tituting the main mass of the roe. in addition, there is a complex of ovocytes, inclusive of the 

 phase with follicle tissue in one single layer. 



Stage V (spawning) . The roe occupies almost the whole body cavity. The membrane of the 

 roe is transparent. Large, light eggs are visible. Ripe eggs fill the oviduct which is sharply 

 separated from the lower part of the ovaries. The roe constitutes about 14% of the fish weight, 

 ranging from 9 to 21%. 



Stage VI (spent) . The roe is strongly shrunk, withered, containing much blood, and of a 

 purple color. A few, degenerating eggs which have not been spawned, are very often found in the 

 ovary. The roe now is smaller, merely constituting about 1% of the fish weight. Histologically, 

 the ovaries in stage VI are characterized by empty follicles and a whole complex of the ovocytes 

 characteristic of stage II. 



The Distribution of Herring According to the 

 Stages of Maturity 



The duration of the various stages of maturity is shown in Figure 12, 



The first stage may be observed throughout the year; in adult specimens during 2-2 1/2 

 months (May-July), in immature fish it may last a few years. 



Stage III is most often observed from July to December, but never in April and May. 



Stage IV usually occurs from January to April. Stage V is especially observed in April. As 

 the maturation proceeds, the duration of the stages is shortened. During the maturation process, 

 the weight of the ovaries (the index of maturity) is increasing by degrees. A sudden, jump-like de- 

 crease in the weight of the ovaries is observed during the transition from stage V to VI, 



In the eastern areas of the Barents Sea, young herring with feebly developed sexual glands 

 are dominant. Maturing herring, constituting approximately 85% of the catches in the central 

 areas of the Barents Sea, are observed in March and April in pre -spawning and spawning concen- 

 trations along the northeastern coasts of Norway (see Figure 12), The pre-spawning concentrations 

 consist mostly of herring in stages III and IV, 



The spawning of the Murmansk herring culminates in April . 



The subdivision of the herring according to uniform physiological condition (length, fat con- 

 tent, stage of maturity and so on) takes place long before the spawning. It is assumed that still 

 another subdivision takes place in the spawning places according to what extent the herring are 

 ready to spawn. 



In areas adjacent to the spjawning places, herring in stages II and VI dominate in May. 

 These stages only differ with respect to the degree of restoration of the sexual glands. The pres- 

 ence of stage VI only indicates the end of the spawning and beginning of the regeneration of the 

 gonads, whereas stage II in the mature specimens in May, indicates the culmination of the regen- 

 eration. The nearer to the spawning area during the period of spawning, the more individuals in 

 stage VI dominate. The farther towards northeast and northwest, the more individuals in stage II. 



The end of the spawning period i ^ indicated by an inconsiderable number of herring in stage 

 V. In June, spawning herring have not been observed at all. 



232 



