Cargados Carajos is a collection of low islets, coral reefs and sandbanks lying 350 km north-north-east of Mauritius, often called Saint Brandon. The area covers several thousand square kilometres, with a land area greatly affected by tides, but averaging around 300 ha on 18 islets. The shoals arise from a limestone plateau, such that water depth seldom exceeds 20 m. The crescent-shaped reef covers around 19,000 ha, and is 38 km long by 5 km wide, cut by three passes. The algal ridge is possibly the largest in the Indian Ocean. Islets, sandbanks and cays are mainly found on the west side of the crescent; the largest are Raphael, Avoquer, Ile Cocos and Ile du Sud. In addition, to the north and west of the reef lie Ile Frégate, Ile Perle, Ile du Nord and Albatros, of which the latter is the largest (101 ha) and highest (6 m) in the shoals. Typical vegetation is thicket of Tournefortia argentea and Scaevola taccada, with grasses and other herbs, although Casuarina equisetifolia, Terminalia catappa and coconut trees occur on a few islands. The seas are very productive and fishing has long been important. The main settlement is on Raphael, comprising a privately-owned commercial fishing station (with a minimum of 35 resident employees), coastguard and meteorological station (with eight residents in 1996). Tiny settlements exist on Avoquer, Cocos and Sud; the settlement on Albatros was abandoned in 1988. Natural resources collected incidentally include nesting sea-turtles (Chelonia mydas and Eretmochelys imbricata), crustaceans such as lobsters Panulirus, Octopus, seabirds and their eggs. Visits other than by fishermen or government personnel are very rare.
See Box for key species. No landbirds are present, and only small numbers of migrant shorebirds occur. However, Cargados Carajos supports large numbers of seabirds. Estimating populations for single colonies is very difficult, and at this site the multitude of colonies and brevity of visits compounds the problem. The most abundant species is Sterna fuscata (although the population has decreased from the 100,000 pairs estimated in 1975), but the numbers of four other tern species (Sterninae) are probably all of global or regional importance. Additional nesting seabird species (all apparently represented by less than 1% of the world population) are Fregata minor, F. ariel, Puffinus pacificus (one colony), Sula dactylatra (200 pairs on Ile du Nord in 1971, and still present 1996) and Phaethon lepturus (rare, 1996). The Fregata species have declined greatly from 1950s populations in the thousands, and Sula sula became extinct in the 1960s.
Non-bird biodiversity: Reptiles: nesting site for the sea-turtles Chelonia mydas (EN) and Eretmochelys imbricata (CR). Marine life: the coral reef and associated waters are extremely diverse, but the reef structure and coral fauna are largely unknown.
BirdLife International (2020) Important Bird Areas factsheet: Cargados Carajos Shoals. Downloaded from http://www.birdlife.org on 25/02/2020.