Diving and Laje de Santos

They say good things come to those who are patient. I never really gave this saying too much thought until just recently…In the name of manta research I have spent six solid weeks (during the winter of 2009 and winter of 2010) diving a remote offshore rock called Laje de Santos in the south of Brazil looking for the elusive giant manta (Manta birostris). Until today, I have searched in vain. I was the one that actually chose this location for part of the worldwide study on this newly discovered species of ray, as this little spec of a rock is the largest documented aggregation site for this species in the southern Atlantic Ocean. But, to tell you the truth, despite my normal determined outlook when working in the field, I was really beginning to loose hope (and that’s pretty bad, since my current international research campaign is ironically named “Ray of Hope’).

Andrea in the field at Laje

But that’s the funny thing about marine field research and, I suppose, diving in general. It doesn’t matter what the ocean throws at you…countless hours of searching, dozens of dives in cold, green water, boat trip after boat trip on rough, windy seas…all of the excruciating effort and disappointment literally seems melt away the second the animal that you have been searching for appears. Your breath catches in your throat, time stands still and everything seems to make sense in the world. And this is why we divers torture ourselves by squeezing into unbearably uncomfortable wetsuits, why we swim around the sea covered in all kinds of tanks and hoses, and why we spend all of our money and time bobbing around in the middle of the ocean. It is precisely for this sensation and these encounters with special marine creatures. For the majority of us, the most precious encounters are with large, elusive megafauna like sharks, whales and dolphins. The object of my affection, of course, is the manta ray.

Andrea patrolling with sat tag

So, as I was saying… all hope seemed lost when about five days into my latest expedition to Brazil a huge storm hit. It poured rain for a week, the wind howled across the sea and the swell was unrelenting, turning the clear, blue, offshore water into the kind of green that divers have nightmares about. When we finally were able to return to the sea, the visibility was only a few meters and the water was bitterly cold. Our only recourse was to patrol up and down the tiny offshore rock… searching for a miracle.

And then one appeared, literally out of the gloom, and it was coming straight for us. It felt like a dream. He was massive, a large mature male manta, and he was ready to be the ambassador for manta ray conservation in Brazil.

Out of the gloom...

Almost as if he understood what was needed of him, he swam right up to us (hovering momentarily to get his belly tickled by our bubbles) and patiently allowed me to take an ID photo him and place a single satellite tag on his dorsal surface. Watch Andrea sat tagging the first giant manta ray in Brazil! Without even the slightest flinch, he continued to swim with us after the tag was inserted, allowing me to check that the tag was secure and more importantly allowing me to get to know him a little better. For several minutes I took detailed images of every important feature from every conceivable angle. I was amazed by the gentle tolerance of this individual; the experience reminded me how incredibly privileged I am to work on them and how much they deserve our respect and protection.

Then without warning he slowly began to move back off into the gloom, ready to lead us on one of the most exciting journeys of my career. The tag that I placed on was archival, meaning that it functions like a mini laboratory, constantly sampling the outside environment and storing the data for me as the manta ray swims around the ocean.

And he is off...

Amazingly, it records the temperate of the surrounding water, the depth the manta is in as it moves along or makes deep dives, light levels (which are used to determine the actual track of the manta) and GPS positioning should he come to the surface periodically. I manually programmed the tag to automatically detach after 180 days (6 months) at which point it will float to the surface and begin to download all of the stored data to the ARGOS satellites. At this stage, ARGOS will magically beam this information to my computer. Just thinking about this process makes me love being a scientist in the 21st century. To have the technology to be able to ask and then answer difficult questions is such a joy.

At this stage, all we have to do is sit back and wait. For the next six months this individual will roam the cold waters of the Atlantic Ocean storing the secrets of his lifestyle and behaviour; secrets that have eluded us until now.

Over the next few months, we will begin to see things from his perspective...

But already this particular manta ray is a part of history. He is the first manta ray to be satellite tagged in South America or in the southern Atlantic Ocean for that matter and the information that he will contribute with be both unique and invaluable.

