es of the Atlantic current. TTie explanation is not that the herring have been more heat-loving, but 

 instead a change in food habits and also a westward migration towards the spawning places. 



The westward movement, to areas of higher salinity and temperature, may have a positive 

 influence on the development of the gonads of the herring. Shelford and Powers (105) have shown 

 by experiments that the Atlantic herring react to differences in temperature as low as 0.2°C. 



Nasonov and Aleksandrov (51) infer that temperature acts as a physical factor causing col- 

 loidal changes in the cell. As a result, chemical processes will follow. The authors are of the 

 opinion that the colloidal changes may act as a physiological stimulus inducing some or other phys- 

 iological process. The living cell, being a complicated colloidal system, is undoubtedly influenced 

 by the surrounding medium. 



The influence of temperature on the ripening of the gonads may be illustrated with some 

 examples from fish culture. 



Carp, held in culture ponds in the central part of the USSR, spawn at a very definite tem- 

 perature, 18-19°C. At other temf)eratures, no spawning takes place . In spring, when the carp are 

 transferred to the spawning ponds, the following may be seen: in the winter ponds, the temper- 

 ature is considerably below 18°C. The breeding carp in these do not show any sign of spawning, 

 but only a few hours after they have been placed into the spawning {X)nds, the spawning begins. In 

 this case the temperature acts as a stimulus . 



Kazanski and Nusenbaum (26) studied the spawning in Misgurnus fossilus in the Leningrad 

 area at temperatures of 12-14 C. Below 11 C, the beginning of the ovulation might be retarded 

 or completely stopped. The authors concluded that the ripening of the females was closely connect- 

 ed with temperature. Frantz (84) states that in plaice the development of the gonads is retarded 

 in winter. 



There are also examples that the development of the gonads may also be accelerated in 

 winter. In pikeperch and whitefish a rapid filling of the ovocytes with yolk is connected with a de- 

 crease in temperature (Gerbil'skiy, 12). In the burbot (Lota lota) the spawning usually takes place 

 in December below the ice in the central piart of the European USSR . 



Among the herrings of the North Atlantic may be found spring-spawners, as well as sum- 

 mer-, autumn-, and winter-spawners. In some races of herring, the ripening of the sexual pro- 

 ducts evidently takes place at an increasing temperature, in others, - at a decreasing temperature. 



The temperature itself does not induce spawning, as the reproduction is dependent on a se- 

 ries of complicated processes which take place in the organism itself. The spawning will not take 

 place until the sexual products have reached a certain stage of maturity. Under other conditions, 

 no spawning will take place, even if the temperature conditions are favorable. It is therefore evi- 

 dent, that we will not be able to obtain direct observations of the influence of temperature on the 

 life processes in the Murman herring. At a certain time, and in a particular locality, we merely 

 record the presence of herring in certain stages of maturity, simultaneously with certain hydro- 

 graphical conditions . 



If this is done all the year round, we will have a possibility of comparing the distribution of 

 herring in various stages with the temperature of the water. In a section along the Kola meridian, 

 the temperature in January-March is about 4°C. At this time of the year the stages I and II dom- 

 inate; stage III is less frequent. Herring with the sexual products more advanced, are taken west 

 of the North Cape bank, and near North Cape. 



237 



