Three species of tilapia (Oreochromis lidole, O. karongae and O. niloticus)
were fed on four planktonic algal diets in the laboratory. The algal concentrations were
measured over a 24-h period and the ingestion rates calculated. In monocultures of large
algae (average filament length=477 µm) O. niloticus had the highest ingestion
rate, but on small algae (particle size <8 µm) O. lidole was the fastest, while
O. karongae enhanced nanoplankton production. With algae of mixed sizes, O.
niloticus was able to remove small algae quicker than the other fish species. Thus,
the presence of larger algae can influence the impact of a planktivorous species on
nanoplankton. O. lidole is likely to have the greatest impact on plankton
communities heavily dominated by smaller algae.