Atlantic Bluefin Tuna report published

23 March 2023

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A report, Tracking Atlantic Blue Fin Tuna, has been published detailing the movement and behaviour of bluefin tuna in Jersey. 

It outlines the findings from the first five satellite tags that were deployed in 2021 and have since detached from the fish. Marine Resources and the University of Exeter have analysed the data which shows: 

• Once tagged and released back into the sea, the tuna stays in the Channel eco-region for between 54 to 111 days
• Atlantic bluefin tuna that gather off Jersey are mostly smaller in size (153 to 212cm) and spend most of their time in the Bay of Biscay 
• The fish spend most time in surface waters during night and in deeper waters during the day 
• Two tuna travelled 10,000km and 8,000km respectively, although they only travelled a distance of 947km away from where they were tagged in Jersey
  

Tags remain attached to the fish for one or two years, until they automatically detatch and float to the sea surface to transmit data via a satellite system. The team can analyse most of the data via satellite, but more detailed information can be received by physically recovering the tags from the sea. 

Over the past two years, a total of 14 tuna were tagged by Marine Resources and the University of Exeter. The second batch of tags, which were deployed at the end of last year, have not yet detached but will help inform future reports when they do.

Marine Science and Research Officer, Alex Plaster, said: “As soon as Atlantic Bluefin Tuna started arriving in Jersey’s waters, it was crucial that a research programme was developed to ensure this resource is sustainably managed for the future.

“The interim findings in the report published today details the movement and behaviour of several tuna in Jersey waters. These findings will be further developed over the next couple of years, when the second batch of tags detatch in September 2023. We’ve already got some interesting insight into what Atlantic Bluefin Tuna are doing in our waters from the first years tagging efforts. With nine more tags yet to pop-off and tagging efforts continuing into 2023, we will have a fantastic dataset to work with.”