Who would have believed that visitors would one day be heading to Belize for a whale watching vacation? Amazing giants of the deep, these majestic and friendly shark whales congregate in southern Belize not far from Honduras two months every year.
Researchers such as Rachel Graham investigate this wonderful natural phenomena. Meanwhile, whale watching vacation packages prepared in conformance with accepted eco tourism guidelines are a new attraction for those visiting Belize, Honduras and the Caribbean.
The sun is hot, rains have slowed and mangoes slowly ripen as the April moon is nearing full. What does this mean? Well, to most folks in Belize, it signals that the dry season is in full swing. In Placencia, these omens all announce the aggregating of reef fish set to spawn, and with them the arrival the largest fish of them all: the Whale Shark – Rhincodon typus. Coming from other areas of the barrier reef and further away, these sharks home in on Gladden Spit during the full moon of every spring in anticipation of the banquet to come.
Whale sharks are the true behemoths of the fish world: they can grow longer than a bus (up to a purported 18 meters long) yet eat little animals no bigger than your finger – known as zooplankton- by filtering them out from the surrounding water, similar to a whale’s feeding strategy. However, finding these big fish is not always that easy. Only 9 places in the world, all located in tropical waters, are known so far to have predictable whale shark visits, and Belize is one of the few chosen countries that the whale sharks predictably visit.
Known locally as “Sapodilla Tom” for the fisherman who first saw them near the Sapodilla Cayes on the southern end of the Belize Barrier Reef, whale sharks congregate at Gladden Spit every March to June. Shaped like an elbow pointing out to the Caribbean Sea, Gladden Spit is also a very important place for over 25 species of reef fish that come together at specific times of the year, usually right around the full moon, to reproduce. At Left: Dr. Graham with whale shark tag. Although some reef fish species reproduce in pairs or in small groups, dog and cubera snappers aggregate in the hundreds or even thousands to reproduce, known as spawning aggregations. During a spawning event, female and male fish rise in the water as groups, releasing millions of eggs and sperm. The fertilized eggs float and are carried by currents until the larvae hatch. A healthy aggregation can produce hundreds of billions of eggs. And like the eggs on our breakfast table, they contain a lot of energy which makes this caviar very attractive to whale sharks. However, the eggs need to be in dense clumps for them to be attractive to the whale sharks and spawned eggs disperse very quickly. So the whale shark and many other species of fish that feed on the eggs are only able to capture some of the fertilized eggs before it is no longer worth their while to target this food.
Local fishermen and tour-guides know the fish’s ways and means better than anyone else. Yet they too have questions about the why’s, how’s, when’s and wherefore’s of fish biology that we as marine biologists can help answer. This makes for a good collaboration! They were curious to know where the whale sharks came from and where they went to after the peak spawning time of April and May. Did the sharks stay around Gladden but remained deep of did they traveled far away, and if so how far? We had our work cut out for us.
We knew from other research results in the Pacific that whale sharks travel across the Pacific Ocean from Baja, Mexico covering almost 13,000km. So it was possible that the sharks in the Caribbean were doing the same thing. But were they stopping off at other places along the way, and were the same sharks coming back to Gladden every year? Also we had no idea how many whale sharks visited Belize or even exist in the world. It is important to study whale sharks since we know so little about their life history and they are becoming an important tourism resource, and primarily because predictable sightings have dramatically declined at certain sites in the Indo-Pacific and greater Pacific Oceans, regions where they are fished for their meat and fins. The consensus among shark biologists is that worldwide populations are low.
So we set out to try and solve the mysteries and find the pieces to this big puzzle. Not an easy task! Imagine having to work out in the sea 40km from the mainland, often in seas 2-3m high with large waves – all in small open 7m boats. How do you keep an eye on the different sharks, count them and make sure you’re not counting the same individuals over again? Also how do you know if, where and when they leave Gladden Spit? To get around all of these problems we use a range of different research techniques that we’ve been able to try – out thanks to the financial support from the UK Darwin Initiative and the Natural Environmental Research Council.
Watch Whale Shark Video
Rachel Graham interviewed by the New York Times
You are a citizen of Belize. Did you grow up here?
No. I spent a large part of my childhood in Tunisia, that little tinderbox that last spring sparked so many changes in the world. I’m very excited to be from there. My British mother and American father were international vagabonds who met while teaching in Sierra Leone. We were this migratory family.
Wherever we lived, I was always bringing home creatures — lizards, snakes, scorpions. Perhaps because I was this blue-eyed tomboy in places where no one else was that, I identified with marginalized animal species. My mother tells the story of my coming home from school, complaining: ”It’s so boring there. Nobody wants to talk about piranhas or sharks!”
What appeals to you about sharks?
They are beautiful and graceful. And they are migratory, like my family was. On an ecological level, they play an important role because they keep their prey species in check.
The other thing is that once you get to know them, you can see that there’s great intelligence there. They haven’t been around for almost 400 million years without having evolved tremendous smarts. One of the species I study – the
whale shark — they are the most brilliant of navigators. They travel thousands of miles without a compass, and they arrive at a certain spot in Belize each year just when the reef fish are spawning and there’s a wonderful buffet for them to eat.
Give us a summary of the state of the world’s sharks.
About 17 percent of 1,200 species of sharks and rays are threatened with extinction. For those species that swim in the open ocean, the numbers are even more dire. The International Union for the Conservation of Nature reports that a third of them are threatened. Most of their decline seems to be due to overfishing for shark fin soup — a prestige food in many parts of Asia. I can see firsthand what those statistics mean whenever I go diving. Twenty years ago, if you went out on the barrier reef here, you’d stand a good chance of seeing several of the giant toothy sharks — a hammerhead or a blacktip. Today, if you’re lucky, you might see a nurse shark or a stingray.
Reference: A Conversation with Rachel Graham – NYT March 2012