What is winterkill?
Winterkill of fish occurs when the dissolved oxygen levels in a lake become too low and fish perish.
Contributing factors to winterkill can include low water levels, early ice-up and/or a late ice-out that contributes to extended total days with ice cover. Additional factors can be:
- How shallow the lake is
- Thickness of ice as well as snow cover
- Extended periods of cloudy weather
- Larger than normal amounts of decomposing organic matter on the bottom of a lake (e.g. plants, algae, detritus)
- High biological oxygen demand from aquatic organisms
- Few or no winter thaw and melt cycles
- Little or no incoming water from streams or drainage systems
Water levels were low in most area lakes due to the 2022 drought, and winter snow totals were near record levels throughout much of the Hutchinson fisheries management area, which includes Brown, Meeker, McLeod, Nicollet, Redwood, Renville and Sibley counties.
Fisheries staff and public reports of dead fish during the winter and at ice-out were compiled to tally winterkill effects on local lakes. The Hutchinson fisheries staff completed nettings on 32 area lakes’ fish populations that were suspected of suffering partial winterkills.
Completed nettings began in mid-April and ran thru May 9. Three to five trap nets were set in each lake to help determine the extent of winterkill through presence or absence of the representative fish species community.
The netting data was used to help decide which species, if any, would need to be stocked later this spring. The results of completed nettings are listed below.
Results
- Altermatt (by Sleepy Eye)
- Winterkilled carp were reported in mid-April. Altermatt has been a receipient of surplus walleye fry stocking; however, surplus walleye fry are not available this year.
- Arvilla Lake (by Kingston)
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Dead bluegill, black crappie, largemouth bass, walleye, and common carp were observed along the shore following ice-out. Fish caught in the trap nets included; bigmouth buffalo, black bullhead, black crappie, brown bullhead, common carp, northern pike, walleye and yellow perch. Winterkill was likely light to moderate in severity. Black crappie and northern pike will likely provide the best angling opportunities following this winter’s partial winterkill. Since Arvilla Lake is connected to Washington Creek, stocking will not be necessary, as migrating fish will reestablish themselves on their own.
- Bear Lake (by Hutchinson)
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Bear is a shallow lake that is occasionally used by DNR Fisheries to raise fingerling walleye. Carry-over adult walleye have provided fishing opportunities between years of winterkill in the past. Dead bluegill, black bullhead and adult walleye were observed along the shoreline. The only two species netted were black and brown bullhead. Winterkill appeared to be severe for carry-over walleye, based on net catches. Bullhead anglers may want to fish this lake. Walleye fry will be stocked for fingerling production this spring, with carry-over adult fishing possible in the future.
- Cedar Lake (by Cedar Mills)
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A low late winter oxygen test indicated the possibility of winterkill in 2023. Dead fish observed at the public access following ice-out included; bigmouth buffalo, black bullhead, bluegill, carp and northern pike. Winterkill is frequent at Cedar and a healthy part of this shallow lake’s functional ecology as it thins the number of bottom-feeding fish, helping the lake establish rooted aquatic plants and clearer water.
Northern pike, a species that is less susceptible to low oxygen levels, may provide the best angling opportunity. A direct connection to Belle Lake will allow fish to migrate into Cedar and repopulate it, if needed.
- Clear Lake (by Cedar Mills)
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Clear is a shallow lake that is occasionally used by DNR Fisheries to raise fingerling walleye. Carry-over adult walleye have provided fishing opportunities between years of winterkill in the past. Shore anglers have also caught bluegill, black crappie, and yellow perch. Anglers fish off the road on the north side of the lake. Dead black bullhead, carp, walleye and perch were observed along the shoreline. Fish caught in the nets included black bullhead and common carp. Black bullhead were moderate in abundance. Walleye were not netted.
- Clear Lake (by Gibbon)
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Clear Lake in Sibley County had a moderate to severe partial winterkill, depending on species and varying low oxygen tolerances. Species found dead include bigmouth buffalo, black bullhead, black crappie, common carp, green sunfish, northern pike, walleye, white crappie, white sucker and yellow perch. Fish caught in the nets included bigmouth buffalo, black bullhead, black crappie, common carp, white crappie and yellow perch. Northern pike and walleye were not sampled in the nets. Black bullhead were abundant and common carp were still present. Crappie may provide the best angling opportunity at this time. A proposal for drawdown is being heard at a public hearing on May 16, 2023 in Gibbon; a more complete winterkill after a drawdown could help re-establish habitat and conditions more favorable for fish and wildlife.
