Imports of oyster spat early in the century brought several unwanted species introductions such as the oyster drill. In addition, cultured non-native species can escape from captivity, such as Atlantic salmon that escape from net pens. The intentional and unintentional release or escape of species into the wild by the industry and the hobbyist aquarium owner has led to introductions. The common goldfish, for example, has become a nuisance species in eastern Washington. Selected non-native species, usually target predators, have been intentionally introduced to control the growth and spread of other introduced species.
History shows that achieving the desired effect is difficult.
Grass carp introduced to control unwanted aquatic plants in inland lakes resulted in native plant species being decimated. The building of channels, canals and locks creates artificial connections between waterways, allowing the free movement of species across physical barriers. It also facilitates the transport of species by vessels. Commercially-sold live worms and other aquatic organisms for the recreational fishing industry, both the bait species and its packing material, can result in introductions through intentional and unintentional release. Individuals discard non-native plants in public waterways.