Spatio-temporal modelling of fish stocks: deriving spatially-explicit MSY references points using a metapopulation model

Abstract

Many fisheries are successfully managed using reference points (RPs) based on the maximum sustainable yield (MSY), in particular fMSY , the fishing mortality rate that achieves MSY. Typically, fMSY is derived assuming fish are homogeneously distributed in space. However, fishing should be spatially allocated to optimize yields and reduce stock depletion, and fMSY should be derived assuming fish are heterogeneously distributed. In this thesis, we apply a deterministic, age-structured model to derive spatially-explicit MSY RPs. We develop a metapopulation model with a source-sink, larval- advection dynamic to calculate fMSY and other related RPs for a two-box model. We also derive MSY RPs for a three-box model for several unique connectivity patterns, and develop a framework to derive RPs for an n-box model. We conclude that spatially-explicit MSY RPs can be more sustainable than values derived through a one-box model RPs, but usually provide less yields.