by James Prosek
The discovery of the general spawning area of Anguilla japonica was the cover story in the journal Nature, as well as Science News. It was heralded in the Japanese press as one of the great events of recent Japanese history (and made for an auspicious story, as it happened in July, very near to Eel Day). In part because of the success of that trip, Miller decided to move to Japan to work with Katsumi, specializing in the study of eel larvae, not only the larvae of Anguilla japonica but all different species of freshwater and marine eels.
Seated at his desk, Mike handed me a glass vial with about half a dozen preserved specimens of tiny larvae that they’d collected on the previous expedition. It was the first time I had actually seen an eel larva, albeit dead. They were beautiful—like clear willow leaves with a barely visible herringbone skeleton. I swirled the leptocephali in their preservative solution. They momentarily danced on their pin-sized heads before I placed the vial back on Mike’s desk and watched them settle like flakes in a snowglobe.
With a combination of perseverance, knowledge (of ocean currents, salinity, and temperature fronts), and luck, Katsumi’s team had managed since 1991 to catch larvae only days old, or perhaps just hours from hatching. But despite several attempts with traps, trawls, and various fishing techniques, they still had not captured a mature spawning eel.
By this time in my visit it was late afternoon, and Mike offered me a cold Kirin beer from a small refrigerator in his office. It was very welcome at the end of a sweltering day.
“The ocean is a whole other wilderness,” Mike said, taking a swig of his beer. “Sky and clouds and water, with pockets of life here and there. It’s beautiful.” He tried to evoke the ocean’s vastness. “There have been attempts to catch adults,” Mike said, “but it’s a big ocean. You could be fifty meters away. It’s an issue of scale. The open ocean is huge. To get to where eels are spawning is almost impossible. You’d have to be very lucky. You set a trap or pull a net fifty meters on the wrong side, you won’t get them.”
What made it even more challenging was that the ocean is amorphous and dynamic, and from year to year the spawning area would never be in precisely the same place. Still, the scientists were certain that with the proper resources and persistence the secret would be revealed. I had not realized until I began my conversation with Mike how close they had come. Not all of their latest discoveries had been published—new information about the eel was being gleaned daily, collected not only on ocean cruises but also in the lab. Mike told me that Dr. Hideki Tanaka and his colleagues at the National Research Institute of Aquaculture were making great advances with hatching and raising eels in captivity.
Mike was interested in the larvae of all catadromous eels as well as those of marine eels, but his primary interest these days was to find the spawning area of the longfin eel of New Zealand.
“The longfin is one of the few Anguilla species that we have no idea about,” Mike said. “We’ve never identified a longfin larva.” His eyes widened at the thought of finding one. “Katsumi funded the pop-up tag research that Don Jellyman had implemented on longfin eels. They got some info,” Mike said, “but there were no clear results. It didn’t solve the mystery.”
After we finished our beers, Mike brought me down the hall to meet Katsumi. He seemed hesitant to interrupt his mentor, but Katsumi welcomed us warmly into his office. He had a gentle demeanor, a tanned face, dark brown eyes, and dark hair with strands of gray. Katsumi showed me the eel icons on votive plaques he’d collected. The eel in Japan, he explained, is among other things a symbol of fertility and safe pregnancy.
Early on in his career, Katsumi became interested in studying fish migration. His first breakthrough was unraveling the mysterious life history of the ayu, also called sweetfish, a prized food fish in Japan.* Katsumi’s team discovered that ayu spawn in freshwater, the larvae go to sea, and then they come back to freshwater in spring (a fish that migrates between fresh and salt water, but not necessarily for purposes of breeding, is called amphidromous).”We figured it out,” Katsumi said. “But the ayu is easy compared to the eel. The eel is very difficult. Takes time to study. We are the closest team. We are very close.”
Katsumi had navigated a good portion of the tropical Pacific and visited countless islands in Polynesia, Micronesia, the Philippines, and Indonesia in search of eel larvae. He mentioned that he’d visited one especially interesting island in Micronesia where there was a clan of people whose totem is the freshwater eel.
