The sea is known for its mysterious inhabitants; every day offers the promise of an exciting encounter. However, no one could have prepared for a mysterious visit from a juvenile oarfish on December 7 2023. Mark Fitzgibbon, Cape RADD’s junior Marine Biologist, was notified by the Simon’s Town Boat Company of a strange looking, and mesmerizing fish swimming in the harbour at the False Bay Yacht Club. Excited to see what it was, he jumped in, fully clothed, with a GoPro in hand, ready to capture his finding. To everyone’s astonishment, he had captured a video of what could be the first live encounter of an oarfish swimming in Southern African waters. Previous recorded encounters are of adult giant oarfish that either washed up and died or oarfish caught as bycatch.
Notice how this fish uses its dorsal fin to propel itself in the water. The sinusoidal movement of the modified fin is almost hypnotic. The caudal (tail) fin is used like a rudder to allow the fish to turn, and the pectoral fins are used for extra stability in the water. During this encounter, the fish remains somewhat upright for most of the time as the dorsal fin provides forward movement, however at 0:38 notice how it can rotate the body to allow for faster movement. The dorsal fins can also be seen changing rhythm to allow for this increased mobility which is fascinating.
They are a rare sighting for divers, even rarer for people swimming on the surface and shallow regions of the coast. This is because of how deep they reside in the water. They inhabit the mesopelagic zone between 200m-1000m depth. What is even rarer is coming across juvenile oarfish. The most recent recorded juvenile, and the first to be captured on camera, was at the Great Barrier Reef on June 16 2022. Tahn Miller, Wavelength Reef Cruises Master Reef Guide, and Marine biologist, Jorja Gilmore, described the juvenile as 35cm-40cm long and approximately 1 meter long. The size of the juveniles can be misleading to their common name, Giant Oarfish. According to ABC7 staff (2023), the most recent recorded sighting of a giant oarfish, approximately 2m long, was late June this year off the northeast coast of Taiwan. The longest length recorded is 11m.
Because the giant oarfish is a rare sighting, only a few studies about their biology, habitat, and ecological significance have been carried out. Oarfish pose no threat to humans, are generally shy and are more likely to swim away than to attack. They have no teeth but rather multiple gill rakers that they use to catch small organisms. Their preferred diet includes but is not limited to shrimp, jellyfish, krill, and squid. The red hue on their fins is caused by the food they eat, krill and other planktonic animals.
The reason for the encounter in shallow waters is unknown. However, the little that is known about their reproduction and life cycle can be used to explain the rare encounter. According to Animal Spot (2023) the reproduction and life cycle of the oarfish can be likened to that of other lampriform fish species. Through broadcast spawning, the eggs are released and float near the surface of the water. They are known to spawn between July and December. The juvenile that was encountered could have potentially been a part of the recently spawned individuals and found its way to the surface of Simon’s Town waters.
This encounter has piqued our interest in further exploring the underwater world. Who know’s what could be lurking underneath the water, waiting for us to document? Join us on a Snorkel for Science expedition and you too could encounter the magical and elusive species of False Bay.
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