SOME RESULTS OF THE INTERNATIONAL FISHERY INVESTIGATIONS. 485 



Again, in the Barentz Sea the fisheries depend on the Atlantic flood- 

 ing. This was shown by the Paissian Fishery Commission in 1902. 

 Two kinds of water enter this area. In the winter water from the 

 Atlantic stream enters it, rounding North Cape. With the entrance 

 of this occurs a " vast immigration of food fishes," which have the 

 character of south fishes, and fishing is then productive. In the spring 

 this Atlantic stream subsides and Arctic water takes its place. The 

 fisheries then cease, but still at this time the Atlantic stream is flowing 

 past North Cape, and cod are still caught in quantity. 



The bottom of the North Sea is a submarine plateau, which towards 

 the north slopes down to the depths of the Norwegian sea. On this 

 northern slope Atlantic water may be found at all times of the year, 

 but at varying depths, according as the incoming stream waxes and 

 wanes. On the bottom is cold Arctic water, and separating this from 

 the overlying Atlantic water is a mixed layer, which contains relatively 

 large quantities of fish, such as the ling and halibut. The Swedish 

 fishermen set long lines on the portion of this slope towards Shetland. 

 In the summer the mixed layer of water is nearer to the surface than 

 in the winter, when the Atlantic stream is gathering volume. Just 

 as this mixed-water stratum is nearer or further from the surface, so 

 the fishermen move about so as to find it. In summer, when it is near 

 the surface, they set their lines near Shetland in about 75-100 fathoms. 

 In autumn, when the growing Atlantic stream forces down the signifi- 

 cant water layer further from the surface, they are obliged to go further 

 north, that is, down the North Sea slope, in order to find it. The lines 

 are then set at depths of 150-200 fathoms. 



The connexion of the herring migrations with the hydrographic 

 changes is now quite certain, though much research is still necessary. 

 There is no doubt that the great summer herring fishery of the east 

 coasts of Britain hangs, in some way, on the periodic flooding of the 

 North Sea with Atlantic waters. The case of the winter herring fishery 

 oft' the coasts of Sweden is, however, a clearer case of the connexion 

 of hydrographic and fishery phenomena. The winter herring is a north 

 fish, and does not inhabit Atlantic water, but rather the mixed " I5ank 

 water " of lower salinity. In the great herring years it has been found 

 that the Atlantic water lay at considerable depths beneath the surface, 

 and that on this warm dense water was a layer of Bank water which 

 covered the coastal shoals and entered the fjords. In this layer the 

 herring was always found. In December, 1896, there was an unusual 

 flooding of the Skagerak with Atlantic water. The level of this had 

 reached so high that only a thin layer of Bank water remained. In 

 this year the winter herring fishery was a failure. 



Much has been done by the International researches to establish 



NEW SEKIES. vol,. VII. NO. 5. 2 K 



