Brock Lake

Brock Lake is a 10-acre lake with approximately .3 miles of shoreline accessible to bank fisherman. A gravel boat ramp and fishing dock is present. Electric trolling motors are the only motors allowed on boats. Brock Lake was enrolled into a fisheries Co-Op agreement with the IDNR in 2019.

Brock Lake is home to Nunley Fields which hosts Dee-Mack Chiefs Softball, Dee-Mack Braves Softball, Mackinaw Township Recreation Baseball/Softball programs, Dee-Mack Warriors Baseball and Dee-Mack JFL which has a dedicated field. 

2021 Report

Largemouth Bass

In 2021, the largemouth bass population was evaluated by 49 bass collected by Pulsed-DC electrofishing.  The largemouth bass population continues to be defined by a high percentage of fish from 5 – 12 inches with a body condition of 85. We did not collect any bass over 13 inches despite a June 2020 stocking of adult fish.  This stocking was a group of 75 brood bass that were being retired from Jake Wolf Fish Hatchery. With an average size of 4lbs these fish should provide some great fishing action as well as introduce a larger size class of bass that previously did not exist in the lake.  The collection rate was 147/hr which indicates a high density. 

At this time the current bass population could use thinning of bass that are under 12 inches in length.  The majority of the current bass population is under approximately 12 inches in length and growing slowly.  This is due to a very high density of bass all competing for the same food resources.  Effective April 2021 the bass regulation will be changed to a Protected slot limit from 12 to 15 inches and allowing the harvest of 2 bass under 12 inches per day and 1 bass over 15 inches per day.  Signage indicating the new regulation is already present at the lake.  


The bluegill population was sampled by 27 fish in the spring electrofishing survey.  They ranged in size from 1 to 8 inches in length with an average body condition rating of 104. The current bluegill population is rated as very good.  An improvement in the bass population size structure as well as continued aquatic vegetation management will help maintain this good bluegill size structure.

Black Crappie

The black crappie population was evaluated by 1 crappie at from 10 inches.  The body condition was good with a value of 95. The high-density bass population has helped in maintain a low-density crappie population with a good size structure of 9-11” fish.

No harvest or length limits are necessary for the crappie population at this time.

Channel Catfish

No channel catfish were collected in 2021.  IDNR has added Brock Lake to the channel catfish stocking schedule and the first batch of 8-10” catfish were stocked in August 2020. Effective April 2021 the catfish regulation will be changed to 3 fish per day. Signage indicating the new regulation is already present at the lake.  

Aquatic Vegetation

Brock lake historically has had an overabundance of submerged aquatic vegetation.  This can lead to the stunting of fish populations. A herbicide treatment of 7.5 gallons of diquat dibromide on 5/25/2021 had excellent results and reduced the amount of vegetation for the duration of the fishing season.  This vegetation control should greatly help the fishery over the next few years. 


On December 22, 2020, 30 “porcupine ball” fish attractors were added to Brock Lake.  They were placed in 2 groups, one in front of the wooden fishing dock and the other off the main point of the lake in around 10-12 ft of water.  Both groups are within easy casting distance of the shore and should be “relatively” snag free


Brock Lake
29550 E. Hoffman Rd.
Mackinaw, Illinois 61755