EFFECTS OF FOOD PARTICLE-SIZE ON PERCA-FLUVIATILIS LARVAL GROWTH

The effects of the size of food particles on the uptake of an artifici al diet by perch (Perca fluviatilis) larvae, reared in tanks for 15 da ys following hatching, were studied. Perch accepted a dry diet with pa rticles smaller than 200 mu m. Average survival rates ranged from 11 t o 25% with daily specific growth of 0.03 mm and 0.08 mg in length and weight, respectively. There were no significant differences in the gro wth of perch fed with food particle sizes in the ranges 0-80, 80-125, 125-160 and 160-200 mu m. The best results were obtained, nevertheless , with particle sizes smaller than 125 mu m during the first week and larger than 125 mu m in the second week. The mouth size of larvae doub led from 0.36 to 0.75 mm and showed a significant and positive correla tion with larvae length. At the and of the experiment, the lipids cont ent in larvae was measured, especially the triacylglycerols fraction. The saturated and mono-unsaturated fatty acids in larvae reflected tho se in their food. The unsaturated C22:6 (n-3) and C18:2 (n-6) were the main component of n-3 and n-6 fatty acids series in perch.