Porbeagle Shark (Lamna nasus) is a common, fast-swimming,
potentially dangerous shark. They are dark gray on top and
white underneath; there is also a small patch of white on
the rear edge of the dorsal fin. Porbeagles have a torpedo-shaped
body and a crescent shaped tail with a secondary keel that
effectively cuts the water during the side to side swimming
motion. This makes them very efficient swimmers. Adults can
attain a size of 12 feet (3.7 meters) weighing about 350-550
pounds (160-250 kg) and have an average life expectancy of
30 to 40 years. This shark has relatively large eyes. The
teeth in the moderately sized mouth are similar in both the
upper and lower jaw (they are smooth-edged with lateral denticles),
although young individuals may lack the lateral denticles.
The porbeagle has a heat regulating mechanism that raises
the body temperature 36.9 to 47 degrees F. (2.7 to 8.3 C.)
above the surrounding water temperature. This allows the shark
to operate more efficiently in the cooler waters it inhabits.
Unlike many other sharks the porbeagle must swim at all times
in order to breathe.
Porbeagles occur on both sides of the Atlantic, and in the
south Pacific and Indian Oceans. In the western North Atlantic
it can be found from Raleigh, Newfoundland at its northernmost
range to the Gulf of St. Lawrence, the Scotian Shelf, the
Bay of Fundy and the Gulf of Maine to New Jersey and perhaps
to South Carolina. Off Nova Scotia the porbeagle is generally
found in waters less than 57 degrees F. (14 C.).
There is apparently little exchange between porbeagle populations.
For example, populations of the northwest Atlantic seem relatively
segregated from those of the northeast, and populations in
the northern hemisphere are separate from those in the southern
The porbeagle shark inhabits water down to a depth of 1,120
feet (370 meters). It is most commonly found on continental
shelves or inshore. It prefers cool waters and is usually
found in temperatures below 57 degrees F. (14 C.).