FISHERY RESEARCH 



333 



be possible to predict 

 three years in advance 

 when another large in- 

 flux into the herring 

 population would occur, 

 because, as has been said 

 before, it is generally 

 three years before the 

 herring has grown large 

 enough to be captured 

 by the nets employed 

 by the fishermen. 



This phenomenon has 

 also been shown to hold 

 good for other fish 

 such as the haddock 

 and the plaice. Indeed, 

 it is only reasonable to 

 suppose that it is the 

 rule rather than the ex- 

 ception for each kind of 

 fish to have both good 

 and bad " survival 

 years." 



In the year 1923 un- 

 usually large numbers 

 of baby haddock ap- 

 peared in the catches of 

 the ring-trawl made by 

 the scientific staff of 

 the Scottish Fishery 

 Board. In consequence 

 of this it was boldly 

 predicted that in three 



Aqe ,n years — 



3 4 5 6 7 3 9 10 II 12 13 14 15 16 17 18 19 20 21 



Fig. 63. — Diagram showing the percentage age 

 composition of the herring caught off Norway 

 each year from 1907 to 1927. The great pre- 

 ponderance of fish born in 1904 in the catches 

 for many years in succession is clearly shown. 

 (After Einar Lea.) 



