Neotropical freshwater fishes are the most diverse on the planet (>5,500 species), although nations in Latin America have been negligent regarding their conservation. National policies have historically encouraged unsustainable practices, and recent decades have witnessed a sharp increase in harmful activities. Our aim with this review was to expose this situation and illustrate how national policies constitute the main threat to freshwater fish biodiversity. We explain that the most devastating, pervasive and systemic threats are rooted in official policies, particularly unsustainable activities (e.g. hydropower, water diversion, mining, aquaculture, agriculture and fishing), poor management/conservation (e.g. fish stocking and passages) and harmful legislation (e.g. poor licensing, non‐native species). We provide a broad portrait of the Neotropical scenario, where unsustainable policies have caused considerable damage to freshwater ecosystems, and focus on major examples from Brazil, where development projects have caused large‐scale losses to fish biodiversity. Such modus operandi of human development is incompatible with the persistence of biodiversity, and no simple solution is available to correct or minimize its effects. The current situation demands a profound behavioural shift towards better practices and policies, or these multiple high‐impact activities will continue eroding freshwater fish biodiversity and impairing essential ecosystem services.

As Brazil undergoes rapid economic growth, short-sighted political decisions can threaten biological diversity and ecosystem services. Recently, the Brazilian Congress proposed a law to allow the rearing of nonnative fish in aquaculture cages in any hydroelectric reservoir of the country. This initiative may "naturalize by decree" some of the worst invasive species in the world (e.g., carps and tilapias) as a means of developing inland aquaculture and economy. The spread of aquaculture facilities will create opportunities for fish invasions to occur throughout the country, with the risk of damaging native biodiversity, ecosystem services, and environmental quality on a continental scale. The proposal ignores ecological theory, historical and/or empirical data concerning fish invasion, including dispersal, establishment, propagule pressure, invasiveness and invasibility, and all the negative consequences that may follow the invasion and establishment of nonnative organisms. This situation inspires reflection about the future of tropical biodiversity worldwide, particularly because Brazil, like many other developing countries, possesses a remarkable diversity of fish and other freshwater organisms yet has taken some political measures that are in conflict with important conservation issues.

Brazil has a highly diverse freshwater fish fauna and their freshwaters provide valuable provisioning ecosystem services in aquaculture and sport angling, especially in the developed regions in the south. Non-native fish now comprise a substantial proportion of the total aquaculture production and value, contributing at least $US 250 million in 2008 (63% of the total value of freshwater fish aquaculture) according to the Fish and Agriculture Organisation. Much of this aquaculture activity is centred in Central and Southern Brazil, such as impounded sections of the upper River Paraná. The non-native fishes used tend to feed at relatively low trophic levels, with the most prominently species being Cyprinus carpio and Oreochromis niloticus. Ecological risk assessment suggests these species are potentially highly invasive and deleterious to the native fish diversity of invaded water bodies. Fishes introduced for the creation of sport fisheries tend feed higher trophic levels through piscivory, such as the peacock basses (Cichla species) from Amazonia. Their introductions have generally resulted in establishment and invasion, which tends to be followed by significant and rapid declines in native fish diversity as a consequence of increased predation pressure. Thus, whilst non-native fish in the upper Paraná River support provisioning ecosystem services of substantial economic value, the principal species used represent high risks to fish diversity and conservation. It is recommended local management should concentrate on reducing these risks through use of more appropriate species in these ecosystem services, with these decisions derived using risk assessment and precautionary principles.

ABSTRACT. Fish species introduction by accidental escape from aquaculture in the high Paraná River Basin. Species composition and abundance of fishes that escaped from aquaculture facilities during catastrophic flooding in the Paranapanema and Tibagi rivers, in January, 1997 was estimated. ln ali, 1,292,000 adult individuais belonging to II species and I hybrid, were introduced into these rivers; only one species was native . The disaster is attributed to the illegal occupation ofthe river banks, and the non observance of standard measures designed to avoid escapement. KEY WORDS . Species introduction, Tibagi river, Paranapanema, river A piscicultura é considerada o principal meio de dispersão de espectes exóticas em novos ambientes (WELCOMME 1988; AGOSTINHO & JULIO 1996). Os escapes com a água efluente, o esvaziamento dos tanques durante o manejo e, principalmente, o rompimento ou transbordamento desses em razão de picos de cheias não previstos durante a construção, são as principais vias de introdução de espécies exóticas pelas atividades de cultivo. Nesse contexto contribui a prática comum da piscicultura brasileira em estabelecer seus cultivos nas proximidades dos rios, dentro da área de preservação permanente, e, portanto, sujeita a alagamentos nos anos de grandes cheias. Uma forma recente de comercialização e lazer, os chamados "pesque e pague", embora ainda não avaliados, devem se constituir em importantes riscos adicionais de disseminação de espécies exóticas (peixes e doenças) .Visando dimensionar os escapes de peixes dos sistemas de cultivo para os cursos de água da bacia do rio Paranapanema em anos de grandes cheias, foi realizado um levantamento em 38 propriedades rurais privadas com atividade aquícola, sendo a grande maioria propriedades de produção para a revenda (31) e poucos pesque-pague (7) (sub-bacias do médio e baixo Tibagi, baixo Cinzas e parte do Paranapanema, figura I), em áreas atingidas pelas cheias de janeiro e fevereiro de 1997.

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