The Canal da Piracema at Itaipu Dam as a fish pass system
Abstract
The Canal da Piracema is the longest (nearly 10 km) fish pass system in the world. The construction of this fish pass was somehow controversial, because it connected two distinct ichthyofaunistic provinces. This study evaluated the ichthyofauna present in the Canal da Piracema and the abundance and distribution of long-distance migratory fish species along this fish pass system (evaluated possible selectivity). The Canal da Piracema was shown to be difficult to sample because of its environmental heterogeneity: artificial ponds, ladders and nature-like fish pass. To solve this problem, we used several fishing gears, adequate for the several biotopes present (unstructured and structured littoral were sampled with seining nets and electrofishing; lentic were sampled with gillnets and longlines (deeper areas); and rapid water areas were sampled with cast nets). The ichthyofauna of the Canal da Piracema followed the pattern for South America and the Paraná River, with a predominance of Characiformes and Siluriformes. The most representative families were Characidae, Anostomidae, Pimelodidae and Loricariidae. We captured 116 species (17 were long-distance migratory) during the period studied. Small-sized species were predominant in unstructured and structured littoral areas, especially Bryconamericus exodon and Apareiodon affinis.The most abundant species was Hypostomus spp. in lentic areas, followed by Iheringichthys labrosus. Hoplias aff. malabaricus predominated in deeper lentic areas. Long-distance migratory species were abundant in rapid waters; they were Prochilodus lineatus and Leporinus elongatus. The sharp reduction in the number of species, including migratory ones, is an indication that the Canal da Piracema is selecting the species that ascend it. Therefore, the search for information on the efficiency of the various fish passes present in the Canal da Piracema is fundamental, to facilitate upward movements of fish. If this is reached, this polemic fish pass has the potential to contribute to the conservation of fish stocks in Itaipu Reservoir and upstream stretches, because of the presence of spawning and development (nurseries) areas for migratory species.
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