Recreational boaters and sea or float planes transport nuisance species in bait buckets or boat wells, often without realizing it. Fouling of vessel hulls by encrusting organisms also provides a mechanism for transfer of species. Aquatic plants, in particular, are easily transported when plant fragments get tangled on boat propellers and fishing gear of recreational boats. 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.
Recreational fishers buy commercially-sold live worms and other aquatic organisms.
Both the bait species and its packing material can result in introductions through intentional and accidental release. Non-native plants are dispersed when discarded in public waterways, or when accidentally attached to other horticultural species. Accidental release of specimens can occur when strict protocols for animal management aren t followed or when protocols do not exist. Specimens may also be intentionally released or may escape. U.S. federal and state agencies imported 19 game fish species into Washington state between 1890 and 1980 to enhance recreational fishing.