(32) A research plan for BFRS was to be prepared after final
selection of the site. The final selection of the site is still
awaited, however. Since a number of the elements of the future
research plan can be considered site-independent (they have high
priority and have to be done anyway), the general plan is presented
here. Much of the detailing will have to be done after final site
selection.
(33) The status of the shrimp culture in Bangladesh as well
as the characteristics of the soil, as stated above, call for the
development of a short-term research plan to meet the immediate needs
of the producing industry, and a long-term research programme for
higher sustained production per unit area under culture.
(34) As stated, this type of research is meant to solve the
immediate needs and problems of the shrimp producing industry. The
major constraints faced by this industry are:
- non-availability of shrimp and/or fish seeds (in time and quantity)
for stocking purposes;
- low survival rates of shrimp in culture operations, resulting in low
production levels;
- the attempts to culture mainly (only) tiger shrimps, Penaeus
monodon, in stead of attempts for better utilization of the aquatic
resources through culture of different candidate species.
In order to combat these immediate problems, BFRS should
tackle the research areas as described hereunder.
(35) Prospects should be investigated for seed resources in
hitherto unexploited river systems. This includes determination of
their seasons of peak abundance, and the physico-chemical and hydrodynamic
parameters influencing that abundance.
The physico-chemical parameters to be studied are:
- water temperature;
- turbidity;
- dissolved oxygen;
- water column (depth of maximum concentration of seeds);
- prevailing salinity.
The hydro-dynamic conditions to be studied are mainly the
flow pattern and the current velocity during different phases of the
rising and ebbing tides, and their relation to the abundance of seed
availability.
(36) The generally tiny seeds (postlarvae) remain in shallow
waters where the current is very mild and where food organisms are
available in abundance. These are drifted to and fro in the estuary
along the marginal waters during the tidal rise and fall. As the
inflow increases the estuary swells and inundates shallow or somewhat
deep depressions and borrow pits in the inter-tide regions. Some of
the flowing seed find shelter in these depressions where thy stay back
and grow. Others toss about with inflowing and receeding tidal
currents. For development of good collection practices it is necessary
that both these environments be expoited.
(37) The present procedures for collection are:
- Shooting net or Behundijal. This is a funnel-shaped net of finely
woven netting material (cotton, nylon or HDP);
- Fyke net. This is usually a shallow water gear. It is also a funnelshaped
net made of fine mesh material with bigger to smaller “rings”
at intervals;
- Hapa net. This is a simple rectangular cloth piece bag made of
beehive type mosquito netting, pulled by two men. It can be used in
shallow, stagnant and swampy areas;
- Dip net. This may be either triangular or circular. The cloth used
should be fine meshed and the frame made of split bamboo or cane;
- Bush method or ‘Bon Bon’ method. This method is practised in deep
depressions of stagnant water or borrow pits, where small plants
and/or tree branches or hay are tied together and kept in water, in
which the young shrimp larvae take shelter. The fishermen slowly
draw the branches near the banks, take them out of water, put a net
below it and shake them. The shrimp sticking to the branches thus
fall on the net and are immediately collected.
(38) None of these methods is expected to be suitable under
different environmental conditions. Therefore, it is needed to take
up a well-designed investigation on statistical principles for
ascertaining the best method of collection under a given set of
conditions.
(39) Transportation of seed from the collection centre to
the fishery proves to be a major constraint. As stated earlier, hardly
50% of the collected seed survive upto the release in the fishery. On
release, it is likely that there is further mortality if the seed are
not properly acclimatized.
It is therefore worthwhile to investigate the proper
salinity level at which the seed survive best under transportation
when packed in oxygen bags. The use of different anaesthesia for
better survival during transportation can be included in this research
project, including their economics. Moreover, the best system of
aclimatizing the transported seed to the prevailing temperature and
salinity of the fish farm in which they are proposed to be released
has to be sorted out.
