What Are Aquatic Invasive Species?

At the most basic level, aquatic invasive species are water-dwelling organisms that are not native to Minnesota. The impacts of aquatic invasive species vary. While some invasive species cause damage to ecosystems, others can cause human or economic harm. 

Priority Species List

Every year at MAISRC, we review the aquatic invasive species that should be prioritized for research. We identify the invasive species that are currently in Minnesota, or are in areas immediately adjacent to Minnesota, and are likely to cause significant damage. A species may be considered as high-priority if there are key uncertainties that prevent researchers/managers from developing effective prevention or management/control programs.

Every other year, MAISRC systematically identifies research needs related to these high-priority aquatic invasive species in order to direct research efforts and investments to the state’s greatest needs. Learn more about our Research Needs Assessment process. View the Priority Species list as a PDF

2019-2020 Priority Species List:

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Invasive fish

Species Impacts Click photo to learn more

Common carp

Cyprinus carpio

Common carp root in lake beds for food and in the process they uproot aquatic vegetation, increasing water turbidity and releasing large quantities of sediment-bound nutrients, which stimulate algal blooms. It is estimated that over 70% of lakes in southern Minnesota have lost their plant cover and suffer from excessive algal blooms due to carp’s foraging activity. 

Bighead carp

Hypophthalmichthys nobilis

Silver and bighead carp are filter-feeders, straining microscopic plants and animals out of the water and away from paddlefish, gizzard shad, and young gamefish which rely on them. This disruption affects native fish and waterfowl and could result in diminished recreational and commercial fishing opportunities in the region.

Silver carp

Hypophthalmichthys molitrix S

Silver and bighead carp are filter-feeders, straining microscopic plants and animals out of the water and away from paddlefish, gizzard shad, and young gamefish which rely on them. This disruption affects native fish and waterfowl and could result in diminished recreational and commercial fishing opportunities in the region. Silver carp also pose a threat to human health due to their propensity to leap out of the water when disturbed by watercraft.

Black carp

Mylopharyngodon piceus

There is high potential that the black carp would negatively impact native aquatic communities by feeding on, and reducing, populations of native mussels and snails, many of which are considered endangered or threatened.

Grass carp

Ctenopharyngodon idella

Grass carp are voracious feeders that pose a threat to terrestrial plants, such as shrubs at the water line. Grass carp can also eradicate aquatic vegetation that serves as a food supply for waterfowl and as refuge from predators for young fishes.

Rainbow smelt

Osmerus mordax

Rainbow smelt negatively impacts native fish populations, particularly young of the year. 


Gymnocephalus cernua

Ruffe grow rapidly, have high reproductive output, and adapt to a wide range of habitat types--because of these traits they pose a threat to native fishes.

Round goby

Neogobius melanostomus R

Round goby impact the population of native fishes by preying on their eggs in large quantities.

Goldfish/Prussian carp

Carassius auratus/gibelio

Where released, goldfish can be responsible for the decline of native fish, invertebrate and plant populations in different areas. Furthermore, it is notorious for increasing water turbidity because of its habit of stirring up bottom sediments during feeding.


Sander lucioperca

Concern exists that zander and walleye could hybridize.

Northern snakehead

Channa argus

Northern snakeheads are predatory fishes that compete with native species for food and habitat. Juveniles eat zooplankton, insect larvae, small crustaceans, and the fry of other fish. Adult snakeheads feed almost exclusively on other fishes

Harmful microbes

Common name Impacts Click photo to learn more


Viral hemorrahagic septicemia virus

As the name describes, the virus can cause internal and external bleeding which in severe cases leads to organ failure and death.

Baitfish diseases

Ovipleistophora ovariaec, Viral Hemorrhagic Septicemia virus, Asian tapeworm, and more.

Live baitfish are hosts to innumerable microbes that live in and on them, some of which may be pathogenic (i.e., causing disease) for wild native fishes. If a pathogen makes its way through the baitfish pathway and is released into a lake with susceptible wild fish population, it could be problematic important native fish species.


Heterosporis sutherlanda

Heterosporis, which is caused by the microsporidian parasite Heterosporis sutherlanda, is known to affect 15 species of freshwater fish, including walleye and yellow perch. The small, microscopic spores of this parasite live inside of the muscle cells of their fish host and liquefy the muscle tissue.

Koi Herpes Virus

Cyprinid Herpes Virus-3 (CyHV-3)

Cyprinid Herpes Virus-3 is a highly contagious pathogen that causes mass fatalities in common carp. MAISRC researchers are studying the virus to confirm that it does not infect native Minnesota fishes. If confirmed, the strategic and careful use of virus could reduce common carp populations without impacting native fishes.

Rock snot

Didymosphenia geminata

Also known as 'rock snot,' didymosphenia geminata alters stream ecology by forming dense algal blooms that can cover up to 100 percent of stream bottoms.

Rickettsia-like organisms (RLOs)

Piscirickettsia salmonis

Chytrid fungus Chytrid fungus is known to feed on living vertebrates. It primarily affects the skin of amphibians, causing the disease known as amphibian chytridiomycosis.

Aquatic invasive invertebrates

Common name Impacts Click photo to learn more

Spiny water fleas

Bythotrephes longimanus

Spiny water fleas are a tiny freshwater zooplankton that invade lakes and can take over the bottom of the food chain. They can decimate populations of Daphnia and other native zooplankton resulting in a decreased food source for native fish and an increase in algal blooms. They can also clog the eyelets of fishing rods, causing problems for recreationalists. There are fewer predators on spiny water fleas than on native zooplankton because small or young native fish can’t consume their sharp, barbed spine.

