Dietary lipidic extracts from Microchloropsis gaditana modulate skin coloration in juvenile clownfish (Amphiprion ocellaris)

Abstract The present study evaluated the effects of partial replacement of fish oil and dietary inclusion of fatty acid- and carotenoid-rich extracts from the microalga Microchloropsis gaditana on growth performance and skin coloration of juvenile clownfish Amphiprion ocellaris over 60 days. These standardized extracts, used instead of whole microalgal biomass, provided a concentrated and controlled supply of lipids and pigments. Four dietary treatments were tested in triplicate: DCT (control), DFA (2% fatty acid extract), DCA (2% carotenoid extract), and DCFA (2% of both extracts). The fatty acid extract replaced 50% of fish oil in the diets. Fish were fed three times daily at 4% of body weight. Survival, growth,and coloration parameters (CIELab: L* = lightness; a* = red-green; b* = yellow-blue) were assessed at 30 and 60 days. Survival after 60 days exceeded 71%. At 30 days, DFA increased body weight, while DCFA improved standard length and reduced weight variability relative to the control. By day 60, no significant differences were observed among treatments for body weight, standard length, weight gain, specific growth rate, or feed conversion ratio, indicating that replacing 50% of fish oil with microalgal extracts did not impair growth. In contrast, pigmentation was affected. Fish fed the DCA diet showed higher L* values and more intense red and yellow coloration than the other treatments at the end of the trial. These results indicate that a carotenoid-rich extract from M. gaditana enhances skin coloration in A. ocellaris without compromising growth, representing a promising strategy for ornamental fish nutrition.