Scientists track epic journey of “Casanova cod”

FISH ecologists are eagerly waiting to see if a big Murray cod (Maccullochella peelii peelii) that they have dubbed the “Casanova cod” will return to the Ovens River upstream of Wangaratta in north east Victoria for the fifth straight year – in a marathon search for love.

Since 2008, ecologists from the Department of Sustainability and Environment’s (DSE) Arthur Rylah Institute (ARI) have recorded the 20 to 25 kilo, one metre-long cod on his lonely annual trip from Yarrawonga up the Ovens River to Wangaratta and his version of the “Heartbreak Hotel”.

ARI Fish Ecologist Jarod Lyon said: “We’ve been able to track this amazing journey thanks to an electronic tracking device implanted in the cod at Lake Mulwala in 2008.”

“Since then he has made the 160 kilometre round trip up the Ovens River four times where it is likely that he arrives at the same location every year during spawning,” Lyon said.

“His journey emphasises the value of river improvement works on the Ovens River, such as
resnagging and the refurbishment of the fishway at the Sydney Beach Weir in Wangaratta. We monitored his movements using tracking stations located at Bundalong and at the junction of the Ovens and King Rivers.”

“So far he has been recorded moving past Wangaratta to his ‘Heartbreak Hotel’ in early spring each year, so we are very keen to see if he does the same thing again this year. The fact that this migration has occurred both in years of drought and in years of flood gives an indication of the importance of large cod such as this to the entire population.”

“Larger Murray cod are often the best breeders, with females of this size producing up to 90,000 eggs, and larger fish also passing on their stronger genetic traits to their offspring, leading to a more robust population.”

“As such we are crossing our fingers that the trip doesn’t actually end in heartbreak for this
particular fish.”

“Funds spent on catchment restoration, in conjunction with factors like the increase we have observed in catch and release angling of these big cod, can really contribute to the ongoing recovery of the species.”

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