Coastal aquaculture in Thailand has expanded rapidly in both area and production in the last decade. The important cultured species are the shrimps (Penaeus monodon and P. merguiensis), sea bass Lates calcarifer, groupers Epinephelus malabaricus and E. tauvina, green mussel Perna viridis, horse mussel Modiolus senhausenii, blood cockles Anadara granosa and A. nodifera and the oysters Crassostrea belcheri, C. lugubris and Saccostrea commercialis. The total production from coastal aquaculture in 1991 was 230,444 tons, consisting of 70.3% shrimp, 28.8% mollusks, and 0.9% fishes. The seaweeds Gracilaria spp., pearl oysters, scallops, and abalones are cultured on a pilot scale in some places. Hatchery technologies have recently been developed for groupers, oysters, scallops, and abalones. Expanded aquaculture has had some adverse effects on the environment and has also suffered from the environmental changes and conflicts due to other sectors using the same water and other resources.

Aquaculture in Malaysia is experiencing rapid growth. Total production in 1992 amounted to 79,699 tons valued at RM 207.4 million. These figures are 23% and 25% higher than the previous year's. Semi-culture of the cockle Anadara granosa was still predominant, contributing about 70% of the total output. Culture and production of the oyster Crassostrea iredalei is still insignificant. Sea bass Lates calcarifer constituted over 80% of the production from marine cages. Cage culture of grouper Epinephelus sp., snapper Lutjanus sp. and pompano Trachinotus blochii were also done in much smaller scale. The mangrove snapper Lutjanus argentimaculatus was recently spawned in captivity and larvae and juveniles were produced. In 1992, the tiger shrimp Penaeus monodon constituted about 87% of brackishwater pond production. Pond culture of the white shrimp P. merguiensis and the mudcrab Scylla sp. is at the experimental stage. Red tilapia hybrid was the major freshwater species cultured in cages, with 1,486 tons harvested in 1992. Freshwater pond production was valued at RM 100.85 million, 22% of which was due to the eel Anguilla japonica. Production of freshwater ornamental fishes is also becoming significant. Other exotic species recently bred and cultured are the African catfish Clarias gariepinus and the pacu Piaractus brachypomus. The indigenous freshwater catfish Mystus nemurus and carp Probarbus julleini have recently been bred in captivity and cultured experimentally. Lately, there have been attempts to culture non-conventional species such as the bullfrog Rana catesbeiana, the soft-shell turtle Trionyx sinensis, and aquatic ornamental plants.

Aquaculture has grown rapidly in Asia. In 1992, out of the 52.8 million tons of total production of aquatic organisms, as much as 17 million tons (32.2%) came from aquaculture. However, unplanned and uncontrolled development of aquaculture has led occasionally to environmental damage and social disruption in many countries. Now attention has focused on the sustainability of aquaculture. Negative impacts of shrimp culture have been well publicized, but problems have also been caused by overinvestments in fish and mollusk culture. As sustainability is a highly complex issue, it is important to develop internationally accepted principles and guidelines for responsible aquaculture, with the use of technologies not detrimental to natural resources, ecosystems and human communities. FAO is now in the process of developing an International Code of Conduct for Responsible Fishing based on the Declaration of Cancun. One chapter of the Code will deal with aquaculture. Unfortunately, information is rather scanty on the environmental impacts of various aquaculture systems and the carrying capacity of aquatic ecosystems, especially in tropical areas. Therefore, research on these topics should receive high priority. Similarly, tightening and enforcing the rules and regulationsgoverning existing and new aquaculture ventures is a pressing task that responsible government agencies can not postpone any longer.

Seafarming is undertaken in the coastal sublittoral zone. Different marine organisms such as molluscs, estuarine fishes, shrimps (pen culture), and seaweeds are cultured along the coast of Thailand. Seafarming, especially for mollusc, is the main activity in Thailand. The important species are blood cockle, oyster, green mussel, and pearl oyster. In 1988, production was approximately 51,000 metric tons in a culture area of 2,252 hectares.Artificial reefs have been constructed in Thailand since 1987 to enhance coastal habitats. Larvae of marine organisms have also been restocked in the artificial reef area.

The paper reviews developments in Seafarming and searanching in the Philippines. Seafarming activities concentrated on seaweeds and molluscs, technology for which are already widely practiced. In Seafarming of oysters and mussels, technology is mature but only applied in traditional sites. As such, the quality of products and consumption is low due to known pollution of oyster and mussel farming areas. Seafarming of giant clams is just beginning. Hatchery techniques of producing juveniles are being refined for mass production and seeding of reef areas to enhance giant clam population. Seafarming of marine fishes is also practiced but constrained by the lack of seed stock. Sea cage fanning operators mainly depend on wild-caught fry and juveniles although the hatchery technology for sea bass has been developed. There is more research work to be done to mass-produce fry and juveniles for Seafarming of other fish species. Seafarming and searanching appear to be the future major means of supplementing the production of animal protein by year 2000 as arable land continues to dwindle. Declining arable land area would not be sufficient to produce the food needs of the increasing population. There is great potential for Seafarming and searanching to enhance coastal resources and produce more food. However, there is a need to provide stronger legal and institutional support for these activities to sustain development efforts.

