Assessment of the performance of stocked northern and Florida largemouth bass and their progeny in Briery Creek Lake, Virginia

This study examined the suitability of Florida largemouth bass (Micropterus salmoides floridanus) for introduction into Virginia and other mid-latitude waters by comparing the performance of northern (M. s. salmoides), Florida, and hybrid largemouth bass in a 342 ha south-central Virginia reservoir, Briery Creek Lake (BcL). Fingerling northern and Florida largemouth bass were stocked into Briery Creek Lake in 1986, following impoundment, and in 1987. Largemouth bass were collected for genotypic and performance analyses in the autumn and spring beginning in 1989 and ending spring 1991. Electrophoretic analyses demonstrated that hybrid largemouth bass (F1 and Fx) dominated the 1987-1990 cohorts and indicated that one or both founding stocks were genetically impure.

Comparisons of electroshock catch composition showed no survival advantage for Florida largemouth bass (FLMB) age-1 and older and no differential vulnerability to angling among the four presumptive genotypes of largemouth bass in Briery Creek Lake. Age-O FLMB proportions declined over both winters (1989-1990 and 1990-1991) indicating relatively high first-mortality in the thermal regime of Briery Creek Lake (3,875 annual mean of heating degree days). Statistical comparisons of growth revealed no consistent differences among the respective bass genotypes, although survival and growth tended to be slightly higher for PI hybrid bass. The average total length of largemouth bass in BCL was below the state's average by age three. Total lengths of age-O FI and northern largemouth bass (NLMB) were higher than FLMB and Fx bass in October, perhaps as a result of earlier spawning among NLMB and between the subspecies. Relative weights of largemouth bass in BCL were generally below 95; and few significant differences in (Wr) were observed among the presumptive largemouth bass genotypes. The suboptimal condition (Wr) of largemouth bass in BCL coupled with the decline in growth and condition of bass with increasing age suggested inadequate prey abundance in Briery Creek Lake.

Overall, Florida subspecific alleles did not increase in BCL over time, but the population genetic composition shifted toward an Fx mixture in the 1990 year class; future generations of largemouth bass should be dominated by Fx individuals. Results of this study did not demonstrate substantial performance differences among northern and Florida largemouth bass, and their hybrids, except for poorer first-year survival of the Florida subspecies. Therefore, this study provides no support for the continued introduction of Florida largemouth bass in Virginia or other mid-latitude regions.