The Biology and Culture of Tilapias

different species varies from coarse vegetation (grasses, young shoots and
leaves of water weeds) to unicellular algae and even bacteria, the teeth also
vary in the degree of coarseness and movability.
Tilapias all exhibit a high degree of parental care and in this function they
are sharply divided into substrate-spawners and guarders of the brood on the
one hand and mouthbrooders on the other (Lowe-McConnell1959).
A division based on diet roughly coincides with one based on reproductive
habits. I say 'roughly' partly because tilapias are flexible and opportunistic in
their feeding habits, but also because of two species that fail to conform.
Tilapia mariae is a substrate-spawner, but its usual diet consists of epiphytic
algal growths and its jaw teeth are fine, slender-shafted and movable. Its
pharyngeal teeth are fine, on a bone whose anterior blade may be as long as
the toothed area and its standard gill-raker count is 12-16: high for a Tilapia.
Sarotherodon niloticus niloticus is a maternal mouthbrooder, but its jaw
teeth are nearly as stout as those of Tilapia zillii and its pharyngeal teeth are
firm, on a triangular area whose length is often greater than the length of the
blade. But the gill-rakers are more numerous than in T. mariae, the standard
count being 18-26.
But this overlap is merely an inconvenience when we try to define the two
groups and no one would doubt to which group each species is related.
The substrate-spawners constitute the genus Tilapia Smith (1840), the
mouthbrooders Sarothemdon Ruppell(1852).
Tilapia was an effort by A. Smith, its author, to spell the Bushman word
for 'fish', which began with a click, rendered 'Til'. Sarotherodon means
'brush-toothed'.
Examples of the two genera hiliar to fish culturists are: Tilapia sparr-
manii A. Smith, T. rendalli Boulenger, T. zillii (Gervais), T. cabm Boulenger,
Sarotherodon melanotheron Riippell, S. galilaeus (Linnaeus), S. niloticus
(Linnaeus), S. aureus (Steindachner), S. mossambicus (Peters), S. niger
(Ganther) and S. macrochir (Boulenger).
The four examples of Tilapia were named after persons who collected
the originals or (T. sparrmanii) had explored their region of origin. The
word melanotheron means 'black-hinged' or 'blackchinned', galilaeus
and niloticus are self-explanatory, 'aureus' refers to the golden-yellow
color of the preserved fish (not the living) and 'macmchir', meaning 'big
hand', refers to the long pectoral fin, the homolog of the forelimb (arm and
hand) of man.
T. sparrmanii feeds on the coarser algae and grasses and also on the
small animal life among them. It is sometimes described as omnivorous.
It is valued for pond use in South Africa because its wide temperature
tolerance enables it to withstand the winters of the High Veldt.
T. rendalli and T. zillii have strong cusped teeth in jaws and pharynx
and are specialized feeders on vascular plants. Ruwet (1963a) has given a
vivid description of the voracious attack by T. rendalli on the newly flooded
grasses of the Mwadingusha dam on River Lufira, Zaire.
These two species, which are not very easily distinguished at sight, have
largely complementary areas of distribution. T. zillii is a Soudanian form,
extending from west Africa through the Chad basin to the Nile, Lake Albert