Hybrid fish model (Pseudoplatystoma reticulatumfxLeiarius marmoratuso) to study feeding behaviour: protein source self-selection and demand-feeding rhythms

We report feeding studies on hybrid fish (carnivorousxomnivorous) 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 +/- 0.05g) were distributed in four aquariums (50L each). First, the system was tested to evaluate the adaptation of catfish (Pseudoplatystoma reticulatumxLeiarius 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 +/- 0.05g) 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 (0.37g per 100g body weight, 24.6%) vs. SP (1.06g per 100g bodyweight, 75.4%) and SP (0.61g per 100g body weight, 38.9%) vs. FP (0.91g per 100g body weight, 61.1%). These findings should be considered when discussing feeding behaviour, nutritional targets and protein sources for future aquaculture feeds.