Food consumption, faecal production and nitrogen excretion by minnows, Phoxinus phoxinus, weighing 1-5.5 g were studied at five rations ranging from starvation to ad libitum and four temperatures ranging from 5 to 15' C.Themaximum rateoffoodconsumption(C,,) was related to body weight ( w a n d temperature ( r ) by the relationship: C m a X = a W P .There were significant daily variations in C,,,. which tended to decline over time. Absorption efficiency increased with increasing ration size and decreasing temperature. Body weight had no significant effect on the faecal production. The equation F = aCV:Tdescribed the relationship between faecal production (F), food consumption (C)and temperature. Ammonia-N predominated over urea-N in theexcreta ofmost experimental fish. The proportion of urea-N in the total nitrogen excreted wasgenerally higher at lower rations than at higher rations. Rates of nitrogen excretion increased with increased ration size and were, to a lesser extent. influenced by temperature. Body weight had no signilicant effect on the nitrogen excretion by feeding minnows. The equation N=a+b,T+b,C described the effects of food consumption and temperature on nitrogen excretion ( N ) other than urea-N excretion. The relationship between urea-N excretion (NJ food consumption and temperature was described by the equation N,=ul>"((C+ l)bx.On the average, I I YO of food energy was lost in faecal production and nitrogen excretion by minnows feeding on whiteworms, Enchyrraeus spp.

The erects of ration and temperature on the body composition. energy content and indices of condition of the minnow. P/~o.~inusphosinus (L.) (Cyprinidae). were studied experimentally. Five ration levels over the range starvation to adlihituni and five temperatures over the range 5-15, C were used. The fish weighed I -5 . 4~. 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 tcmperature-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 of fish in field studies.

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