Massive fish kill hammers crappies

Windom, Minn. — A fish kill in a small, southern Minnesota lake has claimed, strangely, nearly exclusively black crappies – and “thousands” of them, according to DNR officials.

The kill was first noted by DNR Fisheries workers who were conducting follow-up survey work on Long Lake, a 256-acre basin with a maximum depth of 13 feet. The lake is located in Watonwan County, south of St. James and north of Odin, said Nate Hodgins, DNR assistant fisheries supervisor in Windom.

“It was localized to crappies only,” Hodgins said earlier this week. “We went out (for lake survey completion) and were able to take samples of fish that were in the process of dying.”

That was Sept. 6, he said, adding that samples of dead crappies were sent to the department’s fish pathology lab in St. Paul. Results are pending, but given the directed kill of one species only, officials suspect a viral or bacterial cause. He noted that a “heavy algae bloom” had occurred prior to the crappie kill.

Hodgins said Long Lake hosts a variety of other fish species, including bluegills, channel catfish, freshwater drum (sheepshead), largemouth bass, yellow perch, northern pike, walleye, bigmouth buffalo, common carp, and bullheads.

But only crappies had been found among the dead, he said Monday.

“Very, very strange,” Hodgins said.

He said officials from the DNR, state departments of Agriculture and Health, and the Minnesota Pollution Control Agency are investigating the kill.

A crew from the Windom Fisheries office conducted a survey of Long in July, according to Hodgins. Test nets contained largemouths, perch, and a few walleyes and pike, he said. Meanwhile, crappies were “off-the-charts thick” in those same nets – to the tune of 79 collected per net pull.

What’s that mean?

“When (crappies) show up in gill nets like that, it’s an indication you have a bunch of them,” Hodgins said.

Netted crappies averaged about 71⁄2 inches long, he said. The dead ones collected ranged from 7 to 9 inches, roughly.

As part of the survey process, DNR Fisheries workers from the Windom office returned to Long Lake just over a week ago to complete the process. That’s when the dying and/or dead crappies were noted.

“We saw crappies kind of suspended on the surface, lethargic and just hanging around,” Hodgins said. “And the eagles were (focusing) on them.”

In subsequent days, he said, the office received several phone calls from area landowners reporting dead fish along Long shorelines.

Two other DNR Fish and Wildlife Division officials – Tom Burri, limnology consultant and Isaiah Tolo, fish health supervisor – said Tuesday that the Long Lake fish kill might still be occurring, and that, per an update, a largemouth bass and a few bluegills have been added to the kill – along with more black crappies.

However, Burri added, Hodgins reported checking on the lake this week and “didn’t see fish in the process of dying,” as he did a week earlier.

According to Tolo, there have been fish kills in the past in Minnesota in which only crappies have succumbed. One possible reason for that, he said, might be that crappies are more sensitive than are other species to changes in water quality.

“They’re the first to die when there’s an issue,” Tolo said.

Another possible reason: There are viruses specific to centrarchids (sunfishes), including crappies, Tolo said.

He said black crappie kills occurred in 2017 and 2018, one of which was identified as the mostly crappie-specific picornavirus. 

Burri said residents who witness fish die-offs should consult the DNR’s website (mndnr.gov) regarding reporting such events. 

According to that webpage, to report fish die-offs, people should call the Minnesota Duty Officer at (651) 649-5451 or (800) 422-0798 (the officer line is available 24 hours per day, seven days a week). An early report allows timely water and fish sampling or other response actions, if needed. It’s especially helpful to know what sizes and types of fish people see in a fish die-off, the webpage states.

Further, according to the webpage: In mid-spring and summer, fish die-offs are often the result of warming water and opportunistic infections that spread in fish populations that are already stressed after the spawning season. Species commonly observed in these die-offs include sunfish, crappies and bullheads, and, occasionally, largemouth bass and northern pike.

When die-offs of wild fish are the result of disease issues, the affected fish tend to be of a single species and size range. By contrast, when die-offs include multiple species and size ranges, human activity is more likely to be the cause.

Human causes of fish kills can include water discharged at high temperatures; discharges or spills of toxic chemicals, including pesticides and fertilizers; manure runoff; and low oxygen levels in a lake resulting from storm water that runs off urban or rural landscapes. Often, there are multiple causes contributing to fish deaths, the webpage states.

Leave a Reply

Your email address will not be published. Required fields are marked *