Aldabra Atoll IMMA

Criterion A – Species or Population Vulnerability

Aldabra is now the only location in Seychelles where dugongs occur (Hermans and Pistorius, 2008). Classified as Vulnerable on the IUCN Red List, dugongs in east Africa are thought to be more highly threatened (Marsh et al. 1992). Aldabra hosts vast areas of seagrass beds both inside the lagoon (Hamylton et al. 2012) and on the seaward reef flat (Haupt et al. 2015). Spatial analysis of dugong sightings suggests a co-occurrence of dugongs and seagrass beds inside the lagoon (Hamylton et al. 2012). Aldabra therefore contains habitat important for the survival for the dugong and meets Criterion A. Furthermore, Aldabra’s dugongs include breeding females and calves, indicating the site may be a key area for the population and a promising area for population recovery (Appoo et al. 2019).

Criterion C: Key Life Cycle Activities

Sub-criterion Ci: Reproductive Areas

A partial aerial survey of the lagoon in 2013 recorded a minimum of 14 dugongs in the area covered, which is by far the largest number counted to date and suggests that the total population in the lagoon is between 20-25 individuals. The survey also recorded calves, indicating that Aldabra is a breeding or nursery site for the species (Appoo et al. 2019). Humpback whales with calves are observed around Aldabra from July to November (Hermans and Pistorius, 2008; Appoo et al. 2019), coinciding with the breeding period of humpback whales in the region (e.g., Rosenbaum et al. 2009; Fossette et al. 2014). The atoll therefore forms part of the broader humpback whale breeding area known in the region.

Sub-criterion Cii: Feeding Areas

Aldabra’s hosts extensive seagrass beds found inside the lagoon as well as on the outer reef flat. The seagrass beds are considered to be near-pristine due to little anthropogenic impacts and strict protection of the atoll. Aldabra’s large, shallow lagoon and extensive seagrass beds therefore provide ideal foraging habitat for dugongs, which are seagrass specialists. Previous research has indicated a cluster of dugong sightings in the lagoon correlated with seagrass areas (Hamylton et al. 2012). This suggests that the lagoon represents important foraging habitat for this species.

Sub-criterion Ciii: Migration Routes

Aldabra is on the migration route of humpback whales associated with Breeding Stock C as they move annually between feeding areas in the Southern Ocean and breeding (wintering) areas off east Africa, the islands of the Mozambique Channel, Madagascar, and the Mascarenes (e.g., Fossette et al. 2014; Cerchio et al. 2016). Humpback whales make up the highest proportion of marine mammal sightings on Aldabra (Hermans & Pistorius, 2008; Appoo et al. 2019). Humpback whales on Aldabra are seen exclusively between July and November, with calves, indicating that the atoll represents part of the breeding/nursery area for this population of humpback whales (Appoo et al. 2019)