Experimental study of the European river lamprey, Lampetra fluviatilis (L.), migratory behavior in the period of initial dispersion of juveniles

Mechanisms of the initial dispersion of early larvae resident and anadromous forms of the European river lamprey have been experimentally explored. The flow (channel flow and underflow), type of bottom, and illumination are the key factors influencing the beginning and the end of downstream migration. Larvae leave the pebble ground of the spawning area when there is underflow and illumination is reduced to the night level, and then they migrate downstream in the channel stream. It is shown that the individuals dispersing from the spawning areas have switched to exogenous feeding. The end of the dispersion occurs after larvae reach oozy habitats of the riverbed, where they can find optimal feeding conditions.