96 



Growth of Plaice during the First Year. 



This we were able to make out by measurements of little 

 plaice reared in the Port Erin tanks. The results are as 

 follows : — 



Thus, there is considerable variation between individual 

 fish as one might expect. This variation continues, and even 

 becomes greater in subsequent stages of the life-history. In 

 1921 we made collections* of young plaice (and other flat 

 fishes) in the shallow bays in Isle of Man, and on the Lancashire 

 and Cheshire coasts. In May, the length varied from 13 to 

 50 mm. in the case of the Manx fish. From now onwards the 

 plaice grow rapidly, increasing in length about six or seven-fold 

 by the end of the autumn. Precise measurements (averages) 

 for Cheshire shore plaice are as follows : — 



These are all first-year plaice, for each was examined by 

 inspection of the otoliths (or earstones). The latter are, of 

 course, very small, but it can easily be seen that they consist 

 only of the central, opaque " nucleus." Towards the end of 

 the year this central white spot becomes surrounded by a semi- 

 transparent ring, and thereafter an opaque white ring is formed 

 during each summer and autumn, and a semi-transparent ring 

 during each winter and spring. (Chemical tests showed that 



* The ordinary haul " push-net " used by shrimpers in Lancashire was 

 employed. The collector wades in water of about 2-feet depth and pushes 

 the net in front of him. The fish can often be seen. The method is a very 

 admirable one for the collecting of small shore tishes on a shallow, sandy 

 coast. 



