Straminipiles are common inhabitants of marine, estuarine and freshwater aquatic environments. In mangrove habitats, halophytophthorans and thraustochytrids are abundant, both in tropical and sub-tropical areas. Their abundance is attributed to their wide tolerance to environmental parameters such as salinity and temperature, and their ability to produce abundant zoospores. Fallen mangrove leaves supply the bulk of organic material in any mangrove habitat. Straminipiles are one of the initial colonizers of fallen mangrove leaves. The ability of their zoospores to respond chemotactically to nutrients released by the leaves, and to attach firmly on the substrata surface by the release of adhesive materials, make them highly competitive in the colonization process. Thus, they are reported to play significant role in the microbial degradation of fallen mangrove leaves. Moreover, these organisms, especially thraustochytrids, are producers of high amounts polyunsaturated fatty acids (PUFAs). Therefore in the degradation process, they consequently enrich the nutrient content of the leaves for the benefit of other organisms at higher trophic levels, making mangroves an excellent nursery grounds for many fish and crustacean species. Some species of thraustochytrids are also used in the commercial production of PUFAs, for use in aquaculture specifically in larval rearing of marine fish and crustaceans.

This chapter reviews information on nutrient requirements, feeds and feeding practices of milkfish.

Aquaculture, the aquatic counterpart of agriculture, has grown rapidly in recent decades to become one of the most important means of obtaining food from the sea. Impacts of aquaculture on biodiversity arise from the consumption of resources, such as land (or space), water, seed, and feed, their transformation into products valued by society, and the subsequent release into the environment of wastes from uneaten food, fecal and urinary products, and chemtherapeutants as well as microorganisms, parasites, and feral animals. Negative effects may be direct, through release of eutrophicating substances, toxic chemicals, the transfer of diseases and parasites to wild stock, and the introduction of exotic and genetic material into the environment, or indirect through loss of habitat and niche space and changes in food webs. Today, large quantities of fish are caught to produce fish meal–the main ingredient in feed–which may result in overfishing and affect marine food chains, including marine mammals and top carnivores. In some types of aquaculture, fish and shrimp larvae are caught in the wild to be used as seed. This may also result in bycatches of large amounts of other larvae, representing losses to capture fisheries and biodiversity. Large areas of critical habitats such as wetlands and mangroves have been lost due to aquaculture siting and pollution, resulting in lowered biodiversity and recruitment to capture fisheries. The magnitude of biodiversity loss generally increases with scale, intensity of resource use, and net production of wastes, but it is very much dependent on which species is cultured and the method of cultivation. In some cases aquaculture may increase local biodiversity, e.g., when ponds are constructed in dry areas and with integrated aquaculture.

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.

Roots blowers are used to meet aeration requirements at the Tigbauan Research Station (TRS) of the SEAFDEC Aquaculture Department in Iloilo. Air is delivered through a system of PVC pipes and plastic tubing attached to air cocks. Water depth aerated ranges from 0.15 m to 2.1 m. Diffuser aerators and air lift circulators are commonly used. Improvements made since the system was set up in 1974 include burying of PVC lines to prevent rapid deterioration from direct exposure to sunlight and adoption of a closed loop pipe system to achieve even pressure distribution. The aeration system is working well at present, but some improvements and modifications are being worked out. Studies and revisions proposed to further improve the aeration system are: determining rates of oxygen transfer occurring in culture tanks, segregating small tanks from big ones, installation of suitable air filters to eliminate contaminants, and exercise of vigilance in spotting leaks and defective outlets.

The Philippines is an archipelago of more than 7,100 islands with 17,460 km of coastline, including mangrove forests which covered about 450,000 ha in the 1920s. Coastal aquaculture began a few centuries ago when earthen ponds for the culture of milkfish (Chanos chanos) were first converted from mangrove swamps. For a long time, coastal aquaculture was synonymous with milkfish pond culture; while prawns and shrimps were incidental byproducts resulting from wild fry that entered the ponds during tidal water exchange. In 1943, studies on low density monoculture of the giant tiger prawn (Penaeus monodon) using wild fry were initiated at the Dagat-dagatan Experimental Station of the Bureau of Fisheries in Malabon, Rizal Province. Information on the ecology and early life history of P. monodon generated by the Institute of Fisheries Research Development of the Mindanao State University (MSU-IFRD) in the early 1970s was used in setting up the first experimental prawn hatchery at IFRD. This was followed by the establishment of big-tank and small-tank hatcheries at the Aquaculture Department of the Southeast Asian Fisheries Development Center (SEAFDEC/AQD) in Iloilo Province. An active technology transfer program that included short-term, hands-on training courses on small-scale hatchery starting in 1977, contributed to a dramatic hatchery production of 15 million prawn PL in 1978. Based on the earlier Dagat-dagatan studies, SEAFDEC/AQD started higher-density (semi-intensive) growout pond experiments with P. monodon in the mid-1970's. At that time, farmers started stocking more than 10,000 PL/ha using hatchery fry. Soon after, the first intensive culture trials, using imported Taiwanese technology and feed formulations were undertaken by a Philippine food conglomerate. The availability of both seed and feed, and the attraction of lucrative export market prices contributed to the take-off of the prawn industry. In 1983, when the country's 56 hatcheries produced 85 million PL's, and commercial pellets for intensive culture first appeared in the market, pond production totalled 12,100 MT, a quantum leap from a harvest of only 1,800 MT the previous year. Since then production of PL, adults and exports have steadily increased to a peak of 20,000 MT of exports from 40,000 MT of pond harvests in 1988. The following year the bubble burst. From a high of P200/kg (US$1 =P21) in 1988, farm gate prices plummeted to as low as P70/kg in mid-1989 due to Southeast Asian excess production of black tiger prawn, and to prawn exports from China glutting the Japanese market. This chapter discusses the various components of the Philippine prawn industry with a focus on growout, problems of the farming sector, and problems of the industry as a whole. Lastly, recommendations are offerred for long-term viability.

The most important criterion among many used by operators for choosing poostlarvae to stock in ponvds, is the stage of development. THe stages considered suitable for stocking (about PL₂₀) can be identified by examination of anatomical features including the rostal spine number, the length of carapace and sixth abdominal segment. Pigmentation in uropods, size uniformity and activity of post larvae are useful considerations. During Transport,decreasing water temperature to lwer metabolic rate helps ensure the adequacy of oxygen in bags. Upon stocking, acclimation to the temperature and salinity of pond water is very importan. If changes are sudden, regulatory mechanisms may fail, resulting in moralities.

Diseases of prawn in ponds are caused by microorganisn like viruses, bacteria fungi and protozoans as well as factors such as nutritional deficiency, poor pond conditions and environmental pollutants. Most of these may be controlled by environmental and dietary manipulation. Control of transfers or introduction of new prawn species may also reduce the risk of disease occurrence. Chemotherapy is considered only as alast resort in the control of diseases in prawn ponds. The basic features of prawn diseases with emphasis on causative agents and methods of preventio and treatment are discussed.