An eel, silvery and fat, swims out to the ocean, setting off on its final journey back to the Sargasso Sea. How does it know where to go? How does it find its way?
When it comes to the eel, we can allow ourselves to ask banal questions, simply because the banal questions don’t always have immediate answers. We can also allow ourselves to welcome this. We should be glad that knowledge has its limits. This response isn’t just a defense mechanism; it’s also a way for us to understand the fact that the world is an incomprehensible place. There is something compelling about the mysterious.
Because what does it really mean when we say we know the eel procreates in the Sargasso Sea? It means we have good reason to believe this, given Johannes Schmidt spent eighteen years sailing back and forth across the Atlantic, catching tiny, transparent willow leaves. We choose to put our faith in Schmidt’s work, in his observations and conclusions. We believe mature silver eels swim all the way back to the Sargasso Sea to spawn, that it’s the only place they breed and that none of them leave there alive. We believe it because everything points to its being true and because no one has offered any plausible alternatives. We can even go as far as saying we know that’s how it is. “We know now the destination sought,” Johannes Schmidt wrote. After all his years on the open sea, he must have felt he had the right to substitute belief for knowledge.
And yet, in this case, any knowledge comes with qualifications. What we rely on when we say we know where the eel procreates isn’t just observations but also a number of assumptions. And for a person who wants to know for sure, that’s obviously a problem. If you want to be categorical about it, which the scientifically minded tend to want to be, knowledge is not a matter of degrees; it’s binary. You either know or you don’t. Science is much stricter than, for instance, philosophy or psychoanalysis in that regard. Sciences like biology and zoology have on fairly solid grounds clung to the conviction that data need to be empirical and that knowledge requires observation.
To some extent, that’s the ghost of Aristotle still haunting us. All knowledge must spring from experience. Reality has to be described as it appears to our senses. Only what we’ve seen can be said to be true. It’s an interpretation of how humans acquire knowledge about the world that has survived because it’s logical, but also because it carries within it a promise. Before we know it, we have only faith, but the person with patience is always rewarded eventually. The truth will appear under the microscope.
When we say we know the eel procreates in the Sargasso Sea, there are still some essential objections to that statement: (1) No human has ever seen two eels mate. (2) No one has ever seen a mature eel in the Sargasso Sea.
That means the eel question remains unanswered; the truth has not yet appeared under the microscope. This uncertainty clearly acts as a driving force and a gravitational pull for eel enthusiasts. The mystery is there to be solved, questions await their answers, but at the same time the riddle is what sparks and perpetuates interest. For centuries, people who have viewed the eel question as a problem to solve have at the same time clung almost lovingly to the enigma of it.
When Rachel Carson wrote about the eel in her fairy tale–like nature book Under the Sea-Wind, she lingered on the mysterious and unexplained. Being a natural scientist, she could have been frustrated by not knowing, but the opposite seems to have been true. Rachel Carson seems to have been drawn to the uncertainty. She approached the eel and nature not just as a scientist but as a human being.
For instance, about the silver eel’s long journey to the Sargasso Sea, she wrote: “As long as the tide ebbed, eels were leaving the marshes and running out to sea. Thousands passed the lighthouse that night, on the first lap of a far sea journey… . And as they passed through the surf and out to sea, so they also passed from human sight and almost from human knowledge.”
Aristotle, Francesco Redi, Carl Linnaeus, Carlo Mondini, Giovanni Battista Grassi, Sigmund Freud, or Johannes Schmidt might have objected—perhaps they would have been unable to accept that a creature can in fact leave the realm of human knowledge—but to Rachel Carson, there seems to have been something simple and beautiful about the idea of the eels vanishing into the unknown. A creature that actively seeks to avoid human knowledge. As if that’s the way it should be. “The record of the eels’ journey to their spawning place is hidden in the deep sea,” she wrote. “No one can trace the path of the eels.” To her, the eel question, the enduring mystery, seems to have appeared to be preordained and eternal. As though it were a riddle beyond our human comprehension. Like infinity or death.
Tom Crick, the history teacher and narrator of Graham Swift’s novel Waterland, clings to the same feeling of a kind of fated inexplicability when he expounds on the eel: “Curiosity will never be content. Even today, when we know so much, curiosity has not unraveled the riddle of the birth and sex life of the eel. Perhaps there are things, like many others, destined never to be learnt before the world comes to its end. Or perhaps—but here I speculate, here my own curiosity leads me by the nose—the world is so arranged that when all things are learnt, when curiosity is exhausted (so, long live curiosity), that is when the world shall have come to its end. But even if we learn how, and what, and where, and when, will we ever know why? Why, why?”
