Changing freshwater conditions, hydro effects, ocean ecosystems, sea lion appetites and other variables continue to vex fisheries experts who predict how many Columbia River salmon will return to spawn each year.

High dam counts of 3-year-old jack upriver spring chinook salmon last year prompted a forecast that the 2008 return would swell to 269,300 adults this year, dominated by 4-year-olds. However, something less than 180,000 is now expected to be the final count.

And while much of a coastwide chinook run failure this year is blamed on the poor conditions juvenile fish encountered on ocean entry, the same cannot be said for the Columbia upriver run.

That has researchers wondering about other variables, such as sea lions.

"We saw an uptick" in ocean conditions in 2006, when this year's 4-year-old upriver spring chinook went to sea, said John Ferguson, director of the Fish Ecology Division at the NOAA Fisheries' Northwest Fisheries Science Center. The improvement followed a 2003-2005 period when ocean conditions were generally considered generally. Ferguson was asked Wednesday to update the Northwest Power and Conservation Council on a variety of scientific issues being explored by the NWFSC.

NWFSC researchers have since 1996 collected physical and biological ocean data along the Pacific Northwest coast, studying the coastal upwelling of nutrients. They have identified a set of physical and biological indicators – such as food availability and temperatures -- that can directly affect juvenile salmon's well-being during the crucial first several months after ocean entry.

The improved ocean conditions should have bode well for this year's upriver spring chinook return. Washington Councilor Tom Karier asked Ferguson what happened to the fish.

"They're missing 40 percent of the fish" that were anticipated by federal, state and tribal managers, Ferguson said. "My guess is that it's the sea lions."

Male California sea lions surge north during the winter and spring, feeding to fortify themselves for the late summer breeding season on the Channel Islands off the coast of Southern California. Oregon Department of Fish and Wildlife researchers have estimated, based on five years of data, that from 1,500 to 3,000 of the big pinnipeds touch base each year at the East Mooring Basin at Astoria, just inside the mouth of the Columbia.

Large upriver spring chinook runs at the start of the decade, including a record return in 2001, are believed to have attracted the marine mammals and drawn many of them upstream as far as Bonneville Dam. The average annual California sea lion count at the dam from 2003-2007 is 86. During the few decades prior, few sea lions were seen at the dam, some 146 miles upstream.

In 2007, U.S. Army Corps of Engineers researchers estimated that more than 4 percent of the upriver run was consumed by sea lions at the base of the dam. That estimate of nearly 4,000 salmonids taken includes only predation observed by the researchers in the area below the dam.

Ferguson noted that the sea lion impacts are likely much greater. He referenced bi-energetics modeling done by the ODFW in response last year to a Pinniped Fishery Interaction Task Force request. The panel was formed to judge whether the lethal removal of pinnipeds at Bonneville might be warranted to reduce predation on salmon. It asked how many fish 500-1,000 California sea lions might eat below the dam.

The modeling done by ODFW marine mammal biologist Bryan Wright produced a range of from 12,000 to nearly 33,000 over a 32-day span. The modeling estimates the animals' energy (food) needs.

A separate analysis by the Corps plugged in estimated consumption of 86 sea lions over 20 days and came up with a range of from 2,584 to 17,458 salmonids annually. The latter analysis was cited in NOAA Fisheries environmental analysis of the proposed lethal sea lion removal.

The estimates assumed that 95 percent of the sea lions' diet below Bonneville was salmon.

Ferguson told the Council that many believe those numbers are an underestimation of the predation on salmon below the dam.

Wright said Thursday that his analysis had "limited applicability – to the tailrace area" where good data is available on the sea lions' diet. He admitted that the analysis was not as polished as he would like and not appropriate, at this point, for peer review. It has been criticized by the Humane Society of the United States for, as an example, overestimating the energy needed by the fish-chasing sea lions below Bonneville. The bottled up salmon -- pausing to search for a route past the dam -- are likely easy to catch as compared to free-swimming fish.

More daunting would be an estimate of the number of salmon taken by sea lions in the 146 miles from the dam to the Pacific, Wright said. There is little data available about the numbers of sea lions in those river reaches, or their diet.

"There has been a fair amount of discussion about doing that, the need to do that," Wright said of an overall estimate of salmon consumption in the river.

The predation on salmon is likely not as intense elsewhere in the river. Satellite tracking of tagged sea lions has shown that they don't dally, usually making the trip from Bonneville to Astoria, or vice versa, in 1 to 3 days, Wright said.

Sea lion consumption of salmon is not considered when fisheries officials estimate the potential return in any given year. But ocean conditions may soon become a part of the equation.

The NWFSC's Ocean Ecosystem Indicators project produces forecasts that are at this point "qualitative in nature: we rate each in terms of its 'good,' 'bad,' or 'neutral' relative impact on salmon marine survival, " Ferguson said. They are intended to complement existing indicators used to predict adult salmon runs, such as jack returns. Merging the methods is being discussed.

Ferguson told the Council Wednesday that things are looking up. An initial cruise completed last week by NWFSC researchers showed a high abundance of juvenile salmon and plenty for them to eat.

"There's a very high correlation there" between high juvenile counts and good salmon returns, Ferguson said. The fish sampled offshore this year include coho that being returning next year and spring chinook the following year.

For more information about the NWFSC go to http://www.nwfsc.noaa.gov/index.cfm