102 THE SEA FISHERIES 



It is further claimed that the scale gives a graphic representation 



of the growth, since the breadth of the summer zone affords an 



indication of whether the year's growth has been good or not. As 



there are marked differences in the scales it becomes possible to 



distinguish separate races, or at any rate the separate shoals, and 



so trace the migrations. The Norwegian herring fisheries fall into 



four main groups ; for spring herring, which are adult spawning 



herring, caught from January to April off the west coast (between 



62 and 63 N. Lat.) ; for large herring which are taken off the Romsdal 



coast in late autumn and winter ; for fat herring which are unripe 



fish taken in autumn in Northern Norway, and finally small herrmg 



which are taken along the whole coast. The shoals spawn only on 



the west coast, the young herring fry are carried northward along 



the coast by the prevailing currents. The young unripe herring of 



Northern Norway are an early stage of the spring herring, the fat 



herring are a second and the large herring a third stage in the 



development of the same fish, so that all these different fishermen's 



terms for the herring are applied to different stages of one and the 



same race. 



If this view be correct, it is possible, by examining the scales from 

 a large number of individuals of a season's catch in any particular 

 locality, to determine from what year's shoal of the spring herring 

 they originated. In 1904 herring were exceptionally abundant, 

 the " brood " of this year being very numerous. In 1909 the fat 

 herring season was twice as productive as any other year between 

 1901 and 1910 ; investigation of the scales showed that about 

 50 per cent of the August-caught fat herring were born in 1904. 

 Similarly in 1910 and 1911 about three-quarters of the spring herring 

 were traceable to the year 1904. The significance of these facts 

 lies in the possibility opened out of tracing the movements of 

 herring shoals. 



Hjort and Lea go even further than this. They claim that, for 

 some reason or other, the 1904 herring grew badly in their third year 

 of life, and consequently the transparent space between the second 

 and third winter rings is but feebly developed. 



Herring scales, showing (left) normal growth, and (right) abnormal growth 

 of Norwegian herring of 1904 in their third year. 



