Time of spawning can be easily controlled by separating the male and female. Eggs can be collected just after fertilization (for example, one-cell stage embryos) using this method.
1. Put a pair of medaka in a small tank.
2. Put a thin plastic board (“separator”) to separate the male and female in the evening before the day of egg collection.
3. (Next day) Within 2 hours after lighting, remove the separator and allow the fishes to start mating. Be careful not to frighten the fishes before spawning or they will not spawn.
(This movie is the same as M3-2d)