PREFACE
A. REGIONAL AQUACULTURE LEAD CENTRE, DHAULI (BHUBANESWAR) INDIA
B. REGIONAL AQUACULTURE LEAD CENTRE, BANGKOK, THAILAND
One of the major objectives of the UNDP/FAO project for the establishment of a Regional Network of Aquaculture Centres in Asia is the organization of systems-oriented multidisciplinary research for solving the problems faced in the wider application of production or farming systems that have been selected by the countries of the region for large-scale aquaculture development (see Aquaculture Planning in Asia - Report of the Regional Workshop on Aquaculture Planning in Asia, Bangkok, Thailand, 1-17 October 1975. ADCP/REP/76/2: 154 p). It was intended as a support service along with training of key personnel and information dissemination, to accelerate investment in the aquaculture sector and increase production in a reasonably short period of time. Under the project's work plan, one of the first activities proposed was 'the detailed planning of research in the Lead Centres with the help of a team of experts' and identification of the facilities and equipment required for the implementation of the proposed research.
The Aquaculture Development and Coordination Programme (ADCP), responsible for the organization of the regional project, fielded a task force consisting of the following members to carry out these preparatory activities, in respect of two of the Lead Centres: viz. the National Inland Fisheries Institute in Bangkok, Thailand, and the Freshwater Aquaculture Research and Training Centre of the Central Inland Fisheries Research Institute in Dhauli (Bhubaneswar), Orissa, India:
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Dr. N. Fijan |
(Yugoslavia) |
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Dr. J. Olah |
(Hungary) |
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Dr. V.R.P. Sinha |
(India) |
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Dr. P. Suraswade |
(Thailand) |
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Dr. V. Varikul |
(Thailand) |
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Mr. R. Neal |
(U.S.A.) (for Thailand only) |
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Dr. B. Hepher |
(Israel) (for India only) |
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Mrs. M. Delmendo |
(FAO) (for Thailand only) |
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Dr. K.W. Chow |
(FAO) |
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Dr. T.V.R. Pillay |
(FAO) |
Dr. Michael New and Dr. Alex Fedoruk, FAO/UNDP experts working in Thailand, also participated in the discussions and research programme formulation in Thailand.
The task force spent considerable time with the research and extension staff of the two institutions and other agencies concerned; some field visits were made to supplement the information collected through informal and free discussions.
Both the institutions designated as Lead Centres have a wide range of activities, but the farming systems selected for research are high-priority interest items to them as well as the region as a whole. However, there are some significant differences in the involvement of scientific staff in research in the two institutions. The scientific staff of the National Inland Fisheries Institute in Bangkok combines technical services and extension work with research, whereas research and extension work, are to a large extent separated in the Central Inland Fisheries Research Institute in India. The task force did not, therefore, attempt to formulate a uniform approach to research within the two institutions. Instead, programmes were recommended that can be carried out within the existing framework, with possible strengthening and external assistance. In each case, the benefits that can be derived by the host country and the other participating countries of the region, within a reasonably short period of time, were given special consideration.
Although many problems worthy of research could be identified for each aquaculture system, an attempt was made to determine priorities. The research proposals are limited to areas that promise the greatest short-term and medium-term benefits. A major consideration in the formulation of research programmes was the feasibility of the application of improved technologies developed as a result of the proposed research. The general time-frame used for planning was a two-year start-up period followed by a five-year period of concentrated research The task force has limited itself to suggesting research approaches. The actual detailed design of experiments and observations will, naturally, be the responsibility of the multidisciplinary teams to be established for research on each farming system or specified research aspect. It is expected that the services of senior consultants can be made available to assist in this task, as well as to initiate the research programme. If required, external expertise may have to be made available during the course of the investigations and towards the end of the start-up period to evaluate the work and suggest any needed changes in priorities and future approaches.
Even though the task force has, in every case, recommended a multi-disciplinary systems approach to research aimed at improving selected farming systems, it has also considered and emphasized the basic need for the development of essential capabilities in the disciplines involved and the laboratory and field facilities required for research in these disciplines. The task force lays special emphasis on some of the disciplines that are generally not adequately covered in aquaculture institutions such as engineering, economics, and feed technology, even though these may not have been specifically mentioned under the research requirements.
Besides the expertise necessary for developing appropriate designs of fish farms, hatcheries, raceways, cages, pens, etc., there is also a need for the development of suitable farm implements and harvesting devices. Cost-benefit analysis should form an integral part of each of the proposed experiments and should be considered as an important item of research concerning each farming system. Economic studies of farming operations must also be carried out to determine the minimum economic size of farms and enterprises. Similarly, surveys of locally available feed ingredients, determination of the nutritive values of the feed ingredients, and the formulation, preparation, and testing of least-cost feeds for various life stages of the cultivated animals, should form a basic activity in each of the institutions. Experimental and pilot-scale feed mills will be necessary for such work.
Although much of the feed technology work would initially be based on the nutritional requirements of the few warm-water fishes and crustaceans that have already been studied, it is necessary to start nutrition and food requirement studies of the species utilized in the selected farming systems as soon as possible. Similarly, expertise and facilities for diagnosis and treatment of diseases will have to be strengthened in the institutions in order that they participate effectively in integrated research programmes
Though in early research on aquaculture in the region, some attention was given to the hydrobiology of ponds, relatively little work has been done on the management of ecosystems in cultivated water bodies. An understanding of the structure and functioning of such ecosystems, including the production processes, can provide the scientific basis for proper management of a culture system. It is, therefore, necessary to develop or strengthen the capability and facilities for such work.
1. INTRODUCTION
2. BACKGROUND
3. RESEARCH NEEDS
4. RESEARCH APPROACH
The culture systems proposed for study in the Regional Aquaculture Lead Centre at the Freshwater Aquaculture Research and Training Centre at Dhauli (Bhubaneswar) are:
(i) mono- and polyculture of Indian, Chinese, and common carps in ponds,
(ii) systems of carp culture in undrainable, freshwater ponds, and
(iii) culture of carps in reservoirs.
The Central Inland Fisheries Research Institute (CIFRI) from its inception in 1947, has given very high priority to research on problems relating to carp culture. At present, 65 of its research projects relate to this sector of inland fishery work. The Institute, through its Freshwater Fish Culture Division, has done some very outstanding work in the development of carp culture technologies, although greatly handicapped by the lack of adequate experimental and laboratory facilities. The All-India Coordinated Research Project on composite fish culture and fish seed production, operational research projects, and rural aquaculture projects implemented during the last eight years, has given the Institute opportunities to test technologies under field conditions in different states in India and also to carry out adaptive research.
The construction of the Freshwater Aquaculture Research Centre in Dhauli, which is expected to become operational in 1980, will make available to the Institute for the first time, the necessary facilities for well-planned laboratory and field research required for upgrading the technologies involved. The Dhauli centre will have 656 experimental ponds of different sizes, a modern hatchery, a feed mill, 32 laboratories, an aquarium, wet laboratories, cisterns, plastic pools, fibre-glass tanks, a raceway, workshop, and other ancillary facilities. There will be a total of 62 scientists and 94 supporting technical staff of different categories. A farmers' training centre (Krishi Vigyan Kendra) and Trainers' Training Centre are also attached to the Dhauli centre; this would give the research centre greater exposure to the problems of application of technologies in the field and extension work among the farmers. The concept of multidisciplinary systems-oriented research is already accepted and implemented in the Institute. The staffing of the Dhauli centre, with possible strengthening and adjustments, could provide the services of disciplinal units/groups concerned with aquaculture engineering, fish breeding and seed production, genetics, limnology and pond management, nutrition and feed technology, fish pathology, statistics, and economics. It is necessary to develop the laboratory and field facilities for research in these disciplines, to enable effective interdisciplinary investigations.
