Living Silver 



had been doubly right. But then the Baltic must have been warmer 

 than in later centuries or there would have been few herring in it 

 and no Hanseatic League. So it seemed that, superimposed upon 

 the short term cycle of forty to fifty years, there might be a larger 

 cycle, to be measured only by centuries, and it was perhaps in 

 response to that larger oceanic rhythm that the ice was now melt- 

 ing and the cold water gadoids edging northwards. Jan saw clearly 

 that there was no way of deciding which of these alternatives was 

 valid : only a sudden rise in the Baltic population of the herring 

 would have assured him that a large scale hydrographic revolution 

 was, in fact, taking place. 



Once the race theory had been established, the awkward little 

 facts that contradicted it began to pour in. Individual fish, that 

 had been tagged on one of the Scottish coasts would be recaptured 

 off the opposite one. Sometimes these movements would syn- 

 chronise with the appearance of different races in the two spots. 

 A single fish, therefore, was behaving as though it belonged to two 

 different races. And then, too, there was the mystery of the 

 Fladen Ground. Lying plumb centre of the northern North Sea, 

 half-way between Scotland and Norway, Fladen consisted of a 

 large oval valley in the sea-bed, deep water surrounded by shallow 

 water, an unchanging core of cold brine in the middle of all the 

 superficial hydrographic changes of a North Sea summer. To this 

 freak district the herring came in autumn, herring of many races, 

 herring in immense numbers. They came and subsided inert on 

 the muddy bottom. Some observers thought that they came to 

 feed, but they did not rise to the upper layers where the plankton 

 lived. Others believed that they came to rest. There were com- 

 plex attempts to link their behaviour with their need to spawn 

 but no complete explanations emerged. 



Little was known of these Fladen fish when the race theory was 

 first propounded. They lay too deep for a gill net to reach them. 

 Only men, particularly Germans, who trawled for herring appre- 

 ciated the full riches of the Fladen Ground. The race theory was 

 therefore established without reckoning with this example of gre- 



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