Animals

These baby rays are the first of their kind born in captivity

After the historic first birth of five baby spiny butterfly rays in captivity last August, an aquarium in Brazil is ready for the next litter's arrival.Sunday, July 14, 2019

By Jill Langlois
Spiny butterfly rays blend into the sand, camouflaging themselves to hunt small fish, crustaceans, and molluscs. They were bred in captivity for the first time in August as part of project to help conserve the species.

Almost a year after the historic birth of five spiny butterfly rays at the Marine Aquarium of Rio de Janeiro (AquaRio), biologists and veterinarians are preparing to welcome another round of little ones to the family.

In just six months—the gestational period for the Gymnura altavela, native to the shallow coastal waters of the Atlantic, including those that border southeast Brazil—a yet-to-be-known number of babies will join the three males and two females that were the first to be born in captivity in the world last August, a positive sign for a species that could one day go extinct.

Despite the fact that their capture and sale are illegal in Brazil, fishing is one of the main threats faced by the spiny butterfly rays, which can grow to over 6.5 feet wide. They’re targeted by artisanal fishermen to sell commercially and also caught accidentally by coastal trawlers. The other threat hindering their population is pollution. Both have led the species to be labelled by the IUCN Red List as vulnerable with a declining population. In Brazil, they’re considered critically endangered because of the heavy fishing activity off its coast.

Home sweet home

These first-ever captive-born rays were seen by the public for the first time when local TV station Globo was allowed to film them late last month. Marcelo Szpilman, marine biologist and CEO of AquaRio, says they are thriving and he expects they will make their debut in the public Ocean Tank soon, where they will play an important role in educating visitors.

Three of the world’s first captive-bred spiny butterfly rays swim in a tank at the Marine Aquarium of Rio de Janeiro.

"You don't preserve what you don't know," he says. "The aquarium has the role of showing people threatened species and helping them understand the importance of their conservation. You need to know about it to conserve it."

The unprecedented births at AquaRio last August, as well as the preceding gestation and aftercare of the five babies, were all part of a delicate process planned by the aquarium's team.

Because the spiny butterfly rays are particularly sensitive to their surroundings, the researchers needed to create optimal conditions for them to feel comfortable and live the natural life they would have in the ocean. 

"We wanted to make sure we had conditions that allowed the rays to reproduce on their own," Szpilman says. The size of the Ocean Tank, which holds 3.5 million liters of water, its exceptional water quality, and the stable ecosystem created by the several species of sharks, rays, and fish that call it home, are all part of their success, he says.

"Any time you have reproduction in captivity, it's really important for the conservation of the species," says Patricia Charvet, of IUCN's shark specialist group and a biologist specialising in sharks and rays. "It's important because it's a sign that they are being so well kept that they want to leave descendants."

The birth took place in a smaller tank within the Ocean Tank, generally used when divers enter to care for species inside. It allowed the female to stay in her habitat while veterinarians monitored her babies by way of ultrasound and helped the newborns enter the water for the first time. As infant mortality due to natural predators is high in rays, the five were then quarantined, a measure meant to keep them far from the sharks in the big tank.

Now 11 months old, they are thriving and expected to be introduced to the Ocean Tank soon.

A return to open waters

For Izeni Pires Farias, a biologist and professor at the Federal University of Amazonas, it's not just having more rays in captivity that makes the births at AquaRio exciting, but it’s the possibility of reintroducing them to the ocean that makes them so important.

"Once breeding in captivity is successful, the next step would be the future introduction of individuals into nature to repopulate affected areas," she says.

Szpilman hopes they will be able to reintroduce the spiny butterfly rays into the wild someday—"That's really the end goal of this whole process," he says—but they are still years away from that goal because, without a larger population of female and male rays raised in captivity, and without better conditions for them to survive in the wild, it won't make much of a difference. 

He is, however, positive they'll get there. And if for some reason they don't, he's sure the work of the AquaRio team has helped the spiny butterfly ray take one step away from extinction.

"When an animal goes extinct in nature, if there are none in captivity, in zoos or aquariums, that species will be extinct from the world," he says. "If, by chance, this species, the spiny butterfly ray, were to disappear from nature, which is not unlikely, we will at least be able to hold on to the biodiversity of our planet in some way because it will still exist in captivity."

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