The first outbreak of red sea bream iridoviral disease (RSIVD) caused by red sea bream iridovirus (RSIV) was recorded among cultured red sea bream (Pagrus major) in 1990 in Ehime, Shikoku, Japan. Since then, the disease has caused mass mortalities of many cultured marine fishes. From 1990-2000, RSIVD was detected in 31 cultured marine fish species, including 28 Perciformes, 2 Pleuronectiformes and 1 Teteraodontiformes, in 18 prefectures in the southwestern part of Japan. The infected fish are lethargic and show severe anemia, petechiae of the gills, and enlargement of the spleen. Histopathologically, the disease is characterized by the presence of enlarged cells in the spleen, heart, kidney, liver and gills that are deeply stained with Giemsa solution. Diagnostic methods for RSIV, such as the observation of stained imprints or tissue sections, an immunofluorescent (IF) test with a monoclonal antibody (MAb) and a polymerase chain reaction (PCR) technique have been developed. The IF test with MAb is commonly used in the rapid diagnosis of RSIV-infected fish. For an effective control measure against RSIVD, a formalin-killed vaccine has been developed and this showed a significant effect in red sea bream under both experimental and field conditions.

Asia leads the world in cultivated shrimp production with export earnings in the order of billions of US dollars per year. In spite of this success, annual production decreased in the late nineties because of widespread epizootics caused by new viral pathogens. Although, these viruses were no cause for alarm to human health authorities, they were economically crippling for Asian shrimp farmers. In Thailand, shrimp production trends have mirrored those in the rest of Asia, except that recovery from the viral epizootics has been somewhat better than it has for most of its close neighbors. Our work in Thailand has focused on the characterization of the causative viruses and on the development of rapid diagnostic probes for them. Similar work has been done elsewhere. The aim of the work has been to develop effective control measures to help shrimp farmers. We are engaged in similar work on bacteria and parasites. The major viruses of concern (in our estimated order of economic impact for Thailand) are white-spot syndrome virus (WSSV), yellow-head virus (YHV), hepatopancreatic parvovirus (HPV), monodon baculovirus (MBV) and infectious hypodermal and haematopoeitic virus (IHHNV). We have also prepared probes for Vibrio parahaemolyticus and for a microsporidian parasite, Agmasoma penaei. These highly specific and sensitive tools for detection are already helping shrimp farmers and we hope that new technological advances will make them practicable in the field. At the moment, however, the most rapid test is the polymerase chain reaction (PCR) test, which takes approximately 3 hours to complete. This review covers important Asian shrimp diseases for which PCR tests are currently available.

Myanmar has extensive mangrove forests in Ayeyarwady Delta, Rakhine, and Tanintharyi, but these have been drastically reduced due to paddy rice cultivation. Today, only 382,032 ha remain. Myanmar is only now starting to modernize shrimp farming. Current government policy supports and encourages foreign investment in shrimp culture.

Cambodia has 435 km of coastline with 85,000 ha of mangrove forest. A big part of the mangrove area is in Koh Kong province (63,700) where intensive shrimp culture activity is also concentrated. Shrimp (Penaeus monodon) farms occupy 850 ha, producing 450 tons/yr (1995). But lately, production decreased by 20% due to diseases and self-pollution. The government has since placed restrictions on shrimp farming.

Silvofisheries is a form of integrated mangrove tree culture with brackishwater aquaculture. It is a form of low input sustainable aquaculture. This integrated approach to conservation and utilization of the mangrove resource allows for maintaining a relatively high level of integrity in the mangrove area while capitalizing on the economic benefits of brackishwater aquaculture. Silvofisheries is being promoted in Indonesia as part of a mangrove rehabilitation, conservation and management program. Pond-based silvofisheries follow three design models: (1) the basic “empang parit” model that is essentially identical to an extensive aquaculture pond with maintenance of mangrove trees on the central platform; (2) modification of the basic model to include a dike constructed around the treed central platform so that the water level within the mangrove area and the open water perimeter culture area can be controlled separately; and (3) further modification of the second model to completely separate the open water culture area from the mangrove area by a gated dike with the pond culture area consolidated to a square or rectangular shape at the end of the enclosed diked area. The ratio of mangrove tree to open water culture area is 8:2 to 6:4. In addition, various methods of minimizing the costs associated with pond construction are being considered. This includes the cultivation of mangrove crabs (Scylla sp.) in pens. The State Forestry Company in Indonesia has successfully developed and implemented silvofisheries sites (e.g., 6,000 ha in West Java-Cikiong with 1,508 farmers; 5,300 ha in Blanakan with 2,060 farmers). A conditional lease program with non-government organizations providing technical assistance to farmers has been successful. This program exemplifies what can be accomplished in mangrove rehabilitation and management within a controlled and enforced program. Production and financial return from silvofishery varies with the system, site characteristics, the level of energy input (mainly from mangrove litter - green manure) and utilization by cultured species, among other factors. Annual profit of up to $2,000/ha/yr for a milkfish and shrimp polyculture silvofisheries system has been reported. There is a need to refine data and analysis, since all costs are often not included, and revenue projections are often based on expected production rather than actual production. Farm interviews in West Java showed a range in gross income from $313 to $946/ha/yr while net profit per individual farm (1.5-10 ha farm size) ranged from $943 to $1,558/farm/yr. There was greater production effort per unit area by farmers with smaller farms. Individual silvofishery farmers often combine incomes from multiple sources. The application of silvofisheries practices requires reasonable measures of caution as with any activity in an environmentally sensitive area as the mangroves. Additional important considerations in the development of silvofisheries as part of an activity within the mangrove ecosystem include the issues of land ownership, integrated coastal zone planning and development, comparative economic assessment, systems models, optimizing use of inputs, selection of mangrove tree and aquaculture species, better understanding of trophic production and food web utilization, and improvement of economic return.

Although Japan has large-scale aquaculture, there is no aquaculture development in mangrove areas because the total area is small (553 ha) and strictly protected. Mangroves are preserved in comparatively good condition. Future development of aquaculture in mangrove areas is considered small-scale. Rather than aquaculture, Japan practices enhancement and management of wild fisheries. Tourism is another industry that would have an important role in mangrove utilization. But basic research on mangrove ecosystems is essential prior to determining policies for utilization of mangrove areas. International cooperative research work is important to encourage mangrove-friendly aquaculture and protect the environment.

The paper describes some mangrove-friendly aquaculture activities that are practiced in Malaysia. Among these are the culture of cockle and oyster, semi-intensive culture of tiger prawn, fish cage culture, and pen culture of mud crab. Policies, regulations, future directions and priority areas in research and development that can contribute to sustainable mangrove utilization are discussed.

The workshop was conducted to maintain linkage between Southeast Asian Fisheries Development Center, Aquaculture Department and its alumni. It also aimed to: assess the effectiveness of the training alumni and among trainees; inform alumni of the recent technologies developed by the Department; recommend ways to make the training courses more responsive to the needs of the fish farmers and the aquaculture industry. The training alumni identified several problems regarding the capability of the technical staff in aquaculture, i.e. shrimp seed production, marine fish seed production, grow-out culture, and fish diseases. The contributions of the selected participants during the meeting which are contained in this volume are cited individually.

Abstracts of the 17 papers presented at the conference are cited individually in this issue.