44 THE STOCK OF PLAICE 



grow to a larger size before catching them. That, after years of 

 inquiry, was the finding of the International Council in 1913 

 as expressed by Heincke. 



Trawliiig in the Large Plaice Grounds 



The Council went further and attributed the reduction in the 

 number of older and larger plaice landed in part to intensive 

 trawling, especially to trawling on the spawning grounds. 



Shrimj) Trawlers on the Nurseries 



It v/as left to the trawlermen, and to certain Enghsh natural- 

 ists, to point out the immense damage done to the plaice fry 

 by the shrimp trawlers off the Wash, the Norfolk and Essex 

 coasts, and the Thames Estuary, a question which will be 

 discussed more fully later. 



The Effect of Catching immature Fish on the Stock 



There was then a very large consensus of scientific and 

 business opinion that the large catch of immature fish actually 

 reduced the stock of plaice. But on this point opinion is not 

 unanimous. A school, of which Garstang is the protagonist, 

 holds that there was no proof that the falling-off in the catch 

 of large fish was due to the increased catches of small fish. They 

 admit that there were before the war fewer large plaice, in the 

 North Sea generally. Garstang thinks that the trawlers catch 

 (a) numbers of young plaice as they are migrating, and (b) 

 numbers of mature fish on the spawning-grounds. So the 

 central grounds, which are the finest feeding-grounds, do not 

 get their natural supply of fish to graze on them ; and half 

 the large plaice are caught just as they are ' ripe ' for the first 

 time. Hence the increased proportion of small plaice in the 

 trawler's catches. Probably there were before the war actually 

 more small plaice in the sea just because the big ones were 

 killed so extensively that they left more space and more food 

 for the small fish, and so the infant mortality among the small 

 plaice had diminished. 



Their opponents maintain that there is no reason to think 

 that young plaice do die to any great extent for want of food 

 or for want of space. That, on the contrary, they are extremely 

 hardy ; that they do not eat the same food as adult plaice ^ 



^ Professor Garstang's point is that the big fish destroy the parent cockles 

 which would have produced numbers of small cockles on which the small 

 plaice feed. Petersen's investigations seem to show that the ' broods ' of 

 young cockles vary very much from year to year, exacl'y like those of cod and 

 herrings. 



