Effects of rearing tank color on growth indices, body composition, some physiological parameters and expression of growth genes (GH/IGF1) in oscar fish (Astronotus ocellatus Agassiz, 1831)
Fish farm tanks with different colors make different responses to different factors such as growth, physiological responses, survival, hormonal responses as well as fish behavior. Since the color of farming tanks are controllable for fish, so determination of optimal condition for cultured species for success in production and to ensure of ideal fish condition as well, is important. The aim of this study was to investigate the effects of aquarium different colors on growth and feeding performance, physiological responses and expression of growth-related genes of Oscar fish (Astronotus ocellatus). For doing the present study, about 200 oscar fish with similar weight acclimated to laboratory condition and formulated feed for 15 days. Fish were reared in aquariums with four different background colors (blue, white, yellow and red) for 8 weeks. The obtained results indicated that red color has the highest value in final weight and the lowest value in feed conversion ratio compared to other colors (P<0.05). The aquarium background color caused significant differences in body composition including protein, fat, ash and moisture (P<0.05). The highest value of protein and ash were observed in fish reared in white aquarium and the values of fat and moisture in this treatment was lower and showed a significant difference compared to other treatments (P<0.05). The aquarium color showed no significant effects on hematological parameters including RBC count, hemoglobin and hematocrit value, neutrophil and lymphocyte (P>0.05), but WBC count in fish reared in blue aquarium was significantly lower in compare to other treatments (P<0.05). Blood biochemical parameters including total protein, albumin and cholesterol were significantly the highest for fish reared in red aquarium compared to other tr