The not-so-little Murray cod that could: fish tracked swimming 900km along Australia’s biggest river system

A young Murray cod, known as Australia's largest freshwater fish, has traveled approximately 900km through the Murray River and its tributaries, marking one of the longest recorded journeys for this species. The fish, nicknamed "Arnie," was tagged by researchers from Victoria’s Arthur Rylah Institute to track movements post a major mortality event in 2016 due to low oxygen levels. Initially staying close to their nursery habitats, several cod began extensive travels as they approached maturity around the age of four. This discovery highlights the species' capability for long-distance travel, challenging previous perceptions that Murray cod are generally sedentary. The tracking study has been ongoing for over a decade and reveals that these fish can move hundreds of kilometers to disperse and breed.

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