Deep-diving sub will hunt for spawning eels


A team of researchers will put a manned submersible vessel into deep-sea waters in the Pacific near Guam in July to conduct ecological studies on Japanese eels, team members said Thursday.

The researchers come from the Japan Agency for Marine-Earth Science and Technology, which will supply the Shinkai 6500 submersible, and the University of Tokyo. The Shinkai 6500 can dive to a depth of 6,500 meters, according to the agency.

The researchers intend to observe Japanese eels’ activities just before and after spawning and promote studies on preservation of the eels, which are believed to be in danger of extinction.

Japanese researchers have conducted similar submersible studies on eels but could not observe their activities before and after spawning.

Katsumi Tsukamoto, a professor at the University of Tokyo’s Atmosphere and Ocean Research Institute and an authority on eels, said recent studies have narrowed down the location of deep-sea waters where eels spawn, expressing confidence that spawning activities will be observed this time.

Japanese eels are believed to spawn on the southern tip of the West Mariana Ridge near Guam shortly before the new moon between May and August.

The team plans to operate the Shinkai 6500 mainly at a depth of 200 meters during daytime between July 14 and 17, shortly before the new moon, to search for eels and observe their activities.

At night the team will use an unmanned deep ocean floor survey system, called the Deep Tow, that can be outfitted with sonar or cameras and towed with a cable.