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Alien Species Hit Parade
The World Conservation Union/IUCN has prepared a pamphlet identifying 100 of the world's worst invasive alien species. Some of the more catastrophic invasions include:
Zebra mussels, a mollusk originally from Asia, have wreaked havoc on native mussel and fish populations throughout the Great Lakes region and in the large navigable rivers of the eastern Mississippi drainage including the Mississippi, Tennessee, Cumberland, Ohio, Arkansas, and Illinois rivers. They can also be found in the Hudson River on the Atlantic Slope.
Lake Victoria has been blanketed with water hyacinth plants, crowding out native vegetation and animal species and making boat travel on the lake nearly impossible in many areas. Despite an aggressive campaign to eliminate the species two years ago, water hyacinths appear to be reinvading much of the lake.
The comb jelly (Mnemiopsis leidyi) introduced to the Black Sea via the shipping industry in the early 1980s, now comprises up to 95 percent of the biomass in the Black Sea. It feeds on zooplankton, eggs and fish larvae, and is responsible for reducing anchovy stocks and the subsequent collapse of a fishery worth U.S. $250 million a year.
The brown tree snake (Boiga irregularis) was introduced on Guam in the early 1950s. Since then, 12 species of birds have disappeared from the island and several other species are close to extinction. Up to 13,000 snakes per square mile may occur in some forested areas of Guam. Snakes crawling on electrical lines have caused more than 1,200 power outages since 1978, damaging electrical equipment and causing a significant economic burden.
Two species that have established themselves in Florida in the last two years haven't yet made the "worst" list.
Asian swamp eels have colonized in many of Florida's waterways, and are threatening to colonize in the Everglades.
Giant pink jellyfish (Drymonema dalmatina) native to the Caribbean have drifted into the Gulf of Mexico and are cannibalizing common moon jellyfish. The pink jellyfish grow to three feet in diameter, and their tentacles can reach 70 feet (21 meters). The species, first seen in early September 2000, have been seen from the west coast of Florida to west Louisiana. In some parts of the Gulf, scientists have counted thousands of these jellyfish per square mile.