FISHES FROM THE SEA-BOTTOM 453 



the cold bottom water with a temperature below o'' C. is reached, 

 where they are gradually replaced by the cold water fauna pre- 

 viously described. 



The same laws which regulate the distribution of different 

 species in the North Sea apply also in the main to other boreal 

 waters where these species live. Scientific fishing experiments, 

 and above all the mass of information gathered from the fishing 

 industry, have in recent years vastly contributed to our know- 

 ledge on these points. If on the basis of this knowledge we 

 want to compare the actual conditions in different boreal waters, 

 we must compare areas of corresponding depth. In this way 

 we may possibly form an idea as to the part played by the 

 extent of the sea-bottom, and by physical conditions, in regard 

 to the distribution of our northern species. Some examples 

 may illustrate this point. 



In the North Sea the shallow banks in depths less than 40 

 metres cover large areas, while off the coast of Norway there 

 are hardly any such banks, the coast sloping steeply into 

 greater depths. Shallow banks occur off the south and west 

 coast of Iceland, and far north and east in the Barents Sea, 

 as well as round Cape Kanin. Of the fish inhabiting the 

 shallow areas of the North Sea, only the plaice and the cod 

 occur in great quantities on these northern banks of Iceland and 

 Cape Kanin. Sole, brill, and other flat-fish might also find suit- 

 able conditions of depth here, but the temperature is too low. 

 Off the coast of Norway none of these fiat-fish, neither the 

 plaice nor the sole, occur abundantly. Thus we plainly see 

 the important parts played by depth as well as by temperature 

 in respect of the occurrence of various species. 



While the haddock in the North Sea constitutes nearly half 

 of the total weight of bottom-fish landed, the same species 

 constitutes only 3 per cent off the coast of Norway. This is 

 not because Norway is too far to the north, nor because the 

 temperature of the water is too low, since at Iceland and in the 

 Barents Sea, where conditions are similar, haddock amounts to 

 20 per cent of the catch, but because off the coast of Norway 

 there are no great areas of suitable depth and with the soft 

 bottom preferred by the haddock. On the contrary we here 

 meet with great areas of "cod-bottom" (sand, stones, shingle, 

 or rocks overgrown with kelp), and therefore the cod makes up 

 over 80 per cent of all the bottom-fish taken off northern 

 Norway. 



Thus the extent of the area, and the captures made therein. 



