The dense forests of redwood, oak and Douglas fir that once covered much of Sonoma County have for many decades been giving way to pastures, orchards, subdivisions — and vineyards.

Now, those vineyards are emerging as yet another threat to a fish that would go just perfectly with the region’s signature pinot noir: the coho salmon.

Battered by a long history of habitat loss, logging and development, a dwindling number of coho struggle to survive in the rivers and streams where they return every year to spawn. Now they must contend with water-hungry vines, and especially a frost-prevention method that involves spraying plants with 50 gallons of water per acre, per minute. In smaller tributaries, the technique can literally suck stretches of a stream dry.

“There are a lot more grape vineyards than there really is water for,” said Brian Cluer, a scientist with the National Marine Fisheries Service.

The acreage planted in vines has increased as much as 50 percent in some parts of the county over the last decade, and Cluer said the county was still issuing permits for new vineyards without requiring proof of an adequate water supply.

“It’s a water-scarce area,” Cluer said, “and permitting and regulation hasn’t addressed that. It’s been a big mistake.”

Though salmon are the biggest concern, vineyards’ water use has effects that ripple through local ecosystems and communities.

In the last three years, the fisheries service has documented more than 60 vineyard-related deaths of juvenile coho, an endangered species, and steelhead trout, a threatened species, in three streams. It estimated that in one of the events more than 25,000 fry, or baby fish, were probably killed.

Sonoma County enacted an ordinance last year that asks vintners to register with the county if they use water from streams, but it imposes no limits on such use and allows landowners to monitor stream flows themselves. The State Water Board is now preparing to step in with much stricter rules to protect fish.

The proposed rules, along with sporadic efforts to sanction vintners after the fact, have met with vociferous objections from an industry that views itself as environmentally conscious.

Green Pastures Valley, a 10-acre vineyard outside Healdsburg that boasts of its conservation ethic, is disputing a $115,000 fine levied last year by the fisheries service, which said it killed young coho by pumping too much water for frost protection.

“The small farmer is the endangered species here,” Eric Stadnik, a co-owner of Green Pastures Valley, wrote in an email. “I hope we can avoid bankruptcy over this ordeal.”

The Sonoma County Winegrape Commission also objects to the idea that vineyards are responsible for serious environmental harm. “I don’t think the scale of the problem is nearly as large as has been assumed,” said Nick Frey, the commission president.

The fisheries service disagrees. “Common sense tells us that there likely are more events that we aren’t aware of,” said Dan Torquemada, chief investigator with the agency’s Office of Law Enforcement in Santa Rosa.

Environmental organizations have increasingly begun to monitor vineyards’ behavior.

“If we see something out of the ordinary, we initiate the complaint process,” said Steve Krimel, co-chairman of Save Mark West Creek.

Krimel blames viticulture for a steady decline in the stream that flows through his backyard near Santa Rosa. “The local vineyard and the local winery up the road are sucking it dry from the headwaters,” he said.

Chris Poehlman, president of Friends of the Gualala River, describes seeing oddly fluctuating streamflows in areas where vineyards and other heavy water users are found.

“In the summertime,” Poehlman said, “there’s been severe drawdowns with no correlation to the weather. The water level goes up and down, and that takes water from pockets where fish are trying to survive.”

Water levels are only one of the issues worrying Poehlman’s organization, which has spent years opposing vineyard proposals in Annapolis, a remote town west of the Russian River valley. More viticulture means interrupted wildlife corridors and less biodiversity, the group says.

“Once one project gets approved it will set a precedent for others,” said Dave Jordan, a member of the group, adding that he has seen the tide of vineyards overtake neighboring landscapes. “Now all of the trees are gone, and it’s just grapes from one side of the hill to the other. We want to avoid that same fate here.”

This article also appears in the Bay Area edition of The New York Times.