Assessing the impacts of the introduced channel catfish Ictalurus punctatus using the comparative functional response approach

In the metric Relative Impact Potential (RIP), the functional response (FR) of a non-native species can be compared with that of a native analogue and combined with the species abundance to predict its environmental impact. Here, using the River Guaraguacu (Brazil) as a case study, this methodology was implemented to identify the impacts of the non-native channel catfish Ictalurus punctatus (Rafinesque) compared with a native species Rhamdia quelen (Quoy & Gaimard) towards small prey fish. Both species exhibited Type II FRs, but handling times were lower for I. punctatus, resulting in a greater maximum feeding rate in this species. Consequently, an RIP > 1 was found, indicating that I. punctatus represents a superior impact to prey compared with its native analogue. These results demonstrate that I. punctatus is a potential threat to small endangered fish species; therefore, policies to avoid escapes from aquaculture should be created and the abundance of I. punctatus controlled.