A California aquarium says its newest additions, two baby zebra sharks, are the first successfully reproduced through artificial insemination, giving hope for the dwindling populations of sharks in the wild.

Every year some 100 million sharks are killed in the wild and overfishing, loss of habitat and marine pollution have put shark species around the world at risk, says Perry Hampton of the Aquarium of the Pacific in Long Beach.

With the successful birth of the two female zebra sharks, "we are pushing the boundaries of knowledge," says Hampton, a member of the facility's animal husbandry team. "It's beneficial to the species as a whole."

Aquarium biologists have moved the young sharks from a nursery in a non-public area of the facility, where they've spent the last 10 months, into its Shark Lagoon exhibit, where the babies' mother, Fern, is also housed.

Fern is 20 years old and has been at the aquarium since 1997. Her pups hatched about 7 months after she was inseminated.

The young sharks are now between 2.5 to 3 feet long, and will eventually grow as large as their mother, who weighs around 140 pounds and is 7.5 feet long.

Zebra sharks, often called leopard sharks in Australia, are found in the Indo-West Pacific and are nocturnal foragers, feeding on shrimp, crabs and small fish.

The species is listed as vulnerable to extinction under the International Union for Conservation of Nature Red List, due mainly to human activities.

The aquarium has previously had successful births through artificial insemination in some other shark species, but the two baby zebra sharks are the first born in that manner for that species, officials said.

Several years ago bamboo shark babies were born following artificial insemination, says aquarium veterinarian Lance Adams, and the facility's scientists are presently testing the technique on blacktip reef sharks, a species that delivers their offspring alive instead of laying eggs.

"We're taking small steps," Adams says. "We're learning. We don't know what all the possibilities are."

Only two other countries have had success in attempts to perform artificial insemination of sharks, he says: Australia and Japan.

The successes so far have raised hopes that the technique could be used to keep shark species in the wild from going extinct, Adams says.

"If a certain breed became endangered," he says, "if we have a sustainable population in captivity, we can reintroduce it into the wild."