Reconciliation ecology in Neotropical reservoirs: can fishing help to mitigate the impacts of invasive fishes on native populations?

Abstract

Despite the increased use as tool for conservation of native fish, the creation of non-fishing reserves is more recent in Neotropical impoundments and its effectiveness rather variable. Although not intentionally created for conservation purposes, areas located near dams could function as fish reserves, since fishing activity is often forbidden in these sites for security reasons. We investigated the effects of a fishing-restricted area in Lajes Reservoir, a Neotropical reservoir dominated by invasive species, notably the yellow peacock bass Cichla kelberi, subject to intensive local fisheries. Cichlid populations associated with rocky banks of similar size and complexity were compared between fishing and non-fishing sites, after accounting for spatial autocorrelation. Native cichlids were significantly less abundant in the non-fishing area, in contrast to invasive cichlids. Accordingly, there were smaller individuals of the two native species in the fishing-allowed sites, where the mean size of peacock bass was also smaller. Our results suggest that angling can sometimes provide demographical control of large invasive piscivores and hence predation refuges for native fish in highly modified ecosystems such as reservoirs, thus resulting in reconciliation ecology. Fishing prohibition can sometimes be counterproductive for the conservation of native populations, illustrating the importance of context-specific management strategies.