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thickening of the line, indicate the ister stage; i. e. a high percentage of ister and fatty 
matter. The letter S denotes the time of spawning. 
A comparison of the three curves immediately reveals the fact that the rate of 
growth differs greatly in the three species. During the first period of life, the pilchard 
exhibits the most rapid growth, being, however, soon overtaken by the herring, while 
the sprat is from first to last some distance behind. The first spawning takes place, 
in the case of the pilchard and sprat, at 3 years of age; as regards the herring, I have 
in the figure noted this as at 4 years of age. This is true of the herring found on the 
west coast of Norway; as we have seen, however, the North Sea herring frequently spawn 
when only 3 years old, while on the north coast of Norway, 5 or 6 years is the usual age. 
No ister stage is apparent in any of the three species during their first year of life. 
The pilchard and sprat reach their first ister stage when 11% years old; the herring (on 
the west coast of Norway) at an age of 2% years. 
Both pilchard and sprat attain maturity when three years of age, and have there- 
fore an ister stage both in the second and third year of life. As regards the herring, the 
North Sea fish have probably only one, the West Coast herring two, and those of the North 
Coast as many as four ister stages before reaching maturity. A notable phenomenon in the 
fishing industry, viz, the fact that the fat herring (immature fish in the ister stage) are nowhere 
of so great importance in the total herring stock as on the North Coast of Norway, is thus 
explamed. In the North Sea, with its enormous numbers of young herring, the fat 
herring are for the most part confined to a single year class, whereas those of the 
North Coast may include fish of from 2%, to 5% years old. In the case of grown, mature 
herring, the fat-containing organs have an annual period of developement. The spring 
spawning fish have these organs most highly developed in autumn (August and Sep- 
tember), the summer spawning fish in the spring. Thus spring spawning herring are in 
autumn fat and in good condition, while the summer spawning fish are spent and poor, 
the reverse being the case in the spring. 
It will be easily understood, from the foregoing, that herring, pilchard and sprat 
of the same size (1. e. length) must differ widely as regards quality. Of three fish, a her- 
ring, a pilchard, and a sprat, all measuring between 9 and 13 cm., and all taken in sum- 
mer, the sprat will be in best condition. Both herring and pilchard will then be thin 
and poor, the sprat on the other hand, bemg fat and full of ister. 
Tt will be otherwise, however, when a length of 15—16cm. has been reached. A 
sprat of this size will be mature and of little value, while the pilchard is at its best, the 
herrmg not yet having arrived at the “fat” stage. This is not reached, in the case of 
the herring, until a length of some 20 cm. is attamed. The sizes between 20 and 27 cm. 
include, in Norwegian waters, the finest immature fat herring, which are in every respect 
the equal of any other species of herring as regards quality. Pilchard of this size are 
mature, and always meagre, even in summer. 
In winter, all three species are, at all stages, considerably poorer than in summer. 
The quality of all three species must therefore be regarded as a factor varying with age and 
season. 
A point of paramount importance is naturally the question as to how the fish attain 
renewed developement of their fat-contaming organs; the nourishment required for this 
purpose, and the migrations undertaken by the fish in search of the same. For many 
