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Scientist working on White Salmon River screw trap

Detailed Description

USGS scientist, Jill Hardiman, working on a screw trap on the White Salmon River to assess anadromous fish recolonization following removal of a large dam.

A screw trap consists of a large cone suspended between two floating pontoons. River flow rotates the cone and funnels a portion of the migrating fish into an underwater holding tank at the back of the trap. Fish are sampled, data recorded, and then released.


Public Domain.