Experts from the Large Marine Vertebrates Research Institute Philippines (LAMAVE) have successfully documented for the first time a whale shark being cleansed by a "cleaner fish" in the coastal waters of Oslob, Cebu.
"Cleaning interactions between whale sharks and cleaner fish have not yet been observed in any other site in the Philippines, even in pristine reefs such as those of Tubbataha Reefs Natural Park, which provide cleaning stations for other species such as manta rays and turtles," said the non-profit organization dedicated to the conservation of marine megafauna and their habitats in the Philippines.
Based on LAMAVE's study released on Aug. 20, 36 whale shark-cleaner fish interactions have been "opportunistically" recorded during routine photo-identification surveys in Oslob, Cebu between May and September 2019.
Oslob is a popular tourism site banking on the practice of feeding whale sharks to allow human interaction.
LAMAVE said its team was not able to observe the cleaner fish removing the common ectoparasite "Pandarus rhincodonicus," which is commonly seen on a whale sharks skin, rather the fish were observed biting or nipping the skin on the trailing edge of the sharks' fins.
Cleaner fish usually remove parasites, dead tissue and mucus from their "clients" and play an essential role in maintaining healthy marine ecosystems, LAMAVE said.
During the documentation, two species of wrasse, a blue-streak cleaner wrasse and moon wrasse, were observed cleaning the whale shark.
In addition, the team observed that all cleaning interactions were in shallow waters, ranging from three to seven meters in depth where provisioned sharks are fed for extended periods of time on top of the shallow reef and seagrass beds.
"The feeding of whale sharks by the local operators has changed their natural behaviour and the extended time the sharks spend in shallow waters may have created the opportunity for cleaner fishes to interact with these juvenile sharks," LAMAVE said, noting that further investigation is needed on this.
Prior, it pointed out, there was only one other global record of something similar, which is of a whale shark being cleaned by a king angelfish in the Eastern Tropical Pacific at Malpelo Island, Columbia.