The reproductive activity of the fish assemblage in a large Neotropical reservoir was evaluated by surveying the occurrence of ichthyoplankton in response to spatial and temporal variation in environmental factors. Fish reproduction was investigated by capturing larvae along representative spatial gradients in the main body (longitudinal) and arms (lateral) of the reservoir. After identification, the captured larvae were classified into different groups according to the functional traits of their parental stock. Sampling occurred monthly at night from October to March over five reproductive periods between 2009 and 2016, using conical-cylindrical plankton nets with flowmeter. Water samples were taken simultaneously allowing the measurement of environmental factors related to reproductive activity. The relationship between the environmental factors and the functional traits was assessed using RLQ and fourth-corner analyses. An evaluation of 51,995 larvae revealed there was greater larval abundance in the lacustrine and transition zones of both longitudinal and lateral gradients. Occurrences often correlated with temporal instead of spatial gradients. Higher rainfall correlated with abundances of detritivorous and migratory species. Higher water levels correlated with higher abundances of non-native species, species without parental care, with external fecundation, and partial spawning. Dry periods, with lower water and higher dissolved oxygen, correlated with higher abundances of insectivores and sedentary species. Although the presence of a dam-free stretch of river upstream of the reservoir had a positive influence on fish larvae in the fluvial zone, the results did not show differentiation along either gradient. Thus, the composition of the functional groups of fish species that reproduce in the Itaipu Reservoir appears to be predominantly influenced by the temporal variation in environmental factors rather than the formation of spatial gradients.

中文翻译：

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鱼类繁殖活动揭示了在维持新热带水库的高功能多样性方面占主导地位的空间异质性的时间变化

通过调查浮游鱼类的发生情况以响应环境因素的时空变化，评估了大型新热带水库中鱼类群落的繁殖活动。通过沿着水库主体（纵向）和臂（横向）中的代表性空间梯度捕获幼虫来研究鱼类繁殖。鉴定后，将捕获的幼虫根据亲本种群的功能特征分为不同的群体。在 2009 年至 2016 年的五个繁殖期，从 10 月到 3 月的夜间每月进行一次采样，使用带有流量计的锥形-圆柱形浮游生物网。同时采集水样，以测量与生殖活动相关的环境因素。使用 RLQ 和四角分析评估环境因素与功能性状之间的关系。对 51,995 只幼虫的评估表明，在纵向和横向梯度的湖泊和过渡带中，幼虫丰度更高。出现通常与时间而不是空间梯度相关。较高的降雨量与大量的有害物质和迁徙物种有关。较高的水位与较高丰度的非本地物种、没有父母照顾的物种、外部受精和部分产卵相关。干旱时期，水含量较低，溶解氧较高，与较高丰度的食虫动物和久坐物种有关。尽管水库上游的无坝河流段的存在对河流带的鱼类幼虫产生了积极影响，但结果并未显示出沿任一梯度的差异。因此，在伊泰普水库繁殖的鱼类功能群的组成似乎主要受环境因素时间变化的影响，而不是空间梯度的形成。