Thousands of Fish Found Dead as Ice Melts on Minnesota Border Lake

Thousands of dead fish have been found in a Minnesota lake at the same time all its ice melted.

An estimated 2,000 to 3,000 fish were found dead in Lake Traverse, which lies along the border with South Dakota, on March 14, the West Central Tribune reported. They included freshwater drum, crappies, bluegills, white bass and bluegills. There was also a handful of smallmouth bass and walleye.

The phenomenon, known as a fish kill, likely occurred because of unusually mild temperatures, an initial analysis of the incident has shown. Officials have said an infection known as gas supersaturation trauma could be to blame, the Tribune reported.

This condition occurs when air and water mix under pressure, causing harmful bubbles that then affect the tissues of marine animals. The condition is also known as gas bubble disease, which has killed fish in other parts of the state.

Minnesota has seen a record-breaking mild winter, with unusually low temperatures. Many lakes are losing their ice too early. The state Department of Natural Resources (DNR) has already declared that ice is gone on most of its lakes.

The mild temperatures, paired with the right amount of sunshine, have provided the perfect conditions for algae to thrive in the lake.

Isaiah Tolo of the DNR’s fish health laboratory, who worked to analyze the dead fish, told the Tribune that higher than usual algae growth can cause an excess of oxygen and other gases in the water, which allows gas bubble disease to occur.

“Under these conditions the dissolved gases in the blood and tissues of exposed fish can come out of solution and form gas emboli (gas bubbles) leading to various health issues, such as heart or kidney failure, and can ultimately kill a large number of fish,” wrote Chris Domeier, a DNR fisheries supervisor, according to the Tribune.

Early lake ice disappearing in Minnesota began at the end of February. The strangely mild temperatures could be affecting the aquatic animals that call the lakes home.

“Many lakes are setting new records for early lake ice out. There are only four lakes in the state with records back to 1878. Clear Lake in Waseca County has records back to 1874,” Pete Boulay, a DNR climatologist, previously told Newsweek.

He continued: “The old record was March 6, 1878, and that record was broken this year with the new record of March 1, 2024. In general, lake ice out was running about a month ahead of the long-term averages. The new lake ice out record for Osakis is March 8, set this spring with the old record of March 13, 1878. Another lake with a long record is White Bear Lake March 8. The old record was March 19, 2012.”

Earlier this month, hundreds of thousands of fish died in California’s Klamath River, likely from gas bubble disease.

The fish kill followed an initiative from California Department of Fish and Wildlife in which 830,000 chinook salmon fry were released into the river, near the Iron Gate Dam.