Aquaculture in South East Asia: Some points of emphasis

Aquaculture, 20 (1980) 159-168 o Elsevier Scientific Publishing Company, Amsterdam -- Printed in The Netherlands

159

AQUACULTURE IN SOUTH EAST ASIA: SOME POINTS OF EMPHASIS

M.N. KUTTY Fisheries College, Tamil Nadu Agricultural (Accepted

University, Tuticorin - 628003

(India)

7 November 1979)

ABSTRACT Kutty, M.N., 1980. Aquaculture in South East Asia: some points of emphasis. Aquaculture, 20: 159-168. The paper, a keynote address to the conference, addresses the aquaculture potentials which interest the international agencies. It also reviews the many production systems in aquaculture, particularly those which are of interest to or currently practised in Asian countries. Several examples are briefly described, and the need for more research is emphasised.

Culture of aquatic organisms for human welfare has a long history as an art and less as science. This is one area where the East can claim some lead in developments and innovations, mainly for historical reasons. That should not lead us to complacency, but should make us strive harder for further improvements, for our need for cheap animal protein is increasing and there is the basic need to put the age-old, but largely empirical methods, on a more scientific footing. Our present knowledge of aquaculture is impressive (see Bardach et al., 1972; Jbingran, 1975; FAO, 1976), but there is much more to be gained and exploited. We are assembled here as a small group to review some of this knowledge in the context of our experiences made possible through grants by the IFS. Reviewing our publications shows us that our achievements are creditable in spite of the smallness of the projects. We must remember the oft-quoted words that ‘being small is not less important’. Many individual workers (53 out of a total of 251 grantees) are working on aspects of aquaculture with IFS help in different parts of the world. A number of them have assembled here. Our discussions in the next few days will highlight our achievements and indeed our enthusiasm, and perhaps will show what more can be achieved by our scattered researches linked together by the IFS network. Because of the limitations of increased production by capture fisheries and the higher demand for animal protein, there is increased awareness in the importance of aquaculture. There are currently many attempts to increase fish production at all levels, notably by the efforts of FAO and other international

160

bodies including IFS. In this discussion I shall refer to some common problems of aquaculture with reference to increased fish production in Asia, and then briefly point out the aspects and areas which need emphasis. While it is important to achieve increased production by intensive and extensive culture, it is also important to understand the mechanisms involved. Economics is only one important aspect to consider. We have a special responsibility to achieve greater production at any cost in rural aquaculture. We must check the ways by which production can be increased in intensive culture systems, and determine how we can reinforce our empirical knowledge with scientific facts. In this context I shall refer especially to certain aspects of environmental physiology and how they effect survival and growth of the aquatic organism. The aquatic environment, unlike that of the land, is not familiar to man. Man has achieved good agricultural food production systems with mammals and birds. Information on how water as an environment affects aquatic life and how this information can be used to understand aquaculture is of considerable importance to us. This theme will underlie much of our discussions. AQUACULTURE

PRODUCTION

The present world aquaculture production is about 6 million metric tons, and this is expected to double in the next decade (FAO, 1976). It is further predicted by FAO that the total aquaculture production will be about 50 million tons by the year 2000. We must therefore increase and improve our efforts and advance technology to meet this challenge. Aquaculture production in Asia, areas under cultivation, and potentials for expansion are indicated in Table I. The potential area available is almost one hundred times the present cultivated area and we can look to a more bountiful fish harvest in future. According to Pillay (1973) aquaculture can take several forms, for example: (1) Culture for food production. (2) Culture to improve natural stocks. (3) Culture for production of sport fish. (4) Culture of bait for commercial or sport fishing. (5) Culture of aquatic organisms to supply hobbyists and scientific research groups, and for pets. (6) Culture of aquatic organisms as a means of recycling organic wastes. (7) Culture of aquatic organisms for production of industrial commodities, such as oil, pearls, animal feed and drugs. While all these are of interest in one way or another, our main interest in developing countries is culture for food production and culture for recycling organic wastes as it has the double purpose of cleaning the environment and reaping economic benefits. I shall refer to this again. Culture for production of sport fish is a concern of many developed countries. It is practised to some extent in countries like India though on a small scale (e.g., the trout fisheries of Kashmir, Sehgal et al., 1976). But, by and large, the production of salmonids

161 TABLE

I

Aquacultural production and potential area available for increased production for several countries in Asia (Source: Pillay, 1973 in Wheaton, 1977) -.-.. ~~ Country

Present status Area under cultivation (ha)

Bangladesh Burma Cambodia Ceylon India Indonesia Malaysia Pakistan Philippines South Korea Taiwan Thailand Vietnam Total --*Data for 1977.

