Effects of tank color on the growth, survival rate, stress response, and skin color of juvenile hybrid catfish (Clarias macrocephalus x Clarias gariepinus)

This study focused on the effects of tank color on the growth, survival rate, stress response, and skin color of juvenile hybrid catfish (Clarias macrocephalus x Clarias gariepinus) reared in tanks of 5 different colors (white, red, green, blue, and black). Experiments were performed in triplicate with a duration of 8 weeks. Growth performance, feed utilization efficiency, survival rates, stress levels (as indicated by hematocrit, blood glucose, and plasma cortisol levels), and skin color parameters were evaluated in this study. Fish reared in red tanks exhibited a significantly higher mean final body weight (FBW) (27.50 +/- 0.26 g), greater weight gain (WG) (18.57 +/- 0.30 g), and a higher specific growth rate (SGR) (2.08 +/- 0.03% per day) than those reared in tanks of other colors (P < 0.05). In addition, fish reared in red tanks had the lowest mean feed conversion ratio (FCR) (1.23 +/- 0.05), which was significantly different from those reared in green (1.86 +/- 0.10), blue (1.88 +/- 0.04), and black (1.88 +/- 0.16) tanks (P < 0.05). Fish reared in red (95.55 +/- 2.22%) and blue tanks (95.56 +/- 4.44%) had higher survival rates (SR) than fish reared in white (93.33 +/- 3.85%), green (84.44 +/- 5.88%), and black (80.00 +/- 3.85%) tanks. The survival rates of fish reared in red and blue tanks were significantly higher than those reared in black tanks (P < 0.05). The stress indicators revealed the highest levels of hematocrit for fish reared in green tanks (41.80 +/- 2.26%), followed by those reared in black (37.86 +/- 2.19%), blue (37.76 +/- 4.24%), red (36.38 +/- 2.39%), and white (31.06 +/- 4.45%) tanks. Of these, the fish reared in green tanks had a significantly higher mean hematocrit level than those reared in white tanks (P < 0.05). The plasma cortisol levels of fish reared in red tanks (18.73 +/- 4.48 nmol/L) were lower than those reared in tanks of other colors. The skin color of fish reared in white tanks was the lightest (grayish-brown and yellowish-white), followed by fish reared in red, green, blue, and black tanks, which had the darkest skin color (black). This study demonstrated that the lightness (L*) of the tank color had an effect on fish skin color (74%). The assessment of growth performance, feed utilization efficiency, survival rate, stress responses, and skin color indicated that red is the most appropriate tank color for rearing hybrid catfish.