The Water-fern Salvinia molesta in the Sepik River, Papua New Guinea

Since 1977 the Sepik River backwaters between Pagwi and Angoram in Papua New Guinea have become increasingly covered by the exotic water-fern Salvinia molesta. By May 1979, Salvinia covered about 80 km2. Water chemical analyses for dissolved substances give no evidence that nutrients in the Sepik River and ‘lagoons’ might become limiting enough to affect the Salvinia population. The physical impact of the plant is reflected especially in the decline of the fisheries for Saltfish Tilapia (Sarotherodon mossambicus), crocodile hunting, collection of sago-palm, and in the slowing down or complete elimination of water transport. As a consequence, people in a number of villages are unable to reach markets and children cannot go to schools.A programme of management has been formulated which will involve the United Nations, central and provincial governments, and local inhabitants. However, it should be understood that there is little chance of complete elimination of the weed from Sepik River backwaters.