inappropriate, leading to reduction in a stock rather than 

 to sustained yields. Even where the MSY estimates are thought 

 to be fairly accurate, overcapitalization of a particular fish- 

 ery may result in economic pressures to exceed sustainable 

 yields by a constant increase in fishery yields year after 

 year, as opposed to a reduction or a leveling off at MSY levels. 



Insufficient data is not the only problem with the ap- 

 plication of MSY concepts to fishery resource management. When 

 several populations are harvested simultaneously in one eco- 

 system, stock recruitment relationships are blurred, and the 

 constant environment assumptions underlying MSY are particu- 

 larly strained (Gulland, 1978). Consequently, it seems rea- 

 sonable to infer that MSY has often been applied in situations 

 that do not meet the requirements for its application, which 

 may be partly responsible for some of the problems with MSY 

 oriented management. If MSY is not applicable, then increas- 

 ingly refined calculations of MSY estimates based on increas- 

 ingly complete data will not solve the problem of finding an 

 appropriate management strategy. Even if environmental con- 

 ditions are sufficiently constant so that there is an MSY 

 characteristic of a particular stock, and even if that MSY 

 value can be estimated accurately, MSY still may not be an 

 appropriate management goal because it does not take into ac- 

 count relationships between the target species and other pop- 

 ulations within the ecosystem. 



It is important to recognize that management for MSY for 

 several stocks simultaneously does not constitute ecosystem 

 level management. No matter how many stocks are to be managed, 

 MSY is in essence a single species approach because it does 

 not deal with interactions among the stocks that an ecosystem 

 perspective would consider. 



Unfortunately, there probably is not a simple replace- 

 ment for MSY (Gulland, 1978) . The development of a more 

 broadly based management approach, which would take into ac- 

 count environmental variations and ecological relationships 

 between the target species and those associated with or de- 

 pendent on it, appears to be necessary. .A starting point for ^ 

 changing from single species MSY type management to a broader 

 ecosystem perspective can be consideration of the impact of a 

 fishery on predator prey relationships and food availability 

 to natural predators in the ecosystem. Existing predator prey 

 theory can be incorporated and then improved as more complete 

 or more pertinent data are sought and become available. 



29 



