The Place and Role of Downstream Migration of Ammocoetes in the Life Cycle of the European River Lamprey Lampetra fluviatilis (Petromyzontidae)

The migration activity of ammocoetes of the European river lamprey Lampetra fluviatilis does not decline following the primary dispersal from the nest, but continues throughout the larval stage, ensuring the redistribution of juveniles along the river channel. The mechanisms of their diurnal and seasonal dynamics are determined both by the anatomical and physiological development of individuals and by external factors (illumination, water level, availability of sediments and food particles suitable for a particular developmental stage). The generalization of our own long-term studies and literature data shows that larvae are mobile and move mainly downstream, and the migration aspect of this part of the life cycle should be divided into phases: primary dispersal of early larvae, secondary redistribution of ammocoetes, downstream migration of smolts to the sea.