By WCCO-TV Staff

MINNEAPOLIS (WCCO) — The Minnesota Department of Natural Resources is encouraging Minnesotans to report fish die-offs if they find them in lakes or streams this spring.

In a release Thursday, conservation officials said that early reporting of die-offs is important so that sampling of water or fish, if needed, can be done quickly.

READ MORE: Minnesota Auto Shops Swamped with Hail-Damage Repairs

“People can help by reporting fish die-offs right away,” DNR limnology consultant Tom Burri said. “These reports help us determine whether an investigation is needed.”

Specific information officials want to know about die-offs include what kind of fish are falling victim and how big they are. Anyone who sees a die-off can report it by calling the Minnesota Duty Officer at 651‐649‐5451 or by dialing the officer line at 800‐422‐0798.

READ MORE: Minneapolis North H.S. Principal Put On Leave After Attending Sit-In With Students

Many things can cause die-offs, DNR officials say, and often there are multiple factors. Sometimes, snow and ice covering the lake can cut off sunlight to the aquatic plants below, which start to decay and deprive fish of oxygen. They can also be the result of an infection among a single species or rising water temperatures.

Humans can also trigger die-offs. Toxic chemicals, such pesticides or fertilizer, manure runoff, storm water surges, and other discharges can cause fish to die in large numbers.

MORE NEWS: What Happened At Minnesota's 21 Native-American Boarding Schools? Unpacking A Complex History

According to the DNR, as many as 500 fish die-offs can happened each year in Minnesota. When fish of a specific species or size die, it’s generally linked to natural causes, such as disease. But when die-offs affect fish of vastly different sizes, the cause is likely linked to humans.