Production (kg x 103)

( - included in Pakistan) -

2920

-

10,000 607,915 266,300 90,473 30,780 164,414 10,000 39,234

15,000 700,000* 141,075 25,648 37,540 94,573 99,040 56,185 87,864

2600 1,224,636

1484

Potential area available _ Freshwater Salt and brackish water (ha) (ha) 4,335,ooo 10,957,000 438,000 67,730,OOO 4,787,OOO 422,150 682,000 853,063 319,754 533,000 6,077,434

3,292,309

97,134,401

166,000 520,000 50,000 140,000 2,000,000 6,000,OOO 381,412 232,000 53,871 166,000 150,000 9,859,283

and shrimps from capture and culture fisheries is linked to regional economies and not to an interest in sport per se. Production of luxury food (e.g. shrimps in India and Malaysia, and milkfish in the Philippines) will continue to be the main concern of the fisheries industries in both developing and developed countries. The importance of such industries cannot be overemphasized. For example, the Indian shrimp industry (though not based much on aquaculture presently) is bringing about Rs.200 crores of foreign exchange to the country. Even though this amounts to a loss of protein to the country it must be conceded that the Indian fishing industry has gained much by it (Kutty, 1978a) and it has opened the eyes of many to the potential of aquatic resources to fisheries development and aquaculture. The Technical Advisory Committee (TAC) of the Consultative Group on International Agriculture Research in 1974 listed priorities in aquaculture research programmes as: (1) Breeding and seed production. (2) Nutrition and feeds. (3) Genetic selection and hybridization. (4) Intensification of culture systems, including polyculture. (5) Selection of new species for culture. (6) Aquaculture engineering. (7) Aquafarm management.

162

Many international organizations, such as the IFS (Gaillard and Bramsnaes, 1978) and IDRC (Davy and AIlsopp, 1976), have given emphasis to these priorities and given some predominance over others. I will go through certain of these where emphasis must be given, in my opinion, but I shall not refer to them in order or by name. FISH CULTURE SYSTEMS

Intensive polyculture systems, where supplementary feed and fertilizers are applied, have yielded rewarding results. In India polyculture of Indian major carps, ‘Catla’ (C&la c&la), ‘Rohu’ (Labeo rohita) and mrigal (Cirrihinus mrigula), the common carp (Cyprinus carpio), and the Chinese silver carp (Hypophthalmichthys moiitrix) and grass carp (Ctenopharyngodon idefla) have yielded over 8 tons ha-’ year-’ (Chaudhuri et al., 1975). Still more compatible species can be included or replaced in this type of intensive polyculture after a closer study of the food niches and energy flow through the ecosystem, and yields increased. There will be restraints in adoption of this system due to the non-availability of fish seed, and therefore other indigenous species whose seeds are available can be included in this type of culture. An important aspect is the cost of feed and fertilizer, and in India the cost of these materials is almost half (or more) of the sale price of fish. This is true in other countries where intensive culture is established. This creates problems in adopting improved culture methods because of investment difficulties, especially at the rural level. In the hyperintensive fish culture of Israel almost 20 tons ha-’ year-’ is produced, but this is with the adoption of artificial aeration and demand feeders. Indeed, the high temperatures of the tropics favour increased production, unlike those in the temperate regions. One of the major constraints in increased production in developing countries is the cost of feed and fertilizer. It is imperative that both these costs are reduced if a major increase in aquaculture production is to be achieved, especial, ly at the rural level. One of the requirements for reducing feed costs is incorporating cheaper ingredients in the feed. For example, in the Tamil Nadu Agricultural University seeds of wild legumes were incorporated in pelleted feeds (Gropp et al., 1976). Wherever local food ingredients are cheap and available they should be tested as feeds for fish. Liquid cattle manure has been substituted for expensive feed by Moav et al. (1977). Another important way of resolving the ‘food crisis’ in fish culture is the use of sewage. This is practiced widely in several countries of Asia. Such ‘controlled eutrophication’ (Ryther et al., 1972) can certainly be of help. High production has been achieved in the cage culture of fish in sewage streams in Indonesia. The polyculture of Indian major carps and exotic carps has been tested in sewage-fed ponds (Natarajan et al., 1977), and a production of 8 tons ha-’ year-’ has been obtained in small ponds in Coimbatore, India. Artificial aeration of sewage-fed ponds can lead to production as high as 20 tons ha-’ year-’

