The Biology and Culture of Tilapias

is declining, but for computations of production in natural waters growth

rate and biomass data are essential. The relatively few comprehensive studies

of tilapia production yet made in natural waters include those for the Kafue

floodplain and Lake Kariba, both in the Zambezi system, and for the equa-

torial Lake George in Uganda. For these sites the computed abundances

of the fish, their biomasses, production, yield and turnover are indicated in

Table 2.

Table 2. Examples of tilapia (Tilapia and Sarotherodon) production, yield and turnover rates in
natural waters.

Production

Biomass kglhalyr Yield

Abundance kg/ha Total Available kglhalyr Turnover

nlha B A P y~ % AIB

1. Kafue eastern floodplain

lagoons (31 spp.) 11,053 680

channels (24 spp.) 3,894 333

weighted mean (all spp.) 8,191 541

3 spp. tilapia lagoons 2,282 364

3 spp. tilapia channels 2,361 246

3 spp. tilapia mean 317

T. rendalli (1agoons:channels) 706: 187 125 198 110 18 8 1.59

S. macrochir 737:1,327 (^145 145 96 39 23) 1.0
S. andersonii 839: 837 147 119 92 23 15 0.75

2. Lake Kariba
   20 spp. (revised estimate) - 827 1,224 720 400 202
   of these 'preferred' spp. 0.7
   'accompanying' spp. 2.3
   mean turnover ratio (revised) 1.48
   T. rendalli (revised estimate) 957 38 44 30 19 12 1.15

S. mortimeri (revised estimate) 2,122 (^216 178 133 139 103) 0.83

3. Lake George (Uganda)

A11 (lo+) spp. mean 220

(60-900 inshore)

S. niloticus (offshore:inshore) 63:1,094 37(?) mean

S. leucostictus (offshore:

inshore) 7: 649 5(?) mean

catch 137

catch 111