— 53 



B. HEI.LAND-HANSEN 



precediii<> curves and the variation is practically between 30 and 40 cm. The 

 average length of the groups is greater in 1904 (about 35 cm.) than in 1905 

 (about 33 cm.). It is possible that the difference is due to a dissimilar rate of 

 growth in the different years: but the groups are not sufficiently distinct for us 

 to declare with any degree of certainty whether we are here concerned with one 

 or with several year-classes: though the bulk may assuredly be assigned to the 

 Il-group. 



Thus even when the groupings are clear the graphical form of the groups is 

 not such that we can attach much significance to any determination of the average 

 length. Fulton and Heincke have thrown considerable light on the limits of the 

 length-groups; and the material obtained by the Research Steamers cannot give 

 either fuller or better information. As the age has not been determined in any 

 other way it is impossible to tell whether the limits of the few length-groups, 

 which upon the whole are clearly defined, correspond with the limits of the year- 



190^. JULY arlaG 



220 INDIV 



. /•X ^ 



190^ dULY ARtA6 



200 INDIV 



20 25 " ZO i5 'iO ' ' 45 50 55 60 65" 70 7b 3Ö ^ 4o 95~ 



Fig. 34. Two catches of cod both from area G, and from the same time, July 1904 



groups. The different curves obtained from our material are therefore of even less 

 value for age-assessment than the haddock-curves. 



Fig. 34 shows two catches from the same period (July 1904) and the same 

 area (G, off Flambororough Head). The uppermost represents 220 individuals 

 taken in the space of six hours and the lowermost one 200 individuals taken in 

 53/^ hours. There was only an interval of a couple of hours between the two 

 hauls; the distance was merely 3 — 4 nautical miles while the depth and sea-bottom 

 were the same (25 — 27 fathoms, fine sand and mud). But whereas the average 

 number of individuals in the two hauls was the same (367 and .34-8 individuals 

 per hour), the distributi0n of sizes was very different. The uppermost curve (a) 

 shows one of the most marked groups and the average length is 22—23 cm. 

 (I-gr.). The lowermost curve (b) does not show any distinct, groups, but the 

 individuals are spread over the whole length-scale. The following is learned from 

 the tables: 



Station Under 30 cm. Between 30 and 105 cm. Total 



a. 187 33 220 individuals 



b. 63 137 200 — 



