural hydrological connectivity to the Taihu Lake.To elucidate the ecological effects of the full fishing ban policy on local fish assemblages,this study conducted systematic and long-term fish resource surveys across the reserve during two contrasting periods:2017-2018(pre-implementation of the fishing ban)and 2021-2024(post-implementation of the fishing ban).We comprehensively quantified the spatiotemporal variations in fish species composition,multidimensional diversity,and community stability,with the aim of providing empirical evidence for adaptive management of urban shallow lake ecosystems.A total of 24 fish species were recorded in the pre-ban surveys,whereas the post-ban monitoring yielded a remarkable recovery trend:the annual number of detected species was 18,31,29 and 38,respectively,resulting in a cumulative 42 species belonging to 31 genera,9 families and 6 orders.Substantial shifts were observed in trophic structure and migration traits of the assemblage.The large migratory top predator Elopichthys bambusa,which was completely absent in pre-ban records,was newly documented in the post-ban period,indicating improved habitat connectivity and ecological integrity.Meanwhile,the proportion of carnivorous species increased from 37.50%(pre-ban)to 44.83%(post-ban),making carnivores a relatively dominant trophic group.Three widely accepted biodiversity indices,namely Margalef's richness index,Shannon-Wiener diversity index and Pielou's evenness index,increased significantly from 3.33,1.80 and 0.57(pre-ban)to 4.78,2.59 and 0.71(post-ban),respectively.The synchronous improvement in species richness,diversity and evenness demonstrates that the fishing ban has effectively alleviated long-term overfishing pressure,allowing rare and less competitive species to recover,and consequently enhancing the overall complexity and resilience of the fish community.This conclusion was further supported by the shift in species dominance:the dominance of small-sized,r-strategist species such as Carassius auratus and Pseudobrama simoni decreased,while large-bodied filter-feeding species including Hypophthalmichthys molitrix and Aristichthys nobilis became stable dominant taxa.The abundance-biomass curve(ABC)analysis showed that the W statistic increased from-0.12(pre-ban)to 0.12(post-ban),confirming a clear transition of the fish assemblage from a severely disturbed state to a relatively stable condition under the protection of the fishing ban.Considerable spatial heterogeneity in recovery performance was detected between the two sub-lakes(Dongjiu and Tuanjiu)within the reserve.After the fishing ban,the cumulative number of recorded species reached 41 in Dongjiu and 38 in Tuanjiu.Throughout the post-ban period,the Margalef's richness index in Dongjiu(2.65‒4.92)was consistently higher than that in Tuanjiu(2.08-4.73).The index of relative importance(IRI)revealed that the dominant species composition in Dongjiu has reached a stable state,with W values ranging from-0.032 to 0.195,indicating a low disturbance level.In contrast,Tuanjiu exhibited a higher turnover rate of dominant species,and its W values(-0.065 to 0.151)suggested a relatively higher disturbance intensity.Overall,this study demonstrates that the fishing ban policy has effectively promoted the structural and functional recovery of fish communities in the reserve,with significant enhancement in species diversity and community stability.The divergent recovery trajectories across different lake zones are jointly mediated by multiple environmental drivers,including hydrological dynamics,landscape connectivity and lake geomorphology.These findings provide a scientific foundation for implementing zoned and differentiated ecological management in the Yixing reserve,and offer valuable empirical references for aquatic biodiversity conservation and ecological restoration in shallow lakes across the middle and lower Yangtze River floodplain.