Dozens of Japanese huchen, an endangered fish in the salmon family, have been found dead in rivers this summer in the northern Hokkaido region of Soya.

Experts say the fish, dubbed the "phantom fish" for its scarcity, probably died because of a deficiency of oxygen in the water, as the hot summer caused high water temperatures and not enough rain.

Dead Japanese huchen found in the Sarufutsu River system in Hokkaido | COURTESY OF MITSUKI KURODA / VIA KYODO
Dead Japanese huchen found in the Sarufutsu River system in Hokkaido | COURTESY OF MITSUKI KURODA / VIA KYODO