Huge goldfish and other pet fish have been discovered in the rivers of Australia by researchers.
Researchers believe the fish were released by their owners. Following the discovery, the common misconception that goldfish are small, domesticated species best suited to an aquarium has been challenged yet again. Researchers at Murdoch University in Perth have caught goldfish which weigh up to two kilogrammes and grew up to 30 centimetres.
Scientists have previously warned of their harmful impact on natural ecosystems. According to them, goldfish and other abandoned species such as koi carp are destroying habitats for native breeds of fish by eating their spawn and uprooting plants and sediment on riverbeds.
Stephen Beatty, a researcher from the Centre of Fish and Fisheries at Murdoch University, started tagging wild goldfish in the Vasse River near Perth and monitoring their movements. “We used acoustic telemetry, which is the same technology used to track sharks off the coast, just on a much smaller scale,” he told Perth Now.
“We tracked 15 mature fish over a year and that informed us about where they were going in their breeding period.” According to Beatty, introduced species such as goldfish could disturb habitat and consume eggs of native fish. They have also been found to spread a disease which affects the skin of native fish. “They can stir up sediment, increasing turbidity, and they can re-suspend nutrients through their feeding activity because they cruise along the bottom hoovering sediment which can uproot plants as well,” he said.
“The key is really preventing it and getting the message out there that people shouldn’t be releasing freshwater fish in artificial wetlands.” The issue of goldfish growing to unmanageable sizes after being released by their owners has prompted action by governments around the world. Canada has introduced a fine of £51,000 for those who release live fish into certain lakes and rivers.
The largest goldfish discovered was 48 centimetres long. It was found in the Netherlands in 2008.
This article originally appeared on Independent