Maldives Archipelago and Adjacent Oceanic Waters IMMA

Criterion A – Species or Population Vulnerability

The Maldives are at the southern end of the range of the Endangered Arabian Sea sub-population of the humpback whale (Megaptera novaeangliae) population and is within the range of the Northern Indian Ocean Blue Whale (Balaenoptera musculus indica) (Anderson et al., 2012a). Although the status of this subspecies has not been assessed, it was subject to high levels of commercial whaling in the 1960s, and the species as a whole is considered to be Endangered by the IUCN Red List. Sperm whales (Physeter macrocephalus), assessed as Vulnerable, also occur in Maldivian waters; indeed, this species is the one most frequently recorded as stranding in Maldives (Anderson et al., 1999).

Criterion C: Key Life Cycle Activities

Sub-criterion C1: Reproductive Areas

Southern Ocean Humpback Whales (Megaptera novaeangliae) visit Maldives in increasing numbers during June-October. The proportion of sightings with calves increases dramatically in Sept-Oct (RCA pers obs). Several other species are also seen regularly with calves, suggesting that the Maldives is a reproductive area for species such as Spinner Dolphins (Stenella longirostris) and Pantropical Spotted Dolphins (Stenella attenuata) (Anderson, 2005; Dalebout et al., 2003; Anderson et al., 2012b; R.C. Anderson, pers. obs.).

Sub-criterion C2: Feeding Areas

The Maldives are affected by the seasonally oscillating monsoon seasons, which brings two distinct peaks of marine productivity to the archipelago. During the SW monsoon season (April to Oct), ocean currents are from the west, and productivity is high on the eastern side of the atoll chain. During the NE monsoon season (Dec to March), ocean currents are from the east, and productivity is high on the western side of the atoll chain. Many species shift from side to side of the atolls to take advantage of this seasonally shifting abundance of food. This is most obvious for those species closely associated with the outer atoll slopes. The blue whale is the commonest on the seasonally changing upstream side of the Maldives atoll chain, whilst In contrast spinner dolphins appear to be commonest on the downstream side of the atolls (Anderson, 2005; Anderson et al., 2011 & 2012a; RCA pers obs). The waters of the far north of the Maldives appear to be a seasonal feeding ground of particular importance for pantropical spotted dolphins (Anderson et al., 2011).

Sub-criterion C3: Migration Routes

The Maldives are on the migration route of the Northern Indian Ocean blue whales, as they pass seasonally between Sri Lanka and the upwelling areas of the Arabian Sea (Anderson et al., 2012a), their numbers peaking in Dec-Jan and again in April. The far north of the Maldives may be a particularly important migratory corridor, with increasing numbers of humpback whales are recorded each year in June-October (R.C. Anderson, pers. obs.). These are believed to be Southern Ocean animals, at the northern end of their annual migration. Large numbers of spinner dolphins appear to constantly pass through the Maldives. Movements are generally upstream (i.e. into the seasonally changing monsoon currents) although further details of these movements are not known (R.C. Anderson, pers. obs.).

Criterion D: Special Attributes

Sub-criterion D2: Diversity

A total of 23 species of cetacean have been recorded from the Maldives, with many of these species occurring in relatively high densities relative to surrounding areas in India and Sri Lanka (Ballance et al., 2001; Anderson, 2005; Anderson et al., 2015; RCA pers obs). Within a 10-day survey period encounters of 10-12+ species are commonly recorded (Anderson et al., 2015), including striped dolphin, rough-toothed dolphin, Fraser’s dolphin, common bottlenose dolphin, killer whale, melon-headed whale, false killer whale, pygmy killer whale, and Bryde’s whale, During the 5-year round-the-world Voyage of the Odyssey, acoustic detections were recorded consistently, and the Maldives had the highest detection rates recorded for the entire voyage, suggesting particularly high abundance of cetacean species and their diversity (Voyage of the Odyssey, 2009; Clark et al., 2012).