Zooplankton move vertically in the water column in almost all waters throughout the world. These small creatures are photosensitive, they do not like bright sunlight. The daily mass migration cycles everyday. Up in the water column during the evening and nighttime and descending to deeper, darker water during the daylight hours.
They are an important food source for fry and larger insects. Larger fish follow the migration feeding on the smaller fish, insects and the Zooplankton.