草鱼洄游适宜流速条件与适应阈值

洄游通道的连通性及其水文条件,是制约鱼类正常洄游和产卵繁殖的关键因素,现有的生态流量相关研究更多侧重于产卵场栖息地模拟,忽略了鱼类洄游水流条件的重要性。为了探究流速条件对鱼类洄游上溯的影响,选取体长(55±5)cm的草鱼(Ctenopharyngodon idellus)为实验对象,通过搭建鱼类洄游仿真河道,营造不同的流速工况,观察不同情景方案下实验鱼群上溯洄游情况,并利用模糊逻辑法对鱼类上溯洄游率、平均上溯时间及上溯持续性等实验参数进行综合分析,探索草鱼洄游的适宜流速条件与适应阈值。结果显示,在流速0.20m/s以下时,草鱼基本无上溯行为;流速0.25～0.80m/s,70%样本在15min内完成上溯,但0.25～0.30m/s时,鱼群上溯缺乏明显的持续性;0.90～1.00m/s时,80%以上样本在5min快速完成上溯;流速超过1.1m/s时,上溯成功率明显降低。研究表明,实验草鱼洄游的适宜流速范围是0.40～1.00m/s,而刺激草鱼洄游的最小流速阈值是0.20m/s。相关结果可为河流生态水力学模拟和河流生态修复以及水利工程生态调度提供技术支撑。

Suitable Flow Rate and Adaptive Threshold for Grass Carp (Ctenopharyngodon idellus) Migration

Connectivity and hydrological conditions in migratory channels are the key factors limiting fish migration and spawning. Existing studies on ecological flow focus on simulating spawning habitat rather than the importance of hydrological conditions. In this study, we simulated the fish migration channel and explored the effect of flow condition on migration behavior. Grass carps of average length (55±5) cm were selected for testing and their swimming behavior at different flows was recorded by camera. To determine suitable flow rates and migration threshold for grass carp, fuzzy logic was used to analyze fish migration rate, average migration time and migration persistence. The key findings are as follows: (1) At flow rates below 0.20 m/s, test fish did not display migration behavior. (2) In the velocity range 0.25-0.80 m/s, 70% of the fish completed the migration channel within 15 minutes, but were not persistent at 0.25-0.30 m/s. (3) In the velocity range 0.90-1.00 m/s, more than 80% of the fish completed the migration channel in 5 minutes. (4) The rate of successful migration decreased significantly at velocities above 1.1 m/s. Thus, the optimum velocity range for grass carp migration is 0.40-1.00 m/s and 0.20 m/s is the threshold for stimulating migration behavior. These results provide information to support hydraulic simulation, river ecological restoration and ecological regulation of water conservancy projects.