The accidental or planned introduction of invasive species has produced numerous changes in the functioning of aquatic ecosystems in Brazil (Rocha et al 2005). The protection of biodiversity and the conservation of natural communities are extremely threatened by the introduction of species from other basins and other continents. “The introduction of exotic species and the transposition of native species to other basins has been such a widespread practice in Brazil that it is difficult to find a watershed that does not contain alien elements” (Rocha et al 2005). The introduction of exotic fish species and their insertion in dams, lakes and rivers involve not only an interaction in food networks, but also have economic and social repercussions, as they affect fishing communities and the production of native fish species and environmental processes (Agostinho et al 2005).
The policy of increasing fishing productivity, with the expansion of support by agencies in Brazil and abroad, led to the introduction of numerous species from continental waters. With the construction of reservoirs, many invasive species of fish, molluscs and aquatic macrophytes were introduced, aggravating the situation of aquatic biota already modified by the construction of reservoirs (Tundisi & Matsumura-Tundisi 2008). With regard to fish, for example, an inventory carried out in 70 reservoirs in the East and South basins showed that in 90% of them there is at least one introduced species, the most frequent being the carp Cyprinus carpio; the tambaqui Colossoma macropomum; the peacock bass Cichla ocellaris; and the croaker Plagioscion squamosissimus. Rocha et al (2005) list 23 species
exotic fish introduced in Brazil. These species were introduced in order to offer new options for fishing. As reservoirs built in Brazil eliminated native species due to ecological transformations produced by these artificial ecosystems (Tundisi et al 1988), replacement by introduced species with apparent better yields has become common practice.
The most recent case, with a significant impact on the biota of continental waters, is the introduction of mollusk Limnoperna fortunei (golden mussel), which has already caused damage to more than one billion reais to supply systems, hydroelectric reservoirs and water mains in the basin da Prata and in southern Brazil.
The management of these species introduced into inland water ecosystems is a complex problem that needs permanent monitoring, preventive actions to prevent new introductions, experimental studies to control these species and expansion of repopulation programs and reintroduction of native species too the encouragement of basic studies with native species of fish and molluscs for their greater use is another important initiative.
The use of mathematical and ecological models to simulate future invasion impacts biologics in continental ecosystems is another technology that must be developed.
References:
TUNDISI, J. G. & MATSUMURA TUNDISI T. Limnologia. Oficina de Textos Editora 632. PP. 2008.
AGOSTINHO, A. A.; THOMAZ, S. M.; GOMES, L. C. Conservation of the biodiversity of Brazil’s inland waters. Conserv. Biol., vol. 19, n. 3, p. 646-2005.
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