Catching adult fish
Mid-Sep.–early Oct.
• After reaching adult size, the fish swim upstream to the hatchery to spawn. Since not all of them can make it up the fish ladder at peak season, some are caught in dragnets and transported to the hatchery. [40]
Egg collection
Artificial insemination and “eyed eggs”
Oct.–Dec.
• When the eggs reach the “eyed-egg” stage, they are poured into incubator trays.
• The eggs are placed in a hatching tank and shielded from light. They have a diameter of 3.5 to 6.5 mm. Between 200 and 500 eggs can be collected from a single female. [46]
Hatching
Late Dec.–Jan. (1 year later)
• The newly hatched fish, or hatchlings, live at the bottom of the tanks while taking nourishment from their yolk sacs. They are now around 20 mm in length. [28]
Swimming up to the surface
Feb.–Mar.
• Having fully absorbed their yolk sacs, the hatchlings turn into fry and begin swimming.
• The fry start eating. [18]
Releasing the fry
Late June–early July
• The fry are moved to outdoor tanks when they reach about 3 cm in length.
• Their fins are cut on a 5-year cycle to identify their year of birth.
• When they reach 5 to 6 cm in length and 1 to 3 grams in weight, they are released into Lake Towada. [51]
Catching the fish
(1–3 years after release)
• A gill net is used to catch the adult fish, which have now attained a length of 20 to 30 cm and a weight of 100 to 200 grams. [29]
Swimming upstream
Mid-Sep.–early Nov.
When the kokanee fry have grown into adults, they return to the hatchery in droves to spawn. [17]
Fish ladder
A fishway divided into a series of ascending pools enables the fish to swim upstream back to the hatchery. The elevation gain is around 8 meters. [26]
[Photos]
Princess Higashifushimi Kaneko visiting the Wainai Hatchery (1918)
The Wainai Hatchery, with Wainai’s third son, Sadamitsu, at left (Taisho era)
Catching adult fish at the Wainai Hatchery, with Wainai standing at right (Taisho era)
The remains of the Wainai Hatchery today
