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The aim of this study was to evaluate the effect of two diets with different protein/fat ratios (P/F) (diet A: P/F 2.26; diet B: P/F 3.36) on the chemical composition, fatty acid profile and some somatic indexes of meagre (Argyrosomus regius). The trial was carried out on two groups of meagre raised in two different sea cages during 15 months. At the end of the production cycle biometric measures as well as chemical-nutritional analysis of the fillets were conducted on 25 fishes per group. Diet A, with a lower P/F, furnished animals with higher percentages of mesenteric fat (0.48 vs 0.41%; P<0.01) and of fillet yield (51.21 vs 48.12; P<0.01). Moreover, the fillets obtained with the diet A showed higher percentage of fat (3.60 vs 2.41%; P< 0.01), lower moisture (74.10 vs 75.42%; P<0.01), lower losses of water under pressure (16.73 vs 20.20%; P<0.01) and after 48 h of refrigeration (3.08 vs 4.23%; P<0.01). The fatty acids profile of fillets was affected by the diet. Diet A resulted in a higher level of saturated fatty acids (26.44 vs 23.17% of total lipid; P<0.01) and a lower percentage of polyunsaturated fatty acids (31.56 vs 36.08%; P<0.01) in the fillet, mainly due to the lower content of linoleic acid (13.63 vs 19.77%; P<0.01). The atherogenic (AI) and thrombogenic (TI) indexes, which resulted very low in the fish of Group B (AI=0.48 vs 0.60, P<0.01; TI=0.33 vs 0.37, P<0.01), together with the low lipid content of meat in both groups, confirmed the very high nutritional quality of meagre fillets.

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Four one-week growth trials were conducted on green sturgeon fry to determine the effect of feeding rate on their growth performance at 18°C when they were fed a salmonid soft moist feeds containing 445-457 g kg À1 of crude protein and 201-207 g kg À1 of lipid. The fry used in Trials I-IV were 5-8 weeks after their initiation of exogenous feeding. Their average initial body weights were 1.63 AE 0.01, 2.63 AE 0.03, 5.08 AE 0.08 and 7.49 AE 0.05 g, respectively. Six feeding rates used were as follows: 2.5-15.0% body weight per day (% BW day À1 ) with a 2.5% increment in Trial I; 1.25-7.50% BW day À1 with a 1.25% increment in Trial II; and 2.0-7.0% BW day À1 with a 1.0% increment in Trials III and IV. Four replicates with 50 fry per tank in Trials I-III and 30 fry per tank in Trial IV were assigned randomly to each feeding rates. The final body weight, specific growth rate, feed efficiency, protein retention, and whole-body moisture, lipid, and energy contents were significantly (P < 0.05) affected by the feeding rates. The optimum feeding rates determined by the broken-line model were 7.1, 5.7 and 5.3% BW day À1 for Trials I, II and IV, when the fry were 5, 6 and 8 weeks after their initiation of exogenous feeding, respectively.

A factorial experiment was conducted to compare the responses of heat shock protein 70 (Hsp70) in seven different tissues of White Sturgeon Acipenser transmontanus and Green Sturgeon A. medirostris after they were exposed to four different stressors. Three White Sturgeon (2.3 ± 0.1 kg [mean ± SE]) and three Green Sturgeon (2.3 ± 0.1 kg [mean ± SE]) were each subjected to one of four different stressors, after which the Hsp70 levels in seven different tissues were measured using Western blot. The four stressors were heat shock, cold shock, air exposure, and food deprivation; and the seven tissues sampled were mucus, heart, liver, gastrointestinal tract, gill, spleen, and white muscle. We also sampled tissues of three White Sturgeon and three Green Sturgeon without any stressor, and measured their Hsp70 levels as a control. We compared Hsp70 responses of the stressed sturgeon with those of the control, which was set at 100%, and found that Hsp70 responses were significantly (P < 0.05) affected by the different stressors and also varied significantly among the tissues. For both species of sturgeon, heat shock was shown to be the most effective stressor inducing Hsp70 responses and mucus was the most responsive tissue. Under heat shock stress, Hsp70 responses in all tissues except liver were significantly higher in the White Sturgeon than in the Green Sturgeon. When both species of fish were exposed to heat shock, cold shock, or food deprivation, White Sturgeon showed significantly higher Hsp70 responses in mucus than did Green Sturgeon. In summary, heat shock elicited the highest Hsp70 responses and mucus was the most sensitive tissue. Based on the tissue Hsp70 responses, White Sturgeon were predicted to have a better defense mechanism against heat shock than Green Sturgeon.