At the Council’s July 9, 2010 request the ISRP reviewed Idaho Department of Fish and Game’s (IDFG) Accord proposal, Idaho Nutrient Enhancement Project (2008-607-00). This pilot project’s objective is to introduce selected nutrient sources to Idaho streams with the goal of providing benefits to Idaho steelhead populations. A paired treatment/control approach is proposed to evaluate the effectiveness of the nutrient enhancements.
The ISRP requests a response. A few methodological issues need greater detail. In particular, the ISRP would like to see the following issues addressed in a response:
- Describe the analytical approach that will be used to account for the effect of variation in spawner density and habitat conditions on juvenile steelhead density, length at age, and survival.
- Include a methodology for determining the extent to which carcass analogs are directly ingested by juvenile steelhead.
- Discuss the availability of nutrient pellets at appropriate N+P ratios. Describe the methods that will be used to ensure that N+P levels achieved prescribed levels given the alternative application techniques (pellets, carcasses, analogs).
- Address the issues raised about the reliance on algal abundance to determine effective treatment length, and consider incorporating a more robust water chemistry sampling protocol to supplement the algae measurements.
- Describe the process of coordination with other nutrient-addition research projects, including a decision plan and time lines that are based on the results of these research efforts. Especially indicate how negative results from these studies (i.e., lack of response or detrimental impact on steelhead production) would alter the design of this project (including the possibility of cancelling nutrient application).
- Consider incorporating a public outreach/education component into the project.
This project has the potential to contribute important information on the use of nutrient additions as an enhancement technique for steelhead. The evaluation of the logistical challenges of applying nutrients at large scales has not been previously addressed for streams in Idaho. The project also includes an assessment of steelhead response. The ideal salmonid response variable for these types of studies would be the production of smolts per spawner, with consideration of the number of spawners contributing to smolt recruitment, and detection of a recruitment difference caused by nutrients added to the stream. The ISRP recognizes that this type of analysis requires a level of effort and resources beyond that being requested for this study. However, the fish sampling protocols would be strengthened with some additional detail on how the effect of nutrient enhancement on juvenile steelhead density and length-at-age will be distinguished from responses in these variables caused by factors like flow, temperature or spawner density. Some additional consideration of how to assess feeding by steelhead on carcass analogs, should this method be the preferred option, should be included. Also some additional thought as to how to assess the effective treatment length should be incorporated into the proposal.