Evidence Of Zebra Mussels Found In East Okoboji Lake

Iowa DNRThe Iowa Department of Natural Resources (DNR) recently found additional evidence of zebra mussels in East Okoboji Lake.

A mid-June sample from the lake revealed four zebra mussel veligers, which is the larval stage. After the discovery of four juvenile zebra mussels in East Okoboji and Upper Gar Lake last fall, sampling of the Great Lakes and surrounding area lakes has increased.

Water temperatures were still cool during the June sample and the numbers of veligers may increase in the July sample. All lakes in the chain are being sampled monthly.

“We have not found any adult zebra mussels yet,” says Kim Bogenschutz, the DNR’s aquatic invasive species program coordinator, “But this finding indicates there are enough adults in the lake to successfully reproduce. Additional sampling will reveal more.”

The June, July and August samples will reveal the most as reproduction should peak during those months.

Zebra mussels look like small, D-shaped clams that have alternating light and dark bands. Most are less than 1 inch long.

Zebra mussels are native to the Caspian Sea region of Asia and were introduced into the Great Lakes in the 1980s from ballast water of oceangoing ships.  They spread from the Great Lakes to the Mississippi River and were first documented in the Mississippi River in Iowa in 1992.

Zebra mussels are filter feeders that attach to underwater surfaces. They can interfere with aquatic food chains, kill native mussels and clog water intakes.  And there’s no getting rid of zebra mussels once they are in a lake or river.

The documentation of zebra mussels in East Okoboji highlights the spread of invasive species in Iowa waters. The zebra mussels probably arrived on or in a boat that had picked up the mussels in an infested water body.

Young zebra mussels are microscopic and can be unintentionally transported with water in bilges, live wells or bait buckets.  Adult zebra mussels can attach to boats, trailers and aquatic vegetation.

It is illegal to possess or transport prohibited aquatic invasive species such as zebra mussels in Iowa.  And, beginning July 1, boaters will be required to drain all water from boats and equipment before leaving a water body and keep drain plugs removed or opened during transport.

“For boats trailered between water bodies, a critical step is to drain the bilge and live wells before leaving a boat ramp to make sure you are not transporting young zebra mussels,” said Bogenschutz.

“Boaters and anglers can unintentionally spread zebra mussels and other aquatic invasive species if they do not take the proper precautions – clean, drain, dry – after each time out on the water.”

  • CLEAN any plants, animals or mud from boat and equipment before leaving a water body.
  • DRAIN water from all equipment (motor, live well, bilge, transom well) before leaving a water body.
  • DRY anything that comes into contact with water (boats, trailers, equipment, boots, clothing, dogs). Before transporting to another water body either: Spray your boat and trailer with hot, high-pressure water; or Dry your boat and equipment for at least 5 days.
  • Never release plants, fish or animals into a water body unless they came out of that water body and empty unwanted bait in the trash.

Signs are posted at public accesses to remind boaters to stop aquatic hitchhikers and to identify infested waters. More information about aquatic invasive species and a list of infested waters can be found in the 2013 Iowa Fishing Regulations booklet.


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