[Jordan and Evermann, 1896-1900, p. 892, Tetrapterus amplus.]
The marlin parallels the swordfish in the prolongation of the bones of the upper jaw to form a sword. But that of the marlin is slender and rounded above, not broad and flattened as in the swordfish, also only about half as long relatively. The two fish differ widely, too, in the relative sizes of the first dorsal fin, which extends along fully two-thirds of the length of the trunk from the nape backward in the marlin and is, futhermore, of characteristic falcate outline. But more important systematically, if less apparent, is the fact that the adult marlin has ventral fins which the swordfish lacks, though they are reduced, it is true, to one long spine each (actually 5 spines fused together).
Futhermore, the second dorsal fin and the second anal fin of the marlin are relatively larger, and the pectorals smaller than those of the swordfish, while there are two small longitudinal keels on either side of its caudal peduncle instead of one broad one; its body is more slender; and its head is relatively shorter. Careful examination would show that the spearfish is not naked but has small scales imbedded in the skin and that there are small teeth in its jaws and on the roof of its mouth.
The blue marlin differs from its close relative the white marlin in the shape of the apex of its first dorsal fin and of the tips of its pectorals, both of which are pointed; also in the much darker color of its sides and belly; and in the fact that it grows much larger.
The blue marlin is deepest abreast the pectorals, (about 6¼ times as long, not counting the caudal fin, as it is deep), tapering evenly to the caudal peduncle, and its upper jaw in front of the eye (including the sword) is about twice as long as the length of its head behind the eye.
The first dorsal fin, with 47 to 48 stiff rays is separated from the second dorsal by a space about as long as the latter in one fish seen by us; by a shorter space in another. The first anal fin (2 spines and about 12 or 13 rays), situated below the rear part of the first dorsal, is triangular, its long first rays forming a sharp angle. The short second anal is similar to the second dorsal fin and originates a little in front of the latter. The ventrals stand below the pectorals; the caudal resembles that of the swordfish in its lunate outline.
Dark dull blue on the back and on the sides down about to the level of the eyes, washed with coppery reflections, also on the bill, with [page 359] rather abrupt transition to much paler gray-blue lower down the sides and on the lower surface, the belly being as dark as the lower part of the sides; the sides cross-marked with about 13 indistinct violet-blue stripes, about 1 to 1½ inches wide on a fish 8 feet long, showing pale against the dark blue of the upper parts of the body, but dark against the paler blue of the lower part of the sides. First and second dorsal fins, pectoral and ventral fins, and first anal fin dark rather vivid blue. Caudal fin of about the same color as upper part of trunk; second anal fin of same pale gray-blue as the belly.
Blue marlins run fully as large as swordfish. Reports are current of fish of 1,000 pounds being harpooned; the rod and reel record is 742 pounds. Many weighing more than 500 pounds are caught off the north coast of Cuba and on the Bahamas side of the Straits of Florida every year, and one taken on the southern part of Browns Bank, weighed 575 pounds dressed, when landed, or about 700 pounds alive. A very large one may measure as much as 15 feet, but the rod and reel record fish, mentioned above, was only 12 feet 10½ inches long. Another fish caught in the Bahamas weighed 650 pounds (not dressed), and measured 12 feet 1 inch; a third, of 621 pounds was 12 feet 3 inches long.
General range-Warm parts of the northwestern Atlantic, straying northward to the Gulf of Maine. It has been reported near Sable Island, but the very small specimen in question may have been a white marlin (p. 360).
This southern warm-water fish was reported from the South Channel, between Georges Bank and Nantucket Shoals, between 1877 and 1880, by the fishing schooner Phoenix. No other marlins that we can be sure were blues were reported within the limits of the Gulf of Maine until September 5, 1930, when a small one 6 feet 10 inches long, was harpooned on the southern part of Browns Bank. And a very large one was caught in that same vicinity by the Col. Lindbergh the following July, [page 360] and brought into the Boston Fish Pier. A marlin about 5 feet long was taken on Georges Bank by the schooner Ethel Merriam, on August 5, 1925, but this may have been a white (p. 359).
Blue marlins are sighted at long intervals off Marthas Vineyard. And fishermen report them now and then along the southern edge of Georges (any very large marlin is a blue) but do not harpoon them, for they have no market value. They are game fish par excellence, and much sought after off Cuba and in the Bahaman side of the Straits of Florida. They also support a considerable commercial fishery off the north coast of Cuba.
 Jordan and Evermann in their general review of the giant mackerel-like fishes, tunnies, spearfishes, and swordfishes (Occ. Papers, Calif. Acad. of Sci., XII, p. 28, 1926) separate the spearfishes into two genera Tetrapterus with the front of the first dorsal fin little if any higher than the median part of the fin and Makaira, with the front part of the first dorsal higher than the median part of the dorsal.
 Very young marlins have only one continuous dorsal fin, but this separates later into two.
 See Shapiro (Amer. Mus. Novitat., No. 995, 1938) for a study of the changes in proportional dimensions that take place with growth, in the blue marlin.
 Description based on a "blue" about 8 feet long from tip of bill to fork of tail, and weighing 169 pounds, fish taken near Bimini, Bahamas, June 1941, by R. W. Foster, mounted by the well-known fish taxidermist, H. Pfleuger of Miami, Fla., and now in the Museum of Comparative Zoology.
 Caught at Bimini, Bahamas, June 19, 1949, by Aksel Wichfeld.
 See Farrington (in Vesey-Fitzgerald and Lamonte, Game Fish of the World, 1949, p. 154) for a readable account of the blue marlin of Bahaman waters as a game fish.
 The blue marlin is said to reach 26 feet, but we think this much exaggerated.
 Reported to us by Frank Mather, of the Woods Hole Oceanographic Institution.
 This specimen is in the Museum of Comparative Zoology.
 Farrington (in Vesey-Fitzgerald and Lamonte, Game Fishes of the World, 1949, p. 153) gives an interesting account of this fishery.