Two electronic thermometers hidden along a channelized stretch of Larson Creek could help determine whether east Medford's most visible urban stream could get a green makeover to benefit wild salmon.

Two electronic thermometers hidden along a channelized stretch of Larson Creek could help determine whether east Medford's most visible urban stream could get a green makeover to benefit wild salmon.

The thermometers are tracking whether the creek's concrete bed and banks between Olympic Street and Murphy Road are helping raise water temperatures enough that they leave it unfriendly to young wild salmon and steelhead known to grow there.

Common sense may seem like it's a no-brainer: Creek stretches exposed to sunlight are warmer than those shaded by overhanging trees.

"It all depends upon what that magic factor is, and the hypothesis is that shade would help," says Chuck Fustish, an Oregon Department of Fish and Wildlife fisheries biologist who works on improving urban stream habitat in the Bear Creek basin.

Fustish is in the midst of a two-month study of the creek's temperature changes when it flows from the shady confines east of Olympic Street through the concrete channel and past Murphy Road to another stretch of well-shaded banks.

If the difference proves significant, Fustish could join with Medford city officials to ring that hot zone with shade-producing willows and cedars.

It all depends on the data collected hourly on the electronic thermometers hidden in the creek.

"We're always looking at ways to improve the habitat in Larson Creek," Fustish says. "If a lack of shade's the problem, planting trees is a possible solution. But we have to see if there's a problem first."

This temperature test is the latest in a series of Larson Creek improvements spearheaded by city and state agencies as well as students from St. Mary's School interested in improving backyard salmon habitats in Medford neighborhoods.

Recent trapping surveys reveal that Larson Creek at times holds hundreds of wild juvenile coho salmon, which are protected as a threatened species under the federal Endangered Species Act. Other times, it serves as spawning ground for wild steelhead and even large chinook salmon that venture in from Bear Creek.

The mere thought of helping bring fish back to her neighborhood stream delights Gracie Hailey-Callahan enough that she's signed on with Fustish to help in any monitoring efforts.

"I've never seen fish in here, and I've lived here three years," says Hailey-Callahan, whose Olympic Street house borders the creek. "We love this creek, and we'd love to see fish in here."

Research has shown that infant salmon and steelhead venture throughout the Bear Creek basin at varying times in search of the best water available.

In winter, that means darting into smaller tributaries to avoid Bear Creek's roiling waves and tumbling cobblestones during a storm. In summer, that often means searching for the coolest, cleanest water they can find.

Cooler water usually means infant salmon are less stressed, allowing more of their energy to go toward needed growth instead of mere survival.

On Larson Creek, the assumption is that the concrete canal works much like a pizza stone in an oven.

The concrete absorbs sunlight at higher rates than dirt or sand. The warming concrete in turn transfers that heat to the water flowing over it.

"There's no shade here, so you have to figure that's a possibility," Fustish says.

While the computer thermometers have been in the creek about two weeks, Fustish ventured there Friday to use an old hand-held thermometer to take water temperatures himself. Those readings will be used to help verify the computer information once the thermometers are pulled.

"Every time you do a study like this, you have to verify the data is accurate," he says.

If tree planting is the solution, then tending those new trees would be required. Willows, cedars and other shade trees must get regular doses of water for up to two years while the seedlings develop root systems that reach the water table.

"I've seen many, many plantings on Bear Creek that failed because there wasn't any water provided," Fustish says.

Also, any seedlings need deep watering to encourage downward root growth. Shallow watering can entice roots to grow toward the surface, leading to eventual tree failure.

Another option to make this stretch more fish-friendly is placing root wads or piles of wood in stretches. The obstacles would help slow water down and provide spots for young fish to hide and feed.

But that's not a solid option within city limits, where Larson Creek also works as a storm drain to carry runoff away from backyards and into Bear Creek. So the channel needs to remain clear of debris, Fustish says.

"We can't go willy-nilly like we can in the woods, putting piles of wood all over the place to make good habitat," Fustish says. "We have constraints when working within cities. It's a lot tougher than working in the woods."

Reach reporter Mark Freeman at 776-4470, or e-mail mfreeman@mailtribune.com.