循环大系统分散镇定状态反馈控制器H^∞设计

研究了较对称组合系统循环对称组合系统更为一般的系统－循环系统，利用Ｈ＾∞理论及Ｒｉｃｃａｔｉ方程分别就确定性系统和不确定性系统得出闭环系统稳定的分散状态反馈控制器的设计方法。

Effects of spectral composition,photoperiod and light intensity on the gonadal development of Atlantic salmon Salmo salar in recirculating aquaculture systems(RAS)

Artificial lighting regimes have been successfully used to inhibit sexual maturity of Atlantic salmon in confinement.However,when these operations are applied in commercial recirculating aquaculture systems(RAS) using standard lighting technology,sexual maturation is not suppressed.In this study,an L_9(3~3) orthogonal design was used to determine the effects of three factors(spectral composition,photoperiod,and light intensity) on the gonadal development of Atlantic salmon in RAS.We demonstrated that the photoperiod at the tested levels had a much greater effect on the gonadosomatic index and female Fulton condition factor than spectral composition and light intensity.The photoperiod had a significant effect on the secretion of sex steroids and melatonin(P<0.05),and a short photoperiod delayed sex steroid and melatonin level increases.The three test factors had no significant effects on the survival rate,specific growth rate,relative weight gain,and male Fulton condition factor(P>0.05).The optimum lighting levels in female and male Atlantic salmon were LD 8:16,455 nm(or 625 nm),8.60 W/m^2;and LD 8:16,8.60 W/m^2,455 nm respectively.These conditions not only delayed gonadal development,but also had no negative effects on Atlantic salmon growth in RAS.These results demonstrate that a combination of spectral composition,photoperiod and light intensity is effective at delaying the gonadal development of both male and female salmon in RAS.

Evaluation of Feed and Feeding Regime on Growth Performance, Flesh Quality and Fecal Viscosity of Atlantic Salmon(Salmo salar L.) in Recirculating Aquaculture Systems

The effects of different feeds and feeding regimes on growth performance, flesh quality and fecal viscosity of Atlantic salmon （Salmo salar L.） in recirculating aquaculture systems （R.AS） were investigated. Fish （initial body weight of 1677 g＋ 157 g） were fed with four commercial feeds （Nosan salmon-NS, Aller gold-AG, Skretting salmon-SS and Hart ye-HY） in two feeding regimes （80% and 100% satiation） for 78 d. The results showed that salmon specific growth ratio （SGR） and weight gain ratio （WGR） were significantly affected by feed type and feeding regime （P〈0.05）. Feed conversion ratio （FCR） varied between 0.93 and 3.40, which was significantly affected by feed type （P〈0.05）, and slightly improved with increased satiation degree. The activities of digestive enzymes including protease, lipase and amylase were also significantly affected by feed type and feeding regime （P〈0.05）, increasing with satiation degree. Flesh qualities for vitamin E, hydroxyproline （HYP）, liquid loss and muscle pH among all groups showed significant differences （P〈0.05）, ranging from 26.67 to 29.67, while no obvious difference was found in flesh color. Fecal viscosity for different treatments showed no significant difference, though improvement was found in 100% satiation group. From present experiment, it was concluded that both feed type and feeding regime can affect the important quality attributes of Atlantic salmon.

Effect of stocking density on performances of juvenile turbot (Scophthalmus maximus) in recirculating aquaculture systems

Limited information has been available about the influence of loading density on the performances of Scophthalmus maximus, especially in recirculating aquaculture systems （RAS）. In this study, turbot （13.84±2.74 g; average weigh±SD） were reared at four different initial densities （low 0.66, medium 1.26, sub-high 2.56, high 4.00 kg/m^2） for 10 weeks in RAS at 23±1℃ Final densities were 4.67, 7.25, 14.16, and 17.47 kg/m^2, respectively, which translate to 82, 108, 214, and 282 percent coverage of the tank bottom. Density had both negative and independent impacts on growth. The final mean weight, specific growth rate （SGR）, and voluntary feed intake significantly decreased and the coefficient of variation （CV） of final body weight increased with increase in stocking density. The medium and sub-high density groups did not differ significantly in SGR, mean weight, CV, food conversion rate （FCR）, feed intake, blood parameters, and digestive enzymes. The protease activities of the digestive tract at pH 7, 8.5, 9, and 10 were significantly higher for the highest density group, but tended to be lower （not significantly） at pH 4 and 8.5 for the lowest density group. The intensity of protease activity was inversely related to feed intake at the different densities. Catalase activity was higher （but not significantly） at the highest density, perhaps because high density started to induce an oxidative effect in turbot. In conclusion, turbot can be cultured in RAS at a density of less than 17.47 kg/m^2. With good water quality and no feed limitation, initial density between 1.26 and 2.56 kg/m^2 （final： 7.25 and 14.16 kg/m^2） would not negatively affect the turbot cultured in RAS. For culture at higher density, multi-level feeding devices are suggested to ease feeding competition.