A Salmonfly Mystery

It's like something out of the X-Files: The salmonflies in the Logan River have disappeared. The Logan, which flows through northern Utah, once held an abundant population of the big stoneflies (Pteronarcys californica and Pteronarcella badi), but in the late 1970's they completely disappeared. In fact, not a single salmonfly has been seen on the Logan in nearly 30 years and no one knows why.

Everything about the Logan says the huge bugs should be present: Water quality on the river is good, there's abundant salmonfly habitat--and perhaps most puzzling--the Blacksmith Fork, a nearby tributary, has a strong salmonfly population. So why not the Logan?

A group of anglers and scientists has been trying to answer this question for several years without any conclusion. Some speculate that the salmonflies were killed by herbicide that washed into the river or by runoff from chemicals used to remove snow and ice from the roads. Others invoke alien abduction (OK, not really).

While they continue to search for a cause, volunteers from the Cache Anglers, Utah Trout Unlimited and Utah State University's BugLab have begun a one-of-kind project: Stocking the Logan with salmonflies.

The project is now in its third year, and volunteers recently collected 2,000 salmonfly nymphs from the Blacksmith Fork and stocked them in the Logan. So far results have been mixed: emergences of adult salmonflies--from planted nymphs--have been documented, but so far there is no evidence of reproduction.

Ultimately, the goal is to create a self-sustaining population that could one day lead to the return of the abundant hatches that the river once knew.

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