Study on food web of grass carp (Ctenopharyngodon idellus) push-water aquaculture ecosystem by stable isotope analysis

Push-water aquaculture ecosystem is a kind of production mode which integrates recycling aquaculture, high efficiency sewage collection, biological purification and automatic control technology. However, the fate of nutrients in this system is not clear, which results in the waste of food resources and the improper regulation of aquaculture. Therefore, in this study, Ctenopharyngodon idellus push-water aquaculture ecosystem was used as the treatment group, and common pond aquaculture system as the control group. Stable isotope (δ¹³C, δ¹⁵N) technology was used to investigate the bio food composition and system food web structure of the two aquaculture systems. The results show that the stable carbon isotope δ¹³C were (−25.76±0.23)‰−(−22.26±0.20)‰ and (−25.83±0.24)‰−(−22.38±0.15)‰ in the treatment and control groups, respectively. The stable carbon isotope δ¹⁵N were (6.73±0.08)‰−(12.34±0.11)‰ and (6.73±0.08)‰ to (12.14±0.11)‰ in the treatment and control groups, respectively. The stable isotope mixing model reveals that the artificial feed of grass carp and the sediment detritus were the main food sources for consumers in these two groups. To be specific, the artificial feed of grass carp was the main food source for grass carp; the artificial feed of grass carp and the macrozooplankton were the main food source for bighead carp; and the sediment detritus was the main food source for crucian carp. The contribution rate of forage to the food composition of grass carp in push-water aquaculture ecosystem was higher than that in common pond system. Therefore, the adoption of the former can promote the feed intake of cultured organisms and improve the efficiency of feed utilization.