Aquatic Nuisance Species
The Animals
Aquatic nuisance species threaten our fishing, boating, swimming, and other water-based resources. In those states where they have become established, ANS have had untold negative effects. They are expensive to combat, and in most cases where they have become established, they are difficult to impossible to control or eradicate.
To prevent introduction of ANS into our waters, outdoor recreationists should learn to
identify these species and pay heed to recent Equipment Cleaning
and Bait Regulations.
Zebra Mussel
Attaches to rocks, docks, pilings, and junk on the bottom. More than 44,000 mussels per square yard have been reported. In large numbers they can plug municipal water intakes. Feeds by filtering water of organics. Can strain an entire lake in a short time. Found in Pelican Lk. area of western MN, a part of the Red River drainage. Colors vary from sharply contrasting black and white to subtle gray to off-white. Adults and free swimming larvae can survive 14 days or more in moist areas. More information on the zebra mussel from USGS.
New Zealand Mudsnail
Eats all vegetation, algae, dead animal material, and bacteria. Closes up when eaten
by a predator and passes through intestines unharmed. All are females, born alive, already carrying
fertilized eggs. Eggs survive long periods of dewatering, freezing to hatch when conditions
favorable. As many as 30,000 eggs per square meter have been found. Hitchhikes on dirty equipment
not allowed to completely dry out or freeze. Found in trout streams of Colorado, Montana, Wyoming, Great
Lakes. More information on
the New Zealand mudsnail from USGS.
Common Carp
Found in many North Dakota waters too numerous to
list. A prolific fish that out-competes native and desirable sportfish. Survives
high-nutrient waters. Only bullheads tolerate lower oxygen levels. Color almost black to
dark-brownish yellow; fins yellow with bright orange edges.
More information on the
common carp from USGS.
Silver Carp
Lives in large rivers. Concentrates below dams and can drive out desirable fish.
Produces huge numbers of eggs that hatch quickly. Found below
Gavin's Point Dam (Mo. R.) and lower James R. in SD. A tough fish that can weigh in
excess of 60 pounds. When spooked jumps out of the water, creating an airborne hazard to
boaters. More information on
the silver carp from USGS.
Rudd
Less than 10
inches long. Resembles the golden shiner. Females spawn 2-3 times in a year. A one-pound female can
produce 200,000 eggs. Found in eastern US; recently in SD, MN,
and some Rocky Mountain states. Carries parasites, diseases thought to infect
gamefish. More information on
the rudd from USGS.
Ruffe
Less
than10 inches long. Resembles small perch or walleye. Known to out-compete walleye, yellow perch,
and even bullheads. Females spawn several times a season, producing up to 82,000 eggs. Dominant species in some Great Lakes. More information on the
ruffe from USGS.
Goby
Less than 10
inches long. Resembles tadpole: large head, soft body, pot belly. Linked to declines in
yellow perch populations. Now found in the Great Lakes and
tributaries. Female produces between 200-10,000 eggs and spawns multiple times a
season. More information on the
goby from USGS.
Northern Snakehead
A very hardy fish. Survives well in marginal waters. Spawns 3-5 times a year, as many
as 15,000 eggs per spawn. Eats about everything. Competes with perch, walleye, and pike. Preys on
fingerling sportfish, obviating fish stocking programs. Image courtesy USGS, artist Susan
Trammel. More information on
the northern snakehead from USGS.
Spiny Water Flea
Competes with small gamefish. Generally not eaten by fish because of the spines on
their long tails. Adults hitchhike to other waters when tails tangle in fishing lines, nets, etc.
Adults or eggs survive for extended periods in damp areas such as live-wells and bilges. Found in Great Lakes and the Rainy River and Lake of the Woods in
Minnesota. Adults less than 1/2 inch in length, with a distinctive long tail covered
with sharp barbs. Reproduces frequently in summer, female producing up to 10 offspring every two
weeks. More information on
the spiny water flea from USGS.
Hooked-tail Water Flea
Competes with small gamefish. Generally not eaten by fish because of the
spines on their long tails. Adults hitchhike to other waters when tails tangle in fishing lines,
nets, etc. Adults or eggs survive for extended periods in damp areas such as live-wells and bilges.
Found in Great Lakes and the Rainy River and Lake of the Woods
in Minnesota. Adults less than 1/2 inch in length, with a distinctive long tail covered
with sharp barbs. Reproduces frequently in summer, female producing up to 10 offspring every two
weeks.
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