Three invaders: carp, purple loosestrife and Eurasian water milfoil. © DNR Photo
A history of invaders
Exotic species have been hitchhiking their way into Wisconsin for decades.
In 1988, residents of Monroe, Mich. turned on their faucets to find that they had no water.
A small animal about the size of a thumbnail and weighing less than an ounce.
This hitchhiker from Eastern Europe moved into the Great Lakes on an ocean freighter and found the habitat to its liking. First discovered in Lake St. Claire in 1988 by a Canadian researcher, the zebra mussel became the scourge of the Great Lakes and the poster child of invading exotic plants and animals.
Like many invasive species, zebra mussels reproduce in huge numbers, so it's not the size of one mussel that's the problem, it's the millions of mussels matted together that can plug municipal water supply intakes like those in Monroe or the cooling water pipes leading into power utilities.
Zebra mussels were first discovered in Wisconsin in 1990 in Racine harbor. Zebra mussels spread to parts of all five Great Lakes between 1988 and 1990.
Persistent mussels in water intake lines cost Wisconsin municipal water utilities and power utilities about $10 million in 1994 for control systems. Annual maintenance costs run about $100,000 per plant. On the Mississippi River, zebra mussels threaten the state's clamming industry as they encrust native clams that are used as the seed for Asian cultured pearls. People walking Wisconsin beaches where zebra mussels are found also will find millions of tiny sharp shells cutting their feet and the putrid smell of decaying mussel tissue.
Zebra mussels are by no means the only Wisconsin invaders. Early settlers brought plants and animals with them from Europe, some intentionally and some not.
The U.S Fish Commission introduced the common carp in the 1870s as a food source. Pacific salmon also were introduced in the 1870s. Naturalists introduced fresh water snails later in the century to "increase diversity."
More recently, chinook salmon and coho salmon were released in the Great Lakes to consume the abundant and troublesome alewife. Other sport fish intentionally introduced into the Great Lakes are the rainbow and brown trout.
Many invaders have a history of moving along transportation routes.
As locks were opened on the St. Lawrence River in the early 1800s, they provided passage for vessels and fish, such as the sea lamprey and alewife. Passage from Lake Superior to the Atlantic was achieved in 1855, opening the door for the influx of exotics. When the St. Lawrence Seaway was completed in 1959, ocean-going ships could more easily transit the Great Lakes. Exotic hitchhikers caught rides inside these vessels in their ballast and on the hulls.
Wisconsin anglers may see many exotics in lakes Michigan and Superior or in inland lakes. More common are white perch, red-ear sunfish, three-spine stickleback, round goby and ruffe.
The more common aquatic exotic plant species include purple loosestrife, which invades wetlands and forces out native plants, Eurasian water milfoil, curly-leaf pondweed and giant phragmites found in abundance in lower Green Bay.
Zebra mussels are found in 22 inland lakes, mainly in southeastern Wisconsin. Their encroachment was slowed by boaters who cleaned their boats of aquatic plants, drained their live wells, bait buckets and bilge water before leaving launch sites. If there is a good side to the zebra mussel invasion, it is the public visibility it brings to exotic species.
Because of the havoc caused by zebra mussels, Congress passed the Nonindigenous Aquatic Nuisance Prevention and Control Act in 1990, "to prevent unintentional introduction and dispersal of nonindigenous species into the waters of the United States through ballast water management." This act also called for coordinating the activities of federal agencies, to develop control methods and to take steps to understand and minimize economic and ecological damage.
Two parts of the act are of particular interest. One provides $2.8 million a year for research and education. University of Wisconsin Sea Grant has taken full advantage of these funds since 1989. The second section authorizes $4 million a year (but only about $800,000 to $1 million has been appropriated each year) to implement state management plans to control exotic aquatic species. Wisconsin is in the process of developing a plan so the state can qualify for federal funding under the act.
Al Miller is the advisory services director for the University of Wisconsin Sea Grant.
|Exotics in Wisconsin through time|
Opening of the Welland Canal in 1829 connected Lake Ontario and the Atlantic Ocean with the upper Great Lakes and allowed boats and exotic organisms to bypass Niagara Falls.
