Scomber priscus is a fossil mackerel from the Eocene.
Auxis thazard, the frigate mackerel, has the scales of the shoulders enlarged and somewhat coalescent, forming what is called a corselet. The species ranges widely through the seas of the world in great numbers, but very erratic, sometimes myriads reaching our Eastern coast, then none seen for years. It is more constant in its visits to Japan and Hawaii. Fossil species of Auxis are found in the Miocene.
The genus Gymnosarda has the corselet as in Auxis, but the first dorsal fin is long, extending backward to the base of the second. Its two species, Gymnosarda pelamis, the Oceanic bonito, and Gymnosarda alleterata, the little tunny, are found in all warm seas, being especially abundant in the Mediterranean, about Hawaii and Japan. These are plump fish of moderate size, with very red and very oily flesh.
Closely related to these is the great tunny, or Tuna (Thunnus thynnus) found in all warm seas and reaching at times a weight of 1500 pounds. These enormous fishes are much valued by anglers, a popular "Tuna Club" devoted to the sport of catching them with a hook having its headquarters at Avalon, on Santa Catalina Island, in California. They are good food, although the flesh of the large ones is very oily. The name horse-mackerel is often given to these monsters on the New England coast. In California, the Spanish name of tuna has become current among fisherman.
Very similar to the tuna, but much smaller, is the Albacore (Germo alalonga). This reaches a weight of fifteen to thirty pounds, and is known by its very long, almost ribbon-like pectoral fins. This species is common in the Mediterranean, and about the Santa Barbara Islands, where it runs in great schools in March. The flesh of the albacore is of little value, unless, as in Japan, it is eaten raw. The Japanese shibi (Germo germo) is another large albacore, having the finlets bright yellow. It is found also at Hawaii.
The bonito (Sarda sarda) wanders far throughout the Atlantic, abounding on our Atlantic coast as in the Mediterranean, coming inshore in summer to spawn or feed. Its flesh is red and not very delicate, though it may be reckoned as a fair food-fish. It is often served under the name of "Spanish mackerel" to the injury of the reputation of the better fish.
Fig. 207.—The Long-fin Albacore, Germo alalunga (Gmelin). Gulf Stream.
Professor Goode writes:
"One of these fishes is a marvel of beauty and strength. Every line in its contour is suggestive of swift motion. The head is shaped like a minie bullet, the jaws fit together so tightly that a knife-edge could scarcely pass between, the eyes are hard, smooth, their surfaces on a perfect level with the adjoining surfaces. The shoulders are heavy and strong, the contours of the powerful masses of muscle gently and evenly merging into the straighter lines in which the contour of the body slopes back to the tail. The dorsal fin is placed in a groove into which it is received, like the blade of a clasp-knife in its handle. The pectoral and ventral fins also fit into depressions in the sides of the fish. Above and below, on the posterior third of the body, are placed the little finlets, each a little rudder with independent motions of its own, by which the course of the fish may be readily steered. The tail itself is a crescent-shaped oar, without flesh, almost without scales, composed of bundles of rays flexible, yet almost as hard as ivory. A single sweep of this powerful oar doubtless suffices to propel the bonito a hundred yards, for the polished surfaces of its body can offer little resistance to the water. I have seen a common dolphin swimming round and round a steamship, advancing at the rate of twelve knots an hour, the effort being hardly perceptible. The wild duck is said to fly seventy miles in an hour. Who can calculate the speed of the bonito? It might be done by the aid of the electrical contrivances by which is calculated the initial velocity of a projectile. The bonitoes in our sounds to-day may have been passing Cape Colony or the Land of Fire day before yesterday."