The phenomenon of smaller fish consistently traveling with large marine predators is a common sight in the ocean. These associations are often long-term relationships where the smaller fish gain significant benefits from their intimidating companions. The behavior highlights complex ecological strategies where smaller species leverage the size and danger of the predator to thrive in the competitive open ocean environment. This partnership is a key example of how marine life interacts to maximize their chances of finding food and avoiding predation.
Why Fish Associate with Sharks
The relationship between sharks and their fish companions is primarily classified by ecologists as a form of symbiosis, specifically commensalism, where one species benefits while the other is largely unaffected. The smaller fish species gain three significant advantages from remaining close to the shark. The most direct benefit is the significant conservation of energy through transportation, where the fish either physically attach themselves or swim within the shark’s hydrodynamic slipstream.
Remaining near a large predator provides a powerful defense mechanism, as the shark’s presence deters many mid-level predators that would otherwise hunt the smaller fish. The threat of the shark’s size and reputation acts as a living shield against potential attackers. Furthermore, these companions secure a reliable food source by accessing the scraps and fragments of meals left behind after the shark feeds.
While often described as commensalism, the relationship can sometimes cross into mutualism. Smaller fish provide a cleaning service by consuming parasites and dead skin from the sharkâs body. This improves the host’s health and reduces irritation, suggesting a tangible benefit for the shark.
Primary Examples: Remora and Pilot Fish
The two most famous examples of fish that swim with sharks are the remora and the pilot fish, each utilizing a distinct method to secure their symbiotic relationship. The remora, also known as the suckerfish, possesses a unique physical adaptation: a modified first dorsal fin that has evolved into a powerful, oval-shaped suction disc on the top of its head. This disc contains transverse movable laminae that create a vacuum, allowing the remora to latch securely onto the shark’s rough skin without causing harm.
Remoras use this attachment for continuous, effortless transportation across vast distances of the ocean, significantly reducing the energy they would otherwise spend swimming. They detach to feed on scraps of the shark’s prey that drift away during a kill, or they graze on parasites and detritus directly from the shark’s body, including inside its mouth. These fish typically measure between one and three feet in length and can be found attached to the shark’s belly or flank.
Unlike the physically attached remora, the pilot fish maintains a close, but independent, proximity to the shark, swimming just ahead of its snout or along its sides. The pilot fish is easily recognized by its distinctive dark blue to blackish-silver body marked with five to seven prominent vertical dark bands. Its strategy involves swimming within the boundary layer of water surrounding the shark, where the water moves at a speed similar to the shark’s, allowing the pilot fish to travel quickly with minimal effort.
Pilot fish dart in quickly to feed on scraps of food or small organisms disturbed by the shark’s movement, and they sometimes enter the shark’s mouth to clean away food fragments from its teeth. They belong to the jackfish family and are highly maneuverable, enabling them to keep pace with their host. The primary benefit remains transportation and access to food.
Temporary and Protective Associations
Beyond the permanent relationships of the remora and pilot fish, other species of smaller fish will form more transient associations with large sharks for temporary benefits. Schooling fish, such as jacks and trevally, are sometimes observed using the massive body of a shark as mobile cover, especially in the open pelagic zone where there is little other shelter. They position themselves in the shark’s blind spot or shadow, using the large predator as a temporary shield against their own attackers.
This behavior can also be exploited for hunting, as certain fish like the blue runner have been documented using the shark as a moving blind to ambush their own prey. By hiding behind the bulk of the larger animal, they gain a stealth advantage against smaller, unsuspecting targets. These temporary associations are opportunistic and are generally not maintained over long periods, unlike the structured symbiosis of the remora.
Shark-Rubbing
Even species like mackerel have been observed seeking out sharks, deliberately rubbing against their abrasive skin. This action, known as “shark-rubbing,” is thought to be a way for the smaller fish to scratch off irritating parasites or loose scales. These less structured interactions demonstrate that a shark’s presence in the marine ecosystem is utilized in various ways by smaller fish, ranging from permanent hitchhiking to brief, opportunistic encounters for protection or relief.