1897-98.] Migratory Movements of Salmonidce. 
47 
Observations on the Migratory Movements of Salmonidse 
during the Spawning Season. By W. L. Calderwood. 
(Read January 31, 1898.) 
The fact that the salmon comes from the sea and spawns in the 
river has induced the supposition that this fish ascends the river 
only for the purpose of spawning. That the supposition is not 
always justifiable seems, however, sufficiently shown by the fact 
that clean-run salmon with undeveloped reproductive organs may 
be found in fresh water during the spawning season, and indeed at 
any season of the year, and also by the fact that a spring run of 
fish is usual. When we regard the head waters of many of our 
rivers as localities for the natural propagation of the salmon, we 
find, however, that, except at the spawning season, adult fish are 
never present. When, at the same time, we remark that the fish 
which ascend to those waters during the winter months are all 
sexually ripe, we may fairly conclude that the fish are impelled to 
migrate to those head waters for the express purpose of spawning. 
It has been said that the shads ( Clupea allosa and C.finta ) and 
the sea lamprey ( Petromyzon marinus) are examples of fishes 
which have a spawning habit analogous to that of the salmon, 
since they also ascend rivers for the purpose of propagating their 
species. Their habit is, however, more analogous to that of the 
comparatively few salmon which penetrate at once to head streams 
and tributaries, than to the fishes which inhabit the lower reaches 
of a salmon river. They ascend for a limited period only, and 
seek again the salt water whenever the operation of spawning is 
completed. They are marine fishes which spawn in fresh water. 
The common eel may he taken as an example of a fresh water fish 
which spawns in sea water. 
We have as yet very little knowledge about the movements of 
adult salmon in the sea : we know that they are to he found many 
miles from land, and we know that they congregate in great num- 
bers in the estuaries of rivers, presumably the particular rivers 
from which they have originally come to the sea ; that in the 
