AbstractsBiology & Animal Science

Investigating Demographic and Evolutionary Factors Important for Fish Reintroduction

by Nicholas M Sard

Institution: Oregon State University
Year: 2016
Keywords: Reintroduction; Chinook salmon  – Oregon  – McKenzie River
Posted: 02/05/2017
Record ID: 2075072
Full text PDF: http://hdl.handle.net/1957/58902


Reintroduction programs are used to re-establish species back into their historical habitat. Most reintroduction programs have failed and few papers have evaluated factors that may be important to Pacific salmon. The 158 meter tall Cougar Dam has blocked Chinook salmon (Oncorhynchus tshawytscha) from accessing 40 kilometers of historical spawning and rearing habitat for over 50 years. Here, I evaluated a Chinook salmon trap and transport reintroduction program above Cougar Dam on the South Fork McKenzie River, Oregon from 2007 to 2015. First, I evaluated if release location and date correlated with two measures of fitness based on adult assignments to age-0 juveniles collected above the dam and adult offspring returning to the South Fork McKenzie River, respectively. I found that release location and date had little to no effect on either measure of fitness. I also evaluated if there were fitness differences between hatchery and natural origin (HOR and NOR, respectively) adults. I found consistent fitness differences between males (RRS=0.48, p<0.001), but not females (RRS=0.72, p=0.81). In addition, I found that origin (p=0.352) no longer explained variation in fitness after accounting for variation in fork-length, which suggests that HOR fish may be less fit, in part, because they are 2-4 cm (95% CI) smaller, or perhaps younger. I also evaluated a measure of population productivity known as cohort replacement rate (CRR) - defined as the number of future spawners produced by a spawner. Based on genetic parentage assignments to NOR adults returning to the trap and transport facility, hereafter Cougar Trap, I found that adults reintroduced in 2007 and 2008 did not meet demographic replacement (CRR: 0.40 and 0.31, respectively). I also found a seasonal decline in the proportion of NOR adults produced above the dam that returned to the Cougar Trap. I also developed grandparentage assignment methods to determine how many precocial males and adfluvial Chinook salmon, two non-anadromous life history tactics, contributed to population productivity. I found 31 unsampled precocial males, as well as 48 age-4 and -5 probable adfluvial male and female adults contributed to the reintroduced population. My discovery of adfluvial Chinook salmon contributing to population productivity is significant because little is known about this life history tactic, and they provide resiliency to a reintroduced population. I show that adfluvial adults can be produced by anadromous mate pairs. Adfluvial adults increased CRR estimates; however, neither the 2007 or 2008 cohorts met replacement after incorporating this non-anadromous life history tactic (CRR: 0.46 and 0.35, respectively). Finally, I assessed if genetic variation in founding cohorts was maintained in their returning adult offspring returning to the South Fork McKenzie River, hereafter F₁ offspring. On average, 6 alleles were lost per locus between founding cohorts and their F₁ offspring. N[subscript e] estimates were high using either demographic or genetic methods (range: 344 to… Advisors/Committee Members: Banks, Michael A. (advisor), Ardren, William (committee member).