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Snake River Supplementation Project Shows Promise

by Barry Espenson
Columbia Basin Bulletin - October 20, 2000

Improved ocean and in-river migrating conditions in the past year or two have added momentum to efforts intended to boost natural production of Snake River fall chinook above Lower Granite Dam.

A test of hatchery supplementation using the only Snake River basin fall chinook stock in the Northwest reaped benefits last year and this. Combined spawner escapement past Lower Granite Dam in 1999 was estimated at 1,862 fish, including an estimated 905 Snake River "wild" fall chinook, a stock listed as threatened in 1992 under the Endangered Species Act, and a like number of supplementation returns.

In all, 3,381 adult fall chinook reached the dam last year. Of that total, 1,519 marked hatchery adults were trapped and returned to Lyons Ferry Hatchery, where they had been reared and released as yearlings.

The supplementation program's contribution to 1999 Lower Granite escapement could have been greater, according to David Johnson, Nez Perce Tribe production coordinator. He estimated as many as 400 of the fish trapped and hauled back to Lyons Ferry were supplementation fish that were either misidentified or had lost their identifying mark.

The Lyons Ferry facility, located on the Snake River between Little Goose and Lower Monumental dams, has since 1977 served as an egg bank for the unique fall chinook stock. The original eggs were taken from fish trapped at Ice Harbor Dam, according to Bob Foster of the Washington Department of Fish and Wildlife, which operates the hatchery.

Similar return numbers have been achieved this year with the run not yet complete. A total of 3,387 fall chinook adults had been counted at Lower Granite through Tuesday along with a whopping 6,065 jacks, fish that returned prematurely. There were 29 adults and 112 jacks in Tuesday's count.

No analysis of the 2000 return stock composition has been conducted yet, though slightly less than two-thirds of the adults counted through Oct. 11 had adipose fin clips or markings, meaning they are most likely from either the Lyons Ferry releases or Snake River supplementation releases.

Both the wild fish numbers and returning supplementation fish are encouraging. The wild fish numbers had dwindled to as few as 78 fish counted at Lower Granite in 1990 with highs over the past decade of 742 in 1993 and 797 in 1997.

The tribes pushed, and gained support, for the supplementation effort in discussions with state and federal co-managers in U.S. v. Oregon.

The supplementation program, using fish reared at Lyons Ferry from the Snake River egg bank, just began to hit stride in 1996 with the release by the tribe of 114,000 fall chinook yearlings acclimated at a Pittsburg Landing site between Asotin, Wash., and Hells Canyon Dam, a barrier to fall chinook upstream passage.

Congress, in 1996 had instructed the Corps of Engineers to construct, under the Lower Snake River Compensation Plan, final rearing and acclimation facilities for fall chinook to complete Corps' efforts to compensate for fish lost due to construction of lower Snake River dams.

A second acclimation facility, at Big Canyon on the lower Clearwater River, was assembled and operated in 1997 with 198,000 yearlings released at spawning grounds near there and 147,000 yearlings acclimated at Pittsburg and released in the Snake River. About 253,000 subyearlings were released that year in Big Canyon.

A third facility, at Capt. John Rapids on the Snake, was in operation in 1998. All three sites are operated by the Nez Perce Tribe.

In 1999 nearly 1.1 million fish were released in the spring above Lower Granite on the Snake and Clearwater, slightly more than half being subyearlings and the balance being yearlings. Twice that many fish were released this past spring. The increased production was made possible by surplus returns from Lyons Ferry releases and the supplementation outplantings, Johnson said.

"Now you're seeing how quickly these salmon respond," said Johnson, who also acknowledged the assist provided by ocean conditions seemingly more favorable to salmon survival.

As more eggs become available, Idaho Power is expected to join the supplementation effort. Under a settlement agreement signed in 1980 the owners of the three Hells Canyon hydroelectric agreed to provide up to one million fall chinook for release below its lowermost dam, Hells Canyon, said Herb Pollard, National Marine Fisheries Service biologist. That production is supposed to be mitigation for habitat lost with construction of the three dams.

