The natural flood pulse of the Amazon basin has been altered progressively by the installation of hydroelectric dams, which have had a potentially adverse impact on the local fauna. Fish are sensitive to environmental changes, and one the way to assess how they respond is through the analysis of life history traits, such as growth patterns and reproduction. Here, we evaluated the life history traits of two sedentary cichlids, Geophagus argyrostictus and Geophagus altifrons, in the middle Xingu River (upstream and downstream sectors) pre- and post-impoundment including the flood and low water hydrological seasons. The mass-length relationship, condition factor (K), gonadossomatic index (GSI), breeding season, gonadal stages, and the length at 50% sexual maturity (L₅₀) were analyzed. Data on river flow rates and the characteristics of the fish were collected during the pre- and post-impoundment periods. Post-impoundment, the discharge of the Xingu decreased in downstream sector. During the pre-impoundment period, the K of G. argyrostictus and female G. altifrons was lower in the upstream sector in both seasons, but higher in the downstream sector to G. argyrostictus. The GSI was lower in the post-impoundment period in both sectors and seasons in G. argyrostictus, whereas in the G. altifrons females, it was higher in the downstream sector in the low water season, but lower in the upstream sector in both seasons. In G. argyrostictus, spawning occurred in a single phase and was restricted to the low water season in both periods, whereas in G. altifrons, spawning was multiple. There was a reduction in the frequency of immature individuals in the upstream sector post-impoundment. The L₅₀ was lower, principally in the upstream sector, in both species. Our results indicate that the growth patterns and reproduction of the two populations has been impacted, especially in the endemic G. argyrostictus. The construction of dams thus appears to place endemic species under a greatest risk of extirpation. These results provide important insights for the improvement of fish resource monitoring and the development of adequate management techniques.

通过安装水力发电大坝，亚马逊河流域的自然洪水脉冲已逐渐改变，这对当地动物群可能产生不利影响。鱼类对环境变化敏感，评估其反应方式的一种方法是通过分析生活史特征，例如生长方式和繁殖。在这里，我们评价了两种久坐鲷，生活史特点Geophagus argyrostictus和高体珠母丽鱼，在中鑫谷河（下游行业）前后蓄水，包括洪水和低水水文季节。质量长度关系，条件因子（K），性腺机体指数（GSI），繁殖季节，性腺阶段以及性成熟度为50％时的长度（L ₅₀）进行了分析。在蓄水前和蓄水后期间收集有关河流流量和鱼类特征的数据。蓄水后，下游河段的新姑排放量减少。在蓄水前期，在两个季节的上游部门中，G。argyrostictus和雌性G. altifrons的K均较低，但在下游部门中则高于G. argyrostictus。在产后阶段，G。argyrostictus的GSI均较低，而G. altifrons雌性在淡水季节的下游部门较高，而在两个季节的上游部门较低。 。在G. argyrostictus，产卵在一个阶段发生，并且在两个时期都限于淡水季节，而在G. altifrons中，产卵是多重的。蓄水后上游部门中未成熟个体的频率减少。在这两个物种中，L ₅₀均较低，主要在上游部门。我们的结果表明，这两个种群的生长方式和繁殖都受到了影响，特别是在地方性的G. argyrostictus中。因此，水坝的建造似乎使地方性物种面临灭绝的最大风险。这些结果为改进鱼类资源监测和发展适当的管理技术提供了重要的见识。