The paper aims to present an economic evaluation of an integrated prawn (Penaeus monodon) hatchery-floating nursery project using standard economic tools and methods of analysis. The data used in the analysis were taken from SEAFDEC AQD experience at the Batan, Aklan Research Substation hatchery-floating nursery project. The technical bases were gathered from researchers after the peculiarities of aquaculture vis-a-vis other business ventures in agriculture and industry were taken into consideration. The study shows that an integrated hatchery-floating nursery project is a profitable culture system. The rate of return on investment for this integrated project ranges from 29 to 47% while payback period ranges from 1.8 to 2.6 years. A separate economic analysis of a hatchery project and a floating nursery was also undertaken to determine the profitability of independently operating each subsystem. The analysis shows better results for the floating nursery subsystem as compared to the hatchery subsystem. Return on investment and payback period for the floating nursery range from 23 to 78% and 1 to 3 years, respectively, while those for the hatchery range from 20 to 36% and 2.3 to 3.7 years, respectively.

Shrimp experimental ecology studies and the shrimp farming industry in China developed rapidly in the 1970's, and great strides have been made in the mass production of shrimp fry and the growing-out of marketable size shrimp since 1978. The total production of artificially reared shrimp fry and cultivated shrimp increased dramatically in the last few years. The improvement of water quality management and feed supply in larval rearing have resulted in increased production of shrimp fry up to 100,000-200,000 or even 300,000 fry/m3. Advances in the nutritional physiology and biochemistry of the digestive enzymes of juvenile and adolescent shrimp have enabled us to develop different kinds of for mulated feeds with high efficiency and low cost. Techniques for the transplantation and propagation of small benthic crustaceans (e.g. Corophium spp.) or polychaetes (e.g. Nereis spp.) to increase the benthos biomass for natural food of juvenile shrimp in nursery ponds have been developed and successfully practised. Improvement of culture techniques including shrimp pond management, has decreased the mortality of juvenile and young shrimp and increased yields of cultivated shrimp in the country. Highest production of 9,000 kg/ha has been achieved in the semi-intensive culture pond.

Marine shrimp farming is a century-old practice in some Asian countries. Past sluggish development of the industry is mainly due to the inadequacy of hatchery technology resulting in inconsistent and insufficient supply of shrimp fry hence offsetting large scale development of the industry. Recent success in hatchery techniques coupled with high market demand have generated world-wide interest in developing shrimp farms in Asia. This paper attempts to make an in-depth review of the various aspects confronting the development and expansion of the shrimp farming industry. The cultural significance of the various penaeid shrimps cultivated in Asia (Penaeus monodon, P. japonicus, P. indicus, P. merguiensis and P. orientalis) is critically reviewed in relation to other subtropical species such as P. stylirostris and P. van-namei successfully cultivated in South America. The major constraints confronting large scale cultivation of P. monodon and other commonly important species are discussed and research gaps outlined. Present status of hatchery techniques is discussed and the need for standardization of viable techniques for technology packaging and verification is highlighted to ensure reliable source of seed supply. The various problems in hatchery development, including development of artificial larval feeds, are emphasized. This paper attempts to compare the technological and financial inputs in high technology with traditional farming practices in the region. The grow-out technology in relation to farming intensity and level of investment are outlined with special reference to the socio-economic condition in Asia. The need to develop viable and appropriate shrimp farming technology within the technical and financial capabilities of the rural small shrimp growers is discussed.

Since Hudinaga succeeded in the artificial hatching and subsequent culture of larvae of the prawn, Penaeus japonicus, techniques for rearing this prawn from hatching to commercial sizes have been improved in Japan and applied to other penaeid species in Asian and other countries. The nutritional requirements of P. japonicus juveniles started to be investigated about 15 years ago. As a result, this prawn is found to require proteins, lipids, carbohydrates, minerals, and vitamins for normal growth, indicating the deficiency disease, poor growth, and high mortality when reared with diets lacking some nutrients. On the basis of this knowledge, compounded artificial diets are used practically for commercial production of P. japonicus as substitutes for traditional live food such as the short-necked clam and mussel. However, seed production of penaeids has depended on live food such as diatoms, Chlorella and Artemia. Mass culture of planktonic organisms not only requires much manual help and expensive equipment but also fluctuates with climatic conditions. Also, the nutritive value of planktonic organisms is occasionally variable and this makes the use of live food for mass culture restrictive. Therefore, the development of artificial diets for larval penaeids is one of the most important research areas in the field of penaeid culture. We have prepared microparticulate diets for larval penaeids for use both as substitutes for live food and for nutritional studies. In this presentation, I intend to deal with the overview of penaeid nutrition.

