Development of less-polluting diets for practical fish culture. II. Changes in proximate and fatty acid compositions of carp fed low protein-high energy diets due to starvation during winter.

Abstract

This experiment was conducted to examine the effect of a low protein-high energy diet or a high protein-high energy diet given to carp kept in net cages in Lake Kasumigaura before winter on the proximate and fatty acid compositions of carp harvested in spring after starvation for 128 days. Condition factor and visceral and gonad somatic indices were not much affected by the quality of diets in terms of the protein and energy levels given to the fish before winter starvation. Decrease of muscle protein and visceral lipid due to starvation suggested that the fish used mainly visceral lipid and muscle protein as energy source and not so much muscle lipid during winter starvation. In the fatty acid compositions of muscle total lipids from carp on each diet, some fatty acids such as 16:0, 20:1 and 22:1 increased, and 18:1 and 18:3ω3 decreased slightly due to starvation. However, there was no marked difference in the fatty acid distribution between males and females in each lot which showed almost the same pattern in changes of the fatty acid profile before and after winter.