Sharks often evoke images of powerful apex predators with formidable teeth, dominating ocean ecosystems. This perception, largely shaped by popular culture, focuses on species like great white sharks and tiger sharks known for their hunting prowess. However, the vast and diverse world of sharks holds many surprises, prompting a question that might seem contradictory to their fearsome reputation: do sharks eat plankton? This unveils a remarkable aspect of shark biology: some of the largest sharks sustain themselves not on large prey, but on the smallest organisms.
Sharks That Eat Plankton
A select group of sharks feeds exclusively on plankton. The three primary species are the whale shark, the basking shark, and the megamouth shark. These filter-feeding giants efficiently strain tiny organisms from vast quantities of seawater. Their large mouths engulf water containing microscopic prey.
The whale shark, the largest fish in the world, employs both ram filtration and active suction feeding. It can filter immense amounts of water, consuming an estimated 21 to 45 kilograms of plankton daily.
Basking sharks, the second-largest fish, are obligate ram feeders, filtering up to 2,000 tons of water per hour. Their diet primarily consists of zooplankton, particularly small crustaceans called copepods. Megamouth sharks, the rarest of the three, also filter plankton and jellyfish. All three species utilize specialized gill rakers that trap food particles as water passes through their gills.
Understanding Plankton
Plankton refers to any small organism that drifts with ocean currents rather than actively swimming against them. This diverse group forms the foundational layer of marine food webs. Plankton is broadly categorized into two main types: phytoplankton and zooplankton.
Phytoplankton are microscopic, plant-like organisms, primarily algae, that produce their own food through photosynthesis. They are found near the water’s surface where sunlight is available. Zooplankton are animal-like organisms, including small crustaceans like copepods and krill, as well as the larval stages of various marine animals. These tiny animals feed on phytoplankton and other smaller zooplankton, transferring energy up the food chain.
Gentle Giants of the Sea
Despite their immense size, these plankton-eating sharks are known for their docile nature. Whale sharks, for instance, are often described as gentle and can be observed by divers without incident. Their diet of microscopic organisms means humans are not considered prey.
Basking sharks are similarly passive and typically avoid close interactions with people. While their sheer size and rough skin necessitate caution and maintaining distance, there are no verified records of these sharks attacking humans. Megamouth sharks are also considered slow-moving and not aggressive. The calm demeanor and specialized feeding habits of these filter-feeding sharks illustrate a peaceful coexistence between some of the ocean’s largest inhabitants and humans.