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NMFS Ponders Fate of Infected Captive Brood Sockeye

by Wil Phinney
Columbia Basin Bulletin, May 10, 2002

The National Marine Fisheries Service on Thursday had not yet determined a course of action for 68,000 sockeye salmon smolts infected with an untreatable kidney virus, but it's clear that Idaho does not want the fish in three Sawtooth Valley lakes.

State and federal officials confirmed that INHV -- infectious hematopoietic necrosis virus, which also has been called chinook salmon virus, Oregon sockeye salmon virus and Sacramento chinook disease -- has been detected in fingerlings being raised for Idaho in a NMFS captive brood program at Bonneville Hatchery near Cascade Locks in Oregon.

"The decision belongs to NMFS," said Paul Kline, manager of the sockeye program for the Idaho Fish and Game Department. "The official Idaho position, based on the criteria in the NMFS operating permit, is that, unfortunately, these fish cannot come back into Idaho."

Tom Flaggs, program manager for salmon work at NMFS' Manchester Research Station, Northwest Fisheries Science Center, agreed keeping the virus out of Idaho is critical.

"At all costs, the program has to keep IHN out of Redfish Lake or it will undermine everything we've been doing," Flaggs said. "All of the fish-health regulations support guidelines that do not permit the transfer of viruses across state lines or anywhere they do not exist."

IHNV, a rhabdovirus that infects salmon -- particularly sockeye -- and trout, including steelhead, produces an acute disease resulting from the destruction of the hematopoietic tissue in the kidneys. There is debate among fisheries experts about the disposition of infected fish. Some believe the only effective means to control the disease is the complete destruction of infected stocks and hatchery sterilization.

Still, a Wednesday conference call of a multi-agency Technical Oversight Team apparently did not reach consensus to destroy the sockeye smolts. It seems an unlikely option, but officials have not ruled out release of the smolts, recapturing the returning adults at Bonneville Dam and testing them again for INH with hopes that virus-free fish could be used in some manner. NMFS said it has a window of several weeks to make its decision.

"Our choices are to destroy the fish or release them, but releasing them becomes a problem because we have no way of handling returning adults," said Brian Gorman, a spokesman for NMFS in Seattle.

Officials said the situation is worrisome, but will not derail restoration efforts. The supply of sockeye smolts for Redfish Lake, Alturas Lake and Pettit Lake in Idaho's Stanley Basin, west of Boise in Central Idaho, is not limited to Bonneville Hatchery..

"There is no real demographic or genetic risk if we lose these fish. The program is not in jeopardy," said Flaggs. "We'll probably have a lower number of returning adults, but that's a fair trade off for keeping IHN out of Idaho. This situation takes these fish out of the picture, but other fish are reared by Idaho. This has been a reasonable brood year already."

Sockeye are notorious for carrying IHNV, but this group of smolts had been repeatedly evaluated and repeatedly certified as "squeaky clean" at every stage of the life cycle. Obviously, however, because the test is lethal, all the smolts were not tested.

Nobody has a definitive explanation for how the young sockeye contracted the virus, but biologists have some theories. The most likely scenario, they say, is that an infected steelhead introduced the virus after it was washed above a weir in Tanner Creek during recent high water.

Sockeye smolts and adult spring chinook in the captive brood program at Bonneville Hatchery are reared in both well water and surface water from nearby Tanner Creek.

A dead adult steelhead, found two weeks ago above the weir during high flows, "sampled red hot" for INH, said Patterson, who is a member of the Technical Oversight Team for spring chinook

Some fisheries biologists were initially concerned that the virus could pose a threat to chinook salmon at the Bonneville Hatchery, but those adults are segregated from the sockeye smolts. Further, salmon less than two years old are most susceptible to the virus.

"To have it in a captive brood program, that would be a bad thing," said Scott Patterson of ODFW in La Grande, "but it hasn't manifested itself in the spring chinook."

At other hatcheries (not captive brood programs) where IHN is prevalent, the virus is blamed for loss of 5-50 percent of production, said Patterson.

"We had adults on Tanner Creek water but as soon as we heard (about the virus) we put them on well water," said Marla Chaney, who operates the chinook captive brood program for ODFW at Bonneville Hatchery.

