Fleet Fish

Article from: Discovery Channel Magazine; October 2010, pp. 32, 33

The fleet fish is the quickest marine animal in the seas and can outpace many small cars. It can travel up to a maximum speed of 110km/hour and is a sailfish of the family Istiophoridae. It is better at accelerating and can grow up to over 3m, 100kg and live up to 10 years as they have few natural predators. Their various structures and adaptations include:

1. Skin: Unique skin with V-shaped protrusions. Some researchers theroise that this help cut down skin-friction from the water. It can create vortices that change the boundary layer drag slightly, a bit like what the shark skin does.

2. Streamline: They have sickle-shaped fins or flippers, narrow lunate (crescent moo-shaped) tail fins and a classic teardrop-shaped body. All this cuts down drag to a minimum; to a stunning efficient coefficient of 0.0075 to be precise. In comparison, the highly slippery Ferrari Testarossa has a drag coefficient of 0.36.

3. Life cycle: Adult sailfish live in Atlantic and Pacific oceans, in the warm and temperate zones. Females produce millions of eggs but as the tiny fertilised larvae are a favourite food for many other fish, only a dozen or so will make it through to adulthood.

4. Speed: 100km/hour. It does so by lowering its drag (skin friction).

5. Muscle: Also contribute to its fast speed. It has a large reserve of white muscles, great for acceleration but not so goof for long swims. To make up for this, it has additional layers of red (myoglobin-rich) muscle which give stamina for longer swims. The sailfish also makes use of a network of blood vessels that help warm the red muscles, making them more efficient.

6. Sail: The exact function of the sailfish’s huge dorsal fin remains a mystery. Fishermen say it is used to help round up fish before feeding, others say it helps it manoeuvre quickly at its top speeds. It has even been likened to a radiator, for warming the fish’s blood when it is on the surface, so its red muscle can work more effectively.

7. Beak: Beak for feeding. It is necessary though it increases the overall drag. Sailfish swim into a school of fish (sardines, mackerel, anchovies), swinging their beak side to side to whack and stun the unlucky ones. Then, they swim back through the school and eat the floating and insensible victims.