Genetic Relationships of Largemouth Bass from Different Habitats within Coastal Rivers of Northwest Florida

Largemouth Bass are a major component of coastal-river fisheries throughout the southeastern US and are highly valued by anglers. Like most northern Gulf Coast rivers, salinity levels in the upper Escambia and Yellow Rivers are low but may exceed 13 ppt in the lower section of the river. We collected genetic samples from riverine and marsh habitats in the Escambia and Yellow Rivers in Florida to determine if individuals from the two habitats existed as a single randomly mating (panmictic) population.  Analysis of microsatellite DNA genotypes identified significant differences in allele frequency distributions of samples collected from riverine versus marsh habitats in each river.  Both streams were inhabited by intergrade populations that included hybrids between Northern Largemouth Bass and Florida Bass.  Fish in marsh habitats had more Northern Largemouth Bass alleles than fish in riverine habitats in both systems.  Together, these findings indicate fish in the marsh and river habitats do not exist in panmixia, and Northern Largemouth Bass genes are more abundant among fish in marsh habitats versus river habitats.  Northern Largemouth Bass genes may confer greater fitness than Florida Bass genes in estuarine environments of the northern Gulf Coast, possibly explaining their greater abundance in these unique habitats.