- Clear Lake (by New Ulm)
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Clear suffered a moderate winterkill in 2023, depending on species and varying low oxygen tolerances. Dead fish included black crappie, bluegill, common carp, largemouth bass, northern pike, walleye and yellow perch. Winterkilled carp were most abundant. Fish captured in the nets included; black bullhead, black crappie, common carp, white sucker and yellow perch. Black crappie will likely provide the best angling opportunity at this time. Later in 2023, there will likely be an opportunity to stock adult northern pike in Clear Lake ahead of freeze up.
- Clear Lake (by Watkins)
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A low winter oxygen test in early March indicated the possibility of winterkill at Clear Lake, but no dead fish were observed or reported following ice-out. Fishing should be normal at Clear Lake this year.
- Collinwood Lake (by Dassel)
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At Collinwood Lake, dead black bullhead, black crappie, bluegill, channel catfish, largemouth bass, northern pike, walleye, white sucker and yellow perch were observed, although common carp appeared most numerous among the dead fish. Fish captured in the trap nets included black bullhead, black crappie, brown bullhead, northern pike and yellow perch. Single day trap net sets do not adequately sample walleye, so their presence is unknown but may be inferred from angler reports in the near future. Based on strictly the winterkill net catches, northern pike and black crappie may provide the best angling opportunity at this time, but it’s likely other species are available. Walleye fry are scheduled to be stocked in 2024, the same year as the next summer gill net survey, which will give a better picture of the fish community. Bluegill prespawn stocking should occur later in spring 2023.
- Echo Lake (by Hutchinson)
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Echo had a low oxygen test in early March, but no dead fish were seen at the public access or near the outlet culvert flowing into Hook Lake. Winterkill severity is unknown at this time.
- French (by Hutchinson)
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French had a low oxygen test in early March, but not dead fish were reported or observed. An excellent connection to Stahls Lake will allow affected fish species to quickly migrate back into the lake and reproduce.
- Greenleaf Lake (by Litchfield)
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Greenleaf had a low winter oxygen test in late March, but no dead fish were reported following ice-out. Winterkill, if any, was likely extremely limited at Greenleaf in 2023. Connected Sioux Lake, which is much shallower than Greenleaf, is the most likely candidate for some amount of winterkill this year. Fishing will likely be normal at Greenleaf Lake in 2023.
- Hanska Lake (by Hanska)
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Oxygen testing indicated that dissolved oxygen levels were low at the southeast end of Hanska last winter. Hutchinson Fisheries staff boated around much of that section of the lake and only found six dead common carp, six dead channel catfish and two dead walleye immediately after ice-out. Winterkill was light to very light at Hanska Lake in 2023. The low numbers of dead fish indicated that a severe winterkill did not occur.
- High Island (by New Auburn)
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High Island was held in drawdown last winter for the final time as the lake will refill in 2023. Dead bullheads and common carp were reported to the Hutchinson Area Fisheries Office after ice-out. Walleye fry are scheduled to be stocked this spring and the lake will again be used as a walleye rearing pond to raise fall fingerlings for statewide stocking quotas. Unharvested walleye will provide future angling opportunities on this lake and fish and wildlife habitat value will be exceptional.
- Hoff Lake (by Cedar Mills)
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Dead fish observed at ice out at Hoff Lake included bigmouth buffalo, black bullhead, bluegill, common carp, largemouth bass, northern pike, and yellow perch. Dead common carp were most abundant. Trap nets sampled bigmouth buffalo, black bullhead, black crappie, bowfin (dogfish), carp, golden shiner, white sucker and yellow perch. Northern pike and bluegill were not sampled. Black crappie may provide the best angling opportunities at this time. Common carp were seen below the road culvert and were likely already migrating back into Hoff Lake. Winterkill may have been severe on sunfish and largemouth bass, although largemouth bass are not well sampled in trap nets.
- Hook Lake (by Hutchinson)
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The oxygen level dropped at Hook last winter, but did not bottom out until late March and it did not fall below 1.0 ppm at the testing site. No reports of dead fish came into the Hutchinson Fisheries Office following ice-out. Fishing will likely be normal at Hook Lake this spring.
