The Georges River catchment is unfortunately threatened by many introduced animals. Cats and foxes are a big threat to native animals, preying on birds, small mammals and reptiles. Deer, rabbits and some birds also impact on our catchment to varying degrees including damaging vegetation and causing erosion.

In many of the freshwater ponds and wetlands in the Georges River Catchment, European Carp and Mosquito Fish (Gambusia holbrooki) cause significant damage. 

Mosquito fish (Gambusia holbrooki), also known as eastern gambusia or plague minnow, can live in most aquatic conditions and once in a waterbody, are extremely difficult to remove. It is currently illegal to release mosquito fish into ANY waterbody in NSW. Despite the impacts of this fish on the natural environment, mosquito fish are still sold in pet shops as feeder fish or to put into backyard ponds. 

Carp also impact the health of freshwater aquatic ecosystems by increasing water turbidity and nutrient concentrations, destroying aquatic plants, and potentially causing the recurrence of toxic blue-green algae blooms. They also breed rapidly, eliminating native fish, tadpoles and other small lifeforms.

Red eared slider turtles originally come from USA and north-eastern Mexico but have now spread across the world and are considered by the International Union for Conservation of Nature as one of the world’s worst invasive species.

Common Mynas birds eat the eggs of native species and compete for food and nest hollows. Starlings are another pest bird species.