This study was conducted to investigate fish eggs and larvae dispersal in a river stretch influenced by small hydropower plants in Southeast Brazil. The main hypothesis is that the downstream dispersal of free-flowing eggs and larvae is likely to occur given the small size of the studied reservoirs and that passage through the dam may occur, with the fish ladder contributing to it. Eggs and larvae were collected fortnightly, between November 2016 and February 2017, from locations upstream of two dams, including lotic, transition and lentic zones. Additional samples were collected inside the fish ladders at each dam. Downstream dispersal of eggs and larvae was influenced by a combination of rainfall/flow variation and stage of the reproductive cycle, with the peak of rainfall during the summer coinciding with higher abundances. Under these conditions, eggs and larvae drifted downstream through the reservoirs and reached the dams. Once in the dam, they could pass through the fish ladder. This passage was correlated with larval density in the reservoir immediately upstream, although at very low densities compared with the other sampling sites located upstream of the fish ladders.

中文翻译：

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带鱼梯的小水电站级联中鱼卵和幼虫的扩散

本研究旨在调查受巴西东南部小型水电站影响的河段中鱼卵和幼虫的扩散情况。主要假设是，考虑到所研究的水库规模较小，可能会发生自由流动的卵和幼虫的下游扩散，并且可能会通过大坝，鱼梯对此有贡献。2016 年 11 月至 2017 年 2 月期间，每两周从两个大坝上游位置收集卵和幼虫，包括激流区、过渡区和静水区。在每个大坝的鱼梯内收集了额外的样本。卵和幼虫的下游扩散受降雨/流量变化和生殖周期阶段的综合影响，夏季降雨高峰与较高丰度相吻合。在这种情况下，卵和幼虫通过水库向下游漂流并到达大坝。一旦进入大坝，它们就可以穿过鱼梯。该通道与紧靠上游的水库中的幼虫密度相关，尽管与位于鱼梯上游的其他采样点相比密度非常低。