In 1880, about 75 common carp, native to Asia, were obtained by the Nevin Hatchery in Fitchburg from the U.S. Fish Commission. The Wisconsin Fisheries Commission placed as many as 35,000 carp in state waters from 1890 to about 1895 when the program was discontinued. Today, carp are present in at least 63 Wisconsin counties
Sea lamprey invaded the upper Great Lakes in the 1920s from the Atlantic Ocean through the Welland Canal.
Alewives entered the Great Lakes through rivers and canals. They arrived in Lake Erie from Lake Ontario in 1931. In Lake Michigan, their populations exploded in the 1960s and 70s, resulting in huge die-offs. Today alewives are controlled today by stocked salmon and trout. Alewife populations never became abundant in Lake Superior.
The St. Lawrence Seaway was completed, allowing large amounts of ballast water to reach the Great Lakes.
Eurasian water milfoil came to North America from Europe in the 1940s. It spread westward into inland lakes by boats and waterbirds, reaching Midwestern states between 1950 and 1980. Infestations in Wisconsin were reported as early as the 1960s starting in southern Wisconsin and now inhabit 54 counties and 338 Wisconsin waterbodies.
Rusty crayfish were likely brought to Wisconsin, as bait. They may have spread via ballast water or by students after studying crayfish. Populations have expanded since 1960 throughout northern Wisconsin lakes and streams.
Purple loosetrife from Europe and Asia was introduced to the East Coast of North America in the 1800s. It first spread along roads, canals and drainage ditches, and later spread via the nursery trade as an ornamental. Purple loosestrife was detected in Wisconsin in the early 1930s and remained uncommon until the 1970s. It is now found in 70 of Wisconsin's 72 counties.
Northern lakes in Wisconsin were spared the Eurasian water milfoil menace until the mid-1980s when a second wave of infestation hit the state.
The Eurasian ruffe, a perch-like fish, was introduced to the Duluth-Superior harbor in the ballast water of ships in the mid-1980s. Ruffe have been found only in lakes Superior and Huron but are likely to spread to the other Great Lakes. Ruffe may harm valuable perch, whitefish and herring fisheries by competing for food and eating eggs.
The spiny water flea was found in Lake Huron in 1984. It feeds on daphnia, an important food source for young fish and other organisms. Its spiny tail makes it undesirable prey for many predators. The fleas form large clouds in the lake and gum up fishing lines.
The University of Wisconsin Sea Grant established an exotic species program.
The U.S. Nonindigenous Aquatic Nuisance Prevention and Control Act called for a standard for ballast water quality. About 21 billion gallons of ballast water are released into the nation's waters each year. Voluntary ballast exchange for ocean-going ships entering the Great Lakes became mandatory in 1993.
The round goby has spread to many areas of the Great Lakes. This bottom-dwelling fish can displace native fish, eat their eggs and young, take over habitat, spawn multiple times in a season and survive in poor quality water.
While first discovered in a Rachine harbor in 1990, zebra mussels, have expanded their range along the coast. They reproduce quickly, clogging intake pipes that serve industries and water treatment plants. They damage lakes and rivers, and native mussel species. They are spreading to inland waters.
The Wisconsin Department of Natural Resources submitted a Eurasian water milfoil report and a zebra mussel report to the legislature.
The National Invasive Species Act was passed.
The National Aquatic Nuisance Species Task Force approved a plan on the St. Croix National Scenic Riverway that provides funding to protect against the introduction of zebra mussels and other invasive species.
White perch were found in the Green Bay/Fox River system in 1988, in the Duluth harbor in 1986, and in the Milwaukee harbor in 1999. This relative of the white bass, yellow bass and striped bass, is an East Coast native.
President Bill Clinton directed federal agencies to fight invasive species "that are upsetting nature's balance, squeezing out our native species, causing severe economic damage and transforming our landscape."
The International Joint Commission (IJC) completed a study of exotic species in the Great Lakes. Recommendations called for biological standards for ballast water in ships.
A policy is developed by the Great Lakes Panel on Aquatic Nuisance Species to guide ballast water management in the Great Lakes region.