163

(Hepher, 1975). An important aspect is the public health problem -- the transmission of pathogens through fish to man. Screening of pathogens (Enterobacteriaceae) has been performed in fish grown in sewage in composite fish culture tanks at Coimbatore. While Salmonella spp. were not found in the tissues of the fish (skin, gut and muscle), other pathogens were found in the gut. Cooking the sewage-grown fish, by boiling in water, by making curry or frying (in oil) does make the fish pathogen-free. No tests on virus transmission have been reported, but such tests must be made. Recycling human waste for fish production needs serious study. Another system of importance is the integration of aquaculture with agriculture and animal husbandry. This is an age-old practice in the East and can be brought up to date (Woynarovich, 1975). There is a problem of water management which needs considerable technological and engineering skills and these can be borrowed from the agricultural engineers (Pillay, 1976). A very favourable atmosphere has been created in the Agricultural Universities of India for the integration of aquaculture with agriculture, and this is now a major thrust of the Indian Council of Agricultural Research. Such multidisciplinary activities can be fruitful in rural development. An agricultural farmer can readily adopt aquaculture practices in small ponds and tanks in his field, supported by extension work at the Tamil Nadu Agricultural University. Fish-plant interaction at a more sophisticated level in closed systems is also of long-term interest (Naegel, 1977). A knowledge of environmental physiology of the organisms is necessary before complete control and manipulation of such systems is possible. Monoculture systems of the giant prawn, Macrobrachium rosenbergii, and cage culture of several species of fishes are projects in which several IFS grantees are involved. Of major interest in Asia, as demonstrated by work at Penang, is the rearing of estuary grouper, Epinephelus, a popular food fish in South East Asia, in floating net cages (Chua and Teng, 1977). Growing fish in semi-cultural conditions can also be profitable. I refer to activities such as ocean ranching (Joyner, 1975). A similar practice is the stocking of man-made reservoirs with young fish from nurseries. Fish production in several Indian reservoirs, which was about 5-7 kg ha-’ year-‘, increased to 30-160 kg ha-’ year-’ after the introduction of the Indian major carps and tilapia. The investment is mainly in the cost of production of fingerlings, and harvesting. There is no easy control over the fish returns. Because of the extensive area available in man-made reservoirs, and which is increasing in most countries, such exploitation can yield considerable returns. For example, the shallow reservoirs of China have a high fish production as carp culture is combined with utilization of sewage and animal waste. Reservoirs in India are used for stocking and rearing fish in cages. This practice avoids the problem of space for installation of a nursery of the conventional type.

164

FISH SEED PRODUCTION

I have already referred to the problem of seed production. This is a major priority of aquaculture research, and considerable skills have been gained in hypophysation techniques. At the level aquaculture production must be increased, there will be a lack of the required seed for many years. Wild seed collection, such as that of Indian carps (Jhingran, 1975), can yield some resources but there is the problem of separation of seeds. Hypophysation techniques have eased the problem of fish seed supply, but one of the constraints is the shortage of pituitaries. Research into purification of gonadotropins and testing new analogues of pituitary hormones (Pandey and Hoar, 1972; Pandey et al., 1973; Lam et al., 1975; Jalabert et al., 1977) should be intensified. Induced spawning by physiological manipulation, e.g. eyestalk removal in crustaceans (Santiago, 1977; Primavera, 1978), is also of significance. Other productive research is the control of ovulation in fish by regulation of photoperiod and temperature (e.g. Kuo et al., 1974; Kuo and Nash, 1975). ENVIRONMENTAL

