A team of scientists, conservationists and vets will soon set out to achieve a world first in conservation by collecting semen from sharks in the wild.
From 7 to 14 December, around 15 experts will attempt to collect semen from Indo-Pacific leopard shark (Stegostoma tigrinum) males gathering off North Stradbroke Island near Brisbane, Australia. They hope to use the semen for artificial inseminations of female leopard sharks in aquariums across Australia and in Singapore.
The technique for collecting semen from leopard sharks underwater has been pioneered by Paolo Martelli at Ocean Park Hong Kong, but it has only ever been done in an aquarium setting.
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Working at depths of up to 15 metres, the scuba-diving team will first have to subdue the sexually mature adult leopard sharks. Grasping the tail of the shark puts it into an immobile state, says Martelli, the main vet for the Great Australian Stegostoma Semen Expedition (GASSE). 鈥淭hey use this to subdue females when mating, but it also works on males, so we gently grasp the very end of the tail and roll them over onto their backs,鈥� he says. 鈥淲e can keep them in this position for tens of minutes, which enables the procedure to be undertaken.鈥�
Once the shark is immobilised, a tube is inserted into the shark鈥檚 reproductive tract to draw semen into a syringe.听In the aquarium, the process usually takes around 10 to 15 minutes. 鈥淚n the wild, we will be hostages to environmental conditions,鈥� says Martelli. 鈥淪trong or turbulent currents or poor visibility will add to the challenge.鈥�
The team is aiming to collect semen from at least nine wild males, enough to inseminate six sharks in Australia and three in Singapore. A second expedition is planned for March 2025 in Byron Bay on the coast of New South Wales, Australia.
If fertile eggs are successfully produced from the two expeditions, the team plans to ship them to Raja Ampat in Indonesia. Conservation organisation ReShark is aiming to re-establish a healthy, genetically diverse breeding population of Indo-Pacific leopard sharks, which are sometimes known as zebra sharks, in the Raja Ampat archipelago, where the species has been largely eradicated due to hunting.
The global shark and ray population , with sharks often killed听as bycatch in industrial fishing vessels using nets, but also specifically targeted for their fins, used across Asia for shark fin soup.
鈥淥ne issue we have faced all along is the supply of eggs coming from our aquarium partners,鈥� says at Conservation International, one of the founders of ReShark. 鈥淭he GASSE expedition is an attempt to address that issue. If successful, it will enable us to significantly ramp up egg production, and genetic diversity in those eggs, at our partner aquariums. It will also set the stage for potentially expanding the approach to other shark and ray species.鈥�
Being able to harvest semen from wild sharks would address many challenges in aquariums鈥� captive-breeding programmes and boost efforts to restore depleted populations of sharks around the world. 鈥淚t鈥檚 expensive to move sharks and rays between facilities to promote increased genetic diversity through breeding,鈥� says at the University of Queensland, Australia, who is leading the GASSE expeditions.听鈥淭his is potentially a game-changer, in that we can access multiple males at an aggregation site sequentially鈥� and we can bring that genetic diversity into the aquarium for artificial insemination.鈥�
