Estimating Genetic Composition in Introgressed Largemouth Bass Populations: Does Age Matter?

Abstract

In estimating population-level introgression for largemouth bass Micropterus salmoides populations, it is unclear which age-class, if any, is most appropriate to sample and what biases may be introduced by the sampling of specific age-classes. Estimates of introgression between Florida largemouth bass M. salmoides floridanus and northern largemouth bass M. salmoides salmoides in six populations were made based on seven microsatellite loci from different age-classes and combinations of age-classes. Levels of introgression were not significantly different for 40 of 42 pairwise age-class comparisons within reservoirs or for five of six comparisons between age-0 fish and adults. In addition, measures of precision based on each estimate were similar within reservoirs. These results suggest that age-0 largemouth bass samples can be used to make accurate and precise estimates of introgression at the population level. However, these results also suggest that alternate year-classes or combinations of year-classes with or without the inclusion of age-0 samples are equally suitable for estimating introgression at the population level. Thus, the selection of specific age-classes to be sampled for estimating introgression in largemouth bass populations should be based on the efficiency with which the age-classes can be collected.

Received February 15, 2010; accepted November 17, 2010

ACKNOWLEDGMENTS

We thank TPWD Inland Fisheries personnel in the Abilene, Jasper, San Angelo, San Marcos, and Waco districts for collection of the data reported in this paper. Todd Driscoll, Bobby Farquhar, Gene Gilliland, Steve Magnelia, and Ben Neely provided excellent editorial reviews. This research was supported by Federal Aid in Sport Fish Restoration Grant F30R to the TPWD.