Food particle-size preferences and feeding behaviour in warmwater aquaculture of European eel, Anguilla anguilla (L.)

Abstract

European eels [ Anguilla anguilla (L.)] from 0.2 g (elvers) to 88 g were fed commercial granular and pelleted feeds of different diameters in fresh-water at 25°C in laboratory systems. Efficiency of location and capture were assessed by measuring consumption time and, where appropriate, disintegration time of particles. Feeding behaviour was analyzed and the number of sensory location behaviours (visual and contact), ingestion behaviours (inertial suction and snaps), and rejections were calculated for each particle size. The average length of time particles were retained in the mouth before swallowing or rejection was also calculated. Elvers and fingerlings below 10–15 g appear to use gustatory rather than visual location; the reverse is true for larger eels. Inertial suction is the most important means of capturing smaller optimally-sized particles. The upper size limit to efficient feeding is dictated by mouth width, physical nature of particles and hunger motivation, the lower limit by location abilities. Optimum sizes are about 0.4–0.6 of mouth width but small eels take a wide range of sizes with almost equal facility. Granules are more water-stable than pellets and retain attractiveness for longer; both, however, are suitably stable in relation to observed consumption times. Relationships to data for wild eels and to feeding in warmwater culture are discussed and feed size and type recommendations made.