ova, 4 gm. - 7.2 thousand ova, 5 gm. - 13.2 thousand ova, 6 gm.-14.2 thousand ova. 



According to the data of A. P. Vilson, the three-year-old Kandalaksha herring 15 cm. in 

 length and 30 gm. in weight have 7 thousand ova; four-year-old herring 19.7 cm. in length and 62 

 gm. in wei^t have 14.8 thousand ova; and five-year-old herring 20.2 cm. in length and 73 gm. in 

 weight have 16.3 thousand ova. 



Seletskaya found that the number of ova in sprat spawning in Visla estuary, was as follows: 

 2 years - 13 thousand ova, 3 years - 18 thousand ova, 4 years - 28 thousand ova, 5 years - 37.5 

 thousand ova. According to the investigations of A. P. Vilson, two-year-old sprat 12.5 cm. in 

 length from Viborg Bay have 4.2 thousand ova, and three -year -old sprat, 16 cm. in length, contain 

 9.1 thousand ova. A. N. Probatov and A. I. Frolov (20) presented highly interesting data on the 

 fecundity of small herring populating Lake Tonnay (eastern coast of Sakhalin). Two-year-old her- 

 ring approximately 14 cm. in length, have 11.3 thousand ova, three -year -old specimens about 17.6 

 cm. in length have 14.6 thousand ova and four-year-old herring 20.2 cm. in length have 21.5 thou- 

 sand ova . 



The fecundity of sea herring is presented graphically in Figure 11 . The diagram enables us 

 to see the fecundity of different races of herring in relation to the length and age of the fish . It 

 would be even more interesting to establish the dependence between fecundity and weight of the list; 

 however, the data required for such juxtaposition were not found in all the works utilized in this 

 study. 



The conclusion is self-evident - the fecimdity of herring depends to a very considerable de- 

 gree on the size of fish. All the races of small herring are characterized by low fecundity. 



The fecimdity of Atlantic -Scandinavian herring is similar to that of other races of large her- 

 ring. The low fecundity of sea herring is compensated by the great number of spawnings, since 

 these herring are characterized by great longevity. This is particularly well pronounced in Atlantic- 

 Scandinavian herring in view of the fact that they increase considerably in size after the occurrence 

 of sexual maturity and are notable for their great age . 



A female Atlantic-Scandinavian herring releases in the course of five years approximately 

 350 thousand ova, i.e. the number of oa^ cast during 10 years may amount to 800 thousands. 



Mixed composition of the spawning population of Atlantic -Scandinavian herring accounts for 

 a certain stability in their reproductive ability . All the other races of herring that are character- 

 ized by short lives and a simpler composition of the spawning population, have a lower reproductive 

 ability. Moreover, the quantity of eggs released by these latter may be subject to considerable 

 fluctuations as a result of the varying niunber of specimens of different year classes . 



Industrial exploitation of Atlantic-Scandinavian herring . 



Atlantic -Scandinavian herring form the most nximerous school among all the herring of the 

 oceans of the world. The great abundance of these herring is determined by their vast feeding 

 grounds embracing almost the entire boreal zone of the north-eastern Atlantic. Atlantic -Scandina- 

 vian herring utilize the most productive zone of this basin - the region of the polar front, where, 

 as a result of the intensive vertical circulation of water volumes, there are formed outstandingly 

 favorable conditions for plankton development . . The herring feed on zooplankton of both the warm 

 Atlantic and the cold polar waters. 



Good feeding conditions account for the higji growth rate of Atlantic-Scandinavian herring 



54 



