Factors influencing spawner success in a spring Chinook salmon (Oncorhynchus tshawytscha) reintroduction program

Abstract

Dams have contributed to the decline of migratory fishes by blocking access to historical habitat. The active transport (trap and haul) of migratory fish species above existing dams can sometimes support population recovery when the use of fish ladders or dam removal is infeasible. However, little is known about the efficacy of trap and haul conservation strategies. Here we used genetic parentage assignments to evaluate the efficacy of reintroducing adult Chinook salmon (Oncorhynchus tshawytscha) above Cougar Dam on the South Fork McKenzie River, Oregon, USA, from 2008 to 2011. We found that mean reproductive success (RS) declined as adults were released later in the spawning season in 2009 and 2010; however, release location did not affect RS. In 2010 and 2011, we tested for RS differences between hatchery and natural origin (HOR and NOR, respectively) adults. HOR males were consistently less fit than NOR males, but little evidence for fitness differences was apparent between HOR and NOR females. Interestingly, the effect of origin on RS was not significant after accounting for variation explained by body length. Our results indicate that release date and location have inconsistent or no effect on the reproductive success of reintroduced adults when active transport strategies are employed for migratory fishes.

Grandparentage assignments identify unexpected adfluvial life history tactic contributing offspring to a reintroduced population

“…However, as reported in Sard et al. (), among four genetic pedigrees, only 79 ± 7% (mean ± SD) of juveniles assigned to both parents reintroduced from 2008 to 2011. There are a few explanations for this observation, and therefore it is important to test multiple working hypotheses to avoid false or biased conclusions (Chamberlin ).…”

“…Each year, the number of juveniles sampled for genetic analysis was proportional to the total number sampled in the screw trap each month (Sard et al. ). We isolated DNA from adult and juvenile fin clips using a protocol developed by Ivanova et al.…”

“…Simulated parents were assigned to offspring with SOLOMON's no‐known parent Bayesian likelihood approach using methods described in Sard et al. (). For each simulated genetic pedigree, the expected percent of offspring missing one parent due to genotyping error alone was calculated.…”

Early Observations from Monitoring a Reintroduction Program: Return of Sockeye Salmon to a Nursery Lake of Historical Importance

“…; Sard et al. ). Juveniles are a common source for initiating Sockeye Salmon reintroductions into lake systems, while translocation of adult Sockeye Salmon has limited precedence of yielding significant natural productivity in subsequent generations (Burgner et al.…”

Sockeye salmon repatriation leads to population re‐establishment and rapid introgression with native kokanee

“…In response to declining returns of Pacific Salmon ( Oncorhynchus spp) combined with significant contractions of their spawning range, hatchery conservation programs are increasingly being employed to reintroduce or maintain local populations (Anderson, Faulds, Atlas, & Quinn, ; Flagg, Mahnken, & Johnson, ; Fraser, ; Kozfkay et al., ; Nickelson, Solazzi, & Johnson, ; Sard et al., ). These reintroduction or restocking programs are generally undertaken while the underlying mechanisms responsible for population decline, such as the damming of migratory pathways and habitat degradation, are addressed (Pess, Quinn, Gephard, & Saunders, ; Roni, Beechie, Leonetti, Pollock, & Pess, ).…”