This project intends to mitigate marine-derived nutrient loss resulting from salmon extinction due to hydro project development in the Boise/Payette/Weiser subbasin.  We will substitute the natural nutrient cycle provided by returning anadromous fish through application of anadromous fish carcasses, salmon analogues, and liquid fertilizer.  To determine nutrients lost, we will treat 500m segments of twelve small (2-3 meters wide) streams (4 in each sub-basin) with pasteurized fish carcasses (at roughly .5 carcasses/m2) to twelve control streams.  To begin understanding which treatment is the most viable mitigation alternative in ecological and economic terms, we will treat an additional two streams, one with fish analogue and the other with a nutrient fertilizer.  Treatment will occur once a year (in August) for three years.  All treatments will be adding roughly 27.5g N/m2 and 5.5g P/m2 for 500 meters.  The fertilizer treatment may contain metals, however to date we are uncertain as to what types and what concentrations.  Subsequent to application of nutrient treatment, we will monitor aquatic, vegetative, and terrestrial food webs using isotope and lipid analysis of sampled species.  Date from 3 years of treatments will be used to model the relative effectiveness and effects of carcass, analogue, and fertilizer treatments on ecological food webs.  The results of the model will be used to choose the final mitigation treatment type most appropriate for the Boise/Payette/Weiser system.  The replicate watersheds and reaches for the 3 nutrient application types will be chosen with consideration of historic anadromous fish distribution, bull trout distribution, and Idaho batholith geology.   Subsequent to application of nutrient treatment, we will monitor aquatic (bull, red band, cutthroat trout, biofilm and invertebrates), vegetative (streamside trees shrubs, and forbs) , and terrestrial (small mammals) food webs using isotope and lipid analysis of sampled species.  Data from 3 years of treatments will be used to model the relative effectiveness and effects and cost-benefit of carcass, analog, and fertilizer treatments on ecological food webs.  The results of the model will be used to choose the final mitigation treatment type most appropriate for the Boise/Payette/Weiser system.