Diet Selectivity of Introduced Flathead Catfish in Coastal Rivers

In two coastal North Carolina rivers (Contentnea Creek and the Northeast Cape Fear River), we found the food habits of introduced flathead catfish Pylodictis olivaris to be primarily piscivorous, which could restructure or suppress native fish communities through direct predation. Fish or crayfish contributed more than 50% of the stomach contents by percent occurrence, percent by number, and percent by weight in both rivers during each of 2 years. Significant differences in diet composition (percent by number) were found between rivers and between years in the Northeast Cape Fear River but not between years within Contentnea Creek. Chesson's selectivity index values and trends in relative abundances of fish availability relative to those occurring in the diet suggest that flathead catfish feeding is generally random, indicating that these introduced flathead catfish do not selectively feed on prey species with which they did not coevolve. Our research represents the first assessment of prey selectivity by an introduced ictalurid population and provides evidence of the potential impact on native fish communities through their piscivorous food habits.