The specific growth rate (SGRd) of juvenile Fenneropenaeus chinensis shrimp was measured over 35 days under different light intensities: 0, 50, 300, 1300 and 5500 lx. The SGRd of the shrimp under 5500 lx was only 29.4%, 27.1%, 21.1% and 19.7% of those under 0, 1300, 50 and 300lx, respectively ( P<0.05). The maximal and minimal feed intake (FId) of shrimp occurred under 300 and 5500lx, respectively (difference 9.3%). The lowest food conversion efficiency (FCEd) occurred in the 5500 lx group (30.2%, 26.3%, 21.3% and 21.1% of those under 0 lx, 1300lx, 50lx and 300lx, respectively). FCEd values between 5500 lx and other groups were significantly different (P<0.05). The shrimp under 5500 lx gained a lower FI as well as a lowest FCE and therefore exhibited a lower SGR. The results revealed that light intensity affected the growth of the shrimp mainly by influencing FCE, or energy allocation to growth. Therefore, the shrimp may grow better in organically rich earthen ponds that have lower light intensity.

The effects of seawater Na/K ratio on growth and energy budget of juvenile Litopenaeus vannamei Boone, 1931 were investigated. Salinity (S=0ppt) and the total concentration of sodium and potassium in the experimental water were kept constant. Seven treatments were set: R1, R2, R3c, R4, R5, R6 and R7, the Na/K ratios were 25.6, 34.1, 47.3, 85.2, 119.3, 153.3 and 187.4 (mmol/mmol), respectively. The shrimp in R7 (Na/K=187.4) died within 2 weeks after the experiment began. After the 30-day feeding trial, the molting frequency (MF) and feed intake in terms of wet weight (FIw) and energy content (FIe) of the shrimp under the other six treatments were not significantly affected by the different Na/K ratios in the seawater. The final wet weight, weight gain (WG), specific growth rates (SGRw and SGRe) and food conversion efficiencies (FCEd and FCEe) of the shrimp under Treatment R6 were significantly lower than those under the other five treatments. There was a trend that, with all the indices mentioned above, the values of the test shrimp under Treatment R2 was the highest, and the sequence was: R2 (Na/K=34.1)>R3c (Na/K=47.3)>R1 (Na/K=25.6)>R4 (Na/K=85.2)>R5 (Na/K=119.3)>R6 (Na/K=153.3). In the experiment, the percentages of energy deposited for growth (G), energy lost for respiration (R), energy lost in excretion (U) and energy lost in exuviae (E) to the energy consumed in food (C) were significantly affected by the different Na/K ratios in seawater, while the percentage of energy lost in feces (F) to C was not significantly affected by the ratios. The percentage of G to C of the test shrimp under Treatment R6 was significantly lower while the percentage of E to C was significantly higher than those under the other treatments. There were no significant differences among the energy allocations of the test shrimp under Treatment R1, R2, R3c, R4 and R5. According to regression analysis, optimal shrimp growth could be obtained by regulating the Na/K ratio of the seawater to 40-43 at a salinity of 30 ppt.

The effects of temperature changes on oxygen consumption of Chinese shrimp (Fenneropenaeus chinensis Osbeck) were studied. The response of oxygen consumption to a temperature rise was conformed to partial metabolic compensation. No compensatory response was observed at lower temperature. A sudden temperature increase by 12℃ resulted an overshoot in oxygen consumption in shrimp adapted to 19℃, while a sudden decrease by 12℃ in shrimp adapted to 19℃ resulted in an undershoot in oxygen consumption. The shrimp adapted to 31℃ responded with an undershoot in oxygen consumption when a sudden temperature drop by 12℃ occurred. But overshoot in oxygen consumption did not occur when the shrimps were transferred back from 19 to 31℃. The amplitude of oxygen consumption was reduced in shrimp during the process of acclimation to the temperature diel fluctuation. After the shrimp had adapted to the temperature fluctuation, the daily mean oxygen consumption of shrimp at diel temperature fluctuation from 24 to 30℃ was significantly lower than those adapted to the constant temperature at 27℃ (P<0.05). The decrease in metabolic rate may account for the increase in the growth rate of shrimp at a diel fluctuating thermal regime. D 2004 Elsevier B.V. All rights reserved.