Data from a bluefin tuna satellite tagging project has revealed that these highly-prized fish migrate thousands of miles to feed in Jersey waters, travelling from as far as Turkey.
The project – now in its second year – uses satellite tags to understand the movement and behaviour of Atlantic bluefin tuna, which have been regularly spotted in Jersey’s territorial waters since 2016.
The Government of Jersey’s Marine Resources team tagged seven bluefin tuna in 2021, and a further seven fish this year. The tags remain on the fish for one or two years, until the tag automatically detaches.
Four of the seven tags deployed in 2021 have now been collected by Marine Resources and analysed by the University of Exeter.
Alex Plaster, Marine Science and Research Officer at the Government of Jersey, said: ‘The data we receive from the satellite tags tells us crucial information to manage this resource such as how long they are in our waters for and what they are doing here.
‘We have found out some of these fish are travelling as far as Turkey and three of the fish tagged in 2021 were caught within 12 months in the English Channel, Bay of Biscay and Mediterranean.’
Some of the 2021 tagged fish were caught before the tags detached, highlighting the catchability and vulnerability of this species.
The data also shows:
• Bluefin tuna are using Jersey waters for feeding but are also spending a lot of time on the south coast of the UK and surrounding Channel Islands waters
• The fish are arriving from further south, some from the Bay of Biscay and some as far as the Mediterranean spawning grounds
• Not all fish are spawning – some are juveniles whereas others are sexually mature and are returning to known spawning grounds in the winter
• Two bluefin tuna tagged in 2021 returned to Channel Island waters in 2022 with the tags being retrieved by Marine Resources and local commercial fishers
The Marine Resources team will be publishing a full report on the findings next year.
Bluefin tuna are a protected species under Jersey’s Wildlife Law, and it is prohibited to target or land these fish within the Island’s territorial waters.