limits of the allocated resources (i.e., time, money, and personnel) to enable 

 the manager to make a "best" decision. Making this trade-off work involves an 

 iterative exchange of expertise and expectations between modelers and managers. 

 It is critical that the manager and modeler work together from the outset of 

 the project and continue to collaborate during all stages of execution. This 

 will assure that the objectives and modeling approach are pertinent to the 

 decision and achievable. 



Besides assisting in the definition of program objectives, a modeler can, 

 in this initial phase of the program, assemble germane information in a framework 

 that pinpoints the modeling tasks that must be undertaken to meet the program 

 objectives. Once these tasks have been identified, time and funding limits set 

 by management along with the modeling needs will determine the sequence of 

 project activities and staffing requirements. The manager and modeler may have 

 to re-examine and renegotiate the program objectives. 



As field and laboratory specialists become involved in later stages of the 

 program, new and pertinent information will be generated. This additional 

 information, when compared with the objectives and plan of execution, may 

 indicate that another round of reformulation is needed. 



All parties (managers, modelers, and specialists) should jointly participate 

 in the development, calibration, and application of the model. They should 

 also participate in the interpretation of the results, especially with regard 

 to their relation to the management problem and program objectives. 



V. ADVANTAGES AND DISADVANTAGES OF VARIOUS MODELING APPROACHES AND TECHNIQUES 



Ecosystem modeling can be broadly defined as the application of mathematics 

 to quantitatively simulate ecosystem response to changing environmental 

 conditions. There are many different approaches to modeling ecosystem behavior, 

 and each has its advantages and disadvantages. Table 1 summarizes the Panel's 

 consensus on the advantages and disadvantages of various modeling approaches 

 and techniques as they relate to resource management and impact assessment needs, 



VI. AREAS OF HIGH PRIORITY, HIGH RETURN RESEARCH FOR ECOSYSTEM MODELING 



The following areas have been identified as high priority research which 

 would significantly enhance the value of ecosystem modeling as a marine resource 

 management and impact assessment tool. These research areas are not directed 

 towards ecosystem modeling per se. Rather, they define crucial gaps in our 

 understanding of basic ecological processes and interactions. 



1) The key question in fisheries is the stock recruitment relationship 

 which can be addressed by determining what factors affect egg, larval, 

 and juvenile survival. Basic questions which need to be addressed are: 



a) What are the early life histories of the species of concern?; and, 



b) What is the influence of predation as a mechanism for controlling 

 s to ck size? 



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