The development of the commercial culture of penaeid shrimps and prawns has been accompanied by the occurrence of diseases of infectious and noninfectious etiologies. Many of the important penaeid diseases are caused by organisms that are part of the normal microflora and fauna of penaeids. These organisms are opportunistic pathogens that cause disease only under conditions that favor them over the host. Many organisms in this category are ubiquitous, and most have been recognized and/or reported from each of the major penaeid culture areas of the world. Included among this category of pathogens are the filamentous bacteria Leucothrix mucor, Flexibacter sp. and Cytophaga sp. (agents of filamentous gill and surface fouling diseases); the peritrich protozoans Zoothamnium sp., Epistylis sp., and Vorticella sp. (surface epibionts that cause protozoan gill disease and surface fouling diseases), the invasive bacteria Vibrio alginolyticus and V. parahaemolyticus (agents of various bacterial disease syndromes); and the fungi Lagenidium callinectes, Sirolpidium sp., and Fusarium solani (agents of the most common fungus diseases of penaeids). Among the most important disease-causing agents are the penaeid viruses. These penaeid viruses may once have been limited in their geographic distribution in wild stocks, but they have become widespread in penaeid culture facilities. With the advent of commercial penaeid hatcheries, the shipment of broodstock and postlarvae from these culture facilities to others in different geographic regions has often resulted in the spread of these agents outside their normal range in wild populations. Included in this category of the penaeid viruses are the baculoviruses: Baculovirus penaei (BP), P. monodon baculovirus (MBV), baculoviral midgut gland necrosis virus (BMN); the hepatopancreatic parvo-like virus (HPV); the probable picornavirus infectious hypodermal and hematopoietic necrosis virus (IHHNV), and a reo-like virus in P. japonicus. The final group of important diseases of cultured penaeids are the nutritional, physical, and toxic disease syndromes. The ascorbic acid deficiency syndrome called "black death" is the best understood nutritional disease of penaeids. Among the physical diseases occurring in penaeid culture, gas bubble disease and tail cramp are probably the most common. Important toxic disease syndromes include aflatoxicosis and red disease (which may be due to mycotoxins); hemocytic enteritis (due to certain species of filamentous blue-green algae, especially Schizothrix calcicola) and toxic syndromes due to toxic algal blooms. There are five areas of research that should receive emphasis in the next several years in penaeid disease research: 1) Appropriately equipped laboratories in each of the major penaeid culture areas should identify and catalog those diseases occurring in culture facilities in their region; 2) Penaeid diagnostic laboratories should use, or strive to develop for general use, "standardized" diagnostic procedures whenever possible, especially for highly infectious agents such as the penaeid viruses; 3) Penaeid cell culture methods for primary cultures or cell lines must be developed to aid in the development of much needed rapid, sensitive diagnostic tests for the penaeid viruses; 4) Improved methods of disease prevention, control, or chemotherapy are needed for many of the penaeid diseases now adversely affecting the penaeid culture industry; and 5) Approval is needed from those government agencies (such as the U.S. Food and Drug Administration and the Environmental Protection Agency) for the drugs and chemicals used as chemotherapeutics in penaeid culture that may pose a health risk to humans.

Mariculture production in Japan has grown recently to nearly one million tons per year. Mariculture production in the shallow coastal waters of Japan mainly consists of eight species of finfish, six species of shellfish, and three species of algae. Kuruma shrimp culture techniques are highly developed. Nevertheless, only 1,800 tons of kuruma shrimp can be produced yearly. There is a demand for this species but culture grounds have become limited and there is not enough space to raise shrimp. In 1980, 600 million postlarvae were produced but one-half had to be released to the sea. The released shrimp that survived and grew have formed a new basis for the "Sea Ranching Fisheries" industry. The trial releases of postlarvae have proven that sea ranching of shrimp can be successful. To strengthen the foundation of sea ranching fisheries, there must be future research on ecological impact, as well as on physico-chemical water parameters. The life cycle, feeding habits, and predators of the shrimp must also be studied. Recent releases in Hamana-ko Lagoon, Shizuoka Prefecture, made by the research group of the Hamana-ko Substation of the Shizuoka Prefectural Fisheries Research Station have demonstrated the possibilities of sea ranching. This report discusses the research studies obtained at Hamana-ko Lagoon and the main problems of the use of this sea ranching method in mangrove swamp areas of Southeast Asia.