IN SPITE OF ALL OBSERVATIONS AND ATTEMPTS TO UNDERSTAND (until the end of time), there is thus still a lacuna in the story of the eel. We know silver eels leave in the autumn, when the eel darkness descends, usually between October and December. The tiny willow leaves, the leptocephalus larvae, appear in the Sargasso Sea in the spring; the smallest specimens usually between February and May. Which should mean breeding happens around this time. Which in turn gives us a time frame for the eel’s journey. It has at most six months to get there.
Yet even so, it’s something of a mystery why the eel sets its course for the Sargasso Sea and nowhere else. Lots of animals migrate for breeding purposes, but few undertake a journey as long and difficult as the eel, and few are as stubbornly fixated on one single place thousands of miles away, and few do it just once before dying.
There are theories claiming only the Sargasso Sea has the right temperature and salinity for the eels’ propagation. It’s also a fact that eels have been around so long the continents have moved; the first eels likely had a much shorter distance to travel. But as the landmasses of our planet have changed, drifting apart inch by inch over the years, the eel has refused to adapt. It still needs to return to its birthplace, to the exact location it once came from.
More than anything, it’s still a mystery how the eel gets there. What route does it take? How does it find its way and how does it get there on time? How can an eel make it almost five thousand miles from the rivers and waterways of Europe across a deep ocean to the other side of the Atlantic in just a few months?
In 2016, a European research team published a report on the most extensive study ever of the European eel’s journey toward the Sargasso Sea. Over five years, a total of seven hundred silver eels had been tagged with electronic transmitters and released from different locations in Sweden, France, Germany, and Ireland.
As the eels turned west and the transmitters eventually fell off and floated to the surface, loaded with information, the researchers could form a picture of what their journey actually looks like.
At least that was the idea, but as is so often the case where eels are concerned, things didn’t turn out as planned. Of the seven hundred transmitters, only two hundred and six yielded any information at all. And of those two hundred and six eels, only eighty-seven got far enough into the sea for their information to reveal anything useful about what their journey had been like.
But data from eighty-seven silver eels’ journeys toward the Sargasso Sea is still far more than we had before, and the results revealed a lot about what a complex and difficult process this yearly migration really is. The first finding was that the eels swam both day and night and seemed to employ a deliberate strategy to avoid danger. During the day, they moved through the darker and much colder water at a depth of about three thousand feet. At night, under the cover of darkness, they rose up toward the warmer water nearer the surface. Even so, a large proportion of the eels disappeared during the earliest stages of the journey, falling prey to sharks and other predators.
What the researchers could also see was that not all eels are in a hurry. In theory, the journey to the Sargasso Sea is plausible. Experiments have shown that an eel swimming at normal speed moves slightly farther than half its length every second, and a silver eel on its way to the Sargasso Sea, which no longer hunts or eats or lets any of life’s distractions slow it down, can swim without stopping for at least six months using nothing but its fat reserves as fuel. If you draw a line on a map, from any given place in Europe to the Sargasso Sea, and calculate how fast it would need to swim in order to arrive by May at the latest, the eel’s journey is certainly possible. Very long and difficult, but possible.
Among the eels in the study there were, however, many that didn’t seem to realize what was actually required of them, or how little time they had. A few impressive individuals did cover an average of thirty-one miles a day, but others managed only two.
The eels also chose wildly disparate routes. Clearly, many roads lead to the Sargasso Sea. The majority of the eels released on the Swedish west coast, for example, chose a northerly route, up through the Norwegian Sea and then west across the northeast Atlantic. They all chose roughly the same path, apart from a single eel, which after reaching the Atlantic suddenly veered east and disappeared without a trace outside Trondheim, Norway.
The eels released in the Celtic Sea south of Ireland and in the French Bay of Biscay, on the other hand, headed south before turning west. One of them meandered about west of Morocco for more than nine months before making it all the way to the Azores.
The eels released off the German Baltic coast took different routes. Some followed the Swedish eels, setting their sights on the Norwegian Sea. Others headed south through the English Channel. But none of them reached the Atlantic.
The eels released from the French Mediterranean coast swam, predictably, west toward Gibraltar, but only three of them managed to get through the straits and into the Atlantic.
