The sight of small fish swimming closely alongside large, predatory sharks can appear puzzling. The apparent risk to the smaller fish seems high, yet they deliberately maintain proximity to these powerful ocean dwellers. This intriguing phenomenon highlights complex interactions within marine ecosystems, where species often find unexpected ways to coexist.
Benefits for Small Fish
Small fish gain several advantages by associating with sharks, including protection, food, and energy conservation. The mere presence of a large shark often deters other, smaller predators, effectively turning the shark into a living shield. This protective barrier significantly reduces the risk of predation for the smaller fish.
Beyond safety, these small fish often benefit from a consistent food supply. Sharks’ feeding activities can leave behind numerous scraps and fragments of prey. Pilot fish, for instance, feed on these leftovers, acting as a cleanup crew. Additionally, some companion fish consume parasites and dead skin from the shark’s body, providing a cleaning service while securing their meal.
Another advantage is energy conservation. By swimming within the hydrodynamic wake created by a shark, smaller fish reduce their energy expenditure. This allows them to travel considerable distances with less effort. This “hitchhiking” ability provides a significant benefit.
The Shark’s Perspective
Sharks generally tolerate the presence of these smaller fish, and in some cases, even benefit from the association. Sharks do not consume these companions because the small fish are often not worth the energy expenditure to hunt. Their size makes them an inefficient meal for a large predator.
Many companion fish provide a cleaning service. Species like remoras and pilot fish consume parasites, dead skin, and food scraps from the shark’s body and even from inside its mouth. This helps keep the shark’s skin and gills free from irritating organisms and potential infections. Sharks have been observed to slow down, seemingly allowing remoras to attach, indicating a recognition of this beneficial interaction.
The relationship is often described as mutually beneficial; sharks do not perceive these companion species as food due to their behavior and the benefits they offer. This tolerance allows for a cooperative dynamic where both parties gain something.
Specific Examples of Companions
Two well-known examples of fish that swim alongside sharks are pilot fish and remoras. Pilot fish ( _Naucrates ductor_ ) are slender, striped fish often seen swimming directly in front of, or alongside, sharks, rays, and sea turtles. They primarily feed on parasites found on the shark’s body and scavenge on food scraps left over from the shark’s meals. This dietary habit provides the pilot fish with a consistent food source while helping to keep the shark clean.
Remoras, also known as suckerfish, are distinct due to a modified dorsal fin on their heads that forms a powerful suction disc. This unique adaptation allows them to firmly attach themselves to the bodies of sharks, as well as whales and sea turtles, for transport. Remoras benefit from free transportation, access to food scraps, and protection from predators. In return, they help clean the shark by feeding on parasites, dead skin, and uneaten food particles.