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.