“Pohnpei?” I blurted out.
“Yes,” he said, “that’s it. How did you know?”
This was the island that Jonathan Yang, the eel dealer I met in Maine, had told me about. Katsumi said it was well worth the trouble to get there, a beautiful and wild place with mountains and many freshwater rivers. I made a note about Pohnpei in my notebook.
Katsumi suggested that the three of us go get a bite to eat. But before we left the office he signed a copy of his colorful book of photographs from their voyages on the Hakuho Maru, called Gran Pacifico. Katsumi said that it included his thoughts about the beauty and diversity of ocean life made during months aboard the research vessel. In the back of the book was a poem he had written about eels. He attempted a translation, reading aloud.
“Why do they migrate so far?” he said. “Why so far, why,” he repeated to himself. “Why do they choose this hard life? Why do living creatures live, why do living creatures die?”
Katsumi was in an ebullient mood as we walked down the street away from the office. I felt as though my visit and my questions had caused him to reflect on his travels and his successes.
After two beers at a small bar where Katsumi said he used to go when he was an undergraduate at the University of Tokyo, we walked to a restaurant called Sakuraya to eat dinner. Katsumi spoke poetically about the copulation ritual of manta rays. “They reproduce belly to belly!” he said in amazement, his face full of childlike wonder. And I thought, The best scientists are those who never grow up.
Mike and Katsumi ordered eel and other types of sushi and sashimi. We drank sake and more beer.
Katsumi spoke again of the eels’ mysterious migration. He said that long cruises at sea had made him philosophical. “Why spawn, why die?” he said. “Why, why? Eel is very shy and very nervous, but tough, very hard to understand, very powerful … a wide range of unpredictable characteristics.” He put his head in his hands. “It returns to where it was born,” he said. “How does it know?”
That was the last legible thing I wrote in my journal that night. My scrawl had devolved to eel-like scribbles. All I can remember is that there was a warm collective feeling around the table, big smiles, laughter, and a mutual acknowledgment that there were certain things that would never be known.
Why Live? Why Die?
At the end of their long journey the parents spawn
And die
As their children take the ocean currents back
To East Asian rivers from Mariana.
Adults and young both knowingly make their way alone
And through this travel, life is handed down.
For millions of years, birth and death repeats.
It is relentless.
Why do they do these kinds of things?
Why do they choose this hard life?
Why do living creatures live?
Why do living creatures die?
—KATSUMI TSUKAMOTO
In Yoshida, an area south of Tokyo known for its green tea cultivation, David, Kunio, and I visited a large industrial fish farm owned by Yoshio Shiraishi, president of the Maruhaiyoshida Eel Culture Cooperative Association. Here Japanese glass eels are fed fish-meal paste in large cement tanks under black plastic tents that keep the fish in the relative darkness they prefer. The 110°F heat in the tents is oppressive but helps maintain the water temperature at an optimal 90°F.
“The hotter it is, the faster the eels grow,” said Shiraishi.
The government no longer allows glass eels from out
side the country to be raised in Japanese eel farms. Even if they did, conditions could be hostile to American or European glass eels, which require cooler water that is richer in oxygen. Most of the Japanese glass eels are caught in winter and early spring—roughly between December and April. When the wild glass eels arrive at the farm, the first task of the farmer is to acclimatize the juvenile eels to tank life by feeding them a squid-based powder. Shiraishi said it takes six months to two years for an eel to reach kabayaki size in the farm. “Some little guys, like human beings, take more years to grow,” he said.
The price for Japanese glass eels in 2003 was $900 a pound. In 2004, it was $1,100 a pound. In 2005, the year I visited, glass eels were $3,600 a pound. The price was so high, Shiraishi said, because “they did not catch many that year.” At this farm they currently had 150,000 or so eels in cultivation. Each tank could hold approximately 17,000 adult eels. I asked Shiraishi if American eels tasted the same as Japanese eels. He said if they were raised on the same feed, it might be hard to tell the difference.
Our next stop was the lab that could one day supply this farm with artificially reproduced glass eels.
Kunio did not explain until we reached the gates of the National Research Institute of Aquaculture in Nansei that he had timed our visit to coincide with the day and time—Friday at eleven in the morning—when every week Dr. Hideki Tanaka and his team stripped eggs from ripe female eels and fertilized them.
Tanaka, a slim, soft-spoken Japanese man, met us at the side door to the building and walked us casually around the lab. Room after room was filled with tanks made of clear acrylic in various sizes and shapes, but mostly cylindrical, bathed in a fluorescent purple glow, which, Tanaka explained, simulated the light conditions hundreds of feet below the surface of the ocean. Swimming in the tanks were eel larvae, varying in age from seven to two hundred days. This was likely the closest we would ever come to seeing the early moments of an eel’s life in the ocean.
Tanaka encouraged us to peer into the cylinders where hundreds of small clear eel larvae were dancing irregularly. Many had their heads at the bottom of the tanks, apparently feeding on something that had settled to the bottom. The equipment in the room—filters, lights, instruments for maintaining salinity and temperature—were deceptively simple. These eel larvae were the fruit of consistent and rigorous work that had been ongoing since the 1970s.
There was an enormous amount of pressure on the lab to come up with a simple formula for hatching and rearing freshwater eels in captivity. This pressure only increased as wild populations of eels declined. One of Tanaka’s papers states the problem clearly: “To maintain the natural glass eel resources and to obtain reliable supplies of glass eels for aquaculture, development of an artificially induced breeding procedure for eels has been eagerly desired.”
Eggs of Anguilla japonica were first successfully fertilized and hatched in captivity in 1973 at the University of Hokkaido.* The newly hatched pre-leptocephali larvae, however, could not be kept alive beyond their first few days. Once the fish had depleted their yolk sacs (stores of nutrients that carry fish through the first period of life), the biologists could not get them to feed on their own.
The difficulty was to find what the cultivated larvae would eat, especially when they had no way of studying what the wild larvae were eating in the ocean. “We tried everything,” Tanaka said. A short list of attempted foods included zooplankton, eggs of other fish, rotifers, cuttlefish, shrimp, jellyfish, and mussel gonads. Finally, in 2001, Tanaka and his team found that eel larvae would actively ingest a slurry-type diet made from freeze-dried shark egg powder. On this diet they were able to keep the larvae alive for eighteen days, a record at that point. By mixing the shark egg powder with soybean peptide, krill extract, and a variety of vitamins and minerals, they succeeded in extending their lives further. Finally, when the hatchlings were 250 days old and two inches in length, the scientists watched the leaf-shaped larvae metamorphose into glass eels.
The year we entered Tanaka’s lab was the first that they had raised an eel to the size at which they would normally be harvested at an eel farm, roughly eighteen inches. In a tank on the left side of the room two such eels were taking shelter in PVC tubes.* Their heads were misshapen, their pectoral fins abraded. I asked Tanaka if they’d given them names. “No,” he said, “just a number.”
Tanaka said that his lab requires about $1.8 million a year to sustain all of its projects, two-thirds of which are related to eel reproduction. And though they had had significant success, the ratio of eggs hatched to adults reared was not anywhere close to being profitable in a market environment. After 50 days only 4 percent of hatched eels survived; by the 100th day it was down to 1 percent. A mere handful survived to 250 days.
The high mortality and slow growth rates in the lab were likely due to a host of factors, but given how little was known of the eel’s life cycle in the ocean, they could not be easily determined. Hormones injected into the males and females to make them mature adults caused deformities in the offspring. The eel larvae raised in the lab did not look like larvae caught by Mike Miller and Katsumi in the ocean—their heads were malformed and they seemed to have trouble swimming.*
Tanaka took David, Kunio, and me into a small, nondescript white-walled room where they strip the ripe female eels of their eggs. In eel farming almost all of the fish are males. “No one knows why,” Tanaka said.** To create females for the purposes of propagation in the lab, they feed glass eels estrogen.
