This article analyzes the importance of non-use values in the management of natural resources with a model of imperfect competition. By constucting a framework of duopolistic exploiters, the incorporation of non-use values based on self-interest and altruistic motives appears to be significant for determining the degree of inefficiency caused by the problem of common property at the non-cooperative Nash equilibrium. It is found that when the non-use value placed by the altruist exploiter is bounded by that placed by the pure selfinterest exploiter ,the effect of market power is dominated by the effect of common exploitation. In this case.the exploiters harvesting strategy will response in the same direction to the change of each others harvesting at the non-cooperative Nash equilibrium. In contrast ,when the non-use value placed by the altruist is substantially larger or smaller than that placed by the self-interest exploiter,one exploiters increase in harvesting will lead to a decrease in harvesting of the other exploiter at the non-cooperative Nash equilibrium.