LAKEPORT — Biologists are searching for clues to determine what has killed scores of fish in Clear Lake.
Reports have been made over the last few weeks of numbers of fish dying in Cache Creek. Then, over the weekend, hundreds of dead fish mostly carp, as well as some catfish, bass and crappie — were found washed up along the shore in north Lakeport.
Rick Macedo, a Fish and Game biologist, was in Lakeport Monday to size up the situation.
Fish die-offs such as this, said Macedo, have a number of possible causes — including harmful chemicals, infections by bacteria and fungi, changes in runoff and water chemistry, and harmful microorganisms.
However, he said he is not taking samples, running tests for contaminants, or using an electronic oxygen meter to measure the dissolved oxygen. That”s because, Macedo said, there is no indication that the current die-off is a result of any of the above or anything other than a natural phenomenon.
“This is very typical,” said Macedo, noting that the cause is most likely an “oxygen depletion event,” which can occur at anytime.
Oxygen depletion is the most likely cause of fish die-offs, said Macedo, especially during the kind of hot summer weather the county has experienced in the past few weeks.
On Monday, the temperature on the lake was 82 degrees, which was about 10 degrees cooler than reported last week by Record-Bee outdoor columnist Terry Knight.
In addition, Macedo noted, water that has heavy algae or aquatic plant populations, as Clear Lake does, is given to severe oxygen depletion that can result in significant fish mortality.
In recent summers, fish die-offs have occurred, with oxygen depletion once again being held as the cause.
“There is absolutely nothing we can do when the temperature is over 100 degrees for two weeks in a row,” said Pamela Francis, the county”s deputy director of Water Resources. “Unfortunately, the weather conditions have been very conducive to the fish dying off. I would consider it part of the casualties of the recent heat wave.”
Francis said that Water Resources plans to work with the State Regional Water Board to discuss implementation of long-term monitoring procedures — which will include testing for four species of plank tonic algae — to be put in place by summer”s end.
In Lakeport, the acting city manager, Richard Knoll, said Monday they are planning on beginning the work of removing the dead fish today, with city Public Works Superintendent Doug Grider leading the effort.
“We”ve assessed the situation and as far as I know it looks like the biggest problem in Lakeport is in the Rumsey Bay area and the northern part of the city,” Knoll noted.
He added, “I would suggest and encourage property owners along the lake to participate in the clean up as well.”
The county also is planning to aid in the cleanup.
“We have the city and the county working together on this and Public Services is waiving the landfill fees for anyone that helps collect the fish,” said Supervisor Anthony Farrington said. (See sidebar, “How you can help.”)
As for concerns about the lake”s safety, officials say that there are no concerns for the safety of swimmers or boaters.
Also apparently safe, according to Macedo, is the lake”s much-celebrated bass population, which didn”t appear to suffer a significant impact in the die-off.
“I wouldn”t expect there would be a measurable change in bass fishing,” Macedo.
Contact Cynthia Davis at cdavis@record-bee.com.
