The more commonly known manta ray is smaller and more easily seen, usually staying near coasts.
The two types—which are not yet named—also appear visually distinct, exhibiting unique colors and textures.
Andrea Marshall, a Ph.D candidate at Australia's University of
Queensland, presented the findings last week in Montreal at a
first-ever symposium of ray experts.
Manta rays are graceful giants in the ray family that can weigh over 4,400 pounds (2,000 kilograms).
Mantas may have wingspans of almost 25 feet (8 meters). The fish are also harmless and do not possess the poisonous barb found in some of their cousins, including some stingray species.
Australian environmentalist Steve Irwin was killed by such a barb.
While both manta species roam all the oceans, they appear to have a different lifestyle.
The smaller rays—familiar to divers in Hawaii, the Maldives,
Mozambique, Australia, and Japan—are year-round residents of certain
marine spots, such as coral reefs.
Scientists suspect the larger, more mysterious, rays are highly migratory animals that wander the world's seas.
The species discovery was the unexpected result of five years of hard work and a bit of good fortune, Marshall said.
"As luck would have it, it looks like here in Mozambique
is the only [known] location where we see both species interacting on
the same reef," said Marshall, whose effort was funded by the
Switzerland-based Save Our Seas Foundation.
Though much of Marshall's time was spent underwater, she also logged
long hours collecting data around the world in a search for proof that
the species were distinct.
To build her case she pursued evidence from DNA labs and Indonesian
fishing villages, where the migrating species is still commonly caught.
Rachel Graham of the Wildlife Conservation Society in Punta Gorda,
Belize, was impressed by Marshall's work, one of the longest-running
manta studies ever conducted.
"We were just incredibly excited about this," she said. "The work was
very in-depth and I think [for the most part] the group was convinced."
The new species discovery will add to challenges for those seeking to protect the vulnerable, slow-to-reproduce rays.
(Related: "Photo: First Giant Manta Ray Born in Captivity Dies" [June 18, 2007].)
The smaller manta species is at risk because of their limited range.
"If someone comes into a coastline or island group and starts up a
fishery, you could wipe out that population in a year or two,"
University of Queensland's Marshall said.
"That would [threaten] regional extinction like what may [be happening] in the Gulf of California."
The migratory mantas provide their own challenges, she added. They
respect no borders, so protection efforts must involve a complicated
cooperation between many nations and groups.
"Both species face independent issues in terms of conservation
management," Marshall said. "We have to understand the threats to
Copyright: National Geographic News