Regulation of food intake in the goldfish.

Goldfish were trained to press a lever. This response was followed by the delivery of a pellet of food. The fish were then allowed continuous access to the lever under controlled conditions, and their food intake was measured. Goldfish distribute their feeding responses fairly evenly over time, within the limits of the lighting cycle. Some fish eat mainly at night, some during the day, and others seem to be indifferent to the lighting cycle. Goldfish decrease their food intake by one-half to one-third in response to a drop in ambient temperature from 25 to I 5 C, and show a corresponding increase in food intake when the temperature retu rns to 25 C. Goldfish inc rease their food intake significantly in response to dilution of their normal diet with kaolin, and thus seem to eat for calories or nutrient value.