Comparative Diets of Invasive Blue Catfish: Differences Across Rivers and Ontogenetic Stages

Abstract

Blue Catfish (Ictalurus furcatus) are an invasive species with expanding populations in freshwater systems, posing significant ecological challenges to native fauna. To assess their potential impacts in diverse aquatic ecosystems, we examined and compared the diets of non-native Blue Catfish from four rivers in Georgia, USA, two of which drain into the Atlantic Ocean. A total of 936 Blue Catfish were collected from the Altamaha, Ocmulgee, Oconee, and Satilla rivers, with 90.38% of stomachs containing identifiable prey. Stomach content analysis revealed that Asian Clam (Corbicula fluminea) dominated their diet in terms of number (96.76%), weight (69.33%), and to a lesser degree, frequency (36.96%). Across rivers, smaller Blue Catfish (≤ 300 mm TL) had diets with a higher relative importance of insects and vegetation. Ontogenetic dietary trends showed increasing consumption of fishes and crustaceans as fish size increased in the Altamaha, Ocmulgee, and Oconee rivers. In contrast, the Satilla River population exhibited broader dietary diversity and distinct ontogenetic shifts. Stable isotope analysis (δ¹³C and δ¹⁵N) revealed significant differences between Blue Catfish from the Altamaha and Satilla rivers, underscoring their opportunistic feeding strategies in varying habitats. Bayesian niche overlap analysis indicated that size classes within the Altamaha and Satilla rivers had substantial intraspecific overlap, with Satilla subadults exhibiting the broadest niche (SEA_B: 3.83). Factors such as prey availability, density dependence, and environmental conditions likely influence prey selection and feeding strategies in these systems. Understanding these dynamics is crucial for managing the ecological impacts of invasive Blue Catfish in freshwater systems of North America.