Genetic monitoring guides adaptive management of a migratory fish reintroduction program

Abstract

Dams contribute to declines in fish abundance, in part, by blocking access to historical habitat. When fish ladders are infeasible, fish can be trapped below a dam and transported above to provide access to habitat. However, this conservation strategy has received little attention in the literature, and many questions regarding efficacy remain unanswered. Here, we used a genetic parentage approach to evaluate cohort replacement rate (CRR), defined as the number of future spawners produced by a spawner, for a spring Chinook salmon Oncorhynchus tshawytscha trap and transport reintroduction program. We used CRRs to determine if the population can sustain itself in the absence of immigration, which is important when assessing demographic viability. We also evaluated the effects of release locations and dates on the fitness of reintroduced fish. Counts of adult offspring per spawner were used to estimate fitness of salmon reintroduced in 2007 and 2008. We found that fitness decreased slightly as adults were released later in the spawning season in 2007, but not in 2008. Release location did not affect fitness in either year. We also found a seasonal decline in the likelihood that a Chinook salmon collected at the trap and transport facility was produced above the dam. Finally, 2007 and 2008 CRRs were both well below one, indicating that improvements are needed to achieve demographic stability. We demonstrate that genetic monitoring of a reintroduction program helped to inform demographic viability assessments, and suggest that our approach may be broadly applicable to other philopatric species.

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

“…This trap and transport reintroduction approach has enabled the near complete tissue sampling of all the potential anadromous adult parents, thereby allowing for estimates of CRR. Contrary to recently published studies for other Chinook and coho (O. kisutch) salmon reintroductions (Anderson et al 2015;Evans et al 2015), current CRR estimates suggest that the population above Cougar Dam is not replacing itself (Sard et al 2016).…”

“…), current CRR estimates suggest that the population above Cougar Dam is not replacing itself (Sard et al. ).…”

“…The ability to have a more complete understanding of CRRs for reintroduced populations is limited by excluding difficult to sample, or unanticipated, life history tactics from estimates. Sard et al (2016) used genetic parentage assignments to estimate CRR for the population established above Cougar Dam by the reintroduction program. This approach identified anadromous adult offspring returning in subsequent years; however, it does not account for any adults that sexually matured above Cougar Dam because these individuals were never encountered and therefore were not sampled.…”

RAPTURE (RAD capture) panel facilitates analyses characterizing sea lamprey reproductive ecology and movement dynamics

“…By comparing individual genotypes sampled before and after pesticide treatment, one could find some families are over‐ or under‐represented, leading to at least two explanations: (a) Families occupy different habitats, and treatment effectiveness varies among habitats; and (b) families have different physiological tolerances to lampricides (i.e., dead in treatment vs. alive as residuals). The RAPTURE panel described here may be used for similar efforts in the native range for sea lamprey. Large‐scale genetic parentage studies have provided several valuable insights into sea lamprey conservation efforts in native marine systems including estimating population abundance, evaluating environmental correlates of fitness, as well as estimating effective population size (e.g., Duong et al, ; Sard et al, ). Additionally, adaptive loci may be identified and used to inform which fish are reintroduced in specific locations to improve reintroduction outcomes.…”

“…The sea lamprey assessment program could benefit from having the ability to characterize dispersion of larvae from the same fulland half-sibling families. Previously, we have shown (Derosier et al, 2007;Gilmore, 2004) relates of fitness, as well as estimating effective population size (e.g., Duong et al, 2013;Sard et al, 2016). Additionally, adaptive loci may be identified and used to inform which fish are reintroduced in specific locations to improve reintroduction outcomes.…”