122 THE LIFE OF THE SALMON 
That salmon do not invariably enter fresh water 
in an excessively over-nourished state I have already. 
noted. A season occurs now and again during which 
fish in comparatively poor condition leave the sea 
for our rivers. This in all probability means that 
the nature of the food taken in the sea has been 
poor in quality, or, less probably, scarce. Further, 
the common occurrence of so-called bull-trout enter- 
ing our rivers from the sea, pale in flesh, often of 
great size, and having both the gill maggots common 
to the kelt and the sea lice of the fresh run fish 
upon them, suggests the belief that amongst fish 
which adopt the short migration there are those 
which do not adopt the generous feeding habits of 
the silvery well-conditioned migrant. 
Such considerations as these seem to me to prompt 
a certain reserve in accepting the conclusions of Dr. 
Noél Paton that it is the state of nutrition alone 
which is the factor determining migration towards 
the river. We have dwelt at considerable length, 
in the chapter on the results of salmon marking, on 
the habit of long and of short periods of sojourn in the 
sea. Since a salmon in any year can clearly become 
fully nourished during the time of a short sojourn in 
the sea, why should it stay an extra year in salt 
water? The state of its nutrition does not supply 
a sufficient reason. The corollary to the view 
advanced by Dr. Noél Paton is expressed by him 
thus: “When the salmon has accumulated the 
necessary supply of material it tends to return to its 
original habitat.” That the salmon is a native of 
fresh water, in the sense of being born there, I of 
