Hiroyuki Yokomizo
(Department of Biology, Faculty of Sciences, Kyushu University)

06/01/25, 13:30 at Room 3521 (5th floor of building 3 of the Faculty of Sciences)

I consider optimal conservation strategies for an endangered population. In conservation decision-making I must cope with many kinds of uncertainties in the survivorship or density of the population. Assumptions are: the survivorship of an endangered population is affected by unpredictable environmental fluctuations and can be improved by conservation effort, and the exact value of the initial population density is unknown. The conservation strategy involves two aspects: monitoring effort to improve the estimate of the initial population density and conservation effort. Both types of effort imply economic costs. The optimal management strategy minimizes the weighted sum of the extinction probability, the economic cost of the conservation and the monitoring effort. [1] I analyze the optimal conservation and monitoring efforts, when the current population density is known accurately. [2] I consider the situation in which there is only limited information (i.e. a cue) about the population density. [3] I discuss the cases where the cue accuracy can be improved by monitoring of the population. Next I consider optimal conservation strategies for a population whose viability is jeopardized by an alien speciesas well as a random environmental factor. I assume that the survivorship of the endangered population can be improved by a resource-enhancement effort plus an extermination effort that decreases the population density of the alien species. Both efforts decrease the extinction probability of the endangered population, but they are accompanied by economic costs. I derive conditions for the optimal resource-enhancement effort and/or extermination effort to be positive and obtained optimal effort levels.

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