RECENT RESEARCH UPON SALMON 243 
Date of Marking. Description. Date of Recapture. | Description. 
April, 1851 Smolt (13 oz. ?) Aug. 17, 1852 | Grilse, 4} Ib. 
April, 1854 Smolt, 1 oz. July, 1855 Grilse, 33 Ib. 
May, 1855 Smolt (14 oz. ?) Aug. 6, 1856 | Grilse, 63 Ib. 
May, 1855 Two smolts Summer, 1856 | Grilse, 6} and 53 lb. 
The Scottish Fishery Board have, as yet, no returns to 
show from marked smolts; but their list of fish marked as 
kelts and recaptured clean is full of interest. The longest 
interval between such marking and recapture has been 515 
days, in which case a kelt taken in the Spey in March, 1897, 
weighing 7 Ib., was recaptured in the same river in August, 
1898, weighing 19 lb. The stages of this fish may be 
reckoned as follows :— 
Spawn deposited . : : . Autumn, 1891 or 1892. 
Went to seaas smolt . ‘ . Spring, 1894. 
Returned as grilse . ; 5 . Summer, 1895. 
Returned as salmon (8 Ib. ?) . . Spring or summer, 1896. 
Descended as kelt (7 lb.) : . March, 1897. 
Returned as summer fish (19 lb.) . August, 1808. 
Its age, therefore, was five or six years, according to 
whether it left the river as a smolt in its second or third 
spring. But it must not be assumed that all fish of 19 |b. 
weight are necessarily only five or six years old, for the returns 
of twenty-two kelts recaptured as clean fish seem to show a 
remarkable variation in the rate of increase, estimated by 
Mr. Calderwood to range from as low as 77°2 per cent. per 
annum to as high as 813°9 per cent. per annum. This 
estimate, however, appears to be fallacious in one important 
respect, for it is based on the assumption that the rate of 
increase throughout the year is the same as that between the 
dates of capture and recapture. Some kelts travel rapidly to 
the sea, where they will put on flesh at a great rate ; whereas 
