By Dan Breitwieser, WCJB TV 20 News.

Florida Fish and Wildlife biologists were out testing the water Monday near the boat ramp off U.S. 441 in High Springs. The results are in and they think the cause is not enough oxygen in the water.

Oxygen levels were half the optimum level. The lowest optimum level is 3 parts per million (ppm). Monday afternoon at the boat ramp, levels were at 1.6 ppm.

"The size of this fish kill was something we had to call someone," says High Springs resident Sandy Jones. "Usually you don't see hundreds of dead fish floating by."

Biologists blame it on the heavy rains from two weeks ago that flushed decomposing swamp goo into the river... sucking up much of the oxygen available for fish.

"Fish will move upstream, they will be spawning fish up here next summer," says Florida Fish and Wildlife Regional Biologist Jerry Krummrich. "In about another 18 months, it will be back to the way it was."

Krummrich says there's not much more that the FWC can do. He says the fish kill seems to only be affecting an area about two miles downstream from where the Santa Fe comes out of the ground in the River Rise State Preserve.