Koronis (main lake)

A targeted fall night electrofishing survey was conducted for young of year "YOY" (fingerling sized) Walleye on Koronis during October 23, 2025. A targeted survey is generally used for sampling a specific kind of fish or time of year (i.e. spawning season, fall season, etc.) unlike a standard survey which samples a wider range of fish species during the summer months using standard methodology (i.e. standard time of year, set sampling stations, taking water clarity readings and oxygen/temperature profiles, etc.) and gears (i.e. lake survey gillnets, trapnets, and spring electrofishing for Largemouth Bass). Four electrofishing stations were sampled for a total of 60 minutes. The water temperature was 50.0 F. Clarity was good (3 feet plus). Submergent vegetation density was light. We observed abundant numbers of Bluegill, Largemouth Bass and YOY Yellow Perch. We also observed moderate numbers of Northern Pike, White Sucker, Rocke Bass and Smallmouth Bass in the 2025 fall night electrofishing survey. Koronis is a large (2,968 acres), deep (132 feet maximum), and productive lake located primarily in Stearns County. Koronis is a popular fishery for Walleye, Northern Pike, Smallmouth Bass, Largemouth Bass, Black Crappie, Tullibee and Bluegill. Koronis receives moderate recreational use during the summer months. The largest inlet is the North Fork of the Crow River, which enters Koronis along the east shore and outlets near the southeast corner. The greatest volume of nutrient loading is delivered to Koronis via the North Fork of the Crow River. Water levels were above normal during 2025. Zebra Mussels were found in 2022 and currently covering most of the hard substrates. An invasive algal species, starry stonewort, was found primarily in the east and outlet bays of Koronis in 2015 and near the south access of Rice Lake in 2016. Efforts to chemically eradicate starry stonewort had been unsuccessful in Koronis. Starry Stonewort has presently spread throughout the lake. However, Starry Stonewort densities appeared less in 2025 due to high water and potential impacts from Zebra Mussels. Aquatic vegetation densities are variable yearly in the lake. Rice Lake is upstream and connects to Lake Koronis via the North Fork of the Crow River. In the past, Walleye from both Rice and Koronis have spawned in the North Fork of the Crow River upstream of Rice Lake. A Walleye egg take station was operated just upstream of Rice Lake in the Crow River from the 1970's to 1992. However, this Walleye spawning run now appears to be considerably reduced. This is based on anecdotal observations of lower opening Walleye fishing activity near the Koronis inlet bay/narrows area especially since the 2000's and recent (2018-2019) ice out hoop netting in the river near the old egg take station. Walleye fishing activity often was higher during late ice off years at the Koronis inlet bay area due to fish returning from upriver spawning around opening weekend. Walleye also spawn adjacent to the east shores of the three islands in Koronis and the east point of Rice. Since 2001, both Rice and Koronis have been periodic "Spicer Strain" Walleye egg take sites for the statewide Walleye propagation program. Other recent Spicer Strain egg take lakes include Green, Diamond and Elizabeth. Historic spawning sites for Walleye in both Koronis and Rice have been degraded in recent years with increased sedimentation, algal and periphyton growth. Walleye natural reproduction in Koronis has been frequent and often adequate to sustain Walleye numbers based on previous fall and summer surveys and markings. However, natural reproduction contribution has been more variable in recent years due in part to degraded spawning habitat and unfavorable spring conditions. Walleye fry (0.5-2.0 million/year) were stocked during 1996, 2001-2019 and 2021-2025 as a 10% return of Walleye eggs taken for the DNR statewide Walleye hatching program. No Walleye eggs were taken and no fry were stocked in 2020. Approximately 1.1 million fry were stocked during 2025. It is unknown if Walleye fry stocking into upstream Rice Lake is also contributing to the Koronis population due to downstream movement (drift). Walleye fingerlings were stocked in 2004 (2,409 pounds, 48,180 fish). Various combinations of Walleye ages were stocked in 2006 (2,355 pounds, 45,685 fish) and 2010 (867 pounds, 4,887 fish). Walleye eggs were taken recently in 2021 (155.25 quarts), 2022 (98.75 quarts), 2023 (85.25 quarts), 2024 (91.8 quarts) and 2025 (175 quarts) from Koronis. Stocked