Western Indian Ocean

Summary

The West Indian Ocean hotspot covers an area of over 330,000 km2. This hotspot is found in the Mozambique Channel, with 76% taking in the EEZ of Madagascar. Although situated beyond the continental shelf off southwest Madagascar, in the south this hotspot extends from the coast to beyond the 1,000m isobath.

Oceanographical context

Ocean circulation in the Mozambique Channel (west coast of Madagascar) is discontinuous, being dominated by a series of meso-scale eddies. Average sea surface temperature (SST) in the coastal waters of Madagascar are just above 25°C, with temperatures ranging from 22 to 27°C during the cold season (April- September) and from 25 to 29°C during warm season (October-March) (ASCLME, 2012). The tidal regime in Madagascar is diurnal, with two low and two high tides of about equal amplitudes. Tidal ranges are generally larger on the west coast of Madagascar, and in some areas the high tidal range creates strong currents just off the coast (ASCLME, 2012, ODINAFRICA, 2014). The east coast of Madagascar is exposed to the southeast trade winds, creating rough sea conditions on this side of the coast. The western side of the island is sheltered from these winds, resulting in calmer sea conditions. Although monsoon winds affect the northwest coast, the southwest coast is relatively protected (ASCLME, 2012).

Economic and social context

With a gross domestic product of approximately USD 478 per head (2009), a life expectancy of 66.7 years and a population growth rate of 3%, Madagascar is considered as one of the least developed and poorest countries in the world (INSTAT 2010). The population is mainly dependent on agriculture and marine resources for subsistence (Davies et al., 2009). Small-scale fisheries represent nearly 72% of total fish production with men making up 97% of the workforce (Le Manach et al. 2011). Another important coastal economic activity is sand extraction (mining) for ilmenite. In 2011, mining contributed to 22% to the value of exports from Madagascar.

Important fisheries

Some 34% of the countries’ population lives within 100 km of the coast (INSTAT, 2010), and Madagascar’s marine environment is an essential source of both food (Harris, 2011) and income. Traditional/small-scale fisheries are either conducted on foot (gleaning), or using small sail or paddle driven pirogues. (Epps, 2007). Small scale fishing is mainly for subsistence or for local markets, although some of the more valuable products are exported (crabs, lobsters and sea cucumbers) (Mathew, 2002). Reef and pelagic finfish, octopus, squid, lobster, sea cucumbers, sea urchins, turtles, sharks and rays being the main resources targeted (Epps, 2007). The artisanal fishery uses small motorized vessels, targeting fish and sharks (Nageon de Lestang, 2007) for subsistence (FAO, 2008), local and international markets (Narozanski et al., 2011). The industrial fishery is mostly comprised of shrimp trawl fishery which operates mainly within the depth range of 5-30 m focusing on adult peneid shrimp (Razafindrainibe, 2010). 

Biodiversity of the region

Madagascar’s marine diversity stands apart due its range of habitats (Harris, 2011). Southern Madagascar is home to one of the largest coral reef systems in the Indian Ocean (Davies et al., 2009), providing habitats to an estimated 6,000 reef-associated species, including 752 fish species and 340 coral species (McKenna & Allen, 2003 in Epps, 2007). Coral reefs are the most productive and biodiverse marine habitats in Southwest Madagascar (Epps, 2007). These ecosystems support multiple fisheries around the country with an estimated 43 % of all fisheries per year (or 65,090 tons) being based on coral reefs (FAO 1999 in Narozanski et al., 2011). Not only are these reefs of considerable biological importance, but they are also significant in terms of culture and socioeconomics (ASCLME, 2012). Seagrass beds, coastal lagoons and mangrove forests are also of enormous ecological importance, providing essential habitat for fish and invertebrate species, and supporting some of the country’s most productive fisheries (Harris, 2011).

Key Climate Concerns

  • Climate change has already affected the availability and stability of marine and coastal resources
  • Long-term predicted changes in atmosphere and climate include: changes in rainfall, wind, intensity and frequency of cyclones, sea level, wave height and temperature (atmospheric and sea surface). These changes will not only affect agriculture and the coastal communities of Madagascar, but also marine animals.

 

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