The centre will receive UNDP/FAO assistance under the country project 'Intensification of Freshwater Fish Culture and Training (IND/75/031)' in the form of equipment, fellowships, and short-term consultants to (a) strengthen the central research, training, and demonstration facilities required to sustain the future development of freshwater aquaculture at the national level, (b) train the highly specialized staff required for the purpose, and (c) formulate and implement realistic research and demonstration programmes the existing gaps in fish culture technology as well as directed toward the aimed at filling transfer of the newly developed technologies to the producer. The regional project for the Establishment of an Aquaculture Network in Asia (RAS/76/003) will expand and strengthen the national research on carp culture to meet regional needs within an extended time-frame, providing, in addition, essential support for the national development activities in this sector. As the facilities of the Dhauli centre for work on carp culture in reservoirs are limited, investigations on this system will have to be organized at a selected reservoir near Dhauli, for example, Hirakund in Orissa.
2.1 Cultivated Species and Species Combinations
2.2 Fish Farms and the Use of Multipurpose Ponds for Fish Culture
2.3 Breeding, Seed Production and Genetics
2.4 Predator and Weed Control
2.5 Fertilizing and Feeding
2.6 Health Protection
2.7 Harvesting and Economics
2.8 Culture of Carps in Reservoirs
The pond culture of Indian, Chinese and the common carps is probably the most
ancient system of aquaculture in Asia, although its importance and contribution
to fish production differ considerably among the various countries of the region.
There are plans for the expansion of carp culture in almost all the countries
through the transfer of existing technologies and their adaptation and improvement
through research.
The traditional form of carp culture in South Asia is based on the so-called Indian major carps, catla (Catla catla), rohu (Labeo rohita), mrigal (Cirrhina mrigala), and calbas (Labeo calbasu). The three varieties of common carp (Cyprinus carpio) were introduced into India almost a century ago for culture in certain areas, but the interest in the culture of exotic carps became substantial only some two decades ago with the introduction of the Chinese carps (grass carp, Ctenopharyngodon idella, and silver carp, Hypophthalmichthyus molitrix). As the Indian major carps, like the Chinese carps, do not breed in stagnant ponds and generally spawn only in their natural habitat, the farmers had to obtain the seed in the form of eggs, hatchlings, and fry from rivers. The seed of all the species occurred together in nature and could not be sorted out easily according to species. The farmers, therefore, collected and cultured them together in ponds. Thus a system of polyculture evolved.
The zonation in their feeding habits; catla feeding largely on the surface and the mrigal and calbasu at the bottom (the latter feeding also on snails) gave a scientific basis for this combination of species. The CIFRI has conducted considerable research on the species ratios and stocking densities that give high yields under a series of culture conditions. In recent years this species combination has been enlarged to include the Chinese and common carps, generally omitting the calbas. In experimental and demonstrations ponds, CIFRI has obtained a rate of production of up to 10 000 kg/ha per annum with fertilization and supplemental feeding. However, the wide-scale adoption of this practice by farmers would obviously depend on the availability of fry or fingerlings of the various species at the appropriate time and in sufficient numbers. The complexity of culture is also obviously increased when a larger number of species with differing habits and requirements have to be cultured together.
Although the benefits of polyculture are widely accepted and high production
has been obtained, it has not yet been established that the combination of species
now adopted is the most appropriate one, particularly in view of the overlap
of feeding habits of some of the species. It has also not been experimentally
proved that monoculture will not yield high and economically acceptable production,
rendering the overall culture operations simpler. On the other hand, in areas
where the ponds are infested by a large snail population, the addition of a
snail feeding fish like the pangas (Pangasius spp.), which has been shown
to be a good culturable species, may prove valuable. This could replace the
slow-growing calbas, which is now generally omitted from the species combinations.
An important feature of carp culture in the countries of South Asia is the use of ponds and other water bodies constructed for other uses, instead of well laid-out fish farms with dependable sources of water supply. Most of the ponds used for carp culture cannot be drained by gravity and pumps or mechanical devices have not generally been used for this purpose. This leads to the accumulation of large deposits of silt that create unfavourable conditions for fish culture. The value of properly planned fish farms for efficient fish culture is understood, but due to the large initial capital investment for construction, there is a general belief that such farms will not be economical. The majority of fish farms in India, Bangladesh, Sri Lanka, etc., belong to government fishery departments and are generally used only for seed production or for experimental purposes. There is obviously a need to establish the economic viability of such farms, with special reference to the use of sites such as swamps and waste lands that are likely to be available for farm construction, methods of controlling seepage and other water losses, economical means of draining and filling, etc.
As stated earlier, the general practice in at least South Asia has been to culture fish in existing water bodies, such as village and homestead ponds. These are usually constructed for purposes other than fish culture. They are simultaneously used for washing, bathing, watering cattle, and irrigating vegetable crops. The main source of water supply is seasonal rain and, therefore, the depth of water depends on the amount of rainfall, intensity of evaporation, and seepage. Significant fluctuations in water level are a common feature. Many ponds are seasonal and others have only a very low water level during summer months. As the ponds are stocked during or immediately after the rainy season when they have the maximum water level, the biomass of fish in the ponds will be highest during the dry months when the fish have grown in size and the volume of water is lowest. Obviously this creates major hazards to the fish stock. There is often no ready source of water in the neighbourhood to feed the ponds and, even if available, cannot be used for lack of pumping facilities. The present high price of fuel often leads to the view that pumping will not be economical. The use of unconventional sources of energy, such as solar and wind power, has not yet been tried for operating pumps in this region.
The ponds that cannot be drained by gravity can be referred to as undrainable, in the circumstances described. These ponds have heavy deposits of sediments at the bottom and many of them have permanent or seasonal blooms of blue-green algae, mainly Microcystis. A number of studies have been carried out in CIFRI and elsewhere on these plankton blooms, but there is probably not yet a full understanding and reliable quantification of the basic production processes in the water column and sediment-water interface and the role of the reduced, slowly decomposing sediment, to form the basis for suitable management measures.
The development of a dependable source of water supply may serve to minimize
or obviate a number of problems faced in the use of undrainable ponds and other
water bodies for carp culture. The use of shallow or deep tubewells, where groundwater
supplies are adequate, has been considered, and some progressive farmers are
now planning to try this. Such wells, besides providing a source of water for
the ponds, may also serve the domestic needs of villages and thus contribute
to human as well as pond sanitation. Aerators have been used elsewhere to improve
water quality and growth rate of fish in ponds. Thus far, these have not been
tried in the south or southeast Asian countries.
The major highlights of research at CIFRI relate to the induced breeding of Indian and Chinese carps and to the development of improved nursery practices. The technique of induced breeding by the injection of pituitary extract was developed in India as early as 1957 and both Indian and Chinese carps were bred at the Institute. However, India still depends to a very large extent on the collection of spawn from rivers to meet its carp seed requirements. From the point of view of technology, the two major factors responsible for this difference would appear to be the lack of suitable brood fish-rearing techniques and poor hatchery methods. The general practice is to obtain mature or maturing fish from farms or natural bodies of water during, or just before, the spawning season. The Chinese experience would indicate the need to relate the inducing technique to the age, size, and species of carp, as well as whether the individual fish has been bred before and, if so, the number of times it has been bred. There is reason to believe that the response to hormone administration would be higher in older fish that have bred more than once. The need for pituitary extract can possibly be reduced or avoided in such cases and commercially available mammalian or human chorionic gonadotropin used instead. Proper handling methods and the treatment of spawned fish and their feeding and maintenance for future breeding have yet to be developed for both Indian major carps and Chinese carps under Indian culture conditions.
