A new study from the Wildlife Conservation Society and the University of Minnesota suggests that the world's largest and rarest owl -- the Blakiston's fish owl -- can be a key indicator of ecosystem health.

Blakiston's fish owls -- which can weigh up to 10 pounds and can have a wingspan of nearly six feet -- are found in the riparian ecosystems of China, Eastern Russian Hokkaido, Japan, and possibly North Korea.

The research team found that Blakiston's fish owls are linked to the health of some of the last great primary forests of Russia's Far East.

Blakiston's fish owls rely on old-growth forests along streams and rivers for breeding and to sustain healthy populations.

"The large trees provide breeding cavities for the enormous bird, which has a two-meter (six-foot) wingspan. And when these dead, massive trees topple into adjacent streams, they disrupt water flow, forcing the gushing river around, over, and under these new obstacles," Wildlife Conservation Society explained in a statement. "The result is stream channel complexity: a combination of deep, slow-moving backwaters and shallow, fast-moving channels that provide important microhabitats critical to salmon in different developmental stages."

Those populations of salmon are the favorite prey of the Blakiston's fish owl.

Across a study area of 20,213 square kilometers (7,804 square miles), the researchers noted the nesting and foraging characteristics of the Blakiston's fish owl in Primorye, Russia. The bird's nest and foraging sites were primarily distinguished by large old trees and riparian old-growth forest, the researchers observed.

Based on their observations, the study authors contend that proper management and conservation of old-growth forest are essential to sustaining Blakiston's fish owl populations, and the health of those systems is invariably linked to the health of the riparian system's salmon populations as well.

"Blakiston's fish owl is a clear indicator of the health of the forests, rivers, and salmon populations," said lead author Jonathan Slaght of the Wildlife Conservation Society. "Retention of habitat for fish owls will also maintain habitat for many other species associated with riparian old-growth forests in the Russian Far East."

Slaght and his colleagues' research is published in the journal Oryx.