Sullivan

A targeted survey of nearshore fish species in Sullivan Lake, was conducted on June 23rd-24th, 2025, by Area Fisheries staff. Sampling sites were evenly spaced around the lake, and each was sampled by backpack electrofishing and seining with a 50-foot or 15-foot seine, where possible. Backpack electrofishing was completed at 14 sampling stations. Similarly, a 50-foot seine was used to sample 12 stations. Two stations were not seined due to soft bottom, depth, and dense vegetation. Nearshore sampling captured 20 species of fish including five species that are intolerant of disturbance (i.e., Iowa Darter and Johnny Darter) and two species that are tolerant of disturbance (i.e., Fathead Minnow and Green Sunfish). A concurrent summer trap net survey was also conducted by Area Fisheries staff. 12 trap nets were set along the shoreline in locations that encompassed multiple habitat types. Trap net sampling captured 13 species of fish, including one that is intolerant of disturbance (i.e., Rock Bass). Bluegill and Black Crappie comprised a majority of the catch by number, whereas Common Carp and Bluegill comprised a majority by biomass. The nearshore and trap net were combined with gill net data from a July 2025 survey to describe the fish community and provide a fish- based (FIBI) score. The FIBI uses fish community data to measure a lake's health, and the types of fish species present can help identify any stressors that may be negatively affecting the lake environment. In Minnesota lakes, certain fish species cannot survive without clean water and a healthy habitat (e.g., Blackchin Shiner, Iowa Darter, and Rock Bass), while other species are tolerant of degraded conditions (e.g., Green Sunfish and Common Carp). The FIBI score, composed of several fish community diversity and composition metrics, indicates the overall health of a lake by comparing it to what is expected for a healthy lake. For additional information on the FIBI search for "lake index of biological integrity" on the mndnr.gov website. Results from this survey provide evidence that the fish community in Sullivan Lake is adversely impacted by stressors, as indicated by an FIBI score below the general use impairment threshold for aquatic life use determined for similar lakes. These results are similar to previous findings, which indicated that Sullivan Lake is impaired for biological health. The survey results will be considered when the biological health of the lake is assessed during the Mississippi River - Sartell watershed assessment process, which will be completed in coordination with MN Pollution Control Agency. You can help protect the fish community in Sullivan Lake by reducing runoff, maintaining natural shorelines, and preventing the spread of invasive species.

