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the investigations on the young littoral fishes in the Norwegian Skager Rak fjords. 

 In many years quantities of the small cod occurred in all the fjords investigated, in other 

 years however but few. 



What is of special interest for us in these fluctuations is the circumstance, that the 

 possibility of their influence on the results of the fisheries can be detected 

 in some cases. In the years 1904 and 1905, when the commercial class "small haddock" 

 consisted essentially of the year-group 1903, the occurrence of which was so scarce ac- 

 cording to the investigations of the research steamers, the catch of "small haddock" of 

 the Scottish and English steam trawlers sank to a minimum. In the course of the autumn 

 1905 and in the year 1906 the catches of this class again rose very distinctly, because 

 the hauls now consisted of the rich year-group spawned in the year 1904. If however 

 the fluctuations in the occurrence of the youngest year-groups are so great as we have 

 seen here, they also have quite a different character from that which they would show if 

 the cause lay in the influence of the fisheries. As the fisheries are at present practised, 

 their influence must be regarded as to some extent a constantly operating factor. And if 

 it were possible to demonstrate this influence on the amount of the stock or on the 

 numbers within the various year-groups, it would show itself either in a definite limitation 

 of the stock or in a slow decrease. Great fluctuations from one year to another must 

 on the other hand be due to great natural phenomena and the experience, that rich or 

 poor years may suddenly occur in so large a region as the greater part of the North 

 Sea, would indicate that, even if the fishery leads to an ever-growing decrease in the stock, 

 these great fluctuations from year to year in the youngest year-groups 

 of the haddock cannot be due to the fishery. The influence of the fishery 

 cannot be the cause of these fluctuations of the species. 



What now are the great natural phenomena which, we may believe, are responsible for 

 so great a fluctuation in the natural increase of young fish from one year to another? 

 Our investigations can give no direct answer to this; the fluctuations were indeed first 

 determined by means of the investigations. Various observations are to hand, however, 

 which seem to indicate the roads to an explanation of the changes. We have seen that 

 the oceanic currents carry the pelagic young fishes much further in one year than in an- 

 other. It must therefore be possible to investigate later, whether the poverty in a certain 

 year-group in any given water is due to the circumstance that the pelagic stages have 

 been carried far away from this region. Other possibilities may however also be thought 

 of. The statistics of the annual quantity of roe in the Norwegian cod fisheries show 

 great fluctuations. These fluctuations are not only absolute ; there are also great differ- 

 ences from one year to another in the relation between the number of fish caught and 

 the quantity of roe. In other words, the same number of spawning cod gives in the 

 different years quite different quantities of roe (and liver). Extreme years especially, parti- 

 cularly 1902—1904, offer striking examples of this. 



Later investigafions must turn their attention to these problems. We shall here only 



