Clearance of Yellow Pigments Lutein and Zeathanxin in Channel Catfish, Ictalurus punctatus, Reared at Different Water Temperatures

A study was conducted to determine the clearance time of yellow pigments lutein and zeaxanthin in channel catfish at various temperatures. Fish of initial weight of 13.4 g were stocked into flow-through aquaria and fed daily with a pigment-enhanced diet for 11 wk when yellow color became visible in the flesh. All fish were then transferred into tanks in three recirculating systems that were assigned one of the three temperatures (10, 20, and 30 C). During the pigment clearance period, fish were fed a control diet without added pigments daily to satiation for 12 wk. Every 4 wk, fish from three randomly chosen tanks per temperature were euthanized and fillets were analyzed for yellow color intensity (Commission Internationale de l'Eclairage [CIE] b*) and lutein and zeaxanthin concentrations. The b* values of fillets of fish reared at 20 and 30 C decreased linearly as time progressed. There was no significant linear regression of b* value against time for fish raised at 10 C. The rate of pigment clearance was similar for fish reared at 20 and 30 C. Results demonstrate that about 8 wk were needed for catfish to "purge" most of yellow pigment at warns temperatures (20 and 30 C). A longer period of time (>12 wk) was required at 10 C.