Zebra mussels in Whitefish — 2014

Now that we have zebra mussels in the Whitefish Chain, what can we expect?

That question was put recently to Dan Swanson, an Aquatic Invasive Species (AIS) specialist for the Minnesota Department of Natural Resources.

He emphasized that only a few adult zebra mussels were discovered in 2013 in the Whitefish Chain.  The DNR had divers down for several days in several lakes looking for them.

They looked also for “baby” zebra mussels floating in the water.  The DNR invasive species specialists dragged very fine nets through the water looking for the floating (not yet attached) immature veliger form of zebra mussel.  They are so small a microscope is needed to see them.

This plankton netting revealed that these tiny zebra mussel veligers were present throughout most of the waters of the Chain, though in very low numbers. In some nets no veligers were found.

A few boat lifts taken out last fall had an occasional zebra mussel.

Swanson says Whitefish is in the early stage of an invasion.

However, he adds, zebra mussels have the capability to expand their numbers at phenomenal rates.   A female starts producing eggs within 7 weeks after settling in a fixed location and can produce upward of 1,000,000 eggs a year.

Different growth rate on two other area lakes

Zebra mussels were discovered in two other lakes in our county a few years ago, Gull and Pelican.

The rate of growth in each has been very different.

Gull has had explosive growth.  DNR divers in 2012 found 153 adult zebra mussels per square
foot on the bottom of Gull lake.   In Pelican even a single zebra mussel was difficult to find.

What will happen on Whitefish?

Both Dan Swanson and Gary Montz, DNR Research Scientist would not speculate about what might happen in Whitefish.

Talking in general about why some lakes get more zebra mussels than others they say it may depend on a complicated interaction of biologic and chemical factors in the water.

The science is not yet at a point that precise predictions can be made.

Montz said that a chain of lakes with each lake having different water conditions and lake bottom surfaces might very well end up having different concentrations of zebra mussels.

Montz commented that zebra mussels depend on algae for food.  If a lake is short on nutrients it would seem that would limit zebra mussel production.   Those lakes already tend to have little vegetation and very clear water.

What we do know

The water may get clearer. Each zebra mussel filters about a quart of water a day, filtering out algae that they need of food.  This leave less food for fish.

With clearer water plants may grow more prolifically and to deeper depths.

The zebra mussel veligers (tiny immature form) float around for a few days and then  strongly attach themselves to almost anything in the water: docks, buoys, boats, motors, native clams, plants, other zebra mussels and even items made of glass or fabric.

With time the zebra mussels can destroy wood and metal surfaces.

As zebra mussels proliferate they build by glueing onto one another or almost anything else.  They can obstruct pipes–even large ones.  A group of zebra mussels can smother native mussels.

What should boaters do?

Boats and motors are not immune.  Especially if they sit in the water with little use.

The boat’s bottom surface in contact with the water will get covered with zebra mussels as will the outside of the motor and propeller.

Zebra mussels will also proliferate in any hollow space filled with water as long as it doesn’t get too hot.

So live wells with all their piping, boat bilges, and bladders on wake boats are good places for zebra mussels to flourish.

Zebra mussels will die if they get dry, although that can take several days or more depending on the temperature.

Boaters can use lifts to get their boats out of the water.   They should also drain any water remaining in the boat and motor, including the bilge, live wells, and wake boat bladders.