27 



B. HELLAND-HANSEN 



In this same area we find a series of very clear curves with very well-defined 

 groupings. The best of them have been utilised to ascertain the average length 

 of the various year-classes at different seasons; and the results thus obtained 

 have been shown by means of the unbroken line in fig. 15. In the figure a point 

 shows the mean length of a well-defined length-group and a cross shows the result 

 of the scale-investigations previously referred to. The curve gives the approximate 

 size of the haddocks at different ages, and its course corresponds with the average 

 growth in the area round the Great Fisher Bank. It will be seen that there 

 is good accord between Damas' age-assessment obtained from the scales, and 

 the grouping based on a graphical representation of the lengths, 

 cm 



IGr EGr DIGr IVGr 



Fig. 15. Curves of growth for haddock according to the age-groups. Average sizes in the different 

 years and months: D from the Great Fisher Bank area. G from the area off the East Coast of England. 



It will at once become apparent that the growth is rhythmical, and 

 that it attains its greatest vigour during the summer months, from May to 

 October, when it is very rapid : while from October to May it is very much slower, 

 and during some of the winter months it appears to be almost non-existent. From 

 the curve we get the following figures representing the average length of the 

 various year-classes at different seasons: — 



Length in centimeters at the beginning of 



Group 

 I ... 



II ... . 



III ... 



IV ... 



March ■ 



31 



35 



June 

 19 



32 



35'A 



October 



22V2 



29'A 



34'A 

 38 



Thus we notice that while the growth of these groups is not more than 

 I — a'/a cm. during the eight months from the beginning of October to the be- 

 I We have taken March as the commencement of the year for Group I, Group II, &c. 



4* 



