Replacement of MSY as a management concept will not be 

 simple. Sustainable yield calculations that incorporate im- 

 pacts of a fishery on the ecosystem as well as on the stock it- 

 self, and that allow for the impacts on alternate prey of a 

 shift in predation pressure, will be more complicated than MSY 

 calculations because they will involve more variables . More 

 realistic treatment of natural mortality is a good starting 

 place for departure from present MSY theory. New theories should 

 incorporate the effects of a fishery on predators, as well as the 

 effects of predators on a changing fishery stock. Incorporation 

 of more realistic predator prey interactions will be a step toward 

 whole ecosystem considerations in fisheries management. 



G-6 



