The Biology and Culture of Tilapias

prevented the large number of unsuccessful attempts to culture or to intro-
duce tilapias.
This paper is written from a broad ecological perspective, although prac-
tical applications are shown whenever these arise. Five aspects of tilapia
ecology are discussed:

1. Geographical distributions, with special emphasis on assessing the
   success of introductions and transfers. ,


2. Analysis of physical and chemical factors which influence the natural
   distribution of tilapias and characterize their ecological range.


3. Feeding behavior.


4. Reproductive behavior.


5. Selection of microhabitats and dynamics of spatial separation.

Zoogeography and Distribution

The family Cichlidae is widely distributed in Africa (including Madagascar)

and Palestine, in South and Central America, in southern India and in Sri

Lanka (Lagler et al. 1977). The tilapias, however, originated exclusively from

the African continent (excluding Madagascar) and from Palestine (Jordan

Valley and coastal rivers). In Africa they are absent only from the Northern

Atlas and from south west Africa. This is an old pan-African group with a

slow or average rate of speciation, primarily riverine, secondarily lacustrine.

About seventy species are nowadays distinguished as two genera: Tilapia

(macrophagous, substrateapawners) and Sarotherodon (microphagous

mouthbrooders). Their original distributions are given in Figures la, b and

2a, b, c and in Table 1. The data used for this review stem from Thys (1963,

1964, 1968,1971a, 1971b), Trewavas (1966), Fryer and Iles (1972), Ruwet

and Voss (1974), Ruwet et al. (1975) and Balarin and Hatton (1979), which

relate specifically to tilapias, and from other works on African ichthyology,

Giinther (1889), Pellegrin (1921), Poll (1957, 1973), Ruwet (1961, 1962),

Greenwood (1965, 1966, 1974, 1976), Jubb and Farquaharson (1965),

Bell-Cross (1968, 1972, 1973), Daget (1968), Gee (1968b), Petr (1968,

1969,1975), Lowe-McConnell(1969,1975,1979), Jubb and Gaigher (1971),

Gaigher (1973), Green et al. (1973,1978), Trewavas (1973a, 1973b), Johnson

(1974), Eccles (1975), Ottobo (1976), Landau (1979), and other studies

cited below.

The natural distributions of the species reflect two types of factors:

1. those historico-geological factors which led to geographical isolation and to speci-
   ation (endemic species in lakes or stretches of rivers): a knowledge of the past
   geology and hydrography of Africa is necessary to understand the species distribu-
   tions, while, conversely, a knowledge of the species distributions helps in confirm-
   ing hypotheses concerning the evolution of hydrographic basins and their former
   connections.


2. those ecological factors which demonstrate the requirements and preferences of
   the species with regard to temperature, salinity, the chemical composition of the
   water, and the behavioral mechanisms which reflect feeding and reproductive
   strategies.
   Dealing first with the historical factors: for those affecting distribution,