Reservoir “eco-operation” is an ecological flow regulation measure, such as mimicking a flood process to stimulate fish spawning. Since 2011, the Three Gorges Reservoir (TGR) eco-operation trials have been carried out to facilitate the spawning of the four major Chinese carps (FMCC) below the Gezhouba Dam. Until now, the response of FMCC spawning to new hydrologic conditions is seldom documented. Using ecological monitoring data from 2012 to 2017, this study analyses annual variations in environmental factors and FMCC spawning, and the correlations between them. During the date of FMCC egg occurrence, there was no significant difference both in annual mean water temperature (TEM) and water transparency (TRA) among years, while there was significant difference in annual mean river flow. The annual egg abundance of FMCC ranged from 135 to 610 million, with an average of 286 million. The peak spawning of FMCC occurred 3 to 5 times annually, while the scattered spawning occurred about 2 to 3 times. Classification and Regression Trees and Random Forests were used to model the daily egg abundance of FMCC. Daily flow (FLO) and flow increase multiple (FIM) were determined as the most important factors for FMCC spawning. The models predicted daily egg abundance of FMCC in the Shashi section could reach to 3.16 × 10⁷ ind. for FLO exceeding 10,000 m³/s and FIM below 49.12. The results might be helpful to deeply understand the role of flood peak process on fish spawning and the optimization of TGR eco-operation on FMCC spawning.

中文翻译：

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三峡水库下游四大鲤鱼产卵量与环境变量的关系

水库“生态合作”是一种生态流量调节措施，例如模拟洪水过程以刺激鱼类产卵。自2011年以来，开展了三峡水库（TGR）生态运营试验，以促进葛洲坝大坝以下四大鲤鱼（FMCC）的产卵。到目前为止，很少记录 FMCC 产卵对新水文条件的响应。本研究利用2012年至2017年的生态监测数据，分析了环境因子和FMCC产卵的年度变化及其相关性。在 FMCC 卵发生日期，年平均水温 (TEM)和水透明度 (TRA)年间均无显着差异，而年平均河流有显着差异。流。FMCC 的年卵丰度在 1.35 到 6.1 亿个之间，平均为 2.86 亿个。FMCC每年出现3～5次产卵高峰，而分散产卵约2～3次。分类和回归树和随机森林被用来模拟 FMCC 的每日鸡蛋丰度。日流量 (FLO)和流量增加倍数 (FIM)被确定为 FMCC 产卵的最重要因素。模型预测沙市断面FMCC日丰度可达3.16×10 ⁷ ind。对于FLO超过万米³ / s和FIM低于 49.12。研究结果可能有助于深入理解洪峰过程对鱼类产卵的作用以及优化TGR生态运行对FMCC产卵的影响。