Study: Salmon don’t want too much water

One of FishBio’s salmon-counting weirs on the Stanislaus River.
One of FishBio’s salmon-counting weirs on the Stanislaus River. jjardine@modbee.com

Salmon don’t read memos or get emails from the state Department of Water Resources, nor do they consult U.S. Fish and Wildlife Service instruction manuals. So how can they possibly know when it’s time to spawn?

Over hundreds of thousands of years, salmon have learned to “read” signals that nature provides and only they truly understand. Those signals tell them when it’s time to swim upstream.

A group of FishBio scientists working on the Stanislaus River have crunched 11 years of meticulously kept data to better understand those signals. FishBio concluded that, using “adaptive management” techniques, government regulators often sent the wrong signals. In fact, their efforts were sometimes counterproductive in helping salmon populations recover.

Why? Because more water does not equal more fish.

In a peer-reviewed study published this week, FishBio looked at river conditions and flows from October through December, when the most salmon were moving up the Stanislaus River. The scientists caution against jumping to conclusions, but they say the state frequently releases too much water.

Optimum flows to entice salmon to spawn are around 700 cubic feet per second, says the study. That’s roughly 5,100 gallons per second; a lot of water. But it’s far, far less than what the U.S. Bureau of Reclamation, which operates New Melones Dam, usually releases. In 2010, the bureau released at least three times that much for 14 straight days – exceeding 10,000 cfs (15 times the optimum) for three days.

How much water is that? About 4.4 million gallons in a minute, enough in three hours to flood Oakdale 3 feet deep. Over the course of these “spike” flows, the bureau usually sent some 25,000 acre-feet of clear water to attract salmon that often never came.

“If you hold (flows) up for more than a day or two, it’s not providing any benefit,” said FishBio’s Andrea Fuller, one of the authors with FishBio partner Doug Demko and staffer Matthew Peterson. “If we didn’t have the dams in place, we’d have a very flashy system – the flows would spike up to a high degree, then recede quickly. The volume of water we’re putting down in October wouldn’t have happened in even the wettest years.”

Does this mess with the salmon’s internal signals? “Big time,” Fuller said.

“What led to the study, (the bureau) started doing these (adaptive management) releases in the 1990s and there was an agreement that there would be an assessment to see how well they worked,” Fuller said. “But that was never done. We were left asking, ‘How did you come up with the volumes of water you think is needed?’

“This finally gives us a study to see how the fish are responding.”

Those who still cling to the writ of “more water equals more fish” will dispute FishBio’s studies. But the prestigious North American Journal of Fisheries Management subjected it to review by three scientists not associated with FishBio. It’s solid.

The study doesn’t directly address the State Water Resources Control Board’s ongoing efforts to double the amount of water dedicated to environmental purposes on the Stanislaus, Merced and Tuolumne rivers. But it does argue that the state’s “adaptive management” assumptions should be subjected to close scrutiny. It should also convince the Bureau of Reclamation to reduce the water it releases each fall, meaning more would be left behind the dam in April and early May when juvenile salmon are trying to exit the river.

FishBio’s study contains some very important signals. Not for the salmon, but for state and federal scientists. They should reconsider their positions and base their demands on the facts they find on our rivers – not disputable dogma.