— 160 — 
7 to 10 years. If the renewal of the stock is effected by a single year class, so numerous 
as to be of decisive importance in the average size of the stock for years in succession, 
then we should have an increase in the average weight for at least four successive years, or, in 
the case of two rich year classes appearing one after the other, for at least five. The 
curve in Fig. 96 agrees with this, as regards the rises from 1883—1889, 1895—1899 and 
1904—1909. The last named period is naturally of greatest interest, since it is from 
these years that we possess the most extensive material. We can thus understand, that 
the imerease must cease about 1908 or 1909, and a decrease in size take place, as the 
young fish of the 1903 and 1904 year classes begin to appear among the skrei shoals. 
Oldest skrei. 
Among the skrei are always found some large fish beyond the age and size at which 
they appear in any considerable numbers in the stock. In the samples from 1913, the 
size groups over 89 cm. showed the following percentages. 
Percentage of largest skrei 1913. 
Ce 90—94 95—99 100—104 105—109 110—114 115—119 Over 120 
ee 4.2 1.9 Lt) 0.6 0.1 0.03 0.03 
Average longevity of the skrei determined by the fishery? 
Why then, do not more skrei reach such sizes, when some of them can attain those 
here shown? Before answering this question, it is necessary to ascertain whether the 
size of these fish is due to rapid growth or to extreme age. Investigation shows the last 
mainly to be the case. Skrei of 15, 18 and even 20 years old are known, though rarely 
found; moreover, it is difficult to accurately determine the age of such fish, the annual 
rings on the scales of very old specimens being very narrow and indistinct. 
Since however, it is beyond doubt that the skrei can attain an age several years 
beyond that of 10—11 years, at which they are numerous, the question arises, whether 
the natural longevity of the species is affected to any great extent by the fishery. This 
important point can only be decided after material has been collected for a long period 
of years; it 1s however, well worth while to bear in mind, in further consideration of the 
question, the results of our marking experiments in Lofoten in 1913, viz, that every fourth 
or fifth fish was captured in the course of the Lofoten fishery. Moreover, it should be 
remembered that it is the same stock which is fished in the Finmark waters, on the Murman 
coast, and by the trawlers in the Barents Sea. It is impossible to say, as yet, how far 
the results obtained at Lofoten in 1913 may be considered as representative of the skrei 
fishing all along the coast; possibly the fishery is more intense here than on many other 
skrei grounds within the range. Only by continued marking experiments can this 
be satisfactorily determined. It should be borne in mind, however, that the whole spaw- 
ning area of the cod is now, after the investigations of recent years, known, mapped, and, 
for by far the greater part, exploited by the fishery. Thus even though we may not 
at present be able to accurately determine the exact percentage of the stock taken by 
the fishery, we can at least assert that it is very considerable. So much so, indeed, that 
the remarkable diminution in numbers of the skrei as they increase in age may possibly 
be due to the intensity of the fishery, so that for instance a rich new stock of 7 year old 
fish would, after four or five years’ intensive fishing, be considerably reduced in numbers. 
