The ghosts of overfishing past that haunt present day fisheries management

Fish biomass is the most widely used indicator of fish stock health. Stocks whose biomass is or has previously collapsed owing to overfishing, and the management systems built around them, may carry a memory of decline, even if biomass has recovered. This is because stock biomass as the main indicator of stock health does not represent all aspects of stock health and biomass can possibly become a weaker indicator of health after stock collapse. These latent weaknesses have been termed “ghosts of overfishing past”. Not accounting for ghosts can impact the speed of stock recovery and susceptibility to further collapses. This concept has been popularised by Professors Jeff Hutchings, Anna Kuparinen, and others. Ghosts are varied and can include changes in vital rates, phenotypic response, fish behaviour, and aspects of the human system such as institutional inertia, fisheries subsidies, and income portfolios. The presence of ghosts has implications for fisheries management: altering stock biomass objectives (dynamic reference points) may be appropriate for populations that have experienced collapse even if biomass has recovered. Ghosts should be considered when developing management strategies for populations that have previously experienced large declines.