Pacific salmonid populations have declined dramatically across the Columbia River Basin. These population declines are often due to cumulative effects of multiple factors affecting production in freshwater and marine environments. An important result of these population declines is the concurrent nutrient, productivity, and ecosystem function losses associated with significantly reduced marine derived nutrient (MDN) loading rates from the loss of salmon carcass. Anadromous salmon carcasses provide significant amounts of MDN, which historically provided the bases for primary productivity in stream systems, especially in the interior areas which are naturally oligotrophic.  Lower MDN loading from diminished salmon runs results in negative feedback through reduced juvenile rearing capacity for Pacific salmon systems. Recent research has indicated that MDN loading rates as low as 6-15% of historical levels currently exist among anadromous salmon spawning streams in the Pacific Northwest.

This project will quantify and evaluate nutrient status and availability in the Twisp River Basin, a Subbasin of the Upper Columbia River watershed area in north central Washington, in response to diminished anadromous salmon runs. More specifically, this project is conducting a rigorous multi-trophic level sampling program to quantify and evaluate baseline water quality and nutrient availability, primary secondary and tertiary productivity rates including algal, periphyton,  benthic macroinvertebrate and fish communities . A stratified random sampling design was used to select study sites in each of the upper, middle, and lower reaches of the study area (Twisp River). The goal is to develop a comprehensive pre- and any post-treatment (experimental nutrient addition) biological assessment. Finally, this project provides the necessary adaptive management framework to determine if nutrient limitation and/or imbalance currently exist and to generate empirically-based recommendations and prescriptions for restoring limnological conditions needed to increase natural production of anadromous salmonids in the study area (Twisp River).