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An Australian Murray cod nicknamed Arnie has stunned researchers by completing a 530-mile journey through the Murray River system—believed to be a species record. Tagged in early 2022 at Mullaroo Creek, the four-year-old fish surged 470 miles upstream in under two months as barriers were removed to let floodwater pass, then later turned to swim about 60 miles back downstream. Scientists only pieced together the trek after swapping data recently. The scale eclipses previous tracked movements of about 100 miles and will help guide water-flow management for the vulnerable species and its riverine ecosystem.

Prepared by Olivia Bennett and reviewed by editorial team.