Growth Response of Silver Carp, Hypophthalmichthys molitrix Val., to Feed Supplementation in Earthen Fish Ponds

ABSTRACT

Silver carp is one of the most important fish used in polyculturing the earthen fish ponds in semi-intensive fish farms. Silver carp depends mainly on natural foods, and there is no available data focusing the ability of silver carp to consume the artificial diet. Therefore, a 15-week feeding trial was conducted in eight earthen ponds (0.1 ha each) to investigate the effect of prepared diet on the growth of silver carp, Hypophthalmichthys molitrix Val. In each pond, 2,000 fish of silver carp (2.1±0.3 g) were stocked. Four treatments were used in the present study, and two ponds were assigned to each treatment. Fish were cultured in ponds that only received fertilizers (T1), received fertilizers and prepared diet at a rate of 0.5% of fish biomass (T2), received prepared diet at a rate of 1% of fish biomass without fertilization (T3), and received prepared diet at a rate of 3% of fish biomass without fertilization (T4). Fish were fed a diet (25% crude protein) at the specific feeding rate twice daily. The most conspicuous attribute of the feeding rates was its lack of influence on growth and yield. The natural foods in T1 and T2 contributed significantly to the fish growth, while the prepared diet in T2-T4 treatments contributed to 5–8% of fish growth. The results of whole-body proximate analysis indicated that moisture and crude protein contents decreased significantly (P < 0.05), while total lipids increased significantly (P < 0.05) with the increase in feeding rate. No effect on ash content was observed due to various feeding rates. The economic effectiveness varied among treatments. Among the four treatments, culturing of silver carp in fertilized ponds appeared to be optimal, as it significantly (P < 0.05) supported the optimum income and net profit compared with other treatments. This study recommended that if a pond has poor water quality, prepared diet may be supplied to silver carp at a rate of 0.5–1.0% of fish biomass per day.

KEYWORDS:

• Water physico-chemistry
• phytoplankton
• zooplankton
• silver carp
• Hypophthalmichthys molitrix
• growth
• prepared diet
• feed utilization
• natural foods