Wildlife officials say a lack of oxygen likely lead to a fish kill in Isanti County, they also say there have been more than normal this year.

Wednesday, the Isanti County Sheriff’s Office posted on Facebook that it received a number of reports that there was a large fish kill on Lake Francis.

Those who helped clean it up say there were dead fish in the thousands.

“The worst round I’ve ever seen [and] I’ve been here a little over 10 years,” Alton Anderson, president of the Lake Francis Association, said.

“We did a pretty good cleaning job,” Anderson said about their effort to clean up the carcasses.

The sheriff’s office’s post continues to read that after speaking to a Minnesota Department of Natural Resources investigator, “the reason for the kill, it was determined that the lake temperature along with low oxygen levels is the main cause for the kill.”

While it was mostly minnows and panfish that washed ashore, Anderson also found a Northern Pike that may have been impacted.

Limnology Consultant with the DNR, Tom Burri, says many water plants and a few algal blooms on the lake are also leading contributors.

“At night, those plants and algae use oxygen instead of creating oxygen, so that could stress out fish to the point where they die. Or, lack of oxygen and that could kill them as well,” Burri said.

For Burri and his team, he says they’ve had to look into more fish kills than normal this year.

“We are definitely a little above normal due to some of the hot weather that came earlier in the year and then we’ve had some real calm conditions and that can add to some algal blooms and that can cause some fish kills as well,” Burri said.

He adds that if you see a fish kill, call and report it immediately by calling the Minnesota Duty Officer at 1-800-422-0798.

You can learn what to look out for and more about fish kills here.