A research team has found eggs of natural Japanese eels off the Mariana Islands in the Pacific Ocean for the first time, providing answers to longtime mysteries of where and when the fish spawn, it said in the British science magazine Nature Communications.

The team led by Katsumi Tsukamoto, a researcher at the University of Tokyo's Atmosphere and Oceanic Research Institute, said it collected 31 eel eggs near the West Mariana Ridge shortly before the new moon in May 2009.

Most eels used for food are raised in farms using fry caught at sea. The team hopes the discovery will lead to eel farming from eggs and prevent further declines in the eel population.

Using a net for plankton, the team found the eggs estimated to have been fertilized about 30 hours before in a 10-sq.-km area south of the oceanic ridge.

The team also found newly hatched eel larvae concentrated at a depth of about 160 meters, leading the members to believe spawning takes place at a depth of around 200 meters and the eggs gradually rise.