Video surveys show that species of sea snakes are hiding in the depths of Ashmore Reef

New research from the Australian Institute of Marine Science (AIMS) suggests the deeper waters of the remote Ashmar Reef off the coast of Western Australia may be harboring a species of sea snake that hasn’t been seen in shallow water for more than a decade.

Endangered short-nosed sea ​​serpent was one of seven species observed in deeper mesophotic waters (50 to 150 meters below the surface) on reef in video surveys conducted by scientists from the Western Australian Museum, the University of Western Australia and Stantec Australia.

Some of the research was conducted during a deep-sea expedition aboard the Schmidt Ocean Institute research vessel Falkor in 2021.

Ashmore Reef’s shallows were once a global hotspot for a variety of sea snakes, but five species (Dubois, spotted, king, western turtle and shortnose sea snake) had not been recorded at these depths in the decade prior to the survey.

Despite these positive findings, the number of sea snakes observed in deeper habitats was significantly lower than that recorded in previous studies in shallow water.

AIMS scientist Dr. Konrad Speed, who led the analysis of the video survey published recently in the journal Frontiers of Marine Sciencesaid the rediscovery of five species previously thought to be extinct was good news.

“It shows that we have to look deeper than the first 15 meters water column on Ashmore Reef, &c coral reefs for sea snakes and other species. We compared bait video data collected in 2004 and 2016, suggesting that the recovery of shark species and other sea snake predators may be partially responsible for the decline in sea snake numbers in shallow water on Ashmore Reef, although more data is needed to confirm this theory. The recovery of these predators is most likely due to increased fisheries management in the Ashmore Reef Marine Park,” said Dr. Speed.

Study co-author Dr Nerida Wilson of the Western Australian Museum said advances in technology had helped researchers better understand places such as mesophotic zones that were previously hidden from view.

“While we are moving past the shallow reefs, there is much more to discover deeper waters further,” said Dr. Wilson

“In addition to these important sightings of sea snakes, we also saw so many other organisms that we know little about. Such expeditions are only the beginning of many different discoveries.

The study used remote underwater video recorders and a remotely piloted vehicle to collect 288 hours of video in 2004, 2016 and 2021. Eighty sea snakes of seven different species were seen in the video.

Courtesy of the Australian Institute of Marine Science