Are Blue Sharks Dangerous? Everything You Need To Know

The blue shark (Prionace glauca) is an apex predator found in all temperate and tropical oceans around the world. With a sleek, streamlined body and long pectoral fins, blue sharks are powerful swimmers capable of bursts of high speed and migrating long distances. They primarily feed on small fish and squid.

Blue sharks have gained an unfair and largely exaggerated reputation as being the most aggressive and dangerous sharks towards humans. However, the truth is that while blue sharks may investigate humans out of curiosity, they rarely pose any threat.

According to the International Shark Attack File (ISAF), there have been only 13 confirmed unprovoked bites attributed to blue sharks worldwide since 1580, with just 4 being fatal. Their inquisitive nature combined with sharp teeth can lead to accidental bites, but they do not intentionally hunt humans.

The number of confirmed, unprovoked blue shark attacks on humans is extremely low.

Blue Shark Characteristics

Blue sharks can grow up to 4 meters (13 feet) in length, and the largest recorded specimen weighed 205 kg (454 pounds). However, most adults measure 1.7 to 2.2 meters (5.6 to 7.2 feet) long.

They have a vivid blue coloring on their backside that fades to a bright white underside. This counter-shaded pattern provides camouflage from above and below in the open ocean waters they inhabit.

They have a vivid blue coloring on their backside that fades to a bright white underside. This counter-shaded pattern provides camouflage from above and below in the open ocean waters they inhabit.

Blue sharks are fast, agile swimmers capable of reaching speeds of 25 mph in short bursts. They can migrate long distances, swimming thousands of miles between feeding and breeding grounds.

They have an exceptionally keen sense of smell that allows them to detect tiny concentrations of chemical odors over vast distances. This allows them to hunt prey efficiently or find potential mates.

Blue sharks are social animals and are often found together in size-specific groups segregated by age and sex.

Blue sharks have one of the largest global distributions of any shark species. They are found in temperate and tropical waters between latitudes 64°N and 43°S. In parts of their range, they migrate between cold offshore feeding areas and warm inshore breeding areas.

Blue Shark Diet

Blue sharks are opportunistic predators that feed on a variety of prey, primarily small bony fishes like herring and mackerel, as well as squid. Less commonly, they may also eat crustaceans, carrion such as floating whale and turtle carcasses, smaller sharks, and occasionally seabirds.

They capture prey using speed and stealth, sneaking up from below before delivering a sudden snap of their powerful jaws. Their serrated teeth allow them to grip slippery prey effectively. Like most sharks, blue sharks swallow their prey whole and have expandable stomachs to ingest large items.

Blue sharks constantly shed and replace their teeth throughout their life, with older teeth near the center and newer teeth towards the edge of the jaw. An individual may shed and replace over 35,000 teeth in a lifetime. Their teeth are coated with fluoroapatite, which helps them remain stable in water.

Why Are Blue Sharks Perceived as So Dangerous?

So, if blue sharks pose minimal risk to humans, why do they have this largely exaggerated reputation for aggressiveness and danger? There are a few reasons:

Sheer Abundance and Distribution

Blue sharks are the most abundant large sharks in the world’s oceans. Scientists estimate a global population numbering over 20 million individuals.

Their vast global distribution and large numbers mean they overlap significantly with areas of intense human maritime activity, from busy shipping lanes to popular fishing grounds.

The chances of a human encountering a curious blue shark are higher than for most other shark species simply due to the probability of crossing paths in their extensive shared habitat.

Tendency to Investigate Objects and Humans

Blue sharks are naturally very inquisitive creatures that rely heavily on their acute sense of smell to discern objects in their environment.

Upon detecting an unknown stimulus like a boat, floating debris, or human swimmer, blue sharks may approach to inspect the potential food source, threat, or mate. This curiosity and tendency to investigate the unfamiliar leads to frequent shark-human encounters.

Often, a shark will perform one or two cautious investigative passes of a person or object before losing interest and swimming away without incident. Nonetheless, proximity can cause unnecessary alarm and intensify an overblown reputation even when benign in nature.

Sensational Headlines and Misinformation

The media has played a significant role in villainizing blue sharks by selectively highlighting rare shark “attack” incidents involving aggressive behavior and injuries.

These extremely rare events create shocking headlines that instill an exaggerated, disproportionate fear of blue sharks as blood-thirsty killers. In reality, most blue shark bites are just exploratory nips and nibbles with no actual attempt to consume a human as prey.

Shark “attacks” also remain extremely statistically rare events, especially fatalities. You have significantly greater odds of perishing in countless everyday activities than an unprovoked shark attack.

Nonetheless, the instinctive human fear of sharks means any confrontation makes headlines, while millions of docile encounters between blue sharks and humans go unreported. This distorts public perception of the true risk posed.

How Dangerous Are Blue Sharks To Humans?

The risk blue sharks present to humans has been greatly exaggerated. As an apex predator, blue sharks should certainly warrant a reasonable degree of caution and respect, but there is little evidence supporting an enhanced risk to human safety.

Unprovoked Attacks Are Very Rare

Despite occupying such extensive, overlapping ranges with humans, confirmed incidents of aggressive, unprovoked blue shark attacks are extremely rare.

