Blog Post: Being a rubber duck in the Indian Ocean!

The Bertarelli Foundation’s latest expedition to the British Indian Ocean Territory is underway with scientists planning to download data from an array of shark tracking receivers located around the Chagos Archipelago. David Curnick, postdoctoral researcher at the Institute of Zoology, brings us an update on the first few days:

As I write this blog we are currently moored off of Nelson Island, a small isolated island in the middle of the Indian Ocean, being circled by hundreds of frigate birds, terns and boobie birds. It is one of over 60 such islands that make up the British Indian Ocean Territory. But why am I here? The British Indian Ocean Territory was declared a no-take marine reserve in 2010 and since 2012 we have been tagging sharks, mantas and tunas here to better understand how they are using the reserve’s waters and ascertain how effective the reserve is at protecting them.

Manta rays swimming over acoustic receivers in the British Indian Ocean Territory

This year I am part of an international team of scientists, funded by the Bertarelli Foundation, onboard the Tethy’s Supporter, a vessel that came across from the Seychelles to support this expedition. We rendezvoused and boarded the vessel in the Maldives six days ago but unfortunately the weather has not been on our side thus far. Our two-day transit down from the Maldives was dogged by choppy seas resulting in our boat bobbing around the ocean like a child’s bath toy. Those transit days were spent checking dive gear and prepping shark tagging equipment, whilst the nights were spent trying to get some sleep although the ocean and the boat were working in perfect tandem to try and roll us out of our bunk beds. I was regretting my foolish and naive nabbing of a top bunk. It’s a long way down to the cabin floor…. After two pretty much sleepless nights, we were all relieved to arrive to the relative calm of Salomon Atoll. Once inside, we were sheltered from the big swell that had been raging from the west and were able to get some much-needed rest.

Scientists prepare electronic fish-tags whilst en route to the British Indian Ocean Territory

The following morning, we divided into two teams to set about our primary objective, to service the extensive acoustic receiver array network we have installed around the atolls out here. Each receiver logs the occurrence of any tagged shark that may swim within its detection range (~500m) and we have installed 76 such receivers across the archipelago over the last few years. On this expedition we will be SCUBA diving on each one (~20-25m), replacing the old receiver with a fresh new one, and bringing the old receiver to the surface to download the data. That’s the exciting bit – finding out what it has recorded over the last few years.

David Tickler of the University of Western Australia cleans and services one of the acoustic receivers which has been collecting data in the British Indian Ocean Territory

Our first morning however didn’t quite go to plan, with the persistent swell meaning we weren’t able to access some of our sites around Salomon safely in our dive boats. It was no trouble for the resident spinner and bottlenose dolphins however, who we could see effortlessly playing in the rough water around the atoll almost mocking us with the ease with which they managed the swell. Still, they were very cool to see.

As the acoustic array can only detect animals that have been equipped with specific acoustic tags, we of course have to attach these devices to animals. However, the weather conditions have just made it too tricky to tag any sharks or manta rays just yet. So, for now we are focusing on servicing as many receivers as we can and will focus on tagging more once the weather improves. After servicing all of the receivers that we could around Salomon, the following morning we headed west to Peros Banhos atoll. This massive atoll (~25km across) is where the vast majority of our receivers are located. A few days servicing receivers there we headed east to Nelson Island where we are now anchored.

The good news is that the weather is clearing so a shark tagging boat should be going out this afternoon. Will update you on what we catch in the next blog…

For more science updates from the British Indian Ocean Territory, follow @BIOTscience on Twitter.