At first, the results looked random, to say the least. The eels’ movements traced strange patterns on the map, as though someone had tried to draw a maze blindfolded, or as though nothing was predetermined and every journey was the first. But at least one thing was made unambiguously clear: the majority of eels never make it to their spawning grounds. The long journey back to their birthplace remains for most of them a thwarted aspiration.
That may seem like a bleak outcome, both for the eels and for the scientific study. Not one of the seven hundred silver eels released could be tracked all the way back to the Sargasso Sea. It’s impossible to say if any of them reached it. Sooner or later, they disappeared into the depths, leaving the realm of human knowledge while their electronic transmitters floated up to the surface.
Nevertheless, the research team managed to draw some new and fairly remarkable conclusions from their observations. Their initial finding was that the eels’ migration is likely more complex than previously thought, but that it could be explained—at least in part. Because from the observations that at first seemed random and unpredictable, a pattern eventually appeared. Firstly, it was clear that the eel rarely takes the shortest route from its starting point to its goal. Its journey isn’t like the journeys of birds or airplanes. Nevertheless, all of Europe’s eels seem to rendezvous somewhere around the Azores, about halfway through their journey, and continue west toward the Sargasso Sea from there in much closer formation. If the journey starts in uncertainty and slight confusion, it becomes more deliberate as it progresses.
The researchers also discovered something else that complicates our understanding of the eels’ migration. When old specimens of leptocephalus larva caught in the Sargasso Sea were reexamined and compared for size and growth rate, they showed that the eel’s spawning season probably starts earlier than previously thought, possibly as early as December. That would mean breeding commences around the same time the last silver eels set off from the coasts of Europe, which only serves to make the question of how they get there on time even more vexing.
But the explanation, the researchers claimed, must, of course, be that all eels don’t make it across the Atlantic in time for the next breeding season. For some, the long journey back to the Sargasso Sea can take much longer. Perhaps eels simply adjust their speed and route according to their abilities. While some swim as fast as they can in order to reach the Sargasso Sea in early spring, some take a considerably more leisurely approach and wait for the next breeding season instead. While an eel setting off from Ireland, for instance, can travel west in an almost straight line and get there by spring, an eel coming from the Baltic Sea might aim to arrive in December, more than a year after it first set off. That would not only explain the differences in the behavior observed but also lend some kind of logic and relevance to what at first seemed random. Maybe eels are, quite simply, individuals, who not only have different abilities but also different means and methods of reaching their goal. Maybe they’re all aiming for the same destination, but no two journeys back to the origin are exactly the same.
AND THUS, ONE QUESTION REMAINS, AND IT IS ONE THAT APPLIES TO both eels and humans: How do they know which route will take them back to where they came from? How do they find their way back home?
That the eel has special abilities that make it skilled at navigating great distances has long been known. It’s well established, for example, that it has a phenomenal sense of smell. According to the German eel expert Friedrich-Wilhelm Tesch, who wrote the standard reference work The Eel in the 1970s, the eel’s olfactory sensitivity is on par with a dog’s. Put one drop of rosewater in Lake Constance, Tesch claimed, and an eel can smell it. It’s likely that eels use smell in some way during their journey across the Atlantic, either to locate the Sargasso Sea itself or at least one another. It’s also likely that the eel is sensitive to changes in temperature and salinity and that these might offer clues as to which way to go. Some scientists believe the eel’s well-developed magnetic sense constitutes its primary navigational tool. Much like bees and migrating birds, it can feel the earth’s magnetic field and is thus guided toward a certain destination.
We know what that destination is. And somehow, the eels know it, too. They know where they’re going, even if the routes they choose can be both meandering and unpredictable. But how they know is one of the mysteries still surrounding the eel question, one of the enigmas even scientists cherish.
Rachel Carson, for her part, described the eel’s inherited knowledge about its origin as something more than an instinct. In Under the Sea-Wind, she writes about how the fully grown and sexually mature eels one autumn suddenly feel a “vague longing for a warm, dark place,” and how these eels, who have lived their long lives “beyond all reminders of the sea,” in lakes and rivers, now set off into the unfamiliar open ocean, finding there something familiar, something they recognize, a sense of belonging “in the large and strange rhythms of a great water which each had known in the beginning of life.”
Do they remember where they came from and where they’re going now? Do they remember their very first journey across the Atlantic as tiny, transparent willow leaves? No, perhaps not in a human, conscious sense, not according to our definition of memory. But when the European research team who followed the more or less successful attempts of seven hundred eels to reach the Sargasso Sea tried to explain how the eels find their way back to their birthplace, they still described the experience as a kind of memory. It seemed, they wrote, as though “eels follow olfactory cues originating in the spawning area or that eels navigate using oceanic cues imprinted or learned during the leptocephalus phase.”
