NIGHT FEEDING REGIME IMPROVES WATER QUALITY, GROWTH PERFORMANCE AND FEEDING BEHAVIOUR OF EUROPEAN EELS, Anguilla anguilla

Abstract

This study was aimed to explore differences between day and night feeding of farmed European eels (Anguilla anguilla) on: (1) the growth and feeding behaviour of eels; and (2) the subsequent impact on the quality of the culture water. A 30 day field experiment was conducted in which 40 European eels (186.4 ± 9.26 g) were arbitrarily allocated into two replicate concrete ponds (200 x 100 x 125cm) that were divided into two treatment groups, one receiving feed by day (DF) and the other receiving feed at night (NF). Results revealed a significant improvement in eel's growth performance (larger final weight and faster growth) of the fish that were fed by night (NF). Moreover, feeding behaviour was also improved in the NF group with a significantly shorter latency to start feeding and shorter feeding duration. As a consequence of improved feeding behaviour, more favourable water quality conditions (higher dissolved oxygen concentrations and lower ammonia concentrations) were observed in the NF group. In conclusion, feeding eels by night could considerably enhance the culturing of eels by promoting enhanced growth and feeding behavior, and simultaneously improving water quality.Key words: feeding regime; European eel; behaviour; nocturnal feeding; growth; performance