Manta Rays of Závora, Mozambique, with Nakia Cullain

Nakia Cullain is the manager of the Závora Marine Lab, an MMF manta ray scientist, and has just started her PhD on manta ecology and research at Dalhousie University in Canada. I chatted to her from her base in Závora, Mozambique, where she has lived for the past six years. SJP

Jumping into the Deep End

I learned to dive in Mozambique in 2010, on a volunteer project when I was still an undergraduate. The country stole my heart. A few years later, the founder of the Závora Marine Lab, Dr. Yara Tibiriçá, now at the University of Cádiz in Spain, was looking for someone to take over her research station. Závora is a remote fishing village located in the southern part of Mozambique, about an hour and a half drive south of Tofo, where MMF's main office is located. I knew I really enjoyed the country, and it seemed like a cool opportunity, so I inquired. After chatting back and forth, Yara decided that I might be the right person to manage her little baby here, the Závora Marine Lab. 

I came here, and I saw Závora, and I fell in love; but I only had a couple of weeks for Yara to show me the ropes before she threw me to the wolves. There were quite a few projects for me to take over, so even organizing the data handover had to happen fast. It was a very steep learning curve, and it probably took me a year or two to really get on my feet, but over time I started developing my own ideas of what research questions I'd like to answer. It kind of snowballed from there, and I've been here for almost six years now!

From Microfauna to Megafauna

I always thought of myself as a shark person. I traveled to South Africa to work with the white sharks, tag hammerheads, and things like that. I'd never seen a manta in the wild until I came here. Then, in the first week, I had a train of six mantas come through on the reef and hang out with me for 25 minutes. And that was that. 

Yara did her PhD on nudibranchs, so I inherited quite a few monitoring and species identification projects on that group; I definitely didn't realize how much of a passion for nudi's I had until I got here. I'm still keeping up with the nudibranch work, but I've shifted more into the megafauna. Yara was also cataloging manta rays, so I had a baseline database to work with, and I've been building on that to piece together the puzzle of the Závora mantas. 

Mantas of Zavora

We're lucky in that we see both manta ray species, and we can get really large numbers of reef mantas coming in to court, clean, and socialize. The Red Sands, or Witches Hat dive site is their favorite place to aggregate in Závora, by far. It's a really special place when the mantas show up, and that has very much sparked my interest in uncovering what they’re up to, and how their numbers are trending over time. MMF research has shown a decline in sightings around Tofo, so we want to know if those mantas have shifted down here, or whether it’s a separate sub-population.

Závora's mantas have done some interesting things over the last 10-12 years too. They used to be seen in high numbers all year round. That has completely shifted in recent years; they're still seen sporadically through the year, but there's this huge seasonal pulse during our winter, between July and November. Through the year we either see just a few, or like 40–50 at a time, so there’s fairly extreme variation. The Tofo manta season used to be more summer-based, whereas it’s the opposite here. 

I’m starting to dive deeper into the older Závora manta data now and, looking at the earlier years, there were a lot of manta sightings through the summer months. The change is just bizarre to me; I suspect that our season is also getting shorter and shorter now, which is also a bit scary. It has been July to November, then this year they didn't show up till mid-September. I'm hoping they’ll stay for longer this season, but we’ll have to see. So now it’s maybe two months that we have them aggregating here, rather than four months. The environment is changing. I've never seen any mantas feeding here at all, so I’m not sure if it could be food availability; it can’t be due to diver pressure, because there’s hardly any diving here. I just don't know. When Yara was here she’d see a handful of mantas get caught locally each year, but I’ve only seen two over the past six years. Of course, we don’t know what’s happening in commercial fisheries, so that's something I want to look into going forward.

The giant mantas are even more of a mystery. They’re much more transient, and we don’t see nearly as many giants as we do reef mantas. We only see low double digits of giant mantas visiting each year, compared to hundreds of reef mantas. The timing is similar, with a June-July peak, then we rarely see them through the rest of the year. Even over that period, we’ll have 20–30 reef mantas, and maybe 2–3 giants that come in at the same time. 

Volunteer-powered research

 Until last year, I was 100% reliant on Závora Lodge, and their dive center – the only dive operation in the area – to get out on the water and get the research done. Sadly, they didn't survive COVID, and they've closed down permanently.

When that happened I went into a mild panic; what am I going to do? Fortunately, a very kind soul, who has a vacation home here, contacted me. He’d heard that the dive lodge had closed, and wanted to invest in this work. That’s helped me develop a startup dive center. It's not fully operational yet, but it allows us to get back in the water. He saved my butt. With that in place, we've been diving again since the beginning of May. It's definitely challenging to be so dependent on tourism, and to have such little resources, and being in a remote area of Mozambique makes things challenging in general. But I like it, I like a challenge.

To help fund this work, I run expeditions in Zavora where people can join me in the field and support my research. Without them, I don't have the funding to actually launch the boat and get out to sea. They come to get some field experience, to learn about the research work we're doing here, and of course they also get to have some amazing dives with manta rays and other cool species. It's kind of a win-win for all of us. Despite COVID and everything, it's been actually quite busy this year. July and August have been good, and it's just starting to fizzle out now. It'll just be me and a couple of other people left for the next couple of months.

The PhD journey ahead

I formally started my PhD at the start of September. I see my foreseeable future being spent here in Závora, but for the PhD I do need to go to Canada for a semester, to get some stuff done and take some courses. It will be good to meet the team there, and be active in the academic world, after living in the bush here in Africa for so long. I’m really excited and looking forward to the long road ahead. 

I'm still developing my PhD proposal, but I'll be continuing the photo-ID work on the mantas, as well as measuring them and, eventually, once I receive my tags, tagging them. I'm very interested in tracking manta movements in relation to the industrial fishing fleet. We need baseline information on what these vessels are doing, where they're spending most of their time, where most of the fishing effort is, and to see if that overlaps with the activity hotspots for mantas, whale sharks, and other threatened species. It might open up a whole other can of worms. It'll be a good use of the satellite tags.

There's also been some acoustic tagging done previously, a few years ago, so we'll be able to build on that. We've got two acoustic receivers down now, one at the mantas' favorite shallow site, and another on a deeper reef. We definitely want to expand that array in the future. Hopefully, we can start getting more tags out soon too, so we can start getting more information on their movements.

I'm hoping that the work that I'm doing will help us avoid the declines that we've seen elsewhere. To keep them thriving in large numbers. I'm pretty optimistic that I can make a difference here.