Visitors to the Altus reservoir Friday were greeted by an unwelcome sight, dozens of dead fish.

The culprit, according to Altus Public Works Director Bob Stevenson, is a bloom of golden algae.

"We understand this started the same way the fire ants started," Stevenson said. "It came in from Texas."

Stevenson said the source of the algae is unknown. The only flow into the reservoir comes from Lake Altus-Lugert. The algae also may have came from visiting birds.

Stevenson said state Fish and Wildlife officials from Lawton are helping city employees with a treatment regimen to return the water -- and the surviving fish -- to normal health.

In the meantime, although there is no known danger to humans or animals eating fish who succumb to the algae, it is not recommended. For that reason city employees closed a portion of the reservoir

Larry Cofer, a fisheries biologist for the state Department of Fish and Wildlife is one of those officials working to kill the algae.

The process, he said, involves adding ammonium sulfate to the water. This is the first bloom in Southwest Oklahoma and the first in a reservoir small enough to be treated with chemicals in an attempt to get rid of the algae.

Cofer emphasized that the algae toxin only harms fish, not humans. Though the reservoir water has been isolated from the city water supply, Cofer said even if some algae got into the water system, it would not be harmful.

Cofer said he doesn't know how many fish have been killed, but guesses it is a majority of the fish in the reservoir.

The fish kill has enabled biologists to take a census of the types of fish in the reservoir: shad, crappie, sand bass, largemouth bass, saugeye and flathead catfish. To his surprise, Cofer has found no channel cats which are stocked yearly. He surmises that some species are resistant to the algae.

Last winter, Lake Texoma suffered a golden algae fish kill. Officials are monitoring Lake Altus-Lugert, but say if a bloom occurs the lake is too big to be treated.