Whale shark

How do you identify a whale shark?

It is impossible to mistake: a massive body, blue-gray on top and white below, covered in a checkerboard of pale spots and lines, a broad, flat head, and a front-facing mouth more than a meter and a half wide on a 12-meter individual. Three ridges run along each flank to a crescent-shaped tail. The largest individual reliably measured was 18.8 meters long. Most encounters are with animals of 5 to 10 meters, often young males. One specimen of 11 to 12 meters weighed about fifteen tons. The spot pattern is unique to each animal, like a fingerprint: monitoring programs identify individuals from a photo of the left flank, behind the gills.

How does the whale shark live?

The whale shark is a filter feeder. It swims with its mouth open, at about 5 km/h, and its gill rakers trap plankton, krill, fish eggs and small schooling fish. It can also gulp water in bursts when food concentrates at the surface. That is what makes it visible: wherever a current, a tide or a coral spawning loads the water with plankton, it comes up to feed at the surface, within snorkeling range. The rest of the time, it travels and dives deep, down to 1,928 meters, the deepest dive on record. The species lives in all warm seas, between 30 degrees north and 35 degrees south. It is ovoviviparous: a female caught in 1996 carried some 300 embryos, and the pups are born at 40 to 60 centimeters. It only matures at around 8 or 9 meters, and its lifespan is estimated at 80 to 130 years.

Where and when can you see whale sharks?

Each site has its season, tied to the plankton. In Tanzania, the Mafia Island whale sharks come to the surface off Kilindoni from October to March, with a peak from November to February; you meet them snorkeling, never on scuba. In the Maldives, South Ari Atoll has them all year round, along the outer reef. In Thailand, Richelieu Rock sees them pass from February to April. In the Philippines, Donsol remains the natural encounter. At Oslob, on Cebu, fishermen feed the sharks, and the encounter, guaranteed, has nothing wild left about it. In Mexico, Isla Mujeres gathers one of the largest known concentrations from June to September, with a peak in July and August. Elsewhere, Ningaloo Reef in Australia, the Gulf of Tadjoura in Djibouti, Tofo in Mozambique, La Paz in Baja California and the Galápagos Islands are among the regular sites.

How do you approach a whale shark?

A whale shark doesn't bite, but a tail swipe from an animal weighing several tons is not up for debate, and a harassed animal leaves the surface. The codes of conduct at serious sites all say the same thing: at least three meters between swimmer and animal, more from the tail; entry into the water on the guide's signal, from the side, without jumping in front of it; no contact, no flash, no scooter; don't cut across its path, and never hold on to its fin. At Mafia, operators limit the number of swimmers per trip and work with Sea Sense and the Marine Megafauna Foundation, which wrote the code applied on the island. Feeding, as practiced at Oslob, changes the animals' behavior and is not a good idea.

Is the whale shark endangered?

The whale shark has been listed as Endangered on the IUCN Red List since 2016: its numbers have fallen by about 50% in 75 years, and by 63% in the Indo-Pacific. Fishing for its fins and meat, bycatch in nets and collisions with ships are the causes, made worse by late maturity and slow reproduction. It is listed on CITES Appendix II, which regulates its international trade. Tourism, when it respects the distances, tends to work in its favor: it funds photo monitoring of the populations and gives fishing villages, at Mafia as at Donsol, a reason to keep it alive.