262 PISCES 



Teleosts. — Many species of the bony fishes are valued as food. 

 Some of the common food fishes are herring, shad, codfish and sal- 

 mon. Fish are eaten fresh, smoked, dried, salted, canned whole, or 

 flaked, and pickled. Cod, halibut and salmon skins have been 

 suggested as a source of leather, but are not in use by civilized man. 

 The Alaskan Indians have for many years used salmon skins to 

 make shirts and boots. Eel leather has been utilized for pig-tails 

 and flail thongs. Some Southern negroes value eel skins as a cure 

 for rheumatism. The swim-bladder of the sturgeon and some other 

 fish is used to make isinglass and fish-glue. Menhaden are caught 

 by the ton and made into oil and fertilizer. 



Pearl essence is secured from herring, alewives, shad and men- 

 haden. The California sardine is also a source. Pearl essence is 

 securedr-b^y the extraction of the blade-like crystals oi guanin found 

 in the epidermis of the fish. The crystals are separated into uniform 

 sizes and when mixed with gelatin are used to coat glass beads, 

 making imitation pearls. A solution of guanin is also prepared for 

 use as nail-gloss. 



Fish meal is secured from fish and fish waste by cooking without 

 scorching, and pressing the oil out while the fish is hot. Fish meal 

 is used in poultry and stock feed. 



While it will probably never replace cod liver oil, in furnishing 

 Vitamins A and D for human consumption, there is no question 

 that the vast quantities of salmon liver oil will reduce prices for the 

 cheaper grades of fish oil used in cattle feeding. 



Negative. Cyclostomes. — Lampreys attach themselves to the 

 bodies of other fish, cut through the body wall and suck out the 

 blood and soft parts until the victim dies. Hags parasitize marine 

 fishes, entering the body cavity of the host through the hole that 

 they cut. 



Elasmobranchs. — The great white shark called the " maneater " 

 sometimes reaches a length of forty feet and can cut the body of a 

 man in two at one bite. Small dogfish destroy lobsters, crabs, and 

 food fishes, and injure nets and other fishing gear to the extent of 

 1500,000 per year in Massachusetts. Sting-rays or " stingarees " 

 occasionally injure man. Rays and some sharks have poison glands 

 at the base of their dorsal fins. The torpedo or electric ray is able 

 to give a shock of fifteen volts and temporarily disable a man. 



Teleosts. — Certain of the bony fishes are enemies of man. The 

 barracuda, sometimes reaching a length of six feet, is reputed to 



