Rare Salmon Subspecies Rediscovered in Japan

It appears a subspecies of salmon thought to be extinct for seventy years is getting another chance at survival.  The kunimasu, a unique subspecies of sockeye salmon, was recently discovered in a lake in Japan where early re-introduction efforts decades ago were believed to have failed.  The Japanese government is now drawing up plans for how to conserve the rare fish for future generations.

The kunimasu is restricted entirely to Japan—not only that but its range was originally limited to a single site, Lake Tazawako in the northern part of the country.  Unlike more famous salmon species that migrate from freshwater spawning streams to feeding ground in the ocean every year, the kunimasu lives its whole life in freshwater, and is specifically adapted to the lake environment.  However in the 1940s construction of a hydroelectric dam altered conditions in Lake Tazawako in such a way that the waters became polluted and lake acidity rose significantly. 

This rising acidity is believed to have caused the fish’s extinction in its native habitat.  Fortunately some kunimasu eggs had earlier been introduced into a new freshwater ecosystem, Lake Saiko (pictured above).  However until recently it was thought the introduction effort had failed and that a kunimasu population had failed to establish itself in the new lake.

Then last year Japanese fish expert and TV personality Sakan-kun received an unusual preserved fish specimen from Lake Saiko.  The scientist immediately suspected it might be a kunimasu, and consulted with other researchers at Kyoto University to confirm his guess.  Further investigation revealed what seems to be a health population of kunimasu in Lake Saiko—presumably descended from the eggs introduced from Lake Tazawako decades ago.  Though local people have known about and caught the unusual sub-species for years, its persistence had gone unnoticed by scientists.  It is estimated Lake Saiko is home to about ten thousand kunimasu today, and the subspecies is the first fish in Japan to be rediscovered after having already been declared extinct. 

Researchers are now going about the job of informing the public about the importance of the last living kunimasu population.  Nine preserved kunimasu from Lake Saiko were recently displayed at Kyoto University Museum in an exhibit comparing specimens from Lake Saiko with the fish that originally inhabited Lake Tazawako.  It turns out the Lake Saiko kunimasu are slightly smaller, most likely an adaptation to their new habitat evolved over the course of the last seven decades.  The newly rediscovered subspecies has drawn attention from no less a public figure than the emperor of Japan, himself a fish enthusiast. 

The kunimasu isn’t the first species or subspecies in an industrialized country to be declared extinct only to be re-found many years later.  In the United States perhaps the most famous example is the ivory-billed woodpecker, a charismatic bird from the swamps of the Southeast that was rediscovered in 2005.  However while the rediscovery of a new plant or animal is always cause for celebration, it also comes with the inevitable challenge of ensuring the creature doesn’t have to once again be declared extinct.  Fortunately the kunimasu population in Lake Saiko seems to be in good shape, but the fact that the fish is limited to a single location is still a cause for concern.  It is now more important than ever to conserve the lake ecosystem and prevent the type of habitat alterations that wiped out the kunimasu from Lake Tazawako.

If the deep freshwater lake where the last kunimasu live can be kept in healthy condition, there is every likelihood this subspecies will be able to persist into the future indefinitely.  With luck this unique lake-bound salmon will now continue to fascinate naturalists and fish enthusiasts in Japan for decades to come.

Photo credit: Richie Johns

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