Water quality, plankton composition, and growth performance of juvenile yellow catfish (Pelteobagrus fulvidraco) in mono- and polyculture systems

Polyculture systems have been used to increase the production of yellow catfish (Pelteobagrus fulvidraco), an important aquaculture species; however, detailed comparative analyses of polyculture and monoculture systems in ponds are lacking. In this study, an 84-day experiment was conducted to compare the water quality, plankton composition, and growth performance of juvenile yellow catfish in mono-and polyculture systems. Three treatments were assessed in nine earthen ponds of 0.6-0.7 ha, including yellow catfish monoculture (T1), yellow catfish and grass carp polyculture (T2), and yellow catfish, grass carp (Ctenopharyngodon idella), silver carp (Hypophthalmichthys molitrix), and bighead carp (Hypophthalmichthys nobilis) polyculture (T3). In general, the concentrations of dissolved oxygen in the T3 treatment were significantly higher than those in the other treatments (P < 0.05). The contents of total ammonia nitrogen, nitrite nitrogen, total suspended solids, and chemical oxygen demand in T3 were significantly lower than those in T1 (P < 0.05). The contents of nitrate nitrogen, orthophosphate, and chlorophyll a (Chl-a) in T3 were significantly lower than those in T1 and T2 (P < 0.05). The water temperature (WT), transparency, and pH values did not differ significantly among treatments (P > 0.05). The biomass of zooplankton and phytoplankton was high in T2 and low in T3, and there were significant positive correlations between biomass and both WT and Chl-a concentrations. Regarding growth and yield parameters, the survival rates of yellow catfish did not differ significantly among treatments (P > 0.05). The final body weight, weight gain, species-specific productivity, and total productivity in T3 were significantly higher (P < 0.05) than those of T1 and T2. The specific growth rates in T3 and T1 were significantly higher than those in T2 (P < 0.05). Our results suggest that polyculture of yellow catfish with grass carp, silver carp, and bighead carp is a promising method owing to its ecological and economic benefits.