The Progression of Naturalization: Using Parentage-based Tagging to Monitor the Reintroduction of Spring Chinook Salmon to Lookingglass Creek, OR
Populations of anadromous salmonids have been dramatically reduced throughout the Pacific Northwest, especially in the Columbia River Basin, where extensive alterations to the hydrosystem have resulted in the extirpation of populations across subbasins and species. When the cause(s) of an extirpation event are addressed, natural recolonization may occur, but often reintroductions must rely on hatchery stocks to supplement productivity. Reliance on hatchery fish has inherent risks, largely due to potentially reduced fitness associated with domestication selection. In Lookingglass Creek, a tributary to the Grande Ronde River in northeastern OR, a spring Chinook reintroduction effort was initiated via captive broodstock releases in 2000, and the population continues to be supplemented by local, hatchery-origin (HOR) fish. To monitor the progress of naturalization in this system we used parentage-based tagging methods to evaluate the fitness of reintroduced natural-origin (NOR) fish relative to their HOR counterparts when spawning naturally. We used two pedigree reconstruction methods (SNPPIT and COLONY) to identify the number of adult and juvenile progeny attributed to every naturally spawning adult from 2008-2016. These data informed GLMs, which quantified the expected number of progeny by spawners of different origins and sexes within each year, while controlling for other factors that may influence fitness and accounting for differences in the frequency of successful spawning events. We found NOR fish produced significantly more progeny (both juvenile and adult) across all sex and year combinations. Also, return day and fish size were significant predictors of reproductive success (juvenile progeny only). Additionally, we found some relationship between the number of juvenile and adult progeny per spawner, but this was highly variable by year, and therefore likely not sufficient to be predictive. Results suggest that fish which possess HOR ancestry can adapt to the local environment within relatively few generations. Reintroduction programs relying on hatchery efforts would therefore likely benefit by implementing management practices rooted in supplementation and restoration.
Nuetzel, H.M., P. Galbreath, B. Staton, C.A. Crump, L. Naylor, and G.E. Shippentower. 2022. The Progression of Naturalization: Using Parentage-Based Tagging to monitor the reintroduction of spring Chinook salmon to Lookingglass Creek, OR. Oregon Chapter of the American Fishery Society Annual Meeting, Virtual, March 2-4, 2022.