Aquatic Invasive Species in Pennsylvania
- [Professor] Hi, I'm Diane Oleson, Water Resource Educator, here to tell you about a few of the aquatic invasive species of particular concern in Pennsylvania and how to spot them.
I'll talk about just a few of the invasive organisms considered priorities by the Great Lakes Commission and the Pennsylvania Fish and Boat Commission, and some pointers on identifying them.
Aquatic Invasive Species, or AIS, come in many forms, ranging from plants, to animals, to pathogens.
According to the federal definition, invasive species means a species outside its native range, whose introduction does or is likely to cause economic or environmental harm, or harm to human, plant or animal health, and the introduction is caused by human activity.
There are many invasive species in Pennsylvania.
The main problem with invasive aquatic plants is mat formation.
Dense mats of vegetation prevent recreation, clog water intakes, destroy habitat, crowd out native plants, interfere with oxygen entering the water, and when plants die in decay, reduce oxygen levels, leading to fish kills.
Many aquatic invasive plants spread through plant fragments as well.
When removing plants, care must be taken not to make the problem worse.
The water chestnut, Trapa natans, is not the edible variety.
It came to us as a water garden introduction.
The native range for this plant is Europe, Asia, and Africa.
It can grow rooted in up to 16 feet of water, eliminating other plants, and reducing oxygen in the water.
Look for leaves floating in rosettes on the surface of the water, with feathery submerged leaves.
Small, white, four petaled flowers that produce nut-like seeds with four sharp spines that can pierce footwear, giving it its other name, water caltrop.
The seeds can remain viable up to 12 years in the sediments.
This plant is easily spread through plant fragments.
Parrot feather, Myriophyllum aquaticum, is a plant sold for water gardens that originated in South America.
Look for spikes of bright green feathery leaves, growing up to a foot above the water, with limp submerged leaves, that are often reddish-brown.
Leaves grow in whorls of four to six.
A whorl is a group of leaves attached at the same point on the stem that radiate out in a circle.
The stems are sturdy and roots form along the stem.
The plants in North America are all female, so seeds are not a problem, however, the plant is easily spread by fragments of stems and rhizomes.
Hydrilla, formal name Hydrilla verticillata, is an invasive plant of uncertain origin, but is believed to have come from the Indian subcontinent in Korea.
It was imported as an aquarium plant, and can be an unwanted hitchhiker when buying water garden plants.
It is often spread through recreational activity.
Look for a submerged rooted plant with long twining stems, leaves usually in whorls of five to six, with serrated edges.
Hydrilla form tubers on the roots, and a resting form called turions.
It is easily spread by moving plant fragments, tubers or turions.
Hydrilla grows under a wide range of pH, nutrient, and light conditions, in water up to 12 feet deep.
Didymo, or Didymosphenia geminata, is also called rock snot, although it is coarse and cottony, rather than slimy to the touch.
It prefers moderately flowing, nutrient poor water, where it begins attached to rocks from a single cell.
This plant begins as circular brown splotches attached to rocks or plants, form stalk material that can be up to eight inches thick in the stream bed, and the stalk material looks slimy, but has a wool-like feel.
This brings us to prevention.
Clean all mud and plant material from boats and gear.
Drain the equipment or vessel, and disinfect or dry boots and all fishing gear and other recreational gear, boats and trailers, for at least five days before moving unto another watershed.
This is the Pennsylvania Sea Grant site for cleaning methods.
To avoid spreading aquatic invasive species, water gardeners and aquarium enthusiasts should never release any plants or animals, or dump water into natural water bodies.
These are some best practices to prevent from moving any aquatic invasive species.
In general, aquatic invasive animals species cause damage by competing with native species.
If they are a top predator, they simply eat the competition or their food.
They can be ecosystem engineers, changing the habitat by digging holes and banks that increase sediment movement, or destroying plants that provide food and cover.
They can also carry or act as intermediate hosts for diseases and parasites.
Animals are often spread through the pet, water garden, and aquarium trades when they escape, or are released.
Anglers may move invasive species as bait, most young fish look alike.
Crayfish, even worms, should be destroyed rather than released, unless collected in and released to the same watershed.
