Optimization of LED light quality and time for artificial breeding of Haliotis discus hannai

Abstract: Light is one of the key environmental factors that influence the growth, development and survival of aquatic organism. In this study, the effects of different light qualities (red, orange, white, blue, green light and dark setting) and initial stage of lighting (fertilized egg, trochophore, eye spot larvae) on the growth, development and survival of the larvae of Haliotis discus hannai Ino were examined. Experimental results suggested that the hatching rate of larvae under green, blue, and dark setting were all >80% and were significantly higher compared with those under red, orange, or white light (P<0.05). Under red, orange or white light, the abnormality rate of larvae was higher and significant difference was identified if compared to any other light quality group (P<0.05). Under red light, abnormalities occurred in >10% of larvae, which was significantly higher than in any other treatment group (P<0.05). Under blue light, since the trochophore stage, the metamorphosis rate of larvae was significantly higher than any other light quality group. Under red, orange light or in dark setting, the metamorphosis rate of larvae was lower at the initial stage of different lights and no significant difference was identified if compared to any other light quality group (P>0.05). The metamorphosis rate of larvae cultured under blue light since the fertilized egg stage was significantly higher than in any other light quality group lit at the same stage (P<0.05), while the metamorphosis rate among larvae cultured under green or white light was also higher than in the remaining groups, with no significant difference between them (P>0.05). Under blue, green light, the survival rate of juvenile was significantly higher than any other light quality group (P<0.05), but no significant effect on the survival rate of juvenile was identified in the initial stage of different lights (P>0.05). In cultures lit since the fertilized egg stage, trochophore size was significantly larger under blue, green, or dark setting, compared with white or red light (P<0.05), with no significant difference among these blue, green, or dark setting (P>0.05). Under blue, green light, since the stage of trochophore or eye spot larvae, the size of completion of larval shell and metamorphosis was significantly bigger than any other group since the fertilized egg stage (P<0.05). However, the required time of metamorphosis of larvae since the eye spot larvae stage was significantly longer if compared to that of any other group since the stage of fertilized egg or trochophore (P<0.05). Therefore, blue, green light used as light source and lighting starting from the stage of trochophore in the culture and growth of the larvae of H. discus hannai Ino can be highly referential to boost the hatching efficiency of seeds, increase the yield per water body and for the rapid development of the aquaculture industry.