Abstract:
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.