Nonnative species threaten state’s fisheries

With the opening of walleye season Saturday, the Minnesota DNR Fisheries urge residents and visitors alike to heed cautions about transfering invasive species to new lakes and rivers.

By Kevin Peterson, DNR Area Fisheries Manger

Nonnative invasive species pose a threat to Minnesota waters, native plants and animals, and water-based recreation, including fishing.
By now many of you have probably heard about spiny water fleas, the latest nonnative species to invade Rainy Lake. Spiny water fleas were first reported in 2006 and Rainy Lake is now officially designated as “infested waters.” This means it is now unlawful to transport infested water (including in livewells and bait containers) from Rainy Lake and Rainy River or to harvest bait. A number of invasive species have already become established in Minnesota waters and could easily be spread - and new species could enter — if citizens who use state waters don’t take the necessary steps to prevent their spread. Anglers, because they often move equipment, bait, and water from one waterbody to another need to be particularly careful.
If spiny water fleas (a small crustacean zooplankton) aren’t bad enough, there are even worse things out there that threaten our fisheries. A viral disease known as viral hemorrhagic septicemia (VHS) was diagnosed as the cause of huge fish kills in Lake Huron, Lake St. Clair, Lake Erie, Lake Ontario and the St. Lawrence River in 2005 and 2006. Thousands of muskies, walleye, lake whitefish, and yellow perch died. Many Chinook salmon, smallmouth bass, bluegill, black crappie, burbot, emerald shiners and northern pike were diseased but did not die in large numbers.
This is the first time a virus has affected so many different fish species from so many fish families in the Great Lakes. VHS virus is an invasive species, but scientists are not sure how it arrived. It may have come in with migrating fish from the Atlantic Ocean or may have hitch-hiked in ballast water from ships.
VHS was first known as a disease of farmed rainbow trout in Europe in the 1930’s. In 1988 the virus was detected in wild herring and cod from the U.S. Pacific Coast and also in salmon and steelhead that returned to Washington hatcheries to spawn. Since then, the virus has been confirmed in several species on the Atlantic Coast and in Japan.
Virus particles in the water infect gill tissue and then move to the internal organs and blood vessels. The blood vessels become weak, causing hemorrhages in the internal organs, muscle and skin. Fish can also become infected when they eat an infected fish.
Fish that survive the infection will develop antibodies to the virus. Antibodies will protect the fish against new VHS virus infections for some time. However, the concentration of antibodies in the fish will drop over time. This may create a cycle of fish kills that occur on a regular basis.
Based on the diagnosis of VHS virus in Chinook, walleye and lake whitefish from Lake Huron in 2006, fisheries biologists believe the virus is probably already in Lake Michigan, and ballast water discharged from ships may have moved the virus to port cities on Lake Superior. A number of fish from Lake Michigan and Lake Superior were tested in the fall of 2006 and VHS virus was not detected. More testing is planned for 2007. It is important to note that VHS virus is not a human health concern.

What can you do to help?
Anglers and boaters can help prevent the spread of VHS virus from the Great Lakes to inland locations by following a few simple procedures:
• Do not move live fish from one location to another
• Do not empty bait buckets into lakes or rivers
• Drain water from your boat, motor, bilge, live wells and bait containers before leaving the water access
• Disinfect the outside and inside of your boat and other gear after using them in the Great Lakes using 1/3 cup of bleach in 5 gallons of water. Keep the surfaces wet for 5 minutes, and then rinse with fresh water.
• Report fish kills to the DNR
It seems that our lives keep getting more complicated all the time, and anglers will have to adopt some new procedures to help reduce the risk of spreading nonnative invasive species in Minnesota waters. I guess it’s a consequence of living in a world that is more connected. In addition to the steps outlined above, anglers should get in the habit of inspecting their boat, trailer, and equipment and remove visible aquatic plants, animals, and mud before leaving the access site. Simply drying your equipment for at least 24 hours is one of the best ways to prevent spreading spiny water fleas to other water bodies.
Please report any of the following species to the nearest DNR office if found in Minnesota’s inland waters: bighead carp, eurasion watermilfoil, round goby, ruffe, zebra mussel, new zealand mud snail and spiny water flea.
The 2007 Minnesota DNR Fishing Regulation Booklet has information on how to identify these species (found on page 67 and 68) and watercraft inspectors will be distributing information at local boat landings this summer.
As always, contact the International Falls DNR Fisheries office at 218-286-5220 or Email to:kevin.Peterson@dnr.state.mn.us with any questions or concerns.