SOME RESULTS OF THE INTERNATIONAL FISHERY INVESTIGATIONS. 439 



forms the " waterslied " between two deep-water basins differing con- 

 spicuously from each other. On the top of the ridge the water may 

 have a bottom temperature of 2° C. On the southern shapes it is 

 washed by water with a relatively high temperature, 6° C. to 10° C, and 

 even down to a depth of 700 metres the temperature may be as high 

 as 6°. On the other hand, the temperature falls rapidly as we 

 descend the northern slopes towards the Norwegian sea, until we find 

 in the deeps of the latter a mass of sea water the temperature of which 

 is, with one exception, lower than anywhere else in the oceans of the 

 earth. In the deepest part of the Norwegian sea the temperature of 

 the water is l°-3 C. below the freezing point of fresh water. 



Over practically the whole of the liritish and North Sea plateau, on 

 the Norwegian coastal banks, the Faeroese and Icelandic banks, the 

 Baltic and the coastal banks in the Barentz Sea, commercial fishing is 

 carried on. Though the tendency is always for the extension of trawl 

 and line fishing into deeper water, yet tiie greater part of the Norwegian 

 sea is not fished over. Still this extensive area is most interesting from 

 the point of view of the investigator, and many fishing experiments 

 have been made therein. 



This then is the nature of the area over whicii the International 

 Fishery Investigations are being carried on. The accompanying Chart 

 (Fig. 1) shows how it has been divided up so as to apportion the 

 work between the various countries participating in the scheme of 

 research. 



Hydrographic investigations have for their aim the determination of 

 the physical characters of the sea water in the different regions of the 

 extensive area mentioned above. The physical characters to which 

 I allude are : (1) the temperature ; (2) the salinity, that is, the weight 

 of solid saline matter contained in 1000 grammes of sea water ; and 

 (3) the nature and abundance of the gases (oxygen, nitrogen, carbonic 

 acid, sulphuretted hydrogen, etc.) dissolved in it. Other characters are 

 from time to time of importance, but the hydrographic condition of 

 any portion of sea water is usually defined by its temperature and 

 salinity, and the determination of these are the essentials of marine 

 hydrographic research. Not only do these characters vary from time 

 to time in the same region — both temperature and salinity are, for 

 instance, different in the water covering the Dogger ISank in winter 

 and summer — but they may vary with the locality. The water on the 

 Dogger may be physically very different from that present in the 

 Faeroe-Shetland channel or in tlie Cattegat. The determination, then, 

 of both temperature and salinity, simultaneously over the whole area, 

 at periodical times, is the obligatory hydrographic work at present 

 carried on by the International Fishery organization. 