Animals can also be attached to plant debris or carried in bilge water, and even cooling water in outboard motors or jet skis.
The round goby, Neogobius melanostomus, is a small aggressive bottom dwelling fish from Eurasia.
It out-competes native fish for food sources, habitat, and spawning sites.
What to look for.
Young fish are solid slate gray, adults have mottled olive green, black, gray and brown spots.
There is a black spot on the dorsal fin.
It has a fused suction cup shaped pelvic fin.
Gobies reproduce rapidly, several times throughout the year, and are spread through bait bucket release, bilge water, and on plant debris.
The Northern Snakehead, Channa argus, is native to Russia, China, and Korea.
It has the nickname Frakenfish because of its appearance and voracious appetite.
It's a predator that takes insect larvae and small fish when young, graduating to larger fish, frogs, small reptiles, even birds and mammals as an adult.
It has a primitive lung, and can move short distances over moist land to a new pond.
Look for a long cylindrical fish that can reach 33 inches in length, with a large mouth and sharp teeth.
Relatively long dorsal and anal fins with a truncate tail fin, and sides with dark irregular blotches.
It was imported through the live seafood and aquarium trades.
Currently, movement of live snakeheads is banned without a permit from the U.S. Fish and Wildlife Service.
The red eared slider, Trachemys scripta elegans, is native to North America within the Midwestern states in the Mississippi Valley and Gulf Coast basin.
It is aggressive and omnivorous, out-competing native turtles in Pennsylvania.
Look for a unique, broad, reddish-orange patch behind the eyes.
The upper shell, or carapace, is a dark green with black or off-white stripes.
The skin color ranges from olive to brown, with yellow stripes or spots.
Young turtles have numerous dark eye-like spots on the yellow underpart of the shell.
Adult male turtles will reach sizes of five to seven inches, adult females 10 to 13 inches.
They're widely distributed as pets, and are frequently released when pet owners are unprepared for their size.
They tolerate polluted waters, and often contract and spread diseases.
The yellow bellied slider, Trachemys scripta scripta, is native to parts of Virginia and the Carolinas, but is considered invasive in Pennsylvania.
Look for a vertical yellow blotch that runs behind the eye, this is most evident in juveniles and females.
Narrow yellow stripes on neck, legs and arms.
The upper shell, or carapace, is oval in shape, with serrated edges and olive to brownish-yellow vertical bands.
Older turtles can be completely black.
The plastron is yellow with smudge-like markings, and often has two solid black spots toward the rear by the tail.
Adult male turtles will reach sizes of five to eight inches, adult females eight to 13 inches.
It is used in the pet trade, and released or escape of unwanted pets is responsible for its spread.
It can also interbreed with the red eared slider.
The rusty crayfish, Orconectes rusticus, is a large aggressive crayfish, native to the Ohio River basin.
They are native in Western Pennsylvania, but not in other parts of the state.
Adults consume aquatic plants, benthic invertebrates, detritus, juvenile fish, and fish eggs.
Because of their large appetites and aggressive behavior, they out-compete native crayfish and destroy habitat in the streams.
These crayfish can reach a maximum length of four inches.
Males are larger than females when mature, and both sexes have larger, hardier claws than most native crayfish.
Look for dark, rusty spots that are usually apparent on either side of the carapace, but are not always present in all populations, and claws that are generally smooth and grayish-green to reddish-brown in color.
Rusty crayfish are spread primarily through bait release.
The red swamp crayfish, Procambarus clarkii, is a southern crayfish of the Gulf Coast and Mississippi River drainage.
This is a crayfish that prefers marshy, slow moving water, and builds burrows that contribute to sedimentation.
It competes with native species as it feeds heavily on plants, snails, fish, and amphibians.
It's used in crawfish boils, leading to live seafood release, and is also spread through aquarium, classroom, and bait bucket release.
Look for bright red spots on claws and body, and a black wedge stripe on the underside.
This crayfish can reach up to 4.7 inches long, the males are much larger than the females.
Please consult Pennsylvania Sea Grant's Pennsylvania's Field Guide to Aquatic Invasive Species for more detailed information on these and other aquatic invasive species in Pennsylvania.
Frequently Asked Questions