Flahtery

Flaherty Lake is a 450-acre lake located four miles north of the City of Lakefield in Jackson County. Flaherty Lake has a maximum depth of 6.0 feet, and typically has poor water clarity conditions during most of the open water season. Flaherty Lake outlets into a private ditch at the southwest corner of the lake, then flows approximately 1.5 miles downstream into South Heron Lake. Despite a 30 foot drop in elevation from Flaherty Lake to South Heron Lake, fish are able to emigrate from South Heron when water is high. Fisheries management by MNDNR has only occurred on Flahtery Lake since 2015, when a public access was acquired by Jackson County Conservation League. Historically, Flaherty Lake has provided good Yellow Perch and Northern Pike fishing; therefore, the lake is managed primarily for Northern Pike and secondarily for Yellow Perch. In 2021, Flaherty Lake was used as a Walleye rearing pond, so a fishable population of Walleye is also present. A standard survey was conducted the week of July 5, 2023 to monitor fish populations using one gill net and nine trap nets. Despite extensive stockings over the years, only one Northern Pike was sampled in the 2023 survey. Northern Pike adults or fingerlings were stocked in 2015, 2016, 2017, 2019, 2021, and 2023. The one Northern Pike that was caught was 24.5 inches in length. Northern Pike could be moving downstream into South Heron Lake when water levels are high enough to do so, or the Northern Pike simply weren't active during the survey. Additionally, our angler reports have indicated high catch rates of Northern Pike on Flaherty. Northern Pike will continue to be stocked in Flaherty Lake if available. Since 2015, the Yellow Perch catch rate was 44.0 to 69.0 per gill net. In 2023, the Yellow Perch catch rate was 1.0 per gill net, which is below the expected range of catch rates for similar lakes (2.7 to 25.0 per gill net). The trap net catch rate was 2.1 per trap net, which is within the expected range of catch rates for similar lakes (0.3 to 3.8 per trap net). Lengths of Yellow Perch ranged from 4.4 to 7.4 and averaged 5.8 inches. The abundant Walleye population may be decimating the Yellow Perch population through predation. Adult pre-spawn Yellow Perch will likely be stocked in the spring of 2024. The 2023 Walleye catch rate was 34.0 per gill net, which is the highest catch rate observed on Flaherty Lake, and greatly exceeds the expected range of catch rates for similar lakes (2.3 to 18.1 per gill net). The catch was dominated by age-2 Walleye (2021 year class), which comprised 91 percent of aged Walleye. Walleye lengths ranged from 11.4 to 22.5 inches and averaged 15.4 inches. Mean length at capture (July 5, 2023) of the age-2 Walleye was 15.1 inches, suggesting that Walleye grow very fast in Flaherty Lake. Two other year classes of Walleye were sampled including age-1 and age-7. Flaherty Lake has shown that it can be effective at producing Walleye, so it is likely that opportunistic fry stocking will continue in the future. The 2023 Black Bullhead catch rate was 40.6 per trap net, which is above the long-term average of 18.9 per trap net, but within the expected range of catch rates for similar lakes (11.5 to 132.6 per trap net). Lengths of Black Bullhead ranged from 3.6 to 9.9 inches and averaged 5.9 inches. A Freshwater Drum was sampled in the survey, marking the first time that this species has been captured at Flaherty Lake. The Freshwater Drum was 9.3 inches in length and our best guess is it was likely moved in through an angler's bait bucket. Other species sampled included Bigmouth Buffalo, Common Carp, Orangespotted Sunfish, White Sucker, and Yellow Bullhead.

Flaherty Lake is a 450-acre lake located four miles north of the City of Lakefield in Jackson County. Flaherty Lake has a maximum depth of 6.0 feet, and typically has turbid water (secchi depth = 1.0 feet in June 2019). Flaherty Lake outlets into a private ditch at the southwest corner of the lake, then flows approximately 1.5 miles downstream into South Heron Lake. Despite approximately a 30 foot drop in elevation from the water surface of Flaherty Lake to South Heron Lake, fish are able to move from South Heron to Flaherty when water is high. Fisheries management by MNDNR has only occurred on Flahtery Lake since 2015, when a public access was acquired by the Jackson County Conservation League. Flaherty Lake is managed primarily for Northern Pike and secondarily for Yellow Perch. Historically, Flaherty has provided good fishing opportunities for Northern Pike and Yellow Perch. A standard survey was conducted the week of June 17, 2019 to monitor fish populations using one gill net and nine trap nets. Despite recent stockings of Northern Pike in 2015, 2016, and 2017, the gill net catch rate was 0.0 per gill net, lower than the management goal of 3.0 per gill net. However, eight Northern Pike were captured in trap nets (0.9 per net) with totals length ranging from 19.5 to 27.2 inches and averaging 24.4 inches. Historically, Flaherty Lake has had a fishable Northern Pike population that at times was fairly abundant, as a special fish survey in 2000 captured 17.0 Northern Pike per trap net. During the fall of 2019, 763 adult Northern Pike were stocked with the goal of increasing abundance of brood stock in Flaherty Lake. The Yellow Perch catch rate decreased from 69.0 per gill net in 2015 to 44.0 per gill net in 2019, but still exceeded the expected range of catch rates for similar lakes in the Windom management area (3.3 to 30.4 per gill net). Total length of Yellow Perch ranged from 5.1 to 10.3 inches and averaged 7.3 inches. The Yellow Perch population is stable and Northern Pike and Walleye should grow as the feed on the Yellow Perch population. Although Flaherty has not been stocked with or managed for Walleye, the 2019 catch rate was 15.0 per gill net, exceeding the expected range of catch rates for similar lakes in the Windom management area (2.3 to 13.3 per gill net). We suspect the Walleye originated in South Heron Lake, which has periodically been stocked with surplus Walleye fry, and swam upstream into Flahtery Lake during high water events. All of the sampled Walleye were age-3, which corresponds to the strong 2016 year class that was also abundant in South Heron Lake. Walleye growth is fast, as lengths of the age-3 Walleye ranged from 17.6 to 21.5 inches and averaged 19.4 inches. The Black Bullhead abundance was low at 22.0 per gill net. Other species sampled included Bigmouth Buffalo, Common Carp, Green Sunfish, Orangespotted Sunfish, White Sucker, and Yellow Bullhead.

