Abstract:
Growth performance and body color of the fish are important factors in the ornamental fish industry. The present study was conducted to evaluate the effects of stocking density and feed type on growth performance, feed utilization efficiency, percentage survival rate and body coloration of swordtail fish (Xiphophorus hellerii) in an indoor-recirculating aquaculture system (RAS) for 56 days. The experiment used a 2×2 factorial design with two distinct stocking densities (low :15 fish per 60 L and high :30 fish per 60 L) and two types of commercial fish feeds; normal commercial feed (NF) and commercial color enhancing feed (CF). Crude protein%, crude lipid% and carotenoid content of NF was 45.81±0.92, 5.21±0.20 and 26.94±0.31 (μg g-1) respectively while it was 36.42±0.61, 6.25±0.12 and 68.25±0.23 (μg g-1) in CF. Twelve fish groups (0.0640 ± 0.0001g initial mean weight; 10.40 ± 0.01mm initial mean total length) were established at two stocking densities and within each group, two types of feed were allotted. At the end of the study, final body weight, final body length, % Specific Growth Rate (%SGR), % Average Daily Gain (%ADG), Feed Conversion Ratio (FCR), mean feed intake, survival rate and carotenoid content were compared in F-test (Factorial ANOVA). According to the results, the significantly higher final body weight, total body length, %SGR and %ADG were observed in fish reared under low stocking density and fed with normal commercial feed (NF15). The best feed utilization efficiency with a low FCR value was observed in fish at low stocking density and fed with normal feed. However, percentage survival rate and carotenoid content in swordtail fish were not significantly affected by stocking density or feed type (P>0.05). The interaction between feed type and stocking density did not significantly impact any measured parameters. Results of this study revealed that both feed type and stocking density effect growth performance and feed utilization efficiency of swordtail fish.
