— 112 — 



the group at 2V2 years was between 31—52 cm., on an average 40 cm. long 



— - 3V2 — — 33—60 — - 49 _ _ 



— - 4V2 — - 44—70 — — 60 — — 



— - 57^ — — 58-82 - — 69 - — 

 - 6V2 — — 72, 84 and 89 cm. 



Some few specimens of the 7th and 8th year-groups also occurred. Damas is of 

 opinion that in its first year the cod grows in general 12—15 cm., in the second year 

 also 12 — 15 cm., and later in the 3rd, 4th and 5th years annually 8— lo cm. Maturity 

 begins at the earliest in the 4th year. 



If we now calculate with the aid of these results the percentages by number and 

 weight for the different age-groups, we obtain from the curve on fig. 41 the following 

 numbers : 



Number % Weight in % 



up to 2 years (30 cm.) ... 36 3 



2—5 — (60 — ) ... 47 27 



over 5 — (over 60) . . 17 70 



The great difference between number and weight in the youngest year-groups will 

 be noticed here, also the important fact that not less than 70% of the total weight con- 

 sists of the large, mature, over 5 years old fish, whereas their number only constitutes 

 19% of the number of the total catch. 



In connection with the description of the material from the research-steamers we 

 may now mention the results obtained by D'Arcy Thompson from examination of the 

 returns of Aberdeen steam trawlers for the period igoi — 1906. The four figures 43—46 

 reproduce the numbers given by D'Arcy Thompson for the average of "cod" and 

 "codling", converted to kg. per hour of fishing. D'Arcy Thompson's result for all the 

 North Sea areas visited by the Aberdeen steam trawlers amounts to 



"cod" ... 12 kg. per hour of fishing 

 "codling" . 7 — - — and 



total cod 19 kg. 



Since the catches of the research steamers, as shown above, only gave on an average 

 6 kg., the catches of the Aberdeen steam trawlers are on an average more than three 

 times as great. This difference, though very great, is however not so considerable as 

 was the case with the haddock. Of haddock the research steamers had only '/^th of the 

 average quantity taken by the Aberdeen steam trawlers. We shall endeavour to explain 

 his phenomenon later. 



