An alarming number of red stingrays have been spotted swimming upstream in the Isumi river in Chiba, Japan several times since Tuesday.

Kazuyoshi Oogawa (54) was driving across a bridge over the river in Kamogawa city on Tuesday morning when his wife noticed a school of several hundred stingrays making their way slowly upriver (picture here). The surface of the river was carpeted by brown and black shapes as the school passed by, only to disappear completely before noon.

Another school appeared at the same location again a day later on the 18.

While locals point out that it’s not uncommon for groups of stingrays to be found swimming upstream during this time of the year, a breeder at the local Kamogawa Sea World aquarium commented: “While schools sometime appear near the mouth of a river from Spring to Summer, it’s rare for this many adult stingrays to swim up the river at once. I have no idea why they’re doing it.”

This isn’t the first time something fishy has happened in Chiba: just last month literally tons of dead sardines washed up on the shore of Isumi city, about 40km away from Kamogawa.

So what could the fish be trying to warn us about? A change in water temperatures? A huge earthquake near Tokyo? If the latter proves true, a river full of stingrays and a port full of dead sardines will be the least of our problems…

Source: Mainichi JP