Warm water temperatures at Pineview Reservoir east of Ogden apparently are to blame for the recent deaths of significant numbers of yellow perch, a state biologist says.
Boaters and anglers have reported seeing dead and dying fish lining the shores at Pineview last week.Tom Pettengill, the fisheries manager for the northern region of the Utah Division of Wildlife Resources, said the fish apparently died because of an infection brought on by high water temperatures.
Under certain conditions, he said, warm water and large numbers of fish create a breeding ground for bacteria.
"We've got so many little perch that if they get bunched up at a certain level, at a certain temperature, and if the water quality is a little marginal, they'll get stressed and then the bacteria starts taking off," Pettengill said.
He said that although laboratory tests are not yet complete, no health hazards appear to be associated with the fish kill. Because only perch may be affected, Pettengill said he's ruled out chemical spills or other forms of pollution as causing the deaths.
"It's specific to just the one species," he said. "If it were a real serious water-quality problem, it would be affecting all the species and not just one."
Pettengill said the DWR fisheries laboratory in Logan should issue a report in a few days, but that it's expected to indicate a bacterial origin for the fish kill.
Pettengill said the dead perch probably number in the thousands, but the loss should have little impact on fishing. Perch are prolific breeders, and the dead fish are only a tiny fraction of the overall population.
In past years, the DWR has taken steps to reduce the number of perch in Pineview. When the populations of perch grow unchecked, the fish grow very slowly and rarely reach what would be considered a normal size. Pettengill said the recent fish kill should help the overall health of the perch by thinning the population.