Living Silver 



then, they were all herring : they all belonged to the same species : 

 and the scientists were therefore forced to work by analogy with 

 human beings and refer to each of these populations as races. They 

 would identify a herring race by counting the number of vertebrae 

 in the backbone, the number of keel scales that lay along the belly 

 in front of the ventral fin, and by discovering from the ear-stones 

 of the fish and from direct observation whether it spawned in 

 spring, autumn, summer or winter. The principle of herring 

 races within the species once established, the morphologists got 

 to work in an orgy of classifications that soon threatened to create 

 as many races as there were individuals until more sober minds 

 took over and the pendulum swung back almost to the point where 

 it threatened the original principle. But never quite. There were 

 herring races : there was no danger of over-fishing : no single popu- 

 lation made up the main prey of more than one drift-net industry. 



And another possibility began to emerge. The flighty behaviour 

 of the herring, concentrated now off Norway, now off East Anglia, 

 now in the Baltic, had always been thought to be due to the actual 

 movement of individual shoals. The idea of races allowed a differ- 

 ent and more common-sense interpretation of the known facts. 

 Quite simply it could be said that, for complex hydrographic rea- 

 sons that remained unknown, there were historical periods when 

 the Norwegian race of herring was supreme in the North Sea and 

 there were other periods when conditions were more favourable 

 to the East Anglian race. The need to presume that individual 

 herring changed their habitat and spawning grounds every fifty 

 years or so was dispensed with. Each animal went back to its an- 

 cestral home but sometimes that home was an uncomfortable or 

 a dangerous patch of water and many individuals died and the race 

 to which they belonged was diminished. Sometimes again, the 

 same race on the same grounds would grow fat and numerous be- 

 cause conditions were ideal for it. 



By means of the race theory, the apparent movements of popu- 

 lations could thus be interpreted in terms of water movements ; 

 and, since there were many independent signs that hydrographic 



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