Communications: A Method for Assessment of the Efficacy of Feed Attractants for Fish

A procedure is described for the testing of feeding response to dietary attractants by juvenile rainbow trout Oncorhynchus mykiss, The fish were maintained in a controlled environment with minimum visual and auditory stimulation. They were fed once daily following a scotoperiod of 12 h. Feed consumption was recorded over a period of 4 min at successive 1‐min intervals. The feeding response could be assessed as early as 2 min after dispensing feed. The attractants examined to test the procedure were hydrolysates of krill, These were supplied to the control diet in liquid or dried form, as a component of the pellets or as a surface dressing. There was a positive response to the krill hydrolysate, which was greater when the attractant was applied to the surface of the pellets. Incidental to the development of the technique was the observation that the use of feeding attractants may modify feeding behavior to reduce feed wastage, The technique affords a rapid, sensitive, and repeatable method for evaluating feeding attractants.