Mary

Lake Mary (2,450 acres) is located five miles southwest of Alexandria. Water clarity is moderate (8 feet) and aquatic plants are common in shallow areas. Average depth is 17 feet with a maximum depth of 40 feet. Walleye, Northern Pike, Largemouth Bass, and Bluegill are common. Lake Mary has two public accesses. One is located on the southern shoreline off Lake Mary Circle SW. An additional access is located off Minnesota State Highway 27 on the northern shoreline. A standard fisheries survey was completed in August 2025 to evaluate abundance and size distribution of gamefish populations. Lake Mary supports an excellent Walleye fishery sustained through alternate year fry stockings and modest natural reproduction. The 2025 Walleye gill net catch rate (12.9 fish/net) continued a relatively stable trend over the last decade. Walleye growth is above average with fish reaching 14.0 inches at age 3. Fifty-five percent of Walleyes sampled were larger than 15.0 inches and the largest was 27.4 inches. Northern Pike abundance remained at a desirable level (5.1/gill net). Average length was 20.0 inches. The largest pike measured 32.3 inches. Anglers are reminded that new pike zone regulations were implemented in 2018. Lake Mary is located in the North-Central Zone. Anglers can now keep up to 10 pike but not more than two can be over 26 inches in length. All pike between 22-26 inches must be immediately released. Harvesting smaller pike can help shift the population towards larger individuals and reduce the number of predators for young Walleye and other gamefish Due to the lake's quality habitat attributes, Lake Mary supports a robust Largemouth Bass population. Growth rates are similar to the state-wide average with bass reaching 12.0 inches by age 4. Size structure of the electrofishing catch described a quality fishery. Eighty-six percent of the Largemouth Bass sampled during spring electrofishing were over 12.0 inches and the largest was 17.1 inches. Though trophy sized bass were not captured during spring sampling, bass over 20.0 inches were observed in summer trap nets. Bluegill catch rates of 17.7 fish/trap net were above average for Lake Mary. Gill net catch rates of 10.0 Bluegill/net were also higher than average, suggesting fish had moved offshore at the time of the August survey. Growth rates of Bluegill in Lake Mary are moderate and 6-year-old fish averaged 7.0 inches. Very few Bluegill over 8 inches were caught during the survey with the largest fish measuring under 8.5 inches. Similar to the Bluegill catch, a majority of Black Crappie were captured in offshore gill nets. Black Crappie catch rates of 2.9 fish/gill net and 0.2 fish/trap net were the second lowest over the past two decades. Most Black Crappie were less than 10.0 inches and the largest was 13.1 inches. Black Crappie growth rates are moderate; average length of age 4 fish was 10.1 inches. In addition to summer sampling, a targeted panfish survey took place in the spring of 2025 as part of a broader research project investigating panfish populations across Minnesota. As a result, no additional age information was gathered from the August survey. Yellow Perch numbers were low during the 2025 survey. Perch are preferred prey for Walleye, Northern Pike, and Largemouth Bass. Significant predation likely limits the Yellow Perch population from maintaining a size structure appealing to anglers. Additional species sampled include Bowfin, Common Carp, hybrid sunfish, Pumpkinseed, Rock Bass, White Sucker, and Black, Brown, and Yellow Bullhead. The next standard fisheries survey is tentatively scheduled for 2029. Lake Mary was designated as an infested water body after the discovery of zebra mussels in 2013. Recreational users should take necessary precautions to prevent further spread of invasive species. Drain all water and remove all aquatic vegetation from your boat and trailer when leaving any body of water.

Lake Mary (2,450 acres) is located five miles southwest of Alexandria. Water clarity is moderate (5.0 feet) and aquatic plants are common in shallow areas. Average depth is 17.0 feet with a maximum depth of 40.0 feet. Walleye, Northern Pike, Largemouth Bass, Bluegill and Black Crappie are common. Lake Mary has two public accesses. One is located on the southern shoreline off Lake Mary Circle SW. An additional access is located off Minnesota State Highway 27 on the northern shoreline. Walleye are abundant (13.3/gill net) in Lake Mary. Average size was 15.7 inches, but the largest exceeded 26.0 inches. Twelve age classes were present in the 2021 survey. Three-year-old Walleye were the most common and accounted for 56% of the gill net catch. Growth rates were rapid. Walleye averaged 15.2 inches at age 3 in the August survey. Walleye fry are stocked on alternate years to maintain the fishery. Recent young-of-year surveys documented strong numbers of juvenile Walleye. Good fishing opportunities will continue into the coming years. Northern Pike remain abundant (7.9/gill net). Over 76% of all pike collected were less than 22.0 inches. An over-abundance of small pike likely has a negative effect on other fish populations. Anglers are encouraged to take advantage of the liberalized pike harvest regulation (anglers are able to keep up to 10 pike with no more than two fish longer than 26 inches; all fish from 22-26 inches must be released). Abundant aquatic vegetation in Lake Mary provides nearly ideal Largemouth Bass habitat. Average size was 14.3 inches, but large bass are present. Bluegill are common. Average length was 6.0 inches with a maximum length of 8.9 inches. Despite having rapid initial growth, few Bluegill exceed 8.0 inches. Reduced growth and a modest maximum length may be related to competition with other Bluegill for resources. Increased harvest on moderate-sized Bluegill (6.0-7.0 inches) would likely improve growth rates. Black Crappie are common (5.8/gill net) in Lake Mary. Crappie averaged 10.0 inches, with some individuals surpassing 12.0 inches. Strong numbers of age-1 and -5 crappie were present and will likely provide good fishing opportunities for the coming years. Yellow Perch are common (2.8/gill net), but numbers of harvestable individuals is low. Other species recorded in the 2021 lake survey included Bowfin (Dogfish), Brown Bullhead, Common Carp, hybrid sunfish, Pumpkinseed, Rock Bass, Tullibee (Cisco), White Sucker and Yellow Bullhead. The next lake survey is scheduled for 2025. Zebra mussels, an aquatic invasive species, are present in Lake Mary. Anglers are reminded to drain boats and equipment and remove aquatic vegetation prior to moving between bodies of water to minimize the risk of transferring aquatic invasive species to this or other lakes.

A targeted survey of nearshore fish species in Mary Lake was conducted over several days between July 1-15, 2020 by Index of Biological Integrity (IBI) Program 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 all 24 sampling stations, but one station was sampled from the boat due to site conditions. Similarly, a 50-foot seine was used to sample 22 stations, a 15-foot seine was used at one station, and site conditions prevented the use of seines at one station. Nearshore sampling captured 23 species of fish including six that are intolerant of disturbance (i.e., Banded Killifish, Blacknose Shiner, Iowa Darter, Mimic Shiner, Pugnose Shiner, and Rock Bass) and four that are tolerant of disturbance (i.e., Black Bullhead, Common Carp, Fathead Minnow, and Green Sunfish). The nearshore data was combined with gill net and trap net data from an August 2017 survey to describe the fish community and provide a Fish-based IBI (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 and Rock Bass), while other species are tolerant of degraded conditions (e.g., Fathead Minnow and Green Sunfish). 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. Data from this survey will contribute biological information about the health of the fish community during the Long Prairie River Watershed assessment process completed in coordination with MN Pollution Control Agency.

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

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

Mary has a maximum depth of 40 feet and a mean depth of 17 feet, per Minnesota DNR data.

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

Yes — Mary has confirmed zebra mussel. Clean, drain, and dry your equipment to avoid spreading invasives to other waters.