The Stream Doctor

August 30th, 2004

Email YOUR Questions directly to the Stream Doctor. This is your opportunity to get an experts professional opinion on anything stream related.

Q. We recently fished a northern Va stream for trout in Hot Springs (The Homestead), and caught many natives, rainbows, and browns. We kept a couple rainbows for the table and upon cleaning them we realized that they were eating a hard, small type of snail looking thing that was attached to the rocks in the area. All the fish were thin but very healthy and active. What are these snail cone looking things and do trout normally eat them? Thank You.

A. It sounds very much like the trout were feeding on a small, cased caddisfly larva of the genus Helicopsyche. It constructs its case from sand grains or rock fragments and builds it in a coiled spiral that resembles a snail shell. In fact, it was mistaken for a snail for sometime until someone looked at it closely and discovered that it was a caddisfly, not a mollusk. Helicopsyche is the only genus of the family Helicopsychidae that occurs in North America. Trout readily feed on these and other cased caddisfly larvae.

To be doubly sure, I contacted two colleagues at Virginia Tech to verify that this organism is present in VA streams; one verified that it occurs throughout western VA so is probably also in the northern part of the state. The second said that he has also found trout gorged on true snails, but from your description it doesn't sound like they are molluscs.

If you have a question, please feel free to contact me.
~ C. E. (Bert) Cushing, aka Streamdoctor
105 W. Cherokee Dr.
Estes Park, CO 80517
Phone: 970-577-1584

The 'Stream Doctor' is a retired professional stream ecologist and author, now living in the West and spending way too much time fly-fishing. You are invited to submit questions relating to anything stream related directly to him for use in this Q & A Feature at

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