Effects of dietary fat levels on growth, feed efficiency and biochemical compositions of Eurasian perch Perca fluviatilis

A feeding experiment was conducted for 10 weeks with Eurasian perch Perca fluviatilis juveniles (33.1-35.9 g initial body weight) using three dietary fat levels (11.7, 15 and 19.3%). The results showed that increasing dietary fat content increased growth, feed efficiency and protein utilization of perch (P < 0.05) but did not affect mortality. Lipid analysis showed that the composition of some perch tissues were also significantly affected by increasing dietary fat content, with an increase of lipid deposition in the viscera (from 64.9% in fish fed 11.7% fat to 78.8% in fish fed 19.3% fat) and liver (from 12.4 to 23.8%) (P < 0.05), while the muscle composition was not affected by the dietary treament. High docosahexaenoic acid (22:6n-3, DHA) and high docosahexaenoic acid/eicosapentoenoic acid (20:5n-3, EPA) ratios were found in the liver and muscle lipids as compared to the dietary fatty acid compositions, suggesting that Eurasian perch might possess a high capability of converting the long chain highly unsaturated fatty acids, especially DHA from its dietary precursors.