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August 30, 2010

Non-native, exotic invasive fish species on the rise in South Carolina

The incidence of non-native and exotic fish species showing up the state waters of South Carolina appears to be on the increase.

One case involves an alligator gar recently identified by a S.C. Department of Natural Resources (DNR) freshwater fisheries biologist. The alligator gar was reportedly taken by a bow fisherman on Lake Wateree, measured 4 feet in length and weighed in at 27 pounds. Alligator gar are native to the Mississippi drainage and are the largest of the gar family, reaching more than 200 pounds. This may represent the eastern-most documented occurrence of this species.

How such a fish, particularly of this size, travelled so far from its native range is unclear. DNR biologists suspect it may have been through the aquarium pet trade. Often exotic or non-native fish are purchased from out of state internet suppliers. Some species soon outgrow their aquarium environment, although they may have been purchased as juveniles, and owners remove them by releasing the fish into a nearby water body.

One such exotic tropical species being reported in increasing numbers is the red-bellied pacu. These natives of South America are popular aquarium fish and closely resemble and often are mistaken for the carnivorous piranha, which is a close relative. The pacu are not generally considered to be carnivorous. They do grow rapidly in an aquarium and are often released by their owners into the wild.

Fortunately most exotic pet trade species cannot survive the climate and/or environment in South Carolina for extended periods of time. This could change with potential ongoing milder winters and the natural adaptive evolution of the animal.

DNR reminds the public that it is dangerous to release exotic aquarium pets into the wild and encourages owners to thoroughly research any species they intend to purchase. The DNR considers the release of any non-native fish into the state’s waters as being environmentally irresponsible, regardless of whether it is an exotic or one found elsewhere in the country such as the alligator gar. If non-native species do manage to survive they can create devastating consequences to ecosystems by displacing native animals or plant species by rapidly reproducing and competing with native species for food resources. In addition, they may also introduce a variety of diseases or parasites or compromise the genetic integrity of native fish through hybridization.

The U.S. Geological Survey reports that more than 2,000 non-native fish species are imported into the United States every year for use in the aquarium pet trade. This figure represents 150 million exotic freshwater and marine fish.

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