Effect of Gradient and Acute Salinity Stress Experiment on Survivorship and Food Intake of Brown-marbled Grouper,Epinephelus fuscoguttatus

The effects of gradient and a cute salinity stress on performance were determined for artificial rearing of brown-marbled grouper larvae,Epinephelus fuscoguttatus feeding on artificial meal.In the first experiment,performance was assessed after transfer from 30 at fourteen salinity treatments(0,5,10,15,20,25 30,35,40,45,50,55,60,65) at water temperature of 28℃-31.5℃,with the salinity increasing or decreasing 5 per 24h,Survival of fish was best within the range of 10–55,the larvae surviving all the experiments,the feeding behavior of fishes were normal in treatments of 25、 30、35、40、45,while fewer feed were consumed in treatments of 5、55、60.The mean survival time of larvae in treatments of 5,0,60,65 decrease dramatically to 15.16 h,7.92 h,38.51h,10.95h with an survival rate of 19.1%,0%,89.8%,0% in 24 h,or survival rate of 19.1%,0%,89.8%,0% in 48 h,respectively,one-way ANOVA test show significant deferent between both survival rates in 24h and survival time in treatments of 5,0,60,65,p0.01.LSD multiple comparisons show that survival time(ST) in treatments are Significant deferent ST0ST65=ST5ST60STn(STn means all the other treatments).In the second experiment,performance was assessed after transfer from 30 at fifteen salinity treatments(0,5,10,15,20,25,30,35,40,45,50,55,60,65,70) at water temperature of 28℃-31.5℃,with the salinity increasing or decreasing to the target treatment instantly.Survival of fish was best within the range of 5–50,the larvae surviving all the experiments in 48 h.The mean survival time of larvae in treatments of 0,55,60,65,70 decrease dramatically to 13.87 h,44.44 h,29.47 h,6.58 h,3.13 h with an survival rate of 5%,100%,44.4%,0%,0% in 24 h,or 0%,83.3%,11.1%,0%,0% in 48h,survival rate of 0%,0%,89.8%,7.7% in 48 h,respectively.One-way ANOVA test show Significant deferent between both survival rates in 48h and survival time in treatments between 0,65 or 70,and all the other treaments:P0.01.