Dead yellow perch at Long Lake in Sinclair. The fish kill incident on four northern Maine lakes is a natural event, likely caused by warm water temperatures. Credit: Courtesy of Barbara Maynard

Reports of dead fish — most of them yellow perch — on four lakes in northern Maine have prompted questions from the public. While it might seem unusual, the official word from the Maine Department of Inland Fisheries and Wildlife is that the fish die-off is natural. It shouldn’t cause concern.

Frank Frost, the department’s fisheries resource supervisor for the Fish River Lakes Region, said a large number of fish have died on Long Lake, Cross Lake, Square Lake and Madawaska Lake.

“[It’s] certainly not a regular event, like annually, but fish kills do happen on an irregular basis,” Frost said. “I don’t recall such a fish kill in my 25 years of working in the area. Most are likely not even noticed.”

DIF&W fish pathologist David Russell said that fish kills can often be caused by temperature stress.

“Hundreds to thousands of dead juvenile white perch or yellow perch can be observed annually in some waters of the state,” he said. “Numbers and frequency of events are exacerbated by temperature fluctuation and by very warm temperatures.”

Frost said the fact that fish are dying needn’t cause alarm.

“[There is] no cause for concern as it appears to be a natural phenomenon and not due to some pollution event,” Frost said.

Russell said in a July 9 blog post that the department is always interested in hearing about fish kills. He also explained when to be concerned about such an event.

“Regardless of the cause, our staff are interested in knowing about any fish kill to assess the need for a formal investigation, as well as management implications,” Russell said. “Generally, a few dead fish to several dozen (possibly hundreds of dead fish on larger waters) are of less concern, except for when it involves endangered and threatened species such as sea-run Atlantic salmon or sturgeon.”

The department advises people who see fish kills to contact their regional fisheries biologist. Contact numbers and emails can be found on the department’s website.

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John Holyoke

John Holyoke has been enjoying himself in Maine's great outdoors since he was a kid. He spent 28 years working for the BDN, including 19 years as the paper's outdoors columnist or outdoors editor. While...