global aquaculture advocate November/December 2010 69
The culture of fish in cages is a promising
aquaculture technology that has
already proven itself in many Asian countries.
However, cage culture is a relatively
novel concept in Bangladesh, with a brief
and mostly unsuccessful history.
Cage culture was first introduced to
Bangladesh
in the late 1970s. A series of
experiments were conducted by the Faculty
of Fisheries, Bangladesh Agricultural
University, and Bangladesh Fisheries
Research Institute. The Department of
Fisheries also conducted a cage culture
project in Kaptai
Lake during 1985 and
1986. The largest cage culture project,
Cage Aquaculture for Greater Economic
Security, was initiated by CARE Bangladesh
in 1995 until 2000.
Despite successfully demonstrated
technology and a considerable number of
people trained through various projects,
cage culture has yet to be widely adopted.
Cage Culture
Cage culture has advantages over
other aquaculture systems that are potentially
important in terms of uptake by
rural poor and landless people. Traditional
aquaculture in Bangladesh has
focused on pond systems that necessitate
the ownership of a water body. However,
a large number of landless poor do not
have access to ponds. The integrity of the
cage unit means that large, communal
water bodies including rivers can be used.
Bangladesh
is called a “land of rivers,”
as the country is crisscrossed with a network
of around 700 rivers and tributaries
totaling 24,140 km. River fisheries in Bangladesh
are characterized as “open-access”
and “common-pool resources.” Hence,
where access to a river can be achieved,
landless people and poor fishers can grow
fish in cages for food and income.
Freshwater Prawns
Although farming of freshwater
prawns, Macrobrachium rosenbergii, in
cages is a new concept in Bangladesh,
many Asian countries including the Philippines,
Thailand
and Vietnam
have
found success with it. Bangladesh is considered
one of the most suitable countries
in the world for prawn culture in ponds
and rice fields, because of its favorable
resources and agroclimatic conditions.
Prawn farming is currently one of the
most important sectors of the national
economy, and during the last three
decades, its development attracted considerable
attention for its export potential.
In 2007-2008, Bangladesh exported
49,317 mt of prawns and shrimp valued
at U.S. $445 million, of which around
25% was contributed by prawns. A large
number of rural poor are associated with
prawn farming in southwest Bangladesh.
A major constraint to the development
of prawn cage culture by poor communities
is the lack of technologies
appropriate to their social, economic and
environmental context. Although the
Department of Fisheries has been keen to
respond to the opportunity for tilapia
cage culture development, Intercooperation
Bangladesh,
a Swiss foundation, is
beginning to show interest for prawn
cage culture.
In association with Bangladesh Agricultural
University, Intercooperation
Bangladesh
has initiated a feasibility
study to establish prawn cage culture in
the Sunamganj area of northeast Bangladesh.
The aim of this study is to develop
prawn cage culture in rivers to benefit
resource-poor fishers and landless people.
Field Assessment
A field survey was recently conducted
by the author to assess prawn farming in
cages on the Surma
River in the Sunamganj
area. After a reconnaissance survey,
the specific site was selected on the
Surma
River and its surrounding
tributaries.
The Surma
River is a major river in
Bangladesh,
part of the Surma-Meghna
River system. The average depth of the
Surma
River is 86 m.
Field data were collected through
focus group discussions with fishers,
landless poor and day laborers, including
Bangladesh
Study Examines Potential
For Prawn Cage Farming In Bangladesh
innovation
Summary:
With its favorable agroclimatic
conditions and water resources,
Bangladesh
is very suitable for
prawn culture. While the country’s
prawn industry is now based
on pond culture, a feasibility
study was conducted to establish
prawn cage culture in northeast
Bangladesh
to benefit resourcepoor
fishers and landless people.
Despite initial planning, a number
of constraints were reported,
including floods, heavy rain, an
inadequate supply of juveniles
and disease.
Nesar Ahmed, Ph.D.
Department of Fisheries Management
Bangladesh
Agricultural University
Mymensingh 2202, Bangladesh
nesar_2000@yahoo.com
Prawn farming is one of the most
important sectors of Bangladesh’s
national economy.
2720 M a Ny/oJuvneem 2b0e1r0/ D e c gemlobbear l2 a01q0u a
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tually, this results in premature harvests, if not total
crop failure.
Advantages, Disadvantages
The advantages of biofloc technology include very high
biosecurity.
To date, white spot syndrome virus has not been a factor
in the systems. Production and carrying capacity are
typically 5
to 10% higher than in typical culture systems, with zero
water
exchange. Shrimp grow larger and reflect feed-conversion
rations between 1.0 to 1.3. Production costs can be 15 to
20%
lower.
The disadvantages include high energy inputs for aerators.
Power failures over an hour in duration can be critical.
Biofloc
ponds must be lined. The more advanced technology also
demands a greater need to properly train technicians.
Growing Interest
Due to success stories in Indonesia and the United States,
many shrimp farmers are interested in biofloc technology.
The
Indonesia Department of Fisheries and shrimp associations
are
arranging a three-day training workshop on biofloc in Indonesia.
