The Seychelles Bank lies at the northernmost point of the Mascarene Ridge
(north-east of Madagascar) and is a large, shallow area of water (some 31000 km2), mostly not deeper
than 100m. In its center are a number of high granitic islands of continental origin. These have been referred to as a
"micro-continent", having been left behind during the northwards migration of the Indian sub-continent about 135×E6 years ago. These islands are surrounded by widespread but discontinuous
fringing reefs.
Reef Sites of the Seychelles: Coral cover varies, being virtually absent from some
reef structures, but abundant in other areas, including non-reefal slopes and granitic surfaces. The low coralline outer islands to
the south-west of the main island of Mahé are grouped into a number of geographic sections. The largest is that
of the Amirante Islands, which extend along a shallow north-south ridge, with the Alphonse group forming a
slightly separate southern section of this chain. Further south are two small and more disparate island groups, those of
Providence, Farquhar, Cosmoledo, and the Aldabra group. Finally, directly to the south /
south-east of the main island of Mahé are the isolated islands of Platte and Coetivy. The reefs in
these outer island areas are highly varied, and include true atolls (St. Joseph, Alphonse, Farquhar), raised atolls
(Aldabra), submerged or partially submerged atolls (Desroches, Coetivy), and platform or bank structures
(African Banks, Providence-Cerf). Prior to the 97/98 ENSO event, coral cover varied considerably between localities,
ranging from close to zero on some banks and reef slopes (notably the larger Providence-Cerf Bank), to 60-70% on some
atoll slopes. Along the main islands, east coast of Mahé and the west coast of Pralin fringing reefs were
well developed; e.g. reef slopes descending to a floor typically at 8-12m follow reef flats reaching over 2km in width and
terminating in a high algal ridge. Such clearly zoned reefs are less apparent in more sheltered locations where more complex reef
formations have developed. The Seychelles lie in an area of relatively high faunal diversity. Some 100 hermatypic and 7 endemic
coral species (Veron, 2000) and 920 fish species (Spalding; 2001) have been listed. The reef fauna is typical of
the western Indian Ocean, as exemplified by the reef fish: many are widespread across the ocean basin or wider areas of the
Indo-Pacific, however, about 15% are confined to the western part (Spalding, et al, 2001).