Ecologically or Biologically Significant Areas (EBSAs)
published:12 Jun 2015
The Walters Shoals, on the southern part of the Madagascar Ridge are steep-sided and cone-shaped with flat tops (minimum depth 15m) covered by coral reefs of broken and jagged relief, especially long the outer edges. Their base is defined by the 800 m isobath. They are the only known habitat of the recently described giant species of spiny lobster, Palinurus barbarae (Decapoda Palinuridae) (Charles Griffiths, pers. comm.) and 30 to 40% of the shallow water fish fauna of Walters Shoals is endemic to some part of the West Wind chain of islands and seamounts (Collette and Parin 1991).
The Walters Shoals lie on the southern tip of Madagascar. The shoals are cone-shaped with flat tops (minimum depth 15m) and their base is defined by the 800 m isobath. The flat top is covered by coral reefs of broken and jagged relief, especially long the outer edges. The slopes of the shoals are steep; the angle of the incline ranges from 6 to 12°. The Walters Shoals are the only known habitat of the recently described giant species of spiny lobster, Palinurus barbarae (Decapoda, Palinuridae) (Charles Griffiths, pers. comm.) and 30 to 40% of the shallow water fish fauna of Walters Shoals is endemic to some part of the West Wind chain of islands and seamounts (Collette and Parin 1991). Finally, Walters Shoals are believed to be an important foraging area for leatherback turtles and possibly for the population of 450 pygmy blue whales in the area.
Southern Indian Ocean
Between 33°9-16'S, 43°49-56'E. The base of the area is defined by the 800 m isobath.
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The Madagascar Ridge consists of a massive elevation of the bottom, extending between the micro-continent of Madagascar Island and the Western Indian Ridge for a distance of almost 700 miles. The ridge crest is wide and has depths from 1 000 to 2 500 m (at the positions of seamounts, up to 567 m). The minimum depth on the Walters Shoals is 15 m. The shoals are cone-shaped with flat tops, and their base is defined by the 800 m isobath. The flat top is covered by coral reefs of broken and jagged relief, especially long the outer edges. The slopes of the shoals are steep; the angle of the incline ranges from 6 to 12°. The sediments consist of foraminiferous ooze enriched with sand along the crests (Kanaev, Neyman and Parin 1975)(Romanov 2003) (See map). The shoals were discovered in 1963 by the South African Hydrographic Frigate SAS Natal captained by Cmdr Walters. When found, they were reported to support a large population of Galapagos sharks (Carcharhinus galapagensis). This species is classified as Near Threatened by the IUCN.Turbulent currents and upwelling waters from the Madagascar Plateau flow into the southern part of the Mozambique Channel, interact with the waters there (and hence may also influence channel dynamics farther north when carried north in eddies), and the two also merge to form the Agulhas Current off South Africa (Obura et al. 2012). Upwelling and turbulence features produced on the Madagascar Plateau feed into the southern Mozambique Channel and thence into the Agulhas Current system (Obura et al. 2012). It is believed that eddies that cross the Channel to South Africa are important in maintaining genetic connectivity. Approximately 450 pygmy blue whales are estimated to occur south of Madagascar on the Madagascar Plateau. Based on acoustic observations, there is some evidence for range overlap of the different call type populations, with the Madagascar Plateau having only the Madagascar call type (Obura et al. 2012). Walters Shoals are the only known habitat of the recently described giant species of spiny lobster, Palinurus barbarae (Decapoda, Palinuridae), which was found in an unexploited condition (Charles Griffiths, pers. comm.). This may be the unidentified Palinus species found by a Soviet fishing crew in 1981. Three species, a carangid, Trachurus longimanus, a cheilodactylid, Acantholatris monodactylus, and a labrid, Nelabrichthys ornatus, are endemic to the West Wind Drift islands. A serranid, Lepidoperca coatsii, is known from four of the island groups and may also occur at Walters Shoals. Another serranid, Serranus novemcinctus, occurs only at the four Indian Ocean islands and seamounts. A common Gymnothorax is an undescribed species, probably endemic. A specimen of scorpaenid has been described as Scorpaenodes immaculatus, also probably endemic. A second species of Gymnothorax and a species of Plagiogeneion may also be endemic. Thus, 30 to 40% of the shallow water fish fauna of Walters Shoals is endemic to some part of this chain of islands and seamounts (Collette and Parin 1991). Finally, Walters Shoals are believed to be an important foraging area for leatherback turtles.
It was fished by Soviet exploratory fishing vessels in the 1980s (FAO History of Soviet and Ukranian fishing), but fishing activities seem to have been restricted to mid-water trawling (major reported catch: jack mackerel) and pot fishing for lobster. This report commented that more demersal fish were seen but the bottom was too rugged for fishing (Romanov 2003).
Haupt P. 2010. Conservation assessment and plan for fish species along the KwaZulu-Natal coast. MSc Thesis, Nelson Mandela Metropolitan University, South Africa. Lutjeharms, J.R.E. 2006. The Agulhas Current. Springer-Verlag, Berlin, Heidelberg. 333 pp.Obura, D.O., Church, J.E. and Gabrié, C. (2012). Assessing Marine World Heritage from an Ecosystem Perspective: The Western Indian Ocean. World Heritage Centre, United Nations Education, Science and Cultural Organization (UNESCO). 124 pp. Romanov, E.V. [Ed.]. 2003. Summary and Review of Soviet and Ukrainian Scientific and Commercial Fishing Operations on the Deepwater Ridges of the Southern Indian Ocean. FAO Fisheries Circular No. 991. Shotton, R. 2006. Management of demersal fisheries resources of the southern Indian Ocean. Report of the fourth and fifth Ad Hoc Meetings on Potential Management Initiatives of Deepwater Fisheries Operators in the Southern Indian Ocean. FAO Fisheries Circular. No 1020.
Areas described as meeting EBSA criteria that were considered by the Conference of the Parties
C1: Uniqueness or rarityHigh
30-40% of shallow water fish thought to be endemic to this group of “west-wind islands”. Only known habitat of recently discovered spiny lobster Palinus barbarae (Charles Griffiths pers.comm.)
C2: Special importance for life-history stages of species Medium
It is an important foraging area for leatherback turtles (Haupt, 2010).
C3: Importance for threatened, endangered or declining species and/or habitats Low
Reported to be important area for pygmy blue whales (Obura et al. 2012), and whales observed in area (Shotton 2006). Once reported to hold large population of the “Near Threatened” Galapagos shark.
C4: Vulnerability, fragility, sensitivity, or slow recovery Low
Predicted to contain habitat suitable for cold-water corals (Clark and Tittensor 2010; Davies and Guinotte 2011), but local habitat may not be suitable.
C5: Biological productivity Low
The Madagascar Plateau and the Madagascar Channel are the two most productive of the five foraging areas for seabirds in the WIO (Obura et al. 2012). However, this area may be outside the most productive areas and outside the area of high kinetic energy.
C6: Biological diversity Medium
Covers high depth range so will have diversity of communities.
C7: Naturalness High
Fishing appears limited to mid-water trawling and lobster pot fishing in 1980s (Romanov 2003)
Eddies generated on the Shoals probably/possibly constitute an important link in the biological connectivity in the region (Lutjeharms, 2006).