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



finmarchicus shoals, and are not found there in commercial concentrations. In 

 June and July the main mass of Calanus finmarchicus sinks down into the 

 depths, the herring concentration increases, and the herring catch is larger. 

 Once herring has eaten its fill it can thrive in shoals in zones of abundant 

 plankton. 



As in the North Sea, Barents Sea herring avoids places where the algae 

 Phaeocystis and Chaetoceras bloom, but it may be present in commercial 

 numbers at the edges of such zones. Descending to a depth of 100 m the her- 

 ring may shoal in large numbers under the zone where these algae bloom. 

 The amount of plankton needed for herring's food in the southwestern parts of 

 the Sea is reckoned in millions of tons. 



Herring has many enemies — cod, marine mammals, sea-gulls, which often 

 follow the schools, preying on this tasty fish. Caplin (Mallotus villosus) is the 

 herring's most dangerous rival as regards food ; it is a comparatively small 

 pelagic fish of the Osmeridae family, which thrives in the Barents Sea in huge 

 numbers and comes up to the Murman coast to spawn. Polar cod (Boreogadus 

 saida), a small pelagic fish also found in exceptionally large numbers in the 

 Barents Sea, is not so dangerous a rival. 



Their rivalry is weakened by the fact that they live in different parts of the 

 Sea. Herring's main habitat lies in the southwestern part of the Sea, caplin's 

 in the northern and eastern ones, while polar cod keeps mostly near the ice, 

 thriving in cold water with a temperature below zero ; it is the only pelagic 

 fish closely connected with ice. On the other hand these three fishes are all 

 devoured in huge numbers by other fish, mammals and birds. 



The links between the food of polar cod and that of the other inhabitants 

 of the sea are particularly curious. The distribution of this high Arctic fish 

 links it with many floating-ice animals. In S. Klumov's opinion (1935) polar 

 cod feeds on phytoplankton in the summer and zooplankton in the winter. 



The predominant role of phytoplankton in the polar cod diet is, in Klumov's 

 opinion, illustrated and confirmed by its love of ice since diatoms typically 

 representative of the ice phytoplankton are predominant in its stomach. The 

 polar cod food links are illustrated graphically by Klumov in Fig. 72. 



History of fishing and hunting trades. Fishing and hunting trades have existed 

 in the Barents Sea since the fifteenth century. They covered a large area from 

 Finmark to the Pechora River in the east and as far as Spitsbergen to the north. 

 In the sixteenth century some tens of thousands of fishermen, inhabiting the 

 White Sea region, came to the Murman coast in the summer. At the end of 

 the eighteenth century up to 270 craft would in some years appear off Spits- 

 bergen coming from the White Sea. Up till the end of the last century the 

 fishing industry of the Barents Sea was haphazard in character. It was run 

 mainly by small commercial guilds in off-shore waters, in shallow, hardly 

 seaworthy ships equipped with very primitive gear. N. Knipovitch, the head 

 of the scientific and industrial expedition off the Murman coast, discovered 

 that trawling is possible in the open Barents Sea. Foreign trawlers were the 

 first to make use of this discovery at the turn of the century. Only in the last 

 few years before 1914 did an Archangel tradesman, Spade, buy four trawlers 



