Wednesday, March 25, 2015

Chagos 3.0 - Day 7: Chasing Giants



Today finds us at the Egmont Islands, off the south west corner of the Great Chagos Bank. We've come here looking for manta rays, which we know from previous visits to be a common sight around the reefs and within the lagoon. The purpose of our visit here is to acoustically tag some of the manta population and deploy some of our acoustic receivers to track their movements over the coming year. The aim is to understand how resident the mantas of Egmont are, and the influence of the tides and other natural cycles on their daily movements around this small atoll.

Firstly, however, you need to find a manta, and this year we have a new tool at our disposal – a Phantom camera drone. Able to relay live images from a bird eye view to the pilot on the deck of the boat, we can locate groups of mantas and direct the tagging team to the area.

The Phantom camera drone is on the lookout!
Tagging mantas is a somewhat different exercise to the work with sharks – rather than fishing for them (it is too hard to get plankton on a hook) we have to search for mantas feeding near the surface and then apply the tags directly, either from the boat or by free-diving alongside them. A calm approach is needed, both to avoid spooking the animals and sending them to deeper water.
Taylor attempts to tag a manta
The day proved to be rich in mantas, with 12 tags going out and then a reef dive in the afternoon encountering at least eight more feeding at depth along the entrance to the lagoon. The shark work continued in between manta sorties, and we acoustically tagged a further 11 animals, including our largest reef shark of the trip so far – an impressive male silvertip measuring almost two metres. With three days left here we are making good progress.

Aside from the science workload, our most senior scientist and the trip’s doctor have been moonlighting in the galley, producing excellent desserts to complement the already abundant meals aboard. Hopefully all the hard work on deck will keep waistlines in check!

   -Dave Tickler

Saturday, March 21, 2015

Chagos 3,0 - Day 5

Day 5 finds us exploring the northern edge of the great Chagos Bank, terra (or rather aqua) incognita for us. With the important servicing work all but completed, we are focussing our efforts on getting almost 100 electronic tags out on sharks and manta rays, the focal species for this study.

We carry three types of tag on this trip. Our workhorses are the acoustic transmitter tags that communicate with our receiver network. We have acoustically tagged 92 sharks so far in this programme and will be adding another 75 animals to our group on this trip.

Whilst the acoustic tags can tell us about the fine scale movements of shark around our monitored reefs, satellite archival tags collect information on position, depth and temperature wherever the shark goes, and then detatch from the shark, float to the surface, and transmit the data back to the lab via a satellite. This allows us to see, amongst other things, the large scale movements and the diving behaviour of sharks which is vital to understanding how they use a large area like the Chagos Reserve.

Lastly, Dr Taylor Chapple has brought his camera tags with him again this year, and with three deployments already we are building up our shark’s eye view of Chagos.

But before we can deploy any of this technology, we must first catch a shark. This involves early starts and late finishes to take advantage of the fact that predators are often more active at dawn and dusk, and so our chances of an encounter are improved. We use barbless circle hooks that minimise the chance of the shark swallowing the hook, and make for simple removal of the hook after tagging. Baited with fish, the hooks are streamed off the back of the boat and tended by one of the team at all times so that as soon as a shark takes the bait we can bring it on board and tag. It’s all about ensuring the welfare of the animal, so before we lift a shark out of the water we make certain that everything is ready to making the tagging as quick a process as possible, and that the padded tagging mat and the saltwater hose to pump water over the shark’s gills are ready.

A hose is inserted in the shark's mouth to keep oxygen-rich
water flowing over its gills, while the scientists attach an
acoustic tag
Handling even a small shark has to be approached with care as they very strong for their size –both the head and tail are controlled while they are lifted, and once on the mat at least two of the team control the shark while the others operate. The Stanford team have years of tagging experience between them, and their guidance makes sure we stay safe on the swim step.


A small shark is returned to the sea
Acoustic tagging involves a quick incision in the abdominal wall through which the tag is inserted, then a suture to close it. While this is happening another scientist takes blood and biopsy samples for genetic and other tests. Lastly, a marker tag is placed just below the shark’s dorsal fin, identifying the shark as having been tagged internally so that we will know if we capture it again next year. Both the satellite and camera tags are attached externally, one with a titanium dart just below the dorsal fin and the other to the fin itself. Both are used in combination with the acoustic tags, so that multiple types of data can be collected from the movements of a single animal. This increases the amount we can learn from our sample of sharks and rays.

So far this trip we have tagged 20 sharks – with 5 days left in Chagos the pressure is high to keep up the work rate!

      -Dave Tickler

Friday, March 20, 2015

Chagos 3.0 - Day 4

Day four, and we’re racing through our servicing work with 44 of 48 sites visited already, thanks to the support of a great crew on Vava and some of the calmest weather we’ve seen in Chagos. With flat seas and hardly a breath of wind, finding our monitoring equipment is proving easy, and the boat and diving work is a true pleasure!

Most of our monitoring array here is made up of submerged VR2W type acoustic receivers, which require diving on, but with new units ready to go in the water it take a two person team only minutes to remove the cable ties and hose clamp fastening the receiver to the mooring line, and fix the replacement in its place. We would probably all rather the dives took longer as there is always something to distract us down there, whether it is schools of fusileers circling you on a reef wall, or a carpet of garden eels stretching away across the sandy bottom of one of the channels.

