Many divers have seen sharks, whales, dolphins, or even dugongs with remoras attached and wondered why the larger animal would tolerate such pests. Amazingly, these so called suckerfish play an important role in keeping their hosts free of parasites and dead skin. They are commensals in some cases, benefiting from their hosts while causing no harm, and in other cases, they form mutual relationships in which each animal derives benefit. Let’s take a look at these interesting and often misunderstood creatures.
Remora Design and Species
Sometimes called sharksuckers, due to their near constant relationships with the larger animals, Remoras can grow to between one and three feet long. Occasionally found in temperate or coastal waters, they are primarily found in tropical climates. In some species, the distinctive dorsal fin is a sucker-like organ which has smaller structures that open and close to create suction. Other species have suction organs attached to the backs of their heads. To increase suction, the remora slides backward, while swimming forward allowing it to release itself from its host. While remoras are sometimes seen swimming on their own, they lack swim bladders and will sometimes attach themselves to boats or even to divers.
Small remoras can often be found attached to tuna, mackerel, sailfish, sunfish, and swordfish, and some even travel inside the mouths and gills of manta rays. Some remoras will stay with the same host for long periods of time, helping to remove bacteria and parasites, while others tend to scavenge on leftovers. There are eight different species of remora, each with different characteristics.
One of these is the Live Sharksucker, which is found in tropical water and tends to stay near coral reefs. This species has a history of being exploited by fishermen and turtle hunters, who would capture the fish, tie a line to its tail, then release it into the water, knowing it would soon find a host to attach itself to. The species is one that tends to come up to divers; it is long, slender, and has horizontal bands of brown and black that extend from nose to tail. Its cousin, the Whitefin Sharksucker, is found in subtropical waters from the western Atlantic Ocean to the Gulf of Mexico.
Whalesuckers are larger remoras, and will only attach themselves to cetaceans. They tend to have a uniform color ranging from dark to light brown, though some are grey or have a barred pattern. Usually attaching themselves to their hosts’ flanks, they will switch sides if approached, as though using the animal for protection. Juvenile whalesuckers tend to hitch rides with spinner dolphins, while the largest can be found catching a lift from bigger whales. The rarest of all remoras, whalesuckers are found worldwide in tropical and subtropical waters, always in the presence of whales or dolphins.
Other species include the White Suckerfish, which tends to prefer the company of black marlins and manta rays, the Common Remora, which has a pronounced suction cup modification to its dorsal fin, the Spearfish Remora, which can grow to be up to 50 centimeters long, and the Marlin Sucker, a slightly smaller member of the remora family.
If you encounter a remora while diving, and it tries to attach itself to you, you’ll find the experience to be either entertaining or annoying; much depends on your own attitude. The fish can be persistent, following and pestering divers, but they have never been known to cause injury, particularly if they attach to your wetsuit. Not parasites at all, they’re simply along for the ride.