GoDBY. — Growth of Brown Trout in (Janterhiiry . 



45 



label bearing a distinctive number ; at the same time particulars of length, 

 weight, and sex are recorded. Through the kindness of the society, and 

 of anglers who have had the good fortune to recapture tagged fish, I have 

 secured scales from thirteen of these fish when recaptured, and have 

 calculated from these scales the length of each fish when tagged. 



The following table shows the length when recaptured ; the length 

 {a) actual, measured at time of tagging, and (6) calculated from the scales ; 

 tosether with the difference in each case between the calculated and the 

 measured lengths : — 



In no case is the difference between the calculated and the measured 

 length more than ^ in., and in only three cases is it so much, whilst in four 

 cases the agreement is exact. Considering the difficulty of measuring 

 two or three hundred live fish accurately, these results may be taken to 

 fall well within the limits of experimental error in measuring. In practice 

 the fish are generally measured to the nearest i in., and an error of j in. 

 at time of tagging and another J in. when recaptured would be sufficient 

 to account for the largest discrepancy of h in. 



Two scales taken from one of these fish (tag No. 1374) at different 

 times are shown (Plate II. figs. 1 and 2). The scale in Plate II, fig. 1, 

 was taken on the 17th June, 1917, when the fish was tagged, and 

 measured 21| in. The scale in Plate II, fig. 2, was taken on the 28th 

 October, 1917, when the fish was recaptured, and meavsured 23 in. The 

 lengths each winter, calculated from a set of scales taken in June and a 



* Actual measured length. 



