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Aquatic invasive species include zebra mussels, quagge mussels, milfoil, and hydrilla.

Non-Native Invasive Species

Quagga and zebra mussels

Zebra mussels are about the size of a human fingernail. Yet these little creatures cause hundreds of millions of dollars in damage across the United States and pose a serious threat to water supplies, industrial processing, transportation, and recreation.

Several other recent invaders of the Great Lakes also are cause for serious concern. Goby (pronounced “go-be”) populations are expanding and displacing native species. The goby is a bottom-dwelling fish known for being aggressive and voracious feeders. The spiny water flea and the fish-hook flea, nearly microscopic crustaceans, are gradually replacing their native counterparts. They have long spines that make it difficult for small fish to capture and digest them. These species disrupt the food chain and adversely affect native fish species.

Non-Indigenous Aquatic Plants


Purple loosestrife, Eurasian watermilfoil, hydrilla, and water hyacinth quickly establish themselves and can displace native plants. Environmental and economic problems caused by these weeds include impairment of water-based recreation, navigation, and flood control; degradation of water quality and fish and wildlife habitat; and accelerated filling of lakes and reservoirs.

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