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Living with zebra mussels
Farm Island Lake added to MN DNR Infested Waters List for zebra mussels

by Cheryl McDonough July 7, 2020

Click here to read more from the MN DNR.

Tim Plude - the DNR AIS Specialist –– called to let me know that Farm Island Lake (FIL) will be listed on the MN DNR Infested Waters List for zebra mussels.  Information about the Infested Waters List is below.  (FIL has not been added to the list yet).

I have included a lot of information, and I want to thank Tim Plude (DNR AIS Specialist), Rick Bruesewitz (DNR), Steve Hughes (Aitkin County Soil and Water Conservation District), and board member Bill Haroldson for helping so we can provide as much factual information as we can.


Events leading up to the discovery of zebra mussels (zeebs):
1.  A lake association member found a zeeb in Peterson’s Bay a few weeks ago on his anchor.  He sent the photo to Tim Plude.
2.  Tim got a veliger sample in Peterson’s and sent it off, and was planning to scuba dive to look further, but the sample came back positive.
3.  In a matter of days, the St. Paul DNR headquarters decided to list FIL as infested.

Living with zebra mussels
1.  DNR Parks and Trails have posted signs at the public landings.

2.  Aitkin County Soil and Water Conservation District will continue AIS inspections with a focus on prevention and protection from other invasives – i.e. starry stonewart, milfoil, etc.

3.  MN DNR activity will pick up and spend more time on AIS activity, inspections, etc. (during normal years this is true but with the current pandemic we are currently not fully staffed for watercraft inspections).  Tim Plude plans to search area (and downstream) lakes for adult zebra mussels as well as take veliger samples.  The small plankton sample he took in FIL only revealed one veliger but again it was a small sample.  Tim plans to run out to FIL this summer to take a

few more samples, this should give us an idea of the veliger population and the possibility of them moving downstream. 

4.  This is not a doom and gloom scenario. We will probably see zeebs on our watercraft equipment, docks, anchors, rocks and other debris in the water, etc.  Depending on how heavy the infestation we’ll need to be careful walking in the water or when removing docks or lifts because the shells are sharp. You may need to wear water shoes for protection.

5.  Environmentally, zeebs compete with the native mussels in the water. Farm Island Lake water will be clearer.

6.  Fishing implications:
It has been noted that the size of young of year Walleye in Mille Lacs has decreased by about 10%. Mille Lacs has zebra mussels.

Rick Bruesewitz (DNR) comments:

Regarding the effects on young of year Walleye is that the changes in growth on Mille Lacs are likely due to a combination of zebra mussels and spiny waterflea, not just zebra mussels.  Also, zebra mussels do not eat the same thing as young Walleye.  The interaction between the three species is much more complex than just direct competition.  While young Walleye fry do eat zooplankton (the same thing spiny waterflea eat, and not phyto-plankton – what zebra mussels eat) they switch to eating fish almost immediately (in first month of life), mostly perch.  The loss of growth is also not likely in the earliest stages as this would likely then result in a decrease in fry survival, which is not likely happening on Mille Lacs.  There is current research ongoing through the U of M and DNR to try to figure things out.

One issue often associated with zebra mussels is the increase in water clarity.  Clearer water does not usually benefit walleye, but how clear things get varies tremendously from lake to lake.

7.  Every lake that has been infested has their own story – some lakes see zeebs everywhere – over the years on Mille Lacs the zeebs got smaller in size. On Pelican Lake – over 8 years zeebs took off slow, in 3-4 years they were at their peak, and in the past few years they’ve significantly decreased in numbers.

8.  We may never know how the zebra mussel arrived to Farm Island Lake; we will always have them; they do not go away.

9. Tim Plude comment:  It is important for landowners to understand that all water-related equipment (docks, boat lifts, swim rafts, etc.) will have zebra mussels on and inside the equipment.  This equipment needs proper care when being transported away from the lake.  All water-related equipment is required to have a 21-day drying time before being moved to another waterbody and we ask all boats dry off for 5 days prior to moving to another waterbody.  For landowners that store docks and other equipment on their property not much will change and if using a dock company for storage and removal nothing should be needed from the landowner if hiring a DNR-certified Lake Service Provider .  If a landowner needs to transport infested equipment themselves for storage or disposal a permit may be required .

10.   Tim Plude comment:  The other things to consider including in your newsletter are ways to avoid zebra mussels from damaging a boat and not transporting them away from the lake.


If a watercraft is moored for extended periods of time, typically more than 24 hours, it could have zebra mussels attached to the hull, outside of motor and water intakes.  If left uncleaned the zebra mussels can clog a motor’s intake pipes (this could apply to intake pipes for people that pump water out of the lake, finer mesh with larger surface area on the hose end/filter can help along with annual cleaning).  Taking the time to wash and dry for 5 days or disinfect the watercraft after a weekend on the water is a good idea.


People should consider having a boat lift to avoid mussels attaching to watercraft.  Landowners should also make friends, family and guests aware of the zebra mussels and educate them on a few of these points above.


Minnesota law requires boaters and anglers to:

  • Clean all aquatic plants, zebra mussels, and other invasive species from boats, trailers, and water-related equipment.

  • Drain water from your boat, ballast tanks, motor, live well and bait container. Remove drain plugs and keep drain plugs out while transporting equipment.

  • Dispose of unwanted bait in the trash. To keep live bait, drain the water and refill the bait container with bottled or tap water.

Contact information

Tim Plude, Invasive Species Specialist | Ecological & Water Resources
Minnesota Department of Natural Resources
1601 Minnesota Dr.
Brainerd, MN 56401

Rick Bruesewitz, Aitkin Area Fisheries Supervisor | Division of Fish and Wildlife - Fisheries

Minnesota Department of Natural Resources

1200 Minnesota Avenue, Aitkin, MN 56431


Steve Hughes, District Manager | Aitkin County Soil and Water Conservation District
307 2nd St NW #216
Aitkin, MN 56431

How to identify zebra mussels

The FILIA website has a printable document with pictures and a description of zebra mussels.  Click here  

MN DNR Infested Waters List


The DNR will add a lake, river, pond or wetland to the infested waters list if it contains an aquatic invasive species that could spread to other waters. The DNR may also list a lake, river, pond or wetland as infested if it is connected to a body of water where an aquatic invasive species is present.

To reduce the risk of spreading aquatic invasive species, activities like bait harvest and water use are managed differently in infested waters.

How many lakes and rivers are listed as infested?

About 8% of Minnesota's more than 11,000 lakes are on the infested waters list. Less than 3% of Minnesota lakes are listed as infested with zebra mussels. As of October 2019, we have confirmed zebra mussels in 214 lakes and wetlands. We have listed 194 bodies of water as infested with zebra mussels because they are closely connected to a waterway where zebra mussels have been found. 

Click here to read entire article.

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