SHORT-TERM AND LONG-TERM DIETARY-EFFECTS ON FEMALE SEA BASS (DICENTRARCHUS-LABRAX) - SEASONAL-CHANGES IN PLASMA PROFILES OF LIPIDS AND SEX STEROIDS IN RELATION TO REPRODUCTION

Sea bass were fed a natural diet (ND) (trash fish) or two commercial diets (CD1 = 56% (P)rotein, 11% (L)ipids; CD2 = 47% P, 7% L) during two consecutive reproductive cycles in order to assess the effects on the reproductive performance, CD1 and CD2 had lower energetic and PUFA (polyunsaturated fatty acids) content, especially n-3 fatty acids, with respect to ND, During the first spawning, the levels of sex steriods (17 beta-estradiol [E2] and testosterone [T], the percentage of good quality (i.e. buoyant) eggs and the hatching rates were similar between the ND and CD1 groups, Females fed CD2 did not show significant variations in E2 or T, and had few spawnings, low egg quality and no egg survival, At second spawning, the fish fed the commercial diets had reduced fecundity and egg viability, together with lower levels of E2 and T, altered patterns of plasma lipids and early presence of atresia in the ovary, with respect to the females fed ND, The present study provides evidence for the importance of dietary lipid for the reproductive processes in the sea bass, The data suggest that long-term dietary deficiences in n-3 fatty acids may affect the patterns of plasma lipids and may induce early gonadal atresia, For example, follicular atresia could reduce the production of gonadal steroids, the fecundity and the subsequent egg survival.