(40) The low survival rate in culture operations may be due
to various factors which should be properly investigated and
eliminated. A number of these factors are discussed hereunder:
- Saline soils are considered to be low in productivity and the
productivity decreases with increase in soil salinity. In spite of
presence of adequate quantities of nutrients, these are not released
to be made available for organic growth;
- Very often some predators, undesirable bottom dwellers and burrowers
bury themselves deep into the pond bed and escape destruction during
drying operations;
- The quality of pond water determines the quality and health of the
shrimp stock under cultivation. Good quality water for aquaculture
purposes should not be overloaded with metabolites produced by
crowded shrimp stock and should be free from pollutants of various
sorts. Turbid or silt laden waters are also unfit for raising
brackishwater shrimp. If the water is of low quality, the shrimp
stock turns weak and becomes more vulnerable to diseases and
parasites. Some investigators believe that poor quality of the water
causes a stress to the cultivated stock. There are a number of ways
to improve the quality of pond water. Adequate aeration is a major
factor in this regard.
(41) To tackle these factors, it is needed to start a
research programme in which their typical effects are analyzed in
relation to survival rates. This programme could emphasize in first
instance:
- the impact of salinity changes on the availability of nutrients and
oxygen in grow-out ponds during the culture seasons;
- proper pond preparation practices for complete eradication of
unwanted organisms either through use of organic toxicants, if
locally available, or by mechanical means;
- causes for deterioration of water quality in time and space;
- the relation between environmental quality and the occurrence of
diseases and parasites;
- the relation between environmental quality and growth (leading
towards optimum habitat development).
(42) In addition to the factors mentioned before, nursery
rearing of seeds before release in the fishery can decrease later
mortality and, as such, can play a dominant role in increasing
production. Nursery rearing is not a well-organized practice in
brackishwater farming in Bangladesh, due to the inherent practice of
culturing stocks mainly by trapping.
The important steps for nursery rearing are:
- preparation of nursery ponds to receive the stocking material;
- conditioning of the stocking material to respond to the conditions
prevailing in the nursery ponds.
Best nursing practices have to be developed through a
research project. Experiments are either to be done in separate
earthen ponds or in pens (or hapa's) within the main fishery. Both
systems are possible in the farmers' practice: if there is contiguous
area available by the side of the fishery through which proper flow of
water can be maintained without dead space, separate nursery ponds may
be created, otherwise it may be worthwhile to take up nursery
management in pens created within the fishery itself.
(43) The factors to be investigated for nursery development
should be:
- determination of the stocking density of postlarvae to give maximum
survival and growth in minimum time;
- influence of salinity and temperature changes on the rate of growth
and survival;
- development of methods for removal of metabolite wastes;
- impact of supplemental feed on growth and survival.
(44) There is a tendency to culture mainly P. monodon in all
coastal areas of the country. Perhaps this is due to the fact that the
farmers know something about its habits and feel confident to culture
this species. There are a number of other species, however, which are
available in Bangladesh and which demand thorough research into the
development of their culture techniques.
(45) In the semi-saline zone and in the fresh water region
Macrobrachium rosenbergii, the Giant fresh water shrimp, is one such
species which deserves urgent consideration. Unlike many other
countries, Bangladesh has got a rich natural fishery for Macrobrachium
and seed of this species is available in excess in different regions.
Moreover, many of the country's culture habitats are expected to have
environmental conditions that are more suitable for culture of this
species than of P. monodon. Therefore it is necessary to develop
suitable culture technologies for the different agro-climatic
conditions in Bangladesh, so that this resource can better be utilized.
(46) Similarly, the development of culture techniques for
other shrimp species, like Penaeus semisulcatus, P. indicus and
P. merguensis, deserves immediate consideration. These species prefer
slightly higher salinities than P. monodon, and are therefore
culturable in the coastal regions. Also development of polyculture of
these species can be included in the research programme.
(47) In addition, development of a suitable technique for
polyculture of fin-fish and shrimp may be given consideration. Since
the brackishwater environment is unstable in nature, selection of
candidate species for polyculture, has to be based on the following
criteria:
- They should tolerate fluctuations in the salinity and temperature
prevalent during the period of culture;
- They should adapt themselves to the prevailing conditions of the
fishery during the period of culture and should grow well;
- Their seed should be available easily in the near vicinity of the
farming site;
- They should readily take to supplementary feeding, if need be;
- They should not compete for food and/or space with each other;
- They should be easily accepted in the market and fetch a good price,
commensurate with the cost of production.
