Empirical and model-based control rules

From their first incarnation within the International Whaling Commission (IWC), management procedures (MPs) were model based, essentially being stock assessment models with associated harvest control rules (HCRs) (de la Mare 1986). The term model based means that observed data are fitted within a statistical framework that assumes a population dynamics model with associated parameters. The outputs of that fitting process (e.g. abundance, productivity, fishing mortality and trends thereof) are then used in an HCR (as either parameters or driving indices). However, more recently there has been a move towards empirical MPs (Geromont et al. 1999, De Oliveira and Butterworth 2004, de Moor et al. 2011) where derived statistics and trends from the raw observations are used in the HCR. In this chapter I will briefly cover the history of modelbased and empirical MPs, in both the literature and actually implemented, as well as the pros and cons of their utility within a full MSE framework. Finally, including worked examples, I will discuss how recent advances in both stock assessment and MSE suggest that a fusion of both approaches has real potential for future MPs.