| The modeling for feeding system and pollution evaluation of Chinese longsnout catfish (Leiocassis longirostris Giinther) was established by bioenergetics models, based on growth experiments. All submodels for energy budget were built up in relation to ration level, body size and water temperature. Then the model was evaluated by two separate trials in ponds. The five growth experiments investigated the energy budget of Chinese longsnout catfish (6g) at different rations (starvation, 0.8%, 1.6%, 2.4%, 3.2% of initial body weight per day, and apparent satiation); the maximum food consumption (Cmax), specific growth rate (SGR) and energy content (E) of Chinese longsnout catfish (17g-303g) at four rearing temperatures (20°C, 24°C, 28°C and 32°C); the endocrine and immune responses of Chinese longsnout catfish (114g) at four water temperatures (20°C, 25°C, 30°C and 35°C); the diel feeding rhythm of Chinese longsnout catfish (3g); the growth and skin color of Chinese longsnout catfish (5g) reared at different light intensities (0.15, 0.98, 2.46, 3.82 and 5.28 μumol-s-1·m(-2) or 5, 74, 198, 312 and 434 lx). The main results are shown as follows:1 SGR of Chinese longsnout catfish increased with increasing rations while no significant increase in growth was shown over the optimum ration.2 The combined relationship between specific growth rate (SGR, %/d), fish size (W, g) and temperature (T, °C) could be described as: ln(SGRw+0.1)=-14.1 -0.57x lnW+ 1.22xT-0.023xT2. At low rearing temperatures, the activity of pepsin and trypsin could directly decrease the growth and feeding of Chinese longsnout catfish.3 Water temperature significantly influenced growth, plasma insulin levels, free thyroxine and serum lysozyme of Chinese longsnout catfish, but not on plasma free 3,5,3'-triiodothyronine and blood leukocyte phagocytosis. Serum lysozymeactivity showed a better relationship to body growth than other immune andendocrine parameters.Chinese longsnout catfish showed a significant diel feeding rhythm with the peakat 6:00, 11:00 and 17:00. The significant difference of growth of the fish fed atdifferent time was probably caused by feeding rhythm and evacuation time.Growth of Chinese longsnout catfish was significantly affected by light intensity,and a light intensity of 312 lx resulted in high growth rate and survival.The bioenergetics model included the following submodels:Body energy content lnE =1.65091+1.02946xlnW-0.0014xTx lnWFaecal production F = 0.1261 C + 0.0215Excretion energy U = 0.0704C -0.0199Maximum feeding rate lnCmax=-11.9+l.lxlnW+0.6xT-0.01xT2-0.02xTxlnWSpecific dynamic action SDA= (9.03+0.0502xDp-0.0541W)xC/100Standard metabolismand activity metabolism (Ra+Rs)/C= 0.0558RL2 -0.2844RL + 0.8855where C (kJ/fish/d) is food energy, E (kJ/fish) is body energy content, Cmax(g/fish/d) is maximum feeding rate, F (kJ/fish/d) is faecal production, U (kJ/fish/d)is excretion energy, SDA is specific dynamic action, Rs is standard metabolism,Ra is activity metabolism, W (g) is body weight, T (°C) is water temperature, Dp(%) is dietary protein content, RL (%BW/d) is ration level.The optimum feeding model for Chinese longsnout catfish could be described as:Copt=G+Ropt+Fopt+Uopt, where G was close to the growth of fish at maximumration, Ropt was 61 percent of metabolism of fish at maximum ration, the faecalproduction (Fopt, kJ/d/fish) was expressed as: Fopt = 0.1261Copt + 0.0215, thenitrogen excretion (Uopt, kJ/d/fish) was described as: Uopt = 0.0704Copt -0.0199.The bioenergetics model for nitrogen and phosphorus loading was composed ofthe following submodels:Nitrogen intake Ni = FIxNPhosphorus intake Pi = FIxPFaecal nitrogen Nf = (1000xF/Ef)xFp/6.25Excretion nitrogen Ne = 1000xUxl4/17/24.83Faecal phosphorus Pf = (1000xF/Ef)xPFExcretion phosphorus lnPe = 1.0916xln Pi -1.9179where Ni (mg/fish/d) is nitrogen intake, Nf (mg/fish/d) is faecal nitrogen, Ne (mg/fish/d) is excretion nitrogen, Pi (mg/fish/d) is phosphorus intake, Pf (mg/fish/d) is faecal phosphorus, Pe (mg/fish/d) is excretion phosphorus, FI (mg) is predicted food intake, N (%) is dietary nitrogen content, P (%) is dietary phosphorus content, Ef (kJ/g) is faecal energy content, Fp (%) is faecal protein content, F (kJ/fish/d) is faecal energy, U (kJ/fish/d) is excretion energy, 24.83 (kJ/g) is energy coefficient of ammonia nitrogen, PF(%) is faecal phosphorus content.9 The observed values from validation experiments in indoors concrete pools and field ponds agreed well with the predicted growth and nitrogen and phosphorus loading from the present models.In conclusion, the present modeling for feeding system could help to significantly improve feed conversion efficiency, reduce feed cost and waste production. Models for pollution evaluation could predict nitrogen and phosphorus loading. This research provides a new approach for aquaculture management and pollution abatement in China.
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