Proximate and fatty acid compositions in muscle, liver and gonads of wild versus cultured broodstock of Senegalese sole (Solea senegalensis)

Abstract

A complete reproductive failure to spawn viable eggs from G1 cultured Senegalese sole (Solea senegalensis) broodstock compared to successful spawning from wild caught captive broodstock has been described previously. The aim of the present study was to compare the proximate and fatty acid composition of recently caught mature wild versus mature G1 Senegalese sole, to identify possible factors that contribute to this reproductive problem. The composition of 22 wild fish, captured in the Ebro Delta (Tarragona, Spain), was compared with 25 cultured fish raised under natural captive conditions. Significantly higher levels of total lipid were found, in male liver from G1 fish compared to wild fish (3.0- and 2.5-fold higher in female and male respectively). Similarly, the neutral lipid class was significantly higher in liver (88 and 90% total lipids (TL) from female and male, respectively) and male muscle (64% TL) from cultured fish. The relative value of linoleic acid (18:2n - 6) was significantly higher in all tissues from cultured fish (approximately 11, 9 and 7.4% total fatty acid (TFA) in liver, gonads and muscle respectively). However, significantly lower levels were observed in cultured fish for the essential fatty acids, arachidonic (20:4n - 6, ARA) in the liver (4.6-fold down male and 2.4-fold in female), testes (1.4-fold down) and muscle (2.9- and 2.0-fold down in male and female respectively); docosahexaenoic (22:6n - 3, DHA) in liver (1.6- and 1.3 fold down in G1 female and male) and male muscle (1.3-fold down); eicosapentaenoic (20:5n - 3, EPA) in muscle of male (1.4-fold down) and for cholesterol (CHOL) in liver of female (22% in wild and 7.8% in G1) and male (20 in wild and 7.0% in G1). These differences resulted in significantly higher ratios of EPA/ARA in the liver and muscle of cultured fish. The imbalance in lipids and essential fatty acids (EFAs) of G1 fish appeared to be a reflection of the extruded diet used to feed the fish. Future research should consider the effect of the nutritional imbalance on reproductive physiology of G1 fish, specially the effects of ARA and CHOL on prostaglandins (2- and 3-series) and steroid production.