Sharks Ahoy!

by Anonymous (not verified) on

In mid-2014 I completed my honours project focusing on the behaviour of a range of shark species in the Chagos Archipelago (British Indian Ocean Territory) using footage collected via remote underwater cameras. This meant that throughout my honours year I was analysing hours of footage from this tropical paradise completely unknown to most people, seeing everything from small reef sharks to tiger sharks and hammerheads interacting with one another; not to mention the coral reefs themselves with their accompanying plethora of colourful inhabitants. This however, was footage collected during a previous expedition and was all witnessed from the comfort of a computer lab in Perth. Despite having been involved in field trips throughout my studies and voluntary work, such as tagging sharks in Exmouth and studying reef communities at Rottnest Island, I was yet to be involved in an ocean expedition, an experience I felt was required to really cut my teeth, back up that new piece of paper on the wall and actually be able to call myself a marine biologist.

Sharks in Chagos

After working for a few months processing footage from mid-water cameras from such exotic places around the world as Palau and Rapa Iti, again witnessing these ecosystems second hand, the opportunity arose to be part of an expedition to the Chagos archipelago. Given a chance to see this place few have the privilege of visiting, and to finally see the study site of my honours project first hand, I could hardly believe my luck. I was quickly acquainted via my small role, with the amount of organisation that is involved in an expedition of this scale and after a few months of arranging such things as the fabrication of new camera rigs and sourcing and learning the intricacies of VHF transmitters and receivers, I was on a plane to Diego Garcia. On our arrival in DG we collected the kit shipped in from around the world from the various research teams and boarded the vessel that was to become our home for the next 3 weeks, the Pacific Marlin.

Over the following two weeks I’ve seen and learnt a lot. Deploying the camera rigs was hard work at first but our team has fallen into a steady rhythm now and things are running smoothly. The ship’s crew are very helpful, even teaching us how to splice ropes and the best knots to tie in different situations. We’ve seen a range of species associated with different areas; from silvertip, grey reef and silky sharks, and schools of rainbow runner at areas around seamounts to schools of juvenile fish and scad at more oceanic sites, suggesting different areas of the reserve may be important for different pelagic communities. The highlight so far was a whale shark which loomed out of the blue and hung around one of the rigs for about five minutes nudging it and suction feeding the bait plume it produced; this being the first photographic record of a whaleshark in Chagos reinforces how much we still have to learn from studying this area.

I’ve also found it interesting how the data gathered by the various research teams on the boat seem to complement each other and tell an interesting story. For example the oceanographic and acoustics teams provide information on things such as bathymetry, temperature and scattering layers leading to discussions on why we may be seeing differences in pelagic populations among sites and informing sampling structures. It seems that the combining of these as well as other sectors of the scientific community via the Chagos consortium may yield interesting results in the future.

Coconut crab - Chagos

Mid-way through the expedition we had a rest day to visit some of the islands, giving us a chance to relax, drink a fresh coconut on the beach and do some snorkelling. The world under the waves here is incredible, the diversity of reef fish left me in awe and made me realise I need to brush up on my species IDs. We were also lucky enough to see a number of nesting seabird communities, a turtle nesting on the beach and massive coconut crabs (a now IUCN redlisted species) on the islands reinforcing the importance of the reserve’s protective role. 

With the trip drawing to a close in the next few days I can’t help but think that as far as first oceanic expeditions go this trip has set the bar pretty high. I’ve learnt a lot, seen some amazing sites and met a lot of great people. If this is an indication of what’s to come, I think marine biology might just be for me. 

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