Because what their study revealed more than anything was that the farther the eels got, the more they seemed to end up following a predetermined route. Simply put, they seemed to follow the Gulf Stream and the North Atlantic Drift, but in the opposite direction. As though a memory, a map, had been ingrained in them when they made the journey from the Sargasso Sea to Europe as tiny, transparent willow leaves, and as though that memory had survived in the eels, remaining constant through all their metamorphoses, for ten, twenty, thirty, or fifty years, until one day it was time to make that same journey in reverse, straight toward the mighty ocean current that had once carried them helplessly to Europe.
AND SO THE SILVER EEL FINALLY COMES HOME TO ITS BIRTHPLACE, its Sargasso Sea, and at the same time, it disappears out of sight and our realm of knowledge. No one has ever seen an eel in the Sargasso Sea.
Some have tried, however. After Johannes Schmidt’s years-long expeditions in the early twentieth century, it would be a while before anyone set off for the Sargasso Sea to look for the eel again, possibly because Schmidt’s work was so persuasive, but perhaps even more likely because it was so discouraging. But the past few decades have seen an increase in research traffic to the Sargasso Sea, expeditions manned by some of the most prominent eel experts in the world. They’ve gone to seek deeper knowledge of the eel’s migrations and reproduction, to test existing theories by verifying or disproving them, but also to find what no one has yet been able to: a living eel in the Sargasso Sea.
The German marine biologist Friedrich-Wilhelm Tesch went on a major expedition with two German ships in 1979, the eventual result of which was the much-cited article “The Sargasso Sea Expedition, 1979.” The expedition took place in the spring and roved across large parts of the eel’s supposed spawning area. Tesch was able to employ his nets and trawls in the exact location where breeding was thought to occur; like Schmidt, he caught large numbers of tiny leptocephalus larvae, but other than that, he found no sign of the presence of eels. For example, seven thousand fish eggs were collected, but closer examination revealed that not a single one came from an eel. It goes without saying that researchers didn’t see any mature breeding eels either.
The American marine biologist James McCleave, who for more than thirty years has been one of the world’s leading eel experts, went on his very first marine expedition together with none other than Friedrich-Wilhelm Tesch in 1974 and undertook his first journey to the Sargasso Sea in 1981. Since then, he and his team have returned seven more times, using a range of sophisticated methods to try to catch at least a glimpse of an eel. McCleave has posited a theory according to which areas where different bodies of water of different temperatures meet—so-called front regions—provide eels with exactly the right conditions for procreation. It is in such locations that he has caught the smallest specimens of leptocephalus larvae, and it is also where he has most zealously looked for adult eels. James McCleave has sailed back and forth across these regions, with ships equipped with advanced acoustic instruments designed to pick up echoes from breeding eels in the deep. And he has, in fact, recorded echoes very likely produced by living, breeding eels; each time he has tried to catch them, however, his nets have come up empty.
During one expedition, together with a fellow marine biologist, Gail Wippelhauser, McCleave employed almost malicious cunning to lure the shy eels out of the depths. Their team had caught a hundred fully grown female American eels and injected them with hormones to induce sexual maturity. The plan was to bring these females on their expedition and place them in cages fastened to floating buoys in the middle of a front region in the Sargasso Sea. The females were intended as bait, to attract males who had swum there to spawn, and thus force them out of hiding.
But the eels were reluctant participants. The scientists kept the mature females in a laboratory and were about to drive them down to the docks in Miami ahead of departure, but before the ship had even cast off, the majority of the eels had died. By the time the expedition arrived in the Sargasso Sea, only five of the one hundred female eels were still alive.
Regardless, the five surviving eels were placed in cages and tied to the buoys, and McCleave and Wippelhauser took turns monitoring the movements of the buoys around the clock with the help of radar. But inexplicably, they managed to lose them. Eels and cages and buoys disappeared without a trace and were never seen again.
During another expedition, which Gail Wippelhauser undertook without James McCleave, the acoustic instruments picked up echoes from what was believed to be a large group of breeding eels; the researchers threw at it everything they had, lowering no fewer than six nets into the water. And yet there was no sign of any eels.
