In the 200+ years since European settlement, many species have either been intentionally introduced or accidentally released into Australia’s freshwaters for a variety of reasons. Unfortunately, most of these non-native species have had devastating impacts on our native fishes.
In the early days, many of these introductions occurred because people longed for the fishes they knew in the ‘old’ country. Popular angling species, others seen as ‘desirable’ food fishes, and still others were introduced into what were considered to be barren streams and rivers.
With the growth of shipping activities some species even arrived as unseen hitchhikers in ballast water.
To control the hoards of mosquitoes in newly settled areas, Eastern Gambusia (Gambusia holbrooki), was introduced in the 1920’s, and is now widespread in New South Wales, Victoria, and South Australia, and has also been recorded from Queensland, the Northern Territory, Tasmania and Western Australia.
In more recent times, non-native aquarium or ornamental fishes have been intentionally or accidentally released, especially into coastal drainages in eastern Australia.
About 35 species are now thought to have established populations in the wild. These exotic species pose a serious threat to native fauna and freshwater habitats - by becoming serious invasive pests or introducing diseases into our waterways.
The Oriental Weatherloach (Misgurnus orientalis), first recorded in the Yarra River, Victoria, in 1984, is now the most common introduced fish in that river - and is now widespread throughout much of south-eastern Australia, and has recently been recorded in South Australia, and may also be in Queensland and Western Australia.
Author: Martin F. Gomon & Dianne J. Bray