Unintentional Release

Many species are released into new environments without the intention of creating established populations. The release of aquarium pets into the wild is common, although it is not generally the intent of the owners to establish self-sustaining populations. Common species released from aquariums are red piranha (Pygocentrus naltereri) and convict cichlids (Cichlsoma nigofasciatum).

The accidental escape of many cultivated plants from ornamental gardens is a common mechanism for the introduction of aquatic plants. Purple loosestrife (Lythrum salicaria) which now dominates many wetlands in Canada was introduced in this way.

Fishermen dump unused bait into the water in which they are fishing, even though their bait did not come from the same water; a significant example of this is the rusty crayfish (Orconectes rusticus). Many times pathogens are released with stocked fish, or plankton are introduced in fish transport water during fish stocking programs. Other unintentional releases include the introduction of marine algae into brackish habitats from the household disposal of seafood packaging and shells (for example, the green crab (Carcinus maenas)).