CONTROL

OF SURVIVAL

AND GROWTH

OF AQUATIC

ORGAN-

ISMS

Information on lethal and sublethal levels of various environmental parameters, such as ambient temperature and dissolved oxygen, is important in formulating culture practices. Also, the effect of these factors on bioenergetics of the organism, i.e. energy input, energy dissipation and growth, has to be known for understanding optimum feeding and growing conditions. Thus, when intensive culture of an organism is attempted, the whole spectrum of the environmental physiology gives much insight into the culture practices. I refer in this case to intensive culture under’controlled conditions, such as that attempted for Macrobruchium rosenbergii (Shang and Fujimura, 1977), the marine penaeid prawns (Penaeus japonicus, P. monodon, P. semisulcatus and P. indicus) (Shigueno, 1975; Kurata and Shigueno, 1976), salmonids (Brett, 1974), and for other high value food fish. Information on environmental physiology must be obtained by studying resistance and tolerance to the various ecological factors, and subsequently optimum levels of energy utilization and growth. Optimum levels have to be studied with reference to animal size and growth. One aspect which is often not understood is the complexity of respiration and growth. The energy input through the food is only partly assimilated (see Fig.1). Of this assimilated energy, only a portion is metabolized. One part goes for maintenance and the rest can be available for growth (meat production). However, this is complicated by activity, which can demand all or part of the energy which otherwise would go into flesh depending on the behaviour of the fish and external conditions. There is thus competiton between ‘activity’ (behaviour) and ‘growth’ for energy (Brett, 1974) which is of great importance to the aquaculturist (Fig.1). There is a ‘behavioural wastage’ (Kutty, 1978b) by the organism, which can be reduced considerably by obtaining information

165 FACTORS

REGULATING

ENERGY

UTILIZATION

FACTORS INTRINSIC

EXTRINSIC

TEMPERATURE wNlT~(10n

KTIVITYtirotic osmatic)

WATER

CURRENT

o,@.Hdic

and

SCHOOLING

Anoemblc)

WEIGHT SEX

CO2 DH LIGHT

and Anaerob,c)

EXCITEMENT

MATURITY (photoperiod)

CYCLIC

STAGES

EVENTS(Dlel,

PRESSURE

STARVATION

FOOD

FOOD

Monthly, Annual)

QUALITY

COMPETITION

Fig.1. Factors

regulating

energy

utilization.

on its activity and behaviour under various environmental conditions. The aquaculturist will then be able to save on feed costs and get the best returns by growing fish close to resting conditions. There is a need to understand the nutritional requirements (Price et al., 1976) and digestive physiology (Austreng, 1978) of the organisms used for aquaculture. A thorough study exists for the trout (Halver, 1972). We must look at our important fish and prawns under culture in this context: the major carps of India, the milkfish, the giant freshwater prawn, the catfish (Clarias), the grouper, Epinephelus, the marine penaeids, Penaeus japonicus, P. monodon, P. semisulcatus, P. indicus, etc. The multiplicity of aquatic species awaiting domestication is vast (Pihay, 1976). Some of these have to be selected and studies made so that we can put aquaculture on a more scientific base. Other important fields of research are the culture of fish food organisms (e.g. Persoone and Sorgeloos, 1975), which needs priority in aquaculture development, and genetic improvement of fish stocks (Donaldson and Menasveta, 1961; Donaldson, 1970) by selective breeding and hybridization. Even though aquaculture has improved greatly by genetics, for small level researches genetical studies are too expensive. The need for such studies, however, is at the national or regional levels.

166 SUMMARY

I received a grant from IFS for studies on the ecophysiology and growth of the freshwater mullet, and my associates and I have benefitted much by it. Four of my students (Mohamed, 1974; Narayanan, 1974; Sukamaran, 1975; Kasim, 1978) produced Ph.D. theses on different aspects of mullet biology. We now have several other programmes in our faculty of fisheries at the Tamil Nadu Agricultural University. In one way or another all my programmes have benefitted by my association with IFS. I have great pleasure in acknowledging the grant and timely help from the IFS, which has given a great deal of confidence and enthusiasm, especially to the young research group working with me, and has resulted in their productive work. It is a great pleasure to be here amidst the IFS grantees, and I have the great personal honour to give this keynote address to you. I thank the IFS and the organizers at the Universiti Sains Malaysia of this regional meeting for giving me the opportunity. The IFS has made vast strides in the few years of its existence. It has given over 250 grants to individual scientists in developing countries. This meeting serves several purposes. To quote from a letter from Professor Nicolai Herlofson, it promotes personal contacts, in particular between grantees within the region; reviews IFS regional research; brings research results to bear on regional development, seeks new IFS sources of support for practical applications; prepares the transfer of knowledge from one region to another; and forsees improved uses of IFS resources. Let me wish and hope that all these will be achieved in the few days ahead at Muka Head Station, Universiti Sains Malaysia.

