Posted on 06 March 2005
Five species of marine turtles occur in Tanzania’s waters. These include green, hawksbill, loggerhead, olive ridley and leatherback. Two species – green and hawksbill – nest. All are categorised by IUCN as endangered or critically endangered and are listed on Appendix I of CITES.
Populations are declining as a result of habitat destruction and alteration, overexploitation for meat and eggs, and incidental capture in gillnets and trawlers.
Although conservation and management efforts are underway in some areas of Tanzania including the Zanzibar islands of Pemba and Unguja, and Mafia, Bagamoyo, Temeke, Mkuranga and Mtwara districts on the mainland, the conservation status of turtles in Tanzania remains largely unknown. Information concerning population dynamics is incomplete, while knowledge of nesting populations and feeding habitats is patchy and of developmental habitats almost non-existent.
The green turtle is the most common and widespread species in Tanzania. While low density nesting has been reported along the mainland coast from Tanga in the north to Mtwara in the south, the most concentrated numbers of nests appear to be on the offshore islands of Zanzibar, Mafia and possibly the Songo Songo archipelago. The main nesting season is between February and July. Evidence from tag returns indicate that while some green turtles are probably resident, others are highly migratory moving to and from nesting and feeding grounds in Kenya, Seychelles, Comoros, Mayotte, Europa Island and South Africa.
Hawksbills are also widely distributed but are less abundant. Nesting has only been recorded in low numbers on small remote offshore islands such as Misali and Mnemba Islands in Zanzibar, the small islands off Dar es Salaam, Shungi-mbili Island in northwest Mafia and the Songo Songo archipelago. The most important nesting sites in Tanzania are Misali Island, off Pemba, and Mafia Island. The main nesting season is during the northeast monsoon between December and April. Although no animals bearing tags from other countries in the region have been recorded, the hawksbill is a migratory species so it is probable that Tanzania harbours both residents and migrants.
Little is known about the status of olive ridley turtles although they are no longer reported to nest. They were observed nesting on Maziwe Island south of Tanga in the mid 1970s but the island has subsequently submerged and no further nesting records for this species have been made. Local fishers report that they are occasionally accidentally catch in gillnets along the Tanzania coast and net captures have been confirmed in Mtwara, near the border with Mozambique.
Loggerhead turtles are relatively rare in Tanzania and there is no indication that they nest. However, evidence from tag returns signify that southern Tanzania and the Mafia area are important foraging grounds for loggerheads nesting in Tongaland and Natal in South Africa. Very little information is available on leatherback turtles because they are so rarely sighted and because indigenous knowledge is limited. Two leatherback turtles were caught in offshore waters on Pemba Island in 1997 and three were washed up on Mafia beaches in 2002 and 2003. This suggests that they may feed in the area or are en route to nesting sites in Natal.
The main threats to turtles in Tanzania are disturbance of nesting and foraging habitats, incidental net captures (gillnets and trawlers), poaching of meat and eggs, lack of adequate protection and enforcement, limited awareness and land-based development and pollution.
Recommendations for research and monitoring include: further studies on turtle reproduction, nest biology, foraging habitats, genetics and threats; and tagging to determine movements and breeding frequency.
Conservation and management priorities include: protection of key habitats, compulsory use of Turtle Excluder Devices by commercial prawn trawlers and restriction of gillnets in key foraging areas; promotion of community participation in the management of coastal and marine resources through recruitment of Community Turtle Monitors and involvement in Beach Management Units; awareness raising; development of a Turtle Recovery & Action Plan; coordination of activities at national and regional levels by the National Turtle Conservation Committee; and fund raising.