Free Flowing Rivers As a Management Strategy in South America

Most of the large rivers of South America, especially in Brazil, have been impounded for power production. Fisheries management has been based on stocking, fisheries’ harvest limits and the construction of fish passes. However, the low fishery yield and the precarious conservation status of native migratory populations in the dammed rivers indicate that these strategies have not been satisfactory. Because most rivers in South America are serially fragmented, there is substantial risk of confining populations within short regulated reaches lacking critical fish habitats such as reproduction sites and nurseries areas. We propose that by keeping free flowing rivers in the different river basins, we could maintain self-sustainable populations over the long term. When these areas are absent or large reservoirs are created, conservation tools such as the construction of fish passes facilities are ineffective. In Minas Gerais state, Brazil, our data indicate that it would be possible to implement this strategy, transforming long stretches of river channels in conservation units, and losing less than 10% of the hydropower capacity. However, this initiative should be undertaken immediately, since hundreds of new dams are planned to be built, precluding the existence of long enough rivers to keep migratory fish populations.