Filtration of green algae and cyanobacteria by Nile tilapia, Oreochromis niloticus, in the Partitioned Aquaculture System

Nile tilapia, Oreochromis niloticus, held in a timed pulse fed Continuous Stirred Tank Reactor (CSTR) were provided Partitioned Aquaculture System (PAS) algal-rich water dominated by green algae (i.e., Scenedesmus and Ankistrodesmus) and cyanobacteria (i.e., Microcystis and Merismopedia) to determine filtration rates (FR). A similar number and size of tilapias were stocked at 1.5 kg/tank into each of the six CSTRs (127 1) for 58-h experiment period. The cell counts of phytoplankton in water filtered by tilapias indicated significant reduction in green algae and cyanobacteria. Nile tilapia was more effective filtering the larger particle size taxa in both water sources. FR measured as mg of particulate organic carbon (POC) per kg wet fish weight per hour increased as POC increased. A curvilinear filter-feeding rate model provided a maximum filtration rate (FRmax) of 641 mgC/kg/h at 26 mgC/l in green algal-dominated water. The projected FRmax of cyanobacterial-dominated water was 865 mgC/kg/h at 59 mgC/l. The derived filter-feeding rate models will help to describe Nile tilapia filtration kinetics in the PAS and the potential for control of nuisance cyanobacteria. (C) 2003 Elsevier Science B.V. All rights reserved.