Dr. Yoram Avnimelech was invited to lead the workshop in
April.
In China,
a number of shrimp farmers are also interested.
Their fully HDPE-lined, plastic-covered shrimp growout ponds
with high-density culture are ideal for the technology. The
author is currently advising shrimp farms with HDPE-lined
intensive culture ponds in Central
America on biofloc systems.
A group from Brazil
is running commercial biofloc trials.
Malaysia
is currently initiating a 1,000-ha integrated intensive
shrimp-farming project at Setiu, Terengganu by Blue
Archipelago. The company also plans to use the technology.
GOAL
2010
Plan Now To Attend
Network with aquaculture production and market
leaders, and examine issues and solutions at GOAL 2010.
Kuala Lumpur
offers a casual tropical atmosphere with
easy access and affordable accommodations.
Additional information will follow with invitations to GAA
members and past GOAL participants.
Co-hosted by the Malaysia Department of Fisheries
October 2010 –
Kuala Lumpur,
Malaysia
®
global aquaculture
women, on the banks of the Surma River
and in fishers’ houses. A total of 121 people
were conducted through 10 discussion
sessions, where each group consisted of
10-15 persons, and the duration of each
session was approximately an hour.
Focus group discussions were used to
get information on the attitudes of people
regarding prawn cage culture, its possible
constraints, socioeconomic benefits and
environmental issues. Cross-check interviews
were conducted with 15 key informants,
including government fisheries
officers, researchers, policy makers and
non-governmental organization workers.
High Interest
Most respondents were keen to get
involved with prawn cage culture, because
prawns are high-value fish. It is reported
that the current local market price for
prawns (U.S. $4-6/kg) is four to five
times higher than those for Indian major
carp or tilapia.
Moreover, fishers reported that their
income from fishing has fallen due to
declined catch because of overfishing, use
of destructive fishing gear, environmental
degradation, siltation and human
encroachment. On the other hand, fishers
suggested that cage culture may
require relatively modest investment, as
cages can be made locally with available
bamboo and netting.
Culture Planning
A 120-day culture period was planned
for the growout of prawns in cages. In
general, longer culture periods produce
larger prawns that may get higher market
prices. Nevertheless, two production
With access to a river, landless people and poor fishers can
grow fish in cages for food
and income.
global aquaculture advocate November/December 2010 71
cycles per year – from April to November
– were recommended to get higher economic
returns.
It was planned to stock large juveniles
in order to maximize the growing season,
and hence increase production as well as
profit. Prawn juveniles can be purchased
from prawn hatcheries, mostly located in
southwest Bangladesh.
Higher production of prawns in cages
can be achieved if commercial feeds are
used. However, a complete pelleted diet
may not be affordable for resource-poor
fishers. In these cases, locally available
feed ingredients including rice bran,
wheat bran, mustard oil cake, and fishmeal
can be used. Snail meat is widely
applied as shrimp feed in southwest Bangladesh,
where farmers obtain higher
prawn yields and lower production costs
than when using homemade feed.
Other aspects of prawn cage culture,
including cage setup, stocking procedures,
feeding schedule and partial harvesting
of larger prawns were planned.
Moreover, care of cages – cleaning of
aquatic weeds, waste feed and deposited
silt; removal of water hyacinths; checking
cage frames and feeding trays; and monitoring
of water quality – were proposed.
It was also thought to consider prawn
health and disease monitoring throughout
the culture period.
Constraints
Despite the planning for prawn cage
culture, a number of constraints were
reported, including floods, heavy rain,
inadequate supply of juveniles and disease.
On a trail basis, a number of cages
were set up on the Surma River.
However,
a sudden flash flood from the hilly
region affected all cages. Every year the
Surma floods leave thousands of fishers
homeless. It is therefore recognized that
prawn cage culture on the Surma River
may be impossible.
According to key informants, the
floods deteriorate water quality significantly
and increase water turbidity, which
may not be suitable for prawn farming in
cages. Most also suggested that diseases
may be an important issue for prawn culture
in cages. Moreover, supply of adequate
prawn fry from a long distance is
difficult. With these views, all key informants
suggested that prawn cage culture
may not be suitable in the present context
of Bangladesh.
Future Prospects
Despite the success of prawn cage
culture in many Asian countries, Bangladesh
is still behind in this opportunity.
Nevertheless, small-scale tilapia culture in
cages has been successful in some places
of Bangladesh.
Farming tilapia together
with prawns in cages may be an option.
Since tilapia and prawns belong to
different food niches, they can live
together without competing for food, and
thus it would be possible to get higher
yields without increasing the amount of
feed. However, concern may arise about
the sustainability of cage culture. It is
suggested that any initiatives to promote
cage aquaculture must consider social,
economic and technological aspects along
with environmental capacity.
Farming prawns
together with
tilapia may be an
option for more
successful prawn
cage culture.
Since tilapia and prawns
belong to different food
niches, they can live together
without competing
for food, and thus it would
be possible to get higher
yields without increasing
the amount of feed.
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