Dietary supplementation time with shrimp shell meal on red porgy (Pagrus pagrus) skin colour and carotenoid concentration

Red porgy, Pagrus pagrus, is a candidate for aquaculture diversification in the Mediterranean area. The main restriction for the development of this species, under cultured conditions, is the loss of their natural red–pink coloured skin. Several studies, using different dietary astaxanthin sources have given positive results on red porgy skin coloration. However, there is scarce information on the time required for cultured red porgy to obtain adequate skin colour when astaxanthin is included in the diet. This study aims to evaluate the effect of supplementing adult red porgy diet with shrimp shell meal, as a source of esterified astaxanthin, during different periods prior to harvest, on skin colour and skin carotenoid concentration. The experiment was carried out for 180 days, testing a control diet with no carotenoids and a shrimp shell meal diet (SM) with an inclusion of 16% shrimp shell meal in substitution of fish meal. Four treatment groups were established. Control treatment fish fed throughout the experiment on the control diet and SM60, SM120 and SM180 treatment fish fed first on the control diet and thereafter for 60, 120 and 180 days before harvesting on the SM diet. Growth was higher in fish from SM180 treatment group in comparison to control fish. Skin redness (a⁎) increased with increasing feeding period, and skin yellowness (b⁎) only until 120 days of feeding with SM diet. Whereas skin lightness (L⁎) does not seem to be influenced by dietary inclusion of shrimp shell meal for different periods of time. Skin carotenoid concentration also augmented with increasing feeding with SM diet. As a result, cultured red porgy fed for a period of 120 to 180 days, prior to harvest, on the SM diet may achieve similar skin coloration to wild red porgy, only differing in skin carotenoid concentration.