Pollutant may have killed hundreds of Marsh Creek fish

By Tanya Rose
Saturday, September 17, 2005

OAKLEY - Hundreds of fish that turned up dead in Marsh Creek between Tuesday night and Thursday morning could have been killed by a pollutant of some kind, a California Fish and Game warden said. The final tests, however, won't be complete until sometime next week.

Contra Costa-based Fish and Game warden Nicole Kozicki said that between 200 and 500 carp, blue-gill fish and catfish probably died from a single, massive dumping of some kind of contaminant, rather than from a slow toxic release over time.

"It seems something happened between Tuesday night and Wednesday morning -- I think a large amount of pollutant must have been dumped in the creek somewhere between Delta and Cypress roads."

She based the assumption on an observation that, while scores of fish were dead when she arrived on the scene Wednesday, there were also fish alive and thriving.

"The alive ones didn't seem stressed or sick at all," said Kozicki, who took fish tissue samples and later sent those to a laboratory.

"That only makes sense if a massive quantity of something were dumped or released, which then killed some fish and then moved on."

She said she didn't see an obvious indicator -- like an oil sheen floating on the top of the water -- and so she won't know for sure what happened until the samples come back to her.

She said the source could be anything from fertilizer to pesticide to a lack of oxygen in the water.

Biologist Mike Hill said that in locations where there's an abundance of organic matter, higher amounts of bacteria in the water use up more oxygen and then put out carbon dioxide. That, coupled with the fact that hot summer water has a harder time holding oxygen, becomes a liability for fish; they basically suffocate, he said.

"The oxygen issue isn't exactly common, but it's not uncommon, either," he said.

Patrick Foy, a biologist and spokesman from the Fish and Game Department, said a construction company with a project downstream from the "fish kill" site performed its own tests and found the water was clear.

Though the creek feeds into the Delta, a drinking source to 20 million Californians, the dead fish were actually far away from creek intakes, where creek water feeds into the bigger body of water.

"I don't think there's an issue with people's drinking water being affected," Kozicki said.

Ed Greenwell, a 16-year-Oakley resident who often hikes a trail adjacent to the creek, said if there is even the possibility of a toxic substance in the creek, it should be closed to the public.

He also said there are usually birds swooping in and out of the water, but that he hasn't seen any recently.

"It was a nice little ecosystem before this," he said.