Abstract
Effects of a constant magnetic field on the selection of swimming direction by trout (Salmo trutta L.) larvae and fry were investigated in an experimental facility consisting of chambers equipped with magnets as well as magnet-free chambers placed at the entrance. The experiments showed a close relationship between the direction selected by the larvae and fry and the presence or absence of ferritic magnets generating a constant magnetic field. The results obtained indicate during early ontogenesis, when a newly hatched individual is no longer an embryo but also not a mature form, that the larva is sensitive to a magnetic field. This sensitivity seems to be related to an exteroception system that develops at that time involving magnetoreceptors containing magnetite particles.