62 



Growth. — Table IV. gives the average sizes of the herrings for 

 the various ages. These show a difference between the drift net 

 and trawled herrings for those having two and three winter rings, 

 which difference is accentuated somewhat when the time of year 

 the herrings were caught is considered. If the averages be taken 

 for the North Shields drift net samples landed from 28th August to 

 13th September, and the trawled samples which were landed from 

 15th September to 6th October, practically three weeks later, the 

 figures run as follows : — 



Winter Rings. 2 3 4 5 

 North Shields — 



Drift ... 23-3 ... 24*5 ... 25*3 ... 26-1 cm. 



Trawled ... 22-4 ... 24-1 ... 25-4 ... 264 cm. 



At the time that the scales were exammed for age a linear 

 representation of them was made, and following the method of 

 Hjort, Pub. de Circ, No. 53, p. 36, the size at the formation of the 

 different winter rings was then calculated for herrings having tw^o, 

 three, four and five winter rmgs. The older herrings have not been 

 dealt with in this way as the main object of the work, as before, 

 stated, was comparison between drift and trawled herrings, and 

 amongst the former the number having more than five winter 

 rings was so small as to be of little use for this purpose. 



The average sizes at the formation of the winter rings were 

 next obtained for each year group m the samples, and these will be 

 found in Table V. 



It is perhaps worth pointing out that as the herring becomes 

 older the first summer ring of the scales decreases gradually in 

 value when expressed in terms of the total length of the herring, 

 and therefore what comparison is made must be made between 

 herrings of the same age. 



It cannot be said that this part of the investigations throws 

 much light on the difference between the drift and trawled herrings. 



