Species and Origin

Quagga mussels are native to the Dneiper River drainage of Ukraine and most likely they arrived in the ballast water of ocean going ships. The quagga mussel was first sighted in the Great Lakes in September 1989.

Current Status

Starry stonewort is a grass-like form of algae that are not native to North America. The plant was first confirmed in Minnesota in Lake Koronis in late August of 2015. Plant fragments were probably brought into the state on a trailered watercraft from infested waters in another state.

Description

Starry stonewort is similar in appearance to native grass-like algae such as other stoneworts and musk-grass. Native stoneworts and musk-grass are both commonly found in Minnesota waters. Starry stonewort can be distinguished from other grass-like algae by the presence of star-shaped bulbils.

Description

Hydrilla is a submersed herbaceous freshwater aquatic plant. Its rhizomes and stolons root in the substrate of ponds, lakes, canals, and slow moving rivers. The stems can grow up to 30 feet in length. As the stems near the surface, they become branched and spread horizontally. The dentate leaves form in whorls of three to eight at nodes on the stem. The leaves are sessile and about 3/4 of an inch long and 1/5 of an inch wide. Internodes may be up to 12 inches long on the main stem, less on the secondary branches. Tiny six-petaled flowers arise from the leaf axils.

The female flowers grow up to the surface on long peduncles, while male flowers separate from the plant as they reach maturity and float to the surface. There may be modified leaf buds, called turions, in the leaf axils. The turions break from the stem and can develop into a new plant. Tubers, which form at the ends of rhizomes, can also develop into new plants. Hydrilla closely resembles broad-leaved waterweed and Brazilian water-weed. Consult a natural resource specialist for positive identification. 

Species and Origin

A tiny snail that reproduces asexually. Native to New Zealand, it was accidentally introduced with imported rainbow trout in Idaho in the 1980s and into the Great Lakes via ballast water from ocean going ships.

Impacts

Densities can reach 100,000 to 700,000 per square meter. They outcompete species that are important forage for native trout and other fishes and provide little nutrition to fish that eat them.

Species and Origin

Spiny waterfleas are zooplankton (microscopic animals). Native to Europe and Asia, they were introduced into the Great Lakes by ballast water discharged from ocean-going ships. They were first discovered in Lake Ontario in 1982 and spread to Lake Superior in 1987. Adults range from 1/4 to 5/8 inch long. Spiny waterflea have a single long tail with small spines along its length.

Impacts

Spiny waterfleas eat small animals (zooplankton), including Daphnia, which are an important food for native fishes. In some lakes, they caused the decline or elimination of some species of native zooplankton. They can clog eyelets of fishing rods and prevent fish from being landed.

Species and Origin

Rusty crayfish are crustaceans that grow up to 5 inches long. They are native to the Ohio River basin. Their carapace usually has a pair of rusty-colored spots and claws often have black bands at their tips.

Impacts

Rusty crayfish are aggressive invaders. They can harm native fish communities by feeding on their eggs and young, drive out or hybridize with native crayfish, and eliminate aquatic vegetation.

What Does It Look Like? 

At a low level of infection, fish might not display any symptoms. As the infection becomes greater, however, fish will display widespread hemorrhages (bleeding) throughout body surface (eye, skin and fins) and within the internal organs (swim bladder, intestine, kidney etc). Because of the bleeding, gills and liver might appear pale. Sick fish will often be listless, swim in circles, and are frequently observed at the surface of the water.

NOTE: Confirming VHS infection requires sophisticated laboratory testing. A diagnosis cannot be made based solely on observation because many different diseases of fish have very similar symptoms.

For more information, download the VHS flyer.

Species Affected

To date, VHS has caused large-scale mortality in

• black crappie in Budd Lake (Michigan)
• bluegill in Budd Lake (Michigan)
• common carp in Lake Ontario
• freshwater drum in Lake Ontario, Lake Erie and Lake Winnebago (New York)
• gizzard shad in Lake St. Clair, St. Clair River and Lake Erie
• Great Lakes muskellunge in Lake St. Clair
• round gobyin Lake Ontario
• white bass in Lake Erie
• yellow perch in Lake Erie and Lake St. Clair

Species and Origin

The round goby is an aggressive bottom-dwelling fish that lives in lakes and rivers. They resemble sculpins, which are native, bottom-dwelling fishes. They can spawn several times per year. Adult fish are 3-10 inches long and mostly slate gray in color. There is a single scallop-shaped pelvic fin and a black spot on the dorsal fin. It is native to the freshwater region of the Black and Caspian Seas. They were introduced into the Great Lakes within ballast water discharged from ocean-going ships.

Impacts

Round gobies have been found at densities up to 20 per square meter. They compete with native fish for food and habitat, and eat the eggs and young of native fish.

Brazilian elodea was discovered in Powderhorn Lake in the mid-2000's, but was chemically treated and has not been found within the MCWD since.

Appearance

Submersed aquatic plant. Perennial. Can be rooted or free floating.

Leaves

Bushy appearance. Leaves in whorls of 4 to 6. Leaf edges have very small serrations that require a magnifying glass to see.

Flowers

White flowers with 3 petals are on short stalks and are visible above water. Flowers are 0.7 to 1 inch wide.

Reproduction

Spreads by plant fragments. No female plants have been reported in the United States. Since all plants are male, no seeds are produced in the US. 

Species and Origin

Large filter feeding fish that can weigh up to 110 pounds for bighead carp and 60 pounds for silver carp. Both species have low-set eyes below the mouth and large upturned mouths without barbels. Imported from China in the 1970s for use in aquaculture ponds to control plankton. By the early 1980s, both species had escaped into open waters in southern states.

Impacts

They eat huge amounts of plankton and detritus. Because they feed on plankton, these fish compete for food with native organisms including mussels, larval fishes, and some adult fish such as paddlefish. This competition for food could result in fewer and smaller sport fish. Silver carp can jump up to 10 feet out of the water when disturbed by sounds of watercraft. They often jump into boats and can injure boaters, personal watercraft operators, and water skiers.