Zebra mussels found in Big Spirit Lake
Zebra mussels are an invasive species that can be destructive to ecosystems, aquatic food chains, boats and other manmade structures. There is no effective treatment to control zebra mussels once they have infested a lake.
This is the first discovery of zebra mussels in Big Spirit Lake. Adult zebra mussels were identified in other Iowa Great Lakes in the fall of 2012, and have increased in numbers since.
In August, biologists at the DNR’s Boone research facility also found a single larval zebra mussel in a water sample collected from Big Spirit Lake that month. The presence of a juvenile zebra mussel and larva is of greater concern because it may indicate an established population that is multiplying.
“Finding both a zebra mussel veliger [larva] and juvenile indicates to us that zebra mussels have been introduced into Big Spirit Lake,” said Kim Bogenschutz, the DNR’s Aquatic Invasive Species Program coordinator. “It’s too early to tell if there is an established population in the lake, but it is likely since the other lakes in the chain have growing populations.”
Big Spirit Lake is the largest natural lake in Iowa. It is part of the Iowa Great Lakes, and flows over a spillway into the rest of the Okoboji Chain, including West Lake Okoboji.
The State Hygienic Laboratory measures the effects of the mussels and in the past years has worked with two cities that draw their drinking water from West Lake Okoboji, which borders Lakeside Lab. SHL is currently working with the city of Spirit Lake to monitor their drinking water from Big Spirit Lake. These cities treat their water with copper ion to prevent zebra mussels from collecting on intake lines, and routinely test the water for levels of copper. Dennis Heimdal, SHL environmental lab specialist located at Lakeside Lab, sends the samples via the courier to Ankeny for verification of their results.
“Invasive species can easily spread in the Iowa Great Lakes Region, because infested water bodies are within close proximity to other water bodies,” Heimdal said. “Research will need to be conducted to determine what effects zebra mussels are having on lake ecosystems: water clarity, water temperature, nutrient levels, algae abundance and diversity, and benthic invertebrate abundance and diversity.”
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.
The City of Spirit Lake recently completed upgrades to their drinking water intakes in the lake in preparation for a possible infestation.
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. Biologists inspect boat hoists and docks after they come out this fall for storage to check for zebra mussels.
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, for many years has implemented plans to prevent the spread of zebra mussels and other aquatic invasive species when stocking fish.
“Although we can treat the water leaving the hatchery, zebra mussels can clog pipes and valves, making the infrastructure at the Spirit Lake Hatchery vulnerable to the infestation,” said Hawkins. “Important upgrades are needed to protect the facility.”
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.
“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,” said Bogenschutz.
- 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 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.
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, please note its location and contact your local fisheries office or the Aquatic Invasive Species Program in Boone.
