Natural-origin Salmon Abundance:

Analyzing large-scale conservation interventions"

Summary: A recent study that compared 12 wild chinook salmon populations that had been the focus of hatchery supplementation programs and 10 populations of salmon that had never been the focus of supplementation programs found none to small benefits in natural salmon abundance.

The study analyzed information from a 25-year period and determined that densities of natural-origin spawning adult salmon in the Snake River Basin that had been the focus of supplementation programs had increased just 0 percent to 8.4 percent relative to the 10 salmon populations that had not been the focus of supplementation.

There could be several explanations for this, according to the study.

First, other studies have denoted the poor reproductive success of hatchery salmon and they could depress the abundance of wild adults, as well.

Second, the theoretical basis of supplementation assumes that target populations are well below carrying capacity, the study says, and the lackluster performance of supplementation shown in this study could be because populations are closer to carrying capacity than thought.