La Niña conditions bode well for PNW salmonids.

It could be a good winter for salmon, trout and steelhead fisheries according to a report on the Columbia Basin Bulletin. As we shift from warmer, drier El Niño-driven weather to its cooler, wetter twin, La Niña, the chances of above-average precipitation and below-average temps increases. More snowpack and cooler winters means more water in streams over the entire water year (October to October).

At the same time, cooler ocean conditions off the coast favor plankton blooms that feed young fish entering the sea for the first time this summer and coming spring. While these conditions are not the direct consequence of La Niña, they do pair well with the conditions we’re likely to see this winter.

According to the Bulletin:

“An already chilled northeast Pacific Ocean and rapidly cooling equatorial sea surface temperatures likely bode well for Columbia River basin salmonids that start and end their lives in freshwater but spend most of their lives at sea.

The late winter and early spring saw a fading of “El Nino” conditions — elevated sea surface temperatures in the central and eastern equatorial Pacific — that had prevailed over the fall and winter.

El Nino conditions can affect climatic conditions worldwide as well as ocean conditions outside the equatorial zone. El Nino’s presence tilts the odds toward warmer and drier conditions in the Pacific Northwest during the fall and winter.

The reverse is true when La Nina conditions reign. And they do now reign, according to meteorologists.

“During July 2010 La Nina conditions developed, as negative sea surface temperature anomalies strengthened across the central and eastern equatorial Pacific Ocean,” according to an ENSO (El Nino/Southern Oscillation) alert issued Aug. 5 by the National Weather Service’s Climate Predictions Center.

All indicators in the Pacific Ocean show that we are now in the early stages of a La Niña event. Computer models predict the central Pacific will continue to cool in coming months, indicating some further strengthening of the event is likely, according to the Aug. 4 ENSO Wrapup produced by the Australian government’s Bureau of Meteorology.”

The researchers sample the coastal waters off Newport at biweekly intervals during the ocean upwelling season in spring, summer, and fall. The Northwest Fisheries Science Center crew samples various physical ocean conditions, such as temperature and salinity, as well as biological conditions such as the productivity of the food web and availability of food for salmon.

“The ocean’s very cold. Typically that’s been very good for the food web,” said Nathan Mantua, an atmospheric research scientist at the University of Washington and co-director for the school’s Center for Science in the Earth System.

“Survival for chinook and coho tends to be very high when conditions are like this,” Mantua said.

He said that the cooled coastal ocean is probably not La Nina linked but more likely the result of winds and other atmospheric phenomenon. It does give the ocean that welcomes young Columbia River salmon outmigrants a head start. A cool northeast Pacific is, eventually, a consistent end product of El Nino. So an early start means those favorable conditions for a longer period.”


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