Another strange detail is, of course, that it’s not only living eels that have proved elusive in the Sargasso Sea. No one has ever spotted a dead one either, whether in the form of a corpse or as the victim of a larger predator. Swordfish and sharks have been caught with silver eels in their stomachs, but never anywhere close to the Sargasso Sea. A sperm whale was once caught off the Azores with an eel in its stomach that was on its way to spawn, but the Azores are pretty far from the Sargasso Sea. Once eels reach their breeding ground, they universally manage to avoid human detection in both life and death.
It should be said that there is no consensus on how significant it would really be to find a mature eel in the Sargasso Sea. Some scientists feel it’s beside the point, since we already know that’s where the eels are going. Others claim our knowledge of the eel’s life cycle can’t be considered complete until someone has observed an eel at its spawning ground. To these scientists, the elusive eel is something of a scientific holy grail.
In the past few decades, some researchers, such as James McCleave, have started asking another difficult question: If we can’t track all silver eels back to their birthplace, and in fact not even a single one, can we really be completely certain the eel breeds only in the Sargasso Sea? Granted, it took Johannes Schmidt almost twenty years to find the smallest of the tiny willow leaves there, but he had searched only a fraction of the world’s oceans. Schmidt himself wrote in 1922 that until all the seas have been trawled for eel larvae, it would be impossible to say for certain where the eel breeds, or at least where all eels breed. And virtually all eel expeditions since, including James McCleave’s, have focused on the already familiar region of the Sargasso Sea. Perhaps some eels go elsewhere entirely? It’s unlikely, but how can we know for certain?
Moreover, the Sargasso Sea is very large. Is it one big breeding ground, or are there several separate breeding grounds within its borders? Do the American and European eels breed in exactly the same area, or do they prefer different locations? Some scientists, Friedrich-Wilhelm Tesch among them, have claimed that the American eel breeds in the western part of the Sargasso Sea while the European one stays farther east, but that the areas are partially overlapping. Others argue the collected leptocephalus larvae do not support such conclusions. All we know for sure is that when the tiny, transparent willow leaves leave the Sargasso Sea, European and American ones are intermingled, drifting helplessly along in the mighty ocean currents, while their parents appear to remain, die, and decompose.
HENCE, TO THIS DAY, THE WORLD’S LEADING ZOOLOGISTS AND MARINE biologists, the people who are most intimately familiar with the eel, are forced to qualify their reports and results with reservations. “We believe,” they’re obliged to say. “The data indicate …”; “It can be assumed that …” By patiently rejecting less likely scenarios, they are slowly moving toward a probability that in turn closes in on truth.
It can, for example, be assumed that what’s true of one of our eel’s closest cousins, the Japanese eel, is also true of the European eel. And when it comes to the Japanese eel, some of the classic aspects of the eel question are, in fact, slightly less enigmatic.
The Japanese eel, Anguilla japonica, looks essentially like its European counterpart. Its life cycle is also very similar. It hatches in the sea and drifts toward the coast as a willow leaf. It turns into a glass eel and wanders up waterways in Japan, China, Korea, and Taiwan. It becomes a yellow eel and lives out its life in fresh water before many years later turning into a silver eel and wandering back out into the sea to spawn and die. It’s a very popular fish for cooking, particularly in Japan, and it has long played an important role in East Asian culture and mythology, among other things as a symbol of fertility.
When it comes to the question of procreation—where and how it happens—the Japanese eel was long an even bigger mystery than the European one. Scientists were able to pinpoint its spawning ground only in 1991. Employing the same method and dedication as Johannes Schmidt, though not taking quite as long, the Japanese marine biologist Katsumi Tsukamoto sailed around the sea with nets and instruments, searching for increasingly minute leptocephalus larvae. One autumn evening in 1991, he finally managed to find specimens that were only days, or perhaps hours, old. It was far out in the Pacific Ocean, just west of the Mariana Islands.
After this discovery, it wasn’t long before an even more sensational discovery was made. In the autumn of 2008, a research team from the Atmosphere and Ocean Research Institute in Tokyo actually managed to catch fully grown Japanese eels in exactly the area west of the Mariana Islands where the findings situated the breeding area. One male and two females were caught. All three had already spawned and were in bad shape. They died shortly thereafter. But this meant the Asian version of the holy grail of science had at long last been found.
But what did that mean? According to at least one member of the expedition, Michael Miller, nothing, really. It didn’t prove anything we didn’t already know. We already know approximately where they breed. But we still don’t know exactly where, how they get there, or how many of them are successful. We still haven’t seen them procreate. We don’t know why. Why, why?
