Water Log 19.1

Meet the Aquatic Exotics

The oceans, like the mountains and deserts, once served as natural boundaries, isolating one ecosystem from another. But, trade, travel and other human activities are moving organisms from one ocean to another allowing a species to take hold in the estuaries, tidelands, and wetlands of separate continents, touching off more and more invasions. Aquatic invaders can be the most difficult to halt because it is challenging to plug aquatic pathways that allow the species to spread.

One aquatic exotic, the Nile perch (introduced into Lake Victoria, Africa, as a commercial catch), is responsible for the disappearance of some 200 species from the lake resulting in one of the greatest single incidents of extinction ever recorded. Other aquatic exotics are described below.

Zebra Mussel

Originally from the Caspian and Ural Seas, the zebra mussel probably hitched a ride in ballast water to the Great Lakes where they colonized quickly and mercilessly, attaching to pipes, engines, fishing gear and dock pilings. Without a natural predator, the zebra mussel threatens to spread throughout the U.S. with a discovery in Florida in 1998.

Grass Carp

This slender Asian minnow is a voracious aquatic plant eater which can eat two or three times its weight each day, growing to nearly three feet long and up to 100 pounds.

Nutria

Every gulf state has its share of the 10 million nutria living in the coastal marshes, the large South American rodent that resembles a cross between a beaver and a rat. Originally introduced for a commercial trade in fur, it has developed a healthy appetite for the gulf states' aquatic plants.

Hydrilla

The submerged aquatic plant can grow as much as 2 - 6 inches each day. It cleverly edges out other plants by fanning out its stems like a mushroom cloud when it reaches the surface, creating a dense mat that shades out other plants.

Water Hyacinth

The hyacinth is a floating aquatic plant with colorful lavender flowers that also shades out other plants and makes navigation nearly impossible. Its final gift to the ecosystem it invades is that when a large amount of th plant dies at one time, the decomposing material can use all of the oxygen in the surrounding water, killing whatever animal life is present.

Chinese Tallow

A visitor from China, the Chinese tallow has grown quickly and, while it can provide shade from the hot gulf sun, it can also change an ecosystem, turning coastal tall grass prairie into tallow forest.

Sea Lamprey

The lamprey is a predacious, eel-like fish that attaches to a host fish until satiated or until the host dies. Native to the coastal regions of both sides of the Atlantic Ocean, it entered the Great Lakes in 1921 and contributed to the decline of whitefish and lake trout until efforts to establish a sea lamprey control program were successful.

Asian Swamp Eel

This eel is one of the few species known to invade natural wetlands. Discovered in Florida in 1997, the eel has become firmly established there and has the capability of invading freshwater ecosystems through the Southeast, including the Everglades.
 

University of Mississippi