OK, I know these are going to be a very rare visitor to our waters, if at all, but the issue is still relevant. Atlantic bluefin tuna is recognised as an endangered species by the WWF and the IUCN Red List. The EU supported by the UK Government have issued regulations to protect them in UK waters:

Commercial
Vessels must not target bluefin tuna and if caught accidentally they must be returned to the sea, alive and unharmed to the greatest extent possible.

Recreational
Sea anglers must not target bluefin tuna, any caught as a by-catch when targeting other species must be released immediately and not landed or brought onto the boat.

Yet we still see responsible angling magazines and less responsible newspapers publishing pictures of anglers catching and boating bluefin tuna. This is likely to encourage more rules and regulations to apply to all anglers not just those who are obviously breaking the rules.

More information here:

MMO Blog

and here:

www.gov.uk/government/news