CIFRI has carried out some work on the potency of pituitary material and the dosages to be used for breeding, including the ampouling of extracts for ready use. However, considerable work remains to be done to standardize the dozes as the percentage of success in breeding is still variable; at times not more than 50 percent. Besides the low potency of donor pituitary and poor condition of the brood fish, failure may often be due to unfavourable weather conditions. Breeding success is still dependent on hydrological conditions created by monsoon rains. The determinant factors have not yet been clearly decided to make breeding independent of uncertain monsoon conditions.
Work in CIFRI has demonstrated the feasibility of spawning the same fish two or more times during the season. Proper development of the relevant techniques for multiple spawning and shifting of breeding time can prove of great benefit to seed production.
The traditional technique of hatching and rearing larvae in cloth hapas in open bodies of water is widely followed. Although with some improvements the hatching and survival rates have been increased, comparative studies indicate the superiority of modern hatcheries. Even though the initial cost of a hatchery is higher, in the long run it may be more economical in view of the increased efficiency and longer life of hatchery equipment.
The potential benefits of genetic manipulation in carp culture are well recognized in CIFRI and other research institutions of the region, but very little work has so far been done, due to either the lack of expertise or adequate facilities. Once the method of controlled breeding was developed, CIFRI attempted some preliminary experiments in inter-specific and inter-generic hybridization, mainly for the purpose of improving the market quality of the fish (smaller head and deeper body as in crosses between catla and rohu) or obtaining faster growth rates. Even though the results achieved are encouraging, it has not yet been possible to carry out adequate progeny testing due to a lack of facilities. Genetic selection experiments to prevent inbreeding depression or to obtain strains with greater resistance to temperature variations common in tropical ponds, resistance to diseases, enhanced growth rates, etc., have not been attempted.
The availability of pituitary material in sufficient quantities remains a major constraint as there is, at present, no dependable source of supply. The common carp has proved to be a very satisfactory donor and, therefore, it has been suggested that the culture of an adequate number of common carp in each farm, primarily to meet the pituitary requirements, may be an effective way of meeting the need.
As stated earlier, CIFRI's work on nursery practices has resulted in relatively dependable technologies. Survival of fry has been raised to as much as 80 percent and stocking rates up to 10 million/ha. The techniques consist of the eradication of predator and weed fishes with indigenous piscicides, followed by liming and fertilization with organic or inorganic fertilizers, control of aquatic insects which prey upon carp seed, and supplemental feeding. The addition of cobalt chloride (at 0.01 mg/fish/day) is reported to result in high survival rates. The maintenance of a standing crop of the required food organisms is a key factor and appropriate fertilizing schedules for this have to be fully worked out. Some preliminary studies have been undertaken oh the culture of selected fish food organisms such as Chlorella, Daphnia, Moina and Brachionus. However, these studies are still in very early stages of determining the feasibility of producing food organisms in separate cultures for introduction into nursery ponds for mass culture of fry and fingerlings.
Two of the major problems faced in production pond management, besides water supply in undrainable fish ponds, are the control of predators and weeds. Even with repeated fishing, using suitable nets, it is not possible to remove all the predators, particularly because of the deposits of silt and organic matter at the pond bottom. Due to the unavailability of commercial derris powder, CIFRI has made a search of indigenous fish poisons of vegetable origin. Mahua (Basia latifolia) oil cake is now used and recommended by the Institute as it is a selective piscicide, only marginally toxic to fish food organisms. It also serves as a manure, and toxicity is lost in ponds in a short period of time. The roots, bark, and seeds of Barringtonia acutangula have been found to be an effective piscicide. The growing of an adequate number of these trees by the side or on dikes of fish farms may be a convenient means of making a suitable piscicide available for pond treatment.
Aquatic weeds constitute a serious constraint to the reclamation of water bodies
for fish culture, as well as to the management of fish ponds. As a result of
many years of research at CIFRI, effective methods of controlling or utilizing
macro-vegetation have been developed. However, the economic feasibility of the
methods, when incorporated in an intensive pond management system, leading to
increased production and higher profits, has not been determined. The absolute
cost of weed control would not be a useful criterion for deciding the economics
of its use in fish culture. Although some research has been carried out on the
control of algal blooms in fish ponds, a dependable method has yet to be developed,
especially for ponds fertilized with inorganic fertilizer and for undrainable
ponds with permanent algal blooms.
Fertilization with organic manures and inorganic fertilizers is also recommended for fish food production in rearing and stocking ponds. The most commonly used organic manure is cow dung. Studies have been made on the use of inorganic fertilizers such as urea, ammonium sulphate, calcium, and ammonium nitrate, and triple and single super phosphates under different soil and water conditions. The combination of N and P is reported to give high fish production, but a combination of mustard oil cake and inorganic fertilizers (N-P-K) appears to give better results (at least in nursery ponds). Despite these valuable findings, the basic data for the development of definitive fertilizing schedules on a national or regional basis is lacking. In view of the competing demands for the presently-used organic manures and the problems of handling, transporting, and storing large quantities of such manures, greater attention will have to be given to the use of inorganic fertilizers for large-scale fish farming. This will necessitate the simultaneous development of suitable methods for controlling algal blooms, as chemical fertilizers have been observed to promote such blooms.
In carp farming in this region, complete feeding does not appear to have been
tried. Supplemental feeding is done in most nursery ponds and in some rearing
and stocking ponds. The commonly used feeds are rice bran and oil cakes. These
are not inexpensive and also have other uses. Although preliminary experiments
with leaf proteins and other unconventional feeds have been undertaken, a critical
survey of the availability of potential feed ingredients, their nutrient values
and costs, has not yet been made. Some indicative information has been gathered
on the requirements of essential nutrients and this could form the basis for
the preparation of test feeds, pending more detailed information on the nutritional
needs of different life stages of the various species of carps.
Although occasionally fish-kills occur in carp ponds, the incidence of diseases
is believed to be generally low. Most such mortalities are due to sudden changes
in water quality. However, many ecto- and endoparasites have been described
from carps and occasionally unexplained mortalities have also been reported.
With the adoption of more intensive farming techniques including higher stocking
rates, there is every likelihood of increased health hazards. Diagnostic and
control measures must be developed, in advance, to meet such eventualities.
Research in CIFRI 80 far has been restricted to systematics of parasites and
application of some known disease control techniques. Laboratory facilities
for diagnostic work and disease control research and adequately trained personnel
for such work need to be developed for the assessment of disease incidence,
development of systematic health protection measures for rearing brood fish,
hatchery operation, rearing of fry and fingerlings, and production of marketable
fish. Suitable measures will have to be adopted to prevent the spread of diseases
from infected hatcheries and ponds.
Although the seine nets used for harvesting in ponds are reasonably efficient, complete harvesting is seldom achieved in non-drainable ponds. The problem is more serious with certain species, such as the common carp. Very little research or improvisation has been directed so far to this problem.
One of the reasons for slow progress of fish culture in India and other countries of the region is said to be losses sustained because of poaching. Small ponds or farms may not justify round-the-clock watch and ward, but even in larger farms this has not proved to be so efficient, due to social and practical problems. Of all the devices so far used to prevent poaching by CIFRI, placement of barbed wire on identified spots in ponds, appears to have been the most efficient deterrent.
