_ 7 — JOH. HJORT.vNiiO. (I. JOH. PETERSEN 



for the first time, but to whose varied biological and physical conditions no detailed study 

 has as yet been devoted. Although this Atlantic deep-sea fauna has the greatest interest for 

 the study of the geographical distribution of animals, this region has of necessity been kept in 

 the background of the international marine investigations for the sake of the economically more 

 important regions. 



We may mention here also, that the Danish investigation-steamer "Thor", using large 

 pelagic nets, has made the first catches of bathy-pelagic eggs and young stages of deep-sea fishes. 

 The first steps have thereby been made towards a study of the natural history of these deep- 

 sea fishes. _^ 



Whilst the great depths of the Norwegian Sea and the Atlantic Ocean have relatively 

 still masses of water, the upper layers to a depth of 700— 800 m. show some change and 

 movement. The conditions of life here, must accordingly be much more varied and diverse, and 

 it is not merely the momentary relations which have to be considered but the whole change 

 throughout the year. 



3) The slope of the coastal banks towards the depths of the Norwegian 

 Sea must be regarded, both from the biological and physical standpoints, as a specially charac- 

 teristic region. This region embraces the depths from 200 to ca. 600 m., on the long stretch 

 from Spitzbergen and Iceland to the North Sea. It may be divided geographically as follows : 



the slope and banks of Spitzbergen, 



the Barents Sea with the bank of Bear Island, 



the Norwegian coastal banks from Barents Sea to Eomsdal bank, 



the Norwegian channel, which runs along the west coast of Norway from the Skagerak 

 to the entrance of the North Sea into the Norwegian Sea, 



the slope of the North Sea banks, called "Tampen" by the Norwegian and Swedisli 

 fishermen, 



the Fseroe-Island ridge, 



the east slope of the Iceland bank. 



A few years ago, only small portions of these large regions had been investigated with 

 fishing apparatus, and the first comprehensive survey of all these parts of the ocean, now ren- 

 dered possible by very extensive investigations and experiments, represents an important result. 



It is evident from what has been said above, that this region passes over into the cold 

 area of the Norwegian Sea at its lower boundary, and in such a maimer that the boundary 

 between the two regions is subject to certain fluctuations upwards and downwards into the 

 depths. As average depth, perhaps 500— 600 m. can be taken. 



In the layer between 200 and 600 m. there are great variations; we have found that 

 temperatures from -J- 1.5° to 8° can occur, and these differences will probably have great 

 influence on the vertical wanderings of the fishes along the slope, the more so, because the 

 variations of temperature are connected with similar variations in salinity and currents. 



The fish of this region belong everywhere to the same species, and this holds good over 

 the whole stretch from Spitzbergen and Iceland as far as the North Sea slope. The most 

 important forms economically are the following: ling (Molva molva), tusk (Brosmius brosme), 

 Norway haddock (Sebastes marinus), cod (Gadus callarias), halibut (Hippogiossus vulgaris). 



