Musseling Down The Owyhee River


OWYHEE RIVER — The 280-mile-long Owyhee River cuts a series of breathtaking canyons through extreme Southeast Oregon on its journey from Northeast Nevada to where it joins the Snake River near Nyssa, Oregon.

The Owyhee is exceedingly remote, and yet it has served as a home for Native Americans for thousands of years. Later there were fur trappers, then gold miners and then settlers keen on making a life in the desert.

And the Owyhee is home to a menagerie of creatures like bats, otters, bugs, fish, deer, elk and Bighorn sheep.

Also freshwater mussels.

These largely unknown and misunderstood shellfish, which evolved with migrating fish to be able to better move up into a river system, inhabit many Oregon waterbodies, including the Owyhee River.

Freshwater mussels are a type of bivalve mollusk, according to Emilie Blevins, Senior Conservation Biologist with the Xerces Society, a non-profit environmental organization that focuses on invertebrates, or critters that do not have a backbone, and they provide really important ecological functions like cleaning water by filtering it, providing food for other species, including fish and other macroinvertebrates that fish eat.

A live Western ridged mussel.

In other words, freshwater mussels are extremely important to our lake and stream ecologies here in Oregon and around the world.

But their populations are decreasing, and that’s a really big deal. Enough so that Xerces Society’s Emilie Blevins partnered with Oregon Department of Fish and Wildlife’s Southeast District Fish Biologist Dave Banks on a quest to float fifty miles of the Owyhee River to search for them.

For Blevins, the quest was about looking into reports of large mussel die-offs and to determine the overall health of the populations there, while Banks wanted to see if there were any redband trout, a particularly desert-adapted trout, along a fifty-mile stretch of the river that mussels may be using to hitch a ride upstream.

Certain freshwater mussels, including female Western Pearlshell mussels, will wait for passing fish to swim over before they release their glochidia, or parasitic larva, to attach to those fish. For the small price of a little blood from the fish, the young mussels could hitch a ride upstream to new habitat. This is how they spread out, and this is a relationship that is as old as these species are.

“We thought maybe if we could identify some of these mussel beds where some of these Western Pearlshells were, we might be able to say maybe that’s where redband trout are spawning and go back and do some other type of research that would verify that,” Banks said.

Joining Blevins and Banks at the put-in site in Rome, Oregon were ODFW Assistant District Fish Biologist Kirk Handley and Xerces Society’s Emma Pelton, the Western Monarch Lead, who was along to help look for mussels as well as to document Monarch butterflies along the way.

The journey began with a quick search for mussels at the put-in point, to document some historical sightings there, before all five rafts were loaded, and we proceeded downstream.

“… freshwater mussels are extremely important to our lake and stream ecologies here in Oregon, and around the world.”

The rhyolite walls of the canyon made us go silent as we floated through time, and the swirling madness of the cooled lava could make you dizzy for a moment until you looked back at the swirling madness of the water on which you traveled.

The Owyhee River

The Owyhee River is a bit like a time machine. In fact, with every river mile traveled, you move 100,000 years further back in time geologically.

The rocks at the put-in point are roughly 10 million years old, while the rocks at the take-out area are closer to 16 million years old. Moving through the strata is a short one in geological terms but fascinating coming from the perspective of a human, whose entire species’ life history is but a fraction of a moment on that timeline.

The Owyhee plateau is a fairly young, again by geological terms, volcanic area. A river doing what rivers do, cutting into rock and finding the easiest possible way down hill, is the vehicle for this story.

But a glossary of this story, if you’ll forgive me, is the ancient lake that characterized the region since at least the Miocene epoch (20-5 million years ago) if not earlier.

Between the layers of volcanic activity are smaller layers of gravel, or old lake shorelines.

Emilie Blevins, of Xerces Society, studies the shell of a Western Ridged freshwater mussel in the Owyhee River.

And petrified bones of the mammals that existed in the region since the ancient lake formed.

The otters we see along the river are resourceful critters, carving a life out of a very inhospitable place. In fact, the otters and their middens full of shells, or eating areas, are often the most visible clues we need in our search for freshwater mussels.

Otter fossils dating back to the Miocene age suggest they have been living the otter life on the Owyhee River for a very long time, likely subsisting off the constantly replenishing cycle of freshwater mussels, among other food sources.

The otters are still there, and we see them gliding through the water occasionally. Eventually we stumble on their eating areas, known as middens, and we search through them looking for evidence of different age classes of mussels.

Up until this point, we have found full-size Western Ridged mussels at various points in the river, but they were all adults, which can live to be 60-years-old or older.

The otter middens were full of smaller shells though, indicating a younger age class, and on a day of fighting through some strong rapids in search of our quarry, this was an encouraging sign.

The journey continues…

After twenty river miles, which seem longer than highway miles, we have a system established, and we travel in pairs or individually looking hard at the bottom for little hints of white on the shells, but we focus on the best kinds of habitat. For freshwater mussels, this is a cobbled or hard river bottom, where they can wedge themselves between rocks or burrow down into the substrate. Silted in areas or those scoured out by floods are not good for finding intact mussels. Their shells are everywhere though.

Some parts of the Owyhee River require hand-lining the boats down dangerous rapids when the flows are low.

By forty river miles, our arms are sore from paddling, our belonging soaked from numerous plunges into the water courtesy of awkwardly placed rocks and the hydraulics of the river, which act like gravity only horizontally rather than the more vertical impacts we are used to as land-based creatures.

Near the end of our five-day journey through time, we have found evidence of healthy, growing populations of freshwater mussels. We have also found sick mussels, which we collect in towels doused in cold water to take back with us for analysis at the lab. We have documented one redband trout in a river that likely used to teem with them.

We paddled up to the takeout at Birch Creek thoroughly exhausted but more knowledgeable about a part of Oregon that is rarely seen or experienced at that time of year. The biologists had a better understanding of the distribution of freshwater mussels for future comparisons as well as some samples to hopefully shed some light on what’s making freshwater mussels sick and what, if anything, can be done about it.

Partnerships for the betterment of Oregon’s wildlife

Partnerships like the one between Oregon Department of Fish and Wildlife biologists and Xerces Society biologists are important, because each agency has something the other needs for the betterment of Oregon’s wildlife. Whether it’s knowledge of an area or a specific animal, like freshwater mussels, they often rely on each other to observe, collect data or get to hard-to-reach places to better understand and therefore protect Oregon’s fish and wildlife.

The long road out of Birch Creek up to the high plateau above is a good time for reflection on the beauty we are leaving behind and the value of scientific exploration. Three-hours later, and we arrive where it all began, roughly six million years earlier, geologically speaking, and about as far from anywhere as you can be in Rome, Oregon.

About Author

Tim Akimoff is the Social Media Outreach Coordinator for the Oregon Department of Fish and Wildlife.

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