Walleye fry were marked with Oxytetracycline "OTC" during 2001, 2007, and 2011-17. YOY Walleye numbers were abundant (61.00 YOY/hour, 6.86 inches) in the 2025 fall night electrofishing survey. Yearling Walleye numbers were also abundant (77.00 fish/hour, 10.19 inches) in 2025. Two-year-old Walleye were also abundant (10.00 fish/hour, 11.93 inches) in the 2025 fall electrofishing survey. YOY Walleye numbers were abundant (163.00 YOY/hour, 6.15 inches) in 2024. Yearling numbers were abundant (19.00 fish/hour, 9.21 inches) in 2024. YOY Walleye numbers were abundant (120.00 YOY/hour, 7.15 inches) in 2023. Yearling numbers were low (4.50 fish/hour) in 2023. YOY Walleye numbers were moderate (39.00 YOY/hour, 6.55 inches) in the 2022 fall night electrofishing survey. Yearling Walleye numbers were abundant (24.00 fish/hour, 10.40 inches) in the 2022 fall electrofishing survey. We also caught 2.00 fish/hour from the 2020 year class in 2022 fall electrofishing survey. YOY Walleye numbers were abundant (65.00 YOY/hour, 7.23 inches) in 2021 fall electrofishing survey. No Yearling Walleye were observed in 2021. Moderate YOY Walleye numbers (23.16 YOY/hour, 7.62 inches) were captured in 2020 fall electrofishing survey. We also observed moderate numbers of yearling (9.47 fish/hour) and age 2+ (23.16 fish/hour) Walleye in the 2020 survey. Low YOY Walleye numbers were captured in 2019 (1.85 YOY/hour). Abundant yearling Walleye were captured in 2019 (13.85 fish/hour, 9.76 inches). Moderate YOY and yearling Walleye numbers were captured in 2018 (20.57 YOY/hour, 7.20 inches; 8.57 yearlings/hour, 9.71 inches). Abundant YOY Walleye numbers were captured in 2017 (65.60 YOY/hour, 6.03 inches). Oxytetracycline "OTC" marked fish accounted for 33% of the YOY Walleye catch in the 2017 fall. Low numbers of yearling Walleye were captured in 2017 (4.80 fish/hour, 9.90 inches). Low YOY Walleye numbers were captured in 2016 (14.18 YOY/hour, 6.51 inches). OTC marked fish accounted for 40% of the 2016 Fall YOY Walleye catch. Yearling and two year old Walleye numbers were abundant (17.45 fish/hour) in 2016. Low YOY Walleye numbers (3.60 YOY/hour, 5.97 inches) were captured in 2015. There were no OTC marked YOY walleye captured in the 2015 fall electrofishing survey. Yearling Walleye numbers were abundant (22.80 fish/hour, 9.45 inches) in 2015. Abundant numbers of YOY Walleye were captured in 2014 (208.09 YOY/hour, 6.39 inches average length) and 2013 (71.25 YOY/hour, 5.79 inches average length). OTC marked fish accounted for 82% of the 2014 Walleye fingerlings captured in the fall electrofishing survey. Approximately 45% of the 2013 fall electrofishing YOY catch were OTC marked (fry stocked). Moderate YOY Walleye numbers (32.83 YOY/hour, 6.97 inches) were captured in the 2012 fall electrofishing survey. Approximately 92% of the 2012 year class fish captured in the 2012 fall electrofishing survey were OTC marked (fry stocked). Abundant numbers of YOY Walleye (205.50 YOY/hour, 6.50 inches) were captured in the 2011 fall electrofishing survey. Approximately 80% (164.40 YOY/hour) were OTC marked fish in the 2011 fall electrofishing survey. The Koronis YOY Walleye historical average catch rate and average length are 48.89 YOY/hour and 6.67 inches. Walleye abundance was high in 2024 gillnets (27.00 fish/gillnet) compared to the historical average catch rate (1987-present) of 12.86 fish/gillnet for Koronis. The 2024 Walleye average size was moderate (1.83 pounds and 16.68 inches) from gillnets. The Walleye historical average length is 14.39 inches from gillnets. Approximately 69% of the Walleye captured were 15.00 inches or larger in the 2024 survey nets. Walleye growth rates were within the Spicer Area normal ranges for ages 1-4, but below normal for ages 5-8. The 2021 and 2023 year classes (fry stocked and natural reproduction) comprised 40% and 16% respectively of the 2024 Walleye gillnet and trapnet catch. The largest Walleye captured was 28.74 inches in 2024. Current fish management activities on Koronis include protecting the important aquatic vegetation such as bulrush through the permit process, participating in local watershed projects, assisting aquatic plant management and enforcement personnel with invasive species monitoring and education, stocking various species as needed, and stocking Walleye fingerlings after two consecutive years of poor natural reproduction as documented by fall night electrofishing surveys. The Koronis fishery will be surveyed annually for YOY Walleye in the fall and 2027 summer for a standard survey.

