Population Viability Improves Following Termination of Coho Salmon Hatchery Releases

Abstract

Recent genetic studies, meta-analyses, and retrospective analyses have documented reduced productivity of wild salmon and steelhead Oncorhynchus mykiss that interbreed with hatchery-reared fish, raising concerns about the longterm viability and recovery of at-risk stocks. In 2007, the Oregon Department of Fish and Wildlife discontinued a Coho Salmon Oncorhynchus kisutch hatchery program at the Salmon River to support recovery of a wild Coho Salmon population in the Oregon Coast Evolutionarily Significant Unit. This decision constituted a unique management "experiment," allowing for direct measurement of the wild population's response after the discontinuation of a decades-old hatchery program. We used a before-after, control-impact design to examine whether selected viability metrics of the naturally produced population in the Salmon River changed after the hatchery program ended. We compared metrics for the 2006-2013 broods, representing periods after the hatchery program ended, to those for the 1995-2005 broods, when the hatchery program was still releasing 200,000 smolts annually. We also examined neighboring populations during similar time periods to account for changes or variation due to other factors. Although hatchery-origin spawners previously had accounted for most of the adults returning to the Salmon River, the naturally produced population did not collapse, and two viability metrics improved significantly after the Coho Salmon hatchery program ended: (1) adult abundance increased and (2) spawn timing expanded and moved closer to the historical timing. Recruits-to-spawner ratios in the Salmon River, although initially low, are now approximately equal to those of neighboring populations. The results indicate that hatchery closure can be an effective strategy to promote wild population recovery. However, considerable variability in population trends and environmental conditions will require continued monitoring to verify the long-term resilience and viability of the wild population.

Distinct Phenotypes of Native Cutthroat Trout Emerge under a Molecular Model of Lineage Distributions

“…This highlighted the power of side-by-side morphological and molecular analyses, especially when data are obtained from the same specimens. Patterns of lineage differentiation and diversity that remain across SRM drainage basins also supported an emerging thesis in the literature: that phenotypic, genetic, and life history differences of native salmonids are cohesive and often persist (Pritchard et al 2009;Jones et al 2018;Trotter et al 2018) despite high potential for gene flow and admixture with stocked hatchery fish. This is especially remarkable for SRM Cutthroat Trout, given the millions of fish of different species-or different lineages of the same species-that were stocked across the landscape over long periods of time (Metcalf et al 2012).…”

“…; Jones et al. ; Trotter et al. ) despite high potential for gene flow and admixture with stocked hatchery fish.…”

Estimating Juvenile Salmon Estuarine Carrying Capacities to Support Restoration Planning and Evaluation

“…Few studies we reviewed distinguished between hatchery and naturally produced Chinook salmon, so it is likely that our database includes a mix of natural and hatchery origin fish (e.g., Jones et al 2018). The presence and magnitude of hatchery releases in a system can influence capacities; therefore, natural origin densities may be biased low in systems with larger hatchery influence.…”

The role of hatcheries in the decline of Lake Ontario Atlantic salmon

“…Despite strong scientific literature to the contrary, we have not learned our lesson about the use of fish culture to restore wild populations (e.g. Columbia River ) (Lichatowich andWilliams 2015, Lichatowich et al 2018), or the success of wild fish recovery following the cessation of stocking (Jones et al 2018). Instead, the hubris of hatcheries, and the strong personalities of managers and entrenched agency practices that prioritize economic goals, continue to distract the public and fisheries officials from the underlying problems while diverting critical resources away from core solutions about the best methods for population stabilization and recovery of wild fish.…”