- Hope Lake (by Grove City)
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Several hundred dead black crappie were observed along the north shore of Hope Lake in early May. Lower numbers of dead northern pike and yellow perch were also present. A winterkill evaluation netting will not be done here, as there is no official public boat ramp at this lake.
- Little Mud Lake (by Watkins)
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Ice anglers reported seeing dead fish on their underwater cameras at the bottom of Little Mud during late winter. Dead fish observed at the access following ice-out included black crappie, bluegill, golden shiner and largemouth bass. A winterkill trap net assessment turned up black bullheads, but no other species. Little Mud Lake is managed as a put-and-take rainbow trout fishery and trout were already stocked this spring. Rainbow trout fishing should be good starting on the May 13 opener. The warmwater fish species component to the Little Mud fishery may be poor in the interim. Future trout management on Little Mud could be in jeopardy if winterkill becomes a more frequent occurrence. Black crappie and bluegill were stocked in May 2023.
- Little Wolf Lake (by Dassel)
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Dead fathead minnow and yellow perch were seen at the public access at ice out. Trap nets captured northern pike and golden shiner. Anglers may find some pike fishing opportunities. Walleye fry were stocked in 2023.
- Long Lake (by Darwin)
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Winter oxygen testing revealed the possibility of winterkill at Long Lake. No dead fish were observed at the DNR Aquatic Management Area access on the west side of the lake or at various areas of the shoreline. Trap nets sampled very low numbers of black bullhead. No adult carry-over walleye were netted. Winterkill may have been severe and occurred early in the winter, allowing fish to decompose and sink to the bottom before ice-out. The lake will likely be stocked as a walleye rearing pond to produce fall fingerlings for the statewide stocking quota; carry-over fish will provide angling opportunities in the future.
- Long Lake (by Dassel)
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Low numbers of dead fish were observed along the southern shoreline following ice-out at Long Lake. Dead fish observed included bluegill, common carp, largemouth bass, and northern pike. Nets caught black crappie, bluegill, brown bullhead, carp, golden shiner, green sunfish, Hybrid sunfish, largemouth bass, northern pike, pumpkinseed sunfish and yellow perch. The 2023 partial winterkill appeared to be light to very light in severity at Long Lake.
- Long Lake (by Grove City)
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Dead black bullhead, black crappie, northern pike, and yellow perch were observed on the northwest shoreline following ice-out. A qualitative trap netting assessment revealed that black bullhead, black crappie and yellow perch were still present following the 2023 partial winterkill. The presence of live black crappie suggests that northern pike also exist within Long Lake, but were simply not sampled in the nearshore trap nets as it was too late in the spring.
- Otter/Campbell Reservoir (by Hutchinson)
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Around a hundred dead carp were seen at various locations along the shoreline. Lower numbers of dead bigmouth buffalo, black crappie, bluegill, channel catfish and largemouth bass were also present. A short electrofishing winterkill survey revealed bigmouth buffalo, common carp, and green sunfish. A partial winterkill also occurred in 2022 at this reservoir and due to the shallow nature of this waterbody is a frequent occurrence. An additional electrofishing survey is scheduled for September. Fish can easily repopulate the reservoir due to connections to the South Fork of the Crow River.
- Preston Lake (by Stewart)
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A winter oxygen test fell just below 2.0 ppm and rose a couple weeks later. No dead fish were reported to the Hutchinson Area Fisheries Office following ice-out. Fishing will likely be normal this summer at Preston Lake.
- Richardson Lake (by Darwin)
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Thousands of dead fish were observed following ice-out at Richardson Lake. Dead fish included black crappie, bluegill, common carp, flathead catfish, largemouth bass, walleye and yellow perch. The trap netting assessment turned up black crappie, common carp, largemouth bass, northern pike, and yellow perch. Bluegill were not netted. Black crappie and northern pike will likely provide the best angling opportunity at this time. The partial winterkill appeared to be moderate to severe depending on species and varying low oxygen tolerances. Bluegill restocking is planned; Richardson is also due for walleye fry stocking in 2024.
- Round Lake (by Litchfield)
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Lower numbers of dead fish were observed at a culvert inlet and the public access. Dead fish included bluegill and yellow perch. Due to low kill reporting, no winterkill trap netting assessment is planned. Winterkill was likely not severe at Round Lake in 2023. There should still be plenty of northern pike present in Round Lake and connections to Ripley allow for fish movement between the systems.