MYSTERIES HAVE AN ALLURE OF THEIR OWN, BUT THERE ARE SOME things that suggest the timeless eel question will eventually be answered. Not only have silver eels been found after breeding in the Pacific, but researchers there have also pulled off what no one has managed with the European or American eel. They have successful bred the Japanese eel, Anguilla japonica, in captivity. As early as 1973, scientists working at the University of Hokkaido were able to extract eggs from sexually mature female eels, inseminate them artificially, and have them hatch and become larvae. The future of the threatened eel was not their primary concern; the venture had rather narrower economic motivations. The eel is vastly popular on Japanese dinner tables and the subject of a multimillion dollar industry. If it could be farmed, the way salmon is, for instance, it would mean a lot more eel at a fraction of the cost. Consequently, the market is prepared to invest large sums in research that could make farming possible.
Unsurprisingly, the eel has not, however, proved particularly cooperative. The sensational artificially produced little willow leaves at the University of Hokkaido barely had time to hatch and register the lack of ocean currents in their tank before they died. The leptocephalus larvae simply refused to eat. It didn’t matter what the Japanese researchers tried to tempt the transparent little creatures with. The willow leaves went on hunger strike and invariably perished.
For years after that, and over many generations of artificially created but all equally short-lived leptocephalus larvae, Japanese scientists dedicated themselves to finding out how to keep newly hatched eel larvae alive. What do they eat? No one knew. Their feeding habits had never been observed in the wild. A range of foods were offered. Plankton, roe from other fish, microscopic rotifers, parts of octopuses, jellyfish, shrimp, and clams. The tiny larvae stubbornly refused sustenance in each successive attempt and predictably died soon after hatching.
It took the scientists close to thirty years to come up with a meal the larvae could stomach. It consisted of a powder made of freeze-dried shark eggs; armed with this, they managed to keep a handful of larvae alive for all of eighteen days in 2001. It was a sensational new record, but they were still, of course, very far from finding the answer to how to coax the transparent willow leaves into transforming into fully grown, edible eels in captivity.
Furthermore, the eels continued to be difficult in other ways. Even though the researchers were now able to make them eat—the prescribed diet was refined over time until at least some specimens survived into the glass eel stage—most still died within a few days of hatching. Only 4 percent of the larvae lasted for fifty days, and only 1 percent for a hundred. The number that reached the size necessary to turn into glass eels was almost zero.
Moreover, the laboratory eels behaved differently than their peers in the sea. The captured females produced significantly fewer eggs in captivity than in the wild. It also soon became clear that all the eels hatched in the laboratory were male. No one knew why, but to remedy it, glass eels were injected with estrogen to artificially produce females. In 2010, Japanese scientists succeeded for the first time in completing the life cycle of the eels when they produced eggs, and in time leptocephalus larvae, from eels that had themselves been created in the laboratory. The eels were also given hormones to make them grow faster, which lead to severe deformities in their offspring: willow leaves that didn’t look anything like the ones caught in the sea, their heads strangely misshapen, and the animals themselves unable to swim. It was as though the eel were refusing to let anyone else control its creation. As though its existence was its own business.
As of this writing, scientists are working hard to find the correct methods, if they even exist, to farm eels, which would be important not only to the Japanese eel industry but also, by extension, to the survival of the eel globally. They are nowhere near succeeding. But every year brings new technologies, new scientific insights and innovations, and for anyone interested in understanding the eel, there is—all the obvious problems notwithstanding—reason for hope. Perhaps some kind of tracking device will be developed in the not-too-distant future that’s small and light enough to follow a silver eel all the way to its breeding grounds in the Sargasso Sea. Perhaps that will allow us to pinpoint more precisely where on the map reproduction takes place, and perhaps once enough eels have been tracked, we can confirm or reject the idea of multiple breeding grounds. Perhaps by then, we will also have a better understanding of what stops or impedes the eel on its journey back to its birthplace. Perhaps we can even do something about it. Perhaps European and American researchers will, like their Japanese colleagues, manage to fertilize eggs from European and American eels and hatch them in captivity. Perhaps one day, these cultivated eels will survive and grow big and healthy enough to be eaten. Or, of course, to be released into the wild.
A scientifically minded optimist would say it’s just a matter of time. With a focused will and enough time, science will find a way to solve every riddle. The eel question has endured in various guises over millennia, but experience tells us we will find the answer, sooner or later. We just need enough time.
The problem, though, is that time is about to run out.