— 165 — JOHS. S{!HM1J)T 



This brief suiiiniiiry shows at once all tiiat is characteristic in the distribution ol' our 

 gadoids, this true Atlantic group of fishes, and conlirms the importance of the tempera- 

 tures which has been maintained in this work. We see from this that of the shallow- 

 water species (groups a and b) only the species of the Atlantic "southern" group occurs in 

 the Mediterranean and only those of the "northern" group in the Norwegian Sea. As 

 regards the deep-water species (group c) only our "southern" group occurs in the Me- 

 diterranean and not the "northern", whilst neither of them occurs in the Norwegian Sea. 



The fact that only the species of the "southern" group occur in the Mediterranean is 

 naturally connected with the high temperatures there; this seems quite evident and re- 

 quires no further explanation. On the other hand, there is perhaps reason to enter a 

 little further into the comparison between the Atlantic and the Norwegian Sea, more 

 especially as the conditions with regard to the spawning of the gadoids are better known 

 in these waters than in the Mediterranean i. 



As the natural boundary between these two seas we take the Submarine Ridge be- 

 tween Iceland— Faeroes— British Isles 2. To the west of this and the British Isles we have 

 the Atlantic, to the east the Norwegian and North Seas. The condition in the Norwegian 

 Sea as we have seen is, that the whole of its deep basin is filled with ice-cold water of 

 low salinity, as the Submarine Kidge mentioned prevents the warmer and salter Atlantic 

 water at great depths from entering the Norwegian Sea. In consequence of this, 

 none of our Atlantic deep-water species can pass this boundary and spawn 

 in the Norwegian Sea^. 



In the upper layers however there is free passage for the warm and salt Atlantic 

 water, which we can follow on its way into the Norwegian and North Seas off the Nor- 

 wegian coast, as we can see how the temperatures and salinities gradually become reduced. 

 In this way our Atlantic shallow-water species in contrast to the deep- 

 water species are able to find suitable conditions for spawning and living 

 in the Norwegian and North Seas. 



Spawning of our Atlantic shallow-water gadoids in the Norwegian 



and North Sea 



Morth Sea Norwegian Sea 

 "northern" group -|- + 



"southern" group + -r- 



It thus appears that the lower the temperature a species can be contented with 

 during spawning, the further north in the Norwegian Sea may its spawning take place, 



larias, virens, œglefinus, Brosmius) occur on the Atlantic coast of North America, none of the "south- 

 ern" group. 



' What is stated here regarding the spawning of the gadoids in the Norwegian Sea is almost en- 

 tirely from friendly information given me by Dr. Johan Hjort and Dr. D. Damas based on the Nor- 

 wegian investigations. 



^ In his introductory summary of the various reports the Convener of Committee A, Dr. Johan 

 Hjort, includes Iceland and the Faroes to the Norwegian Sea, but his divisions otherwise are the same 

 as those given here. 



ä Compare note p. 164 excepting the deep Norwegian fjords with almost Atlantic conditions in deep 

 water. According to friendly information from Dr. Hjort it is interesting to note that the true Atlantic 

 deep-water species, the blue Hug {M. byrkelange), spawns in a few of these fjords, though not to an ex- 

 tent which may he compared with the conditions in the Atlantic. 



