ABSTRACT
Morphological similarity of G. affinis and G. holbrooki has caused historical changes in the taxonomic status of the two species that confound published scientific findings and stocking records. Both fish were considered subspecies of G. affinis for an extended period and publications did not always distinguish between the two forms (Gerberich and Laird, 1968; Moyle, 2002). After about 1990, species status was reestablished based on morphological differences (Rauchenberger, 1989), genetic studies and geographic distribution (Wooten et al, 1988). Adults of the two species can be distinguished by the numbers of dorsal and anal fin rays and the morphology of the male anal fin or gonopodium: G. holbrooki usually has seven dorsal rays, ten anal rays and a gonopodium with a series of prominent teeth on ray three; whereas, G. affinis has six dorsal rays, nine anal rays and lacks prominent teeth on ray three of the gonopodium. More recently, molecular diagnostic tools have been developed to distinguish between the two species (Vidal et al, 2010).
