WHEN TUNA MET JAWS

Data download reveals nasty end for tagged big bluefin

One of the findings of the UK tagging was the discovery that an estimated 300lb tuna had been eaten by a killer whale.

The ThunnusUK team revealed that a 2018 tagged fish had popped its tag last year. When the data was uploaded as the tag came to the surface, it told a grisly story.

A temperature spike, which lasted for several days, was recorded and also showed repeated, periodic dives and trips to the surface. After several days the tag came to the surface off the coast of Spain. Analysis of the data suggested that the big bluefin had been eaten by a killer whale, which ingested the tag as well, which then exited the orca a few days later.

ThunnusUK has released details of data from nine tags applied in 2018, which released and uploaded data to satellites last year. The tracks showed very wideranging travels. Some fish journeyed thousands of miles across the Atlantic before returning to the Eastern Atlantic and/or Mediterranean. Such knowledge will help inform future management decisions about bluefins in UK waters post-Brexit.

Another tag fitted in October 2019 was set to release after just three days to show immediate post-release behaviour. The data revealed that this fish had travelled a straight-line distance of 380km in only three days, popping its tag in the Bay of Biscay.

In 2019, 26 Atlantic bluefins were captured, satellite tagged and released off Cornwall. Another three were similarly tagged and released in the Celtic Deeps. That added to the 10 fish tagged in the South West in 2018. ■