Temporal genetic structure of an intergrade largemouth bass (Micropterus salmoides) population

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Abstract
Since 1972, numerous impoundments throughout Texas have been stocked with Florida largemouth bass Micropterus salmoides floridanus. In order to examine some of the long‐term effects of such efforts, the present study summarizes past studies and complements those with more current observations on the intergrade largemouth bass population in Aquilla Lake, Hill Country, Texas. The reservoir received 4 annual stockings during the month of May from 1982 to 1985. Collections occurred periodically from February 1984 to June 1987, February to August 1988, and monthly from August 1991 to November 1992. Horizontal starch‐gel electrophoresis was conducted to determine allele frequencies at loci sAAT‐B*, SOD*1. Mean heterozygosity and percent introgression were highest for age‐0 fish of the 1986 year class. Assortative mating was not apparent in 1991 or 1992 year classes. Collections of specific year classes over time consistently indicated decreases in the relative abundance of the northern phenotype. Relative to the northern phenotype, the abundance of Florida year classes remained relatively constant over time. Relative abundances of F1 hybrids and Fx, intergrades (i. e., F1) from specific year glasses were observed to generally increase with age.