INTRODUCTION TO THE STUDY OF CIRCADIAN-RHYTHM OF ACTIVITY AND REST INTERMS OF LIGHT CONDITIONS FOR THE NORTHERN PIKE (ESOX-LUCIUS L)

We have studied the locomotor rhythm of the Pike (Esox lucius L.), at least four months old, in different light conditions. Observations are made, continuously, with an infra-red video system. Each experiment l asts on the average 20 days. Chronobiological data are analyzed using ENRIGHT'S periodogram (1965), SOKOLOVE and BUSHELL (1978) version, and a programming package developed in our laboratory. The obtained resul ts bring up into evidence the synchronisation by the alternance day/ni ght concerning swimming and rest rhythm. In constant conditions, ligh/ light (L.L.): permanent light, or dark/dark (D.D.): permanent dark, th e observations show the persistence of the swimming rhythm. On the con trary, in D.D., the rhythm of rest disappears. So, it seems that the s imple dichotomy swimming - rest is not sufficient for the description of the daily activity.