FAQ's about Invasive Species

This link is a video link of an Asian swamp eel.

They are primarily algae feeders. They feed by filtering the water through a siphon, up to a liter per day. This is why they like the insides of pipes so well, there is a constant supply of water and food flowing by them.

So, what is a zebra mussel? They are a type of mollusk, which also include a wide variety of organisms such as squids, octopuses, snails, oysters, scallops, and clams. Generally, zebra mussels live for four to five years and average about an inch in length. Mussels are also called "bivalves," which means they have two shells or valves. The zebra mussel gets its name because of the dark, striped pattern on each valve. Usually the shell is a light color, either tan or beige, with zig-zag stripes.

The zebra mussel has the potential to inhabit most of the fresh waters of the U.S. and may impact a variety of native aquatic species and eventually entire ecosystems. They also have had a large economic impact already. Many power plants and water users have had to spend millions of dollars cleaning out zebra mussels from their facilities. In addition, more money has been spent on retrofitting facilities with devices to keep zebra mussels out and to monitor for them. These costs, unfortunately, get passed along to the consumers.

The swamp eel has a snake-like body with no noticeable scales or fins. The head is relatively short and the teeth are small and not easily seen. The gill opening forms a V shape on the lower throat area. The body and head are dark, sometimes dark olive or brown above, but their lower side is usually lighter, often light orange. Some are brightly colored with yellow, black, and gold spots over a light tan or almost-white background. The skin produces a thick mucous layer making the eels difficult to hold.

One of the most well documented impacts is that on our native mussels. Zebra mussels are anchoring themselves by the thousands to native mussels making it impossible for the native mussel to function. As many as 10,000 zebra mussels have attached to a single native mussel. Our natives have all but disappeared in Lake St. Clair and the western basin of Lake Erie. Zebra mussels also are filtering the Great Lakes at an amazing rate, making the lake very clear. Most people assume that this increased visibility in the water must mean the water is "cleaner". Not true. All they have done is filter out all the algae which normally would be food for native microscopic organisms.

Chinese tallow has the ability to reach reproductive age in as little as 3 years and to remain productive for at least 60 years. It does not seem to have a preference for disturbed areas over undisturbed areas and can grow in a variety of places. It can also grow in both full sunlight and shade. It is more tolerant of salinity and flooding than quite a few other native species. It grows in subtropical to warm climates but is hardy and able to withstand a few degrees of frost. It is able to thrive in the United States and is resistant to native insects. In addition, it is somewhat resistant to fire.

• Once they are drawn into a pipe filled with water, they can grow and clog the pipe until the water stops flowing.
• Females can lay over one million eggs in a spawning season.
• They attach themselves to a usually hard surface and are difficult to remove. This is a common trait of mussels that live in marine (saltwater) ecosystems, but not of freshwater mussels.
• They can withstanding short periods (several days) out of the water if conditions are moist and humid.
• They have a saltwater relative, the dark falsemussel (Mytilopsis leucophaeata), which is native to our Atlantic coast. This relative looks very much like the zebra mussel and is often mistaken for it. Should you find what appears to be a zebra mussel in saltwater, it is probably the dark falsemussel.
• Zebra mussel larvae (called veligers) are microscopic in size and are undetectable by the human eye. They can be unknowingly transported in boat live wells and bait buckets or anything that carries small amounts of water (even on SCUBA equipment).

Zebra mussels are native to fresh water rivers and lakes in Eastern Europe and western Asia. In 1769, Pallas first described populations of this species from the Caspian Sea and Ural River in Russia. For more information, click http://nas.er.usgs.gov/taxgroup/mollusks/zebramussel/

South Florida is a unique but endangered ecosystem. Prior to significant human activity in the area (mid-1800's), south Florida constituted one of the largest wetlands in the continental United States. The Everglades, referred to by Marjory Stoneman Douglas as the "River of Grass", historically encompassed an area of approximately 4,500 square miles.

Water moved through the system as a very broad slow moving "river", flowing southward into Florida Bay. During this century, human activity and population in South Florida have grown rapidly. The Flagler Railroad was built just after the turn of the century and a series of canals has altered the flow of freshwater through the system.

