ADULT HEKEINGS 167 



of two-year and three-year-old fish, in 1908 of two-year and 

 four-year-olds, and in 1910 of two and three-year olds. The 

 three-year-olds of 1907 were (obviously) four years old in 1908 

 and so on, and the broods born in 1904 and 1907 are printed in 

 black heavy type. Both these spring spawning seasons at once 

 appear to have produced an unusual number of healthy fry. 

 When they are four years old the fat herrings leave the shoals 

 of immature herrings, and join up with the spawners. Samples 

 of these spawners were examined, and the scales showed that the 

 brood fish each year contained the following percentage of 

 herrings born in 1904 : 



1908 34-8% 



1909 43-7% 



1910 77-3% 



1911 70-0% 



Hjort and Lea had thus proved to their satisfaction that the 

 1904 brood was so enormously prolific that the herring stock 

 in certain years contained more 1904 fish than fish of all the 

 other many years represented in the samples put together. All 

 this they described in their paper ' Some Eesults of the Inter- 

 national Herring Investigations, 1909-11 ' {Puhl. de Circon- 

 stance, No. 61, Copenhagen 1911). Most unfortunately, no 

 popular account of this work has been given to the British 

 herring-trade. 



Since its publication Dr. Hjort has, as we have seen, been 

 able to show that the 1912 brood was also abnormally prolific. 

 He is now concerned to determine what conditions prevailed 

 in the Norwegian Sea in the springs of 1904 and 1912 which 

 would account for this great access of young herrings. He is 

 disposed, apparently, to connect the good years with an ab- 

 normal spring harvest of diatomic plants on the sea-bed during 

 the period when the herring larvae first begin to supplement 

 the contents of their yolks with suppHes of sea-food.^ Clearly, 

 if that point can be proved, the investigator of the future will 

 be able to note the amount of diatomic food in the water on the 

 Norwegian herring spawning grounds during the hatching 

 season, and to tell the fisherman whether there will or will not 

 be a big catch of herrings of this particular brood two, three, or 

 four years later. 



Scale Beading in Britain 



This consummation will not be arrived at unless the age of 

 fish can be accurately determined by their scales. And herring- 

 scale reading in this country is complicated by the fact that our 



1 See pp. 94-6 



