Fifteen years of monitoring a suite of 16 physical, biological and ecological “indicators” of ocean conditions has left NOAA Fisheries scientists confident they could now predict with reasonable certainty how young salmon from the Columbia River might fare during their first few months in the Pacific Ocean.
“We feel like we’ve kind of got it figured out… except for this year,” said Bill Peterson, a senior scientist and oceanographer with NOAA Fisheries’ Northwest Fisheries Science Center.
After years of collecting, analyzing and summing up indicator data, researchers began issuing forecasts about relative strength of salmon runs in the years to come. The forecasts are based on the ocean conditions the fish had encountered when entering the ocean as juveniles.
The NWFSC scientists have a seen strong correlation between highly ranked years (favorable indicators) and strong coho and spring chinook adult returns one and two years later, respectively.
In 2008, as an example, the average rank (each indicator is ranked poor, good or average each year) was the best in a 12-year data set. The return of coho last year was the fifth highest since 1970; and the upriver spring chinook was the third best since at least 1980.
The ocean signals measured this year were all over the board, though most were at the low end of the 12 years of rankings. And some went from very bad to great in terms of how they are believed to affect young salmon. The average of all 16 indicator rankings combined for this year is ninth best out of 12 years.
“2010 was a very confusing year,” Peterson told the Northwest Power and Conservation Council during a Wednesday presentation in Portland. He and others involved with the project are still trying to figure out what to make of it, and produce forecasts for the 2011 coho return and the 2012 spring chinook run.
“We’re going to see this year what drives the system,” Peterson said.
Cold is good when it comes to salmon survival and growth in the California Current that runs, sometimes northward and sometimes southward, along the coast.
“It’s not just the temperature itself,” Peterson said. “A different kind of water comes to the coast” when a cold period is in place and the current shifts in spring to bring water from the north that brings foodstuffs and produces an upwelling of nutrients to fuel the food chain.
Coldwater copepods swept down from the north are larger than their warmwater cousins from the south and literally build stores of lipids or fats. They in turn add a rich source to the food chain.
A southward current “fills this food chain with real nutritional stuff,” Peterson said.
A fortified food chain is beneficial to the young salmon in a couple ways. Food is more plentiful for them and helps fill up fish that would eat the juveniles.
The juvenile salmon have two missions in life, Peterson said. No. 1 is “find something to eat, and the other is to not be eaten. They live a simple life.”
There are four physical factors that affect plankton, food chains, pelagic fish and the growth and survival of salmon in the northern California Current, Peterson said. They include large scale water circulation patterns, that season reversal of coastal currents, coastal upwelling and the phase of the Pacific Decadal Oscillation – warm (bad for salmon) or cold.
2010 proved to be a transition year with “El Nino” conditions, which are generally a negative influence on salmon, holding sway until June before a shift to cold La Nina conditions. Likewise the PDO, a climate index based upon patterns of variation in sea surface temperature of the North Pacific, shifted strongly into a cold phase. Its ranking changed from the eleventh worst in the data set for December-March to the third best for May-September.
“In July, just like that, the ocean went cold,” Peterson said. “Conditions (for young salmon) were great later on” in the summer. The jury is still out on whether or not enough of the fish lingered long enough in the current that runs up and down the continental shelf long enough to receive a benefit.
Strangely enough, the sampling of juvenile chinook with a trawler at various sites off the Oregon and Washington coasts during May and June produced relatively strong numbers – the fifth highest. September trawling for coho, however, netted the eleventh ranked class in the date set.
The years of trawling has revealed that the juvenile coho and yearling chinook remain for a time in the shallower waters above the continental shelf. Sampling off the shelf has produced very few fish, Peterson said.
“That’s where they’re living, right in close.”
The research involves long-term monitoring of climate conditions, hydrography, zooplankton (copepods) and juvenile salmon abundance. The indicators are based on physical factors such as the state of the PDO, sea surface temperature, timing of the initiation of upwelling and strength of upwelling, along with biological indicators that index the quality of food within the food chain.
The time of the start of upwelling this year (July instead of April or May) and its duration (likely short because of its late start) were also well down on the chart in 2010, both ranked as the 11th best out of 12.
“The earlier the transition comes, the more upwelling there is..., Peterson said.
More information, go to NWFSC’s website at http://www.nwfsc.noaa.gov and click on “Ocean Conditions and Salmon Forecasting” in the box on the right-hand side of the page.