24 
MUSEUM BULLETIN NO. 13. 
It is evident then, that any method of raising this deep sea 
salmon population above the economic mean of ten per acre 
(number here arbitrarily assumed) will be wasted energy and 
expense unless the enemies at this critical time can be controlled. 
If, as seems likely, the deep sea condition is the controlling 
element in the life of the salmon, increasing the number of fry, 
feeding parr or destroying fresh water enemies will have little 
if any effect on ultimate numbers. 
Protection at other times will no more increase the number 
of mature salmon than enlarging two ends of a pipe, while 
leaving a constricted length in the middle, will increase its flow 
capacity. 
In conclusion it may be said that 
I. The total effect of bird enemies upon salmon is small, 
if any. 
II. Hatcheries and fry planting will compensate for the 
toll of mature fish taken by man. 
III. The number of smolt that go to sea is dependent 
upon the food supply in the streams. 
IV. The number of returning salmon is governed by the 
extent of their deep sea habitat and the number of enemies 
there. 
V. While planting may return an exhausted stream to its 
normal capacity, the number of fish cannot be indefinitely 
increased without a readjustment of other critical conditions. 
VI. Eliminating the question of poaching, stream defilement, 
and other abnormal conditions the problem of increasing the 
salmon rim in the rivers, above the natural capacity of the 
streams, lies between increasing the parr food in them or reducing 
the enemies of the salmon in the deep sea habitat. 
