Project: Steelhead kelt outmigration from the lower Snake river: Abundance, downstream conversion rates, routes of passage, travel times, and survival
Client: USACE - Fisheries Field Unit & USACE - Walla Walla District
Year: 2000 - 2007
Location: Lower Columbia and Snake RiversAs part of this study, we investigated abundance and survival of post-spawned adult steelhead (kelts) in the lower Snake and Columbia rivers. Research used ultrasound imaging to determine the fishes’ sex and maturation status (spawned, post-spawned) and biotelemetry to evaluate and measure dam passage routes, travel times, and survival. PIT tags were used to estimate kelt abundance and repeat spawning rates.
Methods were developed to accurately differentiate kelts from adult steelhead on pre-spawn migrations using rapid, noninvasive ultrasound imaging techniques. Subsequent kelt abundance data revealed that thousands of Columbia River basin kelts attempt outmigration to the Pacific Ocean each spring, and many of these fish are from ESA-listed populations. Although abundant, many kelts die before reaching the free-flowing section of the Columbia River below Bonneville Dam. Mortality estimates for radio-tagged kelts ranged from 20% to 40% for fish tagged at lower Columbia River dams, and from 84% to 96% for kelts tagged at the uppermost passable dam on the Snake River (Lower Granite Dam). High downstream kelt mortality contributed to the relatively low iteroparity (repeat spawning) estimates.
Project required close coordination and collaboration with Columbia Basin tribes, the Corps’ Fisheries Field Unit, NOAA Fisheries, and the University of Idaho.