The few studies on the economics of carp culture so far carried out indicate its high profitability. However, these studies related mostly to culture in existing water bodies, which meant very little capital investment. The need to determine the comparative economics of fish culture in properly designed fish farms and in undrainable village or homestead ponds, has already been pointed out. It has to be determined whether the higher investment can be justified in terms of sustainable returns on a long-term basis. At present, fish farmers grow carps to a size of about 1 kg before harvesting, as that size fetches a good price in the market. Fish of even smaller size, weighing about 500 g, can be sold and it appears necessary to determine the minimum economic size to which carps should be grown in ponds. Similarly, there is at present a lack of necessary basic information to recommend the minimum economic size of farms for carp culture.
Economics form a major consideration in every aspect of commercial aquaculture
but this element has not often been identified and measured in experiments.
The need for appropriate evaluation of techniques is now increasingly recognized
and it can be hoped that future research will yield some of the essential data
required for economic modelling of fish culture operations.
There are extensive lakes and reservoirs in Asia that can be used for fish production by the application of culture techniques. The Chinese manage their lakes and reservoirs, more or less as large fish farms. In other countries, a system of stocking is adopted to increase fish populations. In India, there are about 500 large and medium reservoirs covering a total water area of about 3 million hectares. The All-India Coordinated Research Project at CIFRI undertook a detailed investigation in seven reservoirs, and based on the ecological information obtained, management practices were developed. These practices have served to increase fish yields from 25 kg/ha to 80 kg/ha within a span of five years. This ecosystem-oriented reservoir development includes a stocking policy based on trophic strata in terms of shared, unshared, and vacant ecological niches.
The Dhauli centre does not have any reservoirs in its immediate vicinity to undertake detailed investigations for a critical evaluation of stocking techniques. However, it should be possible for the centre to undertake some experimental work on cage or pen culture of carps in a selected reservoir, such as the one at Hirakud in Orissa State. Cage culture of Chinese carps has already been tried with encouraging results in lakes in Nepal. Pen culture, along the lines of milk fish culture in Laguna de Bay in the Philippines, may also be worth trying. In view of the low survival and catchability of stocked fish in reservoirs, the overall production obtainable from a reservoir can probably be matched by intensive cage or pen culture in a limited area. Technical and economic feasibility must be studied on an experimental basis and the economic benefits and environmental effects critically examined.
3.1 General Problems of Carp Culture
3.2 Special Problems of Undrainable Water Bodies
3.3 Cage and Pen Culture of Carps in Reservoir
Based on the problems faced in the expansion and intensification of carp culture
indicated, the following research needs have been identified (it should be pointed
out that some of these studies have already been carried out on a limited scale
in CIFRI, but have to be repeated and expanded using the upgraded facilities
at the Centre to verify the results achieved):
(i) Selection and establishment of brood stocks
Determination of criteria for establishing brood stocks (origin, morphological, and health criteria); establishing techniques for rearing and maintenance of brood fish; defining the optimum environmental conditions, feeding, and stocking density for best reproductive capacity; study of breeding potentials (fecundity, egg size, hatching rate, larval size and survival) according to species, age and size of brood fish; extending the breeding season and inducing multiple spawning; farming of common carp as donors of pituitary glands.
(ii) Development of hatchery techniques
Standardization of optimal environmental conditions for hypophysation and the release of eggs and milt, determining the best time for hormone treatment; optimization and standardization of hypophysation and the use of alternative hormone sources; adoption and improvement of hatchery equipment and methods.
(iii) Nursing of fry and fingerlings
The culture of natural food organisms for fry; the development of feeds for fry and fingerlings; control of weeds and predators in nursery ponds; the use of chemicals for selective enhancement of zooplankton (Rotatoria) in ponds; determining the rates of fertilization, feeding and stocking for monoculture of fry and fingerlings of various species of carps preventive measures for health protection.
(iv) Fertilization and manuring of ponds
Comparative studies of the effects of fertilization with inorganic fertilizers and organic manures (and their combination) on natural food production, water, soil and sediment chemistry; interaction between fertilization and feeding at various levels of standing crop of fish.
(v) Production methods (mono- and polyculture)
Re-examination of fish combinations based on feeding and other behavioural characteristics at different levels of treatments (fertilization, manuring and feeding) and at different stocking rates; inclusion of mollusc-feeding species in fish combinations, comparative experiments in mono- and polyculture under identical environmental and management conditions, with the examination of economic and logistic problems; determining effect of aeration on yields.
(vi) Nutrition and feed technology
Survey of local feed stuffs and testing their suitability as fish feed (acceptability, digestibility, and effect on fish growth), defining the nutritional requirements of the various carps; formulation and preparation of supplementary and complete diets using locally available ingredients and their testing; production of medicated feeds; establishing the optimum feeding rates for the various species at different temperatures, standing crops, and fish sizes; feed processing at the farm level, and at small-scale or large factory level; feeding techniques (feed dispensers, feeding frequencies, etc.).
(vii) Fish health protection
Development of laboratory diagnostic methods for viral, bacterial, parasitic and other diseases and of fish health monitoring system; study of disease entities in carps (aetiology, epizootiology, prophylaxis and control); incorporation of prophylactic measures.
(viii) Genetic studies
The selection of fish strains with better growth potentials, meat quality, resistance to diseases and environmental hazards, and longer breeding periods; cross-breeding for the prevention of in-breeding depression, for heterosis, and for introgression of the above-mentioned beneficial characteristics into one strain.
(ix) Control of algal blooms
Determination of factors causing algal blooms, particularly blue-greens; their control (including the promotion of the growth of desired species) through chemical means and management (stocking densities of various fish species, water level, desilting, etc.).
(x) Aquaculture engineering
Design of fish farms for easier and better management, use of unconventional sources of energy, such as wind and solar power for pumping water and aeration of ponds; development of different types of aerators; development of effective anti-poaching devices.
(xi) Economics
Determine the economic feasibility of well laid-out fish farms with dependable
water supply; cost-benefit analyses of the use of different sources of water,
pumping, use of unconventional energy, seepage control, mechanical and manual
methods of farm construction; comparative study of small and large hatcheries;
defining the minimum economic size of farmed fish for marketing; determination
of-minimum economic size of farms.
(i) Limnological studies
Defining the effects of water level on the physico-chemical characteristics of water, soil and sediment; determining the effect of pond conditions on fish physiology and growth rate; studying the effect of aeration and silt removal on pond chemistry and fish growth.
(ii) Production methods
Determination of the effect of low water levels and the addition of water on fish yields; study of the effectiveness of harvesting methods; assessment of fish survival; study of the effects of changes in fish density on yield; use of piscicides for complete harvesting.
(iii) Engineering and economics
Draining and refilling by wind or solar driven pumps; shallow and deep tubewells
as sources of water supply; methods of removing silt without draining; development
of more efficient harvesting methods and gear. Analyzing the cost of increasing
water supply by pumping or by other means against benefits of increased fish
production.
Selection of sites for cage and pen culture; selection of species and species combinations for culture with or without artificial feeding; design of suitable cages and pens; management measures including feeding regimes, nature of feeds and feed dispensing; health protection; protection of fish stocks from poaching; rearing of fingerlings and of marketable fish; harvesting methods; economic evaluation and comparison of cost-effectiveness with stocking operations, taking into account costs of fingerlings and survival rates, catchability, need for clearing of reservoir bottom, etc.
Research at the Lead Centre should primarily be based on disciplinal units.
These units should be formed according to the specific research problems of
aquaculture and not necessarily the conventional academic disciplines. In addition
to studying specific problems within their own fields, disciplinal units will
contribute specialists to form interdisciplinary teams as required for investigating
broader and more complex problems relating to the selected carp farming systems.
