least at certain times, to distinguish one from another in a sample merely by observa- 
tion of the degree of maturity exhibited by the genital organs. 
As mentioned in the introduction, Brocx found in the scales of the herring an ex- 
cellent means of determining the age of the fish, and his very first investigations showed 
that the different races exhibit different growth, and that individuals of equal size be- 
longing to different races may differ greatly in point of age. 
International studies as to age and growth. 
These principles have been subjected to far closer investigation and consideration 
in the course of the more extensive and systematic international herring investigations, 
and these have confirmed, in increasing degree, the fact that the rate and manner of 
growth exhibit peculiar characteristic features in the different races. Some score thous- 
and fish from different waters have been measured according to the methods described 
De GE ee 
Pr, 
Nel oa 
4 (©) De 
= SES > 
Fig. 32. Hight herring of equal age (4 years) trom 
1. White Sea. 5. Western part of North Sea. 
2. Lysefjorden (West Norway). 6. Atlantic Ocean. 
3. Zuyder Zee. 7. Iceland. 
4. East Coast of Sweden. 8. West Coast of Norway (Spring herring), 
in the previous chapter, and calculations made as to the size of the individuals at the 
different periods of growth through which they have passed, thus furnishing a very large 
number (nearly a million) of figures for calculation of the average growth of the herring 
in different regions”). 
Some examples will show what can be attained by such investigations. 
*) K. Dant has in his paper “The Scales of the Herring” (Report on Norwegian Fishery and 
Marine Investigations, Vol. II, 1907) suggested that the first winter ring may, in the case of 
autumn spawning herring, be formed, not in their first winter but in the second, when the fish 
are 1!/,, 11/, or perhaps even 12/, years old. He bases this theory partly on the fact of having 
found the first growth zone to be far larger in the case of autumn spawning than in that of 
spring spawning fish, and partly on having encountered, on the Jutland Bank in winter, small 
herring of 4 cm. in length without any scale covering at all. This question has hardly been 
finally solved as yet, and a study of the smallest herring (especially in winter) in the North Sea 
countries adjacent to the spawning grounds of the autumn spawning fish will probably be 
necessary. It should therefore be continually borne in mind, in consideration of the following, 
that the age of autumn spawning fish may have been fixed some months too low. 
