Effect of carotenoids and background colour on the skin pigmentation of Australian snapper Pagrus auratus (Bloch & Schneider, 1801) Ben J Doolan 1,2 , Geo¡ L Allan 2 , Mark A Booth 2 & Paul L Jones 1 1 School of Life and Environmental Sciences, Deakin University,Warrnambool,Vic., Australia 2 NSW Department of Primary Industries and Aqua¢n Cooperative Research Centre, Port Stephens Fisheries Centre,Taylors Beach, NSW, Australia Correspondence: B J Doolan, NSW Department of Primary Industries, Port Stephens Fisheries Centre, Locked Bag 1, Nelson Bay NSW 2315, Australia. E-mail: Ben.Doolan@dpi.nsw.gov.au Abstract Three 2-factor experiments were conducted to deter- mine the e¡ects of background colour and synthetic carotenoids on the skin colour of Australian snapper Pagrus auratus. Initially, we evaluated the e¡ects on skin colour of supplementing diets for 50 days with 60 mg kg  1 of either astaxanthin (LP; Lucantin s Pink), canthaxanthin (LR; Lucantin s Red), apocaro- tenoic acid ethyl ester (LY; Lucantin s Yellow), selected combinations of the above or no carotenoids and holding snapper (mean weight 5 88 g) in either white or black cages. In a second experiment, all snapper (mean weight 5142 g) from Experiment 1 were transferred from black to white, or white to white cages to measure the short-term e¡ects of cage colour on skin L à , a à and b à colour values. Skin colour was measured after 7 and 14 days, and total carotenoid concentrations were determined after 14 days. Cage colour was the dominant factor a¡ecting the skin lightness of snapper with ¢sh from white cages much lighter than ¢sh from black cages. Diets con- taining astaxanthin conferred greatest skin pigmen- tation and there were no di¡erences in redness ( a à ) and yellowness ( b à ) values between snapper fed 30 or 60 mg astaxanthin kg  1 . Snapper fed astax- anthin in white cages displayed greater skin yellow- ness than those in black cages. Transferring snapper from black to white cages increased skin lightness but was not as e¡ective as growing snapper in white cages for the entire duration. Snapper fed astax- anthin diets and transferred from black to white cages were less yellow than those transferred from white to white cages despite the improvement in skin lightness ( L à ), and the total carotenoid concentration of the skin of ¢sh fed astaxanthin diets was lower in white cages. Diets containing canthaxanthin led to a low level of deposition in the skin while apocarote- noic acid ethyl ester did not alter total skin carotenoid content or skin colour values in snapper. In a third experiment, we examined the e¡ects of dietary astaxanthin (diets had 60 mg astaxan- thin kg  1 or no added carotenoids) and cage colour (black, white, red or blue) on skin colour of snapper (mean weight 5 88g) after 50 days. Snapper fed the astaxanthin diet were more yellow when held in red or white cages compared with ¢sh held in black or blue cages despite similar feed intake and growth. The skin lightness ( L à values) was correlated with cage L à values, with the lightest ¢sh obtained from white cages. The results of this study suggest that snapper should be fed 30 mg astaxanthin kg  1 in white cages for 50 days to increase lightness and the red colouration prized in Australian markets. Keywords: astaxanthin, background adaptation, carotenoids, melanophores, snapper Introduction Interest in commercial culture of Australian snapper Pagrus auratus and the recognition that snapper cultured in sea cages have a much darker skin with- out the distinct pink or red pigment found in wild snapper has prompted investigation into methods of altering skin colour to optimize market value. Simi- larly, vast di¡erences in colour between cultured and wild specimens of the closely related red sea Aquaculture Research, 2008, 39, 1423^1433 doi: 10.1111/j.1365-2109.2008.02012.x r 2008 The Authors Journal Compilation r 2008 Blackwell Publishing Ltd 1423