"Nurseries" Prepare Endangered Sharks for Return to the Ocean

- Off the coast of Kri Island in the Raja Ampat archipelago of Indonesia, spotted sharks measuring about one meter long glide underwater, in a scene that environmental advocates say was, until recently, extremely rare. Zebra sharks (also known as leopard sharks) have long inhabited the coral reefs extending across the western Indian and Pacific Oceans, the Red Sea, East Africa, Japan, and Australia.

However, years of habitat destruction and overfishing have led to a decline in their numbers by between 50% and 79% over the past three generations (approximately 57 to 72 years), and they are classified as endangered by the International Union for Conservation of Nature. While the historical decline in their numbers was driven by the shark fin trade, pressures from overfishing continue due to accidental catches in fishing nets and the trade of their skins.

In Raja Ampat, these sharks had almost disappeared less than a decade ago. A group of shark experts from the Species Survival Commission of the International Union for Conservation of Nature estimated that if their numbers in the archipelago were left to recover naturally without intervention, the recovery process could take between 100 and 200 years.

Now, a global group called "ReShark" says it is trying to "restore balance to the ocean" through what it describes as the world's first program to return sharks to the wild. The initiative is known as the "Stegostoma tigrinum Augmentation and Recovery" project, or "StAR" for short, named after the scientific name of the shark.

The project involves breeding leopard sharks in aquariums around the world and then releasing their young into protected waters in Indonesia and Thailand. Mark Erdmann, the executive director of "ReShark," says, "In 2019, we estimated that there were only about 20 adult sharks left in Raja Ampat."

He adds: "Most shark conservation activities usually revolve around creating marine protected areas or managing fisheries. In our case, our specialized field is working on the active recovery of the species."

The idea first emerged during a visit Erdmann made to the SEA Aquarium in Singapore in 2015. There, the staff showed him tanks crowded with juvenile leopard sharks that they had successfully bred in captivity.

Erdmann recalls that they told him: "We actually have a problem; we are producing way too many juveniles, and we don’t know what to do with them." That meeting sparked efforts that lasted 8 years, involving governments, aquariums, non-profit organizations, academics, local communities, and environmental conservation scientists who worked together to release the captive-bred juveniles into Indonesian waters.

Like many shark species, they do not pose a threat to humans. However, unlike most shark species, they reproduce by laying eggs.

In fact, they are the largest species of shark that lays eggs, a trait that makes them very suitable for rewilding efforts. David Ebert, program director at the Pacific Shark Research Center at San Jose State University, who is not affiliated with the ReShark group, says: "About 43% of sharks lay eggs."

As for the species that give birth to live young, there is a completely different set of challenges that need to be addressed. Therefore, this may be a suitable type to start with.

His global efforts to find rare and elusive shark species have made Ebert known online by the title "The Man of Lost Sharks." He sees that the leopard shark has another advantage, which is the "factor of attraction and cuteness," which can help gain public support for environmental conservation initiatives.

"ReShark," supported by the Rolex Perpetual Planet Initiative, has partnerships with about 60 aquariums around the world. Viable eggs are transported from aquariums worldwide to the "ReShark" nurseries in Raja Ampat and Phuket, Thailand.

There, specialized trained aquarium managers, referred to as "shark nurseries," monitor the eggs, care for the young, and prepare them for life in the wild. When the sharks reach a length of one meter and become capable of foraging for food on their own, they are equipped with tracking devices or tags and released into protected waters.

The title "shark nurseries" may sound amusing, but the work is highly technical. These nurseries undergo months of training in animal care and often receive support from large public aquariums.

The program also relies on local residents for practical training instead of international volunteers, aiming to engage local communities. However, some shark experts still approach the program's long-term effectiveness with caution.

For Ebert, who has spent over four decades studying sharks and rays around the world, the program is described as innovative, but still largely experimental. He says, "It's more like an interesting scientific project.

Among his concerns is whether the released sharks will live long enough to reproduce in the wild. Given the belief that leopard sharks need between 5 and 12 years to reach maturity, the earliest that "ReShark" can determine if the first young released have started to reproduce is 2028.

Ebert also questions whether releasing more sharks amid ongoing fishing pressures might inadvertently make them easier targets for fishermen. But Erdmann clarifies that "ReShark" only operates within reserves committed to environmental conservation.

For example, Raja Ampat is a reserve for sharks and manta rays that spans an area of 46,000 square kilometers. Data from "ReShark"'s satellites, derived from tracking the young released into the wild, shows that most of them typically remain within a range of 100 to 150 kilometers from the sites where they were released within the protected waters.

By involving the local community in efforts to return these sharks to the wild, the fishermen themselves have begun to actively protect the leopard sharks. Since 2023, 82 baby sharks have been released, and 15 sightings of healthy individuals have been recorded in Raja Ampat this year, early results that indicate this strategy is achieving success.