The use of chemicals is common in various aquaculture systems, as it is in many agricultural practices. However, with growing worldwide awareness of the need for responsible practices in aquaculture, governments and aquaculturists are increasingly concerned with the effects of the use of chemicals in aquaculture, especially those which appear likely to be hazardous to man, cultured stock and/or the environment. The need to synthesize and disseminate information on the use and management of double prime aquachemicals double prime was recognized by the Fishery Resources Division of the Food and Agriculture Organization of the United Nations (FAO) and the Southeast Asian Fisheries Development Center (SEAFDEC) Aquaculture Department, who convened double prime The Expert Meeting on the Use of Chemicals in Aquaculture in Asia, double prime which was held 20-22 May 1996 at the SEAFDEC facilities in Tigbauan, Iloilo, the Philippines. Support was provided by FAO, SEAFDEC and the Canadian International Development Agency s (CIDA) ASEAN Fund. The World Health Organization (WHO) supported the participation of a human health expert. The meeting was attended by 27 participants and more than 70 observers from the public and private sectors of 20 countries. Among the attendees were representatives from the Network of Aquaculture Centres in Asia-Pacific (NACA), the Fish Health Section of the Asian Fisheries Society (FHS/AFS), the Japan International Research Center for Agricultural Sciences (JIRCAS), the GESAMP Working Group on Environmental Impacts of Coastal Aquaculture, and the ICES Working Group on Environmental Interactions of Mariculture. The results of this expert workshop are presented in this volume. They include the texts of presentations on a wide range of topics (thematic reviews) related to the use of chemicals in aquaculture, with emphasis on the Asian Region, as well as country overview papers summarizing the use of aquachemicals in Asian countries. The contributions of the selected participants during the meeting are contained in this volume.

The environmental impact of marine fish farming depends on species cultured, culture method, stocking density, feed type, hydrography of the site, and husbandry practices. In all cultured systems, however, a very large percentage of organic carbon and nutrient input into a marine fish culture system as feed may be lost into the environment through feed wastage, fish excretion, faeces production, and respiration. The high pollution loading have caused considerable environmental concern in many countries, especially in water with limited carrying capacity. Furthermore, the use of chemicals (therapeutants, vitamins, pigments, and antifoulants) and the introduction of pathogens and new genetic strains have also raised environmental concerns. Despite the high pollution loadings, results from various studies show that some 23% of C, 21% of N and 53% of P of feed input into the culture system is being accumulated in the bottom sediments and the significant impact is normally confined to within 1 to 1.5 km of the farm. The major impact is on the sea bottom, where high sediment oxygen demand, anoxic sediments, production of toxic gases, and a decrease in benthic diversity may result. Decreases in dissolved oxygen and increases in nutrient levels in the water are normally confined to localized areas, and it is unlikely that fish farming activities will cause eutrophication over large areas. There is also no good evidence to support the suggestion that fish farming would increase the incidences of harmful algal blooms, nor that the present use of therapeutants, vitamins and antibiotics, and the introduction of pathogens and new genetics strains would pose a significant threat to the environment. Practical ways to mitigate environmental impact of fish farming include keeping stocking density (and hence, pollution loadings) well below the carrying capacity of the water body. Computer simulation and hydraulic models have been applied to estimate maximum stocking density in which water quality could be maintained in a sustainable manner. Pollution loading and environmental effects can also be significantly reduced by improved feed formulation and integrated culture (using macroalgae, filter-feeders and deposit-feeders).

The present condition of marine resources in the Philippines is critical and a majority of coastal communities live below the poverty line. If it continues, the progressive degradation of coral reefs and overexploitation poses a dangerous trend. Coastal resource management strategies are facing a new challenge: the integration of social, economic and natural sciences in future concepts to reverse the current status of ecosystem destruction and improvement of the people s living conditions. Hence, the primary objective of the coral farm is to provide alternative livelihood to fisher families from their resources on a sustained basis. The second objective is the rehabilitation of degraded reefs. Currently coral colonies of 64 species are taken through fragmentation from the wild. After 6-12 weeks (depending on the species) of grow-out in the farm, the fragments were deployed at the rehabilitation site at an average of 2 fragments per square meter (=12.5% cover). The survival of fragments is high at 84%, despite the fact that some coral colonies were placed in unsuitable substrates by the fisherfolk. More trainings have to be conducted improve their knowledge of coral biology and community structure. The net cost of rehabilitating a one-hectare reef is U$2,100 for 12.5% cover. Additional profit from coral marketing is used for community projects identified by the folk. In this case, coral farming may be an option for livelihood and a cost-effective tool for reef rehabilitation.

