Abstract:
Ornamental aquaculture relies greatly on the colors of fish and nutrient-rich feed is a major contributing factor. Carotenoid sources are the main ingredients that enhance fish color. Here, as a cost-effective alternative for commercial carotenoid sources we aimed to test the effect of Cucurbita maxima peel as a color enhancer for Poecilia reticulata. Three diets, incorporating 5% (T1), 10% (T2), 15% (T3) and 0% (control) C. maxima peel with respect to total feed weight were fed to fish in three replicate tanks arranged in a completely randomized design. Ten male P. reticulata fries with average weight and length of 0.019 ±0.00g and 0.7 ±0.0 cm, respectively, were stocked in each tank. Fish were fed experimental diets of 2% of body weight twice a day for 75 days. Fecal matter was collected semiweekly. DO and pH of water were measured weekly using a multimeter. Fish weight and length were measured fortnightly using an electronic balance and a measuring board. Water quality parameters weren’t significantly different among treatments and control and remained within the optimum ranges (DO>6mg/L, pH 6.8-7.8) for P. reticulata. Incorporating C. maxima peel into the feed positively influenced the growth of P. reticulata. Among the treatments, the highest values for final weight (FW); 0.16 ±0.002g, body weight increase (BWI); 0.14 ±0.00g, percent body weight increase (%BWI); 88.12 ±0.15%, specific growth rate (SGR); 1.89 ±0.0, apparent digestibility coefficient (ADC); 59.97 and the lowest feed conversion ratio (FCR) of 1.42 ±0.02 were recorded in T3. In contrast, the minimum growth was recorded from T1 with the lowest FW (0.130 ±0.00g), BWI (0.11 ±0.00g), %BWI (85.38 ±0.11%), SGR (1.879 ±0.0), ADC (14.00), with the highest FCR; (1.80 ±0.02). Adding C. maxima peel increased the length parameters and survival rate (SR%) but showed no significant statistical difference with the control (P>0.05). T3 had the maximum SR% (76.67 ±5.77%), while the control had the minimum (70 ±0.00%). The maximum body length was recorded from T3 (3.0 ±0.2cm) while T1 (2.6±0.2cm) and control (2.7±0.3) had the minimum. According to the results, the maximum brightness and carotenoid contents were recorded in T3 (Gray value=50.99 ±4.02, carotenoids=4.05 ±0.27 μg/g wet weight) while lower brightness (and carotenoid levels were in T1 and the control. In conclusion, C. maxima can be used to enhance the coloration of P. reticulata, but it needs to be in higher concentrations. The incorporation of C. maxima exhibits a positive influence on fish growth. Changing the process of C. maxima powder or extracting carotenoids from peels is recommended for better results.