A standard survey summer of Lake Koronis was conducted in late July of 2024. In addition, a fall night electrofishing survey was conducted on Koronis during October 9, 2024, to evaluate young of year "YOY" (fingerling sized) Walleye numbers due to natural reproduction and a fry stocking. A targeted survey is generally used for sampling a specific kind of fish or time of year (i.e., spawning season, fall season, etc.) unlike a standard survey which samples a wider range of fish species during the summer months using standard methodology (i.e., standard time of year, set sampling stations, taking water clarity readings and oxygen/temperature profiles, etc.) and gears (i.e., lake survey gillnets, trapnets and possibly spring electrofishing for Largemouth Bass). Koronis is a large (2,968 acres), deep (132 feet maximum), and productive lake located primarily in Stearns County. Koronis is a popular fishery for Walleye, Northern Pike, Smallmouth Bass, Largemouth Bass, Black Crappie, Tullibee and Bluegill. Koronis receives moderate recreational use during the summer months. There are five public access sites on Koronis. The lake is highly developed with approximately 545 homes/cabins/parcels which includes one resort, one bible camp and several recreational vehicle campgrounds. In addition, the city of Paynesville is within two miles of the lake. The immediate watershed is composed primarily of agricultural row crops, hardwood areas, and residential development. Nutrient runoff enters Koronis via 45 inlets/tiles (mostly small inlets) from agricultural, city storm sewer, and lake residential sources. The largest inlet is the North Fork of the Crow River, which enters Koronis along the east shore and outlets near the southeast corner. The greatest volume of nutrient loading is delivered to Koronis via the North Fork of the Crow River. Continual sediment loading into the North Fork Crow River inlet bay and surrounding areas are of concern for Koronis. Water levels were normal or above during 2024. Water clarity was poor (4.5 feet) on July 29, 2024. Zebra Mussels were first observed in Koronis during 2022. An invasive algal species, starry stonewort, was found primarily in the east and outlet bays of Koronis in 2015 and near the south access of Rice Lake in 2016. Current efforts to chemically eradicate starry stonewort have been unsuccessful in Koronis. Aquatic vegetation densities are variable yearly in the lake. Various submergent species (i.e., curly-leaf pondweed, coontail, bladderwort, buttercup, sago pondweed, narrow-leaf pondweed, chara and wild celery) can often become dense in the east bays, outlet bay and near shore areas of Koronis. Submergent vegetation densities were moderate (i.e., sago pondweed, water celery, coontail, clasping-leaf pondweed, curly-leaf pondweed, water moss, bushy pondweed and other pondweeds) in the 2017 standard vegetation transect stations conducted by DNR Spicer Area Fisheries personnel. Muskgrass "chara" (native species of the stonewort family) was found at 94% of 2017 transect stations. Starry Stonewort (invasive species) was found at 28% of the 2017 transect stations. Starry Stonewort occurrence has increased from 17% to 58% of point intercept stations sampled from 2015-2018 by DNR Division of Ecological Services and Waters personnel. Submergent vegetation and Starry Stonewort densities appeared lower during the 2024 summer due in part to high water levels, decreased water clarity and higher algal blooms. Starry Stonewort was abundant in the Highway 55 inlet bay area and east portion of Koronis in 2024. Partial summerkills of Tullibee and White Sucker are common in Koronis during hot summers. A minor summerkill of large sized Tullibee (Cisco) was noted during late July - early August of 2010. A major summerkill of Tullibee occurred in Koronis during 2011, but only a minor kill occurred in Green Lake during the 2011 summer. Drought conditions and extremely high air temperatures were the norm for the area during July and early August of 2012. There were