基于水声学方法的长江朱沱至龙华江段鱼类时空分布特征研究OA

In this study,we explored the spatiotemporal distribution of fish resources and its relationship with the hydrological environment in the Zhutuo-Longhua reach of the National Nature Reserve for Rare and Endemic Fish in the Upper Yangtze River.We aimed to provide scientific support for the formulation of fish resource conservation strategies in protected areas and the optimization of hydrological regulation schemes.From January to December 2024(no survey in February),monthly acoustic detection of fish was conducted in the Zhutuo-Longhua section of Yangtze River,following a zigzag route along the 75 km study reach.Based on survey results and flow data,we characterized the monthly variation of fish den-sity,body length and seasonal differences in spatial distribution,analyzed the response relationship be-tween fish resource distribution and hydrological flow dynamics,elucidated the temporal dynamics of adult fish aggregation and primary driving factors,and identified core fish habitats and spawning areas.The average fish target strength(TS)was(-51.99±5.94)dB and the average body length was 5.8 cm.Both fish density and body length exhibited extremely significant monthly differences(P<0.001).The highest values,4.45×10-3 ind/m³ and 10.67 cm,both occurred in April due to fish aggregation during the peak spawning migration period,while high flows during flood season in July and low temperatures in Decem-ber led to reductions in fish density(0.74×10-3 ind/m³ in July,0.56×10-3 ind/m³ in December).Spatially,fish were distributed in uneven patches,with primary aggregation areas in river sections flowing gently through complex terrain,including the stretches flowing by Zhutuo-Zhuyang Town,Jingangtuo,Youxi,and Longhua Town.Fish density exhibited significant non-linear correlation with water depth(P<0.001),and a depth of 8－20 m was the preferred layer,although high fish densities also occurred at water depths exceeding 20 m during flood season(May-August).There was not a clear linear correlation between fish density and flow rate,but high densities were concentrated in the 5 000－6 000 m³/s range.For adult fish(≥15 cm),the number peaked in April and the proportion peaked in December.Neither the number nor the proportion of adults were significantly correlated with flow rate(both P>0.05),as they were mainly driv-en by spawning habits and overwintering needs.In conclusion,this study clarifies the patterns of spatio-temporal change in local fish resources and the influencing hydrodynamic factors.The results provide a scientific basis for optimizing the balance between conserving fishery resources and regulating river hy-drology.