Asotin and Tucannon steelhead are sole populations within the Lower Snake River Major Population Group (MPG). Both populations include steelhead using small Snake River tributaries that have little or no fish monitoring. All but one of the tributaries (Alpowa Creek) are considered minor spawning aggregations (mSAs) and most of these mSAs are not monitored for adult steelhead abundance or other Viable Salmonid Population (VSP) attributes. Therefore, the proportions of adult natural origin steelhead escapement, or hatchery fish on the spawning grounds, within these mSAs, are unknown for these two steelhead populations (Asotin and Tucannon). NOAA guidance on monitoring ESA recovery (Crawford and Rumsey 2009) lists abundance of naturally produced steelhead as the highest priority for monitoring. They also call for monitoring the ratio of marked to unmarked fish in spawning escapement. The Tucannon and Lower Snake Subbasin Plans, and the Snake River Salmon Recovery Plan also emphasize improved monitoring, especially for adult escapements.

We propose to establish upstream migrant traps on at least two mSA tributaries per year, and rotate them from stream to stream every three years, to: 1) estimate adult steelhead abundance and ratios of hatchery and natural steelhead, 2) collect tissue samples for inclusion in Snake Basin genetic characterization of steelhead (coordinated with New Fast track proposal 202002600 from IDFG) for future run reconstruction estimates at Lower Granite Dam, 3) geographically locate and reference (gps) all redds while conducting spawning surveys in at least one stream to compare the abundance estimate with the trap estimate, and 4) conduct random draws of the data to test and evaluate several different spawning survey designs and determine their precision and accuracy.

Natural adult abundance, and the proportion of hatchery steelhead, in the associated mSA tributaries will be compiled with similar estimates for core Asotin (on-going BPA Project 00205300) or Tucannon steelhead populations (New Fast Track Project 201003400 and Lower Snake River Compensation Plan monitoring by WDFW) to provide more complete estimates of adult abundance and escapement composition (e.g. hatchery proportion and source) over a period of years.