Our whale shark research work has just been featured by National Geographic! Bit exciting. There’s an excellent video (below) and article: “Why the Worlds Biggest Sharks Love Mafia Island.”
Check it out. I’ll wait…
The photos and video were taken by conservation photographer, videographer and all-around great guy Steve De Neef who joined Chris Rohner, Alex Watts and I (with honourable mention to Jesse Cochran) during our field season at Mafia Island in November 2016.
Steve in action
What, you don’t know about Mafia Island? Mafia is a medium-sized island off the Tanzanian coast, a short flight (or long ferry ride) from Dar es Salaam.
It has no known connection with organised crime.
Rather, the name “Mafia” is thought to be derived from the Swahili “mahali pa afya” which translates to “healthy dwelling place”.
It’s a gorgeous island, and one of my favourite places to visit each year.
Of course, short web articles can only ever select a few quotes to use, so I thought I’d add in my full interview with the writer, Alexandra E. Petri. I’ve slightly edited both the questions and answers for clarity, and added a bunch of photos for funsies.
How long have you been studying the whale sharks at Mafia Island? Why did you start?
Our Mafia Island study began in late 2012. It was actually WWF Tanzania who initiated the study, with MMF (in partnership with Dr Michael Berumen’s lab at KAUST) winning a contract to determine why the sharks use this area.
Dr Chris Rohner spent five months there over the 2012/13 summer. He quickly realised that it was a unique situation. There aren’t too many places where you repeatedly see the same whale sharks, but Chris was literally able to name the Mafia contingent.
These days, it’s almost like visiting old friends.
What time of year do you conduct your studies?
We usually stay on Mafia over November and December. Whale shark sightings tend to be good over that period, the weather is normally settled, and it’s a nice quiet time on the island.
Although the sharks often stay inshore for longer, we realised after a couple of years that their high residency meant we could get a good idea of what was going on over a shorter field season.
What is the best estimate of the global whale shark population? At Mafia Island?
At the moment there’s no solid estimate of the global whale shark population. There’s a global online photo-identification database for whale shark sightings, hosting almost 8, 000 identified sharks, so that’s a reasonably useful minimum number.
However, almost all the coastal feeding areas where whale sharks (and researchers) tend to aggregate are dominated by juvenile male sharks. About 70% of the sharks on the global database are male, most of 4-8 m length, so we know we aren’t doing a good job of counting the smaller juveniles, females, or adult sharks of either sex.
We’ve identified just over 130 sharks at Mafia Island, with a few new ones identified each year. It’s a small resident population, but they definitely love the place.
What makes this population of whale sharks unique?
The unique thing about the Mafia Island whale sharks is their long-term residency in the area. Many of the individuals seem to live there, year-round, and even over several years.
It’s easiest to see them over the October to February period, when they tend to move inshore to feed on shrimp at the surface. However, our electronic tagging work has shown that they don’t swim away far away outside these months; they just move further out into the bay and spend less time at the surface. Presumably, they’re switching to another source of prey, but we haven’t got that figured out yet.
What was your initial reaction when you discovered this unique population?
Matthew Potenski from the Shark Research Institute did some initial research work off Mafia over a couple of seasons from 2007. He photo-identified quite a few whale sharks over that period.
What really surprised me is that we’re still seeing many of them.
Once we established that these sharks were living here, not just visiting, it became very clear that Mafia is an amazing site to learn more about whale shark ecology.
If this particular group of whale sharks is feeding differently and has different migration patterns, what does this mean for the global population of whale sharks?
Whale sharks are a very flexible species. Even off Mafia, we see them completely changing their feeding strategies when they switch from chasing small fishes to shrimp or vice versa.
The fact that Mafia whale sharks are so resident shows that both international and legislation are needed to effectively protect whale sharks. In some places, they do routinely move between countries, even on a day-to-day basis. In areas like Mafia, however, local protection can be the most important conservation strategy.
Is there any tourism associated with the whale shark population around Mafia Island? Do tour operators ensure sustainable ecotourism practices?
Mafia is actually a really good place to see whale sharks. The number of tourists there is still small, and operations are mostly run by local Mafia people.
We’ve been working with a Tanzanian NGO, Sea Sense, to deliver annual training sessions to help the industry develop in a sustainable way. With increasing government involvement the prospects are good.
Chris and I lead trips there each year with Aqua-Firma, and our guests have been loving it. Personally, Mafia is one of my favourite places to work, and I hope we’ll be able to continue our research and conservation efforts for many years to come.
