CHORDATA 



»91 



able importance, and has a wide distribution in the Pacil 

 The "American sardine," so extensively put up in tins on the 

 Atlantic seacoast of the United States, is the young menhaden, 

 belonging to a different genus. In a related family is tin- huge 

 Arapaima gigas, found in the rivers of Brazil and Guiana, and 

 not exceeded in size by any strictly fresh-water teleost. It 

 attains a length of from four to five meters, weighing two hun- 

 dred kilos, and is said to be a good food fish. 



Not far removed from the last two groups is the large family, 

 Salmonidae, to which the various kinds of salmon and trout be- 

 long. They are widely distributed in the north temperate and 

 Arctic regions of both continents. Some, like the whitefish, live 

 mostly in lakes ; others, like the grayling and trout, arc found 

 in clear, cold brooks; others, like the salmon, are marine, and 

 ascend the rivers to spawn. The salmon is one of the most 

 important food fishes in the United States and very important 



p^r 



FlG. 297. Salmofarlo. a.l, adipose lobe of pelvic fin ; an, anus ; c.f, caudal fin ; d.f.i, first 

 dorsal fin; d.f.2, second dorsal or adipose fin; /./, lateral line; op, operculum; pet./, 

 toral tin; pv.f, pelvic fin; v./, ventral fin. (After Jaidine, from Parker and Haswell's 

 Manual.) 



to the canning industry. The largest salmon is the quinnat, or 

 king salmon, of the northern Pacific, Oncorhynchus tchawytcha, 

 which sometimes ascends the rivers for a thousand or twelve 

 hundred kilometers or more (six hundred to eight hundred miles) 

 to spawn. They are killed to such an enormous extent by the 

 canners that there appears to be great danger of their extinction. 

 The salmon on our Atlantic coast is Sal mo salar ; it does not 

 extend south of Cape Cod, but is found in northern Europe also. 

 The landdocked salmon, found in some of our inland lakes and 

 in Sweden, is now believed to belong to the same species ; it 

 never makes its way to the sea. Of the many species of trout, 



