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The Orango National Park is part of the Biosphere Reserve of the Bijagós Archipelago of Guinea-Bissau, West Africa (Figure 1). The Park includes 5 main islands and associated islets, covering 268 km², which constitute almost one third of the total land surface of the Bijagós Archipelago. The main islands are low-lying, covered with forest and savannah, and surrounded by large areas of inter-tidal sand, mudflats, and extensive areas of mangrove. The human population is approximately 2500.

Preliminary surveys of the Bijagós found important populations of marine turtles in the area (Limoges & Robillard 1991), mostly concentrated on the island of Poilão (outside the National Park), where thousands of green turtles are thought to nest annually (Fortes et al. 1998). During 1993 and 1994, a survey of all the main beaches of the Orango National Park was conducted by investigators of the Guinean Environmental Agency with financial support from the IUCN. Technical and logistical problems prevent any rigorous quantitative estimates to be made from the data gathered so far. However, field observations are sufficient to draw some general conclusions concerning the status of breeding sea turtles in the Park.

Four species of turtle were recorded nesting during the surveys: green Chelonia mydas, olive ridley Lepidochelys olivacea, hawksbill Eretmochelys imbricata and leatherback Dermochelys coriacea turtles. We estimate that each of the first two species lay at least 200-300 nests per year on the beaches of the Park. Hawksbill and leatherback turtles seem to be very rare and only a few individuals/nests were recorded during two years of surveying. However, the difficulty of distinguishing between the tracks of hawksbill and ridley turtles might have resulted in this species being under-recorded. Although this nesting population of green turtles is probably less significant than that of the neighbouring Poilão and associated islands, Orango National Park is likely to be the most important nesting ground in the Archipelago for the remaining species which are rare or absent in Poilão.

The most important nesting area in the Park is Adonga (see Figure 1), an uninhabited sandy islet 11 km long.

However, turtle nesting was recorded on all sandy beaches facing relatively open waters, i.e. excluding areas in narrow channels between islands.

Green turtles nested mostly during the rainy season (May to October), while peak olive ridley nesting was recorded from December to February. Female hawksbills were seen both in January and June, while leatherback records come from December and January.

Several potentially serious threats affect the sea turtles in the area. Nest predation has not been well quantified but appears to be severe in the Orango National Park, with at least half of all clutches being destroyed. Humans (both local people and foreign fisherman operating in the area), monitor lizards (Varanus sp.) and ghost crabs (Ocypode cursor) are all frequent predators of eggs. Some adult females are also taken by locals while nesting on the beaches. The Park authorities have no means to enforce national legislation that protects the turtles and their nests. There are few Park guards and they seldom patrol the nesting areas.

Another important, yet unquantified threat is represented by demersal fisheries for shrimp, fish and squid in the region that surrounds the Archipelago. The licensed trawling fleet, 202 strong in 1997, included ships from several countries, with large numbers coming from China, Portugal, Spain and Italy. None of these vessels are known to use marine turtle excluder devices in their nets. Semi-industrial and artisanal fisheries for shark, barracuda and other large fish also exist in the area. Although we have information showing that turtles are regularly caught by both industrial and artisanal fishermen, the mortality caused by these activities has not been quantified. Currently we are trying to implement a programme allowing a better estimation of the importance of the bycatch of the fisheries in Guinea-Bissau. In addition, further work will determine the importance of the turtle populations in the whole Archipelago and the possible impact of the harvesting of adults and nests.

FORTES, O., A.J. PIRES & C. BELLINI. 1998. Green turtle, Chelonia mydas, on the island of Poilão, Bolama-Bijagós Archipelago, Guinea-Bissau, West Africa. Marine Turtle Newsletter 80:8-10.

LIMOGES, B. & M. ROBILLARD. 1991. Proposition d'un plan d'amenagement de la Reserve de la Biosphére de l'Archipel des Bijagós. Vols. 1 & 2. CECI/IUCN. 271pp.