The large adult catfish Clarias gariepinus feeds almost exclusively on
S. mossambicus in this lake (as studied in some detail by Bruton), and
both juveniles and adults are preyed on by the numerous birds: cormo-
rants, darters, herons, kingfishers, fish eagles and ospreys.Another east-flowing river, the Pangani in Tanzania, has two endemic
tilapias, S. pangani with a subspecies S. pangani girigan in Lake Jipe where it
is sympatric with S. jipe. In Lake Jipe S.p. girigan feeds on water weeds
(Najus); the former pharyngeal teeth of S. jipe suggest it consumes smaller
particles (Lowe (McConnell) 1955a). A new man-made lake on this Pangani
system, Nyumba ya Mungu reservoir completed in 1965, studied by Bailey
and Denny (1978) and Bailey et al. (1978) has three species of Sarotherodon
(the indigenous S. pangani and S. jipe, introduced S. esculentus) and T. ren-
dalli. These indigenous Sarotherodon grew to a large size, about 50 cm TL
and 1.75 kg (much larger than previously recorded from Lake Jipe). They
were found mainly in the littoral areas of the southern part of the lake, where
S. jipe clearly predominated. The S. esculentus lived in the southern deeper
offshore waters, where it consumed phytoplankton. T. rendalli found in
shallows close inshore to fringing reed swamp was surprisingly rare in the
north of the lake which has marked development of macrophytes. S. jipe
and S. pangani were chiefly browsers of periphyton and bottom deposits
(phytobenthos). In both these species males grew to a much larger size than
females (S. jipe males to 48 cm, females to 27.5 cm; S. pangani males to 47 cm,
females 31.5 cm TL). In Lake Jipe and the Pangani River, where males were
much more numerous than females in catches of these species, male matura-
tion and maximum sizes were also larger than in females (Lowe (McConnell)
1955a).Two endemic species of Sarotherodon live sympatrically in the Malaga-
rasi swamps (over 1,100 km2) which drain westwards into Lake Tanganyika:
S. karomo, whose breeding behavior in the swamps was studied by Lowe
(McConnell) (1956a), and a new species (then referred to as a form of T.
nilotica). These breed at different times of year. S. karomo's teeth appear
beautifully adapted for rasping epiphytic algae off the abundant water lilies
and other macrophytes.
Lake Malawi has a unique species flock of four endemic Sarotherodon
species adapted for openwater life: S. squamipinnis, S. saka and S. lidole
distributed round the lake where there are areas of water less than 40 m
deep, and S. karongae apparently confined to the northern end of the lake
(Lowe 1952, 1953). These fish, often in mixed schools living in midwater,