FISHERY RESEARCH 321 



the eggs of the cod. This discovery stimulated the search 

 for the eggs of other fish and it has since been found that, 

 with only one exception, all our food fish have these drifting 

 eggs. This early piece of fishery research immediately 

 showed its practical value ; for, when the discussion arose- 

 about the necessity of putting restrictions on steam-trawling 

 because of the supposed destruction of eggs, the scientific 

 advisers were able to show that no such danger existed. 



It has been said that there was one exception to the rule 

 that our food fish have pelagic eggs. This exception is 

 the herring, whose eggs (Plate 112) stick in clumps to the- 

 bottom (see page 80). In this case however there is little 

 risk of their destruction by the trawls, because the eggs 

 lie well down in the crevices between the stones on tho- 

 rough ground on which they are laid, apart from the fact 

 that the rough grounds on which the herring spawn are- 

 generally so rocky and strewn with boulders that they are- 

 unsuitable for trawling. 



The eggs of the plaice and the herring having been accur- 

 ately described and identified by means of artificial fertiliza- 

 tion and by hatching, we can now proceed in our search for 

 the spawning grounds of these two fish. There are two 

 obvious ways of searching for these localities, firstly by seek- 

 ing for the eggs themselves and secondly by finding from the 

 statistics of the fishing industry at what places most of 

 the fish containing ripe roes were caught. The last method 

 obviously involves the least trouble (given the necessary 

 statistics), but it has the disadvantage that the results 

 are only approximate, as there is no evidence that the fish 

 would have actually spawned where they were caught 

 since they can swim a considerable distance in a short 

 space of time. 



Let us then consider the first method. Having roughly 

 marked out the spawning region by means of the statistical 



