Small fish swimming alongside or attached to large sharks is a common and intriguing spectacle. This unique interspecies relationship highlights a complex natural arrangement where each participant often finds a way to benefit.
The Companions: Who Are These Fish?
Two primary types of small fish are frequently observed alongside sharks: remoras and pilot fish. Remoras, also known as suckerfish, are distinctive for the oval-shaped suction disc on their heads, which is a modified dorsal fin. This disc allows them to securely attach to larger marine animals, including sharks, whales, and turtles.
Pilot fish, on the other hand, do not attach to sharks but swim closely alongside them. These fish are characterized by dark blue to blackish-silver bodies with five to seven dark vertical stripes. While often seen with sharks, pilot fish also associate with rays and sea turtles. Both remoras and pilot fish have developed distinct behaviors that facilitate their close proximity to these large marine predators.
A Strategic Alliance: Why They Tag Along
The association between these smaller fish and sharks is a strategic alliance offering several benefits to the smaller companions.
Protection
One significant advantage is protection from predators. Few predators are willing to approach a shark, providing a natural bodyguard for the smaller fish. Pilot fish gain security by being close to a formidable predator, as other potential threats are deterred by the shark’s presence.
Food Access
Access to food scraps represents another substantial benefit for both remoras and pilot fish. Sharks are not the cleanest eaters, often leaving behind fragments and leftovers from their meals. Remoras can detach from their host to consume these discarded food particles, while pilot fish actively scavenge around the shark during feeding. Some remora species are even known to consume their host’s feces, extracting nutrients from it.
Transportation and Energy Conservation
Associating with sharks offers a significant advantage in terms of transportation and energy conservation. Remoras save considerable energy by hitching a ride, avoiding the need to expend their own effort swimming across vast ocean distances. Their suction disc is remarkably strong, allowing them to remain attached even as a shark swims at high speeds or makes sudden movements. Pilot fish also benefit from the shark’s movement, as swimming within the shark’s slipstream or boundary layer can reduce their own energy expenditure.
The Shark’s Perspective: Is There a Benefit?
From the shark’s perspective, the relationship with remoras and pilot fish is largely considered commensal, meaning one species benefits while the other is neither significantly helped nor harmed. However, there can be minor advantages for the shark, particularly regarding remoras. Remoras are known to clean parasites and dead skin from the shark’s body, including inside its mouth. This cleaning service can contribute to the shark’s overall health by reducing irritants and potential infections.
Pilot fish also consume parasites that attach to the shark’s skin, contributing to their cleanliness. While the benefits for the shark are often considered negligible compared to the substantial gains for the smaller fish, some studies suggest sharks may tolerate or even understand the advantages of this cleaning behavior. Sharks have been observed slowing down to allow remoras to attach, indicating a level of acceptance or even cooperation.
The sheer size difference means a remora or pilot fish would offer little nutritional value for a shark, making them generally not worth the effort to consume. Sharks also typically do not eat their companions due to the ongoing benefits received from their presence. Instances of sharks consuming remoras or pilot fish are rare and usually occur under specific circumstances, such as during periods of aggression or if the smaller fish are particularly vulnerable.