A study was undertaken to determine the e¡ect of various dietary carbohydrate-to-lipid ratios on growth performance, whole-body composition and tissue lipid content in Senegalese sole (Solea senegalensis) juveniles. Data on the dietary regulation of key hepatic enzymes of the lipogenic and glycolytic pathways (glucose-6-phosphate dehydrogenase, G6PD; malic enzyme, ME; fatty acid synthetase, FAS; pyruvate kinase, PK and glucokinase, GK) were also generated. Four isonitrogenous (crude protein: 52% dry matter (DM)) diets were formulated to contain one of two lipid levels (11% and 21% DM). Within each dietary lipid level, the nature of the carbohydrate fraction (raw or extruded peas) was varied. Triplicate groups of 54 sole (initial body weight: 23.6 AE 1.2 g) were grown in recirculated seawater over 67 days. Fish were fed using automated feeders. At the end of the study, whole-body, liver, viscera and muscle samples were withdrawn for analyses. During the experimental period, the mean ¢sh weight about doubled in all treatments. No signi¢cant di¡erences were found in growth performance (ranging from 1.1% to 1.4% body weight day À1 ) among dietary treatments. High-fat diets increased whole-body fat content. Similarly, daily fat gain ranged from 0.54 to 0.78 g kg À1 day À1 and highest values were found in ¢sh fed high-lipid diets. Dietary treatments also affected tissue lipid content (liver, viscera and muscle), with highest values in ¢sh fed high-fat diets. The nat-ure of dietary carbohydrates had little in£uence on performance criteria, but a¡ected tissue lipid deposition. The activities of G6PD, ME and FAS were depressed by elevated levels of dietary lipid, con¢rming the inhibitory e¡ect of dietary fats on lipid biosynthesis. At both dietary lipid levels, ME and FAS activities were little a¡ected by dietary carbohydrate. Activities of PK and GK were not a¡ected by the starch level of the diets. In Senegalese sole juveniles, the lipogenic pathway is more susceptible to modulation by dietary means (particularly through lipid intake) than the glycolytic pathway.wAquatex 8074 from Sotexpro (Bermericourt, France): 22.5% CP, 1% lipid, 49% raw starch. zAquatex 8071 from Sotexpro: 23.7% CP, 1% lipid, 50% gelatinised starch. ‰Vitamin mixture (IU or mg kg À1 diet): DL-a tocopherol acetate, 60 IU; sodium menadione bisulphate, 5 mg; retinyl acetate, 15000 IU; 3000 IU; thiamin, 15 mg; ribo£avin, 30 mg; pyridoxine, 15 mg; B12, 0.05 mg; nicotinic acid, 175 mg; folic acid, 5 mg; ascorbic acid, 500 mg; inositol, 1000 mg; biotin, 2.5 mg; calcium panthotenate, 50 mg; choline chloride, 2000 mg. zMineral mixture (g or mg kg À1 diet): calcium carbonate (40% Ca), 2.15 g; magnesium oxide (60% Mg), 1.24 g; ferric citrate, 0.2 g; potassium iodide (75% I), 0.4 mg; zinc sulphate (36% Zn), 0.4 g; copper sulphate (25% Cu), 0.3 g; manganese sulphate (33% Min), 0.3 g; dibasic calcium phosphate (20% Ca, 18% P), 5 g; cobalt sulphate, 2 mg; sodium selenite (30% Se), 3 mg; KCl, 0.9 g; NaCl, 0.4 g.Aquaculture Research, 2004 Dietary carbohydrate/lipid...

No abstract

Invasive Pterygoplichthys disjunctivus (Weber, 1991) (synonymy: Liposarcus multiradiatus) armored catfish were first reported in Mexico in 1995 and have spread successfully in several aquatic ecosystems. In Adolfo López Mateos El Infiernillo Reservoir, Michoacán -Guerrero, the population of this armored catfish is growing substantially because natural predators are not present and exploitation by humans does not occur. Over a complete annual cycle, we studied the following population parameters: weight, total and standard length, the relationship of weight to total length, the hepatosomatic (HSI) and gonadosomatic (GSI) indices, total fecundity (TF) and relative fecundity (RF). The average total (TL) and standard lengths (SL) were 248 ± 37.5 and 188 ± 30.7 mm, respectively, and the average weight (W) was 135.3± 66.8 g. The largest fish reported was 520 mm in TL and weighed 1 280 g. The species showed an extended reproductive season from May to November, as indicated by the GSI, TF and RF. The strongest reproductive peak occurred from July through October. During the annual cycle, the highest monthly average fecundity was 2 447 eggs, and the average relative fecundity was 12.6 eggs per g of fish (August and September). This information will be crucial for calculating the current biomass and future growth of the population. The calculation of these results could provide a basis for the exploitation of this resource for human consumption and animal feeds.

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Summary Lethal concentration (LC50) and sub‐lethal effects of NO2‐N on the endemic viviparous fishes Skiffia multipunctata (Pellegrin, 1911) (SM; considered threatened under Mexican regulations) and Goodea atripinnis (Jordan, 1880) (GA; without conservation status) were determined. LC50/96 hr values were 0.002 and 0.359 mg NO2‐N/L for SM and GA, respectively. Sub‐lethal exposure resulted in swelling of the gill epithelium, hyperplasia, fusion of the primary and secondary lamellae, erythrocyte pyknosis, and aneurysms with respiratory stress responses at 0.0012 and 0.244 mg NO2‐N/L for SM and GA. The study demonstrates that sensitivity of both species is strongly related to the conservation status and acceptable nitrite concentrations, which are clearly below those permitted by the Mexican national water quality norm for wildlife preservation. Therefore, this norm is not adequate protection for these species, and where other threatened species may also be affected. Adequate criteria for nitrites in Mexican waters should include the data of all threatened endemic species.