Influence of the daily distribution of light on reproduction in the barbel, Barbus barbus (L.)

The influence of the daily distribution of light on the duration of the breeding season of the barbel was investigated. Interrupted night photoperiods (6L:2D:2L:14D or 6L:8.5D:2L:7.5D) allowed spawnings of male and female barbel (previously maintained under 10L:14D or 16.5L:7.5D) to continue, whereas a 2 or 8.5 h shorter photoperiod (8L: 16D) inhibited both sexes. The number of spawnings for each female was significantly higher under 6L:2D:2L:14D or 6L:8.5D:2L:7.5D (respectively 2.9 and 3.6 spawnings on average) than in control groups maintained under 8L:16D (0.6 and 2.1 spawnings on average). These results suggest that there is a daily rhythm of photosensitivity in the barbel.