A study on the optimal tank design and feed type to the growth of marble goby (Oxyeleotris marmorata Bleeker) and reduction of waste in a recirculating aquaponic system

摘要

Marble goby (Oxyeleotris marmorata Bleeker), a profitable aquaculture species, was cultured in partitioned tanks treated with a water recirculating aquaponic system (RAS). The influence of tank design (with partitions and PVC tubes of different sizes) and feed type (live food and minced fish) on the fish growth and waste production was investigated. The fish cultured in big partitions with PVC tubes showed higher growth (2.5 g/d) and feed intake (468 g/d) than other tank designs (growth: ≤2.2 g/d; feed intake: ≤433 g/d). The growth of fish fed with live tilapia (Oreochromis niloticus) (2.5 g/d) was significantly higher than that of fish fed with live carp (Cyprinus carpio) (1.9 g/d) and minced scads (Decapterus russellii) (1.6 g/d). Fish fed with minced scads showed the highest waste production (ammonia nitrogen (TAN): 262 mg/kg d; 5-d biochemical oxygen demand (BOD_5): 434 mg DO/kg d; total suspended solid (TSS): 2.1 g/ kg d) compared to those fed with live food (tilapia and carp) (TAN: ≤208 mg/kg d; BOD_5: ≤344 mg DO/kg d; TSS: ≤1.9 g/kg d). Live food, particularly tilapia, was found to be the preferential diet for marble goby as indicated by the highest fish growth (2.5 g/d) and feed utilization (feed conversion efficiency (FCE): 0.46), and the lowest waste production (TAN: 140 mg/ kg d; BOD_5: 232 mg DO/kg d; TSS: 1.4 g/kg d) compared to that of fish fed with minced fish (growth: ≤1.6 g/d; FCE: ≤ 0.31; TAN: ≥198 mg/kg d; BOD_5: ≥328 mg DO/kg d; TSS: ≥1.9 g/ kg d). Our results also indicate that the use of culture tank with big partitions and PVC tubes coupled with a RAS show exceptional promise as a means to the reduction of waste by marble goby fed with live tilapia (TAN: ≤140 mg/kg d; BOD_5: ≤ 232mg DO/kg d; TSS: ≤1.8 g/ kg d) and in turn providing a good water quality environment for the culture of the fish.