IMPOVERISHMENT OF THE GROUNDS 269 



1. By the fishing out of an accumulated stock. At 

 one time the great extent of the North Sea was 

 virgin fishing ground. When it was first fished 

 large catches were made : a great weight of fish 

 were secured, because not only were they more 

 numerous, but they were also larger. When the 

 Iceland fishing grounds were first opened up this 

 was the case. Very large plaice were numerous 

 there. 



2. By simple over-fishing. It is possible by 

 ordinary methods of agriculture to raise only a 

 limited quantity of produce from a certain area 

 of agricultural land. So with the sea. There is a 

 definite quantity of ultimate food-material in it per 

 square mile (say), and on this depends the number 

 of fish that area can raise.^ We may fish up to 

 this limit, but if we go beyond it the area becomes 

 impoverished. 



3. By the destruction offish eggs, larva, and immature 

 fishes. It is well known that large numbers of 



spawning fishes are annually captured. The spawn 

 which these animals were producing or would 

 shortly have produced represents potential fishes, 

 and is lost. By the capture of immature forms, 

 fishes are destroyed before they have had time to 

 reproduce. Further, they are caught at a time 

 when their weight is small. 



All three causes have probably operated in the 



1 I do not mean that a fish necessarily confines itself to one square 

 mile of sea-bottom. 



