Exotics of the Great Lakes

Text by Roger F. Thoma.

Phragmites communis

Many exotic species of plant have invaded the Great Lakes basin. This is Phragmites communis which was introduced from Europe. It forms large colonies
and crowds out all other species of wetland plants. Normally our wetlands are a complex mosaic of many species with high diversity that provide excellent habitat for many species of birds, mammals, and fish.

Phragmites grows over five meters high. This colony was located on the shores of Lake Erie at Cattawba Island.

Loosestrife



This is purple loosestrife (Lythrum salicaria). It's an escaped garden plant. It overtakes wetlands replacing all of the native plants. Efforts are underway to biologically control this destructive species by introducing insect predators from Europe. Hopefully it will work as this thing is destroying good fish and duck habitat. It's very pretty, but a big pest!

Dreissena polymorpha

Here's a close up of some zebra mussels (Dreissena polymorpha) attached to a native maple leaf bivalve mussel (Quadrula quadrula). Zebra mussels are
presently overwhelming the substrate of Lake Erie and changing the foodweb of the lake. The greatest impact has been the near total elimination of the native mussels found in the lake. The zebra mussels attach to the outside of the native mussels and smother them. Other impacts of zebra mussels are too many to discuss here but they go all the way from the top of the food web to the very base. They consume phytoplankton, concentrate contaminants, cause changes in benthic organism communities, provide food and habitat for exotic fish species, alter the flow of energy through the ecosystem, and may eventually even impact bald eagles by increasing contamination in the fish they eat.

 

This photograph was taken by Randy Sanders when he worked at the Ohio EPA. He is now at the Ohio Dept. of Natural Resources. The picture is public domain property but an acknowledgment would be nice. Thanks. Roger.

The Ghost Shiner

Notropis buchanani, The first record of this species in Lake Erie, that I know of, came from the Portage River in the 1960s. It has since spread throughout the Lake. It is, as best I can tell, a rather innocuous species. I know of no ecological changes resulting from the establishment of ghost shiners. They are very small, about 30 mm, and are translucent. They seem to do best in those waters that are turbid. I have found them in most of the tributary lacustuaries and only once in the Lake proper. They have been spreading from the western end of the Lake to the east.

The Round Goby

Neogobius melanostomus This species appears to be the result of the zebra mussel introduction. They come from the same part of the world, the Caspian Sea area. Round gobies are a benthic species and eat large quantities of zebra mussels. They likely would not have become established if their favorite food source was not first introduced. They are very territorial and aggressive. It appears they are reducing numbers of other benthic fish species in Lake Erie.

The first record of a round goby was made by David Jude of Michigan in the Lake St. Claire area (located between Lakes Huron and Erie). I caught my first specimens in August of 1993 at the Grand River, Ohio breakwater. Since that date (the first record from Lake Erie) they have spread throughout much of Lake Erie and can now be found in Lake Michigan also. The Ohio Department of Natural Resources has documented populations now in the millions.

continued under photo

  My records over the last seven years indicate that mottled sculpin (Cottus bairdi) and greenside darter (Etheostoma blennioides) numbers are declining
and in many areas can no longer be found in some.

Gobies are eaten by many Lake Erie fish species (the Ohio Department of Natural Resources is studying this) and may be contributing to increases in fish body burdens of toxic chemicals such as PCBs and mercury.

 

Fish of the Great Lakes

Electro fishing on the Great Lakes