Bluefin tuna are back in the sea around the U.K. after decades of absence and a new study says that warming seas can explain why. Bluefin tuna are one of the biggest, most valuable and most endangered fish in the oceans. Sportfishermen excited at the prospect of catching a fish that can grow to over 900 kg have already launched a U.K. campaign to allow recreational fishing for one of game fishing’s top targets. But should we catch and exploit this endangered species or should we make U.K. waters a safe space for this species? Why has this endangered fish suddenly returned to the U.K. after an absence of nearly 40 years? And are bluefin tuna now more abundant, or have they just changed in their distribution?