Semester of Graduation
Master of Science (MS)
Renewable Natural Resources
In the southeastern U.S., populations of the popular sportfish Largemouth Bass (Micropterus salmoides; LMB) are often stocked with Florida Largemouth Bass (Micropterus salmoides floridanus; FLMB) to develop FLMB ancestry in systems north of its native peninsular Florida range, with the ultimate goal of creating trophy fisheries. Stock enhancement through introgression of FLMB ancestry can increase maximum potential size and growth in receiving populations, potentially through hybrid vigor of intergrade subspecies. We collected 60 fish and habitat data from six Louisiana lakes from 2018-2020 (N=360), quantified level of introgression of FLMB with fragment analysis at 12 microsatellite loci confirmed for subspecific identification, and assigned a percent FLMB ancestry to each sample fish with program STRUCTURE, with 20 replicates at K=2. A detrended correspondence analysis (DCA) was used to reduce the dimensionality of the lake habitat data, and linear components were modeled with beta regression to relate physicochemical variables to average percent Florida ancestry by lake. We then used generalized linear models (GLMs) to examine the effects of percent Florida ancestry and measured physicochemical variables on growth, mean length at age, Wr and log-length. DCA2, DCA3, and DCA4 were significant in the beta regression model with average percent Florida ancestry, suggesting a positive relationship between Florida ancestry and highly vegetated lakes with increased turbidity. Wr and mean length at age 1 were also influenced by percent Florida ancestry. However, addition of percent Florida ancestry resulted in an increase in weight and Wr only to a certain point, at which point the quadratic of this relationship became negative, indicating fish with intermediate levels of Florida ancestry were more robust, suggesting possible hybrid advantage. The relationship between length with Florida ancestry changed over age. In early ages, it was more advantageous to be an intermediate hybrid, however ix as a fish aged, greater lengths were associated with “pure” (highest percentages of FLMB ancestry) FLMB. This overall relationship was dampened when physicochemical variables were included, with hybrids possessing 75% FLMB ancestry exceeding pure FLMB in length, indicating habitat may have also played a significant role in determining growth and condition of LMB in Louisiana.
Walsh, Colleen E., "Patterns and Drivers of Introgression in Louisiana's Largemouth Bass (Micropterus salmoides) Stocks" (2021). LSU Master's Theses. 5428.
Kelso, William E.