During a summer survey identifying fresh water mussel species in Johnson Creek, a stunning discovery was made.

A few large beds of native western pearlshell mussels were reported in Johnson Creek above Gresham. And smaller numbers were found as far downstream as Tideman-Johnson Park in Ardenwald.

It was an exciting find, explained Johnson Creek Watershed Council Restoration Coordinator Robin Jenkinson, because “freshwater mussels are arguably the most imperiled animal species of all in North America”.

Serving as food for river otters and fish, beds of fresh water mussels also help filter water, and improve water quality.

“So we wanted to know more about where these mussels were,” Jenkinson explained.

In the following summers of 2011 and 2012, eighty of Johnson Creek Watershed Council's trained volunteers scanned Johnson Creek and its tributaries, including Crystal Springs Creek, searching for western pearlshells and Oregon floaters, the two freshwater mussel species native to the area.

They were also on the lookout for the invasive Asian clam. It's called the “prosperity clam” in its native Southeast Asia, but in the United States the Asian clam is a costly invasive species that eats the larvae of native freshwater mussels, displaces them, develops rapidly, and overpopulates waterways. It survives in more polluted warmer water and emits a destructive ammonia plume when a cluster of them dies off.

Surprisingly, volunteers did find a dense population of Asian clams – not in Johnson Creek, but in Crystal Springs Creek. “We wondered, why are there so many Asian clams in Crystal Springs Creek?” Jenkinson recalled.

Fortunately, Crystal Springs Lake and Creek in Reed Canyon still don’t have Asian clams, reported Reed College's Canyon Restoration Specialist and Naturalist, Zac Perry. “Most of them are down below Westmoreland Park,” Perry said.

A member of the Crystal Springs Partnership, Perry manages the headwaters and the part of Crystal Springs Creek located on Reed College campus. The Crystal Springs Partnership consists of community, civic, and agency groups and individuals, working to improve the Crystal Springs Watershed. Another member, volunteer Patrick Norton of the Lents neighborhood, is an artist and science illustrator who runs the partnership’s website.

Near Johnson Creek Park, at the confluence of Crystal Springs Creek and Johnson Creek, Asian clams are thriving at that location. Norton suggests that may be because the water there is warmer, and more polluted with waterfowl waste, thanks in part to the water streaming in from the Westmoreland Park duck pond, which is soon to be removed.

“You can see the Asian clams if you go down to Johnson Creek Park and look down below the bridge,” Norton said.

A study could shed light on ways to keep Asian clams from populating Crystal Springs Creek. Currently, Norton is recruiting volunteers for additional mussel surveys along Crystal Springs Creek. The surveys are part of an “Xerces Society for Invertebrate Conservation” study, which has two parts that require volunteers.

Before the in-stream work begins to restore Westmoreland Park's duck pond back to being a natural creek, volunteers are needed on July 7 and 8 to salvage as many native mussels as possible that may be in the Westmoreland Park duck pond. Wading in the shallow water, some volunteers will be outfitted with viewing tubes and nets to locate and remove the mussels.

The mussels will then need to be tagged. Rescued mussels will be placed in coolers and transported to other, safer parts of Crystal Springs Creek, where volunteers will return them to the creek bottom.

Later in the summer, volunteers are also needed to survey Crystal Springs Creek, looking for native mussels and the pesky Asian clams.

“The experimental question is what effect do these restoration efforts designed to help native salmon have on native mussels and on Asian clams,” Norton said.

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