SSMSE: An R package for Management Strategy Evaluation with Stock Synthesis Operating Models

Abstract

Management Strategy Evaluation (MSE) is a decision-support tool for fisheries management. MSE uses closed-loop simulation to evaluate the long-term performance of management strategies with respect to societal goals like sustainability and profits (Punt et al., 2014 ; Figure 1;Smith, 1994). Management strategies are pre-defined decision rules that can dynamically adjust management advice given an estimate of population status. In addition to specifying management actions, management strategies may specify how a stock assessment model is configured to determine the size and status of a population (Sainsbury et al., 2000).Within MSE simulations, operating models (OMs) represent the hypothesized dynamics and relevant complexity of the system. Multiple OMs are typically generated for a single MSE to reflect different uncertainties and assess management performance under uncertainty. Developing suitable OMs requires an analyst to, at a minimum, define: the life history characteristics of the population and the fishing effort and selectivity of all fisheries affecting the population; and consider: the spatial distribution of the population and any critical environmental covariates or species interactions. OMs should be calibrated (or "conditioned") on available data to ensure that model projections are consistent with historical observations (Punt et al., 2014). Due to the many considerations, developing sufficient OMs is time-intensive.Fortunately, the requirements for specifying OMs are largely the same as the requirements for developing a stock assessment. Due to the overlap in requirements and the millions of dollars invested in developing stock assessments (Methot, 2015), MSE approaches that build on previous stock assessment products can increase productivity (Maunder, 2014). Stock assessment models for federally managed species in the U.S. undergo substantial scrutiny during a peer review process (Brown et al., 2006;Lynch et al., 2018), and thus stock assessment models provide an excellent starting point for OMs used in MSE.Stock Synthesis (SS3, Methot & Wetzel, 2013) is a generalized single-species population dynamics modeling platform widely used to assess marine fish populations. In the U.S., more