Southeastern rivers and streams have more species of aquatic animals—fishes, mussels, turtles, and salamanders—than anywhere else in the country. Hiding in all of this diversity, however, are alien species--an animal or plant that has been introduced through human activity outside of its native range. Many species that we commonly seen in Tennessee, like bighead carp or even redbreast sunfish, are not native to this region.
Alien species may also be known as nonnative, invasive, introduced, or nuisance species. There are several ways that a species may be introduced into a waterway outside of its native range. Sometimes humans put them there on purpose, such as stocking fish that are popular for recreational and sports fishers. Sometimes nonnative species are introduced by well-intentioned people releasing fish from their home aquariums without thinking about the impact on the environment. Some introductions happen unintentionally. Commercial shipping is a major transporter of invasive species in U.S. bays, major rivers, and the Great Lakes. Ships will take in water, called ballast water, in one area to maintain balance as they travel across oceans and rivers. There are almost always small organisms in that water. When ships reach their destination, they release the water, and with it, any organisms that were taken in at the original port. Many shipping ports now have regulations about releasing ballast water, but this has historically been a major pathway for introductions of nuisance species in the Great Lakes.
Over the next few weeks, we will highlight some different invasive freshwater species and their impact on both humans and the environment. Most are species that can be found in the Chattanooga area, Tennessee, and the southeastern United States. Stay tuned!