REFERENCES Austreng, E., 1978. Digestibility determination in fish using chromic oxide marking and analysis of contents from different segments of the gastrointestinal tract. Aquaculture, 13: 265-272. Bardach, J.E., Ryther, J.H. and McLarney, W.O., 1972. Aquaculture: The Farming and Husbandry of Freshwater and Marine Organisms. Wiley-Interscience, New York, N.Y., 868 pp. Brett, J.R., 1974. Marine fish aquaculture in Canada. In: H.R. MacCrimmon, J.E. Stewart and J.R. Brett (Editors), Aquaculture in Canada. Bull. Fish. Res. Board Canada, No. 188. Dept. of Environment, Fisheries and Marine Service, Ottawa, Ont., pp. 55-84. Chaudhuri, H., Chakrabarty, R.D., Sen, P.R., Rao, N.G.S. and Jena, S., 1975. A new high in fish production in India with record yields by composite fish culture in freshwater ponds. Aquaculture, 6: 343-356. Chua Thia Eng and Teng Seng-Keh, 1977. Floating fishpens for rearing fishes in mining pools, reservoirs and coastal waters in Malaysia. Fisheries Bulletin, No. 20, Ministry of Agriculture, Malaysia. Davy, F.B. and Allsopp, W.H.L., 1976. Progress in tropical aquaculture research. In: FAO Technical Conference on Aquaculture, Kyoto, Japan, 26 May-2 June 1976. FIR: AQ/ Confl76lE.60, Tokyo, 4 pp. Donaldson, LR., 1970. Selective breeding of salmonid fishes. In: W.J. MC Neil (Editor), Marine Aquaculture. Oregon State Univ. Press, Corvallis, Ore., pp. 65-74.

167 Donaldson, L.R. and Menasveta, D., 1961. Selective breeding of Chinook salmon. Trans. Am. Fish. Sot., 90: 160-164. FAO, 1976. FAO Technical Conference on Aquaculture, Kyoto, Japan, 26 May-2 June 1976. Proceedings. Gaillard, J. and Bramsnaes, F., 1978. Review of Area “Aquaculture”. International Foundation for Science, Stockholm, 28 pp. Gropp, J., Koops, H., Tiews, K. and Beck, H., 1976. Replacement of fish meal in trout feeds by other feed stuffs. In: FAO Technical Conference on Aquaculture, Kyoto, Japan, 26 May-2 June 1976,lO pp. Halver, J.E. (Editor), 1972. Fish Nutrition. Academic Press, New York, N.Y., London, 713 pp. Hepher, B., 1975. Waste water utilization in Israel aquaculture. Paper presented to the International Conference on the Renovation and Recycling of Wastewater Through Aquatic and Terrestrial Systems, Rockefeller Foundation, Bellagio Study and Conf. Center, 16-21 July 1975. Jalabert, B., Breton, B., Brzuska, E., Foster, A, and Wieniawski, J., 1977. A new tool for induced spawning - the use of 17&Y-hydroxy-20p-dihydroprogesterone to spawn carp at low temperature. Aquaculture, 10: 353-364. Jhingran, V.G., 1975. Fish and Fisheries of India. Hindustan Publishing Corporation, Delhi, 954 pp. Joyner, T., 1975. Farming the Ocean Range. Oceanogr. Comm. Washington, Seattle. Pacific Northwest Sea,, 8: 12-l 5. Kasim, H., 1978. Ecophysiological studies on fry and fingerlings of some freshwater fishes with special reference to temperature tolerance. Ph.D. Thesis, Madurai University, Tamil Nadu. Kuo, C.-M. and Nash, C.E., 1975. Recent progress on the control of ovarian development and induced spawning of the grey mullet (Mugil cephalus L.). Aquaculture, 5: 19-29. Kuo, C.-M., Nash, C.E. and Shehadeh, Z.H., 1974. The effects of temperature and photoperiod on ovarian development in captive grey mullet (Mugil cephalus L.). Aquaculture, 3: 25-43. Kurata, H. and Shigueno, K., 1976. Recent progress in the farming of penaeid shrimp. In: FAO Technical Conference on Aquaculture, Kyoto, Japan, 26 May-2 June 1976. FIR: AQ/Conf. 76/R.17, 24 pp. Kutty, M.N., 1978a. Fishery Resources of India. Summer Institute on Resource Economics in Agriculture. Tamil Nadu Agricultural University, Coimbatore (mimeo). Kutty, M.N., 1978b. Some points of interaction between fishery biology and fish physiology. Keynote address. Summer School on Fishery Biology, College of’Fisheries, Mangalore, lo-14 April 1978. Lam, T.J., Pandey, S. and Hoar, W.S., 1975. Induction of ovulation in goldfish by synthetic luteinizing hormone-releasing hormone (LH-RH). Can. J. Zool., 53: 1189-1192. Moav, R., Wohlfarth, G., Schroeder, G.L., Hulata, G. and Barash, H., 1977. Intensive polyculture of fish in freshwater ponds. I. Substitution of expensive feeds by liquid cow manure. Aquaculture, 10: 25-43. Mohamed, M.P., 1974. Studies on the influence of hypoxia on fish metabolism and activity. Ph.D. Thesis, Madurai University, Tamil Nadu. Naegel, L.C.A., 1977. Combined production of fish and plants in recirculating water. Aquaculture, 10: 17-24. Narayanan, M., 1974. Studies on the biology of the mullet, Rhinomugil corsuZa. Ph.D. Thesis, Madurai University, Tamil Nadu. Natarajan, V., Vankataramanujam, K., Kutty, M.N. and Rajasekaran, P., 1977. Fish production through recycling waste waters. Seminar on Environmental Impact on Developmental Activities and Adoption of Suitable Guidelines for Project Control in Selected Sectors such as Industries, Agriculture, Irrigation, Transport, Urbanisation etc., Hyderabad, 19-20 December 1977, 16-l-16.10.

