744 BIOLOGY OF THE SEAS OF THE U.S.S.R. 



traversed by the crab during his migration is up to 5 or even 7 miles (L. Vino- 

 gradov, 1941). This migration starts when the young begin to appear. New 

 mating takes place in the shallows. After mating crabs cast their shells and 

 for part of the summer and autumn feed intensively on small bivalves, worms, 

 crustaceans and echinoderms (mainly Echinarachnius parma). Commercial 

 aggregation of the Kamchatka crab is always repeated at precisely the same 

 places. The biology, migrations and formation of commercial aggregations of 

 the Kamchatka crab are being thoroughly investigated by the numerous and 

 intensive researches of Soviet and Japanese zoologists (L. Vinogradov, 

 1933, and 1941 ; I. Zachs, 1936, X. Marukava, 1933). 



Among the other crustaceans such as prawns, chiefly the large forms 

 Pandalus latirostris and Cambaroides schrenckii have great commercial 

 importance. The prospect of the commercial exploitation of molluscs 

 too in the Far Eastern Seas is just as important. These include primarily 

 Ostrea, Pecten, Spisula, Mytilus, Cardium, Area and a few dozen more 

 bivalves, gastropods and cephalopods. Trepang {Stychopus japonicus) might 

 also play an important role in the future. Commerical sea- weed resources in 

 the Far Eastern Seas are very great. 



Sea-birds, which nest on the shores and feed on invertebrates and fish, 

 usually form bird rocks ('loGmenes'). They spend all their non-nesting time 

 over the sea, and thus also play an important role in the total balance of 

 organic matter in the sea, mostly in the neritic zone. Among the most striking 

 and widely known examples of this behaviour are the birds of the coasts of 

 Chile and Peru, mainly guanay {Phalacrocorax bougainvillei) and to a less 

 extent the pelican (Pelecanus thagus) and the blue-footed booby (Sula 

 nebouxii), which consume yearly more than 20 million centners of fish, 

 mainly anchovy {Engraulis ringens). 



Such great aggregations of sea-birds do not exist on the shores of the u.s.s.r. ; 

 they are, however, very large and some are even immense, on the Iona and 

 Tyuleny Islands for example, and on some of the Kuril Islands in the Sea of 

 Okhotsk. Guano is not commercially exploited on the shores of the u.s.s.r. ; 

 some of the sea-birds themselves and their eggs are, however, of commercial 

 importance (Uria species, fulmar, puffins, eiders). 



The main breeds of sea-birds of the Soviet Far Eastern shores (S. Uspen- 

 sky, 1959) are, apart from albatrosses (Diomedea) and shearwaters (Puffinus) 

 which do not form colonies, guillemots {Uria lomvia and U. algae), puffin 

 {Fratercula cirrata, F. corniculata), pelagic shag {Phalacrocorax pelagicus), 

 kittiwake {Rissa tridactyla), petrel {Fulmarus glacialis) and others. In the 

 southwestern part of the Sea of Okhotsk and in the Sea of Japan the following 

 are added to this list: Cerorhinca monocerata, the black-tailed gull {Lams 

 crassirostris), the Ussu cormorant {Phalacrocorax filamentosus), the guillemot 

 {Cepphus carbo) and others. All this abundant bird population consumes an 

 immense number of small fish and crustaceans {Tables 302 and 303). 



VI. ZOOGEOGRAPHY OF THE FAR EASTERN SEAS 

 In estimating the biogeography of the Far Eastern Seas and the adjacent 

 parts of the Pacific Ocean one should proceed from the following premises : 



