Abstract
In the freshwater area of Vietnam’s Mekong Delta,
Barbodes gonionotus (Bleeker), Cyprinus carpio L. and
Oreochromis niloticus (L.) are often reared together in
rice fields. The survival rate and speci¢c growth rate
(SGR) of C. carpio showed a large variance. To understand
the underlying reasons for this variation, we
used multiple regressions for the variables SGR and
survival rate, using the results of eight experiments
in such polycultures at the Co Do rice-fish experimental
station. The SGR of C. carpio declined with increasing
rice density. Interspecific competition with
O. niloticus also had a negative effect on C. carpio
SGR.When fertilizer ormanure is added to the trench
of the rice-fish field or when extra food can be given
to the ¢sh, O. niloticus seems more appropriate than
C. carpio. The survival rate of C. carpio depended on
season, C. carpio stocking weight and density and
the biomass of wild ¢sh species.To obtain higher survival
rates, one should stock fewer ¢sh but of a larger
size, after thorough eradication of wild fish species.