1905-6.] The Smolt to Grilse Stage of the Salmon, 323 
(61 cm.) ; the greatest depth is 4 inches (10'2 cm.), and the depth 
of the caudal peduncle 1J inches (3*7 cm.). 
These recaptures, then, confirm the belief that the smolt does 
not return as a grilse the same year as it descends, but rather 
after a year or fully a year has elapsed. The development shown 
on the scales of grilse, as well as the capture of the Galway 
Dorsal fin of grilse, caught 1st June 1906, marked as a smolt in May 1905. 
(Photograph by P. D. Malloch, Perth.) 
specimen which I exhibited to the Society about a year and a 
half ago, all give evidence that the first normal return of a smolt 
to fresh water takes place when the fish, as a grilse, is three to 
three and a half years old, and after it has been fully a year in 
the sea. From other observations it seems certain that all grilse 
do not, however, enter fresh water, but that many fish pass the 
grilse stage in*the sea and return for the first time to fresh water 
as small spring salmon, four years of age. 
