PELABUHAN RATU, Indonesia -- This small fishing town on Java's southwest coast is best known for the legendary sea queen Nyi Roro Kidul, a spurned princess turned mermaid who is said to snatch whatever man takes her fancy from the kilometers of beach that form the town's frontier with the Indian Ocean.
But the predatory queen is not the only marine enigma swimming through the turbulent undertow off the rain-swept coast.
For Japanese entrepreneur Hisayasu Ishitani, a chain smoking 72-year-old now in his fifth decade in Indonesia, the local waters mean a plentiful supply of eel -- and the opportunity to fill a growing market gap in his homeland.
In Japan, the native eel, Anguilla Japonica, has so diminished in numbers that it is listed internationally as endangered. But Japan eats 70% of the world's consumed eel, or unagi, and there are few signs that the Japanese appetite for this succulent, vitamin-rich fish is about to abate.
So while scientists, conservationists and the Tokyo government debate how to revive the Japanese native eel population, other potential suppliers are stepping up.
Ishitani established Indonesia's first eel farm in 2009. After an initially slow start, the venture was exporting 1 million cultured eels a year by 2013 and employing 50 staff. Now he is hoping to open a second eel farm in Banten province, on Java's western tip.
Despite rapid growth of his business, Ishitani said the eel remains a little understood fish. "So much we don't know," he noted as he slid a list of eel species compiled by the Swiss-based International Union for Conservation of Nature across the desk in his office. The catalog gives the population status of 10 of the 16 listed eel species as "unknown."
"The life cycle of anguillid eels is such that there are gaps in our knowledge for all 16 species; the majority of this lack of understanding is during the marine phases," Matthew Pollock, the IUCN's eel expert, told the Nikkei Asian Review.
Eels are difficult to farm because of their high sensitivity to factors such as water temperature and food. Ishitani buys eel fry, or elvers, from local fishermen, then tries to raise the finicky wrigglers to adulthood, when they are ready for sale. "At first, all die," said Ishitani, talking about his early days as an eel farmer.
Ishitani said that much of what he now knows was learnt by trial and error, because the Indonesian Shortfin Eel Anguilla bicolor had not been farmed before he set up his business, Jawa Suisan Indah. Anguilla bicolor, the species of which the Indonesian Shortfin is a subspecies, is described on the IUCN list as "near threatened -- population trend unknown."
"Research is very important," Ishitani said, noting that a lack of knowledge about the life cycle of the Japanese native eel is thought to have contributed to the decline of the species because of overfishing.
Overfishing in Europe has also led to several species of eel being listed as endangered, including Anguilla anguilla, the European eel. Anguilla anguilla is now subject to a European Union export ban, removing a potential source of eels for export to Japan.
"A concerning pattern of exploitation is already apparent -- when one Anguilla species or population becomes over-exploited or fisheries restrictions are imposed, the industry moves to the next in order to fulfill demand," the IUCN says.
Ishitani said Indonesia's 13,000 islands, stretching across 5,000km, are sure to be rich in eel -- not just the Indonesian Shortfin, but also the hefty Marbled Eel, or Anguilla Marmorata, also known as the Giant Long-finned Eel.
"Marmorata are plentiful around the northern islands of Indonesia," he said. "But the taste is not like other eel, it tastes more like regular fish."
This taste variation means that the Marbled Eel is unlikely to sell in Japan as a replacement for its Japanese cousin in popular grilled eel dishes. "We can export Marmorata to the U.S. however," Ishitani said, adding that the Marbled Eel can be served in North America in seafood dishes.
Ishitani said the Indonesian Shortfin is similar in taste to the Japanese native eel and can help make up for any unagi shortage in Japan. All the same, he said, there are still problems convincing buyers that eels from Java will satisfy gastronomes in Tokyo. "Right now I export more to Russia and America than to Japan," Ishitani laughed.
His response will be to launch what he calls "Jawa Unagi," or Javanese eel -- trying to pitch the flavor of the locally caught Shortfin as a culinary niche to pique the palette of his compatriots.
"With the rising demand [and the decline of] other species' population we are fully confident Jawa Unagi will [be a] success as a new eel commodity in the world, " said Beni Sitanggang, Ishitani's chief assistant at Jawa Suisan Indah.
Indonesia's eel pioneers are seeking government support to ensure that illegal fishing is curtailed and that the country's eel resources are better understood -- a request that is in line with President Joko Widodo's ambition to increase Indonesia's annual fish catch.
Widodo has already ordered the destruction of foreign fishing boats caught operating illegally in Indonesian waters and has promised further action to curb illegal catches.
This uncompromising stance has impressed Ishitani, who said his profits had been undermined by illegal fishing. "Smuggling has been a major problem for us, affecting the price," Ishitani said. "We hope the new president will listen to us."
Toni Ruchimat, director of fisheries resources at Indonesia's Ministry of Marine Affairs and Fisheries, told the NAR that the government was trying to increase understanding of its eel population, to improve the management of what could prove a lucrative resource.
"We are in the process of developing a fisheries management plan for eel resources. At this moment, it will cover eel resources in the southern coast of Java island," Ruchimat said.