Hybrid fish model (Pseudoplatystoma reticulatum♀ × Leiarius marmoratus♂) to study feeding behaviour: protein source self‐selection and demand‐feeding rhythms

We report feeding studies on hybrid fish (carnivorous × omnivorous) to determine the interactions between protein sources during diet selection trials. We also examined behavioural rhythms (feeding and locomotor activity) using a self-feeding system mounted with a feeder connected to an infrared photocell. Twenty fish (28.20 ± 0.05 g) were distributed in four aquariums (50 L each). First, the system was tested to evaluate the adaptation of catfish (Pseudoplatystoma reticulatum × Leiarius marmoratus) to self-feeding (step I). During this 28-day period, feeding and locomotor activity rhythms were recorded. In the second step, to analyse protein self-selection, a group of 20 fish (19.10 ± 0.05 g) was released in the aquaria. The hybrid catfish were given free access to diets (soya bean meal protein (SP) vs. bovine liver protein (BP)) through two self-feeders. The same procedure was used for (SP) vs. fish meal protein (FP). The catfish learned to activate the feeders to demand a daily feed amount equivalent to 1.8% of their body weight. The fish performed most of their actions (89.0% feeding activity and 94.1 0% locomotor activity) in the night. The diet choice by the catfish became clearer with a significantly lower intake of BP (0.37 g per 100 g body weight, 24.6%) vs. SP (1.06 g per 100 g body weight, 75.4%) and SP (0.61 g per 100 g body weight, 38.9%) vs. FP (0.91 g per 100 g body weight, 61.1%). These findings should be considered when discussing feeding behaviour, nutritional targets and protein sources for future aquaculture feeds.