468 SOME RESULTS OF THE INTERNATIONAL FISHERY INVESTIGATIONS. 



and Cuttcgat it varies from 4 to 56 per cent. We may reasonably 

 conclude, eliminating exceptional circumstances, that the intensity of 

 plaice fishing on the North Sea fishing grounds varies from 10 to 25 

 per cent. That is to say, that man, for his own use, removes annually 

 from the sea from one-tenth to one-quarter of all the marketable plaice 

 which are annually produced by the natural reproduction and growth 

 of the species. 



How significant these results are from the point of view of the regula- 

 tion of the plaice fishery and its further exploitation and improvement 

 will easily be seen. The question now arises how far this process of ex- 

 ploitation of the (say) plaice population of our seas can go on without 

 progressive impoverishment of the fishing grounds. There must be some 

 limit up to which these fishing grounds can be depleted without under- 

 going injury; that is, without making them less productive in the future. 

 To discover this limit is the aim of this portion of fishery investigation, 

 and it then remains for the Governments concerned so to legislate that 

 it should not be exceeded. In no way can this knowledge of the 

 extent to which the resources of the sea can be strained be attained 

 than by scientific investigation on the lines indicated and by the 

 careful consideration of reliable commercial statistics. When the Inter- 

 national Investigations are completed and thoroughly discussed we 

 may hope for much more knowledge of the conditions of this problem 

 than we at present possess. 



Then in the result that plaice are so very variable in growth we have 

 a factor of no less significance for the legislators. 



When we find that the growth rate of plaice on a fishing ground 

 is small, we usually find that the number of small plaice present on 

 that ground is unusually large. There is, in fact, this relation between 

 abundance of plaice and their size, that the more numerous the fish are 

 on a certain ground the more slowly they grow. It is a question of 

 the available amount of food for the fishes that we have to consider. 

 Where the number of mouths is small there is all the more food for 

 them and the fishes grow quickly ; on the other hand, where the 

 population is large and the stock of food not proportionately large, the 

 fishes are less well nourished and they grow slowly. How significant 

 this question is when the protection of immature plaice (and other 

 fishes) is being considered is very apparent. In the past the protection 

 of immature fishes per sc has been considered as of undoubted value 

 for the fisheries.* Now we must remember that to " protect " by 

 legislative restrictions the immature fishes of particular fishing grounds 



* In sjiite of tlie declared opinion of Huxley, who deprecated such legislation if 

 incautiously embarked upon (Li/e and Letters of Thomas Henry Huxley, vol. ii. p. 234, 

 1900). 



