THE VERTEBRATES 199 



rays in external appearance are the sawfishes, which belong 

 to this group. The body is elongate and shark-like, and 

 has a long, saw-like snout. This saw, which in large indi- 

 viduals may reach a length of six feet and a breadth of 

 twelve inches, makes its owner formidable among the small 

 sardines and herring-like fishes on which it feeds. The 

 sawfishes live in tropical rivers, descending to the sea. 



Food-fishes and fish-hatcheries. — Most fishes are suit- 

 able for food, though not all. Some are too small to be 

 worth catching or too bony to be. worth eating. Some of 

 the larger ones, especially the sharks, are tough and rank. 

 A few are bitter and in the tropics a number of species feed 

 on poisonous coelenterates about the coral reefs, becoming 

 themselves poisonous in turn. But a fish is rarely poisonous 

 or unwholesome unless it takes poisonous food. Where 

 fishes of a kind specially used for food gather in great num- 

 bers at certain seasons of the year, fishing is carried on 

 extensively and with an elaborate equipment. Such fish- 

 eries, some of which have been long known, are scattered all 

 over the world. Along the shores of the Mediterranean Sea, 

 and on the coasts of Norway, France, the British Isles and 

 Japan are numerous great fishing-places. But "nowhere 

 are there found such large fisheries as those along the north- 

 ern Atlantic coasts of our own continent, extending from 

 Massachusetts to Labrador. Especially on the banks of 

 Newfoundland are codfish, herring, and mackerel caught." 

 Among our fresh-water fisheries the great salmon fisheries 

 of the Penobscot and Columbia rivers and of the Karluk and 

 other rivers of Alaska are the best known. The whitefish 

 of our Great Lakes is also one of the important food-fishes 

 of the world. 



In many places fishes are raised in so-called hatcheries, 

 not usually for immediate consumption but for the purpose 

 of stocking ponds and streams either in the neighborhood 

 of the hatchery or in distant waters which the special species 