no apparent summerkills in Green or Koronis during 2012, but adult numbers were so low that summerkill events may not have been recognizable, especially due to the large numbers of pelicans living on Lake Koronis islands. An adequate narrow band of water temperatures (<23.5 C) and dissolved oxygen levels (1-3 ppm) was present at depths of 20-22 feet in Koronis during late-July survey of 2024. No significant summerkills have been observed since 2012 on Koronis. Rice Lake is upstream and connects to Lake Koronis via the North Fork of the Crow River. In the past, Walleye from both Rice and Koronis have spawned in the North Fork of the Crow River upstream of Rice Lake. A Walleye egg take station was operated just upstream of Rice Lake in the Crow River from the 1970's to 1992. However, this Walleye spawning run now appears to be considerably reduced. This is based on anecdotal observations of lower opening Walleye fishing activity near the Koronis inlet bay/narrows area especially since the 2000's and recent (2018-2019) ice out hoop netting in the river near the old egg take station. Walleye fishing activity was often higher during late ice off years at the Koronis inlet bay area due fish returning from upriver spawning around opening weekend. Walleye also spawn adjacent to the east shores of the three islands and several point (Windmill, Stone Gate, Peterson's) areas in Koronis, and the mid-east point of Rice. Both Rice and Koronis are presently periodic "Spicer Strain" Walleye egg take sites for the statewide Walleye propagation program. Other Spicer Strain egg take lakes have included Diamond, Green and Elizabeth. Historic spawning sites for Walleye in both Koronis and Rice have been degraded in recent years with increased sedimentation, algal and periphyton growth. Standard surveys are scheduled every three for both Koronis and Rice. Fall electrofishing surveys for YOY Walleye are scheduled every year for both lakes. There are presently good fishing opportunities for Walleye, Northern Pike, Largemouth Bass, Bluegill, Black Crappie and Smallmouth Bass on Koronis. Black Crappie abundance was high in 2024 (10.25 fish/gillnet). The 2024 Black Crappie trapnet catch was moderate (2.00 fish/trapnet). The Koronis Black Crappie historical average catch rates (1987-present) are 3.42 fish/gillnet and 1.37 fish/trapnet. The 2024 Black Crappie average size was moderate from gillnets (0.45 pounds and 9.08 inches), but small from trapnets (0.24 pounds and 6.61 inches). The Black Crappie historical average length is 7.87 inches from gillnets. Approximately 20% of Black Crappie captured were 10.00 inches or larger in the 2024 survey. The largest Black Crappie captured was 12.20 inches in 2024. Bluegill abundance high in 2024 (37.64 fish/trapnet) compared to the historical average catch rate (1987-present) of 12.45 fish/trapnet. Abundant numbers of Bluegill were also captured in the 2024 gillnets (6.75 fish/gillnet, 6.39 inches average length). The 2024 Bluegill average size was moderate (0.13 pounds and 5.35 inches) from the trapnets. The Bluegill historical average length is 4.93 inches from trapnets. Approximately 8% of the Bluegill captured were 7.00 inches or larger in the 2024 trapnets. The largest Bluegill captured was 8.07 inches in 2024. Largemouth Bass electrofishing survey was not conducted in 2024. However, Largemouth Bass (post spawn) abundance was moderate (21.00 fish/hour) in the late June 2017 electrofishing survey. The Largemouth Bass average size was small (0.70 pounds and 9.94 inches) from the 2017 electrofishing survey. Gillnet and trapnet survey gears generally under sample Largemouth Bass except for smaller fish. Moderate numbers of small sized Largemouth Bass were captured in the 2024 trapnets (0.79 fish/trapnet, 7.42 inches average length). Koronis is a popular Largemouth and Smallmouth Bass fishery for tournament and league anglers. Northern Pike abundance was high in 2024 (6.75 fish/gillnet) compared to the historical average catch rate (1987-present) of 3.92 fish/gillnet. The 