A long-held belief in Japan that sightings of deep-sea fish foretell major earthquakes is simply a superstition, according to a research team from two universities.
The team, consisting of researchers from Tokai University and the University of Shizuoka, reached the conclusion after comparing cases in which deep-sea fish were found beached or caught in fishing nets over around 90 years with records of earthquakes.
The belief that deep-sea fish sightings are connected with earthquakes has its roots in a mermaid legend found in the "Shokoku Rijin Dan," a collection of strange tales published in the 18th century.
"We thought that if we can understand the connection, it would be useful for disaster prevention," said Yoshiaki Orihara, a specially appointed associate professor of solid earth physics at Tokai University.
Orihara and the team searched for academic papers on sightings of deep-sea fish and examined old newspaper articles at the National Diet Library, assuming that such cases were rare enough to be picked up by regional media.
The team also analyzed online discussions of deep-sea fish and reports of sighting published by aquariums across Japan.
(Deep-sea fish Oarfish found in Toyama Bay, one of the deepest in Japan, in April 2019.)
By comparing the sightings to Japan Meteorological Agency seismic records extending back to 1923, the team found there were 371 cases of deep-sea fish sightings in the period between Nov. 26, 1928 and March 11, 2011, the date of the Great East Japan Earthquake.
The total included 336 cases of eight species of fish purported to be linked with earthquakes, such as oarfish and slender ribbonfish.
In the same period, earthquakes of magnitude 6 or greater were recorded 221 times. However, when the research team investigated how many of the quakes occurred within a 100-kilometer radius of a deep-sea fish sighting up to 30 days prior, they found only a July 16, 2007, earthquake that jolted Niigata Prefecture.
"It was disappointing to find no correlation, but we also want to investigate any connection between mass beachings of dolphins and whales with earthquakes in the future," Orihara said.