Chinook Salmon’s Last Meal?

A cooler ocean is feeding hungry salmon, but their ultimate survival remains uncertain.

November 7, 2008

All of these inland threats have conspired to weaken the salmon’s former resilience, says Peter Moyle, a fish biologist at the University of California, Davis. Since Chinook are naturally adapted to variable freshwater and saltwater conditions, they have historically thrived even when rivers or streams were temporarily unfavorable—such as during a drought—as long as ocean conditions were not equally poor. Similarly, an undesirable ocean environment rarely coincided with unfavorable waters inland. But now, thanks to human-induced impacts, both salmon habitats are often in bad shape.

“It’s the one-two punch idea,” Moyle says.

As human populations continue to climb in the West, so does the impact on salmon. “Everything humans do, from a salmon perspective, is not good. They compete for the same resources,” says Robert Lackey, a senior fisheries biologist at the U.S. Environmental Protection Agency. “If people want cheap food, one of the costs is salmon.”

In 2005, the year that NOAA’s Peterson calls “the worst year in the ocean in God knows how long,” a record amount of freshwater was diverted from the Sacramento-San Joaquin River Delta for irrigation and drinking water. Spain, of the fishermen’s federation, believes poor ocean conditions were “the final straw” for salmon that were already stressed by a multitude of other problems.

Spain describes a zigzagging course with an overall downward trend: “Ocean conditions go up and down, but habitat or water availability gradually deteriorate,” he says. The current Chinook situation may be at a low point in that pattern, ready for an upswing. “And over a period of years,” Spain adds, “every time it goes up people tend to say ‘Oh, we solved the problem’ without realizing that ocean conditions will change and then [salmon populations] will go down deeper if we haven’t really solved those problems inland.”

While the multiple and interacting factors are difficult to tease apart, there seems to be agreement that both the ocean and freshwater systems will be found guilty. A governmental panel, of which Bill Peterson is a member, is attempting to narrow down a list of nearly 50 possible reasons for the Sacramento River Chinook collapse. “Since the returns were so, so, so low,” Peterson concedes, “there must be something else going on other than the ocean.” Future generations of salmon, and dormant fishing poles, anxiously await the verdict.

Related on Scienceline:

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A Brooklyn college professor is experimenting with indoor aquaculture.

How are the oceans in trouble?

About the Author

Lynne Peeples

Lynne Peeples is a freelance journalist focusing on health and the environment. She graduated from NYU’s Science, Health and Environmental Reporting Program, where she was the editor-in-chief of Scienceline. She has also written for Scientific American online, Audubon Magazine, The Harvard Gazette and Amstat News. Before NYU, Lynne worked at Harvard University crunching numbers for HIV clinical trials and environmental health studies, while teaching an introductory biostatistics course. She also holds an M.S. in Biostatistics from Harvard and a B.A. in Mathematics from St. Olaf College. Her resume and clips can be found at: http://www.lynnepeeples.com



Gordie says:

You really need to find a better source on the Pacific Decadal Oscillation than Bill Peterson. Go to this link (http://jisao.washington.edu/pdo/) and read the PDO chart…the cold phases have obviously not shortened to 4 years in the last decade…they’re swinging significantly within longer cycles like they always have.

Mike says:

We’ve had “adverse ocean conditions” in the past. Especially during the last El Nino. What we observed during that time was that the average size of our caught salmon went down during these years – they didn’t have enough to eat to fatten up. Over the last few years though, the average size of our catch kept going UP. This is – or at least should be – directly counterindicative to blaming ocean conditions for the decline of our salmon.
Somebody please tell me what all the Anchovies, Herring and Sardines ate that we found in the bellies of the salmon we caught? Maybe the Anchovies are just plain smarter than the Salmon who prey on them, and that’s why they were eating while our Salmon starved to death….
Also, DFG just recently revived the netpen program. Salmon from the hatcheries are once again being trucked to acclimatization pens in the bay, circumventing the river entirely, where they stay for a few hours before being released. So, if we see increases in Sacramento Salmon populations by 2010, it is due to these netpens, not to changing ocean conditions.
Coleman hatchery recently conducted studies on salmon mortality in the Sacramento River. They found out that 94% – 98% of the salmon they release at the hatchery never even make it to the ocean. If most of our salmon die in the river, it’s no surprise that the returns are low….
And finally I would like to ask the author of this fine article to please let her readers know where/when/how “overfishing” has had any impact on the Sacramento Fall Run Salmon Population???
This one really boggles the little mind of a participant in one of world’s best regulated fisheries.
Thanks for your time

Lynne says:

Thank you for your comments – interesting points on the interpretation of the PDO and implications of hatchery fish.

It is true that overfishing is likely only a small piece of the puzzle. After the discovery of gold in California in the mid 1800’s, the growth of fisheries led to significant Chinook declines in the Sacramento River. Today, harvesting rates, ocean conditions, water diversions, dams, erosion, and pollution all contribute to the problem in varying degrees, depending on the location and time.

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