| Light is a key environmental factor that synchronizes all life-stages of fish,from embryo development to sexual maturation.Most animals possess well-developed photoreceptors and neuronal networks to organize,identify,and interpret sensory information through the perception of light in order to react to environmental changes and adapt accordingly.Light is an indispensable factor in the life activities and metabolism of living organisms.The light under natural conditions has characteristics such as intensity,period,and spectrum.At the same time,the light conditions in the water are also affected by the transparency,refractive index,and absorbance of the water.Therefore,the fish lighting environment in underwater life is particularly complicated.The experiment was conducted under controlled conditions of the recirculating aquaculture system.Through the control of the light intensity and cycle of fish life,explore its influence on the growth and animal welfare of tilapia and Japanese ell.Experiments used double-equation irrepetitive testing method in this study.The three different light intensity denoted by A and the three different photoperiod denoted B combine A1B1,A1B2,A1B3,A2B1,A2B2,A2B3,A3B1,A3B2,A3B3,and nature light intensity and period was the control group,Compared its growth index,conventional blood physiological and biochemical and cortisol content.The results of the study provides a reference to explore the best welfare conditions for the growth of tilapia and Japanese eel,reduce the stress of fish,and promote the development of eel industry.The main results were as follows:1.In 2000 lx,the total weight,daily gain,special growth rate,and growth efficiency was higher than 1000 lx and 3000 lx.But the Feed conversion ratio was significantly less than 1000 lx and 3000lx(p<0.05).the effect of intensity on GPT activities was significant(p<0.05).In 3000 lx,the GPT activities was lower than 1000 lx and 2000lx(p<0.05).Compared with 1000 lx and 3000 lx,the albumin content in 2000 lx was obviously different(p<0.05).there was a significant difference on total cholesterol between 12 h period and 20 h period(p<0.05).The period effect on cortisol was significant.The cortisol In 12 h was the most significantly different from 18 h and 24h(p<0.01).But the difference between 18 h and 24 h was no significant.The SOD In 2000 lx was significantly different from 1000 lx and 3000 lx.The effect of intensity and period on CAT and MDA were significant.The CAT and MDA activities In 12 h were the most significantly different from 18 h and 24h(p<0.01).A significant difference existed between 18 h and 24h(p<0.05).The difference between 1000 lx and 2000 lx was not obvious.But in 3000 lx,CAT and MDA activities were highly significantly different from 1000 lx and 2000lx(p<0.01).2.the final weight gain and daily gain of the 10 lx group were significantly lower than those of 100 lx and 300lx(p <0.05).There was no significant difference in the survival rates of all groups under different intensity.The specific growth rate of 10 lx group was significantly lower than the 300 lx group(P <0.05).While the growth efficiency and feed conversion ratio of 300 lx group were significantly better than those of 10 lx group and 100 lx group(p <0.05).The final weight gain and daily gain of the 12L: 12 D and 18L: 6D group were significantly lower than the 24L: 0D group(p <0.05),while The specific growth rate of 18L: 6D group were significantly lower than 12L: 12 D and 24L: 0D group(p <0.05).The activities of glutamic oxalacetic transaminase of the 24L: 0D and 12L: 12 D group were significantly lower than 18L: 6D group(p <0.05),and the activities of glutamic-pyruvic transaminase of 10 lx group conditions were significantly higher than 100 lx group(p <0.05).Triglyceride of 24L: 0D group was significantly higher than the 12L: 12 D group(p <0.05).The SOD activity of 18L: 6D group was significantly higher than 12L: 12 D group at 10 lx and 300lx(p <0.05),while the opposite of those on 100 lx.Light intensity and photoperiod have a significant difference(p <0.05)for serum cortisol of Japanese eel,12L: 12 D was significantly lower than 18L: 6D and 24L: 0D group on 10 lx and 300 lx.While the 12L: 12 L and 18L: 6D group was lower than 24L: 0D on 100lx(p <0.01).The 10 lx group was significantly lower than 100 lx group on 12L: 12 D and 24L: 0D,while the opposite of those on 18L: 6D. |
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