The ocean

The time that salmon spend in the ocean provides the most questions and the fewest answers as to why they are in decline.

Salmon spend 40 to 75 percent of their lives at sea, so ocean conditions play a vital role in whether these salmon will reach maturity and reproduce.

Yet increasing ocean and salmon research information indicates that ocean-going salmon smolts head into hostile waters when they head out to sea these days.
Monitoring studies of the El Niño ocean warming phenomenon, the deterioration of the ozone layer and shifts in ocean currents seem to coincide with many of the salmons' ocean-going woes: Pollution, predation, lack of food, more diseases and parasites all point to increasing water temperatures and lower survival.

Water temperature is important to salmon, which remain healthier in colder, nutrient-rich water. This kind of water historically wells up from the ocean depths to the surface waters in early spring, just in time for the arrival of the salmon smolts.

The little smolts can feed on the small creatures that eat microscopic plankton--the tiny ocean life forms that are the building blocks of the ocean food chain.

But in the past two years, said John McGowan of San Diego's Scripps Institute of Oceanography, warmer ocean temperatures attributed to the El Niño phenomenon have meant a delayed upwelling of the cold, food-rich water.

Although the colder water finally did arrive a little later in the spring, it may have been too late to save smolts from dying of starvation or being eaten by other creatures whose normal prey species already had died.

Dan Bottom, the Oregon Department of Fish and Wildlife's monitoring coordinator for the Oregon Plan for Salmon and Watersheds, said these large-scale weather changes are further stressing a species already struggling with poor habitat conditions in their freshwater environment.

"We've known for a long time about freshwater conditions important to salmon," Bottom said. "We are only now learning how those are important in the ocean."

Bill Peterson, a biologist with the National Marine Fisheries Service in Newport, has been surveying how much plankton has been available in the ocean during the past few years.

His findings support the idea that delayed arrival of colder ocean waters due to the El Niño phenomenon may be responsible for the poor survival of smolts.

Equally disturbing is the changing chemistry of an ocean that is growing algae in places where the waters had been too cold and clean before--the middle of the Pacific and Atlantic oceans now have been the site of large-scale algae blooms, indicating places where the water temperature is high and oxygen is relatively low.

George Taylor, Oregon's state climatologist, said it appears clear that survival of returning salmon from the ocean is poor during warm, dry long-range weather trends and it improves when the overall long-range weather trend is cold and wet.

Taylor said that scientists will have the opportunity to test that theory again soon, if weather predictions are correct. According to analysis of the ocean area off South America where the El Niño phenomenon begins, the coming winter should be colder and wetter than normal, as all predictions point to La Niña, or colder-than-normal ocean conditions, which could mean more salmon make it home to spawn next spring.

There is no universal agreement that warming of the oceans is a trend that will continue indefinitely, Taylor said.

"There are many variations in global and regional climate we don't fully understand. At this point, to attribute changes in these weather phenomena to human conditions is really stretching the science, in my view," said Taylor.

A remedy for ocean warming conditions will not be easy to find, but Bottom said some action taken on land can help salmon at sea. Among his suggestions:

Hatcheries could release smolts later during El Niño years, so that the arrival of the smolts coincides with the upwelling of the food-rich cold water.

A longer-term solution will require international treaties that seek agreements to limit pollution of the oceans and atmosphere.