34 MANAGEMENT OF HIGH SEAS FISHERIES 



tivity; such limitations and regulations being in accordance 

 with conservation programs based upon scientific research, 

 and 

 (c) The stock is the subject of extensive scientific study designed 

 to discover whether it is being fully lUilized and the con- 

 ditions necessary for maintaining its maximum sustained 

 productivity. 



(4) No abstention will be recommended where the stock is ex- 

 ploited in greater part by countries not party to the treaty. 



Provisions of the 1953 treaty that are critical are the principle of 

 abstention, the provision that this principle is effective east of 175° 

 West Longitude, the requirement that a stock must reasonably satisfy 

 all conditions for abstention, and the provision that evidence indi- 

 cates that the stock is producing at its maximum potential level of 

 yield and is being fully lUilized. 



Fulfillment of these requirements would appear to be fairly 

 straightforward in the case of salmon runs if the size of escapement 

 for different runs can be related to the total size of the resulting rims 

 each year. This, however, is not a simple problem, and the relation- 

 ship shows wide variations which at present are only partly under- 

 stood. There is no doubt, however, that artificial propagation has 

 so far not sufficed to maintain those salmon runs for which it is being 

 used. In addition, it should also be obvious that substantial escape- 

 ment is required to maintain runs by natural propagation. While 

 the International Pacific Salmon Fisheries Commission seems satisfied 

 that an escapement of 20 per cent of the Fraser River run should be 

 sufficient to maintain it, this has not been established for any other 

 stream. The proportion required can be expected to vary. It is also 

 obvious that runs can be killed off if the escapement is sufficiently 

 reduced. Much work remains to clarify the wide range of values 

 between zero and "optimum" escapement. Above all, greater con- 

 sideration must be given to determining the manner in ^vhich the 

 size of escapement of components should be tailored to the annual 

 variations in capacity of the spawning and rearing areas and to the 

 nature of the relationships between the size of runs and the capacity 

 of marine rearing grounds. 



If the interpretation of requirements concerning scientific data 

 now set out in the North Pacific Treaty is obscure for salmon, it is 



