Analysis of Survival and Downstream Migration Characteristics of Steelhead Kelts Using Instream PIT-Tag Arrays in the Potlatch River Drainage, Idaho

Iteroparity has been documented within inland steelhead populations such as those found in the Snake River Basin; however, information on kelt survival and kelt outmigration characteristics from spawning tributaries is still lacking.  To address this issue, we examined PIT-tag interrogation data from instream PIT-tag arrays and dam passage facilities to estimate reach based survival and outmigration travel rates for steelhead kelts from the Potlatch River Basin.  Kelts were captured and released at weirs from two different areas within the drainage, Big Bear Creek (lower drainage) and Upper Potlatch River (upper drainage).  Overall kelt survival from weirs to the mainstem Potlatch River instream array and Lower Granite Dam was 51.6% and 8.6% respectively.  Kelts from Big Bear Creek weirs survived to the mainstem Potlatch River instream array at 62.4%, which was higher than Upper Potlatch River kelts which survived at 21.7%.  Average kelt travel rates from Big Bear Creek to the mainstem Potlatch River instream array, and subsequently from the mainstem Potlatch River instream array to Lower Granite Dam was 4.9km/day and 10.2km/day respectively.  Average kelt travel rate from the Upper Potlatch River to the mainstem Potlatch River instream array was 12.7km/day.  A travel rate from the mainstem Potlatch River instream array to Lower Granite Dam could not be estimated due to low sample size.  Additional evaluations of kelt detection efficiency at Snake and Columbia River dams and kelt outmigration mortality are needed; however, results from this study provide baseline data for evaluating kelt mortality and life history characteristics associated with iteroparity among inland steelhead populations.