Paddlefish Polyodon spathula juveniles food searching behaviour evoked by natural food odour

Abstract

Summary Using the behavioural bioassay, food search behaviour was investigated in paddlefish Polyodon spathula juveniles (2.3, 3.0, 5.0, 15.0 and 35.0 cm TL; and 16, 23, 35, 50 and 130 days post-hatch respectively) evoked by Daphnia water extracts. Main characteristics of this behaviour were increased swimming speed, sinking to the lower water layer, short and straight trajectories in the odour cloud and opening of the mouth. These responses were seldom clearly pronounced and had a fairly short time-pattern. Biting and snapping, common in food search by many other species, were never observed. Ability to respond to food odour developed at the beginning of exogenous feeding. Olfactory sensitivity of P. spathula to natural food extract was relatively low, 10 )1 –10 )2 gL )1 , 2–3 orders of magnitude lower than in some sturgeons. It was concluded that olfaction plays a minor role in the food search behaviour of paddlefish.