PARENT SESSION
Poster Session 17: Modelling
Wednesday, August 10, 5:00 PM - 6:30 PM, Exhibit Hall 220 A-E, Level 2, Palais des congrès de Montréal

A theoretical model for finding the optimal strategy for protection of endemic and extermination of alien species.

Yokomizo, Hiroyuki^*,1, Haccou, Patsy², Iwasa, Yoh¹, ¹ Department of Biology, Fukuoka, Japan² Institute of Biology, Leiden, The Netherlands

ABSTRACT- We consider optimal conservation strategies for a population whose viability is jeopardized by an alien species (such as e.g. a predator) as well as a random environmental factor (e.g. humidity). We assume that the survivorship of the endangered population can be improved by a conservation effort plus an extermination effort that decreases the population size of an alien species. Both efforts decrease the extinction probability of the endangered population, but they are accompanied by economic costs. The optimal conservation strategy minimizes the weighted sum of the extinction probability and the economic costs. In this way we devise practical guidelines for conservation. We derived conditions for the optimal conservation and/or extermination effort to be positive and obtained optimal effort levels. It turns out that, when conservation as well as extermination should be used, the optimal extermination effort level does not depend on the population size of the endemic species.

Key words: protection and extermination, alien species, fluctuating population, theoretical model