Evaluation of Population Characteristic Differences between the Largemouth Bass and Its Backcross Following a Long‐Term Florida Bass Stocking Effort

Abstract

Management agencies throughout the southern United States widely stock Florida Bass (FLB) Micropterus floridanus into extant Largemouth Bass (LMB) M. salmoides populations, with the intent of increasing the trophy potential of those water bodies. These stockings commonly lead to a shift in the systemwide genetic composition toward a population dominated by hybrids, which are predominantly LMB with low levels of FLB alleles (FX‐LMB). Despite the increasing prevalence of FX‐LMB throughout the Southeast, little work has examined FX‐LMB population vital rates and whether these hybrids increase the trophy potential of a water body. Our study fills a void in existing research by comparing the population characteristics of FX‐LMB and LMB using a common garden experimental design. Lake Ouachita is a large Arkansas reservoir that was stocked with over 800,000 fingerling FLB between 2007 and 2015. In 2019, we collected 1,000 bass from throughout the reservoir and determined the level of FLB introgression for each fish by using a panel of species‐diagnostic single‐nucleotide polymorphisms. We then tested for relationships between the percentage of FLB alleles or genotype and the age at 50% maturity, total annual mortality rate, size structure, condition, and growth. In addition, we compared tournament catches of large bass during the pre‐ and poststocking time periods to test whether catch rates of 2.3‐kg and larger bass increased after FLB stockings. Our results indicated that FX‐LMB hybrids likely do not mature earlier, survive longer, have better body condition, or have greater growth potential than native LMB in Lake Ouachita. We also did not observe differences in the number of hours to catch a 2.3‐kg or larger bass or in the number of 2.3‐kg and larger bass captured per tournament between the pre‐ and poststocking time periods. We conclude that a stocking program resulting in a subtle shift in the genetic composition toward the FX‐LMB genotype will not effectively increase the trophy potential of a population.