Common Aquatic Nuisance Species

Aquatic nuisance species are a serious threat to Connecticut's waterways. Introducing harmful non-native organisms into a lake, river, or bay can lead to environmental degradation and millions of dollars in control and clean-up costs—all of which affect boaters. Aquatic nuisance species, such as zebra mussels, quagga mussels, milfoil, and hydrilla, most often spread between waterways by hitching a ride on vessels and trailers. The Department of Energy and Environmental Protection hopes this information will help boaters learn what they can do to protect their favorite waterways from aquatic nuisance species.

Zebra mussels are about the size of a human fingernail. However, these little creatures are expected to cause hundreds of millions of dollars in damage across the U.S. and already pose a serious threat to supplies; industrial processing, including power plants and water treatment facilities; transportation; and recreation. It is suspected that zebra mussel larvae were first carried to the U.S. in the mid-1980s in the ballast water of ships coming from Europe. Since then, the mussels' rapid growth rate, high tolerance of environmental changes, and near absence of natural enemies in U.S. waters have enabled their explosive infestation in our nation's waterways—all the Great Lakes; the Hudson, Ohio, Illinois, Tennessee, Mississippi, and Arkansas rivers; and other streams, lakes, and rivers—which altogether cross 19 states and the Province of Ontario.

Many of Connecticut's lakes and ponds experience nuisance growths of aquatic plants that can interfere with swimming and boating. Eurasian watermilfoil, variable watermilfoil, hydrilla, and fanwort (Cabomba) are some of the exotic plant species that have become nuisance plants over the past 25 years. These plants grow rapidly early in the spring, overtopping and shading native plants. Unlike native plants, they also exhibit the tendency to grow to the surface of the lake and spread horizontally, covering the surface with tangled mats of vines. Unfortunately, eradication of these invasive plants is usually not feasible; therefore, the objectives of most control programs are to contain spreading and to minimize impacts to recreation.