Effect of Stocking Biomass on Solids, Phytoplankton Communities, Common Off-Flavors, and Production Parameters in a Channel Catfish Biofloc Technology Production System

Abstract

The effect of initial channel catfish (Ictalurus punctatus, Rafinesque, 1818) fingerling biomass (1.4, 1.8, or 2.3 kg m-3) on phytoplankton communities, common off-flavours and stocker catfish production parameters was evaluated in biofloc technology production tanks. Stocker catfish size (145.5–172.6 g fish-1) at harvest did not differ among treatments, but net yield increased linearly as initial biomass increased (R2 = 0.633). Mean total feed consumption increased linearly with initial catfish biomass (R2 = 0.656) and ranged from 10.7 to 15.8 kg m -3. Total suspended solids (TSS) in all treatments increased linearly with total feed addition, and high TSS appeared to impact negatively daily feed consumption. Initial phytoplankton populations were dominated by small colonial green algae and diatoms, and later transitioned to populations dominated by a small, filamentous cyanobacteria and diatoms. Low, variable concentrations of 2-methylisoborneol and geosmin were present in biofloc tank water during most of the study and two tanks yielded catfish with 2-methylisoborneol or geosmin concentrations that might be classified as off-flavour. One isolate of actinomycete was isolated sporadically from some biofloc tanks, but its abundance was not correlated with 2-methylisoborneol concentration in tank waters. The microbial sources of 2-methylisoborneol and geosmin in biofloc tanks remain unidentified