Uncertain biomass shift and collapse: Implications for harvest policy in the fishery

This paper addresses uncertain biomass shifts in renewable resources. A biomass shift occurs when a dominant renewable resource stock collapses and its ecosystem niche is filled by a replacement species which increases in abundance after the initial collapse. This paper develops a bioeconomic model for a fishery subject to random biomass shift. Optimal policy for three causes of biomass shift-environmental perturbation, over-fishing, and a combination of these two factors-is derived and compared to optimal policy when the risk of biomass shift is not present. For each cause of biomass shift, the model allows for a valued and non-valued replacement species.