Increases in temperatures over the last century, more intensively after the eighties, were recorded in several databases for the south-eastern Brazil. These increases are likely to change fish communities in aquatic systems by decreasing abundances, biomass and sizes of some species more sensitive to climate change. Reservoirs may be particularly susceptible to the effects of climate change, as they isolate previously connected areas limiting fish dispersal and migration, as well as increasing water temperature and thermal stratification. We assessed temporal changes in the abundance and biomass of the ichthyofauna in an isolate reservoir (inflowing waters from small tributaries in a highland region) aiming to associate changes with climate effects over three decades (1990, 2000, 2010). Two abundant native species, a loricariid Loricariichthys castaneus (Castelnau, 1855) and a cichlid Geophagus brasiliensis (Quoy & Gaimard, 1824), were selected to assess eventual response to climate changes in their geographical distribution in the Southeast Atlantic Hydrographic Region, considering different carbon emission scenarios using ecological niche models. A decrease in the densities and biomass of the ichthyofauna and of the two selected species were observed in both summer and winter over the three decades, coinciding with increases in temperatures. These decreases were correlated with increases in positive anomalies of temperature, which may be an indicator of climatic changes, although with low explanation of the data variation. The mean size of L. castaneus decreased between the nineties and 2010, whereas no significant trend was found for the size of G. brasiliensis. Our predictions of new area for future adequacy indicated a loss in the distribution area for both species (mainly for G. brasiliensis), considering the most pessimistic scenario for 2050 and 2070, possibly due to climatic changes. Both hydroelectric dams and global warming pose threats to freshwater fish diversity, and both will interact. Changes observed in the fish assemblage over the last decades were essential for an assessment of the consequences of global warming in this type of reservoir combining larger scale studies with future projections.

中文翻译：

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巴西东南部热带水库中鱼群变化的评估：全球变暖的后果？

巴西东南部的几个数据库记录了上个世纪的气温升高，80 年代之后更加强烈。这些增加可能会通过减少一些对气候变化更敏感的物种的丰度、生物量和大小来改变水生系统中的鱼类群落。水库可能特别容易受到气候变化的影响，因为它们隔离了以前连接的区域，限制了鱼类的扩散和洄游，以及水温和热分层的增加。我们评估了一个孤立水库（来自高原地区小支流的流入水）中鱼群的丰度和生物量的时间变化，旨在将变化与三个十年（1990、2000、2010）的气候影响联系起来。两种丰富的本地物种，一种 loricariid选择Loricariichthys castaneus (Castelnau, 1855) 和慈鲷Geophagus brasiliensis (Quoy & Gaimard, 1824) 来评估其在东南大西洋水文区域的地理分布对气候变化的最终反应，考虑使用生态位模型的不同碳排放情景。在过去的三个十年中，在夏季和冬季都观察到鱼群和两个选定物种的密度和生物量减少，同时温度升高。这些下降与温度正异常的增加相关，这可能是气候变化的一个指标，尽管对数据变化的解释很少。L的平均大小。栗在九十年代和 2010 年之间下降，而G的大小没有发现显着趋势。巴西人_ 考虑到 2050 年和 2070 年最悲观的情况，可能是由于气候变化，我们对未来充足的新区域的预测表明这两个物种的分布区域（主要是G. brasiliensis）都在减少。水电大坝和全球变暖都对淡水鱼类的多样性构成威胁，并且两者都会相互作用。在过去几十年中观察到的鱼类群落变化对于评估全球变暖对此类水库的影响至关重要，并将更大规模的研究与未来预测相结合。