oS8 WHAT IS OVER-FISHING 1 



order to throw light upon some of the principal ideas concerning this 

 matter. 



Accordingly I take the case of an imaginary fish, species " P," which 

 exhibits the following features : — 



1. It does not migrate out of the Xorth Sea. 



2. It takes three years to grow up to maturity (see Diagram). 



3. It is nearly in every respect closely allied to the plaice. 



The stock of this fish " P " has, during recent years, been reduced in 

 the Kattegat and in the Xorth Sea to such an extent that statistics 

 prove that the weight of ''P" annually caught is not at present so great 

 as formerly, in spite of the catching power being highly augmented. 

 Had not the prices per kilo increased during the same period, nearly all 

 " P " fishing would have been stopped, at least in the Kattegat. 



Xow somebody may say, " Well, you have had to do with a stock of 

 ' P ' accumulated during many years. The III Group (Diagram, Ilia) 

 was accumulated and included all ' P ' of three years and above, possibly 

 up to twenty years, the maximum possible age of a ' P.' In the 

 very beginning you were catching these old III indi^iduals, but this 

 cannot be done every year, since a larger stock will grow up in twenty 

 years than in one. This fact is the explanation of your decreasing 

 statistics." 



This status quo may occur in Xorwegian fjords, where the areas in 

 which the I or II Groups live are very limited, and where the 

 number of indi\dduals in these groups is consequently small compared 

 with those in the III Group. The indi\'iduals of the I and II Groups 

 are very fond of shallow, sandy beaches, but those of the III Group 

 live in much deeper water. Fishery investigations in such fjords have 

 proved that the III Group is really much easier to catch in numbers 

 than are the I and II Groups, and that the average size of the 

 indiWduals of the III Group is thirteen to fourteen inches (Diagram, 

 Ilia). This example of an annually decreasing catch is not strictly an 

 example of over-fishing, at any rate it is only an exceptional kind of 

 over-fishing, which is inevitable, and to some degree desirable. 



An explanation of this kind, however, cannot be used to account for 

 what has happened in the Xorth Sea and in the Kattegat during recent 

 years, since the fishery of "P " in this area is no longer based upon the 

 III Group, but upon the II Group. If we consider numbers instead 

 of weight, the greater part of the total annual catch is now, and has 

 been for many years, made up of indivdduals of the II Group with 

 comparatively few of the III Group. The average size of the III "P" 

 has, moreover, during the same time gone down from thirteen or 



