They have long tails, can arouse panic and are turning up dead on the New Jersey shore and across the Tri-State area. Thresher sharks aren't harmful to humans, but they are being harmed by factors that researchers and authorities haven't quite figured out.

On Labor Day, the Ventnor Beach Patrol pulled an 8.5-foot thresher out of the ocean. Other threshers splashed into the headlines Labor Day weekend, washing up dead Sept. 2 on New York's Rockaway Beach and recently in Toms River and Lavallette.

"I wouldn't think that these occurrences are unusual but rather reflect the distribution of the species and their normal habits," said Eileen Grogan, professor of biology and shark expert at St. Joseph's University in Philadelphia. "Of course, sharks are attention-getters. If you see one at the beach, everyone immediately thinks of the movie "Jaws." So a sighting at the beach will engage the public's attention."

Still, Hollywood-based paranoia isn't what worries thresher researcher Lisa Natanson, of the National Marine Fisheries Service, based in Narragansett, R.I. Natanson has studied the thresher shark for years along the East Coast.

"It's very unusual for thresher sharks to wash up on the beach," she said. "Nobody seems to know much about it. It's not unusual that they're in the area, what's unusual is that they're stranding. Regular people on the beach pick them up and are eating them even."

Capt. Bill Howarth, of the Ventnor Beach Patrol, helped pull the thresher out of the ocean.

"I've been here 39 years; I've never seen a shark in the surf," he said. "It looked disoriented and was swimming in and out. It never left, it just kept coming back in, so I waited for about 10 minutes and thought I might have a shot to grab it and I got lucky and pulled it out backwards."

Before the Brigantine-based Marine Mammal Stranding Center could issue a caution against unknown toxins in the beached thresher's body, Ventnor Beach Patrol took a portion of the shark, MMSC director Bob Schoelkopf said.

Natanson said she'd have to examine a shark's liver during a necropsy to determine the cause of death. But no shark bodies have been available, due to a lack of funding to collect, freeze and transport washed-up threshers.

Possible explanations include scenarios wherein the migrant sharks followed fish to shallow waters - even if they normally tend to stay in deeper waters - or were somehow bitten during the mating process, Grogan said. An algae bloom - a toxic explosion of plankton affecting other fish, also could have tainted the sharks' food source, Schoelkopf said.

Explanations also include damage from fishing, but Natanson isn't buying that.

"What I'm gathering is that it's happening and people are talking about it and all but they actually haven't seen the fish," said Natanson, who has heard of the threshers showing signs of lethary and bleeding but received no physical evidence apart from being offered a piece of flesh without the liver. "Something so uncommon - we would want to find out why."

"It would have to be a fresh animal," said Schoelkopf of any potential for proper examination of a dead thresher. "We don't have money to do over-the-road trips for sharks."

Both the Lavallette and Toms River threshers reportedly appeared lethargic, Schoelkopf said.

To e-mail Amy Kuperinsky at The Press:

AKuperinsky@pressofac.com

WHAT IS A THRESHER SHARK?

Thresher sharks, which feed on fish such as mackerel and squid, are so named for their tails, the most distinguishing characteristic of the shark. They have smaller teeth, mouths and small eyes compared with the stereotypical movie shark, usually a great white. They also are known to shy away from humans.

At birth, threshers are about 3.5 to 5 feet long - sometimes determined by the size of their mother - and can reach 18 feet.

Migratory feeders, thresher sharks also are known to school fish into a configuration with their tails to catch prey. There are reports of threshers stunning prey by slapping them with their tails.

Pelagic, or deeper-water, threshers are blue, big-eyed threshers are brown and common threshers are dark green. Of all, the pelagic - at 10 feet - is the smallest.

The design of a thresher's tail allows it to jump out of the water, although it is unclear why the sharks do this.