2024 Northern Pike average size was large (4.14 pounds and 26.20 inches) from gillnets. The Northern Pike historical average length is 24.49 inches from gillnets. Approximately 26% of the Northern Pike captured were 28.00 inches or larger. The largest Northern Pike captured was 37.28 inches in 2024. Northern Pike growth rates were generally within or above the Spicer Area normal ranges for ages 1-8. The 2020 year class comprised 32% of the 2024 Northern Pike survey catch. Northern Pike possession limit regulations for Koronis in the North-central Zone are as follows: anglers can keep 10 Northern Pike, but not more than two Northern Pike longer than 26.00 inches; and all from 22.00 to 26.00 inches must be released. Northern Pike taken by spearing follow the same rules except one Northern Pike may be between 22.00 and 26.00 inches or two larger than 26.00 inches. Smallmouth Bass abundance was moderate in 2024 (1.00 fish/gillnet) compared to the historical average catch rate (1987-present) of 1.30 fish/gillnet from Koronis. The 2024 Smallmouth Bass average size was large (2.85 pounds and 16.58 inches) from gillnets. The Smallmouth Bass historical average length is 13.05 inches from gillnets. Approximately 75% of the Smallmouth Bass captured were 14.00 inches or larger from the 2024 gillnets. The largest Smallmouth Bass captured was 20.47 inches in 2024. Tullibee abundance was low in the 2024 standard summer survey (0.50 fish/gillnet) but similar to the historical summer average catch rate (1987-present) of 0.67 fish/gillnet for Koronis. The 2024 summer survey average length was large (13.09 inches). The Tullibee summer historical average length is 12.98 inches from gillnets. The largest Tullibee captured was 16.93 inches in 2024. Tullibee numbers were low in the 2023 November targeted gillnet survey (5.00 fish/gillnet, 16.41 inches). Tullibee abundance was moderate (27.50 fish/gillnet, 15.74 inches) in the 2019 November gillnet targeted survey. Tullibee abundance was low (10.33 fish/gillnet) in the 2017 November gillnet target survey. Tullibee abundance was moderate in the 2010 (23.8 fish/gillnet, 15.28 inches) and 2015 (19.7 fish/gillnet, 14.17 inches) November gillnet targeted surveys, but low in 2012 (5.33 fish/gillnet) and 2014 (6.00 fish/gillnet). The Tullibee November historical average catch rate and average length are 28.57 fish/gillnet and 15.12 inches for Koronis. The Tullibee November catch rate in nearby Green Lake was low in 2023 (4.00 fish/gillnet, 10.78 inches), 2019 (1.75 fish/gillnet, 13.94 inches), 2017 (0.50 fish/gillnet, 11.25 inches) and 2015 (10.33 fish/gillnet, 13.66 inches average length). Tullibee growth rates were above the Koronis normal ranges for ages 1-8 in the 2023 November survey gillnet catches. The 2017 and 2015 year classes each comprised 35% of the 2023 November Tullibee survey catch. The last major summerkill of Tullibee occurred in Koronis during 2011. Hopefully, cool summers will occur during the next several years, which may result in a good hatch and survival of Tullibee in Koronis if adequate brood stock numbers are still present. Tullibee are an important forage species for both large Northern Pike and Walleye. We provided fertilized Tullibee eggs from Koronis for university research studies in 2021 and 2024. These researchers were exposing Tullibee eggs and fry to different environmental cues which could be caused by potential climate change conditions. Yellow Perch abundance was high in 2024 (70.25 fish/gillnet) compared to the historical average catch rate (1987-present) of 39.55 fish/gillnet for Koronis. The 2024 Yellow Perch average size was small (0.11 pounds and 6.21 inches) from gillnets. The Yellow Perch historical average length is 6.63 inches from gillnets. Approximately 1% of the Yellow Perch captured were 8.00 inches or larger from the 2024 gillnets. Yellow Perch growth rates were below the Spicer Area normal ranges for ages 1-6. The 2021 year class comprised 74% of the Yellow Perch survey catch. The largest Yellow Perch