Self-feeding of European sea bass ( Dicentrarchus labrax, L.) under laboratory and farming conditions using a string sensor

Abstract

In the present paper, we describe the performance of a bite-and-pull feed-demand system adapted to the behavior of European sea bass. The system is activated by the fish biting and pulling on, which generates an electrical signal that triggers the feed distributor. Experiment I was designed to test the sensor under laboratory conditions, using four groups of four naive fish per sensor (non-trained fish, NTF) and eight groups of four fish per sensor (small groups) that had been trained to use the system 1 year earlier (TF). Experiment II compared the bite-and-pull trigger (BPT) with a screened hanging-rod trigger (ST) using 16 groups of 48 sea bass per sensor (medium groups) under laboratory conditions. Experiment III evaluated the performance of the BPT sensor under farming conditions using four groups of 1000 sea bass per sensor (large groups) held in sea cages. Some of the advantages of the BPT sensor over other sensors are: (1) a shorter learning period, 11–12 days in exp. I, 1–2 day in exp. II and 1 day in exp. III; (2) absence of temporal constraints, allowing sea bass to feed at night (60% of nocturnal demands in exp. II; 23% and 47% of nocturnal demands in September and February, respectively, exp. III); (3) prevents accidental activation by fish, wind or waves; (4) low feed waste when reward level is set correctly; and (5) low costs, durability, and easy replacement of its components. All these features make the BPT a useful system for sea bass self feeding in sea cages.