( 487 ) 
of a quite different nature: it is easy enough to catch samples of 
young salmon so long as they remain in the brooks and smaller 
affluents of the upper course of the river and so it is possible in 
the consecutive months to compare these with one another as to 
their size and to make out their growth; but between the largest 
that are still observed in the river, and the smallest returning from 
the sea the difference in size is at once so great, that it would 
be a hazardous undertaking to derive from it their difference in 
age. The smallest salmon (smolts) going to the sea and at that 
time about 14 months old, have ,a length of 12—16 cm.; along 
with them descend larger ones of a length of 15—20 cm. and 
about 26 months old; moreover stragglers are observed in different 
seasons and at various places in the upper course of the river, 
which have a length of 18—24 cm. and which most probably are in 
their third year. The smallest salmon that return from the sea 
(the so-called grilse) are, however, fishes of a length of 55 67 cm. 
and salmon between that size and the largest of those descending 
to the sea in reality have never been observed. Hence any definite 
rate is wanting when we try to estimate the age of the grilse by 
comparing their length with that even of the largest salmon descending 
to the sea. 
Following the instructive example given in recent years for other 
species of fish (especially for the carp x ) among the freshwater-fishes 
and for the Gadoids ■*) among the seafishes), of late a beginning has 
been made to use the structure of the scales for the determination 
of the age of the salmon 8 ). The scales, once formed, as a rule remain 
with the fish during its whole life; so their number does not increase 
with the growth of the fish, but, on the other hand, their size 
does and in a very conspicuous way. The shape of the scales of the 
salmon is rather regular: in the beginning more oval, later nearly 
circular. They cover one another like roof-tiles; being placed in oblique 
rows, only the hindermost part of each scale emerges freely from 
G. Hoffbauer, Weitere Beitrage zur Alters- und Wachstumsbestimmung der 
Fische, spez. des Karpfens. Zeitschr. f. Fischerei. XII, 1905. p. 111. 
2 ) J. Stuart Thomson, The Periodic Growth of Scales in Gadidae as an Index 
of Age. Plymouth Journal. VII, 1904. p. 1. 
3 ) H. W. Johnston, The Scales of Tay Salmon as indicative of Age, Growth 
and Spawning Habit. ’ p. 63—79. 1 & 6. PI. Appendix II to Part II of 23rd 
Annual Report of the Fishery Board for Scotland (for 1904). 1905. 
- The Scales of Salmon, p. 54-66. 5 PI. Appendix II to Part II of the 25th 
Annual Report of the Fishery Board for Scotland (for 1906). 1907. 
Artur Hutton. Salmon Scales etc. London, 1909; translated in: Allgemeine 
Fischerei-Zeiting. XXXIV, 1909. p. 459. 
