Conduct snorkel surveys to estimate density, distribution, and size structure of Chinook and steelhead parr.  Sites will be selected based on a rotating designs (intensive, and historical panels). All salmonid species observed will be enumerated by length group. At selected sites, detection efficiency of crews will be assessed. 

Actual site bounds may be adjusted to fit within hydraulic controls. The percentage of each habitat type (pool, pocket water, riffle, or run) within the site will be visually estimated and recorded. One to five snorkelers will count fish in each site, depending on the stream size and visibility. All salmonids observed will be counted and individual size estimated to the nearest inch while moving slowly upstream. Steelhead parr will be assigned an age based on length. Non-salmonid species observed will be noted as present. After each site is snorkeled, site length and up to ten widths will be measured to calculate surface area. Gross habitat characteristics are also evaluated.

The efficiency of crews at detecting juvenile steelhead will be evaluated at a subset of sites. A protocol modified from Thurow et al. (2006) will allow for estimates of efficiency through observation of marked individuals. In short, juvenile steelhead will be caught (by angling), measured, marked (caudal notch), and released within the selected site. The next day, snorkeling will begin approximately 50 m downstream of the main transect and number of marked fish will be recorded. Then, the main section is snorkeled and all salmonids are counted and recorded by length group. Finally, a section approximately 50 m in length upstream of the main section is snorkeled and number of marked fish is recorded. The habitat variables described by Thurow et al. (2006) are measured in the target section. The intent is to use these data to validate the use of Thurow et al.’s (2006) model relating habitat conditions to daytime snorkel survey efficiency for O. mykiss. A target of 10% of the sites sampled is desired to assess crew efficiency.

Juvenile Chinook Salmon and steelhead densities (numbers/sq. m) will be estimated by site for all streams in which IDFG performed snorkel surveys. Densities from extensive and intensive panels are summarized for all surveyed reaches by sub-basin. Densities from historical sites are compared across years to assess trends.