First record of Silurus glanis Linnaeus, 1758 in Portugal (Iberian Peninsula)

Species introductions worldwide are becoming more widespread and their impacts more harmful, especially regarding the introduction of predatory fish (Cox and Lima, 2006). Freshwater fish invasions are related to ecosystem consequences, namely, the decline of native species, and contribute to biotic homogenization on a global scale (McKinney and Lockwood, 1999; Vill_eger et al., 2011). The Mediterranean region freshwater ecosystems have a high number of endemic species but are under threat mainly due to non-native fishes (NNF), which currently represent more than 50% of the fish diversity (Smith and Darwall, 2006; Leprieur et al., 2008; Hermoso and Clavero, 2011). Iberian rivers are among the most invaded ecosystems within the Mediterranean region, with more than 25 NNF confirmed in Spain and 16 in Portugal (Elvira and Almod_ovar, 2001; Ribeiro et al., 2009; Ribeiro and Ver_ıssimo, 2014). It is predicted that further Iberian invasions will occur given the prevalent European invasion route (Garc_ıa-Berthou et al., 2005; Leprieur et al., 2008; Ribeiro et al., 2009). The wels catfish Silurus glanis Linnaeus, 1758 is among the largest freshwater fishes worldwide, being native to Eastern Europe and Western Asia and introduced to seven European countries (Copp et al., 2009). Silurus glanis exhibits rapid growth rates and attains a large body size (c. 500 cm total length and 306 kg), characteristics highly appreciated by anglers (Slav_ık et al., 2007; Copp et al., 2009). In recente years recreational fishermen have reported several captures of putative S. glanis; however, species identification lacks confirmation in Portugal. In the present paper, a first observation of the wels catfish S. glanis is confirmed in Portugal.