You might think that swimming is fishes’ best bet for getting around under the sea, but emerging evidence is finding that there are more walking fish species than previously thought, some of which are found in surprising places.
Researchers from the Schmidt Ocean Institute were surprised to come across one such species when studying the depths of the northern Great Barrier Reef. Here, while remotely observing the seabed using an underwater drone called the RV Falkor, they discovered a rare species of walking fish that had never before been recorded in Australian waters. It belonged to the scorpion fish family, a group that contains mostly marine fish including some of the world’s venomous species. Mostly found in the Indo-Pacific, they’re armed with a "sting" that is coated with venomous mucus, which has earned them their Scorpaenidae classification.
The species spotted strolling about the Great Barrier Reef was Rhinopias agriloba, a fish usually only found in the waters around Hawaii. “Walking fish” is a phrase used to describe species that use the fins attached to their chest to navigate the seafloor, similarly to how we use our legs on land. Sure enough, R. agriloba was strutting its stuff in full view of RV Falkor, much to the surprise of the ocean specialists watching on.
One such stunned onlooker was Robin Beaman from James Cook University in Australia. "It was very strange – it had this beautiful red colour and it walked on its pectoral fins like a set of hands," he told BBC Newsround. "Thankfully we had what I call the 'Fish Army' – this group of ichthyologists, fish experts – watching the live feed who could say, 'That has never been seen in Australia – the closest we know of is in Hawaii.'"
Elsewhere in the ocean, four new species of walking shark have been described in the waters off northern Australia and New Guinea. The study published in the journal Marine and Freshwater Research took place over 12 years as a collaboration between Conservation International, CSIRO, the Florida Museum of Natural History, the Indonesian Institute of Sciences, and the Indonesian Ministry of Marine Affairs and Fisheries. The adaptation helps these top predators track down prey using their unusual fins to move along the surface of reefs during low tide.
“At less than a metre long on average, walking sharks present no threat to people but their ability to withstand low oxygen environments and walk on their fins gives them a remarkable edge over their prey of small crustaceans and molluscs,” said Dr Christine Dudgeon from the University of Queensland in a statement. “These unique features are not shared with their closest relatives, the bamboo sharks, or more distant relatives in the carpet shark order including wobbegongs and whale sharks.”
The four new arrivals to ocean science join five other species that are all found in the coastal waters around northern Australia and New Guinea. Exactly why shark species in this area appear to be the only in their genus to have adapted walking fins isn’t clear, but the researchers are confident there are more to be discovered.