A Synthesis of Findings from an Integrated Hatchery Program after Three Generations of Spawning in the Natural Environment

The Cle Elum Supplementation and Research Facility in the Yakima River Basin, Washington is an integrated spring Chinook Salmon Oncorhynchus tshawytscha hatchery program designed to test whether artificial propagation can increase natural production and harvest opportunities while keeping ecological and genetic impacts within acceptable limits.   An unsupplemented population in the adjacent Naches watershed provides a reference for evaluating environmental influences.   The program has been comprehensively monitored from inception.  A synthesis of findings includes:  supplementation increased harvest, redd counts, and spatial distribution of spawners; natural-origin returns were maintained; straying to non-target systems was negligible; natural-origin females had slightly higher breeding success (production of surviving fry) in an artificial spawning channel, while behavior and breeding success of natural- and hatchery-origin males were similar; hatchery-origin fish showed differences in morphometric and life history traits; high rates of hatchery age-2 (mini-jack) production were reported but observed proportions of outmigrating juvenile and adult (ages 4 and 5) returning males were comparable for hatchery- and natural-origin fish; hatchery smolts did not affect levels of pathogens in natural smolts; and, ecological interactions attributed to the program were within adopted guidelines.  Continued study is required to assess long-term impacts to natural production and productivity.