Vava’s bosun, James, puts the finish touches
on a newly installed VR2W receiver
The other two types of receivers used in the Chagos array require very different approaches. The latest addition to the array in 2014, the four VR4-UWM (standing for UnderWater Modem) can be ‘talked’ to directly from the boat using a portable acoustic modem that instructs the unit on the seabed to transmit its data up to the surface. By holding station over or near the receiver, we can retrieve our data without even getting our feet wet!

Dr. Taylor Chapple enjoying some time
out of the sun while he downloads
 one of the Chagos underwater modem receivers
The last type of equipment used out here are our two VR4-Globals. These, as the name suggests, give us access to our data from anywhere in the world through an Iridium uplink build into a surface unit, connected to a hydrophone hanging below. The whole thing is fitted into a buoy that can be anchored in strategic positions to give us live data on shark detections. These are by far the most complicated to service, requiring a team tackling the surface components to coordinate closely with divers working on the hydrophone and cable. Add a ripping current and it makes for a challenging job, but it’s worth the effort to get real time feedback from our tagged sharks when we are back at our desks.

Taylor gets to work on the transmitter…
…while the dive team are busy below


With the vital servicing work nearly complete we are focussing the majority of our effort on catching and tagging sharks. More on that tomorrow.
   -Dave Tickler

Tuesday, March 17, 2015

Chagos 3.0

The team from Stanford University and The University of Western Australia are back for a return trip to the British Indian Ocean Territory (BIOT) to service (rebattery, download data, replace moorings and add new receivers) the acoustic array, as well as tag sharks with various electronic tags, including CATS camera tags, Wildlife Computer MiniPATs and SPOT tags, Lotek pop-ups, and Vemco acoustic tags.

   -Robbie Schallert
Dr. Aaron Carlisle tapes up a
Vemco acoustic receiver
Dr. Jon Dale gets the shark line ready

Friday, October 24, 2014

TAG Canada 2014

TAG Canada is underway. A team from Stanford, Monterey Bay Aquarium and Acadia University  led by Dr. Steve Wilson, Robbie Schallert and Dr. Mike Stokebury are tagging giants in the Gulf of St. Lawrence, Canada. Tuna are being tagged with sophisticated miniPAT tags and long-term acoustic tags, with a goal of understanding how these bluefin utilize the Gulf of Mexico spawning area closures. This is the 7th year the TAG, MBA, Stanford team has been in Canada- and the 145th tuna in Canadian waters to receive these high tech tags.  Some new accelerometry tags are also being tested in an effort supported by ONR, to determine how fast a giant bluefin goes.

Monday, July 28, 2014

IGFA Great Marlin Race Gets Off to a Roaring Start

Today marks the opening day of the 55th Annual Hawaiian International Billfish Tournament in Kailua-Kona, Hawaii. It is also the sixth year for the Great Marlin Race, which was launched here in celebration of the HIBT's 50th Anniversary.

As the teams started arriving at the "Shouting Room" (a giant open-air tent where the angling teams assemble before and after fishing), the IGFA's Eric Combast and I knew that we had our work cut out for us. We had lined up sponsors for 4-1/2 of the 10 tags we had with us, and being optimists, we brought 6 down.

Within minutes, Whangaroa Billfish Club's Keith Allan stepped forward and offered to sponsor a tag to send out with his lovely wife Janice. I was happy to oblige, and glad to have their continued support in this year's race.

I set up tags for Rocky Franich from the Pajaro Valley Game Fish Club, Ralph Czabayski of the Game Fishing Club of South Australia, and last year's winning team of Mitchell and Marty Firestein, who are fishing this year as part of the Laguna Niguel Billfish Club.

Marty Firestein shows off his new IGMR lure while Mitch looks on.

I had the pleasure of getting on Humdinger with co-founders of the Great Marlin Race, Bob and Sally Kurz, also with Laguna Niguel. It was just coming up on 10 AM when a nice 250 lb. blue came up on the short rigger. Sally was in the chair and watched this great fish grayhound across the surface about 50 yards off the stern. Once she dove, though, the fight was on. Sally settled in for a tough battle, gaining only six inches of line at a time. 

Sally Kurz battles a nice blue while husband Bob (left) and deckhand Brett Fay (right) provide support. 


After more than an hour, deckhand Brett Fay leadered the marlin alongside the boat, setting up Bob Kurz for a perfect shot with the tag. Moments later she was away, swimmimng strong.

As it turned out, this was actually the second satellite deployed so far today - the first being the one Keith Allan sponsored this morning, which was placed on a marlin while Sally was battling hers.

This is a fantastic start to the event, and hopefully marks the beginning of a great week. Keep checking back! 

Saturday, March 29, 2014

Success in Chagos!

Team Chagos, composed of scientists from our very own TRCC, Australia and the UK have completed their deployments of new Vemco receivers and Wildlife Computers satellite tags.

Today we have completed the installation of a network of underwater receivers that will provide both real time updates and the capacity to monitor this - the largest Marine Protected Coral Reef Atoll in the world. Our "Wired Ocean" concept is now allowing the international team to follow the reef ecosystem in real time, and over the next decade.  The first ocean observation devices have also been installed providing oxygen and temperature measurements that should enable initiation of long term climate data.

Thanks to our the crew and the scientists, along with the Bertarelli Foundation and Rolex, for helping to make this transfer of technology happen!