Whale Shark

How big is a whale shark?

The whale shark is the largest fish alive. Adults commonly reach 30 to 40 feet and around 20 tons, and larger individuals have been reported. A whale shark is a shark, not a whale: it breathes with gills and its skeleton is cartilage. The name comes from its size and its feeding.

Each whale shark carries a pattern of pale spots and stripes that is unique to the individual, like a fingerprint. Researchers identify and track thousands of them from photographs, which is why a tourist's picture can be real science.

What whale sharks eat

Plankton, fish eggs, krill and small schooling fish, strained from the water through a mouth that can be four to five feet wide. A whale shark swims slowly with its mouth open or gulps actively at the surface where food is thick. Its teeth, thousands of them, are tiny and play no role in feeding.

Where whale sharks live, and the Baja connection

Whale sharks range through warm seas worldwide and gather seasonally where food concentrates: Western Australia, Mexico's Yucatán, the Philippines, and, close to home, the Gulf of California. Bahía de La Paz and Bahía de los Ángeles in Baja California host juvenile whale sharks for months each year, with regulated swim tours a couple of hours' flight from Southern California.

Why whale sharks are endangered

The IUCN listed the whale shark as Endangered in 2016 after population declines of more than half in parts of its range. They are struck by ships, caught in nets, and were long hunted for fins and meat in some countries. They grow slowly and may live 80 years or more, so losses are not quickly replaced. Responsible tourism, with limits on boats and swimmers, has become one of the main reasons to keep them alive.