Electrophoretic genotyping is a contemporary technique that enables aquaculturists and fishery managers to distinguish between domestic and native stocks of largemouth bass Micropterus salmoides and to monitor gene flow between them. Analysis of low-risk tissue samples (erythrocytes, blood plasma, caudal and pelvic fin, and scale-epithelial tissue) allows investigators to obtain considerable genetic information with minimal loss of performance by individual fish. We have identified at least 64 enzyme locus products in Florida, northern, and intergrade strains of largemouth bass by using invasive biopsy or necropsy. Polymorphic loci account for approximately one-third of the loci examined. Low-risk tissue samples allowed adequate electrophoretic resolution of 44 (69%) of the 64 gene products examined. Of the 23 polymorphic loci thus far identified in largemouth bass, at least 16 can be resolved from blood or fin tissues or both. Thus, using only tissue samples that do not significantly debilitate fish, we were able to distinguish with greater than 99% certainty the Florida subspecies from the northern subspecies of largemouth bass. The ability to resolve no fewer than 40 enzyme locus products from caudal fin clips alone may facilitate future genetic studies of populations where sacrifice of individuals is infeasible or undesirable, as for endangered species.