— 49 



B. HELLAND-HANSEN 



be put at about 60 cm. However this dividing line between them is by no meanns 

 stable, and it should perhaps be fixed a little higher (say at 65 cm.). These two 

 market-groups correspond to all intents and purposes with the groups recognised 

 on the Norse coast, the Lesser Cod (Fjord Cod) and the Skrei: and in other lands 

 a similar grouping is also familiar. 



The boundary line between the two market-groups is denoted in Fig. 31 by 

 a dotted line. Working out the average-number for each of the groups, 

 we get : — 



Codling 2'4 fish per trawl-hour 

 Cod 0-8 — — 



Total 3-3 fish per trawl-hour 



To which we must add i-6, the average-number for unmarketable small 

 codling. Thus of the whole average-number of marketable, codling 

 constitutes about three-quarters and cod about one quarter: and in 

 the total catch there are about two-sixths unmarketabe, three-sixths codling and 

 one-sixth cod. The conditions of weight however are absolutely different (page 56). 



The boundary between mature and immature cod varies greatly, though it 

 may roughly be fixed at 60 cm. (Fulton, Damas). We get therefore the same 

 relation between mature and immature fish that we find existing between the 

 market-groups: codling and unmarketable small codling are as a rule immature, 

 while cod are capable of spawning. Accordingly in the whole quantity 

 trawled it is generally speaking only one sixth of the number 

 which are mature. Thus a comparison of the two species forces us to the 

 conclusion that in the North Sea, where examined, there are fewer mature cod in 

 proportion to the whole araoimt than there are mature haddocks in proportion to 

 the total quantity of haddocks trawled. 



In Fig. 33 we have shown the average catches for the whole North Sea, where 



examined, during each of the years 1903 — 1906. From this figure we can see the 



proportion between the different groups of cod. The following are the results that 



we have worked out. 



Average-number per trawl-hour 



Taking the percentages of all the average catches we obtain the following 

 values: — 



Percentages of the Distribution of Numbers 



100 . 100 100 100 



