Effects of 5 representative feeds on hybrid grouper biology and water quality of its recirculating aquaculture systems

FAN Xiangyu; YU Hong; CUI Hongwu; XUE Zhiyong; BAI Ying; QU Keming; HU Haiyan; CUI Zhengguo

doi:10.13984/j.cnki.cn37-1141.2026.01.008

Abstract：Feed is the most important source of nutrients and pollutants in recirculating aquaculture sys-tems(RAS).When RAS industry tries to develop sustainably,the green feed is essential to ensure quality and water quality.An 8-week culture experiment was conducted to investigate the effects of dif-ferent diets on the biology of hybrid grouper and water quality in RAS.Redundancy and Pearson corre-lation analyses were used to establish the association between data.The results showed that the growth efficiency of hybrid grouper is significantly and positively correlated with protein/energy ratio(P/E)and high significantly and positively correlated with dietary apparent digestibility(ADC)in its RAS.The increase of dietary P/E and ADC can reduce the hepatopancreas somatic indices and viscerosomatic somatic indices.When the P/E and ADC were too high,i.e.,when the fish individuals ingest and ab-sorb too much protein which will lead to the decrease of protein efficiency,the serum glutamic oxalace-tic transaminase activity and the increase of total ammonia nitrogen and nitrite nitrogen concentration in aquaculture water will increase.The level of available phosphorus(AP)in feed was positively correla-ted with the concentration of phosphorus pollutants in water.Compared with labile phosphate,availa-ble phosphorus had a greater effect on the concentration of total phosphorus.The water-solubility(WSI)of feed was positively correlated with all water pollutants.In this study,the performance of F3(P/E 36.20 g/MJ,ADC 61.92±1.31％,AP 0.98％,WSI 13.25±0.23％)was the closest to the green feed suitable for hybrid grouper RAS.Our findings provided the data support for the application of green feed in industrial RAS.