Aquaculture is a dynamic activity. To be successful and sustainable in this business, new techniques have to be continually developed, and adopted by farmers. Over the last decade, sustainability has become a key word for many different activities, including aquaculture. Many factors are involved in aquaculture sustainability, and health management has an important role among these. In order for aquatic animal health management at the farm level to aid the achievement of optimum yields, the following issues should be considered: suitable site selection, quality of broodstock and seed, reasonable stocking density, feed and feeding programme, water management, prophylactic and therapeutic treatment, and information dissemination. The sustainability of aquaculture at the national and regional levels requires different considerations among which are national policy, assistance priorities for farmers, legislation needs, technology development, and information needs.

Integrated aquaculture is inclusive of interactive utilization of resources and ecosystems in the artificial rearing of aquatic animals and plants. By the nature, purpose and scale of the operation, integrated fish culture can be categorized into five major modes. One is the traditional small-scale subsistence farming where fish are produced by recycling on-farm wastes in ponds or rice field, two is recycling of human excreta, three is the industrialized commercial operation by integrating medium and large-scale poultry or livestock farms with ponds for fish production, four is integration of aquaculture with natural ecosystems, e.g., shrimp culture with mangroves, cage and pen culture in lakes, cove culture in reservoirs. The fifth is environmental-oriented integration, where waste effluents from intensive aquaculture ponds are recycled to improve water quality and to grow filter feeder/ herbivores or macrophytes as secondary crops. This paper presents concepts and practical examples for some of these systems.

Freshwater, brackishwater, and marine ecosystems are recognized as distinct from each other and aquaculture is often conventionally categorized accordingly. However, the brackishwater aquaculture category is by no means universally recognized. China, India and Japan recognize only two categories: inland and marine aquaculture. Thailand and Vietnam, on the other hand, report production from brackishwater and marine aquaculture together under one category: coastal aquaculture. An examination of the species involved would show that there is such a wide overlap between so-called "brackishwater species" and "marine species" so that the two groups are virtually congruent with each other. Brackishwater species are euryhaline and can survive just as well in varying salinity levels and may also be raised and grown in full-strength seawater. So-called marine species, on the other hand, can tolerate slight dilutions in salinity and can be grown just as well in what are technically brackish waters. Furthermore, most, if not all, of the so-called brackishwater species invariably require marine waters for propagation. Thus, it would appear that the distinction between brackishwater and marine aquaculture is meaningless in categorizing aquaculture species. Saltwater culture of finfish in Southeast Asia may be characterized by low species diversity; sluggish industry growth, continued use and even dependence for some species on wild-caught seedstock, and heavy dependence either on fresh fish biomass or on fish meal for formulated feeds. There are only a few of finfish species or species groups that are now commercially raised in saltwater: milkfish, tilapia, grouper, and sea bass. Mangrove snapper and rabbitfish are to a certain extent aIready being cultured, but have not yet reached a significant proportion. Relative to other aquaculture commodities, particularly penaeid shrimps and seaweeds, the growth of saltwater fish culture in Southeast Asia has not been particularly spectacular. This is not for lack of market since there is a good intemational and local market for groupers. While milkfish and sea bass fry can now be commercially produced in hatcheries, commercial production of grouper fingerlings seedstock remains elusive, despite a long R & D history. There is an urgent need to develop cost-effective feeds with a greatly reduced requirement for fish protein for saltwater aquaculture.