This particular individual happened to be a re-sighted male, which had been previously encountered at Laje back in 2007. He had not been seen since his first encounter, but this is not entirely unusual for the area. It is thought that manta rays only make brief stopovers to this offshore oasis before moving off into the unknown. The ‘Mantas do Brasil’ project  (Laje Viva Institute), managed by Guilherme Kodja, is specifically trying to address this mystery and have teamed up with my Foundation (Marine Megafauna Foundation) to answer some key questions.

Success! 1st satellite tagged manta ray in South America!

Where do these giants come from? Where do they go when they leave this little rock? Why do they mysteriously appear each winter and what are they coming to do? How are humans impacting their movements and their natural behaviour? Are they affected by the massive amount of shipping traffic that occurs in the region? How many are caught each year in gillnet fisheries along the coastline? With next to nothing known about their lives in this part of the world, these answers could prove invaluable to our ability to manage the manta ray population in the region and protect them from anthropogenic threats.

Collaborative research at its best!

As we continue to learn more about these ocean giants, I also continue to learn and grow as a scientist. Patience is an important skill in field research as is the determination to see difficult projects through to completion. In the end, persistence will pay off, and although we sometimes feel that we are racing against time, we are ultimately at the mercy of the animals that we study and the elements of nature. Sometimes sitting back and waiting for them to come to us is the only solution.

A more promising approach to locate shark nursery grounds in Fiji is using local people’s knowledge. Back in 2004 I interviewed a local fisherman living in a village situated on Fiji’s largest river and he told me that he catches sharks in the river in November and December each year. He did not know what species this could be but described his catch as “sharks with a rounded snout and being greyish/brownish in colour”. Most of the sharks he catches are small but he also mentioned that he catches large individuals. When he cuts them open he sometimes finds baby sharks! Pregnant females in Fijian rivers! Well, this was certainly something we wanted to know more about. This summer, we set out to collect more information about the occurrence of sharks in Fijian rivers. We visited a good number of villages situated along the major rivers on Viti Levu and Vanua Levu (the two main Fijian islands) and interviewed the locals. What they told us is way more than what we expected. All interviewees confirmed that they regularly see and catch sharks in the rivers as far up as 30 km inland! Closer to the river mouths they reported to catch small hammerhead sharks and unknown species further up river. We also learned a lot about how they use and regard sharks. All very interesting and exciting! There will definitely be future posts here that report the results from these visits. Stay tuned!

Looking at the depth data from the pop-up tags I attached to bull sharks in the Bahamas, it is obvious that premature release occured because the sharks stayed very shallow and did not change depth much. The tags I attached to bull sharks in Fiji popped up for unknown reasons. Some of them after being on the shark for only one day, but others stayed on for as long as 50+ days. Despite popping up early, they still transmitted a good amount of data except for one tag which never ever transmitted. Some pop-up tags might be malfunctioning or washed up on a beach from where it’s unlikely to get good transmissions. Anyway, so far I was lucky with not hearing back at all from only one tag (out of 22 attached to different shark species).

Unfortunately, this number has recently increased to three with the tags I attached in February being completely silent. Both tags were attached to female bull sharks in Fiji. One was programmed to be on the shark for 20 days and the other should have collected data for three months. I did re-sight both animals with the tags attached a few days after I tagged them. Then, both sharks turned up without their pop-up tags attached. One animal (pictured above) is a regular visitor to the site and we can easily identify her looking at her first dorsal fin. She also has an acoustic tag on her right side just below the dorsal fin. The suspicious white dot you can see below the dorsal fin is where the pop-up tag was attached. This healed within a few days. Knowning that both shark lost their tags I was expecting to hear from them within a few days. But they didn’t. No signal, nothing.

Until today, I have no clue what happened to the tags. Losing them prematurely is one thing but not getting back any data at all is bad. And a waste of money!