74 
BULKETIN OF THE BUREAU OF FISHERIES 
In artificial propagation we have a method designed to oflfset the work of destruc- 
tive agencies, which is at once the hope and the despair of the scientific conservation- 
ist — the hope, in that it is so eminently logical to protect the young of the salmon 
during the early part of their life when the rate of mortality is high, and the despair, 
in that the evidence of its efiiciency is inadequate and conflicting. Many instances 
can be adduced showing, apparently, the beneficial results of artificial propagation, 
but there are other instances in which no such results are to be observed. And if 
the extravagant claims of some of the proponents of artificial propagation were true 
we would long since have ceased to worry about the future of our salmon resources. 
The difficulty apparently lies in the fact that, as at present conducted, the procedure 
of artificial propagation is not based on scientific knowledge. With a gradual in- 
crease in the efficiency of hatchery procedure, which will come with placing it more 
and more on a truly scientific basis, we may hope that artificial propagation will 
come to be one of the most important factors in the preservation of our fishery 
resources. Noteworthy progress is being made by the Bureau of Fisheries toward 
this end, and it seems certain that the future development of artificial propagation 
is most promising. At the present time, however, it must be admitted that the 
importance of artificial propagation as a means of conserving the supply of salmon 
can not be acciirately evaluated. 
We are left, then, with the single alternative of maintaining the intensity of fish- 
ing below the danger point if the salmon run is to be preserved. Just what this point is 
no one can tell, and for that very reason it is essential to see that the intensity of 
fishing is kept down so as to provide what may be reasonably supposed to be a margin 
of safety. It is the duty of all who are interested in conservation to see that this is 
done — especially those officials whose duty it is so to administer the fisheries that 
depletion may not occur. 
Just where do these facts fit into our discussion of the effect of the development 
of outside fishing on the supply of fish in the Columbia River ? We have seen that 
the pack on the river has remained practically stationary for a number of years, 
diuing which time the intensity of fishing has been increased, especially by the addi- 
tion of trolling and purse seining; that the spawning area is being gradually reduced; 
and finally, that a restriction of the amount of total fishing effort is essential to the 
maintenance of the run in the Columbia River. 
It must always be an indication of danger if an appreciable increase in the in- 
tensity of fishing does not provide a corresponding increase in output. It must 
inevitably indicate that the productivity of a fishery is being maintained at a given 
level only by drawing to some extent upon the reserve stock needed for breeding if 
the race is to be maintained. Evidently a surplus of breeding adults is normally 
provided in nature, and it is only from this stuplus that man can draw without 
immediately endangering the continuance of the supply. Any infringement upon 
the necessary breeding reserve is dangerous. A slight infringement may show no 
immediate effect, but if continued over a period of years the effect will be cumulative 
and is certain to end in disaster. The increase in fishing effort on the Columbia 
River by the development of trolling and purse seining has shown no corresponding 
increase in the total pack, and we may assume, therefore, that the present intensity 
of fishing is too great and is resulting in a dangerous reduction of the reserve of breed- 
