Dissolved oxygen, and cage culture 211
and feed conversion ratio 230
and mortalities of S. niloticus 237
tilapias tolerate low levels 122
tolerances discussed 127
see also Oxygen
Distribution, alkalinity and pH 40
and altitude 34
changes associated with floods 52-3
Cichlidae (family) 16
Coptodon (subgenus) 21
and depth 32
by depth of various species 33
and ecology of tilapias 15-59
factors affecting 16-17, 51-5
and habitat diversity 31-2
importance of knowledge 21
limited by temperature 119
most northerly natural occurrence
of tilapias 33
most southerly natural occurrence
of tilapias 34
Nyosalapia (subgenus) 10
Oreochmmis (subgenus) 10
overiapping in Sarotherodon 21
oxygen and dissolved gases 40-1
pH and alkalinity 40
physical and chemical factors 31-41
restricted in some tilapia species 23
and salinity in certain lakes 52
Sarotherodon (genus) 17
Sarotherodon (subgenus) 9
S. andersonii 18,21
S. aureus 22
S. esculentus 22
S. galilaeus 21
S. hornorurn 22
S. lepidurus 20
S. macrochir 18,20
S. melanotheron 20, 21
S. mortimeri 18, 21
S. mossambicus 20,21
S. niloticus 17,20
S. pangani 21
S. placidus 21
S. ruvumae 21
S. schwebischi 10, 20
S. shimnus 22
S. spilunrs niger 21
S. upembae 20
S. umlepis 21
S. variabilis 22
and size 52
and slopes of rivers 32
of Soudanian species 17
and swimming performance 34
and temperature 33-7
and temperature and salinity
tolerances 37
Tilapia (genus) 17, 18
T. congica 19
T. dageti 19
T. guineensis 5, 18, 20
T. rnariae 19
T. rendalli 5,6,18,19
T. sparrmanii 19
T. tholloni 18
T. zillii 4-5
T. zillii and T. rendalli compared 5
of tilapias in hot springs 34
and water currents 32-3
in waters of low mineral content 39
of young fish in relation to temper-
ature, food, and growth 174
Diurnal feeding, in various species 43
Diurnal migrations 53
importance of Dr. Caulton's work 180
survival value 53
DO, see Dissolved oxygen
Dor (Israel), polyculture experiments 190
Dorsal fin-rot, and myxobacteria 255
Dorsal spines, T. zillii and T. rendalli 6
DRIB, daily rate of increase of biomass
218,219,220
Dry pelleted feeds, intensive cage culture
trials 228-9
Duoculture, with Cyprinus carpio 195-7
yields of all-male hybrids 196-7
Dwarf populations 74-6
Dwarfed stocks, compared with typical
stocks 74-5
Dwarfing, in relation to growth and
reproduction 110
Dwarfs, egg size 110
repopulated L. Chilwa 99
repopulated L. Rukwa 99
of S. niloticus parasitized in shallow
waters 89Earthern ponds, care and dedication
needed 290
for hybrid fingerlings and fry 284-6
and sporozoan infections 249
Ecoethological guilds 63
see also Reproductive guilds
Ecological growth efficiency of T. rendalli
in L. Kariba 174