Coho salmon that once called mid-Columbia River tributaries home were decimated in the early 1900s.

And pre-1990s attempts to rekindle populations with hatchery programs were ended because of a failure to produce adequate adult returns.

But one of the latest attempts, led by the Yakama Nation, is showing signs of not only succeeding, but of creating self-sustaining natural populations like those that once flourished in the region.

This past late summer and fall set a modern-day record for coho returns headed to the middle and upper Columbia River, where once there were none. Ten years ago, 12 adult coho returned past Rock Island Dam near Wenatchee, Wash. And that followed a six-year stretch during which only 30 coho, total, climbed Rock Island's fish ladders.

But, in 2000 (1,624 coho counted) and 2001 (10,465), returns began to show the benefits of the YN's Mid-Columbia Coho Restoration Project, which was launched in 1996. Since then the counts have, for the most part, been on the rise.

In 2009 a total of 19,805 coho passed the dam. That was the most ever since counts began in 1977. The previous record was 16,604 in 2007, according to data posted by the Fish Passage Center. Prior to 2001, the highest count had been 1,624 in 1982.

Rock Island is the seventh dam the coho hurdle on their return to the Wenatchee and Methow river basins where the tribal restoration plan is focused. The program is funded by the Bonneville Power Administration, Chelan County Public Utility District, Grant County Public Utility District and NOAA-Fisheries.

"It's gone beyond our expectations," the Yakama Nation's Tom Scribner said of the growing returns and the progress toward developing local broodstock and, ultimately, shutting down the hatchery program when naturally producing populations have become entrenched.

The program is designed to be terminated when a self-sustaining naturally reproducing population is established (natural-origin return escapement of more than 1,500 coho to each subbasin with enough fish available to allow terminal and mainstem harvests in most years). Those involved believe that goal can be reached when coho of hatchery origin have produced five generations in the wild (by approximately 2026).

Scribner, the project manager, said that already a third generation of fish has returned to the Wenatchee to spawn.

The program was started with hatchery-bred fish from the lower Columbia, since no local coho adapted to the mid- Columbia remained.

The early years of the program – when it was called the Mid-Columbia Coho Reintroduction Feasibility Study -- were used to determine whether lower river stocks, some of which had been hatchery bound for many generations, had the stamina to make the long trip upstream and spawn successfully.

"There was a question whether it was really possible to do this so far above the dams," said Roy Beaty, BPA's project manager for upper Columbia coho restoration. "We really didn't know whether the fish could swim that far."

The coho are still hatched and reared elsewhere, but by 2006 the program had reached the point that 100 percent of the coho smolts released in both basins were the progeny of second-generation mid-Columbia broodstock that returned to spawn in the wild.

"We knew how important it was to develop a local broodstock," Scribner said.

About 1.1 million coho smolts are transferred from Willard National Fish hatchery and the Oregon Department of Fish and Wildlife's Cascade Hatchery annually for acclimation at multiple locations in the Wenatchee area, including Leavenworth Hatchery, Winthrop, Rolfing Pond, Beaver Creek acclimation pond and Coulter pond. A unique feature of the ponds is that they are semi-natural, taking advantage of off-channel backwaters.

The adaptation -- making the switch from a lower river hatchery lifestyle to one that starts and finishes in the wild -- is taking place before the biologists' eyes. Scribner said the egg-to-smolt, and smolt-to-adult return survival data from the second generation spawners is comparable to other steelhead and chinook supplementation programs in the mid-Columbia region, many of which now rely on local-origin broodstock.

"It's looking very good. We're comparable to other programs up there," Scribner said.

Mid-Columbia coho salmon populations were decimated in the early 1900s as a result of the construction of impassable dams, harmful forestry practices and unscreened irrigation diversions in the tributaries, along with an extremely high harvest rate in the lower Columbia River, according to the a project description.

The loss of natural stream flow degraded habitat quality and further reduced coho productivity. Over the years, irrigation, livestock grazing, mining, timber harvest, road and railroad construction, development, and fire management also contributed to destruction of salmon habitat.

By the end of the 20th century, no indigenous, natural coho salmon, and very few hatchery fish, remained. A Turtle Rock Hatchery program, which annually produced about 600,000 coho smolts, was terminated in 1994 because of poor returns.

Self-sustaining coho populations were not established in mid-Columbia basins despite plantings of 46 million fry, fingerlings, and smolts from Leavenworth, Entiat, and Winthrop National fish hatcheries between 1942 and 1975.

The failures in part were due to hatchery rearing at high densities in concrete raceways, an incomplete understanding of fish health and nutritional needs, the use of water supplies with unnatural temperature profiles, and unacclimated, non-volitional releases directly from hatcheries into the wild environment produced smolts with low survival rates, Yakama Nation biologists reasoned.

The Yakama program aims to remedy two of the suspected causes of the failures – the absence of locally adapted broodstock and in-basin habitat degradation. The reintroduction program is being carried out in parallel with habitat restoration efforts by the tribe and others.

Upriver coho did not receive protection under the Endangered Species Act, since none were left to protect. That left earlier coho programs as lower priority than programs for other salmonid species.

"Coho are a kind of Rodney Dangerfield of the Columbia River anadromous fish world -- they don't get much respect," said Nancy Weintraub, a BPA project manager who works on coho. "It's great to see them succeed."