Long, slender and snake-like, the giant oarfish is rarely found fewer than 200 metres from the surface of the ocean. Yet in the year leading up to the devastating 2011 Tohoku earthquake and tsunami, between 10 and 20 of the deep sea creatures washed up dead along the coast of Japan. Ancient Japanese fishermen's lore suggests the oarfish - known as the "messenger from the sea god's palace" - rises to the surface to warn of impending earthquakes.
Which is why people in Southern California are a little nervous at the news that, this month alone, at least two oarfish have been sighted on their beaches without any visible signs of injury or disease, leading to speculation that they were affected by some deep underwater disturbance.
Rachel Grant, a lecturer in animal biology at Anglia Ruskin University in Cambridge, said there might be some truth to the Japanese legend, and she has begun a study to test the idea. "It's theoretically possible because when an earthquake occurs there can be a build-up of pressure in the rocks which can lead to electrostatic charges that cause electrically-charged ions to be released into the water," Dr Grant said. "This can lead to the formation of hydrogen peroxide, which is a toxic compound. The charged ions can also oxidise organic matter which could either kill the fish or force them to leave the deep ocean and rise to the surface."
Another possibility is that prior to an earthquake there is a release of large quantities of carbon monoxide gas, which could also affect oarfish and other deep-sea creatures, Dr Grant said. "The geophysical processes behind these kinds of sighting can happen before an earthquake. I will be watching California closely over the next couple of weeks," she added.
A 4.3-metre oarfish was found on a beach near the city of Oceanside last Friday, while a 5.5-metre specimen was washed up on Santa Catalina Island a few days earlier. Tests on the fish failed to find any obvious reason for the stranding, though on the day following the second beaching, a 6.4-magnitude earthquake was recorded in the Gulf of California.
Californians frequently discuss the possibility of "The Big One", a devastating earthquake to match some of the state's historical seismic catastrophes. But local geologists and marine biologists remain unconvinced by the omen. Milton Love, a research biologist at the Marine Science Institute at UC Santa Barbara, said, "If the oarfish popped up an hour before an earthquakes, I could speculate that they were affected by a sound emitted before the quake, or by some toxic gases. But if the event happened a week or more before, I'm not so sure. If anyone can come up with theory for a congruent mechanism, I'd be willing to listen… [but] these animals strand themselves all over the world - even in places with no earthquakes, like Britain."
Dr Grant said she has built up a database of several hundred oarfish sightings over the past two and a half years, and will now see if there are links between the sightings and any earthquakes reported by the US Geological Survey within a 500 mile radius. Love said since records began there have been no more than 10 or 12 total strandings of oarfish in Southern California, though they have been known to beach themselves in pairs previously.
"We do know that there's not an earthquake after every oarfish sighting, but we are going to see if there is an increased probability of oarfish being seen prior to an earthquake," Dr Grant said. "It may be due to seismic activity or it may be due to other factors unconnected with earthquakes, such as infrasound caused by underwater activities, such as military submarines, or pollution."
The oarfish myth is one of several surrounding unusual animal behaviour or observations prior to earthquakes, which have been used anecdotally to predict impending disasters. Elephants were reportedly seen running for the hills of Thailand and Sri Lanka before the Boxing Day tsunami of 2004, and in 1975 officials in Haicheng, China, ordered an evacuation based in part on peculiar animal behaviour. A 7.3-magnitude earthquake struck the city the following day.
However, Dr Grant has shown in earlier research that there was no link between reports of mass migrations of young frogs and earthquakes - a connection made in Chinese folklore.
CALIFORNIA EARTHQUAKE FACTS:
* The San Andreas Fault, where the Pacific and North American tectonic plates meet, runs right under San Francisco and for approximately 810 miles down the length of California.
* The 1906 San Francisco earthquake still ranks as one of the worst natural disasters in US history. The quake and the fires that followed killed around 3,000 people and destroyed more than 80 per cent of the city.
* The most devastating quake in recent memory was the 1994 Northridge earthquake near Los Angeles, which killed 72 and caused some $20bn (£12.4bn) in damage.
* A 2011 study by the US Bureau of Labour Statistics concluded that a massive, 7.8-magnitude earthquake in Southern California - not felt since 1850, but said by scientists to be overdue - would hit roughly 430,000 businesses and 4.5 million employees.
* A report released this month by the Los Angeles Times found that more than 1,000 buildings in the city would be at risk of collapse if a major earthquake struck.