Abstract
Globally the quality and high price of fish feed are important issues for sustainable aquaculture that
warrants the development of low-cost culture systems utilizing natural resources. To develop a low-cost
aquaculture, the present research was conducted in the tidally inundated low-lying coastal wetlands of
Bangladesh utilizing Asian watergrass, Hygrory:a aristata as fish feed. Firstly, the ecology, growth
performance and nutritional status of the grass were evaluated. It was found that the coastal wetlands of
Bangladesh having available nutrients in both water and soil are suitable for higher growth and production
of the Asian watergrass. Reasonably higher content of protein, carbohydrate and minerals were found in
the grass. In the second experiment, the feasibility of the Asian watergrass in culture of the grass carp
(Ctenopharyngodon idella) was examined at a stocking density of 12500 fish ha-l using the grass as feed
directly under three treatments. The grass was planted during plot preparation in treatment one (grass
planted; GP), the grass was collected those grown in an adjacent land and supplied to the fish in treatment
two (grass supplied; GS), and the fish were fed with commercial feed in treatment three (commercial feed;
CD. The highest total production was found in GP (6770 424 kg ha•l). followed by CF (6733 ± 536 kg
ha-1) and GS (5519 ± 483 kg ha-l). The net economic benefit and benefit-cost ratio were found highest in
GP (USS 13375.50 ha-l and 3.32) and the lowest in CF (USS 4958.25 ha•l and 0.42). In the third
experiment, the performance of the grass in polyculure of gmss carp, common carp, black carp and tilapia
with a stocking ratio of was done at a total stocking density of 12500 fish ha-t under the same
number of treatments and replications as in the second experiment. The total production of fish was highest
in GP (9060.70 kg year-I), followed by CF (8469.70 kg year•l) and GS (8001.23 kg haa year-I).
•Ille net economic INnefit and benefit-cost ratio were also highest in GP (USS 17994.96 ha•l and 4.52),
followed by GS CUSS 14261.11 ha•l and 2.78) and CF (USS 4818.63 and 0.32). the fourth
experiment, to get a better species combination in polyculture of fish using the Asian watergrass as feed
the study was done under four treatments for 6 months. Stocking density was same in each treatment
(12500 fish ha-l) but the combinations were different among the treatments (in treatment one, T l:
grass carp 53, common carp 7, tilapia 8, mrigal 7; in T2: grass carp 53, common carp 7, silver barb 8,
mrigal 7; in T3: grass carp 53, common carp 7, tilapia 8, silver barb 7; and in T,: grass carp 53, common
carp 5, tilapia 7, mrigal 5 and silver barb 5). The growth and the total production were significantly
(p<0.05) highest in Ta (5579.04 kg ha-1 6 m") among the treatments. The findings indicated that the
combination of four species, grass carp: common carp: tilapia: silver barb at the ratio of may be
ideal in polyculture of fishes in coastal wetlands using Asian watergrass as fish feed. •Ille research findings
indicated that the coastal wetlands of Bangladesh can be used for commercial aquaculture using Asian
watergrass as fish feed and this culture technique can significantly reduce the fish production cost and play
an important role in the livelihood development of the people living in the coastal areas of the country.