The silky shark, Carcharhinus falciformis, is a large, fast-swimming predator found throughout the world’s tropical and subtropical waters. Named for the smooth texture of its skin, which is due to densely packed dermal denticles, this species is one of the most abundant sharks in the open ocean. It has a slender, streamlined body and is a highly mobile, opportunistic carnivore in the vast pelagic zone. Its diet is dictated largely by the availability of prey.
The Core Diet: Bony Fish
The primary component of the silky shark’s diet consists of a wide variety of bony fish. As epipelagic species, they hunt mainly in the upper water column down to about 200 meters, often near continental and insular shelves. They are intensely sensitive to low-frequency sounds, which they use to locate schools of fish and other feeding animals.
A significant portion of their prey includes small schooling fish, such as sardines, anchovies, and various species of mackerel. The silky shark is particularly known for its association with larger, commercially important pelagic species. They frequently follow and prey upon schools of tuna, especially skipjack (Katsuwonus pelamis) and yellowfin tuna (Thunnus albacares).
The ability to follow these highly mobile tuna schools makes the silky shark a highly effective oceanic hunter. Their hunting strategy sometimes involves driving schools of fish into compacted masses before launching a slashing attack. Other bony fish found in their stomachs include albacore, mullet, and porcupine fish.
Secondary Prey: Cephalopods and Crustaceans
While bony fish form the bulk of their meals, cephalopods and crustaceans also contribute to the silky shark’s diet. Squid are a particularly significant secondary food source consumed across the shark’s global range. Studies show that cephalopods can sometimes make up a substantial percentage of the stomach contents.
Specific cephalopods include jumbo squid (Dosidicus gigas) and various other squid species frequently encountered in the open ocean. They also occasionally consume octopus and nautiluses. The inclusion of these items highlights the shark’s flexibility in exploiting available food resources.
Crustaceans are also consumed, though they typically form a smaller percentage of the overall diet. These often include pelagic crabs, such as the red crab (Pleuroncodes planipes), and various shrimp. The consumption of these smaller prey items is more common among smaller or juvenile sharks.
How Diet Varies by Age and Location
The silky shark’s diet is dynamic and shifts based on the animal’s life stage and geographical location. Juvenile silky sharks begin their lives in coastal nursery areas and consume a higher proportion of smaller fish and crustaceans near the sea floor. This shift in diet moves to higher trophic levels as the shark grows larger.
As they mature, subadults and adults migrate offshore to deeper, oceanic waters. Their diet transitions to larger fish and more cephalopods, primarily targeting fast-moving tuna and other pelagic fish. This change reflects their greater size and ability to hunt in the open ocean.
Geographical location also plays a strong role, as the diet reflects the most abundant local prey. Sharks near oceanic islands may feed on different species compared to those in the open Pacific. For example, in the Arabian Sea, one study found the diet to be split between fish (52.41%), cephalopods (28.28%), and crustaceans (17.93%).