With the world population doubling in size from 3 to 6 billion people from 1960 to 1999 and currently growing at 1.33% per year (or an annual net addition of 78 million people), and expected to reach 7.3 to 10.7 billion by 2050 (with 8.9 billion considered most likely), there are growing doubts as to the long term sustainability of many traditional agricultural food production systems in being able to meet the increasing global demand for food. Nowhere is this more critical than within many of the world s developing countries, and in particular within those Low-income Food-deficit countries (LIFDC ; currently representing over 62% of the world s population), which are net importers of food and lack sufficient earnings to purchase food to cover their basic dietary needs. Of the multitude of agricultural food production systems, aquaculture is widely viewed as being an important potential candidate capable of contributing to reductions in the shortfall in the terrestrial food basket. Aquaculture, the farming of aquatic plants and animals, has been the fastest growing food production sector for over a decade. Total global production from aquaculture more than tripled from 10 million metric tons (mmt) in 1984 to over 36 mmt in 1997, and production grew at an average compound rate of 1 l% per year since 1984. In contrast to traditional livestock food production systems, the bulk of global aquaculture is realised within developing countries (89.6% total) and LIFDCs (80.6% total). Despite its good prospects and apparent potential for continued growth, the aquaculture sector has not been without its problems and critics. In particular, there have been concerns raised related to deficiencies in existing aquaculture legislation and planning methods, the use of certain farming practices, issues of resource use efficiency, disease treatment and control, environmental degradation, social welfare, and employment opportunities, etc. Although the majority of these are not unique to the aquaculture sector, it is imperative that these issues be addressed and resolved if the sector is to emerge into a major global food production sector in the next millennium. In addition, the present paper reviews the origins and salient features of the FAO Code of Conduct for Responsible Fisheries (CCRF), and in particular of Article 9 of CCRF concerning aquaculture development. An overview is also presented of ongoing and planned initiatives concerning the implementation of the code. In particular, the paper attempts to consider the existing socioeconomic conditions of the majority of aquaculture producing countries within the Asian region, and the real basic need of identifying affordable and practical solutions to aid the development of the sector. Particular emphasis is placed on the need of government to provide an enabling economic and legislative environment and umbrella for the sustainable and responsible development of the sector, and the need for increased collaboration between the private and public sector organizations, and government engaged in all stages of the aquaculture development process.

During the last thirty years, seaweed farming has progressed in the region comprising the Association of Southeast Asian Nations (ASEAN). Farm production reached a high of 146,500 mt of dried seaweeds in 1997 from an initial harvest of 500 mt in 1973. In 1997, the ASEAN region produced about 90% of the world s production of carrageenophyte seaweed, providing raw materials for the US$35O million world carrageenan market. Two species of carrageenophytes, Kappaphycus alvarezii (=Eucheuma cottonii) and Eucheuma denticulatum (=Eucheuma spinosum), constitute the base of the seaweed industry in the region. K. alvarezii is predominantly farmed in the Philippines and Malaysia while E. denticulatum is dominant in Indonesia. Vegetative propagation is still applied in all farmed species of carrageenophytes, while the monoline method remains the most popular method of farming. Non-traditional farming areas have been established in central and northern Philippines and in Sabah, Malaysia. The culture technology has been developed for Gracilaria sp.; however, no up-to-date reports on production are available. Seaweed farming has become one of the most important sources of livelihood for at least 100,000 coastal families in Southeast Asia, contributing apparently to the reduction of blast and cyanide fishing and to the relative improvement of peace and order in seaweed farming areas.

The paper discussed the current status of transboundary fish diseases in Thailand. The following were given focus in the paper: status of Koi Herpesvirus in the production of common carp and koi and the status of viral diseases in the production of shrimps and prawn. Surveillance, monitoring and diagnosis of diseases of aquatic animals and the quarantine services to prevent entry of diseases of aquatic animals were also discussed.

The paper discussed the current status of transboundary fish diseases in Philippines. The following were given focus in the paper: status of Koi Herpesvirus in the production of common carp and koi and the status of viral diseases in the production of shrimps and prawn. Surveillance, monitoring and diagnosis of diseases of aquatic animals and the quarantine services to prevent entry of diseases of aquatic animals were also discussed.