Influence of light spectra on the performance of juvenile turbot (Scophthalmus maximus)

Abstract

Appropriate light conditions in aquaculture systems are essential for fish welfare. Light spectrum, as one of the main characteristics of light, has a significant influence on the performance of teleosts. The development of light emitting diode (LED) technology allows for the precise regulation of light spectrum. This study examined the influence of five different LED spectra, red, orange, green, blue and full spectrum (white) on the performance of juvenile Scophthalmus maximus (seven months post hatching), by analyzing specific growth rate (SGR), feed conversion ratio (FCR), serum glucose and lactate contents, hepatic glycogen contents, antioxidative activity and pathogen resistance. A statistically higher SGR was observed in the blue group compared with the red, orange and white groups. Juveniles exposed to blue spectrum exhibited the lowest FCR. Juveniles exposed to red and orange light exhibited increased hepatic hsp70 mRNA levels, as well as increased mRNA expression levels of copper/zinc superoxide dismutase (cu/zn-sod), manganese superoxide dismutase (mn-sod), catalase (cat), glutathione peroxidase (gsh-px) and lysozyme (lzm). However, hepatic and serum total superoxide dismutase (T-sod), Cat and Gsh-px activities were not significantly higher in the red and orange groups. Hepatic Lzm activity was lowest in the red group. There were no significant differences in serum protein carbonyl (PC) and malondialdehyde (MDA) contents. No statistical difference was recorded in blood lactate levels between the five groups. Turbot under red and orange light may have higher carbohydrate metabolism levels, characterized by higher blood glucose and hepatic glycogen content. Overall, the results of the current study suggested that light spectrum had a significant effect on the performance of juvenile turbot, with growth retardation, together with decreased antioxidative activity and pathogen resistance observed in the red and orange groups. Juveniles under blue spectrum exhibited the best growth performance, antioxidative activity and pathogen resistance. Thus, blue spectrum is suggested for rearing juvenile turbot and improving fish welfare in aquaculture systems.