Evidence for upstream dispersion of adult CAD disflies (Trichoptera: Hydropsychidae) in the Columbia River

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Abstract
The radioisotope 65Zn, introduced to the Columbia River in discharges of the U.S. Atomic Energy Commission's Hanford reactors, was used to test the hypothesis that adult caddis flies migrate upstream after emerging from the aquatic environment. The larval stages living downstream of the effluents are known to accumulate appreciable levels of 65Zn. The radioisotope was found in levels above background in shoreline swarms of adult caddis flies as far as 16 km above the uppermost reactor effluent. Whether movement was only upstream and the precise distances flown remain unclear. The upstream movement is important for understanding the biology of riverine aquatic insects and for evaluating the upstream dispersal of radioactive contaminants.