Day Four of our Deep Search Whale Shark expedition (our final day on the water) brought us into contact with a treasure trove of the Yucatan’s ocean denizens, including Manta Rays, Cow-nose Rays, Spotted Eagle Rays, dolphins, schools of jacks, and our now-familiar friends, the Whale Sharks. Before the end of our day, we also had a rare chance to check in on an entirely different habitat:a mangrove forest.
Today’s primary mission was to observe and document the tagging of the Manta Rays by Dr. Graham’s team and Marissa Nuttall, Research Specialist at Flower Garden Banks National Marine Sanctuary. Sea conditions could not have been better: no wind whatsoever (for the first time in the expedition) and flat calm seas. We began in the green, nutrient-rich waters of the nearshore observation site (about 15 miles from Holbox), where one could swim through patches of water so full of life that all the activity actually warms the water. This rich soup of plankton (drifters) and nekton (swimmers) is exactly why the rays are here in such abundance. We observed a dozen of these majestic cousins to the shark, whose “wings” span 3-5 meters or more. Dr. Graham’s team successfully tagged several animals with acoustic tags that will allow them to follow the rays throughout the Caribbean and Gulf of Mexico. This information is crucial to understanding the migratory habits of the rays–and the consequent need to provide them with safe areas to feed, mate and bear young.
Around mid-day, the near-perfect conditions convinced us we should make one last run to the Agua Azúl (“blue water”) another 35 nautical miles offshore. Joining us onboard today were Tim Kelly, head of National Geographic’s film unit, and his spouse Susan. Since they had yet to see the spectacle of sharks to the horizon, they were game to make the trip. We arrived around 1 pm, just as most of the tourist boats were heading back to Isla Mujeres, and found an aggregation of around 30-40 sharks who were following a long, narrow band of plankton. Tim dropped into the water immediately and was rewarded with a ‘traffic jam’ of three or four sharks coming together with Tim floating right in the middle. Imagine trying to direct traffic in an intersection that’s underwater and bounded by nothing but deep blue ocean—with four bus-sized sharks jockeying around you—and you can perhaps get a sense of what Tim saw…
Later, Kip and Shari took off towards a lone female who was feeding vertically. Whale Sharks appear to do this when they find a particularly rich swarm of tiny eggs and other plankton. The shark stops swimming altogether and gently settles into a vertical posture in the middle of the swarm, rhythmically pumping water through its gills and enjoying the feast while supplies last. When the smorgasbord’s over, the shark settles back into a horizontal posture and heads off to find another. As Deep Search team member Shari observed, “It must take a lot of energy for a two-ton semi-vegetarian to gather enough energy from food you can hardly see!”
After a long day in the hot sun, we reluctantly agreed it was time to bid our friendly giants goodbye. Capitán Carmelo hit the throttles and we flew across the water past the great lighthouse on Isla Contoy, then skimmed along a 20-mile beach fringed by palms and frequented by nesting turtles, stopping in for a quick side trip to a placid lagoon tucked away in the mangroves.
There, the team couldn’t resist one more swim, this time a close-up look at the wildly productive nursery to be found among the mangrove’s tap roots. Hundreds of curious snappers, snooks, groupers and goatfish greeted us as timid lobsters probed with their feelers from holes in the sandy bottom. Egrets and pelicans could be seen resting and nesting in the top branches, while terns wheeled and dived into shoals of glass minnows. We could clearly see why mangroves are crucial to the health of coral reefs, as they truly are the nursery for many species of fish and invertebrates that eventually migrate to the reefs offshore. They’re also crucial to the health of humans—giving us protection from storm surges, acting as windbreaks and performing a critical role as carbon sink and oxygen generator. While the Deep Search/NGS contingent explored, our intrepid crew actually grilled panini aboard the boat! ¡Qué vida rica!
In the evening, knowing that tomorrow we must return to our day-to-day lives, we toasted the Whale Sharks and promised to do our all to help our Mexican friends protect their diverse natural environment. Later, after perhaps too many margaritas, your humble blog-writer composed the following poem, dubbing it “In Thanks to Elasmobranchs.”
In our láncha we voyaged to Agua Azúl
To discover a place that’s incredibly cool:
A spot in the sea where the plankton’s so thick
You’re convinced it’s just some kind of cosmical trick.
But the sharks question not, for to them it’s all good,
As they cruise ‘round so slowly, eating tons of great food,
In the hundreds they come for this sumptuous feast
(Well, it’s sumptuous if you’re a Whale Shark, at least!).
Whether tourist or scientist, all who come here
Know our task, while not simple, is perfectly clear;
It’s to save this great place in this beautiful nation
For the many unborn of the next generations…
Those aren’t humans, however, to whom I refer,
Whose protection’s essential, but not yet secure—
No, the ones who most need here a permanent park
Are the marvelous, wondrous and great Whale Sharks!
Photos (c) 2009 Kip Evans