Effects of food limitation on growth, body condition and metabolic rates of non-native blue catfish

Establishment and range expansion of non-native species in novel habitats depend on their energetic requirements and food availability. Knowledge of growth and metabolic rates of non-native fishes at various food levels is particularly critical to inform models that assess their invasion potential. We compared growth rates, body condition and metabolic rates of juvenile blue catfish (Ictalurus furcatus), an invasive species in many lakes, coastal rivers and estuaries throughout the Eastern USA, at three ration levels: ad libitum (3.5% of fish body mass/d), two-third ad libitum and one-third ad libitum. All fish survived the entire duration of the experiment (4 months) regardless of ration level. Blue catfish exhibited routine metabolic rates similar to those of other benthic fishes but below the more active species. Mean growth rates were lower at reduced ration levels, but we found no evidence of ration size effect on body condition or metabolic rates. Blue catfish therefore appear to have mechanisms that enable them to survive low rates of food intake for long periods, indicating the potential of this invasive species to become established in habitats with low prey availability.