Exotic fish are dominating native fish in the Ross River.

While it may seem kinder to free or flush ‘Willy’ into the river or toilet, one Willy can become thousands of pest fish.

It’s suspected that Townsville’s itinerant population is dumping aquarium fish.

The Ross River has the highest number of exotic or introduced fish in Queensland.

Willy may be a Swordtail, Guppy, Platy, or Sailfin Molly.

They are aggressive to native fish, eating their food, chasing them out of their habitat and stealing breeding sites.

Willy’s partner Wilhelmina can produce a larger number of young than her native competitor.

They can live in poor quality water allowing them to survive where our native fish can’t.

Diana O’Donnell from NQ Dry Tropics said for new residents it seems exotic to set up a tropical fish aquarium at home but releasing the introduced fish when moving on, leaves a terrible legacy for the environment.

“When moving arrange for friends to take your aquarium or return the fish to a commercial aquarium but please do not release them.” Diana said.

Aquarium enthusiasts can keep fish indigenous to the tropics of north Queensland, instead of from foreign waters.

Diana said, “The native archer fish, purple spot gudgeon and empire gudgeon, while not as flashy as gold fish, do look very attractive in an aquarium.

The archer fish is an interesting fish to watch in a residential pond. It ‘shoots’ at insects on overhanging leaves as if it has an inbuilt water pistol. They have expert aim!

Jungle perch, Eastern Rainbow and Glass fish are exciting characters to have in your tank and some can even be trained.”

Interesting native species should be purchased from licensed pet shops and small numbers may be caught in local waterways.

There are bag and size limits to catching native fish. This information is found in the book Freshwater Fishes of the Burdekin Dry Tropics -- a guide to fish which belong in north Queensland and to identifying pest fish.

Freshwater Fishes of the Burdekin Dry Tropics is available in selected bait and tackle shops or by calling NQ Dry Tropics 4724 3544.