168 Pandey, S. and Hoar, W.S., 1972. Induction of ovulation in goldfish by clomiphene citrate. Can. J. Zool., 50: 1679-1680. Pandey, S., Stacey, N. and Hoar, W.S., 1973. Mode of action of clomiphene citrate in inducing ovulation of goldfish. Can. J. Zool., 51: 1315-1316. Persoone, G. and Sorgeloos, P., 1975. Technological improvements for the cultivation of invertebrates as food for fishes and crustaceans. I. Devices and methods. Aquaculture, 6: 275-289. Pillay, T.V.R., 1973. The role of aquaculture in fishery development and management. J. Fish. Res. Board Can., 30: 2202-2217. Pillay, T.V.R., 1976. The state of aquaculture 1975. In: FAO Technical Conference on Aquaculture, Kyoto, Japan, 26 May-2 June 1976. FIR: AQ/Conf./76/R.36, 13 pp. Price, K.S., Carriker, M.R., Epifanio, C.E., Srna, R.F., Pruder, G.D., Bolton, E.T. and Smith, K.P., 1976. Mariculture in controlled environment seawater systems. A review of research at the University of Delaware (1968-1975). In: FAO Technical Conference on Aquaculture, Kyoto, Japan, 26 May-2 June 1976, FIR: AQ/Conf./76/E.37, 5 pp. Primavera, J.H., 1978. Induced maturation and spawning in five-month-old Penaeus monodon Fabricus by eyestalk ablation. Aquaculture, 13: 355-360. Ryther, J.W., Dunstan, W.M., Tenore, K.R. and Huguenin, J.E., 1972. Controlled eutrophication - increasing food production from the sea by recycling human wastes. Bio Science, 22: 144. Santiago, Jr., A.C., 1977. Successful spawning of cultured Penaeus monodon Fabricus after eyestalk ablation. Aquaculture, 11: 185-196. Sehgal, K.L., Wani, A.R., Ghulam Nabi and Kuldip Kumar, 1976. Experiments on the efficiency and cost of dry, compound pelletized feed in relation to conventional feed in relation to conventional feed in Kashmir trout farm. J. Inland Fish. Sco., India, 8: l-12. Shang, Y.C. and Fujimura, T., 1977. The production economics of freshwater prawn (Macrobrachium rosenbergii) farming in Hawaii. Aquaculture, 11: 99-l 10. Shigueno, K., 1975. Shrimp Culture in Japan. Association for International Technical Promotion, Tokyo, 153 pp. Sukumaran, N., 1975. Some aspects of the physiology of the freshwater mullet, Rhinomugil corsula, subjected to exercise. Ph.D. Thesis, Madurai University, Tamil Nadu. Wheaton, F.W., 1977. Aquaculture Engineering. John Wiley and Sons, New York, N.Y., 708 pp. Woynarovich, E., 1975. Technical and economic feasibility of duck, poultry and pig farming in combination with aquaculture. Fishery and Fish Culture Development Project, Caracas, Venezuela, Rep. to FAOIUNDP Fisheries Project, Caracas, Venezuela, 36 pp. (mimeo).