Sockeye salmon will be in the spotlight Tuesday when Idaho Gov. C.L. "Butch" Otter takes part in two special events marking Idaho's largest sockeye run in more than three decades.

First, the governor and Idaho Fish and Game Director Cal Groen will release more than 30 adult sockeye into Redfish Lake to spawn naturally. The release will take place at 9 a.m. at the boat ramp on the east side of the lake.

The adult fish are, most likely, the product of the IDFG's Idaho Sockeye Captive Broodstock Program. With the run to central Idaho's Sawtooth Valley faltering severely, the program was begun in 1991 to preserve the genetic stock. The ultimate goal is to revive a sockeye run that is the most imperiled in the Columbia River basin.

The program has been rewarded this year with the largest return to the valley since at least 1975. Through Wednesday 889 sockeye had been counted as they hurdled fish ladders at Lower Granite Dam on the lower Snake River. That's about 400 river miles downstream from their Sawtooth Valley origins.

The most sockeye ever counted previously at the dam was 531 in 1976, the year after the dam was completed. Only seven annual counts since then have exceeded 100 fish. Upon returning to freshwater to spawn, the Snake River sockeye must swim 900 miles up the Columbia, Snake and Salmon rivers and pass eight hydro projects along the way.

By Tuesday 530 of the sockeye had completed their journey. A total of 337 of the spawners have been trapped at Redfish Lake Creek and another 193 at Sawtooth Hatchery. The highest previous return to the program was a surprising 257 in 2000; next best was 27 anadromous sockeye salmon returns to the Sawtooth Valley in 2004.

This reason for this year's bounty is uncertain. The fish may have benefited from favorable river conditions during their journey to the ocean as juveniles, and on their return as adults. And good ocean conditions may have enabled better survival during their two-year ocean sojourn. Federal officials say recent improvements to the hydroelectric dams on the Snake and Columbia rivers have produced increased survival of juvenile salmon heading downstream to the Pacific Ocean.

"Juvenile fish-passage survival at mainstem dams has improved and will improve even more," said Rock Peters, a senior fish biologist for the U.S. Army Corps of Engineers Northwestern Division.

The Snake River sockeye returns this year are mostly fish that were released as smolts in 2006 from Sawtooth Hatchery (39,622) and in Redfish Lake Creek (46,430). The smolts were the product of the captive broodstock program, some reared to that migration-ready stage at Sawtooth and some reared at the Oregon Department of Fish and Wildlife's Oxbow Hatchery at Cascade Locks. About 100,000 smolts were released in 2007, some of which could be returning now as 3-year-old jacks.

Of the returning fish so far this year, 283 are believed to be from the Redfish Lake Creek smolt releases and 98 from the Sawtooth hatchery releases. The fish are identified on their return by fin clips and research tags.

This year's return includes 130 unmarked sockeye so far. They originated from adult spawners released into Redfish Lake, "residual sockeye," or fertilized eggs that were planted in nearby Alturus or Pettit Lakes. Residual sockeye are resident fish whose progeny can take up an anadromous or ocean-going life style.

The sockeye continue to stream into the high country. There were 23 trapped Tuesday. The first sockeye was counted at Lower Granite June 25. The first was trapped a month later at Sawtooth Fish Hatchery.

Most of this year's return passed Lower Granite during the first half of July but a thin stream continues. A single sockeye was counted Tuesday at the dam.

The trapped fish are hauled to Eagle Hatchery near Boise. Some will be spawned in the hatchery; others will be released into Redfish Lake and perhaps other high country lakes to spawn. Tuesday's release will be the first of the year.

Later Tuesday morning the governor will celebrate the opening of a new state-of-the-art sockeye spawning facility at Eagle Fish Hatchery near Boise, part of the Redfish Lake sockeye recovery effort led by the IDFG and the Shoshone-Bannock Tribes.

Otter will join officials from IDFG, the tribes, Bonneville Power Administration and NOAA Fisheries Service at Eagle Fish Hatchery, 1800 S. Trout Road in Eagle, to cut the ribbon on the expanded facility. It is designed to double the capacity of the captive breeding program to further jumpstart the recovery of Idaho's sockeye salmon.

BPA funded the hatchery expansion as part of its responsibility to mitigate for fish and wildlife impacts caused by the Columbia/Snake river hydro system and obligations under the ESA. The agency markets power generated in the federal hydro system. NOAA is responsible under the ESA for protecting anadromous fish stocks and is directly involved in the captive broodstock program, raising adult broodstock at its Manchester facilities in Washington.

Sockeye salmon counts at Bonneville Dam overall this year are close to 213,600, almost four times higher than the 10-year average for this species. Most of those fish are bound for the Wenatchee and Okanagan river basins in central Washington. Bonneville is the first hydro project the fish encounter on their way upriver.

As for what's ahead, biologists say that ocean conditions will always exercise a powerful influence over the salmon's life cycle. According to John Ferguson, a senior biologist with NOAA Fisheries, surveys this year show "very productive" ocean conditions north of Newport, Ore., as well as indicators of very high numbers of juvenile salmon in the ocean -- some of the highest numbers ever seen.

There is a strong correlation between high juvenile numbers and good salmon returns in future years, according to Ferguson. The fish NOAA sampled offshore this year include coho that will return next year and spring chinook that will return in 2010. There were 150,000 Snake River sockeye smolts released in May, which was the largest release yet for the program.