It is recommended, that a survey of suitable species and
their culture opportunities be carried out as a part of the short-term
research programme.
(48) Precise detailing of the long-term research plan can
only be done efficiently after the final site selection. Since,
however, needed facilities have to be known for the selection itself,
a rough outline for a long-term research plan is presented hereunder.
(49) This programme is directed towards understanding of the
interactions between biological, physical and chemical parameters that
influence the productivity under different salinity and temperature
regimes. The studies envisaged will include:
- Determination of the thermal characteristics of the brackishwater
environment and its interaction with aquatic life;
- Determination of rates of change in concentrations of 02 and CO2 in
relation to the system' temperature, salinity and photosynthetic
activity (in the season as well as between seasons); determination
of relations between those concentrations and aquatic productivity;
- Estimation of standing crop in the brackishwater (pond-) system and
its influence on the culture of organisms;
- Estimation of the productivity under different salinity, and
temperature levels as prevalent in ponds; determination of the
optimal relation between these parameters.
(50) Development of suitable fertilization schemes is
expected to be necessary for improvement of natural water fertility
and productivity. The research programme will be directed towards:
- Estimation of available nutrient cycles in the soil and water phases
of the aquaculture ponds between seasons and at different levels of
salinity. To be studied are at least the organic content, the
nitrogen cycle, the phosphorus cycle, the carbon cycle and the
calcium cycle. In addition, iron and sulfur cycles should be studied
in mangrove ecosystems or potential acid sulphate soil environments;
- Determination of the effect of available nutrients on the living
system (incl. establishment of Liebig's “Law of minimum” and
determination of “luxury uptake” of nutrients by phyto-organisms);
- Determination of critical nutrient levels for production under
different salinities and temperatures;
- Determination of effects of deficiencies in nutrients in
statistically designed experiments; determination of the
requirements for each particular nutrient to reach the level of
“critical concentration” and/or “luxury uptake”;
- Development of fertilization schemes based on the nutrient
requirements and their interactions, and directed towards optimum
production under different environmental circumstances.
(51) This programme is directed towards development and
testing of suitable supplementary feeds for post-larvae, juveniles and
growing shrimp as well as the development of feeding methodology. The
studies will include:
- Identification and quantitative estimation of the composition of
natural food for post-larvae, juveniles and growing shrimp under
captivity, vis-a-vis those of the flowing system;
- Determination of the nutritional requirements of post-larvae,
juveniles and growing shrimp; the requirements concern total
protein, amino acids, fatty acids, sterols, phospholipids and
various minerals under different agro-climatic conditions and
salinity levels;
- Culture of preferred live food items for post-larvae and juveniles,
viz. unicellular algae, marine yeast, rotifers and copepods;
development of appropriate culture media as far as possible based on
local available products;
- Isolation and maintenance of stock cultures for mass production of
the required food organisms;
- Formulation of artificial diets from as far as possible local
available ingredients for post-larvae, juveniles and growing shrimp
in relation to their nutritional requirements (particularly
essential amino acids, fatty acids, phospholipids and vitamins);
effects of different binders on the stability and leaching of
nutrients (this research programme will have to be carried out as
part of the nutrition research at FARS, Mymensingh);
- Determination of the utilization rate of formulated dry, semi-moist
and moist diets by post-larvae, juveniles and growing shrimp under
different agro-climatic conditions;
- Determination of the shelf-life of the formulated feeds and of
possible changes in composition during storage;
- Determination of the effects of type of feed formulation, feeding
levels and frequency, and of stocking density on the growth, feed
efficiency and survival of juveniles and growing shrimp;
- Estimation of the pattern of digestion and absorbtion of different
ingredients from various formulated feeds.
