Though there has been much reporting on the salmon crisis, like The Times' recent "U.S. halts commercial salmon season” and the New York Times' "The trouble with salmon,” no one has yet pointed out that the high numbers in 2002 were actually anomalous or that the increasing variability in salmon, bird and plankton populations all point to climate change as the main driving factor.

The crash of salmon populations in California, Oregon and British Columbia this past fall has a lot of people worried. Just a few years ago, we enjoyed record runs of salmon in the Columbia, Klamath, Fraser and Sacramento river systems. Indeed, these runs were so high that they made us forget that salmon have not been faring well in the Pacific Northwest and northern California for some time.

Back in 2002, upward of 800,000 fall-run chinook salmon graced the Sacramento River and 390,000 spring Chinook traversed the Columbia. In 2003, 610,000 fall Chinook were counted at Bonneville Dam. Now, that was truly fantastic -- and wholly anomalous. In the previous two decades, the trend in numbers has been stable or decreasing, with "normal" variation on the Sacramento typically between 200,000 and 400,000 fish.

We have seen low returns like this before. In 1990, for example, there was an "unprecedented" low number of chinook salmon making up the fall run in the Sacramento. Over the last 30 years, 1995 marked the low point for spring chinook and coho (about 10,000 for both species) returning to the Columbia. And 1992 was the second lowest run of fall chinook to the Columbia (about 115,000).

In 2007, we observed poor returns everywhere: coho salmon in Oregon, chinook in the Klamath, coho in the Russian River, even Fraser River sockeye in British Columbia. Variability in numbers seems to be increasing. Salmon are complex creatures, and even the few species addressed here show major differences in their life histories, particularly when they enter the sea. But regardless of the exact date of ocean entry, food needs to be available or the little fish are in trouble. We usually have assumed that the ocean is a stable environment. It is not. Moreover, at present, it is changing very rapidly.

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