A very similar species, Scomberomorus sierra, occurs on the west coast of Mexico. For some reason it is little valued as food by the Mexicans. In California, the Monterey Spanish mackerel (Scomberomorus concolor) is equally excellent as a food-fish. This fish lacks the spots characteristic of most of its relatives. It was first found in the Bay of Monterey, especially at Santa Cruz and Soquel, in abundance in the autumn of 1879 and 1880. It has not, so far as is known, been seen since, nor is the species recorded from any other coast.
The true Spanish mackerel has round, bronze-black spots upon its sides. Almost exactly like it in appearance is the pintado, or sierra (Scomberomorus regalis), but in this species the spots are oblong in form. The pintado abounds in the West Indies. Its flesh is less delicate than that of the more true Spanish mackerel. The name sierra, saw, commonly applied to these fishes by Spanish-speaking people, has been corrupted into cero in some books on angling.
Still other Spanish mackerel of several species occur on the coasts of India, Chile, and Japan.
The great kingfish, or cavalla (Scomberomorus cavalla), is a huge Spanish mackerel of Cuba and the West Indies, reaching a weight of 100 pounds. It is dark iron-gray in color, one of the best of food-fishes, and is unspotted, and its firm, rich flesh resembles that of the barracuda.
Still larger is the great guahu, or peto, an immense sharp-nosed, swift-swimming mackerel found in the East and West Indies, as well as in Polynesia, reaching a length of six feet and a weight of more than a hundred pounds. Its large knife-like teeth are serrated on the edge and the color is almost black. Acanthocybium solandri is the species found in Hawaii and Japan. The American Acanthocybium petus, occasionally also taken in the Mediterranean, may be the same species.
Fossil Spanish mackerels, tunnies, and albacores, as well as representatives of related genera now extinct, abound in the Eocene and Miocene, especially in northern Italy. Among them are Scomber antiquus from the Miocene, Scombrinus macropomus from the Eocene London clays, much like Scomber, but with stronger teeth, Sphyrænodus priscus from the same deposits, the teeth still larger, Scombramphodon crossidens, from the same deposits, also with strong teeth, like those of Scomberomorus. Scomberomorus is the best represented of all the genera as fossil, Scomberomorus speciosus and numerous other species occurring in the Eocene. A fossil species of Germo, G. lanceolatus, occurs at Monte Bolca in Eocene rocks. Another tunny, with very small teeth is Eothynnus salmonens, from the lower Eocene near London. Several other tunny-like fishes occur in the lower Tertiary.
The Escolars: Gempylidæ.—More predaceous than the mackerels and tunnies are the pelagic mackerels, Gempylidæ, known as escolars ("scholars"), with the body almost band-shaped and the teeth very large and sharp. Some of these, from the ocean depths, are violet-black in color, those near the surface being silvery. Escolar violaceus lives in the abysses of the Gulf Stream. Ruvettus pretiosus, the black escolar, lives in more moderate depths and is often taken in Cuba, Madeira, Hawaii, and Japan. It is a very large fish, black, with very rough scales. The flesh is white, soft, and full of oil; sometimes rated very high, and at other times too rank to be edible. The name escolar means scholar in Spanish, but its root meaning, as applied to this fish, comes from a word meaning to scour, in allusion to the very rough scales.
Promethichthys prometheus, the rabbit-fish, or conejo, so-called from its wariness, is caught in the same regions, being especially common about Madeira and Hawaii. Gempylus serpens, the snake-mackerel, is a still slenderer and more voracious fish of the open seas. Thyrsites atun is the Australian "barracuda," a valued food-fish, voracious and predaceous.
Scabbard-and Cutlass-fishes: Lepidopidæ and Trichiuridæ.—The family of Lepidopidæ, or scabbard-fishes, includes degenerate mackerels, band-shaped, with continuous dorsal fin, and the long jaws armed with very small teeth. These are found in the open sea, Lepidopus candatus being the most common. This species reaches a length of five or six feet and comes to different coasts occasionally to deposit its spawn. It lives in warm water and is at once chilled by the least cold; hence the name of frostfish occasionally applied to it. Several species of Lepidopus are fossil in the later Tertiary. Lepidopus glarisianus occurs in the Swiss Oligocene, and with it Thyrsitocephalus alpinus, which approaches more nearly to the Gempylidæ.
Still more degenerate are the Trichiuridæ, or cutlass-fishes, in which the caudal fin is wanting, the tail ending in a hair-like filament. The species are bright silvery in color, very slender, and very voracious, reaching a length of three to five feet. Trichiurus lepturus is rather common on our Atlantic coast. The names hairfish and silver-eel, among others, are often given to it. Trichiurus japonicas, a very similar species, is common in Japan, and other species inhabit the tropical seas. Trichiurichthys, a fossil genus with well-developed scales, precedes Trichiurus in the Miocene.