Managing and Mitigating Salmon-Derived Nutrients: Are Analogs Salmon Avatars?

The paucity of nutrients in anadromous fish watersheds is foundational to the ecological connection of salmon to their freshwater origins.  The importance of these nutrients drove the origins of anadromy in these species in the relatively sterile freshwater systems of the Columbia River Basin.  Moreover, the return and death of those same fish is a net benefit to the nutrient and food web cycles supporting aquatic and terrestrial species in these ecosystems.   Quantifying this connection is important, but given the presumed long-term and foundational importance of MDN in freshwater ecosystem and the increasing anthropogenic impacts on salmon across their range, it is essential we translate MDN benefits into relative measures of impact and mitigation cost:benefit.   Based on experiences in the Columbia River basin, we suggest that MDN management and its mitigation must take a broader more adaptive approach than in the past.  Essential to this are measures of MDN impact and benefit assessment including the effects of MDN on riparian and watershed habitats.   We also recommend that treatments, measures, and models of MDN effects insure that scales of the terrestrial and aquatic systems, populations and habitats being measured match.  And third, we recommend an applied and adaptive approach to implementing MDN treatments and building predictive models rather than waiting for science to quantify MDN effects in a research context.  Looking at past MDN work, much of it has focused on relatively short term and small scale treatments defining relatively localized effects and without comparative measures of existing and historic anadromous fish systems.  We recommend that larger scale treatments and measures, at a minimum the watershed scale, be evaluated for MDN benefits and effects.  To address the often problematic measures of MDN effects on terrestrial wildlife and riparian and watershed habitats over the long term, we believe it is essential to conduct comparative work between systems with ecologically functional anadromous fish stocks, those with functionally extinct stocks, those whose stocks have been extirpated, and historic recreations via the study of museum specimens.  We discuss the above using examples of current efforts to mitigate for loss of marine-derived nutrients in the Boise-Payette-Weiser subbasins in the Columbia River Basin.   Finally, we suggest some outcomes and future scenarios to best enable the science and collaboration necessary to answer management decision making related to wildlife, fish, and habitat management in relation to marine-derived nutrients.