nvestigate the appropriate stocking density of large Nile tilapia placed in cages in earthen ponds
where small Nile tilapia were stocked in open water to utilize the wastes derived from the cages.
Large male tilapia (141 f 11 .l-152 k 2.1 g) were stocked at 30, 40, 50, 60, and 70 fish me3 in
4-m’ net cages. One cage was suspended in each of 15 earthen ponds, and three replicates were
used for each density. Small male tilapia (54 + 2.3-57 k I .2 g) were stocked at 2 fish me3 in
open water of all ponds. Caged tilapia were fed twice daily at 3%, 2.5%, and 2% body weight
day-’ during the first, second, and third month, respectively, with commercial floating pellets
containing 30% crude protein. Water quality was analyzed biweekly.
Stocking densities of caged tilapia had significant (P < 0.05) effects on the survival, growth,
and food conversion ratio of caged tilapia, and on the growth of open-pond tilapia. The survival of
caged tilapia decreased from 91.4% + 5.0 to 57.2% + 8.1 with increased stocking densities from
30 to 70 fish mm3, while survival of pond tilapia was higher than 90.0% in all treatments. The
average treatment mean weights of tilapia harvested from cages ranged from 509 + 26.0 to
565 + 13.9 g. The growth of pond tilapia was quite slow, with daily weight gain increasing from
0.30 f 0.02 to 0.47 k 0.08 g per fish day -I, in response to increased feed inputs to caged tilapia.
The combined net yield of both caged and open-pond tilapia was highest in the treatment with 50
fish m-‘. Water quality analyses indicated that the wastes from caged tilapia were insufficient to
generate abundant natural food for the growth of open-pond tilapia.
nvestigate the appropriate stocking density of large Nile tilapia placed in cages in earthen ponds
where small Nile tilapia were stocked in open water to utilize the wastes derived from the cages.
Large male tilapia (141 f 11 .l-152 k 2.1 g) were stocked at 30, 40, 50, 60, and 70 fish me3 in
4-m’ net cages. One cage was suspended in each of 15 earthen ponds, and three replicates were
used for each density. Small male tilapia (54 + 2.3-57 k I .2 g) were stocked at 2 fish me3 in
open water of all ponds. Caged tilapia were fed twice daily at 3%, 2.5%, and 2% body weight
day-’ during the first, second, and third month, respectively, with commercial floating pellets
containing 30% crude protein. Water quality was analyzed biweekly.
Stocking densities of caged tilapia had significant (P < 0.05) effects on the survival, growth,
and food conversion ratio of caged tilapia, and on the growth of open-pond tilapia. The survival of
caged tilapia decreased from 91.4% + 5.0 to 57.2% + 8.1 with increased stocking densities from
30 to 70 fish mm3, while survival of pond tilapia was higher than 90.0% in all treatments. The
average treatment mean weights of tilapia harvested from cages ranged from 509 + 26.0 to
565 + 13.9 g. The growth of pond tilapia was quite slow, with daily weight gain increasing from
0.30 f 0.02 to 0.47 k 0.08 g per fish day -I, in response to increased feed inputs to caged tilapia.
The combined net yield of both caged and open-pond tilapia was highest in the treatment with 50
fish m-‘. Water quality analyses indicated that the wastes from caged tilapia were insufficient to
generate abundant natural food for the growth of open-pond tilapia.
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