59 



B. HELLAND-HANSEN 



confined to catches by trawlers, and consequently relate to little more than some 

 four or five feet from the bottom in those localities where it was possible to 

 trawl. The higher layers have had to remain neglected in spite of the probability 

 that they are from time to time frequented by quantities of cod and haddock. It 

 is very probable that are frequent movements of these fishes in a vertical 

 direction, as for instance when the cod pursue the herring shoals. (Cf. Henking 

 in Rapp. et procès verbaux, vol. III). We have also had to leave out of account 

 all localities large and small where the bottom was rocky, though we may be 

 sure that there is a constant interchange of population between these localities 

 and the others. 



A statistical material can only be said to be genuinely representative when 

 the investigations express correctly the real conditions not merely throughout 

 extensive areas but also during considerably longer periods of time than those of 

 observation. 



The material of the Research Steamers is very far from being sufficiently 

 representative to give reliable figures showing the true totals of haddock and cod 

 in those localities of the North Sea where researches took place. To obtain a 

 representative material able to satisfactorily accomplish this we should need a vast 

 number of "stations"; so many in fact that it would be absurd to even dream of 

 obtaining it by means of the Research Steamers. The large fishing fleet however 

 which is constantly at work in the North Sea would undoubtedly be able to 

 contribute valuable help towards settling the question of the numbers of any one 

 species, — the haddock for instance. But in that case we should have to depend 

 not merely upon the trawlers, who mainly confine their quest to haddock; the 

 others who fish for different species, and who do not look upon the capture of 

 the haddock as their chief means of subsistence, would have to contribute in equal 

 degree towards furnishing information regarding the occurrence of haddock in 

 places where it is found in relatively poor numbers. It may be that one might 

 thus attain to fairly reliable values, though even then it seems extremely doubtful. 



But even if it might be impossible to ascertain with exactitude the true 

 numerical values of the different species, we could at any rate find an expression 

 for the numerical conditions which would indicate the general composition and 

 variations of the aggregate and which would settle definitely the question of 

 over-fishing. The material which the German and English Research Sfeamers 

 obtained in the case of haddock and cod is fairly homogeneous. As has been 

 previously mentioned, the beam trawl was to some extent used during the 

 "Huxley's" researches, while at all other times during both the English and 

 German investigations the otter trawl only was employed. This trawl has always 

 had the same dimensions, viz: 90 feet, and the duration of the different hauls has 

 been systematically entered in the tables. According to Fulton the capabilities 

 of the beam-trawl are inferior to those of the otter-trawl. In my preceding 

 remarks this has not been taken into account; but in future more exact in- 

 vestigations similar discrepancies would have to be eliminated from the material. 



In the course of our present studies regarding the numbers of haddock, values 

 appeared which showed great variations in the total numbers, not merely as 



