374 



ANNUAL KEPORT SMITHSONIAN INSTITUTION, 19 3 5 



1923 



1926 



1929 



1920 



FifiURB 2. — Comparison between actual halibut yield and yield expected on a basis of 

 theory, showing the total yield and the yield per unit for the grounds north of Cape 

 Spencer, Alaska, 1920-29. A skate is a unit of gear, set once. 



yield per unit. From the economic standpoint the decrease has been 

 the only limit on the intensification of the fishery, the yield per unit 

 being forced as low as would permit the fishery to exist, and the 

 catch being produced from each bank at the greatest possible cost. 

 The abundance on each bank therefore has sought an economic, not a 

 biological, level, although the intensity of the fishery and the result- 

 ant mortality rate did have important biological consequences, as 

 has already been seen. 



Regulation of the intensity of the fishery should therefore have 

 the important initial advantage of tending to correct a wasteful 

 economic process — production of the catch at the highest possible 

 cost and greatest effort. 



The biological principle of this effect of fishing on the abundance 

 is one whereby the Commission may increase the proportion of 

 spawners, and hence of spawn. In addition, it may lead to a far 

 more rational use of the existing supply, whereby the excess of 

 growth over deaths can be taken advantage of, whenever and at 

 whatever age it exists, to increase the total take. It leads to a defi- 