Before us was one of three adult females—number 24—that would be stripped of eggs that week. She had just been removed from a bucket, set on a lab table, and anesthetized. She was a sleek eel maybe three feet long, but the entire middle of her body bulged with eggs. The eel gasped slowly, clearly alive. One technician held her while another technician put pressure on her belly, encouraging yellow glutinous masses of eggs to spill out of her anal vent into a beaker.
Tanaka said it was not unusual for one female to produce ten million to twenty million eggs in the wild, but in captivity they are lucky to get one million. The individual eggs are visible to the naked eye, about 1 millimeter in diameter (smaller than the head of a pin), and there are about 2,000 eggs in a gram. I asked Tanaka if he thought adult eels in the wild expire after spawning. He pointed to the female eel stripped of its eggs; she was now dead. “I think it’s very much like this,” he said. “It is so exhausting for them, they probably die.” This particular female was only three years old, while the average spawning adult in the wild was ten to twenty years old. Her eggs were taken to another room, where they were fertilized with milt from a male eel. If, as Kunio had said, Japan is the end of the road for the eel, in Tanaka’s lab, at least, it is also oddly a beginning.*
After visiting the lab I traveled south with Kunio to his home city, Kyoto, and settled myself in a hotel from which I could access all the major temples and gardens. Two days later, on July 28, Eel Day, Kunio and I met up for a celebratory late lunch of eel.
“Observe how Japanese people eat eel,” Kunio said as we entered an eel restaurant called Hamamatsuya in the Gion district (the Gion is one of the most famous places to see geishas in Japan). We took off our shoes and put on slippers.
Behind a wooden counter the staff were preparing the eels for cooking. One by one the live eels were taken out of plastic tubs and impaled through the head on a metal pin inserted into a hole in a wood cutting board. With the quick sweep of a knife, the eel was butterflied open and the spine and anal and ventral fins taken out, keeping the entire fish still attached by the skin.*
“Japanese food is very delicate—made to order,” Kunio noted. “You prepare and then you eat. If you bring it home in a bento box, you eat it soon. If not, it’s like yesterday’s bread.”
After the eel is gutted and the fins taken out, the head is removed and the fish is cut into two equal pieces. The white meat is skewered with four or five bamboo sticks and placed in a basin of water. A few moments later
, the skewered eel is taken out and laid on a metal grill over a hot wood fire. It sizzles and crackles as the fat in the flesh and skin is slowly rendered (several times it is also dipped in water and returned to the fire to steam the meat). The chef rotates a dozen or so eels around the grill surface at once, swapping, turning, and fanning before glazing the meat with the sweet sauce of soy, mirin, and sugar, and sprinkling it with sansho, mountain pepper.
As the chef stirred the coals they made a sound like dull wind chimes (Kunio said they use a hardwood from China, like oak). I found it hard to understand how the chef could tolerate the intense heat, but the dry heat from the coals was almost a relief from the muggy, sticky air in the streets of town.
No part of the eel goes to waste. The spine is deep-fried and eaten like a cracker—hone senbei. The guts, unagi kimo, are skewered and grilled—“No guts, no glory,” Kunio said as he sampled a mouthful. The eel liver is served in a soup. Eel is most often served at lunch, at the hottest time of day, as the only course. Kunio said that the Japanese tended not to eat rich, heavy food like eel at dinnertime. You eat it, Kunio says, and you feel like you need to do something, like take a long walk. “Japanese have a taste for fatty food,” Kunio said, “but very little. They like a marbled beef like Kobe, but only two or three pieces. And they always eat with rice. It’s more balanced.”
The eel had a crispy skin and tender flesh. It was rich and flavorful, slightly buttery, and smooth like pâté.*