The full-scale cultivation of sugpo, P. monodon Fabricius, could only be realized if there is an assurance of continuous supply of fry. Obviously, a steady supply will depend largely on the availability of spawners. In December 1975, roughly after 2 1/2 years of intensive study, for the first time in the world, SEAFDEC Aquaculture Department has succeeded in inducing P. monodon to mature and produce normally the first generation of postlarval fry, thereby successfully effecting the completion of P. monodon's life cycle while in captivity. Another significant study the Department has initially carried out which could help augment and stabilize the supply of spawners and eventually stimulate the establishment of more prawn hatcheries and the development of ponds for prawn culture as a major export-oriented, dollar-earning industry, is the possible development of ovarian rematuration of spent spawners.

This study was conducted to obtain information for evaluating the present fry fishing practices and for understanding the behaviour of the fry. A description of the milkfish, Chanos chanos, fry fishing gears is presented. Each gear is illustrated and its operation explained.

The observations include: (1) air and sea water temperatures; (2) cloud cover; (3) rainfall; (4) wind direction and speed; (5) salinity; (6) sea wave condition.

The manual provides information on the culture of shrimps and prawns. Considerations regarding farm sites, pond specifications, pond ecosystems and differences between prawn and milkfish culture are examined. Seed supply, farm management practices and economic aspects are detailed.

Disease in prawn is any abnormal condition which may affect adversely the appearance, growth, and function of the animal. It may or may not result in mortalities. Disease outbreaks occur commonly in different culture systems such as hatcheries and grow-out ponds. Disease develops through the interaction of the prawn (the host), the causal agent (the pathogen), and the environment. In the presence of a susceptible host, a pathogen and predisposing environmental conditions (poor water quality, inadequate food, frequent handling, overstocking), disease is very likely to occur. Improved environmental conditions, healthy prawns and absence of disease agents would therefore lessen the chance of a disease outbreak. The causal agents may be pathogenic organisms (viruses, bacteria, fungi, protozoa, helminths, microcrustaceans) or nonpathogenic adverse environmental conditions (extreme temperatures, low oxygen levels, chemical poisons). Living disease agents cause infectious disease which generally result in gradual mortalities. Non-living disease agents cause non-infectious diseases that result in sudden mass mortalities. The environment determines the balance between the prawn as host and the disease agent. Microorganisms are always present in the water and some of them cause disease only when the prawn has been weakened through exposure to stressful environmental conditions. Hatchery personnel should realize that they themselves could transmit disease through their contaminated hands, clothing, and footwear. Equipment such as water pumps, blowers, pipes, and materials such as scoop nets, water hoses, pails, glasswares are also possible carriers of disease agents. Spawners, live natural food like diatoms, rotifers and brine shrimp, and artificial diets could also be vehicles of disease transmission. The prawn culturist, thus, must be able to manage the environment and make it favorable for the prawn. Hatchery management should, therefore, include operation procedures that will reduce the possibility of disease development during larval rearing. This manual recommends practices for disease prevention to prawn hatchery operators and technicians.

This document presents the recommended methodology, nominal projections and partial costs and returns, for extensive prawn culture at two production objectives, and semi-intensive culture with costs and returns breakdown for three production targets. Intensive prawn culture procedures are not discussed. Extensive Prawn Culture System I projects a production yield of about 110 to 160 kg/ha/crop or more in four months and survival rate of from 65 to 70%. The extensive Prawn Culture System II aims for a production rate of about 230 kg/ha/crop in four months at about 70% survival with expected average body weight of about 25 grams. The procedures indicated have been verified and are now widely practiced. Production targets under the Semi-intensive Prawn Culture System I range from 350 to 500 kg/ha in four months at survival rate of about 70 to 75% and expected average size at harvest of about 28 to 30 pcs/kg. This method has been confirmed at different collaborative sites using the modified SEAFDEC diet developed by the Feed Development staff of the SEAFDEC Aquaculture Department.

The techniques for the artificial propagation of milkfish (Chanos chanos ) developed at SEAFDEC are presented. These include: 1) capture and transport of spawners; 2) determination of sex and weight and maturity of fish; 3) induced spawning (preparation of injection, males, females); 4) fertilization and incubation; 5) larval rearing; and 6) mass production of larval food.

Two sexually maturing female milkfish were captured in April 1977 and induced to spawn by means of acetone-dried Pacific salmon pituitary powder. The eggs were fertilized and incubated and the resultant young reared to 74-day old, 11 cm long fingerlings. Newly fertilized eggs averaged 1.16 mm in diameter and each had a narrow perivitelline space containing several cortical granules which disappeared within a few minutes. The yolk was slightly yellowish, devoid of oil globules and very finely granulated. Embryonic development was very similar to that of other pelagic fish eggs and hatching occurred between 35 to 36 hr at a salinity of 32 ppt and a temperature range of 28.4-29.2°C.

Milkfish fry catch from Philippine waters can still be increased. Intensified collections in traditional fry grounds and exploitation of new areas may lead to a reduction of adult stock and the possible collapse of the milkfish fry fishery. The implementation of rational conservation and management measures are of immediate concern not only to increase the productivity and number of fry grounds but also to conserve this important aquatic resource. The present methods of catching milkfish fry involve fry filtration by mobile or stationary devices. The design, construction, area and time of operation of the gears are primarily dictated by the bottom topography of the fry grounds, wind direction, local current patterns and tidal fluctuations. Catching, handling, storage and transport activities expose the fish to undue stress which contribute to poor survival. The simple method of lowering the salinity of the water medium considerably reduces mortality. High mortality in nursery ponds has aggravated the seed shortage problem of the milkfish industry. The development of an efficient mass-production technology in rearing milkfish fry to fingerlings and in stunting fingerlings for longer periods could offer the solution not only in meeting the requirements for milkfish seed but also provide part of the fry requirements of other countries in the region.

The techniques for the artificial propagation of milkfish (Chanos chanos ) developed at SEAFDEC are presented. These include: 1) capture and transport of spawners; 2) determination of sex and weight and maturity of fish; 3) induced spawning (preparation of injection, males, females); 4) fertilization and incubation; 5) larval rearing; and 6) mass production of larval food.