Carnitine treatment has an appreciable effect on the hatchery‐reared sea bass,Dicentrarchus labrax, fry.The administration of the laevorotatory isomer (1‐carnitine) which is engaged in the transport of the acyl and acetyl groups through the mitochondrial membrane, stimulating lipid metabolism, increases the growth rate and the protein content of the treated fry.The dextrorotatory isomer (d‐carnitine), which is an antagonist of the 1‐carnitine, has an opposite effect on the growth and metabolism of the trea