associated with various harvesting levels, and using tech- 

 niques for describing whole ecosystems employed in existing 

 ecosystem models. Future approaches to an ecosystem per- 

 spective can be based on improved data and theory for ex- 

 pansion of fisheries management concepts to replace MSY by 

 considering more variables. 



Conceptual Food Chain Models 



A fairly easy first step in broadening fishery manage- 

 ment perspective to a whole ecosystem basis is considering 

 how a target species fits into the foodweb of the ecosystem 

 of which it is a part. For each region and/or major marine 

 ecosystem within the U.S. FCZ a conceptual model should be 

 written down, just a box and arrow diagram, indicating trophic 

 relationships for all fishery resources and other components 

 of the ecosystem. Such conceptual models can provide a very 

 useful framework for viewing the fishery in its ecosystem 

 context. They are an aid to recalling complicated marine 

 foodwebs , and also to recognizing where factors influencing 

 a stock are unknown. Such conceptual models exist in the 

 minds of scientists and managers, but they should be written 

 down in order to be examined and used. Conceptual ecosystem 

 diagrams should appear as a figure in the background material 

 of each fishery management plan. These conceptual models 

 will be of use to various interest groups, federal agencies, 

 and persons not well grounded in fishery ecology, as well as 

 to fishery scientists themselves, as a reminder of the inter- 

 actions which should be considered in ecosystem level manage- 

 ment . 



Explicit conceptual foodweb diagrams are the first step 

 in an ecosystem perspective on management of any given tar- 

 get species. They merely reflect current understanding of 

 existing ecological relationships and can easily be modified 

 as that understanding increases. The writing of conceptual 

 models should not be confused with the achievement of an 

 ecosystem level management. Conceptual models are merely 

 the first step, a memory aid for ecosystem level management. 



Whole Marine Ecosystem Models 



While single species population dynamics models can be 

 quite elaborate, dynamic models of whole ecosystems are in 

 very preliminary stages. However, some models of marine eco- 

 systems have already been developed. 



43 . 



