PISCES 113 



may produce over a ton of this substance, which is obtained mainly 

 from the liver. This huge fish may attain a length of over 30 feet. 



The skin of certain sharks and skates, armed as it is with sharply 

 pointed, tooth-like scales, is sometimes used as a polisher of wood and 

 other materials and is known as shagreen. 



Pisces. Under this head will be noted some of the more impor- 

 tant of the so-called teleost or bony fishes; the Dipnoans or lung-fish, 

 which also belong in this group, tho extremely interesting zoologically, 

 are not of sufficient economic importance to warrant discussion here. 



It is, of course, as food for man that these fish are chiefly important 

 though there are some other ways in which they are economically im- 

 portant. For example: the swim-bladder of the sturgeon and some 

 other fish is used to make isinglass, fish-glue, mock pearls, etc.; the men- 

 haden, a coarse kind of herring, is caught in seins by the ton and made 

 into oil and fertilizer, several dozen fishing steamers being engaged 

 along our coasts in catching them and conveying them to factories 

 on shore; cod-liver oil is made from the livers of various species of cod- 

 fish. 



The importance of fish as a food product is best appreciated by 

 visiting a large fishery along the North Atlantic coast or on one of the 

 great rivers of either coast. Along both coasts of the North American 

 continents and in the Great Lakes there are thousands of small vessels 

 constantly engaged in the catching of fish. On the Columbia River 

 are the hugh salmon canneries and on the rivers of the east, are the 

 fisheries for herring, shad, etc. Tens, possibly hundreds, of millions 

 of dollars a year result from the fisheries of the United States. 



While most species of fish are suitable for food there are some that 

 are poisonous either at all times or at certain seasons of the year. 

 L. L. Mowbray (116) says: "Much has been said and written about 

 the poisonous fishes of tropical and sub-tropical seas. It is a known 

 fact that among people eating the same species and at the same time, 

 even caught in the same locality, some have been poisoned, while others 

 have not. Among fishes eaten by man, the species considered most 

 likely to be dangerous as food during the season from May to October, 

 are the barracuda, two species of kingfish, three species of jack, red 

 rockfish and tiger rockfish." . . . " All these fishes are carnivorous, 

 preying upon various species of fishes and invertebrates. There is no 

 evidence whatever that they feed at any season upon forms which would 



