Round goby (Neogobius melanostomus)
Origin: Introduced from Europe into the Great Lakes in
1990 from the ballast water of an ocean-going ship.
Aquatic Nuisance Species (ANS): Aquatic animals
Description: Small bottom-dwelling fish. and plants that have been introduced into new ecosystems. ANS
Concerns: Round gobies are aggressive feeders and can have harmful effects on the natural resources in these ecosystems
find food in total darkness. The round goby takes over
prime spawning sites traditionally used by native species, and the human use of these resources.
competing with native fish for habitat.
These are the most aggressive nuisance species that have invaded
Pennsylvania’s aquatic habitats. All have negative effects on
Pennsylvania’s native plants and wildlife. Every effort should be
Zebra mussel (Dreissena polymorpha)
Origin: Introduced from Europe into the Great made to halt their spread.
Lakes in the 1980s from the ballast water of an
Description: Small fingernail-sized freshwater
Concerns: Zebra mussels colonize on Purple loosestrife (Lythrum salicaria)
surfaces, such as docks, water intake pipes Origin: Introduced from Europe in
and native mollusks. Their only known the early 1800s as an ornamental
predators, some diving ducks, freshwater garden plant.
drum, carp and sturgeon, are not plentiful Description: Tall-stemmed plant with
enough to have a significant effect on their lance-shaped leaves. A spike with
Spiny water flea pinkish-purple flowers tops each stem.
numbers. Zebra mussels have greatly affected (Bythotrephes cederstroemi)
the Great Lakes ecosystem and economy. Concerns: Purple loosestrife has been
Origin: Introduced from found in all major river drainages in the
Europe into the Great state. It can invade a wetland and quickly
Lakes in 1984 from the crowd out native vegetation. It has little
ballast water of an ocean- or no value for wildlife.
slightly larger than one Asian clam (Corbicula fluminea)
centimeter (0.4 inches) long. Origin: First introduced from Asia to the West Coast of North
Sea lamprey (Petromyzon marinus) More than two-thirds of America around 1924. By the 1970s, the clam occupied most of the
European ruffe (Gymnocephalus cernuus) Origin: Native to the North Atlantic region and
this length is a long, Mississippi Basin, the Gulf Coast and eastern United States.
Origin: Introduced from Europe into the Great introduced into the Great Lakes early in the 20th century. Description: Small freshwater mollusk.
Description: Primitive eel-like parasitic ﬁsh. barbed tail spine.
Lakes in 1985 from the ballast water of an Concerns: The Asian clam causes serious water supply problems,
Concerns: Even though this species is native to the Concerns: The rapid
ocean-going ship. affecting power and water suppliers and other industries. Asian
Susquehanna and Delaware River basins, the sea reproduction of this
Description: Small fish, close relative of the clams are drawn into intake pipes and block water flow.
lamprey has had a devastating effect on Great Lakes species, lack of predators,
ﬁsheries, where it is non-native. It is a direct parasite and competition with young
Concerns: Because of its aggressive nature,
on large game ﬁsh. fish for food may greatly
the ruffe has the potential to devastate both Red-eared slider
change the food webs of the
perch and walleye fisheries by competing for (Trachemys scripta elegans)
food and habitat. Origin: Native to the southeast
United States. Established
Eurasian watermilfoil populations are the result of the
Hydrilla (Hydrilla verticillata) (Myriophyllum spicatum) release of unwanted pets.
Origin: Introduced from Southeast Asia in the Origin: Introduced from Europe in the 1800s. Description: Medium-sized
1960s, probably through the aquarium trade. Description: Submerged aquatic plant. freshwater turtle with a bright-red
This plant was first reported in Pennsylvania in Featherlike leaves have reddish-brown tips. stripe immediately behind the eye Photo credits: Round goby, Dave
the mid-1990s in Adams and Bradford counties. Concerns: This plant grows so densely that it on each side of its head. Jude; Asian clams, U.S. Geological
Description: Submerged aquatic plant with finely becomes poor fish habitat, clogs propellers, and Concerns: The red-eared slider Survey; zebra mussels, J. Ellen
toothed leaves. Resembles common elodea. restricts swimming. Eurasian watermilfoil is competes for food and habitat Marsden; Eurasian watermilfoil, spiny
Concerns: Hydrilla spreads quickly and creates common throughout the state, but less common in with Pennsylvania’s native waterflea, Minnesota Department of
turtles. This competition could Natural Resources; purple loosestrife
mats of vegetation that are extremely dense. the Northeast where native watermilfoils still thrive.
(left), Ted Walke; purple loosestrife,
These mats may crowd out native vegetation. affect sensitive populations of M. Walter, Michigan Sea Grant;
native turtle species. European ruffe, Gary Cholwek; red-
eared slider, photo courtesy of U.S.
Geological Survey; hydrilla, California
Department of Food and Agriculture;
sea lamprey, Great Lakes Sea Grant.