INTRODUCTION Flaherty Lake is a 450-acre lake located four miles north of the City of Lakefield in Jackson County. Flaherty Lake has a maximum depth of 5.0 feet, and typically has turbid water. Flaherty Lake is located in a predominantly agricultural landscape, which likely accounts for the poor water quality. Flaherty Lake has one major inlet, which includes County Ditch 118 and Judicial Ditch 53, draining approximately five square miles. Flaherty Lake outlets into a private ditch at the southwest corner of the lake, then flows approximately 1.5 miles downstream into South Heron Lake. Despite a 30 foot drop in elevation from Flaherty Lake to South Heron Lake, fish are able to emigrate from South Heron Lake when water is high. Up until this point, Flaherty Lake did not have a public access and therefore was not stocked or managed by MNDNR Fisheries. In 2015, land was purchased on the east side of the lake by the Jackson County Conservation League, and an access was installed by MNDNR during the summer of 2015. Historically, Flaherty Lake has provided good Yellow Perch and Northern Pike fishing; therefore, the lake will likely be managed primarily for Northern Pike and secondarily for Yellow Perch. Additionally, Flaherty Lake occasionally experiences low dissolved oxygen levels, thus management species will include those that are more tolerant of low dissolved oxygen levels such as Northern Pike and Yellow Perch. An initial survey was conducted the week of June 29, 2015 to document size and abundance of existing fish populations using one gill net and nine trap nets. NORTHERN PIKE Zero Northern Pike were captured in the 2015 survey. Historically, Flaherty Lake has had a fishable Northern Pike population that at times was fairly abundant. A special fish survey in 2000 captured 17.0 Northern Pike per trap net. The winter of 2013-2014 proved to be harsh as thick ice and snow resulted in low dissolved oxygen levels in many area lakes. Although dissolved oxygen was not monitored and no reports of dead fish were received, Flaherty Lake likely experienced some winterkill during the winter of 2013-2014, which may account for no Northern Pike being captured in 2015. The Northern Pike population will be reestablished via stocking. Stocking has already begun, as 464 Northern Pike fingerlings (4 fish per pound) were stocked in September 2015. Depending on availability, adult winter rescue Northern Pike from Rice Lake in Aitkin County will be stocked during the winter of 2015-2016. YELLOW PERCH Yellow Perch were abundant in 2015, being captured at a rate of 69.0 per gill net, which is higher than the expected range of catch rates for similar lakes in the area (3.3 to 30.4 per gill net). Size structure of Yellow Perch was small, as Yellow Perch were 4.8 to 10.0 inches and averaged 6.2 inches. The reestablishment of Northern Pike in Flaherty Lake should provide balance to the Yellow Perch population, by reducing abundance and encouraging growth of Yellow Perch. OTHER SPECIES Evidence from years past suggested that Black Bullhead were very abundant in Flaherty Lake. In 2015, Black Bullhead were captured at a rate of 73.0 per gill net which is within the expected range of catch rates for similar lakes in the area (30.3 to 150.6 per gill net). Black Bullhead were 4.8 to 12.8 inches and averaged 8.6 inches. Bigmouth Buffalo were captured at a rate of 9.0 per gill net, which is higher than the expected range of catch rates for similar lakes in the area 0.8 to 7.0 per gill net). Bigmouth Buffalo were 8.8 to 16.9 inches and averaged 12.7 inches. Common Carp were captured at a rate of 2.8 per trap net, which was within the expected range of catch rates for similar lakes in the area (1.0 to 5.5 per trap net). Common Carp were large, with lengths ranging from 7.6 to 30.8 inches and averaging 24.1 inches. One 22.3 inch Walleye was captured in the gill net. Walleye have not been stocked since 1999 (private stocking), so this was likely an illegal introduction. Twelve White Sucker were sampled, ranging in length from 7.9 to 17.7 inches and averaging 12.3 inches. Twenty-three Orangespotted Sunfish were sampled. Plants in the water and at the water's edge provide habitat, prevent erosion, and absorb excess nutrients. Shrubs, trees, and woody debris such as fallen trees or limbs provide good habitat both above and below the water and should be left in place. By leaving a buffer strip of natural vegetation along the shoreline, property owners can reduce erosion, help maintain or improve water quality, and provide habitat and travel corridors for wildlife. Best management practices within the watershed (no-till farming, cover crops, buffer strips, targeted fertilizer application, reduced or metered tiling) would help reduce nutrients entering the lake. High nutrient and sediment input can cause algae blooms and reduce overall water quality. Any improvements in the watershed are likely to have positive impacts on the fishery. Prepared by Jonah Dagel

Based on Minnesota DNR survey data, anglers target Walleye, Green Sunfish, and Yellow Perch in Flahtery. See the full species list above for catch rates, size structure, and quality scores.

We don't have a confirmed public access point on record for Flahtery. Check the DNR LakeFinder page for current access details before you go.

Flahtery has a maximum depth of 6.2 feet, per Minnesota DNR data.

The most recent Minnesota DNR survey data for the main sport fish in Flahtery is from 2023.

No invasive species are on record for Flahtery in Minnesota DNR data. Always clean, drain, and dry your equipment to help keep it that way.