Figure 16. Roe of Norwegian herring taken near Alesund, February 1947. Length of fish 

 298 mm., stage IV- V. Wei^t of roe 60 gm. Index of maturity 19.4. -x 67. 



SUMMARY 



1 . The maturity stages of the sexual products of the Murmansk herring have been worked 

 out from a macro- and microscopic study of the ovaries. 



2. In the females, the sexual products mature during 8-9 months. The beginning of the 

 maturing (transition from stage II to III), as well as the transition from the juvenile stage to stage 

 II, takes place in July. Sexual maturity (stage V) is attained in March-April. 



3. The Murmansk herring will be sexually mature in the 5th-6th year of their life. From 

 our observations the herring spawn each year until they are 14 years old or older. Adult, "sterile" 

 individuals have not been found. 



4. The Murmansk herring belong to the fishes that have a type of total spawning. The ex- 

 trusion of the mature eggs takes place at intervals during a few hours or days . 



As the different schools of herring do not attain maturity at the same time, the period of 

 spawning is extended. 



5. The transition from one stage to another takes place by degrees until stage V; but from 

 V to VI, very suddenly, in a leap. The duration of each stage is not the same. The transitions be- 

 tween the various stages can therefore not be compared. 



6. Each stage of maturity is normally found under special ecological conditions (temper- 

 ature, salinity, light, feeding). 



7 . Each period in the life cycle of the Murmansk herring corresponds with certain stages 

 in the maturity of the ovaries . Each stage may be characterized by a certain state of the fish (fat 

 content, amount of hemoglobin in the blood, the leucocyte formula). 



251 



