We have been extremely honoured to have Dr Rupert Ormond, the Save-our-Seas Foundation’s Chief Scientist, on board as our scientific advisor. We were sad to see him leave the Atoll last week but students were waiting for him in the Red Sea. He kindly wrote a few words and took some images of us, which I have posted below.
Hard to believe my stay on Aldabra is coming to an end. I am having to leave earlier than the rest of the team to run a coral reef course in Egypt. And the past 10 days have been hectically busy, with times of high tides (when we can get out across the encircling reef) and of slack water (when we can work in the channels that connect the outer ocean to the inner lagoon dictating early starts and long days.
As the science “guru” at the Save our Seas Foundation my task was to help launch our hunt for the most impressive marine life that Aldabra has to offer, and support the task of documenting some of this fauna, both on paper and on film (or these days, even in a remote location like Aldabra, in word-processed and digital image form). We have made a good start. Underwater, Aldabra boasts an abundance of reef fish, and an impressive variety of corals, which seem to be recovering well from the high mortality caused by coral bleaching and record high sea temperatures in 1998. And during a lull while we waited outside one of the minor channels for the tidal current to slacken, watching green turtles courting and mating, and the frigate birds harrying the returning red-footed boobies for food, one could imagine that this scene had been played out, unaffected by human influence, for tens of thousands of years.
But we were particularly anxious, of course, to locate and record the very largest animals that Aldabra is believed to harbour – it’s larger sharks. After a week of baiting, chumming and drifting in the most likely places, a clear pattern is beginning to emerge. The small black-tip sharks are common almost everywhere, and given time, lemon and grey reef sharks also turn up, especially in the channels and on the outer reef. But of the tiger shark, the biggest animal haunting Aldabra, there is no sign, though twice during our stay research station rangers think they may have seen one from a boat, the only solid confirmation, short of taking a specimen, would be capturing it on camera. Considering the amounts of bait we have been using, that sharks down current can most likely detect miles away, it’s beginning to look as if there are very few, if any around.
The one possibility is that there are one or two about, but they have been busy elsewhere, hunting turtles or the like in more inaccessible parts of the lagoon (they often enter quite shallow water), or in deep water (where in some areas they prefer to spend the day). Also the home ranges of individuals may be pretty large. Tagging studies have recorded tiger sharks migrating between South Africa and Australia, so the few surviving individuals could easily encompass the other islands and atolls of the Aldabra group within their territory, meaning they could spend most of their time at a distance beyond which they can detect us, or we them.
The other possibility is that tiger sharks may only be willing to respond to our bait and chum at night, though their behaviour in this respect seems to vary between different parts of the world. This is where our remote camera system comes in. Can it document further shark species, or even provide usable footage for our documentary film? James (our science assistant) has valiantly struggled with a whole series of technical glitches, and finally, just a few days ago, got night-time shots of black-tip sharks near the shore. So it was a bitter blow when, on deploying the assemblage to deeper water on the fore reef, the camera control system refused to work. The most likely explanation seems that, now that the computer and power pack box was floating in the sea, rather than on dry land, sea-water got in somewhere and shorted connection. Doubtless it will take more frustrating days to work out. Our hunt for the tiger shark on Aldabra is becoming as convoluted as that for Lewis Carol’s “snark”!