Integrated, Segregated, and Two-Stage Stepping Stone Hatchery Broodstock Programs—Achieving Both Conservation and Harvest Goals

Hatchery reform efforts in the Pacific Northwest were initiated in 2000 in response to the proposed listing of Chinook salmon as a threatened species in Puget Sound.  A Hatchery Scientific Review Group (HSRG) was formed to determine how hatcheries could best be operated in a manner consistent with the conservation and recovery of natural populations while, at the same time, continuing their traditional role of providing fish for harvest.  One of the first conclusions of the HSRG is that all hatchery broodstocks for Pacific salmon and steelhead must be managed as genetically segregated or genetically integrated populations relative to natural populations.  The goal of a segregated hatchery population is to manage hatchery fish as a distinct population from a natural population (2 gene pools, 2 environments).  Any natural spawning by hatchery-origin fish (HORs) from a segregated population is considered “high risk” because those fish are managed as a separate “stock”.  In contrast, the goal of an integrated hatchery population is to manage hatchery fish as an artificially-produced component of a natural population (1 gene pool, 2 environments) where “natural selection” associated with reproduction and survival in the “wild” environment has a greater genetic influence on the population than “domestication selection” and artificial propagation in a hatchery.  This “integrated” approach requires the systematic inclusion of natural-origin fish (NORs) in a hatchery broodstock where the proportion of a broodstock composed of NORs (pNOB) must exceed the proportion of naturally spawning fish composed of HORs (pHOS).  Any natural spawning by “integrated” hatchery fish is still considered a genetic risk, but that risk is reduced by the amount that pNOB exceeds pHOS.   Conflicts between harvest and conservation goals have motivated a third broodstock management approach termed “stepping stone” program.  In this latter program, two broodstocks are maintained: (1) a genetically-integrated broodstock that achieves conservation goals for the population as a whole, including the minimum constraint pNOB > pHOS, and (2) a second “segregated” broodstock that is used to achieve harvest goals where surplus HORs from the first broodstock - and returning adults from the second broodstock, if needed - are used to form the second “segregated” broodstock each year and generation.