Effects of ration, temperature and body size on the body composition, energy content and condition of the minnow, Phoxinus phoxinus (L.)

The effects of ration and temperature on the body composition, energy content and indices of condition of the minnow. Phoxinus phoxinus (L.) (Cyprinidae). were studied experimentally. Five ration levels over the range starvation to ad libitum and five temperatures over the range 5–15°C were used. The fish weighed 1-5-4 g. At each temperature, the relative dry matter content, lipid content and energy content increased with increased ration. The response of the protein content to ration was temperature-dependent. Temperature had a significant effect on body composition and energy content, but this effect was irregular. The Fulton condition factor was less sensitive to ration than the wet or dry liver-somatic index. Temperature had a significant effect on the condition factor and liver indices. Significant, positive correlations were found between growth rate, lipid content and the indices of condition. The liver indices were better predictors of growth rate than the condition factor or lipid content and may provide useful information on the physiological condition offish in field studies.