Abstract:
An experiment was carried out to evaluate the impact of pond sizes on the production potential of mola,
Amblypharyngodon mola with carps for a period of 5 months from mid August 2003 to mid January 2004 at
Sreepur Upazila in Gazipur district. Fifteen ponds were divided into three treatments each with five replicates.
Rohu (Labeo rohita), catla iCatla catla), mrigal iCirrhinus cirrhosusi and exotic silver carp
iHypophthalnnchthys molitrix) were stocked at the stocking densities of 10,0001ha at the ratio of I :0.5:0.5: I,
while small indigenous fish mola (Amblypharyngodon mo/a) were stocked at 25,0001ha and grass carp
(Ctenopharyngodon ide/la) was stocked at 5001ha. Major carps and mola were common in all treatments. All
ponds were subjected to same regime of feeding and fertilization. The commonly available agricultural
byproduct rice bran (100%) was used once per day as supplementary feed at the rate of 3% body weight of
standing crop of fish. Soft grasses and banana leaves were supplied for grass carp on daily basis up to satiation.
All ponds were fertilized with manure (cow dung) at the rate of 1,000 kg/ha at fortnightly intervals. All feeds
and fertilizer inputs were supplied from farmers' households. Various water quality parameters such as water
temperature, transparency, dissolved oxygen, pH, alkalinity and chlorophyll-a were monitored at monthly
interval and found almost similar in three treatments. The mean values of various water quality parameters were
within the suitable ranges for freshwater aquaculture in Bangladesh. The survival rates of carp species were
fairly high and ranged from 79.63 to 91.67%. The production of carps and small fish were together 2,413.25,
2,492.94 and 2,346.66 kg/ha in treatments 1,2 and 3, respectively, which were not significantly different. The
overall best production was obtained in Treatment 2 where the pond size was 10-20 decimal. It was observed
that if partial harvesting is made, polyculture of major carps with small fish, mol a is a better proposition in
terms of biological, nutritional and economic point of view. The farmers can keep the small fish for their family
consumption and can sell the large carps as cash crop.
