Huge alien goldfish are travelling miles in Australia


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Huge alien goldfish are travelling miles in Australia

Dr Stephen Beatty with a super-sized goldfish — these fish are wreaking havoc in Australia and are considered one of the world's worst invasive species. Image by Murdoch University. 

Football-sized goldfish are travelling hundreds of miles each year through the waterways in Western Australia, a discovery that has major implications for controlling this highly invasive species in the area.

Goldfish are native to eastern Asia but are now considered one of the world’s worst invasive aquatic species. Until now, little has been known about the movement patterns of goldfish, which has hampered the development of effective control programs.

Defined as an alien species introduced to Australian freshwater bodies, goldfish can enter river systems after being dumped from aquariums into catchment lakes. Once the fish become established, their eradication is often difficult, which is having a significant impact on Australian ecosystems.

Among the goldfish are some real monsters with many former pet fish weighing more than two pounds, and some as much as double this. 

Dr Stephen Beatty and researchers from Murdoch University placed acoustic receivers to examine the movement patterns of an introduced goldfish population in the Vasse River, revealing the fish displayed a significant seasonal shift in habitats during breeding season, with one fish moving over 140 miles during the course of the year. Another travelled 3.35 miles in just one day.

“The goldfish population in the nutrient rich Vasse River has existed for over two decades and has the fastest known individual growth rate of this species in the world,” says Dr Beatty.

“The results of this study will have important direct management implications, enabling more strategic development of effective control programs for the species such as targeting migratory pathways.

“Once established, self-sustaining populations of alien freshwater fishes often thrive and can spread into new regions, which is having a fundamental ecological impact and are major drivers of the decline of aquatic fauna,” added Dr Beatty.

Dr Beatty said the invasive fish can potentially impact water quality, introduce disease, disturb habitat and compete with native species putting them under serious pressure, which just adds to the existing threats associated with habitat and water quality decline.

The study has been published in the international journal Ecology of Freshwater Fish.