The paper discusses the reasons behind the farming success of Ecuador, as well as the limitations associated with farming throughout the rest of the Americas. Emphasis is given to specific farming practices, management techniques, and physical design characteristics. Through improved techniques the farmer is approaching the point where he can reliably manage his crop size and harvest time as dictated by market trends and postlarval supply. Until recently, pond production has been characterized by relatively small-scale operations often experimental in origin. Due to the farming success in one country, production output has risen from 4,800 tons in 1978 to 23,390 tons in 1983. As evidenced by this dramatic rise in production, Ecuador is in a period of expansion and increasing technical awareness, the combined results of which have led it to become the production leader in pond-grown shrimp. The economic pull towards Ecuador is now slowly giving way to shrimp development in other parts of the Americas. Owing to the technical gains brought about by government programs, universities and private industries, shrimp farming has become a potential activity in many areas previously thought inadequate. Production methods have progressed from the traditional extensive method to sophisticated closed system raceways. All but the latter method are exemplified by the techniques used throughout Ecuador. Presently, Ecuador has in production 50,000 ha of ponds. Of these, 30,000 ha are farmed using the extensive method characterized by low cost and low output. The successful approach referred to as the semi-extensive method occupies approximately 15,000 ha. This style of farming, while requiring increased cost, leads to a proportionately higher production output. The third approach is the semi-intensive method under which an estimated 5,000 ha are in production. Increasingly higher production rates are being achieved through improvements in physical pond design, pond maintenance and preparation, feeding and fertilization regimes, technical management, and control.

Phytoplankton composition and density were studied in three (3) stations in West Bay, Laguna Lake. Blue-green algae and diatoms were the most abundant in terms of cell density. Green algae had the most number of species. Diatoms predominated in the early parts of the year, under intense light conditions. Pulses of green algae were evident toward the end of the year, under high nitrogen concentrations. BIP (Biological Index of Pollution) values were very much affected by seasonal variations in the phytoplankton community.

The backflow of Pasig River into Laguna de Bay was closely monitored beginning April 28, 1997 based on the expected high tide in Manila Bay and the average low lake level of 2.5 m in Station W (N 14°27.7'; E 121°08.5') located at the west lobe of the lake. Saltwater intrusion was first detected during of the highest high tide (i.e., 1.5 m at 1430 h) on April 29. Water from Pasig River flowing into the lake was black and had a characteristic odor of hydrogen sulfide. With the light house (or 'Parola') at the mouth of Pasig River as the reference point, movement of saltwater in the lake was monitored and the area affected estimated with the use of GPS 38 Personal Navigator®. Up to mid May (Week 2), the movement of saltwater into Laguna de Bay was hampered by the intermittent calm weather conditions and moderately strong northeasterly wind ('hanging amihan'). When the wind direction shifted and the southwesterly wind ('hanging habagat') became strong on Week 3 (May 18 to 20), strong water movement and fast diffusion of saltwater into the other parts of the west lobe of the lake were observed. During this period of rapid change in the lake (May 21-24), a high frequency monitoring was conducted in Station W. Fluctuations in chloride ion concentration, conductivity and total dissolved solids, Secchi disc reading, turbidity, dissolved oxygen, and other parameters were noted in the station. Heavy rainfall in the area on May 24-26 and run-offs from the watershed and overflow from the river tributaries increased the lake level. The elevation of the water level resulted in draining out of the lake water into Pasig River to Manila Bay and this practically ended the year's saltwater intrusion into Laguna de Bay. Movement of saltwater reached almost the whole area of the west and central lobes of the lake on the first week of June (week 5) as evidenced by the clearing of water in those areas. It was estimated that clearing of the entire lake because of saltwater movement takes about 2-3 months.

Nile Tilapia, Oreochromis niloticus, cultured in cages in Laguna de Bay, were sampled on two occasions in 1995, each time over a 24-hour cycle. The weights of stomach content were averaged and analysed with the computer model MAXIMS. The model predicted that, in May, larger fish feeding on natural food alone fed continuously from dawn to dusk, ingesting 4.9 to 5.4% of their body weight (wet weight basis) whereas smaller fish had two feeding periods per day, from sunrise to mid-morning and again from mid-afternoon until after sunset, ingesting between 13.0 and 13.7%. In August, fish were given supplemental feed that ran out around mid-day, after which they continued to ingest natural food. The fish ingested 3.8 to 4.0% supplemental feed and 4.4 to 4.7% natural food per day. In May, most of the stomach contents consisted of the blue-green alga Anabaena spiroides, whereas in August, the natural food was made up principally of detritus. On the basis of these findings, it is recommended that supplemental feed be given in several doses spread throughout the day.