captured was 9.33 inches in 2024. Walleye abundance was high in 2024 gillnets (27.00 fish/gillnet) compared to the historical average catch rate (1987-present) of 12.86 fish/gillnet for Koronis. The 2024 Walleye average size was moderate (1.83 pounds and 16.68 inches) from gillnets. The Walleye historical average length is 14.39 inches from gillnets. Approximately 69% of the Walleye captured were 15.00 inches or larger in the 2024 survey nets. Walleye growth rates were within the Spicer Area normal ranges for ages 1-4, but below for ages 5-8. The 2021 and 2023 year classes (fry stocked and natural reproduction) comprised 40% and 16% respectively of the 2024 Walleye gillnet and trapnet catch. The largest Walleye captured was 28.74 inches in 2024. Walleye fry (0.4-2.0 million/year) were stocked during 1996 and 2001-2019 and 2021-2024 as a 10% return of Walleye eggs taken for the DNR statewide Walleye hatching program. Only Spicer strain Walleye fry have been stocked in Koronis since 2014. The Spicer strain was the dominant strain stocked from 2004 to 2013 with only occasional Pike River and Upper Mississippi strains. Spicer strain fry Walleye fry were last stocked in 2024 (403,817 fish). Walleye yearlings or fingerlings (867 pounds, 4,887 fish) were last stocked in 2010. Walleye natural reproduction in Koronis was frequent and often adequate to sustain Walleye numbers based on previous fall and summer surveys and markings. However, natural reproduction contribution has been more variable in recent years due in part to degraded spawning habitat and occasional poor spring weather conditions. Abundant YOY Walleye numbers were captured in 2024 fall electrofishing survey (163.00 YOY/hour, 6.15 inches). Abundant YOY Walleye numbers were also documented in 2023 (120.00 YOY/hour, 7.15 inches), 2022 (39.00 YOY/hour, 6.55 inches), 2021 (65.00 YOY/hour, 7.23 inches) and 2017 fall electrofishing surveys (65.60 YOY/hour, 6.03 inches). Low YOY Walleye numbers were captured in 2019 fall electrofishing survey (1.85 YOY/hour). Abundant yearling Walleye were captured in 2024 (19.00 fish/hour, 9.21 inches), 2022 (24.00 fish/hour, 10.40 inches) and 2019 fall electrofishing surveys (13.85 fish/hour, 9.76 inches). Moderate yearling Walleye numbers were captured in 2020 (9.47 fish/hour, 9.42 inches) and 2018 (8.57 fish/hour, 9.71 inches). Rock Bass abundance was moderate in 2024 (3.75 fish/gillnet). The Rock Bass historical average catch rate (1987-present) is 2.01 fish/gillnet for Koronis. The 2024 Rock Bass average size was small (0.27 pounds and 6.68 inches) from gillnets. The Rock Bass historical average length is 6.63 inches from gillnets. Other species of interest captured in 2024 included low numbers of Black Bullhead (0.25 fish/gillnet, 0.07 fish/trapnet), Common Carp (0.25 fish/gillnet, 0.64 fish/trapnet), Bigmouth Buffalo (0.07 fish/trapnet) and Channel Catfish (0.00 fish/gillnet); high numbers of Yellow Bullhead (8.25 fish/gillnet); moderate numbers of White Sucker (4.00 fish/gillnet) and Shorthead Redhorse (2.00 fish/gillnet). The Koronis historical average catch rates (1987-present) for Black Bullhead are 17.05 fish/gillnet and 2.47 fish/trapnet. The Koronis historical average catch rates for Common Carp are 0.44 fish/gillnet and 1.40 fish/trapnet. The Koronis historical average catch rates for White Sucker and Shorthead Redhorse are 5.87 and 1.49 fish/gillnet respectively. Current fish management activities on Koronis include protecting the important aquatic vegetation such as bulrush through the permit process, participating in local watershed projects, assisting aquatic plant management and enforcement personnel with invasive species (starry stonewort) monitoring and education, and stocking various species as needed. The Koronis fishery will be surveyed again for YOY Walleye in the 2025 fall by electrofishing and 2027 by a standard survey. A November Tullibee survey will be conducted in 2027 with Green Lake. Tullibee eggs will be collected for a University of Minnesota study in 2026 and 2027.

