How are exotic fish introduced?
Some fish have been introduced deliberately, including gambusia which were introduced in the early 20th century in a mistaken attempt to control mosquitos, and trout which have a long history of stocking for recreational fisheries enhancement. Other fish have been accidentally introduced, for example through the escape of ornamental or aquaculture fish (such as carp and goldfish), and the contamination of shipments of fish destined for fish stocking (banded grunter). While most of these species have been in NSW for many decades, recently an increasing number of ornamental fish species have been found in the wild. Some may have escaped or been released accidentally, but it is likely that others were deliberately let go by owners who no longer wanted them and were unaware of the consequences. Once they are in the wild, pest fish can spread naturally through a river system. However, in some cases the spread of pests into new areas is assisted by people, either accidentally or deliberately
