Abstract

Among others who point to environmental variability and managerial uncertainty as causes of ¯shery collapse, Roughgarden and Smith (1996) argue that three sources of uncertainty are important for ¯sheries management: variability in ¯sh 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 ¯sh stock in a discrete-time model. Among other results we ¯nd: (1) when uncertainties are high, we generally reject the constant-escapement rule advocated in much of the existing literature, (2) inaccurate stock estimation a®ects policy in a fundamentally di®erent way than the other sources of uncertainty, and (3) the optimal policy leads to signi¯cantly higher commercial pro¯ts and lower extinction risk than the optimal constant-escapement policy (by 42% and 56%, respectively).

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