THE OVOGENESIS AND ECOLOGY OF THE SEXUAL CYCLE OF THE 



MURMANSK HERRING (CLUPEA HARENGUS HARENGUS L.) 



V. M. Naumov 



The life cycle of the Murmansk herring can be studied on the basis of the sexual cycle . 

 Items of importance to the catch of the herring, such as pre-sjjawning concentrations, migrations, 

 and spawning are related to the sexiial cycle of the fish. 



In contradistinction to other workers who have investigated the sexual cycle of fish, we find 

 it necessary to compare the stages in this cycle with the ecological conditions in the different habi- 

 tats and with other indicators of the physiological state of the herring. 



The material for the present paper was collected by the author on four cruises, three in the 

 Barents Sea (1938-39), and one in the Greenland Sea (1947). Data from the Polar Institute (PINRO) 

 have also been used. 



The investigation of the sexual cycle of the Murmansk herring is not only of theoretical in- 

 terest, but may also be useful to the commercial fishery, especially for predicting the spawning 

 migrations of the herring. 



The Types of Spawning in Herring 



In recent years Soviet ichthyologists have distinguished between two types of spawning, 

 namely, 1) all the eggs are spawned in one batch, and 2) in several portions. 



Gerbil'skiy (12), by the character of the ovogenesis and oviilation, divides the fish into two 

 groups, those with "total" or "complete" spawning, and those with "partial" (in portions) spawning. 

 At first we will define these two ideas, and then state to which group the Murmansk herring belongs. 



In the type with total spawning the ovaries may be characterized in the following way: Once 

 a year a certain quantity of ripening ovocytes are simultaneously sepiarated from the total reserve 

 of ovocytes. This takes place in ovaries in stage EL-III (in a scale with 6 stages). TTie ovocytes 

 are spawned in one batch, or in portions during ? few hours or days . 



A partial spawning Is observed In those species in which the ovocytes that are ripening 

 simultaneously are separated into stage II -III groups three or four times during one spawning period. 



The type of total (isochronal) spawning is characterized by the presence of a complex of 

 ovocytes in the ovary: 1) non-developing ovocytes (pre-ovogonia, ovogonia and ovocytes in the 

 single -layered follicle phase)which constitute the so-called reserve of the next year (the ovogonia 

 constitute the so-called reserve, not only of next year, but also of a series of years), and 2) de- 

 veloping ovocytes, always in one single stage of development only. 



The ovaries of the type of partial spawning are characterized by the presence of 1) non- 

 developing ovocytes, such as in the preceding type, and 2) ovocytes in different phases of develop- 

 ment. For example, in the ovary one part of the ovocytes may be in the first yolk -forming phase, 

 another part in a later yolk-filllng stage, and a third part of the ovocytes may be full of yolk. 



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