Fire-Related Fish Die-Off Isolated, Experts Say

A major fish die-off in Watsonville Slough last week was isolated to the body of water directly behind Apple Growers Ice & Cold Storage Co., the industrial facility that caught fire Wednesday and burned for three days, an expert said Tuesday.

Hundreds of carp, bullhead trout, sunfish, catfish, Sacramento black fish—the only native fish in the slough—and bullfrog tadpoles came up gasping for air Friday when oxygen levels in the water plummeted, according to Jonathan Pilch, director of restoration at Watsonville Wetlands Watch.

On Tuesday, dead fish still bobbed in the shallow water along the shore. The stench of rotting fish and the charred warehouse hung in the air.

"It really was sad to walk out there," Pilch said.

Watsonville Wetlands Watch staff found dead fish as far downstream as Lee Road, just west of Highway 1, according to Craig Breon, executive director of the organization. He sent a letter to members Tuesday outlining what had happened.

"Most likely, the fish died when oxygen levels in the water dropped below tolerable levels," Breon wrote. "City testing has confirmed that dissolved oxygen levels dropped dramatically. The local warden for the California Department of Fish and Game stated that he believes the impacts are over."

And there's an upside. A few, actually.

• The endangered California Red-legged frog wasn't affected by the low oxygen levels. All of the breeding ground for the frogs is happening in off-channel ponds, so the tadpoles survived, Pilch said.
• Adult bullfrogs also made it through unscathed because they could get out of the water. Breon also reported no dead birds have been found.
• Because the die-off was isolated to one area of one slough, there shouldn't be a significant impact on the overall fish populations in the waterways or the food chain, according to Pilch.
• And among the dead fish were some of the biggest Sacramento black fish ever seen in the local sloughs. Pilch said no study of the area's fish has been completed and that Watsonville Wetland Watch staff actually are learning about the local species through the die-off.

The low oxygen levels are being blamed on the flame-fighting foam and soot in the water. Firefighters doused the burning warehouse with about 3 million gallons of water before switching to foam, according to Watsonville Fire Chief Mark Bisbee.

"The fish were already stressed" when firefighters started spraying foam on the blaze Friday, Bisbee told the City Council Tuesday evening.

Fire crews switched to foam after smoke billowed from the massive storage facility for two days. They were aware the foam could cause problems in the slough, which backs up to the warehouse.

“We considered the options; we had a problem with air quality and we had a problem with water quality," Bisbee said.

Pilch said the slough ecosystem is resilient. He expects the fish populations to rebound.

"The sloughs are really amazing. ... They have some inherent ability to clean themselves," he said.

Although Watsonville Wetlands Watch staff and volunteers do a variety of projects throughout the slough system, they plan to leave the dead fish along for the time being.

"As of now, we're going to let nature heal itself," Pilch said.