A great amount of research is being conducted on shrimp culture throughout the world, particularly in developed countries. Much of this research will have direct application in the South China Sea Region: i.e. hatchery technology, disease and parasite control, sexual maturation, and nutritional and food technology. Research is progressing rapidly and techniques and equipment are constantly being revised. Production systems designed in one country, however, invariably need modification to adapt them to local conditions in another country. With these factors in mind, planning and designs for research facilities should be kept flexible. Small scale, pilot type, construction is much easier to modify than large permanent fixtures. Space should be allowed for expansion and modification as new technology is developed.
Most of the research on grow-out in the developed countries is directed toward highly capitalized, intensive methods of culture requiring heavy feeding. In most countries of the region a more extensive type of shrimp farming seems appropriate, because of the availability of vast areas of under-developed land, scarcity of feed materials in some areas, and lack of capital. Consequently, grow-out procedures appropriate to the region will have to be developed locally.
Following, in order of priority, are those aspects of shrimp culture which have particular importance in the South China Sea Region and in which additional research is most essential.
Fertilization experiments incorporating studies of soil and water chemistry should be conducted to gain an understanding of nutrient dynamics in brackish water ponds. The capacity of various types of fertilizer to stimulate pond productivity and support the growth of shrimp has to be determined. Content of major nutrients in ambient water should be recorded so the results could be applied in other areas. Methods of measuring nutrients in pond water suitable for use by extension workers should be developed.
The immediate need is for a reliable, year-round supply of gravid females. Long term application includes genetic manipulation. Appropriate holding facilities have to be designed. Special diets have to be developed, as it appears as if lipids play a special role in ovarian maturation. Research should encompass all indigenous species.
The need for flexibility also holds true when choosing which species to culture. P. monodon has many characteristics such as large size and tolerance to low salinity which make it a favoured species for culture. However, other species should not be neglected. P. merguiensis nad P. indicus mature readily in captivity, are relatively hardy and are abundant throughout the region. The ease with which they can be bred makes these species attractive for culture.
Research is needed to determine the most favourable environmental conditions and production management for all indigenous Penaeidae. Studies to evaluate tolerance of different life stages to extreme culture conditions should be made, especially high temperature and low salinity.
For instance, Piyakarchana, et al (1975) reported that 50 percent of P. merguiensis juveniles averaging 8.5 cm TL became moribund at a temperature of 35°C in an experiment. As temperature in shallow ponds frequently exceeds 35°C, this probably explains the lack of success in culturing P. merguiensis in some areas. Once information on physiological tolerance is known, species can be cultured in areas where environmental conditions are most favourable for their growth or it will be possible, in some cases, to modify grow-out facilities to provide for favourable growing conditions. The latter possibility will be of prime importance in improving production from the existing traditional shrimp farms. It will probably be advantageous to grow different species in different seasons as well.
Shrimp culturists have traditionally relied on brine shrimp as food during larval culture. There is now a world wide shortage of brine shrimp eggs, and research to develop alternate foods is necessary. Efforts should be directed toward evolving methods of culturing live foods such as rotifers, and to develop processed feeds. Processed foods will require different tank designs than those presently used in the region. This is one of the most important reasons for not constructing large expensive hatcheries at this time.
In most areas too little information is known about the availability of postlarvae for seedstock. It is important to know when sufficient numbers of various species will be available for stocking so grow-out production schedules can be planned. Sampling should be done to determine species, numbers, and seasonal abundance of postlarval shrimp. More seedfish resource surveys such as one recently carried out in the Philippines (Deanon, Ganaden and Llorca, 1974) should be carried out in the different countries. Efforts should be made to start artisanal collection of postlarvae in areas where none exist now.
More information is needed on the effects of chemical pollutants on shrimp growth and survival. Research should concentrate on agricultural pesticides and herbicides as there is bound to be more use of these compounds in future years.
Initial work in this field should be to train research workers and extension biologists in methods of preserving diseased specimens for shipment to specialists. Simple preservation in formalin is not adequate, as the preservative frequently destroys the causitive agent. Methods of treatment can be developed later, first the role parasites and disease play in unexplained shrimp mortalities has to be known.
