Twelve diel surveys were carried out in three reservoirs of Sri Lanka viz.
Minneriya, Udawalawe and Victoria, to investigate diel feeding patterns,
daily ration and relative food consumption in fish populations. Stomach
content weights of different size classes of various fish species in the
three reservoirs in 12 diel surveys were analysed using an iterative method,
MAXIMS. Predominantly herbivorous or detritivorous fish species such as
Amblypharyngodon melettinus and Oreochromis niloticus exhibited one peak in
the diel feeding pattern. Two peak feeding periods were evident in
predominantly insectivores and/or zooplanktivores (e.g., Puntius chola and
Rasbora daniconius) and interestingly in macrophyte feeders (i.e., Etroplus
suratensis, Puntius filamentosus and Tilapia rendalli). It might be possible
that all species with two feeding peaks in diel feeding patterns rely on
vision for feeding.
Food consumption per biomass (Q/B ratio) defined as amount of food consumed per
unit weight of an age-structured population of fish was estimated on the
basis of the average quantities of food consumed over a long period of time
by various size classes in order to minimize the bias of estimates.