The sugpo, Penaeus monodon, is a very important prawn species in Southeast Asia. It is extremely euryhaline and fast growing. Interest in the farming of this prawn species is very high. Unfortunately, the supply of natural fry is not sufficient. It is, therefore, necessary to develop the technology of breeding them in captivity and producing sufficient seed material. The Southeast Asian Fisheries Development Center, Aquaculture Department in Tigbauan, Iloilo, Philippines, operates a hatchery to produce fry for experimental rearing in brackish water ponds and for various laboratory studies.

In order to investigate the effect of different protein/energy levels of diets (two commercial and one laboratory) on voluntary feed intake and energy partitioning in tilapia (O. niloticus), 15 fishes with an initial body mass of 33 g were reared individually in respirometric chambers for 42 days and offered 3 diets ad libitum. The protein contents of the diets were 36.1, 33.8 and 36.8% (dry matter base); the energy content 18.9, 18.4 and 19.2 kJ GE/g and 11.7, 10.5 and 15.4 kJ ME/g. The initial body composition and energy content was estimated from a control group. Feed consumption was recorded for each individual fish. Body mass development was monitored weekly. At the end of the experiment, the fishes were sacrificed and their chemical composition (protein as N.6.25, lipid, ash) and gross energy content were determined. To establish energy budgets, ingestion (I) was calculated from feed intake, retention (P) from accretion in the carcass, heat production (R) from oxygen consumption (indirect calorimetry) and apparently non-utilized energy (faecal and non-faecal losses, U) by difference from energy ingestion. In the beginning, food consumption amounted to ~5% body mass equivalent (BME) per day for all groups and gradually decreased to 2.5, 2.8 and 1.6% BME by the end of the experiment. While the food consumption was significantly different between the treatments, there were no significant differences in the body mass development. Average final body mass was 98.6, 93.8 and 103.7 g. Energy retention was 29.7, 29.2 and 44.4% of GE ingested; heat dissipation 32.1, 27.9 and 36.0%; faecal and non-faecal losses 38.2, 43.2 and 19.6%. For all energy budget parameters, values for the laboratory diet were significantly different from those of commercial feeds 1 and 2. Calculation of metabolizable energy from ingested feed revealed no significant differences in the energy uptake, suggesting that the voluntary feed uptake was controlled by the demand for metabolizable energy. The fishes were able to completely compensate for the lower ME content of the commercial feeds by increasing voluntary feed intake.

Fish production from freshwater cages and pens, and marine cages and pens constitute 19% of the total foodfish produced from aquaculture in the Philippines. In 1998, production from freshwater cages and pens contributed about P 2.5 billion or about 10% of the total revenues from aquaculture. Freshwater cage and pen culture is practiced in most of the major lakes and reservoirs in the country. The most important species cultured in freshwater cages are tilapia and bighead carp (Aristichthys nobilis) while milkfish (Chanos chanos) is farmed in freshwater pens at Laguna de Bay. Small water impoundments intended for the irrigation of upland farms are also being used to culture tilapia and other freshwater fish in cages. The unregulated expansion of cages and pens, use of high stocking densities, and excessive feeding has resulted in the deterioration of the water quality in many areas. This has prompted the more informed local government authorities to adopt measures limiting further expansion of cage and pen culture activities beyond the carrying capacity of freshwater bodies to prevent periodic occurrences of mass fish kills. While cage mariculture of groupers has been practiced in the Philippines since the 1980 s, it was only in the early 1990 s that much of the growth and expansion of the industry occurred with the popularization of milkfish mariculture. In the last five years, no less than 1,000 cages with an aggregate capacity in excess of 10,000 metric tons a year have been invested in milkfish sea farming. The species now acounts for about 90% of the production from marine cages. In recent years, a drop in milkfish prices has motivated the industry to focus its attention on other fishes, primarily grouper (Epinephelus spp.), snapper (Lutjanus spp.), sea bass (Lates calcarifer) and siganid (Siganus spp.). Currently, imported species such as red tilapia, yellow-wax pompano (Trachinotus blochii) and red drum (Sciaenops ocellatus) are also being tested by the private sector. A high production cost due to low feed conversion efficiency and high seed cost is presently the greatest concern of marine cage farmers. In some areas, unregulated expansion has already led to problems in water quality.

To relieve pressure on wild stock population, a hatchery technique for the window-pane shell, Placuna placenta Linnaeus has to be developed. A study was conducted to determine the suitable algal diet for P. placenta during gonad development and larval rearing. Sexually immature P. placenta broodstock were reared in the estuary or in tanks for four months. Tank-reared animals were fed daily mixture of Isochysis galbana (T-ISO) Parke and Tetraselmis tetrahele (G.S. West) at 100,000 cells/ml, 1:1 (100-I:T), or 200,000 cells/ml, 3:1 (200-3I:T) combinations. Monthly gonad histological examination showed that sexual maturity was attained by animals fed 200-3I:T diet after four months but not in 100-I:T. Estuary-reared broodstock had the highest gonad index among treatments after the first month, but did not reach sexual maturity until the end of the conditioning period. Sexually mature P. placenta from 200-3I:T fed-group spawned when exposed to UV light-irradiated seawater. One-day old larvae were reared in UV light-irradiated seawater until metamorphosis to plantigrade. Larvae were fed daily with monoalgal diet of I. galbana, T. tetrahele, or Chaetoceros calcitrans (Takano) at densities of 10,000-30,000 cells/ml. Larval settlement was observed in all diets after 14 days. Survival rate at metamorphosis was highest (12.60%) when diet of I. galbana was used, but lowest in T. tetrahele [5.1%) (P<0.05). Average shell length increment during the 14 days rearing period were 11.0, 11.38 and 9.92 µm day^-1, for Isochrysis, Tetraselmis and Chaetoceros fed larvae, respectively.

