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This Year's Colder Ocean Conditions Off NW Coast Good News For Salmon Growth

September 12, 2008 Columbia Basin Bulletin
The physical and biological ocean conditions that greeted young salmon flooding from the Columbia River this past spring have never been better, at least since monitoring began in 1996.

That bodes very well for future returns of coho, spring chinook and sockeye.

"… all signs to date indicate very high returns of coho, almost certainly rivaling the 4 percent numbers seen for fish that entered the sea in 2000 and 2002," according to an adult return forecast updated this week by NOAA Fisheries Service researchers. Coho leave the freshwater each spring as year-old smolts and return the following fall.

State biologists estimate that 1.1 million coho returned to the mouth of the river in 2001, the highest return since 1986. The total in 2003 was 677,000, according to the 2008 Joint Staff Report of the Oregon and Washington departments of fish and wildlife.

"Spring Chinook runs in 2010 and 2011 are also expected to rival the high returns seen in 2001 and 2002," according to the NOAA adult return forecast. The spring chinook also leave the river as yearlings but spend more time at sea. The upriver spring chinook return to the river mouth in 2001 was 437,900, which is the most on a record dating back to 1938. The 2002 return was 331,000.

"I'm really excited about this," Newport, Ore., based NOAA oceanographer Bill Peterson said of the list of oceanic variables monitored as part of the ongoing study. For the first time during the study's 11-year history all were judged favorable for the young fish. A cold ocean off the coasts of Oregon and Washington is good for salmon, as well as other marine fish and bird species.

The winter of 1999-2000 was "the first cold year that we'd had in a long, long time," Peterson said. The coho seemed to respond with a near doubling of their return rate.

Pacific Decadal Oscillation values shifted from neutral through most of 2007 to negative last September, entering a cold phase that turns the California Current cold. The PDO is a measure of climate variability that shifts on at least an inter-decadal time scale and usually on about 20- to 30-year time scales. The current is a 30-40 mile swath of ocean along the West Coast.

Those strongly negative values remained entrenched through August.

"When the behavior of the PDO over the past 11 years is compared, we find that the most negative value of the PDO for the winter months occurred in winter 1999-2000," according to this week's ocean indicators update. "The winter of 2007-2008 is the second most negative. This is an important leading indicator because Logerwell et al. (2003) showed that one pre-requisite for good coho salmon survival is that a cold winter should precede the spring months when the fish enter the sea. We assume that the same is true for yearling Chinook salmon."

The good PDO news has continued through August.

"Should the PDO remain strongly negative through September, the year 2008 will become the most negative PDO summer since the 1950s," the update says.

Each of the monitored "indicators" -- such as food availability and water temperature -- are ranked by the researchers in comparison to the same indicator down through the years. Peterson leads cruises every two weeks to collect on coastal upwelling of nutrients, water temperature and salinity characteristics, and plankton species compositions, among other elements.

Seven of the 12 indicators for which data is available so far this year rank No. 1 among the 11 years of data in terms of being favorable for fish. The mean rank for 2008 for all 12 variables is 1.8 with the lowest ranked indicator being the fourth most favorable recorded in study history.

"As of the end of August 2008, all of our ocean indicators remain highly favorable for high rates of growth and survival of salmon that entered the ocean this spring and summer," the update says. "In fact, by the end of the upwelling season (in September) when all of our indicators are averaged, 2008 will almost certainly be the most outstanding year in our 11 year time series."

The El Niño/Southern Oscillation, another climatic influence that shifts more quickly over time, also favors fish growing off the Northwest coast. Averaged over the January-June period, ENSO values are the most negative in the 11-year history of the NOAA study and the lowest since 1988.

Likewise, sea surface temperatures are now the coolest in 11 years.

The annual "spring transition" began in early March this year, with wind driven currents shifting from a northward to a southward flow. The change brought zooplankton south from the Gulf of Alaska to enrich waters for newly arrived salmon.

"This is a positive sign for fisheries because it means that the food chain was populated by northern species very early in the year," the update says.

A cold PDO and sea surface attracts favored prey. Bigger, fatter copepod species from the north, as opposed to less sumptuous subtropic copepods, give a big boost to salmon growth.

"Of particular interest in 2008 (and 2007) has been the presence of large numbers of the very large and lipid rich Neocalanus species," the research update says of the largest of the copeod species. "They frequently occur off the Oregon coast during winter and spring months, and their presence indicates that sub-arctic waters off Oregon; however during both 2007 and 2008 the species N. plumchrus has been roughly 5 times more abundant than during the previous 'cold phase' of the PDO.

"Moreover, high numbers were seen far offshore to at least 125 miles from shore suggesting that the more oceanic species of fishes will benefit (such as sablefish)."

The NOAA researchers qualify their adult return forecasts as being qualitative, meaning that the understanding of each indicator's influence on the young fish is not yet developed enough to enumerate future adult returns. But that understanding is growing with each passing year, said John Ferguson, head of the Fish Ecology Division at NOAA's Northwest Fisheries Science Center in Seattle. Peterson and other FED scientists are carrying out the "Ocean Ecosystem Indicators of Salmon Marine Survival in the Northern California Current" research.

Trawl surveys conducted in June off the coasts of Oregon and Washington netted the highest number of juvenile spring chinook salmon in those 11 years – 2 ½ time more than the next highest total, Peterson said.

"The correlation would say that if you see them there and they're in good condition, there's going to be stronger recruitment to the adult stage," Ferguson said.

"That's a very important time for them," Ferguson said of those first few months in the ocean. "Physiologically, they are geared to grow."

If a bountiful ocean awaits they will indeed grow quickly, increasing their ability to escape predators and, in general, survive.

"We were buried in fish," Peterson said of the June trawling, which nets mostly spring chinook but also some coho and sockeye. Last year's June catch of sockeye was a record for the study – a total of 58.

"This year it was in the hundreds," Peterson said.

The researchers are getting ready for the annual September trawl surveys, ranging out from as far south as Newport, Ore., and as far north as LaPush, Wash. Those forays net mostly coho.

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