Long-Term Idaho Salmon Supplementation Study Delivers Mixed Results; Not A Stand-Alone Recovery Tool

The Columbia Basin Bulletin –

A newly published study finds that hatchery supplementation after 22 years in two Idaho drainages, increased chinook salmon abundance at some life stages, but the effects did not persist after supplementation of hatchery stock ceased and had no apparent influence on productivity.

The study, according to its authors, represents one of the largest manipulative experiments ever undertaken in the fisheries field. It found that, while supplementation can be a useful tool, the underlying causes of population declines need to be addressed.

It is a distillation of a previous report that was reviewed in 2016 by the Independent Scientific Review Panel (see CBB, August 12, 2016, “Science Review Of Idaho Salmon Supplementation Study Discusses ‘Pivotal’ Questions,”).

In that review, the ISRP said that “The questions addressed by the study are pivotal for salmonid restoration and recovery. The study’s extensive geographic scope, use of treatment and reference populations, long duration, comprehensive field data, and analytical approaches have provided managers and policy makers with insights and recommendations on how supplementation should occur and be evaluated throughout the Basin.”

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