In the last few decades, algal blooms, seagrass die-off, declining shellfish numbers, mercury buildup in the animals, contamination by pesticides, and the widespread invasion of exotic plants have occurred in the ecosystem. Scientists want to find out if these changes are due to natural changes in the system or if they were influenced by human development, or a combination of factors.

If scientists can determine what the ecosystem was like before significant human activity began in the region, then the land-managers responsible for the restoration can set realistic goals. In other words, these studies can help answer the questions "what was the system like before the land was altered?" and "what do we need to do to restore the system to its natural state?" In addition, these studies can determine what portion of the recent changes are due to natural causes, such as hurricanes or El Niño events, and thus can save tax-payer's money by preventing the "correction" of a change brought about by natural events.

Monopterus albus is native to tropical and temperate parts of eastern and southern Asia. The eel has been found in northern Australia, but it is unclear if the eel is native to that continent.

• It breathes air and in addition can achieve up to 25% of respiration cutaneously (through the skin).
• It is able to survive weeks without food.
• After spending part of their life as females, some individuals undergo sex reversal, transforming into males.  All larger individuals are males.
• The large males construct bubble nests at the mouth of burrows and guard the eggs and young. A high degree of parental care is given probably assuring greater reproductive success.
• Because they are air breathers, conventional eradication measures, such as ichthyocides (chemicals which deny oxygen to the gills), are ineffective.

The eels were first found in Florida in 1997. Three populations are known. Sites include canals in the northern Miami area, a small drainage near southern Tampa Bay, and a canal system close to Homestead near Everglades National Park.

• It has the potential to spread from South Florida to the southern half of the country because it can survive both in hot and cold climates.
• It breathes air and can move across land.  This gives it the potential to spread rapidly and makes control difficult.
• It can increase its population without detection because of its 'secretive' behavior.  It is active primarily at night; during the day it hides in small burrows, crevices or thick aquatic vegetation. 
• It has no known predators in the United States.

For a video clip of a Asian swamp eel go to http://gallery.usgs.gov/videos/101.

Swamp eels were first introduced to the United States in Hawaii some time around 1900. It was first identified as being present in the continental United States in 1994 based on specimens collected in ponds at the Chattahoochee Nature Center north of Atlanta, Georgia.

Scientists studying the south Florida ecosystem have learned that invading cattail plants increased in number and are slowly displacing the native sawgrass communities along the margins of the canals. This may be due to increased nutrients entering the system through the canals. Also, scientists have learned that the amount of sawgrass present has fluctuated naturally over time.

In Florida Bay, the studies have shown that salinity and seagrass distribution have fluctuated a great deal over the last 100-200 years. Before 1940, these fluctuations seem to match natural cycles. After 1940, the fluctuations are much greater, and they no longer match natural cycles. The timing of this change coincides with a large part of the canal construction in the Everglades, so it seems that this human activity has had a big influence on Florida Bay. The studies also have shown that seagrass and macro-benthic algae were much less abundant in the 1800's and early 1900's, than in the last half of this century.

Our data provide strong evidence for region-wide ecosystem disturbance in the late 20th century that was accelerated by human activities. Research is continuing to find additional evidence, and to develop a better understanding of the relationships between salinity, seagrass, fresh-water input, and the plants and animals of the region.

Snakeheads are airbreathing freshwater
fishes that are not native to North America. In
scientific terms, snakeheads are divided into two
distinct genera:

• Channa (snakeheads of Asia, Malaysia,
  and Indonesia); and
• Parachanna (African snakeheads).

In the summer of 2002 and again in late spring 2004,one of the Asian species, the northern snakehead, generated national media attention when anglers caught this fish in a pond in Maryland and, more recently, in the Potomac River in Maryland and Virginia. Fisheries scientists consider snakeheads to be invasive species because they have the potential to threaten native fishes, the recreational fishing industry, and aquatic ecosystems.

Snakeheads have a long, cylindrical body with a large mouth and sharp teeth. They have enlarged scales on top of their heads and their eyes are located far forward on their head, similar to the scale patterns and eye positions of snakes. Because their heads are similar to the heads of snakes, they have long been known by the common name "snakeheads." Size and color patterns vary among 29 recognized species. The largest recorded snakehead was almost 6 feet in length. Additionally, the young (juveniles) of many species often have color patterns dramatically different from the coloration of adults. Adult snakeheads superficially resemble the bowfin, a native North American fish.