Michigan's Least Wanted Species Game

Learn More About Michigan's
Least Wanted Species

Scientists are monitoring the spread of four species of Asian carp toward the Great Lakes: bighead carp (Hypophthalmichthys nobilis), silver carp (Hypophthalmichthys molitrix), black carp (Mylopharyngodon piceus) and grass carp (Ctenopharyngodon idella). The fish were originally introduced into fish farming ponds in southern states to help control aquatic plants. Some Asian carp escaped or were released into tributaries of the Mississippi River and have reproduced and expanded their territory. Asian carp can grow up to 100 pounds, reproduce quickly and disrupt the habitat and food supplies of native fish and shellfish. If these fish reach the Great Lakes, they could quickly become dominant species in the system.

The emerald ash borer was first found in southeastern Michigan ash trees in July 2002, though it had probably already been in the state for 5 or 10 years before that. It probably came into the state on wooden packing materials. The pest takes 2 or 3 years to kill an ash tree, which is its only known habitat in Michigan. Pesticide research is starting to show a little progress in controlling the EAB, though quarantines on moving ash trees and ash wood are still enforced.

The round goby is a freshwater fish from Eurasia that probably arrived in the Great Lakes in the ballast of ocean-going ships. They were first discovered in the St. Clair River in 1990 and now live in all five Great Lakes and in some inland lakes. They are aggressive fish that live on lake bottoms and reproduce quickly. Round goby out-compete some native fish for food and spawning habitat, and sometimes steal bait from fishing lines. They also eat the eggs and young of other fish. People can help prevent the spread of round goby by inspecting any bait fish they catch or buy for round goby, emptying their bait containers onto dry land, and killing and removing from the water any round goby they catch.

This freshwater aquatic plant forms thick underwater mats that crowd out native plants and fish and can be a hazard to boaters and swimmers and damaging to municipal water supplies. Hydrilla were imported to the United States in the 1950s from India and Korea for use as an aquarium plant. It "escaped" into Florida's waterways shortly after its introduction and has been spreading across North American waterways ever since. Michigan and the other Great Lakes states and provinces are working hard to keep hydrilla out of the Great Lakes.

This perennial plant that is known for its tall, beautiful purple flower stalks is native to Europe and Asia. It has spread throughout wetlands in the United States and Canada. Unfortunately, it crowds out native wetlands plants such as cattails and makes it difficult for fish and aquatic mammals such as muskrats to move through wetlands. Two types of beetles, Galerucella calmariensis and Galerucella pusilla, have been identified as species-specific feeders (that is, they only eat purple loosestrife). Since their careful introduction into wetlands in Michigan and other states in the late 1990s, these plant-eating beetles have begun to reduce purple loosestrife populations, though scientists say the beetles will never be able to completely wipe out the plants.

This freshwater fish is native to Eurasia and was accidentally introduced into the Great Lakes in the 1980s from ship ballast waters. Ruffe reproduce quickly and outcompete native fish such as walleye and yellow perch for food and habitat. The fish are well-established in the western end of Lake Superior and near Alpena in Lake Huron. Scientists are working to control the spread of ruffe any further in the Great Lakes and inland waterways.

Sea lampreys are primitive, jawless fish that look like, but are not related to eels. They were one of the first nonnative species to invade the Great Lakes, traveling from the Atlantic Ocean to Lake Ontario in the 1830s and to the rest of the Great Lakes after the Welland Canal, which allowed ocean-going ships to bypass the Niagara Falls, was completed in 1919. Sea lampreys spend part of their life cycle as parasites, feeding on the blood of host fish like native lake trout, whitefish and chub. It is estimated that one sea lamprey can kill 15 to 40 pounds worth of fish every year. A combination of control techniques, including blocking access to spawning streams with electrical and mechanical barriers, and applying lampricides (chemicals that kill the lampreys), have reduced the threat to native Great Lakes fishes from sea lampreys.

Zebra mussels are a barnacle-like mollusk (mussel) that are native to the Caspian Sea region of Asia. They were discovered in Lake St. Clair in 1988 and have spread to all five Great Lakes and many inland lakes, rivers and streams. The mussels attach themselves to rocks, docks, navigation buoys, boat and ship hulls, water-intake pipes for water systems and power plants, and slow-moving, hard-shelled aquatic animals such as clams, turtles, and other mussels. Zebra mussels have been compared to cockroaches in their ability to breed quickly (each female can lay up to 1 million eggs a year), spread easily into new areas and survive in a variety of conditions. They feed on plankton and other organisms they filter from the water in which they live. At first this filtering action leads to clearer, cleaner looking water, but can eventually lead to toxic algae blooms and excessive aquatic plant growth as more sunlight reaches deeper water than usual. The filtering can also greatly disrupt established food chains. People can help slow the spread of zebra mussels by cleaning their boats before moving them from one body of water to another, never dumping the contents of bait containers into lakes or rivers, and scraping attached zebra mussels from their boats.

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