Abstract Invasive species can cause negative ecological impacts including biodiversity loss and native species decline. Native to the Mississippi, Missouri, Ohio, and Rio Grande River Basins, now-invasive blue catfish ( Ictalurus furcatus ) were first introduced into southeastern US freshwater reservoirs in the 1960s. Blue catfish subsequently spread downriver to estuaries in South Carolina and elsewhere along the US Atlantic coast due to their tolerance of low salinities. Their generalist diet in native habitats combined with the importance of estuarine ecosystems as nurseries makes understanding the trophic impact of blue catfish in estuaries critical. While diets of adult invasive blue catfish have been examined previously, no studies to date have focused on juvenile blue catfish feeding ecology in estuaries. Therefore, we examined the trophic role of juvenile blue catfish in the Winyah Bay estuarine system along the northern South Carolina coast. We collected juvenile blue catfish ( n = 422; size range 30-230 mm standard length) with monthly otter trawls in four tidal rivers from December 2022 to December 2023 and extracted stomachs for gut content analyses. Juvenile blue catfish diets consisted of nine primary prey groups across a diverse suite of taxa (amphipods, copepods, crustacean parts, shrimp and crabs, fish, insects, isopods, molluscs, worms), along with large proportions of detritus and unidentifiable material. Frequency of occurrence was consistently highest for amphipods, crustacean parts, and isopods across all four seasons. Differences in diet among seasons followed ontogenetic dietary shifts as early life stage blue catfish developed and grew. Differences in diet among rivers in the Winyah Bay estuary were relatively minor. These results represent a critical first step in elucidating potential impacts of juvenile blue catfish on native prey in estuaries.
Kimball et al. (2026) studied this question.