Growth performance of Amur catfish (Silurus asotus) in various aeration rates in an indoor BFT system

Abstract

The development of Biofloc technology (BFT) as a sustainable and environmentally friendly aquaculture technology includes discovering new species suitable for it. Amur catfish (Silurus asotus) is an important freshwater fish in East Asian countries which has potential to be reared in BFT system. This study evaluates growth performance of Amur catfish in an indoor BFT system with aeration rates as variable. Twenty catfish with average weight of 4.17± 0.20 g and length of 8.11±0.32 cm were stocked in eighteen aquaria. Six treatments i.e. 2lpm, 3lpm, 4lpm, 5lpm, 6lpm and 7 lpm aeration rates with equivalent surface area loading rates 43, 64, 85, 107, 128 and 149 m³/m²/d were designed in triplicates. Fish were fed 5% of body weight and dextrose was added at 15:1 C:N ratio. Dissolved oxygen, temperature and pH were monitored twice daily. Total ammonia nitrogen and nitrite along with total suspended solids and floc volume were monitored once a week. Growth was monitored after week 4 and week 8. DO and temperature were maintained at >8ppm and ̴ 240C respectively. The pH was statistically higher in the 128, 149 and 107 m³/m²/d as compared to 43, 64 m³/m²/d SALR. Inorganic nitrogen species were not significantly different while solids were higher at higher aeration rates. Survival of catfish were low and among the treatments with fish in 2lpm aquaria having high mortalities as early as 5th week of the experiment and not exceeding 58% for all treatments. Individual weight and length gain, specific growth rate, condition factor, total weight gain and FCR, were not significantly different among the treatments except for 43 m³/m²/d tanks (which was caused by low survival rate). Aeration plays an important role in the management and control of biofloc in BFT systems however other factors may have influenced the growth performance of catfish in this study such as cannibalism and floc properties.