Seasonal timing and diel activity of lacustrine brook charr, Salvelinus fontinalis, spawning in a lake outlet

The objectives of this study were to determine (1) the seasonal timing and diel activity patterns of lacustrine brook charr when migrating to a lake outlet for spawning, and (2) the homing of reproducing individuals. In 1995, 745 individuals were captured while migrating to the spawning ground compared to 1148 in 1996. In both years, the sex ratio was not significantly different from 1 : 1 but females were significantly longer than males. The spawning migrations lasted about 48 d and were more nocturnal (between 20:00 and 8:00 h) than diurnal. The migration to the spawning ground began when water temperature decreased to 13degreesC and peaked when water temperature decreased from 11degreesC to 7degreesC. Peaks in migration activity were always preceded by a sudden decrease followed by an increase in temperature. The spawning migration lasted until the third week of October, when water temperature varied between 3degreesC and 8degreesC. Males, especially larger ones, arrived on the spawning ground before females in both years. The length of males migrating to the spawning ground decreased during the spawning season while the females' length showed no pattern. Only 9.7% of the 745 fin-clipped individuals from 1995 returned to the lake outlet to spawn in 1996. The results of this study indicate that lacustrine brook charr show similarities to other anadromous and lake-spawning salmonid populations when migrating to spawning grounds.