The Biology and Culture of Tilapias

Table 3 (cont'd)

Europe

geothermal water in Idaho (Ray 1978; TVA

1978); experiments on biological control of

vegetation in California but progressively

abandoned because of mortalities and slow

feeding activity due to low temperature (Hauser

1977 ; Platt and Hauser 1978)

Great Britain introduced accidentally and considered accli-

matized in a canal receiving thermal effluents

from an electricity station (Wheeler and Mait-

land 1973)

T. mariae

America U.S.A. established in natural waters in Florida (Hogg

1976)

T. guineensis

Europe Belgium experiments (abandoned) for rearing in indus-

trial thermal effluents (M6lard and Philippart

1980)

T. sparrmanii

Asia Japan experiments for rearing in industrial effluents

Physical and Chemical Factors Affecting

Tilapia Distribution

Within their original areas of distribution, the tilapias have colonized

widely different habitats: permanent and temporary rivers, rivers with

rapids, large equatorial rivers (Zaire), tropical and subtropical rivers (Senegal,

Niger, Nile, Zambezi, Limpopo), deep lakes (Albert, Kivu, Tanganyika,

Malawi), swampy lakes (Bangweulu, Mweru, Victoria, Kyoga, Rukwa, Chad),

highly alkaline and saline lakes (Magadi, Natron, Manyara, Mweru Wantipa,

Chilwa, Chiuta, Turkana, Tana), other saline lakes (Lake Quarun), hot

springs (for example in Lake Magadi), volcanic crater lakes (Lakes Chala,

Barombi Mbo, Barombi ba Kotto) or meteoritic crater lakes (Lakes Bosumtwi),

lakes with low mineral content (Lake Bangweulu, Lake Nabugabo), some-

times very acidic waters (Lake Tumba), permanent water bodies in the

Sahara (Pellegrin 1921 in Beadle 1974) and in the Namib desert (Dixon and

Blom 1974), open or closed estuaries, lagoons and coastal brackish lakes that

often become hypersaline, marine habitats with normal salinity of Atlantic

water and hypersaline in the Red Sea (Gulf of Suez).

All these different habitats represent (both in terms of absolute amplitude

and in terms of the speed at which fluctuations take place) an extraordinary

varied range of physical parameters (depth, current velocity, turbidity), of

temperature and of chemical composition, especially salinity, pH, dissolved

oxygen (DO) and other gases.

Balarin and Hatton (1979) have collated the extensive literature concerning