Japanese eels, also called nihon-unagi, are a traditional Japanese delicacy. They have also just been listed on an international "red list" of endangered species. This is promoting concerns among owners of Japanese restaurants and food suppliers the animals may soon be protected. 

The International Union for Conservation of Nature (IUCN) listed the eels on their Red List of Threatened Species. This classification could embolden calls for international protection of the animals. 

"Available data for glass, yellow and silver eels indicate that this species has declined in abundance across its range over the last 30 years (ca. three generations) and has been assessed as endangered... indicating that the spawning population has at least halved in this time period," IUCN researchers said

Nihon-unagi has been eaten in the island nation since ancient times, but the IUCN estimates eel populations have declined 90 percent in the last three decades. In the 1990's, European eels started to gain popularity with Japanese diners. That species, the nation's most expensive food fish, was listed as endangered in 2008. 

Japan is responsible for roughly 70 percent of the eel consumed worldwide. Yoshimasa Hayashi, the agriculture minister in Tokyo, called for additional efforts to boost populations of eels in native waters. 

Eel prices have risen in Japan in recent years, due to declining populations of the animals. Some citizens of the country are being forced to cut back on the extravagant dishes as prices rise. This could have a snowballing effects on other types of animals, as well. 

"East Asia is a hub for farming, trade and consumption of this species and its decline has meant that trade in other eel species, such as the Shortfin Eel (A. bicolor) has increased,"  researchers wrote in a detailed species fact page. 

Eels are high in vitamins and minerals. This means that the animals are not just cuisine, but are also used in Chinese medicine. Several species are suffering from population declines caused by overfishing and pollution. 

Efforts to boost eel populations in the area have been hampered by complicated migratory paths dictated by spawning grounds far from the Japanese homeland. 

"This information will allow us to prioritize conservation efforts for eel species and the freshwater ecosystem more broadly," Matthew Gollock of the IUCN said

The IUCN annual report is now in its fiftieth year. It examines 73,686 species, classifying 22,103 as threatened by extinction. 

The report also found that the three-banded armadillo remains vulnerable. This animal is the mascot for the 2014 FIFA World Cup games, taking place now.  

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