Much has been made of and said about the dismal adult chinook salmon run predicted this year for the Sacramento River, normally the second-most productive salmon river (after the mighty Columbia River) on the USA's west coast. There is widespread belief that the Pacific chinook salmon commerical fishing will be shut down this year along all of California and most of Oregon.
Scientists are still not certain why the adult salmon run is expected to be around 63,000, down from almost 900,000 just a five years ago. Here is Jane Kay's article from the San Francisco Chronicle in which she attempts to explain why the run is so low this year.
Amid growing concern over an imminent shutdown of the commercial and sport chinook salmon season, scientists are struggling to figure out why the largest run on the West Coast hit rock bottom and what Californians can do to bring it back.
The chinook salmon - born in the rivers, growing in the bay and ocean, and returning to home rivers to spawn - need two essential conditions early in life to prosper: safe passage through the rivers to the bay and lots of seafood to eat once they reach the ocean.
Yet, the Sacramento River run of salmon that was expected to fill fish markets in May didn't find those life-sustaining conditions. And some scientists say that's the likeliest explanation for why the number of returning spawners plummeted last fall to roughly 90,000, about 10 percent of the peak reached just a few years ago.
The devastating one-two punch happened as the water projects in the Sacramento-San Joaquin River Delta pumped record amounts of snowmelt and rainwater to farms and cities in Southern California, degrading the salmon's habitat. And once the chinook reached the ocean, they couldn't find the food they needed to survive where and when they needed it.
"You need good conditions in the rivers and ocean to get survival and good returns for spawning," said Stephen Ralston, supervisory research fisheries biologist with the National Oceanic and Atmospheric Administration, or NOAA, and a science adviser to the Pacific Fisheries Management Council (PFMC).
It is easy to blame the reduction on the reduced river flows. But Jerry Johns of the California Department of Water Resources (DWR) says there are other factors.
"You can't just simply blame it on the pumps," he said. Ocean conditions, a reduction of phytoplankton in the bay, the amount of salmon fishing, natural die-off and other factors are part of the broader picture, he said.
Johns is correct; you need good ocean conditions in addition to good freshwater conditions, and apparently, those have not been there.
According to Peter Moyle [professor at UC-Davis], good ocean conditions can somewhat make up for drought in the river systems and vice versa. But ocean conditions have been "squirrelly" in the last several years with a number of anomalies that produced abnormally warm conditions not good for salmon, he said.
"Usually, salmon populations are at their worst when conditions are bad in both fresh water and salt water," Moyle said. Some scientists think that is what happened to the 2007 fall run.
Once in the ocean, salmon must gorge on small sea creatures to survive.
In 2005 and 2006, the years that the 2007 fall run needed food near the shore in the Gulf of the Farallones, the upwelling of nutrients apparently came too late to produce the small fish that feed the salmon.
For more explanations see this article by Tom Stienstra, and this editorial, both from the 23 March 20o8 San Francisco Chronicle.
"Let us consider an alternative style of thinking, which we can call 'creative thinking'. It is playfully instructive to note that the word 'reactive' and 'creative' are made up of exactly the same letters. The only difference between the two is that you 'C' [see] differently." -- John Quincy Adams
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