The authors investigated traditional coral reef management practices at Ahus Island, Manus Province, Papua New Guinea, to evaluate their social role in the community and potential to conserve reef ecosystems. At Ahus the reef tambu areas operate within the context of a complicated customary marine tenure system that regulates access to specific reef areas, target species, and harvesting methods. Ahus Islanders claim exclusive rights to all marine resources on the reefs surrounding their island, the neighboring and uninhabited Onetta Island, and the reefs between Ahus Island and the coast of Manus Island. Ownership rights help create an economic monopoly on marine resources among fishing communities (Malinowski 1935). The reefs surrounding Ahus Island are divided into areas owned by specific clans. It is through this clan ownership of delineated reef areas that the tambu areas are maintained and enforced. Some families also own the rights to harvest certain species (including turtle, coral, and sea cucumbers) or harvesting technology (such as traditional nets), which are not restricted spatially. For generations, Ahus Islanders have prohibited spear and net fishing within six delineated areas of their reef lagoon. One to three times per year, fish are briefly harvested from the restricted areas to provide food for ceremonial occasions. Underwater visual censuses of fishes revealed a significantly greater biomass and average size of target species within the restricted areas (205 kg/ha ± 20 [SE]; 102 mm TL [total length] ± 0.7) compared with areas without fishing restrictions (127 kg/ha ± 13 SE; 85 mm TL ± 0.7). The authors estimated the biomass of fish removed during one of the harvest events was 5 to 10% of the available biomass within the restricted area, and in underwater visual surveys conducted before and after a harvesting event and detected no effect of harvesting on fish stocks. Compliance with the fishing restriction is attributed to its perceived legitimacy, its ability to provide the community with direct and indirect benefits, and its reflection of local socioeconomic circumstances. Limited-take closure systems that can serve the needs of a community may provide a viable conservation alternative in situations where compliance with fully closed protected-area regulations is low and resources for proper enforcement are untenable.