While many fish stocks around the world are in peril, fish have been doing well in parts of Papua New Guinea. To maintain healthy fish stocks, the people who rely on these fish for food and trade didn’t turn to some new technology. Instead, they turned to the past. Inhabitants of Ahus Island, Manus Province, Papua New Guinea, have followed a generations-old practice of restricting fishing in six areas of their reef lagoon. While line fishing is permitted, net and spear fishing are restricted based on cultural traditions. The result is that both the biomass (the total weight of the organisms) and individual fish sizes are significantly larger in these areas than in places where fishing is completely unrestricted.
Ahus Island lies in the Admiralty Islands chain off the northern coast of Papua New Guinea, roughly 30 kilometers from the provincial capital, Lorengau. The Enhanced Thematic Mapper Plus (ETM+) instrument on NASA’s Landsat satellite captured this true-color image of Ahus Island on February 20, 2000. In this image, coral reefs stand out from their surroundings because of their shallower waters, shown in aquamarine. Exposed or shallow reefs at the reef edges tend to cause ocean waves to break, showing white foam as the cresting waves appear. White puffy clouds appear throughout the scene. The dense green forests on Manus Island contrast sharply with the dark blue of deep ocean and the aquamarine color of shallow areas. In the large format image, roads in the hills of Manus Island appear in brown and generally follow the tops of ridges.
Even though traditional management of the reefs shown here preserved fish and increased individual fish sizes, these were not the primary motivations for the practice, said the group of biologists who discovered the benefit of fishing restrictions on Ahus Island. Describing their findings in Conservation Biology in 2005, the group said that cultural practices restrict fishing in parts of the reef—sometimes for a period of years—after the death of a prominent individual. After the mourning period ends, inhabitants celebrate with a feast, harvesting the fish they have avoided catching though spear or net fishing. By avoiding over-fishing these stocks, the residents ensure a big supply of food for the celebration. The healthy fish stock also gives the islanders something to trade with mainland village neighbors for goods such as vegetables and timber. Maintaining good trade relations is an important supplement to the livelihoods of the islanders since their agricultural prospects are limited by land shortages and poor soil.
NASA image created by Jesse Allen, Earth Observatory, using data provided by Timon McPhearson, American Museum of Natural History, Science Bulletins.