Murray Cod Completes Remarkable 900km Journey Through Australian Rivers

In a remarkable display of resilience, a young Murray cod has completed an extraordinary 900km journey through the Murray River and its adjoining streams and backchannels. The fish, dubbed "Arnie" in honor of Olympic swimming champion Ariarne Titmus, is one of the longest-traveling Murray cod ever recorded.

Researchers from the Arthur Rylah Institute have been tracking the movements of juvenile Murray cod in the Murray-Darling basin for over a decade. Their findings challenge the common perception of Murray cod as a sedentary species, revealing their ability to cover vast distances to disperse and breed.

The journey began in 2022, when the cod, then about 50cm long and four years old, left its nursery habitat and set out on an epic migration. Taking advantage of the removal of barriers during the 2022 floods, the fish swam into the Wakool and Niemur rivers before eventually making its way back towards its original home range.

The researchers say this level of movement is highly unusual for Murray cod, which are listed as vulnerable under federal environment laws. The species, known as the apex predator of the Murray-Darling basin, is of immense cultural and conservation significance in Australia.

By tracking the fish's movements, the researchers have gained valuable insights into the species' behavior and the importance of maintaining connectivity in river systems. Their findings suggest that in dry years, Murray cod tend to prefer flowing anabranches of the river, while in wet years they are more likely to choose the main channel.

This information has helped inform the way regulators manage flows and gates in the river to support fish breeding and survival, a critical step in the recovery of this iconic Australian species.