Almost all our local fishing waters are productive aquatic ecosystems, reflecting the fertile lands (watersheds) surrounding them. To maintain fish populations in shallow, soft-sediment lakes where wintertime oxygen drops to levels threatening survival (a condition known as winterkill), aeration is sometimes used to mix in atmospheric oxygen.
Aeration systems used to maintain fish populations are operated by local organizations under permit from MN DNR Section of Ecological and Water Resources. Details of the Lake Aeration Program can be found here.
Below is a list of local fishing lakes having winter aeration permits in the recent past. Other waters with aerators or fountains might also have fish populations, but are either 1) not sampled by MN DNR Fisheries 2) lacking public access, or 3) aerated for different benefits (such as to keep marinas ice-free) List Updated March 2014
Carver County Aerated Lakes/Ponds ( * public access limited and/or far from parking areas)
Courthouse (run during autumn/pre-ice), Eagle, Lucy*, Oak*, Rice Marsh*, Susan
Hennepin County Aerated Lakes/Ponds ( * public access limited and/or far from parking areas)
Bass*, Crystal, Gleason*, Hyland, Loring Park Pond, Mitchell, Penn, Powderhorn, Rebecca, Red Rock, Round, Snelling, Sweeney-Twin*, Taft, Wirth, Wolfe Park
Scott County Aerated Lakes/Ponds
Cedar, Cleary, Crystal, pond in Prior Lake Lakefront Park, McColl, McMahon (Carls), Murphy, O'Dowd, Thole
Specifics for each lake's aerator type and operator can be found in the Aeration Permit Annual Report documents (such as the 2012-13 Report [Local aerator information is in Table 6 and Appendix 2.])
Some Notes About Aeration Systems / Aerated Waters Related To Fish Management:
- Thin ice is present when systems are operating; unsafe ice can spread beyond signed areas.
- Aerators can create a refuge of adequate oxygen but typically do not replenish oxygen throughout an entire lake; partial winterkills can still occur in aerated lakes. Beginning aeration late in a season, or once oxgen levels are below 4 parts per million, might not maintain sufficient oxygen levels.
- Winter aeration start times and duration are dependent on ice and weather conditions; during mild or short winters, aerators might not be run at all.
- Permittees (operators) are responsible for running aeration systems safely (including sign posting/moving) and effectively. Inexperience, desire to limit costs, annual variations in ice formation, and other factors can compromise running a system optimally.
- Aerators can stir bottom sediments and create cloudy water or suspended nutrients. Waters and aerator location need to be deep enough so enough water volume can be oxygenated.
- Aeration systems are one lake management tool and not a "cure-all." Aeration cannot fundamentally change problem conditions of shallow, fertile waters (such as thick vegetation/algae, odors, high summer temperatures, and spikes in harmful bacterial levels).
- Once an aeration system is established, advocates resist ever ceasing operation, even when allowing an occasional winterkill could benefit gamefish populations. This MN DNR Fisheries research study describes when leaving an aerator off might improve fishing more than sustaining unbalanced fish communities.