the northernmost range of coast, that of Finmarken, where the fish taken are for the 
most part small (i. e. belonging to the younger year classes), the fluctuations of the fishery 
are particularly abrupt. Thus the statistics report a yield of 23.6 millions in 1880, while 
only three years later, we find the very poor total of 3.5 millions. During the last few 
years, from 1911—1913, the yield of the cod fishery has been unusually good. 
Norwegian herring fishery. 
The herring fishery exhibits perhaps even greater variation, both as regards the 
mature, spawning fish, the “spring herring”, and the younger, immature “fat herring”. 
The spring herring fishery, which is carried on from the Skagerak in the south to Cape 
Stat in the north, has, since the introduction of the statistics, exhibited enormous fluctu- 
ations. In 1866, the yield amounted to over a million hectolitres, sinking, however, 
so rapidly during the succeeding years, that the total catch in 1874 was 24,000 hl., 
in 1875 only 208 hl. In 1883, the yield was still as low as 100,000 hl., rising however, 
in 1884 to 262,000. The years from 1891—93 show an annual yield of over 700,000 hl., 
from 1894—96 less than 400,000. In 1909 a rapid increase set in, and by 1913 the sta- 
tistics note a yield of no less than 114 million hl., the highest figure ever recorded for this 
branch of the fishery. 
The yield of the fat herring fishery (the younger, immature fish,) exhibits similar 
fluctuations, amounting in some years (1892, 1896, 1909) to over a million hectolitres, 
in others (1904 and 1905) to less than 100,000 hl. By 1907, however, it had risen again 
to over half a million hectolitres, and in 1909 exceeded a million. 
Popular attempts to explain the fluctuations. 
These great fluctuations, irregular as they must at first sight appear, have naturally 
for many years past occupied the minds of the population along the coast, and innumer- 
able hypotheses and suggestions have been put forward by way of explanation. Most 
of these theories are, however, valueless save as indications of the state of general know- 
ledge concerning marine biology at the periods in which they arise. 
The earliest rational attempts at an explanation of the causes which give rise to 
these fluctuations in the fisheries naturally took as their starting point the fact that 
the fish were not at all times to be found in the coastal waters. On the Norwegian coast, 
the shoals of spawning cod and herring make their appearance with remarkable regu- 
larity in the first month of the year, often at a certain date, and remain there for only 
two months, or three at the outside. All attempts to capture grown herring or cod on 
the same grounds at other times have given entirely negative results. In the western 
part of the North Sea, (east of the Shetlands) the herring shoals make their appearance 
in June; from this time to the end of the year the locality of the fishing grounds 
gradually shifts southward across to the shallower waters. f 
The theory of migration as a cause of the fluctuations. 
These facts naturally gave rise to the theory of migrations, which were supposed 
to be of great extent, nothing being known as to where the fish were to be found during 
