The compensatory growth of juvenile brown flounder Paralichthys olivaceus (body mass c. 12 g) following different thermal exposure was investigated. Fish were exposed to one of the five temperatures: 8Á5 (T 8Á5 ), 13Á0 (T 13Á0 ), 17Á5 (T 17Á5 ), 22Á0 (T 22Á0 ) and 26Á5°C (T 26Á5 ) for 10 days and fish grew best at 22Á0°C. Then the water temperature in all treatments was equably adjusted to 22Á0°C over 3 days. At the end of the following 30 days after temperature adjustment, there were no significant differences between body masses of fish in the different treatments (wet body mass at the end of the experiment ranged from 22Á13 to 24Á56 g). Results indicated that the juvenile P. olivaceus achieved complete compensatory growth. Analysis of the dynamics of the feeding rates and feed conversion efficiencies indicated that compensatory growth of the fish experienced low temperature (T 8Á5 , T 13Á5 and T 17Á5 ) or high temperature (T 26Á5 ) exposure was mainly dependent on increasing feed intake (hyperphagia) and possibly by improvement in feed conversion efficiency. The moisture content was not affected by different temperature exposure significantly. The lipid and energy content of juvenile P. olivaceus in T 8Á5 , however, were significantly lower than other treatment. Results of the current study indicate that a short period of low or high temperature exposure may not affect annual growth, but may affect lipid and energy deposition.

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Starvation resistance in the juveniles of Chinese shrimp, Fenneropenaeus chinensis Osbeck, was studied by point-of-no-return (PNR) and point-of-reserve-saturation (PRS) experiments. Changes in oxygen consumption rate, ammonia-N excretion rate, and oxygen consumed to nitrogen excreted (O:N) ratio were investigated immediately before and after the period of recovery feeding for each regime to assess metabolic response during starvation and refeeding. There was a significant change in survival rate and wet weight of test shrimp throughout the PNR and PRS experiments (P \ 0.05). The estimated PNR and PRS for F. chinensis juveniles could be directly calculated from the selected equations as PNR 50 = 7.86 days, PNR 100 = 21.42 days, PRS 0 = 1.16 days, and PRS 50 = 11.75 days. A decrease in metabolic rate during starvation as a means of conserving energy was found in F. chinensis juveniles. Furthermore, although F. chinensis juveniles only utilized protein as an energy source during starvation, they showed a shift from pure protein during starvation to an equal utilization of protein and lipid or a lipid-carbohydrate mixture during later satiate feeding. The results in the present study indicate that F. chinensis juveniles have the ability to withstand and recover from relatively prolonged starvation after longer initial feeding periods. The knowledge derived from the understanding of starvation resistance and the corresponding metabolic response of F. chinensis juveniles will be useful in the design of feeding regimes in this species.

In this study, we tested the lower salinity tolerance of juvenile shrimps (Litopenaeus vannamei) at a relatively low temperature (20 1C). In the ¢rst of two laboratory experiments, we ¢rst abruptly transferred shrimps (6.91 AE 0.05 g wet weight, mean AE SE) from the rearing salinity (35000 mg L À 1 ) to salinities of 5000, 15000, 25000, 35000 (control) and 40 000 mg L À 1 at 20 1C. The survival of L. vannamei juvenile was not a¡ected by salinities from 15000 to 40 000 mg L À 1 during the 96-h exposure periods. Shrimps exposed to 5000 mg L À 1 were signi¢cantly a¡ected by salinity, with a survival of 12.5% after 96 h. The 24-, 48-and 96-h lethal salinity for 50% (LS 50 ) were 7020,8510 and 9540 mg L À 1 respectively. In the second experiment, shrimps (5.47 AE 0.09 g wet weight, mean AE SE) were acclimatized to the different salinity levels (5000, 15000, 25000, 35000 and 40 000 mg L À 1 ) and then maintained for 30 days at 20 1C. Results showed that the survival was signi¢cantly lower at 5000 mg L À 1 than at other salinity levels, but the ¢nal wet weight under 5000 mg L À 1 treatment was signi¢cantly higher than those under other treatments (Po0.05). Feed intake (FI) of shrimp under 5000 mg L À 1 was signi¢cantly lower than those of shrimp under 150 004 0 000 mg L À 1 ; food conversion e⁄ciency (FCE), however, showed a contrasting change (Po0.05). Furthermore, salinity signi¢cantly in£uenced the oxygen consumption rates, ammonia-N excretion rates and the O/N ratio of test shrimps (Po0.05). The results obtained in our work provide evidence that L. vannamei juveniles have limited capacity to tolerate salinities o10 000 mg L À 1 at a relatively low temperature (20 1C). Results also show that L. vannamei juvenile can recover from the abrupt salinity change between 15000 and 40 000 mg L À 1 within 24 h. Low salinity and temperature a¡ected survival of whiteleg shrimp P Zhang et al. Low salinity and temperature a¡ected survival of whiteleg shrimp P Zhang et al. Low salinity and temperature a¡ected survival of whiteleg shrimp P Zhang et al. Low salinity and temperature a¡ected survival of whiteleg shrimp P Zhang et al.