APPENDIX a _ 32 — 



North Sea banks occupy the middle parts of the North Sea with depths of 40 — 70 m. In 

 the whole six months of winter, the trawl-steamers took quite as much on the average on the 

 coastal hanks as in the six months of summer. If we compare the average catch per day of 

 voyage, in December with that in July to August, on a line from Horns Eeef to the N. E. of 

 the Dogger Bank, we have the following figures: 



N E of 

 Dogger Bank 



December 226 



July— August 168 



That this increase in the catch on the coastal banks in winter, arises from a movement 

 of larger cod towards them, is seen also in a comparison between the relation of the small to 

 the large cod. In summer the proportion is 1:1, in winter 2.2 : 1. 



In the last portion of the winter six months, namely, in the spawning period of the cod, 

 the proportion on the special spawning places increases to 12 to 1. 



Henking has further shown, that whilst large cod seem to be tolerably evenly distri- 

 buted on the coastal banks from Skagen to the Dutch coast in the first months of winter, the 

 cod shoals collect in the later months of winter, in the spawning time, especially on the districts 



1. Terschelling — Borkum and 



2. Hanstholm — Hirshals. 



From the material of other countries also, much valuable information is forthcoming. We 

 hope that when this material has been worked out, it may also be possible to give a view over 

 all the important spawning places in the North Sea; a geographical description of these at 

 present would lead too far. How complicated the conditions in the North Sea are, appears from 

 this, that in addition to these great collections of spawning cod on the shallow coastal banks 

 in the spring (February — April), cod also spawn in midsummer (August— September) in the 

 deeper parts of the northern North Sea. Fulton has shown this first in 1903, when he dis- 

 covered cod with ripe sexual organs on the fish-market at Aberdeen in September. These 

 were all fished in depths of 160 — 180 m. on the eastern slope of the North Sea bank in the 

 Norwegian Channel. He succeeded also, in determining the occurrence of pelagic eggs at these 

 places. It appears however, that this is of a local nature and cannot in any way be com- 

 pared quantitatively with the spawning in spring. It is very interesting that this spawning 

 occurs in great depths just where the lowest temperature of the locality is found, as these 

 depths have the highest temperature in winter and the lowest during the summer months. Thus, 

 it appears that the difference in point of time between the spawning period in spring and that 

 in midsummer depends upon this, that the diiferent localities in which the fish spawn, have 

 opposite kinds of temperature-changes ; in both cases however, it seems that the cod of both 

 localities spawn in the coldest part of the year. (See what has been said above concerning 

 the temperature-conditions in the deeper parts of the North Sea). 



b) An important question theoretically as well as practically is: 



how large are the spawning cod? 



The shoals which collect in spring on the Norwegian coastal banks show sizes from 

 50 — 60 cm. up to 150 cm. The curve of measurements shows, as a rule, a maximum of about 