After about 10 days in well water, the chinook are back in Tanner Creek water because the surface water triggers maturation mechanisms.

Through variation in temperatures, Chaney said, Tanner Creek provides natural cues that allow the hatchery chinook to mature in sync with their wild counterparts, which sometimes spawn two to three weeks ahead of the captive brood stock.

Documentation indicates that the virus is transmitted horizontally through the water from infected fish and vertically by virus contamination of the surface of infected eggs.

"The vertical transmission in spring chinook is rare and during spawning we use an IOTAR 4 solution on eggs after they are removed from ovarian fluid so there is little chance for IHN," Chaney said.

The Redfish Lake sockeye captive brood effort, which began in May of 1991 -- six months before the species was listed under the Endangered Species Act -- is considered a "gene rescue" program designed to preserve genetic components and stabilize the risk of extinction.

During a seven-year period, from 1991-1998, just 16 Redfish Lake adult sockeye, produced in gravel from wild parents, returned to Idaho. Those 16 adults, captured and incorporated into a conservation-breeding program at Eagle Hatchery near Boise, were needed to raise not only smolts, but also the adults to produce the smolts.

The hatchery component was absolutely essential, Kline said.

"It is a very steep extinction vortex if they are left on their own to survive, if we had not intervened," he said.

The first release of hatchery sockeye was in 1994. The first return from hatchery fish was from the release in 1996.

"We did not return adults for two years because were just starting to learn to culture sockeye salmon. It is a very different type of hatchery. Any other hatchery operating to serve some type of mitigation every year traps adults that have filtered through the ocean, produce eggs, hatch the juvenile, rear for 15 to 18 months and let them go.

"We have to generate our own adults," Kline said. "We've been raising fish to become adults and eventually to become spawning-age adults. Once that occurred, then every spawning year we produce fish for two purposes -- the reintroduction objective and the future brood stock parent objective.

"We are doing a tremendous amount of genetic spawning, pedigree tracking, so we don't expose the fish to an inbreeding risk. The true engine is how we manage spawning, to remain as genetically diversified as we can."

In 1999, seven sockeye adults from hatchery releases returned to Idaho, followed the next year by 257 adults. Last year, in 2001, the number of returning adults declined to 26.

In that banner year, all but 10 of the returning adults were released as yearling juvenile fish. Ten were produced from hatchery adults that were outplanted to spawn or from eggs outplanted to hatchery boxes.

At this point, Kline said, it would not be reasonable to expect to return any truly wild fish.

However, it may be impossible to tell the difference.

Because the program is generating unmarked outmigrants, a pair of adults in Redfish Lake that have all their fins intact would produce offspring that look wild.

Additionally, Redfish Lake may still be home to a small population of "residual sockeye salmon" that share habitat with anadromous sockeye.

"When either spawn, not all the progeny migrate to the ocean. A small percentage stays behind," Kline suggested. "They mature and spawn with anadromous sockeye at the same time and place."

Biologists have captured all the ocean-going adults for brood stock, but even a tiny population of residuals, which were identified in the early 1990s, could produce sockeye that go to the ocean and return. The future of the species, though, would be dim if not for the infusion of migrating adults. Because of the mortality and survival rates in the lake, the chances are slim that any one pair of residual parents could produce offspring that survive to be parents. In fact, Kline said, residual sockeye produce about 300 eggs compared to anadromous sockeye, which produce as many as 3,000 eggs.

"It's very dynamic, a melting pot of unmarked fish," Kline said. "We have a thorough evaluation component, monitoring outmigration of different groups. We're still looking for a pattern of success to determine how best to put the fish back into the habitat."

Gorman concurred.

"It's still an experimental program," he said. "We're not measuring success solely in terms of adult returns. Because the original source of these fish was very limited, we're trying to broaden as much as we can the genetic makeup of the total population. Frequently, we intentionally limit the output, knowing we will get poor returns. That's part of the program. We're not at a stage yet where we're simply trying to increase the number of adults."

Wil Phinney
NMFS Ponders Fate of Infected Captive Brood Sockeye
Columbia Basin Bulletin, May 10, 2002

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