Ever wondered what the large structure beneath the Lewiston–Clarkston Blue Bridge is? It’s a smolt trap, recently rebuilt and now fully operational to support long-term fish monitoring led by the Idaho Fish and Game.
From River to Ocean: The Snake River Smolt Monitoring Program
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Newly rebuilt trap replaces the trap originally built in 1950's
The original trap, constructed in the 1950s, had reached the end of its service life. The new facility improves safety for both fish and staff while ensuring reliable operation for years to come.
The trap captures juvenile salmon and steelhead—known as smolts—as they migrate downstream through the Snake River. Biologists examine each fish to determine species, hatchery or wild origin, and overall condition. Many are fitted with small PIT (Passive Integrated Transponder) tags, allowing researchers to track survival, travel time, and smolt-to-adult return rates as the fish move through the Columbia River Basin.
Information gathered at the site is entered into the PTAGIS, a regional database used by fisheries managers and scientists to guide conservation and management decisions.
This monitoring work helps support sustainable fisheries, local recreation, and the long-term health of salmon and steelhead populations in the Clearwater region. Boaters are reminded that the trap operates beneath the bridge and should use caution when recreating nearby.