Date of Award
8-1-2025
Degree Name
Doctor of Philosophy
Department
Zoology
First Advisor
Heist, Edward
Abstract
Flathead Catfish (Pylodictis olivaris) is a popular sportfish managed for recreational and commercial uses. Currently, managers in Missouri have implemented various reservoir-specific bag and length limits for P. olivaris to create sustainable populations of quality-sized individuals available for anglers to capture. In conjunction with field studies to estimate growth rates and size/age distributions, I developed and scored 15 microsatellite markers to estimate the effective population (Ne) and population structure within 10 Missouri reservoirs. I assessed the power of the markers to get acceptably precise estimates of Ne using NEoGen assuming life-history parameters (e.g., age at maturity, longevity and fecundity) estimated from the literature. I then used the individuals collected from a single reservoir to conduct a sibship and parentage analysis. These results combined with previously published life-history parameters were used to conduct population models to estimate the effects of fishing mortality and changes to length limit regulations. Results from the simulations run in NEoGen indicated that genotypes from at least 60 catfish were required to attain precise estimates of Ne when the true Ne was 30 while Ne values of 100 or more were estimated to require sample sizes >100. Current Ne results show that smaller sampled reservoirs have an Ne of less than 50 while larger reservoirs had an estimated Ne of >100. Results also suggest there is little population structure within larger reservoirs (Table Rock: FST = 0.025, Truman: FST = 0.024) indicating that a single estimate of Ne is sufficient for the entire reservoir. Results from the sibship and parentage analysis suggest there is a higher reproductive variance for male than female P. olivaris. Finally, the modelling results indicated that minimum length limits resulted in the largest total population size (N) and Ne; while increases in fishing mortality resulted in decreases in the N and Ne. The results of this study will help managers choose the best strategies for specific reservoirs to maintain flathead catfish populations with desirable size structure.
Access
This dissertation is Open Access and may be downloaded by anyone.