Sample of Kunimasu, found alive in Lake Saiko. (Photo: pref.yamanashi.jp)
Yamanashi government to farm recently discovered endangered salmon
Wednesday, January 11, 2012, 23:50 (GMT + 9)
Seventy years after the extinction in 1940 of an endangered deepwater salmon, the Yamanashi prefectural government plans to farm the "Kunimasu" species in its original habitat at Lake Tazawa.
Lake Tazawa is a caldera lake located in Semboku, Akita Prefecture, northern Japan. It is the deepest lake in Japan, with the maximum depth being 423 metres.
Culturists at the Yamanashi Prefectural Fisheries Technology Centre will gillnet the salmon in the 2.1 square-kilometre lake, collecting sperm from males and eggs from females for fertilization at a hatchery from February and March during the peak mating season, said Kiyoshi Mitsui, director of the center in an interview with Kyodo News.
The Kunimasu species was last seen in Lake Tazawa in 1940, after acidic water from a close by river was introduced into the lake as a result of a hydroelectric power generation project, killing the fish in the lake.
The species was described as a new species in the genus of Pacific salmon in 1925 and landlocked derivative of the sockeye, or red salmon.
This almost black fish, lives at a considerable depth and has a smaller number of pyloric caeca, finger-shaped pouches used by fish to digest food, than other landlocked variants of red salmon.
In 1935, a project, undertaken by the Lake Saiko Fisheries Cooperative, released a total of 100,000 eyed Kunimasu eggs transported from Lake Tazawa with the intention to increase protein food sources for villagers near the lake, who were undernourished due to poor crops in the area.
It was found recently that the released eggs hatched and that Kunimasu propagated in the lake.
It is thought that one of the key reasons why the Kunimasu survived in the new habitat is that oxygen-rich underground water from the nearby Misaka Mountains springs up from the bottom of Lake Saiko.
Lake Saiko is located in Yamanashi Prefecture and is connected to nearby lakes by underground waterways.
Former chief of the cooperative, Yasuaki Miura, says the current population of Kunimasu in the lake is about 10,000 to 30,000 fish, down from a projected 100,000 during the peak time.
The centre's technology will allow about 80-90 per cent of fertilized eggs to develop eyes, and about the same percentages of those eggs to hatch to become alevin, Kiyoshi Mitsui said.
The director of the centre added that if 300 eggs are collected, they would be able to obtain some 150 to 200 fry.