Invasion note Introduction of the African catfish Clarias gariepinus (BURCHELL, 1822) into Southern Brazil J.R.S. Vitule, S.C. Umbria & J.M.R. Aranha* Departamento de Zoologia, Laborato ´rio de Ecologia de Rios (EcoRios), Setor de Cieˆncias Biolo ´gicas, Universidade Federal do Parana ´, Centro Polite´cnico, Curitiba, Parana ´, 81531-990, Brazil; *Author for correspondence (e-mail: jmaranha@ufpr.br; fax: +55-41-266-2042) Received 18 April 2005; accepted in revised form 30 August 2005 Key words: alien species, catfish, exotic species, invasion, invasive species, South America Abstract We record here the introduction of the African catfish Clarias gariepinus into the Guaraguac¸u River basin in Parana´ State, Brazil, an area with an extremely rich endemic fish fauna, including many catfishes. C. gariepinus was introduced as escapees from ponds built for recreational angling. These catfishes are very large and hard predators, thus posing serious potential for impact on the native fish fauna. The impact of C. gariepinus needs study with emphasis on finding means for controlling its spread. The Atlantic Forest of South America is one of the richest and endangered ecosystems on the planet (Myers et al. 2000). Several rivers flow through the coastal plain of this ecosystem, which contain many endemic fish species. Much of the fish fauna is potentially endangered be- cause of habitat degradation by human activities (Menezes et al. 1990). A new and potentially seri- ous threat to this fauna is the invasion of alien fishes. Even though the negative effects of introduced species are widely recognized, many of them are still being released into the aquatic ecosystems of Brazil without considering their potential impact on native fish and fisheries (Agostinho and Julio Jr. 1996; Agostinho et al. 2005). However, there is an increasing interest in detecting and studying introduced species in Bra- zil to develop solutions to solve the ecological problems they create. Therefore, the Laborato ´rio de Ecologia de Rios (EcoRios) of the Universid- ade Federal do Parana ´ , has developed a program aimed at detecting exotic fish species in the Guaraguac¸ u River basin, Parana´ state, Brazil (25°45¢ S and 48°35¢ W). Of particular concern is the African sharptooth catfish (Clarias gariepi- nus), which has recently been introduced as escapees from ponds built for aquaculturists. In Brazil, only four specimens have been reported previously (Alves et al. 1999; Braun et al. 2003) and their potential impact on the native fauna has been recognized for sometime (Agostinho and Julio Jr. 1996). In this paper, we report the spread and probable establishment of this species and stress upon the potential problems resulting from its introduction. The Guaraguac¸u River is the largest river east of the sub-basin of Paranagua´ Bay, Parana´ coast, Brazil. Its headwaters are in the Serra do Mar, 766 m above sea level, in the Saint-Hilaire/ Hugo Lange National Park and it discharges into the Paranagua´ Bay (Bigarella 1999; Maack 1981). Its drainage area is 395.5 km 2 (APPA/FUNPAR/ CEM, 2005, in press), much of it an extensive coastal plain where the meandering river floods a large area rich in swamps and lateral lakes. This Biological Invasions (2006) 8: 677–681 Ó Springer 2006 DOI 10.1007/s10530-005-2535-8