HYBRIDIZATION AND BIOCHEMICAL GENETICS OF BLACK-AND-WHITE CRAPPIES INTHE SOUTHEASTERN USA

Populations of black crappie Pomoxis nigromaculatus and white crappie P. annularis in Alabama, Arkansas, and Tennessee were examined for iso zyme variation. Twelve diagnostic loci distinguished these two species . Both species exhibited low levels of genetic variation. Percentages of loci polymorphic in populations of black and white crappies were 0- 4.7% and 0-11.6%, respectively. Mean heterozygosities were 0.000-0.008 and 0.000-0.012 for black and white crappie populations, respectively . Although extremely low levels of genetic variation were detected wit hin or among white or black crappie populations when only nonhybrid in dividuals were considered, there were some distinct differences among populations within each species. Populations in Tennessee tended to ha ve a greater number of unique, low-frequency, variant alleles than oth er crappie populations. Black crappies possessing the blacknose trait had allele frequencies similar to those of black crappies with normal coloration. Natural hybridization was common between the two species a nd was the major source of genetic variation. The extent of hybridizat ion varied among reservoirs and hatcheries. In three of eight sites sa mpled, 29.3 to 54.5% of the individuals were F1 or F(n) hybrids (n = 2 , 3, ...); F1 hybrids were more likely to be found in reservoirs than in hatcheries, and F(n) hybrids were found in both reservoirs and hatc heries.