Effect of temperature and phytoplankton concentration on Nile tilapia Oreochromis niloticus (L.) filtration rate

Abstract

Nile tilapia Oreochromis niloticus (L.) held in timed-pulse feeding chambers, were provided with algal-rich water dominated by either green algae (Scenedesmus, Ankistrodesmus, Chlorella and Tetraedron) or cyanobacteria (Microcystis) to determine the effect of temperature and phytoplankton concentration on filtration rates. Green algae and cyanobacteria filtration rates were measured as suspended particulate organic carbon (POC) kg−1 wet fish weight h−1. Ivlev's filter-feeding model described the relationships between filtration rates and suspended POC concentration of green algae and cyanobacteria. Filtration rates of both green algae and cyanobacteria increased linearly as water temperature increased from 17 °C to 32 °C and were significantly higher in the warm-water regime (26–32 °C) than in the cool-water regime (17–23 °C). Filtration rates at 95% saturation POC (FR95) in green algal and cyanobacterial waters were 700 mg C kg−1 h−1 and 851 mg C kg−1 h−1 in the warm-water regime and 369 mg C kg−1 h−1 and 439 mg C kg−1 h−1 in the cool-water regime respectively. The FR95 in warm water were achieved at lower POC concentrations than in cool water.