A targeted survey of Tullibee (Cisco) in Lake Koronis was conducted during mid-late November of 2023 at four lake survey special gillnet stations. A targeted survey is generally used for sampling a specific kind of fish or time of year (i.e. spawning season, fall season, etc.) unlike a standard survey which samples a wider range of fish species during the summer months using standard methodology (i.e. standard time of year, set sampling stations, taking water clarity readings and oxygen/temperature profiles, etc.) and gears (i.e. lake survey gillnets, trapnets and possibly spring electrofishing for Largemouth Bass). Koronis is a large (2,968 acres), and deep (132 feet maximum) lake located in Stearns and Meeker Counties. Koronis is currently infested with invasive species such as Curly-leaf Pondweed, Starry Stonewort and Zebra Mussels. A standard survey (summer gillnets and trapnets) of Koronis was last conducted during mid/late July of 2022. A fall electrofishing survey was conducted on October 4, 2023 to evaluate young of year "YOY" (fingerling sized) Walleye abundance in Koronis. Tullibee were believed to be initially introduced into Koronis and Green Lake during the 1880's. Green is the only other Spicer Area lake with a self-sustaining Tullibee population. Tullibee spawn in 3-6 feet of water over bottom substrates consisting of large rock during late November to early December when the water temperature reaches 41 degrees Fahrenheit "F" or less. Spawning substrates in both Green and Koronis during recent years have been covered by periphyton/filamentous algae except in shallow (<1 foot) windswept shoal areas. Increased phosphorus inputs or availability often result in greater blue-green and filamentous algae blooms. Climate changes (e.g. warmer temperatures, additional growing days, increased storm/runoff activity, etc.) coupled with continued nutrient inputs and Zebra Mussel impacts may be negatively affecting Tullibee natural reproduction and recruitment success in these lakes due to degrading spawning habitat and increasing numbers of warm water fish species (e.g. Rock Bass, Pumpkinseed, Smallmouth Bass, Largemouth Bass, etc.) which prey upon Tullibee eggs, fry or fingerlings. Adult Tullibee are susceptible to summerkill in Koronis if oxygen levels drop (<2 ppm) in the cooler deeper areas (<74 F) of the lake for an extended time (1-3 weeks) during late July to early August. Young Tullibee can tolerate warmer water temperatures than adult Tullibee. A minor summerkill of adult Tullibee occurred in Koronis during 2010, but none was reported in Green. Low dissolved oxygen (<2 ppm) levels were present at depths where preferred adult Tullibee water temperatures (<74 F) occurred for a short time period on Green in the 2010 late summer. A major summerkill of Tullibee occurred in Koronis during 2011, but only a minor kill occurred in Green during the 2011 summer. Drought conditions and extremely high air temperatures were the norm for the Spicer Area during July and early August of 2012. There were no apparent summerkills in Green or Koronis during 2012, but adult numbers were so low that summerkill events may not have been recognizable, especially due to the large numbers of pelicans living on Lake Koronis' islands. A narrow band (1-3 feet) of marginal water temperatures (<74 F) and dissolved oxygen levels (1-3 ppm) was present in depths of 25-30 feet in Green during late July and early August of 2012. Dissolved oxygen levels and water temperatures in Green were at potential summerkill levels of 2 ppm and 74 F on both July 30th and August 9th of 2012. Summer temperature and oxygen conditions were more conducive for Tullibee survival during 2013-2019 for both Koronis and Green. The month of June had warmer air temperatures (up to 90 F) and drier (< 2 inches of rain) than normal conditions during 2020-2022. July air temperatures were near or below normal during those same years. The 2023 summer was warmer and drier than normal especially for June, but no tullibee summerkills were observed in Green or Koronis. Adequate water temperatures and dissolved oxygen levels were present from 17 feet depth (73 F, 6 ppm) to 20 feet depth (70 F, 4 ppm) for tullibee survival on July 28, 2023. Zebra Mussels were first observed in Koronis in 2022. It is unknown the extent Zebra Mussels will affect Tullibee and their corresponding forage base. Koronis was open to public gillnetting for Tullibee in the fall prior to the early 1980's but was closed due to low numbers and high incidental catch rate of other species such as Northern Pike and Walleye. Until recently, Green was the only