September 30, 2020 9:44 pm

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By Kátia Silva, guide and Marine Biologist at CaboTrek.com, edited by Destino Los Cabos

Imagine swimming in the calm waters of the Sea of Cortez and a friendly fish that is as long as a school bus–if not longer–is also swimming just a few feet away from you, making you feel like you're actually swimming together. Its enormous slow moving fins and tail gently navigating it through the water as you swim by its side. During the months of October through April whale sharks visit the Sea of Cortez, so you can have a swimming experience with these breathtaking animals right here in Baja near the city of La Paz, only 1 hour and 45 minutes north of Cabo San Lucas. Let's learn about these immensely interesting creatures: 

Whale sharks (Rhincodon typus) are sharks, not whales. Therefore, they are fish, not mammals. Despite its massive size, whale sharks are the “Gentle Giants” of the ocean and they pose no harm or threat to divers and to humans in general. Unlike their other shark relatives that are meat-eaters, these giants are filter feeders. They are a highly migratory, pelagic species distributed circumglobal in all tropical and warm temperate seas, oceanic and coastal, except in the Mediterranean Sea. The distribution of whale sharks points to the presence of plankton and serves as an indicator of overall ocean and ecosystem health. Their the ancestry goes back to the Jurassic and Cretaceous periods 245-65 million years ago, when the present groups of sharks began to appear. It was not until 1828 when the first whale shark specimen known to science was discovered off the South African coast.

Whale sharks are the largest sharks in the world, truly the biggest fish in the sea. This animal is enormous and reportedly capable of reaching a maximum length of about 18 meters (59 feet), can weigh up to 20 tons and can live to over 100 years. Though they are big, their brains are tiny. As it swims, it sucks water through its gargantuan mouth that can be as wide as 5 feet, then filters out plankton and other microscopic organisms through its gills. They obtain oxygen via their gills, so they have no physiological requirement to swim at the surface - unlike air-breathing whales and dolphins.

Their body coloration is distinguished by light vertical and horizontal stripes that form a checkerboard pattern on a dark background, and light spots mark the fins and dark areas of the body. Like human fingerprints, each whale shark has a unique pattern of spots that allows individual sharks to be identified.

Unfortunately, like many other marine species, there are fewer of them every day. We are losing these animals at a rate which is unprecedented in the history of planet Earth. Whale sharks were listed as endangered in 2016, their survival imperiled by fisheries where they turn up as by-catch, and the demand for shark fins in Asia. Fortunately, a large tourism industry has been developed for viewing whale sharks in the wild. For that reason, and because they are such impressive animals, in most places around the world they are legally protected. The local community in La Paz, researchers, tour operators and authorities have done important work to protect these animals. Supporting ecotourism is one of the ways you can help to save whale sharks, and make sure you choose a responsible tour company to have this incredible experience!

Researchers know very little about whale shark reproduction and life history. Only one pregnant whale shark has ever been physically examined by scientists. This singular shark, caught in a fishery off Taiwan in 1995, carried over 300 pups inside her. That is almost twice as many as any other shark species. They do not know if this is normal. They still do not know how often females produce pups either.

Although the whale shark is usually solitary, it is sometimes found in schools of up to hundreds of individuals. These animals are found mainly in the open sea, but they also come near the shore. There are several sites where large numbers of whale sharks aggregate, attracting tourists from all over the world. Most of the sharks present at these sites are juvenile males between four and nine meters in length.

La Paz, BCS is one of the few places in the world where with just 20 minutes of navigation it is possible to be side by side these animals. A whale shark monitoring program in La Paz operating since 2003 shows that up to 66% of juveniles have been hit by boats. In collaboration with the Mexican government, a Code of Conduct was generated for whale shark tour operators. Regulations include staying 10 feet away from the shark’s head, no more than five people should be in the water with one shark at a time, and no touching the animal. All boats are monitored by GPS.