Thornton

Thornton Lake is a 215 acre lake located in southwestern Aitkin County. Shoreline development is primarily limited to the northwest and northern parts of the lake. The lake has a maximum depth of 21 feet and a mean depth of 7 feet. Thornton Lake is known to experience occasional winterkill events. The last documented winterkill occurred over the winter of 1962, with another suspected winterkill in 1979, and based on this survey a likely partial kill within the last few years. There is no public water access on the lake so anglers interested in fishing Thornton must gain access through private property. Anglers fishing the lake can expect to find northern pike, black crappie, bluegill and largemouth bass. Northern pike catches in 2009 were the second highest recorded at 10.25/net, which is a slight improvement over the 1999 survey. The size structure of the pike population has decreased since last survey, with a mean length of 18.8 inches and 92 percent of the sample being 22 inches or smaller. The largest pike found in the survey was over 32 inches long. A statistically significant decrease in bluegill numbers was documented in 2009. Historically trap net catches of bluegill have ranged between 25 and 52 per net but the 2009 netting showed only 4.9 per net. The average size for bluegill caught in this survey was only 4.5 inches long, while the longest fish was a mere 6.6 inches. Black crappie catches were also at the lowest abundance ever recorded for this lake. The few crappies that were sampled were good-sized with a mean length of over 9 inches and one individual approaching 12 inches. Similar to bluegills and crappies, largemouth bass numbers were also lower in abundance than obsereved in previous surveys. Largemouth bass in this lake did exhibit a quality size distribution and are capable of reaching trophy sizes provided that anglers continue to release these larger fish. Largemouth bass as large as 19.5 inches were caught in this survey. A recent partial winterkill is a likely cause for the low abundance of bass and panfish in the 2009 survey. Partial kills are generally considered favorable for panfish species as growth rates and size structure usually improve afterwards due to reduced competition. In the absence of winterkills, panfish populations will rebuild over time. Northern pike are less susceptible to winterkills, which is why their abundance was still above average. As the panfish abundance rebounds, pike growth rates should begin to improve; this may already be evident since the growth rates of younger pike appear to be improving from what was observed for the population.

Thornton Lake is a small lake with a little over 200 acres of surface area. Shoreline development is limited to the north and west aspects of the lake. The remaining undeveloped shoreline and the islands on the lake lend to the pleasant atmosphere. There is a diverse aquatic plant community creating ample fish habitat. There is no public water access on the lake, which may somewhat limit fishing pressure. Thornton Lake is known to experience occasional winterkill events. The last documented winterkill occurred over the winter of 1962, with a suspected winterkill in 1979. Anglers fishing on Thornton Lake may experience improved northern pike fishing. The population size structure has improved and the average length northern pike is nearly 22 inches. Increased average size may be related in part to a decline in the catch rate of northern pike caught, leading to less competition and better growth for individuals. The index of 8.25 fish per gill net was still in the normal range for this lake type. Although the lake has low abundances of yellow perch and white sucker, which are the preferred forage for northern pike, growth of northern pike was good compared to other lakes in Aitkin county. The bluegill population shows characteristics common to populations elsewhere in the state, with a small average size and a high abundance. The average size for bluegill caught in this survey was just less than five inches long, while the longest fish was only 7.5 inches. These abundant small bluegills provide ample forage for largemouth bass, which were present in large numbers. The size structure of the population appears to be fairly well balanced with good numbers of fish in the 14-16 inch size range. Largemouth bass in this lake are capable of reaching trophy sizes provided anglers continue to release these larger fish. Largemouth bass as large as 20.5 inches were caught in this survey. The abundance of black crappie increased from the level observed in the 1994 assessment, but anglers may notice smaller crappies than in the past. The average size for black crappie in 1999 was 6.9 inches, down from 9.8 inches in 1994. No black crappies larger than ten inches were caught in this survey. This change in size is probably the result of a combination of factors. Selective angler harvest of large fish certainly plays a role in limiting the potential for improvement in the size structure of the population. Variation in year-class strength and increased density leading to decreased growth may also be part of the reason that this change occurred. Good year-classes were produced in 1993-96 and fishing may improve when these fish attain desirable sizes.

Anglers who fish on Thornton Lake will probably experience good catch rates for northern pike and sunfish, however the average size of the fish will be small. Gillnet catches of northern pike were high compared to other lakes of this type. The mean length for northern pike was small, at 18.5 inches in total length, and growth rates were slow. Only three northern pike over 24 inches were caught in the gill nets. Yellow perch and white suckers, the preferred forage species for northern pike, were caught at rates which are below normal for this type of lake.Bluegills were also caught at an above normal rate for this type of lake. Bluegills and pumpkinseeds were small, each averaging just 5.0 inches long in the trapnet sample. The largest sunfish caught in the trap nets was only 7.8 inches long. Sunfish grow slowly and are unable to survive long enough to reach sizes that are preferred by anglers.The small sunfish are certainly preferred by largemouth bass, however. The prey base for bass is very good and spawning habitat is excellent, indicating that largemouth bass fishing is probably very good and is relatively consistent. Largemouth bass up to 17.5 inches long were caught during this survey.Black crappies are not as abundant in Thornton Lake as are the northern pike and sunfish. Black crappies grow quickly, however, and can reach sizes preferable to anglers. The average black crappie caught in the gill nets was 10.0 inches long. Black crappie recruitment is very sporadic and an abundant population may occur only every few years. No upcoming strong year classes were noted in this survey. After the strong 1990 year class declines, probably in 1995, black crappie catch rates will likely be low for a couple of years.

Based on Minnesota DNR survey data, anglers target Black Crappie, Hybrid Sunfish, Largemouth Bass, Northern Pike, and Bluegill in Thornton. 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 Thornton. Check the DNR LakeFinder page for current access details before you go.

Thornton has a maximum depth of 21 feet and a mean depth of 7 feet, per Minnesota DNR data.

The most recent Minnesota DNR survey data for the main sport fish in Thornton is from 2009. Surveys this old should be treated with some caution — fish populations change over time.

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