Acute stress response of European sea bass Dicentrarchus labrax under blue and white light

Recent data suggest that specific light wavelength can alleviate fish acute stress response by counteracting or reducing the stress-induced cortisol increase. The European sea bass Dicentrarchus labrax, widely reared in the Mediterranean, is very sensitive to handling stress, so that typical rearing procedures during on-growing (e.g. grading) are avoided. The present study aimed at investigating whether exposure to blue (480 nm) or white light (BL or WL, respectively) could alleviate European sea bass acute stress response. Fish (initial weight 130.9 ± 0.4 g) were reared (seawater recirculating system) for 63 days under BL or WL and then subjected to 1 hour confinement or left undisturbed (control). Confinement of fish under BL resulted in a higher cortisol increase, no dopaminergic activation and lower brain serotonergic activity than under WL. In contrast, WL confined fish showed a lower cortisol increase coupled with higher brain serotonergic activity and increased levels of brain dopamine. Stress-induced hematocrit increase was lower when fish were confined under BL and triacylglycerides increase was only observed for WL reared fish. Differences in some parameters between unstressed BL and WL fish suggest that light wavelength had an effect on fish physiological status irrespective of stress. Although present results are not conclusive on which fish groups were more or less stressed, they do confirm that light wavelength can differentiate European sea bass response to acute stressors. Further studies to elucidate biological mechanisms of light spectrum effects will reinforce its efficacy as a tool to manipulate intensively reared fish stress response.

► We investigated sea bass response to confinement when under blue or white light.
► A differential stress response was observed for fish reared in blue or white light.
► Cortisol response was higher under blue light.
► Brain serotonergic and/or dopaminergic response was higher under white light.
► Light spectrum emerges as a potential tool to manipulate fish acute stress response.