After Releasing Water For Steelhead, Not Enough Left For Trout

Ryan Cuthbert, front, a biologist with consulting firm Fishbio, and fishery technician Bob Fuller sample juvenile salmon in a rotary screw trap on the Stanislaus River near Oakdale, Calif., in April 2016. John Holland Modesto Bee

Ryan Cuthbert, front, a biologist with consulting firm Fishbio, and fishery technician Bob Fuller sample juvenile salmon in a rotary screw trap on the Stanislaus River near Oakdale, Calif., in April 2016. John Holland Modesto Bee

Not All Water Is Equal

The equation “more water equals more fish” has been pushed as an unequivocal truth by the environmental community and their friends among government scientists for so long that it has passed from theory to dogma.

But is it correct?

“Where does that come from?” asked Doug Demko, co-owner of FishBio, which has been studying California’s rivers for 25 years. “I’m of the opinion that a lot of the government people … just don’t care” if you can prove the theory. “It comes down to wanting more water.”

Government regulators sent billions of gallons of cold water down the Stanislaus River this year to help rainbow trout swim to the ocean and become steelhead. Now, the entire trout population from Goodwin Dam to Knights Ferry is lower than at any time in the past seven years – or for as long as they’ve been studied. The population decrease is so alarming FishBio and the Oakdale and South San Joaquin irrigation districts went public with their findings this week.

To understand why this is important, you need to understand that trout need cold water to spawn; salmon need it to survive.

In a drought, like the one we’ve experienced the past four years, almost the only place to find cold water is in the deepest part of a reservoir – usually just behind the dam. The depth, volume and weight keeps the water cold even as surface water warms. Without the dam, there’s no cold water.

The Cold Water Debate

If you send all your cold water down the river to help a few rainbow become steelhead, you won’t have any left to help the remaining rainbows spawn. That’s what happened on the Stanislaus this year. The New Melones cold pool was purposely diminished in a futile effort – based on the more-water-equals-more-fish calculation – to push rainbows toward the ocean. Virtually none went.

“There were so few,” said Andrea Fuller, Demko’s FishBio partner, “you can’t detect a change in the number.”

Both trout and juvenile salmon “search” water for signals. A tiny fraction of trout find a cue to swim out of the rivers to the ocean where they become steelhead. All the salmon, meanwhile, eventually go. At some point, they decide to return to spawn. The nature of all those signals is an open question.

From the trout’s perspective, the releases of some 5 billion gallons of water from New Melones was wasted. It didn’t prompt any trout to leave and now it’s unavailable for the trout that need it to spawn. Instead of creating a few steelhead, we’re left with far fewer rainbows.

Meanwhile, some 12,500 salmon exited the Stanislaus in April and May this year, but only a handful, maybe 75, went with the water from the cold pool. Most took their cues from something regulators had nothing to do with – rain.

FishBio’s study, said Demko, “will support that pulse flows don’t have a significant influence on migrating Chinook salmon.”

That’s an incredibly important statement, even if it flies in the face of long-accepted dogma.

Understanding Adaptive Management

Cold-water releases and pulse flows are at the heart of “adaptive management” theory. Knowing more water equals more fish, scientists try to time releases to when they believe the fish will be leaving the rivers or returning to spawn. Often, the timing works. But FishBio’s studies show there are likely more factors at play.

What should this tell scientists? First and foremost, you can’t fool fish.

But you can fool people. What worries us about those dogmatic beliefs is that they can be used to facilitate human agendas.

If you can send water down the river to help fish, perhaps you can also pump that water – sometimes at a profit; sometimes for political purposes – to benefit farms and cities far from the reservoir where it was originally stored.

As Demko put it, perhaps it all “comes down to wanting more water.”

Fish need clean, cold water and more of it. But pouring massive amounts down the river without helping a single trout (and precious few salmon) isn’t beneficial use. We need to concentrate on finding strategies that work before putting all our faith in something that sometimes doesn’t.


This article was originally written by: Mike Dunbar and published in The Modesto Bee on August 20, 2016.

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