| 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, Tetraedron, Chlorella and Ankistrodesmus) and cyanobacteria (i.e., Microcystis and Merismopedia ) to determine filtration rates. Cell counts of phytoplankton in water filtered by tilapia indicated a significant reduction in green algae and cyanobacteria. Nile tilapia was more effective filtering the larger particle size taxa in both water sources. A curvilinear filter-feeding rate model provided a maximum filtration rate (FRmax) of 639 and 858 mgC/kg/h at 26 and 42 mgC/l in green-algal and cyanobacterial dominated water, respectively.; Nile tilapia held in CSTRs were provided either by green algae or by cyanobacteria dominated water to determine the effect of temperature and phytoplankton concentration on filtration rates. Filtration rates of both green algae and cyanobacteria increased linearly as water temperature increased from 17° to 32°C and were significantly higher in the warm-water regime (26–32°C) than that in the cool-water regime (17–23°C). Filtration rates at 95% saturation POC (FR95) in green-algal and cyanobacterial water were 700 mgC/kg/h and 851 mgC/kg/h in the warm-water regime and 369 mgC/kg/h and 439 mgC/kg/h in the cool-water regime, respectively. Nile tilapia also achieved these FR95 at lower POC concentrations in warm water than in cool water.; Four different size (390 ± 3, 140 ± 2, 40 ± 2 and 16 ± 1 g) Nile tilapia stocked at the same biomass in CSTRs were provided 27–29°C water dominated by Microcystis (82%) and Scenedesmus (18%) to determine the effect of fish size on filtration rates. The number of Microcystis and Scenedesmus cells filtered decreased significantly from the largest to the smallest tilapia size. Filtration rates of 763, 671, 512 and 300 mgC/kg/h which correspond to 70, 82, 86 and 90% saturation levels were achieved at a POC level of 30, 32, 32 and 33 mgC/l for 16, 40, 140 and 390 g Nile tilapia, respectively. Larger tilapia achieved these rates at lower POC concentrations than smaller tilapia. (Abstract shortened by UMI.)... |
