APPENDIX G 



10 — 



into a southern shallower and a 

 northern deeper region. The 

 transition between these two 

 regions is very sharp at some 

 places. On the north edge of 

 the Dogger Bank, for example, 

 the bottom falls within a distance 

 of a few miles from 60 to 90 m . 

 Further to the east the boundary 

 is less sharp, because the 60-80 m. 

 deep Great Fisher Bank inter- 

 venes between the two regions. 



We have stated above, that 

 the fishes of the two deep regions 

 are very different; not less diffe- 

 rent are the hydrographical con- 

 ditions, if we examine them at 

 different periods of the year. If 

 we compare the two longitudinal 

 hydrographical sections of the 

 North Sea, from Heligoland to 

 the slope of the Norwegian Sea 

 (Fig. 2 and 3), we see that 

 the entire mass of water has 

 almost everywhere a temperature 

 of 6°— 7" in May. In mid- 

 summer (August) the conditions 

 have changed. In the deeper 

 layers (below 60 m.), the same 

 conditions of temperature have 

 persisted, but on the shallower 

 banks we now find temperatures 

 up to 10° and 14°. We thus 

 have the great main difference 

 between the two regions, that 

 the yearly temperature-fluctua- 

 tion amounts at most to one 

 degree in the deep water, whilst 

 variations of 6 — ^8° may be found 

 in less depths. 



The differences in the 

 catches from the different parts of 

 the North Sea are in agreement 



I 



4 



