Effects Of Light Intensity And Wavelength On Characteristics Of Activity, Physiology And Growth Of Juvenile Hybridized Grouper (Epinephelus Fuscoguttatus?×E.lanceolatus?)

In this study,juvenile Hybridized Grouper?Epinephelus fuscoguttatus?×E.lanceolatus??,average length and weight were5.64±0.16 cm,4.99±0.46 g,were cultured in the self-built Recirculating Aquaculture System for 30 days to study the effects of light intensity?0,50,100,200,400,800,1600 and 3200 lx?and wavelength?blue:460-470 nm,green:515-530 nm,yellow:585-595 nm,red:620-630 nm and white:full-spectrum?on characteristics of activity,physiology and growth of the juveniles.According to the theoretical basis of ecology,physiology and immunology,daily performance,ingestion status and growth performance were recorded in seven periods?0d,5d,10 d,15d,20 d,25d and 30d?,and antioxidant enzymes,acid-alkaline phosphatase and cortisol were also measuredat the same time.The results in this paper will give some useful data to analyze the intrinsic and apparent performance which may help us to judge the optimal growth lighting conditions for juvenile grouper cultrue,and also provide a theoretical basis for light-regulation of actual production.The results of this study are as followed:1.Effects of Light Intensity and Wavelength on Activities of Juvenile Hybridized GrouperDaily performance and ingestion status were recorded during the whole experimental period and the results showed that juvenile groupers adapted quickly to the 0 lx and 50 lx intensity since the first day,and been very free.In addition,juvenile groupers in 1 600 and3 200 lx groups did not perform well,and confined to bottom water,been nervous and swam in a high density for a long time.Juveniles in other groups all adapted to the suitable state after 10 days.The water level of ingestion increased with the decrease of illumination,showing a obvious regularity:0 lx>50 lx>100 lx>200 lx>400 lx>800lx>1 600 lx>3 200 lx,while 0 lx and 50 lx groups was significantly higher than that in 1600 lx and 3 200 lx groups before 15 d.On the other hand,the ingestion levels in the groups of intensity range of 0 to 800 lx were significantly higher than that in 1 600 and 3200 lx groups before 10 d?p<0.05?.In the condition of different light intensities,juvenile groupers adapted quickly to the Green and Blue light,and were very free since the second day.The juveniles in other groups did not perform well at the initial stage,but returned to the suitable state after 15 days.The water levels of ingestion were different among different wavelength groups:Blue light>Green light>Red light>Yellow light>White light.During the period before 25 d,the water level of ingestion under Blue light was significantly higher than that under White light?p<0.05?.The ingestion level were different among different wavelength groups also:Blue light>Green light>Red light>Yellow light>White light.2.Effect of Light Intensity and Wavelength on Physiology in Juvenile Hybridized Grouper The enzyme activity of juvenile Hybridized Grouper were showing an analogous regularity under all kind of illumination.Both SOD and CAT were showing a regularity of“Increase-decline-stay in steady level”,GSH-PX was“Decline slightly-increase sharply-drop and keep in steady level”,AKP was“Increase slowly-increase sharply-drop and stay in steady level”,ACP was“Decline-increase-drop slowly”and cortisol was“Increase-decline”.A sharp fluctuations of enzyme activity or cortisol expression were appeared in the 5d-15 d,and then came to a smooth level in 20d-30 d.The groups under high light intensity and short wavelength light suffered more stress due to a higher expression quantity of SOD,while the low intensity and long wavelength light groups suffered less.In the increasing stage of CAT enzyme activity,lower intensity lead to higher enzyme activity,such as short wavelength lighting,and both of them have a high-efficiency ability to clear H₂O_2.AKP and ACP showed a stong self adiectment,a higher expression was appeared in low intensity groups,but there was not different in the wavelength groups.In the 5d period,the content of cortisol in high intensity groups was significantly higher than that in low intensity groups?p<0.05?,but the peak content had been arrived in 10 d and 15 d period,while low illumination groups' peak content had been arrived in the early 5d period.Overall the juvenile groupers under 0-800 lx intensity and short wavelength?blue,green?light show a good adaptability due to less stress and high-efficiency ability to clear harmful substances.3.Effect of Light Intensity and Wavelength on the Growth in Juvenile Hybridized Grouper Juvenile groupers were kept a high survival rate of nearly 100%during the whole experimental period.Total food intake under 0-1600 lx was significantly higher than3200lx?p<0.05?,Feed conversion ratio,food conversion efficiency,etc.performed well also.The similarity had been happened under short-wavelength light?Blue and Green?,but the Yellow light was the worst.Under different light intensity,0-800 lx showed better growth rate and significantly higher than 3200lx?p<0.05?;Body weight under 0-800 lx were the largest,and 0-200 lx groups was significantly higher than 3200 lx groups?p<0.05?;DLG,DWG,WRG,WRG and SGR_BWunder 0-100 lx were significantly higher than3200 lx also?p<0.05?;While SGR_BLand LGR had no significant difference?p>0.05?.Overall there was an excellent growth performance of the juvenile groupers which exposed to 0-800 lx illumination.On the other hand,under different wavelength light the body length and body weight of juvenile groupers were showing a regularity:blue>green>red>white>yellow,no significant difference between groups?p>0.05?;In the 15 d there were some significant differences on length,SGR_BW,DWG,DLG,WGR and LGR,but the difference was not significant as a whole?p>0.05?.Results demonstrated that 0-800 lx intensity and short-wavelength light?blue and green?can improve the growth of juvenile groupers.