Why the salmon are dying

Last fall, scientists were puzzled and worried when they realized that the number of coho and chinook salmon returning to West Coast rivers like the Sacramento were lower than they’d been in 37 years—only one-third of what scientists expected. What could be causing such a drastic collapse?

Today they have a pretty good idea. Early this week, fisheries biologists at the National Oceanic and Atmospheric Administration said their examination of the decline points to unusual changes in weather patterns that in 2005 forestalled a phenomenon called upwelling.

Ordinarily, upwelling stirs the water in the California Current, which flows along the coast from north to south, kick-starting the ocean food web by fostering phytoplankton growth. Without phytoplankton, the web dies. Juvenile salmon entering the ocean that year starved to death, as did millions of seabirds.

It’s not a permanent situation, the NOAA reports; this year, for the first time since 2005, the food web should be very good. In the meantime, though, salmon stocks are extremely low, and the federal Pacific Fishery Management Council is meeting next week to consider whether to close offshore salmon fishing in 2008, a decision that would have disastrous impacts on coastal communities.

We can expect to see more such catastrophes, according to a new study by a team of American, British and Canadian researchers who, sponsored by the National Science Foundation, mapped the impacts of human activity on all of the world’s oceans.

Every square mile of ocean is being affected, even isolated regions, the study notes, and many areas near heavily populated coastlines are nearing collapse. Overfishing, nutrient runoff and, especially, rising water temperatures because of global warming are the biggest culprits.

This is scary stuff. Healthy oceans are essential to life on earth, including human life. Let’s hope the study serves as a wake-up call to manage and protect our oceans in a sustainable way.