A new indicator is described that uses multivariate posterior predictive data arising from management strategy evaluation (MSE) to detect operating model misspecification (‘exceptional circumstances’) due to changing system dynamics. The statistical power of the indicator was calculated for 5 case studies for which fishery stock assessments have estimated changes in recruitment, natural mortality rate, growth, fishing efficiency and size selectivity. The importance of the component data types that inform the indicator was also calculated. The indicator was tested for multiple types of management procedures (e.g. catch limits by stock assessment, size limits, spatial closures) given varying qualities of data. The statistical power of the indicator could be high even over short time periods and depended on the type of system change and quality of data. Statistical power depended strongly on the type of management approach, suggesting that indicators should be established that rigorously account for feedbacks between proposed management and observed data. Management strategy evaluation processes should use alternative.