It is probably safe to say that when most people think of tuna, they think of a small, short, squat can on their supermarket shelf. That's such a shame. For living tunas are some of the most spectacular fishes in the sea, efficient wide-ranging powerhouses - superfishes really!
Everything about a tuna's physical make-up shows that it is a fish of speed. Its body is just about a classic example of torpedo shape (which is figured to be the most efficient shape of moving through the water). Its tail is tall and stiff and it has a keel on the side of its body, right before the tail, for further slicing though the sea. Its long, double dorsal and pectoral fins can be tucked away in special grooves, again, to minimize drag.
A most remarkable feature about a tuna's anatomy is its hot-blooded nature. While it also has a feisty personality, it also has actual hot blood. When circumstantial evidence was recently unearthed indicating that some dinosaurs seem to have been warm blooded lizards, this was headline news. But it has been long established that tunas, although very much being fishes that are supposed to be cold blooded by nature, often have body temperatures as much as 12 or more degrees warmer than that of the water in which they swim.
No wonder a tuna can zip along at 40 to 50 miles per hour, easily outswimming its prey: squid, sardines, and other small fishes. While tunas are famous sprint swimmers, they are long distance cruisers as well. Most species are considered to be extremely migratory, even though they do show a preference to tropical and subtropical seas. Over a dozen of the approximately 50 species of the Family Scombridae (tuna or mackerel family) have been reported in California waters at some point in time, yet it is hard to say exactly when or where any particular species will show up. An Albacore (Thunnus alalunga) that is seen off the West Coast one year may show up the next year near Japan.
The identity of some of these species can be a bit tricky. Although, according to their common names, a yellowfin tuna (Thunnus albacares), bluefin, (T. thynnus), bigeye (T. obesus) and a longfinned (another name for albacore) should be easy to differentiate. But when these fishes get older, the distinguishing characteristics tend to become obscured. Often the only absolutely certain way to know what species is which is by examining the liver. No, this is not some sort of ancient divination method, but while a tuna's outside features may become lost with age, the degree the liver is striated, or covered with blood vessels, does not. Obviously, such is a post-mortem examination, but is useful when trying to establish a record-breaking catch.
For some species, it has become extremely unlikely, though, that new record breaking catches will be landed. This is particularly true of the bluefin, the largest bony fish in the world. The tackle record for this tuna is from the Atlantic Ocean - a veritable monster of 1,496 pounds! Pacific catches tend to be significantly smaller, but still, a fish that is over 500 pounds is something to take seriously.
Because of being such a prized sport-and-eating fish worldwide, the numbers of this species are recognized as having declined radically, perhaps to 10 percent or less of what they were only a couple of decades ago. When the market will pay around $50 a pound for such a tuna, it doesn't take a mathematical genius to realize that a multi-hundred pound bluefin can translate into a swimming gold mine for a fisherman.
For other popular species, the decline in numbers is strongly suspected, but has been harder to actually establish. When dealing with ocean-going nomadic fishes that never seem to stay put very long in any one place, it is hard to get an accurate nose count. Yet the five to six million tons of tuna caught each year around the world has to have some impact on their population.
Much of this, of course, is converted into those small, short, squat cans stacked on grocery store shelves. Why, tunas are sometimes even referred to at times as "chickens." Sure, this is largely on account of their fine eating qualities, but when observed alive in the sea by divers or boaters, it is obvious that tunas are far from being "chickens" in the sense of being whimps. They are instead spectacular, hot-blooded, fast-moving, non-stop cruisers of the world - superfishes indeed!