lake in the Spicer Area open to the public for fall gillnetting of Tullibee during late November or early December from the late 1980's to 2011. Green Lake has been closed for Tullibee gillnetting since 2012 due to the low numbers sampled in recent years. Tullibee are an important forage fish for trophy northern pike in both Koronis and Green. Tullibee eggs were collected using a 300 foot gillnet (2.25-2.5 bar mesh) on November 22, 2021 at Lake Koronis for a doctoral research project. A total of 88 tullibee were captured in the overnight gillnet set. Approximately 2.5 quarts were stripped from 15 females and fertilized with 30 plus males on Koronis. One third of these eggs were immediately shipped to the University of Ohio-Miami. The remaining eggs were incubated in Muskellunge jars at the New London Hatchery for several weeks at 40 F river water and later shipped to the same research facility. The objective of the study was to evaluate the effects of UV light on cisco egg hatching and fry survival. The hatch rate was moderately successful. Local tullibee propagation (incubation, hatching and rearing to fryling stage) is possible at the New London Hatchery if using a recirculation system and a dry diet regime until fish can be stocked in the spring following ice out. Tullibee were present (0.20 fish/gillnet, 17.44 inches average length) in the 2022 Koronis summer survey. Moderate numbers of Tullibee were caught in 2019 (1.80 fish/gillnet, 14.17 inches average length). Tullibee were not present in the 2017 summer standard survey. The Tullibee historical average catch rate is 1.08 fish/gillnet for Koronis. Tullibee numbers were low in 2023 November survey (5.00 fish/gillnet, 16.41 inches). Moderate numbers of Tullibee were captured in Koronis during 2019 (27.50 fish/gillnet, 15.75 inches) and 2015 (19.67 fish fish/gillnet, 14.17 inches), but low numbers in 2017 (10.33 fish/gillnet, 14.41 inches). The highest recorded tullibee catch was 119.83 fish/gillnet on Koronis during 1996. Low tullibee numbers (4.00 fish/gillnet, 10.78 inches) were also caught in Green Lake during 2023. The November Tullibee historical average catch rate and average length are 28.52 fish/gillnet and 15.16 inches for Koronis. Tullibee growth rates were excellent for ages 1-8 in the 2023 November survey gillnet catches. The 2017 and 2015 year classes each comprised 35% of the 2023 November Tullibee survey catch. The inconsistency of Tullibee natural reproduction and inadequate adult Tullibee numbers on the spawning grounds as sampled by the DNR is not a good indication for the long term sustainability of the Tullibee populations in Green and Koronis. Hopefully, consecutive cool summers will continue to occur periodically, which may result in a good hatch, recruitment and survival of Tullibee to maintain a long-term population in Koronis. Improving and maintaining good water quality in Koronis is the key for Tullibee numbers to survive and flourish. Tullibee propagation is an option for maintaining a viable population. Other sampling methodology such as fall electrofishing and summer vertical gillnetting may better sample Tullibee populations in Green and Koronis. Public fall gillnetting season will probably be postponed until the adult population rebounds to adequate levels. Current fish management activities on Koronis include monitoring the fish population on a periodic basis, assisting aquatic plant management and enforcement personnel with invasive species monitoring and education, protecting aquatic vegetation through the permit process, participating in local watershed initiatives, and stocking various fish species as warranted. The Koronis fishery will be sampled in the 2024 summer for all fish species. Tullibee will be sampled by vertical gillnetting and hydroacoustic methods in June of 2024, and November gillnetting in 2025 for both Green and Koronis.

Based on Minnesota DNR survey data, anglers target Northern Pike, Black Crappie, Rock Bass, Largemouth Bass, and Walleye in Koronis (main lake). See the full species list above for catch rates, size structure, and quality scores.

Minnesota DNR records list public access for Koronis (main lake). Check the DNR LakeFinder page for the launch type and directions before you go.

Koronis (main lake) has a maximum depth of 132 feet and a mean depth of 29 feet, per Minnesota DNR data.

The most recent Minnesota DNR survey data for the main sport fish in Koronis (main lake) is from 2024.

Yes — Koronis (main lake) has confirmed starry stonewort and zebra mussel. Clean, drain, and dry your equipment to avoid spreading invasives to other waters.