The EconomistDecember 21st 2019 Holiday specials 311“A
ll the important questions...havebeen settled,” Max
Schultze, a German biologist, opined on his deathbed in 1874.
“Except the eel question.”
Few outside biology would have understood what vexed him.
Fishermen had no trouble finding eels: records of eel fisheries
went back centuries, and the fish made up a third of Europe’s fresh-
water catch by value. Chefs had no shortage of answers on how to
cook them. In the early 20th century, “Larousse Gastronomique”,
the definitive guide to French cooking, listed 45 different ways to
prepare them, from marinated to poached in onions.
Biologists, though, were not interested in the eel’s availability
or utility. They were interested in its reproduction. No one had
ever seen one mate. No specimen had ever been spotted after giv-
ing birth or laying eggs. Nor had any spawn been seen.
In antiquity, Aristotle opined that eels must spring spontane-
ously from river-bottom mud, and for most of the subsequent cen-
turies that sounded sensible enough. By the 19th century such be-
liefs were no longer tenable. Life came only from life; animals were
produced by sex. But eels were not just never observed having sex.
They did not even seem equipped for it. In 1876, not long after
Schultze’s death, a budding scholar dissected some 400 of them
looking for testicles: nary a one. Young Sigmund Freud, discour-
aged, turned his attention to the dissection of brains. When he re-
turned to matters of sex, it was on a less anatomical level.Acenturyanda halfon,progresshasbeenmade.
How and where European and other eels reproduce has
been discovered. They are freshwater fish which go out
to sea—a long way out—to breed, a piscine antithesis
to salmon. But it is still the case that no-one has seen
them at it, or been able to reproduce the process in the
lab—let alone in farm. And this matters. Although they
are not the near staple they once were, people still like
to eat eels, especially in Asia. But there are fewer and
fewer to catch in the wild, and the wild is the only place
they come from. The European eel is now listed as criti-
cally endangered. Depleting its numbers yet further by
smuggling its young to Asia by the suitcase-full has be-
come a lucrative criminal trade.
As a result, their very survival as a species is far
from certain. Today’s “eel question” is whether the spe-
cies has a future.
At their smallest, eels are translucent, worm-like
creatures that give only the faintest hint of what they
will later become (eels grow about 5cm a year in the
wild, mature ones are about a metre long).
In Europe, most of these tiny “glass eels” are found
in the Bay of Biscay. From there, they find their way to
rivers, creeks and ponds anywhere from the Baltic toTheknown
unknowns
ÅLAKUSTEN, SWEDENEels The life and times of a biological enigma