The targeted sampling that was completed on Sullivan Lake in 2025 included a spring electrofishing survey for Largemouth Bass, a spring trap net survey for panfish, a summer gill net survey, an IBI assessment (reported separately) and a fall nighttime electrofishing survey for juvenile Walleye. The lake is primarily managed for Black Crappie, Walleye, and Bluegill and secondarily for Largemouth Bass and Northern Pike. Spring electrofishing on May 14th, 2025, was conducted to assess the Largemouth Bass population. There were 47 Largemouth Bass captured in the one-hour survey and ranged in size from 5.71 to 19.88 inches with a mean length of 13.34 inches. The lake management goal for Largemouth Bass on Sullivan Lake is to maintain a catch rate above 25 bass/hour, which it had met. There was also an abundance of Largemouth Bass over 8 inches on Sullivan Lake. There have been eight Largemouth Bass surveys completed in the past 32 years (since 1993). The largest catch rate was in 2009; 95 bass were measured with a mean length of 11.21 inches and ranged in size from 5.28 to 17.68 inches. Before the 2017 Largemouth Bass survey the maximum length had not been over 17.68 inches, the 2017 and 2025 survey both captured Largemouth Bass up to 19.61 inches. Between 2009 and 2025 the abundance of Largemouth Bass has decreased but the size structure has increased. Spring trap netting was conducted from June 9th to June 12th, to provide data on the Bluegill size structure and evaluate effects of 10 bag limit on sunfish which was implemented on March 1st, 2016. Spring sampling has been consistent providing a desirable range of sizes with past sampling ranged from 169 to 555 Bluegill. In the 2025 sample, 374 Bluegill were captured and measured. Mean length was 6.42 inches and size ranged from 2.87 to 9.92 inches, and out of the 373 (one wasn't measured) 40% of the sample exceeded 7 inches and 10 % exceeded 8 inches with a presence of Bluegill over 9 inches. Prior to the regulation set in 2016, the average percent of Bluegill over 7 inches was 37.8% 7.8% were over 8 inches and 0.6% were over 9 inches. There was an immediate response to the regulation change in 2019 but has slowly decreased since. Summer trap nets used for IBI assessments also captured 191 Bluegill ranged in size from 3.35 to 8.43 inches with a mean length of 5.88 inches. There was 40% of the sample that was between 6 and 7 inches, indicating in future years there should be a higher percentage of Bluegill over 7 inches. The summer of 2025 there was a total of 12 gill nets set between July 7th and July 11th. Walleye catch rate was 2.25 Walleye/gill net meeting the long-range management goal of 4 Walleye/gill net. It did meet the goal of having 8-year classes ranging from Age-1 to Age-11. Sizes ranged from 11.22 to 25.51 inches with the mean length of 16.10 inches. Most of the catches were from Age-1 to Age-4, which should provide good fishing opportunities for the near future. Black Crappie are managed as a primary species and has a goal of sampling 100 with 40% of the catch over 9 inches and Crappies present over 12 inches. In the 2025 spring trap net survey there were 32 Black Crappie captured ranged in size from 5.12 to 12.60 inches with a mean length of 9.09 inches. The summer IBI assessment trap nets captured 51 Black Crappies ranged in size from 2.2 to 10.04 inches and mean length of 6.36 inches. Spring trap nets caught larger range of Crappie as expected for the spring including 12 inches and over but did not capture the goal number that was set. Northern Pike is managed as a secondary species, and its management goal is to obtain a gill net catch rate less than 5 per gill net with 25% being over 24 inches. In 2025, gill net survey the CPE was 5.5 Northern Pike/gill net set. Although the catch rate put it above the management goal, there was 44% that were over 24 inches. Size ranged from 10.16 to 37.17 inches and a mean length of 23.37 inches. Starting in 2017, every odd year has been stocked with fry, 1,000 fry/Littoral Acre or 800,000 fry which included 2025. Fall nighttime electrofishing has been utilized to assess natural and stocked reproduction success. On October 7th, 2025, in one hour of electrofishing, 19 fingerling Walleye were sampled while also sampling one adult Walleye. Fingerling Walleye ranged in size from 4.84 to 7.44 inches and the adult measured at 16.2 inches. In the previous three years catch rates for fingerling Walleye were 23 fish/hour (2022), 4 fish/hour (2023), and 0/hour (2024). The two highest fall electrofishing fingerling Walleye catch rates recorded have been from the non-stocked years 2020 (23 fingerling Walleye) and 2022 (23 fingerling Walleye). Which can indicate good natural reproduction in the lake. Catch rates from fry stocked years since 1999 have ranged from 0 fish/hour (2001, 2003) to 19 fish/hour (2025). The fall fingerling Walleye electrofishing survey catch rates have been a good predictor of year class strength for future gill net surveys too. Other species that were captured in the spring trap nets, summer gill nets and trap nets were Rock Bass, Black and Yellow Bullheads, Yellow Perch, Common Carp, Hybrid Sunfish, Pumpkinseed and Bowfin.

