of the Fishery Board for Scotland. 



293 



Other series are found in the earlier months. Thus, below is a single 

 instance from May : — 



May 27, 1890.— River Eden. 







1*15 



'95 



1*1 



•92 





•9 





•8G 





•67 





•63 





•62 





•6 





•58 





•55 





•54 



Both in May and September we find no break in the series, and we are 

 led to the conclusion that all are of one season's growth — all being, in 

 fact, less than one year old. 



It is possible to assume that the fishes of 3*4 inch are of the same age 

 as those of 1 *6 inch, but there appears to be a perfectly valid reason for 

 believing that there is as great a diversity in age as in size. 



This reason arises from the fact that the spawning period of the plaice 

 extends (at any rate on the East Coast of Scotland) over a considerable 

 period. Facts indicate that the plaice commences spawning in mid 

 January, and continues through February, more abundantly in March, 

 April, and again spawning even into the middle of May. There are, 

 doubtless, isolated cases of even later spawning. We thus find a maximum 

 difference of age in one season's fry of no less than four months. 



Proceeding on this basis, the young fish of 3 "4 inches may approxi- 

 mately be eight months old, and those of 1*37 inch four months. The 

 intermediate sizes represent fish hatched at the period of intermediate 

 months. 



Thus, the fish are placed above in rows, according to the purely arbitrary 

 gradation of J inch from 3| inches downwards, and it will be seen that 

 they form series corresponding, to some extent, with the spawning months. 

 Thus— 



Inches. 



(1) January (latter half), . . 3 specimens 3J-3 



(2) February, 



(3) March, 



(4) April, . . . 



(5) May (early half), . 



14 „ 3-2J 



24 „ 21-3 



18 „ 2-11 



4 ,, 1J-1 



The number of specimens hi each section corresponds, to a large extent, 

 with the curve formed by the spawning period. One does not wish to 

 imply that all those exactly between 2J inches and 2 inches, for instance, 

 are limited to March, &c. ; but the arbitrary adoption of 5 inch per 

 month suffices to show that the variation in numbers of specimens in the 

 different divisions corresponds to the variation in number of spawning 

 parents, the maxima and minima being co-related. 



Applying the same principles to the May series, we find that there is 

 far less diversity in size ; but the fish at the head of the series should, by 

 the scale just laid down, be about 4 months old, which dates them just 

 back to the commencement of the spawning period (mid-January). It 

 U 



