Abstract:
Beira Lake is eutrophic and covered with a bloom of Cyanobacteria. Hybrids
of Oreochromis niloticus and Oreochromis mossambicus dominate the lake.
Present study deals with feeding cycle and digestibility of the bloom by Oreochromis
species. Volume method and the point method were used to determine feeding
intensity of the hybrids. Stomach pH and Chloropityll-a content in stomach and
hindgut were determined at different hours of the day. Four to five diumals were
conducted in the field and in the laboratory.
Results indicated that, oreochromis hybrids commenced their feeding at the 6th hour
and stomachs were filled up to 25%. At the 12th hour, majority of fish were fed from
50% to 75% and on the 18th hour up to full stomach level. Feeding decreased from
75% to 50% at the onset of resti ng phase at the 24th hour. Results were similar under
laboratory conditions.
Al the onset of feeding pH was 7-8 in the stomach, Ch-a concentration in the hindgut
was high. and food passed undigested.
Atthe 12th hour. pH decreased from 3-4 and reached 1-2 at the 18th hour indicating
onset of digestion. From 18th to 24th hour, active digestion occurred.
