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



(1929) notes that in recent years fish which had hitherto been very rare along 

 the Murman coast have begun to appear there, such as Lamna cornubica, 

 Microstomas microcephalus, as well as Gadus merlangus, Trachypterus arcticus 

 and others ; Yu. Boldovsky (1937) has noted the finding of Gadus esmarki and 

 G. poutassou in Murman waters. 



Some boreal forms which formerly were never or very rarely found in the 

 plankton of the Barents Sea have become common there. Among them may 

 be mentioned the cephalopod Ommatostrephes todarus, the siphonophore 

 Physophora hydrostatica, the polychaete Tomopteris helgolandica and a 

 series of others. Sometimes the warm-water pteropod mollusc Limacina 

 retroversa drifts in great numbers into the southwestern part of the Barents 

 Sea. 



Meganyctiphanes norvegica (Euphausiacea), rare in the Barents Sea at the 

 beginning of this century, has now become a common form there. Still more 

 examples could be given as regards benthos. The boreal sea urchin Schizaster 

 fragilis, which according to K. Derjugin (1915) was absent in the Kola Guba 

 in 1908-09, has in recent years become a mass form there. The mollusc 

 Cardium echinatum was also unknown there. Another boreal sea urchin 

 Echinus esculentus has become common on the western Murman coast. A 

 whole series of boreal molluscs has become common in the Kola Guba and the 

 adjacent area of the Barents Sea; as for example Cardium edule, C.fasciatum, 

 С elegantulum, Acera bullata, Doto coronata, Gibbula tumida ; of crustaceans 

 Eupagurus bernhardus, Munida rugosa and others may be mentioned. At the 

 same time Arctic forms are receding eastward. The cold-water mollusc Ser- 

 ripes groenlandicus which at the time of K. Derjugin's explorations (1910 to 

 1914) was a mass form in the Kola Guba has at present (V. Zatzepin, 1946) 

 become a rarity there, and the cold-loving pteropod mollusc Limacina heli- 

 cina has been driven out into the eastern part of the sea. 



The appearance of a whole series of warm-water fish off the shores of 

 Novaya Zemlya and in the Kara and White Seas has been observed (L. Berg, 

 1939). In 1883 the warm- water fish Scombresox saurus was very rarely 

 caught off the North Cape, but in 1937 it was caught at Matochkin Shar. 

 Moreover, herring, mackerel, haddock and coalfish were found off the shores 

 of Novaya Zemlya. Cod and coalfish have apparently begun to multiply 

 there. 



Haddock, coalfish and bass have appeared in the White Sea; Atlantic 

 herring and Barents Sea cod have penetrated into the Kara Sea. 



The quantitative and qualitative composition of the population of the Arctic 

 basin has substantially changed as a result of the warming up of the water by 

 a few degrees. The changes are in three directions : first of all there is a change 

 in the composition of the population, that is in the structure of the biocoe- 

 noses ; then there is migration not only of separate forms, but of whole 

 groups (biocoenoses) from south to north — the Arctic communities recede, 

 the boreal advance; finally there is also a change in the quantitative indices 

 of the density of the population. This colossal process of the general change of 

 the Arctic basin fauna proceeding in a definite direction and taking whole 

 decades to develop deserves most careful investigation. 



