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Marine turtles do not recognize political boundaries, nor do they have regard for Exclusive Economic Zones (EEZ s), cooperative agreements, international conventions, or memoranda of understanding between countries. So is it in the Southwest Indian Ocean (SWIO), a region that hosts some of the most important green turtle nesting sites in the world, most of which are isolated on remote islands (e.g. Europa and Glorieuses, Aldabra and Cosmoledo, Moheli and Mayotte). This region of the world is known to have year round nesting of green turtles but all sites display a marked nesting season. However, very little is known about migratory pathways that sea turtles ply between their nesting and feeding grounds in this region where this species faces numerous threats such as fisheries interaction at both open sea and coastal waters.
From 2009 to 2011, we deployed 81 satellite transmitters on nesting green turtle females during (d) and opposite (o) to the nesting peak in 5 important rookeries of the South West Indian Ocean (SWIO): Europa (Nd=10; No=10), Glorieuses (Nd= 10; No=10), Tromelin (Nd= 10; No=10), Mayotte (Nd=10; No=10) and Mohéli (Nd=7; No=3) and collected previous 24 old tracks in the area for a total of 105 tracks. First results showed that 39.7% of the tracked turtles used Madagascar costal foraging ground while more than 50% used the east African ones (Mozambique (32,0%), Kenya (3.8%), Tanzania (15,4%) and Somalia (2,5%)). It is worthwhile noting that the North Mozambique and South Tanzania remain the most important foraging ground for the tracked turtle (45% of the tracked turtles), but that they are mainly used by turtles tagged during the nesting season. On the other hand, we highlight here that green turtles also use a large range of foraging ground in the area (55% of the tagged turtles), some of them being hot spots (e.g. south of Maputo – Mozambique, Tulear lagoon – Madagascar).
Spatial distribution estimation allowed identifying important year round coastal and oceanic migrating corridors: 2 oceanic corridors, (1) in the north of the Mozambique Channel (11°S - 14°S) and (2) the south of the Mozambique Chanel (17°S - 23°S), more particularly from the north of Europa to the north of Mozambique (38°E - 41°E); and 2 coastal corridors (1) The east African coast, between 16°S (Mozambique) and 7°S (Tanzania), and (2) all the west coast of Madagascar. The extreme north of Madagascar is also an important coastal migratory corridor
The 105 tracked green turtles also crossed as many as nine different EEZs in the region before reaching their foraging grounds, which themselves are shared by six countries.
Such spatial migrating pattern of adult green turtle, the temporal corridors and the regional feeding hot spots identified are of high importance to implement targeted mitigating measures for artisanal and industrial fisheries and encourage conservation on key foraging grounds.
