In spring, the Sargasso Sea teems with thousands of tiny, transparent, leaf-shaped baby eels. They emerge from the deep waters of the sea, an oval area between the West Indies and the Azores, and drift on ocean currents to the north -- making a 6,000-kilometre migration.
Some stay near the American coast. Others continue their odyssey for as long as two years, growing and changing shape until they reach the St. Lawrence River. But then again, no one has ever seen the American eel spawn. After more than a century of research, they remain a mystery. And their future may be uncertain.
The latest data suggest that the population of the American eel in the Great Lakes-St. Lawrence River region has dropped by more than 90 per cent in five decades. Wildlife managers believe this could not only send that community into collapse but could also launch a devastating ripple through the freshwater ecosystem.
"The decline is precipitous," says John Casselman, an eel expert and biologist at Queen's University in Kingston, Ont. "We've gone from a situation where, when the Europeans arrived, eels probably made up half of the inshore fish biomass in the upper St. Lawrence River and Lake Ontario."
For generations, eel were plentiful and fished to satiate palettes across the globe. The Iroquois trapped eels with weirs and speared them at night from their canoes. Jacques Cartier described large vats of eels that the inhabitants of Hochelaga (now Montreal) kept to prepare and eat during the cold winters.
Today, the Swedes celebrate the season of alamorkret (eel darkness) with feasts on eel in all of its forms -- smoked, fried, grilled or stuffed -- paired with a glass of schnapps. The Dutch eat it smoked. They're marinated and grilled for one of Japan's national dishes, kabayaki, and feted each October in the Charlevoix region of Quebec.
All that gluttony has contributed to the eels' decline not only in North America but around the world, eel experts say. Japanese juveniles have dropped 90 per cent since 1980. And European fry have plunged 99 per cent -- creating a black-market for baby eels (called elvers) that fetch about 1,000 euros a kilogram.
Eel poaching is also on the rise. While collecting glass eels for a research project in the Netherlands, Willem Dekker was approached by a mugger with a baseball bat -- though he retreated into darkness when he realized the scientist might not be alone.
Although there are some physical and genetic differences between the European eels and American eels, they are all thought to congregate in the Sargasso Sea to spawn.
Scientists have used eel ladders -- passageways that allow eels to swim upstream past river-blocking dams -- to estimate the size of the American population in the Great Lakes region.
At the Moses-Saunders hydroelectric dam on the St. Lawrence River, the number of juvenile eels dropped to 1,000 a day from 25,000 from 1982 to 1995.
"The eels are a concern at both ends of the pipeline," says John Dettmers, a senior fisheries biologist for the Great Lakes Fishery Commission in Ann Arbor, Mich. "The new recruits [into the St. Lawrence] are greatly reduced and the mature eels coming out of the lake to establish future generations are also down."
But the precise cause of the eel's decline remains unclear. Overfishing, chemical contaminants and hydroelectric dams are all thought to have taken a heavy toll on the American eel. Ocean warming may also be contributing to the population collapse.
Part of the ambiguity comes from the eel's mystifying life cycle. The American eel is thought to be a catadromous fish -- one whose life begins and ends at sea, but spends most of its time in freshwater lakes and rivers.
