CH. VIIl] A CENSUS OF THE SEA I7l 



We know from actual enumerations what is the average number 

 of eggs annually produced by a ripe female cod. Fulton^ deter- 

 mined this in 1890 in the course of a laborious investigation into 

 the average numbers of eggs annually spawned by the various 

 edible fishes. The average number of ova produced annually by a 

 mature female cod is 4,398,700. Now we find a certain number of 

 cod eggs in the North Sea in the spring of 1895. If then we 

 divide this total number of eggs produced during the breeding 

 season of the fish by the average number known to be spawned by 

 each ripe female, we can calculate the total number of fishes of that 

 category present on the sea bottom during the spawning period — 

 that is to say, the number of fishes ivhich have produced the ova. 



Hensen found this total number of ripe female cod in the North 

 Sea during the spring of 1895 to be 44,172,000. 



Numbers of edible fishes in the North Sea. In just the 

 same manner, that is from a knowledge of the total numbers of ova 

 produced during the spawning period (determined by quantitative 

 plankton observations) and from a knowledge of the fecundity of 

 the fishes considered (determined by actual observations), Hensen 

 and Apstein estimated that there were present in the North Sea 

 during the spring of 1895 : — 



Assuming, for the moment, that these figures are accurate we 

 will proceed to expand them. They apply only to the mature 

 spawning females of the species mentioned : the total numbers of 

 each species are obviously much greater. To the numbers given 



1 Ann. Rept. Scottish Fishery Bd. ix. Pt. 3, p. 254, 1891. 

 ^ Drepanopsetta limandoides. 



