In a bid to save a species globally, a world-first method of extracting semen from male leopard sharks in the wild has been pioneered by researchers off South East Queensland.
The University of the Sunshine Coast’s, Dr Christine Dudgeon, who has been researching leopard sharks for 20 years, is among a global collaboration of scientists now awaiting the progeny following the successful artificial insemination of female leopard sharks in captivity on the Gold Coast, Sydney and Singapore.
(Dr Christine Dudgeon getting semen from a leopard shark: video supplied by University of the Sunshine Coast)
“We hope this marine reproduction technique will be a game-changer for international projects aiming to replenish the Stegostoma species globally, particularly in areas such as Indonesia where it is in danger of becoming extinct,” she said.
“Never thought I’d be getting this intimate with sharks underwater,” she joked.
Dr Dudgeon has been harvesting semen for the first time on an animal at depth in waters off North Stradbroke Island.
The ongoing Great Australian Stegostoma Semen Expedition is also designed to increase the genetic diversity of the Indo-Pacific leopard shark, currently categorised as endangered on the IUCN Red List of Threatened Species.
Special attention will be on the DNA of any resulting pups, given documented evidence of the species’ rare ability to lay healthy eggs without fertilisation from males.
Dr Dudgeon said “once these eggs are laid and veterinarians have determined they are fertile, they will be sent to our partners in the Raja Ampat Islands, off West Papua, until they hatch into juveniles that will hopefully help restock those protected waters,” she said.
The research contributes to the Indonesian-led StAR Project, and the global ReShark collective of more than 90 organisations, including UniSC, dedicated to recovering shark and ray populations around the world to help rebalance ecosystems and combat climate change.
Fragmented populations of leopard sharks, called zebra sharks overseas because pups have stripes that develop into spots, can be found in subtropical Australian waters, particularly from the southern Great Barrier Reef to northern New South Wales.
They grow to more than two metres in length, have a flat belly that enables them to swim near the sea floor like a wobbegong, and are considered harmless to humans.
“They are not threatened in Australia because we don’t fish them,” Dr Dudgeon said.
“In other countries they have been over-harvested for fins and meat. Their beautiful, very tough skin has become prized by skin traders for use in the wall linings of expensive yachts, for example.”
Dr Dudgeon, who also works with Biopixel Oceans Foundation, said the team was pleased with the implementation of the technique developed by vet partners at Ocean Park Hong Kong.
“It meant that our five-person team could syringe out semen and blood samples from male sharks underwater in the wild using ‘tonic immobility’, where sharks go into a sleep-state on their backs,” she said.
“Samples were also taken from sharks brought to the surface for the insertion of acoustic tags.
“We can now follow these sharks’ movements via a network of marine acoustic receivers to further inform conservation work for this ambitious restocking project.”
This latest research complements a citizen science program she started in 2012 in Thailand, called Spot the Leopard Shark.
“The program is international and it’s pretty well-known among tourism operators, divers and boaties who are uploading photos to the database from Thailand to Byron Bay,” Dr Dudgeon said.
“That helps further monitor numbers, longevity, habitat use and movements.”
Dr Dudgeon’s team intends to dive off northern New South Wales later this month to collect further samples from wild male leopard sharks and continue the project.
