The main concern appears to be whether it is in fact possible 

 to harvest certain fishery resources at optimum yield levels 

 while at the same time allowing the marine mammal popula- 

 tions which are predators of harvested fish species, to be 

 maintained at or above levels allowing maximum productivity. 

 Similar concerns have been expressed about the impact of 

 fish harvesting at OY levels on the rebuilding of stocks of 

 threatened and endangered species which may depend on them 

 for food. The perceived incompatibility in part appears to 

 rest on an interpretation of the optimum yield concept de- 

 fined in the FCMA as simply MSY . However, the definition of 

 OY is not synonymous with MSY, and incorporates, among other 

 things, a departure from MSY for ecological reasons. Such 

 ecological considerations could and should include the health 

 of the marine ecosystem, the maintenance of optimum sustain- 

 able populations of marine mammals , and support of critical 

 habitat for endangered or threatened species . If the eco- 

 logical factors incorporated in OY are given serious consid- 

 eration, then an interpretation of incompatibility of the 

 FCMA and MMPA does not seem either warranted or possible. 



The concepts of OY in the FCMA and maximum productivity 

 in the MMPA are like two sides of the same coin. The FCMA 

 focuses on potential yield from a given resource population 

 level, while the MMPA emphasizes the production required 

 to support that yield as well as non-consumptive uses of 

 the resource. A discussion of potential yield is not separa- 

 ble from a discussion of the productivity of a resource. Con- 

 sideration of productivity merely shifts emphasis from the 

 amount of the resource that can be removed to what makes the 

 yield possible in the first place. 



If a fishery is treated as the addition of a predator 

 to a system which already has some natural predators for 

 the target species, then the question of optimum yield for 

 the fishery can be considered as an allocation of production 

 among various predators , taking into account the relative 

 importance of, or value placed upon, each predator and the 

 requirements of each. 



It seems clear that with appropriate ecological con- 

 siderations, OY for a fishery can be consistent with support 

 of maximum net productivity of predator populations such 

 as marine mammals. The question of whether MSY, in contrast 

 to OY , is likewise compatible with optimum sustainable 

 populations of marine mammals has not been answered, but 

 will have to be addressed as part of the process of fish- 

 eries management that is compatible with both the FCMA and 

 MMPA. The resolution of that question will be based in 

 part on better operational definitions of optimum sustainable 



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