To some people, fish seem completely devoid of personality. You’ve seen one fish you’ve seen them all. In my experience this hasn’t been true. A few years ago, I volunteered at the research station on Lizard Island. This island is a picturesque tropical paradise, named for the goannas traipsing around the beaches. The island is also home to a resort and the Australian Museum’s research station. Coral reefs surround the island and are used as an underwater lab by researchers and students.
A turtle and its hangers on
One morning before my volunteer work began for the day I snuck down to the beach for a snorkel. Heading offshore I passed beds of seagrass growing out of the sand. Then I came across a green sea turtle having breakfast. This herbivore was feeding on seagrass, which turns the fat in its body green – hence its name.
I watched the turtle as it swam and grazed. There was something weird about this one. Finally, the turtle swam up to take a breath and I could see two large fish firmly attached to the bottom of its shell.
These fish were remoras, more commonly called suckerfish. Their name means delay or hinder, which is an accurate description. Their dorsal (top) fin has evolved into a flat plate on the top of their heads. This suction disc contains collagen fibres to maximise the remoras contact with its host. Collagen comes from the Greek word for glue. You might be familiar with collagen because it is the most abundant protein in your body and gives your skin that plump look. The suction disc also contains thousands of tiny spines that increase friction, helping the fish ‘stick’. This allows remoras to suction themselves onto larger, moving animals. The bond is so strong a remora can stay attached to a dolphin even when it leaps out of the water!
So, what was the remora doing on the turtle? Well it depends on the species. Some remoras just opportunistically feed on their host’s food scraps and get a free ride. They spend little energy when another animal transports them so don’t have to eat much. Other remora species help their host by removing parasites. When both animals benefit this relationship is called commensalism. So, it seems fish can get along with other sea creatures.
Remoras can also have commensal relationships with people. In some parts of the world remoras are used in fishing. How you ask? Well a fisherman attaches a line to a remora, sends it off into the ocean and the remora attaches itself to a turtle or larger fish. The fisherman can then carefully reel in the remora and the animal it is stuck to. The fisherman catches something and the remora is fed scraps for its job.
Snorkel side kicks
I had a hanger on myself once. One afternoon during an internship in Exmouth, Western Australia I went for an afternoon snorkel. My boyfriend and his parents were visiting so I took them to the nearby Bundegi Boat ramp to see what was living underneath. We saw the usual stonefish sitting grumpily in its PVC pipe, the schools of baitfish and the occasional angelfish that had drifted in from the nearby Ningaloo Reef.
A little yellow fish decided to swim with us for most of our snorkel. It was about the size of my pinky, yellow with a few black vertical stripes. It looked a little cartoonish thanks to its large eyes that looked up at me. It would swim along with me for a while, hiding in my shadow then if I duck dived it would abandon me for my partner nearby. Back and forth it swam between us, happily joining our snorkel.
This fish was a juvenile golden trevally. Juveniles of this species often form groups and follow larger fish like groupers, sharks and even SCUBA divers. They do this because the large fish protects them from being eaten by other predators. The large fish doesn’t eat the juvenile trevally because they are fast moving and can out manoeuvre their host.
It is clear to me that individual fish have personalities and science is starting to back this up. In one study of guppies individual fish reacted differently to stressful situations indicating different personality types. Research continues with another study about to begin which examines how much butterfly fish personality varies between individuals living on different reefs. But can fish be your friend? Well this little yellow fish found something to like about us and tolerated the rest. Not that different from any human friend really. These encounters taught me that whenever you get in the water there’s a chance to interact with marine life. Make sure these are positive for all involved.