Agostinho A A, Pelicice F M, Gomes L C
Núcleo de Pesquisas em Limnologia Ictiologia e Aqüicultura-Nupelia, Universidade Estadual de Maringá-UEM, Maringá, PR, Brazil.
Braz J Biol. 2008 Nov;68(4 Suppl):1119-32. doi: 10.1590/s1519-69842008000500019.
Reservoirs have been built in almost all of the hydrographic basins of Brazil. Their purposes include water supply for cities, irrigation and mainly, generation of electricity. There are more than 700 large dams and associated reservoirs in the large rivers of the country. These reservoirs favor local and regional economic development, but they also bring serious and irreversible alterations in the natural hydrologic regime of rivers, affecting habitat quality and the dynamics of the biota. In the impounded area, the main impact is the change from lotic to lentic water, which influences aquatic fauna, including fishes. Impacts of reservoirs present relevant spatiotemporal variations. Immediately after reservoir formation, fish species richness usually increases due to incorporation of surrounding habitats, but richness decreases as reservoirs age. However, impacts downstream of dams appear to be similar or stronger than those that occur within the reservoir. Dams promote discharge control, altering the seasonal cycles of floods. These effects are augmented when dams are constructed in cascades. Therefore, dams profoundly influence composition and structure of fish assemblages. Most affected species are the rheophilics and long distance migratory that require distinct habitats to fulfill their life cycles. Populations of migratory species may collapse or even disappear in intensely regulated stretches. Management actions taken to minimize impacts of dams in Brazil historically considered construction of fish passages, fishery control and stocking. The results of these actions are questionable and/or with clear failures. In this paper, we give emphasis to the Paraná River basin, the most affected by dams in Brazil. We describe some patterns in the alteration and decline in fish diversity in areas influenced by dams. We also discuss negative consequences in the fishery and ecosystems functioning. Finally, we argue the relevance and the success of the management actions taken and present some suggestions to improve conservation of the ichthyofauna in South American basins influenced by dams.
巴西几乎所有的水文流域都修建了水库。其目的包括城市供水、灌溉，主要是发电。该国的大河中有700多座大型水坝及相关水库。这些水库有利于地方和区域经济发展，但也给河流的自然水文状况带来了严重且不可逆转的改变，影响了栖息地质量和生物群落的动态变化。在蓄水区域，主要影响是从流水变为静水，这会影响包括鱼类在内的水生动物。水库的影响呈现出相关的时空变化。水库形成后，鱼类物种丰富度通常会因周边栖息地的纳入而增加，但随着水库老化，丰富度会下降。然而，大坝下游的影响似乎与水库内的影响相似或更强。大坝促进了流量控制，改变了洪水的季节性周期。当水坝梯级建设时，这些影响会加剧。因此，大坝深刻地影响了鱼类群落的组成和结构。受影响最大的物种是需要不同栖息地来完成其生命周期的喜流性和长距离洄游物种。在受到强烈调控的河段，洄游物种的种群数量可能会崩溃甚至消失。巴西历史上为尽量减少大坝影响而采取的管理行动包括修建鱼道、渔业控制和放流。这些行动的结果值得怀疑和/或明显失败。在本文中，我们重点关注巴西受大坝影响最严重的巴拉那河流域。我们描述了受大坝影响地区鱼类多样性变化和减少的一些模式。我们还讨论了对渔业和生态系统功能的负面影响。最后，我们论证了所采取管理行动的相关性和成效，并提出了一些建议，以改善受大坝影响的南美流域鱼类区系的保护。
