In the period September 1980 to January 1981 three experiments were carried out: (1) The effect of different kinds of dry sole food on growth of soles was tested at 20°C and compared with growth with fresh mussel- meat. Growth with standard dry food (code S81-6), was 1 cm/ month or in weight (W) 1% W/day. Addition of 1% fish oil (code S81-10) or 20% yeast resulted in increased growth rates (1.1-1.2 cm/month, 1.2-1.4% W/day). The best growth was observed with fresh musselmeat (1.5 cm/month, 1.5% W/day). Addition of methionine, fishmeal, or phosphate did not improve growth in weight. (2) Groups of soles were kept at 20°C at different daily rations of dry food (S81-10) , increasing from 0(starvation) to 4-5% W/day (= 6.5-7.5% W0.8) .The linear relation was calculated between specific growth in weight is (a, % w0.8/day) and ration (R, 9 dry % ~10.8/day) .alpha (g fresh) = 0.717R -0.795 or alpha (g dry) = 0.167R -0.146. The daily maintenance ration of the dry food was estimated as approx. 9 dry 1% W0.8, the optimum daily ration (maximum bruto conversion) at 3.2% W0.8. Maximum growth was found at a daily ration of 5.8% W0.8 (= kcal 10% w0.8/day. About 24% of the energy value of the food was converted into fish growth. Condition of the fish, % dry weight, and% fat increased with ration size, while % ashweight decreased. A maximum calorific value of the fish (5.5 kcal/g dry) was found at a daily ration of about 4% w0.8. At this level the protein conversion efficiency and fat retention also reached maximum values. (3) Measurements of daily consumption of dry food and oxygen consumption, with groups of soles in closed 100 liter tanks, resulted in the following models: Food intake, 9 dry food/day = 0.042 w0.76 g fresh, oxygen consumption of feeding fish mg O/hour = 0.382 w0.82, starving fish 0.16w 0.82. Ammonia excretion mg NH4-N/hour 0.005w0.73.The oxygen consumption of the soles was higher during the night as compared to the day. It in creased for about 20% over two days after one meal. The extra respiratory energy for digestion of the food (Specific Dynamic Action) was calculated as a % of the energy value of the meal (SDA coefficient). Comparison of metabolism of soles fed with dry sole food (S81-10) or mussel gives the following results in % of dry weight of food: Faeces excretion dry food 12-15% Musselmeat 1.4-1.8% Ammonia excretion: dry food 1-2% Musselmeat 0.5-2.2% SDA coefficient dry food 6-10% Musselmeat 11-22 % At 20°C the routine metabolism of growing soles is about 275 mg O2/hour /kg0.8, ammonia excretion 4-5 mg NH4+-N/hour/kg0.8. At 20°C the density of soles in a rearing tank and the daily ration can be adjusted according to the oxygen content (0, mg.1-1) of the inflowing water (Oi), the oxygen content of the outflowing water (Ou),and waterflow rate D (l.s-1 ) by (Oi -Ou) x D/3.3 = kg dry food/day. |
