MIGRATIONS OF WHALES KELLOGG 471 



tion of plankton reaches its maximum wherever there is a sufficient 

 actinity of light, nutritive sa^s, and an intermingling with warmer 

 currents. 



Vegetation is the ultimate source of food for pelagic animals, 

 and plants are dependent for their existence in part upon sunlight 

 to assimilate carbon and in part on the presence of certain nutritive 

 solutions of salts. Sea water of low temperature has a somewhat 

 higher gaseous content and is richer in nitrogenous compounds. By 

 synthesis of water and carbonic acid under a certain actinity of light 

 the microscopic plants that obtain their food directly from inorganic 

 substances in sea water are abje to combine elementary nitrogen 

 salts with carbohydrate and produce proteids. Microscopic diatoms 

 form the bulk of the vegetation of the colder seas, and they float 

 at or near the surface. Microscopic animals known as peridinians 

 and dinoflagellates are often very abundant. Immense swarms of 

 a small shrimplike crustacean {Ewphausia superba) make their ap- 

 pearance with the approach of Antarctic spring on the whaling 

 grounds, and these euphausids are dependent upon diatoms for 

 their sustenance. (Kemp, 1928, p. 191.) Euphausids are known 

 to feed on copepods, cladocera, and peridinians, as well as diatoms. 

 The duration of Jife of plankton varies in accordance with the 

 temperature of the water, and in sea water of low temperature there 

 exists a vastly larger number of coexisting generations than in warm 

 oceans or in shallow coastal waters of low salinity. Hence in Boreal 

 and Antarctic waters there is an astonishing abundance of minute 

 pelagic animals (plankton) in the upper layers during the spring 

 and summer months, and for this reason the whajes congregate in 

 these regions at this season of the year. In late fall or early winter, 

 with the chilling of the surface water and descent of their favorite 

 food, many of these whales migrate toward the Tropics. 



Information relating to the migrations of whales has been as- 

 sembled from many sources. Some of these data while suggestive 

 need corroboration, and this is especially true of migration records 

 based on whales from which foreign makes of harpoons have been 

 recovered. There are many instances on record of the finding of 

 harpoons which were readily identifiable as the type employed 

 by whalers operating in other parts of the world. Taking into con- 

 sideration the extent of the voyages of many of the whaling vessels 

 during the past century, particularly our own New England whale- 

 men, it is obvious that too much stress should not be laid on this sort 

 of evidence. The whalers of the past century had little actual 

 Imowledge of the migrations of whales, but they were acquainted with 

 localities where whales were accustomed to appear in considerable 

 numbers at definite seasons, and so planned their voyages that they 



