We consider optimal conservation strategies for endangered populations. In decision-making of conservation, we must cope with many kinds of uncertainties in survivorship or population size. Assumptions are: the survivorship is affected by unpredictable environmental fluctuation and can be improved by conservation effort, and the exact value of the initial population size is also unknown. The conservation strategy involves two aspects: monitoring effort to improve the estimate of the initial population size and conservation effort. Both types of effort imply economic costs. The optimal management strategy minimizes the weighted sum of extinction probability and the economic cost of the conservation and the monitoring effort. [1] We first analyze the optimal conservation effort when the current population size is known accurately. [2] Next, we consider the situation in which there is limited information (i.e. a cue) on population size. [3] We subsequently discuss the cases where the cue accuracy can be improved by monitoring of the population. Next we discuss multiple year optimization of conservation effort and monitoring of population size.

We consider the optimal harvest strategy for deer populations in Hokkaido. Large deer populations have damaged forests and agricultural areas. We need to decrease population size to an appropriate level. First, we consider estimation of population size of deer in Hokkaido using computer simulation. Next we estimate the ratio of future population size to that in 1993 in several harvest scenarios. Because the number of hunters is limited, we also examined optimal allocation of hunting effort to eastern Hokkaido and west-central Hokkaido.