Exotic Fish In Australia

carp | goldfish | mosquito fish | redfin | trout | tench | roach | tilapia

Overview

Numerous fish species have been released into the wild in Australia since European settlement commenced in 1778.  Many of these species were deliberately introduced under government authority, a situation which would not be tolerated today.

Many of the species appear to have been introduced in the attempt to reproduce angling opportunities elsewhere and with little or no thought to the consequences for native fish.

Probably the best known are the salmonid group of which attempts have been made with varying success to establish populations of brown, rainbow and brook trout as well as Atlantic and Chinook salmon.  Of these, brown trout have been the most successful in acclimatising to Australian conditions and rainbow trout are a close second being very widespread in cooler waters.

Also introduced for angling purposes have been redfin (English perch) and the coarse angling species carp, roach and tench.

One particularly problematic introduction has been that of the so-called mosquito fish, which did not even achieve the aim of those who introduced it and has caused considerable problems for small native species.

Several species have established populations as the result of liberations and escapes from aquarium use.  The ubiquitous goldfish is widely distributed and, in the last decade or so, weather loach have made alarming in-roads in many waters.  Also two species of cichlids (the black mangrove cichlid and the convict cichlid) have established self sustaining populations in the cooling pondage at the Hazelwood power station in Gippsland, Victoria.

 

carp | goldfish | mosquito fish | redfin | trout | tench | roach | tilapia

Carp

Cyprinus carpio

Attempts to acclimate carp since the 1860s and early this century were largely unsuccessful and eventually carp were recognised as an environmental pest and such attempts were banned.  However, illegal stockings of carp (believed to be from Germany) in the 1960s which co-incided with substantial reductions in native fish for unrelated reasons allowed the species to establish itself in the wild.

Since then carp have become the dominant species in many waters and are a declared noxious species in Victoria.  It is illegal to return live carp to any waters in Victoria and any carp caught must be destroyed.  It is also illegal to hold live carp in Victoria, including koi carp, which are kept by some people as ornamental fish.

Often blamed for any environmental damage in systems where they occur, they do in fact cause considerable damage.  Some native species, notably Murray cod, have learned to feed on carp and young carp form an important part of their food supply at certain times of the year.

Almost universally despised in Australia, carp are not generally sought as a food fish.  There have been a number of attempts with limited success to establish commercial uses for the fish.

Carp were recently discovered in Tasmania and caused much alarm, ironically, because of its possible effects on another introduced species, trout.

 

carp | goldfish | mosquito fish | redfin | trout | tench | roach | tilapia

Goldfish

Carassius auratus

Widely distributed by acclimatisation societies in the 1870s, probably first introduced in the 1860s.  Their spread has been assisted by anglers using goldfish for live bait.

Now form part of the food chain as forage fish for larger natives such as Murray cod and golden perch.

Known to hybridise in the wild with carp producing offspring of mixed characteristics.

Will take a hook, but provides poor sport and the flesh is of poor edible quality.

 

carp | goldfish | mosquito fish | redfin | trout | tench | roach | tilapia

Mosquito Fish

gambusia holbrooki

This species was deliberately introduced under government control in an attempt to control mosquito numbers and to help prevent the spread of some human diseases.  Unfortunately, gambusia have an extremely effective breeding strategy, being live bearers, out compete native fish especially in degraded systems and harass and nip the fins of other small fish.  Gambusia has been implicated in the decline of several small native species.  On top of all that, it is highly debatable that the gambusia is even as good a predator of mosquitoes as the fish it has displaced!

Gambusia are a declared noxious species in Victoria and it is illegal to hold or translocate the fish.

 

carp | goldfish | mosquito fish | redfin | trout | tench | roach | tilapia

Redfin

Perca fluviatilus

Once a very popular angling species, and providing excellent eating, redfin have suffered somewhat of a decline since the introduction of carp in the 1960s.

Redfin are a problematic species, being an active predator of other fish and also host to a viral disease known to effect native fish species.

It is notable that in Lake Mulwala, the premier recreational Murray cod fishery, since carp have been found redfin numbers have collapsed.  Since this collapse, cod and other native species growth rates in the lake have sky-rocketed.  It has been suggested that this may be due to carp interfering with the nests of redfin, thus severely effecting their breeding success and consequently the reduced redfin numbers has reduced competition for food in the lake.

 

carp | goldfish | mosquito fish | redfin | trout | tench | roach | tilapia

Trout

Salmo trutta (brown trout), Oncorhynchus mykiss (rainbow trout)

Popular angling targets, as much for their easy proximity to the major population centres and the Northern Hemisphere fixation of many Australian inland anglers, as for their fighting and eating qualities.  Trout are widespread throughout much of the South East Australian mainland and Tasmania.

Brown trout in the form of fertilised eggs were introduced to Australia in Tasmania in 1864 from the United Kingdom following unsuccessful attempts in 1841 and 1862.  From the original Tasmanian stock, fish were stocked into many of the cooler waters in mainland Australia.  By the end of the nineteenth century trout had been introduced to virtually all waters catchments capable of holding them.

Rainbow trout which are native to North America were introduced to New South Wales from New Zealand (where thay had been previously established) in 1894.  Acclimatisation societies then transferred the fish into Victoria and Tasmania.

Trout have been implicated in the decline of several native fish species, notably Galaxias fuscus and Galaxias olidus as well as the spotted tree frog Litoria spenceri.  In Tasmania, trout are now virtually the only species found in many waters and freshwater fisheries management seems to be focused entirely upon the management of trout.

 

carp | goldfish | mosquito fish | redfin | trout | tench | roach | tilapia

Tench

Tinca tinca

Originally introduced by acclimatisation societies in the 1870s, tench have become widespread although not especially common in Victoria, New South Wales, South Australia and Tasmania.  Tench appear to be gradually being displaced by carp.

Quite edible although not particularly tasty, tench are little known and seldom fished for in Australia.

 

carp | goldfish | mosquito fish | redfin | trout | tench | roach | tilapia

Roach

Rutilus rutilus

Believed to have been introduced into Australia at the same time as goldfish in the 1860s or 1870s.

Little known or studied in Australia and being of poor edible quality, roach are seldom fished for.

 

carp | goldfish | mosquito fish | redfin | trout | tench | roach | tilapia

Black Mangrove Cichlid

Tilapia mariae

In Australia usually called just "tilapia", these fish were originally introduced as tropical aquarium fish.  Illegally released into the Hazelwood power station pondage they have been able to establish a self sustaining population in the heated waters of the pondage.  Due to the lower water temperatures in other Victorian waters, it is considered unlikely that tilapia will establish populations outside the pondage.  However, tilapia pose a substantial threat in the warmer waters of Northern Australia.

 

carp | goldfish | mosquito fish | redfin | trout | tench | roach | tilapia

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