A METHOD FOR ASSESSMENT OF THE EFFICACY OF FEED ATTRACTANTS FOR FISH

A procedure is described for the testing of feeding response to dietar y attractants by juvenile rainbow trout Oncorhynchus mykiss. The fish were maintained in a controlled environment with minimum visual and au ditory stimulation. They were fed once daily following a scotoperiod o f 12 h. Feed consumption was recorded over a period of 4 min at succes sive 1-min intervals. The feeding response could be assessed as early as 2 min after dispensing feed. The attractants examined to test the p rocedure were hydrolysates of krill. These were supplied to the contro l 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 hydrolysa te, which was greater when the attractant was applied to the surface o f the pellets. Incidental to the development of the technique was the observation that the use of feeding attractants may modify feeding beh avior to reduce feed wastage. The technique affords a rapid, sensitive , and repeatable method for evaluating feeding attractants.