Aquatic invaders spread through this pathway in several ways. Anglers can introduce invasive species—often unintentionally—when they harvest invaders from one water body and carry them to another. Commercial supplies may also include invasive species that are hard to distinguish from common baitfish, although this is less common. Even native baitfish and bait bucket water can carry viruses, bacteria or other microscopic invaders. An estimated 109 non-native species have been introduced in the U.S. through the use and release of live bait.
Case in point: Viral hemorrhagic septicemia
Viral hemorrhagic septicemia (VHS) is a deadly fish disease native to Europe. A new strain was discovered in the U.S. in the 1980s and has since been found in over 50 species of freshwater and marine fish, including popular baitfish, across the Northern Hemisphere. After the virus caused massive fish die offs in the Great Lakes, the Animal and Plant Health Inspection Service issued a federal order that prohibited the transport of several live fish species from the region. The order was in place until April 2014.
Case in point: Bighead and silver carp
Two of the most notorious invasive species in the U.S. are believed to have spread in part through baitfish dumping. Anglers who catch their own bait may have confused juvenile bighead and silver carp with gizzard shad, a popular baitfish. Asian carp, as they are more commonly known, are voracious eaters that have severely knocked back food supplies and altered the food web in several Midwestern rivers. And because they jump out of the water when disturbed by boat motors, they also injure boaters and hamper recreation on these waterways.
DiStefano, R.J., M.E. Litvan, and P.T. Horner. 2009. The bait industry as a potential vector for alien crayfish introductions: problem recognition by fisheries agencies and a Missouri evaluation. Fisheries. 34(12):586-597.