"This year they're doing some test rearing and getting ready to pour some concrete at Oxbow (dam)," Pollard said. It is still undecided when and where that production might take place, and how many surplus eggs might be available for the purpose.

The huge jack return is likely a direct reflection of the increased number of fish released in 1999 and returning after a year in the ocean, Johnson said. The jack return includes some "mini jacks" or yearlings released this spring that returned with little or no ocean time, but neither Foster nor Johnson would venture a guess as to their number.

The jacks could be a good omen for next year, when the 1997 brood mates of this year's jacks return as mature 4-year-old spawners.

"Even if the jacks are half the number of adults (that return next year), that's 10,000 adults. That's a huge return for the Snake River," Johnson said.

The timing of the supplementation effort has been crucial to what seems to be early successes. Outmigration conditions were generally favorable and, once in the ocean, salmon have been experiencing improved conditions "that make us all look like geniuses," said Pollard. The NMFS, WDFW, U.S. Fish and Wildlife Service and tribe are monitoring the project to see how well the hatchery fish thrive and reproduce in the natural environment as compared to the wild run.

The goal is to help rebuild, and eventually de-list, the population, which now serves as a primary limiting factor for down river fishers. The NMFS, charged with protecting and recovering listed fish, has set limits on the number of fish that can be taken from upriver "bright" runs, including healthy Hanford Reach stock, as a means of limiting impact on the Snake River wild run. Among the tribal supplementation program's long-term goals is to provide harvest opportunities for tribal and non-tribal anglers.

The NMFS has a recovery goal of rebuilding naturally spawning populations to at least 2,500 fish per year, though that goal may be redefined, Pollard said. If the supplementation program proves successful, those goals seem attainable and possibly not too far into the future, Pollard said.

"A lot of people have written off these upriver runs" saying there is not enough water, protected spawning grounds and that they can't get through the eight dams and reservoirs, Pollard said. "All of a sudden we're saying maybe this (the wild Snake River population) isn't a museum piece."

The returning adults from the supplementation program are not yet counted as full-fledged members of the listed population, despite their carefully guarded genetic lineage. The second generation of spawners -- the progeny of supplementation fish released to spawn naturally -- would be considered as a part of the listed population, Pollard said.

"They're wild. They count so there's the potential for de-listing" if the fish reproduce successful and maintain productivity, Foster said.

The project is "probably one of the best tests of tribal supplementation programs," said Foster. All hatchery fish are from the preferred stock and they are only four generations removed from their wild origins.

"The origin of the hatchery stock is fairly recent," Pollard said. He, Foster and Johnson are all encouraged by early results. Fall chinook redd or nest counts in the Snake and Clearwater rivers more than doubled, from 263 to 552, from 1998 to 1999. Nez Perce data shows that as few as seven redds were counted, in 1986, and the count only approached 200 twice in the intervening years.

The NMFW and WDFW would prefer that all of the hatchery produced that are released for upriver supplementation be marked, but the tribe has won some concession for its preferences that a portion of the subyearling releases be unmarked.

NMFS researchers want marking so that it is easier to identify which returning spawners are from the wild population and which are supplementation returns. One of NMFS key interests is an evaluation of the reproductive success of the hatchery fish as compared wild fish, Pollard said.

With unmarked releases, the evaluations may not be as precise but researchers can use extrapolation -- affixing a return number based on the percentage of unmarked supplementation releases compared to the total number of releases and marked returns, he said.

The supplementation program's success is encouraging, Pollard said, but an ultimate dilemma remains -- estimates are that less than one progeny returns from every three naturally spawning Snake River fall chinook.

"We are just in a holding program depending on hatchery programs," Pollard said.

by Barry Espenson
Snake River Supplementation Project Shows Promise
Columbia Basin Bulletin, October 20, 2000

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