Shelter trap to capture freshwater prawns. Harvesting prawns.
This system is suitable for the present
socioeconomic and market situation in
Vietnam but is relatively recent and has
potential for considerable improvement.
Il relies on the availability Ofjuvcniles,
most of which still come from natural
recruitment. The demand for live juveniles
has created a large and important sector
of freshwater prawn fisheries. Seed
supplies from prawn hatcheries are still
extremely limited, although a couple of
government hatcheries have been recently
built in Vung Tau and Nha Be.
Integrated Vegetable-Prawn Culture
One type of semi-intensive small-
scale prawn culture practised in Vietnam
is the vegctabld-prawn farming system
(Fig. 2). A typical complex, converted
Fig. 2. Vegetable-prawn integrated
culture system.
from a 2,000-m2 riccficld, consists of
ditches for prawn rearing, and platforms
and levées for VcgetabIesand fruit trees.
As the complex is connected directly
to an irrigation canal from the river, the
farmer is able to change pond water
with tidal cycles. Juvenile prawns,
collected from natural waters, are stocked
at 4-6 animals∕m2, and fed twice daily
with a mash of rice bran, cassava chips
and trash fish. Normally, each crop
produces approximately 1OO kg of prawns
every six months and the estimated gross
annual income from prawn culture is
USS300-400, which is three to four times
the income derived from a similar sized
riccficld. In addition, several varieties
of vegetables are planted including
cucumber, eggplant, stringbean and
banana, to provide supplementary income
as well as for domestic consumption.
Such diversification from rice
monoculture has been initiated recently
and already is popular among farmers.
The main constraints to expansion of
this farming system arc lack of capital
to start, shortage Ofjuvenilcs for pond
stocking and inadequate extension
services.
APRIL 1992
25