The Iowa Department of Natural Resources is watching Big Spirit Lake after a resident found a single juvenile zebra mussel attached to a rock in the southwest side of the lake on Sept. 23rd.
Biologists at the DNR’s Boone research facility also found a single larval zebra mussel in a water sample collected from Big Spirit Lake in August. The DNR collects water samples and deploys settlement samplers in lakes across the state each summer to monitor for the invasive zebra mussel.
The first zebra mussels in the Iowa Great Lake chain were discovered in the fall of 2012 and have increased in numbers since. Big Spirit Lake flows over a spillway into the rest of the Okoboji Chain.
Kim Bogenschutz, the DNR’s Aquatic Invasive Species Program coordinator says the discovery indicates that zebra mussels have been introduced into Big Spirit Lake. Bogenschutz says it’s too early to tell if there is an established population in the lake, but says it is likely since the other lakes in the chain have growing populations.
Zebra mussels look like small, D-shaped clams that have alternating light and dark bands. Most are less than one inch long. They are filter feeders that can form dense clusters as they attach to hard underwater surfaces. In the case of large infestations, they may interfere with aquatic food chains, kill native mussels, clog water intakes, increase algae blooms, and cover beaches with dead shells, according to the DNR.
The City of Spirit Lake recently completed upgrades to their drinking water intakes in the lake in preparation for a possible infestation.
Biologists will inspect boat hoists and docks after they come out this fall for storage. Spirit Lake fisheries management biologists say the structures are quickly colonized and are good indicators of how prevalent mussels are in the lake.
The Spirit Lake Fish Hatchery uses raw water from Big Spirit Lake in the production facility. Zebra mussels can be filtered and killed in the water used to haul fish from the hatchery to other water bodies. The Spirit Lake Fish Hatchery, along with other Iowa hatcheries, has implemented plans for many years to prevent the spread of zebra mussels and other aquatic invasive species when stocking fish.
The DNR says the Iowa Great Lakes community has provided important leadership in fighting aquatic invasive species in Iowa.
Hawkins says that strong partnership and the continuation of efforts remains the best weapon against these invaders. He says there is currently no effective treatment to control zebra mussels once they have infested a lake.
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. Boaters must also drain all water from boats and equipment before leaving a water access and must keep drain plugs removed or opened during transport.
Bogenschutz says 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.
The DNR advises the following steps:
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, bait bucket) before leaving a water body.
DRY anything that comes into contact with water (boats, trailers, equipment, boots, clothing, dogs). Before transporting to another waterbody. 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.
More information about aquatic invasive species and a list of infested waters can be found in the Iowa Fishing Regulations booklet.
If you find a zebra mussel, you are asked to note its location and contact your local fisheries office or the Aquatic Invasive Species Program in Boone IA.