In general a comparison of feeding in the same species of tilapia in a large
range of water bodies reveals a very great variability of feeding regime. This
is an element of the remarkable plasticity and ecological adaptability of
tilapias. The general qualitative characteristics of the feeding regime depend
on the following: 1) the type of organisms present, which depends on the
limnological, physicochemical characteristics of the water body; 2) the
accessibility of the food organisms according to their localization (for
example, in certain lakes or reservoirs, some abundant types of food are
situated too deep and are inaccessible to tilapias which are not able to
descend to these depths (see Caulton and Hill 1973 for S. mossambicus) and
3) tne presence of competing species (tilapias or others) which forces each
species to restrict its food spectrum and to exploit its specializations, e.g., in
many tropical waters where competition for food is intense, T. zillii is strictly
a macrophyte-feeder, whereas it eats plankton and benthos in Lake Kinneret,
Israel (Sparatu 1978) and in Lake Qarun, Egypt (Alkholy and Abdel Malek
1972) where the competition is less.Within a given water body, the feeding regime of a species is extremely
variable, depending on size and age, the microhabitats occupied by the fish
and the time of year.
The alevins (both of species which are strictly phytoplankton-feeders or
macrophyte-feeders when adult) generally have a diversified feeding regime
extracting small organic particles from the sediments, phytoplankton,
diatoms, periphyton, zooplankton and benthic organisms (Bruton and Boltt
1975 for S. mossambicus; Gophen 1980 for S. galilaeus and Whyte 1975 for
the Lake Bosumtwi tilapias).
In Lake Sibaya, S. Africa (Bruton and Boltt 1975), the S. mossambicus
adults captured in the marginal vegetation zones feed on diatoms, vegetable
debris and mud, but those fish captured in open water (limnetic zone) feed
on aerial insects (Coleoptera and Hemiptera). In Lake Kinneret, Israel
(Spataru 1978), T. zillii captures prey from the surface in open water and
rarely from the bottom except when breeding and guarding the young
(April-MayJune) when they feed equally on benthic organisms (chironomid
larvae, ostracods, nematodes and sponge gemmules).
The qualitative seasonal variations of feeding regime depend partly on the
annual cycle of production and availability of prey, and partly on the degree
of feeding selectivity of the species and their distribution in different habitats
at different times of year.
Seasonal changes in feeding have been studied in T. zillii, S. galilaeus and
S. aureus in Lake Kinneret (Spataru 1976, 1978; Spataru and Zorn 1978),
and in S. mossambicus in Plover Cove Reservoir, Hong Kong (Man and
Hodgkiss 1977b).
In spring, S. aureus in Lake Kinneret feeds intensively and more or less
selectively on zooplankton which is very abundant. Beginning midsummer,
the zooplankton production slows down and its availability diminishes due
to competition from other species. S. aureus then feeds more on benthic