of the Fishery Board for Scotland. 



237 



From this Table it will be seen how the plaice captured at the various 

 times of the year separate themselves into more or less distinct groups. 

 The distinction is sometimes well marked, as for instance in Series III. 

 (July 16th), where the size of the fishes in the first group begins at 20 

 millimetres, and continues to 70mm. ; while the sizes in the second group 

 begin at 100mm. A closer examination of each of these groups shows, 

 first, a gradual increase in the number of the fishes for each 5 mm. of 

 increase in length, and then a subsequent decline — a peculiarity justify- 

 ing the conclusion that each of these groups represents the fish of different 

 years. As was to be expected, the most distinct groups are those formed 

 by the youngest fishes. Although the proportionate difference in rate of 

 growth in some cases might have been considerable, the fishes are still so 

 young and small that the range in size could not be great. But natur- 

 ally, since the variation in the rate of growth becomes more accentuated, 

 the subsequent groups are more expanded, and in a few cases overlap 

 each other. For this reason it has sometimes been difficult to distinguish 

 these groups. In Table II. the various groups in each series have been 

 separated by a double line (thus ), and although the correct position 

 of these limits in some cases might be a little higher or lower, I think the 

 places chosen are justified from the fluctuation in the numbers of the fish 

 of the various sizes. But whether the few specimens that in each case 

 approach the limits drawn are included in the one group or the other, 

 their influence upon the, average size of each group is generally very 

 small ; and in the following remarks the averages only will be considered. 

 But, when estimating the value of the different averages, the number of 

 fish from which each of them has been deduced must be taken into 

 account, and in Table III. the number of fish in each group is given, 



TABLE III. 



Showing the Average Size in Millimetres and the Total Number 

 of Plaice contained in each Group of the various Series. 





Series I. 



Series TI. 



Series III. 



Series IV. 



Series V. 





Number. 



Average. 



Number. 



Average. 



Number. 



Average. 



Number. 



Average. 



Number. 



Average. 



Groups A, 











667 



40-7 



776 



56-5 



789 



59-5 



„ B, - 



51 



104-9 



83 



112-1 



45 



118-1 



52 



135-9 



31 



138-7 



„ c, - 







6 





1 





18 



214-4 



25 



214-0 





Series VI. 



Series VII. 



Series VIII. 



Series IX. 



Series X. 





u 



tD 



'erage. 



o 



% 



1 



6 

 IP 





6 

 be 



cS 



5 





SP 





s 



S 



0) 



2 



o 



s 



B 



■~. 











< 





> 



< 





> 





> 

 < 



Groups A, 



180 



660 



86 



(60-7) 



22 



65-2 



34 



62-9 



65 



77-2 





50 



(135-0) 



13 



155-0 



2 





1 





50 



156-0 





11 



220-0 



37 



221-5 



8 





16 



226-9 







