Existing and Future Challenges: The Concept of Successful Fish Passage in South America

Abstract

Most of the large rivers of South America are impounded mainly for hydropower production. The construction of fish passes has been one of the strategies adopted by Brazilian authorities and the energy sector to diminish the effects of these barriers on migratory fish communities. Despite the high investments and efforts involved, most facilities have been considered ineffective for conservation purposes. Decades of poor monitoring and the lack of specific studies have limited our knowledge on the real role of fish passes. Efficiency has been frequently defined as the proportion of fish that ascend a fish passage facility, compared to the shoal size that reaches the dam. Inspired by the notion that fishes accumulated below the dam need to migrate upstream, the quantity of fish passed upstream historically indicated successful management, as generally inferred by the fish abundance inside the fish pass. We propose a new concept for estimating fish pass efficiency for South American rivers, based on the capability of the fish pass to maintain viable populations. This broader approach is necessary because knowledge of fish habitats below and above the pass, plus the feasibility of downstream movements of eggs, larvae and adults through the reservoir and past the dam, is needed for assessing whether a fish pass is working as a conservation tool.

Deficient downstream passage through fish ladders: the case of Peixe Angical Dam, Tocantins River, Brazil

“…We hope that these results encourage future studies to consider fish passage management in its totality: a tool that must allow free traffic along the river, both upstream and downstream, as a means of maintaining fish population dynamics. We regret that fishways in Brazil continue to be installed without thorough evaluations, using misleading information and based on nebulous goals (Pompeu et al, 2012). It is clear that fish conservation in impounded areas is a complex issue, demanding broader perspectives and sound ecological information Kraabøl et al, 2009;Roscoe & Hinch, 2010).…”

Fish hatchering and its effects on the morphology of Prochilodus lineatus (Actinopterygii: Prochilodontidae)

“…However, despite being historically applied, the efficiency of stocking, as a management measure, has been not satisfactory in Brazil, since the target stocks have not been recovered (Agostinho et al, 2007). This can be explained by poor habitat quality of the stocked rivers (Pompeu, et al, 2012) and by differences between hatchery and wild environment.…”

Influence of limnological zones on the spatial distribution of fish assemblages in three Brazilian reservoirs

“…Damming establishes physical barriers that limit fish movement (upstream and downstream), contributing to population isolation and extirpation ( Hughes et al, 2005;Araújo et al, 2008;Pompeu et al, 2012). Thus, loss of connectivity is another relevant issue related to river damming, and it is associated with degraded fish assemblage condition (Musil et al, 2012).…”