The Book of Eels, Patrik Svensson [bill gates best books .TXT] 📗

eel, we need to know more about it. We need more knowledge and more studies, and time is short.

And thus, we arrive at the great paradox: The mysteriousness of the eel has suddenly become its greatest enemy. If it is to survive, humans have to coax it out of the shadows and find answers to the remaining questions. And that will, of course, come at a cost. Because throughout history, there have been people who have embraced this mysteriousness, who have been drawn to it and have chosen to cling to it. People who, like Graham Swift, or his storyteller Tom Crick, want to believe that a world where everything’s explained is a world that has come to an end.

It is, if you will, a classic catch-22: Those of us who want to protect the eel in order to preserve something genuinely mysterious and enigmatic in a world of enlightenment will, in some ways, lose no matter how things turn out. Anyone who feels an eel should be allowed to remain an eel can no longer afford the luxury of also letting it remain a mystery.

At least we know one thing about the demise of the eel: it’s our fault. All the explanations put forward by science to date have something to do with human activity. The closer humanity gets to the eel, and the more it’s exposed to the influence of our modern living, the faster it dies. When the International Council for the Exploration of the Sea (ICES) summarized what should be done to save the eel in 2017, it was simultaneously vague and laudably clear: the impact of human activity on the eel should be “as close to zero as possible.” We still don’t know everything about the threat to the eel, but what we do know is enough to identify the only way of saving it: we have to leave it be.

What we know, for example, is that the eel is struggling with disease, and more so now than before. It’s susceptible to, among other things, the herpes virus anguillae, a disease first discovered among Japanese eels in captivity, which has since spread through imports to wild eels in Europe. The first Dutch case was identified in 1996; in southern Germany, tests have shown that nearly half of all eels have it.

For some reason, the virus seems to affect only eels—hence its name—and it’s an unusually unpleasant disease. The virus can lie dormant in its host for a long time, but once it breaks out, it has a quick and aggressive course. The eel develops bleeding sores around its gills and fins. The cells in the gills die and the blood-filled filaments stick together. Its inner organs become inflamed, rendering the eel tired and lethargic until it can move only slowly and near the surface, until its body finally gives up and it dies.

Eels can also catch the parasite Anguillicoloides crassus, a nematode. It, too, was first discovered among Japanese eels and reached Europe in the 1980s, probably piggybacking on live eels imported from Taiwan. In just a few decades, it has since spread across all of Europe and to America. A 2013 study in South Carolina showed that as early as the glass eel stage, 30 percent of eels carried the parasite. The study also indicated the parasite had spread faster due to well-intentioned attempts to save the eel by releasing caught glass eels in new waters.

The nematode is a kind of roundworm that specifically attacks the eel’s swimming bladder, causing bleeding, inflammation, and scarification. An infested eel grows more slowly and becomes more susceptible to disease. It moves into shallower waters and can swim only for short distances. The parasite isn’t necessarily fatal, but an eel infested with Anguillicoloides crassus has very poor prospects of reaching the Sargasso Sea.

What we also know is that the eel is particularly sensitive to pollution. Since it lives for a long time and sits high up the food chain, it’s particularly affected by industrial and agricultural toxins. And as with the parasites, the toxins seem to impede the eel’s ability to make the journey back to the Sargasso Sea. Eels exposed to PCB, for example, have been shown to develop heart defects and edema and problems storing fat and energy, which makes the long migration virtually impossible. Eels exposed to various pesticides have been shown to be less able to transition from fresh to saltwater. And if appearances are anything to go by, if it’s true that fewer silver eels reach their spawning grounds, pollution is at least a likely contributing factor.

Some theories are harder to prove. There are some signs pointing to the eel’s falling prey to other predators more often than before, which may not be directly attributable to humans; but it’s conceivable that eels that are sick, weakened by toxins and parasites and therefore moving more slowly and closer to the surface, also make easier targets for predators like cormorants, who are plentiful and love feasting on eels.

Some modern threats that researchers consider the most serious, and which are unquestionably caused by humans, are the various physical impediments to the eel’s migrations. Locks, sluices, and other artificial means of water regulation can keep young eels from swimming up waterways and mature eels from reaching the sea. And hydroelectric plants, beneficial as they may be for the greater environment, are death to eels. The dams’ turbines kill scores of silver eels on their way toward the Atlantic, with some reports claiming that each power plant kills close to 70 percent of all eels trying to pass through. The fish ladders built to circumvent the dams are, by and large, customized for use by the more shallowly inclined salmon.

One old threat to the eel’s survival is, of course, fishing, though the severity of its impact has long been the subject of debate. Historically, the eel has been a popular food in many parts of Europe; not only have eel fishermen had their own traditions, tools, and methods,