Risk management of non-target fish taxa in the Yakima River Watershed associated with hatchery salmon supplementation

Hatchery cultured salmon have the potential to interact strongly with other valued fish taxa (non-target taxa; NTT) in the natural environment. Monitoring and managing adverse interactions between hatchery supplemented salmon and NTT is one unique characteristic of a hatchery salmon supplementation program in the Yakima River, Washington. In this study, we evaluate impacts of spring Chinook salmon Oncorhynchus tshawytscha and coho salmon O. kisutch reintroduction to 15 NTT after 11 years of stocking approximately one million yearling smolts annually in the upper Yakima Basin between 1999 and 2009. Our risk management monitoring indicated changes in important response variables for NTT were within acceptable limits. Rigorous pre-implementation planning likely prevented many undesirable ecological impacts from the hatchery supplementation program. We illustrate a number of important features associated with risk management of hatchery and wild fish interactions. First, pre-project planning can eliminate many risks of concern and substantially reduce the need for risk containment during project implementation. Second, the sieve approach for monitoring impacts provided an acceptable balance between monitoring effort and risk containment ability, although in some cases, we would not detect impacts of interest. Third, rare and disbursed species that cannot be monitored effectively benefit from risk averse hatchery release strategies. Fourth, risk containment monitoring programs can be used to refute unsubstantiated claims of undesirable impacts. In short, our experience suggests that risk management of ecological interactions can occur by using a combination of pre-project adjustments through risk assessment and risk reduction, and by cost-effective risk containment monitoring and management.