Shadows dart back and forth in the cold, clear stream here in the mountains high above the Sipapu ski valley.

They're native cutthroat trout, and their purity and abundance in Alamitos Creek could be essential to the survival of the threatened species.

That's why the Truchas Chapter of Trout Unlimited is spearheading an effort to build a barrier to protect the population of 4,000 to 5,000 pure strain Rio Grande cutthroats living in about seven miles of the remote creek.

"They may be one of the best allies the cutthroat has," said Juan Martinez, fisheries biologist for the Carson National Forest. "They're instrumental in getting projects like this done."

Because of budget restrictions, manpower limitations and the nature of the federal bureaucracy, such a project could take years for the Forest Service to implement, Martinez said.

But with assistance from the local Trout Unlimited chapter, money has already been secured to pay for an environmental analysis this winter and possible construction of the barrier next summer.

"This is a beneficial project with minimal environmental impact so it shouldn't be a problem," said Martinez, a Taos native with a fisheries and wildlife sciences degree from New Mexico State University.

A concrete fish barrier on the stream would prevent other non-native trout such as brown or rainbow trout from infiltrating the stream and taking over the habitat.

Alamitos Creek links up with the Rio Pueblo, which flows through Peñasco and on down to the Rio Grande.

For years, an aging head gate on an irrigation ditch has helped keep invading trout from moving upstream into cutthroat habitat, but a new barrier is needed to guarantee that doesn't happen.

The pure strain cutthroats in Alamitos Creek could then provide an infusion of life for other cutthroat streams such as Comanche Creek in Valle Vidal, where an ambitious cutthroat restoration project is under way, said Kirk Patten, a fisheries biologist with the state Department of Game and Fish.

Comanche Creek will undergo a second attempt at sterilization this summer to eliminate any non-native fish that remained in about 20 miles of stream after an initial treatment last summer.

Game and Fish then hopes to restock the creek and its tributaries by next summer with pure-strain Rio Grande cutthroats.

The overall plan is to return about 120 to 150 miles of water within the Valle Vidal watershed to exclusive cutthroat habitat.

The Rio Grande cutthroat is the state's native fish but has seen its historic range reduced to just 10 percent with only 13 core populations left in the state, Patten said.

The colorful trout at one time ranged throughout the entire Rio Grande, Pecos and Canadian rivers watershed area, covering about 6,600 miles of water in southern Colorado and Northern New Mexico, said Patten.

The population of pure strain cutthroats in Alamitos Creek could prove invaluable in helping the native trout recover. "It's very important to the overall status of the restoration effort," he said.

Eggs from Alamitos Creek cutthroats can be used to raise fry at the state's exclusive cutthroat hatchery at Seven Springs for eventual restocking in other rivers, creeks and streams. Some of the cutthroats can also join others stored at McClure Reservoir above Santa Fe to be used as brood stock for future breeding applications.

And others could be directly transplanted into a cutthroat stream to mingle with a resident population and increase genetic diversity, Patten said.

Patten, who coordinates the state's Rio Grande Cutthroat Recovery Project, agrees that without the help of organizations such as Trout Unlimited some of the recovery project's goals might be hampered. "We're financially challenged on some of these projects," he said. "It's a big help to have them come up with funds for this."

Arnold Atkins, current president of the Truchas Chapter of Trout Unlimited, said the Alamitos Creek barrier would be the second for which the organization has raised funds.

The group helped raised $100,000 needed to construct a new fish barrier on Comanche Creek on Forest Road 1950 near the confluence of Little Costilla Creek last year.

That barrier will keep non-native fish in the Costilla Creek watershed from migrating upstream into the cutthroat restoration area.

Then work started on Alamitos Creek.

"This may be one of the largest populations of pure strain cutthroats in the state," said Atkins, a semiretired surgeon who grew up in the Española Valley and graduated from Los Alamos High School in 1960. "This was something that could do the most good in the shortest period of time, so we got on it."

The group raised about $7,000 from members and an annual fundraiser banquet. Then it secured another $3,000 from a sister chapter in Austin, Texas, Atkins said. The $10,000 should cover the project's environmental analysis.

The organization's Truchas chapter, in conjunction with the Forest Service and state Game and Fish Department, applied for and received a $50,000 grant from the Western Native Trout Initiative for the barrier's construction.

The estimated cost of construction is $70,000 to $80,000, Atkins said.

The National Fish and Wildlife Federation also kicked in a matching grant of $10,000 and offered to pay chapter members an hourly wage for any work done on the project, Atkins said.

Anyone interested in contributing to the cause can contact the organization through its Web site at www.truchas-tu.org.

Contact Karl Moffatt through his blog at www.outdoorsnewmexico.com">www.outdoorsnewmexico.com.