Annual cycle of plasma lipids in sea bass, Dicentrarchus labrax L.: Effects of environmental conditions and reproductive cycle

1. 1. Plasma lipid concentrations in sea bass were very high compared to reported levels in other fish (mean value: 32.1 g/1 total lipids; range of values: 11.1-107.0 g/1, of which 35.2% were phospholipids and 15.5% were cholesterol). Plasma acetoacetate levels were low and plasma free-glycerol high. No appreciable levels of 3-hydroxybutyrate were detected. 2. 2. Definite seasonal fluctuations occurred in the plasma levels of all parameters studied. Lipid phosphorus (LP), free glycerol (FGly) and acetoacetate (AcAc) presented the greatest variations throughout the year, whereas cholesterol showed more regular values. 3. 3. In summer, plasma levels of the lipidic fractions were low, but during the gonadal maturation period (September-December) transient increases in all lipid parameters were observed. At spawning, when temperature and photoperiod were the lowest of the year, total lipids (TL) and fractions as well as AcAc reached minimal levels. 4. 4. Plasma lipid variations observed in the fish adapted to 3.5%.S are more directly related to the alterations in the reproductive cycle caused by the different environmental conditions, than to the salinity change per se