FUJIKAWAGUCHIKO, YAMANASHI PREF. – The Yamanashi Prefectural Government plans to raise an endangered deepwater salmon species discovered in 2010 in Lake Saiko at the foot of Mount Fuji — 70 years after it died out in its original habitat 500 km northeast in Akita Prefecture’s Lake Tazawa.
Yamanashi Prefectural Fisheries Technology Center culturists will gill-net the “kunimasu” species in the 2.1-sq.-km lake, collecting sperm from males and eggs from females for fertilization at a hatchery in February and March — peak mating season — said Kiyoshi Mitsui, the center’s director.
The kunimasu was classified as a new species in the genus of Pacific salmon in 1925 by David Starr Jordan, a U.S. ichthyologist and the first president of Stanford University, and Ernest McGregor, another ichthyologist, in the authoritative Memoirs of the Carnegie Museum.
The two described the species as “another landlocked derivative” of the sockeye. The fish, being almost black, lives at a considerable depth and has a smaller number of pyloric caeca, finger-shaped pouches used to digest food, than other landlocked variants of red salmon.
The species was last seen in Lake Tazawa in 1940, when water made acidic from a hydroelectric power project was introduced into the lake from a nearby river.
Consequently, the species died out in the lake. It is still listed as extinct in the Environment Ministry’s Red Data Book for endangered and extinct species. The ministry now says it may reclassify the kunimasu when it updates the list in fiscal 2012.
In promoting the aquaculture project, Yamanashi Gov. Shomei Yokouchi has called the rediscovery of the kunimasu “a real drama.”
Emperor Akihito, an ichthyologist himself, called the species “a miracle fish” and said in December 2010, “It is absolutely necessary to disperse the risk so that the kunimasu will not become extinct in the future.”
Mitsui, with the Yamanashi fisheries center, said the local government wants to farm the kunimasu to make it “a signature marine product of Yamanashi Prefecture.”
“We want to promote the kunimasu as a high-class fish as there is documented testimony that it tasted delicious,” he said.
But plans to construct a hotel on the lake’s northern shore threaten to destroy the spawning site of the species, now endemic to Lake Saiko, making the culturing project all the more important for the survival and commercial exploitation of kunimasu, Mitsui and Kyoto University professor Tetsuji Nakabo said.
A total of 100,000 eyed kunimasu eggs transported from Lake Tazawa were released into Lake Saiko in 1935.
The project, undertaken by the Lake Saiko Fisheries Cooperative, was intended to increase protein-rich food sources for villagers near the lake, who were undernourished due to poor crops in the area.
Recently, it was found that the released eggs hatched and kunimasu propagated in the lake. Before the discovery in 2010, even local fishermen believed the attempt had failed and that the species had become extinct years ago. The reality was that kunimasu were mistaken by local fishermen for a different species, the “kuromasu” (black trout).
“When I was a child, villagers called the fish the kuromasu. We thought that the ‘himemasu’ (kokanee salmon) probably blackened after they had completed spawning,” said 60-year-old Hisashi Miura, the current chief of the cooperative. The word kuromasu was made up by the villagers to refer to the fish, but it is not a name that designates a separate species.
One key reason why kunimasu survived in the new habitat is that oxygen-rich groundwater from the nearby Misaka Mountains springs up from the bottom of Lake Saiko, Nakabo and Mitsui said.
“If the natural supply route of oxygen-carrying groundwater from the Misaka Mountains was cut off, it would dry up the spring at the lake’s bottom and destroy the kunimasu’s spawning site,” Nakabo warned, referring to the likely effects of the planned hotel on kunimasu fry living on the lake’s bottom. “The kunimasu could die out again.”
Miura corroborated this analysis, saying a video taken by divers about 20 years ago shows bubbles rising up from a spring at the lake’s bottom.
Yasuaki Miura, 62, former chief of the cooperative, put the lake’s current population of kunimasu at 10,000 to 30,000, down from a projected peak of 100,000.
Nine fish resembling himemasu that Yasuaki Miura caught in March and April 2010 were later identified as kunimasu by Kyoto University researchers.
Kunimasu differ from other species of Pacific salmon in having fewer pyloric caeca (49-59) and more gill-rakers (31-42). The nine “conformed with these figures in having 47-62 pyloric caeca and 37-43 gill-rakers,” Nakabo said.
A gill-raker is a bony projection of a gill arch to filter-feed tiny prey like plankton.
The nine were caught at a depth of 30-40 meters, similar to the 40-50 meter depth reported for kunimasu caught by Akita fishermen in Lake Tazawa during the peak February fishing month prior to 1940, he said.
The center will use cooler-fitted water tanks in the culturing project as kunimasu live and mate only in a habitat of very cold water, Mitsui said, adding that all of the nine fish landed by Miura were caught in Lake Saiko’s 4 degree zone.
When taken to Lake Saiko in 1935, the kunimasu appear to have been able to adapt to the new habitat because the two lakes have almost identical water temperatures, Nakabo said.
The species appears to have developed the unique characteristic of living in very low temperature environments as it evolved from a red salmon species that swam up the Omono River to Lake Tazawa sometime after the onset of the Pleistocene glacial age that began 1.6 million years ago, he said.
Lake Tazawa is a caldera lake established around the early Pleistocene. Climate changes during the Pleistocene and Holocene prompted the species to flee warming water zones nearer the lake’s surface and move into colder and deeper zones, he said.
Satoshi Koshimizu, a researcher at Yamanashi Institute of Environmental Sciences, said the water temperature of Lake Saiko is low as the surface is at an elevation of about 900 meters.
The center’s technology will enable about 80-90 percent of fertilized eggs to develop eyes, and approximately the same percentages of those eggs to hatch to become sac fry, or alevin, Mitsui said, adding, “If we can collect 300 eggs, we would be able to obtain some 150 to 200 fry.
“If we conserve the kunimasu with artificial fertilization, we will enable it to continue to exist, even if the current good conditions in Lake Saiko might cease to exist in the future,” he said.