ALLOZYME VARIABILITY OF ONCORHYNCHUS-NERKA IN THE PACIFIC-NORTHWEST, WITH SPECIAL CONSIDERATION TO POPULATIONS OF REDFISH LAKE, IDAHO

We resolved allozyme variation among 28 enzymes encoded by 58 protein loci in 27 samples of sockeye salmon and kokanee Oncorhynchus nerka in the Pacific Northwest. Of 32 polymorphic loci, 16 were polymorphic at the P-0.95 level (frequency of the common allele less than or equal t o 0.95). We found substantial variation at mAAT-1 and mAH-1,2*, loci not previously described in O. nerka in this portion of its distributi on. Mean heterozygosity per sample ranged from 0.010 to 0.036 and aver aged 0.028 over all samples. Wright's fixation index (F-ST) averaged 0 .153 over 16 P-0.95 loci, indicating considerable allele frequency var iation among samples. The pattern of population differentiation of soc keye salmon, as revealed through genetic distance and principal compon ent analyses, resembled a mosaic in that nearest geographic neighbors were not necessarily similar genetically. Allele frequencies at two to five loci differed significantly between sympatric sockeye salmon and kokanee in three separate localities, indicating genetic and reproduc tive distinctiveness of the two sympatric forms. Sockeye salmon from R edfish Lake (Sawtooth Valley, Idaho) were of particular interest becau se of their extensive freshwater migration and extremely low abundance in recent years. We found no evidence that any of the recorded stock transfers of O. nerka into the Sawtooth Valley (Redfish and Alturas la kes) have had a genetic impact on populations surveyed here. The O. ne rka from Sawtooth Valley presently occupy a distinctive position in mu ltilocus space, particularly with respect to mAH-1,2, mAAT-1*, and AL AT. Continued studies of O. nerka in the Sawtooth Valley are focusing on juvenile outmigrants and ''residual'' sockeye salmon.