Zebra mussel

Dreissena polymorpha

Zebra mussels, though small, have huge impacts on our lakes.& Their presence may greatly reduce lakefront property values and their sharp shells cut swimmer’s feet. Ecologically, they filter enormous quantities of microscopic algae and alter energy flow through aquatic ecosystems—impacting fish populations and smothering and causing extinctions of native mussels.

Quagga mussel

Dreissena rostriformis

Quaggas are prodigious water filterers, removing substantial amounts of phytoplankton and suspended particulate from the water. Their impacts are similar to zebra mussels. By removing the phytoplankton, quaggas decrease the food source for zooplankton and alter the food web.

Faucet snail

Bithynia tentaculata

Faucet snails are an intermediate host for three intestinal trematodes, or flukes, (Sphaeridiotrema globulus, Cyathocotyle bushiensis, Leyogonimus polyoon) that causes mortality in ducks and coots. When waterfowl consume the infested snails, the adult trematodes attack the internal organs and cause lesions and hemorrhage. Faucet snails also compete with native snails and can clog water intake pipes.

Rusty crayfish

Orconectes rusticus

Rusty crayfish are very destruction of aquatic plant beds. They cause the aggressive displacement of native crayfish species and breed with native crayfish, replacing native crayfish populations with hybrids. They also compete with fishes for prey, and consumes fish eggs.

New Zealand mudsnail

Potamopyrgus antipodarum

New Zealand mudsnails outcompete native macroinvertebrate populations for food and habitat. They provide little nutrition to fishes that eat them.

A Ponto-Caspian amphipod

Echinogammarus ischnus


Red swamp crayfish

Procambarus clarkii

Red swamp crayfish outcompete native crayfishes for shelter and food. They compete with fishes directly for prey and indirectly by consumption of fish eggs. They also disturb shoreland areas through the construction of burrows.

Bloody red shrimp

Hemimysis anomala

Bloody red shrimp prey on native zooplankton, including Daphnia, which are an important food source for native fishes, potentially impacting aquatic food webs. They change the kinds and abundance of algae in a lake.

Killer shrimp

Dikerogammarus villosus

Killer shrimp are fierce predators. Their ability to eat and displace other amphipods is a threat to native amphipod diversity if introduced to North American freshwater habitats.

Aquatic invasive plants

Common name Impacts Click photo to learn more

Curlyleaf pondweed

Potamogeton crispus

Curlyleaf pondweed inhibits the growth of native species, interferes with recreational activities, and disrupts valuable services provided by native plants such as stabilizing sediment, improving water quality, and providing support for fish and other animals.

Eurasian and hybrid watermilfoil

Myriophyllum spicatum,

M.spicatum x sibiricum

Eurasian and hybrid watermilfoil grow rapidly and tends to form a dense canopy on the water surface, which often interferes with recreation, inhibits water flow, and impedes navigation. Eurasian watermilfoil is a particularly problematic aquatic weed, due to its ability to reproduce from fragments and spread rapidly, its high growth rate in a range of temperatures and environmental conditions. Some genotypes of specifically hybrid watermilfoil are more tolerant of some herbicides and, thus, more difficult to control.

Hybrid/narrow leaf cattail

Typha x glauca, T.


Narrow leaf cattails can develop large monocultures, outcompete native vegetation and will crossbreed with native, broad-leaf cattails.

Purple loosestrife

Lythrum salicaria

Purple loosestrife creates dense growth along shoreland areas and makes it difficult to access open water. IT overtakes habitat and outcompetes native aquatic plants, potentially lowering diversity. It also provides unsuitable shelter, food, and nesting habitat for native animals and its dense root systems changes the hydrology of wetlands.

Common reed

Phragmites australis

Common reed is a tall, aggressive grass that can take over wetlands and shorelines, push out native vegetation, and reduce habitat quality for wildlife. The aggressive invader can also impact infrastructure such as roads, stormwater ponds, and agricultural ditches.

Starry stonewort

Nitellopsis obtusa

Starry stonewort grows in tall and dense colonies. It is known to form mats on the surface of the water that can interfere with recreation and potentially displace native plant species.


Hydrilla verticillata

Hydrilla crowds out native species, impedes irrigation, and interferes with boating and recreation.

Brittle naiad

Najas minor

Brittle naiad grows into dense mats at the water’s surface and inhibits water recreation. It overtakes habitat and outcompetes native aquatic plants, potentially lowering diversity. It also provides unsuitable shelter, food, and nesting habitat for native animals.

Flowering rush

Butomus umbellatus

Flowering rush creates dense growth along shoreland areas makes it difficult to access open water. It overtakes habitat and outcompetes native aquatic plants, potentially lowering diversity. It also provides unsuitable shelter, food, and nesting habitat for native animals.

Yellow-floating heart

Nymphoides peltata

Yellow-floating heart develops monotypic dense patches that can exclude native plants and create stagnant, low-oxygen conditions in the water below. These areas of stagnant waters can be an ideal location for mosquitos to breed. If the population of yellow-floating heart is large enough, fish and other wildlife may be forced to relocate. The mat-like patches also impede recreational activities such as fishing, water skiing, swimming, and boating.


Cabomba caroliniana

Cabomba is an extremely persistent and competitive plant that grows quickly and crowds out other vegetation. Cabomba forms dense mats that block sunlight penetration to lower water depths and shades out germinating seeds or propagules.

European frog-bit

Hydrocharis morsus-ranae

Free-floating growths of European frog-bit can lead to densely tangled mats, which can crowd and shade out native aquatic vegetation. It can dominate wetlands where it occurs, and the dense mats may effect wildlife as well as native plants.