In 1989, artificial seed production was attained in 37 species of fishes, 16 species of Crustacea, 25 species of shellfishes, and 9 species of other fishery animals in Japan. Eighty species of fishery animal seed, including natural and artificial production, were released in natural fishery grounds during this year. The total mariculture production was 1.3 million tons. This composed of 18% fish, 35% shellfish, 46% seaweed, and 1% of other fishery animals.In recent years, Japan achieved some success in Seafarming and searanching projects. Among these are searanching of Japanese scallop in northern Japan and acoustic habituation system of red sea bream. Searanching of striped jack using artificial seed is also explained.

Seafarming has ecological effects such as pollution and eutrophication of adjacent areas by excess food or by feces or modification of habitats by physical structures. More subtle effects on the communities result from heavy consumption of plankton or benthos by caged or enclosed farmed organisms and consequent reduction of availability of food to adjacent natural communities. Seapens, in which monocultures are reared, develop a radically different benthos from that in adjacent areas. Seafarms can become focal points from which pathogens and parasites can be spread.Searanching, in which stocks are enhanced by the addition of hatchery-reared recruits, has the potential to cause significant changes in the composition and stability of marine communities. Enhanced recruitment of a species will have negative effects on both its prey and its competitors but will enhance the biomass of its predators.Enhanced recruitment of a stock of apex predators will decrease the biomass of its prey and cause changes in the composition of the community. The effects of searanching are amenable to modelling, and the likely effects of proposed searanching schemes should be examined before these are implemented.The magnitude of the effects of searanching will depend on the degree to which the area is naturally saturated with recruits of that species and on the rate of exploitation. Poor management of the stock, resulting in under- or over-exploitation, will have highly destabilizing effects on the communities.Seafarming or searanching can have negative effects on the gene pools of natural stocks and result in changes in life histories or in behavior.

Sustainable development of seafarming and searanching calls for careful planning. Investments in seafarming must take into account environmental, biotechnological, and socioeconomic considerations. Investment planning must be carefully examined as well as the physical design of production systems such that its negative impact is minimized and the positive impact is accentuated.Supply from the wild may not be expected to grow much higher than present levels. Many of the major commercially valuable fisheries are now overfished at or close to their respective minimum sustainable yield levels. Seafarming can attract some of the fishermen out of overcrowded fisheries.Production cost of seafarming produce is a major concern which has to be examined closely if these are to compete with and gradually supplant the supply of fish from the wild. Feed is one of the main inhibiting factors, hence, efficient consideration calls for constantly improving feed conversion and productivity per unit input.Existing government policies are not clear nor conducive to seafarming in terms of use rights of coastal waters. To attract potential investors into seafarming, governments are encouraged to review existing policies governing use rights to coastal waters, package the necessary technology consistent with the country's wage and price structure, and develop investment profile for seafarming opportunities using conservative criteria.

The nine countries in Southeast Asia occupy a land area of 1.85% with a population of 7.4% in the world. In 1991, these countries had a total fisheries production of 10.2 million tons or 10.5% of the world total of 96.9 million tons. In aquaculture in 1990, world total production attained 15.3 million tons (15.7% of total world fisheries production) while the Southeast Asian countries produced 1.7 million tons (11 % of total world aquaculture production). The total fisheries production in Southeast Asia which is mainly capture fisheries has continued to increase gradually by about 3.3% from 1986 to 1990 while aquaculture production has been increasing at the rate of over 8.4% during this period.The major areas for aquaculture in Southeast Asia include inland freshwaters, brackishwaters, and marine waters. Various systems exist in the region including ponds, pens and cages, delimited or fenced open water areas, and culture integrated with other production activities. Highest potential is in Seafarming while ranching is a recent innovation. The species being cultured in the region consist of about 50 fishes, 10 crustaceans, 10 molluscs, 5 seaweeds, and 5 miscellaneous aquatic vertebrates.Aquaculture will increasingly supply food and industrial products considering the worldwide levelling off of capture fisheries production. Southeast Asia has the potential to contribute substantially to this need. Support for the industry inspite of this need is inadequate to meet its technical, economic, and management problems. A sound technological base through research and training and extension needs to be pursued vigorously.