The tuna is a magnificent fish.  It has a beautiful streamline shape with sharp serrated dorsal fins and a tail like a scimitar.  The Atlantic Bluefin (Thunnus thynnus) is a dark blue on top shading to a white underneath and can grow to a size of several metres.  It is related to the Swordfish and is much appreciated as a sporting fish by deep sea anglers. 


The tuna is not a single fish but a family, the Thunnuni,  which includes the Skipjack, Yellowfin,  Bigeye, Bluefin and Albacore.  They are pelagic; they range the upper layers of the ocean feeling on smaller fish, crustaceans and squid.  For most of the year, the Atlantic Bluefin forages off the continental shelves of North America and Europe.  When it comes time to spawn, the populations split, one group goes west to the Gulf of Mexico, the other goes east into the Mediterranean.  Once, when they were more widespread and large numbers of tuna fed in the North Sea, schools several miles long could be seen passing through the channel en-route to the spawning grounds. This made them easy to spot and to fish.


But it is in the spawning grounds where the fish are in shallower waters and closer to  human habitation, that most fishing occurs.  This has devastating effects on populations.  A ban of tuna fishing has been imposed in the Mediterranean, but this is difficult to police.  Illegal hunting for tuna still goes on, encouraged by soaring prices.  


As travellers on a continental scale, tuna are strong active fish.  They have to keep on the move; it is their raison d’etre.  If they stop, they die – literally.  Tunas have no mechanism for pumping water over their gills.  Instead, they swim with their mouths open and their forward movement forces water through the gill arches.    


Tuna are able by a combination of muscle activity and swimming in warmer surface waters to keep their muscles at a constant temperature of 30 degrees Centigrade.  Warmer muscles allow the tuna to maintain high swimming speeds for long periods of time and recover quickly after prolonged exertion.  Their dark muscle contains a combination of large numbers of slow twitch fibres adapted for endurance as well as some fast twitch fibres, which provide the necessary burst of speed for the hunter.  It’s perhaps that mix that creates such a tender yet tasty meat.   


Tuna is one of the most delicious fish to eat – so tender with a clean, slightly acidic taste.  It is delicious raw.  Try thin steaks,  basted with spices, coriander seed, cumin, finely chopped garlic and chilli, pepper and sea salt, and seared in a hot cast iron frying pan, until the outside is a light pink, leaving a core of dark red meat inside.  Serve with pok-choi, steamed for a few minutes so that it retains its crisp texture and mustardy flavour, some oriental mushrooms, lightly fried, and a spoon of rice basmati rice with a little soy sauce dribbled over it.  Other recipes recommend marinating the fish in soy and fish sauce and serving with a rocket and parmesan salad with slices of mango, but it is important not to drown the delicate flavour of the meat.  At £4 a steak, this is a meal of rare delicacy, a meal to savour, and you have the added satisfaction of knowing that Tuna contains large amounts of omega-3 fatty acids, which keep your brain, your joints and your arteries flexible.  


At one time, this fish occurred in abundance.  It speed and wide range meant that it was largely fished locally near the spawning grounds. Stocks were sustainable.  For the last thirty years, the demand for tuna in sushi bars and sandwiches has been so high that it is fished on an industrial scale.  According to the World Wide Trust for Nature, the Atlantic Bluefin is on the verge of extinction. 


Had I realised that before I shopped for last nights’ meal, perhaps I would have chosen something else. Gordon Ramsey has taken tuna off the menu in his London restaurants. I also feel slightly guilty at contributing in some miniscule way to the demand for tuna and being prepared to pay the price. But at least I feel that by respecting savouring this beautiful fish, cooking it carefully with the spices and ingredients to set off its unique flavour, I have honoured it. 


Surely it is better to appreciate an endangered fish in this way than to buy it in cans, mash it up in vinegar and pepper and spread it between two slices of plastic bread or to char it to extinction on barbecues.  Does that sound reasonable to you?.  I am not sure I am convinced.  I still feel guilty.