Susanne Prater, age 13, of Hattiesburg, Miss., for her question:
WHAT DOES THE TUNA EAT?
Tuna is the common name of a number of large schooling fish that are used for food. Tuna rank among the most highly developed of all fishes and they are found in most of the tropical and subtropical waters of the world. They feed mostly on squid and smaller sea animals.
In summer you'll find the tuna as far north as Newfoundland and Norway in the Atlantic and British Columbia and northern Japan in the Pacific.
Tuna, also called tunny, belong to a group of fishes that include the mackerels and bonitas. They are the only fish that have a body temperature higher than that of the sea. The albacore a type of long finned tuna, has a body temperature up to 16 degrees Fahrenheit higher than that of the surrounding water.
A tuna has a sleek, rounded, streamlined body tapering to a narrow junction with the tail. It is built for speed. The pectoral fins fold into grooves on the back and the eyes are flush with the body surface. A widely forked tail with rays extending over the last vertebra provides the driving force for swift swimming.
On each side of the tail base are bony keels that are actually extensions of the caudal vertebra. The design of the tail and the way the tendons connect it to the swimming muscles of the body are unusually successful.
The tuna's body design is further improved by the well developed vascular system under the skin that keeps the body temperature up. This improves the power output of the muscles and speeds the nerve impulses.
The largest tuna is known as the great bluefin tuna. It weighs up to about 1,800 pounds and is up to 10 feet long. It is found in both the Atlantic and Pacific oceans and also in the Mediterranean Sea. It is especially abundant off the California coast.
The yellowfin, a type of tuna, is caught in large numbers near Rhode Island and Florida.
The tuna has long been valued as a food fish. The fish is also popular with fishermen because of its fighting spirit. When hooked, they offer great resistance.
Almost all of the tuna landed at United States ports by commercial fishermen is used for canning. The liver of most tunas yields an oil that is often used in the processing of leather.
Tuna are distinguished from other fish by a series of finlets behind the second dorsal fin and the anal fin.
Tuna are glistening blue above and gray spotted with silver below.
During August and September, tuna approach the coastal areas to spawn, returning to deep water at the beginning of winter. They migrate great distances to spawning and feeding grounds. A fish tagged off California was caught near Japan 10 months later.
Because the tuna has no respiratory mechanism to ensure the flow of water over the gills, only the current caused by its swimming achieves this, so the tuna will die of anoxia of it stops swimming.