The effect of light intensity on the growth of Brachymystax lenok (Pallas, 1773).

A 35-day experiment was carried out to investigate the effect of light intensity on growth of Brachymystax lenok under different light intensities: 10, 70, 240 and 1000 lx. Fish(5.5 ± 0.24 g)used in the experiment were fed to satiation twice a day (08:00 hours, 14:00 hours).The photoperiod was 12L:12D (08:00-20:00 hours). The specific growth rate( SGR) of B. lenok under lower intensities(10 lx,70 lx)was significantly higher than the other groups( P < 0.05).No significant difference in feed intake was observed at different light intensities, but feed efficiency ( FE) in wet weight at lower intensities (1070 lx) was higher than that at higher intensities(240,1000 lx) ( P < 0.05).The final survival rate of juveniles varied from 86.33% to 93.66%,and there was no significant difference between experimental groups. The tested fish under higher light intensities (240 and 1000 lx) spent much more energy in respiration and excretion while depositing less energy for growth than those fish under lower light intensities. It is concluded that light intensity significantly affected growth and optimal light intensity for B. lenok juveniles was about 10-70 lx. [ABSTRACT FROM AUTHOR]