Effect of eco-substrates on water quality and energy budget of largemouth bass (Micropterus salmoides) aquaculture system

To find out the rule of the energy flowing of aquaculture ponds with eco-substrate, we carried out an experiment (the pond with eco-substrates as the treatment group and the pond without eco-substrate as the control group) and studied the effect of eco-substrates on the environment and energy budget of largemouth bass (Micropterus salmoides) aquaculture system. The results show that the eco-substrates could reduce the ammonia nitrogen, nitrate nitrogen, total nitrogen and total phosphorus in the water significantly (P<0.05), but there was no effect on the nitrite nitrogen, soluble reactive phosphate in the water and total nitrogen, total phosphorus in the sediments (P>0.05). In the study, forage fish was the main source of input energy in both two groups, which accounted for 53.26% and 55.02% of the total input energy, respectively. The primary production of phytoplankton was also the important source of input energy, accounting for 44.22% and 45.92% of the total input energy, respectively. The major output of energy was the respiration of plankton followed by the harvest of cultured animals, accounting for 56.68%, 60.01% and 28.78%, 31.99%, respectively. The treatment group had higher net biological output energy, photosynthetic conversion efficiency, feed energy conversion efficiency and total energy conversion efficiency (P<0.05), but lower feed energy consumption per unit of net yield and total energy consumption per unit of net yield (P<0.05). Therefore, the eco-substrates could improve the pond environment, increase the production and enhance the energy utilization efficiency effectively.