At the Council’s June 12, 2009 request, the ISRP reviewed the Shoshone-Bannock Tribes’ Columbia River Fish Accord proposal titled Salmon River Basin Nutrient Enhancement (2008-904-00). The proposed project seeks to partially mitigate for the dramatic decline of anadromous salmonids (and the associated reduction of available marine-derived nutrients to freshwater spawning and rearing habitat) by experimentally enriching nutrient limited upper Salmon River subbasin streams with carbon, nitrogen, and phosphorus using salmon carcass analogs.
The ISRP requests a response before it can make its final recommendation.
The research proposed could be of significant benefit to the development of salmon restoration plans for the Columbia Basin. The enhancement of nutrient availability and food web productivity has been widely promoted as an effective restoration strategy, but our understanding of ecosystem-level responses to nutrient addition is limited. This study will provide new information on the utility of salmon carcass analogs as a potential enhancement tool.
A response is requested to address the following issues:
- Nutrient and food limitation. Provide detailed methodology on the assessment of nitrogen or phosphorus limitation and food limitation in stream fishes. How will researchers determine if nitrogen or phosphorus is the key limiting nutrient? What methods are proposed to determine if food is limiting smolt yield or growth rate?
- Eyed egg boxes may provide inconsistent and variable results and may not ensure the stream is at juvenile carrying capacity. How will the evaluation deal with variable juvenile density in the analysis?
- The key response variable to address effectiveness of salmon carcass analog addition should be wild smolt recruitment as a function of spawner density. This measure will require an estimate of wild smolt production from the study sites. How will this be accomplished?
- Some project elements do not seem to support the overarching objective of the study (effect of salmon carcass analogs on food web dynamics). The response should clearly explain how the nutrient diffusing substrata, nutrient spiraling, and course particulate organic matter transport elements of the study will provide information relevant to the interpretation of the effects of the salmon carcass analogs on stream trophic dynamics and specifically on smolt production.
- Provide some additional detail on the rationale for the variable treatment intensities over the three years of the study. How will potential cumulative impacts of repeated nutrient supplementation be assessed with this design?
- Discuss how the information gathered from these investigations will be used to design larger scale pilot or full implementation of salmon carcass analog applications as a salmon/stream restoration strategy.