CORVALLIS, Ore. – Pacific Ocean conditions off the Northwest coast were truly Jekyll and Hyde-like in 2010 and that is making life difficult for biologists who try to predict future salmon runs by analyzing how well juvenile fish will survive their first few weeks at sea.
The sudden transition from El Niño to La Niña conditions was so abrupt that the impact on fisheries may not be known for a while, says Bill Peterson, a NOAA fisheries biologist at Oregon State University’s Hatfield Marine Science Center.
“The warm El Niño water lasted until June, and then within just a few days, the ocean got as cold as it has been in recent years,” said Peterson, who is a courtesy professor in OSU’s College of Oceanic and Atmospheric Sciences. “It was just plain nuts.
“I don’t think I’m making a forecast this year,” he added with a laugh. “It could go either way.”
For the past 13 years, Peterson and his colleagues have conducting trawl surveys funded by the Bonneville Power Administration in June and September from Cape Perpetua to La Push, Wash., counting the abundance of juvenile salmon along the near-shore waters of the West Coast. The survival rate of juvenile salmon is the key indicator for future salmon runs, says Peterson.
When salmon first enter the ocean, they must have enough food to not only survive, but to grow rapidly enough to avoid predation. The smaller they are, the more potential predators there are lurking offshore. And when ocean productivity is high, other fish like herring, anchovies and sardines provide a dining alternative for those predators.
Which brings us back to 2010.
“During the tail end of the El Niño, in May and June, we had some of the worst ocean conditions we’ve seen in the 13 years we’ve been sampling,” Peterson said. “Then in July, the conditions were as good as they’ve ever been. So it’s a question of timing.
“If the juvenile salmon came out early, they likely died,” he said. “If they came out later, they should be fine.”
Peterson said the juvenile chinook count this summer was the third highest they’ve had in their 13 years, raising hope for future chinook runs.
But, he warned, there is a caveat.
“We caught almost no juvenile coho salmon in September,” Peterson said, “and that worries me.”
Juvenile coho tend to stay just off the Northwest coast and if they migrated seaward too early, Peterson pointed out, they may have encountered a barren ocean.
“We’ll find out soon enough,” he said. “Coho return as adults after 18 months; spring chinook come back after two years and fall chinook, three years or longer. If these fish can make it to adulthood, they should be fine. There’s not much that out there that feeds on them other than sea lions and orcas.
“It’s all about how they fare as youngsters,” he added, “and the jury is definitely still out this year.”
Juvenile salmon spend months in fresh water and can leave estuaries at any time. Scientists aren’t sure exactly what triggers their migration to the ocean, but they should learn quite a bit about the importance of timing this year, Peterson said. “If the fish didn’t come out too early, we should have a great run of chinook salmon in 2013,” he said.
As for next year? That, too, is something of a crapshoot, Peterson says. Fishermen reported large numbers of chinook jack salmon in many Oregon bays and rivers; on the other hand, the coho jack count at Bonneville Dam was 15 percent less than normal, he added.
“Jack salmon can be an indicator of the strength of runs the next year, but in some years, its predictive value is truly awful,” Peterson said. “If the cold ocean conditions persist, we can hope for the best.”