The blue shark, Prionace glauca, is a wide-ranging oceanic shark found across the world’s temperate and tropical waters. This species exhibits a diverse diet, consuming a variety of marine life. Its feeding habits are adaptable, allowing it to thrive in different environments and capitalize on available food sources.
Main Components of the Blue Shark Diet
The blue shark’s diet consists mainly of fish and cephalopods. Squid are particularly important prey, often dominating their stomach contents. Cephalopods consumed include cuttlefish, blanket octopuses, pelagic octopuses, and various deep-water squid species.
Blue sharks also consume a wide array of bony fish. These include pelagic schooling fish such as herring, mackerel, sardine, and anchovy. Other fish species found in their diet are hake, cod, pollock, butterfish, and even larger prey like tuna and swordfish. Beyond fish and squid, their diet can include other invertebrates like lobsters, shrimp, and crabs.
Flexible Feeding Strategies
Blue sharks are opportunistic feeders, consuming whatever prey is available. This flexibility allows them to exploit a wide range of food sources beyond their typical live prey. They are known to scavenge on carrion, such as the carcasses of dead whales and porpoises, which can provide a substantial meal.
Their opportunistic nature also extends to consuming fish discards from fisheries. Blue sharks have been observed attacking and consuming fish caught on longlines, sometimes becoming ensnared themselves. They may also consume seabirds and, in rare instances, krill, which is unusual for a non-filter feeding shark. Blue sharks can exhibit cooperative feeding behaviors, with groups sometimes herding prey into concentrated schools for easier consumption.
Dietary Variations by Age, Size, and Habitat
A blue shark’s diet can vary significantly based on its life stage, size, and the specific habitat it occupies. Younger, smaller blue sharks may consume different prey items compared to larger, mature individuals.
Geographic location also influences prey availability and, consequently, the shark’s diet. Sharks in offshore, deeper waters might primarily feed on mesopelagic cephalopods and fish that inhabit those depths. Conversely, those found in shallower, inshore areas may consume more neritic fish and cephalopods. Seasonal changes in water temperature and prey migration patterns can also lead to shifts in the blue shark’s diet.