The ocean’s depths hold many intricate relationships, and among the most observed is the sight of smaller fish swimming closely with sharks. This natural phenomenon often sparks curiosity about why these smaller creatures choose to associate with large predators, seemingly putting themselves in harm’s way.
The Fish That Follow
Among the most common fish observed alongside sharks are pilot fish and remoras. These agile swimmers do not attach to sharks but instead maintain a close proximity, darting around the shark’s body. Remoras, also known as suckerfish, possess a unique adaptation: their first dorsal fin has evolved into a powerful, oval-shaped suction disc on the top of their heads. This specialized organ allows them to securely attach to the skin of larger marine animals, including sharks. This physical design enables remoras to conserve energy by hitchhiking, while pilot fish rely on their speed and maneuverability to keep pace.
Benefits for the Followers
Small fish gain several advantages by associating with sharks. One significant benefit is access to food. Sharks are often messy eaters, and as they consume their prey, fragments and scraps are often left behind. Pilot fish and remoras readily feed on these discarded morsels.
Some remora species also consume parasites and dead skin from the shark’s body, effectively cleaning their host. This cleaning behavior provides a direct meal for the remora.
Protection from predators is another major advantage for these smaller fish. By remaining near a large predator like a shark, pilot fish and remoras deter other potential threats. Many marine animals avoid approaching sharks, creating a relatively safe zone around the larger fish that benefits its smaller companions. This reduces the risk of predation for the smaller fish.
Furthermore, the association offers efficient transportation. Remoras, by attaching to sharks, can travel with minimal energy expenditure. This “hitchhiking” allows them to conserve energy they would otherwise spend swimming. Pilot fish also benefit from this transport, following their host across wide expanses of water.
The Shark’s Role
From the shark’s perspective, the presence of these smaller fish can range from largely inconsequential to subtly beneficial. For many sharks, the pilot fish swimming alongside are simply tolerated, posing no threat and requiring little energy to ignore. The fast and agile movements of pilot fish make them an inefficient meal for a large shark. Sharks generally do not consume pilot fish due to this dynamic.
Remoras, however, can provide a direct service to their shark hosts. By feeding on ectoparasites and loose skin, remoras help keep the shark’s skin clean. This cleaning activity can reduce irritation and potential health issues for the shark, contributing to its overall well-being. While the impact of this cleaning may be minor for some shark species, others appear to recognize and even encourage the behavior, with some sharks observed slowing down to allow remoras to attach. However, not all sharks are equally tolerant; some species, such as sandbar and lemon sharks, have been known to act aggressively toward or even consume remoras.
The Nature of the Partnership
The relationship between sharks and the fish that follow them is a form of symbiosis. Often, the interaction between sharks and remoras is classified as commensalism, meaning one species benefits (the remora) while the other (the shark) is largely unaffected. The remora gains transportation, food from scraps, and protection, with little to no perceived cost or benefit to the shark.
However, when remoras actively clean parasites from the shark’s skin, the relationship leans toward mutualism, where both species derive a benefit. Pilot fish, by consuming parasites from the shark’s body, also contribute to a more mutualistic interaction. Despite the advantages gained by the smaller fish, there are inherent risks, such as accidental consumption by a hungry shark, though this is rare. This long-standing interspecies behavior highlights the complex and adaptive strategies that evolve in marine environments, demonstrating how diverse life forms find ways to coexist and thrive together.