The basking shark, Cetorhinus maximus, is the world’s second-largest fish, surpassed only by the whale shark. Reaching up to 12 meters (40 feet) and weighing over 5 tons, this marine animal maintains a docile demeanor. It does not actively hunt large prey, instead relying on a unique and gentle feeding strategy that distinguishes it from most other shark species. This filter-feeding habit allows the basking shark to sustain its massive body by consuming microscopic organisms from the water.
What They Consume
Basking sharks primarily consume zooplankton, which are tiny animals that drift within ocean currents. Their diet largely consists of small crustaceans, particularly copepods, such as Calanus finmarchicus and Calanus helgolandicus. These sharks also filter out other minuscule organisms, including larval fish, fish eggs, and various small invertebrates. While zooplankton forms the bulk of their diet, basking sharks also ingest phytoplankton, which are microscopic plant-like organisms. Due to their immense size, these sharks must consume vast quantities of these tiny food sources, filtering millions of individual plankton each day to meet their energy demands.
Their Unique Feeding Method
Basking sharks employ a distinctive feeding strategy known as passive ram filtration. They swim with their mouths open, creating a wide cavity that allows water to continuously flow through. Their mouth can open over three feet wide, acting like a large net. As water passes through, specialized structures called gill rakers, which are dark and bristle-like, efficiently trap the plankton. These gill rakers are long, comb-like processes that extend from the gill arches, preventing food particles from escaping while allowing water to exit through the gill slits. Unlike other filter-feeding sharks that can actively pump water, the basking shark relies solely on its forward swimming motion to push water over its gills, making it a continuous and energy-efficient process. A single basking shark can filter up to 2,000 tons of water per hour, which is roughly equivalent to the volume of an Olympic-sized swimming pool.
Where Their Food is Found
The feeding behavior of basking sharks directly influences their movements and preferred habitats. They are commonly found in temperate and cold waters across the globe, inhabiting both coastal and open ocean environments. Basking sharks are often observed near the surface of the water, especially during seasonal plankton blooms when concentrations of their food sources are highest. Their name itself, “basking,” comes from their habit of appearing to “sun” themselves at the surface, which is actually a feeding activity. These sharks exhibit migratory patterns, often traveling thousands of miles to follow these rich patches of plankton, for example, shifting northward in summer along the North American Atlantic coast and migrating across ocean basins in search of abundant plankton.