بررسي تاثير رنگ هاي مختلف نور بر روي رشد و تغييرات گلوكز خون ماهي سولفورهد Labeotropheus trewavasae

A study on the effect of different colors of light on growth and blood glucose levels in Cichild sulfur head Labeotropheus trewavasae

Light is an effective factor in the metabolism, growth and locomotion of fishes. Due to the importance of vision in the nutrition of fishes in pisciculture, this research was designed to study the effect of different colors of light on certain growth and survival parameters, and glucose levels in Cichild sulfur head (Labeotropheus trewavasae). A total of 150 fishes, each weighting an average of 2 grams were selected, and were randomly transferred to 4 different aquariums (about 12 fishes per tank) in three replicates. After being adapted to their environment, their tanks were illuminated with a different color of light (sunlight red, blue and white light). The 40-50 watt bulbs (blue, red or white) were situated over the tanks at a distance of 40 cm. The photoperiod duration was maintained at a 12-hour photoperiod. Larval feeding lasted for 75 days, and the biometry of the fishes was performed once every 14 days. Data were calculated and analyzed using the ANOVA (Analysis Of Variance). Results indicated that the fishes exposed to white and red lights weighed the most and the least, respectively. The difference between the treated and the control lines were insignificant. The longest and the shortest fishes were the ones treated with white and red light, respectively. The highest and the lowest levels of glucose were observed in red and white light-treated fishes, respectively. The highest and the lowest FCR (Feed Conversion Ratio) was recorded in fishes grown under red and white light, respectively, which was significantly (P<0.05) different between the treatments. The highest SGR (Specific Growth Rate) or CF (Condition Factor) and HSI (Hepato-Somatic Index) were recorded for white light-treated fishes, and the lowest was recorded for the red light-treated ones. The highest and the lowest survival rates were observed in white and red light-treated fishes, respectively, and a significant (P= 0.05) difference was determined between the treatments. The higher wavelength of red light is absorbed at the top layers of water, whereas the white light which is a combination of all the wavelengths present in a light spectrum, including yellowy orange and green is highly absorbed by the Sulfur head fishes. White light resembles the light spectrum of the natural environment of fishes and thus can be an appropriate light for the growth of these fishes.