July and August found me travelling to Isla Mujeres, Mexico. For those not familiar with the region, Isla Mujeres lies in the Caribbean Sea, just a few kilometres off the busy tourist mecca of Cancun on the northern Yucatan Peninsula. It’s popular for it’s beaches, clear warm water and great restaurants. But that’s not why I was there. (Nice bonus, though.)
It’s all about the whale sharks!
Between May and September, hundreds of whale sharks and manta rays turn up here. These fish are caviar aficionados. Each year, there is a huge spawning event where hundreds of thousands of tuna come to breed, carpeting the ocean surface with tuna spawn. These tiny eggs are calorific little bundles of yum for a plankton-feeder. This phenomena is a beacon for Atlantic whale sharks, and Isla Mujeres hosts the largest known aggregation of these threatened giants in the world. A single aerial survey in 2009 counted 420 sharks!
Last year, in partnership with Rafael de la Parra and his team at a Mexican NGO, Ch’ooj Ajauil AC and dive travel agency Aqua-Firma, I started studying the whale sharks here. Aqua-Firma guests help by taking photo-IDs, offer support while we collect tissue samples, and get to ask as many whale shark questions as they like! It works brilliantly in the field, as there are often so many sharks that we need all the help we can get.
These ‘Mexican’ sharks are actually nomads, often spotted in surrounding countries such as Belize, Honduras and the USA. This season, we were lucky enough to resight a couple of celebrity sharks: Rio Lady, who in 2007 was tracked swimming over 7, 000 km south into the mid-Atlantic, and Mr Smith, who has been cruising between Honduras, Belize and Mexico since at least 1999. Although they swim vast distances, many sharks return to this feast every year. I wouldn’t be surprised if we find that a significant proportion of the entire Atlantic whale shark population is in attendance.
While shark numbers this season were lower than last year, we still identified a few sharks each day. Processing all these images is a huge task so I am extremely grateful to one of our previous Underwater Africa volunteers, Michael Pfundt, who has been adding these sharks to the global whale shark database. Several scientists from the region (including Rafael and myself) are collaborating to look at international movements and, hopefully soon, to generate a population estimate for the Gulf of Mexico and Caribbean Sea. Rafael and I have also been collecting tissue samples for chemical analysis. Clare Prebble from MMF will be processing these samples to create a ‘passport’ for each shark using stable isotope and fatty acid analysis. Using the sharks’ photo ID records, combined with a chemical ‘history’ of their movement and diet, we will have a much improved insight into their lives.
For some time now, I have been boring friends with ‘drone talk’. I finally have one, and this was it’s maiden fieldtrip. Following some initial apprehension, I was able to launch our Phantom Vision+ quadcopter drone (US/UK) from the boat to test its performance as an aerial survey tool. Ch’ooj Ajauil AC have routinely flown small plane surveys in past seasons, and they have proven to be an extremely informative way to monitor shark abundance (and feeding locations) over time. Unfortunately, these surveys are expensive. My hope is that small, cheap-to-run quadcopters will offer a useful alternative for counting sharks in dense feeding groups. Our initial work had mixed results, as the sharks were dispersed over several kilometres, but we did get an excellent view of the behaviour of each shark while interacting with tourists at the surface. That will be useful in future studies on sustainable tourism.
Speaking of tourism, there were a lot of boats out looking for the sharks this season. We counted over 80 on some days, with up to 13 boats following a single shark on one particularly slow day. I photographed several sharks bearing propeller injuries, and personally watched boats coming dangerously close to swimmers. Large vessels are also travelling very close to the feeding area, and we saw sharks with major wounds. Both the tourism and shipping traffic need increased management attention. If anyone from the Mexican government reads this post, please support Ch’ooj Ajauil AC’s initiatives to improve practices on the water.
My Mexican fieldwork is now over for the year, and the writing begins! I had a great time over there – I made new friends, caught up with old ones, and introduced a lot of people to whale sharks. We saw plenty of sharks, dolphins and cownose rays, collected IDs, tissue samples and plankton, and I didn’t kill the drone. I definitely call that a win!
Learn more about Ch’ooj Ajauil AC on their website and Rafael’s Twitter. Thanks to Lawrence Staden, Alice Bordini, Ralph Pannell and the Aqua-Firma groups, as well as Ch’ooj Ajauil AC and Cancun Xtreme Trip for help in the field – and Michael Pfundt for processing the images. This work was supported by the GLC Charitable Trust, Aqua-Firma, the Shark Foundation and private donors.
If you would like to join one of our whale shark trips, I’m hosting research trips to Tanzania (in November 2014) and Mexico (in July / August 2015). I’ll also be joining an Indigo Safaris photo trip to the Galapagos in October 2015 to search for truly gigantic pregnant whale sharks. There are year-round volunteer opportunities with Underwater Africa in Mozambique. I hope you can join us to learn more about these gentle giants!
Like geeky animal facts and dad jokes?
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.