Mechanisms of Aquatic Non-native Species Introductions

Although some unwelcome species have been intentionally introduced in the past, most current introductions are the accidental result of human activity. We can inadvertently pick up seeds on our boots while hiking and carry them to another area. Insects can be transported in our plants or potting soil when we move to a new city or location.

Not all nonindigenous organisms will cause problems and many introductions, such as agricultural crops or animals, can be economically beneficial. Some non-native species are introduced intentionally for fishery enhancement, for ornamental landscaping purposes, to stabilize embankments, or to control other pests. However, these organisms may spread far beyond their intended purpose and cause irreversible damage to California's environment.

While there are laws that regulate the movement of some non-native species, people still intentionally introduce organisms into areas for humane reasons or for personal profit. There is also a chance that even a well-intentioned release may get out of control and cause environmental damage. The cost of controlling a new invasion can far outweigh any initial economic gain. Below are some examples of potential pathways through which new aquatic non-native invasive species may be introduced

Pathways of introductions to areas
 Intentional introductionsSport fishing enrichment, soil stabilizing plants, agricultural products, control of other pests.
Live seafood importsEscapes or intentional introductions to establish a market.
Landscaping or Water Gardening Spread from ornamental pond plantings or restoration projects.
Bait use and disposalDisposal of live bait or bait containers with algae, seaweed, or other organisms.
Escaped or released aquarium plants or animalsSome aquarium organisms escape from their environment while others may be intentionally released by someone unable to maintain their aquarium. Plant fragments can also establish if disposed of in yards, storm drains, or near water bodies.
Accidental stowawaysOn recreational boats motors and fishing gear, shipping crates, microorganisms attached to seeds, plants, or animals, or transport from one location to another in a ship's ballast tank.
OtherEscape from transfers of aquaculture or from educational/research institutions or biological supply houses.

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*RIDNIS Project Mechanisms of Introduction Page, September 2003 - September 2005
(*Reducing the Introduction and Distribution of Aquatic Non-Native Invasive Species through Outreach & Education)
University of California Cooperative Extension, Department of Environmental Science and Policy
This project is funded by the CBDA California Bay-Delta Authority in cooperation with the University of California Cooperative Extension.