22 November 2005

USA: Georgia Aquarium hopes to breed whale sharks

Georgia Aquarium officials say they want to breed whale sharks — the biggest fish on earth — at the Atlanta fish tank, a never-attempted feat that would push the bounds of known aquatic science.

The world's largest aquarium, which opens its doors to the public next week, has two juvenile male whale sharks now swimming in a 6.2 million-gallon tank. Officials want to get at least one female for a possible breeding program.

John Spink/AJC Ralph (or is that Norton?) may one day become the proud papa to 300 whale shark pups.

"I would love to breed the whale sharks because very little is known about these animals," said Home Depot co-founder Bernie Marcus, who is funding most of the aquarium’s $280 million construction cost. "The more that we proliferate the species the better. You learn about these animals, and you can save the species by reproducing them."

Aquarium Executive Director Jeff Swanagan said the Ocean Voyager tank was designed with the capacity to hold four to six whale sharks, which can grow to the size of a school bus. He said there are no immediate plans to bring more whale sharks to Atlanta, but confirmed the facility would like to acquire a female.

"This is a long-term venture, and that's why we had to design this exhibit so large," Swanagan said. "This isn't going to happen quickly. It will happen over years and years of research on these animals."

Said Marcus: "Whether or not we get another whale shark, I can't tell you. But if we can, we probably will."

Shark scientist Robert Hueter, who is studying whale sharks off the Yucatan Peninsula, said he thinks breeding whale sharks in captivity is feasible.

"It's all doable, but it would take a major effort to sort all of the issues out," Hueter said.

Hueter, who directs the Center for Shark Research at Mote Marine Laboratory in Sarasota, Fla., said other types of sharks have been bred in captivity. Any breeding program in Atlanta could be years off, he said, because the Georgia Aquarium's two whale sharks, Ralph and Norton, are still sexually immature.

"I can't imagine they would be ready for mating any sooner than three years, and it could be longer than that," Hueter said.

Scientists think male whale sharks do not reach sexual maturity until they are about 27 feet long, Hueter said. Ralph and Norton are growing, but measure less than 20 feet.

Atlanta aquarium officials initially thought they had a male-female pair, which they first dubbed "Ralph and Alice" after the characters in the old TV sitcom, "The Honeymooners."

Ray Davis, the aquarium's vice president for zoological operations, said when the big fish were first captured in Taiwan an initial exam confirmed Ralph was a male.

The other whale shark appeared to be female — males are identified by so-called "claspers" on their underside, organs that are difficult to detect in immature animals.

"They called me [from Taiwan] and said, 'Hey, we have Alice,'" Davis recalled. "I said, 'Are you sure? And they said, 'Absolutely.' So I asked them to go back and get me photographic proof."

A close examination of the photos revealed the truth, Davis recalled.

"It was very hard to discern, but you could see it on the photograph. Alice was really Norton."

Very little is known about whale sharks in general and almost nothing is known about their courtship and breeding behavior, Hueter said. The gentle plankton-eaters, which can grow to more than 40 feet, are found in most of the world’s warm-water oceans.

They are considered a threatened species because they are killed for food in some countries. But no one knows how many exist or how the populations around the globe are related.

A pregnant female killed by Taiwan fishermen has provided a few hints about the creature's reproduction, Hueter said. That huge fish had 300 immature "pups" inside, he said. The Georgia Aquarium's two whale sharks were purchased from a Taiwan fishery where they too were destined for the dinner table.

Many varieties of sharks have been bred in captivity, Hueter said, including sandbar sharks, bonnethead sharks, bamboo sharks, sawfish and rays. Sawfish and rays are closely related to sharks.

Swanagan said scientists have no idea whether a whale shark program would involve natural breeding or artificial insemination.

"All of this would be new ground," he said. "The body of knowledge [obtained], even if we are not successful, can be shared with field scientists as they try to figure out how to manage this animal in the wild."

Swanagan said aquarium scientists have already "explored" what they would do if a female whale shark gave birth to a large number of pups in captivity. They would release the young sharks into the wild at some point, he said, but that would require the clearance of numerous government agencies and a complex plan to raise the whale shark pups to release size in offshore pens.

The pups are only about 18 inches at birth, Swanagan said, and scientists would have to create a "head start program" to get them ready for release.

"You want to improve their chances of survival," he said. "You wouldn't just want to throw them back in."

Sources: www.underwatertimes.com and www.ajc.com


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