The studies to be carried out by disciplinal units in support of systems-oriented
research, are the following:
(i) Fish breeding and seed production
Influence of age and size of brood fish on fecundity, egg size, and hatching rate in the six species of carp; optimization and standardization of hypophysation and use of other ovulating substances; determination of optimal environmental conditions for ovulation of the six species of carp; extension of breeding period and multiple spawning; defining optimal methods of egg treatment and incubation, as well as the indoor holding of yolked larvae.
(ii) Limnology and pond management
Quantification of energy flow; oxygen, phosphorus, and nitrogen metabolisms and cycling in ponds to optimize fertilization, stocking, feeding and water quality control. Algal bloom and pest controls.
(iii) Nutrition and feed technology
Digestibility of feeds and food metabolism; nutritional requirements (complete diets, protein-energy ratios, etc.) of various age groups of the six carp species; survey and evaluation of local feed stuffs; diet formulations and testing; feed processing technology.
(iv) Fish pathology
Development of cell lines for virological studies; characterisation of viral and bacterial fish pathogens, defining histopathological processes in various diseases; definition of conditions that cause outbreaks of diseases; testing of chemicals for prevention and treatment of diseases.
(v) Genetics
Fish marking methods; establishing of genetic lines; progeny testing of various lines and crossbreeds at various stages of life cycle (for survival and resistance to diseases, growth rate, food utilization, etc.); interspecies and intergenetic hybridization for the desired characters.
(vi) Aquaculture engineering
Pond construction (design, depth, inlets, screening, outlets); types of water supply (gravitation, pumping from tubewells or other sources), prevention or reduction of seepage and evaporation; design of cages and pens, feed dispensers, aerators, traps and other devices for predator control; prevention of poaching, sediment removal from ponds; harvesting techniques, transport techniques, use of unconventional energy sources in aquaculture
(vii) Economics
Cost-benefit analysis of various types of fish farms, hatchery layouts as well as of different procedures and techniques based on both experimental work at the Centre and pilot-scale or large-scale production elsewhere.
The more complex studies to be carried out by interdisciplinary teams will
be performed mainly in experimental ponds. Some experiments will also be done
in village or homestead ponds, the purpose of such research is to elucidate
the interactions between different variables (controllable and uncontrollable)
and their effect on fish production. To enable evaluations of as many variables
as possible, a factorial design experiment may be preferable.
The following are the interdisciplinary studies suggested:
(i) Techniques of rearing and maintenance of brood fish in ponds;
units involved: (i), (ii), (iii), (iv) and (v)
Selection of brood stock. Determination of optimal stocking density, supplemental feeding and pond management for optimal growth, sexual maturation, quality and quantity of sexual products; prophylactic measures for prevention of disease transmission, reduction of brood fish losses, egg, and larval mortality.
(ii) Farming of common carp as donor of pituitary material;
units involved: (i), (ii), (iii) and (vii)
Production of donor fish of uniform size and sexual maturity; comparing the efficiency and economy of mono- and polyculture for producing donor fish.
(iii) Nursing of fry and fingerlings in monoculture;
units involved: (ii), (iii), (iv) and (v)
Development of hatcheries and comparative study of the efficiency of hatchery equipment and design. Comparison of methods of preparing drainable and non-drainable ponds for fry and fingerling production, efficiency of feeding with natural food in ponds, natural food produced outside nursing pond, feeding with complete diets under indoor conditions, feeding with complete and supplemental diets in ponds, health monitoring, prophylactic measures, and treatments for health protection.
(iv) Economic methods of increasing yield of carps in ponds;
units involved: (ii), (iii), (iv), (v) and (vii)
Studies on relationships between fertilization, manuring, feeding, carp species combinations, and density; the effect of these interacting variables on the environmental factors, such as dissolved oxygen fluctuations, alkalinity, CO2, etc., as well as on the soil, the accumulation of organic matter, redox potential, and on the natural food sources such as benthos, phytoplankton and zooplankton. Light penetration and primary production analyses.
(v) Effect of water level on fish production;
units involved: (ii), (iii), (vi), and (vii)
(vi) Increase of fish production in non-drainable ponds;
units involved: (ii), (vi) and (vii)
Effect of water level, desilting, control of water blooms, and water supplementation on environmental conditions and yield.
(vii) Cage and pen culture in reservoirs;
units involved: (i), (ii), (iii), (iv), (vi) and (vii)
1. INTRODUCTION
2. CLARIAS AND OPHICEPHALUS POND CULTURE
3. MACROBRACHIUM CULTURE
4. CAGE CULTURE OF PANGASIUS
5. TRICHOGASTER CULTURE IN RICE FIELDS
6. POND CULTURE OF PUNTIUS
7. MUSSEL CULTURE
8. OYSTER CULTURE
The culture systems selected for studies at the Regional Lead Centre in NIFI are the following (listed in order of priority):
(a) Clarias and Ophicephalus pond culture
(b) Macrobrachium pond culture
(c) Cage culture of Pangasius
(d) Rice field culture of Trichogaster
(e) Puntius pond culture
(f) Culture of mussels and oysters on foreshore areas
NIFI personnel are directly concerned with research, extension and technical services relating to the first five farming systems. Culture of mussels and oysters comes under the area of responsibility of the Brackishwater Division of the Directorate of Fisheries. The limited staff assigned for the development of this system is presently engaged in extension work and any expanded research may become possible only after new facilities planned to be constructed with bilateral assistance from Japan are established. These facts account for lower priority given to research on the culture of mussels and oysters, although it is recognized that there is appreciable scope for the improvement and expansion of this system in Thailand as well as the rest of the region. The task force has, however, proposed some preliminary research to be carried out, if the necessary facilities become available.
In formulating the research programme the task force took into account NIFI's current activities, including its heavy commitments to extension work, available scientific and technical manpower and its experimental facilities. The objectives and work programmes of the two UNDP/FAO country projects relating to catfish and Macrobrachium culture and the need for applied research in support of the extension work they are expected to undertake, were discussed in some detail with the assistance of FAO experts concerned. The number of outdoor ponds and tanks at the institute is limited and there appears to be no immediate possibility for expanding these facilities or building new ones in the vicinity. There are enough ponds at the fishery stations directly under the Directorate of Fisheries in the country, but a policy decision has to be made for their utilization, as at present they are all used almost totally for fry and juvenile production. Macrobrachium work of the Directorate of Fisheries is concentrated at the Chacheongsao Fisheries Station and it would be advantageous to organize research on the culture of this species in collaboration with the station staff utilizing some of the field facilities available there. Another possibility is the use of pond facilities of the Kasertsart University and it was indicated to the task force that if the University becomes a cooperating institution in the Lead Centre's research programme, these facilities could be used for experimental purposes. Cooperation with other university centres in Thailand could also be considered for some of the specialized research that may be needed. The third possibility is the use of private ponds, in conjunction with demonstration. This has to be considered if the other two alternatives prove to be unfeasible.
The shortage of scientific manpower at the Institute, especially due to their concurrent responsibilities for extension and technical services, can be met by the recruitment of additional staff or the utilization of Kasertsart University Fishery Faculty staff, who at present have very little opportunity for directed aquaculture research. The services of a limited number of expatriate workers could also be obtained through FAO's associate expert scheme. They could work under the guidance of experts and consultants to be provided under the project.
The task force discussed the feasibility of separating the research and extension or technical support activities at the Institute, but understood that this will be difficult. Since the multidisciplinary research proposed has to be carried out by teams of workers specializing in different aspects of aquaculture it is expected that all the present scientific staff of the institute can participate in the research as members of one or more teams, as appropriate.
From the information provided, it would appear that the Institute has either already obtained or will soon be obtaining most of the equipment required for the proposed research activities. However, there will be need for assistance from the project to remodel or repair some of the equipment already obtained to enable their proper use.
