When a poacher with a baseball bat mugged Willem Dekker for his baby eels, it was further confirmation for the Dutch biologist that the species is in trouble.
The European eel, a snakelike fish with a mysterious life cycle, has managed to survive in rivers and on farms despite overfishing and a loss of natural habitat, thanks to artificial restocking with "glass eel" -- tiny eel fry.
But for reasons not entirely clear, the eel population is collapsing.
For 25,000 fishermen and the countless animals that live off the eels, the future is uncertain.
"The eel population fell to 10 percent of its former levels in the last half-century," Dekker said. "Now it's going from 10 percent to 1 percent."
As glass eels dwindle, their price has tripled to $325 a pound in the past three years, inspiring aggressive poachers like the one who robbed Dekker a year ago of the batch he had caught for research.
Advocacy groups have not lobbied as strongly for the eel as for other species -- perhaps because the strange, writhing fish is not a creature one readily falls in love with.
Yet barbecued eel is a delicacy for sushi lovers, especially in Japan, and eel is eaten in a bewildering variety of ways across Europe.
It is most popular with the Dutch, who eat it smoked, as do Germans and Scandinavians. Belgians and Portuguese stew eels, the French cook them with spinach and white wine, the Spanish eat glass eels as appetizers, and Italians like them at Christmas. "Jellied eel," diced with jelly and vinegar, is popular in southern England.
The eels also feed cormorants, herons, otters and other European wildlife.
Dekker, who has devoted his career to studying eel at the Netherlands Institute for Fisheries Research, believes the decline in glass eel is due in part to over-harvesting. Asian farms are increasingly buying European glass eel to satisfy the Japanese market. But he said there also are problems elsewhere in the eel's life cycle, parts of which remain a mystery.
Eels live in fresh water for 15 to 20 years, and then, turning from yellowish green to silver, swim far out into the Atlantic Ocean, where they are believed to spawn somewhere in the vast kelp bed of the Sargasso Sea.
Eel larvae then apparently ride the ocean currents until they arrive on European and American shores as glass eels.
Because the American eel also is in decline, some scientists believe the real problem may be changes in ocean currents due to global warming or a parasite or virus in the breeding zone.
Dekker predicted that the species will survive but that commercial fishing soon will be impossible.
"On the basis of the silver eels that we've seen, there's one, two, maybe three years' time. Then it's over," Dekker said.
After years of debate, the European Union plans action this autumn to protect the eel, said Ernesto Penas, head of fisheries conservation and stocks at the E.U.'s Agriculture Department.
Despite flaws in the data, Penas said, the trend is "extremely clear . . . toward collapse in the eel population, and no one is calling that into question."
But deciding what to do has been very difficult, he said.
A panel of experts recommended a ban on catching the breeding silver eels, but Penas said that was "politically difficult" because it would appear to favor southern European fishermen -- glass eels are caught mostly on the shores of France, Spain and Portugal, while the northern European industry is focused on adults.
Another problem is that the fishermen use various techniques and each country has different rules.
"Many are very unprofessional. The level of poaching is very high, and it's difficult to control," Penas said.
Arjan Heinen of the Dutch Professional Fishers Association said the best solution would be restrictions on catching breeding adults and a Europe-wide tax on glass eel to finance restocking programs.
"We hope the E.U. does do something, but it has to be across all of Europe," he said. Restrictions for fishermen are "never pleasant, but if we're involved in the decision, we can get behind it."