The Logan River June Bug on Wild About Utah

Mar 17, 2017

“Darling, I’m having a struggle with the trout. They are too much for me in the swift, rushing river. I lose ‘em. Went out yesterday… and lost two—one a large fish. The ‘June Bugs’ – a red bodied insect, as big as the biggest grasshopper you ever saw, fall from the leaves on to the river and are such large juicy mouthfuls that the trout have abundant food, and don’t care much for a fly."

That is an excerpt from a letter from U.S. historian and novice fly angler Frederick Jackson Turner. He was writing to his wife Caroline Mae on June 20, 1924, while visiting Utah Agricultural College in Logan. Turner didn’t know it at the time, but the large red-bodied “June Bugs” were actually salmonflies, a prehistoric-looking stonefly from the genus Pteronarcys. Turner was also unaware that his letter would become the earliest written record showing that salmonflies were once abundant in the Logan River.

Salmonflies are a type of large stonefly that live in many western rivers and are often called “rock rollers” or “shredders” because they hide under boulders and gorge themselves on leaf litter until early summer when they crawl out from under the rocks, shed their exoskeleton, and clumsily fly around hoping to bump into a mate. These bugs love cold, clean, oxygenated water, all of which are hallmarks of the Logan River. Existing records show that salmonflies were well established on the Logan River until at least 1951, after which time something wiped them out. The last time anyone saw a Pteronarcys on the Logan River was September 7, 1966, near Mendon Bridge.

In 2001, the “Disappearance of the Salmonflies,” as it’s now known among bug enthusiasts, sparked the curiosity of Mark Vinson, former director of the Utah State University National Aquatic Monitoring Center, aka the “USU Bug Lab.” Vinson decided to compare the Logan River to nearby Blacksmith Fork River, which continues to support a healthy population of salmonflies. Vinson observed that the absence of salmonflies in the Logan River was one of the few differences between the invertebrate faunas in the two streams. He studied discharge and water temperature regimes between the two and found they were also similar and had not changed since the 1960s. He wrote, “Overall, the Logan River within Logan Canyon remains a beautiful stream and habitat, and water quality conditions have not changed much since 1960, at least not enough to prevent salmonflies from living in the river.” To test his observations Vinson decided to try and recolonize the Logan River with salmonflies from the Blacksmith Fork River. Between 2004 and 2007 volunteers relocated thousands of salmonflies in the hope they would once again call the Logan River home.  Out of the thousands of immigrant stoneflies, Vinson only found two that survived longer than one year. The massive relocation effort was a bust, and proved that there was still something about the Logan River that these critters didn’t like.

Each semester, watershed science students at Utah State University don leaky waders and wander up Logan Canyon to conduct aquatic invertebrate sampling. I was once one of those bright-eyed students, standing in the Logan River with a kick-net and dreams of finding the long-lost Pteronarcys. I never found one. Over the years, researchers have ruled out obvious factors like water quality, stream temperature, or habitat, that might limit salmonfly reproduction on the Logan River. Chemical spills and sagebrush abatement in Logan Canyon during the 1950s may have originally contributed to the bugs’ demise, but doesn’t explain why they can’t survive for long in the river today. Of course, anglers have their own ideas about what going on, including tales of a giant Sasquatch urinating in the river somewhere near Rick’s Spring.

Even today the plot thickens. Continued aquatic invertebrate sampling by the Bug Lab has shown that salmonflies are also absent from Left Hand Fork of Blacksmith Fork River as well as upper Rock Creek. Incredibly, both of these streams are tributaries to the main stem Blacksmith Fork River, which is full of salmonflies. This anomaly has everyone scratching their heads. All anyone can say for certain is that some variable, biotic or abiotic, or possibly even “Sasquatch-iotic” is keeping salmonflies from populating these two tributaries. Could it be the same variable that’s keeping Frederick Jackson Turner’s “June Bugs” from reclaiming the Logan River? The answer to this question, along with whether Turner ever did land a trout, has yet to be answered.