Gambusia holbrooki (sometimes referred to as Mosquitofish) were first recorded in Tasmania in the early 1990’s in a farm dam in the Tamar Valley after being intentionally introduced. There are now several known self-sustaining populations in the upper kanamaluka / Tamar estuary, most notably at the Tamar Island Wetlands Reserve where the largest population has been identified.

G. holbrooki are an invasive species commonly found in lakes and slow-moving waterways. They are an aggressive fish that eats the eggs and larvae of several species including the threatened green and gold frog (Litoria raniformis).

With young that mature very quickly (within two months) and an ability to tolerate a wide range of environmental conditions, Gambusia holbrooki can quickly become well established within aquatic habitats.

Gambusia holbrooki

Green and gold frog (Litoria raniformis)

To gain a better understanding of populations and trends, Gambusia holbrooki have been included as a biological indicator in the Biological Monitoring Program. Long-term population data has been generously collected and provided by volunteers at the Tamar Island Wetland Centre, through the Tasmanian Parks and Wildlife Service.

Including Gambusia holbrooki in the Biological Monitoring Program will help us to:

• identify currently unknown established populations;

• identify emerging populations;

• gain insight into the trends of the Tamar Island Wetlands gambusia population; and

• identifying options to mitigate further spread.

Biological Monitoring Program