Self-feeder systems and infrared sensors to evaluate the daily feeding and locomotor rhythms of Pirarucu (Arapaima gigas) cultivated in outdoor tanks

Abstract This study evaluated the ability of Pirarucu ( Arapaima gigas ) to feed through self-demand feeders, and also determined daily feeding rhythm and locomotor activity. Twenty-four fish (312.58 ± 9.55 g, mean ± SEM) were distributed in six 250-liter outdoor tanks. Each tank was equipped with a feeder adapted to allow fish to self-feed. Self-feeders and occupancy sensors were connected to a computer to allow measurement of feeding and locomotor activity. First, the ability of Pirarucu to use the self-feeding system was assessed. The daily rhythm of feeding activity and locomotion of Pirarucu was then evaluated. The fish learned to trigger the feeders and feeding demand stabilized at 158.79 activations per day. Predominant daytime feeding activity was observed, with 110.86 ± 0.27 counts/day (70% of the total actions) seen during the day, versus 47.93 ± 0.11 counts/day (30%) at night. However, no rhythm in this daily locomotor activity was observed. These study results were based on food being freely available and should be taken into account to improve the supply schedule of the species. Statement of relevance The use of an automatic feeder system activated by the fish could allow the animal to feed at their preferred time and hence reduces waste and improve the food intake of Pirarucu raised for aquaculture. Moreover, the optimum feeding strategies, including times, schedules and regimes, should be determined from detailed investigations of feeding rhythms.