PELAGIC SEALING. 225 



HYDROGRAPHY AND FEEDING- GROUNDS. 



The hydrography of the two island groups offers several interesting differences 

 which probably influence the distribution of the animal life upon which the seals feed 

 and consequently the distribution, of the seals themselves during their stay at the 

 islands. 



The Pribilof Islands are situated within a shallow plateau of scarcely 50 

 fathoms extending toward the north and east to the American continent. The cold 

 waters flowing over this bank are apparently not favorable to the surface forms upon 

 which the seals feed, and the feeding grounds of the Pribilof Island seals are therefore 

 located to the south and west of the islands over very deep water. 



The Commander Islands, on the other hand, are surrounded on all sides by very 

 deep water, rising abruptly, as they do, on nearly all sides from a bottom floor 2,000 

 fathoms and more below the level of the sea, while it is now even doubtful whether 

 any considerably less depth connects them to the Kamchatkan mainland to the 

 northwest. The conditions are here evidently almost equally favorable to the 

 necessary surface life both to the north and to the south of islands, thus giving rise, 

 in connection with the great distance between and different location of the Bering 

 Island rookery and those of Copper Island, to the separate feeding grounds of the 

 seals respectively inhabiting these islands. 



When writing my 1895 account of the feeding grounds of the Commander Islands 

 Eass. Fur-seal Isl., p. 87) the material at hand was too scanty for a clear demonstration 

 of the existence of separate feeding grounds for the Bering Island seals and those of 

 Copper Island, but it was indicated directly by the catches of several schooners to 

 the north of Bering Island, and indirectly by the lack of catches between the Beriug 

 Island rookery and the well established feeding grounds of the Copper Island seals. 

 Another consideration which led me to the same conclusion was the fact that the 

 females had suffered an immense decrease on the Copper Island rookeries, while on 

 the Bering Island north rookery the falling off of the breeding females was 

 comparatively trifling, a condition of affairs w.hich can hardly be reasonably explained 

 under any other supposition. 



Since then sufficient log books of sealers have come to hand which show 

 conclusively that the feeding grounds of the Bering Island seals are located to the 

 north and northwest of that island, while the Copper Island seals feed south and 

 southwest of the latter island (pi. 88). The difference from the Pribilof Island 

 feeding grounds is therefore both interesting theoretically, but also highly important 

 practically as showing that the explanation of the comparatively good condition of 

 the Bering Island north rookery was correct, seeing that it is only during the last 

 couple of years that the pelagic sealers have preyed upon the Bering Island feeding 

 grounds to any great extent. 



PELAGIC SEALING. 



The history of pelagic sealing on the American side and on the Asiatic side is so 

 different, yet the result so identical, that a more detailed comparison seems called for 

 in the present connection. 



Pelagic sealing on the American side originated in the seventies and became 



gradually more and more extensive and important during the early eighties, until in 



1886 nearly 40,000 skins were taken by the pelagic sealers. From then the yearly 



average reached about the same figure until 1891, when it is stated to have been about 



15183— PT 4 15 



