Building Model Credibility

This chapter assesses how state- and prediction-based theory (SPT), as a nontraditional approach to modeling adaptive behavior embedded in a nontraditional population modeling approach, faces a significant credibility challenge. This challenge is complicated by the many ways that models can gain or lose credibility, and widespread confusion surrounding the term model validation. The chapter then addresses the task of testing, improving, and establishing the credibility of individual-based models (IBMs) that contain adaptive individual behavior. The experience with the trout and salmon models provides the primary basis for this discussion, but other long-term modeling projects have produced similar experiences. The chapter summarizes some of the issues and challenges that typically arise and how they have been dealt with, before presenting lessons learned from two decades of empirical and simulation studies addressing credibility of the salmonid models.