DIEL LOCOMOTOR-ACTIVITY OF BROOK CHARR, AS DETERMINED BY RADIOTELEMETRY

Locations by radiotelemetry during eight 24-h sampling periods in 1991 , 1992, and 1993 were used to evaluate the diel activity patterns of a dult brook charr Salvelinus fontinalis in two lakes of the Laurentian Shield (Quebec, Canada). Based on the minimum distance travelled betwe en two consecutive locations, adult brook charr were more active at du sk and at night than during the day. During daylight periods, individu al fish displayed strong site selection, remaining in the same area al ong the shore from day to day. The fish left their inshore position at dusk, were highly mobile during the night, and returned to their foca l point at sunrise, exhibiting diel homing behaviour. These results ar e supported by an increase in gillnet captures of adult brook charr in Lac Melchior at night. Data obtained by gillnet fishing in lakes Bond i and Simpson shelved that juvenile (1+) brook charr were active throu ghout the diel cycle and that young-of-the-year were active mainly dur ing the day, suggesting that there is an ontogenetic change in the die l activity of brook charr. Despite its limitations (restrictions on th e number and size of tracked individuals, post-manipulation mortality, lifetime of transmitter battery), radiotelemetry allows for collectio n of multiple behavioural observations (distances travelled, instantan eous activity, site selection and homing) during the activity cycle of individual fish, and thus provides a finer degree of spatial resoluti on than alternative methods such as gillnetting. (C) 1996 The Fisherie s Society of the British Isles