HISTORY OF SALMON FISHERIES 17 



Acciiiiiiilated knowledge and experience has proven ihat wliere 

 good spawning grounds are available the most promising method of 

 maintaining productivity of the salmon stocks is by natural propaga- 

 tion e\en ^vhere conditions on the spaw^ning grounds have been 

 altered by the activities of man. Artificial propagation is not yet 

 efficient enough to maintain commercial fisheries economically. To 

 maintain natural production it has been found that regulations must 

 be imposed in such manner as to permit escapement from all seg- 

 ments of each particular stock that spawns in each tributary of the 

 different rivers. 



Perhaps most is known about the biology of the sockeye (or red) 

 salmon. In this species the homing instinct is highly developed, and 

 separate stocks seem to be specifically adapted to individual rivers. 

 If, by improper regulation, escapement on a given river is reduced 

 too much, the productivity of that stock ^vill be impaired in succeed- 

 ing years. It can be rebuilt only by stringent control of the catch. 

 Apparently, each separate race is dependent upon its o^vn ability to 

 reproduce. There is little straying of sockeye bet^veen rivers and 

 that ^vhich does occur into barren areas apparently requires many 

 generations to adapt itself. 



On this basis, the present concept of regulation of salmon is to 

 alloAv an escapement of each stock ^vhich ^\ ill utilize fully the avail- 

 able spa^vning and nursery areas. The proportion required varies 

 greatly from as little as 12 to 15 per cent of very large runs to all of 

 badly depleted runs. 



The regulation of such variable runs is extremely complicated 

 because large and small rinis, healthy and depleted rims, regularly 

 occur simultaneously in adjoining rivers or even among the parts of 

 the run to one river. Any uniform or haphazard rate of fishing 

 applied to these runs (as for example on the high seas) is extremely 

 wasteful because of excessive fishing on depleted rinis and luider- 

 fishing on the large healthy runs. This need for careful regulation 

 of the catch from each race has inspired the United States and 

 Canada to ban high seas fishing for salmon wdth nets. 



In addition to the need for selective and precise fishing on each 

 race, it is desirable to catch salmon at their maximum size and best 

 quality. Ricker (1962) has found that during their life in the ocean 

 the populations of salmon, owdng to their rapid growth rate, gain 

 more in total Tveight than they lose through natural mortality. This 



