The basking shark, Cetorhinus maximus, holds the title of the world’s second-largest fish, surpassed only by the whale shark. This immense size immediately sets it apart and makes it a subject of considerable fascination for anyone interested in the giants of the ocean. The massive dimensions of this creature are directly linked to its method of feeding, its physical structure, and its movements across the globe.
Measuring the Giant: Average and Maximum Length
The average adult basking shark regularly reaches an impressive length, typically falling between 23 and 28 feet (7 to 8.5 meters). This typical size is comparable to the length of a full-sized school bus, giving a clear idea of the animal’s substantial presence in the water. An adult male often averages about 26 feet (7.9 meters) in length.
While the average size is already remarkable, some individuals grow considerably larger, reaching up to 33 to 36 feet (10 to 11 meters) long. The largest credibly recorded specimen, caught in the Bay of Fundy in 1851, measured 40.3 feet (12.27 meters). However, modern studies suggest that individuals exceeding 33 feet are rare.
Weight and Defining Physical Structure
The great length of the basking shark translates into a considerable mass. The average adult weighs approximately 4.65 tons (4,220 kilograms). Larger individuals can weigh up to 6 tons (5,440 kilograms) or more, a weight range roughly equivalent to that of a large rhinoceros. This immense body mass requires specific anatomical features to function effectively as a filter feeder.
The defining physical feature related to its size is the five pairs of massive gill slits that nearly encircle the head. These slits are dramatically long, allowing for an enormous volume of water to pass through the gills. The mouth itself is also cavernous, capable of opening up to about 3.3 feet (1 meter) wide when feeding. This enormous oral cavity and the extensive gill apparatus are anatomical necessities that accommodate the shark’s massive scale and its unique feeding strategy.
The conical snout, the large mouth, and the extended gill slits all contribute to a highly specialized head structure designed for bulk water processing. Furthermore, the basking shark possesses a very large liver that can account for up to 25% of its body weight, helping to provide buoyancy.
Life of a Basking Shark: Range and Feeding
The basking shark is a cosmopolitan species, meaning it is found in temperate waters across the globe, including both the North and South Atlantic and Pacific Oceans. It is a highly migratory animal, often seen near the surface in coastal waters during the spring and summer months when zooplankton is abundant. As the seasons change, these sharks migrate over thousands of miles, sometimes moving into deeper, offshore waters during the winter.
This enormous animal sustains its size by feeding exclusively on zooplankton, which are tiny marine organisms like copepods, fish eggs, and larvae. Its feeding method is known as passive ram feeding, where the shark swims slowly forward with its mouth wide open. This action forces water into the mouth and over the gills, where the food is strained out. The immense gill slits house thousands of specialized, bristle-like structures called gill rakers, which act as a sieve to trap the microscopic prey. A large basking shark is capable of filtering up to 500 short tons of water per hour, demonstrating the efficiency required to gather enough small organisms to support its massive body.