The library of the Institute needs considerable strengthening, both as support to the research programme, and to enable the participation of the institute in the proposed information activities of the project. It is essential to have a suitably qualified staff member with the necessary language facility assigned for this work.
Culture of Clarias is well established and profitable in Thailand, with a total annual production of $0 000 tons from ponds. C. batrachus and C. macrocephalus are both commercially important. However, C. batrachus has wider regional farming prospects, for example, in India, Bangladesh and Sri Lanka, whereas C. macrocephalus has potential primarily in Thailand and the Philippines. They are cultured in stagnant or running water ponds, either in monoculture as in Thailand or experimentally in mixed cultures with other species, in India. Experiments are underway in India on production of C. batrachus in cages. Natural feeds are worms, insects, and decaying animal matter.
Since these fish have air breathing capabilities they are generally reared at extremely high densities in Thailand. Stocking rates of 3 to 7 cm fingerlings range from 100 to 300 fish per m2. Feeding with mixtures of trash fish, rice bran, and broken rice results in growth to marketable size (100-350 g) in 4-5 months, with yields averaging 3 kg/m but reaching 10 kg/m2 in some eases.
Pond management practices include only water exchange when necessary and liming of ponds in some instances to create more hygienic conditions. High stocking densities and high feed inputs result in deterioration of the pond environment. Survival from stocking to harvest is usually only 30 to 40 percent and diseases are very common, resulting in losses and reduction in market value of surviving fish.
The primary diseases observed include a disease entity attributed to Aeromonas spp., a syndrome with haemorrhages on the head, Gyrodactilosis and Trichodinossis. These diseases account for a significant proportion of mortality in fingerlings. The diseases are often complex and very likely involve interactions of a number of environmental and nutritional factors. Overcrowding of production ponds, coupled with poor water quality, create conditions stressing the fish and aggravating nutritional and infectious disease problems. With the type of pH fluctuations observed, 20-30 ppm ammonia may be found in the system.
The traditional method of feeding rice bran (10 percent) and trash fish (90 percent) has recently been modified to include a carbohydrate source (broken rice) at a level of up to 10 percent. To this mix is added a feed supplement which contains vitamins and sometimes antibiotics. The coarse ingredients are crudely mixed and extruded through an engine-powered spaghetti type extruder. The quality of the feed depends primarily upon the quality of the trash fish Generally, the moist pellets produced have good water stability because of natural gums present in the trash fish. Pellets are fed twice daily. Advantages of this feeding system are; (a) low cost, (b) simple technology, (c) readily available ingredients with the possible exception of trash fish, and (d) good water stability of feed. Disadvantages are: (a) uncertain quality and composition of trash fish depending on its stage of deterioration, (b) high biological oxygen demand of the feed, and (c) short shelf-life of moist pellets. The feeding of Clarias for commercial production in Thailand is based largely on empirical knowledge. The uncertain quality of raw materials together with rather poor diet preparation procedures, make evaluation of these traditional diets difficult and their effectiveness unpredictable.
Under an FAO/UNDP project, NIFI has already planned extension and demonstration of pond engineering and management practices that should lead to improvement in disease prevention and treatment, as well as to improvement of management practices generally. Additional research is underway on pellet stability, haematology, and parasitology of Clarias. A research project has been completed on the prevention of Aeromonas infections in Clarias.
Ophicephalus is reared using methods similar to those for Clarias, except that only wild fry are captured and sold to farmers. Commercial-scale pond culture of Ophicephalus striatus is practiced in Thailand, where production is 4 500 tons/year, and to a limited extent in Indonesia. While monoculture is common in Thailand, culture with other species is practiced in other countries such as India, where polyculture with Anabas is carried out in certain areas. Natural foods include fishes, prawns, insects, tadpoles, and gastropods.
In Thailand, the common practices are to stock ponds at rates of up to 75/m2; feed with trash fish, rice bran, and broken rice, mixed with a vitamin mix and sometimes antibiotics. Change water when necessary and harvest after about six months when the fish have attained weights of 0.5-1.0 kg. Yields of 9 kg/m2 can be expected. Extremely high mortality rates occur between the time of stocking production ponds and the time of harvest; however, this mortality is accepted by farmers since fry costs are very low (Baht 0.05 each). Poor environmental conditions contribute to losses from disease occurring throughout the growing period.
Problems of commercial culture are almost identical to those for Clarias.
Because of the similarity of culture methods, all the research needs identified for Clarias also apply to Ophicephalus. The more important needs are enumerated below:
(i) Determine acceptable water quality criteria (allowing normal growth rate, food utilization and health), including O2, CO2, pH, NO3, and BOD for fry, fingerlings, and larger fish to provide guidelines for pond management.(ii) Develop a simple field monitoring system and/or device for detecting deterioration of water quality in ponds (for instance, a sensitive indicator fish species, or simple chemical kit).
(iii) Determine optimal stocking density per unit of surface and of water volume for fry, fingerlings, and market fish ponds.
(iv) Investigate the influence of fry and fingerling grading on cannibalism, diseases, and survival rates.
(v) Develop methods for retaining the nutritive value of trash fish by ensiling with organic or mineral acid, and work out feeding systems using such products.
(vi) Study the two emerging specific diseases of Clarias ('Rok boo boam' and 'Kalok raust) and those as yet unidentified in both species of fish, to determine aetiology, epizootiology, and control measures.
(vii) Test selected antiparasitic and antibacterial drugs for efficient and economical bath treatment for fry and fingerlings before releasing into ponds.
(viii) Improve controlled breeding and seed production, including comparison with natural collection regarding impact on natural fish stocks and economy of fish culture.
An integrated research project on Clarias pond culture system is proposed to explore the feasibility of reducing mortality and improving its efficiency. System oriented research will be conducted using pilot-scale production experiments to evaluate selected management procedures. Experiments will be designed, based on the following interacting variables considered to be significant with regard to the improvement of the system:
(i) seed quality in respect to size composition;(ii) stocking density;
(iii) diet, using preserved trash fish or substitutes, more complete rations, and alternative protein sources;
(iv) environmental control, using monitoring and management methods to maintain water quality, and
(v) health protection measures (including improvement of prophylactic measures and in-depth studies of infectious diseases).
Work on controlled breeding can be done by cooperating institutions carrying out the proposed research, or NIFI undertaking such work at a later stage.
The work on Ophicephalus will be carried out in the second phase, after the results on Clarias provide guidelines for detailed research planning.
Macrobrachium culture is a rapidly growing industry in Thailand. Annual production exceeds 250 tons from more than 200 farms with farm sizes ranging from 800 m2 to 40 ha. Average yield is about 1 000 kg/ha. Local demand exceeds supply and considerable quantities are imported from Burma. Current farm gate value of Baht 140/kg has served to stimulate the industry.
Many hatcheries have been established, mainly in the area east of Bangkok, following the example of the Chacheongsao Fisheries Station. These include many small 'back-yard' hatcheries and two modern commercial hatcheries in the Pattaya and Rayong areas. Some hatcheries have their own brood stock ponds; some bring in spawners from production ponds when required. Larvae are nursed in concrete or fibreglass tanks and most hatcheries operate on daily exchange of water rather than recirculation.
The techniques for the production of post-larvae from hatcheries are in a constant state of development and, in the better hatcheries, larval survival to metamorphosis reaches 50 percent. The standard diet consists of an egg custard containing minced fish or mussel meat. This is fed several times per day, together with an evening feeding with Artemia nauplii which counteracts cannibalism at night. Current total postlarvae supply is approximately 30 million per year, of which 6 million originate from the Government hatchery at Chacheongsao.
