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Aquatic Nuisance Species
Click here to view full size picture Nuisance species are organisms that are introduced into areas where they are not native. While many nuisance species are introduced accidently, others are intentionally released, often to enhance recreational opportunities such as sport fishing.

Without pressure from the competitors, parasites, and pathogens that normally keep their numbers in check, nuisance organisms, may undergo large population increases.

Since the 1800's, approximately 140 nuisance aquatic organisms have become established in the Great Lakes. Some of these species are wreaking havoc on the Great Lakes by competing with native organisms and altering ecosystem dynamics. People often unintentionally facilitate the spread of nuisance species - find out what you can do to help the battle against these aquatic exotics. This information came from the Michigan Sea Grant College Program and Inland Seas Education. For more information, visit the DEQ's Aquatic Nuisance Control page.

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Purple Loosestrife
(Lythrum salicaria)

First detected in the mid-1800s, this perennial wetland plant is native to Europe and Asia. Sometimes known as the "purple plague," it invades marshes and lakeshores, forming dense single-species stands. Purple loosestrife replaces native vegetation, thereby reducing the availability of food and shelter for native wildlife. Options for controlling the spread of this plant include cutting, herbicides, flooding, digging and the use of insects that regulate purple loosestrife populations in their native habitat.
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Eurasian Watermilfoil
(Myriophyllum spicatum)

Native to Europe, Asia and Africa, this aquatic plant was first detected in Lake Huron in 1952. Forming dense mats on the water surface, it displaces native vegetation and interferes with many types of water recreation. Its main form of reproduction is through fragmentation, with a small piece multiplying into millions of plants in one year. Spreading rapidly throughout the United States, it is now considered a serious problem in 34 states. Eurasian watermilfoil may be spread by people if it becomes entangled in boat propellers or attaches to the keels and rudders of sailboats.
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Round Goby
(Neogobius melanostomus)

First collected in the Great Lakes in 1990 in Lake Superior, the round goby is native to Eastern Europe. The goby is a bottom-dwelling fish that aggressively defends its spawning sites located in rock and gravel habitats. It can compete for habitat with native species such as mottled sculpin, log perch, and darters. Possessing a well-developed sensory system, the round goby is able to feed in total darkness. The goby can be accidentally transported in livewells, bilge water, bait buckets, and the ballast water of Great Lakes vessels.
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Zebra Mussel
(Dreissena polymorpha)

The zebra mussel is native to the Caspian Sea region of Asia. First collected in 1986 in Lake St. Clair, it has spread rapidly throughout the Midwest and now threatens most watersheds in the United States. Colonizing at high densities, the zebra mussel outcompetes native organisms and clogs water-intake systems of power plants (as shown in the video of the Traverse City Raw Water Intake Crib Structure). Costs associated with controlling this mussel are predicted to exceed $5 billion by the year 2000. Microscopic larvae may be carried in livewells or bilgewater, while adults may spread by attaching to boating equipment that has been in infested water; larvae may also drift downstream through connecting channels.
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Eurasian Ruffe
(Gymnocephalus cernuus)

The ruffe (pronounced rough) is a small and aggressive fish that is native to Eurasia. It was first introduced into Lake Superior in the 1980s, probably through the ballast water of ocean-going vessels. The ruffe has a rapid reproductive rate, with females producing up to 200,000 eggs in one season. The ruffe can thrive under a wide range of temperatures and habitats. Although the effects of the ruffe on the Great Lakes are unknown, it may compete with native fish for food and may prey on the eggs of other fish, such as lake trout. It can be transported by humans through boats, livewells, and bait.
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Sea Lamprey
(Petromyzon marinus)

Native to the Atlantic Ocean, the sea lamprey was first collected in the Great Lakes in 1830. An aggressive parasite, the lamprey rasps a hole in its prey and then consumes the prey's bodily fluids. Because of its feeding style, the sea lamprey contributed to the collapse of the lake trout fishery in the Great Lakes during the 1950s. Concerted control efforts are helping to keep this parasite's populations in check; the number of lampreys in Lake Michigan is currently only about 10% of the peak numbers present in the 1950s.
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Fishhook Water Flea
(Cercopagis pengoi)

Students aboard the Great Lakes Schoolship Inland Seas discovered a new invader to Lake Michigan and Grand Traverse Bay, the fishhook water flea. This discovery was the first reported sighting of the animal in Lake Michigan since it was found in Lake Ontario in July of 1998. The fishhook water flea is known by its long tail spine (up to 1/2 in.) and by the kink near the end of this tail.

