Fishmeal quality and ethoxyquin effects on the weaning performance of ballan wrasse (Labrus bergylta) larvae

Fishmeal diets are shown to be unfavourable for successful weaning of ballan wrasse (Labrus bergylta) larvae. Variable fishmeal quality, and/or a possible negative effect of ethoxyquin (EQ) and/or palatability could be the reason for the reduced growth and increased mortality observed. This study weaned wrasse larvae on either a control diet of freeze–dried shrimp and cod fillet, or fishmeal‐based diets with 0, 11 or 44 ppm EQ, for 1 month. Lower final body weight and higher mortality were related to increased inclusion of EQ. Furthermore, fishmeal diets had increased lipid oxidation values with decreased EQ content, whereas the control diet had the lowest lipid oxidation levels. A combined negative effect of oxidation and EQ supplementation could have lowered the palatability of the feeds and be the reason for the unsuccessful larval weaning. Use of EQ is inevitable in large‐scale production of feed ingredients; however, the use of high‐quality ingredients with low EQ inclusion, or its replacement with other antioxidants, may be necessary for successful intensive culture of some marine fishes.