Post larvae are distributed to farms from the Government hatchery gratis or at a low cost (Baht 0.25 each) and sold by commercial hatcheries at prices varying between Baht 0.50 and Baht 1.00 each, depending on their size (age after metamorphosis). Grow-out prawns are fed a variety of diets ranging from farm produced moist-type pellets to commercial hard pellets meant for poultry. Feed conversion of the wet diets averages 6.0 to 7.0. Stocking density varies between 5/m2 and 20/m2. Harvesting usually begins at five months when a thinning-out process is begun and the larger prawns are sold, optimum market size being 75 g per animal. Harvesting is completed after about eight months.
Total yield per ha is often less than 1 000 kg per year. Survival can be as low as 20-40 percent, particularly when high stocking rates are employed. This low recovery is attributed by many farmers to predators such as crabs, carnivorous fish, turtles, etc. Cannibalism is minimized by placing logs in the ponds to serve as sanctuaries for moulting prawns. Pond water is not normally continuously renewed but some of the larger farms replace up to 20 percent per day by means of mechanical pumps operated for a few hours every day.
It is believed that low survival and low production rates in farms are the
most serious problems. These problems need resolution, through improved management
techniques, pond construction, and better knowledge about the optimum means
of supplying the nutrient requirements of post-larval prawns. Disease does not
yet seem to be a major factor in low survival rates. As mentioned before, constant
improvements are being made in hatchery technology and it is not felt that research
on this topic is a priority item for the Lead Centre. The economic need to find
a replacement for Artemia nauplii as a larval diet has been reduced by
the success of an innoculation programme designed to produce Thai-grown cysts;
in any case, this topic is being studied by many laboratories elsewhere in the
world and duplication is not warranted. The research needs listed below, therefore,
concentrate on grow-out production technology.
There are seven groups of research needs and they are listed below:
(i) Pond management studies including methods for the exclusion and control of predators; investigations on the effect on water quality of the application of various types of diets; and studies on the effects of stocking density, eye ablation (leading to hormonal manipulation), mono-sex rearing, and moult synchronization on feeding and behavioural patterns, and on subsequent growth and survival rates. This will in some cases require laboratory, rather than field experimentation.
(ii) Development of balanced diets for Macrobrachium with desirable commercial attributes for all stages of growth.(iii) Studies on the means of decreasing the wastage of feed applied to ponds due to poor diet stability and the feeding habits of the prawns.
(iv) Investigations on fertilizer application in relation to feeding to establish the optimum balance between natural and artificial feed.
(v) Studies on methods of improving feed dispersal within the pond and on feeding frequency.
(vi) Identification of the major bacteria and parasites affecting the health of the species and the development of prophylactic and treatment measures. This work would include studies on larval as well as post-larval prawns.
(vii) Isolation and identification of potentially harmful macro-organisms affecting the marketability of the final product, and the development of techniques to improve quality and sanitary control in post-harvest operations.
A wide recommended oriented to incorporate field of research is indicated in section 3.2, but the following topics are for immediate investigation by the Lead Centre. This research will be system-increase production and reduce losses, and experiments should be designed to the relevant variables.
(i) Develop improved methods for preventing ingress of predators and pests and for their eradication in ponds.(ii) Study the effect of different pond preparation techniques on productivity.
(iii) Study the utilization of natural food by Macrobrachium, and develop ways of increasing its availability by fertilization where the management system lends itself to this technique.
(iv) Develop diets specifically designed to provide supplementary feed for Macrobrachium in ponds.
(v) Develop a pelleted ration which provides all its nutrient requirements.
(vi) Study the importance of calcium levels in water to production rates in ponds.
(vii) Carry out laboratory and field investigations into the possibility of controlling behaviour, growth, cannibalism, and gender through hormonal manipulation.
The cage culture of Pangasius spp. is a traditional practice in Southeast Asia. In recent years there has been considerable interest in the expansion of the industry and in the introduction of the practice in other countries of Asia. The two most important cultured species are Pangasius sutchi and P. pangasius, although there are also other species that contribute both to capture and culture fisheries in Asia. They are omnivorous in feeding habits and have been found to feed selectively oh molluscs in ponds.
Commercial-scale cage culture of P. sutchi is widely practiced in Thailand and the present production is estimated to be around 1 500 tons per year. The number of cages is reported to be increasing, indicating the profitability of the operations. Marketing of the increased production is reported to be a problem, but this is apparently only in the urban markets such as Bangkok which may not be able to absorb larger quantities than now. Other urban and rural markets may be able to absorb greater quantities, but probably only at a lower price than in Bangkok. It would, therefore, be necessary to lower the cost of production to maintain the level of profitability for the producer. Off-flavour has been reported to be a problem, but the introduction of known techniques of cleansing before marketing can remove the muddy flavour.
The cages presently used in Thailand are made of wood and the sizes vary, the more common size being 20 m3, Families often live on floating homes to which the cages are attached. This facilitates the culture operations and protection of stocks. Farmers stock about 50 fingerlings of 8 to 10 cm length per cubic metre of cage. Although feeds and feeding regimes vary, a mixture of rice bran, broken rice, and trash fish in the ratio of 2:1.1 appears to be the most commonly used feed. Other feeds used include soybean waste and waste vegetables. A typical feeding rate may be 2 percent or less of the body weight per day. The mortality in the cages is very low and the normal yield is about 100 kg/m3 for an 18-month growing period.
Fingerlings are produced in both government and private hatcheries. The farmers may also raise fry in their own farms or use fingerlings collected from the wild.
The culture techniques as presently practiced appear to be satisfactory, insofar
as culture in running water environments is concerned. However, Thailand, as
well as other countries of the region, is interested in the development of cage
culture in lakes, reservoirs and other stagnant or semi-stagnant water bodies.
It would therefore be necessary to develop suitable technologies for such types
of culture.
(i) Economic evaluation of currently adopted culture practices to determine the elements in production costs and the means to decrease them
(ii) Production tests, to test the feasibility of reducing production costs.
(iii) Study of the efficiency and cost effectiveness of the currently used cages and, if found necessary, improvement of their design or the introduction of new designs.
(iv) Formulation and testing of nutritionally balanced diets prepared with local ingredients.
(v) Development of culture technology for cage culture of Pangasius
spp. in stagnant or semi-stagnant waters.
The immediate research will be oriented to the reduction of production costs consistent with optimum production. This will involve use of different cage designs add materials, selected diet formulations and forms of feeds, feeding schedules, different stock densities, and water conditions. It will be necessary to carry out a series of experiments designed to test the effect of each of these factors as well as their interactions.
The above experiments will be carried out both in running water as well as stagnant and semi-stagant environments, in order to compare the results and determine the viability of such culture in the latter type of environment. Special attention will be devoted to the effect of stagnant and semi-stagnant water conditions on the health, survival, growth, and production of fish in the cages, as well as the effect of cage culture on the environmental conditions in the water body, with special reference to water quality and silting.
In Thailand, Trichogaster is primarily cultured in disused paddy fields, modified to form 5-ha ponds by construction of a peripheral ditch and an enlarged dike to maintain water depths greater than are necessary for rice production. In areas where such culture techniques are practiced, it has been found to be more profitable than rice farming. Currently, 100 000 ha are devoted to such types of culture in Thailand, with an annual production in excess of 20 000 tons. The total potential surface area is about 400 000 ha.
