Federal scientists believe that natural forces -- unfavorable ocean conditions -- were the most influential factors in the infamous collapse of Sacramento fall chinook salmon fortunes last year, and the record low return forecast this year.

Infusing the freshwater ecosystem with greater "resilience," and closely watching the marine environment, is needed to help avoid such catastrophes in the future.

"Our thought is to look at the integration across the ecosystems," NOAA Fisheries' John Ferguson said of a budding effort to pin down the causes of the Sacramento fall chinook failure and weakened recent production of other West Coast salmon stocks. The project is being undertaken at the request of the Pacific Fisheries Management Council.

"We want to try get away from the blame game," said Ferguson, head of the Fish Ecology Division at NOAA's Northwest Fisheries Science Center in Seattle. That will require a holistic approach.

The status of the Sacramento stock has forced a near closure of ocean fisheries this summer to assure the greatest possible escapement.

Fishery managers were shocked last year when only 28 percent of the predicted Sacramento fall chinook materialized. The return to the river was estimated at 88,000 naturally produced fish. The minimum conservation goal for Sacramento fall chinook is 122,000-180,000.

As recently as 2002, 775,000 adults returned to spawn but the trend has been downward ever since. A record low jack count last year does not bode well. Even with all ocean salmon fishing closures, the return of fall run chinook to the Sacramento is projected to be only 54,000.

"The Council is particularly concerned with delineating causative factors associated with the unprecedented status of the 2004 and 2005 brood years for the Sacramento River fall chinook run, any factors that can explain current status of Council related salmon stocks in general…," according to an April 10 letter from PFMC Executive Director Donald O. McIsaac to James Balsiger, acting assistant administrator for the National Marine Fisheries Service. Those years produced Sacramento fall chinook that entered the Pacific Ocean in 2005 and 2006 and began returning in 2007 and now 2008, respectively, as adults.

A preliminary look at the situation offered in February by the NWFSC said it was unaware of any widespread event in freshwater that could have caused the fish stock's precipitous decline and that poor ocean conditions that prevailed in 2005 and 2006 likely affected early ocean survival and maturation schedules.

"In summary, pending further analysis, it appears that unusual ocean conditions are the most likely cause of the low returns examined here, and that continued efforts to quantify the effects of ocean conditions on salmon population abundance should be supported," according to the Feb. 22 letter from the science center directors to the PFMC.

The science centers are in the process of assembling a team that will attempt to answer the "important and complicated" questions posed by the PFMC, Ferguson said. It will include expertise in freshwater, estuary and marine science.

While the ocean is likely the primary factor, "there certainly are a lot of freshwater issues," Ferguson said. "There are a lot of physical changes in their system."

The Sacramento fall chinook, part of the Central Valley stock, includes naturally produced fish but is "heavily hatchery influenced," though a general lack of appropriate data prevents a calculation of the ratio, according to Allen Grover, a California Department of Fish and Game biologist and member of the PFMC's Salmon Technical Team.

About 30 million hatchery smolts are released each year. They and the wild juveniles are expected to "survive in a system that is completely dammed," mostly for irrigation, Grover said.

The Sacramento stock has not been extensively studied, in large part because they are not listed under the Endangered Species Act as are its neighbors, winter and spring chinook and steelhead stocks. Little money has been channeled in the past into studies on the fall chinook.

"It's a basic issue of data collection," Grover said. "It's short-sighted."

The NOAA science team will gather what information it can and "try to pull it together into a suit of hypotheses that points to what's going on," Ferguson said. It will also likely propose strategies to address the causes. The PFMC has requested that the science centers report on the results of their investigation at the Council's Sept. 7-12 meeting in Boise.

Ferguson said the scientists will rely on the concept of ecological resilience -- the ability of a system, and its inhabitants, to absorb recurrent disturbances and bounce back. An example, in this case, are ocean conditions, which have been observed to go through cycles, some short and some as long as 20-30 years.

The resiliency of the Central Valley system, like the Columbia's, has been weakened in many ways. Fish abundance propped up for years largely by hatcheries serves to narrow a salmon's life history.

"When you get a perturbation they can't handle that," Ferguson said. The fish adapted diversity through time so that some among them survive the worst of the disturbances.

And "it's not the system it was," Ferguson said of the many changes to the freshwater ecosystem resulting from human development. Restoring some of the system's resiliency would require that holistic approach.

"It's all of the factors. It's the 4Hs all over again," said of the approach employed in the Columbia River system that seeks to address hatchery, harvest, hydro system and habitat issues that affect salmon survival.

The PFMC request poses questions in seven categories -- freshwater biological, habitat and species interaction; marine biological, habitat areas and species interactions and cumulative effects. They ask about spawning levels, disease, hatchery release strategies and fish food. They delve into issues of water conditions, dam operations, pollution, food availability in-stream and the presence of species that prey on young salmon in freshwater and the ocean.

The marine inquiries ask about "conditions" such as food availability, ocean migration routes, oil spills and other factors that might have influenced the decline in fish return numbers.

The PFMC also asked for "any ideas that may improve the advance forecasting of salmon abundance."

"Something's gone wrong with the predictor system down there," Ferguson said. The science centers' February letter said last year's forecasts for chinook and coho, which are used in setting fisheries, "failed to capture this environmental signal" -- the poor conditions that prevailed along the coast when the young fish went to sea.

The potential return has been overestimated in each of the past three years. A sibling-type regression is used, as it is in the Columbia, in which one year's forecast is largely based on the returns of previous years. A healthy return of 2-year-old jacks is seen as a sign that the next year's 3-year-old return will also be strong.

Figuring out a way to put ocean conditions in the equation is a work in progress. The NWFSC has identified, and is monitoring, variables in the ocean such as annual upwellings that flush nutrients – fish food – to the surface.

"They're telling us a lot about our stocks," Ferguson said of the "Ocean Ecosystem Indicators of Salmon Marine Survival in the Northern California Current" tool used by the NWRFS in recent years to make "qualitative" assessments of future years' salmon return potential. The system could eventually be pooled with other systems, such as the sibling regressions, to more quantitative forecasts.

The lack of needed data, such as the overall age structure of the returns, also hampers forecasters in the Central Valley system, Grover said.

For more information about the Northwest Fisheries Science Center go to http://www.nwfsc.noaa.gov/index.cfm