I came across an article titled “In Japan, Captive Breeding May Help Save the Wild Eel” and began reading.
“Hitoshi Imaizumi pushes back the silver quilting of a tent at the National Research Institute of Aquaculture in Shibushi, southern Japan, steps into the pitch-black interior, and switches on a flashlight. A tall, tube-shaped aquarium emerges from the darkness. Inside, slivers of reflected light flicker through the water: Japanese eel larvae, hatched just six days earlier. With huge black eyes set in skull-like heads and flat, transparent bodies, they look like tiny visitors from an alien world—which in a sense they are.
“This is something you’d normally only see out in the middle of the ocean,” says Imaizumi, an aquaculture researcher at the center.”
I felt a pang of regret. But why? I realized it was because a thought had flickered through my mind, a remembrance of eels.
I’ve never encountered eels in the wild. I’ve only seen them in aquariums and on sushi platters. In neither case did they appeal to me very much.
Yet I felt a sort of empathy for the eels, reading of these scientific efforts to breed them in captivity. It was a feeling of regret for eels that may in the future no longer experience their lives in the wild.
My remembrance of eels was actually a memory from reading Rachel Carson’s Under the Sea-Wind. In a movingly evocative portion of that book, Carson writes of the journey of an eel she names “Anguilla” from its home in a freshwater pond to the sea to spawn and die.
Eels begin life in the deep ocean and develop into larvae which metamorphose into “glass eels,” (also called elvers) tiny transparent beings which migrate to the mouths of rivers and then hundreds of miles inland where they live in freshwater until instinct prompts them to descend once again to the open sea.
Carson describes an eel’s life in its fresh water home:
“Anguilla had entered Bittern Pond as a finger-long elver ten years before. She had lived in the pond through its summers and autumns and winters and springs, hiding in its weed beds by day and prowling through its waters by night, for like all eels she was a lover of darkness. She knew every crayfish burrow that ran in honeycombing furrows through the mud bank under the hill. She knew her way among the swaying, rubbery stems of spatterdock, where frogs sat on the thick leaves: and she knew where to find the spring peepers clinging to grass blades bubbling shrilly, where in spring the pond overflowed its grassy northern shore…”
In the article on captive breeding, author Winifred Bird writes that this middle portion of an eel’s life has been reproduced in human aquaculture for decades. The glass eels are caught by the millions in the wild and raised in holding pens until they are big enough for the dinner table.
That life in human-constructed enclosures replaces the wild life in a fresh water pond which Carson details. And it precludes that phase of the eels’ life of which she wrote so vividly that it glowed in my mind when I read the article. That phase is the journey to the sea. Carson describes it:
“At dusk, as the owls began to hoot in the woods, Anguilla left the pool and traveled downstream alone. Soon the stream flowed through rolling farm country. Twice during the night it dropped over small milldams that were white in the thin moonlight. In the stretch below the second dam, Anguilla lay for a time under the overhanging bank, where the swift currents were undercutting the heavy, grassy turf. The sharp hiss of the water over the slanting boards of the dam had frightened her. As she lay under the bank the eel that had rested with her in the pool of the waterfall came over the milldam and passed on downstream. Anguilla followed, letting the current take her bumping and jolting over the shallow riffles and gliding swiftly through the deeper stretches. Often she was aware of dark forms moving in the water near her. They were other eels, come from many of the upland feeder creeks of the main stream. Like Anguilla, the other long, slender fishes yielded to the hurrying water and let the currents speed their passage.”
Once the eels have arrived at the edge of the sea they migrate to deep water and spawn. The stages of life in the deep sea—the beginning and the end—are so complex that scientists have so far been unable to replicate them. Until the mid-20th Century, it was not even known where the eels went once they had migrated into the open sea.
The difficulties that scientists face in developing captive breeding hint at how deeply the eel’s wild life cycle is a part of its very essence.
Bird writes of the scientific efforts, interviewing University of Michigan scientist James Diana for her article:
“The challenge, he explains, is getting fish through a number of ‘bottlenecks’ in their life cycles. Sexual maturation, for instance, is triggered by a complex set of environmental cues including light levels, temperature, and salinity. Meeting the nutritional needs of larval fish is tricky too, because their diet—made up primarily of plankton—is completely different than the adults’.
‘No matter how long you keep a juvenile eel in captivity, it will not mature spontaneously,’ explains Imaizumi. To make matters worse, most farmed eels turn out to be male, even though the gender balance in the wild is equal. Mimicking the natural conditions that determine gender and trigger spawning has so far proven impossible.”
Carson may have added much from her own imagination into her story of the eels’ migration, given the state of knowledge of eels at the time she wrote in the 1930s. But the outline is clearly true to the eels’ life in the waters. Carson writes:
“At last Anguilla neared the mouth of the bay. With her were thousands of eels, come down, like the water that brought them, from all the hills and uplands of thousands of square miles, from every stream and river that drained away to the sea by the bay. The eels followed a deep channel that hugged the eastern shore of the bay and came to where the land passed in to a great salt marsh. Beyond the marsh, and between it and the sea, was a vast shallow arm of the bay studded with islands of green marsh grass. The eels gathered in the marsh, waiting for the moment when they should pass into the sea.”
Scientists are racing, like the eels to the sea, to find a way to re-create the entire eel life cycle so that it no longer includes the long journeys to and from the deep sea. It is because eels are threatened in the wild, their populations in rapid decline, that this complex work is being done. If they do not succeed at this, there may come a time when there are no eels in the wild.
Creating anew the eel life cycle as one controlled by humans is necessary to allow wild populations to survive, given the human pressure on eel populations from fishing. This radical change to the very essence of an eel is what stirred an emotion in me when I read Bird’s article. I entertained an idea that something was being taken from these eels—something vital to their very being. Somehow with captive breeding they are being denied the experience of eelness—what truly defines them as eels. The thought pained me.
The article on eels by Winifred Bird is published at the excellent Yale Environment 360 blog, a publication of the
Yale School of Forestry & Environmental Studies, which you can access at http://e360.yale.edu/