Physiological and Migratory Characteristics of Clearwater River Steelhead Kelts

We are studying the fate of natural origin steelhead trout kelts from three Clearwater River tributaries in Idaho in an effort to understand why few fish are iteroparous. Fish Creek, a tributary of the Lochsa River, supports a natural population of B-run steelhead; the Potlatch River supports a mix of both A and B-run naturally spawning steelhead trout and several documented repeat spawning fish (iteroparous); and Crooked River, a tributary of the South Fork Clearwater River, supports a population of B-run steelhead trout that was restored following the removal of the Harpster Dam in 1962. We have non-lethally sampled blood from steelhead trout kelts at weirs in addition to determining sex, fork length, external body condition, and PIT-tagging each fish.  In 2011, selected kelts were surgically implanted with acoustic transmitters to follow survival and rate of migration in the Clearwater and Snake River corridor. Kelts from lower tributaries of the Potlatch River migrated downstream nearly one month earlier than did fish from upper tributaries. We found a range of sizes of kelts within the Potlatch system, with significant differences in 2010 between weirs on two adjacent tributaries, the East Fork and West Fork Potlatch. The kelts from both Fish Creek and Crooked River were larger than those from the Potlatch, and could be considered B-run fish. In 2010 Female kelts constituted 74%, 68%, and 15% of downstream migrants at Fish Creek, the Potlatch River, and Crooked River, respectively.  Biochemical attributes of plasma samples from fish were correlated with body condition. The highest cholesterol and triglyceride levels were found in good condition fish. We will compare run timing and migration characteristics among tributaries and between years.