The Bull Trout or Sea Trout (S. eriox) most resembles the salmon in appearance and habits, though thicker in proportion to its length, and with larger and more numerous dark spots on the gill-covers and scales.
The Salmon or White Trout (S. trutta) is a more elegant fish, and its flesh is much more delicate in flavor. The habits of both are similar.
The Rainbow Trout (Salmo irideus) of America has been introduced into many parts of the world; in New Zealand, especially in Lake Taupo, it attains the greatest size, many tons being caught yearly.
Whitefish (Coregonus clupeiformis), the common whitefish, is the largest of all the American lake whitefish. It is very highly esteemed for food, ranking, indeed, as one of the finest table fishes. Its range extends from Lake Champlain to the Arctic Circle.
CARTILAGINOUS FISHES (Elasmobranchii)
These fishes have a cartilaginous, pliant, undeveloped skeleton, and are not covered with true scales. They include rays, sawfish, sharks, skates and others.
Ray, a popular name applied to many of the flat cartilaginous fishes: Thornbacks, Electric Rays, Sting-rays, Eagle-rays are representative. They lead a somewhat sedentary life at the bottom of the sea, moving sluggishly by undulations of the pectoral fins which form a large part of the flat body. Many attain a large size, sometimes measuring six feet across.
Sawfish (Pristis) are distinguished by the prolongation of the snout into a formidable weapon bordered on each side by sharp teeth. Some species are found off the southern coasts of North America and in the Gulf of Mexico, and in the Mediterranean and many other seas. With its saw, which is sometimes six feet in length, the sawfish slashes or rips up its prey, and its assault is often fatal to large whales.
Sharks are a group of very simple fishes, which have only a cartilage skeleton, no bone being developed anywhere in them. They have the gill openings on the side of the neck separate, and in all of the common species the mouth is on the lower side of the head instead of at the tip, as in ordinary fishes. The tail has unequal lobes, the upper lobe being much the larger. There are always four paired fins and one or more on the back. The size of the sharks varies from the smaller dogfish, about two feet long, to the great basking shark, some forty feet in length. Most of these species are very voracious, but the tales of man-eating are often exaggerated, although occasionally they may occur. Some of the largest species feed exclusively on shellfish. The flesh of several species is good to eat, but they are mostly neglected in America. The livers are very rich in oil, which commands a good price for use in dressing leather. In some species the skin has small spines and was formerly used (it was called shagreen) instead of sandpaper. Skin with larger plates is sometimes used in the manufacture of pocketbooks, etc.
Skates (Raia batis).—A group of fishes, closely related to the sharks, but having the body flattened from above downward, and with the anterior fins so united to the side of the head and the body that it has a rhomboid appearance and the tail seems like an inconsiderable appendage. The mouth and the gill openings are on the under surface. The animals are bottom feeders, living on clams and mussels, buried in the mud. In Europe some of the smaller species are used for food. Another has a large electric battery on either side of the head, capable of giving very strong shocks. This is called the torpedo.