First record ofSilurus glanisLinnaeus, 1758 in Portugal (Iberian Peninsula)

Spatial distribution patterns of the non‐native European catfish, Silurus glanis, from multiple online sources – a case study for the River Tagus (Iberian Peninsula)

“…This initial putative human-mediated dispersal is the most plausible mechanism as the distance of new records is beyond the limit of the species natural dispersal. Such a pattern is consistent with other NNF (Gante & Santos 2002;Ribeiro et al 2006Ribeiro et al , 2009 because S. glanis has expanded its distribution from eastern to central Iberia due to human-mediated introductions, most likely from the Ebro to the Tagus catchment (Carol et al 2003;Gkenas et al 2015), and then, these have finally spread downstream. An estimation based on these telemetry studies suggests an approximate annual natural dispersion of about 20 km yr À1 , but long-distance dispersal could occur in association with extreme hydrological events such as floods.…”

“…In the present study, a prevalent downstream dispersal of S. glanis along the river network, by both dispersal mechanisms (human-mediated and natural dispersion), was observed. Such a pattern is consistent with other NNF (Gante & Santos 2002;Ribeiro et al 2006Ribeiro et al , 2009 because S. glanis has expanded its distribution from eastern to central Iberia due to human-mediated introductions, most likely from the Ebro to the Tagus catchment (Carol et al 2003;Gkenas et al 2015), and then, these have finally spread downstream.…”

“…For this reason, a conservative approach was adopted regarding acceptance of a record as valid. Furthermore, reliable literature records confirmed the species distribution and invasion pattern in the Tagus catchment, namely the first and most upstream record (G omez 2005) and the most recent and downstream record (Gkenas et al 2015).…”

“…Indeed, online posts from anglers' web fora were already used as the first source of information to detect other NNF, for example Perca fluviatilis L. and Rutilus rutilus (L.), in Portugal (Ribeiro & Ver ıssimo 2014;. Furthermore, reliable literature records confirmed the species distribution and invasion pattern in the Tagus catchment, namely the first and most upstream record (G omez 2005) and the most recent and downstream record (Gkenas et al 2015). the case of the Alpine cyprinid, riffle minnow, Leuciscus souffia Risso, mistakenly reported (Ara ujo et al 1999) for the upper Thames Estuary (see Copp et al 2007).…”

“…Owing to its potential to achieve very large size and its value as a foodstuff, S. glanis has been introduced to other European countries for aquaculture and/or as a highly prized trophy fish (Copp et al 2009). In 1974, S. glanis was introduced to the eastern part of the Iberian Peninsula (Carol et al 2003;Benejam et al 2007), but subsequent records originate from western Spain (P erez-Bote & Roso 2009; Moreno-Valc arcel et al 2013) and Portugal (Gkenas et al 2015). In the River Tagus catchment, angler records on Internet sites vastly outnumber the few confirmed occurrences of S. glanis in the scientific literature, resulting in distinct distribution maps.…”