The characteristic diet of adult tilapias is plant matter and/or detritus
of plant origin. Blue-green and green algae, diatoms, macrophytes and
amorphous detritus are all common constituents of adult tilapia diets (Plate
3). Bacteria are also present and may be very important for some species.
Although tilapias collect their diets from such diverse substrata as macro-
phytes, lake bottoms, rock surfaces and from suspension, it is the uniformity
of their diets that is especially noteworthy. Comparisons of diet composition
for tilapias reveal extensive overlap. Tilapias that feed on macrophytes also
ingest the attached algae, bacteria and detritus. This attached material is
likely to be an important component of the diet. Although quantitative data
are lacking for macrophytes consumed by tilapias per se, the dry weight of
attached material was found in one study to exceed 25% of the total sup-
porting macrophyte dry weight (Bowen 1980a) and could comprise an even
greater percentage of the weight of leaves actually consumed by tilapias.
Tilapias that feed on epiphytes also frequently ingest some of the supporting
macrophyte (Munro 1967). Deposit feeders that feed in the littoral zone
ingest a mixture of algae, detritus and bacteria that is essentially indis-
tinguishable from the material attached to macrophytes. Deposit feeders that
feed in deeper water ingest a mixture of sedimented phytoplankton and
detritus essentially indistinguishable from the diets of suspension feeders.
These various sources provide diets that are so similar that tilapias may
switch from one source to another with little change in diet composition
(Moriarty et al. 1973; Bowen, unpublished). Thus, despite the diversity of
food resources exploited by tilapias, their diets are qualitatively very similar
mixtures of algae, bacteria and detritus with or without macrophytes.
Plate 3. Scanning electron micrograph of typical stomach contents from Saro-
therodon mossambicus in Lake Valencia. Venezuela.