?IOLOCICAL RESEARCH 



Fishing Effort 

 (vessels + gear) 

 expressed in 

 physical terms 



Fish stocks 



Catches 

 (in weight of fish 



for each stock) 



ECONOMICAL RESEARCH 



Cost of Fishing Effort 



Returns 

 from the sales 

 of the landings 



Figure 1. — The basic components of the fishing process. 



fluctuations of abundance. As shown by Figure 

 2, these curves of maximum and minimum yields 

 accentuate departure from MSY as compared 

 to the average curve with increasing fishing 

 effort (and, after the point of MSY, increasing 

 overfishing). The reason is that the more in- 

 tensive is the fishing effort, the faster the year 

 classes are exhausted, as there are often rather 

 wide fluctuations in the strength of the succes- 

 sive year classes. The fluctuations of the catches 

 can only be increased with a faster exhaustion 

 of the best year classes. 



As shown by Figure 2, it is difficult to 

 evaluate the social cost of fishing effort unless 

 we have the simple case of a given fleet exploit- 

 ing a given fish stock. In such a case, the losses 



of years of bad catches are compensated by the 

 profits made in better years. Or, if the market 

 for the landings is also isolated, it might be that 

 the returns are more or less equalized by higher 

 prices when there is a scarcity in landings and 

 lower prices when the landings are more 

 abundant. 



For mixed fisheries. Figure 2 should be 

 transformed into Figure 3, thereby taking into 

 account the fact that the fishing fleet exploiting 

 a given stock at a given average level is maxi- 

 mum when the abundance in the given stock is 

 maximum and when the abundance in the other 

 stocks that can be fished by the same fleet is 

 minimum, and vice versa. No stock can be 

 subject to a stable fishing effort. It will vary 



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