Bang for buck: cost-effective control of invasive species with different life histories

Strategies for controlling invasive species can be aimed at any or all of the stages in the life cycle. In this paper, we show how to combine biological data on population dynamics with simple economic data on control costs options to determine the least costly set of strategies that will prevent an established invader from continuing to increase. Based on biological data alone (elasticities of matrix population models), effective control strategies are sensitive to both life history and rate of population growth. Adding economic considerations, however, can cause the optimal control strategy to shift, unless the costs of intervention are the same across life stages. As an example, we apply our methods to oyster drills (Ocinebrellus inornatus), an economically important aquaculture pest that has been accidentally introduced worldwide. Control efforts are applied to local tidelands through manual removal of adults, although the life history characteristics of the species indicate a low population elasticity for adult survival. Aquaculturists are making bioeconomic decisions to remove adults vs. egg capsules, because of the relative ease of controlling each stage.