Australian Murray Cod Swims Record-Breaking 530 Miles Along Murray River
An Australian freshwater Murray cod has completed an extraordinary 530-mile journey along the Murray River system, a distance believed to be a record for the species, offering new insights into the fish’s migratory patterns.
The fish, nicknamed “Arnie” in honor of Olympic swimmer Ariarne Titmus, was initially tagged in Mullaroo Creek, approximately a 13-hour drive west of Sydney, in early 2022. Researchers at the Arthur Rylah Institute observed that the 3.7-pound, four-year-old cod “took off” following spring floods that year, traveling an initial 470 miles upstream in under two months. The unprecedented journey was facilitated by the removal of barriers along the river, allowing for unobstructed passage during high water levels. “It basically provided free passage for fish,” explained researcher Zeb Tonkin.
Arnie then reversed course over the past year, swimming an additional 60 miles downstream toward its origin. Researchers only recently discovered the full extent of the fish’s travels when sharing data with colleagues. “We’ve been working on these species for decades… and we haven’t come across that sort of scale of movement beforehand,” Tonkin said. “Probably the best we have seen a Murray cod do is around 100 miles.” Understanding the movement of Murray cod is crucial for managing water resources and protecting their habitat, especially as the species is listed as “vulnerable” under Australia’s Environmental Protection and Biodiversity Conservation Act. You can learn more about the challenges facing Australian fish stocks at the Australian Government Department of Agriculture, Fisheries and the Forest.
Murray cod, which can live for over 48 years and grow to weigh more than 180 pounds, are an apex predator in the Murray-Darling Basin. Their health is considered an indicator of overall ecosystem health, and this discovery highlights the importance of river restoration efforts like those supported by the Living Murray program.
Researchers will continue to monitor Arnie’s movements and analyze the data to better understand Murray cod behavior and inform conservation strategies.