General farming procedures may be described as follows:
The peripheral ditch, 3 m wide and 80 cm deep, is filled with water and adult Trichogaster of 100 g size selected from the previous harvest are stocked in sufficient numbers to provide one pair of spawners for each 16 m of water surface. The pond is then flooded to a depth of 50 cm over the central platform area. Subsequent spawning results in fry densities of approximately 185/m. Emergent vegetation which grows rapidly in the centre part of the pond is mowed regularly and applied as green manure to enrich the pond. Other management practices involve changing of water in the pond. Fish are not fed. Harvesting is carried out after a 6-7 month growing period when the fish reach a marketable size of about 100 g. Fish survival, as well as yields, are very low, the latter being about 0.7 t/ha.
The low yields of Trichogaster in converted paddy fields may be due to low fecundity of the spawners and fry survival under the present culture system; poor water quality resulting from green manuring of the ponds and frequent high salinity; and an inadequate water supply.
Trichogaster is also raised in Malaysia, the Philippines and Indonesia.
Improvement of the present culture system should enable expansion of its application
in the region.
Research should focus on improving the ecosystem through new pond designs and the development of effective pond management procedures for increased fish yields.
(i) Design of ponds to ensure adequate supply of water.(ii) Development of pond management procedures aimed at conserving water quality.
(iii) Investigation of the effects of changes in water chemistry (salinity and pH) on fertilization, hatching, and fry survival.
(iv) Determination of the feasibility of bi-culture; e.g., with Clarias or Puntius.
Research should be aimed at ecosystem management to increase the natural production while conserving water quality in the farming system. Experiments should be planned to study the effects of changes in water chemistry on fertilization, hatching, and fry survival, and to determine the feeding habits and food utilization of the cultured species.
There are many species of Puntius in Asia but Puntius gonionotus is the most commonly cultivated species in Indonesia, Malaysia, Thailand, and the Philippines. It has been recently introduced in India for experimental purposes. In Thailand it is extensively raised in paddy fields either in monoculture or polyculture with Indian carp (rohu) and common carp. Semi-intensive and intensive culture of Puntius in ponds is also practiced to a limited extent. In Malaysia, it is cultured with Chinese carps or tilapia. Puntius is also being raised in cages in reservoirs.
Puntius breeds easily in ponds and spawns three to four times a year. It is primarily a macrophyte feeder and has potential as an effective biological agent for the control of aquatic weeds. Being a prolific breeder it may be an excellent source of pituitary material for induced breeding of other fishes.
Seed production and pond culture of Puntius do not pose any major problems in Thailand. Pond fertilization results in yields of 2.4 tons/ha/year and supplementary feeding yields up to 6.0 tons/ha/year. In general, however, culture practices are extensive in nature and the level of operation is usually of subsistence scale with low productivity.
Puntius is easy to handle and lends itself to simple culture techniques
which are adaptable to small-scale farming systems. The cost of production is
relatively low. Because of these attributes, the general transfer of improved
technology has broad regional application. Upgrading of existing pond culture
techniques is, therefore, of utmost importance.
To increase present levels of production, there is a need to study various pond management techniques which would provide optimum output per unit area at minimum cost, using monoculture and polyculture systems. The reproductive cycle of the fish should be further studied with a view to utilizing it for pond management. Being a macrophyte feeder this species has potential as a weed control agent and it would be useful to determine its efficiency for conversion of different species of macrophytes.
As mentioned earlier, Puntius can be a good source of pituitary material as it breeds several times a year. Puntius pituitary was found to be effective on catfish and Asiatic carps. It will be useful to develop procedures for the farming of Puntius as a source of pituitary at the farm level.
Intensification of pond culture systems requires additional inputs in terms
of feeds and fertilizers. Studies on the optimum level of these inputs, their
quality and quantity yielding the highest profit per unit cost of production,
would be necessary. Information on these aspects would provide the farmer with
alternative production levels.
Research on the pond culture of Puntius will be directed toward increasing the levels of production under extensive, semi-intensive, and intensive monoculture and polyculture systems at minimum production costs. Emphasis will be laid on developing pond management techniques that would take advantage of the biological characteristics of the species such that maximum growth is attained within the shortest possible period of rearing without overcrowding due to natural reproduction in the pond. Pond culture technologies that allow a number of production options in relation to soil and water quality conditions, as well as local weather, broad climatic situations, and levels of production inputs, would be developed.
Research on the use of various macrophytes as feed for Puntius and their conversion rate is essential in the culture of the species. Not only would this be useful in cutting down feed costs, but would also provide relevant data on the effectiveness of Puntius as a weed control agent in natural bodies of water as well as in ponds. Studies to assess the potential of Puntius as a donor of pituitary material for induced breeding of other species of fish shall also be conducted.
Mussel culture is carried out on mud-flats with water depths of up to 7 metres using palm stakes. The mussels are harvested at 8 months, yielding about 40 tons/ha. No thinning-out is practiced during the growing period.
Spat is transplanted from one location to another according to phytoplankton availability. Pollution of mussel grounds by domestic and industrial effluents has become a major problem.
The price of mussels is Baht 8-15 for a 15 kg bucket in Thailand. Apart from serving the culinary needs of the human population, small mussels are also used increasingly in preparing feeds for Macrobrachium, and as scratch feed for duck production.
Large coastal areas are available for expansion of mussel culture and very
large quantities can be produced. The level of production technology used in
Thailand is not high and there is considerable scope for improving traditional
culture practices.
(i) Identification and mapping of polluted areas unsuitable for mussel production.
(ii) Hydrobiological studies to identify most productive areas for mussel production (seed and growing).
(iii) Introduction of thinning procedures and spacing of mussels on substrate for improved growth and production.
(iv) Experiments in rope and net hose culture.
Surveys of potential mussel farming areas will result in the mapping of suitable areas, and those that should be avoided. Experimental work on thinning procedures should be designed to determine the increase in size of product, overall yield, and profit that can be obtained against increased labour and other costs.
Rope and net hose culture experiments will be carried out in different types of environments to assess the increased survival, growth and yield that can be obtained and the cost of inputs needed for the purpose.
There are ten species of oysters in Thailand of which three are under commercial cultivation. Primary culture areas are in the Cholburi and Chanthaburi areas covering approximately 1 000 ha of shallow coastal waters. A wide range of suitable oyster rearing areas exists elsewhere in the region and the opportunities for expansion of culture practices are goad.
Spat are collected from nature during the spawning periods from May to November on concrete tube sections, concrete blocks, or rods placed in selected growing areas. Typical spat set is 1/cm2.
Sites for growing oysters are selected on the basis of empirical knowledge of established productive growing areas. Oysters are harvested at 10 months of age when sizes of 6-12 cm are reached. Harvests average 4 oysters/100 cm2 of substrate area. Yields from production areas may average 10 t/ha of surface area,
Problems associated with oyster culture in Thailand include fouling of substrate
by barnacles reducing spat set, and pollution from human activities. At the
current price of Baht 40/kg for small sizes and Baht 70-100/kg for large sizes
(in the shell), oyster culture is a lucrative operation. Large potential exists
for expansion of production in unpolluted areas.
The current low yields per hectare point to the possibility for significant
improvement in culture practices such as improved spat collection, thinning
and transplanting. On-bottom culture techniques may be tried under local conditions
to obtain improved size and conditions of oysters and overall survival and yields.
Identification of the major predators and fouling organisms and the development
of suitable methods for controlling them, should receive special attention.
Surveys carried out in connection with mussel culture investigations will yield the necessary information on sites suitable for oyster culture. Improved methods of spat collection, thinning, and transplantation have to be tried. Comparative experiments in hanging culture techniques, particularly rope culture, should be undertaken to determine cost-effectiveness and improved product quality that can be achieved by the introduction of new techniques. Besides evaluating the efficiency of the new techniques in controlling predation and fouling, experimental work must also be undertaken on other methods of controlling them.
