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What is Over-fishing?* 



By 

 Dr. C. G. Joh. Petersen, Copenhagen. 



(With one Diagram.) 



For the sake of argument I will suppose : 



I. That in a biologically self-contained area, c.ij. in the North Sea, 

 statistics show that the value of the total yearly catch of a certain 

 species of fish is decreasing year by year ; 



II. That the catching power and the prices are not reduced ; 



III. That the physical conditions have not changed in an unfavour- 

 able manner. 



The decrease must then be ascribed to organic factors, either to man 

 or to other organisms. 



If the decrease must be ascribed to man solely, or in some degree, 

 over-fishing has taken place. 



It will be understood that over-fishing cannot easily be proved with 

 regard to many species of fishes, e.g. for true migratory fishes. For 

 example, in the case of the herring and the cod statistics have always 

 shown great fluctuations. For this reason it is necessary that statistics 

 in the case of such fishes should extend over a very long time to prove 

 any decrease beyond the ordinary fluctuations. In dealing with other 

 fishes, e.g. the plaice, the statistics do not fluctuate so much because the 

 plaice is not so migratory. However, if we had statistics alone to 

 depend upon, the problem concerning the influence of man would never 

 be solved. Any decrease might always be ascribed to some or other 

 imagined reasons. Fortunately we can get more than statistical data 

 to rely upon. 



It is not my intention here to discuss all problems about over- 

 fishing, this being impossible. I only wish to give an example in 



• This analysis of the problems of over-fishing was prepared to meet a desire expressed 

 by several members of the International Committee on Over-fishing during the last meeting 

 of the International Council at Copenhagen. — W. G. 



