Manchester Memoirs, Voi. hi. (191 2), No. 3. 



III. Intensive Study of the Scales of three Specimens 



of Sahno snlar. 



By I'HILIPPA C. ESDAILE, M.Sc, 



Honoj'ary Researcli Fellow in Zoology, University ofManchester. 



(Co7nviii7ucated by Professor S. J. Hickson, DSc, F.R.S.) 

 (Received and read October jist, igi i .) 



During the past few years the scales of salmon have 

 been studied with a view to proving that the age and rate 

 of growth of the fish, as well as the occasions on which 

 the fish has spawned, can be ascertained from the periodic 

 growth of the rings or annuli by which the scales are built 

 up. Mr. H. W. Johnston, in the 23rd Annual Report of 

 the Fishery Board of Scotland, explains the method of 

 reading salmon scales. His examination of a parr of 

 known age has shown which part of the scale is formed 

 during the early life of the fish in the river. Fish caught 

 in the sea between the smolt and grilse stages show the 

 beginning of the rapid summer growth after the fish had 

 migrated to the sea. Scales taken from grilse caught in 

 the river show the slower winter growth, after the broad 

 formation caused by the rapid summer feeding, and this 

 slower growth was again followed by rapid increase formed 

 in the sea during the summer just before the fish was 

 caught. Small spring fish show signs of rapid feeding on 

 entering the sea, then the slower growth of the winter ; 

 following this, the broad formation during the second 

 summer, and then at the periphery of the scale, a second 

 period of slow feeding during the second winter spent in 



February i6th, igi2. 