(52) This programme concerns studies of the micro-biological
conditions in the pond bed and of the impact of fertilization and
supplemental feeding on these conditions:
- Establishment of the depth of the euphotic zone in brackishwater
ponds under different salinity levels and agro-climatic conditions;
- Determination of primary production at different depths within the
euphotic zone;
- Determination of respiration at different depths;
- Determination of bacterial growth by measurement/estimation of
bacterial respiration;
- Determination of effects of pond management (particularly feeding
and fertilization) on primary production and total respiration in
the pond and on bacterial growth at the bottom;
- Determination of the growth of meiofauna and macrofauna;
- Determination of effects of fertilization and feeding on the organic
contents of the pond sediment, especially with respect to promotion
of anaerobic processes, like sulphate reduction;
- Determination of the relationship between bacteria and meiofauna
under different management regimes, like fertilization, supplemental
feeding, both, or none of them;
- Estimation of the optimal status of organic matter, meiofauna
production and bacterial production with respect to the maintenance
of good quality pond water for survival and growth of organisms to
be cultured.
(53) This programme aims at the development of stocking
policies for monoculture and polyculture of shrimp and brackishwater
fin fish as well as for integrated farming systems. This programme is
a follow-up of the short-term programme mentioned under section 4.2.7
and also of the research projects on paddy-cum-fish/shrimp culture
that are planned to be carried out at RFRS, Chandpur. The following
elements will be included in the long-term studies:
- Detailed determination of the fishery biology of the candidate
species for the various culture systems, particularly with reference
to their food preference, habitat preference, range of salinity, and
their preference for temperature and dissolved oxygen levels;
- Determination of optimum sizes for stocking for the various culture
systems;
- Determination of optimum stocking densities and ratios for the
candidate organisms for the various culture systems;
- Development of a system of stock manipulation for improved
production in mono- and in polyculture;
- Determination of the physical, chemical and biological parameters of
the environment that play a role in the possible integration of
agriculture and aquaculture in the semi-saline regio, as well as for
the integration of salt production and aquaculture in the saline
zone of the country;
- Determination of the physical, chemical and biological parameters of
the mangrove ecosystem for better utilization of that environment in
integration of aquaculture and silviculture (forestry).
(54) This programme, following the short-term programme of
4.2.2, aims at the development of small-scale hatchery technology for
shrimp. The following elements can be distinguished:
- Determination of the reproductive biology/physiology of the shrimp
species concerned;
- Development of optimum procurement and transportation procedures for
mature shrimp;
- Development of maturation procedures for cultured shrimp by e.g.
eye-stalk ablation techniques;
- Development of cost-effective holding facilities and water supply
and treatment systems;
- Determination of procedures for breeding, hatching and nursing in
the facilities developed;
- Development of simple methodologies for growing of live food for
shrimp larvae in different stages of development;
- Development of feeding techniques;
- Demonstration at field/farmers level.
(55) The objective of this programme is to develop a farm
design, that will create optimum production possibilities under
typical Bangladesh circumstances. The programme will have to be based
on the outcome of a number of the previously mentioned projects and on
achievements reached in other countries. Elements will be:
- Development of cost-effective water exchange structures;
- Development of a system for siltation control and proper
distribution of water (removal of dead space);
- Determination of optimum pond size for different production phases
and integration of various pond sizes into a farm model (modular
farming system);
- Development of specialized farms for larval stunting, nursing and
for culture of special products.
(56) Surveys of reproduction areas and larval movements of
Macrobrachium are included (for the time being) in the research
programme of RFRS, Chandpur. After establishment of BFRS this
programme should be transfered and supplemented with the same type of
research with respect to the penaeid shrimp species. Elements of this
programme will include:
- Survey of places of larval concentrations in space and time;
- Analysis of larval movements and their triggering mechanisms (both
anadromous and katadromous);
- Analysis of the impact of environmental changes on the availability
of shrimp larvae;
- Development of a field key for identification of shrimp larvae.
(57) Presently, shrimp culture causes a number of socio-economic
problems in the south-west region of Bangladesh, mainly
caused by the facts that small farmers are deprived from areas for
freshwater stocking, cattle grazing and fruit growing, and that rich
landowners from elsewhere obtain more and more influence. These social
and economic disturbances will have to be analyzed consciously, and
solutions to overcome them will have to be worked out.
Because of the typical expertise needed for this kind of
research it is suggested to carry it out under the responsibility of
the socio-economic programme at FARS, Mymensingh. Researchers from
that programme can be stationed at BFRS on deputation.
