Allozyme Variability ofOncorhynchus nerkain the Pacific Northwest, with Special Consideration to Populations of Redfish Lake, Idaho

Abstract

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 P0.95 level (frequency of the common allele ≤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 distribution. Mean heterozygosity per sample ranged from 0.010 to 0.036 and averaged 0.028 over all samples. Wrightˈs fixation index (FST) averaged 0.153 over 16 P0.95 loci, indicating considerable allele frequency variation among samples. The pattern of population differentiation of sockeye salmon, as revealed through genetic distance and principal component 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 reproductive distinctiveness of the two sympatric forms. Sockeye salmon from Redfish Lake (Sawtooth Valley, Idaho) were of particular interest because 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 lakes) have had a genetic impact on populations surveyed here. The O. nerka from Sawtooth Valley presently occupy a distinctive position in multilocus space, particularly with respect to mAH‐1,2*, mAAT‐l *, and ALAT*. Continued studies of O. nerka in the Sawtooth Valley are focusing on juvenile outmigrants and “residual” sockeye salmon.

Genetic Analysis of Snake River Sockeye Salmon (Oncorhynchus Nerka), 2003 Technical Report.

“…When the H11 haplotype was included, 90% -100% of the kokanee samples were included, vs. 72% and 90% for the Okanogan and Shuswap sockeye samples, respectively. Similar results were observed by Winans et al (1996), who hypothesized that stream capture in recent geological time (the two river systems are less than 20 km apart) may have allowed gene flow, accounting for the genetic similarity between these sockeye and kokanee populations. Robison (1995) suggested that Shuswap Lake kokanee might have been transplanted to Okanogan Lake.…”

“…Fish passage to Suttle Lake was subsequently blocked by installation of a dam and screen at the outlet in 1930 (Fulton 1970 Comparison of other Snake River kokanee populations sampled revealed a high degree of genetic similarity between Anderson Ranch Reservoir, Deadwood Reservoir, Dworshak Reservoir, and Payette Lake. Their similarity reflects the transfers of kokanee that occurred between these lake systems , Winans et al 1996.…”

“…Previous genetic surveys have shown the genetic diversity of sockeye salmon to be extensively subdivided among major geographic regions and among different lake systems (Wood 1995, Beacham et al 1995, Winans et al 1996). This study utilized mitochondrial DNA RFLPs to analyze the genetic diversity of sockeye populations of the Pacific Northwest.…”

“…Genetic variation has been examined in kokanee and sockeye populations in British Columbia (Wood et al 1994), Alaska (Burger et al 1997), the Pacific Northwest (Winans et al 1996), and the Snake River Basin (Figure 1), covering several year classes (Table 1).…”

Dworshak Reservoir Kokanee Population Monitoring: Project Progress Report, 1999 Annual Report.

“…Four sources of fish were initially used, but the early spawning strain from Anderson Ranch Reservoir, Idaho now populates the reservoir (Winans et al 1996). These fish spawn during September in tributary streams as far as 140 km above the reservoir.…”