Aquarium Eggs: Scientists Find Out How to Protect Endangered Zebra Shark

A leopard cannot change its spots, and a zebra cannot alter its markings. But with its ability to turn the white bands that it is born into spots as it ages, the zebra shark has long delighted ocean divers and aquarium tourists.

Today, the endangered shark is drawing attention: it's at the forefront of an ambitious attempt to restore a wild population of sharks using aquarium eggs.

Zebra Shark Conservation

"Protecting and maintaining this rare and charismatic animal is very important to us," says Charlie Heatubun, a botanist at the University of Papua, Manokwari, and director of the West Papua Science and Development Agency of Indonesia, which is involved in the project.

A few decades ago, the distinctive zebra shark (Stegostoma tigrinum, also known as the Indo-Pacific leopard shark) was a popular draw in Southeast Asia for snorkelers and divers.

The sharks, known as harmless to humans, swim slowly and spend much of their time in shallow coral environments have been decimated in recent years by the shark fin trade-populations of S. tigrinum. In 2016, the International Union for Conservation of Nature (IUCN) placed the shark on its Red List as vulnerable. It is now likely to be locally extinct in Indonesia in many regions.

Around the same time, in aquariums around the world, zebra sharks are flourishing. In fact, in captivity, the animals perform so well that aquariums hold males and females segregated to avoid accidental breeding and excessive egg development.

However, the Association of Zoos & Aquariums (AZA) recently announced that eggs' ready availability has presented conservationists with an ability to repopulate the animals in the wild.

Biological enhancement

Scientists believe the effort, Enhancement, and Restoration of Stegostoma tigrinum, is the first time such a recovery technique has been attempted for elasmobranch species, including sharks and rays.

Some shark species give birth to young humans, but eggs are laid by around 40% of the species, including the zebra shark. And researchers deem them excellent candidates for trans-Pacific air travel because the eggs have hardy, leathery cases.

The participating aquariums aim to transfer about a dozen eggs to conservation sites in Raja Ampat, West Papua, later this year.

The egg cases will be transported in checked luggage, with sea water altered to retain a target temperature at stops along the way. Researchers can mount acoustic tracking tags and release them into underwater protected areas within a few months after the pups hatch and are large enough (about 70 centimeters) and ready to forage for food.

The West Papua provincial government is partnering with aquariums to train shark husbandry specialists and establish hatcheries in expectation of new arrivals. To be the first place for this project is a privilege, says Heatubun, whose team, together with other local partners, will manage the introduction.

End Goal

The aim is to add several hundred sharks over time, bring back numbers, and allow Indonesia's citizens to become self-sustaining.

Consisting environmental organizations, government agencies, aquariums, and research institutions, the international collaboration is collaborating with IUCN officials to decide how many eggs will be required.

Researchers are also preparing to track, using tags and diver surveys, the imported species. There is a special spot pattern for each adult, which would make identification easier.

Urgency

Ultimately, the effort aims to spread to other sectors, perhaps first in Indonesia. And AZA-accredited aquariums are attempting to gather eggs from captured zebra sharks that are genetically identical to wild sharks in the regions where the releases will occur in an attempt to increase the chances of survival.

That's not always possible, though. For instance, in the Raja Ampat archipelago, few zebra sharks remain, so scientists now have no samples from that area.

There is no time to wait for precise genetic matches, says Erin Meyer, the Seattle Aquarium's director of environmental initiatives and collaborations.

This population is not, like other shark and ray species, recovering in Raja Ampat, and we have the chance to save it from extinction," she says." "We're concerned about waiting."