Photopreferendum of migratory and nonmigratory larvae of European river lamprey Lampetra fluviatilis

In the light gradient installation, the larvae of European river lamprey Lampetra fluviatilis of 0+ age, migrating downstream (downstream migrants), are distributed predominantly over the zone of dusk illumination (150–1 lx) and less so over the daylight zone (2500–150 lx) and night illumination zone (<1 lx). In 0+ larvae that passed over to the sedentary lifestyle, the photopreferendum changes: they avoid the dusk and daytime illumination and prefer nighttime illumination. Such photopreferendum is retained in later larvae of lamprey (1+ and older).