The targeted sampling completed on Sullivan Lake during 2024 included: an ice-out trap net survey and daytime electrofishing primarily for Walleye, spring trap netting for panfish, and fall nighttime electrofishing for juvenile Walleye. The lake is primarily managed for Black Crappie, Walleye, and Bluegill and secondarily for Largemouth Bass and Northern Pike. Ice-out trap netting captured 520 Walleye including recaptured fish. All Walleyes netted in the ice-out trap nets received a fin clip as a mark for calculating a population estimate. Trap netted Walleye ranged in size from 12.7 to 30.3 inches and average length was 17.7 inches. A total of 82 fish were sampled by electrofishing in 2024 ranging from 13.9 to 23.3 inches. Average length was 18.8 inches. An estimated population of 1,185 adult Walleye was calculated from the 2024 data . In comparison the 2016 spring population estimate was 851 adult fish. The ice-out trap nets in 2024 provided a sample of 210 Northern Pike. The sample was characterized by an average size of 18.7 inches and a maximum size of 28.9 inches. Fish over 24 inches comprised 10.5% of the catch and 13.3% fell within the 22-26 inch protected slot. No pike over 30 inches were observed in 2024 while 3 pike over 30 inches were noted in the 2016 ice-out survey. Catch rates of Northern Pike in trap nets are highly variable therefore catch rates are not deemed important for reporting. Spring Trap netting was performed June 3-5 to provide data on the Bluegill size structure and evaluate effects of a 10 fish bag limit on sunfish which was implemented in March of 2016. Spring trap netting is the preferred method for evaluating panfish populations and has been conducted on the lake eight previous times since 2001. Spring sampling with trap nets targeting panfish has consistently provided desirable sample sizes with past catches ranging from 169-555 fish. In 2024 there were 386 Bluegills captured and measured. Average length was 7.06 inches and 60% of the sample exceeded 7 inches long. Fish over 8 inches comprised 21% of the catch and 17 fish were greater than 9 inches. The largest Bluegill measured 10.1 inches and was the first fish over 10 inches recorded in targeted panfish trap net surveys. Bluegill size structure goals developed for the Quality Sunfish Initiative aim for at least 50% of the sample to exceed 7 inches, 20% to exceed 8 inches, 5% over 9 inches and the persistent presence of fish 10 inches or longer. The last three assessments performed since 2019 have produced Bluegill size structures that indicate improvement from pre-regulation efforts and progress towards management goals. Though not utilized for evaluating Bluegill size structures and regulation impacts the 2024 ice-out trap netting did provide a measured sample of 83 fish. Many similarities in size structure were found when making comparisons to the later spring trap net results. Fish over 7 inches accounted for 54% of the catch, 36% were greater than 8 inches and 7 fish surpassed 9 inches. The largest Bluegill measured 10.1 inches and average length was 7.11 inches. Black Crappie spring trap net catches can vary considerably due to sampling conditions and the Sullivan Lake catches have demonstrated this variability. Spring trap net catches in Sullivan Lake had ranged from 22 to 184 fish until 2024 when a record 238 were caught. Most previous panfish assessments sampled fewer than 100 crappies. Few favorable size structure characteristics were apparent in the 2024 panfish trap netting. Average length was 8.52 inches, just 8.4% of crappies exceeded 10 inches and maximum length was 11.2 inches. Ice-out trap net catches of Black Crappie have also been quite variable. The 2024 ice-out provided a significant sample of 226 fish. As with the targeted panfish trap netting, most previous efforts produced fewer than 100 fish. Crappies measured in the ice-out nets in 2024 showed a major difference in size structure compared to the later spring sampling. Ice-out crappies averaged 9.69 inches long, 43% were over 10 inches and 5% exceeded 12 inches. The largest crappie in the ice-out trap nets was 14.29 inches. Aging information was collected from crappies in 2024 and showed relatively consistent year class strengths from 2018 to 2021. The absence of the 2017 year class in the sample likely indicates that very limited reproduction occurred that year. Crappies displayed good growth especially as fish reached ages above 4 years old. Six-year-old crappies averaged 11.54 inches in length. Crappies also exhibited considerable longevity adding to their potential to attain large sizes. Three crappies reached ages of 13 to 14 and lengths from 13.4 to 14.3 inches. Pumpkinseeds were captured in moderate numbers with the ice-out nets and panfish nets combining for a sample of 109 fish. The size structure displayed some favorable attributes with 41% of the Pumpkinseeds measuring 7 inches or longer. Two Cisco were caught in the ice-out trap nets and both fish were larger adults (17+ inches). Fall electrofishing for juvenile Walleye was completed in 2024 to assess natural reproduction. Similar evaluations take place during odd numbered years when fry stocking occurs. Fall electrofishing in 2024 failed to sample any young-of-year Walleye (YWAE). A total of seven older Walleye were captured ranging in size from 8.7 to 17.6 inches. Two Walleyes were determined to be yearlings. In the previous three similar efforts aimed at assessing natural reproduction catch rates were 11/hour (2018), and 23/hour in both 2020 and 2022. The two highest fall electrofishing YWAE catch rates yet recorded were from the non-stocked years in 2020 and 2022. Fall YWAE electrofishing catch rates have been a good predictor of year class strength in future gill net surveys. Even catch rates less than 10 fish/hour typically show recruitment in future gill net surveys. However, the absence of YWAE in the 2024 fall electrofishing may indicate minimal natural recruitment from the 2024 year class. Future gill net assessments planned for 2025 and 2029 should provide more definitive evaluation of the relative contribution of the 2024 year class. Maintaining stocking gaps and annual evaluation of juvenile survival via fall electrofishing will be necessary for the ongoing assessment of the relative contributions of fry stocked and naturally reproduced Walleye.

Based on Minnesota DNR survey data, anglers target Largemouth Bass, Black Crappie, Hybrid Sunfish, Northern Pike, and Rock Bass in Sullivan. See the full species list above for catch rates, size structure, and quality scores.

Minnesota DNR records list public access for Sullivan. Check the DNR LakeFinder page for the launch type and directions before you go.

Sullivan has a maximum depth of 57 feet and a mean depth of 17.6 feet, per Minnesota DNR data.

The most recent Minnesota DNR survey data for the main sport fish in Sullivan is from 2025.

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