Thousands of dead fish are piling up across the Bay Area.

From the concrete outer edges of Oakland’s Lake Merritt to the sandy beaches of San Francisco’s Fort Funston, and the pebbled banks of Oyster Point in San Mateo County, the carcasses of fish likely poisoned by a harmful algal bloom — more commonly known as a red tide — are washing up ashore.

It’s a mass-death event the San Francisco Bay hasn’t seen the like of in years, says Jon Rosenfield, senior scientist at environmental group SF Baykeeper.

“From a fish’s point of view, this is a wildfire in the water,” he said.