Effects of feeding schedule on locomotor activity rhythms and stress response in sea bream

Feeding cycles entrain biological rhythms, which enable animals to anticipate feeding times and so maximize food utilization and welfare. In this article, the effect of mealtime was investigated in two groups of sea bream (Sparus aurata): one group received a single daily meal at random times during the light period (random daytime feeding, RDF), whereas the other group received the meal during the light period but at the same time (scheduled daytime feeding, SDF). All the fish showed diurnal behavior, although the SDF group showed a lower percentage of diurnalism (84.4% vs. 79.5% in RDF and SDF respectively) and developed food anticipatory activity some hours before the mealtime. In addition, the mean daily locomotor activity of the RDF group was significantly higher than that of the SDF group (3132 vs. 2654 counts/day, respectively). Although the mean weight differed between both groups on day 30 (115.7 g and 125.6 g in RDF and SDF respectively), these differences had disappeared by day 60. Plasma cortisol and glucose significantly differed in both groups (cortisol: 71.8 vs. 8.7 ng/ml, glucose: 53.7 vs. 43.8 mg/dl in RDF and SDF, respectively), whereas lactate did not differ significantly. The results obtained suggest that altering the feeding time (scheduled vs. random) affects the behavior and physiology of sea bream, indicating that a single daily feeding cycle (compared to random) is beneficial for fish welfare because they can prepare themselves for the forthcoming feed.