Life history variation in upper Columbia River Chinook salmon (Oncorhynchus tshawytscha): a comparison using modern and ~500-year-old archaeological otoliths

Abstract

Conservation planning often occurs only after a species has been extirpated from portions of its historical range and limited information is available on life history diversity prior to development. To provide information on Chinook salmon ( Oncorhynchus tshawytscha ) life history before and after local extirpation, we examined the chemical (87Sr:86Sr, Sr:Ca) and structural composition of modern and archaeological otoliths from the upper Columbia River. We compared otoliths from modern spring (yearling migrant, n = 15) and summer–fall (yearling (n = 7) and subyearling (n = 12) migrants) runs with those from extirpated runs (n = 8) to estimate the number of and similarity among natal environments and reconstruct aspects of the migratory history. Presumptive natal sources were most similar between the archaeological collections and the modern summer–fall run. Chinook salmon represented by the archaeological otoliths also displayed life history traits, including size at freshwater emigration and adult size at return to fresh water, most similar to the summer–fall subyearling run. These data indicate that there is the potential to maintain aspects of predevelopment Chinook salmon life histories in the Columbia River, and strategies that promote maintenance of that life history diversity may be warranted.