According to the International Shark Attack File’s (ISAF) records, there have been 13 confirmed unprovoked cases of blue sharks attacking humans since records began in 1958, resulting in 4 fatalities. That equates to about 1 attack every 4 years globally.

The number of fatal blue shark attacks is even more infinitesimal, with only 4 confirmed deaths occurring in the past decades. You have significantly better odds of being killed by lightning (1 in 700,000 per year), bee stings (1 in 54,516 per year), or accidentally falling (1 in 1,588 per year).

Only 13 unprovoked bites of blue sharks worldwide since 1580

Most Bites Are Exploratory, Not Life-Threatening

The vast majority of the rare bites and nips inflicted by blue sharks are exploratory test bites, not determined full-scale attacks intending to consume a human victim.

Upon encountering an unidentified object, blue sharks may take an investigatory nip and bite to gather sensory information on what they’ve discovered. These are not acts of aggression but rather caution as the shark gathers cues to evaluate if this novel item is prey, threat, or something else entirely.

In most cases, the shark quickly determines the human is an unsuitable meal. They subsequently lose interest and disengage without causing major trauma or injury. While even minor bites require first aid, only a small percentage of bites inflict life-threatening harm.

Humans Are Not Part of Their Normal Prey

Blue sharks feed predominantly on a diet of small bony fish and squid. There is no evidence they actively hunt humans as natural prey.

Shark attacks almost always consist of a case of mistaken identity or opportunity, rather than a determined effort to hunt humans. Conditions like poor visibility, unusual water temperatures, or the scent of bait/blood in the water may cause a shark to confuse a human for its typical prey items during an investigative bite.

But they do not reliably or consistently consume humans as a prey source like their traditional food. Humans remain a rare exception, not a targeted norm in their hunting behavior.

Blue Shark Attack Prevention Tips

While the risk posed by blue sharks remains statistically small, prudent caution should still be exercised in areas they inhabit. Here are some tips for minimizing already unlikely dangerous encounters when in blue shark territory:

  • Avoid excessive splashing, noise, or vibrations in the water, which may inadvertently attract curious sharks
  • Refrain from provocative behaviors towards sharks, like trying to touch them
  • Avoid waters with known shark bait like chumming activity or evidence of bleeding/injured prey
  • Pay attention to signage or expert guidance regarding the seasonal movement of migratory shark populations
  • Take care handling bait/fish onboard boats as residual blood scent may stimulate investigative behavior
  • Carefully release caught sharks by cutting lines close to minimize trauma rather than pulling out hooks
  • Keep medical first-aid kits aboard watercraft in case of accidental bites that need treatment
  • Maintain situational awareness without panicking at first sightings of docile sharks demonstrating routine, harmless behaviors

In the highly unlikely event of an aggressive shark displaying threatening behavior:

  • Remain calm and don’t provoke further aggressive reactions via erratic movements
  • Carefully evacuate the water and notify other people in the immediate area
  • Seek emergency first aid for any sustained bites/trauma
  • Alert local wildlife authorities to persistent aggressive activity

Why Conservation of Blue Sharks Matters

Photo: NOAA Fisheries West Coast

Rather than fear blue sharks, they deserve appreciation and stewardship as a unique, vulnerable ocean dweller we are privileged to occasionally encounter.

Global shark populations, including blue sharks, face severe population declines. Blue shark populations specifically have declined by nearly 50% in the Atlantic over the past 50 years. The latest 2018 IUCN Red List assessment listed the blue shark as Threatened based on substantial population declines over the past few decades. Major threats driving the collapse include:

  • Overfishing for the Asian shark fin soup trade industry
  • Accidental bycatch mortality in commercial longline and driftnet fisheries targeting tuna and swordfish
  • Slow reproductive cycles that hinder rebuilding depleted populations

Up to 20 million blue sharks were estimated to be harvested annually in the early 2000s as bycatch in fisheries worldwide. However, more recent analyses of global shark catch data estimate annual blue shark mortality to be around 7 million individuals. Blue sharks compose 36-41% of the global shark fin trade.

Better reporting, catch limits, finning bans, bycatch reduction in commercial fisheries, and protected sanctuaries are vital initiatives needed to prevent extinction and stabilize fragile blue shark populations.

These apex predators maintain balance in marine food webs critical to ecosystem function and health. Continued exploitation without restraint threatens the whole ocean system.

Rather than vilify blue sharks, we would do well to respect them by overcoming exaggerated fears, rejecting sensationalism, and championing responsible stewardship. Our fate remains intertwined with that of the oceans, and blue sharks have traveled these waters long before we arrived on the scene. They remind us that sharks still occupy a realm where humans barely grasp the rules of survival.


Blue sharks have developed an outsized, largely exaggerated reputation as a premier human-hunting threat among sharks. In reality, aggressive predation of humans constitutes extremely abnormal behavior for this abundant apex fish.

The number of harmful negative encounters is extraordinarily small, given the extensive overlap between human activity and blue shark habitat use. Their inquisitive bumps and bites almost always constitute harmless investigative behavior, not determined attacks to prey on people.

Rather than fear blue sharks, these magnificent ocean migrants deserve appreciation, responsible management, and stewardship to ensure their continued survival among increasingly endangered shark species. Respectful coexistence remains possible with improved public understanding of realistic risk, rejection of sensationalism, and sustainable conservation commitment moving forward.

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