ae 
summer months, but a comparison of the one year with the other reveals a very great 
difference. 
We will then compare the composition in point of age for the two summer months 
of 1911 and 1912. (See Fig. 45). In this respect also the samples for each year agree 
very well together, great difference being, however, apparent between those of one year 
and those of the other. 
In 1911, the year classes 1905, 1906 and 1907 were most strongly represented. In 
1912 however, there were comparatively far fewer of the year classes 1905 and 1906, 
whereas the year classes 1907, 1908 and 1909 were very predominant. Of these again, 
1907 and 1909 appear to have played the most important part, 1908 being both im 1911 
and 1912 less numerously represented. 
As there thus appears to be a similarity between the summer samples of the same 
year, we will proceed to compare the composition in point of age for the month of July 
in the years 1910, 1911 and 1912, considering, not the age classes, but the age of the 
fish. (See Fig. 46). 
In these three years, 1910—1912, we find a great decrease in the average age of 
the herring, the older individuals being comparatively far less numerous than the younger, 
the four year old fish in 1911, and the three and five year olds in 1912. 
Theoretically, this may be explained in two ways, either as due to the death or 
emigration of the older fish, or to the immigration of a large number of new, younger 
individuals. We have seen, from the year 1910, that the composition in point of age 
of the Shetland herrmg may be marked by large quantities of older fish, 5—7 years; 
it would therefore seem reasonable to suppose that in 1911 and 1912 large numbers of 
younger fish occurred, in particular of the 1907, 1908 and 1909 year classes. 
From the Lowestoft district, we have analyses of three samples from the years 1910 
—1912, the 1910 sample taken in October, those for 1911 and 1912 in November. The 
following tables show the degree of maturity of the fish in these samples, and the degree 
of fatness; it will be noticed that in all three cases, the samples consisted almost exclu- 
sively of grown fish, with genital organs highly developed, and little or no fat. 
Lowestoft herring: percentage of fish at different stages of maturity. 
er i it ee 
17. X. 1910 Be A: 2 3.9 96.1 eh ue 
13, XI, Will 02 1.0 0.2 35.6 59.4 He en 3.6 
14. XT. 1912 2.0 1.4 Bol 29.8 52.2 0.4 8.2 2.3 
Lowestoft herring: percentage of fish at different degrees of fatness. 
Quantity of fat. Very fat. Moderately fat Shghtly fat No fat 
17. X. 1910 te a 1.2 98.8 
113}, XCM, USL 1,2 3.2 7.0 88.8 
14. XI. 1912 1.5 4.9 6.5 87.1 
We have thus to deal with fish approaching maturity, and about to spawn in the 
near future. The composition with regard to age will be seen from Fig. 47. In 1910, 
