Gypsy, the gambusia (mosquitofish)
Also known as mosquitofish, exotic mosquitofish, eastern gambusia, plague minnow.
Gambusia holbrooki or Gambusia affinis holbrooki
Howdy. I'm Gypsy the mosquitofish from Calamvale Creek in Brisbane, Australia.
I'm one of thousands of mosquitofish called gambusia that are living in the creek. In fact, we are almost in plague numbers in some Australian waterways.
We are small fish, and I am only 2.5 centimetres (one inch) long. The photographs on this page make me look much bigger than I am. The photo below will give you the perspective.
How can you identify me?
People confuse me with guppies, and with some native fish such as Pacific blue-eyes. But I have a single fin on my back (the dorsal fin), and this distinguishes me from Pacific blue-eyes, which have two dorsal fins.
The top of my head and back are flat, which guppies also have. But guppies are more colourful — particularly their tail. My tail is rounded and clear except for dark flecks.
Female gambusia may grow to about 7 centimetres (3 inches) and males to about half that size. Around Calamvale Creek we are mostly 2 to 4 centimetres.
Our colour varies with the environment. We may be brownish-yellow, olive, or greyish orange. We are usually paler when the waterway bottom is sandy, and darker when it is dark mud.
Where do I live?
Gambusia have adapted to a wide variety of freshwater habitats. I prefer shallow slow-flowing or still waters, and am happy in temperatures that are almost freezing, up to 44 degrees Celsius. What's that little brown critter that has fallen in the water beside me? Is that a spider or a tick? Doesn't it know I will eat almost anything in the creek?
What do I eat?
I'm called a mosquitofish because I supposedly love mosquito larvae. But I only eat mozzie larvae if I can't find anything else.
What is this little brown thing? Let me get a closer look. Nope, I don't like the look of it, so will leave it alone. I prefer worms, crustaceans, plants, dragonfly larvae, ants, flies, frog eggs, snails, water bugs, and even other small fishes.
Why am I considered a pest?
I can't understand why Queenslanders have legislated that I am a noxious species. I'm really quite nice. “Hey, little brown critter, hop on my back and I'll take you for a ride. See what a nice little fishy I am?”
My history in Australia
Great-great grandfather Gambusia and his family came to Australia from the United States via Italy in 1929 as an aquarium fish. Some people emptied us into creeks and other waterways (well, it's better than being flushed down the toilet).
During the Second World War, military personnel and State health agencies introduced us into most of Australia's east coast waterways to control mosquitoes. Ha! But like cane toads, we preferred other food.
So we just grew in numbers everywhere we went. We ate frog tadpoles until there were none left; we ate fish eggs and other fish, and nipped the fins off any we didn't eat; and we ate so much that native fish started starving to death. And we introduced parasites.
How do I breed?
Gambusia are called “livebearers” because, like other members of the Poeciliidae family, we don't lay eggs — we give birth to live young.
Females mature at about five weeks, and can give birth to more than 300 young each season (which varies from two to nine months). We produce small numbers of kids frequently, and this helps build our numbers and increase our survival rate. Our population can double in less than 15 months.
— Gypsy the gambusia