A new research tool involving the simple task of filling a bottle with seawater could revolutionize how scientists track individual whale sharks and monitor their populations. On top of being fast, easy to use, and inexpensive, this method can also be applied in remote or inaccessible areas without compromising safety for researchers or interfering with animal activity.
The Australian Institute of Marine Science and the UWA Oceans Institute have collaborated to develop a new method for tracking gentle giants called “eDNA haplotyping”. The technique is based on genetic clues in seawater that are too small to be seen by human eyes, but large enough so scientists can track these giant creatures.
Ph.D. researcher and lead author Laurence Dugal said while environmental DNA (eDNA) has been used in the past to monitor the presence of certain species, this new method used eDNA to answer an entirely different question.
“Our new method has taken this incredible leap to detect the genetic signature of individual whale sharks just by analyzing the seawater,” she said.
“We have moved beyond species detection and into the realm of population genetics—we’ve opened a new door in what is possible with eDNA.”
Despite their large size, whale sharks are notoriously challenging to track. But like all marine species, they shed their unique DNA codes into the ocean via skin and other biological material. Scientists have developed a new way of tracking these animals by collecting eDNA from oceanside areas where we know that whales swim past periodically.
Scientists at the University of Western Australian (UWA) recently developed a way for researchers to understand how many whales are living off Ningaloo Reef near Perth, where whale shark ‘hot spots’ can be found on this coast line when we swim with these gentle giants who allow us close enough so as not disturb them while trying our best not get bitten or pulled under by accident but still getting just what we need without causing harm–water samples taken through out eDNA haplotyping.
To confirm the signature of each shark the team also collected tissues samples of 28 whale sharks and compared the results.
“The results were incredibly accurate—the tissue biopsies successfully matched, with high accuracy, to all the individual whale shark’s eDNA,” Ms Dugal said.
“Up until now, we have only been able to get DNA samples through tissue biopsies, which is logistically difficult, expensive to collect and require invasive sampling techniques.”
Dr. Luke Thomas, a researcher from the AIMS and UWA Oceans Institute is excited for his team’s research on whale sharks to go beyond just understanding these animals’ movements in order to be applied with other species at risk of extinction due their migratory patterns that are heavily restricted by human activity such as fishing practices.
Dr. Luke Thomas has been studying how whale shark migration routes correlate with fisheries data since 2015 when he first realized that we could use this information about endangered animal populations to create models for mitigating potential conflicts between humans and wildlife while also providing new insights into our planet’s natural systems.
“This new method is faster, cheaper, highly accurate, easier to scale up and minimally invasive,” he said.
“It has the potential to radically change the way we monitor and track megafauna species. It could help answer global population-level questions for other megafauna, such as sharks, rays, marine turtles or dugongs.”
AIMS Principal Research Scientist Dr. Mark Meekan said endangered whale sharks were an integral part of the ecology at Ningaloo World Heritage Area and are worth $20 million per year in ecotourism alone.
“AIMS has been leading the research on whale sharks for decades at Ningaloo—a known hot spot for these majestic giants,” he said.
“Our research has mapped and tracked whale sharks to examine their behavior, feeding patterns, growth and migration.
“It is important our marine environments are responsibly managed to ensure we can use the ocean and its resources sustainably while preserving the future of whale sharks.”
This study was in collaboration with AIMS, UWA Oceans Institute, Curtin University, and a leading eDNA research lab at Aarhus University, Denmark.
The research paper “Individual haplotyping of whale sharks from seawater environmental DNA’ was published in Molecular Ecology Resources.