Twenty years on, tuna tells us tales of the sea

My how you’ve grown…this is not Bluey, but this juvenile southern bluefin tuna has just been tagged behind the dorsal fin.

Australia’s top government research organisation has been reunited with a southern bluefin tuna, “Bluey”, 22 years after she was tagged to study her habits.

We first met ‘Bluey’ when she was approximately two years old. At the time, our scientists were out on the open oceans teaming up with the Commission for the Conservation of Southern Bluefin Tuna to tag over 11,000 SBT in the Great Australian Bight (GAB).

The fish was reeled in by avid fisherman Matt Bell with the help of Skipper Dennis Heinicke, both “citizen scientists” who are the CSIROs regular assistants, near Port MacDonnell in South Australia last week, 800 kilometres east of where she was originally caught – but that is only a fraction of the distance Bluey has travelled in the past 22 years.

…we know from our other more sophisticated SBT tags that Bluey has been undertaking large migrations. As a juvenile, these migrations took her from the GAB to the Indian Ocean; upon maturing, she travelled between the Southern Ocean and the Indian Ocean, just south of Indonesia. It is here that adult SBT spawn each year.

And, my, has she grown.

The fish has more than doubled in size. She weighs 102 kgs and has had a decent growth spurt, from 60 cm to a behemoth 191 cm total length – or if you are a purist for measurements, her ‘fork length‘ is 175 cm (that’s still 5′ 7”, or taller than Tom Cruise).

Adam Knight explains on the CSIRO blog why the find is such an exciting one.

We rely on the cooperation of commercial and recreational fishers to find the tags, and in the vastness of Southern Ocean, finding a tagged fish after such a long time is like finding a needle in a haystack.

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