The remora, often called a suckerfish, is a marine animal known for hitchhiking on larger sea creatures like sharks, whales, and sea turtles. Growing up to 43 inches long, this fish often raises questions about whether it poses a threat to humans. The concern stems from the powerful force of its suction, not a bite or sting. Remoras are generally harmless to people, seeking a host for transportation, protection, and to feed on scraps and parasites.
The Unique Attachment Mechanism
The remora’s reputation stems from the specialized organ on the top of its head, an evolutionary modification of its first dorsal fin. This oval-shaped suction disc allows the fish to adhere firmly to a host’s body. The outer edge of the disc is lined with a fleshy rim that creates a watertight seal. Inside the rim are multiple rows of flat, plate-like structures called lamellae, which can be raised and lowered by muscles. These lamellae are equipped with tooth-like projections known as spinules. When activated, the disc creates a vacuum seal, and the spinules provide friction and grip. The attachment is largely passive, requiring little energy, and the host’s swimming drag often increases the suction’s power.
Assessing the Danger
A direct danger from a remora is low because they possess no venom, are not parasitic, and lack sharp teeth for aggression. Their mouths are small, designed for scavenging food scraps or consuming parasites and sloughed skin.
The only potential for harm comes from the force of the attachment mechanism and the small spinules on the lamellae. If a large remora attaches to bare skin, the suction force and friction can result in minor irritation. Swimmers report a noticeable sucking sensation, sometimes accompanied by temporary red marks, bruising, or minor scratch marks. These superficial marks are temporary and usually fade quickly, similar to a strong suction cup being placed on the skin. The remora’s interest in a person is typically a case of mistaken identity while seeking a new host.
If a Remora Attaches
If a remora attaches to your skin, do not panic or try to pull it straight off. Pulling directly outward is counterproductive because the suction mechanism is designed to resist this force, and you risk injuring the fish. The proper technique is to break the vacuum seal created by the rim of the suction disc.
You should slide the fish laterally, or side-to-side, across the surface of the skin until the seal is broken. This peeling motion disengages the fleshy rim and allows the remora to release its grip without resistance. Once the seal is compromised, the fish will detach easily and quickly swim away. Any resulting marks on the skin from the spinules or suction are generally superficial and will disappear within a short time.