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
Chloropltyll-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 onest of resting phase at the 24th
hour. Results were similar under laboratory conditions.
At the onset offeeding pH was 7-8 in the stomach. Ch-a concentration in the
hindgut was high, and food passed undigested.
At the 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.
