TRAWLING IN THE BAYS ON THE SOUTH-EAST COAST OF DEVON. 487 



3. RATE OF GROWTH OF PLAICE. 



By comparing the sizes of the marked plaice when recovered with 

 their original size when liberated, it should be possible, if due pre- 

 cautions are taken, to obtain a fairly reliable measure of their rate 

 of growth. Nearly seventy of the marked fishes described in the 

 previous section were measured on recapture, partly by Mr. W. J. 

 Sanders at Brixham and partly by Dr. Kyle. Mr, Sanders's measure- 

 ments appear to have been taken in most cases to the nearest quarter- 

 inch ; Dr. Kyle's measurements — which, however, form the minority — 

 were taken to the nearest half-centimetre. The original measurements 

 of the fish at the time of liberation were all taken to the nearest half- 

 centimetre. 



In the following table the plaice, whose ultimate sizes were recorded, 

 have been sorted out in order according to the number of days which 

 elapsed between their liberation and recapture, and the increase in 

 length of each fish has been given as recorded. It will be seen that 

 the increments of growth for the same period vary considerably, and 

 it is not certain that they are all reliable, especially in the case of 

 fishes marked with bone buttons, the numbers on which were, in some 

 cases, obscure. The increments of growth recorded cannot, therefore, 

 be relied upon as an exact measure of the range in growth for any one 

 period. The specimens have been further grouped according to the 

 number of months between liberation and capture. The first month 

 is taken to correspond with the period of thirty days from the six- 

 teenth to the forty-fifth after liberation, the mean of the period being 

 thus the thirtieth day. The second month covers the period from the 

 forty-sixth to the seventy-fifth day, and so on. The fishes have been 

 further sorted out, according to their original size, on liberation, into 

 three groups: (1) fishes from 8 to 11 inches, inclusive (20 to 30 cm.); 

 (2) fishes from 12 to 15 inches (30-5 to 40 cm.); and (3) fishes of 16 

 inches and upwards (40-5 cm. and upwards). Only one instance of the 

 latter size, however, occurs, and it is a somewhat doubtful record. A 

 distinction has also been drawn between the fishes liberated in the 

 autumn of 1901 and those liberated in the spring of 1902, since the 

 rate of growth in winter and summer is already known to differ 

 considerably. 



