Acorn Lake's fishes include most of the species popular with anglers in central Minnesota lakes. Northern Pike, Walleye, Bluegill, Largemouth Bass, Black Crappie, Yellow Perch and several species not typically sought by anglers are part of the fish community. Of these, only Walleyes require stocking in order to sustain a fishery in this lake. The others listed above have ample spawning habitat and conditions to maintain their populations in Acorn Lake.
Bluegill catches remained higher than the lake's historical average after near-historic lows during the 1990's. Bluegills are not particularly fast growing in Acorn and it takes about eight years to produce a seven inch fish. The majority of Bluegills sampled in 2013 were relatively old (older than age five), but a few younger fish were found, as well. Bluegills sampled in trap nets averaged 7.1 inches in length.
There was an excellent forage base of Yellow Perch in the lake. Northern Pike showed good growth rates. In 2013, the average sampled pike weighed 2.4 pounds and the average Walleye weighed 2.6 pounds. Catch rates for both species were near the upper end of the historical ranges for Acorn Lake.
Modest populations of Black Crappie and Largemouth Bass were present. Crappies sampled by electrofishing averaged a little over a half pound each.
As a relatively small lake, Acorn is vulnerable to overfishing. Anglers can help maintain a balanced and healthy fish community by releasing a portion of medium and larger fish and keeping smaller ones for eating.