Some facts about tuna, from Paul Greenberg's book, "Four Fish, The Future Of The Last Wild Food."
"Tuna are among the fastest, most powerful fish in the world. ... [Swimming] in excess of forty miles per hour ... they're faster than the fastest warships ever built."Just a magnificent creature. Look at the size of its head compared to a human's.
Tuna achieve this speed in part by "a weird slot, as hard and fixed as the landing-gear slot on an airplane, into which it retracts its dorsal fin."
And with "a slim crescent of tail, insignificant in size compared to most fish tails, [that] vibrates at astronomical speed while the rest of the body slips forward with barely any bend, pitch, or roll."
"Tuna can be extremely large - in excess of fourteen feet and fifteen hundred pounds."
"The biggest tuna are warm-blooded. ... [Tuna] can redirect the heat that its muscles throw off back into its very flesh and raise its body temperature by as much as twenty degrees above ambient conditions."
Tuna are undoubtedly near the top of the marine food chain. That makes eating these large predators chancy. With a nod to bioaccumulation, Greenberg writes:
"It is the biggest, longest-living fish that tend to have the most mercury, and in the ocean it is harder to find a bigger, longer-living fish than the bluefin tuna."
Photo of bluefin tuna caught up in net from Wired.