Testing assumptions behind alternative recovery strategies for anadromous salmonids in the Yankee Fork Salmon River, Idaho: An analysis of food limitation

Habitat restoration and nutrient additions are currently two of the main mitigation and recovery strategies for Pacific salmon and steelhead in the Columbia River basin.  The rationale for applying these recovery strategies is based on the assumption that habitat and/or food limit populations of anadromous salmonids.  In contrast, the use of hatchery supplementation is based on the assumption that food and/or habitat conditions can sustain additional hatchery fish.  Reconciling these contradictory assumptions through an analysis of limiting factors will help in predicting successful recovery strategies for anadromous salmonids.  In this study we quantitatively assessed food limitation of anadromous salmonids, via a comparison of fish production and energetic demand to aquatic invertebrate production, in the Yankee Fork Salmon River, Idaho.  Our results show that invertebrate production was on average four times larger than fish demand, indicating that food availability is not likely to be the limiting factor for this stage in the life-cycle of anadromous salmonids.  This result suggests that habitat restoration and nutrient additions may not be the best strategy for the recovery of anadromous salmonids in this area, and that downstream factors (hydropower and harvest) may be more limiting to salmon recovery.