This invader joins the growing list of invaders found in Grand Traverse Bay: spiny water flea, zebra mussel, alewife, sea lamprey, and threespine stickleback to name a few.

Cercopagis originates from the Caspian, Black, Azov, and Aral Seas. Ocean-going freighters most likely carried this invader in their ballast water to Lake Ontario. Within a year, ships traveling within the Great Lakes probably carried it to Grand Traverse Bay.

Cercopagis is expected to further upset the current food chain in Lake Michigan. Like the well-known spiny water flea, Cercopagis is a predator on smaller zooplankton. Small fish who feed upon zooplankton are discouraged from eating Cercopagis because of its long spiked tail spine.

Quagga Mussel
(Dreissena bugensis)

The quagga mussel is related to the zebra mussel but is a distinct species. It prefers deeper, colder waters which is consistent with laboratory studies indicating that the quagga has a lower thermal maximum than the zebra mussel. In addition, it may have the same potential as the zebra mussel to clog water intakes. The discovery of this second type of mussel increases the probability that other species of Dreissenidae have been introduced into the Great Lakes.

Spiny Water Flea
(Bythotrephes)

Originally limited to lakes in Eastern and Western Europe and China, the spiny-tailed Bythotrephes is a crustacean that invaded North America in the 1980s and is now established in all the Great Lakes. Bythotrephes is a small shrimp-like zooplankton that grows to an average of 10 millimeters (0.4 inch) in length and feeds on other small aquatic animals. It has powerful limbs for swimming and grasping food items, and a large pigmented eye for seeing light and images in the water. When Bythotrephes captures a food item, it inserts its mouthparts into its victim and, much like a vampire bat, sucks out all the fluids.

A carnivorous zooplankton such as Bythotrephes could have profound effects on Great Lakes fish because it feeds on other zooplankton that small fish depend on for survival. Although Bythotrephes itself is tasty to fish, it is protected from small fish predators by an unusually long tail spine with up to four pairs of protruding barbs. The barbs are not present at birth but appear in pairs as the animal periodically sheds its outer skeleton.

Fish usually manipulate food in their mouths before they swallow it, so they are frustrated by awkwardly shaped food. Researchers watching Great Lakes fish feeding on Bythotrephes in the laboratory found that small fish have great difficulty ingesting the spiny creature. Many fish such as young alewives, yellow perch and lake trout can easily capture Bythotrephes but have difficulty when trying to swallow it. These small fish flare their gills and throat, jerk their head and body, and reject and recapture the animal many times in an effort to swallow it.

Laboratory experiments show that small fish spend 8 to 10 percent more time eating Bythotrephes than other prey, and eventually learn to avoid it. Bythotrephes has more protein than most other zooplankton because of its large size, but the added nutrients may not make up for the extra energy small fish expend trying to eat it.

Fish shift their habitats and food preferences as they grow -- often feeding on zooplankton when they are young and eating other fish when they are older. Food that is difficult for a young or small fish to swallow may not be difficult for a larger fish to swallow. This may be why scientists find large numbers of Bythotrephes in the stomachs of adult fish in the Great Lakes. However, all fish start out small, and so at some point in their lives are vulnerable to the presence of Bythotrephes in the Great Lakes. Smaller fish depend heavily on zooplankton and are vulnerable to predators. Although older fish might benefit from eating Bythotrephes, the losses in energy, resources and time younger fish experience as a result of Bythotrephes may be greater than any later benefits.

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