The Xerces Society and the Johnson Creek Watershed Council lead a survey of the creek for mysterious bivalve-shelled mollusks

By: Jaime Dunkle, Special to The Oregonian
July 29, 2011

Celeste Mazzacano describes the single valve, or half of a shell, found in Johnson Creek at the Gresham Woods survey site on Saturday, July 16.

Johnson Creek is home to a secret treasure. Unbeknownst to many Oregonians, freshwater mussels find solace in different parts of the stream, settling silently among the crayfish and rocks.

A single mussel is capable of filtering up to 18 gallons of water a day, and some mussels live for more than a 100 years. But pollution and stream alterations from urban development can disrupt mussel habitat.

Knowing the distribution of freshwater mussels in Johnson Creek provides clues to both the overall biological condition of the stream and the native fish needed as hosts by larval mussels, says Celeste Mazzacano, aquatic program director of the Xerces Society for Invertebrate Conservation. To that end, next Saturday the Xerces Society and the Johnson Creek Watershed Council lead a survey of the creek for these mysterious bivalve-shelled mollusks. It’s open to all.

“None of our mussels are on the endangered species list, but the Oregon Department of Fish and Wildlife has recognized that they are declining,” Mazzacano said.

During the survey, mussels will be observed purely for research; no one will be snacking on them or keeping them as pets.

“As part of this project, I have a Scientific Take permit,” said Mazzacano. “We’re handling them long enough to measure the shells.”

Wading through the calm creek waters in search of shell life is not just for adults; children are also welcome to participate.

Steve Scannell, a science teacher at Gresham High School, brought his two children to a survey at Gresham Woods last Saturday for their first biological trip. His 5-year-old son, Nathaniel, and his 8-year-old daughter, Rachel, both enthusiastically searched through the shallow creek.

“It’s great to be out in nature,” Scannell said, “It is nice to do some science. We actually found some mussels.”

Robin Cody lives in Portland on Johnson Creek. His first time surveying mussels also was last Saturday at the Gresham Woods sight.

“I grew up around these streams. I didn’t even know we had freshwater mussels,” Cody said, “We grew up playing in these streams searching for crawdads and fishing for trout; we had no idea these guys were here.”

Volunteers can expect the survey to last from 10 a.m. until 1:30 p.m., which includes a 30-minute onsite orientation. Long tubes for viewing mussels, referred to as aqua lens, will be provided to study the water thoroughly.

For more information about the upcoming freshwater mussel survey, contact Amy Lodholz at or call 503-652-7477.

Read the article in The Oregonian