Effects of background color on growth performances and physiological responses of scaled carp (Cyprinus carpio L.) reared in a closed circulated system

Growth performances and physiological responses of Cyprinus carpio after lo ng-term (14 weeks) background color adaptation were investigated. Six group s of ten individuals each (initial body weight 116 g) were reared in black, green and white tanks (two replicate groups for each color). At the end of the experiment, blood (cortisol, glucose, haematocrit, cholesterol, trigly cerides, total lipids, osmolality, electrolytes, pCO(2), pH), liver (total lipids, glycogen, hepatosomatic index) and growth (body weight, specific gr owth rate, food conversion ratio, condition factor, proximate carcass compo sition) parameters were determined. Plasma cortisol levels in white-adapted carp were significantly (P < 0.05) lower than those in black, while in gre en-adapted fish did not differ significantly from those in both other count erparts. White-adapted carp showed the highest specific growth rate and the lowest food conversion ratio, whereas black-adapted fish exhibited the opp osite pattern. In addition, mean (%) increase of body weight in white-adapt ed carp was 4.66 and 3.58% higher than that in black- and green-adapted fis h, respectively. Furthermore in white-adapted carp, blood pCO(2) and pH wer e significantly higher and lower, respectively, than those obtained in blac k- and green-adapted fish. In black-adapted carp, liver total lipid levels were significantly lower, and plasma total lipid levels were significantly higher, than those in white- and green-adapted fish. No significant variati ons were observed in the other parameters. It is concluded that different b ackground colors may lead to different growth performances of scaled carp d epending upon rearing conditions. (C) 2000 Elsevier Science B.V. All rights reserved.