With support from the Marine Conservation Action Fund (MCAF), a team of scientists is surveying the beaches of Senegal documenting the grave toll of bycatch on sea turtles. In the post below, project lead and MCAF Fellow Tomas Diagne, Director of the African Chelonian Institute, shares some background and findings of the study.
Sea turtles of Africa, have long been considered among the least studied of any of the world’s continents. Many African sea turtle mysteries remain unsolved, data gaps unfilled, and an array of serious threats need further study and conservation attention. But Africa is no longer the “Dark Continent” that it once was in regards to sea turtles, and today a vast array of local and international government, non-profit, academic, and community-based activists, researchers and conservationists are shedding new light on its mysteries and challenges.
The team gathers data on a deceased green turtle above and a leatherback below. Bycatch in fishing nets is suspected as the primary cause of death for the numerous turtles found on the beaches of Senegal.
Bounded by seemingly limitless turtle habitats in the Atlantic and Indian Oceans, and the Mediterranean and Red Seas, the principle challenge to fully understanding Africa’s sea turtles is the enormous scale of the task. Africa’s 53 countries (63 political territories) cover approximately one third of the land surface of Earth, an area the size of China, India, the United States and most of Europe combined. Five of the world’s seven sea turtle species (leatherbacks, olive ridleys, green turtles, hawksbills, and loggerheads) inhabit Africa’s waters and nest on these shores from Mauritania south to Angola in the West and South Africa north to Kenya in the East, and spend most or all their lives within the sphere of influence of this super continent. Even the Kemp’s ridley, endemic to the Caribbean and North Atlantic has occasionally been observed off the western coast of the continent as a sporadic visitor. Indeed, only one sea turtle species is completely absent from Africa: the Australian flatback. Virtually all African sea turtles are facing anthropogenic threats of one sort or another, and human pressure has taken an enormous toll over time.
Tomas Diagne at left, founded the Senegal Marine Stranding Network with support in part from MCAF.
The continent’s population of 1.2 billion people is growing fast, and has doubled since 1989. Sea turtles are important components of local culture and folklore among many African peoples, especially those that still cling to traditional animist beliefs, and turtles have been consumed for food and other traditional uses for millennia. In response to these growing threats and to a globally increasing environmental consciousness, most of the coastal African countries have developed national protective legislation for sea turtles.
During the last decade, some countries such as Republic of Congo, and São Tomé and Principe have enacted laws to specifically protect sea turtles, and most of the coastal countries of Africa are parties to international treaties protecting sea turtles, including the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES), the Convention on Migratory Species (CMS), and the Convention on Biological Diversity (CBD). In addition, two intergovernmental agreements enhance sea turtle protections on both sides of Africa: The Indian Ocean South East Asian (IOSEA) Marine Turtle Memorandum of Understanding, and the Abidjan Memorandum.
In Senegal, situated in the westernmost point of the Atlantic Coast of the African coastline, the waters are well known as the migratory hub for different species of sea turtles (Godley et al. 2003). All the following species have been documented and are known to occur in the region: green sea turtles, (Chelonia mydas), loggerhead, (Caretta caretta), olive ridley (Lepidochelys olivacea), and leatherback, (Dermochelys coriacea). However, very little work has been done to understand the unnatural causes of death, abundance, and seasonality of the different sea turtle species using this region.
In 2014, MCAF grantee, Tomas Diagne, director of the African Chelonian Institute (ACI) decided to act and launched the Senegal Marine Stranding Network. Since that time, Diagne and the ACI team have been regularly conducting beach surveys on the Atlantic coastline in the northern part of Senegal from Dakar to St. Louis, covering a total straight line distance of 184 km (see map below).
ACI lead the sea turtle component of these surveys, while other team members surveyed for cetaceans and seabirds. The main objective of these surveys was the first assessment of sea turtle and cetacean mortality along this remote and little developed coastline. During the very first survey, the team found an astonishing 65 rotten sea turtle carcasses including loggerhead, green, olive ridley, and leatherback sea turtles in various states of decomposition. The cause of this massive sea turtle mortality is related to bycatch, because fisheries activities are very intense offshore in this region.
Diagne and ACI are working with partners to continue documenting stranded animals and find ways to reduce this tragic and unsustainable bycatch mortality for West African sea turtle populations. One possible solution may be to implement the use of Turtle Excluder Devices TED to prevent turtles from dying in fishing nets. Stay tuned for more updates from the ACI team!