PORTSMOUTH, N.H. – It was a fisherman’s nightmare that slithered out of the Cambrian ooze when trilobites ruled the world.

Now a group of researchers from the University of New Hampshire is trying to unravel the slimy mysteries of the hagfish, one of the sea’s oldest and oddest creatures.

“We know almost nothing about them – how long they live, their populations, or their reproduction. No one has found a fertilized hagfish egg in the last 100 years,” said Stacia Sower, who heads the research project, funded by the Sea Grant consortium.

As stocks of other fish have dwindled, the strange hagfish have become one of New England’s newest fisheries. They are caught for their hide, which is used to make “eelskin” wallets, and flesh, which is said to taste like clams.

Virtually blind and eel-like with small tentacles around its jawless mouth and pincher-like teeth on its tongue, the hagfish is the world’s oldest vertebrate with habits to match its unlovely appearance.

When annoyed, it exudes gobs of slime from hundreds of ducts lining its pink body – not discreet smears, but bucket-filling blobs and clumps of sticky, fibrous goo – in amounts massive enough to suffocate the unfortunate fish that tries to eat it.

It also slips into the mouths and other openings of dead and dying fish and eats them from the inside out. Gill netters talk with disgust of hauling up seemingly normal fish, only to find a hollow shell with a squirming hagfish inside.

When the slime is too much for even the hagfish, it scrapes off the ooze by tying itself into a knot and then passing the knot along its supple 30-inch body. It also can sneeze to clear its single nostril. “Actually, it’s more of a chuff,” Sower said.

The hagfish is capable of such unique gymnastics because it doesn’t have a real backbone, but an elastic, rudimentary notochord and a cartilaginous brain case that places it somewhere on the evolutionary ladder between the invertebrates and first bony fish.

Five hearts beat in its body – one pumps blood to its brain, others to its gullet and other organs – but its circulatory system is so primitive that when held head-up its blood visibly pools in its tail. Holding a hagfish is unpleasantly like grasping a badly stuffed, biting and very slimy sausage.

The hagfish, which lives more than 325 feet down and spends most of its time burrowing in the muddy bottom, doesn’t give up its secrets easily to researchers.

Still, Sower and her colleagues have developed some clues, including a hormonal trigger that can stimulate breeding and have experimented with it on hagfish both in the laboratory and in cages on the sea bottom.

“Our aim is to learn enough about its habits to help the fishermen develop a sustainable fishery,” Sower said.

Most of the small fishery that has developed off New England in the past decade is for the Asian market, with about 6.8 million pounds landed in 2000.

“There has been a huge influx of new and bigger boats that have come into the industry as other fisheries have closed,” said William Palombo of Newport, R.I., whose Gloucester, Mass.-based boats have been fishing for hagfish for the past seven years.

Palombo recently petitioned the National Marine Fisheries Council to put a moratorium on new boats and begin regulating the catch. The smaller operators fear the population will collapse and they will be squeezed out, he said. A 30-day comment period expires May 6.

The hagfish’s closest relative may be the lamprey, but scientists are sharply divided on whether the two jawless creatures evolved from a single ancestor or along parallel lines.

Hagfish are found in oceans around the world, but scientists can’t even agree on how many species there are. “Its probably somewhere between 20 and 60,” Sower said. The New England hagfish are particularly prized by Korean tanners because of their light skin, she said.

Sower’s research area is the cold, choppy waters off Jeffrys Ledge in the Gulf of Maine, about 20 miles off Portsmouth, where she and her assistants lower pickle barrels with funnel-shaped openings cut in them that allow the hagfish in, but not out.