Less Than 1 Yrs. Post-Discovery, Zebra Mussels Flourishing In Lake Minnnetonka

[hatrack]

Less than a year after they were first discovered in Lake Minnetonka, troublesome zebra mussels have settled into most of the bays of one of Minnesota's outdoor jewels, officials said on Wednesday. In the first of monthly surveys by the Minnehaha Creek Watershed District, the invasive species was detected at most testing sites across the west metro lake.

The district began a three-year study this spring by placing monitoring devices at 32 sites from Grays Bay to Halsted Bay. In the first monthly check in late June, zebra mussels were found at 24 locations.

There was no evidence of zebra mussels at five sites, including Halsted Bay, Harrisons Bay and Coffee Cove. Monitoring devices were lost at three locations and will be replaced. Zebra mussels were first found in the lake's east end, in Wayzata Bay, last summer. They had spread by last fall across much of the lake's eastern half.

"It's no surprise the zebra mussel infestation is spreading west across the lake," said Kelly Dooley, the district's water-quality technician, citing their reputation for fast growth. "We're committed to doing everything we can to prevent its spread to other waters, but we need the public's help."

EDIT

http://www.startribune.com/local/west/125080804.html

[MineralMan]

1. Once they're in a lake, the battle's over for that lake.

Frankly, it's going to be impossible to keep them out of most major lakes in Minnesota. Eventually, they'll get in.

The real thing will be to find ways to adapt to their presence. In some lakes, the problem is starting to diminish. The native fish in those lakes have changed their food preferences and are now gobbling up the little molluscs. It takes a while before they recognize them as food.

This battle against the zebra mussels will be a losing one, just as the battle against the European carp was, many years ago. The lakes will survive. The native fish will survive. The balance will change, though.

[Viking12]

3. The zebra's will exacerbate Minnetonka's other invasive problem, eurasian milfoil

I live on Lake Winnebago in WI. The zebras moved in 8-10 years ago and have dramatically influenced the clarity of water here. Clear water, more light penetration, more weeds. Fortunately, we don't have milfoil (yet, knock on wood). The enhanced weed growth has been good habitat for panfish and we've got the strongest population of bass any one's ever seen. It remains to be seen how the changes will affect walleyes, the lake's most popular species.

[MineralMan]

4. Milfoil is a mixed bag. It's great for forage fish, since it gives

them shelter and breeding areas. As you say panfish and bass love the milfoil, but it's a little harder to fish than some aquatic plant growth. Walleye don't mind going into the milfoil, either, after forage. I catch lots of northerns on the edges of milfoil beds, and a few muskies.

Its biggest problem is that it makes the shallow water tough for boats, etc, and that's a real issue for lakeshore homeowners.

Like the zebra mussels, though, once it's in the lake, that's it. The system just has to adapt to it, and it seems to be doing so.

[MineralMan]

2. Here's some information from the USGS:

"Zebra mussels affect natural ecosystems both directly and indirectly. The greatest direct impact relates to the mussel’s feeding behavior. Zebra mussels are filter feeders and process up to 1 gallon of water per day/mussel. During this process, every particle in the water column is removed and either eaten by the mussels or wrapped in mucus and spit out. This feeding ability, in combination with high population densities, rapidly clears the water of even the largest lakes. Since zebra mussels became established in Lake Erie, water clarity has increased from 6 inches to 30 feet in some areas. Unfortunately, the material removed from the water consists of other live animals and algae that supply food for larval fish and other invertebrates. In response to this changing food supply, populations of some animals have begun to decline.

As the lakes clear, the brighter light levels cause aquatic plants to increase in number and size. This increased plant growth can be beneficial to some fish such as northern pike and to yellow perch. However, the plants do cause problems for recreational boaters and swimming beaches, and can increase taste-and-odor problems in drinking water supplies, and can block water-intake pipes during storm events.

One drastic impact of the zebra mussel invasion is the near extinction of native American unionid clams in Lake St. Clair and in the western basin of Lake Erie. Zebra mussels attach and build colonies on the clams, reducing their ability to move, feed, and breed, eventually leading to the death of the clams within a couple of years.

Zebra mussels have had positive impacts on parts of the Great Lakes ecosystems. Many native fish, birds, and other animals eat young and adult zebra mussels. Migratory ducks have changed their flight patterns in response to zebra mussel colonies. Lake sturgeon feed heavily on zebra mussels, as do yellow perch, freshwater drum, catfish, and all the sunfish. The increase in aquatic plants provides excellent nursery areas for young fish and other animals, leading to increases in smallmouth bass populations in Lake St. Clair and the Huron River."

http://www.glsc.usgs.gov/main.php?content=research_invasive_zebramussel