This paper concerns eggs of captive fish and gonads of wild fish, from the Brittany coast obtained in the 7-18 degree C thermal range. The diameters of eggs, 1.07-1.32 mm are compared to those observed in other areas, especially along the Mediterranean coast. The duration of embryogenesis as a function of temperature and the efficiency of different incubators are discussed. The quality of eggs in relation with larval survival is discussed through the biochemical composition of the eggs collected in captivity compared to that of wild fish gonads. The absolute values of lipids, proteins, fatty acids, lipid classes, phosphatides and minerals measured, also the positive relations obtained between egg dry weight, diameters, mortality during incubation are presented as criteria of egg quality.