— 31 



B. HELLAND-HANSRN 



in figs. 18—20 with the previously given scale-tests from the beginning of September, 

 we will find a fairly close coincidence, when the growth from April to September 

 is taken into account Fig. 18 and 19 should then denote the II group and fig. 20 

 the III group. 



The distribution in a catch from the Dogger Bank at the beginning of July 

 is represented in fig. 21, where the vertical lines once more give the average 

 lengths at the time as per the growth-curves in fig. 15. The same doubts again 

 arise here. Do the three groups correspond with the three year-classes or merely 

 with the two? 



It will appear from these instances that there must be considerable differences 

 in the growth, of haddocks in the North Sea. In the area round the Great Fisher 

 Bank the growth, if 

 we may judge from 

 the material in 'our 

 possession, was fairly 

 uniform; and we 

 could therefore con- 

 struct the growth- 

 curve on the basis 

 of the length-groups 

 in a manner that 

 seems to us un- 

 doubtedly correct 

 In areas G and H 

 also we found 

 well-defined length- 



30 35 *tO 



L^n&TH IM CE.rsTinE.TERS 



Fig. 21. Length-measurements in a catch of haddock from the Dogger Bank 



(July). 



groupings, which allowed us to construct growth-curves showing a slower 

 growth than at D. But these curves are not to be depended upon and they 

 might with equal justification have been drawn in such a manner as to show a 

 growth exceeding the growth at D, if groups III and IV had been set back a 

 year and denoted as groups II — III. By this means it is only group I we can 

 be certain of, while it remains an open question whether we have two sets of 

 the succeeding groups: one with a slow and one with a rapid growth. This is 

 the critical point in these analyses. The curves can be interpreted in such 

 a way that the same year-class falls into two separate groups with 

 a different rate of growth. So that if we cannot ascertain the age 

 in some other manner, we cannot be sure very often whether the 

 length-groupings denote a similar number of year-classes, or 

 whether two of the groups belong to the same year-class. 



To further illustrate what has been said we may refer to Damas, who has 

 found that haddocks in the Skager Rak have a growth very different from the 

 growth along various portions of the Norse coast (e. g. Söndmöre). He has found 

 moreover that the o-group of cod in the Skager Rak often differentiates into two 

 separate size-groups and is not confined to one. 



I have thought it necessary to dwell on these points, at the risk of becoming 





