Resurrecting an extinct salmon evolutionarily significant unit: archived scales, historical DNA, and implications for restoration

Archival scales from 603 sockeye salmon (Oncorhynchus nerka), sampled from May to July 1924 in the lower Columbia River, were analyzed for genetic variability at 12 microsatellite loci, and compared to 17 present-day O. nerka populations—exhibiting either anadromous (sockeye salmon) or non-anadromous (kokanee) life histories—from throughout the Columbia River Basin, including areas upstream of impassable dams built subsequent to 1924. Statistical analyses identified four major genetic assemblages of sockeye salmon in the 1924 samples. Two of these putative historical groupings were found to be genetically similar to extant evolutionarily significant units (ESUs) in the Okanogan and Wenatchee rivers (pairwise FST = 0.004 and 0.002, respectively) and assignment tests were able to allocate 77% of the fish in these two historical groupings to the contemporary Okanogan River and Lake Wenatchee ESUs. A third historical genetic grouping was most closely aligned with contemporary sockeye salmon...