'Extinct' salmon rediscovered

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After having been given up as extinct for almost seven decades, a Japanese salmon subspecies has been rediscovered living in the shadow of Mount Fuji.

The Black kokanee (known to the Japanese as kunimasu) is a landlocked subspecies of the Sockeye salmon (Oncorhynchus nerka) that was once only known from Lake Tazawa in northern part of the Japanese island of Honshu. 

In 1940, a hydroelectric dam was constructed, and combined with acid drainage from a hot spring, killed off all of the Black kokanee (O. nerka kawamurae) then living in the lake (the last Black kokanee was encountered in Lake Tazawa in 1948). 

The subspecies was thought to have gone extinct as a result of this, but some five years prior to the construction of the dam, about 100,000 eggs were transferred to Lakes Saiko and Motosu  (both about 500 km south of Lake Tazawa). Even so, nothing much was thought to result from this transfer and the Black kokanee was officially considered extinct.

However, ichthyologist Tetsuji Nakabo led a research team that rediscovered the Black kokanee living in Lake Saiko. The research team was led to the discovery when TV personality Masayuki Miyazawa presented Nakabo with a blackish fish that had been caught in Lake Saiko. The researchers dissected the fish to examine morphological features of the gut and gills, as well as conducted a DNA analysis, results confirming their identity as black kokanee.

"I was really surprised. This is a very interesting fish — it’s a treasure. We have to protect it and not let it disappear again," said Nakabo. He added that the Black kokanee is present in sufficient numbers in Lake Saiko to be viable, assuming current conditions are maintained. Nakabo also hopes fishermen will refrain from capturing the species.

Although the Black kokanee is still technically listed as extinct by Japan’s Environment Ministry, a review scheduled for 2012 will take it off the list.