— 37 — KNUT DAHL 



Oll all occasions however we have found vigorous movements in those water-layers, 

 where great quanlilios of fry were found to live, and great alterations and contrasts 

 in the occurrence of pelagic eggs and fry were found to coincide with the changes 

 in these water-layers. 



In waters where all stages of tiiese organisms occur it is certainly difficult always 

 to obtain clear and instructive examples of drift by merely studying the organisms, but 

 when the hydrographical changes are an established fact, I consider it justifiable to 

 form conclusion by analogy from the numerous clear proofs, which we now possess of 

 the currents distributing these organisms over great distances ^ 



This experience that pelagic eggs and fry are so dependent on currents, leads to 

 the view, that these organisms can not as a general rule be considered as local, but 

 they evidently form a moving and shifting part of a stock of fry belonging to far wider 

 waters than these small fjords. 



This point is important when judging the value to be attributed to the numbers 

 of larvae turned out by hatcheries. The fry liberated accordingly form a moving part 

 of the moving stock of fry belonging to an area far greater than the quantity of fry 

 liberated may be supposed to or even was intended to affect. 



Our investigations as to the occurrence of littoral cod fry have also shown, that 

 on great stretches of coast seasonal and annual variations occur independent of hatching 

 operations. These variations are so great, that it becomes inconceivable that a liberation 

 of so small quantities of larvae, as the hatcheries turn out, could alter or influence these 

 conditions. See e.g. the diagrams fig. 12 and 13 and compare the different years ^. 



The results also plainly indicate, that the formation of the fish stock (the fish 

 supply) in these fjords is not really much dependent on the spawning and hatching 

 taking place in the fjord itself, it is more dependent on the quantities of fry brought 

 by currents (the circulation of fry). Even in these small South Norwegian fjords it has 

 been possible to observe this fact, although there is no marked difference in the intensity 

 of spawning between the fjords and the coast. This fact may be still clearer illustrated 

 by examples taken from Western Norway, where the contrast between fjords and coast 

 waters is very great as regards the intensity of spawning. I refer to Dr. Damas' 

 description of the conditions in S0ndm0re 1906. He clearly shows that, compared with 

 the coast waters outside, the deep fjords were nearly devoid of spawning cod and also 

 of eggs. In spite of this, immense quantities of pelagic fry were gradually carried 

 through the Skjsergaard, and the fjords rapidly filled with enormous numbers of pelagic fry. 



Considering these conditions, we do not get the impression, that the relative value 

 of the numbers of cod larvae liberated from our Norwegian hatchery (the greatest 

 quantities operated anywhere in the world) can be of much importance. 



' As an example of such drift we may mention the whiting. As a matter of fact very few whiting 

 spawn along the Skagerrack; coast and in the fjords. Nevertheless enormous quantities of fry of the 

 whiting occur in these southern fjords, even in the Kristiania Fjord. The majority of these fry are 

 doubtless brought by the current ft-om open waters, especially the North Sea. 



^ In this connection it is also interesting to note the great variations in the annual occurrence of 

 the different year-classes from the North Sea which have been decribed for haddock as well as for 

 whiting (see the papers published in this report by Dr. Damas and Mr. Helland-Hansen). These variations 

 indicate that the conditions affecting the supply of fry in different years are determined by mighty „-'-'~ — -^ 



forces, which man cannot counteract. /\'v\6'C/4 



/Cv-^' <.' 



