The whale shark, Rhincodon typus, is the largest fish species in the world. These animals are not whales but belong to the class of cartilaginous fishes, known for their massive size and gentle nature. They are easily recognizable by their broad, flattened head and a unique checkerboard pattern of pale spots and stripes against a dark gray or brownish background. This unique pattern acts like a fingerprint, allowing researchers to identify individual sharks. Whale sharks are highly migratory, inhabiting the warm, tropical, and temperate waters of the Atlantic, Pacific, and Indian Oceans.
The World Record Whale Shark
The largest whale shark ever reliably measured reached a total length of 18.8 meters, or about 61.7 feet. This confirmed measurement came from an adult female found in the Arabian Sea and was considered the most accurately documented record in a 2015 scientific review. While there are anecdotal reports of individuals reaching 20 meters or more, these measurements often lack the scientific rigor necessary for official verification. Estimates for the weight of a whale shark of this maximum size suggest they weigh in excess of 20 metric tons.
Verified Maximum Size Estimates
The average maximum size for the species is generally smaller than the record and depends on sex. Recent studies suggest whale sharks exhibit sexual dimorphism, with females growing significantly larger than males. Males typically reach a maximum average length of 8 to 9 meters, the size at which they reach sexual maturity. Females continue to grow past this point, with their estimated average asymptotic length—the size they tend not to exceed—being around 14.5 meters.
Obtaining accurate size data for the largest individuals is a persistent challenge for researchers. Most whale sharks observed at coastal aggregation sites are juvenile males, making it difficult to study large adult females. Scientific estimates, based on growth modeling, suggest the maximum theoretical size of the species could potentially reach up to 21.9 meters in length.
How Whale Sharks Achieve Gigantic Size
The large size of the whale shark is fundamentally linked to its specialized filter-feeding strategy and life history. It subsists on small organisms, including plankton, small crustaceans, and schooling fish. They employ a feeding method called ram filtration, swimming forward with their enormous mouths open to strain food particles from the water passing over their gill rakers. This technique gives them access to a vast, energy-rich food source distributed across their habitat.
Their life history is characterized by slow growth and extreme longevity, a common pattern among large animals. Whale sharks are slow to mature, with estimates placing the age of sexual maturity between 13 and 25 years. This slow development allows them to reach their immense size over a long period. Longevity estimates suggest that whale sharks can live for well over 100 years, with some males potentially reaching up to 130 years.