APRIL 67 



the front of the dorsal fin. Each label bears a number 

 corresponding to one in a log where all particulars of 

 date and dimensions are kept for comparison should 

 the fish ever be recaptured. 



It has been a favourite doctrine with old fishermen 

 that smolts descending to the sea in April or May, 

 averaging about one ounce each, return in late summer 

 or autumn as grilse weighing from two to ten pounds. 

 This rate of growth seemed incredible on the face of it ; 

 but there existed no means of disproving it until the 

 summer of 1906. In the spring of 1905, 6500 smolts 

 were marked with labels in the Tay. Not one was 

 recaptured during that season, but between June 

 1st and August 20th, 1906, forty of these fish were 

 retaken, varying in weight from 2 Ib. 15 oz. on June 

 1st to 7 Ib. 2 oz. on July 28th, showing an average 

 weight of 5 Ib., the average rate of increase being 

 6 oz. per month. This seems to prove that the smolt 

 requires a year or fifteen months of sea fare to develop 

 into a grilse. 



Still more remarkable are the results of the pre- 

 sent year, when three of the 1905 smolts have been 

 recaptured as spring salmon in the Tay ; namely, one of 

 9 Ib. on February 18th, one of 8 Ib. on February 19th, 

 and one of 9 Ib. on February 21st ; thus showing that the 

 run of small spring salmon, which is so characteristic 

 of all early rivers, consists of fish which have not re- 

 entered fresh water as grilse, but have spent that stage 

 of their existence in the sea. 



