Report released on tagged bluefin tuna found off Jersey

The fish spent most of their time in the Bay of Biscay, and were smaller in size compared to other bluefin tuna

A report into the movement and behaviour of tagged bluefin tuna off Jersey has been published.

Seven fish found in Jersey waters were fitted in 2021 with electronic tags in a bid to help protect the species.

The report found once tagged, the tuna stayed in the waters around the Channel Islands for between 54 and 111 days.

The fish spent most of their time in the Bay of Biscay, and were smaller in size compared to other bluefin tuna.

The report outlines the findings from the first five satellite tags that were deployed in 2021 and have since detached from the fish.

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.

'Fantastic dataset'

The tuna were found to be in deeper waters during the day and in surface level water during the night.

Reports found two of the fish travelled 6,213 miles (10,000km) and 4,970 miles (8,000km) respectively.

Research was analysed by the Marine Resources and the University of Exeter.

An additional seven bluefin tuna were tagged in December 2022, but their electronic tags have not yet detached.

A bluefin tuna was first spotted off Jersey in 2016.

Alex Plaster, marine science and research officer, 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.

"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."

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