Figure From Goode. Drawing by H. The cusk is separable from all its Gulf of Maine relatives at a glance by the fact that it has only one dorsal fin. The relationship of the anal and dorsal fins to the caudal and the outline of the latter are distinctive also, for both the dorsal and the anal are continuous with the caudal at the base but are separated from it by notches so deep that they are obviously distinct.
And the caudal is evenly rounded. The cusk is a more slender fish than the hakes, being only about one-fifth to one-sixth as deep as it is long, round-bodied in front of the vent but flattened sidewise behind the vent, and tapering evenly backward to the base of the caudal fin.
The mouth is large, gaping back to opposite the rear third of eye, is set slightly oblique, and is armed with small, sharp, curved teeth. The snout is blunt at the tip. The upper jaw encloses the lower when the mouth is closed; the eye is of moderate size; the chin bears one barbel; and the entire head and trunk are clad with small scales.
The dorsal fin 85 to rays runs the whole length of the back from the nape of the neck, and is of uniform and moderate height from end to end with rounded corners. The anal fin is similar to it in outline but is only a little more than half as long 71 to 76 rays. The pectoral fins are rounded, and about half as long as the head. The ventral fins are about as long as the pectorals, with their 5 rays free at the tips, and are situated a little but obviously in front of the pectorals.
All the fins are so thick and fleshy at their bases that it is only near their margins that the rays are to be seen. The cusk varies in color, no doubt conforming to the bottoms on which it lives. Its upper parts range from dark slaty to dull reddish brown or to pale yellowish, paling to grayish on the lower part of the sides and to dirty white on the belly.