- Round Grove Lake (by Stewart)
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Low numbers of dead walleye and common carp were observed at the public access following ice-out and low winter oxygen tests. A June 2023 trap netting assessment targeting walleye revealed that winterkill severity was light. Over 100 walleye were netted ranging from 7 to 24 inches in length. This lake is scheduled to be stocked with walleye fry this spring and is being managed as a recreational walleye fishery.
- Schilling Lake (by New Auburn)
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Dead fish were reported at Schilling Lake following ice-out, but a winterkill assessment will not be completed as this lake is not a managed fishery.
- Silver Lake (by Arlington)
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Dead common carp and black bullhead were reported at Silver Lake following ice-out. A partial winterkill occurred in 2022 at Silver Lake and another appears to have occurred in 2023. Fishing opportunities may be limited to bullhead at this time. A drawdown is being considered through a public information meeting and public hearing process within 2023, so walleye fry will not be stocked this spring.
- Silver Lake (by Silver Lake)
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Low oxygen tests in early February indicated the possibility of winterkill at Silver Lake, although no dead fish were observed at various locations along the shoreline in late April and no reports of dead fish were called in to the Hutchinson Area Fisheries Office from the public. Severity of winterkill for this year is unknown but may be checked later. The lake was already scheduled to be stocked with walleye fry in 2023 and will no longer be used as a walleye rearing pond as it will be regularly stocked with walleye fry for local angling opportunities.
- Spring Lake (by Dassel)
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Dead fish were observed following ice-out at Spring Lake, including black bullhead, black crappie, common carp, channel catfish, largemouth bass, and yellow perch. Trap nets caught black bullhead, black crappie, brown bullhead, common carp, golden shiner, northern pike, yellow bullhead, and yellow perch, indicating that only a partial winterkill had occurred. Northern pike will likely provide the best angling opportunity this summer. Fish from connected Long Lake can easily enter Spring Lake and help repopulate the lake. An additional short electrofishing survey was done to evaluate the largemouth bass population, as they do not always sample well in trap nets. Black bullhead, common carp, and black crappie were seen while electrofishing in early May. Several pre-spawn largemouth bass along with several dozen pre-spawn bluegill were captured in adjacent Long Lake and stocked into Spring Lake to help rebuild those populations.
- Spring Lake Kids Fishing Pond – (in North Mankato)
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Winterkilled black bullhead and panfish were reported to the Hutchinson Area Fisheries Office following ice-out. No netting was done, but adult Northern pike and black crappie were subsequently stocked in preparation for the Governor’s Fishing Opener, in which Spring Lake Kids Fishing Pond is included in the planned festivities.
- Swan Lake (by Silver Lake)
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No reports of dead fish came into the Hutchinson Fisheries Office this spring from the public and staff checks of the lake at ice out revealed no dead fish. Fishing should be normal at Swan Lake McLeod County in 2023.
- Thompson Lake (by Cosmos)
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Dead black bullhead, common carp, walleye, and yellow perch were observed at ice-out. Walleye fry are scheduled to be stocked in 2023 and the lake will be used as a walleye rearing pond to produce fall fingerlings for the statewide stocking quota. Winterkill appears moderate in severity.
- Todd Lake (by Hutchinson)
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Spear fishermen reported seeing stressed and dead fish in their spearing holes in late January. Dead black bullhead, bluegill, and common carp were observed along the south shoreline following ice-out.Todd was stocked with walleye fry in spring of 2023.
- Willie Lake (by Litchfield)
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Low numbers of dead black crappie, bluegill, common carp, and largemouth bass were observed at the Willie Lake access and outlet area. Due to few dead fish observations, a trap net assessment will not be completed. Winterkill severity was likely light.
- Winsted Lake (at Winsted)
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A partial winterkill occurred at Winsted Lake in 2022-2023. Dead common carp and dead bigmouth buffalo were observed at various locations around the shoreline at ice out. A winterkill trap net assessment revealed live bigmouth buffalo, black bullhead, and common carp. Winterkill may have been severe on other fish species, although Winsted Lake also experienced a partial winterkill in 2021, Walleye fry and black crappie and bluegill adults were stocked in May 2023.