Scientists Say Ocean Is Full Of Fish  

Northwest Fishletter

July 26, 2007

Federal scientists who have been monitoring ocean conditions off the West Coast are cautiously optimistic that this year's crop of juvenile salmon may return to the Columbia River in much higher numbers than their recent predecessors. After the blockbuster returns in the early part of the decade, ocean conditions took a turn for the worse in 2004 and didn't start to bounce back until last year. But thanks to cooler waters, more plankton and no large schools of hake to pick them off on their way to the Gulf of Alaska , the spring run could easily double or triple this year's return.

Ed Casillas, a NOAA Fisheries researcher based in Seattle, told NW Fishletter last week that the annual June trawl survey off the mouth of the Columbia River showed plenty of small chinook with plenty for them to eat. "Numbers were high, but not the highest we've seen," said Casillas, who put this spring's data in the upper third of the information collected over the past 10 years.

He wasn't prepared to get too quantitative, since the numbers are only preliminary and won't be officially reported until September. But it means scientists expect a pretty sizable jack count for chinooks at Bonneville Dam next year--which could signal another blockbuster year that compares with the 2003 adult spring chinook run of 230,000 fish.

But their trawl surveys last year would have ballparked this year's Bonneville Dam jack count at around 14,000, while it actually came in over 20,000--more than a 40-percent difference and a world away from the 3,800 jacks counted last year.

The scientists are careful to stay out of the numbers game, and rely on a green-yellow-red system for estimating biological and physical parameters, with green meaning conditions are good, yellow for caution and red for poor.

Their latest findings say sea surface temperatures are cool enough to go into the green, along with coastal upwelling, spring transition date (when upwelling begins), and deep water temperature and salinity.

Another good sign is the appearance of large amounts of copepods, food for young salmon, and the special kind that show when upwelling conditions have brought nutrients from the deep ocean to feed the plankton blooms upon which many species of fish and birds ultimately depend.

And large schools of hake (whiting), which are normally associated with warmer currents, are gone. In fact, they weren't around much in 2005 and 2006 either, when the scientists expected to see them. They have speculated that the predators moved north early in the season to Canada , with impacts limited to Columbia River juvenile salmon migrating in May.

But the unseasonably wet and cool weather that much of the Northwest experienced over the past week or so put a temporary halt to the upwelling conditions--which are triggered by northerly winds. Now that the southerly storms have dissipated and the high pressure is once again building with the breezes from the north blowing along with coast, upwelling is expected to begin again soon.

Last spring, the coast experienced a hiccup in good conditions as well, when upwelling didn't really begin until late May and remained weak until late June, but picked up once more and continued strong through September. This year, the blip came a month later.

The scientists said biological conditions in 2006 also showed mixed signals with copepod biodiversity high all summer (a bad sign), but northern (cold water) copepods were abundant later in the summer (good sign) and a biological transition to a more productive regime that did not occur until May 30, after juvenile salmon had entered the sea.

They said 2006 catches of juvenile coho in September and spring chinook in June were "just below average, ranking 6th out of 9 years. Taken together, our indicators suggests that adult returns of coho in 2007 and spring Chinook in 2008 will likely be near to, but slightly below, returns averaged over the past decade."

They are not sticking their necks out--but average spring chinook adult returns to Bonneville Dam over the past 10 years have been in the 180,000-fish range. That's 225 percent better than this year's spring return. Chances are next year's return will be a lot higher than that--since this year's Bonneville jack count ended up 250 percent better than the 10-year average.

However, Casillas said one must exercise caution with the jack counts, since they are not always good predictors of the following year's run. He pointed out that 2004 jack counts were high, but the run fizzled the following year, which points to higher mortality for the chinook beyond their first year of foraging in the ocean.

The following links were mentioned in this story:

Ocean Ecosystem Indicators of Salmon Marine Survival in the Northern California Current

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