Knowledge of individual growth and mortality rates of an introduced fish population is required to determine the success and degree of establishment as well as to predict the fish's impact on native fauna. The age and growth of flathead catfish Pylodictis olivaris have been studied extensively in the species' native and introduced ranges, and estimates have varied widely. We quantified individual growth rates and age structure of three introduced flathead catfish populations in North Carolina's Atlantic slope rivers using sagittal otoliths, determined trends in growth rates over time, compared these estimates among rivers in native and introduced ranges, and determined total mortality rates for each population. Growth was significantly faster in the Northeast Cape Fear River (NECFR) than in the Lumber and Neuse rivers. Fish in the NECFR grew to a total length of 700 mm by age 7, whereas fish in the Neuse and Lumber river populations reached this length by 8 and 10 years, respectively. The growth rates of fish in all three rivers were consistently higher than those of native riverine populations, similar to those of native reservoir populations, and slower than those of other introduced riverine populations. In general, recent cohorts (1998–2001 year‐classes) in these three rivers exhibited slower growth among all ages than did cohorts previous to the 1998 year‐class. The annual total mortality rate was similar among the three rivers, ranging from 0.16 to 0.20. These mortality estimates are considerably lower than those from the Missouri and Mississippi rivers, suggesting relatively low fishing mortality for these introduced populations. Overall, flathead catfish populations in reservoirs grow faster than those in rivers, the growth rates of introduced populations exceed those of native populations, and eastern United States populations grow faster than those in western states. Such trends constitute critical information for understanding and managing local populations.

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.

We compared the ability to extract all stomach contents by using stomach tubes or gastric lavage to sample diets from blue catfish Ictalurus furcatus and flathead catfish Pylodictis olivaris. Pulsed gastric lavage (PGL) removed a significantly greater proportion of stomach content mass (95.6%) from blue catfish than did stomach tubes (14.6%). Percent mass of flathead catfish contents removed with PGL (96.0%) was not significantly different from that removed with stomach tubes (86.9%). Based on the greater effectiveness of PGL for blue catfish, combined with a shorter mean time required per sample (69 versus 118 s) and the better preservation of extracted diet material, we recommend using PGL as a nonlethal technique to collect diet samples from large catfishes.