What are some of the biggest threats facing whale sharks around Mafia Island?
People are quite fond of the whale sharks around Mafia, which is a great start.
We work closely with researchers from the Tanzanian Fisheries Research Institute, who have been enlisting net-fishers to participate in studies of how to avoid conflict with the sharks.
The fishers aren’t trying to catch the whale sharks, but the sharks are feeding on the same patches of shrimp as the small fish that the fishermen are targeting. Sometimes, the sharks get tangled in these nets. That can create a situation where both the sharks and people could be injured.
Because the sharks are so resident, it’s really important to minimise the risk of these local threats. We’ve been creating maps of where people tend to fish, and where whale sharks spend most of their time on the surface, so we can identify areas where interactions are most likely to occur.
Because the sharks are only seasonally at the surface, and generally in a predictable area, the prospects are good for creating a managed area where sharks can feed safely without impeding local fishing practices too much.
Where do whale sharks currently face the biggest threats?
The biggest direct threat to whale sharks at this stage comes from a fishery in southern Chinese waters, where several hundred sharks may be caught each year.
The fishery is technically illegal but, at this stage, there seems to be minimal enforcement. Happily, when photos end up on Chinese social media there seems to be a major outcry, which has in several cases led the authorities to prosecute the offending fishers.
In saying that, the fishery really needs to be permanently shut down. Whale sharks can’t handle that level of exploitation. They are slow-growing, and probably don’t even become adults until they are 20-30 years old. If that fishery continues there is a real chance of regional extinction.
What can we learn from the population of whale sharks at Mafia Island that can be applied to larger populations?
I view the Mafia whale shark population as a natural laboratory for whale sharks. It is one of the few places where we can reliably see individual sharks over several years, so we can learn a great deal about their ecology and biology.
One of the major questions I have relates to the few female sharks we see at coastal feeding areas. Because we can look at individual diet, movements and growth over time at Mafia, I’m hoping we can learn more about why this sexual segregation happens all over the world. If we can identify where the different life stages of whale sharks are likely to be at different times, we will be able to create more effective conservation initiatives.
There are a lot of answers to come from Mafia. It’s a fantastic opportunity to learn more about these remarkably enigmatic fish.
What (and where), if any, progress has been made since the species ICUN status change in June 2016?
The recent listing of whale sharks as Endangered on the IUCN Red List has definitely meant that countries are starting to pay more attention to their conservation.
Several countries have expressed interest in supporting a proposal to list the whale shark on Appendix I on the Convention on Migratory Species, which would encourage more countries to protect them on a national level.
Within the research and conservation community too, there’s great collaboration and a real drive to help reverse the decline we’ve seen in these gentle giants.
What are some of the questions you’re currently working to answer?
The whale sharks have definitely been keeping us busy over the last few years.
Outside Tanzania, we have some great conservation initiatives underway in Mozambique to reduce gillnet bycatch of whale sharks. In the Galapagos Islands and St Helena Island, two of the few places where large pregnant female sharks are regularly seen, we’ve been working with other groups to track them with satellite-linked tags to find out more about adult habitat use and reproductive strategies. In Mexico and the Philippines, whale sharks have proven to be a great ambassador species for increasing levels of protection for marine life.
Almost all of our research work is highly applied. Our focus is on identifying human threats and developing practical conservation initiatives.
Is there anything additional you’d like to add?
Whale sharks are one of the few large animals that people can swim with, without any cages or baiting, in perfect safety. I encourage people to find a reputable operator and go visit them. Whale sharks are genuinely awesome fish.
In terms of helping them out, if you’re going to eat tuna then please look for sustainably-caught fish that have not been caught in purse-seine fisheries. Purse-seiners are a major threat to whale sharks, and it’s easy to find tuna that have been caught using more environmentally-friendly techniques.
Miss the video above? Watch it at National Geographic.
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If you enjoyed this article, you might like this one too: “Madagascar: Whale Sharks in the Land of Lemurs.”
Thanks to our research partners at KAUST, TAFIRI, and Sea Sense, along with Liberatus Mokoki and the Whale Safari team. WWF Tanzania, Shark Foundation, Aqua-Firma, and two private trusts supported this work. We couldn’t do it without you!
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I write a few articles just for my mailing list. They normally focus on something interesting, and possibly hilarious, that I've learnt about sharks (or other random animals) that week. There may also be groan-inducing jokes.
Real talk: there will be groan-inducing jokes.