Fishery management under multiple uncertainty

Among others who point to environmental variability and managerial uncertainty as causes of fishery collapse, Roughgarden and Smith (Proc. Natl. Acad. Sci. 93 (1996) 5078) argue that three sources of uncertainty are important for fisheries management: variability in fish dynamics, inaccurate stock size estimates, and inaccurate implementation of harvest quotas. We develop a bioeconomic model with these three sources of uncertainty, and solve for optimal escapement based on measurements of fish stock in a discrete-time model. Among other results we find: (1) when uncertainties are high, we generally reject the constant-escapement rule advocated in much of the existing literature, (2) inaccurate stock estimation affects policy in a fundamentally different way than the other sources of uncertainty, and (3) the optimal policy leads to significantly higher commercial profits and lower extinction risk than the optimal constant-escapement policy (by 42% and 56%, respectively).