This study was conducted to determine the appropriate initial body size and the corresponding stocking density of sea bass, Lates calcarifer, during nursery rearing in illuminated cages. Hatchery-produced sea bass fry of different initial sizes of 7.2 (day 15), 13.2 (day 22), and 15.2 mm (day 29) were stocked at densities between 300 and 1,500 m^-3 in decreasing order with fish size. Nylon net cages (1x1x1 m) set in a protected sea cove area were individually lit at 300 lux using incandescent bulb placed at 1 m above water surface. Artificial lights attract wild zooplankton that served as prey to young sea bass. After 42 days of culture 22-day old sea bass fry with 13.2 mm TL initial size and stocked at 400 m^-3 showed the highest growth (35.3 mm TL, 535.7 mg BW) and survival rates (64.4%). At a stocking density of 800 m^-3, the survival rate was the second highest at 43%. Although day 15-fry at 7.2 mm TL initial size showed higher specific growth rates (11 % day^-1) and size at harvest (29-31 mm TL, 346.2-374.4 mg BW), survival rates (11-15 %) were lower than the day 22- and 29-fry (30-64%). Calanoid copepods of the genus Calanus, Paracalanus and Acartia dominated the diet (81-90%) of sea bass at different size groups. Percentage number of shooters ranged from 0.5-1.4% of total stocks and were not significantly different among treatments. The present results indicate that sea bass should spend 21 days in the hatchery prior to nursery rearing in illuminated sea cages. Sea cages are inexpensive and more cost-effective than ordinary cage or earthen pond for sea bass fingerling production.

Mud crabs are one of the most widely sought crustacean species that inhabit the estuarine areas and tidal rivers and creeks of the Asian and Indo-Pacific regions. Hailed as "food for the gods," the mud crab is recognized as a candidate species for culture in brackishwater ponds and/or other suitable impounded brackishwater environments. In the past, mud crabs were a secondary species to cultured finfishes or crustaceans. Larvae entered ponds with incoming water and became trapped. Although conceived as a fishpond crop, the mud crab has also been considered a nuisance in ponds because it burrows into dikes and causes damage and leaks. Farming of mud crab has been progressing rapidly due to a promising market and profitability. With the availability of mud crab juveniles from the wild throughout the year and the recent development in hatchery technology, there is a strong indication that production of mud crabs on a commercial scale could be a lucrative industry. The information presented here is based on the recently published extension manuals and literature on mud crab culture both in brackishwater ponds and pen enclosures in mangroves.

Salinity tolerance was determined for each zoeal stage of Scylla sp. Larvae from ablated pond-grown females were abruptly transferred to salinities of 12, 16, 20, 24, 28 and 32 ppt. Spawning salinity or previous rearing salinity was 32 ppt, except for Z5 which were previously reared at 26 ppt. The mean median lethal time or LT50 values were compared between salinities. For Z1 and Z2, highest values were obtained at 20–32 ppt. Z3 had highest LT50 values at 20–24 ppt and Z4 at 24–32 ppt. For Z5, highest LT50 values were obtained at 20–32 ppt. Another batch of Z3 and Z4 were subjected to the same abrupt salinity transfers and reared to the megalopa stage. Significantly higher percentages of larvae metamorphosed to the megalopa stage at salinities of 20–28 ppt when transfer to test salinities was at Z3. When transfer was at Z4 or Z5, the highest percentage of larvae moulted to the megalopa stage at 24–28 ppt or at 28 ppt, respectively.

In December 1996, the Supreme Court of India ordered the closure of all semi-intensive and intensive shrimp farms within 500 m of the high tide line, banned shrimp farms from all public lands, and required farms that closed down to compensate their workers with 6 years of wages in a move to protect the environment and prevent the dislocation of local people. If the 1988 collapse of farms across Taiwan provided evidence of the environmental unsustainability of modern shrimp aquaculture, the landmark decision of India's highest court focused attention on its socioeconomic costs. This chapter briefly describes shrimp farming, discusses its ecological and socioeconomic impacts and recommends measures to achieve long-term sustainability including improved farm management, integrated coastal zone management, mangrove conservation and rehabiUtation, and regulatory mechanisms and policy instruments.

A shift in preferred methods employed to contain bacterial diseases in the hatchery phase of shrimp culture has resulted largely from the unsuccessful control by and deleterious effects of chemotherapy. Manipulation of hatchery microbial ecology has gained popularity, but for successful implementation, this niche-filling approach requires a thorough understanding of the epidemiology of bacterial diseases in the hatchery. This study examined the responses of Vibrio harveyi populations, (associated with luminescent vibriosis in shrimp larvae) to various physico-chemical factors and various hatchery components. Results showed that V. harveyi had a wider range of tolerance to environmental parameters than larvae of Penaeus monodon, such that control measures based on manipulation of these parameters might not be feasible. However, it was evident from the results that there were components in the shrimp hatchery environment that could be manipulated to control high populations of V. harveyi. The natural microflora of seawater, as well as the microbial flora associated with the diatoms Skeletonema costatum and Chaetoceros calcitrans negatively affected the survival of V. harveyi in experimental mixed cultures. The successful manipulation of such benign microbial components to compete with and exclude potential pathogens is necessary to sustain ecological balance in the shrimp hatchery environment.