Physiological and migrational characteristics of steelhead kelts in the Snake River, Idaho

Steelhead trout are iteroparous, but the degree of repeat spawning varies throughout their range.  In the Snake River (Columbia River Basin), the proportion of fish repeat spawning is often less than 2%. In a collaborative multi-year study, we are using nonlethal sampling to determine factors affecting the survival of post spawning steelhead (kelts) with a goal of increasing the proportion of iteroparity in the population. To better understand the relationship of physiology, fish condition and migration success, we sampled blood from downstream migrating natural origin kelts at Lower Granite Dam, WA, assessed their external condition, and applied a PIT tag in the pelvic girdle. Tagged fish were either released into the river, trucked, or barged below Bonneville Dam, the lowermost dam on the Columbia River.  Preliminary analyses of the metrics measured from plasma samples from 2009 showed cholesterol, creatine kinase, LDH, glucose, were all significantly correlated with fish condition. Results from non lethal samples will be compared with migration success, and data from lethal sampling of hatchery stocks to provide a predictive model of internal fish condition based on non lethal samples.  Our analysis should assist managers in predicting fish likely to survive return migration and repeat spawning.