First Name:
Daniel
Last Name:
Walker
Major Department:
Biology
Thesis Director:
Michael Gangloff
Date of Thesis:
May 2012
Introduced apex predators can have dramatic effects on community structure and function of invaded ecosystems. Flathead catfish (Pylodictis olivaris) are native to the Mississippi, Mobile and western Gulf drainages. However, this large, piscivorous species has been widely introduced by agencies and anglers and recently-founded populations occur in most Atlantic Slope drainages. I studied P. olivaris diet, condition and growth in the lower Tar River near Greenville, NC. I analyzed size class composition and length-at-age (growth rate) using otoliths and examined stomach contents to the lowest feasible taxon to determine diet composition. Stomach contents revealed that P. olivaris are primarily piscivorous, but also consumed a diverse range of prey items. Fishes accounted for over 60% of stomach content occurrences, however crayfish (Cambaridae) and Asiatic clams (Corbiculajluminea) were also consumed by P. olivaris. A substantial amount of the stomach contents analyzed were unidentifiable fish and invertebrate remains. I found no evidence that larger P. olivaris exhibit lowered body condition, suggesting that this population has likely not yet over- exploited its resource base and may also still be expanding in population size. Larger catfish (>500 mm TL), however, were significantly more likely to have consumed centrarchids than were smaller catfish. Moreover older fish were more likely to exhibit full stomachs, indicating they are feeding more intensively than younger fish. Although I observed a linear relationship between age of fish and length, mass and age exhibited a power law relationship. It seems likely that flathead catfish are exerting effects on Tar River communities similar to effects reported from other recently-invaded drainages.