S. galilaeus (Fishelson and Heinrich 1963; Iles and Holden 1969)
S. karomo (Lowe (McConnell) 1956a)
S. leucostictus (Lowe (McConnell) 1957; Welcomme 1967a; Hyder 1970a,
1970b; Siddiqui 1977a, 197713)
S. macrochir (De Bont 1950; Ruwet 1962, 1963b; Carey 1965; Marshall
1979a, 1979b; Voss and Ruwet 1966; Ruwet and Voss 1966)
S. melanotheron (Aronson 1949; Oppenheimer and Barlow 1968; Pauly
1976)
S. mossambicus (Baerends and Baerends-van Roon 1950; Neil 1966; Bruton
and Boltt 1975; Russock and Schein 1977; Baerends and Blokzijul1963)
S. niloticus (Lowe (McConnell) 1958; El-Zarka et al. 1970a; Babiker and
Ibrahim 1979)
S. varia bilis (Lowe (McConnell) 1956a; Fryer 1961a)
T. guineensis (Voss and Ruwet 1966; Voss 1969)
T. rendalli (De Bont 1950; Ruwet 1962, 1963a; Donnelly 1969 ; Kenmuir
1973; Monfort and Ruwet 1968)
T. sparrmanii (Voss 1972a, 197213)
T. tholloni (Monfort-Braham and Voss 1969)
T. zillii (Daget 1952; El Zarka 1956; Voss 1969; Loiselle 1977; Siddiqui
1979a)
Papers concerning tilapias endemic to the African Great Lakes are syn-
thesized in Fryer and Iles (1972) and more recently Balarin and Hatton
(1979) have collated information in the literature up to 1976.In order to breed, most tilapias need a water temperature of at least 20°C
(Huet 1970; Bardach et al. 1972; Balarin and Hatton 1979), but certain species
are able to reproduce at a much lower temperature (for example T. sparr-
manii at 16"C, Chimits 1957). Other factors also seem to play a releasing
role, notably photoperiodicity and light intensity (see Balarin and Hatton
1979, p. 29) as well as the rainy season, via water temperature (temperature
linked with rains), water level (accessibility of certain spawning grounds) or
other mechanisms. Table 6 presents some data on the periodicity of tilapia
reproduction at different latitudes and altitudes.
In equatorial and tropical waters where the temperature is high through-
out the year, one observes numerous cases of continuous reproduction (e.g.,
S. leucostictus and T. zillii in Lake Naivasha) but the intensity often varies
seasonally (e.g., S. variabilis in Lake Victoria). The same occurs in waters
relatively constant from the point of view of photoperiodicity and temper-
ature, where certain species have a well-defined breeding season generally asso-
ciated with the rainy season (e.g., S. esculentus of Lake Victoria and S.
squamipinnis of Lake Malawi) or the hot season which precedes it (S. saka of
Lake Malawi). In this case, the length of the breeding season and the number
of spawnings per female are very variable. S. lidole, S. saka and S. squamipin-
nis of Lake Malawi represent an extreme case as they produce only one
spawning a year (but see also Berns et al. 1978).
In certain tropical and subtropical regions, low temperature inhibits