Some stingray facts and fiction

September 08, 2006

The Sun asked Alan Henningsen, a fishes research specialist at the National Aquarium in Baltimore, to help answer some questions about stingrays:

How common are fatal ray attacks?

They're very rare. Australian publications report 17 known deaths worldwide as of a decade ago. Only one other case of a fatal ray sting to the heart had been reported by 2001, according to the Medical Journal of Australia.

More commonly, swimmers are stung when they step on a ray that is resting in sand or brush against its spine. It's a very unpleasant experience but not usually life-threatening.

Does anyone know what kind of stingray killed Steve Irwin?

No. Henningsen says he's heard only that it was "large" and "dark." Stingrays that meet that description and swim in the warm waters off Queensland include the cowtail stingray, which can be 6 feet from wingtip to wingtip. Others are the whiptail stingray or the reticulate whipray. Either can grow to 5 feet across.

Why was Irwin attacked?

The ray wasn't trying to kill and eat him. "They don't use their venomous caudal spines [or stingers] for feeding, only in defense," Henningsen says. Rays feed harmlessly on small fish, invertebrates and shellfish. But their stingers are designed to fend off the sharks that prey on them.

It doesn't always work. "I've seen a stingray spine embedded in the mouth of a lemon shark," Henningsen says. Usually, frightened rays will try to swim away. It's likely the ray that killed Irwin felt cornered or threatened.

How did Irwin die?

News reports from Australia said Irwin died because the ray's spine pierced his heart.

Do ray stingers inject nerve poison?

No. The toxin is a protein present under the thin "skin" that covers the spine. The skin breaks on penetration, releasing the poison. It's designed to inflict memorable pain and swelling.

Contrary to common misperceptions, the spines are not at the tip of the tail but nearer the base. Stingrays may have one or as many as five spines.

The spines are very sharp and serrated, causing cuts and sometimes severe bleeding. Pieces left embedded in the flesh can cause infection.

How are ray stings treated?

There is no antivenin. Henningsen says hot water - as hot as the victim can stand without scalding - will "denature," or break down the venom protein and short-circuit its worst effects. It's important to carefully clean the wound and remove fragments. Antibiotics may help prevent infection.

Are all rays venomous?

It depends on your definitions, Henningsen says. "Rays" refers to a large order of animals called "Rajiformes," which includes stingrays, skates, electric rays, sawfish and guitarfish.

Many people confuse skates and stingrays. Skates are not venomous, and they lay eggs. Some rays are venomous, and all give birth to live young. There are also differences in their tails and skeletons.

The manta ray, a filter feeder and the largest of them all at up to 22 feet wide and 3,000 pounds, is not venomous.

Are there stingrays in the Chesapeake Bay?

Yes, and several of the local species are on display at the National Aquarium. They move up and down the bay with the season and salinity changes.

Capt. John Smith was stung by the common cownose ray while fishing near the mouth of Virginia's Rappahannock River in 1610. Legend says he nearly died but was saved when Native Americans found an antidote in the mud of a nearby pristine waterway - known to this day as Antipoison Creek. Smith's one-time fishing spot has a name, too: Stingray Point.

Also in the bay: roughtail stingrays, which can grow to be 6 1/2 feet across; bullnose rays and southern stingrays, both up to 5 feet wide. Cownose rays, some more than 3 feet wide, are very tolerant of low salinity and have been seen as far north as Kent Island.

Have National Aquarium employees been stung on the job?

Yes. But Henningsen says it's rare. The aquarium's 52 rays are "still wild animals, and you have to respect them. But they're pretty docile."

They're accustomed to the divers who feed, examine and perform medical procedures on them. The aquarium also trims their spines to protect the divers and other animals.

Still, the spines grow back, mistakes are made, stings occur and they're quickly treated. "It's very, very painful," said Henningsen, who figures he's been stung four times in 500 encounters with rays here and elsewhere.

How do the rays co-exist with human efforts to revive the oyster fishery?

Not well. Two years ago, hungry rays helped themselves to 1 million oysters that the U.S. Army Corps of Engineers had planted in Virginia's Great Wicomico River. A few months ago, rays gobbled up nearly 775,000 oysters the Chesapeake Bay Foundation and the Nature Conservancy had planted in an artificial reef. The biologists should have known better. They put the reef at Stingray Point.

Why don't we eat stingrays?

For nearly 30 years, Virginia has tried to establish a local market for what has long been considered a pest.

But so far, the big market appears to be South Korea, which imports $18 million worth of frozen ray every year. No word on how baked ray goes down with a glass of sake and a side of kimchi.

frank.roylance@baltsun.com

Sun reporter Rona Kobell contributed to this article.

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