Marine Biology Aboard the Four Seasons ‘Explorer’

From July to September, a diverse selection of marine life megafauna species were observed during the various snorkeling and dive excursions conducted from the Four Seasons luxury live-aboard ‘Explorer’.

Whitetip reef sharks (Triaenodon obesus) represented 31% of all megafauna species sighted, followed by grey reef sharks (Carcharhinus amblyrhynchos). Several rarely-sighted species were also spotted, including:

– blackspotted torpedo ray (Torpedo fuscomaculata),
– silvertip shark (Carcharhinus, albimarginatus)
– zebra shark (Stegostoma fasciatum)
– tawny nurse sharks (Nebrius furriginous)
– giant barracuda (Sphyraena barracuda)
– shovelnose guitar ray (Rhynchobatus djiddensis)

Whitetip reef sharks were the most numerous species of shark observed during dives, whereas the blacktip reef sharks (Carcharhinus melanopterus) dominated shark sightings on the snorkels. This is to be expected as whitetips spend a lot of time resting on sandy bottoms during the day, at depths of around 30m, making it extremely difficult for snorkelers to observe them. Blacktip reef sharks spend the majority of the time in shallow water at depths between one to 10m and are rarely encountered by divers.

A total of 98 Hawksbill turtles (Eretmochelys imbricata) were sighted, generally foraging close to reef crests and drop offs where edible organisms such as soft corals and sponges can be found in abundance. By comparison, only 7 adult green turtles (Chelonia mydays) were recorded, usually feeding in sea grass beds as they are primarily vegetarians at the adult phase of the life cycle. Most of the dive and snorkel sites are located in close proximity to corals reefs rather than sea grass habitats, as the reefs are more aesthetically pleasing and are home to a diverse array of marine organisms. The lack of excursions taking place in sea grass areas compared to coral reefs may explain why hawksbills are encountered at a higher frequency than greens.

Bottlenose dolphins (Tursiops aduncus) were the only cetacean encountered underwater, with approximately 60 individuals being observed in a single 20 minute encounter. Several large individuals of the pod would swim directly towards the snorkelers, retreat, and then again approach the group before eventually losing interest and disappearing into the blue. This is the third bottlenose encounter that has occurred at Viligili (Raa Atoll) in the last 12 months.
Other interesting marine animals sighted included a paper scorpion fish (Taenianotus tricanthus), reef stonefish (Synanceia verrucosa), nudibranchs, moray eels, pipe fish and large schools of various reef fish.

A total of 61 reef manta rays (Manta alfredi) were sighted, with an average wing span of 235cm. Seven other ray species were observed, with spotted eagle rays (Aetobatus narinari) being the most common, followed by marbled sting rays (Himantura oxyrhynacha). The spotted eagle rays had an average wing span of 78cm and most of them were observed at depths below 20m.

One of the highlights of the cruise was a night-feeding manta ray seen at Fesdu Lagoon. The powerful light at the back of the Explorer caused a dense ball of plankton to form, attracting the large manta ray for a feed. The dive and snorkel team were entranced by this manta for 45 minutes, as it performed a series of non-stop barrel-rolls in the plankton cloud. (According to Guy Stevens from The Manta Trust, sometimes more than ten mantas can be seen feeding in this way – a spectacular sight, for sure!)

Thanks to David (our Marine Biologist based at Kuda Huraa) for this special report, and for compiling the following superb underwater HD videos from 2013-2014 snorkelling & diving excursions.

Video : Amazing Underwater World of the Maldives

Video : Amazing Rays of the Maldives