Invasive fish species displacing Australian native fish

Invasive fish species are a major problem in Australian waterways. This is especially true in the tropics, where tropical species from the aquarium trade thrive in the warm water.

Spotted Tilapia (Tilapia mariae) and Mozambique Tilapia (Oreochromis mossambicus) were introduced as aquarium fish and are considered the most problematic invasive fish in Queensland.

Tilapia are out-competing and displacing native Australian fish through efficient breeding strategies, aggressive behaviour, and flexibility around habitat, diet, temperature, salinity, and oxygen levels. Tilapia are now present in 21 of 76 catchments in Queensland.

Detecting and understanding new invasive species is key, and vital for effective management. But, collecting this data across catchments is challenging. Environmental DNA (eDNA) is a promising tool for detecting these species in our waterways.

Using eDNA to track invasive fish in Australian waterways

The TropWATER team are using eDNA to detect the presence of invasive fish in waterways. This technology allows us to determine their distribution, map high-risk areas, and then target these areas for routine surveillance.

eDNA technology detects genetic material left in waterways, such as mucus, scales, and other residues. We collect water samples and analyse them in our laboratory for the gene sequences of the fish species present.

The eDNA assays developed at TropWATER have a high reliability of detection. They have been used to understand the distribution of tilapia in the Mitchell, Townsville, Fitzroy, Pioneer, Wild, and Walsh catchments in Queensland, as well as a recent incursion in northern New South Wales, and undertaking invasive fish monitoring in the Murray-Darling catchment and northern islands of the Torres Strait.

Scientists have also developed eDNA primers for two potentially problematic invasive species: the climbing perch (Anabas testudineus) and snakeheads (Channa striata). The team are using these primers to detect early incursions into northern islands of the Torres Strait.

Another species of biosecurity concern is sleepy cod (Oxyeleotris lineolatus), which despite being endemic to north Queensland, has spread outside of its natural range and can have negative impacts on new ecosystems. The team has developed a primer targeting this species and is using it to detect incursions in the Georgina-Diamantina catchment.

To stop the further spread of invasive fish species to new catchments, it is critical to detect new populations early. Using eDNA techniques will play a key role in this.

eDNA techniques for effective invasive species management

The ongoing work at TropWATER is crucial for bridging the gap between scientific research and practical management actions. By continuing to refine our eDNA methods and expanding our monitoring efforts, we aim to provide science-based solutions that support effective management strategies.

This approach helps managers make informed decisions on where to allocate resources and implement control measures, preserving native fish and keeps Australia's water healthy.