The blue shark (Prionace glauca) is a highly migratory species inhabiting the world’s oceans. Its slender body and vibrant indigo coloration make it one of the most recognizable pelagic sharks. This species is found across tropical, subtropical, and temperate waters globally. This analysis addresses the blue shark’s typical environment and the reality of its threat level to ocean users.
The Blue Shark’s Typical Behavior and Habitat
Blue sharks are creatures of the open ocean, primarily occupying the pelagic zone far from coastal areas. They prefer the upper water column, specifically the epipelagic and mesopelagic zones, where water temperatures range from 12 to 20 degrees Celsius. This offshore preference is the primary reason why encounters with humans are naturally rare, as their habitat does not overlap with near-shore swimming areas. Their diet consists mainly of small, schooling bony fish and cephalopods, such as squid. The blue shark’s teeth are best suited for grasping and cutting soft-bodied prey, reflecting this specialized feeding strategy.
Documented Human Interactions and Attack Rarity
The blue shark is classified as a low-risk species to humans, supported by the extremely limited number of documented incidents worldwide. Historical data from the International Shark Attack File (ISAF) indicates only 13 unprovoked bites attributed to the species across multiple centuries, with only four resulting in fatalities. Interactions are often investigatory rather than predatory; sharks use their mouths to explore unfamiliar objects, which can result in an exploratory bite. This behavior is distinct from the predatory attacks associated with larger coastal species. Since the blue shark’s offshore habitat and diet consist of small pelagic organisms, they have little experience with large terrestrial prey like humans, making unprovoked incidents exceptional events.
Situations That Increase Encounter Risk
While the overall risk remains low, specific human activities significantly increase the probability of an encounter. The blue shark is a highly curious animal known to approach objects, especially when food is present. Spearfishing, which introduces struggling fish and blood into the water, can strongly attract a blue shark and create a high-risk situation. Commercial and recreational fishing practices are another major source of human-shark proximity. Blue sharks are frequently caught as bycatch on longlines, leading to direct contact with people during retrieval and handling.
Situations where a shark is caught, injured, or stressed often lead to provoked incidents, as the animal acts in self-defense. If an encounter occurs, maintaining consistent eye contact is recommended, as it signals the shark has been noticed. A slow, deliberate retreat without splashing minimizes the perception of distress that might trigger an investigatory response. Avoiding areas where chumming or fishing is taking place eliminates potent scent cues that draw this curious predator closer to human activity.