A Stepwise Fitting Procedure for automated fitting of Ecopath with Ecosim models

Abstract

The Stepwise Fitting Procedure automates testing of alternative hypotheses used for fitting Ecopath with Ecosim (EwE) models to observation reference data (Mackinson etal. 2009). The calibration of EwE model predictions to observed data is important to evaluate any model that will be used for ecosystem based management. Thus far, the model fitting procedure in EwE has been carried out manually: a repetitive task involving setting >1000>1000 specific individual searches to find the statistically ‘best fit’ model. The novel fitting procedure automates the manual procedure therefore producing accurate results and lets the modeller concentrate on investigating the ‘best fit’ model for ecological accuracy

Comparing the network structure and resilience of two benthic estuarine systems following the implementation of nutrient mitigation actions

“…We also acknowledge the need to raise the standards of Ecopath models in a management context (Heymans et al, 2011;2016), with similar standards needed in exploring ecosystem theory (Pocock et al, 2016). Within the last few years, a growing number of diagnostic checks, including the PREBAL checks used in this paper, have been developed to establish best practices in creating and using such models (Mackinson et al, 2009;Darwall et al, 2010;Link, 2010;Scott et al, 2016). These guidelines take into consideration the underlying thermodynamic and ecological rules available to users, recommend approaches to balance an Ecopath model, and how to evaluate uncertainty.…”

Better Together: The Uses of Ecological and Socio-Economic Indicators With End-to-End Models in Marine Ecosystem Based Management

“…Fundamental changes to the model structure and behavior would likely occur through the incorporation of indicators to end-to-end models compared to current versions that operate without. For example, including existing indicator time series in the model fitting process (e.g., Scott et al, 2015) or Monte Carlo routine (e.g., Steenbeek et al, 2018) would constrain model outputs, change simulation results, and potentially improve model uncertainty. Much like the integration of harvest control rules for fisheries into end-to-end model MSE simulations, management actions based on systemic properties through indicators can be used in the simulation process to track management actions based on ELRPs (Figure 1).…”

The necessity of a holistic approach when managing marine mammal–fisheries interactions: Environment and fisheries impact are stronger than seal predation

“…The Ecosim model was calibrated using an automated stepwise fitting procedure that searched for vulnerability multiplier parameters that maximized statistical fit to observed time series (Scott et al 2015 ). We used observation data on relative biomasses and catches (1974–2015), obtained from ICES (Tomczak et al 2012 ; ICES 2017a ) for model calibration.…”